Rate-Maximization Scheduling for Downlink OFDMA with Long Term Rate Proportional Fairness

In this paper, we study the sum rate maximization algorithms with long-term rate proportional fairness (RPF) for downlink orthogonal frequency division multiple access (OFDMA). In contrast to the rate-maximization schemes which used short-term RPF in the literature, we propose a weighted channel signal-to-noise ratio (w-SNR) ranking based selective multiuser diversity (SMuD) scheme to achieve long-term RPF for rate maximization. In this approach, we solve the optimal SNR weight factors based on the target RPF, and then use them to implement carrier and power allocation to achieve a long-term target RPF. Analytical throughput and fairness metrics for the proposed w-SNR schemes with equal power allocation (EPA) or waterfilling (WF) over Rayleigh channels are derived. Simulation results show that the proposed long-term fairness scheme achieves a significantly higher rate than the short-term RPF schemes proposed in the literature. Besides better performance, the proposed scheme has a low complexity which is linear to numbers of users and carriers. These results put new insight into the achievable downlink OFDMA performance with proportional fairness and the effects of various system and channel parameters.