How cell phones work abroad – basic information

Phone frequencies

There are four primary GSM frequencies used throughout the world.

  • 850 MHz and 1900 MHz – used primarily in North and South America
  • 900 MHz and 1800 MHz – used primarily in Europe, Asia, Middle East, Africa, Australia and Oceania

An individual country will use one or more of the frequencies listed above. Since not all countries use the same frequency, you will need to ensure that the cell phone you are intending to travel with uses the same frequency as the country you are traveling to. Otherwise, the only way to use your cell phone (if it’s a smart phone) is by connecting to the internet through the device’s Wi-Fi connection.

The frequencies listed above are basically 2G. Many countries have upgraded to 3G technology and some have upgraded to 4G. Note that when you travel, you might not be able to use your cell phone with as fast of a connection as you do at home. If you have a phone that can operate on a 4G network but the country you are visiting does not have 4G yet, you will have to operate on the country’s 3G network (or 2G if it does not have 3G capability yet).

See the excellent guide to the frequencies used by each country including 3G and 4G. Note that 3G and 4G are listed sometimes as different frequencies than the above-noted 2G ones.

Cell phone service technologies

There are two primary technologies used in the world today to process cell phone calls. They are:

  • CDMA (Code Division Multiple Access)
  • GSM (Global System for Mobile communications) – GSM is the world’s most widely used cell phone technology.

Cell phone carriers

Your cell phone equipment gives you the ability to send and receive phone calls or text messages; however, you need a cell phone carrier to transmit those calls and texts to the person(s) you are communicating with. Carriers, such as Verizon or AT&T, transmit your calls by using one of the two technologies noted above (CDMA or GSM).

  • CDMA technology – Verizon, Sprint and Virgin Mobile
  • GSM technology – AT&T and T-Mobile

These are the USA’s primary carriers. Each country, that can provide cellular service, has one or more carriers to handle cell phone calls. Even though Verizon and AT&T will use different technologies to process your calls, they both use the same frequencies to process those calls – namely 850 or 1900 which are the two frequencies used in the USA.

Roaming (sometimes called “international roaming”)

When you are in a foreign country, service providers such as Verizon cannot process your call. Instead they have agreements with the cell phone carriers in the foreign country to process your call. The process of connecting to their cell phone towers (and not connecting to Verizon’s own cell phone towers) is called roaming. The foreign carrier processes your call and in turn charges your normal cell phone carrier who in turn marks up that amount to a higher amount when charging you.

Cell phones

Cell phones are manufactured to connect to one or more of the GSM global frequencies noted above. There are dual band phones (can connect to two frequencies), tri band phones (can connect to three frequencies) and quad band phones (that connect to all four of the world’s frequencies). If you are a traveler, when purchasing your next cell phone, purchase a quad band phone (sometimes called a global phone). It gives you more options when traveling.

Note: The frequencies, noted in the beginning of this section, are the basic 2G frequencies. When looking at a phone’s “specs” you will also see what 3G frequencies (e.g. UMTS) the phone operates at and even the 4G frequency (if applicable).

The frequencies a cell phone can connect to should be noted in the “specs” (aka specifications or tech specs) section of the manufacturer’s website. When comparing the phone’s frequency specs to the country’s frequency, you want to look at the GSM frequencies (e.g. the 850, 900, 1800 and 1900) to understand if your phone will work in the country you are visiting. You can then check to see if the phone’s 3G frequency (e.g. UMTS) matches up to the country’s 3G frequency. If it does, you should be able to connect on their faster 3G network.

Cell phones can make calls via two methods

  1. Using the phone’s radio receiver and connecting to a cellular network. This is how you make calls on a daily basis. Note that putting your phone into “airplane mode”, turns off the radio receiver from accessing its cellular connection.
  2. Using the internet. There are two ways to connect. One is through a WiFi connection (hotel guest room, WiFi hotspot, etc.) and the other is using a cellular data plan.

GSM vs CDMA phone

There are two types of cell phones – GSM phones and CDMA phones. GSM phones work more widely across the world than CDMA phones. If you are going to purchase a phone for international use, buy a GSM phone.

SIM cards

A GSM phone has a SIM card – a small rectangular piece of plastic that contains a microchip. This chip stores basic account information including the cell phone number and address book info. For older cell phones, the SIM card might be behind the battery. Remove the  battery and you’ll find the SIM card. In many newer phones, the SIM card is located in a small compartment on the side of the phone. You will need a piece of metal that has a paper clip type end to open the SIM card slot. This device should come with your new cell phone. Pack it when traveling. If you don’t have it, a paper clip will usually work. The retail store where you purchase a SIM card will normally have this device or a paper clip to install your new SIM card.

Some of the newer smart phones are manufactured with a SIM card smaller than the regular SIM cards. These smaller cards are called micro SIM and nano SIM cards. When you are in a foreign country, the local cell phone provider’s retail store might only sell the micro SIM card size and not the nano. The only thing you need to do is cut the micro down to a smaller size to fit your cell phone. The retail store will usually be able to cut the card down for you and fit it into the SIM card slot.

A GSM phone can be locked or unlocked

A locked phone is connected to a specific provider (e.g. Verizon). All calls are processed/billed by that provider. The SIM card cannot be removed and replaced by another provider’s SIM card. As an example, when you purchase a phone through Verizon at a discounted amount because you are signing a two-year commitment, the phone purchased is a locked phone. Note that some of the newer phones, such as Verizon’s iPhone 5, come unlocked out of the box. An unlocked phone allows you to remove your current SIM card and replace it with another SIM card that can allow you to use the local cell phone network in the country you’re traveling to.

Tip: It is possible for the locked phone to be unlocked by the provider if you call their support desk and ask that the phone be unlocked when you travel abroad. It is my understanding that some providers will unlock their phones and some will not. When you return from traveling overseas, put the original SIM card back into your cell phone to continue making calls through your normal provider.

You can also purchase an unlocked phone, usually at full retail, that is not connected to a specific provider. An unlocked phone allows you to purchase a SIM card from one of many companies allowing you to make calls at a cheaper rate.