Adaptive subcarrier and power allocation in OFDM based on maximizing utility

This paper investigates adaptive resource allocation on the downlink of multiuser OFDM networks to achieve both multiuser diversity and fairness. Utility functions are applied to quantify the level of users' satisfaction derived from the radio resources they occupy. We formulate cross-layer optimization problem as one that maximizes the sum of the utilities over all active users subject to the feasible rate region, which is determined by adaptive resource allocation schemes deployed and the current channel conditions. We present the conditions for optimal subcarrier assignment and power allocation based on utility, and investigate the optimality properties as well. It is also shown that the inherent mechanism of balancing spectral efficiency and fairness is associated with concave utility functions.