Showing papers by "Theodore S. Rappaport published in 1989"
TL;DR: In this paper, a wideband multipath measurements at 1300 MHz were made in five factory buildings in Indiana and the average factory path loss was found to be a function of distance to the 2.2 power.
Abstract: Wideband multipath measurements at 1300 MHz were made in five factory buildings in Indiana. Root-mean-square delay spread ( sigma ) values were found to range between 30 and 300 ns. Median sigma values were 96 ns for line-of-sight paths along aisleways and 105 ns for obstructed paths across aisles. Worst-case sigma or 300 ns was measured in a modern open-plan metal-working factory. Delay spreads were not correlated with transmitter-receiver separation or factory topography but were affected by factory inventory, building construction materials, and wall locations. Wideband path loss measurements consistently agreed with continuous-wave measurements made at identical locations. It is shown that such empirical data suggest independent and identical uniform distributions on the phases of resolvable multipath signal components. Average factory path loss was found to be a function of distance to the 2.2 power. >
429 citations
TL;DR: The extensive empirical data indicate that path loss is dependent upon local surroundings and is log-normally distributed, temporal fading is Rician, and small-scale signal fluctuations due to receiver motion are primarily Rayleigh, although Rician and log-normal distributions fit some of the data.
Abstract: The authors detail the results of narrowband propagation measurements performed at five factories. The extensive empirical data indicate that path loss is dependent upon local surroundings and is log-normally distributed, temporal fading is Rician, and small-scale signal fluctuations due to receiver motion are primarily Rayleigh, although Rician and log-normal distributions fit some of the data. Shadowing effects of common factory equipment likely to obstruct indoor radio paths are also examined. >
292 citations
TL;DR: Radio wave propagation experiments at 1300 MHz, which were conducted by the author in five operational factories, are described, and studies of multipath propagation are discussed, and techniques for overcoming it are considered.
Abstract: The need for reliable, real-time communication for automated factories is discussed. The ability of narrowband digital radio systems to meet that need is examined. The major problems encountered in multipath propagation, resulted from multiple reflections of the transmitted signal from the building structure and surrounding inventory. Radio wave propagation experiments at 1300 MHz, which were conducted by the author in five operational factories, are described. Other studies of multipath propagation are discussed, and techniques for overcoming it are considered. Research on multiple-access networking is summarized. >
187 citations
TL;DR: An experimental position-measuring system has been built and tested, and it demonstrated the ability of this technique to function as a key element in a navigation system for autonomous vehicles.
Abstract: A method for navigating autonomous vehicles is presented. Based on the three-point problem from land surveying, this navigational technique makes use of angular measurements between fixed beacon pairs. Extremely accurate position information can be obtained over a large area with simple trigonometric or analytic geometry calculations. Typical worst-case errors are of the order of 10 cm throughout a 2500 m/sup 2/ workspace. An experimental position-measuring system has been built and tested, and it demonstrated the ability of this technique to function as a key element in a navigation system for autonomous vehicles. >
130 citations
27 Nov 1989
TL;DR: The results of multipath power delay profile measurements of 900-MHz mobile radio channels in Washington, DC, Greenbelt, MD, Oakland, CA, and San Francisco, California, are presented, revealing that at over 98% of the measured locations, RMS delay spreads are less than 12 mu s.
Abstract: The results of multipath power delay profile measurements of 900-MHz mobile radio channels in Washington, DC, Greenbelt, MD, Oakland, CA, and San Francisco, CA, are presented. The measurements have focused on acquiring worst-case profiles for typical operating locations. The data reveal that at over 98% of the measured locations, RMS (root mean square) delay spreads are less than 12 mu s. Urban areas typically have RMS delay spreads on the order of 2 to 3 mu s and have continuous multipath power out to excess delays of 5 mu s. In hilly residential areas and in open areas within a city, RMS delay spreads are slightly larger, typically having values of 5 to 7 mu s. In very rare instances, reflections from city skylines and mountains can cause RMS delay spreads in excess of 20 mu s. The worst-case profiles show resolvable components at excess delays of 100 mu s which are 15 dB down from the first arriving signal. Depending on the precise symbol duration, unequalized 40-kb/s TDMA (time division multiple access) channels will be harmed by multipath at less than 1% to 4% of vehicle locations. >
72 citations
09 Apr 1989
TL;DR: A technique for determining receiver threshold for channel impulse response measurements is analyzed and applied to show that the interpretation of measured results is critically dependent on the value of receiver threshold used.
Abstract: Mathematical models which estimate the number and amplitude of multipath signals in a typical factory environment, and the probability that a multipath component is likely to occur for a given excess delay interval are presented. A technique for determining receiver threshold for channel impulse response measurements is analyzed and applied to show that the interpretation of measured results is critically dependent on the value of receiver threshold used. Models for the number of paths, the likelihood of multipath components, and the strength of the multipath components are given as functions of topography and transmitter-receiver separation. It was shown that a Rayleigh distribution for the amplitude of multipath components is a very good model. The likelihood of multipath was shown to fall off exponentially with excess delay at high threshold values and linearly at lower threshold values. Using a pulse resolution of 7.8 ns, the number of multipath components are shown to fit either a Poisson distribution or a uniform distribution, depending on the received power threshold of the receiver. >
23 citations
01 May 1989
TL;DR: It is shown that the log-normal distribution describes the fading of multipath components over local areas for particular excess delays as well as the distributions of received power within a particular excess delay interval.
Abstract: The secondary statistics for an indoor radio impulse response model in the factory environment are investigated. Under the assumption that multipath signal amplitudes are jointly log-normally distributed over local areas and excess delay, the application of second-order statistics (correlation) is presented. In addition, the distributions of received power within a particular excess delay interval are found for both global and local areas. It is shown that the log-normal distribution describes the fading of multipath components over local areas for particular excess delays. Moreover, individual multipath signal strengths are log-normal about a mean power law of the form d/sup n/. The log-normal distribution is attractive for modeling the impulse response amplitudes because correlation data are easily incorporated. Conditional probabilities of path occupancy are presented which show the effect power control will have on indoor radio systems. >
23 citations
TL;DR: In this paper, the authors describe multipath power delay profile measurements of 900 MHz mobile radio channels in four US cities and show that reflections from city skylines and mountains can cause RMS delay spreads which exceed 20 μs and excess delays which exceed 100 μs.
Abstract: This letter describes multipath power delay profile measurements of 900 MHz mobile radio channels in four US cities. Preliminary data show that for over 98% of the measured locations, RMS delay spreads are less than 12 μs. In very rare instances, reflections from city skylines and mountains can cause RMS delay spreads which exceed 20 μs and excess delays which exceed 100 μs. Such large excess delays have not been previously reported in the literature.
14 citations
11 Dec 1989
TL;DR: In this article, the authors developed statistical indoor radio channel impulse response models (SIRCIM) for the analysis of factory and open plan office communication systems, which will permit research into the development of wideband wireless networks for autonomous guided vehicles (AGVs), vision systems, and portable personal communications inside buildings.
Abstract: This work has developed statistical indoor radio channel impulse response models (SIRCIM) for the analysis of factory and open plan office communication systems. These models will permit research into the development of wideband wireless networks for autonomous guided vehicles (AGVs), vision systems, and portable personal communications inside buildings. Models have been developed which characterize the discrete impulse response of indoor radio channels for both line-of-sight (LOS) and obstructed (OBS) topographies. The effects of transmitter-receiver (T-R) distance and receiver sensitivity are incorporated in the models. Computer simulations which use the models presented here have recreated multipath power delay profiles that are highly representative of actual measurements.
13 citations
11 Jun 1989
TL;DR: OLYMPUS experiments are planned that will include attenuation and fade slope measurements, uplink power control modeling, rain scatter interference measurements, and small-scale site-diversity operation to serve as prototypes for later ACTS experiments.
Abstract: The ESA satellite OLYMPUS and the NASA satellite ACTS (Advanced Communications Technology Satellite) both provide opportunities for 12, 20, and 30 GHz propagation and communications experiments. OLYMPUS is scheduled for launch in 1989 and ACTS in 1992. Measurements are particularly needed on short-term signal behavior and on real-time frequency scaling of attenuation to support uplink power control and adaptive forward error correction techniques. OLYMPUS experiments are planned that will include attenuation and fade slope measurements, uplink power control modeling, rain scatter interference measurements, and small-scale site-diversity operation. These are intended to serve as prototypes for later ACTS experiments. >
TL;DR: In this paper, a radio frequency position location system operating in the 400-450 MHz band was developed and computer simulations based on a hybrid geometric/statistical multipath model of the UHF radio channel were used to determine the distribution of phase and position errors.
Abstract: A radio frequency position location system operating in the 400–450 MHz band has been developed. Computer simulations, based on a hybrid geometric/statistical multipath model of the UHF radio channel, have been used to determine the distribution of phase and position errors in this type of system. Predicted position error distributions agree quite closely with those obtained from experimental tests. Simulations indicate that differential phase errors in the system are well modelled as Gaussian distributed.