Research On Reliable And Effective Social-Based Routing In Cognitive Radio Ad Hoc Networks

With the growing popularity of wireless smart devices and user requirements for high quality wireless services, the radio spectrum has become increasingly limited resources. Recently a cognitive radio (CR) is a promising technology to address the spectrum scarcity problem and improve spectrum utilization, which enables secondary users opportunistically access the vacant spectrum bands allocated to primary users. Due to the specific characteristics of CR, it has broad application prospects. For example, CR technology can be combined with mobile ad-hoc networks, which is called Cognitive Radio Ad Hoc Networks (CRAHNs), in which wireless devices can dynamically establish networks using the vacant spectrum bands allocated to PUs without the need of fixed infrastructures. Therefore, CRAHNs have broad applications, such as military communications, mobile conferences, wireless sensor networks and so on. However, the distinct characteristics of CRAHNs, such as the mobility of nodes and the limitation of spectrum, result in an intermittent connectivity in such networks. It is a challenging problem how to transmit messages reliably and efficiently in CRAHNs. In particular, we consider the problem of social-based routing in CRAHNs.In this thesis, we firstly introduce the concept of cognitive radio ad hoc network, and then focus on the major challenges on the network layer. The lack of a sustainable end-to-end path makes CRAHNs appear to be DTNs (Delay Tolerant Networks). All of the DTN routing methods share a similar characteristic, the "store-carry-forward" fashion. That means a DTN node can store and carry the data until it encounters a suitable node. Therefore, the concept and the routing algorithm of DTN are introduced. In this thesis, a new mobility model is proposed, which can represent the mobility patterns of nodes with the real-world social relationships. Based on this model, a link reliability metric and a prediction algorithm are derived for the SUs with different relationships, taking into account SUs transmission range limitation and interference with PUs. The simulation results show that our proposed scheme is precise enough to predict the link reliability in actual mobile environments. Apart from these, we propose a routing and relay selection protocol based on the social-aware link reliability. In our design, a message is forwarded to the relay with the largest encounter probability and a high link reliability. In order to evaluate the performance of our proposed SoRoute, we implement the algorithms in the Java-based simulator. We demonstrate the proposed social-based opportunistic routing scheme significantly improves the performance compared with the existing routing schemes such as Direct Delivery, First Contact, MaxProp, and Prophet.