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An Enhancement of TCP Fairness in IEEE 802.11 Multi-hop Ad-hoc Networks


Byungjoo Park, In Huh, Haniph Latchman


Vol. 6  No. 8  pp. 1-8


Fairness is an important design criterion for medium access control protocol in wireless multi-hop networks. In the wireless multi-hop networks using IEEE 802.11, TCP performance degradation results from hidden, exposed terminal problems and bandwidth waste caused by exponential backoff of retransmission timer due to node’s mobility, not from collisions. However, in normal DCF algorithm, a failed user increases its contention window exponentially, thus it reduces the success probability of exposed terminal nodes. That is, these problems will cause unfairness transmissions chance frequently in a particular node which already was successful in packet transmission, because the probability of successful packet transmission rate would be increased. This is known as the “fairness problem”. In this paper, we propose a new scheme for determining enhanced contention window size in TCP based on the measured Throughput and Round Trip Time (RTT). Simulation results show that, by using appropriate contention window size and number of retry times for RTS, the proposed scheme can improve the fairness relative to effective aggregate throughput, compared with the existing IEEE 802.11 DCF algorithm.


Multi-hop Ad-Hoc Networks, IEEE 802.11 DCF, Fairness