5G May be Undone by Physics

Someone just analyzed the frequency use by 5G, and physics says that it will burn through batteries like a blow torch through an ice cube:

In 2017, members of the mobile telephony industry group 3GPP were bickering over whether to speed the development of 5G standards. One proposal, originally put forward by Vodafone and ultimately agreed to by the rest of the group, promised to deliver 5G networks sooner by developing more aspects of 5G technology simultaneously.

Adopting that proposal may have also meant pushing some decisions down the road. One such decision concerned how 5G networks should encode wireless signals. 3GPP’s Release 15, which laid the foundation for 5G, ultimately selected orthogonal frequency-division multiplexing (OFDM), a holdover from 4G, as the encoding option.

But Release 16, expected by year’s end, will include the findings of a study group assigned to explore alternatives. Wireless standards are frequently updated, and in the next 5G release, the industry could address concerns that OFDM may draw too much power in 5G devices and base stations. That’s a problem, because 5G is expected to require far more base stations to deliver service and connect billions of mobile and IoT devices.

“I don’t think the carriers really understood the impact on the mobile phone, and what it’s going to do to battery life,” says James Kimery, the director of marketing for RF and software-defined radio research at National Instruments Corp. “5G is going to come with a price, and that price is battery consumption.”

And Kimery notes that these concerns apply beyond 5G handsets. China Mobile has “been vocal about the power consumption of their base stations,” he says. A 5G base station is generally expected to consume roughly three times as much power as a 4G base station. And more 5G base stations are needed to cover the same area.

So how did 5G get into a potentially power-guzzling mess? OFDM plays a large part. Data is transmitted using OFDM by chopping the data into portions and sending the portions simultaneously and at different frequencies so that the portions are “orthogonal” (meaning they do not interfere with each other).

The trade-off is that OFDM has a high peak-to-average power ratio (PAPR). Generally speaking, the orthogonal portions of an OFDM signal deliver energy constructively—that is, the very quality that prevents the signals from canceling each other out also prevents each portion’s energy from canceling out the energy of other portions. That means any receiver needs to be able to take in a lot of energy at once, and any transmitter needs to be able to put out a lot of energy at once. Those high-energy instances cause OFDM’s high PAPR and make the method less energy efficient than other encoding schemes.

Short range, poor building penetration, and high battery consumption.

Heady brew.