| Abstract: | This paper evaluates the performance evaluation of interaction between Transport and the MAC layer protocols operating in a mobile adhoc network. In Adhoc networks, certain QoS parameters like error rate, delay and packet loss are increased and certain parameters like throughput and delivery ratio are decreased in Transport layer is due to MAC problems and disconnection is also possible due to mobility or power failure. So, combine the mechanisms of these two layers to improve the QoS drastically so that people can design the network based on their requirements. We examine the effects of two different MAC protocols— IEEE 802.11and IEEE802.11e with Slow start and Arithmetic Increase and Multiplicative Decrease (AIMD) mechanism of TCP.IEEE802.11uses distributed coordination function (DCF) where IEEE802.11e uses enhanced distributed coordination function (EDCF). Specifically, we access the impact of multiple wireless hops and node mobility on the throughput performance of TCP on each MAC protocol. Additionally the other Qos parameters of throughput, delay, Bandwidth delay product, delivery ratio and packet loss using slow start and AIMD of TCP mechanism with two different MAC protocols is also investigated. Results show that in all instances, the QoS parameters 15-20% improvement in throughput, 40-45% improvement in bandwidth-delay product, 10-15% improvement in delivery ratio, packet loss is reduced drastically to 40-50% in IEEE802.11e with slow start than IEEE802.11. Results shows, the QoS parameters 35-40% improvement in throughput, 25-30% improvement in bandwidth-delay product, 15-20% improvement in delivery ratio, packet loss is reduced drastically to 20-25% in IEEE802.11e with AIMD than IEEE802.11with AIMD. Further analysis show that IEEE802.11e (EDCF) with slow start better than IEEE802.11e (EDCF) with AIMD and delay is 10msec in IEEE802.11e with slow start and it is increased to 35msec in IEEE802.11e with AIMD.
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