What We Do
The Institute for Telecommunication Sciences (ITS) performs cutting-edge telecommunications research and engineering with both federal government and private sector partners. As its research and engineering laboratory, ITS supports NTIA by performing the research and engineering that enables the U.S. Government, national and international standards organizations, and many aspects of private industry to manage the radio spectrum and ensure that innovative, new technologies are recognized and effective. ITS also serves as a principal Federal resource for solving the telecommunications concerns of other Federal agencies, state and local Governments, private corporations and associations, and international organizations. The FY 2015 Technical Progress Report describes research performed in the past fiscal year.
ITS at MILCOM November 1-3
ITS hosted an NTIA booth at MILCOM 2016 November 1-3. On November 1, ITS engineer Chriss Hammerschmidt presented a paper on “Extracting Clutter Metrics From Mobile Propagation Measurements in the 1755-1780 MHz Band” that describes spectrum measurements ITS took during 2015 to inform and validate new radio wave propagation prediction models. ITS has been working to better understand how to factor in the effects of clutter (man-made structures and vegetation) when analyzing and predicting the behavior of radio waves—read about that in the NTIA blog "Understanding Spectrum Clutter—It’s Not About Neatness!" ITS and its predecessor labs within the Department of Commerce have been developing and improving propagation models since about 1909. These mathematical algorithms predict the behavior of radio waves, and they are an essential enabler for spectrum sharing. But increased demand for spectrum, advances in technology, and the tremendous increase in the everyday spectrum usage (sometimes referred to as the “noise floor”), mean that there are tremendous potential benefits from more research and testing to improve the accuracy of existing propagation models. The topic is of special interest to military communications professionals because frequency bands where they operate many critical communications systems are now being opened to sharing. ITS Director Keith Gremban moderated a Technical Panel on Spectrum Sharing - Issues and Approaches on November 2nd where some of the challenges of federal/non-federal spectrum sharing were discussed. Keith also chaired a Technical Paper Session on November 1 on MIMO and Directional Networking, techniques that can help to prevent interference among communications services sharing spectrum.
Research Spotlight: Speech Intelligibility
Speech intelligibility is one of the primary requirements the National Public Safety Telecommunications Council (NPTSC) Broadband Working Group defined for mission critical voice services like those to be delivered over the new nation-wide public safety broadband network that the First Responder Network Authority (FirstNet) is charged with deploying. The NPSTC requirements begin with “The listener MUST be able to understand [what is being said] without repetition.”
For years ITS has conducted various types of subjective testing in tightly-controlled laboratory conditions to sort through myriads of emerging telecom options to find those that sound better or work better in some respect. Where this work was directed towards intelligibility, it has been done through ITS’s participation in the Public Safety Communications Research (PSCR) program, a joint effort with the National Institute of Standards and Technology (NIST), and with the involvement of those who are directly affected—the public safety practitioners. A particular focus has been intelligibility in the presence of background noise to provide comparative intelligibility results for new digital speech and audio codecs, but now the work has expanded to include the condition of the communication network itself.
A new report issued this month describes comparative intelligibility results for new digital speech and audio codecs under different conditions of radio access network (RAN) degradation. Characterizing the relationship between the condition of the RAN and intelligibility is particularly important for mission critical voice because the events that stress the RAN may very well be events that also have critical intelligibility requirements.
One public safety related example would be an event that is escalating, requiring additional personnel to report to the scene. As more and more first responders share radio resources on the scene, those resources will be stressed more and more. As they are stressed, the voice data stream can be corrupted and packets or frames of data can be lost. Voice codecs use various mechanisms to compensate for packet loss or frame erasure—the more successfully they do this, the more “robust” they are and the more likely it is that the listener will be able to understand the message.
The test results published in NTIA Technical Report TR-17-522: Intelligibility of Selected Speech Codecs in Frame-Erasure Conditions can inform codec selection for mission critical voice applications, as well as the design, provisioning, and adaptation of these services and the underlying network. Most importantly, these results can allow those engineering activities to be driven by the critical user experience factor—speech intelligibility.
NTIA Technical Report TR-17-522: Intelligibility of Selected Speech Codecs in Frame-Erasure Conditions
November 2016, Andrew A. Catellier; Stephen D. Voran.
We describe the design, implementation, and analysis of a speech intelligibility test. The test included five codec modes, four frame-erasure rates, and two background noise environments, for a total ...
Conference Paper : Extracting Clutter Metrics From Mobile Propagation Measurements in the 1755-1780 MHz Band
November 2016, Chriss A. Hammerschmidt; Robert T. Johnk.
This paper discusses mobile propagation measurement campaigns in San Diego, CA; Denver, CO; and Washington, D.C. These measurements were made to inform possible clutter models in the 1755-1780 MHz ban...
This Month in ITS History
December 1964: First Description of VLF Propagation Published
Dr. James Wait and Kenneth Spies of the Central Radio Propagation Laboratory (CRPL) published NBS Technical Note 300 on December 30, 1964. “Characteristics of the earth-ionosphere waveguide for VLF radio waves” was an important contribution to understanding radio propagation in the Very Long Frequency (VLF) range between 8kc/s and 30kc/s (3–30 kHz). It was the first description of how VLF waves propagate in the space between the Earth and the ionosphere. Using a man-made waveguide which directs radio waves as a model of the atmosphere, Wait and Spies described the natural phenomenon in simple terms. Today, VLF signals are used for some data (including radio clocks) and navigation services. In 1964, CRPL was investigating VLF for submarine communication, a VLF use that continues today. Tech Note 300 was notable not only for the concepts it described, but because it was the first publication to present the propagation algorithms to describe the behavior of radio waves trapped between the Earth and the ionosphere. The graphical and numerical results in Tech. Note 300 were the only representation of these propagation phenomena available for many years, and were extensively relied upon by researchers of the time. ITS researchers follow in the footsteps of Wait and Spies by investigating and characterizing the propagation of radio waves in all frequencies for improved communications.