针对LTE系统上行链路的SC-FDMA调制解调算法研究

发布时间：2018-04-13 15:43

本文选题：LTE标准 + 单载波频分多址(SC-FDMA)　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：第三代合作伙伴项目(the 3rd Generation Partnership Project,3GPP)提出的长期演进计划(Long Term Evolution,LTE)引入了多方面的技术革新以增强无线通信系统的整体性能。LTE上行链路采用峰均比较低的单载波频分多址技术(Single Carrier Frequency Division Multiple Access,SC-FDMA)技术。同时,发送的帧结构设计成带有循环前缀(Cycle Prefix,CP)的形式以有效抵抗符号间干扰(Inter-Symbol Interference,ISI)和载波间干扰(Inter-Carrier Interference,ICI)。通常CP长度大于信道冲激响应的最大延迟,然而,在一些特殊的通信环境中,例如,开阔的山地、高速的列车等环境,都会造成信道响应具有较大的时间延迟,这直接导致了原本的CP长度不再满足要求,导致传统解调算法性能严重下降。本文基于LTE上行链路的SC-FDMA技术,针对相关的物理层调制解调技术展开研究,本文的主要贡献可以归纳为如下三个方面:1.在充分理解LTE标准的基础上,着重针对上行链路物理层处理的相关技术细节搭建系统级仿真平台,平台主要包括:基于Turbo码的信道编码和译码、SC-FDMA组帧、多径频偏信道模拟,接收端频偏纠正、信道估计以及均衡补偿等算法实现。2.在CP长度充足的条件下,研究并实现了适合LTE上行链路的频偏纠正算法、信道估计算法和均衡补偿算法。研究表明:频偏纠正适合采用基于导频和基于CP的相关算法;对于信道估计,重点研究了最小二乘算法、最小均方误差(Minimum Mean Square Error,MMSE)算法和基于离散傅里叶变换的估计算法,后者更具有性能优势;对于均衡补偿,详尽讨论了线性均衡算法、基于MMSE的残余码间干扰消除(MMSE-Residual ISI Cancellation,MMSE-RISIC)算法和频域判决反馈均衡算法(Decision Feedback-Frequency Domain Equalization,DF-FDE)。基于LTE上行链路的仿真结果同样表明MMSE-RISIC算法对编码SC-FDMA系统的均衡补偿性能具有明显改善。3.在CP长度不足的条件下,本部分主要针对均衡补偿的角度进行研究,论文:一方面,从时域均衡的角度出发,基于等效信道缩短的思想,研究了最大缩短信噪比算法和基于零点消除的信道缩短算法以及自适应盲均衡即冗余重构多载波均衡算法。研究表明:信道缩短算法在SC-FDMA系统中的有效性并不明显;另一方面,从频域均衡角度,在研究了MMSE均衡算法、联合RISIC和CP重构的均衡算法的基础上,论文提出了适用于SC-FDMA系统的基于最小均方误差的判决反馈(MMSE-DFE)算法,并通过搭建的SC-FDMA链路仿真平台验证了提出算法的有效性,在CP不足情况可以获得更好的误码率性能。
[Abstract]:The 3rd Generation Partnership Project 3GPP) has introduced a number of technological innovations to enhance the overall performance of wireless communication systems. LTE uplink uses low peak-average single-carrier frequency division.Single Carrier Frequency Division Multiple access SC-FDMA.At the same time, the transmitted frame structure is designed as a form with cyclic prefix / cycle prefix (CPV) to effectively resist inter-symbol interference (ISI) and inter-carrier interference (ICI).The CP length is usually greater than the maximum delay of channel impulse response. However, in some special communication environments, such as open mountains, high-speed trains and so on, the channel response will have a large time delay.This directly leads to the original CP length no longer meet the requirements, leading to the performance of the traditional demodulation algorithm.Based on the SC-FDMA technology of LTE uplink, this paper studies the related physical layer modulation and demodulation technology. The main contributions of this paper can be summarized as follows: 1.On the basis of fully understanding the LTE standard, a system-level simulation platform is built for the related technical details of uplink physical layer processing. The platform mainly includes: Channel coding and decoding based on Turbo code, SC-FDMA framing, and multi-path frequency offset channel simulation.The received end frequency offset correction, channel estimation and equalization compensation algorithm are implemented. 2. 2.Under the condition of sufficient CP length, the frequency offset correction algorithm, channel estimation algorithm and equalization compensation algorithm suitable for LTE uplink are studied and implemented.The results show that frequency offset correction is suitable for pilot-based and CP based correlation algorithms. For channel estimation, the least square algorithm, minimum mean square error minimum Mean Square error estimation algorithm and discrete Fourier transform estimation algorithm are emphasized.The simulation results based on LTE uplink also show that the MMSE-RISIC algorithm can significantly improve the equalization compensation performance of coded SC-FDMA systems.Under the condition of the lack of CP length, this part mainly studies the equalization compensation angle. On the one hand, from the angle of time domain equalization, based on the idea of equivalent channel shortening,The maximum shortening SNR algorithm, the channel shortening algorithm based on zero cancellation and the adaptive blind equalization, i.e. redundant reconstruction multi-carrier equalization algorithm, are studied.The results show that the channel shortening algorithm is not effective in SC-FDMA system. On the other hand, from the angle of frequency domain equalization, the MMSE equalization algorithm, the equalization algorithm combining RISIC and CP reconstruction, is studied.In this paper, a decision feedback MMSE-DFE algorithm based on minimum mean square error (MSE-DFE) is proposed for SC-FDMA systems. The effectiveness of the proposed algorithm is verified by a SC-FDMA link simulation platform, and a better bit error rate performance can be obtained in the case of CP deficiency.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.5

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