The Analysis Of Connectivity For Wireless Ad Hoc Network

Wireless Ad Hoc network is a self-organized mobile network, compared with the traditional cellular networks, it is formed without the aid of fixed infrastructure. Due to its flexibility and high survivability, it is widely used in military, civilian and commercial areas. The connectivity of Ad Hoc network is critical for its topology is dynamic. Besides, connectivity is a prerequisite for Ad Hoc network and it is the foundation for the design of the higher layer. This thesis studies the connectivity of Ad Hoc network and analysises the factors that affect connectivity based on stochastic geometry.Firstly, bi-connectivity in one and two dimensional Ad Hoc network is investigated. For the one-dimensional case, the basic conditions for bi-connectivity are discussed from the viewpoint of the probability and the closed formula for bi-connectivity probability is derived. Then for the two-dimensional network, based on the mobility of the nodes in Ad Hoc network, a node moving algorithm improving the effectiveness of the link is studied. This algorithm changes the network from 1-connectivity to bi-connectivity and enhances the network connectivity and invulnerability.Secondly, the connectivity based on fading channels is analyzed. According to Poisson point process, the network model is set up. With Rayleigh fading channels, a SIR model is used to calculate the probability of being no isolated node and then the network connectivity probability is obtained.Thirdly, the effects of interference in Ad Hoc network are studied. Based on shot-noise theory, the interference model is set up to calculate the statistical characterisitics of interference. Then the close formula for the probability of being no isolated node is obtained. The simulation validates the correctness of the formula and shows that the interference in the dense network will increase, it is useful to improve the network connectivity by distributing the node rationally and effectively.Finally, interference suppression using CSMA protocol is investigated. The network model is set up based on Matern point process and the new node density is obtained. According to the interference model in CSMA network, the closed formula of connectivity probability is derived. From the simulation results, it is helpful to control interference and improve network connectivity by using CSMA protocol in Ad Hoc network.