English abstract
A mobile ad hoc network (MANET) is a set of mobile nodes communicating with each other in a peer-to-peer manner without any predefined infrastructure. In MANET, broadcasting plays a fundamental communication role for different network applications. It is defined as a process to disseminate a message from a given source node to all other nodes in the network. In MANET, the traditional broadcast approach is known as flooding where all nodes rebroadcast any received message for the first time! This process propagates in a multi-hop fashion until the whole network is covered. Although this approach can be the most suitable approach in a sparse network, the problem start to appear in dense areas where too many unnecessarily redundant retransmissions will cause a high channel contention and excessive collision. This phenomenon is known as the broadcast storm problem, Several broadcasting approaches have been proposed to address the broadcast storm problem. Most proposed approaches try to mitigate this problem by reducing the number of forwarding candidate nodes. However, due to the nature of MANETS where the network connectivity is changing over space and time, any new proposed broadcast solution has to be designed carefully in order to maintain a high reachability with a minimum network latency and overhead. Recently a new GridBased Broadcasting algorithm (GBB) was proposed in the literature. This thesis aims to simulate the new proposed GBB algorithm. The GBB algorithm relieves the broadcast storm problem by minimizing the number of participating nodes in the rebroadcast operation. In order to do that, GBB divides the entire geographïcal region into a logical 2-Dimensional grid of cells. Therefore, nodes are viewed as a cluster of cells and only one node (called gateway) per cell will rebroadcast any new message regardless of the cell density. As a consequence, the number of rebroadcast operations will be minimized significantly. The GBB algorithm uses the normal traffic in the network (broadcast or unicast) to maintain gateway nodes, therefore no gateway election or topology information is needed. A simulation model based on Network Simulator (ns-2) has been developed to measure the performance of the GBB algorithm. In order to have a clear view of GBB performance, this thesis implements the simple flooding and the probabilistic based (PROB) broadcasting algorithms available in the literature for evaluation. Most common system parameters are evaluated in this study under the following network conditions: node mobility, network density, traffic load and domain size. Simulation results revealed that GBB has improved considerably compared to simple flooding and PROB algorithms in terms of the number of saved rebroadcast packets, average reachability, collision rate and end-to-end delay.
