lteadvanced系统中下行多用户mimo研究.docx

摘要
摘 要
随着移动通信的快速发展,用户对多媒体等高速率数据传输业务有了更高的要求。当今频谱资源紧缺,如何更有效的利用有限的频谱资源是下一代移动通信亟待解决的问题。3GPP LTE/LTE-Advanced 作为高速率、低延迟的第 4 代移动通信的重要代表, 通过利用 OFDM 和 MIMO 技术期待解决这一问题。在 LTE-Advanced 系统中不仅仅是单用户 MIMO , 还引入了多协作用户的虚拟 MIMO(Multi-user MIMO)技术。本文针对 LTE-Advanced 下行链路系统的 MIMO 技术做了细致的研究。
单用户 MIMO 技术包括:发射分集、空间复用和 Beamforming。发射分集通过发送信号多个副本,提高系统传输可靠性。空间复用将数据复用在多根天线上同时发送,提高了系统吞吐量和频谱利用率。Beamforming 技术定向发送数据,对用户尤其是小区边缘用户的性能提高作用明显。本文对三种技术的接收检测算法也做了相应研究。
MU-MIMO 的最大问题是协作用户之间的多用户干扰。本文针对消除多用户干扰和优化各协作用户信号强度研究了多种预编码算法,包括迫零、MMSE、 BD/BD+SVD 和 MET 算法。预编码通常需要发送端知道一定信道状态信息,针对 TDD 与 FDD 双工模式反馈信道信息方案的区别,分别用了基于信道状态信息、基于长期信道相关矩阵和基于码本序号的反馈算法。
为了验证提到的 MIMO 预编码算法,搭建了基于 LTE 物理层协议标准的 MATLAB 仿真平台。仿真结果很好的验证了理论分析的正确性。本文提到的算法从实现的复杂度和性能的角度,都具有很强的工程价值。
关键词:增强型长期演进,多用户多天线,预编码
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ABSTRACT
ABSTRACT
With the rapid development of munication, high-speed multimedia data transmission services have higher requirements. Today's spectrum scarcity of resources, how to make more effective use of limited spectrum resources is the big problem for the next generation of munication to be solved. As an important member of the fourth generation munication which has the feature of high-speed and low-latency,3GPP LTE/LTE-Advanced use OFDM and MIMO as its core technology to solve the problem. LTE-Advanced system, not just single-user MIMO, also introduces a collaborative user virtual MU-MIMO (Multi-user MIMO) technology. In this paper, MIMO technology of the downlink system in LTE-Advanced was meticulously researched.
Single-user MIMO includes three schemes: transmit diversity, spatial multiplexing and beamforming. Transmit diversity by sending several copies of the signals to improve the reliability of system transmission. Spatial multiplexing data multiplex signals on multiple antennas at the same time to improve the system throughput and spectral efficiency. Beamforming transmitted directional signals to improve the performance of cell edge users. Detection algorithms of receiving system of the three techniques were also i