Research Of Cooperation Spectrum Sensing Technology Under Different SNR Conditions

Along with the radio multi-media service increased and wireless networkbandwidth widened，the contradiction between business needs and limited frequencyresource become bigger than before. But for now, the radio communication spectrumresources is a kind of special precious natural resources, generally by government ormanagement agencies authorized to use. If a transceiver machine wants to use it, itneeds to get government’s permission. As all kinds of wireless communicationtechnology and content networking developing rapidly, allocated spectrum resource isbecoming scarcer and scarcer. In order to solve this problem, it must to improvespectrum efficiency. Cognitive radio technology is put forward in this situation.As a kind of intelligent communication system, cognitive radio can detect theexistence of spectrum hole in authorized frequency band through the spectrumperception technique, and then adjust its transmission power, carrier frequency,modulation mode to take up authorized frequency band. When found the authorizeduser, the cognitive user will change the parameter of itself in order not to disturb theauthorized user (including not affect the normal authorized users to send and receivesignals). Spectrum sensing technology is one of the most important prerequisitesdepend on which the cognitive radio can work efficiently. Therefore, this topic willfocus on the research of cognitive radio spectrum sensing technology. In this paper,we do some work on spectrum sensing technology as follows:Cooperation spectrum sensing technology could overcome "hidden terminal"problem. However, in the process of cooperation spectrum sensing, each cognitivenode locates in different places respectively. Every cognitive node doesn’t knowwhether it is far away from the authorized user or not. At the same time every channelenvironment is different from each other and independent. The signal-to-noise ratios of received mixed signal at the receiver of the cognitive users are also different fromeach other. Signal-to-noise ratio will influence the final spectrum detectionperformance. Besides, when cognitive users cooperate with each other in the type ofrelay or cluster, some of them need to choose those whose trust level is higher thanothers to transmit information for them. The concept of trust will be used here tocomplete cooperation spectrum sensing. According to these two points, we will usethe combination of weighted signal-to-noise ratio and trust to fusion the verdict underdifferent SNR conditions. The "different SNR" means all signal-to-noise ratio of thesereceived signal are normal distribution and independent with each other. Based onthis, we put forward a new fusion algorithm, employing different fusion algorithmaccording to different value of signal-to-noise ratio. In this case, we can not onlyensure timely spectrum sensing in good signal-to-noise ratio environment but alsoensure high probability of detection in low signal-to-noise ratio environment. At thesame time we will make simulation shows to explain the performance of the proposedalgorithm. Later, considering the stability of the system, we make improvement to thetrust weighted model and prove its superiority through simulations on incredible usersand malicious users.In conclusion, this paper has finished the following works:(1) We make simulation shows to explain the performance of the collaborationspectrum sensing using SNR weighted method under different SNR conditions, theperformance of the collaboration spectrum sensing using the combination of weightedsignal-to-noise ratio and trust.(2) In allusion to the different SNR conditions, we put forward a new fusionalgorithm based on the signal-to-noise ratio decision threshold.(3) We make improvement to the trust weighted model and prove its superioritythrough simulations on incredible users and malicious users.