【作者】 何弦；

【导师】 苗建松；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2013， 硕士

【摘要】 本文针对在高速铁路TD-LTE系统下发生小区切换时存在掉话频繁,信号质量差等问题展开研究,着眼于切换过程中切换测量和切换判决阶段参数的选择和计算,提出适合高速环境的参数优化算法,并搭建LTE仿真平台进行验证。首先从理论上对LTE系统的架构、协议以及切换过程进行详细的分析,搭建了基于高速山地环境切换过程的仿真平台,以便对后续优化的算法进行验证。针对切换测量过程,提出测量参数优化算法,搭建物理层链路级仿真平台,对优化算法进行验证,得到不同的信道环境对切换测量参数RSRP和RSRQ的影响,提出不同的测量参数组合方案以适应不同的信道环境。为了减小信道环境中阴影衰落的影响,实现了滤波过程,结合LTE系统级仿真平台对不同速度下的滤波参数进行确定。最后,基于LTE协议标准中的A3事件,提出适合高速山地环境的自适应切换算法,根据前面提供的系统参数对优化算法进行仿真,得到不同速度下的最优控制参数HO_Hyst和TTT的组合,验证了自适应算法的性能,该算法可以使发生乒乓切换和链路连接失败的概率降到最低,大大提高用户体验。更多还原

【Abstract】 The purpose of this paper is to research on the problem of frequent dropping calls and poor signal quality of TD-LTE system in high-speed railway environment. The paper mainly discusses the parameters of handover measurement and handover decision in the handover process. The handover algorithms are proposed and the simulator is used to perform this process and illustrate algorithms and results. Firstly LTE system architecture, protocols, and handover process are analysed as a theoretical basis. In order to verify optimized algorithms, a simulation platform in a high-speed hilly environment is set up. For handover measurement process, a optimized algorithm about measurement parameter is proposed and verified in physical layer downlink level simulation platform. Moreover the simulation result is to evaluate the impact of channel environment and bandwidth on the RSRP and RSRQ measurement. To reduce the impact of the Shadow fading environment, the filter process is utilized. The filter parameters for the different speeds are determined by LTE system level simulation platform. Finally, the adaptive handover algorithm is proposed for high-speed hilly environment. The optimal combination of control parameters HO_Hyst and TTT under different speeds are achieved. In that condition the performance of the algorithm is verified. The algorithm can minimize the probability ping-pong handover and radio link failure, greatly improving the user experience.更多还原