The wide variety of cell phones available today come in many sizes and shapes, and offer many different features. However, many of these phones share similar underlying architectures, in the form of three network technologies. Here’s a quick introduction to the three cellular networks in the United States.
- CDMA (Code Division Multiple Access) – network technology used by Verizon and Sprint. Phones that operate on CDMA networks do not have SIM cards, which means they are tied to the carrier they are programmed to. The 3G data service provided by CDMA networks is called EvDO (Evolution Data Only / Optimized). CDMA networks are most common in the US, with little roaming ability overseas.
- GSM (Global System for Mobile communications) – network technology used by AT&T (formerly Cingular) and T-Mobile. Phones from carriers using GSM networks use SIM cards (small memory cards that hold carrier connection information and the user’s contacts), which allows users to switch an unlocked phone (which involves entering a code to untie the phone from its designated carrier) to another GSM carrier’s network. The two 3G data services provided by GSM networks are HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), and the 2G service available is EDGE (Enhanced Data rates for GSM Evolution). GSM is the most popular type of network in Europe.
- iDEN (Integrated Digital Enhanced Network) – network technology used by Sprint Nextel (and its lessees, including Boost Mobile) and smaller regional carriers. iDEN phones use SIM cards, allowing users to swap their service between unlocked iDEN phones or phones with the same carrier subsidy. iDEN-powered networks provide the unique push-to-talk walkie-talkie feature, in addition to voice and data services. Currently, iDEN networks do not provide any 3G data service, only slower data services are supported.