高速移动环境下TD-LTE上行链路传输技术的研究

发布时间：2018-03-14 04:20

本文选题：高速铁路　切入点：上行链路传输系统　出处：《兰州交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：为了满足高速数据传输业务以及需求,新一代长期演进的移动通信系统(LTE)应运而生,其下行采用了正交频分复用多址(OFDMA)的技术,上行采用了单载波频分复用(SC-FDMA)的技术。高速运动环境下多普勒频移的增大会使得信道产生快速时变的衰落,并且破坏了子载波之间的正交性,使得系统尤其是上行链路的性能受到严重的影响。因此,对于高速移动环境下上行链路传输系统,本文从多普勒频偏的估计技术和时变信道的估计技术两个方面来进行了较为深入的研究,下面即为本文主要的研究工作内容:首先进行了上行链路信道的研究,分析研究了高速移动传输信道以及影响上行链路传输系统性能的主要因素,给出了国内外的高铁信道模型,进行了国内的高铁在不同场景下信道传输模型的研究,并且得到了上行链路传输系统的时变信道模型。此外,从相同信道场景和不同信道场景两个方面,分析了影响TD-LTE上行链路系统性能的几个主要因素。其次进行了上行链路中多普勒频偏估计技术的研究,研究了现有的传统频偏估计的算法,提出了改进的频偏估计算法。在高速场景下,改进方法采用粗估计与精估计结合的方法,利用自回归模型在子帧之间对于频偏估计值进行跟踪处理,因此提高了估计的精度,降低了噪声的干扰以及计算复杂度。给出了改进算法与现有算法系统性能仿真比较,结果表明改进算法具有更好的性能增益。最后进行了上行链路中时变信道估计技术的研究,分析了现有的信道估计算法,根据现有信道估计算法的不足之处提出了改进算法,即先在重新定义的变换域中处理,在一子帧的长度上利用多项式拟合的方法得到信道上所有符号上的参数估计值,在子帧间采用带有变化跟踪因子的AR模型进行跟踪处理,因此提高了信道上导频符号两端数据符号参数估计值的精度,再根据信道之间的转换关系,将其从变换域转换到频域中。所得到的信道估计响应是可以进行频域均衡的。仿真分析比较了改进算法与现有算法系统的性能优劣,改进算法降低了系统计算复杂度,因此更具优势。
[Abstract]:In order to meet the needs of high-speed data transmission, a new generation of long-evolving mobile communication system (LTEs) emerges as the times require, and its downlink adopts OFDMA (orthogonal Frequency Division Multiplexing) technology. The uplink uses SC-FDMA (single Carrier Frequency Division Multiplexing) technique. The increase of Doppler frequency shift in high-speed moving environment will cause fast time-varying fading of the channel and destroy the orthogonality between subcarriers. The performance of the system, especially the uplink, is seriously affected. Therefore, for the uplink transmission system in high-speed mobile environment, In this paper, the Doppler frequency offset estimation technique and time-varying channel estimation technology are studied in depth. The following is the main work of this paper: firstly, the uplink channel is studied. The high speed mobile transmission channel and the main factors affecting the performance of uplink transmission system are analyzed, and the domestic and foreign high-speed rail channel models are given, and the channel transmission models of the domestic high-speed rail transmission system under different scenarios are studied. Moreover, the time-varying channel model of uplink transmission system is obtained. Several main factors affecting the performance of TD-LTE uplink system are analyzed. Secondly, the Doppler frequency offset estimation technology in uplink is studied, and the existing traditional frequency offset estimation algorithms are studied. An improved frequency offset estimation algorithm is proposed in this paper. In high speed scene, the improved method combines coarse estimation with refined estimation, and uses autoregressive model to track the frequency offset between subframes, so the estimation accuracy is improved. The simulation results show that the improved algorithm has better performance gain. Finally, the time-varying channel estimation technique in uplink is studied. In this paper, the existing channel estimation algorithms are analyzed, and an improved channel estimation algorithm is proposed according to the shortcomings of the existing channel estimation algorithms, that is, it is first processed in the redefined transform domain. The parameter estimation of all symbols on the channel is obtained by polynomial fitting on the length of a subframe, and the AR model with variable tracking factor is used to track the parameters between subframes. Therefore, the accuracy of the estimation of the data symbol parameters at both ends of the pilot symbols on the channel is improved, and then according to the conversion relationship between the channels, The channel estimation response can be equalized in frequency domain. The performance of the improved algorithm is compared with that of the existing algorithm. The improved algorithm reduces the computational complexity of the system. So it has an advantage.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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