Research On The Capacity And Connectivity Of Cognitive Radio Ad Hoc Networks Based On Stochastic Geometry

With strong government support on the "Interent Plus" action plan in the past few years, the Mobile Internet industy is facing a new round of opportu-nities, which leads to the rapid expansion of the wireless network infrastruc-ture and the significant increase of wireless data traffic. However, the limited frequency resource are not able to satisfy the ever-increasing bandwith require-ment. But in the meantime, recent report shows that a large part of the allocated spectrum remain idle, which indicates that the precious spectrum resources re-main underutilized under the current static spectrum allocation strategy. The problems on how to further improve spectrum utilization and satisfy the wireless data traffic demand need urgent solutions. The cognitive radio technology is born under such a background and it greatly improves the spectrum efficiency,which is becoming an important supplementary technology to future commu-nication systems. The basic idea of cognitive radio technology is to allow the secondary users access the authorized spectrum dynamically in an appropriate way without interrupting the operation of the primary users.CRAHN are the combination of cognitive radio technology and wireless Ad Hoc networks, which thus possess the advantages of high spectrum effi-ciency and self-orgnized network architecture. The perfromannce characteri-zation of CRAHN attract much attention from the researchers. In this thesis,by applying tools from stochastic geometry and other mathematical theory, we study the transmission capacity and connectivity of the CRAHN. The main con-tent and contribution of this thesis are illustrated in three aspects and summa-rized as follows.1. We study the transmission capacity of an inhomogeneous CRAHN,where the primary network are distributed as a PPP and the secondary network are distributed as an independent MCP. Based on underlay spectrum sharing approach, the secondary users deploy the concurrent transmissions with pri-mary users by limiting their density to meet the network outage constraints. By applying stochastic geometry and other mathematical tools, we analyzed the upper and lower bounds of successful transmission probability of the CRAHN,further the upper and lower bounds of transmission capacity for this CRAHN are derived. The impact of inhomogeneity on transmission capacity are studied through simlation.2. We study the node isolation probabilty of an inhomogeneous CRAHN,which is an important connectivity metric for network local connectivity. Based on underlay spectrum sharing approach, the secondary users deploy the concur-rent transmissions with primary users by limiting their density to meet the net-work SIR constraints. By applying stochastic geometry and other mathematical tools, we analyzed the upper and lower bounds for the expect number of users which connects to the typical user. Furhter we derived the upper and lower bounds for node isolation probability of the CRAHN. Through simlation, the impact of network parameters from the inhomogeneous CRAHN are studied.3. We study the connectivity of the CRAHN by applying tools from per-colation theory. The primary and secondary networks are modeled as two in-dependent PPPs, respectively. Under the physical model, we shows that the network is percolated if the targeting SIR threshold is a small value. Further we proposed a 2D conectivity region which can be used to evaluate the con-nectivity status. By studying the area of the connectivity region, the optimal network parameters which achieves the maximum area of the connectivity re-gion are obtained. Under the potocol model assumption, the combined impact of primary user's density and interference range on network percolation are in-vestigated, and a 3D connectivity region is established. Further the sufficient and necessary consditions for network percolation are derived. Simulaiton re-sults are consistant with our conclusion.It is our hope that the work in this dissertation can help further advance the understanding and deployment of CRAHN in the future wireless communica-tion systems.