Cross-Layer Rate Optimization in Wired-cum-Wireless Networks

In this paper, we address the end-to-end rate optimization problem in a wired-cum-wireless network, where CSMA/CA based wireless LANs extend a wired backbone and provide access to mobile users. The objective is to achieve proportional fairness amongst the end-to-end sessions in the network. Since the network contains wireless links whose attainable throughput is ‘elastic’ and is a non-convex and non-separable function of transmission rates of the neighboring links, the problem requires joint optimization at both the transport layer and the link layer. A dual-based algorithm is proposed in this paper to solve the rate optimization problem. It is implemented in the distributed manner, and works at the link layer to adjust transmission rates for the wireless links in the basic service sets, and at the transport layer to adjust session rates. We prove rigorously that the proposed algorithm converges to the globally optimum points. Simulation results are provided to support our conclusions.