Broadcast Algorithm Research In Mobile Ad Hoc Networks

A mobile ad hoc network is a multi-hop and temporary autonomous system which consists of mobile devices equipped with wireless communication capacities. One of the fundamental operations in wireless ad hoc networks is broadcasting by which a source node disseminates messages to all other nodes. It can be used to delivery control message, update topology and send important data and warning message, etc. It is also an important means to finding a route. In mobile ad hoc networks, the simplest way to broadcast is flooding. It can achieve higher coverage; however, blind flooding causes a large number of redundant transmissions, channel contentions and package collision which are called as broadcasting storm. Broadcasting storm heavily affect the throughput of network and other Quality of Service metrics. Meanwhile, packet collisions lead to broadcasting unreliability.After analyzing the broadcasting storm and the broadcasting unreliability, we proposed the distance and cooperation based broadcasting algorithm (DCBB). Based on the number of neighbors and the distance between neighbors, it selects four neighbors at most to forward broadcast packets. Redundancy can be reduced by limiting the number of relay nodes. And through time-division forwarding scheme, every node can reduce channel contending and improve the network utilization effectively. The simulation results show that DCBB can achieve higher reachability and lower retransmitted ratio compared to DP (Dynamic probabilistic broadcasting algorithms). Moreover, it can achieve lower delay when the nodes are in dense environment.Nodes in mobile ad hoc networks are usually portable terminals which have limited power. Therefore, energy is crucial for the lifetime and performance of the ad hoc networks. DCBB can reduce the redundancy and improve the delivery ratio. However, due to frequent exchange of Hello message, DCBB incurs additional energy consumption. Therefore, we propose the distance and energy-balance based reliable broadcasting algorithm (DEBRB). In DEBRB, every node computes the distance and gets neighbors’information based on all kinds of packets it receives. The priority of a node to forward the broadcasting packet is determined by the distance and its residual energy. Then, the node forwards the packet in a time-division manner according to its forwarding priority. As such, a network can alleviate the channel contending and packet collision. Retransmission mechanism is also used in DEBRB to enhance broadcast reliability. Simulation result shows that DEBRB can achieve higher packet delivery ratio, lower delay and balance energy consumption compared to DCBB and DP.