An improved amplify-and-forward strategy for user cooperation channels

A new amplify-and-forward (AAF) strategy is proposed for user cooperation channels. Differing from the previously reported ones in which users either send independent signals, i.e., Azarian´s AAF, or do not directly send information to the base station, i.e., Laneman´s AAF, the proposed AAF strategy allows users to send signals that are correlated with the previously transmitted signals. The achievable rate region is presented. Numerical results show that the proposed AAF outperforms the traditional AAF, and can provide a larger achievable rate region than the full duplex decode and forward (DAF) relaying strategy and the full duplex estimate and forward (EAF) relaying strategy under certain conditions.