The FCC's Technological Advisory Council (TAC), an advisory group to the FCC operating under the Federal Advisory Committee
Act, is investigating changes and trends to the radio spectrum noise floor to determine if there is an increasing noise
problem, and if so, the scope and quantitative evidence of such problem(s), and how a noise study should be performed. In
this public notice, the Office of Engineering and Technology (OET) announces the TAC's public inquiry, seeking comments
and answers to questions below for the TAC about
radio spectrum noise.
The TAC is requesting input to help answer questions about the study of changes to the spectrum noise floor over the
past 20 years. Noise in this context denotes unwanted radio frequency (RF) energy from man-made sources. Like many spectrum
users, TAC members expect that the noise floor in the radio spectrum is rising as the number of devices in use that emit
radio energy grows. However, in search for concrete evidence of increased noise floors, we have found limited available
quantitative data to support this presumption. We are looking to find ways to add to the available data in order to answer
important questions for the FCC regarding this topic.
"Radio spectrum noise is generated by many different types of devices. Devices that are not designed to generate or emit
RF energy but do so as a result of their operation are called Incidental Radiators. Most electric motors, light dimmers,
switching power supplies, utility transformers and power lines are included in this category. There is little regulation
governing the noise generated by these devices. Noise from such sources is expected to be minimized with "Good Engineering
Practices."
Devices that are designed to generate RF energy for internal use, or send RF signals by conduction to associated equipment
via connected wiring, but are not intended to emit RF energy, are called Unintentional Radiators. Computers and many portable
electronic devices in use today, as well as many new high efficiency lights, are included in this category. Current regulations
limit the levels of emitted RF energy from these devices.
"Unlicensed Intentional Radiators, Industrial, Scientific, and Medical (ISM) Radiators, and Licensed Radiators are devices
that are designed to generate and emit RF energy by radiation or induction. Cellular phones and base stations, unlicensed
wireless routers, Bluetooth devices, broadcast TV and radio stations, and radars of many types, are all examples of licensed
/ unlicensed intentional radiators, and microwave ovens, arc welders, and fluorescent lighting are examples of ISM equipment.
Such emitters contribute to the noise floor with emissions outside of their assigned frequencies. These are sometimes generated
as spurious emissions, including, but not limited to, harmonics of desired frequencies and intermodulation products. Regulations
that permit the operation of these devices also specify the limits of emissions outside of licensed or allowed (in the case
of unlicensed devices) frequencies of operation.
We are looking for responses to the following questions to help us identify aspects of a study to determine trends in
the radio spectrum noise floor.
1. Is there a noise problem?
a. If so, what are the expected major sources of noise that are of concern?
b. What services are being most impacted by a rising spectrum noise floor?
c. If incidental radiators are a concern, what sorts of government, industry, and civil society efforts might be appropriate
to ameliorate the noise they produce?
2. Where does the problem exist?
a. Spectrally i. What frequency bands are of the most interest?
b. Spatially i. Indoors vs outdoors? ii. Cities vs rural settings? iii. How close in proximity to incidental radiators
or other noise sources? iv. How can natural propagation effects be accounted for in a noise study?
c. Temporally
i. Night versus day?
ii. Seasonally?
3. Is there quantitative evidence of the overall increase in the total integrated noise floor across various segments
of the radio frequency spectrum?
a. At what levels does the noise floor cause harmful interference to particular radio services?
b. What RF environment data from the past 20 years is available, showing the contribution of the major sources of noise?
c. Please provide references to scholarly articles or other sources of spectrum noise measurements.
4. How should a noise study be performed?
a. What should be the focus of the noise study?
b. How should it be funded?
c. What methods should be used? d. How should noise be measured?
i. What is the optimal instrumentation that should be used?
ii. What measurement parameters should be used for that instrumentation?
iii. At what spatial and temporal scales should noise be measured?
iv. Should the monitoring instrumentation be capable of determining the directions of the noise sources? If so, how would
those data be used?
v. Is there an optimal height above ground for measurements?
e. What measurement accuracy is needed?
i. What are the statistical requirements for sufficient data? Would these requirements vary based on spectral, spatial
and temporal factors?
ii. Can measurements from uncalibrated, or minimally calibrated, devices be combined?
iii. Is it possible to "crowd source" a noise study?
f. Would receiver noise measurements commonly logged by certain users (e.g. radio astronomers, cellular, and broadcast
auxiliary licensees) be available and useful for noise floor studies?
g. How much data must be collected to reach a conclusion?
h. How can noise be distinguished from signals?
i. Can noise be characterized and its source identified?
ii. Is there a threshold level, below which measurements should be ignored?
