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Issue No. 08 - Aug. (2012 vol. 11)
ISSN: 1536-1233
pp: 1412-1423
Ying Jun Zhang , The Chinese University of Hong Kong, Hong Kong
Zhigang Cao , Tsinghua University, Beijing
Wei Chen , Tsinghua University, Beijing
Juan Liu , Tsinghua University, Beijing
There have been increasing interests in integrating cooperative diversity into Cognitive Radios (CRs). However, conventional cooperative diversity protocols require at least two randomly available idle timeslots or temporal spectrum holes for one transmission, thus leading to limited throughput and/or large latency. In this paper, we propose a novel cross-layer approach for efficient scheduling in CR systems with bursty secondary traffics. Specifically, cooperative beamforming is exploited for Secondary Users (SUs) to access busy timeslots or spatial spectrum holes without causing interference to primary users. We first propose a basic cooperative beaMforming and Automatic repeat request aided oppoRtunistic speCtrum scHeduling (MARCH) scheme to balance available spectrum resources, namely temporal and spatial spectrum holes, between the source and the relays. To analyze the proposed scheme, we develop a tandem queuing framework, which captures bursty traffic arrival, dynamic availability of spectrum holes, and time-varying channel fading. The stable throughput region and the average delay are characterized using a structured matrix-analytical method. We then obtain delay optimal scheduling schemes for various scenarios by jointly optimizing the scheduling parameters. Finally, we propose a modified scheme, MARCH-IR, which combines MARCH with Incremental Relay selection to further improve the system performance. Simulation results reveal that the proposed schemes provide significant Quality of Service (QoS) gains over conventional scheduling schemes that access only temporal spectrum holes.
Cognitive radio, Decoding, Array signal processing, Interference, Optimal scheduling, Quality of service, Markov processes, structured matrix-geometric method., Cognitive radio, opportunistic scheduling, cooperative beamforming, tandem queuing, Markov chain

Y. J. Zhang, Z. Cao, W. Chen and J. Liu, "Delay Optimal Scheduling for Cognitive Radios with Cooperative Beamforming: A Structured Matrix-Geometric Method," in IEEE Transactions on Mobile Computing, vol. 11, no. , pp. 1412-1423, 2012.
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