Superposition of Broadcast and Unicast in Wireless Cellular Systems

Practical application of superposition coding in multiplexing broadcast and unicast for OFDM-based mobile cellular systems is discussed. Superposition coding, whose gain is increased as the superposed signals have larger difference in signal-to interference-plus-noise ratio, is well matched for unicast and broadcast in a single-frequency network configuration. Combined with interference cancellation technique, broadcast signals from multiple base stations can be cancelled in a single step, minimizing the interference from broadcast to unicast. Issues related with scheduling and strategy for time, frequency and power resource sharing between broadcast and unicast are discussed. The application of superposed broadcast and unicast is then extended to MIMO systems. Simulation results in a practical mobile cellular environment are also provided, showing significant throughput gain of superposed broadcast and unicast.