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GSM vs CDMA – differences between GSM and CDMA phone unlock procedures

GSM vs CDMA – differences between GSM and CDMA phone unlock procedures

GSM (Global System for Mobiles) and CDMA, also known as Code Division Multiple Access, are the two major competing wireless technologies used today by the cell phones industries. LTE is also a standard for wireless data communications technology and an evolution of the GSM/UMTS standards with high capacity and speed of wireless data networks. It is actually anticipated to become the first global standard for mobile phones, although it uses different frequency bands in different countries, which means that only multi-band phones are able to use LTE in all countries where it is supported.

So let’s find more about GSM vs CDMA phone unlocking procedures!

The GSM standard

is taking about 82% of the market share globally, being the dominate standard worldwide except US, and having the more complete global coverage due to roaming and international roaming contracts. Most of Europe and also China uses GSM. Users of GSM handsets can travel to Europe, India, and most parts of Asia, having the possibility to use their phones, as GSM carriers generally accept any GSM-compliant phone. So GSM vs CDMA carriers, don’t have a complete control of the phone you are using.

One of the key features of GSM vs CDMA is the use of detachable SIM cards (Subscriber identity module) that stores all users’ subscription information, phone book and calendar information. With the memory SIM CARD device that identifies and stores the subscriber’s information, the user can change operators by keeping the handset and simply by changing the SIM.
Most operators usually restrict the use of the phones to specific countries and networks by allowing only the use of the SIM card they have issued. This practice is called SIM locking and it is a very common procedure especially if subsidized phones are sold with prepaid contracts.

How to unlock a GSM phone?

GSM network providers use the IMEI number to identify their valid devices. The IMEI number (The International Mobile Station Equipment Identity) is usually a 15 digits unique number used to identify all GSM, LTE phones and has no permanent or semi-permanent relation to the subscriber. On most phones you can find the IMEI by entering *#06# into the keypad, or you can find it printed on the label inside the battery compartment of the phone.

Using the IMEI number, GSM phones can be permanently unlocked by using an unlock code that once entered, the phone will allow the use of any SIM card in the SIM card slot. A GSM phone can not be used on a CDMA network provider no matter if it is unlocked or not.

The unlock code is verified by the handset and is generated by the network provider by an algorithm based on the IMEI number. Many carriers do not provide unlocking codes, and some who do determine the consumer to pay a fee for this service. At the end of the contract period, the network provider might be issuing the unlock code for free to the subscriber, when asked.

A more affordable way to unlock your phone at anytime is to use the online unlocking services. These services require the IMEI number, country and operator details of the handset that needs to be unlocked. The company will then provide the unlock code for the handset via email or on web site. This unlocking method is fast, permanent and safe for you device.

CDMA standard

CDMA standard originally designed by Qualcomm is the primarily used standard in US today, being a method of digitizing and compressing wireless phone calls to allow several calls to share the network at the same time. U.S. is mainly a CDMA country as five of the first seven cellphones providers use CDMA standard: Verizon Wireless, Sprint, Virgin Mobile USA, Cricket, Metro and U.S. Cellular. T-Mobile, AT&T, Boost Mobile, and Nextel use GSM.

CDMA does NOT use a SIM card slot. While GSM phones use a semi-universal software security lock, placed on the SIM card slot that tells the phone what SIM card is allowed to be used, on CDMA the carrier’s information are stored in the phone’s software. Similar with the GSM detachable SIM card advantage, CDMA operators resolve the problem of subscriber’s flexibility with their own service that stores users data (phone book and scheduler information) on the operator’s database. This service allows subscribers not only to switch to a new handset easily, but also gives users the possibility to recover personal data in case the phone is lost or stolen.

CDMA offers no multiband capability being quite difficult to use your phone in multiple countries when traveling. Also CDMA networks are not largely spread in Europe and phones are incompatible with most GSM networks (also lack of SIM cards).

How to unlock a CDMA phone?

CDMA phones technically can be unlocked but not in the same sense that people think about GSM/LTE unlocking. Since CDMA phones do not use a SIM card, they are like being hardwired to the provider that sells them. As there is no built in locking software mechanism, there is no simply unlocking method. Instead, CDMA phones can be reprogrammed to another CDMA carrier options through a process called flashing. More accurately, the phone is physically flashed with a different firmware with the new CDMA carrier’s information in it, making possible for the phone to access that new network.

CDMA network providers use the ESN (Electronic serial numbers) and MEID (Mobile equipment identifier) to identify mobile phone devices. As ESNs have essentially run out, a new serial number format, MEID, was created and it is a unique number identifying a physical piece of CDMA mobile station equipment. The carriers use network-based white lists of ESN/MEIDs to verify their subscribers, so they know if a phone that isn’t on their network is trying to be activated. CDMA carriers check for clean/bad ESNs, and have the possibility to see if a phone has a foreign ESN. So if you own a CDMA phone, you can switch to other network provider only with the carrier permission. Although technically it is possible, a carrier doesn’t usually accept any particular phone onto its network.

In order to unlock your CDMA phone and switch to a different CDMA carrier, you need to call the receiving carrier and ask them to activate your phone onto their network. Most of the time the carrier can activate your phone over the air. A CDMA phone can not be used on a GSM network provider regardless if it is unlocked or not.

Another possibility is to find a CDMA flasher service in your area and physically give them your phone to flash it to whatever new network provider you want to use (it can only be flashed to one carrier at a time). This is not a 100% safe method as it possible that many of the features will not work correctly.

You can also read our topic on How to switch CDMA carriers and keep your phone?

If you confront any difficulties when unlocking a HTC device, please address our Help Center  for any support, instructions and troubleshooting you might need. In order to unlock any HTC handset and use it free with any other  network, you can have the safest, time-efficient and hassle free unlocking experience by using our service.


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