GSM, CDMA, and how it affects your mobile experience

by Joe P on February 26, 2008

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If you believe those AT&T commercials, we’re all in tune with acronyms. Unfortunately, not all of them are as straightforward as “IDK” and “BFF.” In the mobile industry, acronyms are everywhere — and I’m not even talking about as they relate to text messages. I’m talking particularly about GSM and CDMA. These two acronyms are at the very core of cellular communications, and are essential for a basic understanding of the industry. It doesn’t help that many writers use the terms as if they’re familiar to everyone. So today I’m going to explain what the two are, and what they mean to your mobile experience.

Global System for Mobile communications

Various studies estimate GSM covering about 82 percent of global cell phone usage. This is because its origins stretch back to 1982, during the European Conference of Postal and Telecommunications Administrations. They decided there that they wanted uniformity in their mobile communications.

GSM technology is often related to multiple conversations occurring in the same room. If all conversations over cellular airwaves occurred as they do at a party, you’d hear all the other conversations in the background. And since millions of conversations are going on a given time, you wouldn’t hear much of anything but garbled tones.

So GSM uses Time Division Multiple Access (TDMA) to separate the conversations. What this does is slice up each channel into time sequences. From there, each piece travels through the channel one at a time. These are constantly being pushed through, so in the end it mirrors real time.

A signature of GSM networks is the use of a SIM card. These were created to make personal data, including phone number, account information, and contact lists, portable.

There are two major carriers in the U.S. which use GSM technology: AT&T and T-Mobile. Now, what does this mean?

Well, for one, it means that GSM networks are in some way compatible. When you hear about unlocking phones, it mostly refers to GSM networks. The presence of the SIM card makes unlocking a bit easier. This is because phones aren’t required to be programmed for the network, as they are with CDMA networks. Rather, the presence of a SIM card allows access to the network.

So if you unlock an AT&T phone and put in a T-Mobile SIM card, the phone will work on the T-Mobile network. Conversely, if you want to unlock a Verizon phone for the Sprint network, a level of programming will be required to make it compatible with Sprint. There is no way to unlock an AT&T or T-Mobile phone and activate it on Verizon or Sprint, and vice versa.

Code division multiple access

CDMA technology, developed initially by Qualcomm, is a bit more advanced than GSM at the moment. The call quality is said to be a bit better, and the means of conveyance is more efficient. Security is also an advantage of CDMA — the U.S. military uses it for confidential communications.

You’re really only going to find CDMA networks in the U.S. and Canada. As I mentioned, Sprint and Verizon use it in the U.S., while Telus and Bell use it in Canada — though the former is reportedly considering a conversion to GSM. Beyond those, a number of regional networks in the U.S. use CDMA, including Alltel, U.S. Cellular, and Leap Wireless.

We can use the conversation analogy with CDMA, too. Instead of slicing up conversations and pushing them through one-by-one, CDMA technology lets them go through simultaneously. How do they accomplish that without the crowd noise? While each conversation is being held at the same time, each one is coded — in other words, each conversation is being spoken in a different language. So while you and your friend are conversing in “English,” your neighbor down the street is talking to someone in “Swahili.”

Efficiency is the big selling point of CDMA. It requires fewer cell sites (meaning those towers you see along the highway), and it provides a much greater call capacity — up to five times greater than GSM.

While CDMA has great advantages, it’s biggest drawback is the Qualcomm ownership of patents on most CDMA technologies. So companies much purchase a license from them in order to use those technologies in their phones. Other drawbacks of CDMA phones are that they generally cannot roam internationally, and that they cover a smaller market compared to the more universal GSM, so new features usually don’t appear as quickly on CDMA phones. For example, Nokia, the world’s No. 1 handset maker, doesn’t really delve in the CDMA market any more.

How they’ll come together

As we progress to the next level of technology, it doesn’t make a whole ton of sense to stay on divided platforms. Why create a rift when so many more opportunities will be available with a convergence?

Well, it appears that merger is in the offing. Verizon Wireless, the largest CDMA carrier in the world, has selected Long Term Evolution (LTE) technology to power its next-geration network. LTE is a GSM technology. AT&T, America’s largest GSM network, is also using LTE for their next network.

It would make sense, then, for the other CDMA carriers to follow suit. If they chose Ultra Mobile Broadband, they’d likely be faced with a handset deficiency. Since the two largest networks in America, in addition to most other networks around the world, will be on LTE, most handset makers will focus on that as their main area of business. To keep with CDMA could end up being corporate suicide.

With handset makers more focused on one technology, we might see a greater output, rather than seeing the same or similar models launched over two networks. And that, my friends, will be a boon for the mobile phone user.

Filed under : Cell Phone Service