Cooperative MMSE OFDM receiver for half-duplex and multiple-relays system

Recently, cooperative communication has drawn much attention because it can provide extra cooperative diversity gain to improve network quality. In this paper, we investigate the design of orthogonal-frequency-division multiplexing (OFDM) receiver for the multiple-relays system under the frequency-selective channels and derive the receiver solution in the minimum-mean-squared error (MMSE) sense. The communication network adopts half-duplex amplify-and-forward (AF) protocol. In this first phase, the source simultaneously sends OFDM signal to the destination and relays. In the second phase, the relays amplify the signals in accordance with the AF protocol and then send the signals to the destination. Finally, the two signals received at destination are combined with the MMSE filter coefficients. Extension to two antennas is also presented. Simulation results indicate cooperative communication OFDM receiver can benefit from cooperative diversity gain.