Symbol Error Rate of Underlay Cognitive Relay Systems over Rayleigh Fading Channel

Khuong HO VAN  Vo Nguyen Quoc BAO  

IEICE TRANSACTIONS on Communications   Vol.E95-B   No.5   pp.1873-1877
Publication Date: 2012/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E95.B.1873
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
decode-and-forward,  cognitive radio,  underlay,  Rayleigh fading channel,  

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Underlay cognitive systems allow secondary users (SUs) to access the licensed band allocated to primary users (PUs) for better spectrum utilization with the power constraint imposed on SUs such that their operation does not harm the normal communication of PUs. This constraint, which limits the coverage range of SUs, can be offset by relaying techniques that take advantage of shorter range communication for lower path loss. Symbol error rate (SER) analysis of underlay cognitive relay systems over fading channel has not been reported in the literature. This paper fills this gap. The derived SER expressions are validated by simulations and show that underlay cognitive relay systems suffer a high error floor for any modulation level.