A Cross-Layer Architecture for DiffServ in Mobile Ad-hoc Networks Bosheng Zhou, Alan Marshall, Tsung-Han Lee School of Electrical and Electronic Engineering Queen's University of Belfast Belfast, UK Email: (B.Zhou, A.Marshall, Th.Lee)@ee.qub.ac.uk Abstract: The delivery of service differentiation in mobile ad hoc networks presents a number of technical challenges because of the inherent constraints due to the dynamic nature of these environments, such as limited bandwidth and energy capacity. This paper proposes a Cross-Layer Architecture for implementing DiffServ (CLAD) in IEEE 802.11 based mobile ad hoc networks. This provides differentiated services to four types of applications: Conversation, Streaming, Interactive, and Best-effort, by defining Per Hop Behaviours (PHBs). Novel features of CLAD include a Least Busy Routing Protocol (LBRP) which is designed to discover the least busy routes and evenly distribute the net-work load; a hybrid Signalling System which is used to dynamically monitor route states and to regulate adaptive real time applications; and an adaptive rate controller which controls traffic rate. Preliminary simulation results demonstrate that CLAD can provide efficient service differentiation in MANETs. Keywords: MANET, DiffServ, QoS, Routing, Signalling, Adaptive Rate Control. 1. INTRODUCTION QoS provisioning in mobile ad hoc networks presents a number of technical challenges because of the network restrictions compared with their wired counterparts. First, the bandwidth of a wireless link is normally relatively low in comparison with a wired link. Second, fading wireless links are usually intermittent while the wired links are very stable. Third, the ad hoc networking environment is dynamic. The topology changes unpredictably as each node can move freely. A node can join a network on the fly and shutdown without any notification. In addition to these, a mobile node is usually powered by a battery with limited capacity. Because of the above reasons, the provision of QoS in MANETs has been a hot topic in recent years [1-5]. The existing solutions for QoS provisioning in MANETs can be generally classified into two categories, namely stateful and stateless. Stateful approaches such as INSIGNIA [1] are based on resource reservation. Stateless approaches, on the other hand, do not rely on resource reservation, and try to provide a certain degree of service differentiation. SWAN [2] is a stateless protocol that provides service differentiation. It applies a distributed rate control algorithm in conjunction with a source-based admission control scheme to prioritize real time traffic. In SWAN, real time traffic is admitted with a certain maximum ITC19/ Performance Challenges for Efficient Next Generation Networks LIANG X.J. and XIN Z.H.(Editors) V.B. IVERSEN and KUO G.S.(Editors) Beijing University of Posts and Telecommunications Press 513-522