Abstract
We consider a wireless relay network with Rayleigh fading channels and apply distributed space-time coding (DSTC) in amplify-and-forward (AF) mode. It is assumed that the relays have statistical channel state information (CSI) of the local source-relay channels, while the destination has full instantaneous CSI of the channels. It turns out that, combined with the minimum SNR based power allocation in the relays, AF DSTC results in a new opportunistic relaying scheme, in which the best relay is selected to retransmit the source's signal. Furthermore, we have derived the optimum power allocation between two cooperative transmission phases by maximizing the average received SNR at the destination. Next, assuming M-PSK and M-QAM modulations, we analyze the performance of cooperative diversity wireless networks using AF opportunistic relaying. We also derive an approximate formula for the symbol error rate (SER) of AF DSTC. Assuming the use of full-diversity space-time codes, we derive two power allocation strategies minimizing the approximate SER expressions, for constrained transmit power. Our analytical results have been confirmed by simulation results, using full-rate, full-diversity distributed space-time codes.
Highlights
Space-time coding (STC) has received a lot of attention in the last years as a way to increase the data rate and/or reduce the transmitted power necessary to achieve a target bit error rate (BER) using multiple antenna transceivers
We propose a decision metric for opportunistic relaying based on maximizing the received instantaneous SNR at the destination in amplifyand-forward (AF) mode, when statistical channel state information (CSI) of the sourcerelay channel is available at the relay
(i) We show that the distributed space-time coding (DSTC) based on [7] in which relays transmit the linear combinations of the scaled version of their received signals leads to a new opportunistic relaying, when maximum instantaneous SNR-based power allocation is used
Summary
Space-time coding (STC) has received a lot of attention in the last years as a way to increase the data rate and/or reduce the transmitted power necessary to achieve a target bit error rate (BER) using multiple antenna transceivers. In [7], a cooperative strategy was proposed, which achieves a diversity factor of R in a R-relay wireless network, using the so-called distributed space time codes (DSTCs). In this strategy, a two-phase protocol is used. It was shown in [7] that the relays can generate a linear space-time codeword at the receiver, as in a multiple antenna system, they only cooperate distributively This method does not require decoding at the relays and for high SNR it achieves the optimal diversity factor [7].
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