Algorithm Research Of Dynamic Spectrum Management In Cognitive Radio

Cognitive radio technology is the basic technology to realize the spectrum sharing andredistribute the existing spectrum resource. It is an effective measure to solve the contradictionbetween the shortage of open spectrum resources and the low utilization rate of special authorizedspectrum. In this article, we study the dynamic resource allocation and spectrum handofftechnology of cognitive radio.At first, the definition， characteristics and key technologies of cognitive radio areintroduced,and a brief overview of its development both in china and abroad is given.Secondly, spectrum allocation algorithm based on graph theory is presented. Subject toavailable spectrum matrix and interference matrix, the spectrum allocation algorithm based onchannel performance is proposed. The proposed algorithm takes the relative availability andchannel gain which affects the optimal allocation into account, and reconstructs the actual benefitmatrix. The simulation results show that the algorithm can reduce switching probability andsystem’s bit error rate, also can improve the system efficiency.Thirdly, spectrum handoff method based on multiple attribute is discussed. Under the model ofthe flexible perception spectrum handoff, some factors affecting the selection of target channel toswitch are second users’ transmission power, fading factor, bandwidth, and channel availability onthe authorized channel. In this article, a spectrum handoff strategy based on dynamic weights’adjustment is presented, considering the degree of each factor’s importance and dynamic changewhich are not fully considered in multi-attribute decision. The proposed method sets the dynamicweights by the change of environment and the previous experience. Then we get the value of utilityfunction through multiple attribute of simple weighted algorithm. The target channel to switch isdetermined by its descending order. The simulation results show that the proposed algorithm canreduce the switching times of secondary users, and increase the effective transmission rate.At last, the spectrum handoff based on adaptive weight adjusting is presented. The historicalinformation in cognitive wireless network is not premeditated by the spectrum handoff strategybased on dynamic weights’ adjustment. The traditional adaptive algorithm is applied in spectrummobility innovatively. The expected utility function value is derived that should be1, and anadaptive weights adjusting algorithm and spectrum handoff algorithm using the past information offactors are proposed. Simulation results show that the proposed adaptive weight adjustment algorithm is convergent, and the spectrum handoff algorithm can effectively reduce the switchingfrequency and handoff delay in the transmission cycle, and increase the effective transmission rateas well as the completion rate.