A Joint Network-Channel Coding Scheme for Relay-Based Communications

A bandwidth-efficient joint network-channel coding scheme based on distributed turbo codes is proposed for relay-based wireless communications systems. The proposed scheme provides a solution to increase the transmission rate and/or improve the error performance. To enhance the system performance over the adverse block fading channels, the relay not only delivers the additional parity bits as in the conventional turbo coded systems but also repeats a portion of systematic bits by using higher-order constellations. This increases the number of information bits having a diversity order of 2. As a result, the proposed scheme yields a 3-dB gain in the transmitted power compared to the conventional scheme for the case of symmetric channels. The gain is further increased when the relay has a better channel condition to the destination than the users.