Institute For Telecommunication Sciences Research Articles

Guest Editorial

Guest Editorial

Anita Longley's Legacy: The Longley-Rice Model - Still Going Strong After Almost 50 Years [Historical Corner

At the dawn of the computer age, Anita Longley, Phil Rice, and their colleagues at the Central Radio Propagation Laboratory (CRPL) (now the Institute for Telecommunication Sciences (ITS)) realized that the computational capabilities of the new machines could result in vast improvements of the modeling - and design - of radio systems used by the military and the public in a wide array of applications. The necessity for propagation modeling became evident during World War II, as it was vital for pilots to have reliable communications systems. I In the late 1960s, when the Longley-Rice model was developed, land mobile radio and television systems required better engineering than had been available up to that point in time [1]. Marrying an empirical model (based on electromagnetic theory) with measured data (terrain features and radio measurements) provided that better engineering, and resulted in algorithms still in wide use today.

Understanding the Impact of Network Impairments over Internet-Based Telemedicine Video Traffic

The Internet is designed to provide best effort service, which is not suitable for real-time applications. Therefore, carrying real-time applications over the Internet presents a number of challenges. While quality of service technologies can overcome some of these challenges, most medical facilities and patient homes do not utilize them since there is a high cost associated. Telemedicine and related technologies provide a promising opportunity to improve our healthcare reach to wider populations. The low cost and ubiquity of the Internet can help deliver healthcare to a wider population. However, the unreliable connection properties of packet-based systems hamper the quality of Internet-based telemedicine applications. This research is aimed to explore the delay, jitter, and drop cutoff points for Internet-based videoconferencing applications where video quality stays above the acceptable peak-signal-to-noise-ratio value (25dB). An experimental study is conducted on our testbed where behavior of the Internet is emulated on a Linux PC using NIST Net, a network emulation tool. Video file utilized during these experiments is an ophthalmology telemedicine session and it was obtained from the Regenstrief Institute for Health Care. Video quality measurements are computed using Video Quality Metric (VQM) software, which was developed by the Institute for Telecommunication Sciences (ITS). Our analysis and results indicate that jitter has a severe effect on the video quality whereas the effect of delay is almost invisible. Drop effects are similar to jitter with less impact on video quality. Results presented in this paper include the cutoff points for these variables as well.

Video compression quality metrics correlation with aided target recognition (ATR) applications

Tactical battlefield surveillance systems will require the transmission of compressed video to utilize the limited communication bandwidth and data capacity of these systems. Any compression techniques used will result in some loss of information. It is important to assess the quality of the output video to determine its performance in aided target recognition applications. The traditional rate of distortion formula is shown by Mallet [S. Mallet, Understanding wavelet image compression, Proc. SPIE Wavelet Apps. IV 3078 , 74–93 (April 1997); A theory for multiresolution signal decomposition: The wavelet representation, IEEE Trans. Pattern Anal. Mach. Intell. 11 , 674–693 (1989)] to be inappropriate for wavelet compression in high compression ratios. The reason is that the histogram changes from all gray scale to a concentration singularity near the origin of very low bit rate such that the discrete approximation of the density function of the histogram is no longer valid. Thus we cannot theoretically predict the distortion due to wavelet compression. Therefore we conduct an empirical investigation to evaluate the spatial and temporal effects of lossy wavelet compression and reconstruction on tactical infrared video. We quantify localized peak signal-to-noise ratio and feature persistence measure measurements and objective assessment techniques developed by the Institute for Telecommunication Sciences, U.S. Department of Commerce, to assess video impairment based on quality measurements. We therefore measure video degradation rather than absolute video quality, which is difficult to quantify.

Federal organizations and the commercialization of technology

The United States Government advanced several initiatives to stimulate the commercialization of technologies. The Federal Technology Transfer Act of 1986 provided the legal basis for the private sector's access to government facilities and technical resources. In 1987, the Malcom Baldridge National Quality Award was established to "stimulate American companies to improve quality and productivity for the pride of recognition while obtaining competitive edges through increased profits." Then, in 1988, the Omnibus Trade and Competitiveness Act entrusted the US Department of Commerce with the promotion of innovation. The cumulative effect of all these steps has been to involve the Federal scientific institutions, including the standards-setting organizations, in industrial and commercial activities. Particularly affected were two institutes under the US Department of Commerce, the National Institute of Standards and Technology (NIST), and the National Telecommunications and Information Administration (NTIA). NTIA, which was formed in 1977, includes the Institute for Telecommunication Sciences (ITS), located in Boulder, Colorado.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Foreword: Ionospheric effects on communication and related systems (IES)

The special section contained in this issue of Radio Science is the second of two which have been developed from papers presented at the 1987 symposium on the Effect of the Ionosphere on Communication, Navigation, and Surveillance Systems (IES 1987). This technical conference was jointly sponsored by the Naval Research Laboratory (NRL), the Office of Naval Research (ONR), the Air Force Geophysics Laboratory (AFGL), and the Army Communications‐Electronics Command (USACECOM). The symposium was held in Springfield, Virginia on May 5–7, 1987 in cooperation with the Defense Nuclear Agency (DNA), the Naval Ocean Systems Center (NOSC), the Institute for Telecommunication Sciences (ITS), and the Voice of America (VOA). See the May‐June 1988 issue of Radio Science for a more complete foreword (Radio Sci., 23, 209, 1988).

Jamming to the HF broadcasting service

The Institute for Telecommunication Sciences has been actively involved in an internationally coordinated monitoring program to determine the location of emitters of harmful interference (jamming) to the high-frequency (HF) broadcast service. four monitoring programs were undertaken between October 1984 and June 1986. The procedures that have been used and the results that have been obtained are summarized. The locations of the emitters that cause jamming to the HF broadcast service are shown and selected characteristics of the jamming environment are described. The degree to which jamming that is directed to certain broadcasters adversely impacts the performance of other broadcast services that operate on the same or adjacent channels as the targeted broadcaster is examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Foreword: Ionospheric effects on communication and related systems (IES)

The special section contained in this issue of Radio Science is the second of two which have been developed from papers presented at the 1987 symposium on the Effect of the Ionosphere on Communication, Navigation, and Surveillance Systems (IES 1987). This technical conference was jointly sponsored by the Naval Research Laboratory (NRL), the Office of Naval Research (ONR), the Air Force Geophysics Laboratory (AFGL), and the Army Communications-Electronics Command (USACECOM). The symposium was held in Springfield, Virginia on May 5–7, 1987 in cooperation with the Defense Nuclear Agency (DNA), the Naval Ocean Systems Center (NOSC), the Institute for Telecommunication Sciences (ITS), and the Voice of America (VOA). See the May-June 1988 issue of Radio Science for a more complete foreword (Radio Sci., 23, 209, 1988).

Comparison of HF oblique transmissions with ionospheric predictions

High‐frequency oblique transmissions made for a short period of time during the maximum phase of the past solar cycle are compared with the frequencies predicted utilizing the ITS‐78 and the IONCAP (ionospheric communications analysis and prediction) ionospheric prediction programs developed by the Institute for Telecommunication Sciences. The external atmospheric noise levels predicted by the ITS‐78 program are also compared with experimental data. The measurements conducted in the northeastern U.S. reveal that, for undisturbed solar‐geophysical conditions, the experimental data are in good agreement with the theoretical predictions.

An improved model for earth‐space microwave attenuation distribution prediction

The Dutton‐Dougherty (DD) model for predicting microwave attenuation distribution on an annual basis on earth‐space telecommunications links was first developed at the Institute for Telecommunication Sciences in 1973. The version for making predictions throughout the United States, with year‐to‐year variability allowance, was developed in 1977 and had been essentially unmodified until the present improvement efforts were undertaken. The refinements of the Dutton‐Dougherty model discussed in this paper include an extension of the attenuation distribution prediction range to 0.001% of a year, whereas it had previously extended only to 0.01% of a year. This extension is accomplished in two alternative ways: empirically and analytically. Both extension procedures give nearly identical prediction results. An analysis is conducted of the pertinency of ‘effective path length’ models for evaluating rain attenuation at microwave frequencies to the DD model. It is determined that whereas effective path length methodologies may be useful in their own right, it would be difficult and unwieldy to incorporate this concept into the DD model, at present.

Field‐aligned scattering from a heated region of the ionosphere—Observations at HF and VHF

Radio scattering measurements have been made of a region of the ionosphere above the Institute for Telecommunication Sciences' ionospheric heating facility at Platteville, Colorado. Strong scattering was observed at frequencies in the HF and VHF bands. The scattering has been shown to originate from electron density fluctuations that are highly elongated in the direction of the geomagnetic field. Radar scattering cross sections of 70 to 80 dbsm are measured in the HF and low VHF bands. The scattering cross section decreases at a rate of 20 to 30 db per octave at the high end of the VHF band. The scattering irregularities are produced by operation of the heating facility with o‐mode polarization at frequencies that reflect within the ionosphere. The strength of the scattered energy decreases at a rate of at least 10 db per degree for observation geometries that do not match the geometry for specular reflections from long cylinders aligned with the geomagnetic field. The spatial distribution of irregularities has been estimated for both E‐ and F‐region heating. The temporal properties of the scattering have also been determined including the frequency spectrum of the scattered signals. The processes by which ionospheric heating produces these irregularities are not yet fully explained. Several potentially useful applications of radio scattering from such irregularities are discussed.

Algorithm 433: interpolation and smooth curve fitting based on local procedures [E2

article Free Access Share on Algorithm 433: interpolation and smooth curve fitting based on local procedures [E2] Author: Hiroshi Akima U. S. Department of Commerce, Institute for Telecommunication Sciences, Boulder, CO U. S. Department of Commerce, Institute for Telecommunication Sciences, Boulder, COView Profile Authors Info & Claims Communications of the ACMVolume 15Issue 10Oct. 1972 pp 914–918https://doi.org/10.1145/355604.355605Published:01 October 1972Publication History 44citation1,329DownloadsMetricsTotal Citations44Total Downloads1,329Last 12 Months35Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Design and performance of four buried UHF antennas

As a result of a 10-month study by the Institute for Telecommunication Sciences, four UHF antennas were designed and fabricated, and their absolute power gains for elevation angles from 1\deg to 45\deg and azimuthal patterns at 5\deg elevation angle were measured with each antenna buried beneath 1 m of refractory concrete. Relative response of the four antennas, placed in solid granite, to a signal transmitted from an aircraft at ranges up to 300 km were recorded. The performance of the best buried antenna was comparable to that of a \lambda/4 monopole fed against a 1\lambda diameter ground plane resting on the ground surface near the buried antenna.

Radio wave propagation over irregular terrain in the 76- to 9200-MHz frequency range

Descriptive and statistical analyses of radio propagation data over irregular terrain are presented with emphasis on communications between low antennas in VHF and UHF bands. Measured data are evaluated for medians and ranges of basic transmission loss and height gain, and results are compared with estimates from a propagation model developed by the Institute for Telecommunication Sciences. Effects of vegetation near the path terminals are demonstrated. Analysis results provide first estimates of propagation parameters in many terrain types and information regarding applicability of the propagation model.

Electromagnetic science series

The ESSA/CU series of short summer courses in electromagnetic science will again be offered in two sections from July 27 through August 8, 1970.Sponsored by the Institute for Telecommunication Sciences (ITS) of the Environmental Science Services Administration (ESSA) and the Electrical Engineering Department of the University of Colorado, the classes are another in the continuing series of tutorial and specialized courses dating back to the radio propagation courses offered by the former Central Radio Propagation Laboratory.

ESSA and Its Components: The Environmental Science Services Administration . Including the Coast and Geodetic Survey, the Weather Bureau, the Institute for Telecommunication Sciences and Aeronomy, and Other Related Services. Roy Popkin. Praeger, New York, 1967. x + 278 pp., illus. $5.95. Praeger Library of U.S. Government Departments and Agencies.

ESSA and Its Components: <i>The Environmental Science Services Administration</i> . Including the Coast and Geodetic Survey, the Weather Bureau, the Institute for Telecommunication Sciences and Aeronomy, and Other Related Services. Roy Popkin. Praeger, New York, 1967. x + 278 pp., illus. $5.95. Praeger Library of U.S. Government Departments and Agencies.

The Environmental Science Services Administration. Including the Coast and Geodetic Survey, the Weather Bureau, the Institute for Telecommunication Sciences and Aeronomy, and Other Related Services. Roy Popkin. Praeger, New York, 1967. x + 278 pp., illus. $5.95. Praeger Library of U.S. Government Departments and Agencies

The Environmental Science Services Administration. Including the Coast and Geodetic Survey, the Weather Bureau, the Institute for Telecommunication Sciences and Aeronomy, and Other Related Services. Roy Popkin. Praeger, New York, 1967. x + 278 pp., illus. $5.95. Praeger Library of U.S. Government Departments and Agencies

Ionospheric Electron‐Density Profiles With Continuous Gradients and Underlying Ionization Corrections. III. Practical Procedures and Some Instructive Examples

A description is given of procedures developed at the Institute for Telecommunication Sciences and Aeronomy (ITSA) to permit accurate extraction of virtual‐height data from ionograms in a form easily usable by digital computers. Criteria are described for identification of the significant interval limits along ionogram echo traces.

Ionospheric Electron‐Density Profiles With Continuous Gradients and Underlying lonization Corrections. I. The Mathematical‐Physical Problem of Real‐Height Determination From lonograms

Any numerical method for inversion of the integral equation h'(f)= p.'(/N(z),f)dz must satisfy certain requirements in order to avoid introducing features into the true‐height profile which are not indicated by the ionogram. These requirements are first investigated by considering the equation as an integral transformation of fN(z) for several model distributions. In order to satisfy the above‐mentioned criteria a second‐order lamination process was developed; its mathematical principles are presented in this paper and its implementation at the Institute for Telecommunication Sciences and Aeronomy is discussed in the two following papers.

Ionospheric Electron‐Density ProfiJes With Continuous Gradients and Underlying Ionization Corrections. II. Formulation for a Digital Computer

Details are given of a practical computer formulation of the solution to the ionogram real‐height problem developed at the Institute for Telecommunication Sciences and Aeronomy (ITSA) by A. K. Paul. The method can make full joint or independent use of the ordinary and extraordinary group‐height information available from modern high‐quality radio soundings of the ionosphere. It takes advantage of the strong dependence of group height on the vertical electron‐density gradient at the reflection level to provide a profile with continuous gradients; this is an important feature when applying profile data to radio ray tracing or certain aeronomical problems. Corrections for the “starting” and “valley” portions of the distribution (not directly observed on the soundings) are made by fitting simple models for these regions to portions of the ordinary and/or extraordinary echo data. The problem of numerical convergence of integrals involving the group refractive index infinity is solved by a new expression for the index in which the singular part can be integrated explicitly. The layer maximum is obtained by a parabolic extrapolation which maintains the continuity of gradient to the layer peak and which does not require an independent estimate of the critical frequency.