车载超短波电台电波传播预测模型研究

针对实战环境中车载超短波电台通信距离和质量受地面附着物和地形地貌影响的问题，文中基于射线追踪和机器学习，建立了车载超短波电台电波传播预测模型。采用装甲车辆与车载天线的一体化建模获得车载天线辐射方向图，融合电子地图，建立了基于射线追踪技术的电波传播仿真模型。利用随机森林机器学习算法和仿真模型的数据结果，建立了基于随机森林的电波传播预测模型，并与经典电波传播模型如Egli模型和Okumura-Hata模型进行对比。结果显示，基于随机森林的电波传播模型预测精度更高，均方根误差达到2.190 1 dB,决定系数达到0.960 1,可准确预测战术通信环境中的电波传播情况。     

电波传播抛物方程模型在航空通信中的应用

针对航空通信中电波传播损耗预测需要满足精确性、实时性及复杂环境适应性的要求,在分析电波传播损耗对航空通信系统作用范围的影响基础上,采用抛物方程模型研究了航空通信中电波在空间区域的传播特性。该模型利用分步傅里叶算法实现快速求解,采用边界平移法处理复杂地形边界,并通过非均匀网格技术提高空间任意一点的场强计算精度,从而改善了复杂环境下电波传播损耗预测的精确性和实时性。将该模型应用于真实地形环境下的航空通信仿真算例中,仿真结果表明：该模型能有效预测复杂环境下电波的传播损耗,评估在正常通信条件下飞行器的飞行范围、最大飞行距离以及最低飞行高度等性能。     

海面电波传播损耗模型研究与仿真

研究了海面电波传播损耗预测模型,指出对该类传播损耗预测的仿真模型宜采用Longley-Rice模型,并对模型作了适应性修正和补充以适应海上编队通信链路的仿真.还推导了Okumura-Hata模型和Longley-Rice模型电波传输损耗预测的具体算法,数值仿真结果显示本文提出的方法预测结果与实测数据相符,最后给出对1 km以内和飞机飞行高度在10 km以上时的修正和补充方法.     

复杂地形条件下电波传播特性预测

电磁环境计算是战场电磁环境预测仿真系统的核心,为了准确预测不同环境下的电波传播特性,从复杂地形条件展开研究,给出一种基于PE模型的电场强度计算方法,仿真比较了辐射源在不同地表类型下的传播损耗,仿真预测了复杂地形条件下电波传播特性,仿真结果表明地表电磁特性对传播损耗的影响较小,相比于地表电磁特性,不规则地形对电波传播影响更为明显。     

DTMB单频网规划中电波传播模型的选取与校正

研究了某地区DTMB单频网规划中电波传播模型的选取和校正方法,基于连续波测试理论采集和处理实测数据,基于ICS telecom仿真对不同电波传播模型下的接收功率进行预测,以预测值和实测值之间的均方误差最小为准则选取了一种适合该规划地区的电波传播模型,并采用最小二乘法对该模型进行校正,得到两种不同传播环境下(市区、郊区)的电波传播模型。与原模型相比,校正后模型对链路损耗预测的均方误差有较大程度改善,这对提高该规划地区单频网规划的科学性、准确性和可靠性有重要的作用。     

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.     

复杂地形中的电波传播损耗预测研究

远距离不规则复杂地形中,电波传播损耗计算精度较低,对此,文中提出了一种基于地理信息系统并根 据实际地形提高电波传播损耗计算精度的算法模型,构建了可视化的软件显示平台。首先,根据国际电信联盟(ITUR) 的P 系列电波传播建议书,结合实际地理信息情况获取了地形和环境因子的数据。然后,通过数字地图模型,针对 传播路径上各种不同地形区域,分别建立传播模型来计算电波传播损耗,并完成仿真计算界面的设计和实现。最后,给 定收发天线高度和频率,依据实际地形,建立完整的电波传播模型进行仿真实验。结果表明,该算法模型不仅能得到传 播路径上每一个点的损耗,而且与传统的Hata 模型对比,该算法在不同区域和地形中敏感度更高,可以有效提升传播 损耗计算精度,更适用于计算实际地形中远距离不规则复杂地形下的电波传播损耗,帮助改善通信质量。     

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.     

基于改进地形重构的SSPE传播预测方法

针对复杂环境下电波传播预测分析难的问题,提出了一种基于地形重构的分步抛物方程(split-step parabolic equation, SSPE)传播预测方法. 该方法采用具有广角传播因子且步长可变的双向SSPE解法,并利用基于改进地形重构的SSPE传播预测方法对真实地形的电波传播特性进行仿真分析和试验验证. 与现有的电波传播预测方法相比,该方法结合了真实地形,通过改进重构算法对地形建模效果进行完善,并利用变步长双向SSPE解法进行传播损耗的预测. 仿真试验结果表明,此预测方法6 dB以内的精度满足了高精度电波传播模型的要求,表明该方法具有实际意义与推广价值.     

加速多镜像法对城市微小区电波传播的分析计算

基于电波传播基本原理,利用射线追踪方法、一致性绕射理论和镜像法,建立了一种新型圆柱体障碍物的城市微小区电波传播模型.采用遮挡测试、背面采集和降维处理等加速运算方法,加快了程序运行速度和镜像点的1找寻,最后给出了该环境下的路径损耗.并与实验结果相比较,其采集数据和理论数据基本吻合.     

无线信道的半确定性建模

无线电波传播环境的构建是无线通信实验室仿真试验中的关键部分,它决定了试验结果的可信度和准确度。针对特定环境中无线信道的建模问题,提出一种半确定性的无线信道建模方法,该方法以统计模型为基础,通过对环境中散射体进行分类和结果叠加的方法得到电波在该环境下传播效果,具有运算量小,配置灵活的优点。     

通信对抗试验外场超短波传播损耗模型修正方法

以移动通信的场强预测方法为基础,提出了一种应用于通信对抗试验外场区的超短波电波传播损耗预测模型的修正方法,根据实际测量数据利用最小二乘法求解模型中参数,实现传播模型的本地化,结果证明修正模型能够达到较高的精度。     

The study of the transmission of GHz waves.in the oceanic low altitude waveguide in the PEM-based gridded method

A parabolic equation method （PEM）-based discrete algorithm is proposed and is used to obtain the field distribution in the evaporation duct space. This method not only improves the computing speed, but also provides the flexibility to adjust the simulation accuracy. Numerical simulation of the wave propagation in the oceanic waveguide structure is done. In addition, the initial field distribution and progressive steps are determined. The loss model in the waveguide is solved through the numerical solution. By comparing the characteristics of the radio wave propagation in the duct and in the normal atmospheric structure, we analyses the radio transmission over the horizon detection in the oceanic waveguide.     

基于多源异构数据融合与RT的高铁网络优化系统

在高速铁路建设中,采用的电力拖车、路堑、站台、桥梁、明洞等特殊、形状不规则的建筑物,会对电磁波传播机理和多通路产生一定的影响,使其呈现出明显的衰减特性。从空间上看,呈现出强烈的空间异同性和频度相关,从而导致经验模型无法准确表征铁路场景的电波传播特性,成为制约无线网络规划精确度与效率、限制铁路移动通信系统高质量发展的理论瓶颈之一。针对这一挑战性难题,本文开展了基于多源异构数据融合的铁路移动通信高精确度网络规划及优化系统研究。采用高性能射线跟踪(RT)技术针对铁路通信930 MHz频段下的高铁场景进行了网络优化仿真。仿真结果表明,90%的接收信号强度相较于优化前提高了13.9 dB,显著提升了铁路复杂场景中的无线网络质量。     

Performance of a spread spectrum packet radio network link in aPoisson field of interferers

Results on the modeling of interference in a radio communication network and performance measures for the link as a function of distance are presented. It is assumed that a transmitter-receiver pair in a radio network is affected by a set of interferers, using the same modulation and power, whose positions are modeled as a Poisson field in the plane. Assuming a 1/r^γ propagation power loss law, the probability distributions for the noise at the receiver are found to be the stable distributions. Results are given for the probability of symbol error and link capacity as a function of the distance between the transmitter and receiver for direct sequence and frequency hopping spread spectrum schemes. It is found that the frequency hopping schemes are inherently superior and their performance is not dependent on the synchronization of the hopping times for the different users     

Simulation of burst error models and an adaptive error controlscheme for high speed data transmission over analog cellularsystems

To realize high-speed data communication in a cellular system, the characteristics of mobile radio propagation paths (MRPP) and a robust error control scheme for poor circuit quality are studied. MRPP are analyzed by computer simulation, and an analysis method is described that uses a Markov model for burst errors generated by the simulation. By simulating the locus of moving vehicles, the relationship between the carrier-to-noise ratio (CNR), the fading frequency of a moving vehicle, and the three-states Markov model is obtained. An adaptive error control scheme (AECS) is developed as an effective high-speed data communication scheme in an analog cellular system. The effectiveness of the AECS is analyzed by simulating its application in a subcarrier transmission system with a 4800 b/s data transmission rate, using the three-states Markov model. The analysis method is verified and the characteristics of the AECS are evaluated using field data     

适用于海上卫星通信终端的快速测试系统

针对海上卫星通信终端在性能调试、系统联试和试验现场环节中关键特性的快速检测需求,设计和开发了一套便携式测试系统。测试系统可模拟生成码片速率为3.069 Mchip/s的星地前向扩频信号,接收解调数据速率最大为2.0 Mb/s的返向正交相移键控(Quadrature Phase Shift Keying,QPSK)调制信号,且具备快速检测终端捕获和跟踪卫星信号时间是否优于7.0 s的能力。采用软件无线电思想,基于Matlab的卫星信号模拟程序替代现场可编程门阵列(Field Programmable Gate Array,FPGA)完成数据的组帧、加扰和扩频处理,降低了测试系统开发难度和周期,并提高了适应性和灵活性。各阶段的应用结果表明,便携式测试系统能够快速测试卫星通信终端的关键特性,为现场及时发现并定位问题提供了可靠依据。     

UHF propagation prediction for wireless personal communications

Propagation characteristics of radio signals in the UHF band place fundamental limits on the design and performance of wireless personal communications systems, such as cellular mobile radio (CMR), wireless LANs, and personal communication services (PCS). Because the radio link is direct to each subscriber, the prediction of signal characteristics is most important in urban areas where subscriber density is high, and the buildings have a profound influence on the propagation. The paper starts by reviewing the characteristic signal variations observed in CMR systems employing high base station antennas to cover macrocells having radius out to 20 km. Theoretical models incorporating diffraction are shown to explain the observed range dependence and shadow loss statistics. For the low base station antennas envisioned to cover microcells of radius out to 1 km for PCS applications, signal propagation is more strongly dependent on the building environment and on the location of the antennas in relation to the buildings. Various levels of theoretical modeling of this dependence are discussed in conjunction with measurements made in various building environments. Finally, the paper discusses advances in site specific prediction for outdoor and indoor propagation     

Radio wave propagation characteristics in lossy circular waveguidessuch as tunnels, mine shafts, and boreholes

We present the characteristics of radio propagation in a circular lossy waveguide whose walls are composed of earth soil materials with frequency-dependent properties. This type of structure is used to represent a radio link for an underground wireless communication channel such as a tunnel, mine shaft, or borehole. We present calculated results of the attenuation constant for various propagation modes in the soil waveguide structure for various soil constituents and moisture levels. Transverse field plots of the various modes for different soil types are also presented. Finally, it is shown that for small |k₂a| (where k₂ is the wavenumber in the soil and a is the radius of the waveguide) some modes in the waveguide disappear and a discussion of this behavior and how it relates to excitation problems is given     

海面环境700MHZ频段传输特性测试与模型校正

在海面环境下通过船-岸测量方式对700 MHz频段的无线传输特性进行测量.基于实测数据分析,引入海面双径传输损耗模型对ITU-R P.1546-5标准传输模型进行校正,该校正模型可实现700 MHz频段无线传输损耗预测.在仿真中,分别利用自由空间模型、ITU-R P.1546-5模型和ITU-R P.1546-5校正模型对700 MHz频段的海面无线传输损耗进行预测,通过与实测数据对比分析,证明ITU-R P.1546-5校正模型预测结果准确性更高,能够为海面无线通信系统的设计提供重要依据.