An nonlinear amplify-and-forward protocol for cooperative communication networks

Cooperation diversity is a new technology of spatial diversity. It obtains diversity gain through a virtual antenna array which is formed by sharing resources among different users. We propose a new strategy called nonlinear amplify-and-forward (NAF) based on some fundamental strategies such as amplify-and-forward (AF) and decode-and-forward (DF) in cooperative communication networks. In this new strategy, we give a closed-form solution of the optimal signal estimation at the relay by the minimum mean square error (MMSE) criterion. Furthermore, it has been proved that NAF can help the destination to obtain a higher SNR than AF and prevent the case in DF that all power is used to transmit the incorrect signals. Both of the theoretical analysis and simulation results show that NAF outperforms AF and DF, and it can achieve full spatial diversity.