CDMA and GSM: Understanding the Differences and Which is Best for You

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CDMA and GSM are two different technologies available for mobile wireless service. While GSM has gained dominance around the world, CDMA has remained in use in just a few places, including the USA. What are the differences between these two technologies?

The GSM standard was created by a European industry consortium called European Telecommunications Standards Institute (ETSI) and was adopted by the region as the standard for mobile communications, hence its name. GSM is an acronym for Global System for Mobile Communications. 

It went on to be adopted not just by Europe but across the vast majority of the world. So, most mobile networks elsewhere adopted GSM technologies, while in the USA and Canada, CDMA (Code Division Multiple Access) became the standard.

CDMA was the handwork of an American company named Qualcomm (yes; the chipmaker). The practical advantages of GSM gave it wider spread adoption globally. Even in the USA and Canada where CDMA once ruled, some carriers have switched to GSM.

The technical parts of the differences between CDMA and GSM are a bit complicated, but you are probably interested only in how the two practically affect you, so let’s get to those.

CDMA and GSM: What are the practical implications to you?

If you are living in the USA or travelling there, you need to know that there are two types of carriers operating there: one set operate GSM networks while another set run CDMA networks. This is true for Canada as well.

GSM phones are not compatible with CDMA networks, and CDMA phones are not compatible with GSM networks. This is important, so you do not buy a smartphone that will not work on your carrier.

One of the easy ways to know if a phone is GSM or CDMA is to check if it uses a SIM card. CDMA phones do not need a SIM and are locked to their carrier. You cannot switch carriers as you will if you are using a CDMA phone.

On the other hand, with a GSM phone, you can more easily switch carriers by buying a different SIM card for use. Note though that some GSM carriers also lock phones they sell to their networks.

But the general principle is that GSM phones use a SIM card. This may change soon as eSIMs are becoming a thing and gaining widespread use. Eventually, we may come to a time when even GSM phones do not require a physical SIM any more.

GSM phones and devices use GSM 900 and 1800 frequencies, while CDMA phones use 850 and 1900 frequencies.

Lastly GSM phones and carriers are identifiable with terms like GSM, GPRS, and EDGE. CDMA phones have terminologies like CDMA and EVDO attached to them. Note the terms CDMA and EVDO – those are CDMA-specific terminologies.

Some US-specific phones support both CDMA and GSM technologies, so you can buy them and freely use on any type of carrier.

A Cell tower is used to transmit both CDMA and GSM network signals.

List of GSM Carriers in the USA

  • AT&T
  • T-Mobile
  • Virgin Mobile
  • LycaMobile
  • Cricket Mobile (uses AT&T towers)
  • Broadpoint
  • H2O Wireless (uses AT&T towers)
  • Pure Prepaid (uses AT&T towers)
  • Pure Talk USA (uses AT&T towers)
  • Consumer Cellular (uses AT&T towers)

Travellers to the US will be able to use their GSM phones on the above carriers.

List of CDMA Carriers in the USA

  • Verizon
  • US Cellular

If you are travelling to the USA, your GSM smartphone may not work on the above networks unless it is a quad band phone and suppoorts both GSM and CDMA networks.

List of US Carriers that use both CDMA and GSM

  • MetroPCS
  • Boost Mobile
  • Google Fi
  • Straighttalk
  • Ting
  • TracFone Wireless

The above-listed US carriers use both CDMA and GSM technologies, so whichever type of cell phone you have should work with them.

The information on this page may not be accurate or out of date, as the dynamics of the US mobile industry changes. For example, new technologies keep being developed, new carriers are born, and old ones acquired. It is always a good thing to ask questions at the point of purchase of service.

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By Mister Mobility

I have been tech blogging since 2003, I have owned and reviewed hundreds of smartphones since my first in 2001.

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