【作者】 贺智轶；

【导师】 陈伟；

【作者基本信息】 武汉理工大学 ， 通信与信息工程， 2009， 博士

【摘要】 移动到移动(mobile-to-mobile,M2M)通信系统是一种不基于固定式基站的移动通信系统,为两个或多个移动用户提供直接的端到端无线通信,即在M2M通信系统中,移动终端彼此直接互连,相互交换无线数据业务而无需基站转发。M2M通信系统具有广泛的应用前景,典型的如ad-hoc网络和目前较为热门的协作分集网络,以及未来的移动宽带网状网和应用于智能交通的车辆间通信系统。我们知道,对于设计一个新的网络架构的无线通信系统首要任务之一就是要弄清楚无线通信链路的信道特性。只有有了可靠的无线信道信息才能有效、及时、和实用地设计并测试该通信系统。信道的认知要求理解各种损耗,如多径衰落、时变衰落、频率选择性衰落等。利用这些信息,通信系统才能设计得具有理想或接近理想的性能。M2M通信信道不同于经典的蜂窝网络信道,目前已有的许多信道模型不能运用于M2M通信系统,也没有已知的信道模型可以直接用来描述M2M信道的衰落和空-时-频域行为。同时,多输入多输出(MIMO)技术作为提高信道容量和增强信道可靠性的一种重要技术手段,将广泛应用于未来的M2M通信系统。因此,在研究M2M通信系统衰落信道的同时,必须建立MIMO信道模型,充分研究信道的空间特性。为此,本文以M2M衰落信道特性研究为主题,结合理论研究和计算机仿真等手段,在M2M信道建模和统计特性分析方面展开研究,致力于建立新的M2M通信信道模型及反映真实街道传播环境的信道模型。尤其是结合MIMO技术,研究空-时-频域中的M2M衰落信道统计特性。论文的主要研究工作和创新点如下:(1)基于确定性仿真模型建模方法,分析了精确多普勒扩展(MEDS)和Lp-norm算法的确定性模型参数算法,研究了这两种算法所建立仿真模型与随机模型的逼近精确度,分析了仿真模型谐波数量对相关特性的影响,并针对M2M衰落信道确定性模型参数对两种算法进行了改进,为M2M信道确定性仿真模型的建立提供了理论基础。(2)采用基于几何散射模型的信道建模方法,提出了残缺双环几何散射分布模型,给出了宏蜂窝MIMO M2M频率非选择性衰落信道参考模型,研究了该模型的时域自相关特性以及空域互相关特性,并给出了功率谱密度的闭合形式。为宏蜂窝MIMO M2M频率非选择性衰落信道仿真模型的建立奠定了基础。(3)在宏蜂窝MIMO M2M频率非选择性衰落信道参考模型的基础上,针对参考模型的随机性导致模型统计结果的不确定的缺点,提出了确定性仿真模型。同时采用了MEDS和Lp-norm算法对模型参数进行确定性计算,分别给出了时域自相关闭合表达式、空间相关表达式以及空.时联合相关函数闭合形式。并分析了2x2天线阵列发射和接收天线振子之间的相关性以及普遍采用的4x4天线阵列、6x6天线阵列的平均信道容量。研究结果证明了该仿真模型的有效性和可靠性,为分析M2M衰落信道特性和设计M2M通信系统提供了理论依据。(4)建立基于室外街道散射环境的MIMO车辆对车辆(vehicle-to-vehicle,V2V)信道模型。提出了街道交叉路口传播环境的散射模型,简称T-模型。并建立了发射角(AoD)和到达角(AoA)之间的准确关系,该关系的确立对角度扩展的研究具有指导意义。另外,该模型的建立同时引入了单次散射机制和双重散射机制,通过对不同散射能量分布的调整,使得模型更加适用于真实的交叉路口传播环境。进一步研究分析了T-模型的统计特性,包括空-时-频互相关特性。该研究工作所提出的信道模型对于智能交通的车辆间通信系统的设计、测试和分析具有一定的参考价值。更多还原

【Abstract】 Mobile-to-Mobile (M2M) communication system is a kind of mobile communication system which is not depending on the fixed base station. In M2M communication system, two or more mobile terminal communicate each other in directly, which means mobile users share their information without fixed base station relay. There are many potential applications of M2M communication, such as ad hoc network, cooperative distribution network, wideband mobile mesh network and inter-vehicle communications.However, the most risk task of designing a wireless communication system is figuring out the characteristics of the channel. Only after get reliable wireless propagation properties of the channel, the system could be designed successfully. The reorganizations of the channel require understanding kinds of deterioration, such as multi path loss, time varying fading, spatial selecting fading, etc. By using these information, the performance of the system could approach the ideal or Quasi-ideal. Furthermore, M2M communication system is totally different from modern cellule systems, the exist channel model could not be used to describe the propagation properties of the M2M fading channels, meanwhile, there are not sufficient research results could be used to explain the space-time-frequency characteristics of M2M channels. Modern communication systems rather tend to exploit the channel knowledge for increasing system reliability and capacity by employing techniques such as MIMO. Schemes such as MIMO diversity are being employed in future mobile communication systems. Thus, a good understanding of the space properties of MIMO channel is the key for extending the limits of M2M communication systems.With those views in mind, we focus on the research of M2M fading channel properties, by utilizing the computer simulations method, modeling the M2M channel model and analyzing the statistical properties of the channel. We committed building the new M2M fading channel model for real street wireless propagation conditions. The main contains of the paper and research contributions are briefly summarized as below.(1) Deterministic simulation model parameters methods analyzing. This analyzed spread Doppler extends method and Lp-norm method, and measured the correspondence between the simulation model and statistical model. And then explained the effects caused by numbers of the sinusoidal harmonic function. Finally, we extended the methods to fit for the M2M fading channel modeling. The theory research work is basic work for M2M channel deterministic modeling.(2) Geometrical modelling for a wireless transmission link between two mobile stations. We show how a reference model for the path gains can be derived from the geometrical model and provide general expressions and close forms for the transmit and receive space-time correlation functions. The procedure presented in the paper provides an important framework for macro cell MIMO M2M frequency non-selective fading simulation modeling.(3) Deriving a MIMO M2M channel simulation model from a non-realizable reference model presented in our paper. We present a closed-form solution of the model parameters by using MEDS and Lp-norm method. In case of isotropic scattering, we illustrate some numerical results for space-time correlation functions. Meanwhile, extended the reference model in 2×2 antenna elements with respect to an arbitrary number of antenna elements, such as 4×4, 6×6, at the transmit and receive side. Finally, simulation results show an excellent correspondence between the statistical and time average of the MIMO channel capacity.(4) Modelling a new wideband MIMO fading channel model for vehicle-to-vehicle (V2V) communications. The MIMO V2V channel model, called for brevity T-model, captures the propagation effects that occur if vehicles move towards a junction with a side road and corner buildings. The starting point for the derivation of the T-model is a new geometric T-junction scattering model, where both single- and double-bounce scattering mechanisms are assumed. Our geometry-based channel model takes into account the exact relationship between the angle-of arrival (AoA) and the angle-of-departure (AoD). The statistical properties of the T-model are studied under the assumption of non-isotropic scattering. An analytical solution is provided for the space-time-frequency cross-correlation function (STF-CCF) from which several other important characteristic quantities like the temporal autocorrelation function (ACF) can directly be obtained. The achieved theoretical results are illustrated for a typical T-junction propagation scenario. This research work provides designers of MEMO V2V communication systems an important tool in form of a wideband spatial channel model enabling the performance analysis of new high data rate transmission schemes under propagation conditions occurring at T-junctions.更多还原