Joint beamforming and space‐time coding in limited‐feedback cooperative networks with threshold‐based MIMO selection relaying

Abstract

AbstractIn this paper, a limited‐feedback decode‐and‐forward cooperative network with multiple relays is considered where each relay is equipped with multiple antennas. To combat error propagation, each multiple‐input multiple‐output relay participates in relaying phase, according to its received signal‐to‐noise ratio. In our scheme, space‐time coding is independently employed at each relay. At relay, the detected symbols are forwarded using a novel beamforming method proposed in this paper. In the proposed technique, relays employ only two‐bit quantized phase information of the channel between relay and destination, which reduces the overhead of the feedback channel. Our results highlight that using a simple maximal ratio combining at destination, the received SNR after combining the space‐time coded signals is enhanced significantly compared with other existing methods. We further investigate the bit error rate performance of the general family of M‐ary modulation schemes and show that the proposed design attains full diversity order without any rate or bandwidth cost. Also, closed form expressions are derived for optimal threshold and end‐to‐end bit error rate of the system. Numerical results illustrate a good agreement between the analytical and simulation results.