GSM: Difference between UMTS SIM (USIM) and GSM SIM

SIM and USIM

SIM cards (Subscriber Identity Module) are used to communicate on GSM networks and USIMs were introduced together with UMTS or 3G network.

Although it's possible to access 3G with a simple SIM card, the USIM have many advantages as compared to the SIM:

• A USIM is a tiny computer which is able to handle several mini internal applications, for instance a contact-less e-purse for the subway, a local service portal giving you access to your phone bill, etc, while SIM's analog is simple SIM menu which can't compute something by own other than communicating with carrier's server;
Bigger and Improved phone-book: USIM allows you to store thousands of contacts (limit on SIM is 255). Each contact can now contain email id and more than one phone number;

• A 3G (UMTS) handset equipped with a USIM card can be used to make video calls on 3g network;

• New and improved security algorithms are used to prevent unauthorized access to phone line, encrypt your calls and internet traffic and store contacts securely;