Method and system for a turbo trellis coded modulation scheme for communication systems

Abstract

Method and System for evaluating a turbo-coding scheme suitable for VDSL2 systems. The scheme is a Turbo-Trellis Coded Modulation TTCM that makes use of a Parallel Concatenated Convolutional Code (PCCC) including an inner Latin square/rectangular matrix of Random sequence pattern Interleaver (LRI) of approximately 2044 bits. In the presence of the outer Reed Solomon Code but without an outer interleaver (fast mode), the method and system provides 7.1 dB of average net coding gain, i.e., 2.6 dB of coding gain improvement relative to the standard 16 states 4-dimensional (4-D) trellis code used in current ADSL2 systems. The substantial coding gain achieved through the method and system, leads to an increase in the VDSL2 rate by 38% at 6 kft against local exchange carriers, such as ILEC (SBC) conditions with approximately 1.5 ms of latency. By encoding only two bits per tone (i.e., 1 bit per dimension), the turbo code implementation complexity is kept reasonable. Finally, the coded modulation scheme supports very small constellations, allowing transmitting spectral efficiency as low as 0.5 bit/sec/Hz over Binary Phase Shift Keying (BPSK) constellations at a signal-to-noise-ration (SNR) very close to the Shannon bound.

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