Efficient broadcasting in mobile ad hoc and wireless sensor networks

In this research, we study the problem of using probabilistic approaches to improve broadcasting and route discovery performance in wireless ad hoc and sensor networks. Our contributions can be summarized as follows. First, we propose a selfish node based approach. In this approach, we categorize MSs into normal nodes and selfish nodes. Normal nodes forward packets for other nodes while selfish nodes do not. The advantage of using selfish nodes is that the total rebroadcast traffic can be reduced. The disadvantage is that we may miss the optimal route and suffer from a low delivery rate. In this approach, we use a probabilistic method to set up a proper number of selfish nodes. Using a combination of gossiping and dominating set, we can reduce the route discovery cost by minimizing the number of rebroadcasts, while achieving higher delivery rate due to the reduction of rebroadcast traffic, thereby reducing the number of collisions. Second, we propose a leveled probabilistic approach. In this approach, we use a pre-assigned probability model to avoid redundant packet relays. In our protocol, a MS probabilistically sends relay packets (rebroadcasts) according to its neighborhood information. Our approach categorizes MSs into four groups. For each group of nodes, we assign a specified value of rebroadcasting probability. The MSs with more neighbors are given higher rebroadcasting probability. Using this method, we can reduce routing cost by minimizing the number of rebroadcasts in route discovery phase without significantly affecting the network connectivity. Third, we propose a dynamic probabilistic approach. In this approach, we dynamically adjust the rebroadcasting probability as per the node distribution and node movement. This is conducted based on locally available information. In addition, our approach does not require any assistance from accurate distance measurements or exact location determination. This approach can further reduce routing cost by adapting its behavior according to the environment changes. Fourth, we compare MANETs and WSNs (wireless sensor networks). We realize the difference between MANETs and WSNs in tennis of the node characteristics, energy consumption, mobility model and the traffic model. We also evaluate sensing coverage and communication coverage for different sensor range or communication range. Fifth, we propose a broadcasting scheme using connecting regions. We assign/select connecting regions during the network start up period. Only the connecting region head node located inside one of the connecting regions is responsible to rebroadcast the packet while the nodes outside the connecting regions do not rebroadcast. By choosing the size of the connecting region and the placement of the connecting regions, we can reduce the rebroadcasting cost while maintaining the reachability. Sixth, we propose a scheme that is based on redundant degree of each sensor. In this approach, we evaluate the redundant degree value of each sensor node and use this value to decide whether to rebroadcast packet or not. The rebroadcast from a node with high degree of redundancy has high possibility to be redundant. We set up a threshold to allow nodes with low enough degree connectivity to rebroadcast packets. (Abstract shortened by UMI.)