Standardization of Cognitive Radio Networking: A

Comprehensive Survey

Ahmed Khattab, IEEE MemberElectronics and Electrical Communications Department

Cairo University

Giza, Egypt

akhattab@ieee.org

Magdy A. Bayoumi, IEEE FellowThe Center for Advanced Computer Studies (CACS)

University of Louisiana at Lafayette

Lafayette, LA, USA

mab@cacs.louisiana.edu

Abstract—Cognitive radio networking has recently presenteditself as a key technology to alleviate the severe spectrumunderutilization and provide a solution for spectrum scarcity.Cognitive Radio Networks (CRNs) are foreseen as the futurewireless Information and Communications Technologies (ICT)that exploit dynamic spectrum access (DSA) strategies to providewireless connectivity. The enabling component of CRNs anddynamic spectrum access is the cognitive radio (CR). A CR is awireless device that senses the surrounding radio environmentand opportunistically accesses the unutilized spectrum bandsbased on the activities of the surrounding primary licensednetworks. In this article, we provide a comprehensive overview ofthe recent and ongoing standardization activities of the differentICT standardization bodies related to CRN and DSA systems.

Keywords—cognitive radio; cognitive radio networks; software-defined radio; dynamic spectrum access; standardization

I. INTRODUCTION

Cognitive radio networking allows the exploitation ofunutilized spectrum bands in an opportunistic manner to pro-vide wireless connectivity via heterogeneous wireless archi-tectures and dynamic spectrum access techniques. Over thepast decade, Cognitive Radio Networks (CRNs) and DynamicSpectrum Access (DSA) have received tremendous interestfrom both the research and industry communities [1]. The maingoals of such efforts are to improve the capabilities of theCognitive Radio (CR) wireless devices – originally defined byMitola in his seminal work [2] – and to present system-widetechniques to boost the spectrum usage flexibility and radioaccess adaptability.

Thus motivated, several standardization efforts have beeninitiated to (1) regulate the development of the various ideasrelated to CRNs and DSA into commercial products, and en-sure compatibility between the different products developed byvarious manufacturers, (2) enable the different types of CRNand DSA communication networks and systems to efficientlycoexist, and/or cooperate with each other, and (3) overlook theeconomics and business case scenarios of CRNs and DSA incompliance with the regulations in various countries.

In this article, we present a comprehensive study of thevarious standards that address CRNs and DSA. Figure 1depicts a general overview of such standards grouped bythe standardization body. We classify the CRN/DSA-relatedstandards to TV White Space (TVWS) standards, coexis-tence standards, and other standards which implement someform of CRN/DSA in other Information and Communications

Technologies (ICT) systems. TVWS standards, such as theIEEE 802.22, IEEE 802.11af, and ECMA-392, define thearchitectures, the operation, and/or the physical (PHY) layerand Medium Access Control (MAC) layer designs of CRNs op-erating in the TVWS bands. The propagation characteristics ofthe TVWS band make it a desirable and convenient spectrumfor many wireless transmission services. More specifically, thematerial obstruction in the TVWS band is less harmful andthe low operating frequency of TVWS significantly reducesthe path loss compared to the unlicensed industrial, scientific,and medical (ISM) bands (2.4 and 5.7 GHz).

Meanwhile, coexistence standards, such as the IEEE802.19, IEEE 802.16h, IEEE 1900 (DySPAN), ITU-R SG1 andITU-R SG5, aim at standardizing the definitions, procedures,and the interoperability rules of CRNs. Such standards are re-sponsible for developing the policies for the use of the wirelessspectrum, the requirements of DSA wireless technologies tocontrol the radio interference levels, and the coordination be-tween the different technologies which include network man-agement functions and information sharing schemes amongstdifferent DSA network realizations.

Our focus in this article is on these two categories ofCRN/DSA standards. However, there exists other ICT stan-dards that employ one form or another of CRN and DSA. Forinstance, the 802.11y-2008 standard amendment extends theIEEE 802.11-2007 standard to allow lightly licensed 802.11devices to operate in any 5, 10, or 20 MHz channel thatregulators make available by simply adding entries to thecountry and regulatory information [3]. The 802.11y stan-dard supports the 4.9 GHz, 5 GHz, and the IMT-Advancedcandidate bands (450–862, 2300–2400, 2700–2900, 3400–4200, and 4400–5000 MHz). Another example is the 3GPPAccess Network Discovery and Selection Function (ANDSF)which targets allowing 3GPP networks to use the resources ofcollocated IEEE 802.11 and 802.16 networks [4]. However,such standards are beyond the article scope due to spacelimitations.

II. TV WHITE SPACE STANDARDS

A. IEEE 802.22 Standard: Wireless Regional Area Networks(WRANs)

Despite the recent growth in the wireless communicationsindustry, there still exist large unexploited markets for broad-band wireless access in unserved/underserved areas where thewired infrastructure is economically not feasible to deploy.

Fig. 1. Classification of CRN/DSA standard organized by the standardization body. TVWS standards are shown in white boxes and coexistence standards areshown in blue boxes.

Thus motivated, the IEEE 802.22 standard: “Wireless RegionalArea Networks (WRANs): Enabling Rural Broadband WirelessAccess Using Cognitive Radio Technology in TV Whites-paces” was initiated to provide a reliable and secure broadbandwireless connectivity to underserved and unserved commu-nities. TV White Spaces (TVWS) are the unused spectrumresources at specific times and locations in the broadcast TVoperating frequencies known as the VHF/UHF band that can beexploited through spectrum sharing. In the United States, theabandoned television frequencies are primarily in the upperUHF 700 MHz band, covering TV channels 52 to 69 (698to 806 MHz). Other non-continuous vacant bands between54 MHz and 698 MHz are also available. In other countriesworldwide, the abandoned television channels are in the VHFband as the case in Europe where the TV broadcast range isfrom 470 MHz to 790 MHz. The TVWS band is still usedby a large variety of licensed protected services. Examplesinclude terrestrial TV broadcast services and program makingand special event (PMSE) services that have been operatingover these bands for nearly 100 years. Being officially licensed,the incumbent users of the TVWS bands are protected frominterference within their service area. In order to allow CRdevices to operate in the TVWS band, they must not interferewith the protected incumbent users in their specified operatingarea.

The IEEE 802.22 incorporates advanced CR capabilities in-cluding dynamic spectrum access, incumbent database access,accurate geolocation techniques, spectrum sensing, regulatorydomain dependent policies, spectrum etiquette, and coexistenceto increase the efficiency of spectrum utilization in spectrumcurrently allocated to, but unused by, the TV broadcast service.The IEEE 802.22 standard takes advantage of the favorabletransmission characteristics of the VHF and UHF TV bandsto provide up to 22 Mbps broadband wireless access overa cell radius of up to 100 km (if power is not an issue1)

1Current specified coverage range is 33 Km at 4 Watts CPE effectiveisotropically radiated power (EIRP).

without interfering with the reception of existing TV broadcaststations, using the so-called white spaces between the occupiedTV channels. While the initial version of the standard doesnot allow mobility, the physical layer of the IEEE 802.22standard can support mobility of up to 114 kilometer perhour. The IEEE 802.22 Working Group (WG) was initiated asthe first worldwide effort to develop a CR-based air interface(i.e., the PHY and MAC layer specifications) in November2004 and the standard was published in July 2011 as ”IEEE802.22-2011TM Standard for Cognitive Wireless Regional AreaNetworks (RAN) for Operation in TV Bands” [5]. Severalextensions and amendments are available including:

• IEEE 802.22.1-2010TM: ”Standard for the EnhancedInterference Protection of the Licensed Devices”which was published in November 2010. This standardenhances the harmful interference protection for lowpower licensed devices operating in TVWS Bands

• IEEE 802.22.2-2012TM: ”Standard for RecommendedPractice for Installation and Deployment of IEEE802.22 Systems” which was published in September2012.

• IEEE P802.22a: this is as amendment to the IEEE Std-802.22-2011TM for ”Management and Control PlaneInterfaces and Procedures and Enhancement to theManagement Information Base (MIB).

• IEEE P802.22b: this is an amendment to the IEEEStd-802.22-2011TM for ”Enhancements for BroadbandServices and Monitoring Applications”.

The IEEE 802.22 system specifies a fixed point-to-multipoint wireless air interface whereby a Base Station (BS)manages all of the associated Consumer Premise Equipments(CPEs) within the cell as shown in Figure 2. The centralizedBS is responsible for the spectrum access decision and thetransmission parameters (e.g., modulation, coding, and fre-quencies of operation) for all of the associated CPEs in both

Fig. 2. Typical IEEE 802.22 deployment as reported in [6].

the downlink and uplink directions. Each BS is equipped with aGlobal Positioning System (GPS) receiver which would allowits position to be reported. The location information wouldthen be used to obtain the information about available TVchannels through a central server. The IEEE 802.22 standardadopts a strict master/slave relationship in which the BS actsas the master and the CPEs are the slaves. Such a master/slaveapproach ensures the protection of incumbent services such asthe TV service and wireless microphones. Furthermore, theCPEs are not allowed to transmit before receiving the properauthorization from a BS.

In order to improve the accuracy of spectrum sensingand ensure proper incumbent protection, the IEEE 802.22 BSexploit distributed sensing which has various CPEs performingdistributed measurement activities. A BS distributes the sens-ing load among the CPEs within its service area. Based on thereceived information, the BS better decides the best course ofaction to be taken.

B. IEEE 802.11af Standard: IEEE Draft Standard for TVWhite Spaces Operation

The IEEE 802.11af draft standard, released in June 2013,defines the modifications to both the 802.11 PHY and MAClayers to meet the legal requirements for channel access andcoexistence in the TVWS bands [7]. Similar to the IEEE802.22 WRAN standard, the IEEE 802.11af draft standardallows white space devices (WSDs) to share the underutilizedTVWSs in many geographical locations when the primaryincumbent services (such as licensed TV broadcasters andPMSE services) are not using such bands. The IEEE 802.11afstandard guarantees the protection of incumbent users ofthe TVWS band from interference in their operating region.Furthermore, the IEEE 802.11af aims at exploiting the superiorpropagation characteristics of the TVWS bands to achieve highperformance. Due to the difference in TVWS bands worldwide,the IEEE 802.11af standard provides an international frame-work that adapts to the different TVWS operating parametersand regulatory domains around the world. Therefore, the IEEE802.11af supports different channel bandwidths which arelearnt from an approved geolocation database the keeps trackof which channels are available and for how long. The WSDsimmediately cease transmissions when the database informsthem to stop in order to not interfere with the incumbent users.

Fig. 3. General architecture of a typical IEEE 802.11af network [7].

The IEEE 802.11af standard is commercially known as ”SuperWi-Fi” or ”White-Fi”.

Figure 3 depicts the general architecture of a typical IEEE802.11af deployment (see [8] for further details). The maincomponents of the IEEE 802.11af are:

• Geolocation Database (GDB): This database storesthe permissible frequencies and operating parametersto fulfill the regulatory requirements for differentgeographic locations. The accuracy of the geolocationinformation values as specified by the standard is 50meters.

• Registered Location Secure Server (RLSS): Thisserver acts as a local database that contains the geo-graphic location and operating parameters for a smallnumber of basic service sets (BSSs). The operation ofthe access points (APs) and stations (STAs) in a givenBSS is based on the RLSS information.

• Geolocation-Database-Dependent Enabling Station(GDD-Enabling STA): This component correspondsto the AP of legacy IEEE 802.11 standards. TheGDD-enabling STA controls the operation of the STAswithin it BSS service area. The GDD-enabling STAgets the available channel information from the GDB,and transmits the contact verification signal (CVS).The CVS is used to verify that the GDD-dependentSTAs are still within range of GDD-enabling STAs,as well as for checking the list of available bands.

• Geolocation-Database-Dependent Dependent Sta-tion (GDD-Dependent STA): A GDD-dependentSTA uses the available TVWS channels under thecontrol of the serving GDD-enabling STA. The GDD-dependent STAs obtain a White Space Map (WSM)from either the GDD-enabling STA or the RLSSthat identifies the permissible operating frequenciesand regulatory parameters in the operating area. Theused communications protocol is called the Regis-tered Location Query Protocol (RLQP). The GDD-dependent STAs are equivalent to the STAs in the BSSarchitecture of legacy IEEE 802.11 standards.

Both the IEEE 802.22 and IEEE 802.11af standards, which

exploit the excellent propagation characteristics of the TVWSbands, already have commercial products in the wireless com-munications market. While both standards share many simi-larities such as the use of TVWS databases and geolocationservices, they still have many differences. Table I summarizessuch similarities and differences.

TABLE I. COMPARISON OF THE IEEE 802.22 AND IEEE 802.11AF

STANDARDS

IEEE 802.22 IEEE 802.11af

Coverage Range 17-33 km (up to 100 km) 100 m - 1 km

Max. PHY rate 22 Mbps 12 Mbps

Power 4 W (36 dBm) 100 mW (20 dBm)

Sensitivity -97 dBm -64 dBm

MAC TDMA CSMA

Topology Cellular Mesh

Mobility Supported Not Supported

Geolocation Devices Used Used

TVWS Database Used Used

Spectrum Sensors Used Not Used

C. ECMA-392

Another standard that specifies the PHY and MAC layerdesigns for personal/portable cognitive wireless networks op-erating in TV bands is the ECMA-392 standard [9]. TheECMA-392 PHY operates in the VHF/UHF TV broadcastingfrequencies in the range between 47 MHz and 910 MHz,subject to regulation. The ECMA-392 defines a number ofprotection mechanisms for incumbent services which are usedto meet regulatory requirements. This standard is published byECMA International which is an industry association foundedin 1961. ECMA International primary goal is to develop –in co-operation with the appropriate national, European andinternational organizations – standards and technical reports inorder to facilitate and standardize the use of ICT and consumerelectronics. The standard supports three device types: master,peer, and slave, and three channel bandwidths: 6 MHz, 7 MHz,and 8 MHz, with the support of multi-antenna modes.

The architecture of the ECMA-392 MAC is either master-coordinated or fully distributed. A device provides the re-quired MAC functions and optional functions according toits device type. The MAC service specified in the ECMA-392 standard provides communication between devices withinradio range on a single channel using the PHY based on eithera reservation-based channel access mechanism or a prioritized,contention-based channel access mechanism. The standard alsodefines a synchronization facility for coordinated applications.

In order to enable the coexistence of concurrently activehigher layer protocols within a single device, a MUX sub-layeris specified. The ECMA-392 MUX sub-layer routes outgoingand incoming MAC service data units (MSDUs) to and fromtheir corresponding higher layers.

III. COEXISTENCE AND INTEROPERABILITY STANDARDS

A. IEEE 1900 Standard: Dynamic Spectrum Access Networks(DySPAN)

The Dynamic Spectrum Access Networks Standardiza-tion Committee (DySPAN-SC), formally known as the IEEEStandardization Coordinating Committee 41 (SCC41), targetsfacilitating the development of the research ideas related todistributed CRNs into standards to expedite the use of such

ideas in commercial products [10]. This standardization effortis based on the IEEE P1900 initiative started in 2004. TheDySPAN-SC goals are to:

• Standardize DSA radio systems and networks whilefocusing on improving the spectrum utilization.

• Develop new DSA techniques and CR networkingmethods as well as the management of radio transmis-sion interference in such heterogenous environment.

• Coordinate the activities and the deployment of dif-ferent wireless technologies to share the availablespectrum.

The DySPAN standard consists of seven Working Groups(WGs), only six of which are currently active.2 The IEEE 1900WGs can be summarized as follows.

1) IEEE 1900.1: Definitions and Concepts for DSA: Ter-minology Relating to Emerging Wireless Networks, SystemFunctionality, and Spectrum Management: The IEEE 1900.1standard provides the definitions and explanations of the keyconcepts in the fields of spectrum management, cognitiveradio, policy-defined radio, adaptive radio, software-definedradio, and related technologies. Such a common dictionaryof terms is critical to the CR community to ensure a unifiedunderstanding of the used technical terms. The IEEE 1900.1was approved on September 2008. In February 2011, theIEEE 1900.1 WG started the IEEE 1900.1a amendment toincorporate the updated terms and definitions that resulted fromother IEEE 1900 WGs into the standard. The IEEE 1900.1aamendment was published in January 2013.

2) IEEE 1900.2: Recommended Practice for the Analysisof In-Band and Adjacent Band Interference and CoexistenceBetween Radio Systems: Motivated by the emergence ofdifferent spectrum management, policy-defined radio, adaptiveradio, and software-defined radio systems, the IEEE 1900.2initiative aims at improving the spectral efficiency and allowingthe coexistence of different CR technologies. The resultingrecommended practice provides the technical guidelines foranalyzing the potential for the coexistence – or in contrast theinterference – between radio systems operating in the samefrequency band or between different frequency bands. TheIEEE 1900.2 was approved on July 2008.

3) IEEE 1900.3: Recommended Practice for ConformanceEvaluation of Software Defined Radio (SDR) Software Mod-ules: The objectives of this WG was to provide the recom-mended practices (a set of tests and evaluation methods) tohelp evaluating the IEEE 1900.2 output in order to assurecompliance with requirements for spectrum use by usingformal mathematical concepts and methods. However, theIEEE P1900.3 WG was dismantled in 2008 due to the lackof volunteers.

4) IEEE 1900.4: Architectural Building Blocks EnablingNetwork-Device Distributed Decision Making for OptimizedRadio Resource Usage in Heterogeneous Wireless AccessNetworks: In February 2009, the IEEE has approved theIEEE 1900.4 standard. The purpose of 1900.4 is to addressradio resource management and reconfiguration management

2In addition, the DySPAN-SC has created the ad hoc on Dynamic SpectrumAccess in Vehicular Environments (DSA-VE) to define the DSA rules forvehicular communications.

in composite wireless networks comprising multiple radioaccess technologies. It addresses the optimization of resourcesin both fixed and DSA contexts. The IEEE 1900.4 standard de-fines the architectural building blocks enabling network-devicedistributed decision making for optimized radio resource us-age in heterogeneous wireless networks. The building blockscomprising (i) network resource managers, (ii) device resourcemanagers, and (iii) the information to be exchanged betweenthe building blocks, for enabling coordinated network-devicedistributed decision making that will aid in the optimizationof radio resource usage, including spectrum access control,in heterogeneous wireless access networks are defined. TheIEEE 1900.4 defines a policy-based management frameworkfor decision making. The IEEE 1900.4 dynamic policy-basedapproach makes it well suited to the changing and non-homogeneous white spaces context.

The DySPAN-SC then started two work groups basedon the 1900.4 standard: the IEEE 1900.4a and the IEEE1900.4.1. The IEEE 1900.4a amendment is concerned with thearchitectures and interfaces for DSA networks in TVWS bands.The final standard would include the definition of the newdevices and interfaces required for operating over the TVWSbands in addition to IEEE 1900.4 entities and interfaces. Whilethe TVWS bands vary with the country or the region, the IEEE1900.4a standard provides a common management systemthat is independent of the radio interface of choice. Such aunique management system enables the white spaces devicesto comply with the regulation irrespective of the geographiclocation and time. Hence, the protection of broadcast systemswill be absolutely reliable. On the other hand, the 1900.4.1:“Standard for Interfaces and Protocols Enabling DistributedDecision Making for Optimized Radio Resource Usage in Het-erogeneous Wireless Networks” is responsible for providingthe details of the interfaces and service access points definedin the IEEE 1900.4 standard in order to ensure interoperabilitybetween network side and terminal side components of theIEEE 1900.4 system.

5) IEEE 1900.5: Policy Language and Policy Architecturesfor Managing Cognitive Radio for Dynamic Spectrum Ac-cess Applications: This standard defines the policy languageand the associated architecture requirements for interoperable,vendor-independent control of DSA functionality and behaviorin radio systems and wireless networks. In other words, itdefines the relationship of policy language and architectureto guarantee consistency between the regulator, the operator,the user, and the network equipment manufacturer. The workon the IEEE 1900.5 standard started in August 2008 and thedraft standard was published in January of 2012.

The IEEE 1900.5 WG has recently issued two projectauthorization requests for extension standards: the P1900.5.1and the P1900.5.2. The P1900.5.1 draft standard for “PolicyLanguage for Dynamic Spectrum Access Systems” aims atdefining a vendor-independent policy language for managingthe functionality and behavior of DSA networks based on thelanguage requirements defined in the IEEE 1900.5 standard.Meanwhile, the P1900.5.2: “Standard Method for ModelingSpectrum Consumption Scope” defines a vendor-independentgeneralized method for modeling spectrum consumption ofany type of use of spectrum and the attendant computationsfor arbitrating the compatibility among models. The P1900.5.2authorization requests was approved in March 2013. The IEEE

1900.5 WG is further planning to initiate the P1900.5.a asan amendment to the standard. This amendment defines thedetailed interfaces between policy architecture components.

6) IEEE 1900.6: Spectrum Sensing Interfaces and DataStructures for Dynamic Spectrum Access and other AdvancedRadio Communication Systems: The objective of the IEEE1900.6 WG is to define the interfaces and the data structuresrequired to exchange sensing-related information in order toincrease the interoperability between sensors and their clientsdeveloped by different manufacturers. The logical interfaceand supporting data structures are defined abstractly withoutconstraining the sensing technology, client design, or data linkbetween the sensor and the client. It also defines the involvedentities and the exchanged parameters in this process. Thisstandard further elaborates on the service access points, serviceprimitives, as well as the generic procedures used to realizethis information exchange. The IEEE 1900.6 standard waspublished in April 2011. In June 2011, the IEEE 1900.6 WGstarted working on the IEEE 1900.6a amendment: “Procedures,Protocols and Data Archive Enhanced Interfaces”. The goalof this amendment is to provide the specifications that allowthe integration of 1900.6–based distributed sensing systemsinto existing and future DSA networks. It enables existinglegacy communication systems to benefit from adopting theIEEE 1900.6 interface as an add-on to these systems andto claim standard conformance for an implementation of theinterface. Furthermore, this amendment facilitates the sharingof spectrum sensing data and other relevant data among 1900.6based entities and external data archives.

7) IEEE 1900.7: Radio Interface for White Space DynamicSpectrum Access Radio Systems Supporting Fixed and MobileOperation: This WG targets specifying a radio interface in-cluding the MAC sub-layer(s) and PHY layer(s) of white spaceDSA radio systems supporting fixed and mobile operation inTVWS bands, while avoiding causing harmful interferenceto incumbent users in these frequency bands. The goal isto provide means to support P1900.4a for white space man-agement and P1900.6 to obtain and exchange sensing relatedinformation (spectrum sensing and geolocation information).The standard is not approved yet.

B. ETSI Reconfigurable Radio Systems (RRS)

A parallel effort to DySPAN standardization is the oneconducted by the European Telecommunications StandardsInstitute (ETSI). ETSI Reconfigurable Radio Systems Tech-nical Committee (RRS TC) is leading the European effort toinvestigate the future development of Reconfigurable RadioSystems (RRS) in Europe and define regulatory matters for theintroduction of reconfigurable radio devices and Cognitive Ra-dio Systems (CRSs) in general, especially in the UHF TVWSband and the 2.3-2.4 GHz band in Europe. Consequently, ETSIwill provide the standards for CRSs in order to foster the earlyintroduction of CR devices in the European market.

The ETSI RRS TC has four WGs: WG1 which focuses onthe system-level aspects, WG2 which focuses on Software-Defined Radio (SDR) radio transceiver architecture, WG3which focuses on cognitive management, control, and func-tional architecture, and WG4 which focuses on public safetyand collects and defines the related RRS requirements [11].

C. IEEE 802.16h: Improved Coexistence Mechanisms forLicense-Exempt Operation

In 2010, the IEEE 802.16 WG – widely known as WiMAX– has published amendment 2: ”Improved Coexistence Mecha-nisms for License-Exempt Operation” [12]. The primary goalsof this amendment to IEEE Std 802.16-2009 are to (1) specifyimproved mechanisms (policies and MAC enhancements) thatenable the coexistence among license-exempt systems basedon IEEE 802.16 standard, and (2) facilitate the coexistence ofsuch systems with primary users. The IEEE 802.16h standarddefines a set of CR capabilities in all of the bands in which802.16-2009 is applicable (regulatory licensed or license-exempt bands).

The IEEE 802.16h standard defines two modes of opera-tion: uncoordinated coexistence mechanisms (WirelessMAN-UCP) which does not require much interaction among the dif-ferent systems, and hence, adequate for heterogeneous systems,and coordinated coexistence mechanisms (WirelessMAN-CX),which addresses the required coordination of neighboringsystems in order to reduce the interference generated to eachother.

1) Uncoordinated Coexistence Operation: This IEEE802.16h mode of operation deals with the scenario in which aWiMAX network coexists with licensed users (denoted in theamendment as specific spectrum users) and other unlicensedusers (denoted as non specific spectrum users). Since theWiMAX network shares the same frequency bands with suchusers, the different interference caused by the WiMAX networkin this secanrio is classified into: (1) Acceptable Interference:which does not cause significant degradation in the receiverperformance for a given choice of modulation and/or coding.Hence, it is admissible for both licensed and unlicensed users.(2) Harmful Interference: which is the strong interference thatdecreases the link performance in terms of modulation and/orcoding. Such interference must be avoided at licensed users,however, it can be acceptable for unlicensed users (as it stillallows some successful communications). (3) Destructive In-terference: which does not allow the receiver of either licensedor unlicensed users to decode the received signal for anyavailable modulation at the transmitter. Therefore, it must beavoided. The IEEE 802.16h standard provides the following setof mechanisms to achieve these acceptable interference levels:testing channels for other users, discontinuing operations afterdetecting channel activity, detecting other users, schedulingfor channel testing, requesting and reporting measurements bydifferent nodes, and selecting and advertising a new channel.

The uncoordinated coexistence (WirelessMAN-UCP) modeof IEEE 802.16h operation adopts a distributed architecture forradio resource management. A typical network is composed ofone 802.16 base station (BS) and its associated subordinatednodes. Each BS has a distributed radio resource managemententity to execute the spectrum sharing policies of 802.16hand to build up a database for sharing information related toactual and intended future usage of radio spectrum. Figure 4depicts WirelessMAN-UCP architecture. This database can berecovered from a master entity with the required informationor from different devices (e.g. using the GPS, IP address,operator information, radio signature scheduling info, etc.).The radio resource management entity performs a real-time,adaptive scheduling, which can be done in terms of channelor even interference free regions within a MAC frame based

Fig. 4. IEEE 802.16h WirelessMAN-UCP inter-network communicationarchitecture as reported in [12].

on the available information.

2) Coordinated Coexistence Operation: On the other hand,this IEEE 802.16h mode of operation deals with scenario inwhich multiple CRNs coexist in the same region. The standardwill have such networks to collaborate and coordinate theirtransmissions by building a neighbor relationship such as thatshown in Figure 5. The standard defines the following threebasic mechanisms for achieving coexistence: (1) MAC FrameSynchronization: which is used to separate the transmissionsand enable the operation in synchronized zones. (2) DynamicChannel Selection (DCS) and Adaptive Channel Selection(ACS): which are used to find a less interfered or less usedfrequency. (3) Coexistence Frame: which is used – combinedwith coordinated scheduling and a fairness criterion – to sepa-rate any remaining interference in time domain. The standarddefines a coexistence control channel based on a series ofglobally synchronized time-slots and used for inter-networkcoordination.

D. IEEE 802.19: Wireless Coexistence WG

The IEEE 802.19 WG targets the development of standardsfor coexistence between wireless standards of unlicensed de-vices. It mainly reviews the coexistence assurance documentsproduced by other IEEE 802 working groups developing newwireless standards for unlicensed devices. The objectives ofthis WG are to (1) enable the family of IEEE 802 standards touse the TVWS bands in the most effective way, and (2) developcoexistence methods among dissimilar or independently oper-ated TVWS networks and devices. Currently, the WG entitledthe IEEE 802.19.1 subgroup to work on developing a standard:”Standard for Information Technology - Telecommunicationsand Information Exchange Between Systems – Local andMetropolitan Area Networks – Specific Requirements – Part19: TV White Space Coexistence Methods” [13].

Fig. 5. WirelessMAN-CX neighbor BSs discovery and definition of coexis-tence neighbor and community as reported in [12].

E. International Telecommunication Union (ITU) Recommen-dations

Finally, we overview the CRN/DSA standardization effortscarried out by the International Telecommunication Union(ITU). ITU is an United Nations agency that is leading theworldwide ICT. It acts as the global focal point for gov-ernments and the private sector in developing networks andservices. ITU has its three Sectors: (1) RadiocommunicationSector (ITU-R), (2) Telecommunication Standardization Sec-tor (ITU-T), and (3) Telecommunication Development Sector(ITU-D).

ITU-R is responsible for the management of the radio-frequency spectrum and satellite orbits, finite natural resourcesthat are increasingly in demand from a large number ofservices such as fixed, mobile, broadcasting, amateur, spaceresearch, meteorology, global positioning systems, monitoringand communication services that ensure the safety of life [14].

ITU-R uses radiocommunication world experts to producerecommendations in the form of reports. A report is a technical,operational or procedural statement, prepared by a StudyGroup (SG) formed by ITU on a given subject related to atopic (referred to as a Question). A particular ITU-R set ofrecommendations that addresses CRN and DSA is the oneentitle Spectrum Management (SM) which includes topics suchas the economic aspects of spectrum management (SM.2012),definitions of Software Defined Radio (SDR) and Cogni-tive Radio System (CRS) (SM.2152), the parameters of andmeasurement procedures on H/V/UHF monitoring receiversand stations (SM.2125), etc. While compliance with suchITU-R recommendations is not mandatory, they have highreputation and worldwide implementation, having the statusof international standards in their domain of application.

The two main ITU study groups that are dealing withCRN and DSA questions are study group 1 (SG 1): SpectrumManagement and study group 1 (SG 5): Terrestrial Services.

ITU SG 1 - Spectrum Management is responsible fordefining (1) spectrum management principles and techniques,(2) spectrum sharing general principles, (3) spectrum moni-toring approaches, (4) spectrum utilization long-term strate-gies, (5) economic plans to national spectrum management,and (6) automated techniques and assistance to developingcountries (in cooperation with the telecommunication devel-opment sector). SG1 has three Working Parties (WPs): WP1A - Spectrum engineering techniques, WP 1B - Spectrummanagement methodologies and economic strategies, and WP1C - Spectrum monitoring.

Meanwhile ITU SG 5 - Terrestrial Services does notsolely focus on CRN and DSA. SG 5 scope covers thequestion related to general systems and networks for fixed,mobile, radio determination, amateur and amateur-satelliteservices. However, several working parties that are workingunder SG 5 are primarily dealing with CRN and DSA. Morespecifically, ITU-R WP 5A ”Land mobile service above 30MHz*(excluding IMT); wireless access in the fixed service;amateur and amateur-satellite services” and ITU-R WP 5D”International Mobile Telecommunications (IMT) Systems”.The term IMT is use by ITU-R to describe the radio interfacesfor mobile telecommunication such as 3G and 4G cellulartelecommunication services. WP 5D is working on an ITU-Rreport for ”Cognitive radio systems specific for IMT systems”.

IV. CONCLUDING REMARKS

In this paper, we have presented an overview of the recentand ongoing standardization efforts for cognitive radio net-works. We have classified the CRN/DSA standards accordingto their objectives and purposes of standardization into twomain categories: TVWS standards and coexistence standards.TVWS standards, such as the IEEE 802.22, IEEE 802.11af,ECMA-392 standards, define the PHY/MAC layer designs andnetworking architectures to exploit the excellent propagationcharacteristics of the TV white spaces that have recentlyemerged in the TV bands worldwide. The wireless communi-cation market already has commercial products that implementsuch standards. On the other hand, coexistence standards, suchas the IEEE 802.19, IEEE 802.16h, IEEE 1900 (DySPAN),ITU-R SG1 and ITU-R SG5, define the policies and regulationsgoverning the interaction and the interoperability betweendifferent CRN and DSA implementations. While the abundantstandards discussed in this article reflect the viability andperformance of various facets of CRN and DSA, we are stillin the wavefront of such technologies. We believe that suchstandardization efforts will continue progressing for the nextdecade at least.

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