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.

38 GHz wideband point-to-multipoint radio wave propagation study for a campus environment

Abstract: This article presents the results of a fixed millimeter-wave short-hop radio wave propagation study at 38 GHz. A wideband measurement campaign was performed using three cross-campus radio links from April to August 1998 at Virginia Tech. 73,963 power delay profiles (PDPs) were recorded during different weather events such as clear sky, rain, and hail. Rain/hail attenuation, short-term signal variation, and multipath statistics were studied. The measured rain attenuation (in excess of free space) slightly exceeds the Crane (see Electromagnetic Wave Propagation Through Rain. New York: John Wiley and Sons, 1996) model prediction. Short-term variation of received signal strength during rain follows a Rician distribution with a K factor inversely proportional to the rain rate. The wideband measurements indicate that multipath can occur due to foliage and reflections from wet surfaces during rain.

Free-space optics and high-speed RF for next generation networks $propagation measurements

Abstract: Due to the consistently growing demand for high-speed wireless data access, future communication systems will necessarily have to enable real-time data access and high reliability as well as having superior weather resilience. Hybrid communication networks that integrate free space optics and RF systems are uniquely positioned to satisfy all the bandwidth, reliability, security and 'all-weather functionality' requirements. Unfortunately, the technology has been growing at a pace that far exceeds our understanding of the effect of wireless propagation channels on these hybrid systems. The paper attempts to present some of the preliminary propagation measurement results for typical picocell scenarios and their impact on the design of hybrid communication systems. In addition to clear-sky and rain attenuation measurements, the paper presents frequency diversity measurements for fixed RF systems at the 38 GHz and 60 GHz frequency bands.

Minimum time length link scheduling under blockage and interference in 60GHz networks

Abstract: In this paper we tackle the problem of minimum time length link scheduling in 60GHz wireless networks, under both traffic demand and Signal to Interference and Noise Ratio (SINR) constraints. A constrained Binary Integer Programming (BIP) problem is formulated by incorporating a flexible interference model for directional transmissions and a Markov chain based blockage model. We then propose two effective solution algorithms, including a Greedy Algorithm (GA) that finds the maximum instant throughput for each time slot, and a Column Generation based algorithm (CG) that iteratively improves the current link schedule. The performance of the proposed algorithms is validated with simulations.

Effects of circular and linear polarized antennas on wideband propagation parameters in indoor radio channels

Abstract: Results are presented from an experiment that used a variety of antennas inside two buildings. An important result is that directional circularly polarized (CP) antennas reduce RMS delay spreads when compared with omnidirectional and directional linearly polarized (LP) antennas at identical locations. The variation of RMS delay spread over distances of several wavelengths is also greatly reduced when CP antennas are used in place of LP antennas with similar gains. >

Multipath propagation models for in-building communications

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.

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.