REAL-TIME TRAFFIC SUPPORT IN DISTRIBUTED WIRELESS LAN

Abstract

In this dissertation, a new mechanism called Real-Time Enhancement Assistance Mechanism (REAM) is proposed over the MAC layer which uses distributed control algorithms to deliver service differentiation between real-time traffic and best effort traffic in mobile wireless ad hoc networks. The proposed mechanism is simple, scalable and robust. REAM is designed to follow stateless approach without the need for the introduction and management of per-flow state information in the network. REAM supports real-time applications with appropriate QOS overcoming the challenges in ad hoc networks like dynamic change of topology and network load conditions due to rerouting among mobile devices. In particular, REAM uses rate control for UDP and TCP best-effort traffic, and end-to-end admission control for UDP real-time traffic. REAM uses Explicit Congestion Notification (ECN) to dynamically regulate admitted real-time traffic in the face of network dynamics brought on by mobility or traffic overload conditions. A term "soft" real-time services is used to indicate that real-time sessions could be regulated or dropped due to mobility or excessive traffic overloading at mobile wireless routers. REAM is capable to limit such conditions. REAM takes care that the Best effort traffic is not starved and provide absolute level of service for real-time traffic in highly loaded conditions. A novel aspect of REAM is that it does not require the support of a QOS capable MAC. Rather, soft real-time services are built using existing best effort wireless . -MAC technology. REAM, IEEE 802.11e are implemented in ns-2.26. I identified and removed a couple of bugs in the ns-2 802.11 DCF model. Further Simulation and results show that real-time applications experience low and stable delays under various multi-hop, traffic and mobility conditions.