Design of superposition coded modulation for unequal error protection

For multimedia communications in wireless channels, it is desirable that the quality of the multimedia service is gracefully degraded when the channel conditions deteriorate. To that end, unequal error protection (UEP) plays an essential role, by which the coded bit streams of different significance are given different levels of protection. We design power- and bandwidth-efficient coded modulation scheme for UEP. Motivated by the information-theoretic results, a superposition coded modulation scheme is designed by using shaping techniques. The carefully-designed shaping can successfully reduce the interference between the fine-level code and the coarse-level code. The performance of the proposed scheme is evaluated through both analysis and simulations. Simulation results indicate that the proposed scheme outperforms those without shaping by more than 3 dB in the region of interest for UEP