AlertServiceCentreArg  Message

This service is used between the HLR and the interworking MSC. The HLR initiates this service, if the HLR detects that a subscriber, whose MSISDN is in the Message Waiting Data file, is active or the MS has memory available. This service is also used between an MME (via an IWF), SGSN or an MSC using Deployment Option 2 (see subclause 8.2.4a.1 of 3GPP TS 23.272 and 3GPP TS 23.040 and the SMS-GMSC (possibly via an SMS Router), to indicate that a MS, for which one or more MT SMS have been requested to be retransmitted at a later time, is now available for MT SMS delivery or has moved under the coverage of another MME, SGSN or MS

Reference: TS 29.002-f30