An anonymous reader quotes a report from Ars Technica: AT&T smartphone users who see their network indicators switch from “4G” to “5G” shouldn’t necessarily expect that they’re about to get faster speeds. In PCMag’s annual mobile-network testing, released today, 5G phones connected to AT&T got slower speeds than 4G phones in 21 out of 22 cities. PCMag concluded that “AT&T 5G right now appears to be essentially worthless,” though AT&T’s average download speed of 103.1Mbps was nearly as good as Verizon’s thanks to a strong 4G performance. Of course, AT&T 5G should be faster than 4G in the long run — this isn’t another case of AT&T misleadingly labeling its 4G network as a type of 5G. Instead, the disappointing result on PCMag’s test has to do with how today’s 5G phones work and with how AT&T allocates spectrum. The counterintuitive result doesn’t reveal much about the actual differences between 4G and 5G technology. Instead, it’s reflective of how AT&T has used its spectrum to deploy 5G so far. As PCMag explained, “AT&T’s 5G slices off a narrow bit of the old 850MHz cellular band and assigns it to 5G, to give phones a valid 5G icon without increasing performance. And because of the way current 5G phones work, it often reduces performance. AT&T’s 4G network benefits from the aggregation of channels from different frequencies. “The most recent phones are able to assemble up to seven of them — that’s called seven-carrier aggregation, and it’s why AT&T won [the PCMag tests] last year,” the article said. 5G phones can’t handle that yet, PCMag analyst Sascha Segan wrote: “But 5G phones can’t add as many 4G channels to a 5G channel. So if they’re in 5G mode, they’re giving up 4G channels so they can use that extremely narrow, often 5MHz 5G channel, and the result is slower performance: faux G. For AT&T, using a 5G phone in testing was often a step backward from our 4G-only phone.” Read more of this story at Slashdot.