Application to Person Messaging via Custom SMS Gateway in 5G

Question

I am researching about implementing an SMS gateway that supports sending Application to Person (A2P) SMSs (in both MO and MT directions) over a 5G network. It is something similar to an ESME (External Short Messaging Entity), which talks directly to the SMSC on 2G/3G networks.

As illustrated in the above diagram it should be able to forward SMS AOMT received from the third-party application to the 5G Network as well as to forward SMS MOAT received from the 5G network to the third-party application.

To implement the above functionality for SMS over NAS (SMSoNAS) I want to understand,

1. Where this SMS gateway fits in the 5G Network architecture? (i.e. Should I implement an SMSF / a component similar to AMF which provides only uplink functions / an MSGin5G server / MSGF ?)

Should I consider the SMS gateway to be an NF consuming the SMSF?

Or should I consider the SMS gateway to be an MSGF?

2. Which components should the SMS gateway talk to? (i.e. SMSF / UDM / SMSC)
3. Which protocols should the SMS gateway implement? (i.e. SS7-MAP / Diameter / Rest-Based N20/Nsmsf)

I have refered several 3GPP and ETSI 5G specifications including ETSI_TS_129.540, 3GPP_TS_23.502, 3GPP_TS_22.262 and yet was not able to find any answer to above points.

So can you please help me to understand the correct architecture for my SMS gateway

Answer 1

In the 5G ecosystem, SMSF will be your SMS Gateway to connect conventional SMSC to 5G network. SMSC still stores and forwards SMS in its legacy network. SMSF will connect to SMSC through SGd interface. SMSF also connects 5G control plane network functions; AMF and UDM. Using service-based interface SMSF provides SMS MO/MT services based on the SMS over NAS through AMF.

• It performs SBI processing through Namf / Nudm / Nnrf / Nsmsf .
• Using Nudm interface, it manages SMS Management Subscription Information with UDM
• Using Nsmsf interface, it generates/deletes subscriber context information
• Using SGd, it processes OFR/A (MO-Forward-Short-Message-Request/Answer) and TFR/A (MT-Forward-Short-Message-Request/Answer).

Abbreviations used ;

• SMSF(Short Message Service Function)
• AMF(Access and Mobility Management Function)
• UDM(Unified Data Management)
• MO(Mobile Originating)/MT(Mobile Terminating)

Answer 2

I was able to contact GSMA regarding this particular question. According to them since ESME/SMPP and 5G are being orthogonal to each other implementation of 5G will not prevent the SMPP based ESMEs from connecting to the SMSCs residing in 5G networks.

In other words, the interface defined in SMSCs with SMPP, which allows ESMEs to communicate with the SMSC, and the MAP / Diameter based interfaces defined in the SMSCs, which enables to deliver SMS messages to devices/subscribers are two separate things. Therefore it is unlikely to have an impact from one on the other.

Hence even in 5G it is possible to implement A2P or P2A messaging over SMS (SMSoNAS) using the same old approach by connecting the ESME to SMSC using the SMPP interface defined in the SMSC.