Time-Reversal Minimum-SER-Based Adaptive Protocol for Full-Rate Cooperative Communications

Cooperative communications have recently emerged as novel communication schemes for future wireless communications because of their diversity gain, achieved by sharing each cooperation user´s antenna to form a virtual antenna array in the wireless network. In this paper, we investigate an adaptive protocol for full-rate cooperative communications based on minimizing a tight approximate symbol error rate (SER). We then propose a time-reversal-mirror approach to estimate an instantaneous channel variance, needed for computing such approximate SER used in an adaptation process, based on a least square (LS) estimation. A mean square error (MSE) upper bound for such estimation is also derived. Simulation results indicate that the adaptive protocol employing the time-reversal-mirror estimation performs essentially similar to an ideal adaptive protocol for quasi-static fading channels, where a lower SER compared with existing protocols is achieved. For nonquasistatic fading channels, the proposed scheme is still be able to work acceptably with a SER penalty in high signal-to-noise ration (SNR) regimes.