Research On Resource Optimization Algorithm In Cooperative And Cognitive Networks

With the development of wireless communication technology, the new wireless ap-plication and high quality serves (i.e. real-time video conference, online game) increaseexplosively. These wireless application and serves always need wide bandwidth and largerate. However, they do not have enough resource to use due to the limit resource andstatic resource allocation method. It is the main obstructions to develop wireless com-munication technology. As an efective way to relieve this conflict, resource optimizationalgorithms design is always the hot topic for scientists. Optimized resource can efective-ly improve the utilization of the resource. Meanwhile, it can satisfy the requirement ofthe high qualified service and application.Cooperative diversity makes the relay possible to receive the signal of the source byusing the broadcast nature of radio waves. After some proceeding, the relay help forwardthe signal of the source to the destination node. Thus, diferent users can share theirantennas and obtain MIMO (Multiple Input and Multiple Output) efects. It can efectivelyuse the spectrum and improve the quality of the communication. Cognitive radio canopportunistic access the primary spectrum by adaptively sensing the neighboring wirelessenvironment and timely adjusting the parameter of the system (i.e. modulation technique,working frequency, transmission power) while guaranteeing the primary transmission. Itmakes the best use of the limited spectrum, which can efectively improve the utilizationof spectrum. Thus it can help improve the performance of the wireless communicationsystems.OFDM(Orthogonal Frequency Division Multiple) is one of the key technology inthe next generation wireless communication network. It can efectively use the spectrum.Also, it can combat the influence of the frequency selective channel. This dissertationinvestigates the next generation wireless communication network. Based on the analysisof literature in China and abroad, the resource optimization in cooperative and cognitivesystem mainly by using OFDM technology is studied. Meanwhile, the spectrum bargain-ing problem in cognitive system by using bargaining method is analyzed. A cooperativespectrum access method based on Nash bargaining is proposed and the resource optimiza-tion in this method is investigated. The main work and innovative points are expressed asfollows. Firstly, the system model and key technology of cooperative diversity and cognitiveradio is introduced. The system model of cooperative diversity is introduced at first. Thenseveral classical relay protocols is describe, and the performance and characteristics ofthese protocols is analyzed. At last, the key technology of cognitive radio which includesspectrum detection, spectrum sharing and spectrum management is introduced.Secondly, a resource optimization in OFDM fixed relay system with one relay multi-source is proposed, in order to combat the low resource utilization of resource optimiza-tion algorithms in cooperative system. In our propose algorithms, one fixed relay is ableto help forward information of multiple sources in one OFDM symbol. It can efcient-ly utilize the available bandwidth, improve the system capacity and reduce the outageprobability. A joint sub-carrier matching and power allocation algorithm to maximize thechannel capacity is proposed.Thirdly, the spectrum utilization can not be fundamentally improved with the staticspectrum allocation. Cooperative OFDM spectrum access methods base on amplify-and-forward (AF) and decode-and-forward (DF) is proposed respectively, by combining thetechnology of cooperation and cognition. In our proposed methods, the cognitive user actsas a relay of the primary user, in which the cognitive user uses some of the subcarriersto help forward the primary signal, then uses the left orthogonal subcarriers to transmitits own signal to gain spectrum access. Thus, there will be no interference anymore. Itcan efciently use the limited spectrum to further improve the system performance. Acentralized AF spectrum access method by theoretically analyze is proposed at first. Thiscentralized method can achieve the upper bound performance, but it needs exchange toomuch information. It is hard to use in distributed system. Thus, a distributed method isproposed. If the cognitive user can decode the signal of primary user, the cognitive usercan use DF cooperation to forward the signal of primary user. A spectrum access methodbased on DF cooperation is proposed, in which the cognitive user do not need to pair thesubcarrier with primary user in the second slot.Fourthly, in most existing underlay spectrum access methods, the cognitive user canaccess the spectrum of primary user if the primary transmission is guaranteed. And thetarget of these methods is to maximize the rate of cognitive user. A cooperative spectrumaccess method based on Nash bargaining to extend these limit is proposed. In our pro-posed method, if the cognitive user can help improve the performance of the primary user,the primary user will lease a part of the transmission time to cognitive user to improve its own performance. In this spectrum access method, not only primary user can improveits performance, but the cognitive user can obtain spectrum access. Thus gain win-winefect.