Research On TCP Enhancement In Cognitive Network Based On Cross-layer Designing

With the development of new wireless service, the demand for spectrum resource becomes larger and larger. Meanwhile, the utilization rates of many authorized spectrums in time and space domain are pretty low. Traditional spectrum allocation theory and technology have been unable to adapt to or meet the demand of kinds of continuously developing wireless network. Because of these problems, Cognitive Radio(CR) has come into being. Cognitive Radio Network(CRN) is the communication network based on the spectrum utilization technology of CR. In CRN, cognitive users(CUs) need to be qualified with the function of spectrum sensing. When primary users(PUs) access, CUs must switch to another free channel at once in order to avoid the interference to PUs. So the largest difference between CRN and traditional wireless network lies in the function of spectrum sensing and channel switching. However, Transmission Control Protocol(TCP) of the traditional layered protocol stack cannot recognize the behavior of spectrum sensing and channel switching at the lower layers. Therefore, cross-layer technology is needed to make TCP sense these cognitive behaviors of the lower layers, and on this basis, it is necessary to improve traditional TCP to make it adapt to the spectrum sensing and channel switching in CRN. The cross-layer designing between TCP and MAC can eliminate retransmission problems caused by the spectrum sensing, and the proposed “TCP-improved algorithm” can solve the problems of low utilization of bandwidth and network congestion as cognitive users switch its channel. Experimental results show that the “TCP-improved algorithm” can effectively reduce the influence of spectrum sensing and channel switching on TCP, and enhance the TCP performance of CUs.