%0 Journal Article
%T Partial Relay Selection with Feedback Delay and Cochannel Interference: Performance Analysis and Power Optimization
%A Xuanxuan Tang
%A Weifeng Mou
%A Fang Fang
%A Yueming Cai
%A Weiwei Yang
%A Tao Zhang
%J International Journal of Distributed Sensor Networks
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/629348
%X The performance of a dual-hop amplify-and-forward (AF) relay system is studied with the th worst partial relay selection (PRS) protocol under the joint impact of feedback delay and multiple cochannel interference (CCI) at the relay nodes. In our analysis, the closed-form and asymptotic expressions of the outage probability are derived and the achievable coding gain and diversity gain of the system are accurately revealed. Further, based on the asymptotic analysis we propose a power allocation scheme, which can lead to SNR performance gains of more than 1£¿dB compared to the equal power allocation scheme. Finally, Monte-Carlo simulation results are presented to verify the validity of our theoretical analysis. 1. Introduction Deployment of multiple relays in the wireless communication offers a series of significant performance improvements, including the system¡¯s throughput ability enhancement and the signal coverage advancement. In such systems, performance can be improved by selecting one of the relay nodes [1¨C7]. And two popular protocols of relay selection have been presented, that is, opportunistic relay selection (ORS) [1] and partial relay selection (PRS) [2]. In the opportunistic relaying, the source always selects the best relay according to the global (two-hop) channel state information, which results in the great increase of system¡¯s complexity and cost in ad hoc and wireless sensor networks. Such problems have promoted the development of PRS protocol, which requires only single hop information and the network lifetime can be prolonged in resource-constrained wireless systems such as wireless sensor networks. In practical partial relay system, the PRS is implemented in time-varying channels and the outdated channel state information (CSI) would be used for relay selection due to feedback delay. In other words, the selected relay may not be the best at the instant of actual transmission. In [3], asymptotic lower and upper system capacity of a fixed-gain PRS scheme was investigated with feedback delay. The performance of PRS system affected by feedback delay was quantified by obtaining outage probability and average bit error rate (BER) and further analyzed at high SNR regime in [4]. On the other hand, frequency reuse gives rise to the so-called cochannel interference (CCI) in the cellular network. The authors of [5] investigated the performance of PRS scheme affected by CCI with variable gain relaying and derived the probability density function (PDF) of the received SNR and an asymptotic exponential expression. Kim and Heo studied the
%U http://www.hindawi.com/journals/ijdsn/2014/629348/