The Analysis Of Performance In Cognitive Ad Hoc Networks Based On Stochastic Geometry

The self-organization of Ad Hoc networks makes it becomes not only the most widely used network model, but also the focus of current research on Ad Hoc networks. It can be used in many emergency and extreme scenarios, solving many practical problems. On the other hand, cognitive radio technology is a key technology to solve the problem of scarce radio resource, which cognitive users search frequency hole and communicate through the hole by spectrum detection technology, in order to improve the utilization rate of spectrum and avoid the events that a lot of spectrum is idle but many users cannot communicate with each other happen. In view of their advantages, cognitive Ad Hoc networks combine these two kinds of technology, in which each node communicates via the idle spectrum. This mechanism improves the utilization rate of spectrum, at the same time, brings cumulative interference which affects the performance of whole network seriously. This thesis mainly studies the cumulative interference and performance through the statistic, analysis and modeling of interference, obtains the exact expressions of related performance, also simulates the results.Firstly, this thesis studies the statistic method of general Ad Hoc networks, and calculates the interference introduced by all users based on stochastic geometry. Further, under the influence of two key factors, that is path loss and network geometry, it obtains the exact expressions of interference in different networks, and gives the outage performance of one-dimensional and two-dimensional space networks.Secondly, according to the statistic expression, this thesis models the cumulative interference in cognitive Ad Hoc networks, builds different fading channel interference model and calculates the characteristic parameters of model as well as outage performance also the performance of the whole network. The simulation results show that the theoretical results are basically the same with the simulation results, which the proposed interference model is accurate.Finally, under a constraint condition of the outage probability of cognitive primary user, transmission capacity which describes the communication density in terms of cognitive secondary user is defined. Non-fading channels and fading channels are derived respectively, their outage probability and transmission capacity are given. Also deep analysis is performed on fading channels, obtaining the performance expression both in Rayleigh fading channels and Nakagami fading channels. The analysis results and simulation results have some mathematical significance, more importantly, they have some vital practical significance for practical network layout.