Bandwidth efficient turbo coded OFDM systems

Abstract

In this paper, bandwidth efficient turbo codes, commonly known as turbo trellis coded modulation (TTCM) is used in orthogonal frequency division multiplexed (OFDM) systems. It improves the error performance and spectral efficiency simultaneously, which are the major requirements for modern communication systems. The throughput can be improved by puncturing. In addition to TTCM, data interleaver (DI) is incorporated to boost the performance of the system further. BCJR algorithm is used at the receiver to decode iteratively the received turbo trellis coded interleaved OFDM signals. Frequency selective Rayleigh fading channel in presence of additive white Gaussian noise (AWGN) and frequency offset is considered. To the best of the authors' knowledge there is only one earlier work, which simultaneously addresses the problem of timing and carrier synchronization, channel estimation and turbo decoding of OFDM signals transmitted through frequency selective Rayleigh fading channels. This paper is an extension of the earlier work wherein the code rate is increased from half to unity using puncturing and TTCM. Therefore our baseline for comparison is the ideal coherent receiver.