In this paper, we propose Transmission Control Protocol (TCP)-aware cross layer scheduling algorithms in a multipoint-to-point network such as the uplink of an IEEE 802.16 (WiMAX) network. Inadequate bandwidth allocation to a TCP flow may lead to timeout and since TCP source drops its congestion window ( @math ) immediately after a timeout, it may affect the average throughput adversely. On the other hand, since the TCP source increases its @math only linearly upon the availability of bandwidth, any excess assignment of bandwidth may remain underutilized. The proposed scheduling algorithms address this by allocating the resources based on @math and TCP timeout. Moreover, since we focus on uplink scheduling, we consider that only flow level resource requirement is communicated to the Base Station ( @math ) instead of per packet information. The schedulers also take into account the wireless channel characteristics and are thus cross layer in nature. Through exhaustive simulations, we demonstrate that the proposed schedulers exhibit enhanced throughput and fairness properties when compared to that of Round Robin (RR) scheduler under different shadowing. We demonstrate a gain between 3.5 to 15 in throughput and 15 to 25 in channel utilization over RR scheduler under different shadowing.
The primary concern of broadband wireless technologies is to provide the end-to-end Quality of Service (QoS) for integrated real-time and non real-time applications. The main focus of the IEEE 802.16d e MAC layer is to manage the radio recourse in an efficient way. The basic functional blocks of the QoS model are addressed by the standards to support five different types of service classes. However, the detailed admission control, radio resource management and scheduling are left for implementation perspective and many research efforts are on going to assure the QoS for end customers. In this paper we propose a hybrid uplink scheduling algorithm (P+E) for subscriber station (SS), which is the combination of priority and Earliest Due Date (EDD) scheduling methods to maintain QoS and utilize the radio resource allocated by the BS in an efficient manner. Simulation results demonstrate the advantages of the proposed hybrid scheduling algorithm.