Proportional Fair Scheduling for Downlink OFDMA

In this paper, the author studies the sum throughput maximization with proportional fair scheduling (PFS) for downlink orthogonal frequency division multiple access (OFDMA) channels. The author proposes selective multiuser diversity (SMuD) schemes with normalized channel signal-to-noise ratio (n-SNR)-based ranking for user selection at each carrier, and assigns the transmit power to the assigned carriers using either equal power allocation (EPA) or water-filling (WF). The author also proposes a modified absolute channel SNR (a-SNR)-ranking based SMuD scheme, which provides an improved performance than the original a-SNR SMuD scheme. Closed-form throughput and average access probability (AAP) expressions for both n-SNR and a-SNR SMuD schemes with EPA over independent but not necessarily identically distributed (i.n.d.) Rayleigh channels (for different users and carriers) are derived. These results put new insight into the achievable downlink OFDMA performance with proportional fairness and the effects of various system and channel parameters.