Research on Cognitive Radio Networks at Real-Time Computing Laboratory

July 16, 2009
Kang G. Shin | The University of Michigan, Ann Arbor, Michigan

Static spectrum allocation has resulted in low spectrum efficiency in licensed bands and poor performance of radio devices in crowded unlicensed bands. To remedy these problems, we have been exploring ways of exploiting the concept of “spectrum agility” such that radio devices can dynamically and opportunistically utilize idle spectral bands. Cognitive radio (CR) is one such device that enables dynamic spectrum access and environment-aware wireless networking.

We studied several key elements of CR and obtained a series of interesting results. First, we proposed a unified framework of CRs that defines necessary interactions between intra- and inter-CR devices. Second, we studied one of the most essential components of CRs, spectrum sensing, and its PHY- and MAC-layer research issues, such as: (1) MAC-layer sensing scheduling for maximal and fast discovery of spectrum opportunities via out-of-band sensing, (2) protection of legacy spectrum users via in-band sensing, (3) an optimal spectrum sensing framework that jointly exploits sensors’ cooperation and sensing scheduling, and (4) an attack-tolerant cooperative sensing scheme where clustered sensors cooperatively safeguard distributed sensing. We have also been designing a comprehensive and cohesive cognitive framework across the wireless networking stack, built upon the CR platform. This framework consists of cross-layer algorithms exploiting awareness at multiple levels (e.g., PHY/MAC, transport) to optimize operations and improve overall application performance. Finally, we have built a CR testbed that consists of heterogeneous wireless systems including MadWiFi-enabled 802.11 devices, mobile robots, and USRPs with GRU Radio capability.

This is joint work with my former graduate students (Chun-Ting Chou and Kyu-Han Kim), current graduate students (Hyoil Kim, Ashwini Kumar, Alex Min, Eugene Chai, and Xinyu), and former post doctoral fellows, Bechir Hamdaoui and Young-June Choi.

Speaker Details

Kang G. Shin is the Kevin and Nancy O’Connor Professor of Computer Science and Founding Director of the Real-Time Computing Laboratory in the Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan.His current research focuses on QoS-sensitive networking and computing as well as on embedded real-time OS, middleware and applications, all with emphasis on timeliness and dependability. He has supervised the completion of 61 PhD theses, and authored/coauthored about 680 technical papers (about 250 of which are in archival journals) and numerous book chapters in the areas of distributed real-time computing and control, computer networking, fault-tolerant computing, and intelligent manufacturing. He has co-authored (jointly with C. M. Krishna) a textbook “Real-Time Systems,” McGraw Hill, 1997.