Short Message Service (SMS) SMS provides paging functionality for alphanumeric messages of up to 160 characters to be exchanged with other GSM users. The network itself can also generate messages and broadcast to multiple MSs or to a specific MS. | Short Message Service SMS SMS provides paging functionality for alphanumeric messages of up to 160 characters to be exchanged with other GSM users. The network itself can also generate messages and broadcast to multiple MSs or to a specific MS. For example a welcome message can be sent to a subscriber when he or she roams onto a new network in addition it can provide useful information such as how to retrieve voicemail. The SMS service also transfers ring tones and logos to the MS. The SMS slightly blurs the image of the user traffic being separate from signaling because in a sense the messages are user traffic they are for human processing written and read rather than for communication between network entities. The SMS does not have subcategories. It has the following operations forwardSM sendRoutingInfoForSM reportSMDeliveryStatus readyForSM alertServiceCentre informServiceCentre The following sections examine each of these. forwardSM Both the mobile originating MO-SMS and mobile terminating SMS MT-SMS procedures use the forwardSM operation to carry text messages between the MSC where the subscriber roams and the SMS-IWMSC or the SMS-GMSC respectively. Figure 13-8 shows the MO-SMS procedure. Figure 13-8. MAP Operations Involved in Sending an SMS from MS to the SMS-SC In Appendix L Example L-6 contains a trace that shows the decode of a MAP operation forwardSM including its SMS text. sendRoutingInfoForSM The SMS-GMSC uses this message during an MT-SMS to deliver an SMS to the MSC in whose area the subscriber is currently roaming. The message contains the subscriber s MSISDN and the result contains the destination MSC s ISDN number. SCCP then uses this ISDN number to deliver the SMS using a forwardSM message. Figure 13-9 shows the MT-SMS procedure. Figure 13-9. MAP Operations Involved in Sending an SMS from the SMS-SC to the MS View full size image In Appendix L Example L-2 shows a trace showing a VLR s decode calling an HLR to perform a location update . .
