Before Unlocking Your Phone: GSM versus CDMA

Cell phone unlocking is done for one reason: remove a mobile phone’s carrier restriction so that it may be used with another carrier. If you’re thinking of unlocking your phone, read on. There’s one thing you should find out before you proceed to unlock your cell phone – and that is whether or not your phone can use the service of your target cell phone provider (the carrier to which you wish to switch).

Some people immediately unlock their cell phone – only to find out later on that they can’t actually use it with the carrier they want. It could be that their cell phone has support only for the GSM network standard, whereas their target carrier uses the CDMA network technology.

One of the basic steps for unlocking your cell phone, therefore, is discovering whether your handset is a GSM phone or a CDMA phone.

Do You Have a GSM or a CDMA Handset?

In the United States, cell phone providers mainly use one of two mobile communications standards: GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access).

[Note: CDMA is actually a technology – a channel access method – rather than a mobile communications standard like GSM. CDMA 2000 is one of the mobile phone standards that use the CDMA channel access method. For the purposes of this discussion and in the interest of simplicity, however, this article uses CDMA and CDMA-based network technologies like CDMA 2000 interchangeably.]

GSM mobile communications standardCell phones for GSM networks are card-based. That is, they are used with a Subscriber Identity Module (SIM) or SIM card. Thus, if a GSM phone is unlocked, you should be able to use it with any SIM card provided by any network with GSM support. In the US, the wireless providers that use the GSM platform include AT&T (also Cingular, which is now part of AT&T) and T-Mobile.

Cell phones that operate on CDMA networks (at least in the US), on the other hand, are traditionally card-free. In other words, they are pre-programmed with the CDMA network’s service settings and could not be used with any other network or carrier without first being reprogrammed. It is for this reason that CDMA networks (at least in the US) must provide their subscribers with handsets.

When a CDMA network subscriber wishes to change phones, his information (his subscriber identification programmed in his old phone) is transferred to the new phone, so the old phone basically becomes useless (unless it is programmed for a new user). In the US, the wireless providers that use CDMA include Verizon and Sprint.

CDMA 2000 mobile communications technology[Note: Some CDMA handsets come with card access. The card used in such phones is known as the Removable User Identity Module or R-UIM card.]

The Real Question: Does your phone support GSM or CDMA?

If your cell phone is card-based or has card-access, it should be easier to switch networks. After you unlock your phone, chances are high that you can use it with another network.

If your phone does not have card access, you’ll find it hard to switch to another carrier. Phones without card access have to be reprogrammed to work with your new network.

Rule of Thumb: GSM to GSM, CDMA to CDMA

If you use your phone with a GSM network, you should have no problem using that phone with another GSM network after unlocking your phone. All you need to do is switch SIM cards.

If you use your card-based phone with a CDMA network, you should have no problem using that phone with another CDMA network after unlocking your phone. All you need to do is switch R-UIM cards.

Now, there are phones that offer even greater flexibility. New-generation cell phones usually have support for all types of network platforms. After unlocking, you should be able to use that phone with any carrier using any mobile communications standard. All you’ll need to do, in this case, is to get the card from your new network. This card can be a SIM card if it is a GSM network, an R-UIM card if it is a CDMA network or a smart card (known as the Universal Integrated Circuit Card) which comes loaded with the necessary application so it can work with a GSM, CDMA or any other type of network architecture or platform.

[Note: The UICC can contain SIM provisioning so it can work with GSM networks, CDMA Subscriber Identify Module (CSIM) so it can work with CDMA networks or Universal SIM (USIM) provisioning so it can work with UMTS (Universal Mobile Telecommunications System) networks. Carriers that issue a UICC with their handsets do so mainly to let theirUMTS mobile communications standard subscribers access other carriers on a different network platform when these subscribers are traveling to a place where the home network is unavailable. Of course, the subscribers’ access to other networks in this case is subject to roaming charges.]

Final Tip

To find out if you can use your cell phone with your target carrier or wireless provider (that is, if your phone has support for the mobile network technology used by your target network), check your phone’s specifications in the phone manufacturer’s website. You must do this before unlocking your cell phone.

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Unlocking versus Roaming

Which is better: unlocking or roaming?

Let’s say you’re traveling to another state, another country or anywhere your home network (your current cell phone carrier) offers no network coverage. While traveling, you don’t want to be out of touch with your friends, family and colleagues. Unfortunately, your cell phone is SIM-locked or locked for use with your home network.

This means you have to either activate roaming on your phone or unlock your phone so you can use it with whatever GSM network is available in your travel destination – which brings us back to our original question.

Which is better: unlocking or roaming?

Unlocking your Cell Phone for Travel


When a phone can be used with only one network, that phone is SIM-locked. Unlocking removes this SIM lock so that the phone may be used with other GSM networks.

Roaming when Traveling

Roaming is a service offered by most cell phone networks. Network roaming makes it possible for traveling customers to benefit from uninterrupted cell phone service.

When roaming is activated on your phone and you are somewhere outside your home cell phone towernetwork’s coverage area, your phone automatically searches for a carrier in your current location that it can use as an alternative. In other words, a phone on roaming uses the signal of a different carrier to provide its owner with continued wireless communications services.

Roaming is available only if your home network has a roaming agreement with other carriers, however. If you travel to a place where your home network offers no coverage and where your carrier has no roaming agreement in place with a local network, your phone will become unusable and virtually useless.

Unlocking or Roaming: Which is better?

Now we’re back to our old question. When traveling, should you unlock your phone or simply activate roaming? To answer this question, let’s compare unlocking and roaming across various factors and considerations:


Activating roaming on your phone is very easy. All you need to do is call your network. Some networks even offer roaming services to their customers from the get go. In this case, you won’t need to call your carrier to activate roaming on your phone.

Unlocking, however, is also quite easily done. All you need to do is buy an unlock code from an email unlocking service and, in as little as 10 minutes, your phone can be unlocked and ready for use with a different network.

The verdict: If you have to leave immediately, roaming is the easier option. Activate roaming on your phone then simply unlock your phone when you have more time.

Uninterrupted service

Unlocking means you can use your phone anywhere there’s a network that offers wireless communication services. With an unlocked phone, all you have to do to use your phone where your network does not provide service is remove your current SIM card and replace it with the SIM card furnished by the network you wish to use. You can be in the US, the UK, Australia, or Zimbabwe – it doesn’t really matter where you are. You’ll never have to do without a network signal.

Roaming can also provide uninterrupted service, but this is not always guaranteed. Roaming availability ultimately depends on your carrier. If your home carrier has a roaming agreement in place with a cell phone carrier in your destination, that’s great. Otherwise, your phone will lose coverage.

The verdict: If you never want to lose cell phone coverage, unlocking is the better option. With an unlocked phone, you can use whichever network is available in your destination.

Money Savings

With cell phone unlocking, you can take advantage of zero to low tariff rates on local calls in your destination. Wherever you may be, you can simply pick and choose which network offers the cheapest rates and use its SIM card on your phone. You’ll save a lot of money this way. Of course, you initially have to pay a fee to have your phone unlocked, but this is just a one-time expense.

Activating roaming on your phone will not cost you anything initially. However, the costs can add up the moment you start using your phone on your travels. With roaming, a network charges its customers for the use of another carrier’s signal – and roaming rates are often more expensive than regular rates. Roaming charges, therefore, can be quite expensive. Often, moreover, you don’t just pay for calls you make and messages you send out while on roaming. You also have to pay tariffs for calls and messages you receive.

The verdict: Unlocking means a small out-of-pocket initial expense, but roaming leads to expensive recurring charges. Overall, unlocking saves more money (especially for the frequent traveler).


Unlocking eliminates the need for different handsets. With just one handset, you can access any network in any country. With roaming, you get the same benefit but only on the condition that your network has a roaming agreement with another network in your destination.

The verdict: Unlocking offers greater convenience than roaming.

Unlocking Is Better than Roaming

unlock phone for traveling

Photo Courtesy of Photos8

From the above discussion, it is obvious that unlocking benefits surpass those of roaming. Unlocking is more convenient, saves you more money (especially in the long run) and gives you uninterrupted cell phone service. Unlocking a phone is also quite easy, although roaming is still easier when you’re pressed for time.

Important tip for travelers: Before traveling, remember to check the band frequency used by networks or carriers in your destination to ensure your phone’s compatibility with it. If your phone is not capable of receiving any network’s signal in your destination, neither unlocking nor roaming will help you. You’ll have to buy a new cell phone in this case.

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