Research Of Multiple Primary Users Power Allocation Strategy Based On Sensing/Transmission Frame Structure In Cognitive Radio System

With the development of wireless communication,the number of wireless communication users has increased,occupying more and more frequency band resources.The demand of information transmission rate and transmission quality are constantly increasing,and the phenomenon of low spectrum utilization is also evident.These make the spectrum resources scarce,so the Cognitive Radio came into being.In cognitive radio,users are divided into primary users(PUs)and secondary users(SUs).Cognitive radio has the ability to learn and exchange information with the surrounding environment.The SU accesses or exits the licensed frequency band by the state of the frequency band,and adjusts the operating parameters at any time.This can limit and reduce conflicts between users to obtain higher frequency band utilization,so that protect the primary user.Therefore,cognitive radio,as a method to solve the shortage of spectrum resources effectively,has become a research hotspot in wireless communication.But how to make full use of the resources of multiple primary users,design an access strategy under imperfect sensing,and improve the performance of the system,still need further research.The work is mainly in the following aspects:In traditional frame structure,one frame is divided into two parts,which are sensing time slot and transmission time slot,and two time slots work separately.In the sensing time slot,the SU obtains the state of the PU by sensing;in the transmission time slot,the SU accesses the licensed frequency band to transmit data.However,the total duration of sensing and transmission time is one frame,so there is an inherent problem of balance.In the sensing/transmission frame structure used herein,a decoding device is added.This device is added to the receiver of the SU,so SU can decode the sensing results from the transmitted data,thereby synchronizing transmission and sensing.It can also avoid the inherent balance of sensing and transmission,and extend both time to one frame length.In traditional power allocation methods,it is assumed that there is only one primary user and one secondary user in each system,and different transmission powers are used for data transmission according to the state of the primary user.But in actual situations,there are usually multiple authorized channels.There is a problem that the channel resources cannot be reasonably utilized based on only one authorized channel.In order to get closer to the actual scenario,a multi-user scenario is introduced,and a four state three kinds power allocation strategy in multiple PUs situations is proposed with theoretical analysis results.Based on the sensing results,the SU selects the most suitable channel at this time,thereby improving the throughput.In the end,the new allocation strategy is simulated and verified by MATLAB simulation,and compared with the traditional model.The impact of factors such as primary user activity on the system is considered.