Scheduling Heterogeneous Wireless Systems for Efficient Spectrum Access
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Research Article Scheduling Heterogeneous Wireless Systems for Efficient Spectrum Access Lichun Bao (EURASIP Member)1 and Shenghui Liao2 1 Computer
Science Department, Donald Bren School of Information and Computer Sciences, University of California, Irvine, CA 92637, USA 2 Department of Electrical Engineering and Computer Science, University of California, Irvine, CA 92637, USA Correspondence should be addressed to Shenghui Liao, [email protected] Received 22 August 2009; Accepted 30 September 2009 Academic Editor: Benyuan Liu Copyright © 2010 L. Bao and S. Liao. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The spectrum scarcity problem emerged in recent years, due to unbalanced utilization of RF (radio frequency) bands in the current state of wireless spectrum allocations. Spectrum access scheduling addresses challenges arising from spectrum sharing by interleaving the channel access among multiple wireless systems in a TDMA fashion. Different from cognitive radio approaches which are opportunistic and noncollaborative in general, spectrum access scheduling proactively structures and interleaves the channel access pattern of heterogeneous wireless systems, using collaborative designs by implementing a crucial architectural component—the base stations on software defined radios (SDRs). We discuss our system design choices for spectrum sharing from multiple perspectives and then present the mechanisms for spectrum sharing and coexistence of GPRS+WiMAX and GPRS+WiFi as use cases, respectively. Simulations were carried out to prove that spectrum access scheduling is an alternative, feasible, and promising approach to the spectrum scarcity problem.
1. Introduction According to a recent spectrum usage investigation conducted by the FCC [1], the RF wireless spectrum is far from fully utilized. According to the report, typical channel occupancy was less than 15%, and the peak usage was only close to 85%. On the other hand, traffic demands on the wireless networks are growing exponentially over the years and quickly overwhelm the network capacity of wireless service providers in some parts of the regions, such as hotspots or disaster-stricken areas where limited number of base stations remain. Adaptive and efficient spectrum reuse mechanisms are highly desirable in order to fully utilize the wireless bands. Femtocells and cognitive radios are two of the widely adopted solutions to improve spectrum utilization. However, we take a different approach from femtocells that stayed within the same wireless network system architecture except for adjusting the power footage of base stations or cognitive radios which opportunistically share the RF spectrum that was originally allocated to the primary spectrum users.
In this paper, we propose a spectrum access scheduling approach to heterogeneous wireless systems coexistence, in which all wireless systems are considered
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