Research On Spectrum Switching In Cognitive Wireless Networks

Primary users in cognitive radio network authorized band will randomly appear to interrupt at any time in the cognitive user communications services, therefore,spectrum handoff technology is to ensure that cognitive users in cognitive radio network communication continuity of key technology.The main research work of this paper are as follows.In view of the future trend of network integration, wireless communication network will also may contain authorized spectrum and without authorization spectrum of these two kinds of communication frequencies, called the mixed spectrum network in this paper.This paper designs an improved spectrum based on the mixed spectrum network scheme, because without authorization channel to the spectrum of no high and low priority level, cognitive users won’t happen communication interruption phenomenon, by increasing the use without authorization the channel on the spectrum as the cognitive users handoff frequency spectrum of the target channel, does not need to authorized channel to the spectrum of business spare time to improve the frequency spectrum of the cognitive users handoff performance.Based on preemption priority(PRP G/M / 1 queuing model and the common queue(M/M/C) model for mixed spectrum environment cognition the average user switch time delay and the average switching frequency is analyzed and simulated, the simulation results show that the cognitive users to select the target channel, using the algorithm of random arrival rate when the main users in 0.2(reach number per second), and only authorized as compared to switch the target channel,the channel to the spectrum of mixed spectrum network handoff scheme scheme can shorten the average about 10% of the cognitive users switch delay.Based on the study of the cognitive users in authorized spectrum spectrum on the channel model based on the handoff frequency spectrum of cognitive users against the spectrum of limited ability to switch the actual condition, introduced by usingspectral handoff factor to represent the spectrum of cognitive users switch ability, this paper, by using the continuous time markov model to analyze the blocking probability of different spectral switch ability and cognitive users, forced interrupt probability and spectrum access efficiency.Through analysis and simulation results it can be seen that at the time of design spectrum handoff algorithm, if you don’t consider the actual channel handoff ability is limited, will cause the service performance of cognitive users to overestimate.Based on current hardware conditions, in a general communication channel condition, the ideal handoff algorithm will overestimate the network performance, in the actual network planning, ignoring the actual effect, can bring harm to the overall performance.