Research On Localization Of Primary Users In Cognitive Radio Networks

With the rapid growth of wireless communication services, most of the availablespectrum resources have been occupied. The limited spectrum resources problem bringsabout the imbalance between supply and demand of spectrum resources. Flexible,intelligent, reconfiguration is the salient feature of cognitive radio. Under the premise ofdo not interfere with the primary users, cognitive radio can realize the spectrum sharingthrough the spectrum sensing to detect spectrum holes. New opportunities for spectrumuse can be obtained by increasing the spectrum efficiency. In cognitive radio networks,the primary users’ location information is very important to implement the powercontrol, provide location based services, location aided network optimization, locationaided transceiver optimization, environment identification and so on. In this paper, thelocalization of primary users technology in cognitive radio networks is studied, the maincontents are as follows.1) Localization of primary users in cognitive radio networks includes themeasurement phase and the processing phase. In the measurement phase, the cognitiveusers measure the wave parameters, such as time of delay, angle of arrival, receivedsignal strength after receiving the transmitted signal from the primary users. In theprocessing phase, cognitive users according to the obtained estimated wave parameters,based on stochastic signal processing technology to calculate the location information ofmeasured node. This paper summarizes the analysis of radio wave propagationmechanism and typical radio propagation model. Principles, characteristics andapplicable scope of the based on TOA, TDOA, RSS and AOA measured wirelesspositioning technology are elaborated. In the analysis of positioning solutions,respectively introduces the basic principle of the circumferential positioning method,the hyperbolic positioning method, the azimuth measurement positioning method andthe lighthouse approach to localization. This paper also defines a wireless positioningperformance evaluation.2) According to the need for the localization of primary users in cognitive radionetwork, the RSS localization technology and the AOA localization technology isstudied. Respectively, waves received signal strength and distance between the nodesrelationship model, angle of arrival waves and the distance between the nodes relationalmodel are established. Weighted least squares method is adopted to solve the position problem. The wave propagation path loss exponent, the distance between the primaryusers and the cognitive users have influence on the positioning performance is described.On this basis, the hybrid AOA-RSS localization algorithm is put forward. Via setting areference standard, the decision maker chooses the RSS-WLS location algorithm orAOA-WLS location algorithm as the final algorithm for the primary user’s positioning.The simulation results show that, compared with the only RSS-WLS location algorithmor AOA-WLS location algorithm, the performance of the proposed algorithm hasimproved significantly.3) In consideration of the secondary users cannot learn the primary users’transmission power parameters, the RSS-IWLS localization algorithm for the primaryuser is designed. The algorithm also uses the weighted least squares method to estimatethe location information of primary users setting the signal power sent by primary usersas an unknown variable. The proposed cognitive RSS-IWLS localization algorithmtakes account of all the error affecting factors, namely noise, shadowing and error inpath loss exponent estimation. Simulation results show that the proposed algorithmoutperforms the existing RSS-WLS algorithms in estimation accuracy by reducing themean and variance of estimation error.