Effects of antenna directivity and polarization on indoor multipathpropagation characteristics at 60 GHz

In millimeter-wave indoor communications systems, the radiation patterns and polarizations of the antennas at base stations and remote terminals have a significant influence on channel characteristics. The work reported in this paper investigated the effects of the radiation patterns of the antennas at remote terminals on multipath propagation characteristics. These effects were investigated by indoor propagation measurements at 60 GHz conducted in a modern office room and by ray-tracing simulations based on geometrical optics. Multipath channel characteristics are compared in terms of impulse responses and their root-mean-square (rms) delay spreads for an omnidirectional antenna and for three directive antennas with different beam widths. From the results of measurements and ray-tracing simulations, the use of a directive antenna at the remote terminal is demonstrated to be an effective method of reducing the effects of multipath propagation. Further reduction in the multipath effects is found to be achieved by the use of circular polarization instead of linear polarization with the directive antennas     

Polarization Effects for Indoor Wireless Communications at 60 GHz

This letter studies the performance of indoor wireless communication systems operating at 60 GHz with different polarization schemes. Circular polarization is known to reduce multipath effects in line-of-sight (LOS) environments in the 60 GHz band. We propose a modified channel model based on the IEEE 802.15.3c channel model to incorporate the polarization effects. We then use this model to evaluate the error performance of a wireless communication system that uses circular polarization. The results are compared with linear polarization for LOS environments.     

Radar image study of simulated breaking waves

Radar images of electromagnetic scattering from one-dimensional simulated ocean breaking waves are described. Backscatter results from 10-14 GHz at 60/spl deg/ to 80/spl deg/ incident angles are considered for surfaces that satisfy an impedance boundary condition. The generalized forward-backward method with spectral accelerations was used as an exact numerical solution to obtain backscatter returns from several surface profiles, and radar images are formed through back-projection tomography. Detailed investigations of the images are provided to clarify major and secondary scattering events, as well as the polarization dependence, and a ray-tracing analysis is performed to interpret multipath scattering mechanisms. By adding surface roughness outside the breaking region, small-scale roughness scattering effects are also investigated.     

Multipath scattering in ultrawide-band radar sea spikes

This paper presents sea scatter data collected with an ultrawide-band (UWB) polarimetric radar system that indicates that multipath scattering plays an important role in the generation of sea spikes. The radar system used in this study produces short pulses with a bandwidth of approximately 3 GHz centered at 9 GHz for a range resolution of approximately 4 cm. Pulse-to-pulse switching allows collection of the microwave echoes produced by all four combinations of linear transmit and receive polarizations [vertical-transmit vertical-receive (VV), horizontal-transmit horizontal-receive (HH), horizontal-transmit vertical receive (HV), and vertical-transmit horizontal-receive (VH)] each of which is collected by a sampling oscilloscope utilizing equivalent time sampling. In June 1996, upwind sea scatter data at grazing angles of 10°, 20°, and 30° were collected while the system was deployed on a research pier on the Outer Banks of North Carolina. An analysis of the strongest echoes (sea spikes) from this data set is presented and discussed. First, the cumulative distribution functions are presented. Second, an increase of approximately 5 dB is shown to occur in the polarization ratio (HH/VV) of the strongest echoes as the grazing angle decreases from 30° to 10°. Third, differences in the spatial and spectral characteristics of the VV and HH spikes are described. Through comparisons with laboratory results and a simple scattering model, these observations are explained by the presence of a multibounce scattering mechanism. The use of the model to extract wave height from the sea-spike frequency response is also explored     

Wideband Channel Sounder With Measurements and Model for the 60 GHz Indoor Radio Channel

In this paper, a wideband channel sounder and measurement results for the short range indoor 60 GHz channel are presented. The channel sounder is based on a 1 gigasamples/s dual channel arbitrary waveform generator and A/D converter/software demodulator, which synthesize and detect a baseband PN sequence with 500 MHz bandwidth. A heterodyne transmitter and receiver translate the baseband PN sequence to and from the 60 GHz band. Ten channel measurements taken across the 59 GHz to 64 GHz range are concatenated to provide a continuous channel measurement covering 5 GHz of bandwidth, resulting in 0.2 ns time domain channel impulse response resolution. The dynamic range and maximum sensitivity performance of the channel sounder are discussed in detail. Comparisons of results with a vector network analyzer based system are shown to verify the accuracy of the sounder. In an extensive measurement campaign with vertically polarized omnidirectional antennas, several different rooms (offices, labs, conference rooms and others) in four different buildings have been investigated. Over 700 channel measurements are the basis for a comprehensive characterization of the short range 60 GHz indoor radio channel with omnidirectional antennas. Finally, a simple stochastic static multipath channel model is derived from the measurement results.     

Superresolution of multipath delay profiles measured by PNcorrelation method

Time resolution of multipath delay profiles measured by using the autocorrelation of a pseudonoise (PN) code sequence is generally limited by the chip interval of the PN code sequence. A superresolution PN correlation method (SPM) is proposed which improves the time resolution of delay profiles measured by the conventional PN correlation method. The SPM is based on a decomposition of the eigenvector space of the correlation matrix of the delay profile data vector and gives the number of paths and their delay times with higher resolution. It is verified by computer simulations and experiments using coaxial delay lines that the SPM can resolve two paths with a delay difference of a few tenths of the chip interval. The applicability of the SPM to the analysis of an indoor multipath environment in which many delayed waves arrive with short delay differences is demonstrated by an indoor radio propagation experiment at 2.3 GHz     

Comparative study of millimeter wave propagation at 30 GHz and 60 GHz in indoor environment

The millimeter wave band appears to be a favourable choice for personal wireless communication systems for indoor environment, as it meets the requirements for sufficient bandwidth, small terminal dimensions and sporadic usage for commercial applications. In this paper measurements of millimeter wave propagation in both 30 GHz and 60 GHz bands, are presented in a comparative way. The topology of measurements covers both a line-of-sight situation and also a case where a direct path between transmitter and receiver does not exist. Although the second case does not seem obvious for outdoor applications in these frequencies, in indoor environment the multipath signals produced by objects like walls, doors, furniture etc., can be utilised in order to overcome the man-made shadowing. Both slow and fast fading characteristics of the received signal are studied and the measurements are modelled by the conventional Rician and Rayleigh distributions. Both frequency bands offer advantages for usage in in-house wireless communication systems. Although in 30 GHz band the coverage area is bigger than in 60 GHz (with the same transmitting power), frequency reuse is easier in 60 GHz band. because even if millimeter waves ‘escape’ through ‘windows’, the specific attenuation due to atmospheric oxygen (15 dB/km) at 60 GHz eliminates the interference between communication channels in neighbouring buildings.     

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     

In-building wideband partition loss measurements at 2.5 and 60 GHz

This paper contains measured data and empirical models for 2.5 and 60 GHz in-building propagation path loss and multipath delay spread. Path loss measurements were recorded using a broadband sliding correlator channel sounder which recorded over 39000 power delay profiles (PDPs) in 22 separate locations in a modern office building. Transmitters and receivers were separated by distances ranging from 3.5 to 27.4 m and were separated by a variety of obstructions, in order to create realistic environments for future single-cell-per-room wireless networks. Path loss data is coupled with site-specific information to provide insight into channel characteristics. These measurements and models may aid in the development of future in-building wireless networks in the unlicensed 2.4 and 60 GHz bands.     

The Dependence of Sea-Surface Microwave Emission on Wind Speed, Frequency, Incidence Angle, and Polarzation over the Frequency Range from 1 to 40 GHz

The dependence of sea-surface microwave emissive prop erties on wind speed, frequency, incidence angle, and polarization arn discussed in detail, in terms of wind-speed sensitivity of the brightnes temperature (defined as a change in brightness temperature with a un, change in wind speed) to the last three observational conditions, ovet the frequency range from 1 to 40 GHz, comparing our results at 6.7 and 18.6 GHz with many investigators' results at various levels from surface to satellite. This wind-speed sensitivity shows marked incidence angle and polarization dependencies. In vertical polarization, a wind-induced increase in the brightness temperature decreases with incidence angle. Then, the vertically polarized brightness temperature of the roughened sea surface is equal to that of the calm surface at an incidence angle between 50 ° and 600, and is higher below, and lower above, this angle; in other words, the above sensitivity is higher and takes a positive value at lower incidence angle and it is lower and takes negative value at higher incidence angle, with a wind-speed-insensitive angle existing between 500 and 600. A wind-induced change in the horizontally polarized brightness temperature shows no marked incidence angle dependence, but a uniform increase over the incidence angle. Both polarizations do not essentially change their characteristics in the above dependencies but gain wind-speed sensitivity with frequency; however, the horizontal polarization is much more sensitive to wind speed than the vertical one over the entire incidence and frequency ranges.     

An empirical model for high elevation angle land-mobile satellitechannels at urban environment

A land mobile satellite system (LMSS) propagation measurement campaign at 1.8 GHz was launched in Athens city center during June 1996 for high elevation angle (60°, 70° and 80°) channels. Four narrow streets with large building blocks and heavy traffic were tested. A new empirical model is extracted to calculate the link margin required to compensate for multipath fading in urban environments. A comparison with an existing model is presented. The results show a considerable increase in the fade depth compared to suburban and rural environments. In general, the fade depth decreases with increasing elevation angle, and the overall analysis indicates a strong dependence of the signal attenuation on the width of the streets, the average building height and the vegetation at the edges of the streets     

Measurements of copolar attenuation through the bright band at 4 and 7 GHz

This paper presents some initial results from an experiment designed to measure microwave propagation through the bright band at 4 and 7 GHz. Preliminary measurements taken at 7 GHz indicate bright band attenuation to be many times (in dB per kilometer) greater than attenuation due to equivalent amounts of rain. These measurements also suggest that refractive multipath might occur during bright-band propagation conditions. An experimental design based on remote telemetry is described to improve resolution in future measurements and to help model bright-band propagation phenomenon.     

Crossed-dipole arrays for asynchronous DS-CDMA systems

In this paper, the use of a crossed-dipole array is proposed in joint space-time channel estimation for asynchronous multipath direct sequence code division multiple access (DS-CDMA) systems. The polarization diversity offered by such an array, unlike linearly polarized arrays, is able to detect and estimate any arbitrary completely polarized signal path. By utilizing the polarization information inherent in the received signal to construct the polar-spatio-temporal array (polar-STAR) manifold vector, the accuracy and resolution of the polar-STAR parameters' estimation are significantly improved, and its signal detection capability is enhanced. To alleviate the need for a multidimensional search in the polarization space, a computationally efficient joint polarization-angle-delay channel parameter estimation algorithm is proposed for a "desired user" that operates in an asynchronous multiuser and multipath environment. The proposed algorithm, which can be seen as an application of MUSIC-type techniques, is based on combining a two-dimensional STAR-Subspace type technique with a set of analytical equations and is supported by representative examples and computer simulation studies.     

Application of TSVR algorithm in 5G mmWave indoor networks

A robust algorithm based on Twin Support Vector Regression and discrete wavelet transform applied to millimetric wave (mmWave) channel prediction is proposed in this work. The 60 GHz band is appropriate for small-scale high-speed data transmission applications in future 5G indoor network solutions. The experimentation takes place in an enclosed complex conference room setting with furniture and computer equipment. The proposed algorithm is applied to mmWave multipath channel with higher order modulation scheme with receiver sensitivity thresholds being ? 80 dBm, ? 90 dBm, ? 100 dBm and ? 110 dBm corresponding to 41, 89, 195 and 250 paths, respectively. The Channel Impulse Response of 60 GHz multipath wireless system is generated by the “Wireless InSite” ray tracer by Remcom. Compared to other traditional algorithms, numeric experiments confirm the effectiveness of the proposed solution under several multipath configurations.

     

A study of field strength height profiles caused by multipath fading

The height dependence of the field strength was studied on a line-of-sight link, 43 km in length, at 9.3 GHz. At the receiving site, 14 antennas were mounted one above the other at 2 m spacing. Height profiles with deep fades or marked enhancements of the signal caused by multipath propagation were investigated. The parameters of a propagation model with two or three partial waves were evaluated from the measured data. These parameters were the amplitudes, the differences of the angles of incidence, and the phase differences. Only a small part of the events is covered by the two-path model. The three-path model proves to be much more adapted to this purpose.     

基于簇的块稀疏压缩感知的60GHz信道估计

基于压缩感知设计适用于60 GHz毫米波通信系统的信道估计方案,深入研究了正交匹配追踪(OMP)算法和正则正交匹配追踪(Regularized OMP)算法的60 GHz信道估计性能;在此基础上,充分发掘60 GHz无线多径信道所呈现出的分簇特性,提出一种新颖的基于簇分级的稀疏压缩感知重构算法。新算法在有效减少重构迭代次数的前提下,亦能显著降低信道估计误差。综合对比分析了基于簇分块稀疏压缩感知重构算法和现有压缩感知算法在60 GHz信道估计应用中的重构性能,仿真结果表明,压缩感知算法可有效应用于60 GHz系统信道估计,而新设计的基于簇分级的稀疏压缩感知算法则在估计精度和实现复杂度方面具更优越性能。     

Experimental characterization of the MIMO wireless channel: data acquisition and analysis

Detailed performance assessment of space-time coding algorithms in realistic channels is critically dependent upon accurate knowledge of the wireless channel spatial characteristics. This paper presents an experimental measurement platform capable of providing the narrowband channel transfer matrix for wireless communications scenarios. The system is used to directly measure key multiple-input-multiple-output parameters in an indoor environment at 2.45 GHz. Linear antenna arrays of different sizes and construction with up to ten elements at transmit and receive are utilized in the measurement campaign. This data is analyzed to reveal channel properties such as transfer matrix element statistical distributions and temporal and spatial correlation. Additionally, the impact of parameters such as antenna element polarization, directivity, and array size on channel capacity are highlighted. The paper concludes with a discussion of the relationship between multipath richness and path loss, as well as their joint role in determining channel capacity.     

Centimeter wave propagation experiments using the beacon signals of CS and BSE satellites

The wave propagation experiments using Japanese geostationary satellites CS (20/30 GHz) and BSE (12/14 GHz) satellites have been performed at the Kashima earth station of the Radio Research Laboratories (RRL). Cumulative rain attenuation and cross-polarization discrimination (XPD) statistics are given for the period of three years at 11.7 GHz (vertical polarization) and for the period of four years at 19.5 GHz (circular polarization). It is shown that the yearly rainfall rate and attenuation distributions are well approximated by log-normal distributions, and the XPD distribution is well approximated by a normal distribution. Monthly and time-of-day variation of the attenuation and XPD distributions are presented. Duration statistics of attenuation and XPD are presented and characterized. Other characteristics in the wave propagation, such as effective path length, frequency dependence of attenuation, and joint statistics of attenuation and XPD are derived and discussed. Rainfall events are classified into three rainfall types, "stratus," "cumulus," and "others" using measurements of the radar reflectivity factor along the satellite-to-earth path, and the dependence of XPD characteristics on the rainfall type is also presented and discussed. Some prediction methods of calculating attenuation and XPD statistics are applied to the data obtained in these experiments and the predicted results are compared with the measured ones. It is found that some corrections are needed when the XPD statistics are predicted from the attenuation statistics using the theoretical relation between XPD and attenuation.     

一种应用于无线通信系统的MIMO天线

MIMO系统是通过不同的分集技术,以实现在相同带宽和发射功率的条件下大幅改善系统容量和可靠性,减小信道失真。作为系统关键模块之一的天线,则要求有着好的分集特性,并接收较多的这波。这里提出的MIMO天线工作在2．4GHz,天线单元是等边三角形贴片天线。三角形天线的宽波瓣可以使MIMO天线接收更丰富的多径这波,与天线单元的高增益相结合能较好改善MIMO系统的SNR和抗干扰能力。通过对天线端口间的互耦和相关性分析,该系统能实现好的极化和方向图分集,获得高的分集增益。     

Research on characterization and modeling for 3D wideband time-varying channels for urban microcells at 2.55 GHz

Based on the outdoor microcell MIMO channel measurement campaign at 2.55 GHz,the time-evolution characteristics of three-dimensional wideband channel were studied.The SAGE algorithm was used to extract multipath parameters such as azimuth and elevation angle of departure and arrival.A bidirectional matching algorithm was applied to tracing multipath and the "birth-death" process.The statistical characteristics of multipath birth,lifespan,multipath initial and evolution parameters were analyzed and modeled based on the cross-correlations of multipath parameters.A time-varying channel model with multipath birth-death process was developed.The model parameter table and a detailed flowchart were offered for time-varying channel simulations.The proposed model was validated by comparing the root-mean-square (RMS) of delay spread and angular spread between the simulated and measured results.The channel model proposed can be applied in time-varying channel simulation for urban microcells and it’s also very important to be referred in 5G dynamic channel modeling.