How do CDMA networks manage identity?
Naturally, CDMA networks also need to keep track of their subscribers’ identities — which phones carry which phone numbers and belong to which people. Instead of a removable card, CDMA networks use data carried in the circuits of each telephone. The Electronic Serial Number (ESN) and Mobile Equipment Identifier (MEID) are numbers unique to each CDMA telephone, and used by CDMA networks to manage service to phones and users. Because CDMA networks rely on unique data in each telephone’s non-removable circuitry, it’s generally more difficult for CDMA subscribers to start using a different phone. CDMA cellphones don’t have a slot for accepting a SIM card, and GSM and CDMA are mutually incompatible radio systems. SIM (well, RUIM) comes to CDMA The Telecommunications Industry Association (TIA) has developed a standard that will allow SIM-like cards known as removable user identity modules (RUIMs) to be used on CDMA networks. The RUIM would fill the same role for CDMA as SIM cards do for GSM
