It is now commonly accepted that the unit disk graph used to model the physical layer in wireless networks does not reflect real radio transmissions, and that the lognormal shadowing model better suits to experimental simulations. Previous work on realistic scenarios focused on unicast, while broadcast requirements are fundamentally different and cannot be derived from unicast case. Therefore, broadcast protocols must be adapted in order to still be efficient under realistic assumptions. In this paper, we study the well-known multipoint relay protocol (MPR). In the latter, each node has to choose a set of neighbors to act as relays in order to cover the whole 2-hop neighborhood. We give experimental results showing that the original method provided to select the set of relays does not give good results with the realistic model. We also provide three new heuristics in replacement and their performances which demonstrate that they better suit to the considered model. The first one maximizes the probability of correct reception between the node and the considered relays multiplied by their coverage in the 2-hop neighborhood. The second one replaces the coverage by the average of the probabilities of correct reception between the considered neighbor and the 2-hop neighbors it covers. Finally, the third heuristic keeps the same concept as the second one, but tries to maximize the coverage level of the 2-hop neighborhood: 2-hop neighbors are still being considered as uncovered while their coverage level is not higher than a given coverage threshold, many neighbors may thus be selected to cover the same 2-hop neighbors.
Being the broadcast protocol used in , has been the subject of miscellaneous studies since its publication. For example in @cite_3 , authors analyze how relays are selected and conclude that almost $75
@cite_3
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OLSR is a recent routing protocol for multi-hop wireless ad-hoc networks standardized by the IETF. It uses the concept of Multi-Point Relays (MPR) to minimize the overhead of routing messages and limit the harmful effects of broadcast in such networks. In this report, we are interested in the performance evaluation of Multi-Point Relays selection. We analyze the mean number of selected MP= R in the network and their spatial distribution.