Two basic technologies in mobile phones, CDMA and GSM, represent a gap you can't cross. They're the reason you can't use older 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 (2G and 3G) used in cell phones. In this story, I'll try to explain who uses which technology and what the real differences are.
We have been updating this story since 2012. In 2020, it's absolutely time to get off of CDMA and GSM. Verizon will turn off its CDMA network and T-Mobile will turn off its 2G GSM network by the end of 2020. In 2021, AT&T and T-Mobile will keep their 3G networks in very low-bandwidth modes mostly designed to support devices like electric meters and vending machines. Now that T-Mobile owns Sprint, it's likely to do the same with Sprint's old CDMA network. That means 2G/3G reception and call quality will likely be poor, if you get a signal at all. It's a 4G LTE world now, and if you aren't in it yet, it's time to switch over.
1G, 2G, 3G, 4G, 5G
When cell phone providers talk about a "G," they mean a generation of wireless technology. Each generation is able to support more users, and has better data transfer capabilities.
The first generation was analog cellular phones. When carriers switched to 2G digital systems in the 1990s, they chose between several competing options; some of them died out, but CDMA and GSM are the two 2G camps that survived. They remained split during the '00s through the third generation of cellular, which added better data speeds but stayed incompatible.
The CDMA/GSM split ended, in theory, as carriers all switched to LTE, a single, global 4G standard, starting in 2010. But the difference remained because phones still needed to access the older 2G and 3G networks, primarily for voice calls. AT&T, T-Mobile, and Verizon all started to phase in voice calling over 4G in 2014, but it's been slow going. All four carriers now support voice over 4G.
Now carriers are starting to install 5G, which after a few false starts will be a single global standard called 5G-NR.
How about 6G
