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SMSC for MVNOs/MNOs and A2P messaging

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SMS is an essential service in a telecom network. To enable the messaging service, a telecom network provider needs to deploy a Short Message service Centre (SMSC) within their home network. ComCode provides a feature-rich and reliable SMSC platform as a software product that enables MNOs/MVNOs or any other service provider (e.g., A2P) to send/receive text messages to/from a mobile device.

1. How ComCode’s SMSC is deployed ?

The above diagram depicts the deployment architecture of ComCode SMSC within a telecom network.

SS7 and IMS Network: These represent the originating network comprising both 2G/3G infrastructure and 4G/5G VoLTE infrastructure.

STP and IMS-S-CSCF: Signals from the SS7 domain are routed to ComCode SMSC via STP (Signal Transfer Protocol) which uses traditional GSM MAP 09:02 based messaging.

IMS-S-CSCF (Serving Call Session Control Function) acts as a session controller for LTE and 5G users. SIP-based messages from IMS subscribers are delivered through IMS S-CSCF.

ComCode SMSC: Sitting in the center, this acts as a single convergence point – processes messages from both the networks, SS7 (via STP) and IMS (via S-CSCF), and decides how to deliver them.

SMPP and HTTP: The external entities to send or receive SMSs. The HTTP application can send text messages to the given number, while the EMSE can connect to the SMSC over the SMPP protocol to send or receive messages.

2. Features of SMSC

ComCode’s SMSC delivers a comprehensive set of features ranging from basic P2P messages through enterprise A2P bulk delivery to IMS-based next-generation messaging flows along with legacy SS7/Sigtran based network. Some of the key features are listed below:

MESSAGING FLOWS:

  1. Mobile Originated Short message (MO)
  2. Mobile Terminated Short Message (MT)
  3. Application to Person (A2P)
  4. Person to Allocation (P2A)

PROTOCOL SUPPORT:

  1. HTTP API to send SMS from a web-based application/http client
  2. SMPP to send an SMS to a device for enterprise aggregators
  3. SMPP to receive an SMS from the device
  4. Sigtran(M3UA) over SCTP – Redundant Stack Architecture

IMS SUPPORT:

  1. IMS support for messaging over LTE and 5G data-only networks
  2. Built-in IP-SM-GW functionality.

ROUTING AND DELIVERY:

  1. REST APIs and GUI for managing/configuring SMSC
  2. Multiple data coding schemes such as UCS2, GSM7, URF8, etc.
  3. Home Routing with Fake IMSI generation.
  4. Store and forward with customized retry plans

ALERT SERVICE CENTRE AND MWD:

  1. Alert SC- Subscriber availability trigger
  2. Automatic redelivery
  3. MWD- Message waiting data
  4. Validity Period and Expiry Management

3. How does SMS service work with SMSC?

The essential messaging service is known as P2P messaging. A mobile user writes a text and sends it to another mobile number. The phone encodes the message and sends it to the nearest base station. The SMS reaches the nearest base station, e.g BTS in 3G, from BTS to MSC, and then MSC carries the message towards SMSC. This process is known as an SMS submission.

Once an SMS is submitted , SMSC receives the incoming MO-SM. It stores the message, validates the sender and verifies whether it is a P2P or a P2A message and tries to deliver the message to the destination number. If destination is another subscriber, it queries HLR and performs an HLR lookup with destination HLR to find their current location and network. If the mobile subscriber is available and attached, the result is IMSI and serving MSC address.

After HLR lookup, the SMSC sends the text to the serving MSC or the destination subscriber’s current MSC. From there, it was delivered to the mobile subscriber via BTS.

4. SMSC and Data Only network (e.g. LTE and 5G)

After 3G, the next generation networks (e.g., LTE or 5G) are the data-only networks. To support voice and SMS, the SIP-based network is used, known as Internet Multimedia Services (IMS).

ComCode’s SMSC has inbuilt IMS support to work with LTE and 5G network.

The diagram below shows the complete SMS architecture of the ComCode SMSC, handling both the SS7 and IMS worlds simultaneously. MSC and STP deliver 2G/3G SMS, the IMS chain delivers the modern VoLTE SMS, and the SMSC in the middle processes everything and delivers the message via SMPP.

  • IMS Path: A subscriber’s device first hits the P-CSCF (IMS entry proxy). The signal is forwarded to I-CSCF(Interrogating CSCF) whose job is to query HSS and find out which S-CSCF (Serving CSCF) is serving this subscriber. Once the signal is found, it reaches S-CSCF, which authenticates the subscriber and forwards the SIP message to ComCode SMSC.
  • HSS →  SMSC: The HSS sets the Initial Filter Criteria (IFC) on S-CSCF during UE attach for IMS,  to forward the UE originated SIP MESSAGES to the SMSC. While UE registration, the S-CSCF sends a SIP REGISTER to the SMSC, for SMS services. The SMSC stores the UE registration information.

CCode SMSC: This is the convergence point. It receives messages from both the paths – MAP messages from STP and SIP messages from S-CSCF, process them and delivers via SMPP.

5. P2P and A2P messaging over IMS in SMSC:

P2P over IMS:
In P2P messaging, a mobile user submits SMS over the IMS network to the SMSC. It travels as an SIP message through the IMS chain: P- CSCF → I-CSCF → S-CSCF → SMSC. If the destination subscriber is also IMS registered, SMSC delivers the message back through the IMS chain as an MT SMS to the destination device.

A2P over IMS:
In case of A2P, the enterprise application ESME submits the message to SMSC via the Submit SM flow, to the SMSC over SMPP – not through the IMS chain. If the destination subscriber is IMS registered and attached on IMS for messaging, the SMSC submits the MT SIP Message to the S-CSCF, which delivers it to the subscriber’s device.

6. How 3G, LTE and 5G message Interoperability is supported

As the LTE and 5G are the data only network. To support SMS over IP, devices register over SIP network for messaging.  The SMS interoperability means that SMS can be sent from 3G to 4G/5G and vice versa.

Once a text is submitted (from any network 3G, LTE or 5G)  to the SMSC, it checks if a subscriber is registered on IMS, if no – it uses SS7 path to deliver the text to the mobile device.

7. Supported 3GPP standards

M3UA – 4666
SCCP → Q.711 to Q.716
TCAP → Q.771 to Q.775
GSM MAP 09:02
3GPP TS 23.038
3GPP TS 23.040

8. Online Billing (OCS) for SMS:

If a mobile operator needs to bill and SMS in real time, the Online charging system (OCS) is used. It uses same interface (Gy) as for mobile.
When the user sends the text, the SMSC connects to the OCS. The SMSC then sends a CCR to the OCS, checking if the user has enough balance. OCS saves the required funds and sends  a CCA to confirm the delivery.

9. How is SMSC addressed?

In case of 3G, the SMSC number is stored in the device, which is an SCCP Global Title(GT). An MO SMS has this global title as the called address in SCCP addressing.

In IMS the UE sets up an IPSec tunnel with P-CSCF.  A MO SIP MESSAGE reaches to the S-CSCF. From there based on IFCs, the MESSAGE is passed to the SMSC.

Fuel Your Network with Precision Power

ComCode’s SMSC system is tuned to keep your messaging services fast and reliable, even during peak hours, so you never miss a beat. Get ready to elevate your network services and grow without limits.

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