Asymptotically Fair Scheduling on Fading Channels

The problem of scheduling data for a DS-CDMA downlink, over a fading channel is considered. We show that high speed downlink data is most efficiently supported by time division of the channel, by letting only one single user in each cell access the channel at a time. For efficient resource utilization, some form of scheduling is required to determine which user should transmit at any given instant of time. Scheduling algorithms of different adaptation rate are suggested and compared. To avoid unfair performance, an algorithm that schedules a user to transmit when its channel is the “relatively best” is analyzed. We show that this algorithm asymptotically provides the same fairness as a round robin scheduler, but the throughput is significantly improved. For a Rayleigh fading channel, we show that the scheduling gain is in fact equal to the gain of a selection diversity scheme.