The biggest update in the new iOS beta is compatibility with the 3.45GHz "mid-band" 5G spectrum that AT&T is rolling out. Other big U.S. carriers like T-Mobile and Verizon already have major mid-band presences on iPhone, so it's good that AT&T's now supported too.
T-Mobile subscribers have also received a boon in iOS 16.4 in the form of 5G Stand-Alone support. Plus, carriers' ability to combine cell frequencies (known as carrier aggregation) for faster data transfer has been improved in the beta as well, which unlike the other upgrades is not exclusive to any carrier.
Mid-band is considered the best compromise when it comes to 5G frequency. It balances the speed of high-band 5G (such as mmWave) with the coverage of low-band 5G, meaning more people get quicker data speeds.
Testing of AT&T mid-band 5G on an iOS 16.4 beta-equipped iPhone by iClarified showed up to 10x download speeds compared to previous performance, since this spectrum is being rolled out to areas without previous mid-band coverage.
Annoyingly, it's only the iPhone 14 that this will work with. AT&T promised previously that older 5G-compatible iPhones would also be covered by its mid-band 5G, but now only the most recent models will get updated to support it.
If you have the beta installed, you can try out these new 5G bands now on an iPhone 14, but otherwise you'll need to wait for the full iOS 16.4 release. That probably won't be far off though, as the final stable release is thought to be coming around March.
iOS 16.4 contains more goodies than 5G improvements. It'll also introduce new emoji, updates to the Music and Podcasts apps, new always-on display settings and other small refinements. We'll be keeping track of all the updates during the betas, as well as giving you our final thoughts when the stable version is released in a few weeks' time.