中文摘要：

我国高速铁路的快速发展迫切需要更可靠的传输技术以保障列车安全.MIMO分集技术中的极化分集和空间分集可以有效提高在城区富散射环境下的传输可靠性,但两者在高铁这种直射径较强环境下的分集性能需要进行分析研究.本文基于WINNERⅡ（Wireless World InitiativeNew RadioⅡ）D2a高铁信道模型对LTE下行链路在不同接入方式和不同列车运行速度下两种多天线（Multiple Input Multiple Output,MIMO）分集方法的误比特率（Bit Error Rate,BER）性能进行了仿真比较.结果显示,在WINNERⅡD2a信道模型中空间分集的BER性能优于极化分集.

英文摘要：

There is an urgent need for more reliable transmission technologies in order to ensure the safety of train because of the rapid development of the high-speed rail.The spatial and polarization diversity which are two different implementations of MIMO diversity can effectively improve the transmission reliability in a rich scattering environment as urban.However,the diversity performances of the two methods need to be analyzed and researched in the environment as high-speed rail scenario which has a strong LOS（Light of Sight） path.The BER（Bit Error Rate） performances of the two diversity methods in LTE downlink under different access schemes and velocities are simulated and compared in this paper based on WINNERⅡ D2a high-speed rail channel model.The results indicate that the BER performance of spatial diversity is better than polarization diversity using WINNERⅡ D2a channel model.