GSM & CDMA: Definition & Differences

Instructor: David Gloag

David has over 40 years of industry experience in software development and information technology and a bachelor of computer science

Cell phones are a big part of most people's lives these days. But how is it that you can talk to another person? How are the billions of calls that happen everyday handled? In this lesson, we'll take a look at two cell phone communications technologies, GSM and CDMA, what they are, and how they differ.

The Cell Phone Glut

Have you ever wondered how calls on your cell phone get through? Think about it: how many times have you made or received a call when someone in the immediate area is also on their cell? This is even more amazing when you consider how many cell phone calls are made each day. There are billions and billions of cell phone calls made each day in the United States of America. It's a whopping big number. So how is that they don't collide and cause endless problems? Well, there are two significant cell phone technologies taking care of that: GSM and CDMA.

What is GSM?

GSM is an acronym for Global System for Mobile communications. It is the enabling technology used by AT&T and T-Mobile in the United States, as well as Europe and most of the rest of the world. GSM has gained wide adoption because the technology was developed by an industry group, and as such, doesn't have licensing issues or costs. It is a multiple access technology, which is another way of saying that it provides the means for several calls to use the same radio channel. The technology uses either the 900 MHz band, or the 1.8 GHz band, of the ultra-high frequency (UHF) spectrum.

What is CDMA?

CDMA stands for Code-Division Multiple Access. It is the enabling technology used by Sprint, Verizon and US Cellular. CDMA has not seen wide adoption because the technology is controlled by Qualcomm and has licensing fees associated with it. It is also a multiple access technology, although it works differently than that of GSM. We'll talk more about that in a little further on in the lesson. The technology uses either the 800 MHz band, or the 1.9 GHz band, of the UHF spectrum.

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