aeronautical communications panel joint meeting …

DRAFT ACP/WGM9/WP__

1 Version 1.0

AERONAUTICAL COMMUNICATIONS PANEL

Joint Meeting

WORKING GROUP M

9th Meeting

Montreal, 26 October – 02 November 2004

WORKING GROUP B

17th Meeting

Montreal, 20-29 October 2004

Agenda Item 3: On-board integration issues with VDL Modes 2, 3 and 4.

VDL Mode 4 Cosite Interference Investigations: Status report

Prepared by N. Fistas and John Micallef, EUROCONTROL

SUMMARY

This paper provides information on the current activities in EUROCONTROL in relation to the VDL Mode 4 cosite investigations.

Following discussions with interested partners a VDL Mode 4 Cosite Investigations Plan was agreed. Using this plan, EUROCONTROL has initiated the work which is divided in three phases. This paper provides a description of the key activities in these phases and presents a status of the current work (in Phase 1).

In addition the paper provides information for other EUROCONTROL activities in the framework of cosite investigations. In particular, it describes the results of the analysis EUROCONTROL has undertaken to develop a profile of DSB-AM voice transmissions as well as the analysis of the expected power levels of desired voice receptions.

DRAFT ACP/WGM9/WP__

2 Version 1.0

1 Background The VDL Mode 4 Airborne Integration Study (VM4AAS) provided an analytical investigation of the co-site interference performance of DSB-AM, VDL Mode 2 and VDL Mode 4 when any two of them would operate simultaneously.

In terms of the co-site interference the principal conclusion of the study is that co-site VHF interference between DSB-AM and VDLs (in general) or between VDLs is unlikely to be further mitigated by technical means. As a result of this conclusion the study proposed to investigate in detail the impact of interference into the operational use of voice as well as datalink.

The cosite interference was considered previously in ICAO as issue to an implementation issue and therefore it was not fully addressed in the development of SARPs material. However the issue was discussed in ANConf/11 (October 2003) and it was decided that the question of the cosite interference should be addressed at ICAO level. As a result, ACP is tasked to investigate the cosite impact of the considered systems.

1.1 Cosite Investigations Plan for VDL Mode 4 As a follow up of the VM4AAS work, EUROCONTROL hosted a meeting on the 12th of March 2004 to discuss the next steps in the cosite investigations for VDL Mode 4. The meeting was attended by various participants interested in the VDL Mode 4 investigations. A draft investigations plan was discussed as initial input and finally agreed among the participants.

Attachment 1 of this working paper is the VDL Mode 4 Cosite Investigations Plan as agreed in the meeting of the 12th March 2004.

2 Work Plan and Current Status Based on the agreed plan and in general the discussion in the above meeting, EUROCONTROL is scheduling the cosite investigations in three phases.

The first phase deals with the development of cosite interference testing scenarios to represent real operational cases of cosite interference and the detailed testing plans in the form of executable instructions for how to do the testing. The detailed plans will be on a per system basis and the priority will be given to the investigations in relation to voice DSB-AM. Impact to and from other systems will be considered as required depending on the indications of investigations.

The second phase (Phase 2) will be the execution of the testing plans developed by Phase 1 and the documentation of the results.

The third phase (Phase 3) will put together (evaluate and analyse) the testing results together with other input as required (e.g. simulations) aiming to produce a report detailing the operational impact of the cosite interference in the VDL Mode 4 case.

As already mentioned, the key priority of the above work is the cosite impact between VDL Mode 4 and DSB-AM. Currently, EUROCONTROL has placed a contract with ISA Telecoms for the Phase 1 work. The final results of Phase 1 work are expected to be available by the end of 2004. However, a presentation of the status of the ongoing work will be made to this joint WGM and WGB meeting for the early information of the ACP participants and to request comments on the approach taken.

Overall, the target is to have the final results (especially in relation to voice DSB-AM) completed by Q3 2005.

DRAFT ACP/WGM9/WP__

3 Version 1.0

3 Other relevant work

3.1 Investigation into voice transmission profile In relation to the cosite investigations and to support the investigations, EUROCONTROL has developed a report on the DSB-AM voice transmission by an aircraft. The report used real data for one European airline and analysed the information to provide statistics for:

minimum and maximum number of voice transmissions

minimum and maximum duration of a single voice transmission

cumulative voice transmission times and load as percentage of flight time

statistical analysis of voice transmissions (average duration and standard deviation)

analysis of voice transmissions over the phases of flight (take off, climb, cruise,

descend, and land)

probability distribution of duration of voice transmissions

analysis for simultaneous and chained voice transmissions

The report provides some limited analysis for the HF voice transmissions and concludes with recommendations for a detailed DSB-AM voice transmissions profile.

The report also proposes a simplified profile as described in the following Table:

Short/Medium/Long – haul flights ATC AOC ATC+AOC

Standard load (% of flight time): 3.5/2.5/2 0.5 4/3/2.5 Standard duration (s): 4 6 5 Average number of transmissions 70/105/150 10/15/20 80/120/170

Average nb of transmissions – Take off 10 2 12 Average nb of transmissions – Climb 19 1 20 Average nb of transmissions – Cruise 12/42/84 2/5/11 14/47/95 Average nb of transmissions – Descend 30 4 34 Average nb of transmissions – Land 8 2 10

Probability (%)that a transmission will be greater than x seconds X=1 95 90 95 X=2 65 70 65 X=3 45 50 45 X=4 25 40 27 X=5 15 35 20 X=6 10 30 15 X=7 8 25 10 X=8 7 22 8 X=9 6 20 7 X=10 5 18 6 X=15 2 15 5 X=20 1 10 2 X=25 0.1 5 1 X=30 0.01 1 0.2

Table 1: DSB-AM voice profile for short/medium/long -haul flights The above DSB-AM voice transmissions profile proposed in the above report will be used in the VDL Mode 4 cosite investigations to characterise the DSB-AM interferer case.

Attachment 2 of this paper is the detailed report with the voice transmissions profile.

DRAFT ACP/WGM9/WP__

4 Version 1.0

3.2 Preliminary investigation into voice receptions The report described in the previous section addressed only the voice transmissions. To complete the picture it is important to have information also on the voice receptions.

The development of a detailed voice reception profile on board an aircraft would be useful. However the extrapolation of real transmissions data for the reception profile is a complex process requiring knowledge of the traffic distribution as well as the respective power levels pf the received voice messages during the various phases of flight.

As an alternative an estimation of the minimum received power levels of the desired signals was developed. Table 2 is summarising the conclusions of the report of this investigation:

Scenario Phase Victim Aircraft location

Min Received Signal (dBm)

Distance (Km)

Ground Departure Taxiway/Runway - 75 3

Climb Departure TMA - 80 150

En route En route - 82 200 Airborne

Descent Arrival TMA - 80 150

Ground Arrival Taxiway/Runway - 75 3

Table 2: Minimum received voice signal level onboard an aircraft (per flight phase) and corresponding distance to transmitter

Attachment 3 of this paper is the detailed report on the received voice signal levels.

3.3 Internet information dissemination All attachments of this working paper can also be downloaded from the EUROCONTROL VDL Mode 4 webpages at the following address:

http://www.eurocontrol.int/vdl4/public/subsite_homepage/homepage.html

Of particular relevance is the subpage for “Cosite” under the “Activities” page:

http://www.eurocontrol.int/vdl4/public/standard_page/cosite.html

ACP/WGM9/WP__ Attachment 1 to ACP/WGM9 paper: “VDL Mode 4 Cosite Interference Investigations: Status Report”

VDL Mode 4 Cosite Investigations Plan

1 version 1.0

VDL Mode 4 Cosite Investigations’ Plan

(Operational impact of the VHF cosite interference in the VDL Mode 4 case)

1 Introduction The purpose of this plan is to describe the activities, which should be performed to analyse and investigate the cosite interference impact in the VDL Mode 4 case. This plan describes activities that are to be performed by various interested parties. The plan intends to identify all relevant required activities on the understanding that not all activities are of the same priority and importance/criticality. This version takes into account the discussions and the comments by the participants of the meeting organised by EUROCONTROL on the 12 March 2004 aiming at planning and coordinating the relevant activities. In this meeting there were participants from Airbus, Avtech, EUROCONTROL, LFV, OTE, and Rockwell-Collins. A brief summary of the meeting’s discussions and presentations is provided in Appendix 1.

1.1 Background Co-site interference is not an issue specific to VDL Mode 4 but applies to all VHF systems used in aircraft. Since DSB-AM voice, ACARS, VDL2 and VDL4 systems may operate in the same platform, co-site interference due to interactions between these systems is likely to occur and needs to be quantified. In particular for VDL4, since it is considered as a candidate for advanced and critical datalink applications for communication as well as surveillance applications, its sensitivity to co-site interference merits detailed analysis. The following interference cases need to be distinguished in general:

• Transmission on transmission interference • Transmission on reception interference

1.2 Scope The first interference case (transmission to transmission) is not raising concerns especially in an end state implementation as described in the VDL Mode 4 Airborne Architecture Study (Deliverable D3.1, architecture comprising interconnected multi-mode radios1 and using existing antennas. In the case of a single multimode radio being installed/used, then the possibility of interfering with transmissions is possible. However, this is rather an issue of conflict/priority between the supported applications than a cosite transmission to transmission interference case. Therefore this case will not be considered in this plan. This investigations’ plan concentrates in the main co-site interference problem that is transmission on reception interference.

1 Availability of multimode radios (supporting DSB-AM, VDL2, VDL4 ..) would facilitate integration of VDL4

onboard the a/c avoiding the need to install new antennas, and minimising the impact on space (no new boxes), maintenance and logistics. Multimode radios can support transmission co-ordination thus minimising transmission conflicts (e.g. they can mitigate transmission to transmission interference) but they cannot prevent VHF transmission on reception interference.



2 version 1.0

The transmission to reception interference analysis in the VDL Mode 4 case can be further classified in the following sub cases2:

• VDL Mode 4 transmissions on DSB-AM voice reception • DSB-AM voice transmissions on VDL Mode 4 reception • VDL Mode 2 transmissions on VDL Mode 4 reception • VDL Mode 4 transmissions on VDL Mode 2 reception • VDL Mode 4 transmissions on VDL Mode 4 reception

It is important to point out that from the above cases the first priority should be to examine the cases of the cosite interference involving DSB-AM voice, as this is the only system for which a clear co-existence requirement will be applicable. However the other cases are also of interest in order to complete the analysis and provide input on decisions. Furthermore, it is important to note that as is the case today, there will be (is) some level of co-site interference. Therefore in these co-site investigations we need to determine the maximum operationally acceptable level of co-site interference (this may be application specific and phase of flight dependent). The following sections will describe the required investigations for the identified cases. This investigation plan will be the starting point to develop detailed plans for testing for each of the considered cases.

2 Impact of VDL Mode 4 transmissions to DSB-AM voice reception The impact of VDL Mode 4 transmissions on the voice receptions will depend mainly on the duration, frequency and power of transmissions for the transmitter side and the duration and power of received voice signal for the receiver side. If the VDL4 transmission is sufficiently long and/or strong to lift the squelch, then there will be audible interference (clicks corresponding to the VDL4 transmissions). If the VDL4 transmission is short/weak and does not lift squelch, then the impact of the audio clicks will be restricted to periods of reception of DSB AM voice transmissions. In addition to the above, the successful reception of low power voice transmissions (e.g. from distant aircraft/ground stations) in the presence of VDL4 transmissions need to be investigated.

2.1 Required information For the investigations it is required to obtain information in relation to the:

• VDL4 transmission load (cases for point to point, broadcast, ATC and AOC) • DSB AM voice receptions.

See Appendix 2 for load information.

2 This plan assumes operation of VDL Mode 4 in the band 118 to 137 MHz. The cosite interference impact of

VDL Mode 4 to and from systems operating in the VHF NAV band (ILS, VOR, GBAS) should also be accessed if VDL Mode 4 frequencies were to be assigned in this band (108 to 118 MHz). Furthermore, this plan focuses on VDL Mode 4. Other ongoing activities consider the VDL Mode 2 cosite investigations especially in relation to DSB-AM voice. These investigations are not covered by this plan.



3 version 1.0

2.2 Testing Need to develop detailed testing scenarios to reproduce real cases and carry out measurements. It was agreed that the testing scenarios need only to examine the cases when squelch is lifted. Lab (or controlled environment) testing seems more appropriate as it will allow to set up more correctly the different scenarios. Flight testing need also be considered (possibly in a second step) to confirm/verify the results of the lab testing in a real environment. It is proposed to measure various parameters (signal strength etc) as well as to record voice receptions in the presence of cosite interference to be analysed by listening panels or serve a record of the performance.

3 Impact of DSB-AM voice transmission to VDL Mode 4 reception The impact of voice transmissions to VDL Mode 4 receptions will depend on the duration and power of the voice transmissions and the duration and power of intended for reception VDL Mode 4 messages. The potential impact in this case would be the garbled reception of VDL4 transmissions from other aircraft/ground stations. Depending on the isolation achieved between transmission and reception subsystems, loss of reception might be complete (blanking) or it could depend on the received signal power level (hence the distance between the aircraft and the "victim" transmitter).

3.1 Required information to perform the testing For the investigations it is required to obtain information in relation to the:

• VDL4 expected receptions (cases for point to point, broadcast, ATC and AOC) • DSB AM voice transmission load.

See Appendix 2 for load information.

3.2 Testing Need to develop detailed testing scenarios to reproduce real cases and carry out measurements. The testing scenarios need to examine the impact to time critical applications supported by VDL Mode 4 for the following cases:

• Impact to point to point communications • ATC • AOC (likely to be of longer duration than ATC)

• Impact to broadcast transmissions As the VDL Mode 4 protocols already consider losses of some messages, the testing (or analysis) should examine:

• For broadcast transmissions, the likeliness that voice transmissions are longer than two VDL Mode 4 consecutive transmissions,

• For point to point transmissions, the likeliness that voice transmissions span a longer period than the VDL Mode 4 retransmission timers’ expiration period.



4 version 1.0

Lab (or controlled environment) testing seems more appropriate as it will allow to set up more correctly the different scenarios. Flight testing need also be considered (possibly in a second step) to confirm/verify the results of the lab testing in a real environment.

4 Impact of VDL Mode 2/4 transmissions to VDL Mode 4/2 receptions The impact of VDL Mode 2/4 transmissions to VDL Mode 4/2 receptions will depend on the duration frequency and power of the VDL Mode 2/4 transmissions and the duration frequency and power of intended for reception VDL Mode 4/2 messages. The potential impact would be the garbled reception of VDL transmissions from other aircraft/ground stations. Depending on the isolation achieved between transmission and reception subsystems, loss of reception might be complete (blanking) or it could depend on the received signal power level (hence the distance between the aircraft and the "victim" transmitter). At this stage, the cosite investigations address primarily the impact in relation to the voice DSB-AM system. The information for the inter-VDL impact will be useful and important in considerations to operate simultaneously and with no coordination on the same platform, multiple VDL systems. However, as this is not really decided/agreed at this stage, these investigations are proposed to be considered following the DSB-AM investigations.

5 Impact of VDL Mode 4 transmission to VDL Mode 4 reception It was agreed that in general, as VDL Mode 4 supports organised media access, this case is not of particular concern, especially as in the end state there will be different channels supporting the bulk of point to point and broadcast applications. This type of interference may occur with use of random access protocols and with no valid reservation table information. It may be worthy, however to confirm the impact on VDL Mode 4 applications of such interference in the specific case of increased random access and increased broadcast load. The case to consider would be information to be received from other a/c transmitting with no reservation and the destination a/c transmitting in the slot containing also the received transmission.

6 Impact to and from systems in the NAV band This section is provided as a placeholder to describe future investigations to address the cosite interference impact to and form systems operating in the NAV band. If the frequency assignments for VDL Mode 4 are only above 118 MHz, then such investigations are not necessary. If such investigations will be done, then the frequency band 112 to 118 MHz should be of considered in accordance with the EUROCAE and ETSI documents3.

7 Evaluation of Results

7.1 Impact to DSB-AM To analyse this impact measurements and recordings of interfered voice transmissions to be evaluated by listener's panels would be required.

3 WRC2003 has allowed the use of VDL Mode 4 in the complete 108 to 118 MHz Navigation band, under the

condition that priority is given to the navigation service. However, the EUROCAE and ETSI specifications cover only the 112-137 MHz frequency band.



5 version 1.0

7.2 Impact to VDL Mode 4 We can foresee two types of investigations:

1) what is the actual (“instantaneous”) impact on specific cases and 2) with simulations to estimate the overall impact on link performance (capacity,

throughput, etc) in an environment that includes cosite interference.

7.3 Impact to VDL Mode 2 To be considered in a next step. As considered in other ongoing investigations (cosite impact of VDL Mode 2 and DSB-AM)

7.4 Impact to NAV Band systems To be considered in a next step

8 Activities and Scheduling The following specific activities have been identified: Development of Cosite Interference Scenarios: Identify and describe testing scenarios to

reproduce real cases. Development of Detailed Testing Plans: Using the relevant scenarios, develop detailed

testing plans that could be carried out and repeated by interested parties and specify what is required to be measured. There will be separate testing plans for the different investigations.

Review of Scenarios and Plans: Provide comments and enhance the scenarios and the testing plans.

Measurements: Using the detailed testing plan, carry out the measurements. It is not intended (and is unlikely) that the measurements for the different investigation will be carried out all by the same team.

Simulations (for VDL Mode 4): Using input from measurements and analysis carry out performance and capacity simulation involving different loading and application scenarios to predict the impact on performance.

Confirmation of results: Perform additional measurements (as required), flight testing (as appropriately) and analysis to confirm the validity of measurements (especially) results.

Evaluation of results: Analyse and evaluate the results to characterise the cosite interference impact of the VDL Mode 4 operation.

The following table indicates the likely participation and contributions of various participants in the different activities as discussed in the 12/03/04 meeting in EUROCONTROL.

Sce

nario

s

Test

ing

Pla

ns

Rev

iew

Mea

sure

men

ts

Sim

ulat

ions

Con

firm

atio

n

Eva

luat

ion

Airbus y Avtech ? ? EUROCONTROL y y ? y y LFV y y ? y y OTE Y y Rockwell-Collins Y y y

TABLE 1: Participation and Contributions



6 version 1.0

The above is not an exhaustive list as additional partners may also participate in carrying out these activities and changes may occur also for the mentioned partners. The following figure shows the likely interactions and sequencing of the cosite investigations activities as described in this plan. The big arrows represent other external input.

FIGURE 1: Sequencing of activities

9 Timeline In terms of timing, the target is to have a report describing the cosite impact at least in relation to voice DSB-AM by the end of 2004. It is highlighted that the timely execution of this plan depends on all the contributors to these investigations. Advance planning is important and each participant needs to ensure the timely sequence and execution of the activities under their responsibility. In order to initiate the planning, it was agreed that the output of the Scenarios and Testing Plans activities should be available in May 2004. It is understood that an iterative process may be required between these two activities (refinement of the scenario description taking also input for the testing plan description). This first priority in this plan will be to carry out the investigations described in sections 2 and 3 of this plan (impact to DSB-AM and VDL Mode 4).

Scenarios

Testing Plans

Review

Measurements

Simulations

Confirmation

Evaluation



7 version 1.0

Appendix 1: Brief Meeting Report

Planning of VDL mode 4 Cosite Investigations Meeting

12/03/04, EUROCONTROL Introduction EUROCONTROL hosted an informal meeting to discuss and coordinate the activities in relation to the cosite investigations for VDL Mode 4. The first objective of the meeting was to agree on a plan of VDL Mode 4 activities that need to be undertaken to satisfactorily address the cosite interference questions and to be able to provide clear information on the operational impact of cosite interference. The second objective of the meting was to discuss and agree on potential cooperation and collaboration among parties in carrying these activities. In the meeting there were participants from Airbus, Avtech, EUROCONTROL, LFV, OTE, and Rockwell-Collins. The company Chelton also participated and presented their cancellation techniques for information. CNS Systems and Telerad were not able to participate but they have asked be kept informed of the developments as they would be interested to participate. In the first part of the meeting, there were various presentations for information and in the second part of the meeting there was detailed discussion on a draft investigation’s plan and the coordination of the relevant activities. The agenda of the meeting was as follows:

Item By 1. Introduction - Objectives EUROCONTROL

2. Presentations 2.1 Voice DSB-AM usage profile EUROCONTROL 2.2 Interference cancellation techniques Chelton 2.2 Proposed strategy and activities for cosite investigations LFV 2.3 Presentation on VMMR Study Rockwell Collins

3. Draft Investigations Plan ALL

4. Discussion – Next Steps ALL 4.1 Refinement of Plan 4.2 Coordination of future activities

Summary of Presentations This section provides the main points of the presentations. The complete presentations are available form the EUROVONTROL VDL Mode 4 webpages in: http://www.eurocontrol.int/vdl4/otheractivities.html. EUROCONTROL presented a draft paper, which described the analysis of data from an airline about the voice DSB-AM transmissions during a flight. It was agreed that this will be a useful tool in the investigations and comments were made to improve the draft paper and also to identify other missing information, which will be useful in the investigations. The



8 version 1.0

importance of data also for the voice DSB-AM reception profile (in addition to transmissions) was highlighted. EUROCONTROL will complete the analysis and update the document to take into account the comments that will be received. Bob Horner from Chelton presented their interference cancellation technology. This system is used in military platforms, and is based on the principle of cancelling the cosite transmission interference by injecting in the received signal a suitably adjusted and with opposite phase signal. This technology could be used to avoid receiver saturation as the reaction time is short. It was indicated that this technology can be used to cancel within 15 microseconds, undesired cosite signals that are up to 100 KHz close to the desired signal and with a transmission power of 50W to 100W. The system is a passive device and there is an insertion loss of 1 to 2 dBs. LFV presented a proposal on a roadmap of activities to pursue for the cosite investigations. The proposed approach involves the development of statistical/probability model to give a realistic view of the cosite interference and application of the model on the various applications. At a second stage, a series of testing will need to be carried out in the real environment to verify the validity of the model. This presentation provided input for the investigations plan discussion. Rockwell Collins presented an overview of their study to develop a VHF Multi-Mode Receiver which is being carried out in WP27 of the NUPII. This Study uses the RC VHF2100 radio as a baseline and investigates the integration of VDL Mode 4 in terms of technical and industrial (market value) feasibility. In the technical aspect the study is progressing satisfactorily and a few remaining issues are to be addressed. The study is now addressing the market value and the projected cost of the radio with assumptions for the applications to be supported (the technical solutions contribute to costs and ultimately the applications determine the value). The final study results are expected in May 2004. Discussion on the investigations’ plan EUROCONTROL presented a draft plan to initiate the discussion and facilitate the progress. The purpose of the presented plan was to describe a view on the activities, which should be performed to analyse and investigate the cosite interference impact in the VDL Mode 4 case. It was clarified that the plan described activities that are to be performed by various parties interested in the outcome of these investigations. The VDL Mode 4 cosite investigations are included also in the intended work programme of NUP II (WP27, lead by Avtech). Investigations should be coordinated. The draft plan was discussed in detail and amendments were agreed during the discussions based on the input of the participants. A new amended plan has been agreed (VDL Mode 4 Cosite Investigations Plan, version 1.0). This agreed plan will be the starting point to develop detailed plans for testing for the various cosite interference cases. This plan will also be sent to ICAO/ACP for information and comments. In summary, the following specific activities were identified in the meeting and agreed that need to be carried out:

• Development of Cosite Interference Scenarios • Development of Detailed Testing Plans for Cosite Interference • Review of Scenarios and Plans • Measurements • Simulations (for VDL Mode 4 performance)



9 version 1.0

• Confirmation of results • Evaluation of results

In terms of timing, the target is to have a report describing the cosite impact at least in relation to voice DSB-AM by the end of 2004. It is highlighted that the timely execution of this plan depends on all the contributors to these investigations. Advance planning is important and each participant needs to ensure the timely sequence and execution of the activities under their responsibility. In order to initiate the planning, it was agreed that the output of the Scenarios and Testing Plans activities should be available in May 2004. It is understood that an iterative process may be required between these two activities (refinement of the scenario description taking also input for the testing plan description). List of participants: Name Company/Organisation Patrick Lelievre Airbus Bengt Nilsson Avtech Bob Horner Chelton Fredrick Lindblom LFV Paolo Maltese OTE Okko Bleeker Rockwell Collins Clotilde Gonzalez Rockwell Collins Rick Heinrich Rockwell Collins Nikos Fistas EUROCONTROL John Micallef EUROCONTROL Costas Tamvaclis EUROCONTROL



10 version 1.0

Appendix 2: Load information to be considered in the cosite

investigations. This appendix provides only the sources of information to be used. The detailed loading to be used is required to be provided in the detailed testing plans. VDL Mode 4 For the VDL Mode 4 transmission load (transmission and reception) we can use information from the testing plan for the development of frequency planning criteria for VDL Mode 4. We also consider the loading information developed for the cosite evaluation of the LINK2000+ applications (using VDL Mode 2). It was suggested that the ICAO OPLINK Panel may also have information on the loading for datalink applications. DSB-AM voice For the DSB AM voice transmission load, EUROCONTROL has analysed data describing the voice VHF DSB-AM transmissions originating from an aircraft for all types of communications (ATC and AOC). A report on the results is finalised and this will provide the required information for the investigation. For the voice receptions we need information on the frequency (rate), duration, and the signal strength of the received message. (Does such information exists? How to get this information? What are the options: use of CVR ?, install measurement equipment on test aircraft?, existing report? other method?) In the absence of specific such information, the information on the voice transmissions (EUROCONTROL report) will be used to extrapolate/approximate the voice reception using simple free space propagation and various distances for the received signal strength. VDL Mode 2 Use the information from ongoing investigations for VDL2 NAV band systems To be developed when required


EUROCONTROL/CSM DRAFT

06/04/04 1 version 1.0

DRAFT version 1.0

An Investigation into the Aircraft VHF Voice Transmissions (Aircraft DSB-AM Voice Usage Profile)

N. Fistas and J. Micallef

EUROCONTROL

1 Introduction This paper reports the results of an investigation onto the current usage of VHF-DSB AM voice radio communications by the flight crew during the various phases of flight. The scope of the analysis in this paper concerns voice transmissions and does not consider voice receptions.

It is intended that this paper will provide input to cosite investigations for the current VHF systems. In addition the information in this paper may be also useful in the investigations for a future communications system by providing a better understanding of the use of the current voice system.

1.1 Background

The need for such investigations became apparent in the progress of the work in the VDL Mode 4 Airborne Architecture Study (VM4AAS). The VM4AAS concluded that co-site VHF interference between digital and analogue communication systems in general is unavoidable and that it is not possible to completely eliminate the interference by currently utilised technical means.

Thus one of the primary recommendations of the VM4AAS is to investigate in detail the impact of interference into the operational use of voice and datalink communications. This paper is a report of a follow up activity of the VM4AAS in the field of cosite investigations and it analyses data from commercial revenue flights. As the analysis concerns generically the current use of the DSB-AM system, these results are applicable in all cases in which the impact to and from DSB-AM for any system is of interest.

1.2 Methodology and objectives

For the purposes of this investigation, data relating to voice transmissions as recorded by the Quick Access Recorder (QAR) are used. The QAR is equipment that allows the recording of a series of parameters and registers various events throughout the duration of a flight. Data are recorded at one second intervals and for some types of data there are more than one recording per second. One recordable such event which relates to the voice usage is the pressing of the push-to-talk (PTT) button. When a crew presses the PTT button (to initiate a voice DSB-AM transmission) this event is recorded in the QAR database.

In particular this activity seeks to provide statistics on the key-down time for the VHF voice radios1. Furthermore, in order to get a more accurate voice usage profile for the

1 The airline operational data obtained cover the key down time for all three VHF radios as well as the

two HF radios. At this stage the analysis concentrates mainly on the VHF radios and only some data are



06/04/04 2 version 1.0

duration of the flight and to be able to associate the transmissions to the different phases of flight other information for the aircraft status at the moment of the transmission is also recorded.

This information can be used to build a detailed profile of the VHF DSB-AM transmissions originating from an aircraft. Such information will be mainly useful in investigations of the cosite interference impact of voice DSB-AM transmissions to datalink messages reception. For the opposite case (impact of datalink transmissions to voice DSB-AM messages reception) the available information from the QAR could be used to provide some indications and approximations2.

1.3 Airline Operational Data

For the purpose of these investigations a subset of the QAR recorded data relating to the voice transmissions were obtained from an airline. It is intended that in future updates of this report the obtained data will be integrated with similar data from other airlines to ensure that the results are representative in general.

The obtained data concern various types of flights of different duration. The available flights are classified in three types in terms of duration: short, medium and long-haul flights as in the following table:

Short-haul flights Less than 2.5 hours

Medium-haul flights Between 2.5 and 6 hours

Long-haul flights More than 6 hours

Table 1: Flight classification in terms of duration

The investigation in this report considered a statistically significant number of flights (205). In particular, and in accordance with the above classification, there were 61 short-haul flights (average flight duration of 1H45M55S), 44 medium-haul flights (average flight duration of 4H08M46S) and 100 long-haul flights (average flight duration of 9H01M07S). The average flight duration considering all (205) flights is 5H48M52. This investigation considered three different types of aircraft3.

1.4 Data provision method

All data considered for this analysis is derived from flights on commercial revenue flights which took place early in 2004. The data was sampled and recorded by the aircraft QAR throughout the flight, and was subsequently downloaded for processing by the airline. Generally, the data set for each aircraft type differs in some ways, depending on the type of QAR and aircraft systems installed. Therefore for each aircraft type a template describing the relevant information had to be developed.

provided for the use of HF radios. Traditionally the third VHF radio is used for ACARS transmissions or as a back-up radio. However as the ACARS transmissions are not recordable events in the QAR, therefore the data for the third radio represent only voice DSB-AM transmissions (back-up radio).

2 For the analysis of the impact of datalink transmissions to voice receptions, the information on when a VHF DSB-AM message is received on the aircraft and the received signal power level would be the useful information. However such information may not be obtained through the QAR recordings and recording such information seems to be not a straight forward task (would require installation of new equipment on board the aircraft).

3 The aircraft fleet from which the data is derived comprises the B747-400, B767 and B737-400.



06/04/04 3 version 1.0

Table 2 provides a template which represents generically the desired information for each flight.

Time radio activity Other information to help determine the phase of flight in which a transmission occurs (altitude, air/ground status etc.)

… … … … … …

Table 2: Generic template of the obtained data elements

For information, the actual data templates for the different types of aircraft used in this investigation are provided in Appendix 1.

1.5 Document structure

Section 2 of this report provides the analysis of the airline data, considering various investigations for specific information items. In Appendix 2, a small sample of the calculated data based on the airline data is also provided. The analysis in section 2 is based on the complete set of the data.

Section 3 provides a summary of the principal observations and proposes a generic profile of the voice DSB-AM transmissions.

Appendix 3 provides information on similar investigations. Finally Appendix 4 provides a limited analysis for the HF usage profile of the considered flights. If required this section will be expanded in a future version.

2 Aircraft voice transmission profiling results This section uses the summarised results for all the considered flights to provide a statistical evaluation of the aircraft DSB-AM voice transmissions. The recorded information in the QAR does not allow identifying directly if the transmission is an ATC or an AOC type of communication. However by convention one VHF radio (VHF Left or VHF1) is used for ATC, another radio (VHF Right or VHF2) is used for AOC and the third radio (VHF Centre or VHF3, when available) is used for ACARS and as a backup for ATC and AOC. It is important to note that the airline from which the data were obtained makes extensive use of ACARS for AOC communications. The use of ACARS may be related also to pilot preferences but it is likely that it reduces the volume of voice AOC communications in the analysed data. Data from airlines which make no use of ACARS will be useful to confirm this point. This point does not affect the ATC communications.

In the analysis in this paper, the transmissions for the radio whose control panel is next to the pilot (VHF LEFT or VHF1) will be considered ATC transmissions and all the others (VHF RIGHT/VHF2 and VHF CENTER/VHF3) will be considered AOC transmissions. It is worthy noting that in some flights it is only the “ATC” radio that is used through out the flight.

2.1 General statistics on the profile of the transmissions

2.1.1 Number of transmissions and cumulative transmission time

The following table provides the minimum and maximum number of transmissions during a flight and the cumulative number of transmissions for all flights and for the individual classes of flight (short, medium and long) and for ATC and AOC



06/04/04 4 version 1.0

transmissions respectively. The transmission times are expressed in seconds and also as a percentage load of the total flight time. The numbers for duration in seconds and as a percentage of the total flight time for a particular type of flight do not necessarily correspond to the same flight (i.e. the minimum or maximum transmission times in seconds and as percentage of flight time for a type of flight maybe from different flights belonging to this type of flight).

Number of transmissions

Cumulative transmission time (s) and % of flight time

minimum Maximum minimum Maximum All flights (ATC+AOC) 41 287 132.5 1% 1492 6.5% All flights (ATC) 41 281 132.5 0.9% 986 5.9% All flights (AOC) 0 93 0 0% 711 1.9% Short-haul (ATC+AOC) 41 101 132.5 2.1% 347 6.5% Short-haul (ATC) 41 93 132.5 1.2% 294 2.3% Short haul (AOC) 0 25 0 0% 97 1.8% Medium-haul (ATC+AOC) 58 158 192 1.6% 521 3.4% Medium-haul (ATC) 58 136 192 1.5% 485 3% Medium-haul (AOC) 0 23 0 0% 122 0.9% Long-haul (ATC+AOC) 95 287 297 1% 1492 4.6% Long-haul (ATC) 79 281 247 0.9% 986 2.8% Long-haul (AOC) 0 93 0 0% 711 1.9%

Table 3: VHF Voice transmissions per flight: frequency and cumulative duration

The figure below illustrates the trend in transmission frequency with increasing flight time. The cumulative transmission time per flight follows a similar trend. Note that whereas the total number of transmissions is stably below 100 for the short flights, the scatter increases for longer flights

0

50

100

150

200

250

300

num

ber o

f tra

nsm

issi

ons

per f

light

short haul medium haul long haul

Figure 1: Variation of transmission frequency with flight length

In Figure 2 it is shown that the transmission load falls steadily for longer flights. Note that the voice load stabilises beyond a certain flight time such that the loads for medium and long haul flights are very similar. Indeed for some of the longest flights recorded, the voice load is higher than that of the average medium haul flights.



06/04/04 5 version 1.0

0

1

2

3

4

5

6

7

% v

oice

load

(all

radi

os)

short haul medium haul long haul

Figure 2: Variation of voice load as a percentage of total flight time

2.1.2 Duration of transmissions

In general the duration of a VHF voice transmission ranges from 0.5 sec to 62 sec. If only the ATC communications are considered the duration ranges from 0.5 sec to 36 sec. The smallest maximum duration in a flight of an ATC transmission among all the considered flights is 6 sec.

For short-haul flights the duration of a VHF voice transmission ranges from 0.5 sec to 24 sec. If only the ATC communications are considered the duration ranges from 0.5 sec to 14 sec. The smallest maximum duration in a flight of an ATC transmission among the considered short-haul flights is 6 sec.

For medium-haul flights the duration of a VHF voice transmission ranges from 1.0 sec to 62 sec. If only the ATC communications are considered the duration ranges from 0.5 sec to 14 sec. The smallest maximum duration in a flight of an ATC transmission among the considered medium-haul flights is 5 sec. The maximum value of 62 seconds was encountered for one flight only and the next maximum value for medium-haul flights was 32 seconds. The 62 second transmission was the only transmission from the AOC radios for this flight.

For long-haul flights the duration of a VHF voice transmission ranges from 1.0 sec to 43 sec. If only the ATC communications are considered the duration ranges from 1.0 sec to 36 sec. The smallest maximum duration in a flight of an ATC transmission among the considered long-haul flight is 8 sec.

The following table summarises the above information:



06/04/04 6 version 1.0

minimum duration (s)

maximum duration (s)

Smallest maximum duration (s)

All flights 0.5 62 All flights (ATC radio only) 0.5 36 5 short-haul 0.5 24 Short haul (ATC radio only) 0.5 14 6 medium-haul 0.5 62 medium-haul (ATC radio only) 0.5 14 5 long-haul 1.0 43 long-haul (ATC radio only) 1.0 36 8

Table 4: VHF Voice single transmissions duration characteristics

2.1.2.1 Statistical spread per flight (average and standard deviation)

In general the average duration of a VHF voice transmission ranges from 2.6 sec to 6.4 sec and the standard deviation from 1.2 sec to 7.1 sec. If only the ATC communications are considered the average duration ranges from 2.6 sec to 5.0 sec and the standard deviation from 1.1 sec to 5.1 sec.

For short-haul flights the average duration of a VHF voice transmission ranges from 2.6 sec to 4.3 sec and the standard deviation from 1.2 sec to 3.1 sec. If only the ATC communications are considered the average duration ranges from 2.6 sec to 4.3 sec and the standard deviation from 1.1 sec to 2.3 sec.

For medium-haul flights the average duration of a VHF voice transmission ranges from 2.7 sec to 4.1 sec and the standard deviation from 1.2 sec to 5.9 sec. If only the ATC communications are considered the average duration ranges from 2.6 sec to 3.9 sec and the standard deviation from 1.1 sec to 2.7 sec.

For long-haul flights the average duration of a VHF voice transmission ranges from 3.0 sec to 6.4 sec and the standard deviation from 1.5 sec to 7.1 sec. If only the ATC communications are considered the average duration ranges from 3.0 sec to 5.0 sec and the standard deviation from 1.5 sec to 5.1 sec.

The following table summarises the above information:

Average duration (s)

Standard deviation of average duration (s)

minimum maximum minimum maximum All flights 2.6 6.4 1.2 7.1 Al flights (ATC radio only) 2.6 5.0 1.1 5.1 short-haul flights 2.6 4.3 1.2 3.1 short-haul (ATC radio only) 2.6 4.3 1.2 2.3 medium-haul flights 2.7 4.1 1.2 5.9 medium-haul (ATC Radio only) 2.6 3.9 1.1 2.7 long-haul flights 3.0 6.4 1.5 7.1 long-haul (ATC radio only) 3.0 5.0 1.5 5.1

Table 5: VHF Voice transmissions Average duration characteristics

The results of the above table show that the spread of transmission durations is smaller when the ATC transmissions are only considered.



06/04/04 7 version 1.0

2.1.3 Statistical spread across flights (average and standard deviation)

The following table provides averaged information about the VHF voice transmissions over the short, medium and long haul flights, for the ATC and AOC communications. Average

x-haul No of TX’s

Total TX time (s)

Mean single TX time (s)

‡Standard deviation (s)

TX load (% of flight time

Short 70.5 227.4 3.2 0.4 3.7

Short (ATC) 66.0 208.0 3.2 0.4 3.4

Short (AOC) 4.5 19.4 3.2 1.77 0.3

Medium 109 359.8 3.3 0.4 2.5

Medium (ATC) 102.7 331.2 3.2 0.4 2.3

Medium (AOC) 6.4 28.6 4.9 9.1 0.2

Long 162.6 656.3 4.0 0.7 2.0

Long (ATC) 144.3 539.5 3.7 0.4 1.7

Long (AOC) 18.3 116.8 5.4 3.3 0.4

All 123.7 465 3.6 0.7 2.6

All (ATC) 112.0 396.1 3.5 0.5 2.3

All (AOC) 11,6 98.9 4.7 5.0 0.3

Table 6: Voice transmission characteristics averaged over the three classes of flight Note ‡ The standard deviation in this table is calculated as the standard deviation of the set of the

average duration of the transmissions for the various flights and the various categories (ATC+AOC, ATC only and AOC only). Therefore it is different from the standard deviation considered in Table 5.

The above data show that there is some variability for the AOC data especially for the long-haul data.

2.1.4 Voice transmission profile with altitude

The following figures illustrate how a typical profile of voice transmission evolves throughout the flight as a function of altitude for a short and a long haul flight (medium haul flights have a similar profile to long haul flights). The typical flight profile from take-off through cruise to landing is shown in a solid line. The voice transmissions over the five flight phases (take off, climb, enroute, descend and land) are superimposed on the flight profile, where the relative concentrations and distributions of ATC and AOC transmissions can be visualised.



06/04/04 8 version 1.0

-500

4500

9500

14500

19500

24500

29500

0 1000 2000 3000 4000

ATCAOC

Figure 3a: ATC Voice transmissions versus flight altitude for a typical short haul flight

0

5000

10000

15000

20000

25000

30000

35000

40000

0 5000 10000 15000 20000 25000 30000 35000

flight time (s)

altit

ude

(ft)

ATCAOC

Figure 3b: ATC Voice transmissions versus flight altitude for a typical long haul flight

Due to the scale in the above diagram, the insert in Figure 3b provides an enlarged view of specific areas to reveal more detail on the transmissions in these example areas.

15000 17000



06/04/04 9 version 1.0

This type of data analysis gives an indication on the overall distribution of voice transmissions which is useful information to consider when determining the expected level of impact on individual applications when considered from an operational point of view.

During cruise, ATC voice communications are usually handoffs between sectors, requests for altitude changes, and occasionally flight path deviations to avoid weather. For longer haul flights, the contribution of ATC voice transmissions is increasing due mainly to more frequent sector traversing. It is worth noting that especially in long haul flights, AOC transmissions are observed mostly in the latter part of the cruise and during the initial descent4.

The table below shows the average percentage distribution of total ATC and AOC transmission time duration amongst the five phases of flight.

ATC (%) Takeoff Climb Cruise Descent Land

Short 12 27 17 37 7 Medium 9 17 40 26 7 Long 6 12 61 17 4 All 7 15 51 22 5

AOC Takeoff Climb Cruise Descent Land


ATC+AOC Takeoff Climb Cruise Descent Land


Table 7a: Distribution of ATC and AOC total transmission duration across the flight phases

4 Some activity is also recorded on the ground, mostly in the arrival phase.



06/04/04 10 version 1.0

ATC Takeoff Climb Cruise Descent Land

Short 12% 25% 17% 38% 7% Medium 10% 16% 40% 28% 7% Long 7% 13% 56% 20% 4% All 9% 15% 45% 25% 6%

AOC Takeoff Climb Cruise Descent Land


ATC+AOC Takeoff Climb Cruise Descent Land


Table 7b: Distribution of ATC and AOC total number of transmissions across the flight phases

An interesting observation is that the percentage decomposition of the number of transmissions is similar with the percentage decomposition for the total duration of transmissions for the various phases of the flight.

For short-haul flights, the transmissions during climb and descent outweigh those during cruise. This observation is an expected consequence of the short cruise time (30% of the short haul flights analysed have a cruise period of less than 15 minutes), during which a typical flight is unlikely to make many transmissions. The level of transmission activity during cruise is higher for the medium and long haul flights. The crossing of sector boundaries, and/or changes in flight profile5 for these flights are potential contributors to this large proportion of transmissions. Note that during the cruise phase of a typical oceanic long haul flight the aircraft is potentially out of VHF range of any ground station for some hours. In this case, ATC control is accomplished through other means, including HF radio and in some cases SATCOM data communications.

The following table summarises the minimum and maximum number of ATC and AOC transmissions observed for the individual phases of flight, and for the three classes of flight (short, medium and long).

5 From the flight data considered in this analysis, it is observed that manoeuvres that involve a change in

cruise altitude are frequently accompanied by an increase in voice transmission activity during that period.



06/04/04 11 version 1.0

Number of Transmissions Take-Off Climb Cruise Descent Land

Min Max Min Max Min Max Min Max Min MaxShort (ATC) 3 14 5 35 0 27 14 38 1 18 Short (AOC) 0 15 0 5 0 5 0 9 0 17 Medium (ATC) 5 23 7 25 9 71 12 49 2 23 Medium (AOC) 0 17 0 6 0 13 0 10 0 22 Long (ATC) 4 37 6 32 18 219 0 53 0 38 Long (AOC) 0 58 0 18 0 58 0 33 0 26 All (ATC) 3 37 5 35 0 219 12 53 1 38 All (AOC) 0 58 0 18 0 58 0 33 0 26

Table 8: Number of ATC and AOC transmissions per flight phase

The minimum and maximum bounds for the number of both ATC and AOC transmissions during cruise increase steadily for longer flight times, albeit a minimal AOC load for short haul flights. The number of transmissions in take-off/climb and descent/landing is generally in the same order for all flights. Figures 4a and 4b illustrate this trend graphically (plotted on the same scale) for the cruise and climb phases when considering the entire set of flights6.

0

50

100

150

200

250

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000

Cruise phase duration time (s)

num

ber o

f tra

nsm

issi

ons

Figure 4a: Number of transmissions for the cruise phase

6 The descent phase displays a similar trend to that of the climb phase.



06/04/04 12 version 1.0

0

50

100

150

200

250

0 500 1000 1500 2000 2500 3000

climb phase duration (s)

num

ber o

f tra

nmis

sion

s

Figure 4b: Number of transmissions for the climb phase

One case was observed of a flight in which no transmissions from the left (ATC) radio were made during the descent. This is reflected in the zero minimum bound for ATC transmission for long flights for descend and land in Table 8. Investigation of the QAR recordings of this flight showed that transmissions on the left radio ceased in mid-cruise and the voice transmission load in the rest of the flight was taken up by the right radio, indicating that the left radio probably failed. Although in this case the ATC transmissions were made by a radio whose transmissions are considered as AOC, the overall AOC statistics are unaffected since other long flights have genuine levels of high AOC loading.

2.1.5 Probability distributions of transmission durations

The figures below represent the distribution profile of the duration of transmissions for all classes of flight, considering ATC, AOC and ATC+AOC transmissions respectively. The transmissions are clustered in bins of one second duration and all the transmission more than 35 seconds are clustered in the last bin (35).



06/04/04 13 version 1.0

ATC

0

5

10

15

20

25

30

35

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35transmission duration (s)

% o

f occ

uren

ce ShortMediumLongAll

Figure 5a: Percentile distribution of transmission durations for ATC transmissions

AOC

0

5

10

15

20

25

30


% o

f occ

uren


Figure 5b: Percentile distribution of transmission durations for AOC transmissions



06/04/04 14 version 1.0

ATC+AOC

0

5

10

15

20

25

30

35


% o

f occ

uren


Figure 5c: Percentile distribution of transmission durations for ATC and AOC transmissions

Finally Figure 5d shows the relative contribution of the ATC and AOC transmissions for all the flights. Similar diagrams can be drawn for the short, medium and long-haul flights.

All flights

0

5

10

15

20

25

30


% o

f occ

uren

ce

AOCATC

Figure 5d: Percentile distribution of transmission durations for ATC and AOC

transmissions for all flights and relative contributions of ATC and AOC transmissions

Overall, ATC and AOC voice transmissions exhibit similar profiles with the exception that AOC transmissions show an additional peak (bimodal distribution). For all type of communications, most transmissions have duration of between 1 and 5 seconds with a peak at 2 and 3 seconds. Figure 5d confirms that the majority of transmissions is due to ATC transmissions. The tendency for longer (but infrequent) AOC transmissions is shown in Figure 5b where the distribution shows some transmissions with durations of



06/04/04 15 version 1.0

up to 35 seconds and more. For AOC transmissions, a second (smaller) peak exists in the 20 to 24 seconds range. The second peak shows some long AOC transmissions but not so frequent.

The following table shows the percentage probability that any single transmission for the different categories (ATC, AOC and both type of transmissions and for Short, Medium, Long and All flights) will be greater than a given number of seconds.

Probability (%) that a transmission will be greater than x seconds ATC AOC ATC+AOC x= S M L A S M L A S M L A 1 91 89 88 89 83 82 85 85 91 89 88 89 2 62 61 64 63 60 60 66 64 62 61 64 63 3 34 35 40 38 40 38 48 46 35 35 41 39 4 19 18 24 22 30 30 37 35 20 19 25 23 5 10 10 15 13 23 22 30 28 10 10 17 15 6 4 5 10 8 19 18 26 24 5 6 12 10 7 2 2.3 7 5 15 15 23 21 3.0 3.0 9.0 7 8 0.9 1.3 6 3.9 15 13 20 19 1.8 1.9 7 5 9 0.5 0.7 4.6 3.1 12 10 19 17 1.2 1.2 6 4.4 10 0.2 0.4 3.6 2.4 9 8 17 15 0.8 0.8 5 3.5 15 0.0 0.0 1.0 0.7 2.9 2.5 13 10 0.2 0.2 2.3 1.5 20 0.0 0.0 0.2 0.1 1.1 1.1 9 7 0.1 0.1 1.2 0.8 25 0.0 0.0 0.03 0.02 0.0 0.7 3.6 2.9 0.0 0.04 0.4 0.3 30 0.0 0.0 0.01 0.01 0.0 0.4 0.9 0.8 0.0 0.02 0.1 0.08

Table 9: Transmission Duration Probabilities

2.2 Other considerations

2.2.1 Simultaneous voice transmissions

The total transmission overlap time over the entire flight for all flights shows that, in general, there is very little simultaneous use of two VHF radios during a flight. More precisely in 65% of all flights analysed there was no simultaneous use of two radios at all, and in the remaining 35% there was between 1 and 20 seconds of total overlap transmission time7. The figure below illustrates the distribution of overlap time for this latter portion of flights that display simultaneous transmissions.

7 The total overlap time for all the flights is almost 4.5 mins for a total of flight time of around 1300

hours.



06/04/04 16 version 1.0

Figure 6: Distribution of flights with simultaneous transmissions

2.2.2 Identification of chained transmissions

An important consideration for cosite voice radio usage profile is the maximum period of continuous activity. A comparison of the maximum key-down time for all three radios considered individually gives the primary indication, as indicated above. However, the complete picture on maximum voice transmission activity is obtained by considering in addition any instances of chained8 transmissions, where a transmission from one radio is staggered in time with transmissions from another. Out of the 175 flights analysed, 75% did not display any chained transmissions. For the remaining 25%, the distribution of flights with staggered transmissions is summarised in the figure below.

Figure 7: Distribution of total number of chained transmissions per flight

Generally, ATC related transmissions occur before and in periods of transition or manoeuvring. AOC communications occur largely during the cruise and descend phase. The analysis confirms that ATC and AOC transmissions do not coincide. When

8 For this analysis any transmissions separated by up to two seconds are considered as part of the same

chain.

Transmission overlap profile

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Total overlap time (sec)

Num

ber o

f flig

hts

Number of chained transmissions per flight

0

5

10

15

20

25

30

1 2 3 4

Number of chained transmissions

num

ber o

f flig

hts



06/04/04 17 version 1.0

this does happen, the maximum “chained” transmission time in the considered flights was found to be 32 sec which is lower than the maximum single transmission duration (see section 2.1.2).

2.2.3 Identification of strings of transmissions

TBD

This section will be developed in a future version of this report if requested, and will provide information on the occurrence of closely spaced voice transmissions.

3 Summary of Observations and Proposed Profile

3.1 Observations

The average transmission time for ATC communications is between 3.2 and 3.7 seconds. The average transmission time of AOC communications is between 3.2 and 5.4 seconds. The upper bounds correspond to long-haul flights.

The ATC communications form the bulk of the voice transmissions. The AOC communications are slightly longer on average but significantly less frequent.

The AOC transmissions occur in most cases during the cruise part of flight at altitude. This is the case especially for longer flights (medium and long) where as for short flights most AOC transmissions occur in the descend phase. The AOC transmissions rarely, if ever, do they overlap or stagger with the ATC communications.

With the exception of the cruise phase, a significant portion of the ATC and AOC transmissions occur in the descend phase.

The total voice transmission load (as percentage of the total flight time) decreases steadily with the flight duration. For short medium and long haul flights the average load is 3.7, 2.5 and 2% respectively.

The probability distribution of the ATC transmissions shows a maximum around 2 to 3 seconds with a cumulative probability of 55 to 60 %. The ATC transmissions show little spread with few transmission more than 10 seconds. The AOC transmissions show a greater spread in duration and for the AOC transmissions there are two peaks in the duration distribution. One is as in ATC (2 to 3 seconds) with a cumulative probability of 40% to 45% and the other is around 21 to 24 seconds with a cumulative probability of around 5%.

There is very limited simultaneous use of any two radios, and consecutive transmissions are no longer than the longest single transmissions.



06/04/04 18 version 1.0

3.2 Recommendations – Voice DSB-AM Profile

Based on the information in section 2, the following statistical profile in Tables 10a and 10b is proposed to represent the originating from an aircraft voice DSB-AM transmissions for the different types of transmissions and the different types of flight as well as phases of flight:

Proposed DSB-AM voice profile - DRAFT

Transmission Duration and Number of Transmissions

Short haul flights Medium haul flights Long haul flights

ATC AOC All ATC AOC All ATC AOC All

Overall load (% of flight time):

3.4 0.3 3.7 2.3 0.2 2.5 1.7 0.4 2.0

Standard load (% of flight time):

3.5 0.5 4 2.5 0.5 3 2 0.5 2.5

Average duration (s): 3.2 3.2 3.2 3.2 4.9 3.3 3.7 5.4 4.0

Standard duration (s): 4 4 4 4 5 4 4 6 5

Average total number of transmissions

70 10 80 105 15 120 150 20 170

Average nb of transmissions – Take off

9 2 11 11 2 13 11 2 13

Average nb of transmissions – Climb

18 1 19 17 1 18 20 1 21

Average nb of transmissions – Cruise

12 2 14 42 5 47 84 11 95

Average nb of transmissions – Descend

27 5 32 30 3 33 30 4 34

Average nb of transmissions – Land

5 2 7 7 5 12 6 3 9

Table 10a: DSB-AM voice profile: Transmission Duration and Number of Transmissions



06/04/04 19 version 1.0

Proposed DSB-AM voice profile - DRAFT

Single Transmission Duration Probability Distributions Probability (%) that a transmission will be greater than x seconds x = ATC AOC ATC+AOC 1 95 90 95 2 65 70 65 3 45 50 45 4 25 40 27 5 15 35 20 6 10 30 15 7 8 25 10 8 7 22 8 9 6 20 7 10 5 18 6 15 2 15 5 20 1 10 2 25 0.1 5 1 30 0.01 1 0.2

Table 10b: DSB-AM voice profile: Transmission Duration Probability Distributions

For simplicity, the information in the above Tables could be summarised in a more compact from according to the interest of an investigation.



06/04/04 20 version 1.0

For example the following table provides a simplified DSB-AM voice profile based on the information in Table 10 assuming in general worst cases. When only one value is provided then this is to be used for all types of flight (short, medium and long haul). When three values are provided then they correspond respectively to short, medium and long haul flights.

Short/Medium/Long – haul flights ATC AOC ATC+AOC

Standard load (% of flight time): 3.5/2.5/2 0.5 4/3/2.5 Standard duration (s): 4 6 5 Average number of transmissions 70/105/150 10/15/20 80/120/170

Average nb of transmissions – Take off 10 2 12

Average nb of transmissions – Climb 19 1 20 Average nb of transmissions – Cruise 12/42/84 2/5/11 14/47/95 Average nb of transmissions – Descend 30 4 34 Average nb of transmissions – Land 8 2 10

Probability (%)that a transmission will be greater than x seconds x=1 95 90 95 x=2 65 70 65

x=3 45 50 45 x=4 25 40 27 x=5 15 35 20 x=6 10 30 15 x=7 8 25 10 x=8 7 22 8

x=9 6 20 7 x=10 5 18 6 x=15 2 15 5 x=20 1 10 2 x=25 0.1 5 1 x=30 0.01 1 0.2

Table 11: DSB-AM voice profile for S/M/L haul flights: an example

ACP/WGM9/WP__ Attachment 2 to ACP/WGM9 paper: “VDL Mode 4 Cosite Interference Investigations: Status Report” EUROCONTROL/CSM DRAFT

06/04/04 21 version 1.0

Appendix 1: Data Templates

The main elements of the required data concern the usage of the three onboard VHF radios, whose activity is determined by the triggering of the PTT switch on the flight deck. A set of additional flight parameters is also considered. These additional parameters help determine the stage of flight in which transmissions occur.

Thus a validation of a template was required to ensure that the data obtained is compatible across the aircraft types considered. However, the area where most of the differences occur is the “sampling rates” of the different QARs. For the set of data considered by this analysis it was readily verified that the source data are compatible across the three aircraft types and that the sampling accuracy is well within the statistical tolerance.

737-400

Timing information/data integrity VHF Radio usage Other Flight parameters

Par

amet

er

Sub

-fram

e

Tim

e

Ev

i

GM

T TI

ME

-BN

R (H

RS

)

GM

T TI

ME

-BN

R (M

IN)

GM

T TI

ME

-BN

R (S

EC)

VH

F C

ENTE

R K

EY

ING

VH

F LE

FT K

EY

ING

VH

F R

IGH

T K

EY

ING

CU

RR

ENT

FLIG

HT

MO

DE

LEFT

GE

AR

DO

WN

NO

SE

GE

AR

DO

WN

RIG

HT

GE

AR

DO

WN

FLA

P P

OS

ITIO

N

PA

RK

ING

BR

AK

E

ON

/OFF

AIR

/ G

ND

NO

SE

A

IR/

GN

D

RA

DIO

ALT

ITU

DE

PR

ES

SU

RE

ALT

ITU

DE

R

IGH

T (U

N-

CO

RR

ECTE

D)

Sam

ples

9

n/a n/a n/a n/a 1 1 1 2 2 2 1 1 1 1 1 1 4 4 4 1

9 The sampling rate is quoted over a period of one second.


06/04/04 22 version 1.0

767-300 Timing information/ data integrity VHF & HF radio usage Other flight parameters

Par

amet

er

Sub

-fram

e

Tim

e

Ev

i

GM

T TI

ME

-BN

R (H

RS

)

GM

T TI

ME

-BN

R (M

IN)

GM

T TI

ME

-BN

R (S

EC)

VH

F K

EY

- C

EN

TRE

VH

F K

EY

- LE

FT

VH

F K

EY

– R

IGH

T

HF

KE

Y -

LEFT

HF

KE

Y-R

IGH

T

CU

R-R

ENT

FLIG

HT

MO

DE

ALL

GE

AR

DO

WN

AN

D

LOC

KED

FLA

P P

OS

ITIO

N

PA

RK

ING

BR

AK

E P

OS

ITIO

N

AIR

GN

D R

ELA

Y (D

MU

)

AIR

/GR

OU

ND

SW

ITC

H

NO

SE

GE

AR

SQ

UA

T S

WIT

CH

AIR

GN

D S

YS

-L

AIR

GR

ND

SY

S-R

RA

DIO

ALT

- C

EN

TRE

RA

DIO

ALT

- R

IGH

T

RA

DIO

ALT

- LE

FT

PR

ES

SU

RE

ALT

Sam

ples

n/a n/a n/a n/a 1 1 1 1 1 1 1 1 1 1 1 1 4 4 1 1 1 4 1 1 1

747-400 Time/Data integrity/Aircraft identification VHF & HF Radio usage Other Flight parameters

Par

amet

er

Sub

fram

e

Tim

e

Ev

i

A/C

IDE

NTI

FIC

ATI

ON

A/C

IDE

NTI

FIC

ATI

ON

4TH

CH

AR

A/C

IDE

NTI

FIC

ATI

ON

5TH

CH

AR

A/C

IDE

NTI

FIC

ATI

ON

6TH

CH

AR

A/C

IDE

NTI

FIC

ATI

ON

7TH

CH

AR

DE

RIV

ED

GM

T H

OU

RS

DE

RIV

ED

GM

T M

INU

TES

DE

RIV

ED

GM

T S

EC

ON

DS

VH

F K

EY

ING

#C

VH

F K

EY

ING

#L

VH

F K

EY

ING

#R

HF

KE

YIN

G #

L

HF

KE

YIN

G #

R

FLIG

HT

MO

DE

(CM

C IN

PU

T)

GEA

R D

OW

N/L

OC

KE

D N

OS

E P

RI

FLA

P L

EV

ER

PO

S

PAR

K BR

AKE

SET

PA

RK

ING

BR

AK

E S

ET

AIR

GR

OU

ND

RE

LAY

(DM

U)

AIR

GR

OU

ND

RE

LAY

(DM

U)

NO

SE

SQ

UAT

RE

LAY

AIR

/GR

OU

ND

FM

C #

L

RA

D A

LT -

LEFT

RA

D A

LT- C

ENTR

E

RA

D A

LT -

RIG

HT

PR

ES

SU

RE

ALT

CO

MB

INE

D

Sam

ples

n/a n/a n/a n/a 1 1 1 1 1 1 1 1 2 2 2 2 2 1 1 1 1 1 16 1 2 1 1 1 1 4


06/04/04 23 version 1.0

Appendix 2: Summarised data on aircraft radio transmissions

The following tables provide a sample of the resulted analysis data for the VHF LEFT and VHF RIGHT radios for some of the flights. The purpose of these tables is only to provide some insight on the data collected and evaluated and do not cover all the data analysis undertaken.

Short-haul flights

A/C TYP

FLT NO Duration RADIO

LFT TOT TX's

LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD RADIO

RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG Global_SD

737 XX2915 00:54:05 VHFLL 45 141 6,5 1,5 3,13 1,31 4,34 VHFRL 4 16 3,88 2,3 0,48 49 157 4,82 3,19 1,39

737 XX2902 00:55:06 VHFLL 64 194 8 1,5 3,03 1,33 5,87 VHFRL 3 14 4,5 1 0,41 67 208 6,28 3,1 1,35

737 XX2903 00:55:06 VHFLL 55 156 7,5 0,5 2,84 1,46 4,72 VHFRL 5 27 5,4 5,3 0,82 60 183 5,54 3,05 2,09

737 XX2914 01:00:07 VHFLL 43 141 6,5 1 3,27 1,4 3,9 VHFRL 0 0 0 0 0 43 141 3,9 3,27 1,4

737 XX8109 01:02:32 VHFLL 48 149 7,5 1 3,09 1,55 3,96 VHFRL 3 17 5,5 7,4 0,44 51 165 4,4 3,24 2,18

737 XX8089 01:05:04 VHFLL 41 133 7,5 0,5 3,23 1,52 3,39 VHFRL 0 0 0 0 0 41 133 3,39 3,23 1,52

737 XX8108 01:07:58 VHFLL 63 163 8,5 0,5 2,59 1,39 4 VHFRL 3 9 3 1,5 0,22 66 172 4,22 2,61 1,39

737 XX2839 01:08:49 VHFLL 56 168 7,5 0,5 3 1,41 4,07 VHFRL 4 11 2,75 1,2 0,27 60 179 4,34 2,98 1,39

737 XX8088 01:10:05 VHFLL 42 142 8 1 3,37 1,69 3,37 VHFRL 7 35 4,93 5,1 0,82 49 176 4,19 3,59 2,45

737 XX8110 01:10:51 VHFLL 64 175 8,5 0,5 2,73 1,48 4,12 VHFRL 0 0 0 0 0 64 175 4,12 2,73 1,48

737 XX8121 01:11:42 VHFLL 61 219 9,5 0,5 3,58 2,13 5,08 VHFRL 3 14 4,67 4,7 0,33 64 233 5,4 3,63 2,25

737 XX2838 01:14:27 VHFLL 62 180 8 0,5 2,9 1,32 4,03 VHFRL 6 15 2,42 1,8 0,32 68 195 4,35 2,86 1,36

737 XX7952 01:36:21 VHFLL 62 197 8 1 3,17 1,33 3,4 VHFRL 4 29 7,13 4,3 0,49 66 225 3,89 3,41 1,85

767 XX478 01:45:30 VHFLL 64 211 8 1 3,3 1,67 3,33 VHFRL 4 14 3,5 1,7 0,22 68 225 3,55 3,31 1,66

767 XX249 01:50:58 VHFLL 47 179 10 1 3,81 2,09 2,69 VHFRL 0 0 0 0 0 47 179 2,69 3,81 2,09

767 XX548 02:11:58 VHFLL 57 190 7 1 3,33 1,65 2,4 VHFRL 4 16 4 1,4 0,2 61 206 2,6 3,38 1,63

767 XX566 02:13:02 VHFLL 76 261 14 1 3,43 2,05 3,27 VHFRL 8 59 7,38 5,6 0,74 84 320 4,01 3,81 2,79

767 XX780 02:15:37 VHFLL 84 255 7 1 3,04 1,4 3,13 VHFRL 0 0 0 0 0 84 255 3,13 3,04 1,4


06/04/04 24 version 1.0

A/C TYP

FLT NO Duration RADIO

LFT TOT TX's

LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD RADIO

RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG Global_SD

767 XX481 02:17:10 VHFLL 70 229 8 1 3,27 1,78 2,78 VHFRL 1 1 1 0 0,01 72 231 2,81 3,21 1,8

Medium-haul flights

A/C TYP FLT NO Duration RADIO

LFT TOT TX's

LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD RADIO

RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG Global_SD

767 XX781 02:33:27 VHFLL 72 261 9 1 3,63 1,74 2,835 VHFRL 7 25 3,57 2,7 0,27 79 286 3,11 3,62 1,82 767 XX869 02:38:50 VHFLL 89 285 7 1 3,2 1,59 2,99 VHFRL 3 9 3 1,73 0,09 92 294 3,08 3,2 1,58 737 XX2884 02:42:09 VHFLL 58 192 9,5 0,5 3,31 1,58 1,973 VHFRL 0 0 0 0 0 58 192 1,97 3,31 1,58 737 XX777 02:43:22 VHFLL 80 244 8 0,5 3,04 1,55 2,484 VHFRL 0 0 0 0 0 80 244 2,48 3,04 1,55 767 XX549 02:55:38 VHFLL 94 264 7 1 2,81 1,31 2,505 VHFRL 0 0 0 0 0 95 265 2,51 2,79 1,32 767 XX549 02:59:50 VHFLL 81 268 9 1 3,31 1,57 2,484 VHFRL 10 31 3,1 2,56 0,29 91 299 2,77 3,29 1,69 767 XX479 03:11:06 VHFLL 88 264 8 1 3 1,6 2,302 VHFRL 14 55 3,93 4,53 0,48 102 319 2,78 3,13 2,22 767 XX869 03:27:39 VHFLL 115 343 8 1 2,98 1,51 2,753 VHFRL 6 24 4 3,79 0,19 122 368 2,95 3,02 1,68 767 XX872 03:31:57 VHFLL 95 305 8 1 3,21 1,64 2,398 VHFRL 3 11 3,67 2,08 0,09 98 316 2,48 3,22 1,65 767 XX632 03:39:14 VHFLL 84 262 9 1 3,12 1,72 1,992 VHFRL 4 19 4,75 4,92 0,14 88 281 2,14 3,19 1,95 767 XX872 03:40:26 VHFLL 101 376 11 1 3,72 1,81 2,843 VHFRL 5 20 4 5,61 0,15 106 396 2,99 3,74 2,08 767 XX461 03:44:23 VHFLL 78 205 7 1 2,63 1,4 1,523 VHFRL 22 78 3,55 3,19 0,58 100 283 2,1 2,83 1,95 767 XX634 03:45:06 VHFLL 103 338 10 1 3,28 2,02 2,502 VHFRL 23 117 5,09 5,42 0,87 126 455 3,37 3,61 3 767 XX633 03:47:58 VHFLL 87 269 7 1 3,09 1,44 1,967 VHFRL 13 37 2,85 2,27 0,27 100 306 2,24 3,06 1,56 767 XX873 03:49:59 VHFLL 104 370 10 1 3,56 1,88 2,681 VHFRL 5 15 3 1 0,11 109 385 2,79 3,53 1,85 767 XX549 03:59:31 VHFLL 96 321 9 1 3,34 1,75 2,234 VHFRL 14 58 4,14 3,57 0,4 110 379 2,64 3,45 2,07 767 XX873 04:21:18 VHFLL 120 436 13 1 3,63 2,09 2,781 VHFRL 13 43 3,31 2,06 0,27 133 479 3,06 3,6 2,08 767 XX631 04:22:45 VHFLL 124 402 11 1 3,24 1,93 2,55 VHFRL 3 28 9,33 7,57 0,18 127 430 2,73 3,39 2,33 767 XX163 04:35:17 VHFLL 93 331 11 1 3,56 1,78 2,004 VHFRL 2 16 8 8,49 0,1 95 347 2,1 3,65 2,07 767 XX165 04:39:09 VHFLL 107 308 8 1 2,88 1,43 1,839 VHFRL 5 17 3,4 2,7 0,1 112 325 1,94 2,9 1,49 767 XX165 04:40:25 VHFLL 120 361 10 1 3,01 1,66 2,145 VHFRL 7 25 3,57 3,15 0,15 127 386 2,29 3,04 1,76 767 XX162 05:34:07 VHFLL 135 362 6 1 2,68 1,12 1,806 VHFRL 23 122 5,3 6,28 0,61 158 484 2,41 3,06 2,73 767 XX164 05:40:59 VHFLL 108 339 12 1 3,14 1,74 1,657 VHFRL 8 39 4,88 4,45 0,19 116 378 1,85 3,26 2,06

Long-haul flights A/C TYP

FLT NO Duration RADIO LFT TOT TX's

LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD

RADIO RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG

Global_SD

767 XX164 06:08:02 VHFLL 142 444 15 1 3,1 2 2 VHFRL 27 112 4,1 4,3 0,5 170 557 2,5 3,3 2,5


06/04/04 25 version 1.0

A/C TYP


LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD

RADIO RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG

Global_SD

747 XX125 06:11:02 0VHFL 157 613 17 1 3,9 2,6 2,8 0VHFR 4 17 4,3 2,9 0,1 161 630 2,8 3,9 2,6 747 XX125 06:13:29 0VHFL 157 497 15 1 3,2 1,8 2,2 0VHFR 10 50 5 2,9 0,2 170 562 2,5 3,3 1,9 747 XX075 06:21:21 0VHFL 130 550 18 1 4,2 2,8 2,4 0VHFR 25 265 11 8,9 1,2 158 831 3,6 5,3 4,9 767 XX081 06:24:02 VHFLL 116 376 14 1 3,2 2,4 1,6 VHFRL 31 262 8,5 9,3 1,1 147 638 2,8 4,3 5,2 747 XX074 06:31:27 0VHFL 120 474 13 1 4 2,8 2 0VHFR 27 323 12 12 1,4 147 797 3,4 5,4 6,4 767 XX1502 06:43:47 VHFLL 81 302 19 1 3,7 2,8 1,2 VHFRL 13 45 3,5 2,9 0,2 95 348 1,4 3,7 2,8 767 XX228 06:48:18 VHFLL 109 340 10 1 3,1 1,9 1,4 VHFRL 6 19 3,2 2,3 0,1 116 360 1,5 3,1 1,9 747 XX176 07:01:54 0VHFL 125 434 16 1 3,5 2,3 1,7 0VHFR 21 68 3,2 1,7 0,3 146 502 2 3,4 2,2 747 XX178 07:02:22 0VHFL 93 352 21 1 3,8 2,9 1,4 0VHFR 9 45 5 7,2 0,2 102 397 1,6 3,9 3,5 747 XX222 07:04:15 0VHFL 105 339 16 1 3,2 2,1 1,3 0VHFR 2 9 4,5 2,1 0 107 348 1,4 3,3 2,1 747 XX017 07:09:10 0VHFL 105 413 14 1 3,9 2,7 1,6 0VHFR 4 13 3,3 1 0,1 109 426 1,7 3,9 2,6 747 XX177 07:11:49 0VHFL 101 380 17 1 3,8 2,3 1,5 0VHFR 2 6 3 1,4 0 103 386 1,5 3,7 2,3 747 XX092 07:12:14 0VHFL 107 373 16 1 3,5 2,6 1,4 0VHFR 5 25 5 3,8 0,1 112 398 1,5 3,6 2,6 747 XX117 07:14:46 0VHFL 114 520 15 1 4,6 2,7 2 0VHFR 7 33 4,7 3 0,1 121 553 2,1 4,6 2,8 747 XX215 07:15:33 0VHFL 127 432 17 1 3,4 2,4 1,7 0VHFR 15 79 5,3 5,4 0,3 142 511 2 3,6 2,9 747 XX066 07:23:39 0VHFL 106 354 14 1 3,3 2 1,3 0VHFR 18 68 3,8 1,8 0,3 124 422 1,6 3,4 2 747 XX183 07:24:42 0VHFL 97 318 9 1 3,3 1,8 1,2 0VHFR 8 26 3,3 1,8 0,1 105 344 1,3 3,3 1,8 767 XX229 08:01:05 VHFLL 112 338 12 1 3 2 1,2 VHFRL 15 51 3,4 2,9 0,2 128 390 1,4 3 2,1 747 XX208 08:10:47 0VHFL 100 342 25 1 3,4 2,9 1,2 0VHFR 7 28 4 3,1 0,1 107 370 1,3 3,5 2,9 767 XX252 08:18:19 VHFLL 98 293 18 1 3 2,3 1 VHFRL 3 15 5 5,2 0,1 102 309 1 3 2,4 747 XX176 08:18:42 0VHFL 151 502 15 1 3,3 2,4 1,7 0VHFR 31 121 3,9 2,5 0,4 182 623 2,1 3,4 2,4 747 XX214 09:05:19 0VHFL 121 415 17 1 3,4 2,5 1,3 0VHFR 33 103 3,1 2,3 0,3 154 518 1,6 3,4 2,5 747 XX010 09:07:50 0VHFL 146 582 15 1 4 3 1,8 0VHFR 25 100 4 2,9 0,3 172 683 2,1 4 3 747 XX084 09:07:51 0VHFL 157 557 25 1 3,5 3,5 1,7 0VHFR 10 26 2,6 1,5 0,1 167 583 1,8 3,5 3,4 747 XX9150 09:18:34 0VHFL 140 522 13 1 3,7 2 1,6 0VHFR 9 45 5 4,9 0,1 149 567 1,7 3,8 2,3 747 XX035 09:29:49 0VHFL 167 577 14 1 3,5 2 1,7 0VHFR 28 131 4,7 3,9 0,4 195 708 2,1 3,6 2,4 747 XX209 09:31:45 0VHFL 138 460 16 1 3,3 1,9 1,3 0VHFR 6 38 6,3 7 0,1 144 498 1,5 3,5 2,4 767 XX253 09:41:42 VHFLL 101 445 14 1 4,4 2,6 1,3 VHFRL 9 29 3,2 1,8 0,1 110 474 1,4 4,3 2,6 747 XX085 09:42:18 0VHFL 114 448 20 1 3,9 3 1,3 0VHFR 4 16 4 4,1 0 118 464 1,3 3,9 3 747 XX138 10:01:47 0VHFL 168 563 13 1 3,4 2 1,6 0VHFR 7 37 5,3 3,6 0,1 175 600 1,7 3,4 2,1 767 XX046 10:02:39 VHFLL 157 523 14 1 3,3 2,4 1,4 VHFRL 29 352 12 10 1 187 876 2,4 4,7 5,6 747 XX049 10:05:02 0VHFL 128 486 21 1 3,8 3,2 1,3 0VHFR 25 102 4,1 2,8 0,3 153 588 1,6 3,8 3,1 747 XX138 10:06:22 0VHFL 175 554 12 1 3,2 1,7 1,5 0VHFR 6 38 6,3 4,6 0,1 181 592 1,6 3,3 2 747 XX007 11:29:22 0VHFL 184 732 19 1 4 3,2 1,8 0VHFR 0 0 0 0 0 184 732 1,8 4 3,2 747 XX059 11:32:06 0VHFL 139 538 17 1 3,9 2,9 1,3 0VHFR 45 452 10 12 1,1 204 ### 2,6 5,4 6,5 747 XX027 11:52:09 0VHFL 182 718 17 1 3,9 3,2 1,7 0VHFR 18 145 8,1 11 0,3 200 863 2 4,3 4,5 747 XX025 11:52:30 0VHFL 234 986 20 1 4,2 2,8 2,3 0VHFR 3 40 13 20 0,1 237 ### 2,4 4,3 3,5


06/04/04 26 version 1.0

A/C TYP


LFT TOT KEY-DWN

LFT MAX KEY-DWN

LFT MIN KEY-DWN

LFT AVG KEY-DWN

LFT SD KEY-DWN

LFT % LOAD

RADIO RHT TOT TX's

RHT TOT KEY-DWN

RHT AVG KEY-DWN

RHT SD KEY-DWN

RHT % LOAD

TOT Tx's

TOT KEY-DWN

% TOT LOAD

TOT AVG

Global_SD

747 XX058 12:03:42 0VHFL 151 648 14 1 4,3 2,8 1,5 0VHFR 37 549 15 12 1,3 188 ### 2,8 6,4 7,1 747 XX028 13:29:34 0VHFL 203 872 14 1 4,3 2,7 1,8 0VHFR 9 39 4,3 3,4 0,1 212 911 1,9 4,3 2,7 747 XX026 13:32:10 0VHFL 187 706 15 1 3,8 3 1,4 0VHFR 17 57 3,4 2,6 0,1 204 763 1,6 3,7 3 747 XX018 14:05:59 0VHFL 209 854 15 1 4,1 3,1 1,7 0VHFR 13 65 5 5,1 0,1 222 919 1,8 4,1 3,2 747 XX018 14:17:43 0VHFL 260 915 16 1 3,5 2,7 1,8 0VHFR 20 81 4,1 4,3 0,2 280 996 1,9 3,6 2,8

Data integrity considerations

The data obtained from the QAR experiences occasional anomalies which affect the integrity of the data. The QAR monitors the data and logs the errors within the data itself with a resolution of one second. The analysis presented in this paper accounts for these errors and applies a series of criteria to determine if a transmission actually occurred.

Since there are several error profiles the analysis tool includes a number of error traps that filter the transmission data and ignore any transmissions that fail the pass criteria. In brief, these criteria (described in the table below) ensure that any single-frame transmission that is marked "Bad" is excluded from the overall transmission count. Similarly, any multi-frame transmission that has frames marked "Bad" throughout its entire length are also excluded from the transmission count.

Table: Illustration of criteria used to determine real transmissions

Flight Profile Considerations

In order to characterise the altitude profile of the flights, the data extraction tool was designed to detect the transition points based on estimations of climb rate. This is

Time (s) Error indicator

Transmit activity

Test for effective transmissions

To+0 . To+1 B K To+2 B K To+3 K

Pass

To+4 . To+5 K To+6 B K To+7 B K

Pass

To+8 . To+9 B K To+10 B K To+11 B K

Fail

To+12 . To+13 B K Fail


06/04/04 27 version 1.0

sampled at multiple points to account for individual variations in flight profile such as temporary shifts in altitude. For some flights it was noticed that a procedure called Continuous Descent Approach (CDA) was used. Although this is not to date an officially published procedure, it is common practice to have this gradual form of transitional descent in less busy sectors. This is likely to be also dependent on traffic levels and hence time of flight. A ramification of this is a shortened cruise time that is replaced by a longer and more gradual descent, resulting in a shorter overall cruise time. In this analysis any sustained descent after the maximum altitude attained in a flight was classified as the start of the descent phase.



06/04/04 28 version 1.0

Appendix 3: Comparison with other investigations

The results of another investigation of voice DSB-AM transmissions are described in Working Paper 20 of ACP/WGB/16th meeting. This investigation concerned some of the analysed parameters in the investigation described in this report. In particular the previous investigation covered for short and long haul flights the following information elements: average and maximum number of transmissions, average and maximum transmission duration, average cumulative transmission time as a percentage of flight time and probabilities of transmissions of a particular duration transmission.

A detailed one to one comparison is not possible as the previous analysis considered a subset of the parameters investigated in this analysis. The table below compares the statistics of the previous investigation (A1) with the present investigations (A2) for the items that were investigated in both analyses.

ATC AOC

Short haul flights

Long haul flights

Short haul flights

Long haul flights

A1 A2 A1 A2 A1 A2 A1 A2

Average number of transmissions per flight

66 66 137 144.3 2 4.5 3 18.3

Maximum number of trans-missions in one flight

126 93 344 281 23 25 47 93

Average transmission duration (s)

3.2 3.2 3.7 3.7 3.2 3,2 3.7 5.4

Maximum transmission duration (s)

23 14 53 36 28 24 46 43

Average cumulative TX time (% of flight time)

3,5 3,4 1,6 2.0 0,4 0,3 0,08 0,4

Table: Comparison of results with other investigations

The comparison shows that there are no significant deviations. Furthermore the comparison of the transmission duration probability distributions shows similar results.



05/04/04 29 version 1.0

Appendix 4: HF profile usage

A generic utilisation profile for the HF radio is provided below. Data extracted for HF radio utilisation reveals HF transmission activity during long haul flights only10. The summary in Table 9 indicates a similar load distribution between the left and right HF radios.

Left Radio Right Radio Maximum number of transmissions 98 52 Maximum cumulative transmission time (in seconds and as % of flight time)

551s (1.33%)

443s (1.23%)

Average transmission time 5.57s 5.27s Standard deviation of average duration (min) 1.08s 0.58s Standard deviation of average duration (max) 8.35s 10.17s

Table: HF Voice transmissions statistics for the left and right HF radios (long haul)

The figure below shows an example HF transmission profile for one of the flights. All HF transmissions are concentrated towards the mid-cruise timeframe. This is consistent with the expected usage of HF voice radios in oceanic areas. However, a number of flights that operate on continental routes (Bahrain, Tel Aviv, Hong Kong and Tokyo) do not make use of the HF radio at all. In most cases, the usage of the left and right radios occurs at distinctly separate times (not simultaneously or alternately).

0

5000

10000

1500020000

25000

30000

35000

40000

0 5000 10000 15000 20000 25000 30000

flight time (s)

altit

ude

(ft)

HF RightHF Left

Figure 8: HF radio usage profile for a long haul flight from Africa to Europe

10 10% of the long haul flights indicate no HF activity at all.

6850 8250

DRAFT ACP/WGM9/WP__ Attachment 3 to ACP/WGM9 paper: “VDL Mode 4 Cosite Interference Investigations: Status Report”

EUROCONTROL/CSM 1 Version 0.8

DRAFT Version 0.8

An Investigation into the Aircraft VHF Voice Receptions (Minimum Expected Received Voice Signal Level)

1 Scope This paper complements the information in the document “Voice DSB-AM Aircraft Transmissions Profile”, [1], developed previously by EUROCONTROL. That document investigated the statistical characteristics of the aircraft voice transmissions using real airline data and proposed a Transmissions Profile based on the statistical analysis. The current paper provides information to be used in relation to the reception of voice messages. The use of real data for the analysis of the receptions is not as straightforward as in the case of transmissions and therefore this paper provides an analytical only investigation on the subject. During a flight an aircraft receives transmissions from ground stations as well as from other aircraft. However, the crew is practically interested in listening only to a subset of the transmissions related to their flight. This subset includes all the transmissions that are addressed to the aircraft itself, as well as transmissions intended for other aircraft in the vicinity for situational awareness purposes. The aim of this paper is to calculate the expected signal level of the desired transmissions received on board an aircraft. This draft version is issued for comments with regard to the assumptions taken with respect to the scenarios used as a basis to derive the minimum received signal strength. For the calculation of the received signal level, the appropriate separation distances are derived by considering in the various operational scenarios the maximum distance1 separating the aircraft from ground stations or other aircraft. This maximum distance is then used to calculate the power budget and the corresponding minimum received signal level among the desired receptions throughout each flight phase.

2 Operational Scenario considerations

2.1 Airport surface (Ground) scenario

2.1.1 Distance to ground station The distance between aircraft and the ground station antenna is a function of the airport layout. In most airports the VHF antennae are mounted on the control towers or similar high structures that are normally located close to the airport terminal. Considering the size of an average international airport, the maximum separation between the ground antenna and the parked aircraft is assumed to be 1000 m. Since ATC requires being able to communicate with any aircraft on the airport surface, the maximum separation

1 Throughout this paper, the distance between aircraft and a ground station and between aircraft and other

aircraft refers to the distance between antenna pairs.



distance between an aircraft operating on some remote part of the airport and the ground station antenna is assumed to be 4 km.

2.1.2 Distance to other aircraft on the ground The distance between aircraft depends on their location on the airport surface. The distance separating active aircraft in the same timeframe in the gate (i.e. departing during the same period from different gates) depends a lot on the layout of the individual airports. Large airports have their terminal buildings located within a 1 km radius. Therefore in the worst case a separation of 1 km is assumed at the gates. For aircraft operating on taxiways the critical case occurs in the incursion zone nearby the runway. Since a typical large runway is 10,000ft long it is assumed that the runway incursion zone is of similar dimensions so the maximum separation between taxiing aircraft on the airport surface is assumed to be 3 km.

2.2 Airborne (Climb-out, En route and descent) scenario

2.2.1 Distance to other aircraft and ground stations in en route airspace

In the case of airborne aircraft, the distance to a ground station is a function of altitude and the horizontal separation. In en-route sectors most of the aircraft are at cruise altitude which is generally above FL300 (around 10 km). Furthermore, the aircraft may be at large horizontal distances from the ground station site. On observation of a number of sectors2 it is evident that shape of sectors is generally very irregular, so the maximum range between aircraft varies from one sector to another. On close observation of some sectors, the absolute largest distance across (considering the fixed route structure) is just over 300km; but this is very exceptional. Considering several sectors, the most frequent typical maximum distance is 150km, followed by 200km for the larger sectors. Thus the size of a sector varies. Considering that a ground station is generally situated close to centre of the sector3, it will be assumed that maximum distance between the ground station and an aircraft situated at the sector boundary is 150 km4. In en route airspace, aircraft are required to maintain a forward separation that runs into several kilometers and depends on a number of factors. However, in general airborne aircraft have a typical forward separation of 50 NM (approx. 90 km) in a radar environment, and up to 80 NM in procedural airspace. Although aircraft at cruise are capable of receiving transmissions from afar5, the most critical transmissions originate from aircraft in the nearby region. This includes aircraft on parallel as well as on non-parallel paths, and aircraft at different altitudes. For the purpose of determining the weakest signal of interest, a balance needs to be struck between what is the largest 2 A number of sectors in the Upper Airspace in the Benelux region were observed. 3 One of the considerations in sector design is optimal VHF signal coverage. This partly depends on the

ground relief but generally antenna stations are situated towards the centre of the sector airspace for optimal coverage in all directions.

4 This is a representative value that also accounts for sectors overlying the sea where the ground stations are at a distance.

5 The line of sight distance increases at high altitude and can span several hundred kilometres.



separation distance and that what is operationally relevant to the flight. With these two criteria, and bearing in mind that the separation between aircraft at this FL is at least 50NM (90km) it seems reasonable to assume that an aircraft would be operationally interested in 1-2 aircraft downstream; so one can consider a maximum aircraft-aircraft en route distance of 200km. The case of flights operating in oceanic or other remote airspace is an exception. It is noted that the dimensions of such an en route sector are likely to be much larger than those of a typical core (continental) area sector. An aircraft operating in oceanic airspace may still receive transmissions from a ground station until line of sight coverage permits6. This means that some receptions may originate from aircraft or from a ground station at a distance greater than the 100 km considered above. At typical cruise altitudes of 43,000ft the line-of-sight distance is about 470 km. Nevertheless, such receptions from other aircraft or ground stations at such large distances are unlikely to be of any operational interest to a flight, particularly when operating in low density airspace. The distance of 470 km is considered in this paper in order to provide the lower bracket (absolute minimum) of the desired received signal strength.

2.2.2 Distance to aircraft and ground station in TMA airspace In the TMA aircraft operate at slower speeds and the separation distances are less than that during cruise. Although arriving and departing traffic operate on designated routes to maximize their separation (SIDs and STARs), the critical case involves the operation of aircraft within the TMA and the surrounding transitional airspace. Thus since departing and arrival traffic are segregated by virtue of the route structure (note they are typically on different frequencies), the departing aircraft are operationally interested in transmissions from other departing aircraft. Further, since a given aircraft is interested in a subset of the downstream traffic, the TMA aircraft-aircraft separation distance is smaller than the en route figure; hence 150km7 is considered to be in the right order. On a similar basis, the ground-aircraft separation distance is expected to be nominally 1/2 the max aircraft-aircraft distance since the ground station antenna is expected to be located centrally for optimal coverage. Accounting for the irregularity of the sector shapes (optimal ground station location also depends on terrain relief) one could foresee a worst case factor of 3/4 instead of the above 1/2; thus 150km for enroute and 110km for TMA.

2.3 Summary of results: ground and airborne scenarios The following table summarizes the maximum separation distances for all the cases considered above.

6 Communications with Oceanic Air Traffic Control Centres is normally maintained on HF when out of

VHF coverage. 7 Note that within the TMA aircraft could operate within as close as 5 km in the holding pattern and final

approach but for the weakest signals we are interested in the aircraft that are furthest away.



Victim aircraft location From Aircraft (km) From Ground Station (km) Ground 3 4 TMA 150 110 En route 200 150 En route (remote) > 100 470 Table 1: Summary of estimated maximum separation distances for all the scenarios.

3 Received Signal Power for each flight phase For each phase of the flight a power budget is constructed on the basis of the maximum separation distance estimations of Table 1. The received voice signal levels on board an aircraft for each phase summarized in the Tables 2a and 2b below represent the worst case for the weakest signal received onboard the aircraft. For the purposes of the power budget calculations, the ground station transmitter output power is assumed to be 25W (44 dBm) on the airport surface and 100W (50 dBm) for ground to air communications (TMA and enroute), while the aircraft transmitter power is assumed to be 25W8. The power budgets for the ground scenarios assume a ground-space propagation model which accounts for multi-path effects. The propagation losses include additional terms that are a function of transmitting and receiving antenna heights above the ground plane. The largest losses occur when the height of the transmitting antenna above the ground plane is higher than that of the receiving antenna. The worst case is when the both antennae are at the lowest height of 3m (bottom antenna on the fuselage). However as a representative case9 the transmitting aircraft is assumed to use the top antenna (6 meters above the ground) and the receiving aircraft is assumed to use the bottom antenna (3 meters above the ground). Consistent with the assumption of a large airport surface (see 2.1), the antenna of the ground station is assumed to be mounted on a high structure 90 m above the airport surface. The power budgets for the airborne scenarios assume free space loss. In all cases, the aircraft cable losses are assumed to be -3dB and the antenna gain 0 dB. The cable loss and antenna gain for the ground station are assumed to be-3 dB and 2 dB respectively. The calculation of the power at the aircraft receiver input is based on the following formula: Power = [Output power – cable loss + antenna gain]transmitter - propagation losses10]free space/ ground plane + [antenna gain – feeder loss]receiver

8 The MOPS value of 25W is assumed here. Note that the maximum transmit output power for the

ARINC 750 class radios is 40W (46 dBm). Using this transmit power increases the received power by about 2 dB.

9 In reality, a DSB-AM radio is using the same antenna for transmitting and receiving. However, the allocation of antennae to the radios may vary in the aircraft installations and all radios may be used.

10 The formulae used to calculate the propagation loss term are: for free space: -27.5+20*LOG10(F(MHz))+20*LOG10(D(NM)) and for the ground plane 130.7+40*LOG10(D(m))-20*LOG10(htx(m))-20*LOG10(hrx(m)) where D is the separation distance in nautical miles, F is the operating frequency in MHz, htx is the

transmit antenna height in metres and hrx is the receive antenna height in metres.



where the propagation losses are calculated on the basis of the maximum ranges specified in Tables 2a and 2b, which are based on the information of Table 1. The calculated received signal power of voice receptions on the ground is between -57 dBm and -75 dBm from other aircraft and between -31 dBm and -56 dBm from the ground station. The latter values are consistent with results from practical measurements reported in [2]. This measurement activity considered a ground station radio situated on high structures and the signal strength was sampled at a variety of ranges on the airport surface. One of the tests was carried out at Paris CDG airport with very similar conditions as those assumed in the link budgets below, i.e. transmitter power 25W, transmit antenna height 90 m, receive antenna height 3m. In these conditions, a signal of -52 dBm was measured at a range of 3069 m and a signal of -27 dBm was measured at a range of 990 m. Although the test conditions were not the same as those assumed for the calculations in this report (e.g. antenna height), the model used to predict the received power levels on the ground in this report compares very closely to the above measurements11. Although there are no comparable values for signal strengths received at the aircraft, one set of measurements taken at a small airport (Angers) where the transmitter was mounted at a height of 21 m, a signal strength of -44 dBm was measured at a range of 1160 meters. This is consistent with the view that the received signal power decreases with decreasing transmit antenna height, as is observed by comparing the ground rows of Tables 2a and 2b12. Scenario Phase Maximum Range (km) Received Power (dBm)

Departure gate 1 - 57 Ground Taxi 3 - 75 Climb-out/Descent 150 - 80 Airborne En route 200 - 82 Table 2a: Received voice signal level (other aircraft source)

Scenario Phase Maximum Range (km) Received Power (dBm)

Departure gate 1 - 31 Ground Taxi 4 - 56 Climb-out/Descent 110 - 68 En route 150 - 72 Airborne En route (oceanic) 470 - 82 Table 2b: Received voice signal level (ground station source)

4 Summary - Conclusions The following table summarizes the minimum voice signal level which is expected to be received on board an aircraft during the various phases of the flight. Table 4 considers the worst case (minimum of the received signal levels from aircraft or ground station sources in Tables 2a and 2b) for each flight phase. 11 The model in this report predicts -31 dBm for a distance of 1 Km and -51 dBm for a distance of 3 Km. 12 Note that the transmitter height above the ground plane for the aircraft is assumed to be 6 m (top

antenna).



Scenario Phase Victim Aircraft location Min Received Signal (dBm) Ground Departure Taxiway/Runway - 75

Climb Departure TMA - 80 En route En route13 - 82 Airborne Descent Arrival TMA - 80

Ground Arrival Taxiway/Runway - 75 Table 4: Minimum received voice signal level onboard an aircraft (per flight phase)

5 References [1] An Investigation into the Aircraft VHF Voice Transmissions (Aircraft DSB-AM

Voice Usage Profile), Version 1.0, EUROCONTROL, April 2004. [2] Proposed Modifications to the Ground-Ground interference scenario, AMCP

WGB/11 WP2, EUROCONTROL, August 2001.

13 The weakest signal considered is that of -82 dBm from other aircraft in the sector. The signal level of

-82 dBm from ground stations for aircraft in oceanic airspace (see Table 2b) is an extreme case (distance 470 km) and in general in this region, the crew may rely on other than VHF modes of communications. Therefore such a signal level may not be critical for reception. However it is seen that this signal is in the same order of the weakest airborne signals.

aeronautical communications panel joint meeting …

Documents