| On the issue of allocation of Radio spectrum,the traditional "one to one" fixed allocation mode causes the waste of a large amount of spectrum resources.Therefore,Cognitive Radio(CR)technology is introduced,which aims to use its excellent learning ability to dynamically access the idle spectrum.The spectrum sensing technology is used to obtain the information of Primary User and determine the transmission parameters of Secondary Users(SU),so that SUs can access the spectrum opportunely and avoid interference to PUs.Therefore,cognitive radio provides a research direction in improving spectrum efficiency and energy efficiency of the system,which is also of great practical significance for realizing green communication and reducing carbon pollution.In view of the high Energy cost,low frequency spectrum efficiency and massive Access of Internet of Things devices to CR network,this paper will combine Energy Harvest(EH)technology and Non-Orthogonal Multiple Access(NOMA)technology to conduct research and analysis.In order to realize the energy self-circulation and improve the energy efficiency of the secondary user system,the main contents are as follows:(1)Firstly,this paper studies the resource allocation problem of CRN system aiming at maximizing the energy efficiency of SUs system.In this paper,SU users are clustered and cluster head selection algorithm is studied.The relative position of SU,signal-to-noise ratio between PU and SUs and channel gain are considered comprehensively.Then combined with the energy collection technique in PU maximum interference threshold,SUs minimum initial energy,maximum transmission rate,perception of time constraints,consider two cases of system throughput formula,based on OFDM system energy efficiency maximization problem are studied.By using the improved artificial fish algorithm(ADAFSA algorithm),The optimal transmitting power solution is searched by setting constraint conditions and adaptive searching parameters.Simulation results show that the energy efficiency of EHCRN based on the proposed algorithm is higher than that of traditional artificial fish swarm and water injection algorithms.(2)Secondly,the energy efficiency optimization of CR-NOMA system based on multicarrier NOMA is studied.In order to maximize the energy efficiency of SUs system,this paper presents the problem of channel allocation and power allocation.The optimization problem mainly involves sub-channel allocation and power allocation of superimposed users.After allocating sub-channels,the power of SU users is optimized.Finally,combining the Dinkelbach algorithm and the idea of Successive Convex Approximation(SCA),an iterating-based user assignment algorithm(SPOEE)is proposed,which updates the key parameters with increasing iterations to satisfy the set threshold.The power suboptimal solution of superimposed users is obtained.Simulation results show that the CR-NOMA system using the proposed algorithm has better energy efficiency than OMA system and traditional fixed power allocation algorithm. |
