28 GHz MIMO无线信道特性分析与研究

基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28 GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度扩展等信道参数,研究了MIMO信道容量及空间相关性对容量的影响.结果表明:莱斯K因子、时延扩展以及角度扩展值取决于测量环境及场景;LOS条件下时延扩展的累积分布函数(Cumulative Distribution Function,CDF)曲线与正态分布拟合优于NLOS条件下的数据;MIMO天线空间相关性越大信道容量越小.本文结果可为28 GHz无线通信系统设计提供有用信息.     

Experimental investigations of 60 GHz WLAN systems in office environment

This paper presents the results of an experimental investigation of 60 GHz wireless local area network (WLAN) systems in an office environment. The measurement setup with highly directional mechanically steerable antennas and 800 MHz bandwidth was developed and experiments were performed for conference room and cubicle environments. Measurement results demonstrate that the 60 GHz propagation channel is quasioptical in nature and received signal power is obtained through line of sight (LOS) and reflected signal paths of the first and second orders. The 60 GHz WLAN system prototype using steerable directional antennas with 18 dB gain was able to achieve about 30 dB baseband SNR for LOS transmission, about 15-20 dB for communications through the first-order reflected path, and 2-6 dB SNR when using second-order reflection for the office environments. The intra cluster statistical parameters of the propagation channel were evaluated and a statistical model for reflected clusters is proposed. Experimental results demonstrating strong polarization impact on the characteristics of the propagation channel are presented. Cross-polarization discrimination (XPD) of the propagation channel was estimated as approximately 20 dB for LOS transmission and 10-20 dB for NLOS reflected paths.     

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.     

Multipath propagation model for line-of-sight street microcells inurban area

This paper proposes a multipath propagation model for line-of-sight (LOS) street microcells with building roof base sites (BS) in urban areas, Multipath propagation characteristics are of great importance in evaluating the performance of digital systems and designing wireless links. Typical delay profiles are measured to clarify their statistical characteristics in LOS street microcells. The channel sounder used is a sliding correlator with 30-Mb/s PN code and a center frequency of 2.6 GHz. The measurements clarify the features of delay profile and mean RMS delay spread. The proposed delay profile model explains one plausible mechanism of multipath propagation. The delay profiles calculated using the model agreed well with the measured profiles. Furthermore, the factors influencing the RMSs delay spread are investigated, and the regression equation of medium RMS delay spread on a sidewalk is established. The proposed model can evaluate the transmission characteristics of wireless digital communication systems in multipath propagation environments     

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(del...     

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。     

Characteristics of vector propagation channels in dynamic mobilescenarios

In wireless communications, the performance of a smart antenna system depends heavily upon vector channels describing channel propagation between an antenna array and a mobile subscriber. The smart antennas perform quite well in stationary mobile environments in which channel propagation characteristics are stable. However, in dynamic wireless environments where the mobile user is in motion, knowledge of how vector channels are affected is necessary for the proper operation of smart antennas. Here, we experimentally investigate the variation of vector channel parameters such as spatial signatures, directions-of-arrival (DOAs), and complex path attenuations with small movement (2λ) of the mobile under typical line-of-sight (LOS), line-of-sight with local scatterer (LOSLS), and nonline-of-sight (NLOS) propagation scenarios. The experiments are conducted using a 1.8-GHz smart antenna testbed developed at The University of Texas at Austin and a mobile transmitter. The results show that with small displacements, DOAs remain approximately unchanged and spatial signatures change due primarily to complex attenuations. Spatial signatures are very susceptible to the movement in the NLOS scenario, reaching up to 90% relative angle change within 2λ displacement. However, in the LOS scenario, they exhibit small and periodic fluctuations with a period of 0.6λ     

基于射线跟踪法的73 GHz走廊环境MIMO信道特性研究

为了研究5G室内走廊环境的毫米波传输特性,通过射线跟踪仿真方法预测了室内走廊环境下73 GHz毫米波MIMO信道特性。介绍了实验的仿真环境和射线跟踪仿真预测的实验方法和具体参数设置。研究了室内走廊环境下73 GHz毫米波MIMO信道的路径损耗、RMS时延扩展和MIMO信道容量变化。发现了路径损耗斜率和RMS时延数值较小。研究MIMO容量随距离变化时发现,收发机沿走廊纵向方向中间处会产生容量峰值,主要是由于该处散射丰富,NLOS分量大。研究MIMO容量特性发现增大天线间距和增大天线阵列规模可以提升容量,但是采用4×64 Massive MIMO相对于采用4×4 MIMO时容量提升较为有限。实验证实了73 GHz毫米波MIMO可以用于室内走廊环境。     

Empirical characterization of wideband indoor radio channel at 5.3GHz

Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines     

Spatial and temporal characteristics of 60-GHz indoor channels

This article presents measurement results and models for 60-GHz channels. Multipath components were resolved in time by using a sliding correlator with 10-ns resolution and in space by sweeping a directional antenna with 7° half power beamwidth in the azimuthal direction. Power delay profiles (PDPs) and power angle profiles (PAPs) were measured in various indoor and short-range outdoor environments. Detailed multipath structure was retrieved from PDPs and PAPs and was related to site-specific environments. Results show an excellent correlation between the propagation environments and the multipath channel structures. The measurement results confirm that the majority of the multipath components can be determined from image based ray tracing techniques for line-of-sight (LOS) applications. For non-LOS (NLOS) propagation through walls, the metallic structure of composite walls must be considered. From the recorded PDPs and PAPs, received signal power and statistical parameters of angle-of-arrival and time-of-arrival were also calculated. These parameters accurately describe the spatial and temporal properties of millimeter-wave channels and can be used as empirical values for broadband wireless system design for 60-GHz short-range channels     

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.     

UWB室内视距环境多径传播模型

提出了一种全新超宽带(UWB,ultra-widebandwidth)室内视距(LOS,line-of-sight)环境的多径传播模型(简称多径模型)。该模型以南加州大学UltRa实验室的UWB室内LOS环境实测数据为基础,信道冲激响应具有两个确定的簇,每个簇内具有随机到达的多径射线。模型有效地利用特定环境的几何参数数据,在预测室内LOS环境的小尺度多径传播特性(平均附加时延、RMS时延扩展、最强多径数量)上较传统的统计模型更加简化和准确,与传统的确定模型相比,明显地降低了模型建立的复杂度。     

Wideband Millimeter-Wave Channel Characterization in an Open Office at 26 GHz

Based on the newest frequency allocation for the fifth generation (5G) radio systems at 26 GHz millimeter wave band by the World Radio Communications Conference, this paper investigates the wideband channel properties by measurements carried out in the LOS and NLOS environments at 26 GHz with 1 GHz bandwidth in an open office at KeySight Beijing, China, which is a representative of an indoor hotspot scenario. In the time domain measurements, an omni-directional biconical horn is used at the transmitter, while at the receiver a 24.3 dBi horn is applied and rotated with 5° angular step in the whole azimuth plane, and from ?20° to 30° in the elevation plane with 10° angular step. In the work, two kinds of path-loss models are developed, namely directional and omni-directional models by using close-in and float intercept methods. The directional path-loss model is useful for adopting beamforming techniques. The large scale channel parameters such as the shadow fading, root mean square (RMS) delay spread, RMS angular spread in the azimuth and elevation planes, Ricean K-factor, number of clusters and their correlations are investigated for the fifth generation (5G) link and system level simulations. A new method for extracting number of clusters is proposed to find the peak power within a sliding window. The power angular profiles are employed at the measurement locations for propagation mechanisms studies. We believe that the newest results in this work are useful in the simulations and planning for future 5G radio systems at 26 GHz.     

室内多径时延扩展的实验研究

本文介绍关于室内环境中时延扩散的实验，实验采用基于伪随机码滑动相关法的无线信道探测器，在典型的室内环境中对ＵＨＦ（９００ＭＨｚ）无线信道功率时延曲线进行实地测量，通过对大量实测数据的处理和分析得出了一些很有价值的结论，如在ＬＯＳ及ＮＬＯＳ情况下的时延扩展均方根值和方差；时延扩散与收发距离、路径损耗及收发天线不同线极化方向的关系等等。     

Pulse propagation characteristics at 2.4 GHz inside buildings

The growing use of unlicensed wireless systems has spurred interest in the 2.4-GHz ISM band. In order to facilitate the design of such systems, measurements of the pulse response characteristics have been made inside commercial buildings. From the measured pulse response, the statistical properties of the amplitude variation for individual pulses was determined, in addition to the path loss, mean excess delay, root mean square (RMS) delay spread, and the coherence bandwidth of the indoor channel     

Verification of Fresnel Zone Clearance for Line-of-sight Determination in 5.9 GHz Vehicle-to-Vehicle Communications

The determination of the path clearance is one of the most important factors for channel propagation models because most of them classify their models into line-of-sight (LOS) and non-LOS (NLOS) environments. In particular, the path for vehicle-to-vehicle (V2V) communication is more easily obstructed owing to its characteristics such as low antenna heights and high mobility. In this paper, we verify the first Fresnel zone clearance, which is a widely employed method for the determination of path clearance in V2V scenarios. In the analytical model of the first Fresnel zone in V2V scenarios, the ground acts as an obstacle and thus induces NLOS environments for farther than a certain distance. In contrast, our measurement results reveal no additional loss due to the ground obstruction. Therefore, we conclude that the first Fresnel zone calculation is not applicable for determining the path clearance in V2V scenarios, which has significant impact on the accuracy of channel propagation modeling.     

Multibeam Selection for Indoor MIMO Systems: Two Cases of Study

The performance of multiple-input multiple-output (MIMO) systems using beam selection is investigated in this paper. Based on the results of a channel sounding campaign carried out at the University of Manitoba for line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios, it was possible to contrast the results of transmitter, receiver and joint beam selection in rich scattering environments. The channel was characterized in the 1-2.4 GHz frequency band with a multipath delay resolution better than 5.8 ns. The beam selection was performed by exhaustive search method. The results led us to important conclusions regarding the beam selection procedure and its potential to improve the indoor channel capacity. In LOS, the single input single output (SISO) system that favours the maximum power direction of arrival (DOA) maximizes the capacity. Capacity improvements are observed by increasing the number of receiver beams (RBs) only at high signal-to-noise ratios (SNRs) for omnidirectional transmission. The best performance in transmitter beam selection in LOS is observed by increasing the number of transmitter beams (TBs) for high SNRs. In the case of NLOS, the capacity performance is improved when more than a single beam is used in either, transmitter or receiver side. The joint transmitter-receiver beam selection exhibits best capacity performance only for large SNRs in LOS while the SISO systems outperforms any joint beam selection alternative for low SNRs. In contrast, in NLOS environments, the use of joint beam selection shows a constant capacity performance improvement starting from lower SNR than in the LOS case     

Characterization of the Ultra-Wideband Channel in Confined Environments with Diffracting Rough Surfaces

Accurate channel models are extremely important for the design of communications systems. Knowledge of the features of the channel provides communications system designers with the ability to predict the performance of the system for specific modulations, channel coding, and signal processing. This paper presents a statistical characterization of an Ultra-Wideband (UWB) propagation channel in an underground mine. Measurements were carried out in the 2–5 GHz frequency band. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios. The measurement procedure allows us to characterize both the large-scale and the small-scale statistics of the channel. The aim here is to study in more details the statistical characteristics of the UWB propagation channel in an underground mine and to provide insight for future statistical channel modeling works. Channel characteristics examined include the distance and frequency dependency of path loss, shadowing fading statistics, and multipath temporal-domain parameter statistics such as the mean excess delay and the RMS delay spread. This work has been carried out by the underground communications research laboratory LRCS (The LRCS laboratory aims to develop research programs related to wireless telecommunications in underground mines. Research is conducted at its own facility as well as the CANMET experimental mine in Val-d’Or, Quebec, Canada), and the experimental mine CANMET (Canadian Center for Minerals and Energy Technology) in Val-d’or, Canada.     

Autoregressive modeling of wide-band indoor radio propagation

Based on frequency domain measurements in the 0.9-1.1-GHz band, an autoregressive model for the frequency response of the indoor radio channel is introduced. It is shown that a second-order process is sufficient to represent the important statistical characteristics of the channel both in the frequency domain and the time domain where each pole identifies the arrival of a cluster of paths. A comparison is made between the statistical characteristics of the empirical data and of the channel responses regenerated from the second-order AR processes. Four methods to regenerate the indoor radio channel responses from a second-order AR model are proposed. The accuracy of the methods is examined by comparing the cumulative distribution functions of the RMS delay spread and the 3-dB width of the frequency correlation function with that of the measurements performed in global, local, and mixed indoor radio propagation experiments