Low-complexity coding methods for high-data-rate channels

Bandwidth-efficient and power-efficient, high-speed, coded octal phase-shift keying (8-PSK) systems are presented. It is shown that coded 8-PSK modulation systems having rates higher than 2/3 and based on a class of periodically time-varying trellis codes (PTVTCs) yield bandwidth efficiencies greater than 1.5 bit/s/Hz, with a power efficiency comparable to or better than that of QPSK systems. Viterbi decoder complexity is comparable to that of a rate of 2/3 rather than a general rate k/n code. A construction method to generate a class of PTVTCs of rate (2P + i)/3P, where P is not less than 2 and i is less than P and greater than or equal to 1, for 8-PSK modulation is described. Optimum Euclidean distance codes of rates 7/9, 5/6, and 8/9 with 4, 8, and 16 trellis states are constructed. It is shown that the class of PTVTCs with a normalized Euclidean free distance of not greater than 2 are maximum-likelihood decodable by using the trellis structure of rate 2/3 codes. Computer simulation results are presented for the performance of rate 7/9 and rate 8/9 codes with 16 states over specific channel environments.