面向5G的非正交多址接入下行链路接收机仿真研究

发布时间：2018-05-08 06:36

本文选题：NOMA + 5G　；参考：《西南交通大学》2017年硕士论文

【摘要】：随着4G网络的商用部署,5G移动通信技术的研究已经如火如荼,面对5G海量连接、高频谱效率和高容量的要求,非正交多址接入(NOMA)技术以其优异的频谱效率引起了业界广泛地关注。NOMA技术引入功率域,实现多用户功率域复用,在接收端通过串行干扰消除技术达到信号检测的目的。由于NOMA技术在发送端主动引入了干扰,因而接收端的信号检测成为NOMA关键技术点。本文针对NOMA系统下行链路信号的检测以及接收机展开研究。论文首先对NOMA技术的基本原理做了介绍,并以两个用户的系统模型为例,定量验证了相较于OFDMA系统,NOMA系统带来的性能增益。随后论文介绍了功率分配和信号检测两个关键技术,以及MIMO技术相关原理。然后,利用模块化的思想搭建NOMA系统下行链路的链路级仿真平台。基于该平台分别研究了单天线与多天线场景中Ideal SIC接收机、Symbol-level SIC接收机以及Codeword-level SIC接收机的接收性能。通过仿真分析发现,在合理分配发送功率前提下,Codeword-level SIC接收机误码率性能与Ideal SIC接收机基本保持一致,而Symbol-level SIC接收机的性能则较差;随着用户间功率分配因子差值的增加,接收机的性能有所提高;提高用户调制阶数,接收机对错误传播更加敏感,性能变差。此外,在单天线场景中,以最大化加权和速率为功率分配准则,对功率分配算法进行了研究,得到结论功率分配因子取值不仅与用户信噪比差值有关还与自身信噪比有关。在多天线场景中,研究了传输分集和空间复用两种模式下接收机的性能,仿真结果表明,传输分集模式下接收机的性能均好于空间复用模式下接收机的性能。在多天线场景中,由于不仅存在用户间的干扰,还存在流间干扰,使得Symbol-level SIC接收机对错误传播更加敏感,导致Symbol-level SIC接收机的接收性能大幅度降低,故针对错误传播(EP)问题对容量的影响进行了仿真分析,仿真结果表明EP会很大程度的影响系统容量。最后,引入了一种基于联合检测的算法,在接收端通过联合星座图直接检测用户信号,减少了干扰信号重建的过程。通过仿真发现,该接收机性能远远优于Symbol-level SIC接收机,且与Codeword-level SIC接收机相比,复杂度降低大约50%。
[Abstract]:With the commercial deployment of 4G network, the research of 5G mobile communication technology has been in full swing, facing the requirement of 5G mass connection, high spectrum efficiency and high capacity. Non-orthogonal multiple access (NOAA) technology has attracted wide attention because of its excellent spectral efficiency. Noma technology is introduced into power domain to realize multi-user power domain multiplexing and signal detection is achieved by serial interference cancellation at the receiver. Because the interference is introduced into the transmitter by NOMA technology, the signal detection at the receiving end becomes the key technology of NOMA. In this paper, the detection of downlink signal and receiver of NOMA system are studied. Firstly, the basic principle of NOMA technology is introduced, and the performance gains compared with OFDMA system are quantitatively verified by taking the system model of two users as an example. Then the paper introduces two key technologies of power allocation and signal detection, as well as the related principles of MIMO technology. Then, the link-level simulation platform of NOMA downlink is built by modularization. Based on this platform, the performance of Ideal SIC receiver Symbol-level SIC receiver and Codeword-level SIC receiver in single-antenna and multi-antenna scenarios are studied. The simulation results show that the BER performance of Codeword-level SIC receiver is basically the same as that of Ideal SIC receiver under the premise of reasonable allocation of transmission power, but the performance of Symbol-level SIC receiver is poor, and with the increase of power allocation factor difference between users, the BER performance of Codeword-level SIC receiver is basically the same as that of Ideal SIC receiver. The performance of the receiver is improved and the receiver is more sensitive to the error propagation and the performance becomes worse when the user modulation order is increased. In addition, in the single antenna scene, the maximum weighted sum rate is taken as the power allocation criterion, and the power allocation algorithm is studied. It is concluded that the power allocation factor is not only related to the difference of the user's SNR but also to its own signal-to-noise ratio (SNR). In the multi-antenna scene, the performance of receiver in transmission diversity mode and spatial multiplexing mode is studied. The simulation results show that the performance of receiver in transmission diversity mode is better than that in spatial multiplexing mode. In the multi-antenna scene, the Symbol-level SIC receiver is more sensitive to error propagation due to not only interuser interference but also inter-stream interference, which results in a significant decrease in the reception performance of the Symbol-level SIC receiver. Therefore, the effect of error Propagation (EPN) problem on the capacity is simulated and analyzed. The simulation results show that EP will greatly affect the capacity of the system. Finally, an algorithm based on joint detection is introduced to detect user signals directly through joint constellation at the receiving end, which reduces the reconstruction process of interference signals. The simulation results show that the performance of the receiver is much better than that of the Symbol-level SIC receiver, and the complexity of the receiver is reduced by about 50% compared with the Codeword-level SIC receiver.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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