Design On Routing Metrics And Algorithms In Cognitive Radio Ad Hoc Networks

As the rapid growth of wireless communication services and the user’s needs, available radio spectrum resources become increasingly tense. Spectrum licensing is a traditional method which allocates spectrum resources to different communication systems. However, surveys indicate that it is imbalance in current global spectrum resource utilization, some non-licensed bands of spectrum is crowded, while most licensed bands of spectrum utilization is low. Cognitive radio as a new intelligent wireless technology, making the second users intelligently select and use primary users’ idle spectrum by detecting primary users’spectrum without affecting the work of authorized users, was proposed to greatly improve the existing low efficient spectrum utilization. Current researches on cognitive radio network have almost focused on the spectrum sensing and spectrum management, the routing algorithm in cognitive radio network is still an open issue.The main contents and innovation of this thesis is organized as follows:1. This thesis briefly overviews the definition and development, the key technologies and challenges of cognitive radio, describes the classification of cognitive radio networks, explains the reason why routing algorithm is a challenge in cognitive radio Ad Hoc network. And then we introduce several typical routing protocols in Ad Hoc networks, we consider that AODV routing protocol is more suitable for cognitive Ad Hoc networks because of the on-demand route discovery process and the maintenance of neighbor information in nodes along path. However, AODV routing protocol cannot be used directly in cognitive Ad Hoc networks since it is based on single frequency point networks, in which the channel do not have the diversity and primary user pattern ever. In this thesis, we propose a cognitive radio AODV (CAODV) routing protocol based the two aspects above.2. Different end to end performance can be obtained when we use different metrics in path selection. The thesis analyzes several typical routing metrics used to get the common feature of routing metrics, which pave the way for our own routing metrics. The routing algorithms in cognitive Ad Hoc networks are not only for selecting next hop node, but also for the applied channel between two hops. The thesis proposes new routing metrics, which combine the primary user pattern with the signal interference noise ratio. Simulation results show that better end to end performance of chosen path can be obtained by using the new routing metric for path selecting.3. Network simulator NS2has properties of open source code and scalability. In the thesis, we carefully studied the language structure and simulation theory of NS2, especially the wireless module. Since the NS2itself is a single-channel simulator, this thesis firstly expand it into a multi-channel multi-interface to suit the cognitive radio Ad Hoc network scenarios, then we propose the CAODV routing protocol, which will select the channel causing the least interference to transmit data and make the choice of next hop at the same time. Simulation results show that the network performance is improved significantly because the CAODV selects the channel with least interference, thus reducing the routing overhead and increasing the network throughput.