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K.L. Blackard

Bio: K.L. Blackard is an academic researcher from Virginia Tech. The author has contributed to research in topics: Path loss & Delay spread. The author has an hindex of 6, co-authored 6 publications receiving 913 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors present the results of average and impulsive noise measurements inside several office buildings and retail stores at 918 MHz, 2.44 GHz, and 4 GHz with a nominal 40-MHz, 3dB RF bandwidth.
Abstract: The authors present the results of average and impulsive noise measurements inside several office buildings and retail stores. The noise measurement system operated at 918 MHz, 2.44 GHz, and 4 GHz with a nominal 40-MHz, 3-dB RF bandwidth. Omnidirectional and directional antennas were used to investigate the characteristics and sources of RF noise in indoor channels. Statistical analyses of the measurements are presented in the form of peak amplitude probability distributions, pulse duration distributions, and interarrival time distributions. Simple first-order mathematical models for these statistical characterizations are also presented. These analyses indicate that photocopiers, printers (both line printers and cash register receipt printers), elevators, and microwave ovens are significant sources of impulse noise in office and retail environments. >

496 citations

Journal ArticleDOI
M.J. Feuerstein1, K.L. Blackard1, Theodore S. Rappaport1, S.Y. Seidel1, H.H. Xia 
TL;DR: The results presented in this paper provide insight into the statistical distributions of measured path loss by showing the validity of a double regression model with a break point at a distance that has first Fresnel zone clearance for line-of-sight topographies.
Abstract: This paper presents results of wide-band path loss and delay spread measurements for five representative microcellular environments in the San Francisco Bay area at 1900 MHz. Measurements were made with a wide-band channel sounder using a 100-ns probing pulse. Base station antenna heights of 3.7 m, 8.5 m, and 13.3 m were tested with a mobile receiver antenna height of 1.7 m to emulate a typical microcellular scenario. The results presented in this paper provide insight into the statistical distributions of measured path loss by showing the validity of a double regression model with a break point at a distance that has first Fresnel zone clearance for line-of-sight topographies. The variation of delay spread as a function of path loss is also investigated, and a simple exponential overbound model is developed. The path loss and delay spread models are then applied to communication system design allowing outage probabilities, based on path loss or delay spread, to be estimated for a given microcell size. >

308 citations

Proceedings ArticleDOI
10 May 1992
TL;DR: Measurements concluded inside three large office buildings in the San Francisco Bay provide an extensive database for propagation models at 915 MHz and 1900 MHz, and show variability in path loss and delay spread caused by multiple floors between communication terminals, and multipath scattering from surrounding buildings.
Abstract: The impact of surrounding buildings on path loss and multipath delay spread for personal communication services (PCS) operating inside buildings is studied. Measurements concluded inside three large office buildings in the San Francisco Bay are provide an extensive database for propagation models at 915 MHz and 1900 MHz, and show variability in path loss and delay spread caused by multiple floors between communication terminals, and multipath scattering from surrounding buildings. Quantitative models provide prediction of the propagation effects caused by surrounding buildings for wireless personal communications system design. >

62 citations

Proceedings ArticleDOI
K.L. Blackard1, M.J. Feuerstein1, Theodore S. Rappaport1, S.Y. Seidel1, H.H. Xia 
10 May 1992
TL;DR: In this article, the authors present the results of wideband path loss and delay spread measurements for two representative microcellular environments in the San Francisco Bay area in the 1900 MHz band.
Abstract: Results of wideband path loss and delay spread measurements for two representative microcellular environments in the San Francisco Bay area in the 1900 MHz band are presented. The results provide insight into the statistical distributions of measured path loss by showing the validity of a double regression model with a break point at a distance that has first Fresnel zone clearance for line-of-sight topographies. The variation of delay spread as a function of path loss is investigated, and a simple exponential overbound model is developed. The path loss and delay spread models are then applied to communication system design allowing outage probabilities, based on path loss or delay spread, to be estimated for a given microcell radius. >

42 citations

Proceedings ArticleDOI
23 Jun 1991
TL;DR: Analysis of noise level distributions, amplitude probability distributions, pulse duration distributions, and interarrival time distributions indicate that photocopiers, printers, elevators, and microwave ovens are significant sources of impulsive noise in office and retail environments.
Abstract: The authors describe average and impulsive noise measurements inside several office buildings and retail stores The receiver had a 70 dB dynamic range and operated at 918 MHz, 244 GHz, and 40 GHz with a nominal 40 MHz 3 dB RF bandwidth Omni-directional and directional antennas were used to investigate the characteristics and sources of RF noise in indoor channels Statistical analyses of the measurements are presented in the form of noise level distributions, amplitude probability distributions, pulse duration distributions, and interarrival time distributions These analyses indicate that photocopiers, printers (line printers and cash register receipt printers), elevators, and microwave ovens are significant sources of impulsive noise in office and retail environments >

23 citations


Cited by
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Journal ArticleDOI
TL;DR: The motivation for new mm-wave cellular systems, methodology, and hardware for measurements are presented and a variety of measurement results are offered that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.
Abstract: The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.

6,708 citations

01 Jan 1993
TL;DR: The principles of radio propagation in indoor environments are reviewed, the channel is modeled as a linear time-varying filter at each location in the three-dimensional space, and the properties of the filter's impulse response are described.

1,735 citations

Journal ArticleDOI
01 Jul 1993
TL;DR: In this paper, a tutorial survey of radio propagation in indoor environments is presented, where the channel is modeled as a linear time-varying filter at each location in the 3D space, and the properties of the filter's impulse response are described.
Abstract: In this tutorial survey the principles of radio propagation in indoor environments are reviewed. The channel is modeled as a linear time-varying filter at each location in the three-dimensional space, and the properties of the filter's impulse response are described. Theoretical distributions of the sequences of arrival times, amplitudes and phases are presented. Other relevant concepts such as spatial and temporal variations of the channel, large-scale path losses, mean excess delay and RMS delay spread are explored. Propagation characteristics of the indoor and outdoor channels are compared and their major differences are outlined. Previous measurement and modeling efforts are surveyed, and areas for future research are suggested. >

1,696 citations

Journal ArticleDOI
TL;DR: Experimental measurements and empirically-based propagation channel models for the 28, 38, 60, and 73 GHz mmWave bands are presented, using a wideband sliding correlator channel sounder with steerable directional horn antennas at both the transmitter and receiver from 2011 to 2013.
Abstract: The relatively unused millimeter-wave (mmWave) spectrum offers excellent opportunities to increase mobile capacity due to the enormous amount of available raw bandwidth. This paper presents experimental measurements and empirically-based propagation channel models for the 28, 38, 60, and 73 GHz mmWave bands, using a wideband sliding correlator channel sounder with steerable directional horn antennas at both the transmitter and receiver from 2011 to 2013. More than 15,000 power delay profiles were measured across the mmWave bands to yield directional and omnidirectional path loss models, temporal and spatial channel models, and outage probabilities. Models presented here offer side-by-side comparisons of propagation characteristics over a wide range of mmWave bands, and the results and models are useful for the research and standardization process of future mmWave systems. Directional and omnidirectional path loss models with respect to a 1 m close-in free space reference distance over a wide range of mmWave frequencies and scenarios using directional antennas in real-world environments are provided herein, and are shown to simplify mmWave path loss models, while allowing researchers to globally compare and standardize path loss parameters for emerging mmWave wireless networks. A new channel impulse response modeling framework, shown to agree with extensive mmWave measurements over several bands, is presented for use in link-layer simulations, using the observed fact that spatial lobes contain multipath energy that arrives at many different propagation time intervals. The results presented here may assist researchers in analyzing and simulating the performance of next-generation mmWave wireless networks that will rely on adaptive antennas and multiple-input and multiple-output (MIMO) antenna systems.

1,417 citations

Journal ArticleDOI
TL;DR: Propagation parameters and channel models for understanding mmWave propagation, such as line-of-sight (LOS) probabilities, large-scale path loss, and building penetration loss, as modeled by various standardization bodies are compared over the 0.5–100 GHz range.
Abstract: This paper provides an overview of the features of fifth generation (5G) wireless communication systems now being developed for use in the millimeter wave (mmWave) frequency bands. Early results and key concepts of 5G networks are presented, and the channel modeling efforts of many international groups for both licensed and unlicensed applications are described here. Propagation parameters and channel models for understanding mmWave propagation, such as line-of-sight (LOS) probabilities, large-scale path loss, and building penetration loss, as modeled by various standardization bodies, are compared over the 0.5–100 GHz range.

943 citations