Optimal path selection in a link state QoS routing protocol

A link state routing approach makes available detailed information about the connectivity and the topology found in a network. The OLSR (optimized link state routing) protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. OLSR introduces an interesting concept, multipoint relays (MPRs), to mitigate the message overhead during the flooding process. The heuristic for MPR selection limits their number in the network and ensures that the overhead is as low as possible. However, there is no guarantee that OLSR finds the optimal path in terms of QoS requirements. Moreover, in QoS routing, if the same heuristic used in the standard OLSR protocol for MPR selection is applied, the good quality links may be hidden to other nodes in the network. We introduce two algorithms for MPR selection based on QoS measurements. Analysis, numerical evaluation and simulations are presented. We show that the QOLSR protocol with the second proposed algorithm for MPR selection (QOLSR_MPR2) finds optimal widest paths on the known partial network topology and presents the best performance.