Tech Blog

The above fig illustrates sms flow between GSM and CDMA network.CDMA network uses the concept of sudo HLR for SMS routing.

· MOBILE subscriber from GSM network initiates an Originating SMS to be delivered to a CDMA network.

· Now MSC A forwards the SMS packet to SMSC-A (MO-FORWARD-SM).

· ROUTING USES SCCP CALLING ADDRESS: GT OF MSC AND SCCP CALLED ADDRESS GT OF SMSC(SERVICE CENTRE ADDRESS)

· INFORMATION CONTANS: SMS,A NUMBER, B NUMBER, SC ADDRESS

· SMSC AFTER CHECKING BASIC AUTHENTICATION, RESPONDS WITH MO-FORWARD-SM-ACK

· ONCE THIS ACK REACHES TO HANDSET, ORIGINATOR KNOWS THAT HIS MESSAGES HAS BEEN SUBMITED INTO THE SMSC

· NOW SMSC NEEDS TO KNOW THE LOCATION OF SUBSCRIBER B. SO SMSC INITIATES SRI QUERY(SEND ROUTING INFORMATION). SMSC SENDS THE PACKET TO GW MSC-A, WHICH FURTHER FORWARDS TO CDMA-GWMSC.

· CDMA GWMSC FORWARDS THIS PACKET TO PSEUDO-HLR (RESIDES WITHIN SMSC-B).

· PSEUDO-HLR RESPONDS WITH A FAKE-IMSI, FAKE-VLR ADDRESS(GT OF SMSC-B)

· SMSC DOES NORMAL MT-FSM TO THIS FAKE-VLR GT RECEIVED IN SRI-ACK.

· SMSC-B RESPONDS TO THIS MT-FSM WITH MT-FSM-ACK.

· SMSC-A KNOWS THAT ITS MESSAGE HAS BEEN DELIVERED AND INFORMS ORIGINATOR SUBSCRIBER IF “STATUS-REPORT” HAS BEEN REQUESTED.

· SMSC-B NEEDS TO KNOW WHERE ITS CDMA SUBSCRIBER B IS LOCATED

· SO SENDS SMS-REQ MESSAGE TO LOCAL HLR.ONCE THE LOCATION OF SUBSCRIBER IS KNOW

· SMS IS DELIVERED USING MT-SMDPP MESAGE.

{src : Innternet libraries}