GSM vs. EDGE vs. CDMA vs. TDMA

These standards are the reason some phones can't switch networks

Woman looking at cell phone in room above city
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The type of technology a wireless carrier uses (GSMEDGECDMA or TDMA) matters when you buy or sell a cell phone. While selecting the right mobile phone service plan at your carrier of choice is important, so is choosing the right carrier in the first place. We've examined the different techs wireless carriers use to help you tell the difference.

Not all of the protocols in this article are still in use.

Overall Findings

GSM EDGE CDMA TDMA
Information stored on SIM cards Based on GSM May use SIM cards 2G system
Switching phones just means switching cards Three times faster than GSM Provider stores information Predates GSM
Most widely used, especially internationally Used by AT&T and T-Mobile Can't change phones without provider approving No longer in use
Can also switch SIM cards to use phone in other countries without roaming   Used by Sprint, Virgin Mobile, and Verizon Wireless  

For years, the two major types of mobile phone technologies, CDMA and GSM, have been incompatible competitors. This incompatibility is the reason many AT&T phones won't work with Verizon service and vice versa.

EDGE is a faster version of GSM, and TDMA is effectively obsolete, so the latter is not a viable choice anymore. It all effectively comes down to GSM and CDMA, with GSM beating out CDMA for user-and consumer-friendliness.

Speed: EDGE Has the Advantage

GSM EDGE CDMA TDMA
3G network Three times faster than GSM 3G network 2G system
Max speed of about 7.2Mbps   Only about 1Mbps No longer available
Average speed of 2.11Mbps      

Both GSM and CDMA are 3G networks, but between the two of them, GSM is the faster option.

CDMA shows an effective download speed of about 1 megabit per second, while GSM claims speeds of up to 7 Mbps. Testing has put the practical speed of GSM closer to 2.11Mbps, which is still twice as fast as CDMA.

EDGE is three times faster than GSM and is built upon that standard. It is designed to accommodate streaming media on mobile devices. AT&T and T-Mobile have EDGE networks.

User-friendliness: GSM Is Easiest to Transfer

GSM EDGE CDMA TDMA
Uses SIM cards to store user data Works similarly to GSM Doesn't use SIM cards Unavailable
Transferring to a new phone just means swapping the SIM card   Carrier must release or transfer user data to a new phone  
Better for international use      

GSM network providers put customer information on a removable SIM card. This approach makes it easy to switch phones; you just take the SIM card out of your old phone and insert it into your new one. GSM technology is widespread in Europe. Combine that fact with a phone with a removable SIM, and you have a phone you can use on overseas visits with just a SIM change.

CDMA phones may or may not have SIM cards, but the user information is stored with the service provider, which must give its permission for you to switch phones. CDMA phones must be programmed with every carrier you use. Whenever you switch carriers, the phone must be reprogrammed for that carrier, even if it is an unlocked phone.

Providers: Look for Your Favorites

GSM EDGE CDMA TDMA
T-Mobile Same as GSM Sprint Incorporated into GSM
AT&T   Virgin Mobile  
More popular internationally   Verizon Wireless  

GSM is the world’s most widely used cell phone technology, popular in both the U.S. and internationally. Cell phone carriers T-Mobile and AT&T, along with many smaller cellular providers, use GSM for their networks.

GSM is the most popular cellular technology in the U.S., but it is even bigger in other countries. China, Russia, and India all have more GSM phone users than the U.S. It is common for GSM networks to have roaming arrangements with foreign countries, which means GSM phones are good choices for overseas travelers.

EDGE is an evolution of GSM, so it has the same availability as that older standard.

CDMA competes with GSM. Sprint, Virgin Mobile, and Verizon Wireless use the CDMA technology standard in the U.S, as do other smaller cellular providers.

Since 2015, all U.S. carriers have been required to unlock their customer's phones after they fulfill their contracts. Even if you decide to have your phone unlocked or to buy a new unlocked phone, it is either a GSM or CDMA phone at heart, and you can only use it with compatible service providers. However, having an unlocked phone gives you are a wider range of service providers to pick from. You aren't limited to just one.

TDMA, which predates the more advanced GSM technology standard, has been incorporated into GSM. TDMA, which was a 2G system, is no longer in use by the major U.S. cell phone service carriers.

Final Verdict

The quality of the phone service has nothing to do with the technology the provider uses. Quality depends on the network itself and how the provider structures it. There are both good and not-so-good networks with GSM and CDMA technology. You are more likely to run into quality concerns with smaller networks than with the big ones.