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.

Cellular broadband millimeter wave propagation and angle of arrival for adaptive beam steering systems (invited paper)

Abstract: The advent of inexpensive millimeter wave devices and steerable antennas will lead to future cellular networks that use carrier frequencies at 28 GHz, 38 GHz, 60 GHz, and above. At these frequencies, the available RF bandwidth is much greater than that of current 4G systems, and high gain millimeter wave steerable antennas can be made in much smaller form factor than current products. This paper presents an extensive measurement campaign and initial results for base-station - to - mobile propagation situations at 38 GHz carrier frequencies in an outdoor urban environment using directional, steerable antennas. This work provides angle of arrival (AOA) and RF multipath characteristics for highly directional antenna beams that may exploit non-line-of-sight propagation paths for futuristic channels at 38 GHz. This work yields data for a variety of antenna pointing and antenna beamwidth scenarios in line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios.

Position Location for Futuristic Cellular Communications: 5G and Beyond

Abstract: With vast mmWave spectrum and narrow beam antenna technology, precise position location is now possible in 5G and future mobile communication systems. In this article, we describe how centimeter-level localization accuracy can be achieved, particularly through the use of map-based techniques. We show how data fusion of parallel information streams, machine learning, and cooperative localization techniques further improve positioning accuracy.

Path Loss, Shadow Fading, and Line-of-Sight Probability Models for 5G Urban Macro-Cellular Scenarios

Abstract: This paper presents key parameters including the line-of-sight (LOS) probability, large-scale path loss, and shadow fading models for the design of future fifth generation (5G) wireless communication systems in urban macro- cellular (UMa) scenarios, using the data obtained from propagation measurements at 38 GHz in Austin, US, and at 2, 10, 18, and 28 GHz in Aalborg, Denmark. A comparison of different LOS probability models is performed for the Aalborg environment. Alpha- betagamma and close-in reference distance path loss models are studied in depth to show their value in channel modeling. Additionally, both single-slope and dual-slope omnidirectional path loss models are investigated to analyze and contrast their root-mean-square (RMS) errors on measured path loss values. While the results show that the dual-slope large-scale path loss model can slightly reduce RMS errors compared to its singleslope counterpart in non-line-of-sight (NLOS) conditions, the improvement is not significant enough to warrant adopting the dual- slope path loss model. Furthermore, the shadow fading magnitude versus distance is explored, showing a slight increasing trend in LOS and a decreasing trend in NLOS based on the Aalborg data, but more measurements are necessary to gain a better knowledge of the UMa channels at centimeter- and millimeter-wave frequency bands.

Smart Antennas : Adaptive Arrays, Algorithms, & Wireless Position Location

Abstract: The interdisciplinary field of smart antennas has matured significantly in the 1990s. It has become clear that this area of work will provide a key technological boon for the wireless communications industry. By early 1999 there will be nearly 300 million wireless subscribers throughout the world, yet there has been relatively little radio spectrum provided to the mobile communications industry since the late 1970s and early 1980s, when cellular telephone systems around the world hosted their very first subscribers. Such rapid consumer growth brings with it radio frequency (RF) interferences and spectral crowding, as well as an urgent need to deploy additional base stations in a wide range of environments with minimal test and measurement. Couple this immense growth with the speed and miniaturization of today's digital signal processing devices, and the growing competition created by multiple wireless carriers, and it can be seen that the demand for smart antennas is just around the corner. This compendium contains classical publications and research papers which have and will continue to impact the emerging field of wireless adaptive arrays. The papers have been compiled based on graduate student research at the Mobile and Portable Radio Research Group (MPRG) at Virginia Tech. Papers are grouped according to the following topics: introductory readings; algorithms; architecture, hardware and applications; channel models; and performance evaluation. This book is a handy, single-source reference to assist graduate students, researchers and practitioners involved with the design, development and deployment of smart antenna technology.

Statistics of the sum of lognormal variables in wireless communications

Abstract: Schwartz and Yeh's method (1982) and Wilkinson's method are widely used to compute the moments of the total co-channel interference in wireless communication, usually modeled as the sum of lognormal random variables. The accuracy of these methods has been studied in previous works, under the assumption of having all summands signals (individual interference signals) identically distributed. Such assumption rarely holds in practical cases of emerging wireless systems, where interference may stem from far-away macrocells and nearby transmitters, causing the interference signals to have different moments. In this paper we present an analysis of Wilkinson's method and Schwartz and Yeh's method, for the general case when the summands have different mean values and standard deviations in decibel units. We show that Schwartz and Yeh's method provides better accuracy than Wilkinson's method and is virtually invariant with the difference of the mean values and standard deviations of the summands, and the number of summands.

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.