PDF of this tutorialA call arrives at the S_MSC for the prepaid subscriber. Recognizing the subscriber's ID, the S_MSC sends a location request invoke message (LOCREQ) to its home location register (HLR). The HLR returns a location request return result message (locreq) to the S_MSC, indicating that the S_MSC should send an ANLYZD to the RSU.
Upon receipt of the ANLYZD from the S_MSC, the RSU queries the market server to determine if the MIN is a prepaid account and, if so, the amount of talk time available to the MIN. The market server validates the MIN, calculates the available talk time, and forwards the available talk time to the RSU. The RSU sends an anlyzd to the S_MSC to indicate that call processing can continue. The S_MSC routes the call to the subscriber.
The RSU starts timing the call when the subscriber answers. The calling party is then connected to the subscriber.
When the subscriber ends the call, the S_MSC sends a termination disconnect invoke message (TDISCONNECT) to the RSU. The RSU stops timing the call and sends the call duration to the market server. The market server prices the call and decrements the subscriber's account. The RSU sends a termination disconnect return result message (tdisconnect) to the S_MSC. The S_MSC releases the call.
Figure 3: Positive-Balance Call Termination
