Recent research on opportunistic schedulers for wireless data transmissionhas shown that link utilization is greatly improved by exploiting theindependent variations in the wireless channels of users. The trade-offbetween spectral efficiency and fairness among users at the link level hasbeen well studied in the literature. The focus of this paper is theimpact of the variable rate and delay jitter induced by opportunisticscheduling on the congestion control and avoidance mechanisms of TCP.

We use extensive simulations to expose the linkage between scheduling atthe medium access (MAC) layer and TCP performance. The results in thispaper underscore the need for careful design of opportunistic schedulingmechanisms in order to ensure that gains in MAC layer are also realized by TCP.