摘要为迎合时代对大数据量通信的需求，国际标准化组织3GPP在Release 8中完成LTE标准化，作为第四代移动通信技术（4G）的代表，目前已在全球范围内投入运行并日趋成熟。LTE系统中，DL-SCH和PDSCH承载有效用户数据的传输，作用尤其重要。无线信道对传输信号造成失真，其不可预见性使得接收端有效的信道估计和均衡技术至关重要。本文研究LTE-FDD物理层下行传输链路，具体研究内容如下：69360

（1）研究物理层中DL-SCH和PDSCH处理，以及LS信道估计和ZF信道均衡两大接收技术，采用QPSK、16QAM、64QAM调制方式，搭建了SISO和2×2开环空分复用两种模式的传输链路，在平坦衰落信道中的仿真结果表明：DL-SCH处理在信噪比（Signal-to-noise ratio，SNR）大于6dB时显著改善误码性能；SISO传输速率低于MIMO模式，但低信噪比时有更好的误码性能，SNR大于15dB后两者均可实现无误码信息传输。

（2）考察天线相关性、频率选择性及多普勒效应对系统性能影响。仿真结果表明：天线相关性对系统性能影响显著，在使用ZF检测的PDSCH中，相关性系数从0增加至0.9，在10-3误码率下系统损失近14dB的信噪比，DL-SCH对性能改善有限；频率选择性使误码率下降趋势变缓，对各阶调制影响基本相同。多普勒效应下，经两层处理后系统性能无明显下降。

毕业论文关键词  LTE-FDD下行链路  DL-SCH  PDSCH  LS信道估计  ZF均衡  误码率

毕业设计说明书外文摘要

Title    Design and simulation of OFDM-based  wireless transmission downlink of LTE system       

Abstract

In order to satisfy the demand of mobile communication all over the world, 3GPP finished the standardization of LTE in Release 8. Recently，it has come into service and become increasingly matured. Data traffic is transmitted in DL-SCH and PDSCH channels. Efficient channel estimation and equalization is important to implement the reliable transmission in wireless channel because of distortion. We focus on the study and simulation of the LTE downlink transmission, which are as follows.

Firstly, We investigate on processing in PDSCH and DL-SCH, least squares (LS) channel estimator and ZF detector. Two downlink schemes using QPSK, 16QAM and 64QAM are designed and their transmission modes are SISO and 2×2 open-loop multiplexing, respectively. The simulation result shows that, DL-SCH processing significantly decreases BER when signal-to-noise ratio (SNR) is greater than 6dB in flat fading channel. Data rate of SISO system is lower compared to MIMO system while the former performs better in low SNR region. Both systems are error-free after SNR>15dB.

Secondly, we do simulation to study the impact of antenna correlation, Doppler Effect and frequency selectivity, respectively. The result shows that, antenna correlation has a great impact on BER performance. As the correlation coefficient of transmit antennas increases from 0 to 0.9 and BER is 10-3, the system SNR loss is about 14dB for ZF detection in PDSCH. The improvement of DL-SCH processing is limited. Frequency selectivity slows the decrease of BER and has similar influence on each modulation method. Doppler spread has no obvious impact on BER performance. 

Keywords  LTE-FDD  DL-SCH  PDSCH   LS estimation   ZF equalization

目   次

1  绪论 1

1.1  移动通信发展历史 1

1.2  3GPP LTE标准及研究现状 2

1.3  本文主要工作即内容安排 5

2  LTE物理层概述 6

2.1  LTE物理资源 6

2.2  物理层基本概念 8

2.3  本章小结 9

3  基于LTE-FDD的下行物理层传输链路仿真设计 10