Spectrum Allocation Based On The Time-Varying Characteristic Of The Spectrum Holes In Cognitive Radio

Nowadays,spectrum resources are regulated via fixed spectrum assignment policy. This allocation mechanism has lead to a scarcity of precious spectrum resources because of the increase in spectrum demand.To significantly improve the spectrum utilization efficiency, Cognitive Radio (CR) technology is proposed.In Cognitive Radio (CR) technology cognitive users/Second Users(SUs) are allowed to access the licensed spectrum bands (namely, Spectrum Holes(SHs)) without interfering with Primary Users (PUs, licensed users).SUs are reasonable for monitoring the returning PUs on the SHs they are currently using so as to vacate the SHs to avoid interfering with these PUs.If the SUs have monitored the returning PUs, they will promptly vacate the SHs and perform spectrum handover, which results in the utilization of SHs for SUs is instable.This instability, which has been researched by current studies, is one of the factors involved the Time-Varying Characteristic (TVC) of SHs.Besides the activity of PUs, two factors need to be considered.These two factors support the fact that the TVC of SHs is in connection with its SUs. According the analysis of the factors for the TVC of SHs, spectrum allocation algorithm is proposed to reduce probability of spectrum handover in the second system.In the paper, firstly we introduce the research background.The develop history, the key technologies and the network structure of the cognitive radio is analyzed. On this basis, the design principles and the classification of spectrum allocation methods of the cognitive radio network is analyzed. What's more, we introduce the allocation models based on the game theory, the graph coloring theory and the competitive auction theory, and there is comparison between them. Then we analyze the current research for TVC of SHs, and the factors for TVC of SHs are studied in detail,and the "absolute reliability" and "relative reliability" are introduced for the quantitative analyses on them. Finally the balance of the spectrum handover frequency and the efficiency on SH assignment are represented.Repeated Greedy Algorithm (RGA) is proposed based on both the concern of the balance and the relative reliability and the simulation result supports this algorithm.