An Efficient Core Migration Protocol for Providing QoS in Wireless Ad hoc Networks

Mobile ad hoc networks consist of wireless mobile hosts that communicate with each other, in the absence of a fixed infrastructure. Multicast applications have certain desired Quality of Service (QoS) requirements like low delay, high bandwidth, minimum hop count routing, etc. which should be met by the mobile ad hoc networks (MANET). Multicasting is usually accomplished by constructing a multicast tree and transmitting the packets over this tree, replicating packets at the branch points. In a group shared multicast tree, the choice of the root (core) plays an important role in influencing the organization of the tree and affecting the performance of packet delivery. The objective is to construct a tree whose leaves achieve the desired qualities of the multicast application. Existing multicast routing protocols like CBT and PIM-SM proposed for establishing and maintaining the group-shared tree ignore the issues of core selection and migration, and are not QoS sensitive. We investigate an algorithm which migrates the core on a hop-by-hop basis, so as to continuously adapt to the network dynamics and whenever the topology remains constant for a sufficient duration, the core reaches an optimal position which corresponds to the specified QoS. Our algorithm is more practical for mobile ad hoc network environments than other protocols, since it does not rely on topology based metrics and has less overhead. This is accomplished by averaging the specified QoS metric using periodic QoS measurements for packets acknowledged at the current core node. We present proofs of correctness to show that our algorithm moves the core toward an optimal position corresponding to the desired QoS. Our work also analyzes the performance of the core migration protocol through simulations.

see thesis and presentation.