Research: Faster Devices Call for Revamped Safety Standards
A multidisciplinary team from New York University has provided research that suggests
regulators should reconsider how they evaluate the health risks of high-frequency radio waves. At issue is millimeter wave (mmWave) wireless
technology, which can deliver a massive amount of raw bandwidth and multi-Gigabit-per-second data rates and therefore makes it a "promising
candidate" for future broadband mobile communication networks. The problem is that the way that government bodies such as the
Federal Communications Commission (FCC) measure radio frequency exposure may not be
sufficient when it comes to mmWave.
Current regulations by the FCC and the International Commission on Non-Ionizing Radiation
Protection use a "power density" model that stipulates how powerful the dose of radiated power given off by "localized exposure scenarios"
— somebody holding a cellphone to his or her ear — can be.
Most mmWave radiation energy is absorbed within a few millimeters from the skin surface. So the main safety concern of mmWave is heating of
eyes and skin. The research project involved development of four simulations — a naked human body, a clothed human body, an exposed forehead
and a covered forehead — to evaluate the thermal effects of mmWave radiation on one-dimensional models of human tissue.
What the researchers found was that the power density model doesn't work when mmWave devices are used close to the body. The simulations
showed the steady state temperature at different body locations varies even when the intensities of the electromagnetic wave radiations are the
same. Power density as a measure doesn't consider the reflection or transmission of mmWave energy across boundaries (such as clothing or skin),
making it less useful for assessing safety.
The alternative proposed for evaluation of safety compliance: a temperature-based technique. Because magnetic resonance imaging provides an
efficient way to map thermal changes in the body, the researchers suggested that MRI be used by wireless manufacturers and regulatory groups in
the future.
The work profiled in "The Human Body and Millimeter-Wave Wireless Communication Systems: Interactions and Implications" was performed by NYU Polytechnic School of Engineering doctoral student Ting Wu,
NYU Wireless Director Ted Rappaport, and Christopher Collins, a professor of radiology at
the NYU Langone School of Medicine. NYU Wireless is a research
center focused on next-generation mass-deployable wireless devices.
"MRI systems utilize electromagnetic energy at a wide range of frequencies to provide high-resolution, three-dimensional images at
ever-increasing scan speeds, and researchers in our group have shown that MRI can be used to map temperature increases caused by
electromagnetic fields — from the low radio frequency to millimeter wave regime," explained Collins in a prepared statement. "It can thus be
employed to guarantee the safety of communications devices well into the future."
"Because future devices will operate on a spectrum with different properties than today's communications devices, FCC rules and regulations
on safety must be reviewed and adjusted accordingly," said Rappaport in the same prepared statement. "Additionally, current safety rules
regarding radio frequency exposure don't specify limits above 100GHz, but because spectrum use will inevitably move to these bands over time,
safety metrics must also be codified at these frequencies."
The research paper, which was presented at the 2015 IEEE International Conference on
Communications,
is freely available online.
About the Author
Leila Meyer is a technology writer based in British Columbia. She can be reached at [email protected].