basiccall flow part 2

7/30/2019 Basiccall Flow Part 2

1/14

Basic Call Flows Part 2

1


2/14

Table of Contents:

1. Call Flows in case of call

handling..3

1.1 MAP message details in general

case.4

1.2 MAP message details in roaming

case4

2. Call Flows in case of Operation and

Maintenance..5

1.1 Subscriber

tracing

5

1.2 Miscellaneous:sendIMSI

...6

3. Call Flows in case of

SMS7

3.1 MAP message in case of intra

network7

3.2 MAP message in case of inter

network9

2


3/14

4. Call Flows in case of

GPRS10

1. Call Flows in case of Call Handling:

In this section we will discuss MTC scenario because HLR come into role in

this only.

Call handling does not have subcategories of operations; it simply has thefollowing two operations:

sendRoutingInfo provideRoamingNumber

Details of MTC scenario step by step:

1. In the case of an MTC, a subscriber from within the PSTN/ISDN dials themobile subscriber's MSISDN, thereby generating an ISUP IAM message

(alternatively, TUP could be used) that contains the MSISDN as thecalled party number. Based on the information contained in theMSISDN (national destination code and the country code), thePSTN/ISDN routes the call to the GMSC in the PLMN.

2. The GMSC then identifies the subscriber's HLR based on the MSISDN,and invokes the MAP operation sendRoutingInformationwith theMSISDN as a parameter towards the HLR to find out where the MS ispresently located.

3


4/14

3. Because of past location updates, the HLR already knows the VLR thatcurrently serves the subscriber. To obtain a mobile station roamingnumber (MSRN), the HLR queries the VLR using the operationprovideRoamingNumberwith the IMSI as a parameter. The VLR assignsan MSRN from a pool of available numbers and sends the MSRN backto the HLR in an acknowledgement.

4. Because the GMSC now knows the MSC in which the MS is currentlylocated, it generates an IAM with the MSRN as the called party number.When the MSC receives the IAM, it recognizes the MSRN and knows theIMSI for which the MSRN was allocated. The MSRN is then returned tothe 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 (SRI)

In the case of a mobile terminating call, the GMSC sends this message to thecalled party's HLR to obtain routing information, such as the MSRN. Uponreceiving the message, the HLR sends a provideRoamingNumber request tothe VLR where the subscriber is currently roaming.

provideRoamingNumber (PRN)

The VLR uses this message to provide routing information (MSRN) to the HLRin the case of a mobile terminating call, which is sent to the GMSC. SeeFigure and the description of sendRoutingInfo for more information.

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

roaming somewhere):

4


5/14

invoke sendRoutingInfo

invoke provideSubscriberInfo :

This MAP message is invoked by HLR to MSC to get info regarding

current location area of subscriber.Significance 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.

returnResultLast provideSubscriberInfo :

This MAP message is response of previous message which give location

info to HLR.

returnResultLast sendRoutingInfo

This is response of SRI send to HLR by GMSC.This message give camel

related info to GMSC.If subscriber has balance and it will be able toreceive call, then only it will proceed with next MAP message.

invoke sendRoutingInfo

After checking balance related info of subscriber,it send SRI to HLR to

have roaming numer ie MSRN to establish connection.

invoke provideRoamingNumber :

This is invoked by HLR to MSC to get MSRN.

returnResultLast provideRoamingNumber

This is response of previous message.

returnResultLast sendRoutingInfo :

This is response of SRI send by HLR to GMSC .It gives GMSC MSRN of

subscriber.

2. Call flow in case of Operation and Maintenance

Operation and maintenance can be divided into the following categories:

Subscriber Tracing Miscellaneous

5


6/14

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

Subscriber Tracing

Subscriber tracing has two MAP operations:

activateTraceMode

deactivateTraceMode.activateTraceMode

The HLR uses activateTraceMode to activate trace (subscriber tracking) modefor a particular subscriber (IMSI); the OSS requests activateTraceMode. TheVLR waits for that particular MS to become active, at which time it sends arequest to its MSC to trace the MS.

Figure. MAP Operation Sequence to Initiate and Terminate 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.

6


7/14

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 theVLR. 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 flows in case of SMS.

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

7


8/14

Details of MAP message :

forwardSM

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

sendRoutingInfoForSM

The SMS-GMSC uses this message during an MT-SMS to deliver an SMSto the MSC in whose area the subscriber is currently roaming. Themessage contains the subscriber's MSISDN, and the result contains thedestination MSC's ISDN number. SCCP then uses this ISDN number todeliver the SMS using a forwardSM message. Figure shows the MT-SMS

procedure.

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

8


9/14

reportSMDeliveryStatus

If the SMS-SC cannot deliver the MT-SMS to the MS (because the subscriber is notreachable, 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 SMS-

IWMSC 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 analertServiceCentre 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

9


10/14

INTER-OPERATOR SMS FLOW

The above fig illustrates the scenario where sms originates from GSM network anddeliverd to different GSM network.

MS originate SMS

Now MSC forwards the packet to SMSC-A through MO-FORWARD-SMmessage.

For routing it uses SCCP calling address: GT of MSC and SCCP called addressGT of SMSC(Service Center Address)

MO-FORWARD-SM message contains :SMS,A number,B number,SC address.

SMSC after checking basic authentication , responds withMO-FORWARD-SM-ACK

Once this ACK reaches to handset, originator knows that his messages hasdelievered into the SMSC.

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

So it does SRI query.

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

10


11/14

For routing we use SCCP calling address :unique GT of SMSC and SCCP calledaddress :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 MT-FSM(MT-FORWARD-SM).

SCCP calling address : GT of SMSC and SCCP called address : GT of nodewhich SMSC has received in SRI-ACK is used for routing.

Remote MSC/VLR will respond back (MT-FSM-ACK) using SCCP callingaddress: GT of MSC/VLR and SCCP called address : GT of SMSC.

Response message has information about success/Failure of SMS to B partynumber.

4. Call Flows in case of GPRS:

Figure : GPRS-attach procedure

11


12/14

Details of MAP message:

Invoke updateGprsLocation :

This message is sent by SGSN to HLR to update location informationrelated with GPRS service of subscriber in its database.

Invoke insertSubscriberData :

HLR send this message to insert GPRS related data of subscriber inSGSN.

returnResultLast

This is acknowledgement of previous message.

returnResultLast updateGprsLocation

This message shows successful l GPRS location update of subscriber.

cancelLocation

HLR send this message to SGSN to delete subscriber in SGSN

MOBILE ORGINATING SMS FLOW

SMS MO callflow

12


13/14

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 thesupplementary 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.

13


14/14

basiccall flow part 2

Documents