Researchers call for reform of safety standards for millimeter-wave devices

Researchers call for reform of safety standards for millimeter-wave devices

Technology News |
As wireless networks scramble to deal with an exponential demand in data, many are turning to mm-wave frequencies for small cells and for backhaul within dense urban environments. With the drive to 5G, millimeter-wave (mmWave) wireless technology promises to support high-bandwidth content at speeds exceeding 10 gigabits per second — a thousand times today's current mobile phone download speeds.
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With these developments in the pipeline, comes public concern about the health risks associated with utilizing the high-frequency radio waves in that spectrum. As this evolution to ever higher frequencies continues a quantitative measurement of the heating effect on body tissue due to mm-wave radiation would ensure deices are safe. Today, the heating effect from current devices is negligible.

A multidisciplinary team of NYU researchers notes that unlike X-rays and gamma rays, which are called "ionizing radiation" and are known to cause genetic mutations due to their excessive energy levels, millimeter waves are "non-ionizing," with a million times less energy, and are known to cause mainly heating effects, which their simulations have shown to be negligible at levels below current exposure guidelines.

Recently the researchers — NYU Polytechnic School of Engineering doctoral student Ting Wu, NYU WIRELESS Director Theodore "Ted" Rappaport, and Christopher Collins, a professor of radiology at the NYU Langone School of Medicine — published "The Human Body and Millimeter-Wave Wireless Communication Systems: Interactions and Implications," detailing their study, which used four models representing different body parts (both clothed and unclothed) to evaluate the thermal effects of mmWave radiation on humans.

Their simulation showed the steady state temperature increases — even of clothed parts with less blood flow such as the forehead of a person wearing a hat — are negligible compared with the environmental temperature variations when the exposure intensity is similar to that likely to be used in a next-generation cellphone.

Their paper — which was chosen as the best from several hundred entries at the 2015 IEEE Conference on Communications, one of the flagship gatherings of the IEEE Communications Society — called for temperature changes in the tissues of the body to be used as a safety metric for mobile devices operating at mmWave frequencies, rather than power density, now the standard.

"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," says Rappaport, who is the founder and director of NYU WIRELESS, the first university center to combine wireless engineering, computing, and medical applications research and home to pioneering experimentation with the mmWave spectrum. "Additionally, current safety rules regarding radio frequency exposure don’t specify limits above 100 GHz, but because spectrum use will inevitably move to these bands over time, safety metrics must also be codified at these frequencies."


Because magnetic resonance imaging (MRI) provides an efficient method of mapping thermal changes in the body and because the cost of such imaging is decreasing, the researchers suggest that it be employed by wireless manufacturers and regulatory bodies in the future.

"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. It can thus be employed to guarantee the safety of communications devices well into the future," says Collins.

The research paper is available at https://www.mathpubs.com/detail/1503.05944v1/The-Human-Body-and-Millimeter-Wave-Wireless-Communication-Systems-Interactions-and-Implications.

https://nyuwireless.com
https://engineering.nyu.edu

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