Design And Implementation Of Key Technologies In Mac Layer Protocols Based On Crahns

In the past20years, the rapid development of information technology industry has promoted the diversification of a variety of wireless communication technologies. As a result of people’s increasing demand for a higher communication rate, spectrum has increasingly become scarce resources. The deficiency in existing policies governing spectrum management and the unreasonable strategies concerning static distribution of spectrum mainly contributed to the shortage of spectrum resources. In1999, Dr. Joseph Mitola first proposed the concept of cognitive radio which can improve the unreasonable distribution of spectrum and the efficiency of the utilization of allocated spectrum.In this paper, a new cognitive radio Ad hoc networks MAC protocol is designed which is implemented on GNU Radio platform and based on USRP hardware. Finally, the demonstration of the function of the communication system software is carried out.By introducing the background knowledge of cognitive radio technology, this paper has carried out a thorough research of the MAC protocol in CRAHNs. Currently the classified studies of MAC protocols in CRAHNs are typically carried out in following areas, the access mode (Contention Protocol, Allocation Protocol, Hybrid Access Protocol), the use of global common control channel, the number of transceiver ect..Based on the existing research, this paper designs a cluster-based polling MAC protocol in CRAHNs. Without the global common control channel, the protocol uses a cluster-based polling mode. The communication system works in time-division multiplexing. The Control beacon and the data signaling share the same frequency band to communicate. So it can eventually improve the security of the system without opening up additional control channels while reduce the overhead switching between data channels and control channels. The control beacon may use any free frequency band to be transported, which can improve the communication system security and robust. When the control channel are disrupted or authorized user come back to the frequency of control channel, this MAC protocol can still work. In the cluster-based MAC, the user in the cluster can communicate with each other by the cluster head node which is selected dynamically. The cluster head will not only simplify the process of the communication, but also improve the stability of the communication system. Then this paper focuses on the improvement of the MAC protocol, especially in the key technology. Finally, detailed design and implements of the cognitive radio Ad hoc network system based on USRP platform are verified through actual test and then the final results are demonstrated.