Research On Some Key Technologies In Cognitive Relay Networks

With the rapid development of the wireless communication,available frequency spectrum becomes more severe.The Cognitive Radio(CR)technology is envisioned as a primary solution for the spectrum scarcity problem in wireless communication networks.Cognitive radio Networks(CRNs)provide wireless connectivity via heterogeneous wireless architectures and dynamic spectrum access techniques in order to improve spectrum utilization.Meanwhile,the heterogeneity of both spectrum availability and traffic demand in secondary users has brought significant challenge for efficient spectrum allocation in cognitive radio networks.Moreover,Cooperative relay is proposed to be used to solve the problem.Cooperative relay technology is regarded widely as a key technology for increasing transmission diversity gain in various types of wireless networks.The open nature of wireless communications allows for the signals to be received by all users within the communication range.Thus,wireless communication is vulnerable to eavesdropper.It is urgent to solve the security problem of cognitive wireless network.With the development of cognitive wireless network,the quality of the user'experience gets more attention.Many experts and scholars have gradually started to optimize the performance of the network from the perspective of the subjective experience of the user.Therefore,on the basis of cognitive relay networks,the paper studied something about the physical-layer security and quality of experience(QoE).The research contents are as follows:Firstly,we investigate jammer selection from relays using fuzzy logic for physical-layer security in amplify-and-forward-based cognitive radio networks(CRN).Taking the interference power limited at the primary user(PU)into consideration,the jammer is selected from some relays and the rest of relays forward the message to achieve physical-layer security.In our work,the fuzzy logic for cooperative systems with the goal of maximizing the achievable secrecy sum rate is proposed.The method requires the channel state information from the relay to the destination and the total transmit power of relays as fuzzy parameters.The performance of the proposed method is compared with the semi-definite programming method(SDP).Simulation results confirm the feasibility and the lower complexity of the method for the secrecy sum rate maximization problem in CRN.Secondly,we concentrate on the quality of experience in amplify and forward(AF)relay cognitive network,where some secondary users(SUs)communicate with their receiver on the same band with a primary user(PU).In this paper,we study the problem of QoE,which is defined as the comprehensive subjective experience of the user to the quality and performance of device,network and system,application or service and so on.We can consider the comprehensive subjective experience as the comfort of business and applications.We evaluate QoE according to the method of mean opinion score(MOS).Then we use two methods to optimize MOS,including generalized eigenvalues and SDP.Simulation results demonstrate the difference between the two methods.