ISO/IEC 15429:2003 specifies the signalling protocol for the support of the Wireless Terminal Location Registration supplementary service (SS-WTLR) and the Wireless Terminal Information exchange additional network feature (ANF-WTINFO) at the Q reference point between Private Integrated services Network eXchanges (PINXs) connected together within a Private Integrated Services Network (PISN).

SS-WTLR is a supplementary service which enables a WTM user to register at, or deregister from, the current location within the PISN. The ability to register at different locations in the PISN at different times enables the WTM user to maintain the provided services (including the ability to make and receive calls) at different access points. Deregistration is used to inform the PISN that the WTM user is temporarily unable to make use of the provided services (including the receipt of calls).

ANF-WTINFO is an additional network feature which enables transfer of restriction information between Home PINX and Visitor PINX. ANF-WTINFO also enables the Visitor PINX or Home PINX to initiate a check of the current location information.

The Q reference point is defined in ISO/IEC 11579-1.

Supplementary Service specifications and Additional Network Feature specifications are produced in three stages and according to the method specified in ITU-T Rec. I.130. This International Standard contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ISO/IEC 15428.

The signalling protocol for SS-WTLR and ANF-WTINFO uses certain aspects of the generic procedures for the control of supplementary services specified in ISO/IEC 11582.

ISO/IEC 15429:2003 also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between SS-WTLR and other supplementary services and ANFs.

ISO/IEC 15429:2003 is applicable to PINXs which can interconnect to form a PISN.