The new LTE Apple Watch Series 3 doesn't have the CDMA radio system upon which Sprint and Verizon have long relied. And yet it makes phone calls. No Sprint device has combined those factors before, and the watch's abilities hint at a future when a wider range of devices will be available on these networks.
Beyond being technically interesting, this opens up hope that Verizon and Sprint subscribers will be able to use phones that haven't been pre-approved by their carriers. There's some good news and bad news there.
CDMA, Make Way
CDMA2000 is a 2G mobile standard that's used by Verizon, Sprint, U.S. Cellular, and carriers in China, Japan, Korea, Indonesia, and a few other countries. It's less popular than the bigger GSM/UMTS standard. One of its aspects that carriers love, but consumers tend to hate, is that CDMA carriers can restrict their networks so only approved phones can be used. GSM networks must accept any compatible phone.
Both Verizon and Sprint want to rusticate their CDMA networks … eventually. It's a 2G, 20th-century technology that is reaching the end of its useful life. Verizon has set a date at the end of 2019 to kill CDMA.
Sprint's in a tougher position because it hasn't matched its CDMA coverage with 4G LTE yet. It's not giving a date to turn off CDMA, I think because it's waiting for confidence that it can offer LTE coverage everywhere it currently has CDMA.
Other than coverage, the one thing CDMA does well is make phone calls. Verizon has been working on moving all of its users to VoLTE, voice-over-LTE, which lets Verizon users make calls on 4G LTE without having to touch that 2G network.
Sprint hasn't yet announced any rollout date for industry standard VoLTE. But it has a stopgap. In June, the company introduced "Calling Plus," which essentially routes Wi-Fi phone calls over the LTE network. It isn't the broad VoLTE standard that the other carriers use, iako, which means that phones have to support Sprint Calling Plus as a special extra feature.
But wait! It gets even weirder. According to Sprint, the Apple Watch doesn't use Calling Plus ili VoLTE. It uses another form of voice-over-IP to make phone calls, which I couldn't get more details on.
Both carriers have had a few LTE-only devices. Sprint's Slate 8 and Slate 8 Plus tablets, and its LTE-only mobile hotspots, didn't have to make phone calls. The Watch is the first "phone" on Sprint to run without CDMA. (I have to insert here: Sprint doesn't call it a phone, they call it a wearable. But it's a wearable that works like a phone.) That's a major technical milestone for Sprint.
Verizon has been experimenting with LTE-only devices for longer than Sprint has, in part because it has better LTE coverage. It currently has the Asus Zenfone AR smartphone and a flip phone, the LG Exalt LTE, running as LTE-only phones.
No CDMA Doesn't Mean Freedom
Here's the rub, iako. It doesn't look like getting rid of CDMA is going to create consumer freedom on Verizon's and Sprint's networks.
For now, supporting phone calls on Sprint means supporting proprietary Sprint software, which means working with Sprint.
Verizon says it uses global LTE standards. But we've tried a few devices that Verizon hasn't approved, and mysteriously, they don't work. They just don't authenticate. Users of the ZTE Axon 7 phone have seen how their supposedly compatible phone needs to be constantly attended to, massaged, and sometimes hacked to continue to work on Verizon. So for now, Verizon subscribers will have to stick with phones approved by Verizon.
This step is generally good news for Verizon and Sprint and their users, iako, for a different reason. The two carriers devote a lot of their valuable wireless spectrum to CDMA. As they get more LTE-only devices online, they can flip more of that spectrum over to LTE, reducing LTE congestion and increasing speeds. So your cellular Apple Watch will help to contribute to a better calling experience for everyone on your network.