World Mobile Roaming

Here are the general rules for international mobile-phone roaming.

Two Rival Technologies

It is important to understand that there are two completely incompatible systems of mobile telephony in use. The first is GSM ("Groupe Spécial Mobile") which is in use world-wide. The second is CDMA ("Code-Division Multiple Access") which is used mostly in North and Central America.

In the United States, GSM networks are available however due to historical issues regarding the way wireless bandwidth was allocated by the Federal Government, these GSM bands are not on the same frequencies as in the rest of the world.

GSM frequencies in use throughout the world

As you will note, all regions except North America have a 900Mhz band available, the U.S. only has an 850Mhz band.

As a consequence of this, and speaking In general, non-prepaid non-US mobile phones will work in the United States. This includes CDMA phones from Mexico or Canada and GSM phones from around the world.

U.S. mobile phones typically do not work outside The Americas because of two reasons:

1. The majority of North American carriers use a CDMA network (Verizon, Sprint)
2. The U.S. carriers using a GSM network (AT&T, T-Mobile) use it on the 850Mhz and 1900Mhz bands).

However, most U.S. mobiles work thought the Americas, except Nextel devices which work almost no-where except the U.S. due to the proprietary "iDEN" network they use. Prepaid devices also only work in their own home country, regardless of underlying technology.

Some of the more expensive mobiles in the U.S. are capable of receiving the additional frequencies, with the very expensive "quad-band" phones being able to receive all global frequencies.

International Roaming

International roaming and international dialing are extremely expensive. You must check your carrier for details.

An option available to some GSM device users is to put a prepaid sim-card from their destination country in their U.S. device. If your phone is "unlocked" it can accept any sim-card. A sim-card is a small chip that instructs the phone on how to tune to a carrier's network. This method only works if all of the following are true:

1. Your phone is a GSM phone (AT&T, T-mobile).
2. Your phone is "unlocked".
3. Your phone supports the GSM frequencies of your destination.

External Links

• Comprehensive table of world mobile-phone compatibility
• Legal phone unlocking procedures (Illegal unlocking procedures exist but we will not tell you anything about them.)

Categories: Mobile