Digital communication system

摘要

Methods and apparatus for use in communication systems using recursive modulation schemes with a Low Density Generator Matrix code (including an irregular repeat accumulate (IRA) code) are described that have reduced complexity and thus reduced cost compared to prior art systems. A communication system is described in which the transmitter concatenates a low density generator matrix code with an accumulator followed by a recursive modulator in order to eliminate the use of an interleaver, and in which the receiver combines the decoder for the accumulator and the soft demodulator into a single joint decoder in order reduce the number of components and complexity. Another variation is also described in which the transmitter is further simplified by eliminated the accumulator altogether, and in which the receiver is further simplified by replacing the joint decoder with a soft demodulator prior to the LDGM soft decoder.

主权项

1. An apparatus for receiving a transmission in a communication system implementing a recursive modulation scheme and an Irregular Repeat Accumulate (IRA) code, the apparatus comprising:
a soft demodulator comprising a joint recursive modulator and accumulator soft decoder for receiving a transmit signal and configured to demodulate the received signal using a trellis based algorithm using a joint trellis for the accumulator and recursive modulation scheme to generate a plurality of coded symbol estimates, wherein the soft demodulator does not include a de-interleaver to demodulate the received signal with the joint recursive modulator and accumulator soft decoder; and a Low Density Generator Matrix (LDGM) decoder for receiving the plurality of coded symbol estimates from the soft demodulator and decoding the coded symbol estimates to generate a plurality of source bit estimates.