Optimal scheduling and resource allocation using hierarchical modulation in wireless networks

We investigate the network utility maximization (NUM) problem when layered modulation is used at the physical layer of a downlink wireless system. The key idea is to transmit to more than one users with favorable and unfavorable channel qualities at the same time by employing hierarchical constellations. We demonstrate that average throughput of users with unfavorable channel conditions are significantly improved without any penalty on the overall system utility. We employ stochastic network optimization tools to derive and prove the stability and optimality of a cross-layer algorithm that performs joint flow control, scheduling and transmission power control.