室外3.5 GHz电波传播特性研究

由于目前对下一代移动通信的备选频段——室外3．5GHz电波传播特性的研究还很少,基于此,应用射线跟踪法对室外3．5GHz频段的电波传播特性进行了研究。介绍了城市微小区中的电渡传播机制、射线跟踪法的基本原理和几种常用的射线跟踪方法,并在3．5GHz对街道拐角绕射、发射天线的高度对传播特性的影响以及3．5GHz的功率时延特性进行了研究,得出了路径损耗与建筑物的分布及街道宽度有关以及对发射天线高度不是很敏感的结论。     

基于改进射线跟踪法和BP神经网络算法的室外微蜂窝毫米波信道特性研究

在28 GHz与39 GHz毫米波频段室外微蜂窝场景下,基于改进射线跟踪法和反向传播(back propagation, BP)神经网络算法对毫米波单发单收信道及单发多收信道进行建模仿真研究. 在得到的无线信道仿真数据基础上,研究分析了毫米波信道的路径损耗、均方根(root-mean-square, RMS)时延扩展(delay spread, DS)、接收功率等传播特性. 通过与现有文献的测量结果对比分析验证了改进射线跟踪法的正确性与有效性. 通过BP神经网络方法拟合得到的路径损耗模型参数结果与改进射线跟踪法仿真得到的路径损耗参数结果对比发现,两者吻合程度很高,验证了BP神经网络算法能很好地对室外微蜂窝毫米波信道大尺度参数进行预测. 同时,文中给出了一种普遍适用的用来表征室外微蜂窝视距(line-of-sight, LoS)与非视距(non-line-of-sight, NLoS)场景下28 GHz与39 GHz毫米波信道的路径损耗模型. 结果表明:LoS场景下的RMS DS和接收功率都小于NLoS场景下得到的结果;LoS场景与NLoS场景下RMS DS、水平方向到达角、多径簇的个数累积分布函数均服从高斯分布;RMS DS在毫米波频段微蜂窝场景下,随着频率的升高而增大,到达接收端的多径成簇呈现稀疏性.     

室内带金属家具环境的电波传播特性研究

射线跟踪方法是研究室内复杂环境电波传播特性的有效技术。基于改进的入射及反弹射线法和镜像法研究了室内有金属家具的电波传播特性,仿真结果与已知文献测量结果对比,一致性良好,证明了该方法在室内复杂环境预测电波传播特性的正确性和有效性。仿真结果表明：（1）视距传播（LOS）绕射对接收功率贡献很小,可以忽略;非视距范围内（NLOS）绕射贡献较大,不可忽略,三次反射对整个室内的接收功率影响都很小。（2）金属家具的存在导致了视距范围内接收功率的剧烈波动,非视距范围内的接收功率波动不明显。（3）有金属家具房间的均方根时延变化幅度大。（4）到达角在空房间中近似于均匀分布,加入金属家具后,在视距范围内波动剧烈。（5）受到达角的影响,多普勒频移变化情况与到达角分布一致。分析结果为室内有金属家具环境的无线通信系统设计提供了有效的理论依据。     

一种对室外到室内的电波传播进行预测的混和方法

射线跟踪(RT)法和时域有限差分(FDTD)法是研究无线电波传播的重要的方法,本文对基于混和法的室外到室内的电波传播预测进行了详细的介绍和讨论,同时通过计算结果来验证了此方法的有效性和准确性.     

视距传播模式下粗糙度对接收功率的影响

本文基于入射及反弹射线法对视距传播模式下的信道电波传播特性进行研究。在不同粗糙度条件下,针对接收功率的分布情况以及其特点进行了比较分析。仿真结果与文献已知结论一致性良好。     

基于SBR/IM的超宽带信号室内传播特性仿真和分析

基于入射及反弹射线法/镜像法对室内环境的超宽带信号传播进行了仿真和分析,仿真结果与测量结果的一致性良好,这验证了该方法的正确性.同时比较分析了仿真中得到的视距传播（LOS）和非视距传播（NLOS）的多径传播、接收波形、时延扩展和到达方向角分布等传播参数,仿真结果表明：（1）三次反射以上的射线对接收功率影响很小；（2）发射、接收天线极化方式一般可选择垂直极化；（3）超宽带（UWB）信号经历频率选择性衰落；（4）到达角分布近似于均匀分布.这些分析结果为超宽带通信系统室内覆盖提供了依据.     

毫米波室内传播场景的蚁群优势路径搜索方法

为更高效地实现毫米波室内传播特性分析，提出了一种基于蚁群算法的快速射线追踪方法. 该方法利用蚁群分布计算和启发式搜索原理寻找电波传播优势射线路径，并选取室内传播中能量较高的优势射线路径代替所有射线路径进行分析，用于降低算法复杂度和提高执行效率. 通过典型室内场景下28 GHz、32 GHz和38 GHz三个频率信道特性的仿真分析，对比WinProp工具分析结果，呈现较好的一致性，预测误差小于0.8 dB；对比传统射线追踪法，计算效率提高了378.9%. 上述结果表明本文方法在保证预测精度的前提下有效降低了计算复杂度，具有工程应用价值.     

28 GHz室内毫米波信道路径损耗模型研究

毫米波信道建模是第五代（the 5th Generation,5G）移动通信系统的关键技术,而路径损耗是表征毫米波信道传播大尺度衰落影响的重要参数.为了更好地理解毫米波信道的传播特性,应进行广泛的信道测量与建模.因此,对28 GHz室内环境进行了信道测量,并给出了相应的毫米波信道路径损耗模型,同时基于入射及反弹射线法/镜像法仿真分析了路径损耗传播特性.研究结果表明:实测结果与仿真结果一致性吻合良好,从而验证了入射及反弹射线法/镜像法的正确性;自由空间邻近（Close-In,CI）参考距离路径损耗模型表达式更简洁,鲁棒性更强.最后,本文给出了一种普遍适用的用来表征室内视距（Line-of-Sight,LOS）与非视距（Non-Line-of-Sight,NLOS）环境28 GHz与60 GHz毫米波信道的路径损耗模型.     

通信基站电磁辐射场强的系统建模与数值仿真

基于数字城市管理和射线跟踪算法的基本原理,采用三维实体环境建模、反向射线跟踪路径搜索和辐射场源射线多途径传播的场强合成算法,建立了一种对城市小区移动通信基站附近的电磁辐射场强进行系统建模与数值仿真的新方法.该方法有效克服了传统电波传播预测模型不能适应不同小区环境下的复杂建筑模型以及其他确定性方法不能精确找到电波传播路径的局限性.在城市小区的不同空间分布区域,本算法的计算机软件数值仿真结果与实地测量结果的良好一致性验证了该方法的实用性、有效性和正确性.     

改进射线跟踪法效率的新方法

提高射线跟踪法的运算效率一直是进行电波预测的一大难题,本文分析了影响射线跟踪法效率的诸多因素,提出了一种改进二维微小区室外环境射线跟踪法效率的有效方法。该方法对室外建筑物环境进行分组,同时对环境中的绕射点进行绕射分区,以减少射线同建筑物的求交运算次数,大幅提高射线跟踪法的计算效率。仿真结果表明这种方法是有效的。     

A hybrid technique based on combining ray tracing and FDTD methodsfor site-specific modeling of indoor radio wave propagation

The paper presents a hybrid technique based on combining ray tracing and finite-difference time-domain (FDTD) methods for site-specific modeling of indoor radio wave propagation. Ray tracing is used to analyze the wide area and FDTD is used to study areas close to complex discontinuities where ray-based solutions are not sufficiently accurate. The hybrid technique ensures improved accuracy and practicality in terms of computational resources at the same time since FDTD is only applied to a small portion of the entire modeling environment. Examples of applying the method for studying indoor structures and penetration of wave from outdoor to indoor are given at 2.4 GHz. Numerical results are compared with known exact solutions or results of the full wave analysis or traditional ray model to demonstrate the accuracy, efficiency, and robustness of the novel method. Numerical results are also compared with reported measurement results for waves at 1.29 GHz penetrating an external wall with metal-framed windows. Cumulative distributions of field envelope obtained from the hybrid method show close resemblance to the Rayleigh distribution, which conforms to the reported measurement results     

Three-Dimensional Urban EM Wave Propagation Model for Radio Network Planning and Optimization Over Large Areas

A new 3-D urban electromagnetic wave propagation model is presented. It provides fast 3-D deterministic predictions in urban radio configurations and over large areas. The various techniques to make it suitable to the network planning and optimization of large wireless networks are described. The resulting radio propagation maps exhibit seamless coverage between the various environments (dense urban, urban, and suburban). The model efficiently addresses all types of outdoor transmitter configurations (macrocells, minicells, microcells, and picocells) and all types of receiver locations (at ground level, over the rooftop, and at high building floors). It predicts the field strength as well as the dominant specular contributions of the impulse responses to build ray spectra (including delays and angles). Thus, the model may also be used to estimate the performances of new radio systems [diversity and multiple-input–multiple-output (MIMO)]. The narrowband power prediction of the model is evaluated by comparison with microcell measurements. The evaluation stresses the advantage of 3-D modeling compared with the vertical-plane approach or 2-D ray tracing. Finally, the ability of the model to simulate radio wideband characteristics in a complex environment is demonstrated by comparing delay-spread estimates to measurements collected from a high-macrocell transmitter in a hilly city and to arrival angles collected in a suburban macrocell area.      

预估城镇小区电波传播损耗的一种三维抛物方程算法

为城镇小区电波传播问题建立了一种三维抛物方程模型,并且用二维分部傅立叶变换方法求解。计算了几种不同地形上建筑物障碍分布的小区电波传播衰减因子,和UTD理论及数值积分方法计算出的结果吻合得比较好,从而验证该模型的有效性,同时也说明了三维抛物方程模型能更准确地反映出小区建筑物宽度对场的绕射作用,为城镇小区电波传播问题的估算提供了一种更为准确的算法模型。     

39 GHz室外微蜂窝信道测量、建模与仿真研究

基于39 GHz室外微蜂窝场景实测数据,开展了毫米波段路径损耗、阴影衰落和大尺度参数的建模与仿真研究.介绍了毫米波段喇叭旋转测量系统下空间交替广义期望最大化(Space-Alternating Generalized Expectation-maximization,SAGE)算法信号模型,优化的分簇算法与莱斯因子计算方法.基于SAGE提取多径参数,利用优化的分簇算法提取并分析了簇参数,包括簇内角度扩展、簇内时延扩展以及簇的数目,并根据测量结果验证了第三代合作伙伴计划(The 3rd Generation Partnership Project,3GPP)第五代(the 5th Generation,5G)移动通信标准推荐的仿真平台准确定性无线信道产生器(Quasi-Deterministic Radio Channel Generator,QuaDRiGa)在39 GHz的可用性.结果表明:在视距径下,方向性路损和全向路损在固定截距和浮动截距两种拟合方式下与自由空间路损模型接近;大尺度参数统计特性与基于毫米波的第五代集成通信移动无线电接入网络(Millimetre-Wave Based Mobile Radio Access Network for Fifth Generation Integrated Communications,mmMAGIC)、3GPP结论接近;视距径与非视距径的簇参数差别较小,且簇的个数较6 GHz下的频段更少.本文为5G毫米波39 GHz频段信道仿真和系统设计提供了重要的信道模型和参数.     

Millimetric wavelengths radiowave propagation for line-of-sightindoor microcellular mobile communications

Discusses millimeter waves for indoor microcellular communications. The results of propagation experiments conducted at 60.4 GHz (the oxygen absorption band) and 38.25 GHz to determine multipath characteristics in a number of indoor microcell channels employing omnidirectional antennas are presented. Cumulative distribution functions for received signal envelope, as well as corresponding power spectra are given. In addition, a comparison between the fading statistics measured at 60.4 GHz and 38.25 GHz under similar conditions is made. The change in multipath characteristics due to the presence of different building materials is also illustrated. A ray model is developed to represent indoor microcell propagation by considering a direct ray plus rays which have undergone single and double reflections from the walls. Specular floor-reflected and ceiling-reflected rays are included when the antennas radiation pattern does not preclude them. Using this simple model, the signal variations and the amplitude of reflected rays with respect to the line of sight (LOS) ray as functions of mobile receiver position are predicted and used to assist in interpreting experimental results. Theoretical results are found to be in good agreement with measured ones, with the model also being used to predict structure-induced root mean square (rms) delay spread along receiver routes in an indoor microcell environment. This parameter is a measure of multipath conditions in a mobile radio channel and is inversely proportional to the maximum usable data signalling rate of a channel     

Efficient ray-tracing acceleration techniques for radio propagationmodeling

Ray-tracing and uniform theory of diffraction techniques are already widely applied to site-specific radio propagation modeling for wireless applications. Software tools using such techniques may take considerable computation time in the analysis of the propagation conditions in a given environment even for a short mobile terminal route. Efficient acceleration techniques are required to make such analysis tools practical for the design of modern radio systems. To reduce computation time, ray-tracing routines must be applied only to those areas where rays are likely to exist. This is achieved by using ray-path search algorithms prior to performing any actual ray tracing. An efficient ray-path search algorithm is presented. First, a two-dimensional version is described, which is valid for indoor and microcell studies. Then, an extension to the three-dimensional case is explained in detail. Finally, the software tool Radio Tracer using such techniques is briefly described, and some comparisons between experimental results and computed predictions for indoor and outdoor scenarios are shown     

面向高速铁路车站场景的多频段信道特性

为助力我国铁路数字化转型升级,需加快推进智能铁路的总体建设。以厦门北高铁车站为目标场景,结合我国铁路实际,采用射线跟踪(RT)技术对932 MHz、2.1 GHz、41 GHz和93.2 GHz 4个频段的铁路综合数字移动通信系统(GSM-R)、铁路5G(5G-R)、毫米波通信系统3种制式的信道特性展开研究。依托高性能射线跟踪仿真,精准刻画了不同频段下高铁车站场景的电波传播特性,对多频段、多制式下的多维度信道特性进行比较和研究。结果表明,电波频率越高,无线信号覆盖范围越小;且经由散射体产生的多径越少,多径信号在时间域和空间域的色散程度越弱。本文研究基于高铁车站的应用场景,为铁路专用移动通信系统的设计与改善提供了相应的理论依据、数据支持。