Greetings from our team!!!
Since MNP started materializing in INDIA, there has been lot of interest growing on MNP call flows. We have received quite a few requests for MNP SMS flow.
Here we have tried to explain basic MNP SMS flow. Terms which came into existence due to MNP are already explained in earlier posts.
So let us start.
Assumptions: A and B both are Vodafone Delhi Subscribers (Ported In or normal).
A is postpaid number.
Let us now go through signalling flow.
1) A sends an SMS to B. Mobile Originated Forward Short Message (MO-FSM) is send to STP/MNP with destination as SMSC address(SMSC GT). SMSC address is already stored in SIM. MO-FSM also contains B number to which SMS is sent.
2) MNP check its database attaches RN/LRN to B number and forward MO-FSM to SMSC.
3) SMSC acknowledges the MO-FSM by FSM Response to MSC. This three steps complete the MO leg of SMS Flow and handset receives an indication "SMS sent" at this point of flow.
4) Step4 marks the beginning of SMS terminating flow. SMSC checks this is our own RN/LRN removes RN from B number and sends Send Routing Info- Short Message (SRI-SM) to STP/MNP. This message can be directly send to HLR also that depends on network topology.
5) SRI-SM is forwarded to HLR with B number.
6) HLR responds SRI-SM Response with the VLR address where subscribers is currently registered and IMSI of B number.
7) On receiving VLR address now SMSC knows where to send MT-FSM. SMSC send MT-FSM to that particular VLR with B number IMSI and SMS data.
Here after MSC tries to deliver this message to B Subscriber using standard MT SMS flow.
8) MSC/VLR acknowledge SMSC by MT-FSM response which contains status of MT SMS.
i.e delivered or failed cause if SMS is not delivered to B number.
This sums the SMS flow in case of MNP,our main motive was to highlight the difference between normal and MNP SMS Flow. Hope we fulfilled that and hope this post was informative for you.
Keep checking for new posts till then HaPPy Reading.
Comments/Criticism/Queries/Appreciations are most Welcome as they are lifeline of this blog.
Telecom Tigers Team