Performance analysis of hierarchical coded modulation systems

In this paper, analytical performance bounds are presented for a hierarchical coded modulation system of the type which has been proposed for backward compatibility and/or variable error rate protection. This system uses two convolutional encoders (and two Viterbi (1989) decoders) with a hierarchical 16-QAM constellation, and is compatible with an existing QPSK based coded system. In the AWGN channel, we derive upper bounds for four different schemes (two decoding schemes, multi-stage decoding (MSD) and independent decoding(ID), and two labeling schemes, Gray labeling (GL) and non-Gray labeling (NGL)). We show that the performance of the simple GL with ID scheme is nearly optimum in the AWGN channel. Then we analyze the GL with ID scheme in the Rayleigh fading channel. Simulation results are given for comparison with the bounds.