Routing Strategies Based On QoS Metric In Mobile Cognitive Radio Network

With the rapid growth of wireless communication service and user’s demand, especially the wide range application of mobile Internet and smart mobile terminals, the shortage of spectrum resources becomes more and more essential. As a kind of new intelligent network technology, mobile cognitive radio network(MCRN) combines the technology of cognitive radio technology and mobile ad hoc network technology, which can adapt to the dynamic changes of network environment and optimize the end-to-end performance. So it can achieve the efficient use of network resources. At present, it is mostly assumed that the primary and secondary users are still, when the cognitive radio network routing is researched. And the cognitive radio network performance is studied from the aspects of spectrum availability, channel allocation and so on. For MCRN, due to the mobility of nodes and the activity of primary users, the link between two secondary users is not stable and the network topology is dynamic. It is difficult to use the fixed QoS to measure the network performance. Therefore, the research on the link dynamic characteristics of MCRN from different aspects is very important since it contributes to solve the routing optimization problem with multiple parameter constraints based on QoS. In view of dynamic network topology, dynamic characteristics of the links, different QoS requirements and uncertainty of the routing, the research work which includes link connectivity, link stability, link power consumption and link outage probability is carried out. The local cognitive topology control algorithm and the network routing algorithm according to certain QoS metric are further studied. The simulation results experimentally and theoretically reveal the benefits of the proposed schemes to improve the end-to-end QoS and spectrum usage in MCRN effectively. The dissertation content and contributions are summarized as follows:Considering the dynamic link which is affected by multi factors, a mobile cognitive radio network model with multi parameters is proposed, and the mobility of primary users and secondary users makes the changes of the links and the network topology. The effects of these changes on the link performance of cognitive radio networks are summarized, which lays a foundation for the research of link performance and routing strategy in the following chapters.Considering the cognitive network model proposed in chapter 2 and combining with the application of one dimensional mobile cognitive ad hoc network, the analysis method of network connectivity for one-dimensional mobile cognitive radio network is proposed based on random waypoint mobility model. The link connectivity is analyzed and expressed in connectivity probability. The end-to-end network connectivity is analyzed, and the closed formula of connectivity probability has been derived to evaluate the network connectivity according to the activity of PUs and the mobility of SUs in this model. Finally, simulation results corroborate the theoretical analysis under different scenarios. And it shows that the network connectivity is related to the number of primary users, the activity factor of primary users, the number of secondary users, the transmission range of secondary users, the maximum interference range and the moving speed of secondary users and so on.Considering the dynamic changes of MCRN topology, a local cognitive topology control routing algorithm(LCTCR) is proposed. The algorithm is based on the mobility of nodes and the interference from secondary users to primary users to predict the cognitive link availability. LCTCR combines the link stability with link power consumption to form a multiobjective metric of link weight, and the link weight is considered as the link cost. LCTCR captures the dynamic changes of the topology with the local Dijkstra algorithm and constructs an efficient and reliable topology under the conditions of network connectivity, which is aimed at selecting the optimal network path and optimizing the end-to-end performance. At last, simulation investigation is also provided and used to verify the theoretical analysis. And this dissertation analyzes the effect of power consumption and link stability on cognitive radio network path selection, and the effect of network parameters on average node degree, average link cost, and unit path power consumption. Compared with the single QoS metric routing, the proposed method has more cognitive function and is better suited to the cognitive network environment.Considering the complex electromagnetic environment between primary users and secondary users in cognitive radio network, the multi parameter cognitive network model is simplified as a cognitive relay network, and a routing algorithm based on outage probability is proposed. According to signal transmission fading characteristic and the relative position of nodes in MCRN, the influence of channel environment change on link communication quality and network routing selection is analyzed, and the closed expression of link outage probability is derived through analyzing the link SINR distribution function in Rayleigh fading channel. And the closed formula of the end-to-end outage probability is obtained. Thus it provides an effective method to study the effect of maximum transmission power of SUs, interference power of PUs, transmission power of PUs, the secondary transmission link channel quality, and interference link channel quality on the network outage performance. In the analysis of network routing, the network path selection criteria based on minimizing the end-to-end outage probability is proposed. Simulation investigation is also provided and used to verify the theoretical analysis, and it shows the mutual interference between secondary users and primary users can not be ignored when network performance analysis and network path selection are carried out, especially the interference of primary user has a significant effect on the network path selection of secondary users. Compared with the network routing, which ignores the interference impact of the primary users on the secondary users, the proposed routing algorithm is closer to the real wireless communication environment.