Distributed Amplify-and-Forward with Ring-TCM Codes

This paper proposes a new distributed Amplify-and-Forward (AF) scheme which is integrated with the Ring-Trellis Coded Modulation (TCM) codes in order to achieve both high spectral efficiency and large diversity gain. In the distributed AF scheme, more users cooperate with each other. Each user still uses half of its transmission freedom for relaying others' signal. However, different to the conventional AF scheme, each user further partitions its relay transmission into smaller divisions in order to help more users. As a result, for each user, the distributed AF scheme will have the same spectral efficiency as the conventional AF scheme, but creating more diverse transition paths and providing better diversity gain. In the scheme, output symbols are demultiplexed into several subframes, each of which will be relayed by a different user. As a result, each output symbol from a trellis transition branch can be relayed by a different user, assisting error-correction performance of the decoder. This distributed coding scheme is suitable for different wireless access systems, such as WiLAN and WiMAX systems. Our simulation results show that with the same spectral efficiency, the distributed coded AF scheme can significantly outperform the conventional coded AF scheme.