Improvement Of MAC Layer Mechanism Of DSA Network And Emulation Technology

In the current communication system,spectrum is a scarce non-renewable resources based on the principle of fixed allocation for use.Users have exclusive right to the authorized spectrum.On one hand,with the rapid development of wireless spectrum resource allocation,the wireless spectrum for the future is less.On the other hand,the utilization of the authorized spectrum is quite low.Dynamic spectrum access technology can increase the reuse rate of the spectrum resources in time domain,airspace and frequency domain.It can solve the problem of low utilization rate effectively.As a kind of invasive communication technology,DSA always switches to other spectrum during the communication process frequently.The switch of spectrum will cause the decline in network throughput,data packet loss and the phenomenon such as network latency,leading to huge effects on the network performance.The study of this problem is relatively small now.Therefore,in this thesis,we give a method to reduce the influence of spectral switch on DSA network performance.Through analyzing the changes of MAC layer parameters when spectrum switches in DSA network in time,combing with the idea of cross-layer,we design a MAC layer congestion control algorithm.And by using DSA network Emulation platform,we verify the proposed improvements mechanism of the MAC layer.Finally,we design several simulation scenarios and write some simulation script to illustrate the effectiveness of the proposed improvement mechanism in the platform.Emulation is a kind of ways combined by network simulation and experimental bed.In the process of Emulation,there is a certain amount of real nodes and virtual nodes.It can transfer real data stream flow interacting with virtual network.The method inherits the advantages of network simulation and test bed to ensure the relative accuracy of the test results and improve the precision of the experiment,avoiding the complexity of the experiment.By analyzing the features of DSA network and the structure of open source simulation software NS2,This thesis designs a DSA Network Emulation platform.The platform can be easily analyzed the changes of MAC layer of DSA network during the spectrum sensing and switching,it can also be a good mechanism to verify the correctness and effectiveness of the proposed improvements.So this thesis uses Emulation Technology to verify the proposed improvements of the MAC layer mechanism.