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Most cell phone owners around the world only have to worry about a single carrier technology called the Global System for Mobile Communications, or GSM for short. As its name implies, this standard was developed for, and has been adopted by, almost the entire globe as the way to communicate via cellular calls.

But not everyone has jumped on the GSM train. An alternative cellular standard known as Code Division Multiple Access, or CDMA, is used by many carriers around the world. It is most popular in the United States and Russia, but it’s also used in some Asian and African countries, often alongside competing GSM carriers.

Here’s what cell phone users stuck on choosing between them should know before purchasing a phone.

GSM vs. CDMA: What’s Better?

talking-on-phone

This the first question many potential owners ask, and it makes sense, but in this case there’s no easy answer to that question.

GSM and CDMA are different ways to accomplish the same goal, and the fact that extremely popular networks are built on each simply proves that it’s the quality of the network, not the standard, which is important. For instance, in the United States, two of the four major carriers (Verizon and Sprint) use CDMA while the other two (AT&T and T-Mobile) use GSM.

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Technically, neither is the better in terms of quality, but there are some things here for your consideration. GSM phones are able to be unlocked Is It Legal Or Illegal To Unlock My Smartphone In The US? Is It Legal Or Illegal To Unlock My Smartphone In The US? Unlocking your cellphone is now legal in the United States thanks to a bipartisan bill signed into law by President Obama, but it only lasts until 2015. Care to learn more about the legality of... Read More and moved between carriers, but CDMA phones are often locked to a single carrier and unable to be transferred.

Additionally, most phones only come in GSM or CDMA models, so your choice of phone could determine which standard you end up using, and it all depends on which carriers are available to you in your area. Some areas may be better covered by GSM-providers, while CDMA-providers will have better coverage in other areas.

Which Phones Support Which?

Many phones are compatible with either GSM or CDMA, but not both. For CDMA phones, you will need to buy a phone made for your specific carrier, and the easiest way to do this is buy directly from your carrier. For example, if you want an iPhone on Verizon, you need to buy a Verizon-branded iPhone — not a Sprint- or AT&T-branded iPhone — because it has the specific bands and compatibility with Verizon. However, if you ever want to leave Verizon, you won’t be able to take your phone with you; it is locked to that carrier.

unlockedphone

If you don’t want to be trapped with one carrier The Future Is Prepaid: How To Save Hundreds On Your Mobile Phone Bill In 3 Easy Steps The Future Is Prepaid: How To Save Hundreds On Your Mobile Phone Bill In 3 Easy Steps Cutting your mobile phone bill in half takes only three simple steps - first, find a carrier that offers discounted plans, such as an MVNO. Second, get an unlocked phone. Third, and optionally, you can... Read More , however, you can also look for unlocked GSM phones from third-party retailers — these phones will work with any GSM carrier simply by popping in your SIM card Why Do Cellphones Need a SIM Card? Why Do Cellphones Need a SIM Card? Haven't we come far enough with technology that such a thing as SIM cards shouldn't matter anymore? What is a SIM card and why is it so important? Read More . For example, Amazon sells tons of unlocked GSM phones, and Google sells their Nexus 5 and a couple Google Play Edition phones unlocked. Any retail or online store dealing in cellular phones should provide information regarding the networks a phone works with.

You must be careful when examining a phone’s network compatibility, though. Phones sold in markets that service both standards often come in a GSM version or a CDMA version, but only a few phones are compatible with both. If you buy a CDMA phone from a third-party retailer, you’ll need to call your carrier to have it activated. If you buy a GSM phone, you’ll need to purchase a SIM card to put into your phone that will activate your phone’s network capabilities.

gsm-sim-card

Owners of CDMA phones don’t need to worry about SIM cards, but this is more a curse than a blessing. CDMA phones bake in compatibility restrictions that are difficult to get around, while GSM owners can simply take out their SIM and replace it with one from another carrier. Most CDMA networks do not allow the use of a phone originally purchased from another carrier even if the phone is otherwise technically compatible. This is an important restriction to remember when going with a CDMA network. If you decide to switch networks later you’ll likely need to buy a new phone even if the network you’re switching to also uses CDMA Never Buy a Phone From Your Carrier! Buy Unlocked Phones and Save Hundreds Never Buy a Phone From Your Carrier! Buy Unlocked Phones and Save Hundreds Never buy a smartphone from a carrier—ever. Most consumers don't know that they can purchase their phones from retailers and pay less than if they did from the carrier. The key word that you're looking... Read More .

While GSM is more open, the frequency bands supported by a phone can still restrict access. There’s a number of bands from 380 MHz to 1900 MHz and the bands used can vary from market to market. You should double-check your local carrier’s band usage and make sure the phone you’re buying supports the same.  With that said, GSM is concentrated around a core of four bands, those being 850, 900, 1800 and 1900. A phone that supports all four can be used in most countries, which is why GSM phones compatible with all four bands are often called a “world phone.”

LTE Cometh… and Carries Confusion

If you now understand the importance of GSM and CDMA, awesome! Now let’s entirely destroy your assumptions by talking about the newcomer, Long Term Evolution (LTE).

LTE is a new standard Wireless Alphabet Soup Explained: What Is 4G, 3G, LTE, & More [MakeUseOf Explains] Wireless Alphabet Soup Explained: What Is 4G, 3G, LTE, & More [MakeUseOf Explains] We just absolutely love acronyms, don't we? So much so that we use them literally everywhere to have a shorter way to name something. Whether it's an official acronym such as USB or something unofficial... Read More that’s come into vogue over the last few years. Though based on the principles of GSM, LTE is its own separate standard that operates apart from existing GSM and CDMA networks — it’s the real fourth generation of cellular data.

verizon-4g-lteunltd

The highest adoption of LTE can be found in South Korea, where it commands the majority of the market, but it is also popular in Japan, Australia, Sweden, and the United States. So far it’s used primarily for data, but standards have been drawn up for using LTE as a replacement to traditional cellular networks. Verizon Wireless in the US, for example, has announced its plan to roll out LTE-only phones in late 2014.

This standard uses a SIM card, so users can switch networks by replacing the SIM if the phone is compatible with the new network. With that said, at this time phones that use LTE generally use it only for data, but not for voice. This means CDMA/LTE phone owners are still locked into a network. That will change as carriers like Verizon move to LTE-only networks, but this process could take many years.

While it has the potential to be a global standard, there are some obstacles in the way. Outside of South Korea there’s no market where LTE’s reach is more than a quarter of the services available. South Korea in general, and Verizon Wireless in the US, are exceptions to the rule; in most markets, even carriers that offer LTE only offer it in a slim selection of the total area they cover.

lterollout

And then there’s the problem of spectrum. Remember how GSM/CDMA operates on many different bands? The same is true of LTE. You need to check that the compatibility of your phone matches the frequency band supported by your carrier, and you won’t be able to use an LTE phone on other networks with the same standard, but a different frequency band. It’s unclear at this point if this standard will ever become “global” in the same way as GSM, which settled on a core of four frequencies across the world that are supported by most GSM phones.

Wrapping It Up

Take a deep breath; it’s time to review this buffet of confusing information.

First, neither GSM or CDMA is technically better; they ultimately provide the same service and the quality of a network depends on the carrier, not the cellular standard used.

Second, GSM phones can be unlocked and switch carriers, whereas CDMA phones are locked to a carrier. It’s usually cheaper to buy unlocked GSM phones Save Money By Switching To An MVNO: 4 Requirements You Must Know Save Money By Switching To An MVNO: 4 Requirements You Must Know In the United States and Canada, getting ripped off doesn't take any effort, just a signature. When you sign a contract for cellular service, you also sign away your freedom. Read More than on-contract CDMA phones.

Third, you need to check what bands your chosen phone supports carefully. Most either work on GSM or CDMA, and both standards offer multiple frequencies that differ across the globe.

Finally, LTE is being rolled out as a potential global standard, but it falls victim to even more frequency division than GSM and CDMA. The technology also suffers from limited adoption because it’s relatively new.

Hopefully this has cleared up any questions you had, but cellular service is undergoing constant evolution and the standards commonly supported by phones can change from year to year. Feel free to leave your questions and comments below.

Image Credit: Wikimedia/Jon RaviMan’s hand holding black GSM SIM card and Good looking guy on a cell phone from Shutterstock.

  1. Eliot
    November 19, 2016 at 5:14 am

    No comment but a question. I ordered a iPhone 6s , unlocked so I could get a GSM Sims card and activate it with at&t service. Was I supposed to tell Apple that I needed a GSM type iPhone or am I OK ?
    .

  2. Shabbir Sh.T. Shakir
    August 1, 2016 at 10:59 am

    thanks for the info, but technically which is better?

  3. Christa
    January 21, 2016 at 8:58 pm

    The biggest difference I see between GSM and CDMA phones is that the FIRST troubleshooting step for a GSM is to remove and reinstall the SIM card. This was something I did on my Huawei and Blu phones many times, without a failure.

    However, not all phones have such robust SIM slots.

    I have tried to load the Consumer Cellular SIM into new MOTO G 3rd Gen phones and 3/4 of the time had to replace the phone. Consumer Cellular uses a compound SIM (Their nanoSim is inside a frame to make it microSim size, and a Standard SIM frame is around all of that.

    Twice the microSim card broke on insertion, leaving shards of plastic from the microSIM frame inside the SIM slot. On another attempt, the microSIM separated from the Standard Sim frame neatly and easily enough, but broke off a gold contact on insertion.

    I don't know whether Motorola considers Consumer Cellular's compound SIM system to be
    "use of an adapter" which would violate Motorola's warranty.

    I understand that adapters vary in quality, and surely understand why Motorola wouldn't warranty a phone with a homemade adapter. On the other hand, without an adapter to provide a smoother surface, I fear that it's a very risky proposition to plan on routine re-installation of a Consumer Cellular SIM into a MotoG phone.

    Otherwise, we love the Moto G III. We're living on Social Security and can't afford $500 phones. We have loved and recommended Consumer Cellular for their customer service and low cost (we were spending $38/mo altogether for 2 phones.) However, I can't figure out how we can use both because of this problem with the SIM cards.

    Any suggestions? After talking with both companies (which blame each other), we're getting desperate.

  4. Lin
    January 12, 2016 at 4:30 am

    How does straight talk fit into this?

  5. kona sam
    December 18, 2015 at 2:03 pm

    CDMA phones also come with sim card. Infact CDMA phones without sim card are extinct now.

  6. Joshi Dare
    October 21, 2015 at 6:49 am

    , LTE is being rolled out as a potential global standard, but it falls victim to even more frequency division than GSM and CDMA. The technology also suffers from limited adoption because it’s relatively new. so how this GSM &CDMA are work!!!!!!!!!!!!!!!!!!!111

  7. Ivan Durst
    October 17, 2015 at 10:07 pm

    This GSM/CDMA stuff gets a bit confusing, thanks for breaking it down. I noticed a few people in the comments asking what network supports which technology - I got some good info here, I thought y'all might find it useful: http://gsmorcdma.com/

    Thanks for the good stuff makeuseof, keep it coming!

  8. Benjamin Maringa
    June 18, 2015 at 10:36 pm

    Good stuff

  9. Daudi Steve
    May 26, 2015 at 4:03 pm

    Quality Article

  10. Robert
    March 31, 2015 at 7:33 pm

    I live in Arizona. I have a couple of questions. First, I have a Samsung Galaxy S4. It's both cdma and gsm. I'm switching it over to straight talk. What does Verizon towers use, cdma or gsm? Also, I'll be in Alaska for a couple of months and I saw they don't support cdma. If I go with cdma will I still be able to use the phone while I'm in Alaska?

    • Garland
      May 22, 2015 at 5:00 pm

      @Robert: Verizon uses CDMA.

  11. Gary Lasereyes
    March 20, 2015 at 3:32 pm

    Great Article thanks!

  12. deepu
    February 12, 2015 at 10:40 am

    i get a phone lgvol that from USA cdma version of sprint.can i work this cdma phone by using a indiannetworkprovider.

  13. Saimum
    February 8, 2015 at 6:52 pm

    Thank you.

  14. Eugene Ochieng
    January 23, 2015 at 6:08 pm

    Thank you so much for the information

  15. tino
    January 21, 2015 at 8:48 am

    my cdma operator starts charging when the phone starts ringing, but not when the other party answers

  16. Susan D
    January 15, 2015 at 9:36 am

    Thanks for the great write-up!
    I'm trying to decide if I should switch from my Sprint iPhone5 to t-mobile... and if I do, which phone would be best for USA coverage and frequent 3rd world travel. :-/
    Any suggestions? I mostly use data, in the states and abroad.

  17. BrokeMyPhone
    January 14, 2015 at 7:34 pm

    After reading your article, I was wondering if I could buy an iphone 5s with a AT&T contract, and then use it overseas with another sim-card when I need to.

  18. Jay
    December 21, 2014 at 12:19 am

    GSM is better. Someone needed to say it.

  19. pat jones
    December 21, 2014 at 12:01 am

    I just bought a zte valet from TracFone for $29. From what I understand it operates in Verizon's CDMA network which covers most of the Unted States excluding Alaska and some rural areas. Coverage is better than my old T-mobile flip phone that only operates on 1900 MHz; it doesn't even roam onto at&t's network in the countryside.

  20. Lionel Lombendencio
    December 7, 2014 at 6:25 pm

    Great info I'll just go with the GSM. Honestly here in our country we don't have HDMA phones here SIM card is rampant where we have dual SIM phones. He he he he

  21. Richard
    December 3, 2014 at 2:47 am

    OK, I have a Samsung Galaxy mini that someone brought from South America and it takes a sim card, Can I take my sim card from my tracfone and use it in the galaxy?

    • happyhal
      March 6, 2015 at 2:54 pm

      no sim cards are locked to a particular phone once the phone is turned on first time. have to get new sim card for different phone

    • Richard
      March 19, 2015 at 8:23 am

      I've moved sim cards between phones without having to do anything else. It just has to be a phone set up for the same carrier.

  22. Gene
    December 1, 2014 at 6:17 pm

    Does one network over the other put a drain on your battery? Or am in left about this? :)

  23. Melano S
    August 26, 2014 at 3:37 am

    You must be careful when examining a phone’s network compatibility, though. Phones sold in markets that service both standards often come in a GSM version or a CDMA version, but only a few phones are compatible with both. If you buy a CDMA phone from a third-party retailer, you’ll need to call your carrier to have it activated. If you buy a GSM phone, you’ll need to purchase a SIM card to put into your phone that will activate your phone’s network capabilities. Good post. I need it
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    • Moe
      November 2, 2014 at 7:50 am

      Not true. I have Verizon. I can talk and surf the Web all at the same time. I have a Motorola RAZR Maxx and Note 4. None have issues .

  24. John
    August 22, 2014 at 11:31 pm

    GSM iPhones could do Data and Voice SIMULTANEOUSLY, CDMA can not so, if you're on a Voice call on your Verizon or Sprint iPhone and need to check Data, you must first end the Voice call. With a GSM based iPhone, the Voice call can continue while you access the online Data you need. I thought the when Verizon adopted 4G/LTE, Verizon would gain this capability. I'm told by Verizon reps that it is not the case. Even on a 4G/LTE Verizon phone, you still can do Voice OR Data but NOT BOTH TOGETHER.

    • Anonymous
      August 23, 2014 at 12:25 pm

      Unless you're connected to a wifi then you are able to do voice and data simultaneously.

    • Anonymous
      August 23, 2014 at 1:26 pm

      On Verizon, simultaneous voice and data is supported. Sprint, however, drops to 1x during voice call, so the network doesn't support voice and data simultaneously.

  25. LB
    August 22, 2014 at 11:07 pm

    Actually 4G is defined by data rates and other two-way spectrum comms protocols: 1 GB stationary DTR and 100 MB mobile. The FCC caved to vendor pressure to redesignate current (LTE) data rates as "4G" for marketing purposes. Wimps.

  26. Hirst
    August 22, 2014 at 9:20 pm

    The missing fourth is 3G, which are WCDMA and UMTS technologies. Please search Wikipedia for more info about 2G, 3G and 4G, since they are nit necessarily easy to explain.

  27. Robert B
    August 22, 2014 at 4:44 pm

    Hey Matt, you said that LTE is the real fourth generation of cellular data, but primarily mentioned GSM and CDMA... What is the missing fourth? Just curious

  28. Ankit
    August 22, 2014 at 6:10 am

    Looking at the heading of the article, I was excited I would get to know the difference between CDMA and GSM. But to my my disappointment the whole article revolves around just the pros and cons. No difference highlighted. Poor construction.

    • Jimjiminy
      December 19, 2014 at 5:59 pm

      CDMA uses code to mux (multiplex) a voice signal into a dedicated data path containing multiple voice signals. GSM uses TDM, or time division multiplexing which assigns a call to one channel in the bit stream, similar to a T1 (DS1).

  29. Greg Iles
    August 22, 2014 at 3:53 am

    You left out the biggest deficiency of CDMA vs. GSM, that is, that you cannot use your phone and data at the same time on CDMA. IF you are browsing, foe example, and the phone rings, you are cut off from the internet if you answer and cannot get back on until you hang up. TO me, CDMA has absolutely no advantage over GSM.

    • david bartlett
      March 12, 2015 at 6:46 pm

      From a carrier standpoint it means more capacity. More devices on the same channel. Where on GSM you can only have one device on each channel.

    • Jay
      May 24, 2015 at 6:47 pm

      That is actually irrellevant as Verizon has had advanced calling. It's enables mobile data while on a call. They came up with that feature years ago when 3G was being being rolled out and AT&T turned up the heat as they were able to do that but Verizon wasn't.

  30. Dels
    August 22, 2014 at 3:10 am

    Lucky for us here in Indonesia, each GSM found are sold unlocked, even if you buy it from carrier (off-contract). As for CDMA carriers here, currently are 2 but by the end of 2015 CDMA will be totally dead here as carriers are forced to use GSM/LTE 2600 Mhz

  31. elzafir
    August 22, 2014 at 1:48 am

    Some CDMA phones can swap "SIM" cards too, but they are called R-UIM (Removable user identity module), which is the old standard, and CSIM (CDMA Subscriber identity module), the new standard, instead of SIM (Subscriber identity module).

  32. Tom W
    August 21, 2014 at 10:48 pm

    I've used both a HTC Sensation and a Samsung Galaxy S3. Both of them allow switching between GSM, which is better for voice and text signal, and WCDMA, which is better for mobile data speeds. I don't know whether it is because I live in the UK, or if I just got lucky with the phones I bought.

    • Arun S
      August 22, 2014 at 4:32 pm

      WCDMA is different from CDMA WCDMA actually refers to 3g and GSM refers to 2g in the context u r talking as far as indian technology is concerned

    • Tom W
      August 23, 2014 at 11:54 am

      That makes sense, thanks. It's annoying that they use two confusingly similar acronyms to mean different things.

  33. Ant Man
    August 21, 2014 at 10:09 pm

    Due to FCC spectrum agreements, Verizon is required to not lock their LTE phones.

    i.e. iPhone 5S, and 5C are compatible with AT&T, T-Mobile and Verizon.

    • John Dugue
      August 22, 2014 at 6:42 pm

      True, but verizon is being slow to allow this, the last I knew.

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