Whats the deal with the different digital technologies, like CDMA, TDMA and GSM?
Not much, if you’re not a telecom engineer. Sprint and Verizon employ CDMA (Code Division Multiple Access), in which each call is tagged with its own digital code–sort of how two people speaking a foreign language can hear each other across a crowded room. CDMA is the leading system in the United States; all other things being equal (they never are!), it offers the most calling capacity. AT&T and Cellular One use something called TDMA, short for Time Division Multiple Access, in which multiple calls are squeezed into the same chunk of frequency by assigning each one its own fraction-of-a-second repeating time slot. VoiceStream uses GSM (Global System for Mobile communications); based on time-division principles as well, it’s the oldest and most popular technology worldwide. GSM’s standout feature here is the subscriber identity module (SIM) card, which can be swapped in and out of different phones to transfer a phone number and account information. Nextel, in turn, uses a different te
