Performance Analysis And Optimization Of Relay And IRS-Assisted Short Packet Communication System

In recent years,with the rapid growth of wireless communication users,5G(Fifth Generation)networks have become a common choice for achieving the Internet of Things.The three major application scenarios of 5G mobile communication are en-hanced mobile broadband,massive machine communication,and ultra-reliable and low-latency communication(URLLC).Currently,short packet communication,intelligent reflecting surfaces(IRS),non-orthogonal multiple access(NOMA),unmanned aerial vehicle(UAV)communication,and new channel coding and decoding technologies are regarded as potential key technologies for achieving URLLC in the new generation of wireless communication systems.NOMA technology has been regarded as a promising multiple access technology in recent years,which can significantly improve the spectrum efficiency of mobile com-munication networks and has become one of the key technologies of 5G.With the rapid development of UAVs,the advantages of low cost and rapid deployment have made UAV communication a research hotspot in the communication field.UAVs can be flex-ibly deployed to achieve high-probability line-of-sight communication between ground nodes and UAVs.The rapid development of artificial electromagnetic materials has made IRS based on metamaterials a potential key technology that can significantly im-prove system performance in beyond-5G and even 6G mobile communication.This thesis mainly studies the system performance analysis and optimization prob-lems of NOMA,UAV,IRS,and short packet communication technology combined.The specific contents are as follows:(1)Cooperative NOMA and short packet communication system performance anal-ysis.This thesis studies the power allocation problem of the system with limited block length,optimizes the power allocation factor of the system on the Rayleigh fading chan-nel with the total average effective throughput as the performance indicator.Firstly,the closed-form expressions of the average block error rate(BLER)and effective through-put of two users are derived.Secondly,the optimal power allocation factor that maxi-mizes the total average effective throughput under high signal-to-noise ratio is derived.Finally,some theoretical and simulation analysis results are given,and the results verify the correctness of the theoretical analysis.(2)Performance Analysis and Optimization of UAV-Assisted Short-Packet Com-munication System.This thesis analyzes the performance of a ground short-packet com-munication system assisted by UAV,which uses unmanned aerial vehicles as wireless relays to achieve ultra-reliable low-latency communication between base stations and user devices.Firstly,the Gauss-Legendre integral method is used to derive the closed-form expression of the overall average block error rate(BLER)at the user end.Sec-ondly,under the constraints of terminal reliability and latency,the bisection method and one-dimensional search algorithm are applied to jointly optimize block length,trans-mission power and UAV flight height,so as to maximize the energy efficiency of UAV.Finally,the correctness of the theoretical analysis results is verified by Monte Carlo simulation.(3)Performance Study of IRS-Assisted Short-Packet Communication System.This thesis comprehensively analyzes the average block error rate(BLER)performance of IRS-assisted short-packet communication system under Rician fading channel.Accord-ing to whether there is a direct link between the base station and the user,the commu-nication scenarios are divided into two types,and two types of phase errors are con-sidered to facilitate the design of systems based on instantaneous channel state infor-mation(CSI)and statistical CSI.Firstly,the distribution of user end-to-end channel and received signal-to-noise ratio(SNR)under different phase adjustment strategies is derived.In addition,a more accurate Q-function approximation is proposed to obtain the closed-form expression of the average BLER.Then,numerical and simulation re-sults are used to verify the accuracy of the theoretical analysis,and the influence of the number of IRS units,phase adjustment strategies,and CSI design on the average BLER performance is studied.Finally,the BLER performance generated by instantaneous CSI and statistical CSI under larger Rician factor parameters is compared,and it is found that the performance generated by statistical CSI is better,and its low complexity im-plementation makes it more suitable for ultra-reliable low-latency communication.