Adaptive Decode-and-Forward Cooperative Networks with Limited Feedback

We analyze the performance of an adaptive communication scheme in which by employing limited feedback, the source will decide to transmit signal to the destination either by the direct link or by the direct and relaying links. Specifically, by using the instantaneous SNR as the metric, if the S-D link is better, the source will transmit to destination directly. Otherwise, the two-phase transmission mode will be triggered in which source cooperates with the relay or transmits twice within two time slots based on the quality of the received signal at the relay. Initially, the spectral efficiency is derived by calculating the probabilities of direct transmission and two-phase transmission mode. Subsequently, the BER performance for the adaptive cooperation schemes is analyzed by considering the BER routines of two events: the source transmits the signal alone or cooperates with the relay. Also, the optimum power allocation is studied based on the BER result. Finally, Monte-Carlo simulation results are presented to confirm the performance enhancement offered by the proposed scheme. key words: Adaptive cooperation, decode and forward, spectral efficiency, BER performance, power allocation.