Research On Performance Of Cooperative Communication System For Cognitive UAV

In recent years,with the rapid development of UAV devices and wireless communication technologies,UAVs are often deployed as trunking or access points in various wireless communication systems due to their flexibility,low cost and high efficiency.In addition,Non-orthogonal Multiple Access(NOMA)and Cognitive Radio(CR)are recognised as effective ways to improve spectrum utilisation.SWIPT communication enables simultaneous transmission of energy and information and can improve the energy efficiency of communication systems.Conventional terrestrial base stations are affected by obstacles,which reduce their coverage area and create a blind spot.In order to solve this problem,and to improve the spectral efficiency and energy efficiency,this paper uses UAVs as mobile relays and combines NOMA and SWIPT technologies to investigate the performance of cognitive UAV systems,accomplishing two main tasks.1.To analyse the outage performance of the next user in the underlay spectrum sharing mode for a cognitive UAV communication system with non-orthogonal multiple access.Theoretical expressions for the probability of subscriber outage are derived considering two channel environments,Rayleigh fading and Rician fading.Simulation experiments are conducted to verify the correctness of the theoretical derivation and to reveal the influence of channel parameters and UAV location on the sub-user interruption performance.The simulation results show that when the UAV flight radius r=0.7m,the sub-users U1 and U2 have the minimum interruption probability when the UAV flies to the and position respectively.At the same flight radius,the transmission with NOMA technology has better interruption performance than the sub-user with OMA technology.2.In order to solve the energy constrained problem of cognitive UAS,this paper introduces SWIPT technology into cognitive UAS.In order to investigate the advantages brought by SWIPT combined with cognitive UAS,a theoretical expression for the probability of sub-user interruption under the underlay spectrum sharing mode is derived.Simulation results show that the SWIPT-based cognitive UAV relay communication system has slightly worse interruption performance compared to the non-SWIPT cognitive UAV relay communication system,but the energy efficiency is improved by 46.67% through the introduction of SWIPT technology.It can be concluded that there is a trade-off between transmission reliability and energy efficiency,and the system designer can make a judgement based on the results of this performance analysis.