What’s the difference between CDMA and GSM?

When consumers think about mobile network providers, their primary concern is with regards to coverage, quality, support, pricing, and other factors but when you pick a network carrier, you also make the choice between a GSM network or a CDMA network, at least in the US.

You might have come across these terms in the past when picking a mobile phone, or when first joining, or switching network carriers, but what do they mean? And what is the difference between the two?

GSM stands for Global System for Mobile Communication and is now considered the standard for communication globally, particularly in Asia and Europe, with its availability in over 210 countries worldwide. It functions on four distinct frequency bands, 900 MHz and 1800 MHz in Europe and Asia, and 850 MHz and 1900 MHz in North and South America. The two primary US carriers that are compatible with GSM are AT&T and T-Mobile.

CDMA, or code division multiple access, was a standard designed and patented by Qualcomm, but subsequently used as the basis for the CDMA2000 and WCDMA standards for 3G. However, because of its proprietary nature, CDMA hasn’t seen the global adoption that GSM has, with less than 18% of the networks around the world using CDMA, and is primarily found in the US, with Verizon Wireless and Sprint both using CDMA networks. You can find the full list of CDMA networks here.

Both are multiple access standards, which means that multiple calls can go through a single tower, but as you can see, the major difference between the two has to do with the way your data is converted into the radio waves that your phone broadcasts and receives. There are, of course, more practical considerations that matter more for us as a consumer, which you can find listed below:

• SIM cards: Before the advent of 4G LTE, the obvious difference between GSM and CDMA devices were with regards to the SIM card. GSM handsets came with a SIM card slot, while CDMA phones did not. In other words, CDMA is a handset-based standard, with a phone number linked to a particular device. If you wanted to upgrade to another phone, you would have to get in touch with the network carrier, de-activate the old device and activate the new one. On the other hand, with GSM devices, the phone number is linked to the SIM card, so when switching devices, all you have to do is pop the SIM card into a new phone and you are good to go. (This is obviously without taking into consideration GSM devices being locked to network carriers, as seen in the US).
• Network coverage: Network coverage doesn’t depend on whether it is a GSM or CDMA network, but rather on the infrastructure the carrier has in place. GSM networks are far more popular globally, but in the US, Verizon Wireless, a CDMA network, boasts the highest number of subscribers and broadest coverage in the country.
• International roaming: In your home market, it doesn’t matter what kind of network it is, with the focus instead on the available coverage. However, when it comes to international roaming, GSM has the upper hand, with a lot more GSM networks around the world, along with roaming deals between these providers. With a GSM phone, you also have the advantage of picking up a local SIM card wherever you are, assuming that you have an unlocked device. You may not get full access to data connectivity, depending on the device and network compatibility though.