Showing papers by "Theodore S. Rappaport published in 2002"
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TL;DR: The measurement results confirm that the majority of the multipath components can be determined from image based ray tracing techniques for line-of-sight (LOS) applications and can be used as empirical values for broadband wireless system design for 60-GHz short-range channels.
Abstract: This article presents measurement results and models for 60-GHz channels. Multipath components were resolved in time by using a sliding correlator with 10-ns resolution and in space by sweeping a directional antenna with 7/spl deg/ half power beamwidth in the azimuthal direction. Power delay profiles (PDPs) and power angle profiles (PAPs) were measured in various indoor and short-range outdoor environments. Detailed multipath structure was retrieved from PDPs and PAPs and was related to site-specific environments. Results show an excellent correlation between the propagation environments and the multipath channel structures. The measurement results confirm that the majority of the multipath components can be determined from image based ray tracing techniques for line-of-sight (LOS) applications. For non-LOS (NLOS) propagation through walls, the metallic structure of composite walls must be considered. From the recorded PDPs and PAPs, received signal power and statistical parameters of angle-of-arrival and time-of-arrival were also calculated. These parameters accurately describe the spatial and temporal properties of millimeter-wave channels and can be used as empirical values for broadband wireless system design for 60-GHz short-range channels.
650 citations
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500 citations
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TL;DR: New envelope probability density functions (PDFs) that describe small-scale, local area fading experienced by narrow-band wireless receivers and novel PDFs that describe theLocal area fading of two specular multipath components in the presence of other diffusely propagating waves are developed.
Abstract: This paper presents new envelope probability density functions (PDFs) that describe small-scale, local area fading experienced by narrow-band wireless receivers. The paper also develops novel PDFs that describe the local area fading of two specular multipath components in the presence of other diffusely propagating waves. These PDFs are studied in the context of classical fading PDFs such as the Rayleigh, Rician, and other distributions.
367 citations
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TL;DR: Some of the key technological advances and approaches that are now emerging as core components for wireless solutions of the future are explored.
Abstract: the 21 st century. ireless communications has emerged as one of the largest sectors of the telecommunications ,industry, evolving from a niche business in the last decade to one of the most promising areas for growth in the 21st cenW tury. This article explores some of the key technological advances and approaches that are now emerging as core components for wireless solutions of the future.
328 citations
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12 Feb 2002
TL;DR: In this article, a method and system for creating, using, and managing a three-dimensional digital model of the physical environment combines outdoor terrain elevation and land-use information, building placements, heights and geometries of the interior structure of buildings, along with site-specific models of components that are distributed spatially within a physical environment.
Abstract: A method and system for creating, using, and managing a three-dimensional digital model of the physical environment combines outdoor terrain elevation and land-use information, building placements, heights and geometries of the interior structure of buildings, along with site-specific models of components that are distributed spatially within a physical environment (Fig. 18). The present invention separately provides an asset management system that allows the integrated three-dimensional model of the outdoor, indoor, and distributed infrastructure equipment to communicate with and aggregate the information pertaining to actual physical components of the actual network (183), thereby providing a management system that can track the on-going performance, cost, maintenance history, and depreciation of multiple networks (189) using the site-specific unified digital format.
273 citations
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TL;DR: A statistical geometric propagation model for a macrocell mobile environment that provides the statistics of angle-of-arrival (AOA) of the multipath components, which are required to test adaptive array algorithms for cellular applications are developed.
Abstract: We develop a statistical geometric propagation model for a macrocell mobile environment that provides the statistics of angle-of-arrival (AOA) of the multipath components, which are required to test adaptive array algorithms for cellular applications. This channel model assumes that each multipath component of the propagating signal undergoes only one bounce traveling from the transmitter to the receiver and that scattering objects are located uniformly within a circle around the mobile. This geometrically based single bounce macrocell (GBSBM) channel model provides three important parameters that characterize a channel: the power of the multipath components, the time-of-arrival (TOA) of the components, and the AOA of the components. Using the GBSBM model, we analyze the effect of directional antennas at the base station on the fading envelopes. The level crossing rate of the fading envelope is reduced and the envelope correlation increases significantly if a directional antenna is employed at the base station.
256 citations
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23 Apr 2002
TL;DR: In this article, a system for creating a computer database model of either measured data network throughput properties or wireless communication signal properties within a facility by measuring the desired properties at a plurality of locations within the facility and embedding the measured properties at the location of measurement represented in a three-dimensional facility drawing database is presented.
Abstract: A system for creating a computer database model of either measured data network throughput properties or wireless communication signal properties within a facility by measuring the desired properties at a plurality of locations within the facility and embedding the measured properties at the location of measurement represented in a three-dimensional facility drawing database.
173 citations
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17 Sep 2002
TL;DR: In this article, a method for displaying the results of predicted wireless communication system performance as a three-dimensional region of fluctuating elevation and/or color within a 3D computer drawing database consisting of one or more multi-level buildings, terrain, flora, and additional static and dynamic obstacles (e.g., automobiles, people, filing cabinets, etc.).
Abstract: A method for displaying the results of predicted wireless communication system performance as a three-dimensional region of fluctuating elevation and/or color within a three-dimensional computer drawing database consisting of one or more multi-level buildings, terrain, flora, and additional static and dynamic obstacles (e.g., automobiles, people, filing cabinets, etc.). The method combines computerized organization, database fusion, and site-specific performance prediction models. The method enables a design engineer to visualize the performance of any wireless communication system as a three-dimensional region of fluctuating elevation, color, or other aesthetic characteristics with fully selectable display parameters, overlaid with the three-dimensional site-specific computer model for which the performance prediction was carried out.
172 citations
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10 Dec 2002TL;DR: In this paper, measured data for 2.4 GHz and 60 GHz in-building partition loss are presented. But the authors focus on the 2.5 GHz band and do not consider the 60 GHz band.
Abstract: This paper contains measured data for 2.5 and 60 GHz in-building partition loss. Path loss measurements were recorded using a broadband sliding correlator channel sounder which recorded over 39000 power delay profiles (PDP) in 22 separate locations in a modern office building. Transmitters and receivers were separated by distances ranging from 3.5 to 27.4 meters, and were separated by a variety of obstructions, in order to emulate future single-cell-per-room wireless networks. These measurements may aid in the development of future in-building wireless networks in the unlicensed 2.4 GHz and 60 GHz bands.
77 citations
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16 Dec 2002
TL;DR: This technical overview outlines some key network research issues, and differentiates the features of wireless networks and the services that they will support.
Abstract: This technical overview outlines some key network research issues, and differentiates the features of wireless networks and the services that they will support. As the Internet becomes ubiquitously delivered on mobile platforms, new approaches to wireless networking that build upon the advances of wireline networks and cellular system design will be required.
39 citations
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04 Nov 2002TL;DR: In this paper, a system and method for measuring and monitoring wireless network performance in campus and indoor environments provides for embedding measured network and signal properties at one or more locations within a facility into a site specific computer model which represents the facility.
Abstract: A system and method for measuring and monitoring wireless network performance in campus and indoor environments provides for embedding measured network and signal properties at one or more locations within a facility into a site specific computer model which represents the facility. The computer representation is preferably three dimensional. The system and method allows for automatic, periodic, or location specific taking of measurements, and automatic or periodic embedding of measured data. The system and method allows real time or non-real time measurement and storing of performance data, and the invention is useful for test, measurement, verification, and in-situ or remote monitoring for on-going validation and maintenance of wireless networks.
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10 Dec 2002TL;DR: 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 and frequency diversity measurements for fixed RF systems at the 38 GHz and 60 GHz frequency bands.
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.
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22 Aug 2002TL;DR: A set of dynamic data structures is proposed here to balance the memory requirements with execution time, while simultaneously adapting to arbitrary problem size to make the DIRECT global optimization algorithm efficient and robust.
Abstract: The DIRECT (DIviding RECTangles) algorithm [23], a variant of Lipschitzian methods for bound constrained global optimization, has been applied to the optimal transmitter placement for indoor wireless systems. Power coverage and BER (bit error rate) are considered as two criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. The performance of a DIRECT implementation in such applications depends on the characteristics of the objective function, the problem dimension, and the desired solution accuracy. Implementations with static data structures often fail in practice because of unpredictable memory requirements. This is especially critical in S 4 W (Site-Specific System Simulator for Wireless communication systems), where the DIRECT optimization is just one small component connected to a parallel 3D propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations, and surrogate functions for a WCDMA (wideband code division multiple access) simulator are also used to estimate the channel performance. Any component failure of this large computation would abort the entire design process. To make the DIRECT global optimization algorithm efficient and robust, a set of dynamic data structures is proposed here to balance the memory requirements with execution time, while simultaneously adapting to arbitrary problem size. The focus is on design issues of the dynamic data structures, related memory management strategies, and application issues of the DIRECT algorithm to the transmitter placement optimization for wireless communication systems. Results for two indoor systems are presented to demonstrate the effectiveness of the present work. ACKNOWLEDGEMENTS I would like to express my appreciation for the support and guidance that I received from my advisor Dr. Layne T. Watson in the past two years. Also, I want to thank the other two members of my advisory committee, Dr. Calvin J. Ribbens and Dr. Eunice Santos, for their sincere support and advice. for their work on WCDMA (wideband code division multiple access) simulations and the corresponding surrogate MARS (multivariate adaptive regression splines) modeling (documented in Chapter 5.2). I would also thank S. Rappaport for their effort in organizing research meetings to help students collaborate with each other. In this project, many practical optimization applications were provided for exploring this global search algorithm—DIRECT. Finally, I would like to thank Dr. Srinidhi Varadarajan for his administration on the 200 node AMD Athlon Beowulf cluster at the Laboratory for Advanced Scientific Computing and Applications (LASCA). Without such computing power, …
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09 Oct 2002
TL;DR: In this paper, an automated method for quickly generating a complete bill of materials and total cost information in real-time is presented, where components for a desired system are specified and/or replaced by substitute components while continuously predicting the wireless system performance.
Abstract: An automated method for quickly generating a complete bill of materials and total cost information in real time. Components for a desired system are specified and/or replaced by substitute components, while continuously predicting the wireless system performance. A design engineer builds a model of the desired wireless communications system and specifies each component necessary to provide sufficient or optimal system performance. A parts list is maintained, in real time, that contains a definition of each system component and its associated performance and cost parameters. As the user changes wireless system designs through a series of “what-if” scenarios, components are replaced with substitute components, cable lengths are modified, antenna systems and base station parameters are re-designed and moved to alternate locations, etc. The bill of materials is automatically updated and component costs and total system costs are immediately available to the design engineer. The designer may choose to swap components for less expensive components or may investigate several alternate radio frequency distribution and antenna schemes, etc. The performance characteristics of the system are automatically updated as is the system cost as the designer to assesses the trade-offs between performance and cost at the same time.
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07 Nov 2002TL;DR: Based on the performance, transmitter location optimization in indoor environments is considered and results indicate that the effective diversity order is retained even when high cross correlation exists and power imbalance exists between signals from different antennas.
Abstract: This paper presents the performance of space-time block coding based transmit diversity (STTD) in WCDMA on correlated fading channels and on unbalanced transmitted power. Then, based on the performance, transmitter location optimization in indoor environments is considered. Results indicate that the effective diversity order is retained even when high cross correlation exists and power imbalance exists between signals from different antennas. Also, a global optimization algorithm with the help of a ray tracer can find transmitter locations which are optimal (global optimum) in the sense of power coverage or overall BER in the area of interest.
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TL;DR: BSML is designed to integrate with a PSE or application composition system that views model specification and execution as a problem of managing semistructured data.
Abstract: We describe a binding schema markup language (BSML) for describing data interchange between scientific codes. Such a facility is an important constituent of scientific problem solving environments (PSEs). BSML is designed to integrate with a PSE or application composition system that views model specification and execution as a problem of managing semistructured data. The data interchange problem is addressed by three techniques for processing semistructured data: validation, binding, and conversion. We present BSML and describe its application to a PSE for wireless communications system design.
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01 Jan 2002TL;DR: This chapter presents a novel theoretical framework for relating the small-scale fading characteristics of a wireless channel to multipath angle-of-arrival, and three shape factors that have simple, intuitive geometrical interpretations are shown to describe the statistics of received signal fluctuations in a fading multipath channel.
Abstract: This chapter presents a novel theoretical framework for relating the small-scale fading characteristics of a wireless channel to multipath angle-of-arrival. A method is presented for reducing a multipath channel with arbitrary spatial complexity to three shape factors that have simple, intuitive geometrical interpretations. Furthermore, these shape factors are shown to describe the statistics of received signal fluctuations in a fading multipath channel. Examples demonstrate how the shape factors may be applied to real-life problems in channel measurement, level-crossing rate and average fade duration calculations, and coherence distance estimation.
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TL;DR: In this paper, a statistical framework for assessing wireless systems performance using hierarchical data mining techniques is presented, where the authors consider WCDMA systems with two-branch STTD (space time transmit diversity) and 1/2 rate convolutional coding (forward error correction codes).
Abstract: This paper presents a statistical framework for assessing wireless systems performance using hierarchical data mining techniques. We consider WCDMA (wideband code division multiple access) systems with two-branch STTD (space time transmit diversity) and 1/2 rate convolutional coding (forward error correction codes). Monte Carlo simulation estimates the bit error probability (BEP) of the system across a wide range of signal-to-noise ratios (SNRs). A performance database of simulation runs is collected over a targeted space of system configurations. This database is then mined to obtain regions of the configuration space that exhibit acceptable average performance. The shape of the mined regions illustrates the joint influence of configuration parameters on system performance. The role of data mining in this application is to provide explainable and statistically valid design conclusions. The research issue is to define statistically meaningful aggregation of data in a manner that permits efficient and effective data mining algorithms. We achieve a good compromise between these goals and help establish the applicability of data mining for characterizing wireless systems performance.