Cross-layer Congestion Control and Scheduling in Multi-hop OFDMA Wireless Networks

In this paper, we consider joint end-to-end congestion control and multiuser scheduling in multi-hop wireless networks, where orthogonal frequency-division multiple access (OFDMA) is the air interface. Compared to its single-channel counterpart, this problem is significantly more challenging because subchannel assignment and power allocation for all nodes and network traffic need to be jointly optimized. To avoid co-channel inference, we first consider an OFDMA subchannel separation problem in multi-hop communication scenarios. Then, we address this cross-layer optimization problem by decomposing it into two subproblems: a TCP layer congestion control for traffic allocation and a weighted scheduling for OFDMA subchannel assignment and power control. Observing that the scheduling for multiuser OFDMA in multi-hop wireless networks is inherently NP-hard, we propose a low-complexity algorithm that ensures a solution converging to the optimum. The performance of the algorithm is demonstrated through simulations.