Research On Spectrum Sharing And Power Allocation In Cognitive Radio System

With the increasing number of mobile devices and the expanding scale of wireless communication networks,the static spectrum resource allocation method can no longer satisfy the needs of the current communication.As a popular emerging technology,cognitive radio,which intelligently schedules idle authorized spectrum among multiple users,improves the utilization of radio spectrum,and effectively alleviates the increasing tension of spectrum resources.How to design spectrum usage rules and related access mechanisms,coordinate all participants' behaviors and achieve effective spectrum sharing is especially important for cognitive radio system.Interference alignment is a interference management technology that can effectively improve communication network throughput and eliminate interference between users.It is widely used in cognitive radio networks,allowing more users outside authorized users to share spectrum.However,in the actual communication environment,there are still some problems,such as the decline of signal to noise ratio of the desired signala nd the interference leakage,which affect the service quality of the authorized users.In view of the above problems,this thesis focuses on the following points:1)This thesis systematically discusses the cognitive radio and interference alignment principle,builds a cognitive radio network model based on interference alignment,which is utilized to eliminate the mutual interference between users caused by the cognitive users accessing the licensed spectrum,and analyzes the water-falling power allocation algorithm for cognitive network based on the interference alignment.On this basis,a dynamic power allocation algorithm is proposed,which is added to the state factor of the user's communication activity.Compared with the traditional power allocation algorithm,the algorithm can obtain higher data transmission rate and can allocate power according to the active state of the user.2)This thesis analyzes the reason of the authorized user' SINR declining,proposes a spectrum sharing algorithm for multiuser diversity in IA-based cognitive network,and researches the impact on the system performance that system imposes though selecting cognitive user according to the communication status of cognitive users when more cognitive users request access to the authorized spectrum with mutual interference not ideally completely eliminated in the network conditions.3)When the number of cognitive users requesting access to the network is increasing,and the signal-to-noise ratio of the authorized user is close to the theoretical maximum,the power allocation algorithm based on multi-user diversity is proposed for the disturbance of the cognitive user's activity to the system channel parameters.While guaranteeing the rights and interests of the authorized users,it also optimizes the whole network performance and improves the overall transmission rate of the network.In addition,an adaptive adaptation algorithm based on the change of channel state and cognitive user's influence on the communication state of authorized users is proposed.