For effective, efficient communications, standardization is critical, and nowhere is this more evident than in the areas of mobile computing and cellular telephony.
If you need data access or e-mail through your cell phone, you're likely to be using one of two different technologies. In the U.S., the main approach for voice communications is called Code Division Multiple Access (CDMA), and it is the basis for the major network services offered by Verizon Wireless and Sprint Nextel, among others.
In Europe and most of the rest of the world, however, a very different technology called Global System for Mobile Communications has dominated the market. GSM uses a Time Division Multiple Access approach to frame structure. GSM service is available in the U.S. primarily through T-Mobile USA and Cingular Wireless. These carriers maintain GSM networks that are distinct from (though connected to) their other digital networks.
Both CDMA and GSM are second-generation (2G) technologies, and they have co-existed for several years. Each technology has its supporters. CDMA phones are engineered specifically for an individual carrier, whereas GSM phones make use of a removable memory card called the Subscriber Identity Module (SIM). Physically smaller than a secure digital flash memory card, a SIM card contains all the key information required to activate a phone, including the user's telephone number, personal identification number, address book and encoded network identification details. A user can easily move a SIM from one phone to another.
Though GSM phones are interoperable with one another, different countries use different parts of the frequency spectrum, so "world phones" typically must be capable of using several frequencies.
Today, the fastest-growing use of cellular networks is for the transmission of all kinds of data and rich media, including Web sites, video, music, images, and maps and driving directions. The older 2G networks simply couldn't handle that volume of traffic, and they couldn't offer the speed needed for transmitting large files. The answer was to make the services faster and build out the networks to deal with more traffic.
Here, too, the CDMA and GSM paths continued their separate but parallel development. CDMA brought us CDMA2000 and 1xRTT networks. The most recent developments are 1x Evolution Data Optimized, or EV-DO, and 1x Evolution Data/Voice, or EV-DV.
Similarly, GSM begat General Packet Radio Service, or GPRS, which begat enhanced data rates for GSM evolution, or EDGE. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384Kbit/sec. The latest generation is called Wideband Code Division Multiple Access (WCDMA).