You may have heard the term "world phones" used by someone in the IT department at the office, but what exactly does that mean and how would it concern you if you decided to take a business trip overseas?
What Are World Phones?
To put it very loosely, world phones are mobile phones that can be used in different parts of the world with little to no additional intervention on the part of the cell phone user. More specifically, you must also know about the core technologies involved with the phone that you would like to use.
Carriers like Verizon Wireless in the United States make use of a cellular technology called CDMA, which stands for Code Division Multiple Access. By contrast, other carriers like AT&T and T-Mobile use something called GSM technology, which stands for Global System for Mobile Communication. Generally speaking, phones that operate on CDMA will not work on GSM networks and vice versa.
With a few noted exceptions, the majority of the industrialized world uses GSM-based technology for its cell phone networks. This includes international destinations like the United Kingdom, Hong Kong, and Australia. However, this does not mean that your AT&T iPhone 4 will necessarily work when you go traveling to Melbourne, Australia. GSM-based technology operates on different frequencies (sometimes called a "band") and these must be compatible.
If the bands are compatible, you may be able to effectively use the phone in different parts of the world. However, if you keep your domestic SIM card in place, you will likely incur what are known as "roaming" charges. These can prove quite pricey, as roaming minutes can cost several dollars and roaming data can cost even more.
That said, this is much more convenient than renting a phone at your destination or purchasing a new (local) SIM card at the country that you are visiting. It also means that you are able to retain the same phone number that you are using back home, although international callers may need to enter a prefix to reach you. Whatever the case, it can prove useful to have a true "world phone" that has as many GSM bands on its as possible. Several Nokia smartphones have this notable feature.
Are Unlocked Phones the Same Thing?
While there are certainly some parallels between world phones and unlocked phones, they are not exactly the same thing. The former, as described above, is meant to be used in international markets thanks to its compatibility with international networks. You could then typically keep the same phone number and SIM card in place, incurring the related roaming charges as a result. These phones may not necessarily be "unlocked," though.
Unlocked phones, on the other hand, are devices that can accept foreign SIM cards and SIM cards from carriers other from the original supplier. This adds a great deal of flexibility, as you are able to save significant amounts of money by avoiding roaming charges. Prepaid phone cards in certain markets like Hong Kong can be quite a bit cheaper than their counterparts in Canada and the United States.
GSM/CDMA Dual Mode Cell Phones
With all this talk of GSM, where does this leave CDMA phones? As it turns out, there are world-compatible phones with CDMA technology as well. Generally speaking, these world phones are known as "dual mode" phones, because they contain both CDMA and GSM compatibility.
In general, these types of phones sold through carriers like Verizon Wireless will have the CDMA radio that works when the customer is still in the country, but it can "roam" on international GSM networks. These phones typically do not have the GSM radio bands that are compatible with domestic carriers.
This is one way to take advantage of "the network" while home, but still using the same phone when traveling abroad as well.