baldini et al. - 2013 - the evolution of cognitive radio technology in europe regulatory and...

8/16/2019 Baldini Et Al. - 2013 - The Evolution of Cognitive Radio Technology in Europe Regulatory and Standardization Aspects

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Several studies like McHenry (2005) and FCC (2002) have shown that spectral bands assigned with a licensing approachmay be underutilized in time or space. Furthermore, because of the growing number of radio communication services andthe need for ubiquitous broadband connectivity, spectrum underutilization represents an obstacle to innovation andcompetitiveness.

Over the last several years, there have been several important developments in the spectrum policy and regulatorydomains to address the growing demand of radio communication services. Beyond the licensed bands, the currentspectrum allocation is also based on dedicated unlicensed bands (for example, WiFi) and variable-exibility licensed bands

related to the concept of spectrum trading and refarming ( ECC, 2011 ). New approaches and technologies have also beenconsidered including cognitive radio (CR) and dynamic spectrum access (DSA). Regulators have produced numerousconsultations, vision reports, memoranda of opinion and other documents considering or highlighting the potential of CR and DSA to increase use and access to radio frequency, with some regulators progressing towards the creation of appropriate vehicles to support the creation of new potential markets. Ongoing activity is also taking place within theInternational Telecommunications Union (ITU), IEEE, ECMA and the European Telecommunications Standards Institute(ETSI) in developing denitions, standards, and regulatory regimes for using these new technologies.

In this paper, the following denitions are used:

K CR. From ITU (2009) :‘‘Cognitive radio system (CRS) : A radio system employing technology that allows the system to obtain knowledge of its operational and geographical environment, established policies and its internal state; to dynamically andautonomously adjust its operational parameters and protocols according to its obtained knowledge in order toachieve predened objectives; and to learn from the results obtained.’’

K DSA. From IEEE (2008) :‘‘DSA is the real-time adjustment of spectrum utilization in response to changing circumstances and objectives,where, changing circumstances and objectives include (and are not limited to) energy-conservation, changes of theradio’s state (operational mode, battery life, location, etc.), interference-avoidance (either suffered or inicted),changes in environmental/external constraints (spectrum, propagation, operational policies, etc.), spectrum-usageefciency targets, quality of service (QoS), graceful degradation guidelines, and maximization of radio lifetime.’’

In spectrum management approaches based on CR and DSA, more than one radio communication service is assumed tocoexist or share the same spectrum. This coexistence does maintain the concept of spectrum rights of use, wherebylicensed services are usually called primary and opportunistic services are called secondary. Secondary radio servicesshould cause no harmful interference to primary radio services. Network equipment based CR technology should be able todynamically adjust its operational parameters to minimize the risk of harmful interference and to optimize the use of radio

frequency spectrum. As described in ECC (2011) , individual rights of use may be described as a spectrum license thatcovers a dened part of the radio spectrum within a geographically dened area. In this paper harmful interference isdened as ‘‘interference which endangers the functioning of a radio navigation service or of other safety services orseriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with theapplicable community or national regulations’’, as per the European Radio and Telecommunications Terminal Equipmentdirective ( R &TTE, 1995 ).

Several authors have suggested the potential applications for CR and DSA as described in Chapin and Lehr (2007) andWang, Ghosh, and Challapali (2011) . For example, opportunistic spectrum access as in the case of TV White Spaces (TVWS)can improve spectrum utilization by exploiting spectrum gaps in time and space of digital TV (DTV). Another application isspectrum trading, described in Chapin and Lehr (2007) and Farquhar and Fitzgerald (2003) , where incumbents couldunbundle the investment in spectrum rights by leasing spectrum, which is licensed but not utilized both in time (for ashort-term lease) or in space (in a geographical region where the incumbents do not have an infrastructure). CR conceptscould also be utilized in unlicensed bands currently used by WiFi technology. An additional application investigated lately

is Operator-governed Opportunistic Networks, operating for example, in the Industrial, Scientic and Medical (ISM) bandor in TVWS. Such Operator-governed Opportunistic Networks can be exploited as ad-hoc coverage extensions or capacityextensions of infrastructure networks as described in Stavroulaki et al. (2011) .

A detailed list of the use cases, where CR and DSA could be applied is presented in Section 4 .This paper presents a review of the main regulatory and technical challenges for the deployment of CR and DSA,

provides an overview of the European activities, and presents a road map for addressing the identied challenges andfacilitating the introduction of CR and DSA. CR raises several important regulatory questions that are important for boththe technical direction of the technology and its widespread acceptance. This paper surveys the role of regulatory andstandardization bodies in the emergence and future direction of CR and DSA. While few authors ( Anker, 2010 ; Barrie,Delaere, Anker, & Ballon, 2012 ; Roberson & Webb, 2010 ) have underscored the role of certain regulatory assignments andthe different directions that regulations and standards may take, there is a paucity of research examining the role of regulation and standardization in detail in Europe.

The remainder of this paper is organized as follows. Section 2 describes the European regulatory and standardization

bodies responsible for CR and DSA. Section 3 describes the shortcomings of the current spectrum management approach.Section 4 identies the main regulatory, standardization and technical challenges for the deployment of CR and DSA in

G. Baldini et al. / Telecommunications Policy 37 (2013) 96–107 97


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the market. This section also describes the current activities of European regulatory and standardization bodies to addressthese challenges. Section 5 describes a potential roadmap and the related actions. Finally, Section 6 concludes the paper bysummarizing the main themes.

2. Regulatory and standardization bodies for CR and DSA in Europe

In Europe, the main entities, which participate in spectrum regulation and related standardization processes, are:

The European Conference of Postal and Telecommunications Administrations (CEPT) , within which policy makers andregulators from 48 countries across Europe collaborate to harmonize telecommunication, radio spectrum and postalregulations ( CEPT, 2008 ).

The European Communications Ofce (ECO), which is the Secretariat of the CEPT. The ECO provides advice and support tothe CEPT to help it develop and deliver its policies and decisions in an effective and transparent way.

The European Telecommunications Standards Institute (ETSI) , which is responsible for most of the European telecommu-nication standardization activities together with CEN (Comite ´ Europeén de Normalisation) and CENELEC (Comite Éuropeén de Normalisation E ´lectrotechnique). Within ETSI, the ETSI Technical Committee (TC) on Recongurable RadioSystems (ETSI-RRS) is working on the standardization of SDR and CR technologies, while the ETSI TC on ElectromagneticRadio Matters (ETSI-ERM) is working on radio-frequency and spectrum-related issues.

The European Commission (EC), which is the Executive Body of the European Union and is composed of variousdepartments or directorate generals (DG). One of the objectives of the DG of the Information Society (INFSO) is to deneand implement a regulatory environment that enables rapid development of Information Communication Technology(ICT) services. The DG Enterprise (ENTR) is responsible for standardization and certication of communication devices.

The Radio Spectrum Policy Group (RSPG), which is a high-level advisory group that assists the European Commission(i.e., DG INFSO) in the development of radio spectrum policy.

The Telecommunications Conformity Assessment and Market Surveillance (TCAM), which is an advisory and regulatorycommittee that assists the European Commission in matters regarding conformity assessment and market surveillanceincluding the Radio and Telecommunications Terminal Equipment Directive (R&TTE Directive), which is currently(i.e., June 2012) under revision.

The relationships among the described entities are shown in Fig. 1. Unbroken lines represent permanent activities/relationships and the broken lines represent temporary activities for a specic topic.

As indicated in Fig. 1, the CEPT can request feasibility studies from the Electronic Communications Committee (ECC),which is composed of working groups (WGs), task groups, and project teams. In particular, WG SE43 has the responsibilityto dene technical and operational requirements for the operation of CR systems in the TVWS of the UHF broadcastingband (470–790 MHz). Representatives of national spectrum regulators participate to the activity of CEPT WGs. WG SE43and the ETSI Technical Committees (TC) collaborate through Liaisons Statements (LS). The requirements specied in WG

Fig. 1. Relationship among entities involved in European spectrum regulation for CR.



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SE43 are the input for the denition of the standards created in ETSI TCs. As indicated in the picture, the EC can requestspecic standardization mandates from CEPT and/or ETSI on specic technologies, but no mandate has been currentlyissued on SDR or CR technologies (as from May 2012). Both CEPT and ETSI TCs collaborate with TCAM for the revision of the R&TTE directive and they are in contact with international regulatory and standardization bodies.

3. Limitations of the current spectrum management approach based on the licensing regime

The decision process of spectrum regulators around the world is focused on introducing new services and applicationswhile avoiding or mitigating the risk of wireless interference among services. Exactly because spectrum is an expensiveresource, manufacturers and telecom providers have invested a signicant amount of R&D effort to improve the spectrumefciency (bit/s/Hz), coverage and trafc capacity. Long-term evolution (LTE) is the result of those efforts, combiningimproved spectrum efciency in comparison to UMTS for channels larger than 10 MHz, as well as pervasive coverage (forexample, femtocells). These investments are driven by the explosive demand for both voice and data services over the lastseveral years. The trend towards pervasive broadband wireless communication and innovative data services is not likely toslow down, while the theoretical and technical limits for spectrum efciency and coverage are close to being reached asunderlined in Jabbari, Pickholtz, and Norton (2010) .

Spectrum regulators around the world are aware of the growth in wireless services and they are addressing the relatedissues in various ways depending on the local regulatory context.

In Europe, the following issues are identied:

1. Measurements campaigns have shown that, in most cases, spectrum is not used efciently in time or space.2. The regulatory process may require a considerable amount of time to introduce a new radio communication service or

spectrum management approaches (for example, UWB). In Europe, the fragmented nature of the regulatory bodies isanother element retarding spectrum regulatory decisions.

3. The current spectrum management regime gives preference to existing services and existing wireless infrastructure.This is understandable, given the large investments in existing wireless communication infrastructures and spectrumlicenses.

4. The current approach imposes nancial barriers to entry for small enterprises for new radio communication services.5. In many cases, the current European and national regulatory frameworks do support the transfer of spectrum rights of

use. A more exible approach based on the leasing of spectrum rights of use described in ECC (2011) has also beenproposed. Nevertheless there are limited technical standards or solutions to support the transfer of rights and telecomoperators have not made extensive use of this possibility.

In the past, the inefciencies in spectrum utilization of the licensing regime were tolerable because the demand forwireless broadband services was limited. Furthermore, there were no technical alternative to having wireless devices andnetworks transmit only in bands dened during the design phase. However, the recent technological developments in CRtechnology provide the opportunity for new spectrum management approaches not possible before.

As described in the remainder of this paper, the current debate is whether the regulator has the right to allowadditional users into a band already licensed to a particular operator. Many regulators are still adopting a cautious outlookand they are requesting additional studies to ensure the harmonious existence for license holders in the radio frequencyspectrum. However, some observers such as Jabbari et al. (2010) or Wyglinski, Nekovee, and Hou (2010) have noted thatwhat was once considered the greatest challenge, regulatory hurdles, may no longer be valid due to the willingness of keyregulatory bodies (for example, FCC, Ofcom) to consider CR technology. This and other challenges are described in thefollowing sections.

4. Regulatory, technical and business challenges for the deployment of CR

The deployment of CR and DSA presents many challenges at the regulatory, market and technical level. This sectionidenties these challenges and describes how they are being addressed by the main regulatory and standardizationentities identied in Fig. 1.

The relevance of the challenges depends on the use cases where CR concepts could be applied.Table 1 provides a description of the main use cases based on Mueck and Noguet (2011) and Buddhikot (2007) .

4.1. Identication of challenges

The following regulatory and business challenges are identied:

[R1] Appropriate regulations for various operational scenarios : The regulatory process for CR and DSA is signicantly more

complex than conventional radio communication services and is dependent on the specic business scenarios.A signicant tradeoff is between avoiding the risk of wireless interference to primary users (due to constraints on CR



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emissions, which are too loose) and not hampering the commercial success of CR and DSA (due to constraints whichare too restrictive). This challenge is present in the use cases [UC1], [UC2], [UC3] and [UC4].

[R2] Certication and protection against misbehavior : In comparison with conventional wireless communications systems,which are designed to operate in specic frequency bands, CR equipment is theoretically able to transmit in a widerange of frequencies. As a consequence, there is an increased risk of wireless interference which can be bothintentional (for example, malicious devices) or unintentional, whereby a radio is inadvertently unable to detect theprimary usage of a frequency channel (for example, because of shadowing effects or hidden-node problem). CR devices clearly present new challenges from a certication point of view in comparison to conventional devices. Thischallenge is present in [UC1], [UC2], [UC3] and [UC4] and potentially in [UC8], if the CR device ignores the rulesdened by the license holder.

[R3] Complex spectrum trading schemes : CR and DSA provide the possibility of spectrum trading, whereby bands can betemporarily re-allocated from a provider to another. As described in Barrie et al. (2012) the implementation of spectrum trading can be quite complex from the regulatory point of view. Bykowsky (2003) has also pointed out thattelecom operators may have little incentive to sell excess spectrum if such spectrum will be employed bycompetition to provide similar services. This challenge is present in [UC5] and [UC8].

[R4] Complex international framework : The introduction of new radio communication services often requires a complexand lengthy coordination process among international, European and national spectrum regulators. Regulators andmanufacturers must also address cross-border issues for CR devices moving from one spectrum regulatory area toanother. This challenge is present in all use cases.

[R5] Stakeholders conict : Incumbents are usually against spectrum sharing approaches because they do not want to loseor share their rights on spectral bands, based on considerable economic investment (for example, UMTS auctions) orneeded for operational reasons (for example, public safety and military bands). This challenge is present in [UC1],[UC2], [UC3], [UC4] and [UC5].

[R6] Lack of exibility of existing licensing schemes : Lack of exibility in some existing licenses, because of existing regionalor international agreements or because the license has prescribed specic technical conditions. This challenge ispresent in all use cases.

[R7] Lack of precise data for spectrum utilization : Even if various measurement campaigns have been performed in variousparts of the world, there is a lack of clear consensus on the available spectrum, which can be exploited by CR devicesthrough opportunistic access. This challenge is present in [UC1], [UC2] and [UC3].

[R8] Alternative techniques to mitigate trafc demand : A potential market challenge for CR and DSA commercial success isthat stakeholders may identify alternative ways to address the lack of available spectrum for broadband applications.The approach of ofoading trafc from cellular networks to WiFi hotspots is already proposed by telecom operatorsas described in Balasubramanian, Mahajan, and Venkataramani (2010) . Another approach would be to design anddeploy cellular networks with smaller cells in higher frequency bands (i.e. over 5 GHz) and implement adaptiveresource management techniques like Self Organizing Networks (SON) in LTE as described in Honglin, Jian, Xiaoying,Yang, and Ping (2010) . These approaches can be considered evolutionary rather than disruptive because they are

Table 1Use cases.

Id Use case Use case description

UC1 Ad-hoc CR in White Spaces frequency bands This use case is based on White Spaces frequency bands. The CR devices (handheld terminals andother devices like access points) communicate with each other to share information and to run joint applications

UC2 Mid/long range wireless access over WhiteSpaces frequency bands Internet access is provided from a base station to the end users by utilizing White Spaces frequencybands over ranges of 0–10 km

UC3 Short range wireless access over WhiteSpaces frequency bands

Internet access is provided via short range (for example, 50 m) wireless communication from anaccess point or base station to the end users by utilizing White Spaces frequency bands

UC4 Short range with spectrum underlay In spectrum underlay, secondary radio services transmit at very low power in the same spectrumbands of primary radio services to avoid harmful interference. One example is UltraWidebandtechnology

UC5 Dynamic Exclusive-Use At any given point in space and time, only one radio service has exclusive rights to the spectrumbut the type of radio service or type of use can change

UC6 Uncontrolled commons When a spectrum band is managed using the uncontrolled commons model, where no radio servicehas exclusive license to the spectrum band

UC7 Managed commons In managed commons, a spectrum band is owned or controlled jointly by a group of entities

UC8 Private commons It is a type of managed commons, where the ultimate ownership of the licensed spectrum is stillcentralized with the license holder. It is described in FCC (2004b) .



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based on existing technologies, networks and intellectual property and they may be preferred by telecommanufacturers and operators. This challenge can affect [UC1], [UC2], [UC3] and [UC5].

The following technical challenges are identied:

[T1] Accurate spectrum sensing : CR devices may use spectrum sensing to acquire knowledge of primary users in the area. Thiscapability can be negatively affected by many factors (for example, propagation errors, the hidden-node problem) asdescribed in Barrie et al. (2012) . In comparison to spectrum sensing by a single CR device, collaborative sensing canimprove the accuracy of the CR network. This challenge is present in [UC1], [UC2], [UC3], [UC4] and [UC6].

[T2] Extendable front end : CR devices able to transmit in a wide range of frequencies are difcult to implement because of the limitations of front-end components (for example, lters, ampliers). This challenge is present in [UC5].

[T3] Lack of interfaces among heterogeneous networks : DSA may require joint resource management among differentwireless communications technologies. In most cases, these interfaces do not exist or they are not dened in therelated standards. This can require a considerable standardization effort. This challenge is present in [UC5].

[T4] Complex spectrum etiquette : Beyond the denition of technical interfaces among different radio services, there is alsothe need to dene rules of engagement among stakeholders and spectrum users in a specic area or rules to regulatethe coexistence of different radio services. For different reasons, this challenge is present in all use cases; however itis more relevant in the commons use cases [UC6], [UC7] and [UC8].

Beyond the regulatory and technical challenges, CR can be viewed as a disruptive technology that can provide, at the sametime, other benets and disadvantages for various stakeholders. Table 2 summarizes the benets and challenges described in theprevious sections and other issues, which can become signicant for users, government, manufacturers and incumbents.

Table 2Benets and disadvantages of CR for different stakeholders.

Government (for exampleregulators)

Manufacturers Incumbents Users

BenetsImprove spectrum utilization New market opportunities Possibility of spectrum trading/auctioning Improved access to

wireless services andapplications

Support innovation Support evolution of communications technology

Adaptability to changing trafc demand Lower cost-per-bit

Could minimize the burden of spectrum management whilstmaximizing spectrum efciency

Quicker technology life-cycles Reduced barrier to entry for smaller operators,for example, virtual network operatorsbecoming real network operators

Greater competition: Couldlead to value-addedservices and lower cost

Potential signicant economicbenet

New end-user equipmentmanufacturing; explosion in amountof communications hardware

Spectrum costs decrease General economicimprovement and ease of life/business

Potential eventual new governmentincome streams; charging/tax forsecondary access

New infrastructure equipment, forexample, database managers

Improved spectrum utilization

Active secondary spectrum market could leadto increased review streams

DisadvantagesMore complex regulatory regime Increased technical complexity Risk of Wireless Interferences Potential higher costs

of devicesComplexity in evaluation of new

devices/hardware/software andcertication

Higher costs to validate hardware tomeet specic regulatoryrequirements

Commercial benets in spectrum sharing notalways clearly identied or motivated

Potential lowercommunication QoSbecause of interference

Risk of lowering the value of thespectrum; decreased governmentrevenue?

Potentially a negative effect on salesof legacy hardware

Increased competition as barriers to entry arereduced

Potential reduction inbattery life for the newtechnologies

Need to create new certicationschemes

Market shift from hardwaremanufacturers to softwaremanufacturers

More value-chain participants (i.e. MVNOs)

Need to create economic models forspectrum trading and markets

Hidden node problem andshadowing if sensing functionality isneeded

Operators may miss trend

Need to monitor and control risk of wireless interference

Greater competition; reduced incomeper bit or user



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In recent years, many of the challenges identied in Table 2 , have been investigated by European regulatory andstandardization bodies, which have commenced various activities. These are discussed in the following section.

4.2. Regulatory activities in Europe

In May 2004, the EC requested the RSPG to develop and adopt an Opinion on a coordinated EU spectrum policyapproach for wireless electronic communication radio access platforms, to be addressed to the EC. It was recognized thatdeployment of innovative radio communication services and technologies may be hampered by the reservation of certainuseful frequency bands for quite narrowly dened services (challenge [R6]). As a consequence the Wireless Access Policy for Electronic Communications Services (WAPECS) project was launched, which is focused on introducing a more exiblespectrum use in the near future, provided that certain technical requirements to avoid interference are met.

WAPECS (2005) has identied the spectral bands described in Table 3 as candidates for a exible spectrummanagement approach:

The WAPECS proposal was submitted to a public consultation ( RSPG 2005 ), where the following suggestions wereproposed:

Spectrum harmonization across Europe is still considered a primary goal for economies of scale, roaming andinteroperability.

WAPECS should include both public and private applications in the study. There is a need for a closer integration of standardization and regulatory bodies at national, European andinternational level.

In response to the WAPECS mandate, the CEPT developed the concept of block edge mask (BEM), which is a spectrummask that is dened in ECC (2009) as a function of the frequency, relative to the edge of a block of spectrum that is licensedto an operator. On one side of this frequency is the in-block power limit (for in-band radio services coexistence) and on theother side is the out-of-block spectrum mask (for out-of-band radio services coexistence). As described in Deschamps,Moessner, and Smith (2010) , one of the purposes of the BEM concept is to allow technology neutrality and the shared useof a frequency band by different operators applying different technologies and offering different electronic communicationservices within the same radio service. In this context BEM can be used to address challenges [R2] and [T4].

The European Commission also recognized the need for an efcient use of the spectrum and indicated that the creationof a future European spectrum market could be based on technological neutrality and trading of spectrum rights. In May

2007, the European Commission requested the RSPG to develop and adopt an Opinion on Aspects of a European Approach toCollective Use of Spectrum . This study complements the previous studies on WAPECS and trading of spectrum rights. TheEuropean Commission recognized that a coherent approach to Collective Use of Spectrum (CUS) can stimulate thedevelopment of DSA in Europe.

More recently, in February 2010, the RSPG published the rst report on cognitive technologies ( RSPG, 2010 ), whichprovided an overview of CR and DSA and identied challenging issues requiring further attention. The report addressedmost of the challenges described in Section 4.1 .

As a follow-up of the report, on November 4, 2010, DG INFSO issued a public consultation on CR technologies, whichaddressed the prospects of the implementation of CR technologies at the EU level. Various responses were provided fromthe industry, national regulators and research communities, revealing the following:

The concept of a spectrum database was supported by most of the responses; however various implementation issueswere identied, including the certication of spectrum databases (challenge [R2]) and cross-border coordination.

Identifying parameters for the role of European and national bodies and the adoption of a worldwide or Europeanstandardized approach to address challenge [R4] were also raised.

Table 3WAPECS bands (WAPECS2005).

Spectrum bands Notes

470–862 MHz Used for broadcasting today

880–915 MHz/925–960 MHz, 1710–1785 MHz/1805–1880 MHz

European bands for GSM mobile services today

1900–1980 MHz/2010–2025 MHz/2110–2170 MHz; European bands are used for third generation (3G) mobile services(IMT-2000/UMTS) today

2500–2690 MHz 3G mobile services

3.4–3.8 GHz Used for broadband and satellite communications



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Spectrum sensing technology was not considered suitably mature or economically viable to avoid the risk of wirelessinterference in primary/secondary scenarios (challenge [T1]). Further research is needed in this area.

Individual rights of use or trading of spectrum rights was supported by various opinions, and it was suggested thatfurther EU research/testing is needed in this area (challenge [R2]).

In some cases, there was a clear opposition to spectrum sharing from incumbents (challenge [R5]).

The EC also mandated the ECC to investigate the introduction of CR in the television bands: the commonly called WhiteSpaces. The ECC Report 159 ( ECC, 2010 ) describes a range of possible deployment scenarios for White Space Devices(WSDs) and provides protection criteria for each of the incumbent services identied in the study (challenge [R1] and[R2]). The study showed that the amount of White Space in the broadcasting bands might be limited in Europe (challenge[R7]). The study further indicated that the feasibility of the introduction of CR devices remains questionable as thefeasibility of cognitive sharing schemes has not yet been conclusively demonstrated.

Clearly, more studies are needed in this area. In an effort to address these issues and the described challenges, the EChas nanced research projects under the Framework Program:

End-to-End Efciency (E 3 ) project ( www.ict-e3.eu ), devised, among others topics, a functional architecture to addresschallenge [T3] and provide an effective management of complex, heterogeneous CR networks.

The FARAMIR project ( http://www.ict-faramir.eu/ ) focuses on developing techniques for increasing the radio environ-mental and spectral awareness of future wireless systems, primarily through the development of radio-environmentalmaps. FARAMIR also addresses challenges [R7] through extensive measurement campaigns and challenge [R1] throughresearch in spectrum sensing.

The CROWN project ( http://www.fp7-crown.eu/ ) focuses on the realistic implementation of CR for better, morespectrally and nancially efcient wireless communications. Thus, CROWN addresses challenges [T1] and [T4].

COGEU project ( http://www.ict-cogeu.eu/ ) has the purpose to provide cognitive access to TVWS with secondaryspectrum trading mechanisms in a real demonstrator (challenge [R3]). COGEU will also dene new methodologies forTVWS equipment certication and compliance addressing coexistence with the DVB-T/H European standard(challenge [R2]).

In Europe, national spectrum regulators have also been quite active in investigating new CR technologies and theirregulatory and market impact.

In 2007, in the UK, Ofcom commissioned an extensive study on CR technology ( QinetiQ, 2007 ), supported by aworkshop, where representatives from industry provided important feedback. The report recommended:

The creation of various functions and enablers to support regulators: spectrum databases with location (i.e., geolocationdatabase) to identify the primary users in an area, spectrum monitoring system and policy management frameworks toimpose spectrum policies (challenges [R2], [T4]).

A close collaboration between regulation and standardization bodies was recommended, especially for the denition of the main interfaces (challenge [T3]).

Revisions to the certication of CR and SDR devices (challenge [R2]).

Furthermore, the report also suggested the allocation of a test band for CR, to support research and proof of concepts ina similar way to what FCC has done.

Most of the CR and DSA activities by other European spectrum regulators have been channeled through CEPT; howeversome national spectrum regulators have also supported independent programs. In Finland, the testing of CR is alreadypossible in the 470–790 MHz band if they do not cause interference to other radio trafc. Other European member states

like Spain, The Netherlands and Austria are considering the introduction of WSD in the 470–790 MHz band ( CGCRS, 2011 ).

4.3. Regulatory activities outside Europe

Outside of Europe the USA has been on the forefront of development and regulatory movement. The FederalCommunications Commission (FCC) issued a docket ( FCC, 2004a ) to permit unlicensed opportunistic access to TVWS inthe TV bands by CR secondary devices. In parallel, the FCC sent requests for opinion to representatives from industry andresearch organizations on a more efcient use of spectrum. On November 4, 2008, the FCC adopted a Second Report andOrder ( FCC, 2008 ). This document established the rules that will allow new, CR wireless devices to operate, as a secondaryuser, in the broadcast television spectrum. To avoid harmful interference to primary users, the FCC suggested theimplementation of spectrum databases where the operational parameters, range and location of primary users can beregistered.

In September 2010, the FCC ( FCC, 2010 ) eliminated the sensing requirement for Television Band Devices that includegeo-location/database functions, as petitioners argued that the sensing technology was not sufciently mature for


http://www.ict-e3.eu/http://www.ict-faramir.eu/http://www.fp7-crown.eu/http://www.ict-cogeu.eu/http://www.ict-cogeu.eu/http://www.fp7-crown.eu/http://www.ict-faramir.eu/http://www.ict-e3.eu/


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consumer devices and would delay market entry (challenge [T1]). The FCC has recently issued a call for administrators of the TVWS spectrum database.

The certication of CR devices and SDR devices (challenge [R2]) was also investigated by the FCC. It adopted rulechanges to address the certication of SDR and CR equipment, which are considered a new class of equipment withstreamlined equipment authorization ( FCC, 2001). The FCC amended the equipment authorization rules to permitequipment manufacturers to make changes in the frequency, power and modulation parameters without the need to le anew equipment authorization application with the Commission. The certication rules were updated in 2005 to eliminate

the rule for a manufacturer to supply radio software to the FCC upon request because this may become an unnecessarybarrier to entry ( FCC, 2005 ).One of the main recommendations of the US National Broadband Plan (NPB) is to free up 500 MHz of spectrum for

broadband use in the next 10 years with 300 MHz being made available for mobile use in the next ve years. As describedin Wang et al. (2011) , the NBP urges the FCC to initiate further proceedings on CR and DSA beyond the already completedTVWS proceedings.

4.4. Standardization activities

The strong interest from the research, industry community and regulators has driven the need for coordinated work onCR standardization. The prominent standardization bodies in the telecommunications sector have addressed differentoperational scenarios and technical issues for CR and DSA.

The following main standardization bodies can be identied:

IEEE : IEEE is leading the standardization process through the IEEE 802.22 standard and the IEEE SCC41/P1900 series of standards. Enhancements on existing IEEE 802 standards towards CR are also being developed (for example, IEEE 802.11af).

ETSI : Since March 2008, ETSI has established a technical committee (TC) for recongurable radio systems (RRS), whichincludes SDR and CR. concepts.

ECMA-392: This standard species a medium access control (MAC) sub-layer and a physical (PHY) layer for personal/portable cognitive wireless networks operating in TV bands.

These standardization bodies address the regulatory and technical challenges described in the previous sections.A detailed description of all the standardization activities is out of the scope of this paper; rather this section outlines themain contributions to the challenges described in Section 4 .

ETSI Technical Committee for Recongurable Radio Systems (RRS) is composed of four working groups: WG1 SystemsAspects, WG2 Radio Equipment architecture, WG3 Cognitive Management and Control and WG4 for Public Safety. On theregulatory aspects, ETSI TC RRS has focused their efforts to the following challenges:

The revision of the R&TTE Directive regime in relation to the challenge [R2].A new work item has also been created toidentify potential security threats and misbehaviors in SDR and CR.

Feasibility studies on the spectrum requirements of TVWS devices in the UHF TV bands in relation to challenge [R1].Liaisons statements are exchanged with CEPT SE43 and ETSI TC ERM.

ETSI TC RRS is also addressing the following technical challenges:

Denition of the SDR/CR device architecture, with a uniform radio interface for different radio access technologies(challenge [T2]).

Identication and study of communication mechanisms on CR channels (CCC) for CR systems: (1) for the coexistence and

coordination of different CR networks and nodes, (2) for the management of Opportunistic Networks (challenge [T3]).

The IEEE Dynamic Spectrum Access Networks (DYSPAN) Standards Committee (formerly IEEE Standards CoordinatingCommittee 41 (SCC41)) published the IEEE 1900.4 standard ( IEEE, 2009) related to the efcient operation of heterogeneousCRS by introducing a CCC in the form of a so-called radio enabler .

IEEE 802.22 was one of the rst standards for CR technology. Standard 802.22 is aimed at using CR techniques to allowsharing of a geographically unused spectrum allocated to the TVWS, on a non-interfering basis, to bring broadband accessto rural environments. The draft standards species the air interface, including the cognitive MAC and PHY, of point-to-multipoint wireless regional area networks, comprised a professionally installed xed base station with xed and portableuser terminals operating in the unlicensed VHF/UHF TV broadcast bands between 54 MHz and 862 MHz (TV white space).The technical requirements for spectrum sensing are well dened (challenge [T1]). The standard also denes protectionschemes against security threats through the denition of security sub-layers (challenge [R2]).

The ECMA-392 standard is also related to TVWS application. It describes the PHY and MAC layer for a CR network,

which includes security protection techniques (challenge [R2]). Both IEEE 802.22 and ECMA-392 do not dene externalinterfaces to other wireless technologies and they do not address challenge [T3].



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Tables 4a and b summarize the regulatory and technical challenges and the related activities described in the previoussections.

5. Potential roadmap for the deployment of CR and DSA

In an extreme paradigm, all radios would be smart devices following a spectrum etiquette and the entire radiofrequency spectrum will be shared. This futuristic/utopian vision is similar to the Internet model and the evolution of thespectrum commons model, which has brought economic and social value. This vision is, however, not easy to realize or itmay not even be appropriate for some stakeholders in the context of spectrum. Radio communication services for criticalapplications may still need dedicated spectrum to guarantee their availability. The evolution of CR and DSA should follow astep-by-step approach, which could be based on the following activities:

(1) Identication of specic spectral bands where a exible spectrum management could be adopted. In Europe, theWAPECS initiative has already dened potential spectral bands. This activity should be complemented by rigorousspectrum utilization measurements across Europe to provide hard facts for the denition of the spectrum for CR orbusiness scenarios. The deployment of permanent spectrum measurement networks could also be considered formonitoring purposes even if the associated costs may be high.

(2) Introduction of CR with the current spectrum management approach in specic allocated frequency bands to evaluatethe technical challenges. For example, in order for regulators to permit DSA approaches, conclusive proof must besupplied that CRs can use the available spectrum while at the same time not unduly interfering with primary users.Spectrum regulators in the USA, Finland, Ireland and Australia have already allocated test bands for CR. Therecommendation is to dene a European test band where cross-border issues could also be addressed.

(3) Continue the support to research projects and activities with close links with standardization (for example, ETSI).(4) Creation of market for trading of spectrum property rights at the European level in close association with national

spectrum regulators. Removal of spectrum trading barriers.

(5) The R&TTE directive is currently under revision at the European level. The denition of a new certicationprocess for CR devices should also include mechanisms to enforce conformance to regulations for CR devices

Table 4aRegulatory challenges and related activities/actions.

Regulatory challenges International USA (FCC), IEEE EC-CEPT-ETSI European Member states

[R1] Appropriate regulations forvarious operational scenarios

WRC-12 AgendaItem 1.2 and 1.19

FCC (2008) for white spacesIEEE 802.22, IEEE 802.11af

ECC (2010) , ETSI TC ERM

[R2] Certication and protectionagainst misbehavior FCC (2001) and FCC (2005) forcertication of CR devices Revision of R&TTE directive Qinetiq.2007

[R3] Complex spectrum tradingschemes

FCC (2002) RSPG (2010) Qinetiq.2007

[R4] Complex internationalframework

ITU-R WorkingGroup 5A

[R5] Stakeholders conict FCC National Broadband Plan RSPG (2010)

[R6] Lack of exibility of existinglicensing

FCC National Broadband Plan RSPG (2010) Qinetiq.2007

[R7] Lack of precise data forspectrum utilization

– Spectrum Bridge White SpacesMaps

Measurement campaignsthrough FP7 research projects

Measurementcampaigns in UK,Germany– FCC Spectrum Dashboard

Table 4bTechnical challenges and related activities.

Technical challenges International USA (FCC) EC-CEPT-ETSI European Member states

[R1] Accurate spectrum sensing IEEE 802.22 FCC (2010) , ECC (2010)

[R2] Extendible front end JTRS research projects FP7 research projects

[R3] Lack of interfaces amongheterogeneous networks

IEEE 1900.4 ETSI TC RRS

[R4] Complex spectrum etiquette DARPA XG research projects FP7 research projects Qinetiq.2007



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(for example, shutting down a CR node, policies enforcement). These mechanisms are currently investigated both in Ecand ETSI TC RRS.

(6) Identication and denition of European entities and tools to support CR technologies. The list includes spectrumdatabases, certication authorities for CR devices, authorized spectrum trading centers and others.

6. Conclusions

CR technology has the potential to improve spectrum utilization and create value for citizens and industry. Thedeployment of new technologies and spectrum management models (for example, CR, DSA) however requires signicantchanges at the regulatory level and must be supported by associated standardization and research activities. In this paperthe authors described the operational scenarios and subsequent regulatory, technical and business challenges. Theydescribed current regulatory and standardization activities in Europe and around the world, revealing a concentratedeffort to progress towards the realization of CR. They showed that despite the progress and acceptance by some regulators,CR faces several key challenges. A roadmap of potential actions was proposed to address these challenges and support theadoption of CR technology. Beyond the specic regulatory and technical challenges, a critical issue is the timelycooperation among government, market, industry and research entities.

Acknowledgment

This work was funded by the EC through the FP7 project ACROPOLIS (257626). The authors would like to thankeveryone involved.

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