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.     

室外微蜂窝小区3.5GHz 电波传播特性仿真和分析

射线跟踪方法是研究室外微蜂窝小区电波传播的有效方法。基于入射及反弹射线法/ 镜像法对室外微小区环境中3. 5GHz 电波传播的路径损耗进行了仿真和分析,仿真结果与文献所给的结果一致性良好,验证了该 方法的正确性。提出了一种新型的射线管判收方法,可有效判断到达接收机的所有射线管。分析了仿真中得到的接收功率、均方根时延扩展、波达方向等传播参数,并比较了视距传播(LOS)和非视距传播(NLOS)的传播特性,这些分析结果可为3. 5GHz 频段无线通信系统的覆盖提供相应的理论依据。     

基于射线追踪法的毫米波高架桥信道仿真

信道特性分析是通信网络规划、设计通信系统的基础。针对高架桥毫米波信道特性问题，基于射线追踪法仿真了37GHz毫米波信道，分析了大尺度路径损耗模型和小尺度多径模型，分别得出了两者在高架桥场景下表示信道损耗的影响因子和参数，如路径损耗、莱斯因子等。使用正态分布对附加阴影损耗进行建模，得到路径损耗模型。对莱斯因子和均方时延扩展使用正态分布拟合累计分布函数，获得建模参数。该参数的明确，为高架桥信道建模提供了理论依据。     

65.5 GHz毫米波信道测量与分析

毫米波技术和大规模多输入多输出天线技术是5G移动通信系统的关键技术. 为了研究60 GHz毫米波频段宽带信道特性,在会议室进行了65.5 GHz频段的信道测量活动. 首先基于方向性路损模型,研究路径损耗指数和阴影衰落特性;然后基于空间交替广义期望最大化（space-alternating generalized expectation-maximization, SAGE)参数化分析算法,提取水平到达角、时延和幅度信息;最后根据多径分量距离方法,对多径分量进行分簇,分析均方根时延扩展和均方根角度扩展特性. 实测结果表明:视距情况下,方向性路损在固定截距和浮动截距两种方式的拟合下与自由空间路径损耗模型相近;65.5 GHz下环境中的簇具有稀疏性;时延扩展和角度扩展的结果与第三代合作伙伴计划（the 3rd Generation Partnership Project, 3GPP）的结果相近. 本文提供的信道参数对于5G毫米波60 GHz频段信道建模和仿真具有重要参考意义.     

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.     

三维室内视距模型的极化特性研究

极化方式是电波传播的重要特性,也是在信道传播特性中的关键要素.文章基于入射及反弹射线/镜像方法(SBR/Image)研究了室内无线电波传播特性,考虑了两次(甚至任意次)反射的极化特性,建立起三维的室内视距模型.通过仿真计算,首先证明了研究极化特性的必要性;然后将仿真结果和已知文献结果对比,两个结果一致性良好,同时验证了本文的正确性.     

基于射线追踪技术的多类工业环境28GHz信道特性研究

工业物联网是第六代移动通信技术（6th Generation Mobile Communication Technology,6G）的典型应用场景,工业环境无线信道特性是构建工业物联网应用的基础。本文基于射线追踪技术,研究三类典型工业环境（车间工厂、食品工厂、仓库工厂）在28GHz频段的信道特性。研究结果表明不同工业环境的路径损耗特性相差较大,本文对差异的产生原因进行了阐述,还对比了视距与非视距情况下的均方根时延扩展特性。本文研究结果可以为室内多场景下28GHz信道特性的建模与研究提供帮助。     

室内长廊环境中毫米波传播特性仿真和分析

基于入射及反弹射线法/镜像法对室内走廊环境的毫米波传播进行了仿真和分析,仿真结果与测量结果一致性良好,验证了该方法的正确性.同时分析了仿真中得到的接收功率、均方根时延扩展、波达方向、均方根角度扩展和多普勒频移等传播参数,为毫米波通信系统室内覆盖提供了依据.     

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。     

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。     

Measurement‐Based Propagation Channel Characteristics for Millimeter‐Wave 5G Giga Communication Systems

This paper presents millimeter‐wave (mmWave) propagation characteristics and channel model parameters including path loss, delay, and angular properties based on 28 GHz and 38 GHz field measurement data. We conducted measurement campaigns in both outdoor and indoor at the best potential hotspots. In particular, the model parameters are compared to sub‐6 GHz parameters, and system design issues are considered for mmWave 5G Giga communications. For path loss modeling, we derived parameters for both the close‐in free space model and the alpha–beta–gamma model. For multipath models, we extracted delay and angular dispersion characteristics including clustering results.     

面向6G的毫米波多频段多天线信道测量系统构建及实测验证

毫米波是5G和6G无线通信系统的关键技术.设计满足6G多频段、多天线、高动态范围需求的信道测量系统是6G无线信道研究面临的首要挑战.针对这一需求,本文构建了一种毫米波多频段多天线信道测量系统,可以覆盖24.25～28.5 GHz、31.8～33.4 GHz、37～42.5 GHz等毫米波频段,支持最高16×16天线配置.首先介绍该信道测量系统的架构与性能指标,提出多通道并行校准方案以及测量数据处理算法;其次,基于该信道测量系统开展26 GHz室内外场景的信道测量实验,分析路径损耗、时延扩展以及奇异值扩展等信道统计特性.通过对实测结果分析,验证了该信道探测器用于毫米波段测量的有效性.     

Empirical millimeter-wave wideband propagation characteristics of high-speed train environments

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.     

Wideband indoor channel measurements and BER analysis of frequencyselective multipath channels at 2.4, 4.75, and 11.5 GHz

Results from propagation measurements, conducted in an indoor office environment at 2.4, 4.75, and 11.5 GHz, are presented. The data were obtained in small clusters of six measurements, using a coherent wideband measurement system. The channel characteristics for the three frequencies are compared by evaluating path loss, rms delay spread, and coherence bandwidth. An analytical model for evaluation of the bit-error rate (BER) of the stationary frequency selective indoor channel is developed for a coherent binary phase shift keying (BPSK) receiver, based on the complex impulse response of the channel. Computational BER results are obtained for data rates up to 50 Mb/s, using the measured multipath channel impulse responses. The BER results for a number of clusters are presented and compared for the maximum reliable data rate as inferred by the measured rms delay spread of the channel     

Indoor channel characteristics based on wideband MIMO measurements at 5.25 GHz

Extensive indoor channel measurements were conducted in Beijing with wideband multiple-input multiple-output （MIMO） sounder at 5.25 GHz. Both line-of-sight （LOS） and non-line-of-sight （NLOS） propagation were measured in the indoor office and hotspot scenarios. On the basis of measured data, statistical channel characteristics are presented in this article, including the empirical path loss （PL） models, three excess delay parameters, circular azimuth spread （CAS）, and circular elevation spread （CES）. Comparative analysis of different propagation mechanisms in two scenarios is conducted. These values are significant for indoor coverage and technical research of MIMO and orthogonal frequency division multiplexing （OFDM） for the international mobile telecommunications-advanced （IMT-Advanced） system.     

Millimeter-Wave Propagation Channel Characterization for Short-Range Wireless Communications

This paper presents and analyzes the results of millimeter-wave 60-GHz frequency range propagation channel measurements that are performed in various indoor environments for continuous-route and direction-of-arrival (DOA) measurement campaigns. The statistical parameters of the propagation channel, such as the number of paths, the RMS delay spread, the path loss, and the shadowing, are inspected. Moreover, the interdependencies of different characteristics of the multipath channel are also investigated. A linear relationship between the number of paths and the delay spread is found, negative cross correlation between the shadow fading and the delay spread can be established, and an upper bound exponential model of the delay spread and the path loss is developed to estimate the worst case of the RMS delay spread at given path loss. Based on the DOA measurements that are carried out in a room [line of sight (LOS)] and in a corridor with both LOS and nonline-of-sight (NLOS) scenarios, radio-wave propagation mechanisms are studied. It is found that considering the direct wave and the first-order reflected waves from smooth surfaces is sufficient in the LOS cases. Transmission loss is very high; however, diffraction is found to be a significant propagation mechanism in NLOS propagation environments. The results can be used for the design of 60-GHz radio systems in short-range wireless applications.     

Narrowband Short Range Directive Channel Propagation Loss in Indoor Environment at Three Frequency Bands

Propagation loss models for indoor environment are presented. The narrowband directive channel propagation loss in indoor environment at three frequency bands namely (2.4, 3.3 and 5.5) GHz is measured. Sets of directive panel antennas are used in the measurements. RF signal generator and a spectrum analyzer are used in the measurement campaign. It is found that propagation loss is sensitive to the scenario configuration. It is noticed that the propagation loss can be modelled by a single slope propagation model or two slopes propagation model.     

基于机器学习和卫星图像的路径损耗预测

基于反向传播神经网络（back propagation neural network,BPNN）构建了一种路径损耗预测模型. 通过卫星图像的红、绿、蓝（red, green and blue,RGB）通道的颜色信息来表征无线通信电波传播路径的环境特征,结合路测点与基站的距离特征构建数据集,迭代训练网络参数,以预测传播路径损耗. 结果表明,对跨基站路测点的预测结果与实测数据之间的相关系数达到0.83,绝对平均误差控制在0.66 dB,标准差控制在6.65 dB,说明在缺乏某一场景的详细模型和材质参数时,本文模型也能可靠预测无线通信电波的传播路径损耗. 此外,本文信道模型与传统信道建模方法多方面的对比与分析表明,本文模型在相同计算资源下可以提供和传统信道建模方法相差很小的预测结果,同时大大缩短预测所需的时间,说明本文模型对传播路径损耗做出快速预测的能力可以用于无线通信网络系统的优化.