Theodore S. Rappaport

Bio: Theodore S. Rappaport is an academic researcher from New York University. The author has contributed to research in topics: Path loss & Multipath propagation. The author has an hindex of 112, co-authored 490 publications receiving 68853 citations. Previous affiliations of Theodore S. Rappaport include University of Waterloo & University of Texas at Austin.

Using RF channel sounding measurements to determine delay spread and path loss

Abstract: Time dispersion in RF dhannels, induced by multipath caused by reflectors. and scatterers in the propagation environment, must be considered when designing high-rate digital radio systems and wireless modems. This article describes the parameters used to characterize time dispersion and path loss in an RF channel from measured data. Following a discussion of the time dispersion parameters, the analysis and results of measurement data taken in a large train yard in the 902 928 MHz IBM band are presented.

Radio frequency noise measurements and models for indoor wireless communications at 918 MHz, 2.44 GHz, and 4.0 GHz

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 >

Indoor radio channel models for manufacturing environments

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. >

Application of second-order statistics for an indoor radio channel model

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. >

A preliminary 3D mm wave indoor office channel model

Abstract: With the ever increasing demands in higher data rate, there is a growing interest in exploiting the millimeter wave (mmWave) spectrum for future access communications. Aiming at characterizing the mmWave indoor propagation channel, a wideband measurement campaign using directional antennas has been conducted at 73 GHz in New York City in an office-type environment. In addition, ray-tracing using a database with the same environment has been performed to predict channel parameter statistics in conjunction with the measured data. A preliminary 3GPP-like 3D mmWave indoor channel model is proposed including the distance-dependent elevation model. The estimated channel characteristics such as delay spread and angular spread are validated with the measurements. The proposed channel model can be used in simulating mmWave indoor communications in office-type environments using multi-input multi-output (MIMO) antenna arrays.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Cooperative diversity in wireless networks: Efficient protocols and outage behavior

Abstract: We develop and analyze low-complexity cooperative diversity protocols that combat fading induced by multipath propagation in wireless networks. The underlying techniques exploit space diversity available through cooperating terminals' relaying signals for one another. We outline several strategies employed by the cooperating radios, including fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes that adapt based upon channel measurements between the cooperating terminals, and incremental relaying schemes that adapt based upon limited feedback from the destination terminal. We develop performance characterizations in terms of outage events and associated outage probabilities, which measure robustness of the transmissions to fading, focusing on the high signal-to-noise ratio (SNR) regime. Except for fixed decode-and-forward, all of our cooperative diversity protocols are efficient in the sense that they achieve full diversity (i.e., second-order diversity in the case of two terminals), and, moreover, are close to optimum (within 1.5 dB) in certain regimes. Thus, using distributed antennas, we can provide the powerful benefits of space diversity without need for physical arrays, though at a loss of spectral efficiency due to half-duplex operation and possibly at the cost of additional receive hardware. Applicable to any wireless setting, including cellular or ad hoc networks-wherever space constraints preclude the use of physical arrays-the performance characterizations reveal that large power or energy savings result from the use of these protocols.

Cognitive radio: brain-empowered wireless communications

Abstract: Cognitive radio is viewed as a novel approach for improving the utilization of a precious natural resource: the radio electromagnetic spectrum. The cognitive radio, built on a software-defined radio, is defined as an intelligent wireless communication system that is aware of its environment and uses the methodology of understanding-by-building to learn from the environment and adapt to statistical variations in the input stimuli, with two primary objectives in mind: /spl middot/ highly reliable communication whenever and wherever needed; /spl middot/ efficient utilization of the radio spectrum. Following the discussion of interference temperature as a new metric for the quantification and management of interference, the paper addresses three fundamental cognitive tasks. 1) Radio-scene analysis. 2) Channel-state estimation and predictive modeling. 3) Transmit-power control and dynamic spectrum management. This work also discusses the emergent behavior of cognitive radio.

An application-specific protocol architecture for wireless microsensor networks

Abstract: Networking together hundreds or thousands of cheap microsensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. These networks require robust wireless communication protocols that are energy efficient and provide low latency. We develop and analyze low-energy adaptive clustering hierarchy (LEACH), a protocol architecture for microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. LEACH includes a new, distributed cluster formation technique that enables self-organization of large numbers of nodes, algorithms for adapting clusters and rotating cluster head positions to evenly distribute the energy load among all the nodes, and techniques to enable distributed signal processing to save communication resources. Our results show that LEACH can improve system lifetime by an order of magnitude compared with general-purpose multihop approaches.