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SMS MO and MT call flow

This Article on SMS covers following:
SMS basics and types
SMS network and elements
SMS MO MT call flow
SMS versus MMS

As we know SMS has become everyone's daily need.In this article we will know MO and MT SMS call flow.

Let us assume that MS-A is sending SMS to MS-B as shown in the figure. SMS delivery will go through two phases before it is finally delivered. The phase of SMS travelling from originating mobile subscriber A to SMSC is referred as MO(Mobile Originated) call and the phase from SMSC to mobile subscriber B is referred as MT(Mobile Terminated) call w.r.t. SMS.

SMS Mobile Originated and terminated Call Flow

The diagram below depicts message flow or signals between various network elements when SMS is sent from MS-A to MS-B.


Behind this SMS, there are basic protocols such as SS7(Signaling System No.7) and SMPP(Short Message Peer to Peer Protocol). SS7 supports communication between core network elements. SMPP is used in IP domain. SMPP is responsible for communication between SMS center(SMSC) and ESME(e.g. service provider/content provider).

Following are the steps for entire SMS process from originating mobile(MO) to terminating mobile(MT).

•  The SMS-SUBMIT is the MO FSM message(Mobile originating forward short message) which is between origin MSC and origin SMSC.

• The message received by SMSC is acknowledged to the origin subscriber MS-A by SMS-SUBMIT REPORT. The MS-A gets indication message as "message sent" from origin SMSC.

• Origin SMSC gets the required information from HLR regarding destination MSC/VLR to route the SMS. This information is obtained by SRI SM request(Send Routing information for short message). HLR responds the required information to origin SMSC in RESP message.

• After receiving the routing information origin SMSC delivers the message to respective destination MSC/VLR, which in turn delivers the SMS to MS-B. The same is indicated in the figure by MT-FSM and MT-FSM ACK.

• Once the SMS is delivered to the MS-B, MS-A gets indication message as "message delivered" OR "message succeddfully delivered". The same is mentioned by SMS-STATUS REPORT in the figure.

Please note that connection from MS-A and MS-B is with the BTS as shown and BTS is connected with BSC and BSC is interfaced with the MSC.

Testing Mobile Originated and Mobile terminated SMS using Agilent 8960

MO SMS TEST from mobile subscriber:

>0001000491214300150B48692074686572652E2E2E <PRESS ctrl+shift+Z>
Agilent 8960 displays message received.

Following are the steps to perform MT SMS TEST from Agilent 8960:

•   click short message service
•   click point to point
•   click send message, it will display sending
•   finally Agilent 8960 should get message status as "Acknowledged by DUT"
For detail kindly download Agilent manual and refer.


GSM RF planning  Mobile Terminated Call  GSM downlink PS data call flow  GSM uplink PS data call flow  GSM Tutorial   GSM protocol stack   GSM physical layer   GPRS protocol stack   GPRS tutorial   CS vs PS 


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