November 26, 2018
Behind every initiative to share spectrum are models of how radio waves in a particular band propagate through different environments. How far will a signal travel before it becomes too faint to be useful or to interfere with another signal? What happens when a signal encounters a tree, or a hill, or a house? Accurately measuring real-world spectrum usage and the performance of spectrum-dependent systems is the best way to improve and validate propagation models.
If we can accurately model how radio waves will behave, it can dramatically increase the odds that sharing mechanisms will work. Reliable, validated propagation models can help to facilitate expedited and expanded entry of commercial communication systems into frequency bands previously reserved for Federal systems.
ITS has long been a primary resource in designing and conducting measurement campaigns, applying its decades of experience to ensuring measurements are accurate and provide meaningful data. Over the past several years, we have been working closely with the Defense Spectrum Organization’s (DSO) Spectrum Sharing Test & Demonstration (SST&D) program on a measurement campaign aimed at helping to improve propagation models that are particularly relevant to sharing scenarios that involve Department of Defense communications systems.
NTIA Tech Memo TM-19-535, “Best Practices for Radio Propagation Measurements,” outlines how to calibrate, document, verify, and validate propagation measurements. This handbook of best practices builds on a century of past experience as well as on working papers developed during an intensive measurement campaign to help improve propagation models used by the SST&D program. Its publication continues our long tradition of transferring knowledge and technology into the public domain to advance the state of radio science for all.
“Propagation measurements, while seemingly straightforward, are prone to errors and other uncertainties that potentially decrease the confidence in measurement results and associated application,” says Howard McDonald, DSO’s Advanced Access Initiatives Branch Chief. “The NTIA/ITS ‘Best Practices’ report is a valuable resource to reduce the uncertainties of propagation measurement campaigns.”
TM-19-535 delves into the details of assembling and calibrating a measurement system, discusses the pros and cons of using different instruments for measurement, and provides practical guidance for conducting laboratory and field measurements to optimize accuracy and repeatability. To DSO Chief McDonald’s concern about uncertainties, the tech memo also describes how to quantify the uncertainty of a measurement system, why that matters, and how to meaningfully analyze collected data along with the associated uncertainties.