he last decade has witnessed the proliferation ofmobile devices driven by significant advances in devicearchitectures, mobile operating systems, and enhanced bat-tery life such that they are now competing with laptopsand desktops, and have become the platforms of choice formillions for personal communications and even computing.There are thousands of applications continue to be devel-oped at the present time especially targeted toward mobiledevices.

The proliferation of mobile devices and the popularityof the services they provide have necessitated a hugedemand for additional spectrum to meet the growingbandwidth requirements of such data applications. As youmight know, most of the spectrum in several (nearly all)countries is already allocated to national priorities such asdefense, communications, navigation, and radar; therefore,additional spectrum can only be created by some sort ofreallocation of existing frequency assignments or utilizingthe unused spectrum even though licensed opportunistical-ly. The utilization of white spaces in the TV band is thebest known example of spectrum reallocation, whereasdynamic spectrum access (DSA) networking research (e.g.,primary/secondary systems) is a prime example of oppor-tunistic spectrum sharing facilitated by cognitive radios.

Both approaches to spectrum sharing rely on usingeither a spectrum database or real-time spectrum sensing,or both, to provide needed bandwidths for applications.The database approach in TV whitespaces has proven tobe successful, while those relying on sensing have not beendue to several reasons, primary among them being ques-tionable accuracy of the sensing mechanisms, complexity,and platform costs, among others. As a result, even todaywe do not see large-scale deployments of DSA-based cog-nitive radio networks.

Wireless multimedia and gaming are among the mostpopular mobile applications of today. It turns out thatthese applications are not only bandwidth-hungry but alsodelay-intolerant, and thus require quality of service (QoS)provisioning from the network. The TV white space net-working may be able to provide QoS support because spec-trum remains available for sufficiently long durations. Butthe same argument does not hold for opportunistic accessnetworks due to the unpredictability in the availability ofappropriate size spectrum for a given duration as well ascomplexities associated with frequent switching of spec-trum.

Given such a scenario, our first article, “ResourceManagement for QoS Support in Cognitive Radio Net-works,” covers an area of immediate interest: properlymanaging a finite and limited radio spectrum to maximizeutilization while stil l maintaining QoS parametersrequired by many licensed and unlicensed services. As thearticle notes, much work is ongoing in this area, particu-larly for using TV white spaces (TVWS) opened up bythe switch to digital broadcasting systems. The articlehighlights some of the challenges in cognitive radio net-works, particularly when QoS must be guaranteed, andthen lays out a framework for addressing these chal-lenges. The application of the framework to some keyscenarios is also covered.

The next article, “Improving Bandwidth Efficiency inE-Band Communication Systems,” deals with an entirelydifferent subject area: the system design issues andapproaches required to deal with 70–80 GHz (E-band)RF links. The International Telecommunication Union(ITU) made fixed service allocations in the E-band morethan 30 years ago at WARC-79, but it remained underuti-lized until the recent explosion of high-speed data ser-

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RADIO COMMUNICATIONS: COMPONENTS, SYSTEMS, AND NETWORKS

Join the online discussion group for this Series Topic here:http://community.comsoc.org/forums/commag-features-and-series

Thomas Alexander Amitabh Mishra

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vices in the microwave frequencies. Both the FCC andCEPT have now established “light licensing” rules for E-band service to spur the development of nearly 10 GHzof underutilized spectrum. However, as described in thearticle, significant issues in propagation, transceiverdesign, multiple-input multiple-output (MIMO) and radiolink architecture remain to be overcome. The article pro-vides an overview of these issues and covers the ongoingwork address them.

As we move on to future issues of this Series, we planon devoting each issue to a particular theme that repre-sents an emerging trend in wireless communications andnetworking research and development. Obviously, this is asubject that should receive a significant number of contri-butions from our community of authors. We would like toinvite you all to submit your recent research to RadioCommunications so that we can bring it to the readers ofIEEE Communications Magazine. We are also solicitingyour suggestions and feedback regarding special topics thatyou would like to see covered in future issues of RadioCommunications.

BIOGRAPHIESTHOMAS ALEXANDER [M] (talexander@ixiacom.com) is a senior architect atIxia. Previously, he has worked at VeriWave Inc (acquired by Ixia), PMC-Sier-ra Inc, and Bit Incorporated (acquired by PMC-Sierra), and prior to that wasa research assistant professor at the University of Washington. He has beeninvolved in various aspects of wired and wireless networking R&D since1992, in the areas of ATM, SONET/SDH, Ethernet, and (since 2002) wirelessLANs. He is also active in standards development, and has served as Editorof IEEE 802.3ae, Chief Editor of IEEE 802.17, and Technical Editor of IEEE802.11. He received his Ph.D. degree from the University of Washington in1990.

AMITABH MISHRA [SM] (amitabh@cs.jhu.edu) is a faculty member in theInformation Security Institute of Johns Hopkins University, Baltimore, Mary-land. His current research is in the area of cloud computing, data analytics,dynamic spectrum management, and data network security. In the past hehas worked on the cross-layer design optimization of sensor networkingprotocols, media access control algorithms for cellular-ad hoc interworking,systems for critical infrastructure protection, and intrusion detection inmobile ad hoc networks. His research has been sponsored by NSA, DARPA,NSF, NASA, Raytheon, BAE, APL, and the U.S. Army. In the past, he was anassociate professor of computer engineering at Virginia Tech and a mem-ber of technical staff with Bell Laboratories working on the architectureand performance of communication applications running on the 5ESSswitch. He received his Ph.D. in electrical engineering from McGill Universi-ty. He is a member of ACM and SIAM. He has written 80 papers that haveappeared in various journals and conference proceedings, and holds fivepatents. He is the author of a book, Security and Quality of Service in Wire-less Ad hoc Networks (Cambridge University Press,2007) and a TechnicalEditor of IEEE Communications Magazine.

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