IS-41 / ANSI-41

US Telecoms Industry Association Interim Standard 41 (IS-41, also known as ANSI-41) is an Inter Cellular Network Communication Protocol which was developed to support interoperability between differing networks for mobile telephony, such as AMPS, D-AMPS and IS-95. The protocol provides functionalities like call delivery to and from the mobile network, intersystem handover and roaming, short message delivery and validation and authentication through an inter-system messaging protocol.

Specifically, IS-41 functions provide operations and procedures to:

• Detect the presence of a mobile subscriber in a visited system.
• Authenticate a subscriber for service.
• Allow access to subscribed services while roaming outside the original service area.
• Provide continuity of in-progress calls through the handover process between systems.

The IS-41 standard for mobility management is similar to GSM and includes the Home Location Register (HLR) and Visitor Location Register (VLR).