Cross layer design to enhance TCP performance in multi-hop ad hoc networks

In this paper, we propose a new cross-layer scheme Cooperation between channel Access control and TCP Rate Adaptation (CATRA) aiming to manage TCP flow contention in multi-hop ad hoc network. In CATRA scheme, we collect useful information from MAC and physical layers to estimate channel utilization of the station. Based on this information, we determine the optimal Contention Window (CW) size to control station contention. This method can achieve fair channel access of each station and efficient spatial channel usage. Moreover, the fair value of bandwidth allocation for each flow will be calculated and sent to Transport layer. Then, we determine the optimal sending rate to solve TCP flow contention. By transmitting packets from Transport layer according to this optimal sending rate, the throughput of each flow becomes fairer. The performance of CATRA scheme is examined on various multi-hop network topologies by using Network Simulator (NS-2).