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.

A simulation study of urban in-building cellular frequency reuse

Abstract: This article describes a simulation methodology for accessing capacity of secondary indoor wireless systems that share spectrum with conventional outdoor cellular systems. The techniques described may be used to predict the capacity of the indoor system over a multiyear time window. The results for the channel capacity for indoor "parasitic" cellular systems in a 48-story office building are presented over a 6-year time window. The simulations illustrate that the capacity of the indoor system varies with time as well as with the height above ground. Parasitic indoor systems are assumed to operate with RF power levels low enough that they cause negligible interference to the outdoor cellular system, so this work concentrated on the interference to the indoor system caused by the outdoor cellular (macrocellular) network.

An Open-Source Archiving System

Abstract: Establishment of a Web-based repository for wireless multipath channel measurement data would make it possible for the researchers to pool their datasets to yield more reliable or broadly applicable results or to extract additional value from data that may have been collected for other purposes. It would also allow the validity of models derived from certain data sets to be more easily tested against other data sets than at present. Moreover, ongoing developments in Web technologies will greatly add to the capabilities of such repositories in the coming years. While the wireless community would greatly benefit from the establishment of such a repository for channel measurement data, account must be taken of the significant differences between wireless channel-response data and data collected in other scientific fields. A particu ar challenge is to ensure that essential details concerning the measurement equipment used to collect the data, the manner in which the equipment was calibrated and verified, the data collection procedure, and details of the environment in which the data were collected are adequately documented and linked to the channel response data. Nevertheless, it seems likely that the return from such a wireless channel-response data repository would justify the effort required to set up and maintain it.

Autonomous roving vehicle navigation, control and communication

Abstract: As part of an ongoing project to develop an Intelligent Factory Transport System based on small, inexpensive, fast moving, autonomous vehicles, a number of theoretical and experimental investigations have been carried out to determine the most effective methods for navigating, controlling, and communicating with them in a factory environment. AGVs operating without a physical guidepath require a navigation system capable of maintaining vehicle postion control over extended time and spatial intervals. The navigation and control system that has evolved obtains vehicle position and heading by integrating incremental path changes as determined from shaft encoders on the rear wheels of the vehicle. These quantities are maintained in a global coordinate system containing all possible vehicle paths. An error analysis of the dead reckoning performance indicates . the necessity for supplemenary external inputs and also suggests a straight forward method of calibrating the system in which the error sources are essentially uncoupled. The primary variable used to control position is the crosstrack error of the front wheel relative to the desired path with heading error used during turns. These local coordinates are computed by an appropriate transformation of the global coordinates maintained in the navigation system. Simulations and experiments showed that controlling the crosstrack error of the front wheel relative to the desired path gave a simpler and more stable system than control of the position of the rear wheels .. It was found that, with proper design, excellent performance can be achieved. Because sufficient data was not available to properly characterize the indoor factory radio channel, extensive measurements were made · at five different industrial sites .. It was found that fading characteristics arc strongly dependent on the topography of the work place. Shadowing and large scale loss models have been developed that nrc suitable for use in design of narrowband radio links. Widcband measurements revealed that because of the serious multipath present in· the indoor· factory environment, high data rates arc not possible with conventional modulation systems and new, robust techniques must be developed to meet such needs. -I

Statistical Channel Model with Multi-Frequency and Arbitrary Antenna Beamwidth for Millimeter-Wave Outdoor Communications

Abstract: This paper presents a 3-dimensional millimeter-wave statistical channel impulse response model from 28 GHz and 73 GHz ultrawideband propagation measurements. An accurate 3GPP-like channel model that supports arbitrary carrier frequency, RF bandwidth, and antenna beamwidth (for both omnidirectional and arbitrary directional antennas), is provided. Time cluster and spatial lobe model parameters are extracted from empirical distributions from field measurements. A step-by-step modeling procedure for generating channel coefficients is shown to agree with statistics from the field measurements, thus confirming that the statistical channel model faithfully recreates spatial and temporal channel impulse responses for use in millimeter-wave 5G air interface designs.

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.