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We analyzed different models to estimate absorption at W-band by gaseous species by taking advantage of the collocated CloudSat–Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) measurements. We used the power backscattered by the surface in the green visible wavelength of the lidar of CALIPSO as a reference to infer CloudSat's 94-GHz ocean surface backscatter in clear air and infer the attenuation introduced by gaseous absorption. Different millimeter-wave propagation models (MPMs) and different sources to determine the profile of atmospheric thermodynamic state are used to estimate CloudSat attenuation. These estimates are compared to the observations to calculate the residual dispersion. We show here that we need to adjust the empirical constants of preexisting water vapor absorption models to minimize the dispersion. Our results indicate an overestimation of absorption by the water vapor continuum at 94 GHz in Liebe-based MPM. We also propose a new empirical model to better represent the absorption of the water vapor continuum near 94 GHz. When this model is used in combination with the Advanced Microwave Scanning Radiometer for the Earth Observing System water vapor path and the Global Modeling and Assimilation Office water vapor vertical profile distribution, it leads to the lowest dispersion of the data on a statistical basis (global data over one month). The improved model is expected to optimize water vapor correction applied to CloudSat data and, potentially, also to improve interpretation of brightness temperature measurements in the W-band (e.g., 85- and 98-GHz radiometric channels). [ABSTRACT FROM AUTHOR]

In order to solve a key problem with multi-Gbps transmission in the 60 GHz band—communication interruption by human body crossing, this paper proposes a method to create more reflected waves by installing artificial reflector(s) in two-dimensional arrangements; we show that it reduces the disconnection probability from 80 to 20% (with one artificial reflector) and from 80 to 5% (with two reflectors). The interruption by human crossing is modeled and locations of transmitters and receivers are freely set on any node of a 50 centimeter grid (room sizes are defined by IEEE802.11ad) to get statistically meaningful data. Computer simulations are carried out with various TX and RX antenna HPBWs (Half Power Beam Width), several receiver sensitivities corresponding to 3 Gbps to 0.5 Gbps transmission and assuming a fixed TX antenna direction and a beam-forming receiver antenna that can track the incoming reflected wave(s) in the case of LOS (Line of sight) path interruption. The required minimum reflector radius and disconnection probability can be estimated from the chart described herein given the diagonal dimension of the room and data rate as inputs. By using the chart, the improvement in disconnection probability achieved by installing reflectors can be estimated easily. The improvements by the proposed method are generally applicable to similar indoor communications environments. [ABSTRACT FROM AUTHOR]

Tropospheric scintillation can become a significant impairment in satellite communication systems, especially in those with low fade-margin. Moreover, fast amplitude fluctuations due to scintillation are even larger when rain is present on the propagation path. Few studies of scintillation during rain have been reported and the statistical characterization is still not totally clear. This paper presents experimental results on the relationship between scintillation and rain attenuation obtained from slant-path attenuation measurements at 50 GHz. The study is focused on the probability density function (PDF) of various scintillation parameters. It is shown that scintillation intensity, measured as the standard deviation of the amplitude fluctuations, increases with rain attenuation; in the range 1–10 dB this relationship can be expressed by power-law or linear equations. The PDFs of scintillation intensity conditioned to a given rain attenuation level are lognormal, while the overall long-term PDF is well fitted by a generalized extreme value (GEV) distribution. The short-term PDFs of amplitude conditioned to a given intensity are normal, although skewness effects are observed for the strongest intensities. A procedure is given to derive numerically the overall PDF of scintillation amplitude using a combination of conditional PDFs and local statistics of rain attenuation. [ABSTRACT FROM PUBLISHER]

After a review of the physical/mathematical definitions of anisotropy and canting angle, parameters currently used for describing the depolarization of electromagnetic waves due to hydrometeors, we present some specific algorithms to retrieve these parameters from measurements of the atmospheric polarization transfer matrix, based on data collected during the Italsat propagation experiment at 50 GHz in a slant path with elevation angle 37.7^\circ. The data analysis, conducted after applying particular “ad hoc” procedures and severe editing, allowed to separate in many cases the ice- from the rain-effects, both in single events and statistically. We also present mathematical models derived from the observed behavior of the descriptive parameters, hopefully applicable also in different conditions. [ABSTRACT FROM AUTHOR]

Previous work on rain spatial classification for terrestrial PMP radio systems has been extended in this communication to stratospheric systems—high altitude platform systems. It was found that the rain spatial parameter concept can also be effectively applied to HAP systems, although specific adjustments have had to be made to the method. The differences between terrestrial and stratospheric systems are discussed with regard to the new derived dependences. [ABSTRACT FROM PUBLISHER]

This paper contains measured data for desktop propagation path loss at millimeter wave band. Different ratios between transmitting antenna height and receiving antenna height were studied based on a vector network analyzer system. Transmitting and receiving antenna were separated by distances ranging from 5 to 300 cm on a wooden desktop, and the antenna heights were varied from 5 to 25 cm. Average path loss data are coupled with the path loss exponents and the breakpoint locations of piecewise model to provide insight into large scale propagation characteristics of desktop millimeter wave communication systems. These measurement results may aid in the development of future short range wireless propagation in millimeter wave bands. [ABSTRACT FROM AUTHOR]

A compact four-step 90-degree waveguide twist is designed for operation over the full W- band. The waveguide cross section is modified from the conventional sharp-corners rectangle to comply with the fabrication constraints. The designed twist is fabricated by two processes; CNC machining of the four steps then assembling, and 3D printing through direct metal laser sintering (DMLS). Both of the realized twists measure better performance than that of the commercially-available longer and more expensive twists. Moreover, they are better suited for integrated systems and delicate machining restrictions in W band. [ABSTRACT FROM PUBLISHER]

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 quasi-optical 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 duster 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. [ABSTRACT FROM AUTHOR]

We present a cross-layer modeling and design approach for multiGigabit indoor wireless personal area networks (WPANs) utilizing the unlicensed millimeter (mm) wave spectrum in the 60 GHz band. Our approach accounts for the following two characteristics that sharply distinguish mm wave networking from that at lower carrier frequencies. First, mm wave links are inherently directional: directivity is required to overcome the higher path loss at smaller wavelengths, and it is feasible with compact, low-cost circuit board antenna arrays. Second, indoor mm wave links are highly susceptible to blockage because of the limited ability to diffract around obstacles such as the human body and furniture. We develop a diffraction-based model to determine network link connectivity as a function of the locations of stationary and moving obstacles. For a centralized WPAN controlled by an access point, it is shown that multihop communication, with the introduction of a small number of relay nodes, is effective in maintaining network connectivity in scenarios where single-hop communication would suffer unacceptable outages. The proposed multihop MAC protocol accounts for the fact that every link in the WPAN is highly directional, and is shown, using packet level simulations, to maintain high network utilization with low overhead. [ABSTRACT FROM AUTHOR]

The conversion of rain-rate cumulative distributions from any integration time, T, to one minute is a viable option whenever local one-minute data (time series or cumulative distribution functions) are not available for microwave system design. This paper reviews some of the most common rain-rate cumulative-distribution conversion methods. For selected models, it provides a complementary set of coefficients for regional and global application by performing regression to a measurements database. The performance of each model is analyzed, together with its adaptability to various climatic regions. Finally, recommendations with regard to the global applicability of models are given. [ABSTRACT FROM AUTHOR]

A site-specific desktop propagation model is presented at 60 GHz. The desktop materials involved are wood, glass, and marble. The reflection coefficients versus Tx–Rx separation distance using vertical and horizontal polarization are investigated. Path loss data are then computed using improved two-ray propagation model. Obtained values are compared with the measured data published in IEEE 802.15 TG3c and shown to have a more precise fitting than that predicted by conventional model. The regression model can be used as empirical values for 60 GHz desktop channels. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 907–910, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24192 [ABSTRACT FROM AUTHOR]

A model is presented that extends the applicability of the propagation data collected during a long measurements campaign in a particular site and for a particular radiolink, to a generic link in a generic site. In fact, the objective of the model is to create a set of attenuation time series to be used in the design of advanced TLC systems. The model assumes that the marked differences of the rain statistics observed in various locations are, in first approximation, mainly due to the different frequency of occurrence of the various rainy events rather than to their shape. Starting from this assumption the model selects, from a large database of rain attenuation events collected in a particular site, a subset that, after an appropriate frequency and elevation scaling, can be used to represent time series of attenuation recorded in other experimental conditions (as for both site and link). The model has been applied to the attenuation data collected at Spino d'Adda (Milan, Italy) during the ITALSAT propagation campaign in order to simulate attenuation time series in several different links and sites. The model demonstrated good performance both in link conditions and climates, similar and different from the Spino d'Adda ones. [ABSTRACT FROM AUTHOR]

We measure and characterize the 55-65 GHz wireless channel for a typical desktop environment. The Saleh-Valenzuela (S-V) model is used to describe the desktop environment. Key S-V model parameters such as cluster decay factor, ray decay factor, cluster arrival rate, and ray arrival rate are extracted from measured data. [ABSTRACT FROM AUTHOR]

Signal propagation at frequencies above 10 GHz suffers from significant attenuation due to precipitation. This has to be taken into account when planning point-to-multipoint (PMP) wireless systems operating in the millimeter wave band. Given the nonuniform spatial distribution of the rain rate, the site diversity concept emerges as one of the mitigation techniques. For propagation studies of PMP systems during rain events, rain spatial properties and their corresponding impact on system behavior has to be investigated. An extensive database of rainfall radar data for various types of rain events has been established. System outage improvement was studied using space-time simulations of PMP systems under specific rain conditions. A new approach to rain spatial classification according to its impact on system performance is proposed, using a single rainfall spatial parameter. Examples of its calculation are presented. [ABSTRACT FROM AUTHOR]

The predictions of rain rate and rain attenuation are the most important steps when analyzing a satellite link operating in the Ku and Ka bands. It can be a time-consuming process, especially when the analyses are made on a large number of sites, as might be the case with the broadband satellite systems of today. In this paper, tools for the prediction of rain rate and rain attenuation are given in the form of contour maps for a tropical region (Colombia). The maps presented use the rain rate predicted by different methodologies, and the attenuation caused by these rain rates, using ITU recommendations. The information from these maps can then be entered into attenuation-prediction or system-planning tools. Additionally, a review of the results of the most important rain-rate and rain-attenuation campaigns is presented. [ABSTRACT FROM AUTHOR]

The growing demand for broad-band wireless communication links and the lack of wide frequency bands within the conventional spectrum, causes us to seek bandwidth in the higher microwave and millimeter-wave spectrum at extremely high frequencies (EHF) above 30 GHz. One of the principal challenges in realizing modern wireless communication links in the EHF band are phenomena occuring during electromagnetic wave propagation through the atmosphere. A space-frequency approach for analyzing wireless communication channels operating in the EIIF band is presented. Propagation of the electromagnetic radiation is studied in the frequency domain, enabling consideration of ultrawide-band modulated signals. The theory is employed for the analysis of a communication channel operating at EHF which utilizes pulse amplitude modulated signals. The atmospheric absorptive and dispersive effects on pulse propagation delay, pulse width and distortion are discussed. The theory and model are demonstrated in a study of ultrashort-pulse transmission at 60 GHz. [ABSTRACT FROM AUTHOR]

In the case of depolarization due to rain or to ice crystals, the differential attenuation, the differential phase shift, and the canting angle of the depolarizing medium can all be calculated independently from dual polarized measurement results. However, this is not possible when rain and ice are causing depolarization at the same time. This paper presents a calculation method which makes it possible to derive during simultaneous rain and ice depolarization some of the characterising parameters of each part separately. The method makes use of an a priori known relation between the differential attenuation and the differential phase shift of rain and of ice. The calculation method is tested on measured depolarization events, and yields good results. [ABSTRACT FROM AUTHOR]

The theory is presented for one method of determining the effective polarization parameters of the rain medium in the problem of polarization information processing of detecting target. The determination of the effective polarization parameters of the propagation medium is from the data of propagation measurements over a line-of-sight link. The polarization parameters ϕ the effective average value, σ the effective standard deviation and F the effective shape parameter of the propagation medium are obtained by means of the method of inverse scattering, showing a good agreement with the data from direct measurements. [ABSTRACT FROM AUTHOR]

As the operating frequencies of communication systems more higher into the millimeter wave range, and the density of particles in medium is more denser, the effects of multiple scattering in sandstorm become more significant. This paper treats the problems of electromagnetic multiple scattering in strong sandstorm by the Monte Carlo method. Based on the analytical theory of multiple scattering, the millimeter wave propagation and scattering in discrete random media are investigated by means of the particle-tracking technique. The millimeter wave is regarded as a Markov chain of wave particle collisions in a medium in which it is scattered and absorbed. Considering the effect of multiple scattering, millimeter wave attenuation induced by strong sandstorm is simulated numerically. The values of theoretical calculation are in good agreement with the measured results of simulated experiment at 34 and 93 GHz. [ABSTRACT FROM AUTHOR]

This paper presents the scheme of a software planing tool for single microcells of broadband radio access systems operating at millimeter waves, providing local multipoint distribution services (LMDS), particularly in urban or suburban areas. The aim of this planing tool is to provide operators with information, which supports the assessment of the profitability by calculating link budgets and the area coverage and by roughly estimating the maximum number of potential customers, i.e. the total number of households in a~certain area, as well as the number of customers (households) which will actually be covered from a site. A household is here considered as a single apartment or flat, thus a building usually consists of several households. This novel household-estimation model is able to estimate the number of households based only on the 3D-data of buildings, without using residential data. Besides the optimization of line-of-sight (LOS) coverage, also the possibility is considered to enhance the coverage into shadowed areas by using optimized reflectors as passive repeaters up to distances of 1 km from the base station, depending on the system margin and the rain climate zone. All calculations are based on 3D-databases of both, buildings and vegetation.

In the above article , Wu et al.. would like to point out a figure misuse caused by our negligence when editing. Fig. 21 in the original article is updated as Fig. 1 in this correction. [ABSTRACT FROM AUTHOR]

A brief overview of wireless broadband communication systems, those providing a data rate higher than 2 Mb/s and up to 155 Mb/s, is done by addressing some of the applications and services that are foreseen, as well as some of the technical challenges that need to be solved, and by referring to some safety considerations. After an introduction, the need for high data rates is justified, and possible applications are listed and compared, concerning user mobility and bandwidth. Then an analysis of the propagation aspects at the bands foreseen for these systems-microwaves, millimeter waves and infrared-is presented, also addressing the issue of the antennas and batteries for these systems. [ABSTRACT FROM PUBLISHER]

Thanks to the authors of for their interest in our article, and their valuable comments. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the author discusses various reports within the issue on topics including difference between microwave and millimeter wave propagation on 5G systems, impact of body and blockage for millimeter wave, and millimeter-wave versus synthetic beamwidth.

We acknowledge the anonymous reader’s comments on the above article. We have carefully checked the equations in as well as the corresponding computer code. Equation (1) in is incorrect, as kindly pointed out in the above-mentioned comments. It should be corrected as (2) in the comments. However, in our computer code, we used the correct equation. Thus, parameters f1 and W in are both correct. [ABSTRACT FROM AUTHOR]