【作者】 王俊峰；

【导师】 滕建辅；

【作者基本信息】 天津大学 ， 信息与通信工程， 2012， 博士

【摘要】 作为第三代移动通信标准之一的TD-SCDMA系统，从2009年工信部正式向中国移动发放牌照以来，得到了广泛的应用。随着TD-SCDMA网络建设工作的不断扩大和深入，需要考虑各种应用场景的需求，如高铁环境。为了使移动台在各种环境下能够稳定、良好地运行，通常需要首先分析环境特点并给出比较精确的仿真模型，然后分析此环境对移动台接收信号产生的影响，最后给出相应的解决方案。基于上述提高系统性能的分析思路，本文在天津市科技创新专项基金的资助下对信道建模、频率偏差估计和信道衰落系数估计三方面的关键技术进行了深入研究，主要工作内容和研究成果归纳如下：1、介绍了无线信号传播环境的特征，分析了用于物理层设计和性能分析的小尺度衰落模型的几种基于正弦波叠加法产生频率平坦Rayleigh衰落信道的方法的利弊。针对这些方法的不足，利用不同于现存模型的正余弦函数、入射角等参数，提出了两种改进的能产生不相关Rayleigh衰落波形的方法，同时推导了这两种方法的统计特性，并通过仿真实验验证了其性能。基于上述改进方法，通过叠加视距成分，提出了频率平坦Rician衰落信道模型，然后给出了其统计特性，并对其进行了仿真验证。在此基础上，给出了频率选择性Rician衰落波形的生成方法。所提方法不仅能够满足本论文中广义不相关散射信道模型的需要，而且通过对其修改也可以应用于多输入多输出信道建模。2、分析了频率偏差对系统性能的影响，研究了各种环境下系统的频偏补偿方法。为了克服现有方法未考虑载波频偏和多普勒频移共存的情况和在Rician快衰落信道下的不足，分别提出了频率平坦和频率选择性Rician快衰落环境下TD-SCDMA系统下行链路频偏估计的算法。这两种方法首先给出了受加性高斯噪声影响，并包含未知载波频偏、未知Rice因子和未知多普勒频移等参数的接收信号的二阶和四阶统计量，然后对这些统计量通过合理的参数设置和具体的数学运算推导出频偏估计的闭式表达式，最后通过仿真验证了所提算法的性能。对比两种环境下频偏估计方法发现其实现步骤相同，因此本算法降低了硬件实现的复杂度，特别适合于TD-SCDMA系统下行链路频偏估计。3、总结了现有信道衰落系数估计方法，针对现有算法在Rician快衰落信道下的不足和未考虑载波频偏的情况，将TD-SCDMA系统的时隙结构进行了轻微的改动，研究了残留频偏存在情况下TD-SCDMA系统修改时隙结构后信道衰落系数的特性，通过分析发现修改时隙后任意分组模块中带有残留频偏成分的信道衰落系数可以近似为时间参数的线性函数，并对其进行了仿真验证。基于上述分析，利用最大似然准则，提出了残留频偏存在下TD-SCDMA系统下行链路频率选择性Rician信道衰落系数估计算法。然后，进一步讨论了接收数据同时受高斯噪声和其他用户的加性干扰影响的情况，利用最小二乘准则估计了残留频偏存在下频率选择性Rician信道快衰落系数。最后，通过仿真验证了所提算法的性能，实验结果表明所提算法具有较小的均方误差。更多还原

【Abstract】 As one of the third generations of terrestrial-based mobile communicationsystem standards, Time Division-Synchronous Code Division Multiple Access(TD-SCDMA) system has been widely implemented since it granted its first license in2009. With the development of the construction of network for the TD-SCDMAsystem, variously applied scenarios should be considered, such as high speed railway.To make mobile station (MS) run on the safety and the steady, commonly, thecharacteristics of environments should be analysed firstly, and its accurate simulationmodel should also be established. Then, the effects of the circumstances on thereceived signal of the MS will be studied. At last, the scheme for solving thecorresponding problems should be put forward. Based on the above analyses, theproject founded by the Science and Technology Innovation Foundation of Tianjinunder Grant10FDZDGX00400has been set up, and three key technologies onchannel simulator, frequency offset (FO) estimator, and estimation for channel fadingcoefficients (CFCs) have been considerably studied in this dissertation. The mainresearch contents and contributions are as follows:First, the characteristics of wireless propagation environments are introduced,and the pros and cons about several methods of frequency-flat Rayleigh simulatorbased on sum-of-sinusoids are analysed. In order to overcome these deficiencies, twoimproved methods are proposed to simulate the uncorrelated Rayleigh fadingprocesses by applying a smart parameter computation method to the arrival angle andemploying some parameters and functions that differ from those in the existingmodels. Meanwhile, the statistical properties of these two models are derived andverified by simulation. Based on the above methods and the zero-mean stochasticsinusoid, a new stochastic frequency-flat Rician fading simulation model is proposed.Its properties are presented and verified. Then, an approach is presented to generatethe frequency-selective Rician fading waveforms. The proposed methods can not onlysatisfy requiments of this dissertation, but also use for the multiple-inputmultiple-output channel simulation by revising them.Second, the effects of FO on the performance of radio mobile system areanalysed, and the methods about the correction of the FO are studied. Unfortunately, all of the aforementioned works are unavailable for the Rician fading channels.Furthermore, to the best of our knowledge, all the existing methods are unable toprovide satisfactory frequency estimation for frequency-flat or frequency-selectiveRician fast fading channels when the carrier frequency offset (CFO) and Doppler shiftcoexist. To solve the problems for these situations, two FO estimation algorithms areproposed for the downlink of the TD-SCDMA system over frequency-flat andfrequency-selective Rician fast fading channels, respectively. The proposedalgorithms present second-order and fourth-order statistics of the signals whichcontain unknown CFO, unknown Rice factor, unknown Doppler shift, additive whiteGaussian noise (AWGN), etc. Based on flexible parameters setting and concretemathematical operations for these statistics, an expression for FO estimation isderived in closed-form. The simulation results are provided to illustrate the accuracyand reliability of the proposed method. The same realized steps of the proposedapproaches are found by comparing them, so the computational load is low, which cansatisfy the downlink of the TD-SCDMAsystem extremely.Finally, the estimated methods for CFCs are summarized. Aiming at thedeficiencies over the Rician fading channels and reckoning without the CFO for theexisting algorithms, the burst structure is slightly modified, and the characteristics ofthe CFCs over the modified burst are studied. Then, the CFCs with a residualfrequency offset (RFO) for each block of the modified burst structure is modeled as alinear function of time, which is analysed and verified by theory and computersimulation, respectively. Based on this approximation, a new scheme is proposed toestimate the frequency selective Rician CFCs for the downlink of the TD-SCDMAsystem in the presence of a RFO. In addtion, taking account of the case where theAWGN and additive interference coming from other users coexist, the algorithm forthe CFCs in this condition is proposed. The simulation results illustrate that theproposed method leads to small mean square error.更多还原