CDMA vs. GSM: What's the Difference?

pcmag.com:

Two basic technologies in mobile phones, CDMA and GSM, represent a gap you can't cross. They're the reason you can't use old AT&T phones on Verizon's network and vice versa. But what does CDMA vs. GSM really mean for you?

CDMA (Code Division Multiple Access) and GSM (Global System for Mobiles) are shorthand for two older radio systems (also known as 2G and 3G) used in cell phones. We first published this article in 2012 and kept it updated it throughout the 2010s, when it was important to know the differences between these two technologies. But in 2022, it's absolutely time to get off of CDMA and GSM. Those networks are going away! If you have a phone that only uses 2G or 3G, you need to get a 4G or 5G phone, pronto.

AT&T has already shut down its 2G GSM network and most recently said it will shut down 3G GSM/UMTS in February 2022.

T-Mobile will shut down 3G GSM/UMTS in July 2022. It has not set a date to turn off 2G, but has greatly reduced its coverage and quality.

T-Mobile will shut down the 3G CDMA network used by some Sprint and Boost customers on March 31, 2022.

Verizon will shut down its 3G CDMA network on December 31, 2022.

In the twilight years of these networks, they're being turned down to levels primarily designed to support devices like electric meters and vending machines. That means 2G and 3G reception and call quality will likely be poor, even before the formal shutdowns. It's a 4G LTE world now, with 5G coming up fast. No matter how much you love your old phone, it's time to switch over.

Yes, there are some 2G-only and 2G/3G-only phones still for sale, especially unlocked GSM phones. Don't buy them. They'll work poorly, and pretty soon they won't work at all.

Don't weep for CDMA and GSM. They've had