【作者】 王琳；

【导师】 李平安；

【作者基本信息】 武汉理工大学 ， 通信与信息系统， 2014， 硕士

【摘要】 多输入多输出（MIMO）系统为了实现空间分集，在发送设备和接收设备上配置了多根天线，这样能够很好的提高无线通信系统的传输速率和频谱效率。第三代合作伙伴（3rd Generation Partnership Project,3GPP）通过开展第三代移动通信系统的长期演进（Long Term Evolution,LTE）项目，以适应移动通信行业的发展。MIMO是LTE项目中的一项关键技术，受到了广泛关注和研究。LTE中定义了8种MIMO传输模式。当UE移动速度较慢，并且信道环境较好时，闭环MIMO传输方案带来的吞吐量增益良好；而当UE移动速度较快，并且传输信道信噪比较高时，可以采用开环MIMO方案。当信道的质量较高时，eNodeB（LTE基站）为了提高系统吞吐量，可以使用空间复用的方案；而当信道质量较低特别是信道相关性较强时，提高传输的可靠性，应采用传输分集方案。但没有任何一种传输模式能适应所有无线信道环境的场景，所以为了能够同时满足传输质量和吞吐量的要求，需要根据实际信道特性对传输模式进行动态的切换。由于用户在移动且需求具有异构性，信道状态也具有时变性，基站以及终端在满足传输可靠性的前提下，需根据传输环境的变化迅速地切换到符合信道条件的传输模式，提高频谱利用率，增加系统容量。但是LTE协议中没有给出MIMO传输模式间切换算法和方法。本文旨在研究LTE系统下行链路MIMO模式间的切换技术。提出TM2（传输模式2）与TM3（传输模式3）和TM2（传输模式2）与TM4（传输模式4）之间的切换算法。并编写C代码对算法进行实现，分别给出了L3（RRC层，RadioResource Control：无线资源控制）判决模式切换流程、TM2切换到TM3流程、TM3切换到TM2流程以及开关配置流程。最后搭建实验测试平台，在此平台上测量模式间切换门限值，并对模式间切换功能进行验证。实验结果表明，LTE下行MIMO模式TM2与TM3和TM2与TM4之间的切换技术得以实现。更多还原

【Abstract】 Multiple input multiple output (MIMO) system configure multiple antennas onthe transmitting device and receiving device in order to achieve space diversity, andthis is conducive to increasing the transmission rate and spectrum efficiency ofwireless communication system. The3rd Generation Partnership (3rd GenerationPartnership Project,3GPP) adapts to the development of mobile communicationsindustry through the long-term Evolution of the third Generation mobilecommunication system (Long Term Evolution, LTE) projects. MIMO is a keytechnology of the LTE project, which has received wide attention and research.LTE defines the eight kinds of MIMO transfer modes. When the UE move slowerand channel environment is good, the closed-loop MIMO transmission scheme bringsbetter throughput gain good; When the UE moves faster and transmission channelsignal noise ratio (SNR) is high, LTE can use open-loop MIMO scheme. When thechannel is high, the quality of the eNodeB (LTE base station) can use the spatialmultiplexing scheme in order to improve the system throughput; When channelquality is low especially channel correlation is strong, In order to improve thereliability of transmission, transmit diversity scheme should be adopted. However, notransfer mode can adapt to any kind of scene all radio channel environments. so Inorder to satisfy the transmission quality and throughput requirements, LTE shouldswitch the transmission mode dynamically according to the actual channelcharacteristic. Due to user demand in mobile and heterogeneity, also has atime-varying channel status, base stations and terminals on the premise of meet thetransmission reliability, based on the transmission environment changes quicklyswitch to meet the requirements for the channel transmission model, improve thespectrum efficiency, increase the system capacity. But the algorithms and methods to switch the MIMO transmission mode are not provided in LTE protocol.The purpose of this paper is to study the switching algorithm between MIMOmodels in the LTE system downlink link. The paper proposes the switching thresholdmethod between TM2(transfer mode2) and TM3(transfer mode3), and betweenTM2(transfer mode2) and TM4(transfer mode4), and write C code to achieve thealgorithm. At the same time, the paper respectively gives switching process ofjudgment mode in the L3(RRC layer, Radio Resource Control: Radio ResourceControl), and the process switching from TM3to TM2.Finally we set up theexperimental test platform to verify the rationality of the algorithm. The experimentalresults show that the switching threshold between TM2and TM3, and between TM2and TM4is consistent with the theory in the LTE system downlink link, and theswitching threshold method is verified by measurement.更多还原