Basiccall Flow Part 2

 

Basic Call Flows Part 2

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Table of Contents:

1. Cal Calll Fl Flows ows in c case ase o off ca call ll handling………………………………………………… handling……………………… ……………………………………………..3 …………………..3

1. 1.1 1 MA MAP P me mess ssag age e de dettai ails ls in ge gene nera rall case………………………………………………………….4 1. 1.2 2 MA MAP P me mess ssag age e de dettai ails ls in roam roamin ing g case…………………………………………………………4

2. Call Flow Flows s in case of O Operat peration ion a and nd Maintenance……………………………………………..5

1.1 Subscriber tracing……………………………………………………………………………… …………5 1.2 Mis Misce cella llaneo neous: us:sen sendIM dIMSI… SI……… …………… ……………… ……………… ……………… …………… …………… ………… … ……………………...6

3. Cal Calll F Flow lows s in cas case eo of  f  SMS……………………………………………………………………………………7

3.1 MA MAP Pm me essag ssage e iin nc cas ase eo off iint ntrra network…………………………………………………………7 3.2 MA MAP Pm me essag ssage e iin nc cas ase eo off iint nte er network…………………………………………………………9

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4. Cal Calll F Flow lows s in cas case eo of  f  GPRS…………………………………………………………………………………10

1. Call Flow Flows s in cas case e of of Call Hand Handling ling::

In this section we will discuss discuss MTC scenario because because HLR come into role in this only. Call handling does not have subcategories of operations; it simply has the following two operations: • •

sendRoutingInfo provideRoamingNumber Details of MTC scenario step by step: 1. In the cas case e of an MTC, a subscriber subscriber from from within the PSTN/ISDN dials the the mobile subscriber's MSISDN, thereby generating an ISUP IAM message (alternatively, TUP could be used) that contains the MSISDN as the called party number. Based on the information contained in the MSISDN (national destination code and the country code), the PSTN/ISDN routes the call to the GMSC in the PLMN. 2. The GMSC then identifies identifies the the subscriber's subscriber's HLR based on on the MSISDN, MSISDN, and invokes the MAP operation sendRoutingInformation with the MSISDN as a parameter towards the HLR to find out where the MS is presently located.

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3. Because Because of past past location location updates updates,, the HLR already already knows knows the VLR that that currently serves the subscriber. To obtain a mobile station roaming number (MSRN), the HLR queries the VLR using the operation  provideRoamin  provideRoamingNumber  gNumber  with the IMSI as a parameter. The VLR assigns an MSRN from a pool of available numbers and sends the MSRN back to the HLR in an acknowledgement. 4. Because Beca use itthe GMSC GMSC now know s the MSC in which wh the MS is curre currently ntly located, generates an knows IAM with the MSRN asich the called party number. When the MSC receives the IAM, it recognizes the MSRN and knows the IMSI for which the MSRN was allocated. The MSRN is then returned to the pool for use on a future call. MAP Operations When the GMSC Requests a Routing Number for the MSC When the Subscriber is Roaming

Details of MAP message in this scenario: sendRoutingInfo sendRouting Info (SRI) In the case of a mobile terminating call, the GMSC sends this message to the called party's HLR to obtain routing information, such as the MSRN. Upon receiving the message, the HLR sends a provideRoamingNumber provideRoamingNumber request to the VLR where the subscriber is currently roaming.

 provideRoamingNumber ingNumber (PRN)  provideRoam  The VLR uses this message to to provide routing routing information information (MSRN) to the the HLR in the case of a mobile terminating call, which is sent to the GMSC. See Figure and the description of sendRoutingInfo sendRoutingInfo for more information. information.

Details of MAP message in roaming scenario(When called party is roaming somewhere somewhere): ):

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invoke sendRoutingInfo sendRoutingInfo

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invoke provideSubscriberInfo provideSubscriberInfo :  This MAP message message is invoked by by HLR to MSC to get info regarding regarding current location area of subscriber.Signific subscriber.Significance ance of this message is that HLR provide camel info for subscriber to GMSC and now GMSC will check whether given subscriber has balance or not.

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returnResultLast returnResu ltLast provideSubscriberInfo provideSubscriberInfo :  This MAP message message is response response of previous message which which give location location

info to HLR. 

returnResultLast returnResu ltLast sendRoutingInfo sendRoutingInfo  This is response response of SRI send send to HLR by GMSC.This GMSC.This message message give camel related info to GMSC.If subscriber has balance and it will be able to receive call, then only it will proceed with next MAP message.

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invoke sendRoutingInfo sendRoutingInfo After checking balance related info of subscriber,it send SRI to HLR to have roaming numer ie MSRN to establish connection. connection.

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invoke provideRoamingNumber :  This is invoked invoked by HLR to MSC to to get MSRN.

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returnResultLast returnResu ltLast provideRoamingNumber provideRoamingNumber  This is response response of previous previous message.

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returnResultLast returnResu ltLast sendRoutingInfo sendRoutingInfo :  This is response response of SRI send send by HLR to GMSC GMSC .It gives GMSC MSRN of 

subscriber.

case e of Ope Operati ration on and Mai Mainten ntenance ance 2. Call flow in cas Operation and maintenance can be divided into the following categories: • •

Subscriber Tracing Miscellaneous

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 The following following sections review review the MAP operations operations that are are used in each each of  these categories.

Subscriber Tracing

Subscriber tracing has two MAP operations: 

activateTraceMode

  deactivateTraceMode.

activateTraceMode

 The HLR uses activateTraceMod activateTraceMode e to activate trace (subscriber (subscriber tracking) mode for a particular subscriber subscriber (IMSI); the OSS requests activateTraceMode . The VLR waits for that particular MS to become active, at which time it sends a request to its MSC to trace the MS. Figure. MAP Operation Sequence tto o Initiate and Terminate Subscriber Subscriber Tracing

deactivateTraceMode

Upon receiving this message, the HLR turns off the trace mode and sends the message to the VLR, which also disables trace mode for that particular subscriber. Miscellaneous

The only MAP operation in the Miscellaneous subcategory : 

 sendIMSI.

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Following the OMC's request to the VLR to identify a subscriber based on his Mobile Subscriber ISDN Number (MSISDN), the VLR and HLR exchange sendIMSI messages. If the MSISDN cannot be identified, an unknown subscriber indication is passed to the VLR. Otherwise, the IMSI is obtained from the HLR and returned to the VLR. Figure . MAP Operation Sequence When an Operations and Management Center (OMC) Requests Subscriber Identity

3. Call flow flows s in in case case of of SMS. SMS.

Figure . MAP Operations Involved in Sending an SMS from MS to the SMS-SC

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Details of MAP message :

forwardSM

Both the mobile originating (MO-SMS) and mobile terminating SMS (MT-SMS) procedures use the forwardSM operation to carry text messages between the MSC where the subscriber roams and the SMSIWMSC or the SMS-GMSC, SMS-GMSC, respectively. Figure shows the MO-SMS MO-SMS procedure.

sendRoutingInfoForSM

 The SMS-GMSC uses this message during an MT-SMS MT-SMS to deliver an an SMS to the MSC in whose area the subscriber is currently roaming. The message contains the subscriber's MSISDN, and the result contains the destination MSC's ISDN number. SCCP then uses this ISDN number to deliver the SMS using a forwardSM message. Figure shows the MT-SMS procedure. Figure . MAP Operations Involved in i n Sending an SMS from the SMS-SC to the MS

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reportSMDeliveryStatus

If the SMS-SC cannot deliver the MT-SMS to the MS (because the subscriber is not reachable, for example), then the SMS-SC returns a negative result to the SMS-GMSC. Upon receiving this result, the SMS-GMSC sends a reportSMDeliveryStatus to the HLR, which, in turn, sets a message waiting flag in the appropriate subscriber data. alertServiceCentre

When SMS delivery fail, HLR sends an alertServiceCentre message to the SMSIWMSC to inform it about the negative SM delivery and waits until the subscriber can be reached. readyForSM

When the VLR (also aware of SM delivery failure) detects that the subscriber is again reachable, it sends a readforSM message to the HLR. The HLR, in turn, sends an alertServiceCentre message to the SMS-IWMSC, which informs the SMS-SC. The delivery process then begins again with a forwardSM message. informServiceCentre

If a sendRoutingInfoForSM is received for a subscriber that is currently unavailable, the HLR sends this message to the SMS-GMSC.

Special case:

GSM INTER-OPERATOR SMS FLOW 

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INTER-OPERATOR SMS FLOW

  The The above fig illustrates the the scenario where where sms originates originates from GSM GSM network and deliverd to different GSM network. • •

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MS originate SMS Now MSC forwards the packet to SMSC-A through MO-FORWARD-SM MO-FORWARD-SM message. For routing it uses SCCP calling address: GT of MSC and SCCP called address GT of SMSC(Service Center Address) MO-FORWARD-SM message contains :SMS,A number,B number,SC address. SMSC after checking basic authentication , responds with MO-FORWARD-SMACK  Once this ACK reaches to handset, originator knows that his messages has delievered into the SMSC.

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SMSC needs to know the subscriber subscriber B location to rout the SMS to B number.

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So it does SRI query.

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So SMSC will connect to HLR directly or will give to the gatewayMSC to send the SRI query to B party network.

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For routing we use SCCP calling address :unique GT of SMSC and SCCP called address :subscriber number +SSN B party HLR receives the SRI query,it rtesponds back with the SRI-ACK. For routing purpose SCCp address : GT of HLR and SCCP called address : unique GT of SMSC is used. Once the location and availabilityof B of B party is known through SRI-ACK  SMSC needs to forward the SMS to MSC/VLR B.it use MAP message MTFSM(MT-FORWARD-SM). SCCP calling address : GT of SMSC and SCCP called address : GT of node which SMSC has received in SRI-ACK is used for routing. Remote MSC/VLR will respond back (MT-FSM-ACK) using SCCP calling address: GT of MSC/VLR and SCCP called address : GT of SMSC. Response message has information about success/Failure of SMS to B party number.

 

 4. Call Flows in case of of GPRS:

  Figure : GPRS-attach procedure  

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Details of MAP message: Invoke updateGprsLocation updateGprsLocation :  This message message is sent by SGSN SGSN to HLR to update update location information information related with GPRS GPRS service of subscriber subscriber in its database. database.

Invoke insertSubscriberD insertSubscriberData ata : HLR send this message message to insert GPRS related related data of subscriber subscriber in SGSN.

returnResultLast   This is acknowledgement acknowledgement of previous previous message. message.

returnResultLast updateGprsLocation  This message message shows successful successful l GPRS GPRS location update update of subscriber. subscriber.

cancelLocation

 

HLR send this message message to SGSN to delete subscriber subscriber in SGSN

MOBILE ORGINATING SMS FLOW  

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SMS MO callflow

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1. The mobile station transfers the short message to the MSC.

2. The MSC queries the VLR to verify that the message transfer does not violate the supplementary services invoked or the restrictions imposed on the subscriber.

3. The MSC sends the short message to the SMSC using the forwardShortMessage operation.

4. The SMSC delivers the short message to the SMC.

5. The SMSC acknowledges the successful outcome of the forwardShortMessage operation to the MSC.

6. The MSC returns the outcome of the short message operation to the mobile station.

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