Low complexity and high performance coded modulation systems

摘要

The main focus of this dissertation is to design low decoding complexity and high performance modulation codes for both the additive white gaussian noise (AWGN) and the Rayleigh fading channels. The dissertation consists of three parts.;The first part presents a simple and systematic technique for constructing multi-dimensional MPSK Trellis Coded Modulation (TCM) codes. The construction is based on a multilevel concatenation approach in which binary convolutional codes with good free branch distances are used as the outer codes and block MPSK modulation codes are used as the inner codes. Conditions on phase invariance of these codes are derived and a multi-stage decoding scheme for the codes is proposed. Codes have been constructed for both the AWGN and the Rayleigh fading channels and compared with the existing multi-dimensional MPSK TCM codes. Study shows that these codes perform very well and achieve significant coding gains over uncoded reference modulation systems.;Part two of the dissertation uses the concepts developed in part one to design nested concatenated coded 8PSK modulation schemes for the AWGN channel. These schemes are designed to achieve good error performance, large coding gains and high spectral efficiency with reduced decoding complexity. In the concatenation, Reed-Solomon (RS) codes, are used as the outer codes and multi-dimensional trellis 8PSK codes constructed in part one of the dissertation are used as the inner codes. These schemes are analyzed and upper bounds on their error performances are derived. Results show that these schemes perform extremely well and achieve impressive coding gains over uncoded reference systems.;The final part of the dissertation presents a powerful technique for constructing MPSK block modulation codes using product codes. Existing basic multilevel block modulation codes turn out to be a special case of this construction. Codes have been constructed for both the AWGN and the Rayleigh fading channel and compared with the existing basic multilevel block modulation codes. Conditions on phase invariance of these codes are derived and two multi-stage decoding algorithms for these codes are proposed. Study shows that these codes perform very well and achieve significant coding gains over uncoded reference modulation systems.