A coded modulation scheme for a broadcast AWGN channel

This paper proposes a coded modulation scheme for transmission of two classes of information on a broadcast AWGN channel. The scheme is based on multilevel coding with a nonstandard partition of a 32-QAM constellation. The QAM constellation consists of four groups of 8-PSK subconstellations instead of 8-QAM subconstellations. This results in a constellation with reduced peak-to-average power ratio. As component codes of the multilevel construction only one binary convolutional code and a punctured version of it are used. The nonstandard partition allows parallel decoding of the component codes in a multistage decoding algorithm. The error performance of the proposed scheme is obtained. In comparison with Wei´s scheme with similar parameters, the proposed scheme achieves higher coding gains for the most important class at the cost of a small degradation in performance for the less important class. Although only results for a specific constellation are presented, the design principles can be easily extended to other QAM constellations