short-range rf wireless proximity networks technology assessment

3 April, 2006 DRAFT 0.10

document title/ titre du document

IRELESS ECHNOLOGY OSSIER

IRELESS NBOARD PACECRAFT AND IN PACE XPLORATION

Annex A DRAFT 0.10z Short-range RF Wireless (Proximity) Networks Technology Assessment for Space Applications

REF. TOSE-1B-DOS-4 prepared by/préparé par Rodger Magness reference/réference REF. TOSE-1B-DOS-4 TOS-EDD/2004.3/RM issue/édition 0 revision/révision 10 Draft date of issue/date d’édition 3 April 2006 status/état Under Review Document type/type de document Technical Note Distribution/distribution P. Perol, P. Armbruster, P. Plancke

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A P P R O V A L

Title titre

TEC-E Technology Dossier: Wireless Onboard Spacecraft and in Space Exploration, Annex A, Short-range RF Wireless (Proximity) Networks Technology Assessment for Space Applications

Issue - DRAFT issue

0 revision revision

10

author auteur

Rodger Magness date date

3 April 2006

approved by approuvé by

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C H A N G E L O G

reason for change /raison du changement issue/issue revision/revision

date/date

Rev Draft 0.8 update. Draft 0 8 1 December 2005

Rev Draft 0.9 update. Draft 0 9 1 January 2006

Rev Draft 0.10 update. Draft 0 10 3 April 2006

C H A N G E R E C O R D

Issue: 0 Revision: 10

reason for change/raison du changement page(s)/page(s) paragraph(s)/paragraph(s)

Rev Draft 0.8 update. pp. 18-19, 24-25. Tables 3 and 4.

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reason for change/raison du changement page(s)/page(s) paragraph(s)/paragraph(s)

Rev Draft 0.9 update. pp. 14, 18-19, 24-25 and p. 46. Added references pp. 85-87.

Tables 2, 3 and 4. Added new section 4.19.

Rev Draft 0.10 update. pp. 18-19, 24-25. Added references pp. 88-90, revised Conclusions Section, and included Addendum 6.

Tables 3 and 4 and table notes. 6.1 - 6.5, and added Addendum 6.

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1. Overview _________________________________________________ 7

2. ESA Applications of Wireless Proximity Networks __________ 11 2.1. Microsensor Proximity Networks ____________________________ 12

2.1.1. Microsensor Proximity Network Nodes____________________________ 12 2.1.2. Microsensor Deployment and Configuration _______________________ 13 2.1.3. Microsensor Proximity Network Organization ______________________ 14 2.1.4. Microsensor Proximity Network Operation _________________________ 15 2.1.5. Wireless Technologies and ESA Microsensor Proximity Network Applications ________________________________________________________ 15

2.2. Intra-Spacecraft Proximity Networks _________________________ 17 2.2.1. Intra-Spacecraft Proximity Network Nodes ________________________ 17 2.2.2. Intra-Spacecraft Proximity Network Deployment and Configuration ___ 18 2.2.3. Intra-Spacecraft Proximity Network Organization ___________________ 18 2.2.4. Intra-Spacecraft Proximity Network Operation _____________________ 19 2.2.5. Wireless Technologies and ESA Intra-Spacecraft Applications _______ 19

2.3. Inter-Vehicular Proximity Networks __________________________ 23 2.3.1. Inter-Vehicular Proximity Network Nodes__________________________ 23 2.3.2. Inter-Vehicular Proximity Network Deployment and Configuration_____ 24 2.3.3. Inter-Vehicular Proximity Network Organization ____________________ 25 2.3.4. Inter-Vehicular Proximity Network Operation_______________________ 25 2.3.5. Wireless Technologies and ESA Inter-Vehicular Applications ________ 26

2.4. EVA Proximity Networks ____________________________________ 30 2.4.1. EVA Proximity Network Nodes___________________________________ 31 2.4.2. EVA Proximity Network Deployment and Configuration______________ 31 2.4.3. EVA Proximity Network Organization _____________________________ 31 2.4.4. EVA Proximity Network Operation________________________________ 31 2.4.5. Wireless Technologies and ESA EVA Proximity Network Applications_ 32

2.5. Advanced Planetary Exploration (mobile atmospheric micro nodes) ________________________________________________________ 32

3. Characteristics of ESA Wireless Proximity Networks________ 32 3.1. Proximity Networks Characteristics__________________________ 32 3.2. Summary of Proximity Networks Characteristics______________ 34 3.3. A Refined Proximity Network Taxonomy _____________________ 36 3.4. Key Characteristics of Proximity Network Classes ____________ 36

3.4.1. Micropower Proximity Networks__________________________________ 37 3.4.2. Intelligent Proximity Networks ___________________________________ 38

4. Technologies and Resources Potentially Applicable to ESA Proximity Networks _________________________________________ 40

4.1. The Internet Engineering Task Force (IETF) __________________ 40 4.2. The Internet Protocols ______________________________________ 41 4.3. Ad Hoc Routing Protocols __________________________________ 42 4.4. Wireless Internet Research__________________________________ 43 4.5. Header Compression Techniques ___________________________ 44

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4.6. Internet Quality-of-Service Technologies _____________________ 44 4.7. Time Synchronization ______________________________________ 44 4.8. Location Determination _____________________________________ 45 4.9. Energy-Efficient Protocols __________________________________ 46 4.10. Power-Aware Routing Algorithms __________________________ 46 4.11. IEEE 802.15.4 WPAN_______________________________________ 47 4.12. IEEE 802.15.1 Bluetooth ___________________________________ 47 4.13. IEEE 802.11 Wireless LAN Standards _______________________ 48 4.14. Proximity-1 Space Link Protocol ___________________________ 48 4.15. IEEE P1451.5 Internetworking (WLAN / Bluetooth / IEEE 802.15.4)_______________________________________________________ 49 4.16. RFID: Battery-less sensors -- Micropower over Microwave and Materials Tracking______________________________________________ 50 4.17. Narrowband and Narrowband ISM RF (868 MHz, 915 MHz, 2.4 GHz) __________________________________________________________ 51 4.18. WiMedia, IEEE 802.15.3a Ultra Wideband, and Wireless IEEE 1394 (Very High Rate, High QoS) ________________________________ 51 4.19. IEEE 802.15.3c WPAN Millimetre-wave Alternate PHY Layer __ 53 4.20. IEEE 802.16-2004/e Wireless MAN Standards and WiMax _____ 53 4.21. Ultra Wideband (and Pulse-based UWB) ____________________ 54 4.22. IEEE 802.15.5 Mesh WPAN Networks _______________________ 55 4.23. SOIS Wireless WG of CCSDS (Potential WG – currently a BoF) 55

4.23.1 Preliminary Classifications of Applications and Services ____________ 56 4.23.2 Preliminary Classifications based on Performances and Robustness (RAMS) Requirements _______________________________________________ 57 4.23.3 Added Value of Wireless Services Compared to wired Solutions _____ 59 4.23.4 Introduction Prioritization Strategy _______________________________ 60

4.24. Identification of Services to be Considered in Priority Within the CCSDS SOIS WG_______________________________________________ 61

4.24.1 Proximity Low Power Sensing Network___________________________ 61 4.24.2 Proximity Intelligent Network ____________________________________ 61 4.24.3 Proximity Command and Control Network ________________________ 62

5. Key Technologies for ESA Proximity Networks _____________ 62 5.1. Hypothetical Architectural Skeletons for ESA Proximity Networks_______________________________________________________________ 62

5.1.1. Hypothetical Micropower Proximity Network Architecture ____________ 62 5.1.2. Hypothetical Intelligent Proximity Network Architecture______________ 63

5.2. Proximity Network Technology Requirements ________________ 63 5.2.1. Network Architectures and Protocols for Proximity Networks _________ 63 5.2.2. Efficient Addressing Scheme ____________________________________ 64 5.2.3. Physical Layer Requirements____________________________________ 64 5.2.4. Link-Layer Protocols ___________________________________________ 66

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5.2.5. Network-Layer Protocols________________________________________ 67 5.2.6. Transport-Layer Protocols ______________________________________ 68

5.3. Technology Readiness Assessment _________________________ 68 6. Conclusions and Recommendations_______________________ 69

6.1. Focus Proximity Network Research Investment on Micropower Networks_______________________________________ 69

6.2. Promote Common Hardware and Software Platforms _________ 70 6.3. Promote Integrated Demonstration Projects __________________ 70 6.4. An ESA Wireless Roadmap _________________________________ 71 6.5. Looking Beyond the Immediate Horizon – Trends in Wireless__ 71

Addendum 1 _______________________________________________ 77

Technology Readiness Levels _______________________________ 77

Addendum 2 _______________________________________________ 78

Representative RF Wireless Technologies Characteristics_____ 78

Addendum 3 _______________________________________________ 81

Representative Current and Near and Mid-term Manned Spaceflight Wireless Needs _________________________________ 81

Addendum 4 _______________________________________________ 82

IEEE 802.11 WLAN Standards _______________________________ 82

Addendum 5 _______________________________________________ 84

IEEE 802 LAN / MAN Standards ______________________________ 84

Addendum 6 _______________________________________________ 86

Further Reading ____________________________________________ 86

References_________________________________________________ 88

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TEC-E Wireless Technology Dossier Annex A

issue 0 revision 10 - 3 April 2006 REF. TOSE-1B-DOS-4 TOS-E

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…”it is highly desirable to develop communication solutions and a constellation design that will allow for use of existing media access techniques such as the IEEE 802.11 wireless Ethernet standards.” Excerpt from a recent NASA study, Architecture Study of Space-Based Satellite Networks for NASA Missions, 2003) [133]. “[Concerning] the future…such satellites with coherent inter communications and precise knowledge of relative position promises a resilient reconfigurable and highly adaptable entity in orbit, capable of communications, remote sensing by radar or optical observations. In many ways we have already created the PC in space, and our future technology may resemble closely a wireless internet!” Sir Martin Sweeting, Chief Executive of Surrey Satellite Technology Ltd and Director of the Surrey Space Centre, writing about current developments at Surrey Space [151].

1. Overview

This dossier annex summarizes an assessment performed by ESTEC TEC-EDD, of technologies applicable to wireless proximity networks used in ESA space bound applications. It was compiled and written from a systems engineering perspective with knowledge of state-of-the-art wireless techniques, software protocols and protocol stacks, TEC-EDD personnel wireless background in both commercial wireless

electronics and software, and a thorough, though informal, commercial markets survey. The work has been facilitated by investigations over the past two years and supported in part by the ESTEC Wireless Data Communications Onboard Spacecraft – Technology and Applications Workshop 14-16 April 2003 [54, 55], and the efforts of several members of the ESA / Industry Wireless Onboard Spacecraft Working Group and the international, inter-agency wireless e-Group, SpaceWLAN as well as numerous discussions with persons within the Science Directorate, Robotics section, the Aurora programme, ESA Advanced Concepts Team, individuals participating in CDF studies and several sections of D-TEC within ESTEC. The author offers a thank you to all these contributors.

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This dossier and annex should be viewed as a living document as research and development in RF spread spectrum and commercial applications are two of the most active areas in microelectronics and data communications today, and foreseen to remain so for a number of years. Within such an active area of R&D, the user can expect this document to be updated continually. The convergence of a diverse array of current developments, such as highly miniaturised mixed-signal SoC, zero (or near zero) intermediate-frequency and all CMOS radio, robust and high noise immunity digital data over RF, very positive EMC characteristics, mature IEEE standards, highly developed commercial firmware and available software (usually freeware) supporting ad hoc or self-organising networks, the positive implications of deep-sub-micron CMOS w.r.t. radiation tolerance, and the dramatically increasing availability of the European intellectual property (IP), facilitate considering commercially-derived RF wireless for many space applications. Detailed discussion and specifications of the various commercial wireless PHY and MAC layers are not included here, but are found on the IEEE or ISO websites. Also, the term spacecraft as used herein, applies to both payload and launcher. Several application categories listed in Table 3 are also potentially applicable to aircraft as well. And one potentially very beneficial area for ESA and the aerospace community that is not explicitly covered in this dossier is ground testing. Many wireless advantages are relatively simple to realise: wireless sensors for instance, in launcher booster testing, and spacecraft environment/validation/certification testing. The Wireless Data Communications Technology and Applications Workshop, 14-16 April 2003 proceedings are at: ftp://ftp.estec.esa.nl/pub/ws/Wireless2003_Wshop/ [54]. The 2003 workshop proceedings are also available at the ESA ESTEC library: ESTEC Library ESA-X-3410 400080345 CD-ROM The second in the workshop series was the Wireless for Space Applications Workshop and Round Table, 10-13 July 2006. Proceedings are found at: http://www.congrex.nl/06c10/ [136]. The 2006 workshop proceedings are also available at the ESA ESTEC library: ESTEC Library ESA-X-3XXX 400080??? CD-ROM The ESA sponsored Wireless e-Group: http://groups.yahoo.com/group/spacewlan/ The original ESA Wireless Onboard Spacecraft website: http://wireless.esa.int/ is currently being improved and redesigned to ESA web standards, and is to be relocated to a more secure ESA-ESTEC Spacecraft

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ftp://ftp.estec.esa.nl/pub/ws/Wireless2003_Wshop/

http://www.congrex.nl/06c10/

http://groups.yahoo.com/group/spacewlan/

http://wireless.esa.int/


Engineering website. The reader is expected to have already acquired a fundamental understanding of the underlying principles utilised and advantages offered in much of current wireless technology, e.g. spectrum spreading techniques, significantly lower Tx power spectral density, advanced coding and keying algorithms, topologies characteristics, etc. Those background documents, tutorials, and advanced topics papers are readily available on the web in enormous volume and for several technologies, as well as in the ESA workshops proceedings and references.

One further note for the reader: the papers and other references listed in the References section of this dossier annex are but a small representative fraction of the total the author has collected over the course of this assessment. Wireless proximity networks are relatively small, fairly short-range, often ad hoc, wireless networks typically dedicated to tasks such as transporting in situ sensing data, among others. The number of nodes contained within a proximity network is expected to be comparatively small, perhaps tens or hundreds of nodes at most. While "short-range" is relative, many wireless proximity networks will have a physical diameter on the order of a few metres or less, hundreds or perhaps thousands of metres (although some have suggested that a few of these networks might be as large 100-400 km [13, 38]).

Wireless proximity networks will operate in a variety of distinctly different environments. These different environments are likely to impose different requirements on proximity networks and demand different networking technologies. To facilitate this analysis, TEC-EDD initially divided proximity networks into five subclasses described in greater detail below:

• Microsensor Proximity Networks (e.g., microsensor-lander networks) • Intra-Spacecraft Proximity Networks (e.g., spacecraft/human health

monitoring networks ) • Inter-Vehicular Proximity Networks (e.g., lander-rover, robot-robot

networks) • EVA Proximity Networks (e.g., human and robotic EVA networks) • Advanced Science Proximity Networks (e.g., mobile atmospheric

planetary microsensors) Informal descriptions of the operations of proximity networks in ESA application case scenarios were developed. These descriptions provided the basis for a more thorough examination of proximity networks. They were also intended to elicit more detailed information about the behaviour of and requirements for proximity networks from subject-area experts (a role analogous to that played by "use cases" in some object-oriented software

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analysis methodologies).

Furthermore, most of the proximity wireless technologies discussed herein are members of the IEEE 802.1 and IEEE 802.2 family of network management, and are for the most part, internet ready. To investigate wireless without the context of the Internet Protocol suite, Internet capability, or at least Internet interoperability is, in the author’s view, a mistake for the long term.

A detailed list of the characteristics of the different types of proximity networks was compiled. This compilation shows that the initial five subclasses of proximity networks can be usefully aggregated into two classes:

• Micropower Proximity Networks (microsensor, intra-spacecraft networks and Advanced Science networks) and

• Intelligent Proximity Networks (inter-vehicular, EVA). These above classes should be considered in two separate time frames, as off-the-shelf technologies to achieve micropower proximity networks slightly lag the available technology to realise intelligent proximity networks.

The technologies required to implement proximity networks were identified and categorised by proximity network subtype (microsensor, inter-vehicular, etc.) and protocol layer, scope or function (e.g., link layer, node architecture, gateway).

Finally, the maturity of each of the identified technologies was assessed. However, some of the discussion in this dossier is specifically not targeted to specific commercial-off-the-shelf wireless technologies, as the wireless world evolves very quickly. Regardless, the “spin-in” of off the-shelf wireless intellectual property may have significant cost advantages, even if some characteristics are slightly less than ideal for space use. The intent is that this dossier identifies the space application roadmap, somewhat independent of particular off-the-shelf technologies or devices, from now to a horizon of 15 years or so.

This assessment concludes that the technologies required for micropower proximity networks are somewhat less mature than those needed for intelligent proximity networks. However, micropower proximity networks (the micropower category includes both microsensors and intra-spacecraft sensors) offer ESA the greatest potential return for its proximity network research investments. Common hardware and software platforms for micropower proximity network research, development, and deployment would enhance the opportunities for collaboration between projects, enable projects to more easily leverage the results of prior ESA-funded work and

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increase the overall productivity of ESA's research euros. System-level demonstrations by ESA researchers of micropower proximity networks would help focus research on identifying and solving real-world problems, as well as provide an empirical assessment of the effectiveness of proposed technologies. 2. ESA Applications of Wireless Proximity Networks

ESA identified five potential applications [53] of wireless proximity networks for the purposes of this study, which are summarized in the table below.

Application Number of Nodes Max link range Node mobility Robotic & in situ sensing for planetary exploration (fixed nodes)

5-100 100-1000 m None

Robotic & in situ sensing for spacecraft health monitoring

2-100 100 m None

Robotic & in situ sensing for planetary exploration (mobile nodes)

1-5 1000 m Medium

Data delivery for EVA 2-5 100 km High Advanced planetary exploration (mobile atmospheric microprobes)

2-10 100 km None/ Medium

Table 1. ESA Applications of Wireless Proximity Networks

Upon initial examination, TEC-EDD concluded that each of these applications was distinctly different than the others. As a result, TEC-EDD divided proximity networks into five categories, corresponding to each of the applications identified. These categories were assigned shorter, more descriptive names:

• Microsensor Proximity Networks - robotic in situ sensing for planetary exploration (fixed nodes)

• Intra-Spacecraft Proximity Networks - robotic in situ sensing for spacecraft health or astronaut health monitoring

• Inter-Vehicular Proximity Networks - robotic in situ sensing for planetary exploration (mobile nodes), near formation flying, on-orbit assembly, etc.

• EVA Proximity Networks - data delivery for extra-vehicular activity (EVA) • Advanced Science Proximity Networks (e.g., mobile planetary microsensors)

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Informal overviews of the operations of these networks are presented in this section, including descriptions of the nodes that participate in the networks, and the deployment, configuration, organization, and operation of the networks. These operational scenarios represent how, in the view of the author, these networks ought to behave, assuming that the requisite technologies and products have been developed and matured.

2.1. Microsensor Proximity Networks

Microsensor proximity networks support the operation of sensor systems composed of numerous (perhaps tens or even hundreds) tiny, dedicated nodes containing integrated sensing, computing, and wireless communications capabilities, referred to here as "microsensor nodes" or more simply "microsensors". ESA and other researchers have called these networked, collaborative

collections of microsensor nodes "sensor webs" [18, 3]. A microsensor proximity network transports sensor data collected by the sensor web to an external network connection (or gateway), through which the data are forwarded to external users for archive and analysis.

Microsensors and microsensor networks are topics of active research. Many approaches to designing microsensor nodes and networks have been proposed and investigated, but no single approach has yet emerged as dominant. Likewise, there is not universal agreement on the precise characteristics of microsensors. Therefore, this section is a snapshot of some of the current thinking on microsensors and microsensor networks, with an emphasis on topics relevant to ESA applications.

ESA applications of microsensor webs and microsensor proximity networks include in situ monitoring of terrestrial and planetary environments. For example, a microsensor web might be deployed to collect in situ sensor surface data in the vicinity of a planetary lander; deployed via a rover, deployed from an orbiter, or dropped from an aerobot.

2.1.1. Microsensor Proximity Network Nodes

Microsensor nodes are, as the name indicates, small – they generally are only just large enough to accomplish the task of acquiring, communicating and perhaps processing sensor data. Research prototypes of microsensor nodes range in size from a 15-centimetre cube [32, 1, 15] to approximately 100 cubic millimetres (with an

objective of demonstrating a microsensor node only a few cubic millimetres in size) [48].

Microsensors are networked and in some applications collaborative. Numerous

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microsensors are deployed over an area to be monitored. After deployment, the microsensors configure themselves into an autonomous network, which communicates sensor information to the external world. In some designs, the network also supports collaborative processing of sensor data (sensor data fusion) among the microsensor nodes [7, 22, and 45].

Batteries are generally used to power microsensors, so the lifetime of a microsensor is essentially the lifetime of the battery. As a result, power conservation is perhaps the dominant consideration in microsensor designs. Numerous hardware-based power conservation strategies have been explored, including using low-power components, using lower-function components (e.g., 8-bit or 16-bit processors rather than 32-bit processors), and putting the microsensor to sleep for extended periods of time.

The compute power contained in microsensors varies widely, from 8-bit processors with only a few tens of bytes of memory to 32-bit processors with several megabytes of memory. Naturally, the functionality of microsensor nodes varies over a similar range, from relatively unintelligent nodes that merely forward sensor data to an external user for analysis, to nodes that employ complex data fusion algorithms to analyze and reduce the data within the microsensor web.

Microsensors may be described as "disposable". This term is apt in the sense that microsensors are deployed for a narrow, specific, data-collection objective. The mission ends when the batteries become depleted, at which time the microsensors are abandoned in place. As a result, many higher-level functions have limited utility, such as being able to remotely reprogram microsensors after they have been deployed.

Numerous research groups, both within and outside of the European realm, are exploring designs for microsensor nodes. However, beyond basic issues such as the paramount importance of energy conservation, there is little consensus about the most appropriate architecture and design tradeoffs for microsensor nodes. However, gathering significant commercial momentum is the IEEE 802.15.4 standard and the ZigBee commercial alliance [87] for very low power wireless sensors.

2.1.2. Microsensor Deployment and Configuration

The life of a sensor web includes deployment of the microsensor nodes, autonomous configuration of the nodes, creation of the microsensor proximity network, and operation of the sensor web until the batteries in the last remaining nodes become exhausted. The first two topics are discussed in this section, while the remaining topics are explored in following sections.

Nearly every imaginable method has been proposed for disseminating microsensors. Terrestrially, it is often practical to place these nodes by hand. Another common model

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is to scatter them over an area of interest from an unmanned aerial vehicle (UAV). In planetary exploration applications, a rover is a logical tool for microsensor deployment. However they are deployed, the exact placement of individual microsensors will be imprecise and difficult to predict. Because the ultimate location of the nodes cannot be accurately predicted, the possible topologies of the microsensor network cannot be accurately determined in advance. Given this environment, microsensor nodes cannot be pre-configured prior to deployment (because their precise location and network neighbours cannot be predicted), nor can they be remotely configured (because the external connectivity necessary for remote configuration doesn't exist until it is configured). Microsensor webs must autonomously configure themselves after deployment.

In some applications, microsensor nodes must determine or configure additional attributes. Some microsensors need to determine their location, either with respect to a global reference system or relative to other microsensors [40, 51]. Likewise, microsensors may need to synchronize their clocks, again either with respect to each other or with an external time reference (e.g., UTC). The requirement for time and spatial synchronization is generally derived from the application or mission of the microsensor web, rather than from any inherent need of the microsensor nodes themselves. As a result, the detailed requirements for time and spatial synchronization (e.g., precision or relative versus absolute measurement systems) must be consistent with the scientific mission of the microsensor web.

2.1.3. Microsensor Proximity Network Organization

The microsensors' first task after deployment is to organize a microsensor proximity network among themselves. The most appropriate structure for microsensor networks is the topic of active research. Some researchers advocate a flat network structure among homogeneous nodes, while others have suggested that a hierarchical network structure can extend the life of a battery-powered sensor web [31]. Networks of heterogeneous nodes, where a few more powerful nodes (e.g., nodes with greater computational power or greater transmission range) are scattered among the microsensor nodes, have also been explored. The common characteristics of all of these solutions are:

. • the microsensor nodes autonomously configure the network; the network is not pre-configured prior to deployment and is not manually or remotely configured after deployment, and . • data must be routed within the network; communications between any two nodes is likely to involve forwarding by intermediate nodes. Alternative network organizations for microsensor webs are examined in more detail in Section 4, "Key Technologies for ESA Proximity Networks".

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2.1.4. Microsensor Proximity Network Operation

Microsensor nodes do not move on their own volition, at least in likely ESA applications. As a result, the topology of a microsensor network will change only slowly, perhaps as the result of equipment failure or battery exhaustion. Nonetheless, the nodes must be able to reconfigure themselves to adapt to changes in the network topology.

Precisely how a microsensor proximity network ought to behave, however, is the subject of numerous design decisions. Perhaps most fundamentally, a decision must be made about the rate at which sensor data will be communicated. Battery-powered microsensors have a fixed amount of energy and therefore can transmit a fixed number of bits over their lifetime. These bits (or this energy) can be consumed over a short timeframe by transmitting sensor data with only short time intervals between readings or over a more extended timeframe with correspondingly greater intervals between readings. The scientists, not the microsensor designers, should decide how to allocate those bits over time, e.g., whether to use them to transmit the sensor readings over a short period of time or to transmit these readings over a longer period of time.

The rate at which sensor data will be transmitted, that undoubtedly will be different for different scientific applications, has significant implications for the design of the microsensor web. If, for example, sensor readings are transmitted much less often than the rate at which the topology of the microsensor network changes, it probably makes sense to compute routes when needed, rather than save likely outdated information about the topology of the network. Conversely, if the topology is stable relative to the traffic patterns, saving and reusing information about routes within the network can likely extend the life of the sensor web.

A corollary to these observations is that it is entirely possible that no one set of design decisions will be optimal for all ESA microsensor networks. Unfortunately, the range of solutions necessary to meet the requirements of all potential ESA applications is not entirely clear. 2.1.5. Wireless Technologies and ESA Microsensor Proximity Network Applications

The table below summarizes the author’s' assessment of currently available and soon available commercial technologies versus known and anticipated ESA space applications and missions, including the Aurora programme and Science Directorate that potentially involve microsensor proximity network

data communications. Use cases could be atmospheric measurements, various planetary surface analyses, radiation monitoring, seismography, surface area variable profiling

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utilising multiple microsensor nodes, or even subsurface in planetary caverns [137] etc.

Microsensor** Wireless

WiMedia Wireless

USB/IEEE 1394

Milli-metre Wave

Application

RF-ID based (ISO-

18000)

Narrow band RF

or Low ISM

Band

IEEE 802.15.4

and 802.15.4a/b UWB/DSSS

IEEE 802.15.1 Bluetooth

FH

IEEE 802.11a/b/g/n DSSS/OFDM

IEEE 802.15.3 Very hi-

rate OFDM IEEE

802.15.3a UWB

IEEE 802.15.3c

60 Ghz

And Other

Standards

Custom Deterministic

UWB (Pulsed)

Battery-less Sensors

Micropower over microwave

X (future)

Energy scavenging Lo-rate sensors /

transducers

X (future) X X X (c)

Networked planetary miniature surface instrumentation

X X X

MEMS and/or extremely

miniaturised sensors / transducers &

packaging (Automot.-Avionics-

Health-Space)

X X X (c) X (c) X (future?)

Mobile micro-sensor network or web

(dropped or otherwise)

X (a) X

Fixed planetary micro-sensor web

(surface)

X (b) X (b, c) X X (c)

Table 2. ESA Applications of Microsensor Wireless Proximity Networks Proposed initial ESA areas of interest. Proposed secondary ESA areas of interest. Proposed third ESA area of interest.

Proposed tertiary and future ESA areas of interest.

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(a) ESA D-SCI Technology Reference Study, DALOIMIS, including A Data Transmission and Localization System for Swarms of Microprobes, demonstrator drop test in early 2006.

(b) Several ESA D-SCI and ESA Advanced Concepts Team studies underway ranging form a network of seismometers on an asteroid to planetary free-falling atmospheric micro-sensors and planetary surface sea-of-sensors.

(c) European Union FP6 Integrated Project IST-026461, e-Cubes 3-D-Integrated Micro/Nano Modules for Easily Adapted Applications. Consortium of 21 entities, including ESA. The space application target is a planetary wireless sensor web.

** Note: this table does not attempt to account for the already known non-European applications, i.e. NASA, DARPA, U.S. Air Force and U.S. University, of which there are hundreds of activities.

2.2. Intra-Spacecraft Proximity Networks

Intra-spacecraft proximity networks support wireless sensors that monitor the environmental or structural health of a spacecraft. The wireless sensor nodes are likely to be powered by either batteries or the spacecraft. Wireless sensor

nodes eliminate the weight and space of cables for data and perhaps power. Their untethered operation also makes them much easier to provision, particularly after the spacecraft has been built or is operational, because the need for additional cabling is minimized or eliminated.

From a networking perspective, battery-powered wireless sensor nodes used to monitor spacecraft environmental or structural health are indistinguishable from the microsensor nodes discussed earlier. The primary design objective is to maximize the amount of data successfully transmitted from the network before the batteries expire. It is entirely likely that in practice spacecraft-powered wireless spacecraft health-monitoring nodes are also (from a networking perspective) indistinguishable from microsensor nodes. Nonetheless, for the purpose of this section, the two types of proximity networks are kept separate.

2.2.1. Intra-Spacecraft Proximity Network Nodes

These wireless sensor nodes are very similar to the microsensor nodes described earlier, with the possible exception that they may receive power from the spacecraft. They are small, special-purpose devices tailored to a single task, namely monitoring the structural or environmental health of a spacecraft.

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These networks may be used to monitor the cabin environment of a manned spacecraft. Shuttle mission STS-101 carried the Micro-Wireless Instrumentation System (micro WIS), provided by Invocon, Inc. (presented at the ESA Wireless Onboard Spacecraft Workshop 2003 at ESTEC) a collection of wireless, battery-powered temperature sensors, which provided real-time measurements of cabin air temperature [43, 44]. The micro WIS can transmit temperature measurements to a laptop for up to five months. The wireless system reduces the cost, weight and power requirements, and significantly increases the flexibility, of data acquisition systems. More recently in 2005, an array of miniature wireless accelerometers were aboard the Space Shuttle’s key return to flight mission to detect any break-away foam debris impacting the Shuttle’s wings [91, 92].

A number of researchers are exploring intelligent structures and smart materials that contain embedded sensors. These sensors are designed to provide heretofore-unavailable information about the behaviour of these structures in use and advanced warning of structural problems [39, 11].

2.2.2. Intra-Spacecraft Proximity Network Deployment and Configuration

Intra-spacecraft network nodes will be deployed by hand on manned missions in many applications, such as the micro WIS onboard the Shuttle, and during the AIT phase for unmanned spacecraft. Presumably, manual placement of these devices will permit them to be repositioned to enhance propagation between nodes or reduce multipath interference. Alternatively, an internal spacecraft propagation model could be developed to optimise placement.

In theory, the network could be manually configured after the nodes have been deployed. However, the adaptive, self-configuring network technologies that must be developed for microsensor proximity networks can easily and productively also be used in intra-spacecraft proximity networks. The use of these technologies would make intra-spacecraft proximity networks more robust in the face of a changing environment (e.g., nodes failing or a human or equipment situated so as to impede propagation) and minimize the risk of human error.

It is conceivable that interoperability will, in some cases, be more important for these networks than for microsensor proximity networks. For example, a spacecraft might host a semi-permanent gateway or data collection device with which different sensors are expected to interoperate over time. Note that this possible requirement does not in any way reduce the opportunity to use common technologies for microsensor and spacecraft health monitoring proximity networks.

2.2.3. Intra-Spacecraft Proximity Network Organization

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3 April, 2006 DRAFT 0.10 Early intra-spacecraft and microsensor proximity networks have

demonstrated that useful networks can be constructed with simple technologies, such as star topologies in which every sensor can communicate with a central gateway (e.g., laptop, in the case of the micro WIS). However, more advanced networking technologies, such as ad hoc routing protocols, can

make these networks more robust, adaptable, and longer-lived, even as they can for microsensor proximity networks.

The networking technologies developed for microsensor webs are directly applicable to intra-spacecraft proximity networks.

2.2.4. Intra-Spacecraft Proximity Network Operation

In a similar fashion, the behaviour of microsensor proximity networks provides a highly accurate model for that of intra-spacecraft proximity networks.

2.2.5. Wireless Technologies and ESA Intra-Spacecraft Applications

The table below summarizes the author’s' assessment of currently available and soon available commercial technologies versus known and anticipated ESA space applications and missions, including the Aurora Programme and Science Directorate that potentially involve intra-spacecraft data communications. In addition to the more

obvious use cases listed in Table 3 are crew dosimetry and biomedical monitoring [82], crew location tracking, crew experiment procedures via PDA or PDA-like devices, work instructions, general habitat WLAN, propulsion monitoring, launcher structural monitoring (strain, fatigue, temperature), crew communications, high data rate instrument SpaceWire wireless extension, manned or unmanned spacecraft internal housekeeping / environmental monitoring, and PDA devices enabling spacecraft AIT, etc. Already there are many areas of interest with activities underway, with and without ESA funding; the TU Delft student satellite, Delfi-C3 is likely to be the first in the European space segment to actually fly RF Wireless data handling in an intra-spacecraft application [83, 130], and is not funded by ESA. A more ambitious programme at the Netherlands national level is MiSAT, targeting UWB intra-spacecraft TM-TC onboard data handling [130].

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Intra-S/C** Wireless

IEEE P1451.5 (f) WiMax WiMedia

Wireless USB/IEEE

1394

Milli-metre Wave

Application

RFID based (ISO-

18000)

Narrow band RF or

Low ISM band

IEEE 802.15.4


IEEE 802.15.1 Bluetooth

FH

IEEE 802.11 a/b/g/n

DSSS/OFDM

IEEE 802.16/e OFDM

IEEE 802.15.3

Very hi-rate OFDM IEEE

802.15.3a UWB

IEEE 802.15.3c

60 Ghz

And Other Standards

Custom Determi

nistic UWB

(Pulsed)

Battery-less Sensors

Micropower over microwave

X (u)

Energy scavenging Lo-rate sensors / transducers

X (future) X X

Materials and supplies ID and tracking

X (k)

General S/C sensor / transducer network

X (e, r?,s?)

Xº (r?, t) X (d) X¹ (s?)

Astronaut health monitoring/Telemedicine/

Work-experiment procedures/Virtual

Reality-robotics control

X X (a, q) X (m, n, q)

S/C health Monitoring

X (h) X (d, g) X (c) X (n, p .11)

MEMS and/or extremely miniaturised sensors /

transducers & packaging (Automot.-Avionics-

Health-Space)

X (future) X X (i, j) X (p .11) X (i) X (future)

Hi-rate sensor network

X X (future)

SpaceWire extension Point-to-point

Xº X

Manned Lunar/Mars habitat

X (b) X (future)

General S/C TM-TC Network

X (r?) X (r?, v) X² X² (11b) X (future)

S/C Environment Monitoring System

GSEM (study)

?³ ?³ ?³

Hi-rate Onboard TM

X² (11a/g) X (future)

Highly-deterministic TC (Control)

X (future)

Table 3. ESA Applications of Intra-spacecraft Wireless Proximity Networks

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Proposed initial ESA areas of interest. Proposed secondary ESA areas of interest. Proposed third ESA area of interest.


(a) Wireless biomedical monitoring was an option for the ESA ISS Eneide mission March 2005. Continued development by Emxys and Alenia Spazio for biomedical monitoring [82].

(b) ESA CDF Aurora Manned Lunar study for habitat (completed March 2005) baseline: IEEE 802.11g WLAN.

(c) EADS Astrium Ltd. demonstrator Micropack wireless temperature transducer developed 2004.

(d) EADS Astrium Ltd. current development for a Micropack class of a class of MEMs wireless transducers, including accelerometer, pressure. Future developments may include: radiation, particle detectors, and gas detectors. Currently exploring launch opportunity onboard a Surrey Space nanosatellite.

(e) TNO (The Netherlands) completely wireless quadrant sun sensor design [83] to be launched 2006-2007 on TU Delft Delfi-C3 satellite [130]. (f) CCSDS SOIS Wireless Birds-of-a-Feather exploring standardizing

interoperability of several wireless protocols for onboard spacecraft under P1451.5.

(g) ESA TEC-EDD has achieved licence agreements for WPAN IEEE 802.15.4b intellectual property (IP) with Duolog Technologies, Ireland, via GSTP4 development. Baseband and MAC Layer VHDL IP Cores will be available to ESA and ESA Space contractors at a cost advantage, middle of 2007 under GSTP4 licence agreements.

(h) ESA TEC-EDD currently pursuing LEON2 + wireless intellectual property (IP) via ESA Space Incubator with Y-Lynx, Switzerland via an ESA Space Incubator project.

(i) European Union FP6 Integrated Project IST-026461, e-Cubes 3-D-Integrated Micro/Nano Modules for Easily Adapted Applications. The project consists of a consortium of 21 entities, including ESA. Aircraft avionics is a target application.

(j) Recently received Innovation Triangle Initiative proposal from Carlo Gavazzi Space for a MEMS accelerometer plus wireless IEEE 802.15.4 demonstrator. (Not Approved due to ITI competition.)

(k) RFID utilised by MIT at Devon Island, the Canadian Space Agency’s Haughton-Mars Project analogue site for investigating wireless communications, logistics and Mars surface mission planning and interplanetary supply chain management scenario execution in 2005. http://www.spacedaily.com/news/mars-base-05n.html

(m) ESA ESTEC-SWM astronaut refresher trainer application planned for ISS, based on PC / PDA wireless connection.

(n) Initial ESA-ESTEC contact in April 2006 with NASA Goddard over Wireless and Wireless LAN applications for NASA Crew Exploration vehicle (CEV).

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http://www.spacedaily.com/news/mars-base-05n.html


(p) ESA-ESTEC TRP, contract AO/1-3387/98/NL/NB, for a wireless MEMS accelerometer network completed 2003, AD Telecom and UPC. See ESA Wireless Workshop Proceedings, 14-16 April 2003, and the final report.

(q) ESA-ESTEC HME investigating RF Wireless (Bluetooth or WLAN) for an Astronaut Head-worn Virtual Reality/Controller for ISS. And also RF Wireless for PDAs for other astronaut informatics/interaction devices for ISS and potentially NASA CEV.

(r) ESA-ESTEC EXR-EP (Education Section) call for application of wireless intra-S/C data handling for a student satellite as part of a future ESA lunar mission.

Following approval by ESA in March 2006, the ESA Education Projects Division and the

SSETI Association are pleased to announce that the official Call For Proposals to European students for participation in the European Student Moon Orbiter (ESMO) Mission Phase A Feasibility Study is now open. The Call solicits proposals from student teams across ESA member states and associated countries for the definition of all spacecraft subsystems, all ground segment elements, and the scientific payload. In addition, individual students not in a student team are encouraged to apply for positions in the System Engineering Team. The Call will remain open until the proposal submission deadline of 15th August 2006.

http://www.sseti.net/ (s) ESA TEC-EC FUTURE TECHNOLOGY STUDIES FOR APS STAR

TRACKERS, TRP T603-36EC. The contractor shall investigate potential new star trackers technologies that may be of use in the future to further reduce the cost while improving the robustness (dynamic conditions, straylight/blinding, false stars and radiation) and functionalities (sensing of moon or earth/asteroid/planet position for example, direct entry to tracking). These shall include the mandatory consideration of LCMS APS detector by Cypress (Fillfactory) - designed specifically for this purpose-, baffle construction materials, plastic lenses, black coatings, alternative construction techniques, single chip electronics (all processing in the same ASIC/FPGA), and wireless communication.

(t) ESA CDF study (2006) for a Technology Development Mission FIRI (Far Infra Red Interferometry) of the cosmic vision program with a mission launch targeted for 2020. Flying 2 telescopes on booms, the IR beams go to the central hub where interferometry is performed as well as data acquisition and processing. In order to avoid harness, it is proposed to use a wireless connection to command and control the telescopes. Six send/receive node pairs operating at around 250kbps utilising DSSS is the baseline concept.

(u) Remote RF powering and Passive Telemetry link for a Wireless Strain Sensor System, June 2006, GTF REF 147, proposal via Greek Incentive Task Force, highly recommended for final consideration. NCSR “Demokritos”, Institute of Microelectronics.

(v)Wireless smart transducer network (WSTN) architecture for intra-spacecraft sensing and control, June 2006, GTF REF 124, proposal via Greek Incentive Task Force, recommended for final consideration. TEI of Piraeus, Dept of Electronics.

(w)CNES and ESA begin cooperation September 2006 investigations into RF wireless structural monitoring and other wireless transducers on the Next Generation European Launcher. Technologies are yet to be decided.

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http://www.sseti.net/


0- ESA TEC-EDD TRP planned 2006. 1- MiSAT [130], planned as successor to MicroNED -- Dutch National technology

programme of three satellites, beginning with Delfi-C3 nanosatellite to launch 2006-7, TU Delft, also similar by TNO-TPD Defence.

2- ESA TEC-EDD TRP ongoing. 3- ESA TRP ongoing, other ESA divisions. ** Note: this table does not attempt to account for the already known non-European applications, i.e. NASA, DARPA, U.S. Air Force and U.S. University, of which there are hundreds of activities.

2.3. Inter-Vehicular Proximity Networks

The term "inter-vehicular proximity network" is used in this document to denote ESA proximity networks composed of a small number (perhaps fewer than ten) of relatively capable (in comparison to microsensors), possibly mobile, nodes. Planetary landers, rovers, robots and robotic agents, formation flying spacecraft and orbiters are typical of the devices that might participate in this class of networks. An immediate example is that of ESA’s Eurobot (though an external-to ISS robot could be classified as “robotic EVA”. A thorough

specification and study [65] was performed by a European space contractor, concluding with a clear preference for IEEE 802.11a WLAN among many possibilities.

Concerning satellite constellations and formation spacecraft data inter-communications, a recent study from 2003, Architecture Study of Space-Based Satellite Networks for NASA Missions [133], the report states: Media access between the mother ship and sensor spacecraft needs to be defined and will be determined by the requirements of the constellation. A new media access technique may be required depending on the type of timing, the synchronization, and the criticality of the data being transmitted between sensor spacecraft and the mother ship. However, it is highly desirable to develop communication solutions and a constellation design that will allow for use of existing media access techniques such as the IEEE 802.11 wireless Ethernet standards. 2.3.1. Inter-Vehicular Proximity Network Nodes

A renewable power source, such as solar or nuclear cells, and a larger power storage capacity are the distinguishing characteristics of nodes that may participate in this class of proximity networks. The resulting larger system-level power budget permits these devices to possess much greater functionality than found in the minimalist designs of

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microsensor nodes. This has numerous implications for the design of the devices and the networking solutions. . • The lifetime of the inter-vehicular nodes is long compared to that of battery-powered microsensors; planetary orbiters have design lifetimes measured in years. Of significance to the design of the communications systems, these longer-lived devices are likely to need to interact with devices that were designed by a variety of organizations and launched over a period of years. As a result, interoperability between independent protocol implementations is important for this class of proximity networks. . • The power budget of the communications system is not traded off directly against the lifetime of the device (i.e., every extra bit transmitted does not correspondingly reduce the overall life of the device). Increased power for communications can be applied towards improved interoperability, enhanced reliability, increased flexibility and greater functionality, perhaps at the expense of additional bits transmitted. . • Individual nodes in inter-vehicular proximity networks are generally critical to the success of the mission. This contrasts with sensor webs, for example, where the web can continue to provide valuable data in spite of the demise of some of the microsensor nodes. Poor protocol design must never cause contact to be unnecessarily lost between, for example, a lander and a rover. . • Additional computational power may be available in these nodes, which may be used to provide services to lower-functioning devices. As described above, this class of devices might host gateways for microsensor proximity networks that would perform some functions on the relatively electrical power-rich inter-vehicular proximity network nodes, rather than the severely resource-constrained microsensor nodes. 2.3.2. Inter-Vehicular Proximity Network Deployment and Configuration

The mobility characteristics of these devices influence the requirements for and design of network solutions. Nodes in inter-vehicular proximity networks will exhibit one of three types of mobility:

. • Immobility, such as planetary landers • Self-mobility, such as autonomous or teleoperated rovers, robotics, and . • Planetary orbits. As a result of these mobility characteristics, the potential for communications between two nodes may be very predictable, or may be difficult to predict. For example, communications opportunities between an orbiter and a lander are very predictable and are determined by the orbit and the lander's location. In a similar fashion, communications between a teleoperated planetary rover and a lander may predictable, inasmuch as the rover is never driven out of range of the lander. On the other hand, some have suggested that radio repeaters may be necessary be deployed to extend the range of

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communications between a lander and rovers [2]. Depending on the networking characteristics of these repeaters (i.e., whether they behave, in networking terms, as bridges or routers) potential or optimal communications paths become more difficult to predict. In particular, it may be difficult to predict in advance for a particular location whether the rover should communicate with the lander directly or via the repeater. Inter-vehicular proximity network technologies should effectively adapt to the different styles of connectivity experienced by these devices, including continuous (e.g., a rover near a lander or other robotics), predictable and episodic (e.g., an orbiter and a lander), and unpredictable (e.g., a rover potentially using a repeater). Protocols that can autonomously adapt to a changing environment (e.g., determine whether a rover should communicate with a lander directly or via a repeater) are required by more complex networking environments, such as those represented by repeaters. Moreover, many planetary surface scenarios involving humans and/or robotics may well be supported by the latest out-of-doors wireless, namely IEEE 802.16 or commercially, WiMax, without the need for repeaters.

2.3.3. Inter-Vehicular Proximity Network Organization

Because of the small number of nodes involved, the topologies of inter-vehicular proximity networks are fairly simple. These networks can easily be treated as a small collection of point-to-point links. In fact, in current and near-term implementations, these networks are simply a single point-to-point link. For example, the Proximity-1

Space Link protocol [13, 14a, 14b, 14c] implemented on the Odyssey Mars orbiter creates a point-to-point link between the orbiter and a lander, but does not provide a mechanism for routing traffic through intermediate nodes.

When several of these devices can potentially communicate with each other simultaneously, traditional network-layer functions (specifically, routing through intermediate nodes) can significantly enhance the functionality of communications solutions. For example, the operating range of a rover could be extended if it were able to route data through an intermediate device, such as a strategically placed repeater or another rover.

While this section uses the term "repeater", a stationary communications device intended to extend the range of a network will be much more capable and much more useful if it is a network device, specifically a router, rather than a simple analogue RF repeater.

2.3.4. Inter-Vehicular Proximity Network Operation

There are two potential strategies for operating an inter-vehicular proximity network. The network could be remotely operated from

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Earth, with detailed configurations and operational plans uploaded into the vehicles. Alternatively, the network could operate autonomously, requiring manual configuration or intervention only rarely and under exceptional circumstances.

In an analogous fashion, devices that participate in these networks could be operated remotely (presumably from Earth) or could operate autonomously. For example, a rover could be teleoperated from Earth, with the activities of the vehicle controlled by carefully planned, detailed commands issued by earthbound engineers. Alternatively, a rover could operate autonomously, where the vehicle uses onboard intelligence to achieve higher-level goals (e.g., search for a rock different than what has been collected so far).

Network technologies designed to operate autonomously can be used with systems that are operated remotely (e.g., autonomous network technologies could be used with a teleoperated rover or other robotics, either homogenous or heterogeneous robotics). However, it is unlikely that protocols designed to be operated remotely can easily or reliably be modified to either operate autonomously or to support autonomous systems. To the extent that ESA intends to investigate the autonomy of planetary exploration devices, inter-vehicular proximity network technologies should be able to operate either autonomously or under remote control, depending on the requirements of the mission. Much work and research in these areas was presented at the iSAIRAS 2005 Symposium in Munich.

Inter-vehicular network nodes will generally need to be able to determine their location and synchronize their clocks with a standard time reference. A variety of communications- and network-based mechanisms have been proposed or developed to provide these services [40, 42, 51].

2.3.5. Wireless Technologies and ESA Inter-Vehicular Applications

The table below summarizes the author’s' assessment of currently available and soon available commercial technologies versus known and anticipated ESA space applications and missions, including the Aurora Programme and Science Directorate that potentially involve inter-vehicular data communications. In addition to the more typical use cases and scenarios listed in Table 4 (Lunar and Mars excursions) are

close-range formation flying spacecraft (from 1 to 1000s metres) where extreme electronics miniaturisation is required to form space sensor webs (analogous to terrestrial networked and correlated space telescopes); fractionated spacecraft [76] (a virtual spacecraft composed individual identical (ideally), multiple independent spacecraft) function as an integrated unit in many or all respects – and are likely to benefit from economies of scale (in numbers) as well as minimised launch costs; autonomous on-orbit assembly [81]; and mobile or robotic agents with or without SWARM intelligence. Recent investigations have shown that the COTS-derived Wireless LAN PHY Layer

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Intellectual Property may be adapted to allow networks to range several thousands of km for formation flying proximity network scenarios [123, 124]. The Aurora Technologies for Exploration Dossier, (ESA Document Nr. SP-1254) describes that “innovative activities are planned for wireless onboard communication and evolvable/reconfigurable hardware” [69].

ESA Advanced Concepts Team is investigating many future mission classes that utilise highly integrated RF wireless, such as: spider robots (along with JAXA and Vienna University of Technology) that create functional structures on-orbit over flexible fabrics [84].

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Inter-Vehicular

and EVA** Wireless

WiMax WiMedia WUSB/IEEE

1394

Application

Micropower over

microwave (RFID based)

Narrow band RF

or Low ISM

Band

IEEE 802.15.4


ESA

Custom Spread

Spectrum @2.2GHz

IEEE 802.15.1

(Bluetooth) FH

IEEE 802.11 a/b/g/n

DSSS/OFDM

IEEE 802.16/e OFDM

IEEE 802.15.3

Very hi-rate OFDM IEEE

802.15.3a UWB

Custom Deterministic

UWB (Pulsed)

Networked planetary surface

robotics

X (e, m?) repeaters

likely needed

X (e, m?)

Mobile or robotic agents

X X X

Networked in-orbit robotics

X (h) X (h) X (a, b)

Low-rate formation flying networked S/C

X (c2) X (c1, c2?)

Fractionated S/C and On-orbit

Assembly

X (l?) X (l?) X (n) X

Hi-rate formation flying networked S/C, Sensor Webs

X (c2, p?, j, t) X X (future?)

S/C Docking ranging / data

comms

X (d) X (d) X (future)

Gossamer, inflatable or

flexible structures and smart

materials sensors

X (future) X X X (n) X (future)

Spacesuit advanced com’d

and control

X X X (k)

Manned Lunar/Mars inter-

system comms and EVA short

range <8km

X (o, q) X (e, f, i, o, q)


system comms and EVA medium

range <30km

X (e, f, i, o, q) X (e, f, i, o, q)


system comms and EVA long range >30km

X (e, g)

Table 4. ESA Applications of Inter-vehicular Wireless Proximity Networks

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Proposed initial ESA areas of interest. Proposed secondary ESA areas of interest. Proposed third ESA area of interest.


(a) ESA/Alenia Spazio study for ISS-to-Eurobot data communications, robot operations control and video data (completed February 2005) baseline: IEEE 802.11a. Project expected to have full Phase B funding in early 2006.

(b) Investigation ongoing by Terma/Dutch Space for adding a wireless colour camera to ESA European Robotic Arm.

(c) c1 -- ESA CDF study, Xeus near formation flying spacecraft study (completed January 2005) baseline: based on IEEE 802.15.4. c2 – Surrey Satellite, University of Surrey, U Kent, U Edinburgh, others (UK) and BNSC are currently investigating low-rate wireless and WLAN for inter-spacecraft formation flying data communications and large aperture synthesis, integrating ESA’s LEON2 microprocessor and WLAN in a SoC, AES encryption, and efficient microprocessor operating systems for nanosatellite formation flying. ESPACENET: Evolvable Networks of Intelligent and Secure Integrated and Distributed Reconfigurable System-On-Chip Sensor Nodes for Aerospace Based Monitoring and Diagnostics, http://www.ee.surrey.ac.uk/SSC/G3/P23/ and http://www.see.ed.ac.uk/~SLIg/ESPACENET.html .

(d) ESA custom (non-COTS) SS for ATV to ISS docking to fly on first ATV, Jules Verne in 2006. Astrium is investigating COTS based WLAN for next generation ATV.

(e) Steve Braham, Simon Fraser University, Vancouver Canada [2]. Review this work at the Haughton-Mars Project (HMP). http://www.marsonearth.org/

(f) ESA CDF Aurora Manned Lunar study (completed March 2005) baseline: IEEE 802.11g WLAN with option for IEEE 802.16e WMAN.

(g) Scenarios greater than 30 km have not yet been fully studied by ESA. (h) University Bremen exploring self-assembly space robotics utilising RF wireless. (i) CCSDS CIS-Lunar draft rationale documents include WLAN for lunar surface

communications. (j) Innovation Triangle Initiative proposal from Surrey Satellite Tech. Ltd. and

University of Surrey for adapting free standing compact (COTS) wireless motes for comms between spacecraft subsystems and between low cost formation-flying spacecraft or ad-hoc swarm. Study kicked-off June 2006.

(k) Steve Braham, Simon Fraser University, Canada; CSA and NASA: advanced spacesuit control -- were the first to demonstrate remote command and control of a spacesuit test bed in 2000, with Hamilton-Sundstrand at the Haughton-Mars Project (HMP).

(l) ESA “Mission Concept for Autonomous on Orbit Assembly of a Large Reflector in Space” [81], Dario Izzo, Mark Ayre, ESA Advanced Concepts Team, ESTEC,

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http://www.ee.surrey.ac.uk/SSC/G3/P23/

http://www.see.ed.ac.uk/~SLIg/ESPACENET.html

http://www.marsonearth.org/


Lorenzo Pettazzi, ZARM, University of Bremen, Germany, 56th International Astronautical Congress, Paper IAC-05-D1.4.03.

(m) ESA Lunar Exploration Architecture Team funded study (2006), “Mobile Telecommunication Networks for Robotic Applications” underway via ESA’s “Call for Innovative Concepts / Technologies" for Lunar Exploration addressed to the European Academic Institutions.

(n) The Japanese Aerospace Exploration Agency (JAXA) is planning to test a Furoshiki spacecraft in January 2006. Assisted by ESA's Advanced Concepts Team, it has chosen the robotics institute of the Vienna University of Technology to develop the small (Spider) robots to demonstrate on-orbit assembly of functional structures using flexible fabrics.

(o) ESA D-TEC ETC/ETN soon to issue in 2006 a GSP for identifying potential and methods to couple localisation, ranging and eventual navigation capabilities to existing WPAN, WLAN and WMAN technologies for planetary exploration.

(p) ESA-ESTEC EUI-T Telecommunication planning a study in 2006 involving the adaptive Internet Protocol (IP) suite routing, ad hoc routing and on-satellite data processing as a possible future experiment among close-formation, multiple micro-satellites in collaboration with University of Wurzburg and others.

(q) ESA-ESTEC EUI-P FEASIBILITY STUDY FOR A REDUCED PLANETARY NAVIGATION AND COMMUNICATIONS SYSTEM, Programme Ref. GS 06/B24. The study will assess the feasibility and preliminary performance and system definition for a reduced planetary (Lunar/Martian) navigation and communications system, complemented with local navigation and local communication infrastructure for specific areas under special interest [121].

(r) ESA TEC-SP FORMATION FLYING DEMONSTRATION MISSION, AO Nr. 1-5088. The mission shall validate RF and optical metrologies, coarse and fine formation flying, main type of formation configurations and related manoeuvres and GNC as well as advanced technologies required by formation flying (e.g. collision avoidance, propulsion). The launch shall take place before 2009 to bring sufficiently in advance valuable results for future missions. Specific wireless technologies investigated are unknown.

(s) ESA TEC-EDD CDF study for “Fly-by-Wireless” planned for 2006. Several wireless technologies investigated based on ESA PROBA3 concept.

(t) Study and paper: IEEE 802.11 Optimisation Techniques for Inter-Satellite Links in LEO Networks – possibly as a SpaceWire extension, Kawsu Sidibeh and Tanya Vladimirova, Surrey Space Centre, University of Surrey [123, 124].

** Note: this table does not attempt to account for the already known non-European applications, i.e. NASA, DARPA, U.S. Air Force and U.S. University, of which there are hundreds of activities.

2.4. EVA Proximity Networks

Extra-vehicular activity (EVA) proximity networks support humans, manned vehicles and robots operating outside of a

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spacecraft.

From a networking perspective, EVA proximity networks are nearly identical to autonomous (rather than remotely configured and operated) inter-vehicular proximity networks, and common networking solutions can and should be developed for both classes of proximity networks.

2.4.1. EVA Proximity Network Nodes

EVA proximity networks can be viewed as being composed of "mobile" nodes (e.g., humans, manned vehicles, and robots) and, relative to the mobile nodes, "stationary" nodes (e.g., the ISS, moon or a planetary base station). The mobile nodes share many characteristics with inter-vehicular proximity network nodes, specifically renewable sources of power (e.g., recharging

spacesuit batteries prior to an EVA) and less onerous mass constraints that those for microsensors. These nodes potentially could support significant amounts of computational power, similar to inter-vehicular proximity network nodes. The stationary nodes have access to substantial electrical power, (relative to other proximity network nodes).

2.4.2. EVA Proximity Network Deployment and Configuration

EVA proximity network nodes are "deployed" as the host nodes (humans, manned vehicles, or robots) undertake EVAs.

While theoretically EVA networks could be manually or remotely configured, in a manner analogous to some inter-vehicular networks, this approach is impractical, unreliable, hazardous and unnecessary.

EVA networks should be self-configuring, likely ad hoc, and ought to require little if any, manual network configuration after the device is initially placed into service. 2.4.3. EVA Proximity Network Organization

EVA network topologies are very similar to those of inter-vehicular networks: they contain a relatively small number of nodes, and the topologies are fairly simple, although it would be highly advantageous for these devices to be able to forward data between other devices in the network

2.4.4. EVA Proximity Network Operation

The topology of the network may change as nodes move relative to each other. The network must adapt quickly and reliably to the new topology, in a manner similar to

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inter-vehicular networks composed of mobile nodes.

2.4.5. Wireless Technologies and ESA EVA Proximity Network Applications

Portions of Table 4, included in the above section 2.3.5, reflect EVA Proximity Network Applications. As described in previous similar sections, these are compared to currently available and soon available commercial technologies versus known and anticipated ESA space applications and missions that potentially involve EVA data communications including

the Aurora Programme and Science Directorate. Unique in this topic could be digital EVA assistants, EVA astronaut health monitoring (a most demanding case of human health monitoring), EVA work instructions, explorer communications including data and voice (voice over IP), in-orbit spacecraft external inspection (human or robotic), advanced space suit command and control, etc.

2.5. Advanced Planetary Exploration (mobile atmospheric micro nodes)

Yet to write…ESA DALOMIS microprobes e.g. etc. See Table 2.

3. Characteristics of ESA Wireless Proximity Networks

The informal descriptions of the previous section provided the basis for a more detailed analysis of the characteristics of the different subclasses of proximity networks. This section opens with an enumeration of the attributes of proximity networks that the author identified as the most important or distinguishing.

Next, these attributes were evaluated for each of the four subclasses of proximity networks. An examination of these attributes showed that the four subclasses of proximity networks could productively be aggregated into two classes. This section concludes with a brief discussion of the most significant characteristics of these two aggregated classes of proximity networks.

3.1. Proximity Networks Characteristics

Studying the characteristics of the different subclasses of proximity networks can

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provide a basis for determining the technologies required by those networks. The following attributes were examined:

. • Example application The ESA applications typical for each subclass of proximity network were briefly noted, reflecting the information contained in the preceding section. . • Engineering objective Two primary design objectives were identified: power conservation intended to maximize the life of battery-powered nodes and the provision of reliable communications to mobile nodes. . • Resource constraints The overall resource constraints (relative to other classes of proximity networks) including power, mass, and size were summarized. . • Power replenishment opportunity The possibility of replenishing power, perhaps using solar cells to recharge batteries or manually installing fresh batteries, significantly changes the role of power conservation in the design of proximity networking technologies and nodes. It also determines whether the lifetime of the mission is limited by the lifetime of the battery-powered network nodes. As energy scavenging and harvesting techniques develop for the commercial world in support of various microsensors, the possibility increases for energy harvesting space applications [136]. . • Communications as percent of system power The intent of this attribute is to suggest the likely effect on the overall system design of modest incremental increases or decreases in power consumption by the communications subsystem. When communications requires only a small portion of the total power budget, increasing communications functionality may be easier to justify. . • Typical processor power and memory size Highly power-constrained nodes are likely to have less processing power and less memory available than will nodes for which power is not as limited or valuable. Additional processor power and memory, of course, provide an opportunity to embed greater functionality in the network node. . • Network size The approximate size of a typical network provides a sense of the potential complexity of the network topology, and the resulting complexity faced by the routing protocols. . • Node mobility In some networks, nodes will be highly mobile and the network protocols will need to adapt quickly to potentially rapidly changing network topologies. In other cases, the network topology may change only slowly. . • Traffic and flow diversity Some proximity networks will need to transport only one class of traffic (e.g., sensor data) while others will potentially need to transport several different classes of traffic simultaneously, each of which may have different requirements (e.g., data, voice, video, and text messages). Greater traffic diversity may increase the need for the network to provide quality of service (QoS) assurances to the different classes of traffic. In a similar fashion, some networks may have fairly simple, predictable flow patterns (e.g., all traffic in sensor networks is directed towards external gateways), while other networks may have much less predictable traffic patterns. . • Intra-network routing In some cases, data will typically traverse several nodes before exiting the network, while in other cases data will traverse only a small number of intermediate nodes, if any, before exiting the network. The extent of intra-

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network routing affects the complexity of the traffic flows, the requirements for a routing protocol, and the potential for congestion at intermediate nodes. . • Direct external access to network nodes In some applications, such as a teleoperated robotic vehicle, external devices may need to interact directly with a node on a proximity network. In other networks (e.g., microsensor networks) there is little need to provide external devices direct access to individual proximity network nodes. . • Direct access to external networks In some instances, it will be necessary for proximity network nodes to directly access external information sources, such as an astronaut accessing an earthbound database during an EVA. Microsensor nodes, on the other hand, are unlikely to ever require direct access to devices external to the proximity network. . • Network management access More intelligent devices, such as robotic vehicles, may benefit from external network monitoring or management. (It most likely makes more sense for network management functions to be automated and performed from nearby platforms, such as the ISS, rather than from more distant locations, specifically the Earth.) However, other types of proximity networks and their nodes, such as microsensor networks, will most likely have little need or ability to be directly monitored or managed by external network management systems. . • Interoperability requirement Interoperability is the ability of two independent implementations to communicate gracefully and effectively. Achieving interoperability is trivial in a network composed of homogeneous nodes. It becomes more important, and more difficult to achieve, when the network is composed of devices developed by independent groups or projects, perhaps at different times. . • Backward compatibility requirement Backward compatibility is the ability to interoperate with older versions or older implementations of a communications protocol. Backward compatibility is important when a new device needs to communicate with existing, long-lived devices that may use slightly different versions of some protocols. . • Communications subsystem reliability requirement In proximity networks where the individual nodes are very valuable and may become useless if their communications subsystem fails, the reliability of the communications subsystem is very important. In contrast, the loss of an individual sensor node may have a minimal effect on the overall mission of the sensor web. In these instances, the reliability of the communications system may reasonably be traded off against other objectives, such as increased battery life. . • Data reliability requirement In a similar fashion, the loss of some sensor data may not adversely affect the scientific success of a mission, and highly reliable data transfer might be reasonably traded off against other objectives. On the other hand, the loss of a message containing a command to a robotic vehicle may have adverse consequences, and the risk of this loss should be minimized. 3.2. Summary of Proximity Networks Characteristics

The table below summarizes the author’s' assessment of the attributes described above for each of four subclasses of proximity networks. It

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is important to note that these assessments are ideals, and assume that the requisite network technologies have been successfully developed.

Proximity Networks Taxonomy and Characteristics (Add Advanced Planetary Science Exploration)

Micropower Proximity Networks Intelligent Proximity Networks Characteristic / Subclass Microsensor Intra-Spacecraft Inter-Vehicular EVA

Example application

microsensor/lander communications

spacecraft health monitoring

lander/rover/robot communications

human and robotics EVA comms

Engineering objective

maximize data transferred per battery

life

maximize data transferred per

battery life

reliable mobile communications

reliable mobile communications

Resource constraints

high fixed battery life moderate / high fixed battery life?

moderate mass, power moderate mass, power

Power replenishment opp.

none (possible energy

harvesting)

none or very high moderate high

Comms as per cent of system power

high high low - moderate low

Typical processor power, memory size

8-bit processors, 100bytes -few kilobytes

of memory

8-bit, 16-bitprocessors,

100bytes - kilobytes of memory

32-bit processors, megabytes of memory

32-bit processors, megabytes of

memory

Network size 10s - 100s of nodes 10s - 100s of nodes 10s of nodes at most 10s of nodes at most

Node mobility none none moderate high Traffic and flow diversity

low low potentially high potentially high

Intra-network routing

yes yes some some

Direct external access to networks nodes

none none potentially potentially

Direct access to external networks

none none maybe potentially

Network management access

not needed not needed potentially useful potentially useful

Interoperability requirement

low moderate high high

Backward compatibility req.

none moderate moderate high

Comms subsystem low - moderate moderate high high

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reliability req. Data reliability requirement

moderate moderate high high

Table 5. Attributes of Subclasses of Wireless Proximity Networks

3.3. A Refined Proximity Network Taxonomy

A cursory examination of the characteristics of proximity networks, summarized in the table above, reveals that microsensor proximity networks are very similar to intra-spacecraft proximity networks and that inter-vehicular proximity networks are very similar to EVA networks. The author concluded that the five original subclasses could reasonably be aggregated into two classes of proximity networks, which are referred

to (for the purposes of this document) as:

• Micropower proximity networks, composed of microsensor proximity networks and intra-spacecraft proximity networks, and

• Intelligent proximity networks composed of inter-vehicular proximity networks and EVA proximity networks.

3.4. Key Characteristics of Proximity Network Classes

All proximity networks, such as wireless communications, share numerous characteristics. One common characteristic that warrants mention is the presence (in almost all instances) of a gateway, a network device that acts as an intermediary between the proximity network and external networks. While there is no consensus on the architectural structure of the gateway or the precise services that it ought to provide, the gateway will generally be fairly capable (compared to proximity network nodes). The gateway is likely to be hosted by a vehicle that has enough electrical power to support a reasonable amount of computational power (e.g., a 32-bit processor with megabytes of memory). Conceivably, a gateway could offload certain processing from less-powerful proximity network nodes. While the presence of a gateway will be typical, the responsibilities of a gateway may be different for different classes of proximity networks, and several architectures for gateways may eventually coexist. The most appropriate architecture for proximity network gateways is a topic of continuing research and debate.

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Proximity Network Gateway Function

3.4.1. Micropower Proximity Networks

The mission of micropower networks (named to reflect the importance of power conservation) is to transport sensor data towards an external network connection. Many of these networks will be battery-powered. Because the lifetime of a battery-powered network is equivalent to the lifetime of the batteries, power conservation becomes an important, probably the important, engineering consideration. As a result, the designs of the nodes and network technologies are narrowly focused on transporting sensor data. Even when these nodes are powered by external sources (e.g., intra-spacecraft networks that receive power from the spacecraft) minimal, single-purpose designs similar to battery-powered designs are appropriate and likely. Distinguishing characteristics of micropower proximity networks include the following.

. • Battery power Non-renewable batteries will power most micropower proximity networks. That is, the networks function only until the batteries are exhausted. As a result, power conservation is a major design objective. . • Generality and functionality may be traded off against power conservation In keeping with the objective of maximizing the amount of sensor data that are transported over the lifetime of the network, many common network services may not be implemented. For example, in some applications, it may make more sense to transmit data on a best-effort basis, rather than to expend power on a data acknowledgement mechanism. Tradeoffs such as this ought to be made in the context of the science objectives of the mission, but generally accepted guidelines for making these tradeoffs do not yet exist. . • Focused mission By necessity, micropower proximity networks have a very focused mission, namely to transport as much sensor data as possible before the batteries become exhausted (unless energy scavenging is utilised). . • Potentially limited computational power A common power-conservation strategy is to minimize the amount of computational power included in micropower nodes. Eight-bit processors are common, although some systems have used 32-bit processors, (perhaps with the assumption that the 32-bit processors will conserve power by sleeping much of the time). . • Autonomy Micropower networks will undoubtedly be largely autonomous. First, inasmuch as wireless transmissions require tremendously more power than do computations, it is generally more power-efficient to design the nodes to be autonomous. Second, by their very nature, micropower networks are very difficult to

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configure and operate remotely. . • Less focus on interoperability Because these networks are likely to be composed of identical nodes and will have a limited lifetime, interoperability concerns are all but moot— it is unlikely that two uncoordinated, independent implementations will be deployed simultaneously in the same area and be expected to communicate. (This is not to suggest that the other advantages of reusing standard, proven technologies are unimportant to micropower proximity networks, merely that interoperability doesn't have the importance that it does in most other environments.) . • Little need for direct external connectivity Micropower proximity networks are unlikely to support direct end-to-end connections with external nodes. Rather, the gateway will act as an intermediary between the micropower network and external networks. It will translate between the different protocols and addressing schemes used by the proximity and external networks. This conclusion is based on two factors: the task of transporting sensor data simply doesn't require direct external connections, and the resources required to support external connections are better applied to the network's primary mission, namely to transport sensor data. The node that originates specific sensor data will be identified in most applications, but that doesn't imply either a need or a capability for the sensor node to communicate directly with external nodes. . • System-level, not node-level reliability The life of a sensor web transcends the lives of individual sensor nodes; in most cases the sensor web will continue to return scientifically valuable data even if a small proportion of the sensor nodes fail. As a result, it may be more appropriate to increase the number of sensor nodes deployed, rather than increasing the communications reliability of the individual sensor nodes at the expense of being able to deploy fewer sensors. It is highly unlikely, for example, that sensor nodes will contain redundant communications systems that will permit communications even in the event that one system fails. One consequence of these characteristics is that tailoring network technologies to the specific needs of this environment may be an effective way to extend the life of micropower networks and maximize the science data that they return. Possibly unfortunate corollaries of this observation are that standard or existing solutions may not be optimal for micropower proximity networks and that network solutions tailored to the requirements of micropower networks may not be well suited for other environments.

3.4.2. Intelligent Proximity Networks

Because intelligent proximity networks don't operate under the same severe power constraints as micropower networks, they generally have more computational power available, hence the name. These networks will behave more like traditional networks, in the sense that they will be expected to provide a broad range of services and support a variety of types of traffic.

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. • More functional, complex devices Nodes in intelligent proximity networks will be much more complex than those in micropower networks. They will include, for example, humans (spacesuits), robotic vehicles, and manned vehicles. These nodes will be much broader, more varied missions (compared to a micropower network's narrow mission of transporting sensor data). These broader missions will place greater expectations and stronger requirements on intelligent proximity networks.

• More varied traffic Many intelligent proximity networks will be expected to simultaneously transport several different types of traffic, such as voice, data, video, and text. Quality of Service (QoS) assurances will become important in these environments, for example to ensure that video traffic doesn't displace critical data traffic. . • Direct external connectivity Direct connectivity between intelligent proximity network nodes and external network nodes will be important in many applications. For example, ground-based engineers may want to communicate directly with a specific robotic vehicle, perhaps to determine or diagnose its current condition. Note that a requirement for end-to-end connections does not necessarily imply a requirement for transparent end-to-end connections. Different protocols may be used in the intelligent proximity network and the external networks, but the gateway will probably need to support connections established by intelligent network nodes to external network nodes, as well as the converse. . • Individual nodes important Individual nodes on intelligent proximity networks will be extremely valuable – the loss of a single node will likely have severe adverse consequences for the overall mission. The intelligent proximity network must include reliability mechanisms to ensure that communications are maintained if at all possible. • Interoperability, backward compatibility more important Because nodes in this class of proximity network are much longer-lived than battery-powered sensor nodes, interoperability and backward compatibility are much more important. While it is unlikely that a spacesuit and a robotic vehicle will be manufactured by the same organization, it is very likely that the two devices will be expected to communicate with each other. The usual techniques for ensuring interoperability between independent protocol implementations (e.g., complete, well-written, well-reviewed, well-tested protocol specifications, hence ESA ESTEC’s initiative of the CCSDS SOIS Wireless BoF [52], interoperability testing, and reusable implementations) are applicable to intelligent proximity networks. In a similar manner, the relatively long lives of these nodes increases that the likelihood that the intelligent proximity network protocols will evolve over time and that backward compatibility with older protocol versions will be a requirement. Again, the traditional techniques of ensuring backward compatibility apply to these networks. The requirements for intelligent proximity networks are broader than for micropower proximity networks, and have great similarity with the requirements for many traditional networks. This immediately leads to several conclusions: • Micropower and intelligent proximity networks have vastly different requirements and most likely will require different networking solutions and protocols. . • Intelligent proximity networks have much broader requirements, and will therefore require a broader range of networking technologies than will micropower proximity networks. As a result, the cost of developing and maintaining unique network

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solutions for intelligent proximity networks will be much greater, in contrast to the improved cost savings, reliability and interoperability if existing, proven technologies are used.

4. Technologies and Resources Potentially Applicable to ESA Proximity Networks

Numerous networking technologies are potentially applicable to ESA proximity networks. Some of these technologies can be used directly without modifications, others may require substantial modifications or extensions to meet ESA's needs, and still others are largely research results or general techniques

that often remain to be implemented. This section identifies a number of potentially applicable technologies, and discusses their use with the requirements for ESA proximity networks.

4.1. The Internet Engineering Task Force (IETF)

The Internet Engineering Task Force (IETF) http://www.ietf.org, the organization responsible for standardizing the Internet protocols, unquestionably represents the broadest, deepest repository of network protocol research, design, and operations expertise. Many of the technologies described below have been or are being developed within the IETF. When examining these technologies for use in ESA proximity networks, however, it is important to understand how some of the assumptions, objectives and prejudices of the IETF may differ from those necessary to develop effective proximity network protocols.

• Focus on terrestrial environments While some have suggested that protocol designers shouldn't design protocols that couldn't be used between Earth and Mars (e.g., protocols shouldn't have fixed-value timers that would preclude their use in dramatically different environments) the IETF has generally focused on wired, terrestrial environments. Extensions to TCP to improve its performance over satellite links (e.g., the TCP window scale option [34] and selective acknowledgement [21, 41]) were standardized well after their desirability was identified by a number of organizations, including ESA.

On the other hand, there are significant benefits to extending existing Internet protocols for use in space, rather than creating new protocols. Many of the protocol

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http://www.ietf.org/


extensions necessary for TCP to effectively use high-bandwidth, long-delay links are now widely available, even in some Microsoft Windows operating systems. A new transport protocol designed specifically for satellite links would not be nearly as widely available.

• Verbose on-the-wire representations The IETF has generally been quick to trade concise or efficient on-the-wire packet formats for other objectives. Historically, bandwidth was assumed to be cheap and ubiquitously available so minimizing the number of bits transmitted simply didn't seem important. More recently, as vendors began to dominate IETF discussions, ease-of-implementation generally outweighed efficient protocol representations. (See, for example, the desire to align protocol header fields on 32-bit boundaries, or the verbose, but easy to implement, text-based protocols such as HTML.) While this attitude is changing somewhat as wireless networks and wireless Internet access become more prevalent, it is still reflected in the design of many Internet protocols. Clearly, micropower proximity networks require a much different balance between efficient on-the-air packet formats and other objectives.

• The end-to-end argument The end-to-end argument [50] asserts that many

networking functions are best performed in the end devices (the hosts) rather than in the network. That is, for the most part, the network should merely transparently pass data between hosts with minimal modification. Based on this principle, devices such as firewalls and network address translators (NATs) are considered architectural abominations, at best. In fact, in spite of their widespread use, the IETF has only recently (and grudgingly) begun to consider the appropriate design and role of NATs. While research on wireless networks, particularly those connected transparently to the Internet, has raised some question about whether wireless/wired gateways should be completely transparent to the end systems, the end-to-end argument still dominates the Internet architecture and protocol design. Effective solutions for micropower proximity networks are likely to conflict with the end-to-end argument, and so care must be taken in uncritically applying the conclusions of the IETF and the Internet to proximity networks.

4.2. The Internet Protocols

The Internet protocols are among the most widely deployed, the most heavily researched, and the most sophisticated. NASA has explored both using the Internet protocols directly for space communications [25] and has created modified versions tailored to the requirements of space communications [36]. The Internet protocols or variants of the Internet protocols appear to closely match the requirements of intelligent proximity networks. On the other hand, the demanding requirements of micropower proximity networks can most likely not be met by even modified versions of the Internet protocols; new protocols and solutions are undoubtedly required for this environment.

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4.3. Ad Hoc Routing Protocols

The challenges of designing network architectures and protocols for mobile ad hoc networks are similar to those presented by proximity networks. Mobile ad hoc networks are autonomous systems of mobile, wireless nodes that cooperate to form a network. The participants in an ad hoc network are not known in advance. Rather, the network is composed of the

nodes in the same general area (or "proximity") that wish to communicate. The nodes must identify their neighbours and determine routes within the network. In some cases, some of the nodes are able to communicate with, and act as gateways for, external networks, such as the Internet. In these configurations, information about external connectivity must be propagated throughout the ad hoc network. By definition, ad hoc networks are autonomous; they cannot assume or rely upon pre-existing infrastructure, such as wireless access points or cellular base stations.

Routing protocols tailored to the characteristics of mobile ad hoc networks (ad hoc routing protocols), have been the primary focus of research in this area. Numerous approaches have been proposed, often based on different assumptions about the behaviours of ad hoc networks, including NASA's Source-Initiated Adaptive Routing Algorithm (SARA) [26, 27, 28, 29, 47, 35, 12, 46, 23, 24, 49]. Attributes that differentiate approaches to ad hoc routing protocols include: . • Distance-vector versus link-state routing protocols Mobile ad hoc routing protocols have been developed using both major approaches to computing routes, distance-vector protocols, which distribute reachability information among the nodes and link-state protocols, which distribute information about the topology of the network. Neither approach, nor no single ad hoc routing protocol, has yet been demonstrated to be superior in all common ad hoc network reference configurations. • Continuous versus on-demand routing information distribution Some solutions continuously distribute routing information among the nodes, while others only distribute information when a node wishes to communicate with another. As might be expected, the suitability of continuous versus on-demand route information distribution depends on the characteristics of the specific ad hoc network, particularly the traffic patterns and the rate at which the topology changes. The ad hoc network model matches the needs of ESA proximity networks fairly well. One or more of the ad hoc routing protocols developed for use in the Internet may be directly applicable. On the other hand, there are some important differences between the assumptions embodied in many ad hoc routing protocols and the needs of ESA proximity networks, particularly micropower proximity networks. . • Mobile ad hoc network research assumes no pre-existing infrastructure, and so they must be entirely self-sufficient. This assumption is probably not consistent with many ESA applications. Rather, from the perspective of proximity networks, pre-existing infrastructure most likely will or can exist. A lander, rover or orbiter could provide services for planetary exploration micropower webs. Furthermore, micropower proximity networks could be designed such that resource-intensive tasks are performed

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on the relatively resource-rich lander, rather than on the resource-constrained micropower nodes. How responsibilities might be best distributed between a lander and a micropower proximity network to enhance the functionality or extend its life is a topic worthy of further exploration. . • Use of the Internet protocols is almost universally assumed by mobile ad hoc network research, an assumption that is questionable for ESA micropower proximity networks (because the easiest way to extend the life of a micropower web is to use a protocol with a concise on-the-air representation). Nonetheless, the algorithms and techniques employed by the Internet ad hoc routing protocols may be applicable, even if the complete protocols aren't used. . • Power conservation is rarely a major consideration of mobile ad hoc network research, rarer still to the degree necessary when designing micropower networks. As ad hoc routing protocols are evaluated for use in micropower proximity networks, particular attention should be paid to their power consumption (e.g., the rate at which data are transmitted on the air). . • Most ad hoc routing protocols are designed to deal with rapid topology changes (the classic example of rapidly changing topologies being two truck convoys passing each other while travelling in opposite directions). The topology of micropower proximity networks will change (perhaps because nodes die, or perhaps because there is a need to redistribute responsibility among the nodes to equalize power consumption) but will change slowly compared to the design objectives of many ad hoc routing protocols. . • Micropower networks will probably have very distinct traffic patterns. If little processing of the sensor data is performed within the network, then the predominant traffic flow will be towards the egress point or points (presumably a lander). On the other hand, ad hoc routing protocol research typically assumes a more arbitrary distribution of traffic flows. 4.4. Wireless Internet Research

While the lower-layer Internet protocols were designed to accommodate a wide range of link characteristics, they may perform poorly in some environments. Performance problems that result when wireless networks are connected to the Internet spurred numerous research projects. Work on wireless/wired gateways, intended to mediate between the low-bandwidth, high-error-rate wireless network and the high-bandwidth, low-error-rate wired network, is particularly applicable to the design of proximity networks. Some creative work has been done in designing transparent gateways [5]. The less-transparent proxies may be particularly useful for micropower proximity networks (even at the risk of not being consistent with the end-to-end argument) [4].

The IETF Performance Implications of Link Characteristics (PILC) working group is developing a collection of documents that summarize many of the lessons learned about using the Internet protocols with different link-layer technologies, including wireless links. Proximity network protocol designers should be familiar with the contents of many of the PILC documents, including:

• Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations [10]

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• End-to-end Performance Implications of Slow Links [16] • End-to-end Performance Implications of Links with Errors [17] • Advice for Internet Subnetwork Designers [37] • Advice to link designers on link Automatic Repeat reQuest (ARQ) [20] 4.5. Header Compression Techniques

In spite of the promise of ubiquitous broadband Internet access, many users continue to access the Internet through low-speed dial-up lines, though this is now rapidly changing. This drove one Internet researcher to improve the performance of his Internet link by inventing a method of significantly compressing the IP packet headers. The prospect of widespread (but low-speed) wireless Internet access has further motivated efforts to improve the bit-efficiency of the Internet protocols. The IETF Robust Header Compression (ROHC) Working Group is exploring techniques to improve the performance of Internet protocols over wireless networks by compressing the protocol headers. The results of this work are likely to be useful in intelligent proximity networks, but micropower proximity networks probably require more radical solutions. 4.6. Internet Quality-of-Service Technologies

Intelligent proximity networks will need to provide quality-of-service assurances (e.g., to ensure that critical traffic or time-sensitive traffic isn't displaced by less-important or less-time-sensitive traffic). One or both of the two approaches to providing QoS assurances in the Internet may be applicable. The initial approach to providing QoS in the Internet was the Reservation Protocol (RSVP) which enables hosts to explicitly reserve bandwidth within the network. It was quickly apparent that permitting every host to explicitly request bandwidth simply wouldn’t scale to large networks (e.g., the Internet). In response, Differentiated Services (DiffServe) was developed, which provides QoS assurances by classifying traffic into one of a small number of classes, and treating the classes differently within the network (e.g., a low-delay, low-bandwidth class for voice, etc.)

The utility of QoS assurances is less obvious in micropower proximity networks, because only one class of traffic is likely to be transported (i.e., sensor data).

4.7. Time Synchronization

While time synchronization is an important function for many network nodes, the precise requirements for time synchronization vary between environments and applications. Two aspects of time synchronization warrant additional comments.

. • Local versus global synchronization The most common form of time synchronization is to ensure that a system's clock is "reasonably" close to a standard time

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reference, such as Universal Time Coordinated (UTC). In some applications, however, it may be adequate and easier to ensure that the clocks in a collection of nodes are synchronized with each other, but not necessarily with an external, standard time. For example, the nodes in a micropower proximity network could synchronize their clocks with each other, but make no effort to synchronize their clocks with anything outside of the proximity networks. Conceivably, a gateway on a nearby lander could translate the local proximity network time to a global time, when necessary. . • Accuracy The accuracy of different time synchronization techniques spans eight to ten orders of magnitude. The Network Time Protocol (NTP) [42] the most widely used network time synchronization protocol, easily maintains clocks synchronized within 100 milliseconds. NTP used in conjunction with the Galileo Global Navigation Satellite System (GNSS) or Global Positioning System (GPS) receivers designed for time synchronization and modified kernel software can keep clocks synchronized within a microsecond, even on PC hardware. Some have claimed synchronization to within 1 part per 10E-12, using state-of-the-art GPS receivers, rubidium oscillators, and crystals in temperature-controlled ovens. (The US Naval Observatory usually keeps its master clock within 10 nanoseconds of UTC, but at the cost of 50 caesium-beam frequency standards and a dozen hydrogen masers.) The question for proximity network designers and users is not "How accurately can time be synchronized?" but rather "How accurately do we need time synchronized, and how much are we willing to pay to do it (primarily in terms of power consumption)?" Unfortunately, TEC-EDD is not aware of an answer to this last question. The U.S. Global Positioning System is commonly used in terrestrial and near-Earth environments to provide time synchronization. Some GPS receivers will provide time synchronization to well within 100 nanoseconds of UTC. GPS-based solutions aren't necessarily applicable to proximity networks because GPS receivers require a lot of power (compared to micropower nodes) and the system won't be available in planetary environments.

Network Time Protocol is the most widely deployed, most sophisticated, and most heavily researched collection of protocols and techniques for network-based clock synchronization.

Precise time synchronization is critical to space operations. ESA has a long history of developing techniques for time synchronization. Some of these techniques and services may be of use to proximity networks.

4.8. Location Determination

Just as proximity network nodes often need to know what time it is, they often need to know where they are. In fact, in many instances the questions of time and location are closely intertwined. GNSS and GPS receivers are often used by terrestrial sensor nodes, but may not be appropriate for micropower nodes and will not be useful in planetary

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environments.

The requirements for location determination are similar to those for time synchronization, namely whether location must be determined relative to other nodes or to a global location reference, and the accuracy with which the location must be determined.

Several research groups are exploring non-GPS-based location determination techniques specifically designed for sensor networks [40, 19].

4.9. Energy-Efficient Protocols

The energy required to transmit one bit over a radio frequency (RF) link is many orders of magnitude greater than the energy required to execute one computer instruction. This leads directly to several obvious power-conservation strategies. First, highly efficient on-the-air message formats should be used to minimize the power consumed transmitting data over an RF link (which is why the Internet protocols, with their relatively verbose representation, are rarely used in micropower networks). Second, where possible (e.g., where compute power is available in the proximity network node) compute cycles should be traded off against bits transmitted on the air. However, because developing general rules for making these tradeoffs is very difficult; this area continues to be a topic of active research. For example, the utility of saving routing information (rather than generating it on demand) varies with the rate at which the route is used, the rate at which the network topology changes, the patterns of the traffic flows, and numerous other factors. Solutions that are advantageous under one set of assumptions often perform poorly when applied against different sets of assumptions.

4.10. Power-Aware Routing Algorithms

Power-aware computing research has developed several results that are applicable to micropower networks. The most fundamental, although somewhat straightforward, conclusion is that the resource consumption of a sensor web can be reduced, and its lifetime extended, by routing traffic through intermediate nodes. That is, because the power required to transmit data increases at between the second and fourth power of the distance, power can be conserved by reducing the transmit power used and relaying the message through intermediate nodes.

Other work has demonstrated that organizing micropower nodes into clusters and electing a node to handle communications external to the cluster can further conserve power [9, 30]. Rotating this responsibility can equalize the power consumption of the nodes, thereby extending the life of the micropower web [31].

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While the work on power-aware routing is similar to the work on ad hoc routing protocols, it doesn't appear that any research group has yet integrated the two sets of results.

4.11. IEEE 802.15.4 WPAN

IEEE 802.15.4 is a short-range radio link that uses the 868 MHz, 915 MHz or optionally, the 2.4 GHz unlicensed Industrial, Scientific and Medical (ISM) band. Its objective is fairly simple, low-speed communications targeted at long-lived battery applications in wireless sensors, toys, and home automation. WPAN devices under IEEE 802.15.4 may number to 255. The range of communications is approximately 15 metres in a Non-LoS office environment, to 75 metres in free-space.

WPAN exhibits characteristics that are be applicable to micropower proximity networks. These are: interesting transmit low-power consumption, 8-bit microprocessor and sleep capability, its range and network size. IEE 802.15.4a is an ongoing IEEE WG to include an additional UWB PHY layer, while the 15.4b WG is preparing MAC layer enhancements and other channel (additional European channels in 2.4Gz band) enhancements. At the time of this writing, the 15.4b WG is concluding and recommendations being balloted. The 15.4a WG has a much more difficult task set underway, and is not expected to conclude until 2007. The 15.4a UWB PHY version will provide quite precise ranging: centimetre accuracy in the 10 metre range. This family of WPAN is considered to be the most promising for several ESA use cases, including microsensors. Further characteristics and details of most all of the IEEE wireless described in this section and in the succeeding sections are found in the addendums to this document. 4.12. IEEE 802.15.1 Bluetooth

The Bluetooth standard has now been revised and included under the IEEE umbrella of standards. It is a short-range radio link that uses the 2.4 GHz unlicensed Industrial, Scientific and Medical (ISM) band [8]. Its original objective was to replace cables in personal electronics devices (e.g., between a PDA and a phone or a keyboard and a computer). Bluetooth stations can form piconets composed of a master and up to seven active slaves. The range of Bluetooth communications is expected to be approximately 10 metres, although some vendors claim ranges up to 100-300 metres in specific configurations.

While Bluetooth contains technologies that may be applicable to Micropower proximity networks (e.g., interesting transmit power control facilities), its range and network size limitations severely limit its applicability to ESA proximity

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networks

4.13. IEEE 802.11 Wireless LAN Standards

The IEEE 802.11 family of standards provides a range of wireless LAN solutions. While the power demands of 802.11 standards and products preclude their use in micropower proximity networks, conceivably commercial, off-the-shelf 802.11 technologies could be useful in at least some intelligent proximity networks. Note that the 802.11a/b/g/n PHY-MAC alone is not a complete networking solution; it requires additional protocols that provide higher-layer functions, usually the common TCP/IP suite. The specification and development of next generation, very high rate WLAN, 802.11n, up to 120 Mbps to 400 Mbps (utilising antennae multiple-input-multiple output techniques, MIMO) is nearing completion under IEEE (expected ratification and deployment in 2008) as well as numerous enhancements to 802.11 under active IEEE WGs. These include improved QoS, mobility, inter-networking among others – the 802.11x list reads almost as long as the alphabet. The author deemed these not yet mature enough (or yet certain) to enumerate here (but see Addendum 4). Nevertheless, if and when enhancements to 802.11 are available, IEEE, with its huge global and commercially-dependent market base, usually insures a maximum of backward compatibility and interoperability with un-enhanced versions. The anticipated improvements of 802.11n over 802.11a/g are quite dramatic, with performance at the physical layer expected to reach, in initial products, 300Mbps using two antennas, and over time scaling to 600Mbps using four antennas. Actual throughput at the application level is expected to be 100Mbps, equivalent to 100/10BaseT wired Ethernet networks. The range of 802.11n is also expected to improve by as much as 50 percent using Beam Forming technology that focuses energy in a particular direction on both send and receive. Another technology called Space Time Block Coding (STBC) will reduce signal dropout by using multiple antennas for redundancy. This technology in particular is key to enhancing the VoIP user experience. Finally, packet aggregation and block acknowledgement protocols will reduce power consumption and data collisions in a congested environment by building a so-called super-frame to send multiple packets simultaneously. The protocol allows designers to create a beacon that tells other devices to be quiet and tells all devices using the same access point when their timeslot is and when they can transmit. This prevents collision. It also allows devices to stay asleep saving power until it is their time to send or receive. IEEE 802.11n recommendations document is now in formal draft and expected to be adopted by early 2007. Refer to Addendum 4, IEEE 802.11 WLAN Standards for an overview. 4.14. Proximity-1 Space Link Protocol

Because the CCSDS Proximity-1 Space Link protocol is nominally designed for use in

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(rather long distance) proximity networks, a brief examination of how it matches the requirements identified in this document is warranted.

Perhaps the most striking aspect of the Proximity-1 protocol is the extent to which it is adapted to a very specific environment and a very particular operational model.

On its surface, the Proximity-1 protocol was designed for remote operation. The protocol is a point-to-point protocol that assumes a strong primary/secondary or master/slave relationship between the end points. The presumably highly knowledgeable master node directs the behaviour of the slave. Negotiation mechanisms that exist in many protocols are absent, so the secondary node isn't even able (within the Proximity-1 protocol) to indicate that it is unable to operate in the fashion directed by the primary.

Micropower proximity networks require balanced, autonomous protocols. A model of primary/secondary communications partners is all but impossible to apply to a collection of homogeneous microsensor nodes, not to mention of highly uncertain utility. As described earlier, micropower proximity networks must autonomously configure and operate themselves, a model that conflicts sharply with the operational model that appears to be inherent in the Proximity-1 protocol.

There are features of the Proximity-1 protocol that could be useful in proximity networks, such as support for time synchronization, ranging, and forward error correction. However, as is described in greater detail below, it would be beneficial if facilities such as these could share a link with other protocols, rather than be embedded within a specific link-layer protocol. Before selecting the Proximity-1 protocol because of specific, unique services it provides, it may be prudent to examine whether these services could be provided through mechanisms that share a link with other link-layer protocols. Also, current flight implementations for Proximity-1 utilise narrowband RF. No current implementations use any form of spectrum spreading. 4.15. IEEE P1451.5 Internetworking (WLAN / Bluetooth / IEEE 802.15.4)

This WG concluded its work in late 2006, summarized with recommended revisions to IEEE P1451.0 and P1451.1 base standards, as well as an internetworking recommendation, P1451.5 specification, and sub-specification for each of Bluetooth, WLAN/IP suite and the WPAN 802.15.4 utilising ZigBee. An interesting aspect of this work is the provision for some relatively uniform QoS over the three subnets, as well as a unified, single set of application software primitives that can be utilised regardless of these three underlying homogenous or heterogeneous wireless subnets. The WG originated in the sensors interest area (the WG chairman is of the U.S. NIST) and has recently performed demonstrations of the reference implementation and software. Reference code implementations in C++ are available upon contacting the chairman or key members.

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4.16. RFID: Battery-less sensors -- Micropower over Microwave and Materials Tracking

It is now possible (indeed has already been commercially deployed) to construct sensors not only without cables or wires, but without a battery as well [77]. While much innovative and possibly quite beneficial research in now underway regarding energy-scavenging (thermal, angular momentum, vibration, light, etc.) for microelectronics and wireless sensors in particular, micropower transmission over microwave has been deployed based on the commercial RFID ISO-18000 [78] standard. Others include: ISO 14443 and ISO 15693.

RFID, developed on the ISO standards is a new dynamic family of emerging wireless technologies, now entering the European arena and much of the world with similar force as it has previously in the United States. Initially used for materials and product identification and tracking, it has far-reaching applications in many portions of the supply chain, including manufacturing, distribution, wholesale, and retail business areas as well as the military in material and supply logistics.

Commercial Supply Chain Applications of RFID:

• ISO 17358 - Application Requirements, including Hierarchical Data Mapping

• ISO 17363 - Freight Containers

• ISO 17364 - Returnable Transport Items

• ISO 17365 - Transport Units

• ISO 17366 - Product Packaging

• ISO 17367 - Product Tagging (U.S. DoD)

• ISO 10374.2 - RFID Freight Container Identification

All indications are that NASA plans its utilisation in material and supplies ID and tracking in future manned space missions. RFID was utilised by MIT at Devon Island, the Canadian Space Agency’s Haughton-Mars Project analogue site for investigating wireless communications, for logistics and Mars surface mission planning and interplanetary supply chain management scenario execution in 2005. http://www.spacedaily.com/news/mars-base-05n.html

RFID is not limited to supply chain identification and tracking: it may be applied to almost anything tangible. Others include:

• Animals

• Road Transport Telematics

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http://www.spacedaily.com/news/mars-base-05n.html


• Application and conformance standards

• Financial/transport cards – people related, indeed already in U.S. passports

• Many others, e.g. archiving, robot-assisted retrieval, sensors,

ISO Data Content Structures are also ISO based:

• ISO 15963 - Unique Tag Id

• ISO 15961/62 – Data protocols and encoding

• Multiple data objects – EPC – RTI

• Complex data – sensors – need identified but yet to be standardised

For example, ESA received in late 2005 a proposal through the Innovation Triangle Initiative for an Earth-Observation Cartridge Data Retrieval System for HSM Off-line Archives using passive RFID technology. The proposed new method will replace or integrate existing bar code solutions and provide the operator for a real time presence verification of the cartridge inside the Off-line archive and identification of its position.

ISO 18000 currently implements 7 sub-specifications, based upon use-case and operates with air interface frequencies at: <135 KHz, 13.56 MHZ, 2.45 GHz, 860-960 MHz, 433 MHZ (active RFID).

RFID’s potential for use in battery-less wireless sensors has only recently been realised, and is anticipated to grow quickly in specialised and niche uses.

4.17. Narrowband and Narrowband ISM RF (868 MHz, 915 MHz, 2.4 GHz)

Current implementations for wireless sensors on Space Shuttle and ISS, designed and manufactured my Invocon. Inc. for NASA, utilise both narrowband RF in the very lowest ISM band as well as WLAN DSSS (IEEE 802.11b) at 2.4GHz.

Both have proven successful, though for the long term in intra-spacecraft internal data communications, spectrum spreading has robustness advantages, with a small penalty in overall power consumption, even though peak power is reduced. Nevertheless, narrowband in general may yet be most appropriate for some specific applications where complexity must be kept at an absolute minimum and benefits of advanced networking topologies are not needed, as in the case of the ESA D-SCI DALOMIS TRS for Venus atmospheric probes (See Table 2).

4.18. WiMedia, IEEE 802.15.3a Ultra Wideband, and Wireless IEEE 1394 (Very High Rate, High QoS)

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This technology is potentially very promising for space, especially in intra-spacecraft high data rate, high QoS and high determinism and/or data streaming applications. A potential application is a SpaceWire wireless extension utilising IEEE 1394 (Firewire) over RF wireless. The WiMedia Alliance [105] industry consortium is currently well underway. (High rate data transmission using IEEE 1394, Firewire, over RF wireless has already been demonstrated employing OFDM.). Despite the failure of the IEEE 802.15a WG to achieve a consensus (see last paragraph of this section), the WiMedia consortium has completed a High-Rate UWB Multi-Band-OFDM PHY-MAC standard and radio standard in December 2005, through ECMA International: ECMA-368 and ECMA-369. These are available on the web. The standard provides for a PHY-MAC consisting of 100 (one-hundred) data sub-carriers (plus 22 pilot and guard sub-carriers) and a mixed prioritized CSMA (PCA) plus a version of TDMA medium access, i.e. Distributed Reservation Protocol (DRP). WiMedia may utilise all or part of spectrum from 3.1 to 10.6 GHz, embracing the concept of a High-Rate WPAN shared among users such as Wireless USB, next generation Bluetooth and Wireless 1394-Firewire.

Since WiMedia is an industry alliance outside any independent standards body, the success and longevity of these standards may be much more closely linked to the WiMedia Alliance commercial success. *ECMA International - European association for standardizing information and communication systems – is based in Geneva. In 1987, when TC97 became part of ISO/IEC JTC 1 ; ECMA became A-liaison member of JTC1.

*To reflect the international activities of the Europe-based ECMA organization the name was changed in 1994 to: ECMA International - European association for standardizing information and communication systems. Before 1994 it was known as ECMA - European Computer Manufacturers Association.

The ECMA-368 contains the following disclaimer within the introduction: this ECMA specification is not intended to represent the regulatory requirements of any country or region.

General Regulatory Challenges/Successes for UWB

In July 2002, the International Telecommunication Union Radio Sector (ITU-R) assigned Task Group TG 1/8 the charter to study the appropriate spectrum management frame work related to the introduction of UWB devices and the compatibility between these devices and radio communications services. The TG was also divided into four Working Groups:

• WG1 - UWB technical and operation characteristics

• WG2 - compatibility with other radio services

• WG3 - spectrum management framework

• WG4 - measurement techniques for UWB emissions

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http://www.jtc1.org/


ITU Recommendations are still pending. European countries in particular are looking more favourably upon UWB with its better control of spectrum and out-of-band emissions based on MB-OFDM, especially as it pertains to cellular phone systems. However, there does remain some controversy regarding UWB at 24GHz for collision-avoidance radar.

The U.S. is currently the only major market where UWB is officially approved for use. Korea and Japan are expected to follow in early 2005 with preliminary regulations. In Europe, Germany has taken the lead on UWB and seems most likely to be the first to adopt regulation policy. Given the current momentum, it is likely that regulatory efforts will have been completed in a majority of the world markets by the end of 2006.

Note that the IEEE 802.15.3a (UWB) WG has failed to reach agreement or produce a recommendation. The WG was completely disbanded in January 2006 by a majority vote of more than 75% during the interim IEEE WG meetings in Hawaii, after failing to break a deadlock between the two internal models supporter factions. IEEE had already formed the 802.15.3c WG, as described in the following section.

4.19. IEEE 802.15.3c WPAN Millimetre-wave Alternate PHY Layer

The IEEE 802.15.3 Task Group 3c was formed in March 2005. TG3c is developing a millimetre-wave-based alternative physical layer (PHY) for the existing 802.15.3 Wireless Personal Area Network (WPAN) Standard 802.15.3-2003.

This mm wave WPAN will operate in the new and clear band including 57-64 GHz unlicensed band in the U.S. (defined by FCC 47 CFR 15.255). The millimetre-wave WPAN will allow high coexistence (close physical spacing) with all other microwave systems in the 802.15 family of WPANs.

In addition, the millimetre-wave WPAN will allow very high data rate over 2 Gbps applications such as high speed internet access, streaming content download (video on demand, HDTV, home theatre, etc.), real time streaming and wireless data bus for cable replacement. Optional data rates in excess of 3 Gbps will be provided. The EU nations ETSI and ESA are currently addressing additional low-power GHz unlicensed bands for Europe.

4.20. IEEE 802.16-2004/e Wireless MAN Standards and WiMax

Now newly being deployed literally en masse around the world, the wireless MAN (Metropolitan Area Network) could be truly be “the next big thing” not only in wireless, but in the commercial data communications world overall.

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An estimate of WiMax chipset revenue growth:

Geographic breakdown: WiMAX chipset revenue forecast (US$m)

Region 2005 2009

North America 2.76 227.45

Europe/Middle East 3.53 208.49

Asia Pacific 2.76 398.03

CALA 2.10 113.72

Source: In-Stat, compiled by DigiTimes, December 2005

Just as most all traditional “wired” POTS (plain old telephone service) has been crushed under the force of the Internet for handling not only data but voice -- again voice over Internet Protocol (VoIP) – a global revolution is well underway to move exclusively to IP for traditional telephone companies, the wired telecoms companies and unwired telecoms start-up suppliers have been deploying Wireless MAN in the form of WiMax, a commercial technology that is quickly becoming the de facto standard ahead of the finalisation of the IEEE 802.16e mobile MAN standard version (IEEE completed the /e adoption in December 2005). Operating at 2-10GHz (3.5GHz in Holland, for example) and 11-60 GHz these technologies provide high data rates up to 70Mbps via robust OFDM up to 30 km in range to navigate urban canyons and connect longer distances (50km) to suburban neighbourhoods.

WMAN is a most attractive wireless for high data rate planetary surface exploration, and have been extensively evaluated (and other wireless, IEEE 802.11b, for example) in Lunar and Mars analogues for NASA and CSA in the Haughton-Mars Programme (HMP), and subsequent programmes by Stephen Braham of Simon Fraser University, Vancouver Canada, and numerous others and international teams. NASA has already invested in applying both WLAN and WiMax (and WiMax-like) technologies, and is currently entertaining proposals for realising Radiation-Tolerant implementations of each technology for Mars exploration programmes [89, 90].

4.21. Ultra Wideband (and Pulse-based UWB)

Technically, UWB is defined as spectrum spreading over 500MHz or more in bandwidth, appearing to be very low-level, near-white noise in its signature. It is one other wireless technology that has already enjoyed a full and busy life within the military sphere, and has now emerged into the commercial world, advanced even more, miniaturised, and will

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http://www.digitimes.com/news/a20051214PR210.html


likely again “spin-in” once again into the military domain, just as spectrum-spreading techniques in general have already done with wireless LAN and DSSS. (COTS WLAN, commercially derived WLAN and even rugged-ized, militarised and radiation-tolerant (?) WLAN are already deployed around the world by NATO, the EU and the U.S.).

UWB, and especially shaped-pulse UWB, offers perhaps the lowest peak power of any spectrum spreading available today. It is a very attractive option for the future in both spacecraft and avionics as a whole. IEEE is currently provisioning for UWB options and additions to existing wireless PHY layers, specifically, WPAN (and also WBAN) IEEE 802.15.4a, and IEEE 802.15.3a. Some non-standardised UWB implementations in military aircraft are already beginning to appear, such as voice over IP (VoIP) utilising UWB on helicopter crew communications, and UWB wireless sensors on aircraft. It is characterised by a very high data rate, up to 400Mbps+ over very short distances, 3 metres or so, with decreasing data rates to around 200kbps at 100metres. Ranging measurements to within a few centimetres are possible with UWB; this capability in being included in some newer IEEE wireless standards.

While the FCC (US) has recently finalised the UWB spectrum usage and mask (-41.25 dBm, 3-10 GHz for indoor applications), requirements in the U.S., ETSI, ITU and the EU nations have yet to conclude their work, though now well underway.

4.22. IEEE 802.15.5 Mesh WPAN Networks

IEEE 802.15.5 is a quite new WPAN mesh networking WG focused mesh networking adaptations to the 802.15.3 MAC and above. These mesh networks possess not only the ability to self-configure, self-organise and perform multi-hop functions, but also the ability of self-healing in the case of a node failure. The IEEE 802.15 Task group 5 is chartered to determine the necessary mechanisms that must be present in the PHY and MAC layers of WPANs to enable mesh networking.

A mesh network is a PAN that employs one of two connection arrangements, full mesh topology or partial mesh topology. In the full mesh topology, each node is connected directly to each of the others. In the partial mesh topology, some nodes are connected to all the others, but some of the nodes are connected only to those other nodes with which they exchange the most data.

This characteristic could be interesting for aerospace and space applications necessitating high FDIR or redundancy requirements.

The 802.15.5 work is founded upon the WPAN IEEE 802.15.3 PHY-MAC and 802.15.4 PHY-MAC and attempts to maintain backward compatibility with these. For the 802.15.4 WPAN, the commercial ZigBee Alliance [87] is also worthy of consideration for their mesh networking technology.

4.23. SOIS Wireless WG of CCSDS (Potential WG – currently a BoF)

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The CCSDS SOIS Wireless Birds-of-a-Feather (BoF), in concert with the ESA Wireless WG, has initially proposed the following abstractions regarding RF wireless for space applications (The SOIS Wireless BoF is applying for a full CCSDS WG status. Also, currently the BoF is slightly more generally oriented toward manned spaceflight – non-planetary surface -- regarding RF wireless than the ESA Wireless WG, which embraces all possible application of RF Wireless, manned, unmanned, planetary surface, and formation flying, etc.). 4.23.1 Preliminary Classifications of Applications and Services

Classification of applications and services The main criteria for the classification of applications will be related to: Physical parameter: Distance or range (cm, m, km…) The range will classify the domain of application from local to the S/.C (intra-spacecraft), local to S/C and immediate vicinity (intra and inter S/C) such as short distances formation flying, local rovers and landers, free flyer auxiliary vehicles (for inspection, monitoring purposes etc.). The fact is that a WLAN is implemented within a S/C or outside to connect separate elements in some collaborative work should not impact too much the protocol to be used. Of course, for RF main differences will be in the RF front end since within a small S/C cavity, the transmitted power will be very small compared to off-board communications even if the same protocol is used for both applications. Propagation characteristics: The atmosphere composition and density (or lack thereof) directly influences propagation. Our Earth, Mars, and Venus and free space have significantly different propagation characteristics. Electrical environment: Is it a clean or disturbed environment (noise, interferences). This may impact the complexity of the system (e.g. signal processing). Required Performances: Throughput (in bps), tolerated delay (time bounded constraints on real time system) or both. In short, the degree of determinism required and related QoS issues. Functional parameters: Data systems in space applications can easily be categorized relatively to the RAMS requirements (Reliability, Availability, Maintainability, Safety) attached to the main function that they have to fulfil, allowing to rank them from non critical to safety critical applications: Non critical: Housekeeping – engineering monitoring – science TM The loss of data can be tolerated time to time as a function of the reliability figure required by the mission. Typically the loss of few thermistors data time to time will not jeopardize the mission or the lost of few bytes in the TM from an imager instrument is acceptable as long it does mot occur systematically.

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Critical: monitoring related to system FDIR or Health monitoring for manned missions. Similar to above at the difference that the data to be acquired are part of some functional chain, related to FDIR (Failure Detection Isolation and Recovery) for example and hence the loss of those data shall be avoided. If this happens, an alarm may not be triggered. However in a sound designed system, the FDIR shall be made such that major system failure could be caught by different means (redundant paths, multi-level FDIR). Reliability critical: Fly by wireless types of applications for unmanned S/C The failure can potentially reduce the life time of the mission; however the mission design shall have taken this into account by providing the necessary redundancies (cold or warm). Availability critical: Fly by wireless types of applications for unmanned S/C The system cannot tolerate any interruption of service, failure to do so can potentially endanger the mission or the spacecraft if not corrected. Typical example is a planetary orbit insertion manoeuvre that has to be executed in time and without interruption. The design shall have taken this into account by providing the necessary redundancies (cold providing a reasonable reconfiguration time in the order of 10 ms is tolerated, warm for a very short reconfiguration time (ms) or hot (no interruption of service is permitted, errors have to be masked on line). Safety critical: Fly by wireless types of applications in man tended environment Similar to either reliability or availability critical but in a man tended environment which means that the failure can potentially endanger directly or indirectly human health or life. Generally the system is designed with hot redundancies. Other difference is that the on board systems can be maintained by human (but not always like for ATV which is jettisoned after its mission). 4.23.2 Preliminary Classifications based on Performances and Robustness (RAMS) Requirements

It can become easily a multi-dimension problem but we propose a relatively simple classification considering on one side the performances and on the other side the functional ‘robustness’ defined as the level of criticality supported by the services. (See the table below.)

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Table 6. Abstraction of Functional Parameters vs. Capability-Criticality for Space

of Onboard Wireless Proximity Networks (*) Number refers to application review of Addendum 3 When considering wireless candidates, it is obvious that non critical services can be covered by COTS standards: IEEE 802.15.4 for sensor bus type, WiFi for medium to high rate. When increasing the robustness requirements, we may expect that the basic capability of the COTS standard will not be sufficient to cover the system needs. However, it does not mean that the COTS standard is not usable but it means that it has to be extended for providing the required level of robustness. The same approach has been used when flying automotive buses like CAN or multimedia like Firewire that are naturally robust for what concerns transmission errors but which do not provide natively cold, warm or hot redundancies. Also the BER or Frame error rate might be sufficient for lower criticality level but not sufficient for fly by wireless or safety critical mission, then extra coding might be necessary.

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Also it might be necessary to complement an existing standard for what concerns real-time control issues such as bounded delay. Obviously the best COTS candidates will be those that will require a minimum effort to be upgraded to fulfil our needs and hence the work of SOIS Working group will be to define and propose what standard extension shall be provided and also the tailoring of the standard if this is appropriate. 4.23.3 Added Value of Wireless Services Compared to wired Solutions

Another important criterion to be used for selecting the service to be considered in priority is the “added value” to the system or the Spacecraft that can be gained from the introduction of such a service. As such these may be categorised under: added value of wireless services compared to wired solutions within system or applications.

- Mass and AIT effort reduction This is an obvious one by reducing drastically the number of wires and connectors, the flight harness mass is decreased as well as the integration and testing time during S/C integration. It is also worth to note that much time is lost during testing and integration due to errors or faults in the auxiliary equipment and related test harness. - Electronics miniaturisation mass reduction In many instances the mere miniaturisation of the electronics is substantial enough to merit use, such as for transponders for a swarm of nanosats.

- Mobility and Portability This is particular interesting for Man in space and Man tended systems. Typical case is the crew heath monitoring of astronauts: they need to be constantly monitored in a non intrusive manner and keep their full freedom for moving around the station or man tended

vehicle. - Non intrusive monitoring of S/C during launch Wireless techniques could provide the possibility of monitoring in real time the passenger S/C (thermal, vibration, mechanical) whilst being launched which is not possible to day.

- Rotating mechanism-articulated structures-separable composites Wireless techniques would be the easiest and sometimes only way to implement contact-less data communications and acquisition systems. - Retrofit Wireless techniques when available would allow bringing new or up graded functionalities to existing platform for a minimum cost.

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Typical examples are the wireless sensor (micro-accelerometers) flown on the last Shuttle flight.

- Opportunity payload in late development phase Wireless techniques can allow the late integration of opportunity payloads on a S/C at a stage where modification of the harness is not possible. Typical example is the introduction of monitoring devices such as micro-camera for the deployment of appendices or separation manoeuvres. - Flexibility in S/C design and equipment accommodation Wireless techniques can provide new options to the S/C designer when accommodating equipment in the 3D space, especially when coupled with autonomous powering or energy scavenging techniques.

- Common network for on board and off board communications The possibility offered by wireless techniques to be used both for on board and off board can be of interest for some special cases such as robotic surface elements within some Exploration mission scenarios. - New functionalities Different users communicating at different speed can share the same Wireless channel. This is not possible with standard wired solutions since high speed signals required specific cables (shielding, coaxial). New redundancy concept / reconfiguration/plug and play: being layout independent, wireless techniques may bring additional flexibility when implementing fault tolerance and system reconfiguration. In standard

systems, the cross-strapping of on board equipment is always a delicate issue. - Enabling new classes of devices for on board and off board communications The possibility offered by wireless techniques to be used both for on board and off board can be of interest for new device classes.

4.23.4 Introduction Prioritization Strategy

The strategy is to consider as being a priority: 1) The services that bring a high ‘added value’ to existing systems (compared to ‘wired’ based services) 2) Low risk in term of feasibility 3) Progressive introduction in on board systems giving initially the preference to the support to low criticality functions such as monitoring unless we have a good case

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(project support) for implementing a higher criticality level (crew health monitoring, for example) in a short term. 4.24. Identification of Services to be Considered in Priority Within the CCSDS SOIS WG

Three classes of services have been defined covering the spectrum of applications of wireless proximity networks identified today. The work effort shall follow a ‘spiral’ approach, starting first by monitoring services that are relatively easy to implement whilst providing an interesting added value to on board systems and finishing by the more stringent requirements of command and control related applications. 4.24.1 Proximity Low Power Sensing Network

This relates to the current interest for the wireless acquisition of the data from miniaturized low power sensors ranging from few tens up to the order of thousands. There is to day a large interest for this approach in commercial and industrial systems with standards such as the 802.15.4 and the IEEE 1451. For space, application can be found on board S/C (housekeeping, engineering monitoring), off board (science mission) as well as in the integration and test facilities that are great consumer of small sensors (thermal vacuum and mechanical tests). The added value is obviously the reduction of harness, especially if the sensor is autonomously powered or self-powered (or energy scavenging). The technology risk is limited since this is currently an active field and we may expect spin-in from terrestrial industrial systems and in addition benefit from synergies with on going R&D activities within ESA and the EU Framework Projects, and others, to be identified. The services to be specified shall cover non critical monitoring (capability set A) and critical monitoring (capability set B). Main difference will be that Capability set A shall basically relate to low power sensing network with many nodes (for example thermistors channels can be in the order of several hundred to thousand on a single S/C) whilst capability B shall relate to a network for a reduced number of sensors but requiring a higher quality of services. 4.24.2 Proximity Intelligent Network

In our context, the qualifier of “intelligent network” relates to the communications of data between intelligent units or nodes (computer based) by opposition to the low power sensing network composed a priori of numerous non-intelligent sensors connected to a few intelligent units acting as concentrators. The services to be specified shall cover non critical (capability set A) and critical data (capability set B) information transfer allowing peer to peer communication and broadcasting among users. Non critical information transfers will generally be IP based. Capability set A shall basically rely on existing

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standards (at least for RF) whilst Capability set B may add additional requirements or QOS to those standards. 4.24.3 Proximity Command and Control Network

This relates to the data transfer of information participating to command and control functions on board a S/C or off board (commanding of external elements). The capability set A shall be defined to cover Reliability critical applications and the capability set B shall be defined to cover Availability/Safety critical. 5. Key Technologies for ESA Proximity Networks

As detailed in the previous section, there are a large number of technologies that could potentially be used in proximity networks. The task of a proximity network designer would be to create an integrated solution composed of complementary technologies. Good network architecture can provide useful guidance to a proximity

network designer. Unfortunately, a complete, mature architecture for proximity networks within the European Space domain does not yet exist.

5.1. Hypothetical Architectural Skeletons for ESA Proximity Networks

Proximity networks are the topic of a many current research projects. However, there is not yet consensus on the most appropriate architectures for proximity networks (papers with "architecture" in their titles notwithstanding [32]). Micropower proximity networks and intelligent proximity networks are very different: they have different objectives and requirements, require different technologies, and will have different architectures. Micropower proximity networks will undoubtedly use unique, highly efficient protocols and technologies focused on minimizing power consumption, while intelligent proximity networks will provide a broader range of services and may even use protocols similar to the Internet protocols (if not the Internet protocols themselves). Based on these observations, the broad outlines of likely proximity networks architectures are described below.

5.1.1. Hypothetical Micropower Proximity Network Architecture

Micropower proximity networks have a simple, narrowly focused objective, namely to transport as much sensor data as possible before their batteries expire. These networks will, by necessity, offer few services beyond transporting sensor data towards an external connection. The protocols used within the micropower network will be unique and tailored to the requirements of these networks. The gateway will translate between the vastly different protocols used in the micropower network and external networks; direct connections between micropower and external networks will not be supported.

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5.1.2. Hypothetical Intelligent Proximity Network Architecture

Intelligent proximity networks will be, in contrast to micropower proximity networks, very similar to traditional wireless networks. They will support a broad range of traffic types and services; features such as QoS assurances will be important in some configurations. Conceivably, these networks could use many of the Internet protocols, presumably in conjunction with some of the extensions being developed for use with terrestrial wireless networks (e.g., header compression).

5.2. Proximity Network Technology Requirements

This section contains a compilation of requirements for proximity network technologies, many of which were identified or described earlier in this document.

5.2.1. Network Architectures and Protocols for Proximity Networks

A much better understanding of the most effective architectures for proximity networks is needed. This need is greatest for micropower proximity networks, where traditional

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networking solutions don't provide the proper focus on power conservation and narrowly targeted mission. A proximity network architecture ought to provide guidance on:

• services provided by the network • distribution of function between devices (e.g., between proximity network nodes and

gateways) • functions performed by different protocol layers, and distribution of function between

protocol layers • behaviour of and algorithms implemented by network devices • network protocols, and • operational models. 5.2.2. Efficient Addressing Scheme

Globally unique addresses are a fundamental assumption of the Internet architecture. Unfortunately, globally unique addresses are huge. IPv6 packets may contain up to 384 bits of addresses (two 48-bit MAC addresses, two 128-bit network addresses, and two 16-bit port numbers). Micropower nodes can afford to transmit only the address bits actually necessary to identify the nodes within a proximity network (e.g., 10 bit addresses for a proximity networks of up to1024 nodes). In order to conserve address bits (and more importantly power) a single address should perform the functions performed by independent MAC-layer and network-layer addresses in most protocol suites.

The packet formats for most protocols contain both source and destination addresses. Because it is a connection-oriented, point-to-point protocol, the Proximity-1 protocol is able to include only one address in its packets. A single-address, connection-oriented, point-to-point protocol, such as the Proximity-1 is inadequate for the needs of micropower proximity networks.

5.2.3. Physical Layer Requirements

Based on the requirements of proximity networks, particularly micropower proximity networks, as well as TEC-EDD's experience with low-level protocols, the following facilities will simplify the tasks of higher-level protocols.

. • Receive signal strength indication It is valuable for a node to be able to determine the strength of received signals. This information can allow the transmitter to reduce its power, indicate the approximate range to the transmitter, and provide a basis for forming clusters, a technique for conserving power. . • Transmit power control A transmitter can conserve power by reducing the transmit power to only what is necessary for reliable communications, which can also reduce potential RF channel contention or interference. . • Wake on receive The ability for the processor to sleep until a packet is

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received, rather than requiring that the processor remain active while waiting for a packet, can expand the range of technologies that can be applied to micropower proximity networks (e.g., asynchronously transmitted packets become much less expensive). Note that this facility can be difficult to implement on some processors, which have wake times that are long compared to the time required to receive a packet. However, new developments, such as IEEE 802.15.4, are explicitly designed to support device wake, with a synchronized beaconing. . • Variable clock speed Being able to reduce the speed of the processor clock may permit power to be conserved during periods of light processing load. . • System sleep capability Many power-conservation strategies assume that the processor can be put to sleep, either for a specified period of time or until some specific event occurs, typically an interrupt. . • Subsystem sleep capability Being able to put select subsystems, or even select portions of the processor, to sleep enables additional power-conservation strategies. . • Hardware support for clock synchronization Appropriate hardware features can ease the task of accurate network clock synchronization. While the Proximity-1 protocol specifies that the processor determine when a specific transition of the last bit of the synchronization sequence is transmitted, it is probably adequate for the hardware to provide an indication (interrupt) when, for example, the last bit of a packet is transmitted. The hardware is probably less complex and doesn't need to understand as much about the link-layer protocol; the processor can then compute when the event specified by the Proximity-1 protocol occurred. Note that, depending on the link-layer protocol, determining when to generate a receive interrupt may be more difficult. However, before too much effort is spent on this topic, proximity network designers ought to determine how accurately clocks need to be synchronized and whether these features are even necessary. . • Reasonably accurate clocks The task of keeping clocks synchronized is much easier if the clocks being synchronized are well behaved. Of course, extreme environmental conditions make this task more challenging. . • Hardware support for range determination Several techniques have been suggested for determining the range between two devices. Some of these techniques require that that one device echo information being transmitted by another device. This loop-back function can be performed at any of several different levels, including the analogue level (a "bent pipe"), at a digital or bit level, or even at a packet level. The lower level loop-back implementations will permit more accurate range determination, but require more cooperative hardware. Again, the technique selected ought to match the requirements for range determination accuracy. . • Hardware support for RF channel contention resolution How RF channel contention ought to be avoided or resolved is a fundamental physical-layer design decision. Over the decades, countless techniques have been developed, and researchers are continuing to propose new solutions tailored to proximity networks [33, 6]. At this time, TEC-EDD doesn't have a strong opinion about whether, for example, the assignment of time slots (time-division multiple-access, TDMA) is more beneficial than, for example, carrier-sense, and multiple-access (CSMA) schemes. Nonetheless, the design of the contention-resolution mechanism ought to be coordinated with the higher-

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level protocols (e.g., so that the higher-level protocols don't incorrectly assume that they can transmit asynchronously) and the hardware ought to support whatever channel contention mechanism is selected. Many of the above issues are currently being sorted-out within the commercial wireless sector as new improved and sometimes, competing technologies and standards are rapidly coming to market. It is very likely that given some time, many or most of the needs of RF wireless for space will be eventually addressed in the commercial marketplace. 5.2.4. Link-Layer Protocols

Link-layer protocols are responsible for the error-free transmission of data between nodes. Proximity network link-layer protocols must provide many of the traditional link-layer services, plus some that are specific to proximity networks.

. • Highly efficient on-the-air representations Micropower proximity networks require a link-layer protocol with a highly efficient on-the-air representation. This requirement precludes the use of an existing protocol for these networks. . • Error detection Link-layer protocols must detect transmission errors, typically by using a frame check sequence (FCS). Cyclical redundancy checks (CRCs) are a powerful, commonly used technique for determining the integrity of a received packet. Hardware CRC generation is useful, because software CRC generation executes slowly and is tedious to program. . • Balanced, peer-to-peer protocol By their very nature, micropower proximity networks require a balanced, peer-to-peer link-layer protocol (i.e., one that doesn't have a primary/secondary or master/slave relationship). Most modern link-layer protocols meet this requirement. . • Forward error correction Link-layer protocols for micropower proximity networks should include a forward error correction mechanism, the addition of redundant information by the transmitter that will permit the reconstruction of an error-free packet by the receiver in some cases when a packet is received with transmission errors, in order to make the best use of the available transmit power. . • Multi-hop retransmission Because link-layer (hop-by-hop) retransmission mechanisms often interact poorly with retransmission mechanisms implemented at higher protocol layers (e.g., end-to-end retransmissions), the design of the link-layer protocol must be coordinated with the design of the higher-level protocol [20]. While the question of where retransmissions ought to be implemented can stir vigorous debate, the most important result is that the decision must be coordinated between protocol layers. . • Connection-oriented versus datagram operation Link-layer protocols may provide datagram services (e.g., Ethernet) or may establish a connection between communications partners before data are transferred (e.g., Proximity-1). The behaviour of micropower networks (particularly in the presence of an ad hoc routing protocol) appears to match datagram-style link-layer protocols. While it may be possible to create a scheme for using a connection-oriented link-layer protocol in micropower proximity

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networks, ensuring that it interacts gracefully with, for example an ad hoc routing protocol, will be a challenge, plus the utility of the result is not at all clear. . • Cooperation with range determination techniques Link-layer protocols for micropower, and probably for intelligent, proximity networks ought to share the link with range determination techniques (rather than embed range determination within the link-layer protocol). That is, a mechanism should be provided that passes control of the link to the range-determination facility, when necessary. This approach will allow range-determination techniques to evolve independently of the link-layer protocols, and will allow the reuse of link-layer protocols across environments that may have different requirements for or different approaches to range determination. . • Time-synchronization services NTP provides very good network time synchronization as an application-level protocol, although it provides better results when interrupt jitter is minimized (and when interrupt latency is known). Certainly, fairly direct support for time synchronization services can be embedded within a link-layer protocol. On the other hand, simple techniques such as minimizing transmit and receive queuing delay for time synchronization packets may be adequate for many applications. (The Proximity-1 protocol specification appears to provide a time-synchronization service. However, all it really does is 1) specify how a timestamp relates to the transmission or reception of a packet and 2) specify a special link-layer format for transporting timestamp information, which could just be as easily be transported as link-layer data.) . • Compression While the most efficient method of compression is often for the application to avoid transmitting information that is not needed by the receiver, it can sometimes be useful for the network-layer protocol to provide a facility to compress application data. . • Link-layer reliability Link-layer protocols can provide best-effort service (transmit a packet and hope it reaches its destination) or reliable service (retransmit a packet if the intended recipient does not acknowledge receipt of the packet). Of course, reliability comes at the cost of transmitting sequence numbers and acknowledgements. The trade-off between transmitting less sensor data more reliably versus transmitting more sensor data with less reliability should probably be examined in the design of sensor webs. In many cases, the scientific mission of the sensor web may have a strong influence on this choice. 5.2.5. Network-Layer Protocols

Network layer protocols are responsible for the end-to-end transfer of data, by potentially forwarding the data through intermediate nodes. Routing and addressing are the fundamental issues in network-layer protocol design. An ad hoc routing protocol, combined with the efficient addressing scheme identified above, matches the needs of micropower proximity networks, (although which ad hoc routing protocol best meets the needs of micropower networks is not immediately clear).

Quality of service (QoS) assurances are typically provided at the network layer, so mechanisms are need to identify the service class of each packet. This information is typically included in the packet header, although alternative approaches are possible (e.g.,

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packets sent to a particular node are known to have low priority).

5.2.6. Transport-Layer Protocols

Transport protocols manage the end-to-end flow of data, ensuring that the data are received reliably and in order. They often include congestion control and flow control features.

The role of transport-layer functions in micropower proximity networks is not entirely clear, and needs to be integrated with other design decisions. One approach is to not include a transport protocol, perhaps by time stamping sensor data so that out-of-order data delivery is not an issue and simply dropping packets in response to congestion or if the receiver is temporarily unable to accept additional packets.

5.3. Technology Readiness Assessment

TEC-EDD examined the current state of the technologies required for micropower proximity networks and intelligent proximity networks. The results of this examination are summarized in the table

below, which includes the following attributes.

• Technology The technology being assessed is identified. • Applicability An "M" indicates that a technology is applicable to micropower

proximity networks, while an "I" indicates that a technology is applicable to intelligent proximity networks.

• Reliability The reliability of a technology is an indication of how likely a technology, in its current state of development, is to provide solutions or operate gracefully over a broad range of environments.

• Scalability Scalable technologies are those that can reliably support large networks with few operational anomalies or significant changes to the technologies.

• Longevity A technology has longevity when it appears less likely that it will be supplanted by new, alternative technologies.

• Technology Readiness Level (TRL) The estimated ESA Technology Readiness Levels are summarized for the convenience of the reader in Addendum 1 of this document (1 is the lowest, 8 the highest).

Technology Applicability Reliability Scalability Longevity TRL

Micropower network architectures M low medium low 2 Intelligent network architectures I medium high high 3 Ad hoc routing protocols M/I medium medium low 2-3

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Micropower physical-layer protocols

M medium N/A low 2

Micropower link-layer protocols M medium N/A low 3 Micropower network-layer protocols

M medium high medium 3

Internet Protocols I high high high 5 Time synchronization techniques I high high high 5 Time synchronization techniques M medium medium medium 3

Table 7. State of the Technologies Required for Micropower Proximity Networks and Intelligent Proximity Networks

6. Conclusions and Recommendations

This dossier annex takes the long view. Considering this, micropower proximity networks (the micropower category includes both microsensors and intra-spacecraft sensors) offer ESA perhaps the greatest potential return for its proximity network research investments. Common hardware and software

platforms for micropower proximity network research, development, and deployment would enhance the opportunities for collaboration between projects, enable projects to more easily leverage the results of prior ESA-funded work and increase the overall productivity of ESA's research euros. System-level demonstrations by ESA of micropower proximity networks would help focus research on identifying and solving real-world problems, as well as provide an empirical assessment of the effectiveness of proposed technologies. 6.1. Focus Proximity Network Research Investment on Micropower Networks

Micropower wireless proximity networks and wireless intelligent proximity networks are distinctly different, and demand different architectures and technologies. Many of the technologies required to create effective micropower proximity networks are still fairly immature, and there is little agreement on the most appropriate architectures for these networks. The requirements of intelligent proximity networks, on the other hand, can largely be met by existing technologies.

The immaturity of micropower wireless proximity network solutions presents both a risk and an opportunity to ESA. Micropower proximity networks can enhance the success of future ESA missions, if mature solutions that meet ESA's unique requirements are available. ESA investments in wireless micropower proximity network research today can ensure that solutions are available for ESA missions in a timely fashion, and that consideration of ESA-unique requirements is integral to the

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research and development of these networks.

6.2. Promote Common Hardware and Software Platforms

The development of a common family of micropower proximity network hardware and software platforms could effectively extend ESA's research and development funds by:

• Enabling ESA-funded research projects to more easily collaborate, share results, and leverage prior work, because they would be using compatible hardware and software environments • Facilitating and speeding the transfer of technologies from research to development to production, again because the use of compatible hardware and software would minimize the rework required • Helping to focus research projects on identifying and solving real-world problems, by increasing the similarity between the research and production environments. The functionality identified in Section 5.2.3, "Physical Layer Requirements" could be used as a straw horse to stimulate discussions about the properties of a common hardware platform for ESA micropower proximity networks. However, as noted earlier in this document, divergent opinions still exist over the desirability of using 8-, 16- or 32-bit processors in micropower networks. As such, it may be desirable to create a family of micropower research platforms that share a compatible software environment and support compatible peripherals.

Of course, the challenges of developing a common family of hardware and software platforms for ESA are complicated by the need to balance the risk of stifling innovation with the benefits of enhancing sharing and collaboration. However, the concept of “family” as applied to RF wireless for space has potential for significant contribution to design, implementation and deployment efficiencies by capitalising on common HW, such as ESA’s LEON microprocessor as a MAC layer processor and the IEEE 802.1 and IEEE 802.2 family of network management standards (see Addendum 5).

6.3. Promote Integrated Demonstration Projects

Wireless Sun Sensor 3x4x1 cm

Demonstrations offer valuable opportunities to communicate and empirically evaluate the effectiveness of system-level solutions. Numerous technologies have been proposed for micropower proximity networks, but there is not yet consensus within the space industry on which technologies, much less which architectures

composed of collections of complementary technologies, best meet ESA's requirements. The prospect of real demonstrations would help focus researchers on integrating technologies and creating system-level architectures that will provide the micropower wireless proximity networks required to enhance the success of future ESA missions. The

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above inset photograph of a matchbox size completely wireless sun sensor is an excellent example of a micropower sensor demonstration project [83]. 6.4. An ESA Wireless Roadmap

Tables 2, 3 and 4 perhaps give a very good indication of where the road ahead lay. Having initially identified expected initial, secondary, third areas and tertiary areas of interest within each of the use categories: microsensor, intra-spacecraft, inter-vehicle and EVA and advanced science, three wireless technologies score repeatedly: narrowband RF, WPAN IEEE 802.15.4, and

WLAN IEEE 802.11a/b/g. These, plus IEEE 802.16-2004/e (WiMax) for longer-range planetary surface manned-mission comms and the promise of IEEE 802.15.3 or WiMedia for a SpaceWire point-to-point extension should constitute the immediate way forward. However, for intra-spacecraft (internal to the S/C) data handling of most varieties, shaped-pulse UWB holds the most promise because of its extremely low, near Gaussian-like noise, signature, lower complexity electronics (lower than WLAN for example), and significantly lower power consumption. Ultimately this leads to a customised and perhaps deterministic (TDMA) pulsed UWB specifically for intra-S/C control, if these become available as Intellectual Property in the commercial segment, or even ESA-developed.

5 mm

While the conclusion of the investigation within this dossier Annex recommends to begin with ESA funding Micropower Proximity Networks for space development, the development of Intelligent Proximity Networks should soon follow, as there is growing certainty of a less-far-termed and more well-defined

ESA Lunar/Mars programme, encompassing either robotics, a manned programme or both. For either Micropower Proximity Networks or Intelligent Proximity Networks, it is quite reasonable that some commercial technologies’ Intellectual Property, in some applications, may be used as-is, without any modification except for adaptation to the various space environments, radiation tolerance, etc. For other applications, tailoring the commercial Intellectual Property to a space usage may be both required and reasonable. In either case, it is certain that the cost benefit of such an approach will succeed over an ESA-custom developed wireless technology, given roughly similar functionality and performance. 6.5. Looking Beyond the Immediate Horizon – Trends in Wireless

Given that the wireless domain remains very heavily researched and an extremely swiftly moving commercial development area, both evolution and revolution are possible. Many people and organisations cite wireless as a

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disruptive technology [139] (this is not a necessarily a negative term in an academic sense – the inventor later renamed the concept disruptive innovation). This author tends to agree with this view, though more history can only be the ultimate judge. As such, the implications for applying wireless to space projects, systems and data handling should be further assessed by ESA and the space industry. Several of author’s views of trends for the very near future are below. Like most bodies of predictions, some inevitably will be wrong; some will indeed come to pass. Nevertheless, these are food for thought.

1) The cost of wireless intellectual property (IP) and IP cores for wireless will continue to decline over time.

2) The diversity of wireless IP and IP cores will continue to increase over time. 3) The proportion of specialty, proprietary wireless standards (non-IEEE or other

generalised standards body) to non-proprietary wireless will continue. For example: compressor (air, gas) manufacturers are defining their own wireless system to be applied to their family of compressor product.

4) Availability of these IP and specifically VHDL IP cores within Europe will continue to increase, though more slowly than in the Far East and the U.S.

5) The nuclear size of these IP will eventually fragment, so that future commercial wireless designers will themselves have a wider and deeper IP toolbox from which to construct more diverse and even more advanced wireless designs, eventually finding their way as standard IP into the commercial HDL or digital development environment, and into HDL designers’ and analogue front-end and radio designer’s tool boxes.

6) IEEE will remain the dominant worldwide standardising body for wireless. This could be a plus, as there is a good track record, especially in the wireless domain, for encouraging business progress while maintaining as much “as is reasonable” backward compatibility and interoperation. It is regrettable that the ETSI HiperLAN has not been more successful in the market place; it remains to be seen if the EU and ETSI attempts in restricting competition to its new HiperMAN will succeed in shoring-up against the WiMax and IEEE 802.16 MAN onslaught.

7) European participation in IEEE is likely to remain underutilised. This is true especially in the many wireless standards areas (dozens upon dozens of active subgroups) where the various IEEE standardisation efforts are represented by the U.S. (about 45%), far-east (35%) and the rest of the world (20%).

8) The proliferation of wireless standards is likely to continue for several if not many years, though not likely (and hopefully not) at the pace of the two most recent years.

9) Interoperability between the various wireless technologies will emerge as a new growth area for both standards and regulating bodies (IEEE, ETSI, ISO, ITU, FCC, IETF, etc.), as well as for the wireless commercial industry to achieve an emerging and sustainable “worldwide wireless grid”.

10) The upper limit of speed and performance of the high-end of RF wireless systems has not yet been reached – millimetre wave and pulsed UWB have

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http://en.wikipedia.org/wiki/Disruptive_technology


not began to be commercially exploited. 480 Mbps over a 10 metre distance will soon be reality in the commercial domain.

11) Increased speed and performance will serve in moving to ever higher-level encryption algorithms without penalty. Already the NATO military utilises commercially-derived WLAN IEEE 802.11b with 256-bit U.S. military encryption on the battlefield. The U.S. is planning for much, much, more [88].

12) The Software Defined Radio will be first realised within the defence and military markets sometime between 2007 and 2009.

13) Cognitive Radio Technology, wireless that is aware of its operational environment and automatically adjusts itself in terms of frequency band, transmitted power, antenna orientation, modulation, and bandwidth, to maintain the desired communications, is already on the horizon. [134]

14) In general, mobility will be an ever increasing focus for most wireless technologies, including several varieties of wireless internet.

15) The wireless sensor revolution will take hold in Europe in the coming next years.

16) Energy scavenging and harvesting for wireless sensors will become common. 17) RFID will gain enormous support and very wide deployment in the

manufacturing, distribution and supply chain worldwide within the next few years in Europe and will quickly displace barcodes in many applications.

"The number of RFID tags produced worldwide is expected to increase more than 25 fold between 2005 and 2010, reaching 33 billion”, according to market research company In-Stat in early 2005. Total production of RFID tags in 2005 reached more than 1.3 billion, according to a recent report. RFID production will vary widely by industry segment for several years -- for example, RFID has been used in automotive keys since 1991, with 150 million units now in use, a quantity that greatly exceeded other segments until recently, according to In-Stat. "By far the biggest RFID segment in coming years will be supply chain management," said Allen Nogee, In-Stat analyst, in a statement. "This segment will account for the largest number of tags/labels from 2005 through 2010."

18) Several wireless technologies will be close-coupled with Galileo-GNSS giving rise to new classes of wirelessly-enabled devices in areas such as health care, transportation and logistics and communications. The PDA mobile telephone with both embedded GNSS and WLAN will debut in Europe in 2006.

19) The wireless body-area-network (BAN) will emerge as a commercial reality of some force, giving rise to new classes of embeddable, wearable electronics and new ways of interacting with one’s environment.

20) The national and international RF spectrum governing bodies, i.e. ETSI, FCC, etc., are likely to open-up additional spectrum available to low-power non-licensed users, as is currently underway.

21) Wireless growth areas are: communications devices (combined GPRS, WLAN VoIP telephones, i.e. VoWLAN), materials tracking, vehicle tracing, leisure oriented devices, domotics, industrial robotics, the manufacturing and process industries as a whole, industrial controls (sensing and SCADA),

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mobile internet; the automotive, health care, avionics both onboard aircraft and on the airport tarmac, music-related devices, and home entertainment industries, service industries anywhere some kind of handheld device may be employed for business/service added value, time or cost efficiency, or employee/user convenience.

22) The internet and Internet Protocols are essential for all, both wired and unwired.

23) Major/minor comms carriers, combined, seamless wired and wireless data/VoIP systems will soon emerge on a large scale making use of wireless backhaul and wireless user systems. WiMax (IEEE 802.16-2004/e) will emerge as one of the most important major technologies in decades. The rollout in Europe begins in 2006. Certified devices will appear immediately.

24) Very soon the average wireless user will not need to be an IT engineer. The WLAN in your notebook PC, PDA or Blackberry will automatically find, connect and route (and bill) your desired communications to any device on earth (space?) possessing an IP address (permissions and firewalls permitting), without any special user expertise. Virtual availability (accessing any information from anywhere on earth) will increasingly become a reality.

25) Wireless proximity networks of many species will become ubiquitous in tomorrow’s modern society: on commercial aircraft, on trains, onboard ships in engine rooms, on/in animals, automobiles, upon, inside and beside roads, on bridges, within tunnels; environmental monitoring, many varieties of structures monitoring, various kinds of security, emergency systems, disaster monitoring and communications, industrial manufacturing, equipment diagnostics and troubleshooting, retail sales (already partially displacing optical bar code), entertainment, service and maintenance roles, telemedicine, energy management, defence, military, sports, health care and delivery, health systems, in-body sensors, materials delivery, transportation and logistics, materials tracking, localisation of objects and people, in your clothes, and comprising the virtual mobile office, in short, most everywhere. Cameras with embedded WLAN debuted in late 2005. A wireless iPod-like device, developed by Microsoft, linked via WiFi to the www will be a reality before 2007. On demand video-streaming to handheld devices (PDA, PDA-like, combi-phones) are currently emerging; on-demand digital television and video-on-demand (i.e. non-broadcast) IPTV via the IP suite and wireless (such as WiMax) to handheld devices will soon emerge and could eventually be cost-free to the end-user. A Skype - specific WiFi mobile phone by Netgear has already emerged in May 2006. If you purchase a new upmarket automobile in 2006, it is likely to employ at least 6 wireless systems, including embedded wireless tyre pressure sensors with energy scavenging from tyre angular momentum, or centrifugal force and passenger compartment RF wireless multi-media. Ambient intelligence will become a way of life in by 2015.

26) UWB will emerge as a key technology not only for short-range wireless communications, but also in low-cost and miniature consumer/industrial RADAR, imaging, ranging, and localisation applications. For example, UWB

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http://www.skype.com/intl/nl/

http://www.popgadget.net/2006/05/netgear_wifi_ph.php


is expected soon to be widely deployed in automobiles for collision detection/avoidance, and is now used in the military for imaging thru structures and walls, even multiple concrete walls (most recently in 2005, employing a hand-held device).

27) The current and more importantly, the next generations of commercially-derived RF wireless will be a key enabler for: ubiquitous and pervasive computing, distributed computing, embedded computing, distributed intelligence, mobile learning, location awareness, geographical information systems, telemedicine, multimedia, software-defined radio, cognitive radio, etc. in both the civilian and the military domains.

28) For space, given that the ever increasing complexity of digital portions of wireless components (the vast majority of the complexity resides in each the digital silicon and supporting lower-layered firmware and upper-layers software), wireless may well be able to make significant strides, as the space industry silicon foundries migrate to finer sub-micron CMOS technologies that are also immune to radiation TID effects, and providing substantially increased gate counts of 5 to 5.5 Million Gates / ASIC device. The proportion of a space-qualified radiation-tolerant wireless device’s SEU mitigation, on the other hand, will necessarily increase.

From these above, new opportunities will likely arise over the long term for adapting commercial technologies for space applications.

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Acknowledgements A substantial portion of the core of this annex is drawn from a public domain, October 2003 report to the U.S. National Aeronautics and Space Administration (NASA), Washington, DC 20546-0001, prepared by: Timothy J. Salo, Barry A. Trent, and Timothy Hartley Architecture Technology Corporation 9971 Valley View Road Eden Prairie, Minnesota 55344

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Addendum 1

Technology Readiness Levels

Brief descriptions of the Technology Readiness Levels are reproduced here.

Basic Technology Research:

Level 1: Basic principles observed and reported

Research to Prove Feasibility:

Level 2: Analytical and experimental critical function and/or characteristic proof of concept

Technology Development:

Level 3: Component and/or breadboard validation in laboratory environment

Technology Demonstration:

Level 4: Component and/or breadboard validation in relevant environment

Level 5: System/subsystem model or prototype demonstration in a relevant environment (ground or space)

System/Subsystem Development:

Level 6: System prototype demonstration in a space environment

System Test, Launch and Operations:

Level 7: Actual system completed and "flight qualified" through test and demonstration (ground or space)

Level 8: Actual system "flight proven" through successful mission operations

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Addendum 2

Representative RF Wireless Technologies Characteristics

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Addendum 3

Representative Current and Near and Mid-term Manned Spaceflight Wireless Needs

For ISS, Space Shuttle, CEV (Crew Exploration Vehicle), LSAM (Lunar Surface Access Module), and other Habitat

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Addendum 4

IEEE 802.11 WLAN Standards

You may check http://en.wikipedia.org/wiki/IEEE_802.11 for an updated online version. The following IEEE standards [http://www.standards.ieee.org] and task groups exist within the IEEE 802.11 working group:

• IEEE 802.11 - The original 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard (1999)

• IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001)

• IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999)

• IEEE 802.11c - Bridge operation procedures; included in the IEEE 802.1D standard (2001)

• IEEE 802.11d - International (country-to-country) roaming extensions (2001)

• IEEE 802.11e - Enhancements: QoS, including packet bursting (2005)

• IEEE 802.11F - Inter-Access Point Protocol (2003)

• IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003)

• IEEE 802.11h - Spectrum Managed 802.11a (5 GHz) for European compatibility (2004)

• IEEE 802.11i - Enhanced security (2004)

• IEEE 802.11j - Extensions for Japan (2004)

• IEEE 802.11k - Radio resource measurement enhancements

• IEEE 802.11l - (reserved, typologically unsound)

• IEEE 802.11m - Maintenance of the standard; odds and ends.

• IEEE 802.11n - Higher throughput improvements

• IEEE 802.11o - (reserved, typologically unsound)

• IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and passenger cars)

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http://en.wikipedia.org/wiki/IEEE_802.11

http://en.wikipedia.org/wiki/IEEE

http://standards.ieee.org/

http://en.wikipedia.org/wiki/IEEE_802.11c

http://en.wikipedia.org/wiki/IEEE_802.1D

http://en.wikipedia.org/wiki/IEEE_802.11d

http://en.wikipedia.org/wiki/IEEE_802.11e

http://en.wikipedia.org/wiki/Quality_of_service

http://en.wikipedia.org/wiki/IEEE_802.11F

http://en.wikipedia.org/wiki/Inter-Access_Point_Protocol

http://en.wikipedia.org/wiki/IEEE_802.11h

http://en.wikipedia.org/wiki/IEEE_802.11i

http://en.wikipedia.org/wiki/IEEE_802.11j

http://en.wikipedia.org/wiki/IEEE_802.11k

http://en.wikipedia.org/wiki/IEEE_802.11m

http://en.wikipedia.org/wiki/IEEE_802.11p


• IEEE 802.11q - (reserved, typologically unsound, can be confused with 802.1q VLAN trunking)

• IEEE 802.11r - Fast roaming

• IEEE 802.11s - ESS Mesh Networking

• IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics

• IEEE 802.11u - Interworking with non-802 networks (e.g., cellular)

• IEEE 802.11v - Wireless network management

• IEEE 802.11w - Protected Management Frames Note - there is no standard or task group named "802.11x". Rather, this term is used informally to denote any current or future 802.11 standard, in cases where further precision is not necessary. (The IEEE 802.1X standard for port-based network access control, is often mistakenly called "802.11x" when used in the context of wireless networks.) Note – if there is not a date beside the WG, the work is not yet finalised. Note - 802.11F and 802.11T are recommendations, not standards and are capitalized as such.

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http://en.wikipedia.org/wiki/IEEE_802.11r

http://en.wikipedia.org/wiki/Roaming

http://en.wikipedia.org/wiki/IEEE_802.11s

http://en.wikipedia.org/wiki/IEEE_802.11T

http://en.wikipedia.org/wiki/IEEE_802.11u

http://en.wikipedia.org/wiki/IEEE_802.11v

http://en.wikipedia.org/wiki/Network_management

http://en.wikipedia.org/wiki/IEEE_802.11w

http://en.wikipedia.org/wiki/IEEE_802.1X


Addendum 5

IEEE 802 LAN / MAN Standards

IEEE 802 refers to a family of IEEE standards about local area networks and metropolitan area networks. More specifically, the IEEE 802 standards are restricted to networks carrying variable-size packets. (By contrast, in cell-based networks data is transmitted in short, uniformly sized units called cells. Isochronous networks, where data is transmitted as a steady stream of octets, or groups of octets, at regular time intervals, are also out of the scope of this standard.) The services and protocols specified in IEEE 802 map to the lower two layers (Data Link and Physical) of the seven-layer OSI networking reference model. In fact, IEEE 802 splits the OSI Data Link Layer into two sub-layers named Logical Link Control (LLC) and Media Access Control, so that the layers can be listed like this:

• Data link layer

o LLC Sublayer

o MAC Sublayer

• Physical layer The IEEE 802 family of standards is maintained by the IEEE 802 LAN/MAN Standards Committee (LMSC). The most widely used standards are for the Ethernet family, Token Ring, Wireless LAN, Bridging and Virtual Bridged LANs. An individual Working Group provides the focus for each area. See its working groups:

• IEEE 802.1 Higher layer LAN protocols

• IEEE 802.2 Logical link control

• IEEE 802.3 Ethernet

• IEEE 802.4 Token bus (disbanded)

• IEEE 802.5 Token Ring

• IEEE 802.6 Metropolitan Area Networks (disbanded)

• IEEE 802.7 Broadband LAN using Coaxial Cable (disbanded)

• IEEE 802.8 Fiber Optic TAG (disbanded)

• IEEE 802.9 Integrated Services LAN (disbanded)

• IEEE 802.10 Interoperable LAN Security (disbanded)

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http://en.wikipedia.org/wiki/IEEE

http://en.wikipedia.org/wiki/Local_area_network

http://en.wikipedia.org/wiki/Metropolitan_area_network

http://en.wikipedia.org/wiki/Isochronous

http://en.wikipedia.org/wiki/Logical_Link_Control

http://en.wikipedia.org/wiki/Media_Access_Control

http://en.wikipedia.org/wiki/Data_link_layer


http://en.wikipedia.org/wiki/Media_Access_Control

http://en.wikipedia.org/wiki/Physical_layer





http://en.wikipedia.org/wiki/Ethernet


http://en.wikipedia.org/wiki/Token_bus


http://en.wikipedia.org/wiki/Token_Ring


http://en.wikipedia.org/wiki/Metropolitan_Area_Network






• IEEE 802.11 Wireless LAN

• IEEE 802.12 demand priority

• IEEE 802.13 (not used)

• IEEE 802.14 Cable modems (disbanded)

• IEEE 802.15 Wireless PAN

• IEEE 802.16 Broadband wireless access

• IEEE 802.17 Resilient packet ring

• IEEE 802.18 Radio Regulatory TAG

• IEEE 802.19 Coexistence TAG

• IEEE 802.20 Mobile Broadband Wireless Access

• IEEE 802.21 Media Independent Handoff

• IEEE 802.22 Wireless Regional Area Network

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http://en.wikipedia.org/wiki/Wireless_LAN


http://en.wikipedia.org/w/index.php?title=IEEE_802.14&action=edit

http://en.wikipedia.org/wiki/Cable_modem


http://en.wikipedia.org/wiki/Wireless_PAN


http://en.wikipedia.org/wiki/Broadband_wireless_access



http://en.wikipedia.org/w/index.php?title=IEEE_802.19&action=edit





Addendum 6

Further Reading

Title: Protocols and architectures for wireless sensor networks; Catalog Number: 131353; Author: Karl, Holger and Willig, Andreas; Subject: LAN (Local Area Network), computer networks, communication, sensors; Publisher: Wiley; Year Published: 2006; ISBN: 0-470-09510-5 Library: ESTEC – NL; Shelf Location: 561.2.KAR; Item ID: 400085129 Title: Protocols for high-efficiency wireless networks; Alternate Title: ISBN 1-4020-7326-7; Catalog Number: 50041; Author: Andreadis, A.; Giambene, G.; Subject: mobile communication systems, satellite communication; Publisher: Kluwer Academic Publishers; Year Published: 2003 Library: ESTEC – NL; Shelf Location: 560.AND; Item ID: 400077531 Title: Ultra-wideband communications: Fundamentals and applications; Catalog Number: 131436; Author: Nekoogar, Faranak; Subject: wideband communications, broadband; Series/Contract: Prentice Hall Communications engineering and emerging technologies series; Publisher: Prentice Hall; Year Published: 2006; ISBN: 0-13-146326-8 Library: ESTEC – NL; Shelf Location: 561.NEK; Item ID: 400085204 Title: UWB [Ultra-wideband communications]: Theory and applications; Catalog Number: 131658; Author: Opperman, Ian; Hamalainen, Matti; Iinatti, Jari; Subject: wideband communications, broadband; Publisher: Wiley; Year Published: 2004; ISBN: 0-470-86917-8 Library: ESTEC – NL; Shelf Location: 561.OPP; Item ID: 400085466 Title: 802.11 WLANs and IP networking: Security, QoS and mobility; Catalog Number: 131486; Author: Prasad, Anand R. and Prasad, Neeli R.; Subject: LAN (Local Area Network), computer networks, communication, standards, security; Series/Contract: Artech House mobile communications library; Publisher: Artech House; Year Published: 2005; ISBN: 1-58053-789-8 Library: ESTEC – NL; Shelf Location: 561.2.PRA; Item ID: 400085288 Title: Microwave devices, circuits and subsystems for communications engineering; Catalog Number: 131437; Author: Glover, I.A., Pennock, S.R., Shepherd, P.R.; Subject: microwave circuits, microwave equipment; Publisher: Wiley; Year Published: 2005; ISBN: 0-471-89964-X Library: ESTEC – NL; Shelf Location: 506.GLO; Item ID: 400085205

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Title: Technologies for the wireless future: Wireless World Research Forum (WWRF); Catalog Number: 131435; Author: Tafazolli, Rahim; Subject: computer networks, communication, wireless communication systems; Publisher: Wiley; Year Published: 2005; ISBN: 0-470-01235-8 Library: ESTEC – NL; Shelf Location: 561.2.TAF; Item ID: 400085203 Title: Advanced RF engineering for wireless systems and networks; Catalog Number: 131434; Author: Hussain, Arshad; Subject: computer networks, communication, wireless communication systems; Publisher: Wiley; Year Published: 2005; ISBN: 0-471-67421-4 Library: ESTEC – NL; Shelf Location: 561.2.HUS; Item ID: 400085202 Title: OFDM for wireless multimedia communications; Alternate Title: ISBN 0-89006-530-6; Catalog Number: 50355; Author: Van Nee, R.; Prasad, R.; Subject: telecommunication, multimedia; Publisher: Artech Housem Publishers; Year Published: 2000 Library: ESTEC – NL; Shelf Location: 560.NEE; Item ID: 400078029 Title: Wireless communications; Catalog Number: 131532; Author: Molisch, Andreas F.; Subject: computer networks, communication, wireless communication systems; Publisher: IEEE Press/Wiley; Year Published: 2005; ISBN: 0-470-84888-X Library: ESTEC – NL; Shelf Location: 561.2.MOL: Item ID: 400085334 Title: RFID and beyond: Growing your business through real world awareness; Catalog Number: 131533; Author: Heinrich, Claus; Subject: inventory management, radio frequencies, automation; Publisher: Wiley; Year Published: 2005; ISBN: 0-7645-8335-2 Library: ESTEC – NL; Shelf Location: 090.HEI; Item ID: 400085382 Title: The innovator's dilemma: When new technologies cause great firms to fail; Catalog Number: 131490; Author: Christensen, Clayton M.; Subject: business management, creativity; Series/Contract: The management of innovation and change series; Publisher: Harvard Business School Press; Year Published: 1997; ISBN: 0-87584-585-1 Library: ESTEC – NL; Shelf Location: 090.CHR; Item ID: 400085293 Title: Cognitive Radio Technology; Editor: Bruce A. Fette, General Dynamics, U.S.; ISBN: 0750679522, ISBN-13: 9780750679527; Year Published: September 2006. Title: Mars Analog Research, includes CD-ROM; Alternate Title: AAS science and technology series, Vol. 111; Catalog Number: 132083; Author: Clarke, Jonathan D.A.; Corporate Source: AAS science and technology series; Subject: Mars (planet); Publisher: Univelt for American Astronautical Society (AAS); Year Published: 2006; ISBN: 978-0-87703-529-9; ISSN: 0278-4017; Catalog Notes: + CD-ROM Library: ESTEC – NL; Shelf Location: 797.SCI; Item ID: 400085683

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Space-based MANETs 1x1. https://www.cs.tcd.ie/Stephen.Farrell/ipn/background/challenges.pdf 1x2. Considerations on Communications Network Protocols in Deep Space http://ieeexplore.ieee.org/iel5/7416/20151/00931276.pdf?isnumber=&arnumber=931276 GPS for Satellite On-orbit localisation 1y1. http://tebinuma.tripod.com/publications/b10_ACA2004.pdf Wireless Spacecraft Bus 1z1. Wireless Spacecraft Bus- A Radio Frequency based data communication architecture, Dr. Min Song, Sachin Shetty, Dr. Bob Ash, Kenneth Bone, Old Dominion University, ICNS Conference, May 2005. http://spacecom.grc.nasa.gov/icnsconf/docs/2006/02_Session_A1/07-Song.pdf Biomedical, Wireless and ESA’s LEON2 Microprocessor 1a1. A Wireless Communication Platform [based on ESA’s LEON2 microprocessor] for Long-Term Health Monitoring, Fourth Annual IEEE International Conference on Pervasive Computing and Communications Workshops 2006 (PERCOMW'06), pp. 474-478, Daniel Dietterle, Jean-Pierre Ebert, Gerald Wagenknecht, Rolf Kraemer, IHP microelectronics GmbH, Germany. http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/proceedings/&toc=comp/proceedings/percomw/2006/2520/00/2520toc.xml&DOI=10.1109/PERCOMW.2006.25 1a2. The Body Area System for Ubiquitous Multimedia Applications (BASUMA) Project. http://www.basuma.de/index.php?lang=en 1a3. LEON-2: General Purpose Processor for a Wireless Engine, Z. Stamenković, C. Wolf, G. Schoof, IHP GmbH, Frankfurt (Oder), Germany and J. Gaisler, Gaisler Research, Göteborg, Sweden. http://ieeexplore.ieee.org/iel5/10974/34591/01649569.pdf?isnumber=34591&prod=CNF&arnumber=1649569&arSt=+48&ared=+51&arAuthor=+Stamenkovic%2C+Z.%3B++Wolf%2C+C.%3B++Schoof%2C+G.%3B++Gaisler%2C+J. More Wireless on European Aircraft 1b1. Proposed EADS RF Wireless Sensors and RFID on European Aircraft www.innosys-nrw.de/file.php?file=/MEDEA_DAC/4.2.-Bovelli.pdf&type=down History and Future of Wireless

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http://tebinuma.tripod.com/publications/b10_ACA2004.pdf

http://spacecom.grc.nasa.gov/icnsconf/docs/2006/02_Session_A1/07-Song.pdf

http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/proceedings/&toc=comp/proceedings/percomw/2006/2520/00/2520toc.xml&DOI=10.1109/PERCOMW.2006.25



http://www.basuma.de/index.php?lang=en

http://ieeexplore.ieee.org/iel5/10974/34591/01649569.pdf?isnumber=34591&prod=CNF&arnumber=1649569&arSt=+48&ared=+51&arAuthor=+Stamenkovic%2C+Z.%3B++Wolf%2C+C.%3B++Schoof%2C+G.%3B++Gaisler%2C+J.



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1c1. The Evolution of Untethered Communications, Committee on Evolution of Untethered Communications [for DARPA], Computer Science and Telecommunications Board, Commission on Physical Sciences, Mathematics, and Applications, National Research Council (U.S.), National Academy Press, Washington, D.C. 1997. http://fermat.nap.edu/html/evolution/index.html ___________________________________________________________________ Other Refs Leon Microprocessor and Wireless 1d1. Web site for a U.S. manufacturer of tracking devices based on the Leon2 microprocessor and WLAN IEEE 802.11b that incorporates functions of high-rate data communications, ranging and localization and embedded sensors, G2 Microsystems. http://www.g2microsystems.com/ NASA Space Communications SBIR July 2006 1e1. National Aeronautics and Space Administration Small Business Innovation Research & Technology Transfer 2006 Program Solicitations, TOPIC: O1 Space Communications http://sbir.nasa.gov/SBIR/sbirsttr2006/solicitation/SBIR/TOPIC_O1.htmlhttp://sbir.nasa.gov/SBIR/sbirsttr2006/solicitation/index.html Misc. Refs 1f1. Wireless Sensor Networks for Area Monitoring and Integrated Vehicle Health Management Applications, Henry O. Marcy, Jonathan R. Agre, Charles Chien, Loren P. Clare, Nikolai Romanov, and Allen Twarowski, Rockwell Science Center, Thousand Oaks, CA 91360, AIAA-1999-4557, AIAA Space Technology Conference and Exposition, Albuquerque, NM, Sept. 28-30, 1999. http://wins.rockwellscientific.com/publications/WINS_for_AIAA_99-4557.pdfhttp://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=3222 1f2. The Space Communications Architecture Working Group (SCAWG) 2005 report of NASA Space Communications and Navigation Architecture Recommendations for the years 2005-2030. https://www.spacecomm.nasa.gov/spacecomm/programs/architecture.cfm DTN – Delay Tolerant Networking IETF and / or for space 1g1. LTP-T: A Generic Delay Tolerant Transport Protocol, Stephen Farrell, Vinny Cahill, Distributed Systems Group, Department of Computer Science, Trinity College Dublin, Ireland. https://www.cs.tcd.ie/publications/tech-reports/reports.05/TCD-CS-2005-69.pdf

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http://www.g2microsystems.com/

http://sbir.nasa.gov/SBIR/sbirsttr2006/solicitation/SBIR/TOPIC_O1.html

http://sbir.nasa.gov/SBIR/sbirsttr2006/solicitation/index.html

http://wins.rockwellscientific.com/publications/WINS_for_AIAA_99-4557.pdf

http://www.aiaa.org/content.cfm?pageid=406&gTable=mtgpaper&gID=3222

https://www.spacecomm.nasa.gov/spacecomm/programs/architecture.cfm

https://www.cs.tcd.ie/publications/tech-reports/reports.05/TCD-CS-2005-69.pdf


ADD RESEARCH REFS ON FLY-BY-WIRELESS AIRCRAFT (3) ADD REF TO NASA STUDIES ON SPACE-BASED MANETS (4) ADD PAPERS ON CROSS LAYER SUPPORT FOR SPACE ASSETS (5) ADD REF TO NASA STUDIES ON WIRELESS EMC FOR AIRCRAFT (2) ADD REF TO ESA D-SCI TRS PAPERS / WEBSITE (4) ADD OTHER TNs FROM ESA OWDT PROJECT OUTPUT (4) ADD PAPERS ON FORMATION FLYING (15) ADD PAPERS ON ROBOTICS AND ISAIRAS CONFERENCE (6) ADD PAPERS ON MEMS FROM ESA MICRO-NANO CONFERENCE (4) ADD RELATED FROM WIRELESS NEWSLETTER, e.g. MIT SWARM (15) ADD LATEST CCSDS SOIS BOOK REFS (5) ADD OTHER PAPERS ON SWARM CONCEPTS (3) ADD PAPERS ON GPS FOR SATELLITE ON-ORBIT LOCAIZATION (5) ADD OTHER PAPERS ON MULTI-HOP PROTOCOLS (2) ADD OTHER LATEST AIAA PAPERS WIRELESS REFS (8) ADD OTHER PAPERS FROM ESA SDSS, CHEOPS ETC. (3) ADD PAPERS FROM ESA ADVANCED CONCEPTS 2006 WORKSHOP (3) http://www.esa.int/gsp/ACT/ariadna/ongoing_studies_05_4109.htm ADD PAPERS ON RF WIRELESS AND MEMS (6) ADD PAPERS ON WIRELESS, SPACE BIOMEDICAL AND TELEMEDICINE (12) ADD PAPERS ON ON-ORBIT ASSEMBLY (7) ADD PAPERS ON FROM ESA ACT (FEB 2006) SYMPOSIUM (3)

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ADD PAPERS ON SMART DUST (5) ADD PAPERS ON WIRELESS FOR AIRCRAFT (5) ADD PAPERS ON DELAY TOLERANT NETWORKS FOR SPACE -- DTNs (7)

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short-range rf wireless proximity networks technology assessment

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