A Novel Dynamic Hybrid MAC Protocol For Cognitive Radio Ad Hoc Network With Reliable Control Channels

With the rapid development of wireless technology, the demand of the radio spectrum is bigger and bigger. However, the existing fixed spectrum allocation policy makes the radio spectrum resources become increasingly scarce. At the same time some spectrum exists the phenomenon of low utilization rate, for example, analog TV spectrum. Utilization rate of some spectrum is very high, for example, mobile communication frequency. Some of the spectrum is especially crowded, for example, the ISM band. Most of spectrum resources have been allocated. When the new wireless applications and wireless technology appear, it is difficult to have enough spectrum to meet the new requirements.Cognitive radio (CR) technology can solve the above problem effectively. It is a kind of intelligent spectrum sharing technology, which can dynamically sense spectrum hole in radio environment and make good use of it. So it arises at the historic moment to use the advantage of CR technology method to solve the shortage of spectrum in wireless network.Cognitive radio network (CRN) is a kind of network with adaptive adjustment functions which can sense external radio environment. Each node in CRN is equipped with cognitive module, which can dynamically sense radio environment and takes good advantage of spectrum holes by means of certain mechanism. Efficient and reliable MAC protocol is one of the key technologies to implement these functions. As existing wireless MAC protocol does not apply to the dynamic channel condition, and the secondary users (SUs) in CRN must not interfere with the primary users (PUs). So it is necessary to come up with a new MAC to adapt to this situation. Compared with cellular architecture, Ad Hoc network has no infrastructure support, so the MAC protocol research becomes more challenging.The research target of this thesis is the cognitive radio Ad Hoc network (CRAHN) MAC protocol. This thesis tries to seek a more effective way to solve control channel selection and dynamic channel allocation problem.Firstly, this thesis introduce CRAHN and several existing CRAHN MAC protocols.Secondly, this thesis points out the shortcomings of existing relevant protocols, and then proposes a novel dynamic hybrid MAC protocol for cognitive radio Ad Hoc network with reliable control channels, which is also called RCCDH-MAC. RCCDH-MAC makes a number of enhancements on the basis of OMC-MAC and DDH-MAC. RCCDH-MAC is a dynamic hybrid MAC protocol with double antenna, one for the real-time sensing spectrum holes, and another for data transmission. Channel number, free channel list (FCL) and common free channel list (CFCL) are stored in Table Channel-Table, which is stored in each SUs. In the early phase, control information exchange on common control channel (CCC). When PUs re-claim the data channel or other factors lead to data transmission failure, RCCDH-MAC introduces secondary common control channel selection mechanism to implements the automatic synchronization process of secondary common control channel (SCCC). Secondary common control channel selection mechanism makes the choice of dynamic control channel have a higher reliability. At the same time, RCCDH-MAC introduce backoff mechanism to reduce the collision.Based on the theory and simulation, this thesis analyses the new MAC protocol. Results show that the new MAC protocol improves throughput and average transmission delay, compared to existing protocols, and enhances the overall performance of the network.Finally, the work of the overall thesis is summarized, and some suggestions are given for future work.