Improving performance of the asynchronous cooperative relay networks with maximum ratio combining and transmit antenna selection technique

Abstract

In this paper, a new amplify and forward (AF) asynchronous cooperative relay networks using maximum ratio combining (MRC) and transmit antenna selection (TAS) technique is considered. In order to obtain a maximal received diversity gain, the received signal vectors of all antennas of the each relay node are jointly combined by MRC technique in the first phase. Then, only one the selected antenna of each relay will amplify and retransmit the resulting MRC signal vectors to the destination node in the second transmission step of network. The proposed scheme not only offers to reduce the interference components induced by inter-symbol interference (ISI) among the relay nodes, but also can effectively remove them with employment near-optimum detection (NOD) at the destination node as compared with the previous distributed close loop extended-orthogonal space time block code (DCL EO-STBC) scheme. The analysis and simulation results confirm that the new scheme outperforms the previous cooperative relay networks in both synchronous and asynchronous conditions. Moreover, the proposed scheme allows to reduce the requirement of the Radio-Frequency (RF) chains at the relay nodes and is extended to general multi-antenna relay network without decreasing transmission rate.