【作者】 常连；

【导师】 刘宝玲； 张建华；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2013， 硕士

【摘要】 无线信道中传输的电波信号会由于多种衰落机制的共同作用而引入失真、噪声和干扰。为了有效抑制无线通信系统性能的恶化,必须在收发端选择合理的调制、编码、均衡等信号处理技术。在进行抗衰落技术研发和设计的过程中,为了对算法和系统的性能进行评估,首先需要对无线信道的衰落特性进行深入的研究并建立起相应的数学模型。然而无线信道是一个时变的衰落信道,其易变性是目前电波传播理论研究领域的主要难点。为此,本论文以移动通信系统电波传播理论为背景,按照实际测量与理论分析相结合的研究路线,在信道模型与时变衰落特性两个方面开展了理论研究和工程实践,主要工作包含两个方面：(1)宽带移动通信系统电波传播信道模型的仿真研究。工程实践中,信道模型的应用主要有两种：用于基带算法数值分析的计算机蒙特卡洛仿真和用于频带系统性能评估的信道模型仿真仪表。面向第一种仿真应用,本论文结合室内、外典型场景下的信道测量数据,分析比较了ITU-R以及WINNER所提出信道模型(即M.2135模型以及WINNER Ⅱ模型)对无线信道频率相关性以及多径相关性的仿真结果。随后,基于两种信道模型生成的信道冲激响应(Channel Impulse Responses, CIRs)分别开展LTE链路级仿真。通过对误比特率以及小区吞吐量仿真结果的统计比较,本文分析了ITU-R以及WINNER所提模型对仿真结果的影响,同时,基于对仿真结果置信区间以及模型参数收敛速度的统计分析,本文进一步探讨了上述两种模型对仿真效率的影响。基于上述分析结果,本文对仿真过程中的模型选择给出了建议。面向第二种仿真应用,本文提出了一种通用的信道模型仿真仪表评估方案。通过对信道模型仿真仪表内嵌信道模型程序生成的信道参数以及从仪表输出的衰落信号中提取的信道响应进行验证,该方案能够从软件程序和硬件实现两个方面来对信道模型仿真仪表进行校准和评估。(2)移动通信系统电波传播的时变信道分析与估计。首先,本文简单概述了传统的多径束识别算法,在此基础上,针对时变信道中多径束动态变化的特性,提出了一种多径束的连续识别算法。该算法通过m阶马尔科夫随机过程来模拟无线信道参数的变化过程。利用该算法,本文从外场测量的时变信道冲激响应中提取了无线信道的时变传播特性,并对其变化过程进行统计建模。此外,本文基于优化的导频设计提出一种新的时变信道估计算法。该算法在有效地抑制由于子载波间干扰所引起的估计误差的同时,有效地避免了由于导频密度增加而导致的频谱效率下降。本文的宽带信道模型评估方法以及信道模型仿真仪表验证方案为信道建模与仿真领域的研究工作提供了工程性的参考,相关分析结果对移动通信系统性能仿真而言也具有一定的借鉴意义。本文基于Markov随机过程提出的多径束连续识别算法可广泛应用于时变信道电波传播特性的分析中,同时,文章通过对时变信道估计算法的研究在未来高速移动通信系统接收机的设计领域也进行了积极的探索。更多还原

【Abstract】 Due to the complicated fading mechanisms, signals may encounter severe distortion, noise and interference when they propagate in the radio channels. To suppress system performance deterioration, the appropriate signal processing techniques, such as modulation, coding, and equalization, should be employed at both transmit and receive ends. During the research and development of anti-fading techniques, the in-depth investigation and reliable model of the fading characteristics provide important foundation for the performance evaluation of algorithms and systems. However, due to the dynamic properties of wireless environments, the radio channels show time-varying characteristics, which is one of the biggest challenges in the radio propagation research. So, taking the radio signal propagation theory as background, this thesis dedicates to the investigation and research of the wireless channel models and time-varying properties for the mobile communication systems. Based on the channel measurements and theoretical analysis, some solid achievements have been obtained in this thesis. The main contributions of this thesis are as follows,(1) The radio channel models of wideband mobile communication systems are evaluated and researched. Generally, the typical engineering applications of radio channel models include the Monte-Carlo simulation of baseband algorithms and channel model emulator designed for radio frequency (RF) system validation. Regarding the first engineering application, this thesis compares the frequency correlation and multipath correlation of the channel models proposed by the ITU-R and WINNER (i.e. the M.2135model and WINNER Ⅱ model), based on the indoor and outdoor channel measurement data. Moreover, these two models are used to generate channel impulse responses (CIRs) for the LTE link level simulation. According to the bit error ratio (BER) and cell throughput statistics, the effects of M.2135and WINNER Ⅱ on the simulation results are studied. Based on the analysis of confidence interval and convergence rate of the simulation results, the effects of M.2135and WINNER Ⅱ on the simulation efficiency are also investigated. This thesis also provides related suggestions for the model selection considering specific simulation requirements. Regarding the second engineering application, this thesis proposes a general validation scheme for the channel model emulator. By validating the channel parameters generated by the integrated model programs of Propsim-F8and CIRs extracted from the fading signals, the scheme verifies the reliability of channel emulators from the perspective of software and hardware.(2) The fading characteristics and channel estimation algorithms of time-varying channels are investigated in this thesis. The traditional multipath cluster identification algorithm is introduced, following that, a continuous identification algorithm, which uses the m-step Markov process to model the channel variation, is proposed for the multipath clusters in time-varying channels. Based on the continuous identification algorithm, this thesis investigates and models the time-varying fading properties of realistic radio channels obtained through measurement. Moreover, this thesis proposes a novel time-varying channel estimation algorithm with optimized pilot pattern. The proposed algorithm effectively reduces the estimation deviation induced by inter carrier interference and avoids the increase of pilot density and decrease of spectrum efficiency.The wideband channel model evaluation method and channel emulator validation scheme proposed in this thesis provide practical references for channel modeling and simulation research, and the relevant analysis results are informative for mobile communication systems simulation. Moreover, the Markov-based cluster identification algorithm can be widely used in time-varying channel analysis, and the proposed time-varying channel estimation algorithm provides the foundation for the receiver design of high-speed mobile communication systems.更多还原