Utility-based joint physical-MAC layer optimization in OFDM

In this paper, joint physical-MAC layer optimization in OFDM systems using adaptive modulation and subcarrier allocation is investigated based on utility theory. Since utility qualifies the level of users' satisfaction derived from the radio resources they occupy, it is ideal for a network optimization metric. We formulate the cross-layer optimization problem as one that maximizes the sum of the utilities over all active users through rate adaptation and dynamic subcarrier allocation with the limited radio resource and time-varying wireless channel constraints. Two effective subcarrier allocation algorithms with low complexity are proposed to solve the constrained optimization problem. Simulation results demonstrate the significant improvement of utility-based cross-layer optimization in OFDM.