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The Scientific World Journal
Volume 2014, Article ID 548082, 10 pages
Research Article

Performance Analysis of Relay Subset Selection for Amplify-and-Forward Cognitive Relay Networks

1Department of Electrical Engineering, Air University, Islamabad, Pakistan
2Department of Electronics Engineering, IIU, Islamabad, Pakistan

Received 31 August 2013; Accepted 9 October 2013; Published 6 March 2014

Academic Editors: G. De Marco and A. Svigelj

Copyright © 2014 Kiran Sultan et al. 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.


Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs), which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs) active in the frequency band of the primary users (PUs), which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF) based underlay cognitive relay networks have been very well studied in terms of outage probability (OP) and bit error rate (BER), which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF) of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results.