Research: Faster Devices Call for Revamped Safety Standards

• By Leila Meyer
• 06/15/15

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.