The latest barrier to 5G speeds? The summer

Enlarge / 5G is here, but that doesn’t mean you have to buy into it.

Thermal throttling is a fact of life for smartphones. SoCs generate a lot of heat, and when this heat can’t be dissipated, processors react by slowing down and thereby generating less heat. Usually this is just an issue for heavy 3D gaming sessions or a phone directly exposed to sunlight for a long time, like when mounted on a car windshield. In the era of 5G, though, heat is also an issue for your modem.

While the vast majority of people don’t yet have access to a 5G phone or 5G service, PCMag’s Sascha Segan has been flying around the country testing out the carriers’ nascent implementation of 5G. So far, the heat generated by Qualcomm’s first-generation chips is an issue. Segan writes:

On a hot Las Vegas morning, my two Galaxy S10 5G phones kept overheating and dropping to 4G. This behavior is happening with all of the millimeter-wave, first-generation, Qualcomm X50-based phones when temperatures hit or exceed 85 degrees. We saw it with T-Mobile in New York, with Verizon in Providence, and now with AT&T in Las Vegas. It’s happened on Samsung and LG phones, with Samsung, Ericsson, and Nokia network hardware.

As we wrote back in December, Qualcomm’s first-generation 5G design is a significant regression from the fully integrated 4G chips we’ve been used to. A modern 4G LTE smartphone packs everything into a single main chip, which houses all of the usual computer components along with the LTE modem. Today’s 5G design requires that same chip, along with a separate chip for the 5G mmWave modem and several more chips for the mmWave antenna modules. The result is that 5G takes up a lot more space and generates a lot more heat than 4G, and when this heat gets to be too much, all that 5G circuitry just shuts off.