Income-selling-store Management System Based On The Cmmi Specification And Ssh Framework

As radio resource is becoming increasingly scarce, the contradiction betweenfrequency resource scarce and lower frequency utilization become obvious. CognitiveRadio technology can effectively solve this problem. Cognitive Radio as a intelligencefrequency share technology is becoming a hot research topic in wirelesscommunication field．In this paper, we introduce the background and related concepts about CognitiveRadio and spectrum sensing technology, analysis the single spectrum sensingtechnique, after comparing each detection algorithm, chose energy detection algorithmas a research focus. Mainly analyzes the principle of energy detection algorithm, studies the performance under AWGN channel and Rayleigh fading channel, andsimulate the performance of energy detection algorithm under different channelrespectively．Due to multi-path fading and shadowing, single detection performance is ratherbad. Consequently, we study the cooperative spectrum sensing for further to overcomethe disadvantages in single node detection. According to the analysis of structure incooperative spectrum sensing system, we do research on centralized and distributedcooperative spectrum sensing and compare the performance of them. On this basis, westudied the data fusion rule based on centralized cooperative spectrum sensing, andanalyzed the performance of spectrum detection by simulation experiments．In the end, the paper researches the cognitive radio network from the point of thebandwidth constraints, therefore, two censoring schemes based on vote fusion rule andAND fusion rule for cooperative spectrum sensing are proposed to decrease theaverage number of sensing bits to the fusion center. Consequently, the bandwidth issaved efficiently．The performance of spectrum sensing is investigated for both perfectand imperfect reporting channels and the close formulations of the detectionprobability are presented. Finally, the MATLAB is used to simulate the three censoringcooperative spectrum sensing methods and analyze the performance．Simulation resultsshow that these three methods all can save many sensing bits with less sensing performance loss, but the performance of the censoring scheme based on vote fusionrule for cooperative spectrum sensing is the best one．It means that the average numberof sensing bits decreases greatly with fine sensing performance．...