Sensing-based opportunistic channel access

Enabled by regulatory initiatives and advanced radio technologies, more flexible opportunistic spectrum access has great potential to alleviate the spectrum scarcity. In this paper, we study the channel selection issue of secondary users in spectrum-agile communication systems. We focus on the sensing-based approach because it is simple and has low infrastructure requirements. We propose a two-step approach for channel selection. The first step is to determine whether or not a channel is idle and thus accessible to secondary users. We propose three algorithms to perform the accessibility check based on measurements of primary signals. Then we address the question whether an accessible channel is a good opportunity for a secondary user. Xin Liu received her Ph.D. degree in electrical engineering from Purdue University in 2002. She is currently an assistant professor in the Computer Science Department at the University of California, Davis. Before joining UC Davis, she was a postdoctoral research associate in the Coordinated Science Laboratory at UIUC. Her research is on wireless communication networks, with a focus on resource allocation and dynamic spectrum management. She received the best paper of year award of the Computer Networks Journal in 2003 for her work on opportunistic scheduling. She received NSF CAREER award in 2005 for her research on “Smart-Radio-Technology-Enabled Opportunistic Spectrum Utilization.” Sai Shankar N received his PhD degree from the department of Electrical Communication Engineering from Indian Institute of Science, Bangalore, India for his work in the area of performance modeling of ATM networks. In 1998, He was awarded the German Fellowship, DAAD, in the department of mathematics, University of Kaiserslautern, Gernany to work on queueing approaches in manufacturing. In 1999, he joined Philips Research, Eindhoven, the Netherlands, where he served as Research Scientist in the department of New Media Systems and Applications working on various problems involving Hybrid, Fiber, Co-axial Cable (IEEE 802.14) Networks and IP protocols and provided efficient algorithms to improve protocol efficiency. In the year 2001 he joined Philips Research USA, Briarcliff Manor, NY and worked in the area of Wireless LANs/Ultra Wide Band (UWB), Cognitive Radios and Cooperative Communications. He was a key member in shaping the QoS related issues in IEEE 802.11e standardization and was one of the prime authors and inventors of the WiMEDIA UWB MAC protocol for which he was nominated as one of the five finalists in the Innovator of the year category by EE Times in year 2004. Besides these he has authored nearly 10 papers in the area of cognitive radios and holds fundamental patents on the design of MAC for cooperative communications. He has chaired numerical conferences and technical sessions and has delivered more than ten tutorials in leading international conferences of which two will appear in IEEE COMSOC webpage. He is also the Senior Member of the IEEE and has authored more than 50 conference and journal papers and holds more than 35 patents. Currently Sai Shankar is with Standards Engineering department of Qualcomm Inc. working on issues related to UWB and cognitive radios.