A TCP-Driven MAC Resource Allocation Scheme in a WiMAX Network

The paradigm of a traditional wired network protocol stack is a hierarchy of services provided by each individual layer, but the ability of such paradigm to handle an error-prone physical medium is severely compromised in wireless networks. Several approaches, including cross-layer techniques, have been developed to address this problem. While much cross-layer research endeavour focused on interactions of the lower layers, in this paper, we present a cross-layer technique that involves the transport and MAC layers. In particular, our approach allows the MAC layer of a WiMAX network to be made aware of the network congestion condition perceived by TCP at the transport layer. This cross-layer technique allows the scarce radio resource to be distributed in a more intelligent fashion among the stations in the network. More specifically, our resource allocation scheme at the MAC layer adapts to the congestion window sizes passed down from TCP. We have developed analytical and simulation models to understand the dynamics of the proposed technique and quantify the resulting performance gains. Our results show that our proposed algorithm delivers a better performance in average end-to-end delay, file download time, and throughput when the traffic intensity of the network is moderate to high.