invited paper white space communication systems: an ... · 2. white space communication systems 2.1...

IEICE TRANS. COMMUN., VOL.E97–B, NO.2 FEBRUARY 2014261

INVITED PAPER Special Section on Technologies for Effective Utilization of Spectrum White Space

White Space Communication Systems: An Overview of Regulation,Standardization and Trial

Hiroshi HARADA†a), Fellow

SUMMARY This paper summarizes the current status of regulations,standardization efforts and trials around the world regarding white space(WS) communications, especially television band WS (TVWS). Afterdefining WS communication systems configurations and function and thecategories of white space database, the TVWS regulations in United States,United Kingdom, and Japan are summarized. Then regarding status ofstandardization for TVWS devices, IEEE 802 and IEEE 1900 standardsare summarized. Finally ongoing pilot projects and trials of WS commu-nications in the world are summarized, and trends and future direction ofresearch on WS communication systems are summarized.key words: white space, IEEE, cognitive radio, database, standardization

1. Introduction

In order to cope with issues due to the exhaustive fre-quency assignments demanded by the expansion of broad-band wireless communications, wireless communications in“the white space (the WS) [1]–[20]” have been expectedaround the world. The communication systems are called“WS communication systems [1]–[20].” The existence ofWS allows secondary systems to share the operational fre-quency band of existing licensed wireless systems (primarysystems) provided that they impose no harmful interferenceon the primary systems. Wireless communication systemsthat are based on cognitive radio (CR) and dynamic spec-trum sharing (DSS) are expected to increase the capacity forcurrent wireless communication systems.

To realize the WS communication systems, severalpoints need to be considered. The first point is its oper-ational frequency band and its regulation for WS commu-nication systems. Needless to say, there are WS resourcesin all frequency bands, but only the UHF-TV band is be-ing actively considered for WS communications. This isbecause the band suits the systems that currently use mi-crowave bands such as wireless broadband in order to takelonger transmission range and more number of channels.We sometimes call the band TV white space (TVWS). TheTVWS regulations for the use of TVWS are being discussedall over the world.

The second point is white space database (WSDB) [2]that decides possibility of WS usage by predicting servicecontour of primary and secondary systems in order to pro-tect interference to primary systems from secondary sys-tems and share spectrum between primary and secondary

Manuscript received July 16, 2013.Manuscript revised September 30, 2013.†The author is with NICT, Yokosuka-shi, 239-0847 Japan.

a) E-mail: [email protected]: 10.1587/transcom.E97.B.261

systems.The third point is the air interface for WS communi-

cations. Many interfaces will be candidates for several usecases. Wireless regional area network (WRAN) [13], [20],wireless local area network (WLAN) [14] and wireless per-sonal area network (WPAN) [15], [20] including sensor net-work and machine-to-machine (M2M) communications arethe representative air interfaces. The air interfaces mustbe standardized to reduce price of wireless unit and to in-crease the number of unit suppliers, and to expand applica-tion fields. There are several standardization organizations(SDOs) or bodies to discuss the standardization. IEEE is oneof major standardization bodies. Moreover, several whitespace pilot projects have been launched in the world by us-ing wireless units compliant with standards and WSDB. Ifmissing parts in the current regulations are found in the pilotprojects, regulators may modify their regulations. In sum-mary, the ecosystem between regulation, research and de-velopment, standardization, and pilot project is configuredas shown in Fig. 1.

In this paper, current regulation status and standardiza-tion activities on white space are summarized. Regardingstandardization, activities on IEEE 802 and IEEE Dyspan-SC (IEEE 1900.x) are summarized. Then this paper de-scribes current status of several pilot projects in the world.Finally future recommended direction is described.

Fig. 1 Ecosystem between regulation, research and development,standardization, and pilot project.

Copyright c© 2014 The Institute of Electronics, Information and Communication Engineers

262IEICE TRANS. COMMUN., VOL.E97–B, NO.2 FEBRUARY 2014

2. White Space Communication Systems

2.1 System Configuration

Figure 2 shows a fundamental configuration of WS commu-nication systems. As assumptions, all primary users and sec-ondary users can access to WSDBs. The primary users op-erate licensed systems. In TV band, primary users provideTV services. Secondary users operate their wireless com-munication systems by using white space devices (WSD).The WSDBs can decide possibility of WS usage by pre-dicting service contour of primary and secondary systems.The WSDB has information on radio parameters of primarysystems. The radio parameters may include location, an-tenna height, transmission power, antenna pattern, and an-tenna tilt.

2.2 Function of WSDB

In order to protect interference to primary systems from sec-ondary systems and share spectrum between primary andsecondary systems, WSDB has the following functions:

a Predict contour of primary systems by using informa-tion on radio parameters (location, antenna pattern,transmission power, etc.).

b Predict contour of secondary systems by using infor-mation on radio parameters (location, antenna pattern,

Fig. 2 A fundamental configuration of WS communication systems.

transmission power, etc.). This is an optional function.

By the two contour prediction results and threshold level ofinterference, the WSDB provides radio parameters of sec-ondary systems to keep coexistence between primary andsecondary systems. As shown in Fig. 2, all secondary sys-tems can coexist with primary systems because the contoursof primary and secondary systems are not overlapped. How-ever, it is something difficult to keep coexistence betweensecondary systems. This means that some secondary sys-tems may interfere with the others. So to reduce the in-terference, WSDB for the coexistence between secondarysystems is needed. The WSDB has the following functions:

i Predict contour of secondary systems by using infor-mation on radio parameters (location, antenna pattern,transmission power, etc.)

By the contour prediction results and threshold level of in-terference, the WSDB provides radio parameters of sec-ondary systems to keep coexistence between secondary sys-tems. The secondary systems may use different wirelessaccess schemes or common wireless access schemes. Sothe WSDB for coexistence between secondary users may becategorized into two; for secondary systems used differentwireless access schemes and for ones used common wire-less access schemes shown in Fig. 2. Table 1 summarizesthe categories.

HARADA: WHITE SPACE COMMUNICATION SYSTEMS: AN OVERVIEW OF REGULATION, STANDARDIZATION AND TRIAL263

2.3 Category of WSDB

To introduce the WSDBs in the real situation, there are threestages shown in Table 2. The difference between stages isthe response time to get available WS frequency map. Inthe first stage, the response time is longer than 24 hoursbecause it may take longer time to predict contour of pri-mary and secondary systems and calculate recommendedradio parameters for the secondary systems. In the stage,only fixed wireless communication is available, because theWS radios cannot move until available WS frequency mapis obtained. As the second stage, the response time will bereduced within 24 hours. Moreover the WS radios need toaccess to WSDB and get the map again when the equipmentworks every certain meter. In the case, the WS radios witha small mobility may be supported. As the third stage, theresponse time becomes much faster within several secondsand the WSDB will support WS radios under highly mobileenvironment.

2.4 Discussion Points

To make WS communications feasible, the following pointsneed to be discussed.

1. Radio regulations for WS communications: Opera-tional frequency bands, maximum transmission power,spectrum mask, and so on.

2. WSDB specifications and operational guideline.3. Requirement and category for WSD.4. Specification of WSD

Table 1 Category of WSDB.

Table 2 Scenario of WSDB Introduction.

3. Radio Regulations for WS Communications

3.1 United States

3.1.1 History [1]–[6]

In United States, Federal Communications Commission(FCC) is mainly discussing on the regulation for WS com-munication systems. Table 3 summarizes the history of reg-ulation. United states considered TV bands for the WS com-munication systems, and WSD in TVWS is called televi-sion band device (TVBD). TVBD is discussing in licence-exempt category.

3.1.2 Category of TVBD

As category of TVBD, there are two classes: fixed and per-sonal/portable devices. Table 4 summarizes requirementsof the devices. The personal/portable devices are moreovercategorized into two: Mode I and Mode II. The Mode I is aclient device and activated by a fixed device or a Mode II de-vice. Mode II device is an independent device with capabil-ity to access WSDB to access available channels. In Table 4,there is one more category, sensing only personal/portabledevice that required performing spectrum sensing prior tooperation.

3.1.3 Requirement for WSDB

The requirement for WSDB in FCC is summarized in Ta-ble 5. FCC requests TVBD to access WSDB every 24 hours.

Table 3 History of regulation in FCC.

Table 4 Category of TVBD in FCC.


Table 5 Requirement for WSDB in FCC.

All devices except for Mode I and sensing only device musthave a geolocation capability with accuracy up to +/−50 mand send the information to WSDB.

3.1.4 Transmission Power and Spectrum Mask

As shown in Table 4, fixed devices are permitted to trans-mit up a 4 W equivalent of effective isotropic radiated power(EIRP). The EIRP 4 W includes 1 W output power and a6 dBi gain antenna as maximum value, respectively. Per-sonal/portable device are permitted to transmit up to 20 dBmequivalent of EIRP. However, the transmission power is lim-ited to 16 dBm in operating in a channel adjacent to an in-cumbent licensed user and within the protected area of theWS communication services. Moreover, spectrum density isconstrained to 12.6 dBm and 2.6 dBm per 100 kHz for fixedand personal portable devices, respectively.

Regarding spectrum mask, it is required to achieve ad-jacent channel attenuation of 55 dB below the highest powerin a 6 MHz operating channel in 100 kHz bandwidth.

3.1.5 Operational TV Channel

The channel spacing of TV channel is 6 MHz. Fixed devicescan use VHF channels 2-13 and UHF channels 14-51 exceptfor 3, 4 and 37 channels. Personal/portable devices can useUHF channels 14-51 except for 14-20 and 37 channels.

3.2 United Kingdom

3.2.1 History [7]–[12]

In United Kingdom, Office of Communications (Ofcom) ismainly discussing on the regulation for WS communica-tion systems. Table 6 summarizes the history of regulation.TVBD is discussing in licence-exempt category.

3.2.2 Category of TVBD

As category of TVBD, there are two classes: master andslave devices. The master deices can contact a WSDB to

obtain a set of available frequencies in their area. In the op-eration, device model number tells whether it has antennasmounted outdoor. The master devices then manage slavedevices, maintaining record of slave devices. The slave de-vices obtain the relevant information from master devicesbut do not contact the WSDB themselves and communi-cate with only master devices. The master devices moreovercease transmission immediately when instructed by the mas-ter device or within 5 seconds of not receiving a responsefrom the master devices to transmission.

3.2.3 Requirement for WSDB

The requirement for WSDB is summarized in Table 7.WSDB must provide a response within 10 seconds. Time-validity stamp to the WSDB is required. Push technologycan be implemented but not as a regulatory requirement.The WSDB returns an information set which must includestart and end frequencies for available bands, associatedmaximum power levels, a time validity for the information,and a notification of any requirement for sensing to be usedin addition.

3.2.4 Transmission Power and Spectrum Mask

The maximum transmit power is determined based on dig-ital terrestrial TV (DTT) protection levels i.e. the cognitivesignal should be at least 33 dB below the received DTT sig-nal.

3.2.5 Operational TV Channel

The channel spacing of TV channel is 8 MHz. The opera-tional channel starts from 470 MHz and ends 790 MHz byusing channel numbers from 21 to 60. TVBD can use chan-nels 21 to 60 except for 31-38 channels.

3.3 Japan

3.3.1 History

Since Nov. 2009, white space operation has been discussed


Table 6 History of regulation in Ofcom.

Table 7 Requirement for WSDB in Ofcom.

in Ministry of Internal Affairs and Communications (MIC)in order to secure bandwidth. Table 8 summarizes the his-tory of regulation. Five main applications are under discus-sion in the Council for White Space Promotion in MIC.

- Wireless microphone- Area broadcasting- Sensor network- Wireless broadband- Wireless access systems for emergency situation (dis-

aster)

Currently area broadcasting services have been permitted todo actual services in TV white space. This is a license-basedsystem, and the actual services have started in several placesof Japan.

The area broadcasting service is based on ISDB-T(ARIB STD-B31) and standardized as ARIB STD-B55. TheISDB-T has 13 OFDM segments in a channel. The ARIBSTD-B55 standardized specifications in the case when one

segment or full segment is used. Table 9 shows fundamentalspecification of one segment type area broadcasting. MostJapanese mobile phone have capability to receive one seg-ment ISDB-T broadcasting services. New service operatorscan start new area-dedicated broadcasting services by usingthe standard in TVWS. The spectrum mask is also shown inTable 10.

Currently usage of WSDB has not been discussed andMIC manages the spectrum license. To get license, the areabroadcasting operators submit license application form toMIC and MIC provides license on the basis of radio regula-tion and interference level to primary users.

Wireless microphone is categorized in higher prioritythan other WS communications and area broadcasting ser-vices. This is because the wireless microphone is forcedto move to white space from 700–900 MHz bands in orderto secure bandwidth for next generation mobile phone sys-tem. To support usage of wireless microphone, MIC pro-vides WS channel lists. The wireless microphone operatorssubmit their license application forms to MIC and MIC pro-vides licenses on the basis of radio regulation.

Licensing to both systems looks good. But new issuesarise, co-existing issue between area broadcasting and wire-less microphone. To discuss the coexistence mechanism,coexistence working group (WG) is launched under councilfor white space promotion [21] from the following view-points.

• Who will provide available channel map on whitespace?• Who will permit to use white space?• Will WSDB be used?


Table 8 History of regulation in Japan.

Table 9 Specification of one segment type area broadcasting.

• Who will manage coexistence between WS systems?

A coexistence procedure between wireless microphone andarea broadcasting was issued in 2013.

3.3.2 Coexistence Mechanism

Figure 3 shows a coexistence mechanism considered inJapan. In the previous section, application procedure to getlicense of wireless microphone has been introduced. Af-ter getting the license, wireless microphone operators reportthe operational bands to the wireless microphone promotionalliance or forum. The alliance or forum may request thewireless microphone operators to do coexistence with pri-mary and secondary operators.

When area broadcasting service operators apply licenseto the MIC, the operators need to discuss with wireless mi-

Table 10 Spectrum mask of area broadcasting.

crophone alliance or forum to find white spaces that do notinterfere with wireless microphone. After getting the infor-mation, area broadcasting service operators start to applylicense to MIC. After area broadcasting service operatorsget licenses. The licenses information will be reported toarea broadcasting promotion alliance or forum. Both wire-less microphone and area broadcasting promotion alliancesor forums share the information of their operational bands.

4. Standardization of TVBD Specification in IEEE

Table 11 summarizes standardization activities of TVBDspecifications in IEEE. Currently IEEE 802 and IEEE Dys-pan standards committee (1900.x) have actively discussed


Fig. 3 A coexistence mechanism considered in Japan.

Table 11 Standardization activities of TVBD specifications in IEEE.

the topic. The IEEE 802 mainly has standardized air inter-faces for several WS use cases. For example, IEEE 802.22,IEEE 802.11af, and IEEE 802.15.4m standardize air inter-faces for WRAN, WLAN, and WPAN, respectively. On theother hand, the IEEE 1900 mainly has standardized enablingtechnologies to operate WS communications smoothly. InTable 11, IEEE 802.22, IEEE 802.11af, IEEE 802.15.4m,IEEE 802.19.1, IEEE 1900.4a and 1900.4.1 issued theirspecification document. This section introduces the stan-dards.

4.1 IEEE 802.22 [13]

IEEE 802.22 is a standard specification of PHY and MACfor wireless regional area networks: WRAN in TVWS. Ta-ble 11 shows the fundamental specifications. The IEEE802.22 WRAN network is composed of base station (BS)and customer premise portable equipment (CPE). The BSand CPE can provide a point to multipoint network. ThePHY layer specification is shown in Table 12. The MAC


Table 12 802.22 physical layer specification.

Fig. 4 Frame structure of MAC layer in 802.22.

layer adopts time division duplex (TDD) and OFDMA ismainly used. The frame structure of MAC layer is shownin Fig. 4. To do coexistence with primary systems, severalfunctions are standardized as options. The first is to insert“quiet period” in MAC frame to do spectrum sensing in eachTVBD. In the quiet period, nobody send any message. Thesecond allows CPE to send BS a message when primaryusers are detected by CPE. The third is a function of BS torequest CPE shifting to new operational band. To promotethe standard and to make the standard interoperable one,WhiteSpace alliance (http://www.whitespacealliance.org/)has actively been working.

Moreover, to support enhanced broadband services andmonitoring application, 802.22b project that specifies al-ternate PHY and necessary MAC enhancements to IEEE802.22-2011 standard was launched. The standard definesnew classes of 802.22 devices to address these new appli-cations and supports more than 512 devices connection in anetwork.

4.2 IEEE 802.11af [14]

IEEE 802.11af is an amendment standard that defines mod-

Table 13 802.11af physical layer specification.

Fig. 5 Configuration of IEEE 802.11af.

ifications to both the 802.11 physical layers (PHY) andthe 802.11 medium access control layer (MAC), to meetthe legal requirements for channel access and coexistencein the TV whit space. Table 13 shows the fundamentalspecifications. As shown in Fig. 5, IEEE 802.11af stan-dard is a combination standard by IEEE 802.11 familiesand the PHY has compatibility with IEEE 802.11ac onthe basis of OFDM. IEEE 802.11ac is based on 40 MHzbandwidth with 128-point FFT. In the case of TV chan-nel with 6 MHz channel spacing, the occupied bandwidthis 6 MHz*128/144=5.33 MHz Therefore downclocking ofIEEE 802.11ac is required.

To protect primary users, a procedure to access toWSDB is defined. Also to keep coexistence with other sec-ondary users based on 802.11af system, the standard recom-mends using registered location secure server (RLSS) andthe RLSS stores operational parameters of 802.11af basedsystems and control the parameters if there are interferencebetween systems. To promote the standard and to make thestandard interoperable one, WiFi alliance (http://www.wi-


Table 14 IEEE802.15.4m FSK specification.

Table 15 IEEE802.15.4m OFDM specification.

Table 16 IEEE802.15.4m NB-OFDM specification.

fi.org/) has actively been working.

4.3 IEEE 802.15.4m [15]

IEEE 802.15.4m is an amendment standard that specifies aPHY for 802.15.4 meeting TV white space regulatory re-quirements in as many regulatory domains as practical andalso any necessary MAC changes needed to support thisPHY. Tables 14–16 show the fundamental specifications.IEEE 802.15.4m has three modes; FSK, OFDM, and NB-OFDM. The FSK supports up to several hundred kbps andNB-OFDM supports from several hundred kbps to severalMbps, and OFDM supports higher transmission rate. Re-garding MAC, IEEE 802.15.4m supports IEEE 802.15.4-2012 including IEEE 802.15.4e. The standard also consid-ers a technique to do carrier aggregation between WS andfrequency bands originally used for IEEE 802.15 such assub-GHz or 2.4 or 5 GHz bands.

4.4 IEEE 1900.7

IEEE 1900.7 is developing a draft standard that specifies a

Fig. 6 System architecture of IEEE 802.19.1.

radio MAC sublayer(s) and PHY layer(s) of WS dynamicspectrum access radio systems supporting fixed and mobileoperation in white space frequency bands, while avoidingcausing harmful interference to incumbent users in these fre-quency bands. The consideration of radio regulations, usecases, general requirements, and channel model was final-ized in March 2012. Selection of frequency bands and topol-ogy was done in June 2012. The potential topics for the draftdevelopment phase, which is the current on for the WG,are as follows: Reference model, PHY layer, MAC sub-layer, Convergence sublayer, Security sublayer, and Cogni-tive plane. IEEE 1900.7 is still preparing its draft document.

4.5 IEEE 802.19.1 [16]

IEEE 802.19.1 specifies radio technology independentmethods for coexistence among dissimilar or independentlyoperated TVBD networks and dissimilar TVBD. In short,the standard defines specification of WSDB for the coexis-tence between secondary systems. Figure 6 shows a sys-tem architecture of the standard. The architecture is com-posed of three entities: coexistence manager (CM), coex-istence enabler (CE), and coexistence discovery and infor-mation server (CDIS). Table 17 describes details of the en-tities. In Fig. 6, CM obtains radio operational parametersfrom TVBD network or devices through CE. By using theinformation and also using information from WSDB relatedto primary systems, the CDIS calculates the interferencelevel and finally the CM decided the capability of coexis-tence between TVBD networks or devices.

4.6 IEEE 1900.4a and 1900.4.1 [17]–[19]

A coexistence mechanism similar to IEEE 802.19.1 is stan-dardized in IEEE 1900.4a. IEEE 1900.4a is based on IEEE1900.4. IEEE 1900.4 is a baseline standard to provide aframework for developing intelligent management systemhaving the capability to optimize spectrum usage across dif-ferent frequency bands, radio access technologies (RATs),and operators. To reach this goal, the standard defines anarchitecture of the management system, which is comprisedof the component entities of the management system, ser-


Table 17 Details of the entities in IEEE 802.19.1.

vice access points (SAPs) of these entities, and interfacesbetween them.

As shown in Fig. 7, four management entities are de-fined on the network side: the Operator Spectrum Manager(OSM), the RAN Measurement Collector (RMC), the Net-work Reconfiguration Manager (NRM) and the RAN Re-configuration Controller (RRC). The details are summarizedin Table 18. To support scalable operation, the RMC, theNRM, and the RRC may be implemented in a distributedmanner.

On the other hands, three management entities aredefined on the terminal side: the Terminal MeasurementCollector (TMC), the Terminal Reconfiguration Manager(TRM) and the Terminal Reconfiguration Controller (TRC).Each terminal has one TMC, one TRM, and one TRC. Thedetails are also summarized in Table 17.

IEEE 1900.4a amends the IEEE 1900.4 to enable mo-bile wireless access service in white space frequency bandswithout any limitation on used radio interface (physical andmedia access control layers, carrier frequency, etc) by defin-ing additional components of the IEEE 1900.4 system. Cur-rently considered architecture of IEEE 1900.4a is shown inFig. 7. Compared to IEEE standard 1900.4, four new enti-ties are currently considered in IEEE 1900.4a: the CognitiveBase Station (CBS) Measurement Collector (CBSMC), theCBS Reconfiguration Manager (CBSRM), the CBS Recon-figuration Controller (CBSRC), and the White Space Man-ager (WSM). The details are also summarized in Table 18.

Based on system architecture in Fig. 7, IEEE 1900.4.1 Fig. 7 System architecture of IEEE 1900.4 and 1900.4a.


Table 18 Details of the entities in IEEE 1900.4 and 1900.4a.

provides detailed description of interfaces and service ac-cess points defined in the IEEE 1900.4. In the standard,message and interface between 1900.4 management entities,service access point, and primitives are defined.

5. Pilot Projects and Trials of WS Communications

There are several pilot projects and trials in the world. Butthe projects and trials are categorized into two: internationalcollaboration trials and domestic collaboration trials. Forexample, Japan has done only domestic collaboration trialsfor WS communications. Table 19 summarizes the interna-tional projects and trials [22]–[28]. In the Table, there areseveral tendencies.

• WS communication trials have been doing in Africa[27], [28], Europe [23], [24], [26], South East Asia[22], [25] and so on and adopting the WS system toreduce digital divide between city central and country-side.• Fixed point-to-multipoint rural broadband access ap-

plications are taken.• UHF band is mainly used and WSDB may be used

because some countries still have enough vacant fre-quency bands in TV bands. So dynamic spectrum shar-ing by cognitive radio technique may not be needed.• All finished trials have not used radio equipment taken

existing WS standard.

Regarding first to third bullets, TVWS communicationsystems can achieve a longer-range communication in com-parison with microwave band communications. So ruralbroadband access is one of important applications. But asshown in Table 20, other applications must be considered.Especially WLAN for wireless broadband in house and pub-lic area and WPAN for smart utility, smart grid and sensornetwork are the representative applications. This is becausecurrently the frequency bands for both use cases are fully oc-cupied and new bands are needed. In addition, for both usecases, carrier aggregation between WS and frequency bandsoriginally used for WLAN and WPAN must be considered.

Regarding fourth bullet, there is no development ofstandard compliant WS communication equipment exceptfor NICT for the time being. NICT has developed world’sfirst IEEE 802.11af, IEEE 802.22, and IEEE 802.15.4m(NB-OFDM). Figure 8 summarizes the developed proto-types [15], [29], [30]. The important points are to providelow price WS radio equipment by manufacturers and thedeveloped equipment shall meet regulation provided by reg-ulators. But to develop low price equipment, a big marketthat includes several to several tens million users must beproduced. This is a further discussion point.


Table 19 International projects and trials on WS communications.

Table 20 Applications by WS communications.

6. Conclusions

This paper summarized current status on regulations, stan-dardization and trials in the world regarding WS commu-nications. After defining system configuration and func-tion and category of WSDB, radio regulations in UnitedStates, United Kingdom, and Japan were summarized fromthe viewpoint of history, TVBD category, TVWS require-ment, transmission power, spectrum mask and operationalTV channel. Then as status of standardization for TVBD,IEEE 802 and IEEE 1900 standard related to WS were sum-marized. Finally pilot projects and trials of WS commu-

nications were summarized and trend and future directionof promotion on WS communication systems were summa-rized.

As conclusions, WS communications are expectedto realize two benefits: longer communication range andachievement of more capacities. And several trials of ru-ral broadband access are being actively pursued and trialsof new applications are needed. For the regulation, thereare several discussions in several regions. But to have com-mon knowledge and sense and to promote dynamic spec-trum sharing based communication systems, the establish-ment of a worldwide alliance is needed.


Fig. 8 Prototype of standardized WS communication systems: (a) 802.11af, (b) 802.22, and (c)802.15.4m.

Acknowledgments

The author would like to express sincere thanks toMr. Homare Murakami, Dr. Fumihide Kojima, Dr. KentaroIshizu, Dr. Zhou Lan, Dr. Ha Nguyen Tran, Dr. Chin SeanSum, and Dr. Chang-Woo Pyo for their supports to summa-rize status of standardization and trial. This research wasconducted under a contract of R&D for radio resource en-hancement, organized by the Ministry of Internal Affairs andCommunications, Japan.

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Hiroshi Harada is director of smart wire-less laboratory at National Institute of Informa-tion and communications technology (NICT).He joined the Communications Research Lab-oratory, Ministry of Posts and Communications,in 1995 (currently NICT). Since 1995, he has re-searched Software Defined Radio (SDR), Cog-nitive Radio, Dynamic Spectrum Access Net-work, Smart Utility Network (SUN) and broad-band wireless access systems on the VHF, TVwhite space, microwave and millimeter-wave

band. He also has joined many standardization committees and forums inUnited States as well as in Japan and have fulfilled important roles for them.He has served currently on the board of directors of Wireless InnovationForum (formerly SDR Forum), WhiteSpace Alliance, DSA Alliance, andWi-SUN alliance, and also the chair of IEEE Dyspan Standards Committee(formerly, IEEE SCC41 and IEEE 1900) since 2009 and the vice chair ofIEEE P1900.4, IEEE P802.15.4g, TIA TR-51, and IEEE P802.15.4m since2008, 2009, 2011, and 2011, respectively. He moreover was the chair ofthe IEICE Technical Committee on Software Radio (TCSR) in 2005–2007and has been the chair of Public Broadband Mobile Communication Devel-opment Committee, ARIB since in 2010. He is also involved in many otheractivities related to telecommunications. He has been a visiting professorof the University of Electro-Communications, Tokyo, Japan, since 2005and is the author of Simulation and Software Radio for Mobile Commu-nications (Artech House, 2002). He received the achievement award andfellow of IEICE in 2006 and 2009, respectively and the achievement awardof ARIB and Funai Prize for Science in 2009 and 2010, respectively, on thetopic of cognitive radio research and development.

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