DocumentCode :
1478837
Title :
Cooperative Beamforming for Cognitive Radio Networks: A Cross-Layer Design
Author :
Liu, Juan ; Chen, Wei ; Cao, Zhigang ; Zhang, Ying Jun
Author_Institution :
Dept. of Electron. Eng., Tsinghua Univ., Beijing, China
Volume :
60
Issue :
5
fYear :
2012
fDate :
5/1/2012 12:00:00 AM
Firstpage :
1420
Lastpage :
1431
Abstract :
Cognitive Radio (CR) can significantly improve the utilization of the precious radio spectrum by allowing Secondary Users (SUs) to borrow the licensed spectrum if they do not cause harmful interference to Primary Users (PUs). As a wireless technology, CR confronts the challenges of wireless channels inevitably and thus wishes to employ node cooperation to achieve spatial diversity gain. However, conventional cooperative diversity technologies require two idle timeslots for each transmission. This implies two temporal spectrum holes are needed for each transmission when the technologies are applied to CR Networks (CRNs). This can cause severe delay, as temporal spectrum holes are only available from time to time in CRNs. In this paper, we present a cross-layer approach, where cooperative beamforming is adopted to forward messages in busy timeslots without causing interference to PUs, so as to achieve cooperative diversity gain and improve Quality of Service (QoS) for SUs without consuming additional idle timeslots or temporal spectrum holes. In the physical layer, the beamforming weight vector and the cooperative diversity gain are obtained using a geometric approach. The MAC layer of the cooperative communication in CRNs can be modeled by a tandem queue, where the source queue is the bottleneck. Therefore, we propose an optimal opportunistic priority scheduling scheme in the MAC layer, the timeout probability of which is obtained using an absorbing Markov chain. A cross-layer optimization of the transmission rate is then carried out to jointly reduce the timeout and outage probabilities. Its significant QoS gain is demonstrated by simulations.
Keywords :
Markov processes; access protocols; cognitive radio; cooperative communication; diversity reception; quality of service; queueing theory; radio spectrum management; scheduling; wireless channels; MAC layer; absorbing Markov chain; beamforming weight vector; cognitive radio network; cooperative beamforming; cooperative communication; cooperative diversity gain; cross-layer approach; cross-layer design; cross-layer optimization; geometric approach; licensed spectrum borrowing; node cooperation; optimal opportunistic priority scheduling scheme; physical layer; primary user; quality of service; radio spectrum utilization; secondary users; spatial diversity gain; tandem queue; temporal spectrum hole; timeout probability; transmission rate; wireless channel; wireless technology; Array signal processing; Delay; Fading; Interference; Quality of service; Relays; Vectors; Cognitive radio; cooperative beamforming; cross-layer design; opportunistic scheduling; tandem queue;
fLanguage :
English
Journal_Title :
Communications, IEEE Transactions on
Publisher :
ieee
ISSN :
0090-6778
Type :
jour
DOI :
10.1109/TCOMM.2012.031712.100284A
Filename :
6175085
Link To Document :
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