Soft Decode and Forward of MQAM Modulations for Cooperative Relay Channels

A novel approach for extension of soft decode and forward strategy into higher order MQAM modulation is proposed. A new soft mapping function is introduced to map soft bits onto a point in the complex plane. It is shown that the proposed soft decode and forward (SDF) scheme attains the same level of diversity as amplify and forward (AF) scheme while improves the overall system spectrum efficiency through forwarding with higher order modulations. Simulation results show that new scheme outperforms DF for different links conditions.