5G waveforms in dispute
- Ken Foster & Niels Kuster disagree on averaging times
Very little has been written in the popular media about the waveforms used in 5G signals. Two outstanding questions are: How fast are the pulses? How powerful are they?
In 2018, Esra Neufeld and Niels Kuster of the IT’IS Foundation in Zurich issued a warning in a paper in Health Physics, urging that existing exposure standards be revised with shorter averaging times to address potential thermal damage from short and strong pulses:
“Extreme broadband wireless devices operating above 10 GHz may transmit data in bursts of a few milliseconds to seconds. Even though the time- and area-averaged power density values remain within the acceptable safety limits for continuous exposure, these bursts may lead to short temperature spikes in the skin of exposed people. ... [Our] results also show that the peak-to-average ratio of 1,000 tolerated by the ICNIRP guidelines may lead to permanent tissue damage after even short exposures, highlighting the importance of revisiting existing exposure guidelines.”
In a letter to the journal, Kenneth Foster* of the University of Pennsylvania countered that their claims do not hold up:
“Because real-world communications technologies produce pulses of much lower fluence than the extreme pulses considered by Neufeld and Kuster, the resulting thermal transients from them will be very tiny in any event.”
Neufeld and Kuster’s response to Foster is here.
(Keep in mind that as the averaging time increases, radiation peaks smooth out and compliance with exposure limits becomes easier.)
FCC Proposes Shorter Averaging Times
In its proposed revision of its own RF rules, issued last December, the U.S. FCC appeared to side with Kuster, expressing concern over the many wireless devices that “transmit in short bursts.” Here is part of what the FCC stated:
The FCC put forward shorter averaging times for signals at higher frequencies —dropping down to 1 second above 95 GHz. These are detailed in the table below. In contrast, the averaging times in the ICNIRP and IEEE standards are as high as 25 minutes.
Now, the wireless industry is asking the FCC to favor Foster’s views over Kuster’s. Last week, a team from the Mobile & Wireless Forum (MWF) —formerly known as the Mobile Manufacturers Forum (MMF)— held a virtual meeting with members of the FCC’s Office of Engineering and Technology (OET) and lobbied for the withdrawal of the proposed new averaging times.
The PowerPoint slides of MWF’s presentation are here and its cover letter to the FCC is here. (Chuck Eger, who signed the letter, was formerly in Motorola’s Washington office. He mistakenly used old MMF letterhead.)
Members of the MWF include Apple, Huawei and Samsung. Foster’s research has been supported by the MWF.
Will the FCC formalize the new averaging times in its final RF rules, or follow the MWF request and scrap them? Stay tuned.
* For more on Ken Foster’s work on this issue, see these two recent papers; both are open access:
• Kenneth R. Foster, Marvin C. Ziskin, Quirino Balzano and Akimasa Hirata, “Transient Thermal Responses of Skin to Pulsed Millimeter Waves,” IEEE Access, 2020;
• Kenneth R. Foster, Marvin C. Ziskin, Quirino Balzano and Akimasa Hirata, “Thermal Analysis of Averaging Times in Radiofrequency Exposure Limits Above 1 GHz,” IEEE Access, 2018.
Each paper acknowledges the support of the MWF.
Q. Balzano, a coauthor of the two papers, is a member of the board of the IT’IS Foundation. In their 2018 Health Physics paper, Neufeld and Kuster acknowledge Balzano for his “insights and guidance on emerging wireless communication systems.”
This article is adapted from a thread of seven tweets posted by Microwave News yesterday. If you are not yet following Microwave News on Twitter, give us a try, @microwavenews.