Communication in the form of broadcast-based information dissemination is important in ad hoc networks, both for application purposes and also for various control message purposes in the network. Optimized link state routing (OLSR) is a popular routing protocol for ad hoc networks. OLSR attempts to reduce protocol overhead in network-wide broadcast communication by introducing multi-point relay (MPR). Each basic node finds an MPR node (one hop from it) to help it reach a two-hop neighbor at least once. The OLSR method relies on single transmission of the MPR nodes, but this kind of approach is vulnerable to various factors in lossy wireless media. On the other side, there are protocols (such as robust OLSR (ROLSR)) that select too many MPR nodes, thus incurring very high overhead and unnecessary redundancy. Based on these observations, the authors propose a new MPR selection method that achieves robustness in broadcast communication with only limited redundancy.

In the proposed MPR selection method, each node tries to effectively select its MPR nodes from its one-hop neighbors, so that its two-hop MPR nodes are covered at least m times. This is enabled by the exchange of one-hop neighbor information (through hello messages) among neighbor nodes. The hello message use results in the classification of neighbor nodes into three types: symmetric neighbor, non-symmetric neighbor, and MPR neighbor. The MPR neighbor is further classified into friend MPR (FPR) and robust MPR (RPR). After proposing the method, the authors theoretically compare the size of the MPR node set between ROLSR (redundant method) and the proposed method. The analysis also includes a theoretical estimate of medium access control (MAC) throughput of data. The methods are also compared in a simulation environment with the carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol in an IEEE 802.11-based network setup. The evaluated performance parameters are throughput, MPR node set size, delivery ratio, and forwarding efficiency; all are evaluated with various network sizes.

Overall, the theoretical and simulation performance studies are useful for the analysis of broadcast communication efficiency in ad hoc networks using OLSR-based routing protocols. This is a good read for those interested in the performance of broadcast-based information dissemination in ad hoc networks with MPR selection or backbone nodes.