Analysis of QoS by Combining MAC and Routing Protocols with TCP mechanisms In MANETS

摘要

This paper evaluates the performance evaluation by combining Network layer and MAC layer protocols with Transport layer congestion control mechanisms 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 because the network layer is not able to detect the path to deliver the packets. So, combine the mechanisms of these three layers to improve the QoS drastically. We examine the effects of two different MAC protocols-IEEE 802.11and IEEE802.11e with AODV and DSR of routing algorithms with Slow start and Arithmetic Increase and Multiplicative Decrease (AIMD) mechanism of TCP.IEEE802.11 uses 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 with two routing algorithms. Additionally the other QoS parameters of delay, Bandwidth delay product, delivery ratio and packet loss 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 AODV algorithm in network layer and slow start mechanism in transport layer. Similarly 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 AODV algorithm in network layer and slow start mechanism in transport layer. But if DSR algorithm is used in the network layer instead of AODV it affects the QoS parameters. In both cases DSR algorithm increases the packet loss which in turn affects the throughput and packet delivery ratio. The reason is analyzed and suggests the suitable mechanisms implemented in each layer to enhance QoS parameters.