Study on differential service in ad hoc networks

Providing quality of service (QoS) multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine what packet would be transmitted in the ideal dynamic priority scheduler. In this paper, we study two mechanisms for QoS communication in multi-hop wireless networks. First, we will study distributed priority scheduling, a technique that piggybacks the priority tag of a node´s head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. Second, we observe that congestion, link errors, and the random nature of medium access prohibition exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termed multi- hop coordination so that downstream nods can increase a packets relative priority to make up for excessive delays incurred upstream. This paper investigates differentiated services in wireless packet networks using a fully distributed approach that supports service differentiation, radio monitoring and admission control. Service differentiation is based on the IEEE 802.11 Distributed Coordination Function (DCF) originally designed to support best-effort data services. We study the extend Distributed Coordination Function to provide service differentiation for delay sensitive and best-effort traffic. Two distributed estimation algorithms are studied. A virtual MAC (VMAC) algorithm passively monitors the radio channel and estimates locally achievable service levels. A virtual source (VS) Algorithm utilizes the virtual MAC to estimate application level service quality. Finally, we discuss a distributed service level management scheme that builds on the studied algorithm to offer continuous service with handoff.