Research On Cooperative Communication Technology In Cognitive Radio

With the widespread application of wireless communications,spectrum resources are increasingly scarce.Cognitive radio technology can sense the spectrum,dynamic access and exit the authorized frequency band in time,and maximize the use of spectrum resources.It is a potential research direction in the field of wireless communications.At the same time,the ever-increasing energy costs have made it urgent for more energy-efficient wireless communications.As one of the green communication technologies,cooperative communication technology can effectively improve the wireless transmission rate and system reliability through diversity gain,and has wide application prospect.Radio channel fading affects cognitive radio system performance,so it is very important to study the cooperative communication technology under cognitive radio.In this paper,we study the energy efficiency of cooperative transmission of secondary networks under two modes of cognitive user access spectrum.The specific work is as follows:Based on the characteristics of licensed users' parallel access of frequency in Underlay mode,this paper proposes a trunking selection and power allocation algorithm for single relay and multi-relay cooperation models.Under the constraint of total transmit power and interference power,a single relay cooperative transmission system considers the secondary user's residual energy information and establishes an optimization model to maximize energy efficiency.Gradient descent method to obtain the optimal power distribution factor and the maximum energy efficiency.A relay game model is established in cooperative transmission of multi-relay,and a cooperative game based relay selection and power allocation algorithm is proposed to achieve an effective compromise between performance and power consumption of cooperative transmission system.Simulation results show that this scheme can dynamically select the appropriate relay station,adjust the power distribution,reduce energy consumption and achieve efficient collaborative transmission.Based on the characteristics of cognitive users having the opportunity to access the licensed spectrum in overlay mode,this paper proposes a spectrum sensing and power allocation scheme for cooperative transmission system in cognitive radio.Combined with channel perception results,a joint parameters optimization of system energy efficiency is carried out.Firstly,the average throughput and energy efficiency formula of relay transmission are deduced theoretically.Restricted by the maximum allowable transmission power and the maximum average interference power,an optimization model involving three parameters of perceived time,perceived threshold and node power is established.In order to simplify the solution,the entire problem is divided into two sub-optimization problems.The gradient descent method is used to solve the power distribution scheme.The numerical analysis method is used to solve the perceptual parameter optimization problem.Finally,a fast convergence iterative algorithm is proposed.The simulation results show that the proposed algorithm has lower complexity and can effectively improve the performance.The content of this dissertation belongs to one of the components of NSFC's project research and publishes an essay.