On TCP-aware uplink scheduling in IEEE 802.16 networks

In this paper we propose two polling based scheduling schemes for applications based on TCP in a multipoint-to-point IEEE 802.16 network. The first scheme uses TCP congestion window (cwnd) size, whereas the second one uses cwnd size and TCP timeouts to allocate time slots among the contending TCP flows. We ensure fairness among the users by using a credit-based approach in which the user which misses the chance to transmit due to bad channel condition gets more weightage when its channel condition favors scheduling. We also propose a method to compute an optimal polling interval which maximizes the slot use and TCP throughput. Implementation of the proposed schemes requires a cross-layer based feedback protocol stack at the base station (BS) and at the subscriber stations (SS). Through exhaustive simulations, we demonstrate that the proposed schedulers provide fairness in terms of slot assignment and amount of data transmission.