Enhancing QoS Provision by Priority Scheduling with Interference Drop Scheme in Multi-Hop Ad Hoc Networks

It is well-known that TCP has difficulty in achieving desirable levels of performance in multi-hop ad hoc networks. TCP implements a loss-based congestion control mechanism for adjusting traffic in the networks. However, when TCP reacts to a loss event in a multi-hop ad hoc network, contentions raised in the IEEE 802.11 MAC layer among nodes usually becomes excessive. This problem eventually induces packets scheduling variation at the MAC layer. As a result, the quality of service (QoS) assurances given to multimedia traffic streams, such as UDP traffic, are violated. This paper focuses on preventing the TCP congestion window (CWND) size at the network layer from becoming excessive. We propose an interference drop scheme (IDS) at the network layer to prevent excessive increases in MAC contention by dropping over-delayed packets held by local queues. Simulations show that the proposed approach yields better a TCP performance and the assurance of QoS provision to UDP flows in multi-hop ad hoc networks.