Mitigating Intra Flow Interference Over Multi Hop Wireless Ad Hoc Networks

Transmission Control Protocol (TCP) is a predominant transport layer protocol for data transmission. The burst nature of TCP congestion control mechanism has often lead to heavy link layer contentions over multi hop ad hoc networks. Acknowledgements (ACK) that compete with the data packets for medium access in the reverse path, further add up to the contention levels. Such intense contention paves way to interference and reduces the throughput. In this paper, we propose a framework that ties up rate controlled cross layer transport solution (CLTSP) with opportunistic network coding to minimize the intra flow interference over wireless ad hoc networks. CLTSP performs rate controlled transmission to prevent self interference among data packets by spacing them out at an appropriate interval. The time interval between the deliveries of successive data packets is dynamically measured based on four hop propagation delay and an appropriate correction factor that are collected from intermediate nodes. Besides, we perform network coding over the data and ACK packets pertaining to the same connection to reduce intra flow contention. We use the basic idea of piggy code and incorporate effective buffer management which is opportunistic with CLTSP. We evaluate the performance of our protocol with TCP New Reno, Piggy code and show significant improvement in terms of throughput, Packet Delivery Ratio, Packet drops and Link layer collisions.