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GSM vs. CDMA vs. iDEN – Differences.

GSM vs CDMA vs iDEN Differences

GSM and CDMA are two the most popular types of mobile network currently accessible today. Both technologies are available in North America and almost every part of the globe. The iDEN popularity declined in recent years, however, there are still few service providers that offer service using this technology. Understanding differences between GSM, CDMA and iDEN them will surely help you choose the right phone more suitable for your needs.

If you curious about which network your phone runs on, below we present a short guide explaining differences between GSM, CDMA and iDEN how to determine whether you use CDMA or GSM phone.

What’s the difference between GSM, CDMA and iDEN phones.

GSM Phones (Global System for Mobile Communications)

GSM phones use SIM cards – each phone can get access to the service by placing an activated SIM card into the phone. In the US, this technology is utilized by T-Mobile, AT&T, Metro PCS, Cricket service providers.

Worth to highlight that GSM network is the most common technology used worldwide, so if you have a handset that is SIM lock free (unlocked) you will be able to use the phone with any GSM service provider across the world.

CDMA Phones (Code Division Multiple Access)

CDMA phones carry an unique Electronic Serial Number, also known as ESN, which must be activated by a carrier on your account in order to connect the phone to the network.

In most cases CDMA phones do not support SIM card slots with exemption for 4G LTE smartphones requiring SIM card for access LTE network and global dual-band phones that support both CDMA and GSM frequencies. In the US – Sprint, Verizon, Alltel, and US Cellular represent CDMA service providers.

iDEN Phones (Integrated Digital Enhanced Network)

iDEN support Nextel, Boost Mobile and SouthernLINC Wireless SIM cards similar way as GSM SIM card. Although iDEN mini SIM cards are identical to GSM cards in terms of shape and dimension, these cannot be used with GSM phones due to support for different technologies.

How to check if your phone is CDMA or GSM?

There are two most common methods helping you to determine on which network operates your carrier. First method focuses on the phone itself, second regards your service provider.

Determinate if the phone support SIM Cards.

The simplest way to check whether your phone bases on CDMA or GSM is to determine if it requires a SIM card. If you need a SIM card to activate, your phone you run on GSM network, since CDMA devices usually don’t require SIM cards to work, except for smartphones with 4G LTE support.

If you’re not sure whether your phone uses a SIM card, you can find it out easily. All you need to do is to remove the back cover case from your phone and open the battery compartment. The SIM card slot is in most cases located beneath the battery.

Sometimes you may also find the SIM card tray on the outside of the phone, especially with the ones with sealed battery. For example, if you use the iPhone 5, the GSM variant will have a SIM tray located on the right side of its body case, whereas the CDMA model of the handset lacks the tray. Of course, if you can’t find the slot, you may always refer to your phone’s user manual.

Search for device’s serial number.

Additionally, every handset has be a special sticker usually located underneath the battery. If there’s an IMEI number printed on it, then you surely have a GSM-based handset. But, if the sticker has HEX (Hexadecimal) or DEC (Decimal) number, then the phone is a CDMA device.

Check your service provider.

Try to determine which technology is used by your carrier. If you’re a Verizon or Sprint subscriber, then you your network is CDMA. One the other hand, if your carrier is AT&T or T-Mobile then you’re definitely on a GSM network.

If you can’t find sufficient information on the type of network of your service provider, you may always try to reach out your carrier customer service and ask about the technology their service runs on.

Keep in mind that most CDMA phones don’t operate on international frequencies, so if you often travel abroad, a GSM phone will be a better option for you if you want to stay in touch with your friends and family. If you are Sprint or Verizon customer you may always opt to Sprint Global Phone or Verizon Global Phone.

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84 Responses to “GSM vs. CDMA vs. iDEN – Differences.”

  1. Hi Jason, I want to send iPhone 4 from AT&T to Brazil right away, without unlock it, can it be done over there even if ATT&T doesn’t exist over there? Thanks a lot for your help!

  2. Dear Jason,

    I have a Verizon-unlocked Motorola Razor M. I would like to send it to India and help out a college student that I am sponsoring. According to the Verizon people, the unlocked phone can work in India. If it doesn’t require a sim card, does it mean that the student has to subscribe a cellular service and data plan?

    • Hi Maria, any quad-band unlocked phone will work with India. Your student will need to have a SIM card from its local service provider to use the phone for talk, text and data services. Please let us know if you have any further questions.

  3. Will a sim card reader for GSM/CDMA also read IDEN sim cards ?

    Dekart is the only brand that actually states IDEN compatible .

  4. Hi Jason, I wanted to know if the DROID RAZR M can be used on Straight Talk. I am told it can by the clerks at store, yet the site says no.

    • Richard, the Droid RAZR M indeed supports GSM bands, which means that the handset sports SIM card slot, however, the phone will need to be unlocked in order to accept Straight Talk SIM card.

  5. I have a GS4 from Cricket before it merged with AT&T. It is operating on CDMA – EvDo Rev. A. However, in 2015, it won’t be compatible with Cricket’s new network. What can I do or which carrier I can sign up with (in California) to keep my phone? Is this phone (model SCH-R970C) dual band?

    • Jack, you may consider bringing the phone to Straight Talk service. They allow to use some CDMA phones on their network. Here is a link to Straight Talk website where you can verify if the phone can be activated on their network. Hope you find this helpful.

  6. I have a nextel/motorola i730. Can I use it on a GSM network if I get it unlocked and a new carrier sim card? . If not does it have any value or should I recycle it? Thank you

    • Carl, you won’t be able to use iDEN phone, such as i730, on GSM network. Also it cannot be unlocked. It does not have much value since iDEN network is actually dead.

  7. I’m looking to buy an Iphone 4 to use as a gps laptimer only, don’t care about phone sevice. It seems the used Verizon Iphones are generally the cheapest. Will they work for my purposes? Anything I should look for or stay away from?

    • I don’t think its a good idea since for GPS you will need to have access to data services. I would recommend purchasing a phone that is compatible with your service provider.


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