Quality-of-service-aware multicast routing for multimedia applications in mobile ad hoc networks

Abstract

The conceptual shift in the expectations of wireless users towards multimedia andgroup-oriented computing has a significant impact on today̕s networks in terms of needfor mobility, quality of service (QoS) and multicast routing. Mobile ad hoc networks can provide users with these features. However, it is imperative for them to combine QoS andmulticast routing strategies in order to utilize the wireless medium efficiently.This work defines the ad hoc QoS multicast (AQM) routing protocol, which achievesmulticast efficiency by tracking the availability of resources for each node within its neighbourhood. Computation of free bandwidth is based on reservations made for ongoingsessions and the requirements reported by the neighbours. The QoS status is announced atsession initiation and updated periodically to the extent of QoS provision. Nodes areprevented from applying for membership if there is no QoS path for the session. When nodes wish to join a session with certain service requirements, a three-phase processensures that the QoS information is updated and used to select the most appropriate routes.The allowed maximum hop count of the session is taken into account in order to satisfy thedelay requirements of the multimedia applications. To cope with the continuous nature of streaming multimedia, AQM nodes check the availability of bandwidth within theirneighbourhood not only for themselves but within a virtual tunnel of nodes. Objectionqueries are issued prior to reservation to avoid excessive resource usage due to allocationsmade by nodes which cannot detect each other directly. A priority queue determines thetransmission order of data packets according to their traffic classes to support even those applications with more stringent QoS requirements. AQM evolves the initial multicast treeinto a mesh during data flow to improve robustness. New performance metrics areintroduced to evaluate the efficiency of AQM regarding the satisfaction level of session members. Simulation results show that, by applying novel QoS management techniques,AQM significantly improves multicast efficiency for members as well as for sessions.