Single- and multi-user adaptive pragmatic trellis coded modulation for OFDM systems

OFDM has recently been considered as one of the main next-generation broadband wireless access solutions because of its robustness over heavily impaired links and its high spectral efficiency. In this paper, OFDM-based adaptive TCM schemes in both single- and multi-user environments are proposed. The adaptive scheme employs the family of pragmatic TCM to combine different coded modulation modes into one codeword while reducing the hardware complexity. A set of switching levels is analytically derived to determine the appropriate modes for each value of the received SNR. The error and throughput performance of the proposed system is analyzed and it is shown that adaptive single user TCM results in considerable performance improvement. It is also demonstrated that by jointly optimizing the overall spectral efficiency while guaranteeing a minimum data rate and a desired BER level to each user, the spectral or power efficiency can be further improved in the multi-user environment.