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Performance Analysis and Power Allocation for AmplifyandForward Cooperative Networks over Nakagamim Fading Channels
Zhaoxi FANG Xiaojing BAO Liangbin LI Zongxin WANG
Publication
IEICE TRANSACTIONS on Communications
Vol.E92B
No.3
pp.10041012 Publication Date: 2009/03/01
Online ISSN: 17451345
DOI: 10.1587/transcom.E92.B.1004
Print ISSN: 09168516 Type of Manuscript: PAPER Category: Broadcast Systems Keyword: cooperative diversity, amplifyandforward, performance analysis, power allocation, Nakagamim fading channels,
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Summary:
In this paper, we consider a dualhop wireless cooperative network with amplifyandforward (AF) relaying. The output signaltonoise ratio (SNR) at the destination of the AF cooperative networks is in the form of the sum of harmonic mean of the sourcerelay channel SNR and the relaydestination channel SNR. Instead of deriving the exact probability density function (PDF) of the output SNR, we study the series expansion of this PDF around zero. This result is then applied to evaluate the performance of the AF cooperative systems over Nakagamim fading channels, and closedform highSNR approximations of the average symbol error rate (SER) and the outage probability are derived. Next, we investigate the optimal power allocation (OPA) among the source node and the relays to minimize the approximate SER as well as the outage probability. It is shown that the optimal power allocation depends on the channel m parameters and the ratio of the sourcerelay channel gain to the relaydestination gain. In addition to the optimal power allocation, we also propose a low complexity suboptimal power allocation (SubOPA) scheme. The performance improvement with optimal and suboptimal power allocation is analyzed and validated by numeric results. It is shown that equal power allocation is near optimal when the relays are close to the source, while significant performance improvement is observed by both the optimal and suboptimal power allocation schemes when the relays are close to the destination.

