Optimization Realization And Performance Analysis For Cognitive Radio System Of Antenna Selection

With the rapid growth of the wireless communications business needs, the availablespectrum resources are increasingly scarce. However, research found that the allocated spectrumresources are idle of different degree and it is static radio spectrum management that results inthe shortage of spectrum resources. Therefore cognitive radio, an intelligent dynamic spectrumsharing technology, is proposed.Cognitive radio continuously sense, analysis, learn and judge all kinds of information of theexternal environment. Then the suitable working parameters are selected to realize highlyreliable communications of anytime and anywhere and effective spectrum utilization, withoutharmful interference to licensed user.The current research mainly includes spectrum sensing, dynamic spectrum management,power control and the fusion of cognitive radio and existing communication technology etc.Game theory, information theory and a variety of optimization theory has been used to resolvethe issues and access to a wealth of results.Cognitive radio aims to improve the spectrum utilization. The multi-antenna technology ofexisting wireless communication technology can also improve the spectrum utilization to someextent. Therefore, the combination of the two will have a multiplier effect undoubtedly. In thispaper, a multiple antenna technology is introduced into the cognitive radio system. Thisdissertation is mainly discussed as follows:1. According to the general characteristics of the models, an optimization algorithm has beendesigned.2. A fixed power cognitive radio system combined with antenna selection. Through mathematicalderivation, the mathematical expressions of the channel capacity and bit error rate are obtained.Simulation verifies the correctness of theoretical results and shows the system exists an optimaltransmit power makes the system performance optimal. In addition, the impact of the distanceradio of cognitive user transmitter to primary use and to cognitive user on system performanceand the optimal transmit power has been studied.3. A fixed power cognitive radio system jointly combined with antenna selection and usersscheduling. Through mathematical derivation, the mathematical expressions of the channelcapacity and bit error rate are obtained. Simulation verifies the correctness of theoretical results and shows the system exists an optimal transmit power makes the system performance optimal.In addition, the impact of users number on system performance and the optimal transmit powerhas been studied.4. A variable power cognitive radio system combined with antenna selection. Throughmathematical derivation, the mathematical expressions of the channel capacity, bit error rate andoutage probability are obtained. Simulation verifies the correctness of theoretical results. At thesame time, the impact of the variation of maximum transmit power and antennas number on thechannel capacity and bit error rate and the impact of the variation of interference threshold andantennas number on outage probability has been studied.In conclusion, we have set up a more practical cognitive radio antenna selection systemmodel, derived the closed form of the channel capacity and bit error rate expressions andanalyzed the influence of various parameters on system performance. Furthermore, anoptimization algorithm has been designed and the system performance has been improved.