Cellular Frequently Asked Questions
Cellular carriers in the United States operate on one of two network types. Code Division Multiple Access (CDMA) or Global System for Mobile Communication (GSM). While both will transmit both voice and data, they do so in different ways so the systems are not compatible.
This depends on your coverage needs. CDMA currently has better overall coverage in the United States. GSM is used in more countries, however, GSM runs in four different frequencies (see additional information below). Check the coverage maps provided by the carriers to determine which service best meets your needs. For U-M campus see Cellular Coverage in U-M Ann Arbor Campus Buildings (except the hospitals and health centers).
A phone should be chosen based on your individual needs, what features or functionality are most important to you. Each cellular provider offers phones with a wide range of features.
It depends on the cellular network technology that is used. There are two major cellular network technologies in the world: Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA). The GSM Association is an international organization that oversees the GSM standard. CDMA is a proprietary standard designed by Qualcomm in the United States. It has been the dominant network standard in the United States, Canada, and parts of Asia. The two network technologies are not compatible. Viewing coverage maps provided by cellular carriers will help you determine where your cell phone can be used.
It depends. GSM is run on four different frequencies: 850, 900, 1800, and 1900. The GSM frequency in the United States is 850/1900Mhz. However, the GSM frequency used in the majority of countries is 900/1800Mh. They are not compatible. (Canada, Mexico, Japan, Korea and some Central/South American Countries do not use 900/1800Mhz.). For additional information and a complete list of countries see GSM World.
In order to have a phone that will work in the more than one country, make sure your phone either tri or quad-band phone. Be certain your phone uses the correct network type (CDMA or GSM) as well as the correct frequency. For additional information and a complete list of countries see GSM World or CDMA Worldwide.
There are two kinds of dual-band systems. One is 900/1800 MHz. This kind of cell phone will work well in many countries. However, it will not work in the United States. The other is 900/1900 MHz phone. These phones work on the United States GSM network, and on some of the international GSM networks.
Triple band means the phone capabilities include either; both international frequencies plus one United States frequency; or both United States frequencies and one international frequency. Quad-band means the phone capabilities include all four frequencies.
Most modern phones are tri-band or better. We recommend you select a tri or quad-band phone if you want to use your phone outside of the United States.
The following table shows the frequency bands used in some countries.
It is possible that your phone is SIM locked. This means there is an electronic lock on your phone that will allow the phone to only operate on a specific carrier network.
Before you travel be certain to check with your carrier to see if your phone does have a SIM lock and what your carrier's policies concerning unlocking phones are. If the carrier permits phones to be unlocked, they will also provide needed instructions or procedures to unlock the phone. NOTE: Most GSM phones can be unlocked (T-Mobile/AT&T). CDMA phones cannot be unlocked (Sprint/Verizon).
A SIM card or Subscriber Identity Module is a portable memory chip used in some models of phones. The SIM card holds personal identity information, cell phone number, phone book, text messages and other data.
If you travel internationally very often and visit several different countries, a multiband phone will serve you best. For full compatibility you will need a quad-band phone. AT&T and T-Mobile offer International Service plans for MultiBand phones. Another alternative is to purchase or rent a different phone either from a carrier in the country or countries you are visiting or an international cell phone carrier that provides service in the country or countries you are visiting. Compare rates, minimum fees and processing fees offered to find the plan that best meets your needs.
If you travel to a country regularly, or stay in one country for an extended period of time and want to use the same phone, you will need to have a MultiBand phone that can be unlocked. Then purchasing a pre-paid SIM card that gives you local service for that specific country is a good option. Other alternatives are to purchase or rent an additional phone either from an international cell phone carrier or from a carrier that provides service in the country you are visiting.
Yes assuming the phone you are using includes the same cellular network and frequency as used in the country you are visiting. The SIM card automatically configures your phone to send and receive SMS messages. Be certain to check the international cost for this service with your carrier before you travel. Costs vary and can be quite expensive.
Yes assuming the phone you are using includes the same cellular network and frequency as used in the country you are visiting. The SIM card automatically configures your phone to receive your voicemail messages. Be certain to check the international cost for this service with your carrier before you travel. Costs vary and can be quite expensive.
If you can use your phone in other countries, be sure that you bring the right charger! The battery charger must be dual voltage—It needs to operate on all voltage from 110V to 240V and on frequencies between 50-60Hz.
No, if you'd rather use your own phone number and use international roaming, you do not need to change your SIM card. Be certain to check with your cellular carrier to make certain your phone will work in the country you are visiting. Also check their international rates to send and receive calls before you travel. Costs vary and can be expensive.
The Internet and other technology is widely available and makes communication more convenient than ever. Other ways to communicate with friends, family or business contacts while traveling include: Skype and International phone cards.
International phone cards are available from many companies. Select the card that provides the best rates and service for the country or countries you will be visiting.
Webopedia does a good job of explaining the differences.
For departmental purchases using a U-M ShortCode refer to Purchasing Services Procurement Services for additional information.
Yes, but a credit card must be used.
The number and variety of smartphones continues to grow. Be certain to check carrier web sites for the latest information concerning the products they sell and support. At this time, the major cellular carriers sell iPhone, Android, Windows Mobile, BlackBerry, Palm Web OS and Symbian phones.
This is hardware dependent. Some Smartphones also include built in WiFi.
If you use IMAP e-mail:
If you use Exchange e-mail:
Even if your phone cannot connect directly to the Exchange server, you can still send and receive e-mail with the Exchange server via IMAP. See ITS Exchange Mobile Device Support.