非正交多址系统中基于Raptor码的下行传输设计与优化  

Raptor Coded Downlink Transmission Design and Optimization in Non-orthogonal Multiple Access System

作　　者：张昱 李昊 彭宏[1] 卢为党[1] ZHANG Yu;LI Hao;PENG Hong;LU Wei-dang(College of Information Engineering,Zhejiang University of Technology,Hangzhou 310023,China;National Mobile Communications Research Laboratory,Southeast University,Nanjing 210096,China)

机构地区：[1]浙江工业大学信息工程学院,杭州310023 [2]东南大学移动通信国家重点实验室,南京210096

出　　处：《小型微型计算机系统》2021年第8期1735-1740,共6页Journal of Chinese Computer Systems

基　　金：国家自然科学基金项目(61871348,61871349,61803336)资助;东南大学移动通信国家重点实验室开放研究基金课题项目(2020D10)资助。

摘　　要：本文研究了块衰落信道下非正交多址系统(Non-orthogonal Multiple Access,NOMA)中基于Raptor码的两用户下行传输系统.基站将要发送给两用户的信息先分别进行Raptor码编码及调制,再将其按一定功率分配因子进行叠加后广播给两个用户.各用户选择采用串行干扰消除(Successive Interference Cancellation,SIC)或直接利用置信传播算法(Belief Propagation,BP)恢复所需信息.为了进一步提升系统性能,本文针对基站仅具有信道统计状态信息下,以最大化系统平均下行速率为目标,利用外信息(Extrinsic Information Transfer,EXIT)分析,联合优化了两用户的Raptor码度数分布以及基站叠加编码功率分配因子.本文所提出的优化方法不需要实时信道状态信息,因此可以减少系统反馈开销.仿真结果显示,本文提出的优化方法能够降低系统误码率(Bit Error Rate,BER)以及提升系统平均下行速率.This paper studies two-user downlink transmission based on Raptor codes in a non-orthogonal multiple access system(NOMA)under block-fading channel.At the base station,the message intended for each user is encoded by Raptor code and then modulated.The signals for both users are superimposed with a certain power allocation factor and the resulted signals are broadcast to both users.Each user either uses Successive Interference Cancellation(SIC)or directly applies the Belief Propagation Algorithm(BP)to recover the required message.In order to enhance the system performance further,under the assumption of solely statistical channel state information(CSI)at the base station,we aims at maximize the average downlink system throughput over all possible channel states.We resort to external information(EXIT)analysis to jointly optimize the Raptor code degree profiles for both users and power allocation factor.Instant CSI is not required by the proposed optimization scheme,therefore,the system feedback overhead can be reduced.It can be shown by simulation results that the proposed scheme can reduce the system bit error rate(BER)and improve the average system downlink throughput.

关 键 词：非正交多址 RAPTOR码 串行干扰消除 置信传播 外信息传递 

分 类 号：TN914[电子电信—通信与信息系统]