GSM Call Routing

RK

GSM-Introduction

Mobile Station (ME+SIM)

HLR, VLR

Location Update

Call Routing Scenarios

Mobile Originated Sequence

Mobile Terminated Sequence

Mobile-to-Mobile Long distance

Mobile in Roaming (Domestic, International)

Call Handover

Questions

AgendaAgenda

Mobile Station(MS)Mobile Station(MS)

HLR / VLR

Home Location Registers (HLR)

o permanent database about mobile subscribers in a large service area(generally one per GSM network operator)

o database contains IMSI, MSISDN, prepaid/postpaid, roaming restrictions, MSC/VLR, supplementary services.

Visitor Location Registers (VLR)

o Temporary database which updates whenever new MS enters its area, by HLR database

o Controls those mobiles roaming in its area o Reduces number of queries to HLR o Database contains IMSI, TMSI, MSISDN, MSRN,

Location Area, authentication key

GSM ArchitectureGSM Architecture

EIR AuC

Three types of Location Update :

Brief Introdution to Location UpdateBrief Introdution to Location Update

Periodic Location UpdatePeriodic Location Update

IMSI Attach/DetachIMSI Attach/Detach

Normal Location UpdateNormal Location Update

Please give the sequence:1.The called MS is powered off.2.The called MS activates the CFU to a PSTN No.3.The called MS has been barred all incoming call.4.The Called MS are not known at HLR

QuestionsQuestions

1. The called MS is powered off

GMSCMS BSS MSC VLR HLR GMSC

(

(

MSISDN+91 9885 xxxxxx

Initial and Final

1 Address Message

2 Send Routing Info

3 Routing Info Ack

Subscriber Absent The Calling Mobile hears the announcement of mobile is powered off

AP Vodafone AP Airtel

MSISDN+91 9885 xxxxxx

CFN

4 IFAM

MS BSS MSC VLR HLR GMSC PSTN

2. The called MS activates the CFU to a PSTN No.

Initial and Final

1 Address Message

2 Send Routing Info

3 Routing Info Ack

MSISDN+91 9885 xxxxxx

MSISDN+91 9885 xxxxxx

+91 40 66235307

3. The called MS has been barred all incoming call.

MS BSS MSC VLR HLR GMSC

Initial and Final

1 Address Message

2 Send Routing Info

3 Routing Info Ack

GMSC

MSISDN+91 9885 xxxxxx

MSISDN+91 9885 xxxxxx

Call Barred

4. The Called MS are not known at HLR

MS BSS MSC VLR HLR GMSC

Initial and Final

1 Address Message

2 Send Routing Info

3 Routing Info Ack

GMSC

MSISDN+91 9885 xxxxxx

MSISDN+91 9885 xxxxxx

Unknown Subscriber

GSM Architecture Cntd…GSM Architecture Cntd…

Call Routing

Scenarios

2 REQ. FOR SERVICE

1 CHANNEL REQUEST

DCCH ASSIGN

SIGNALING LINK ESTABLISHED

6 COMPLETE CALL

CALL PROCEEDING

3 AUTHENTICATION

SET Cipher MODE

4 SET-UP

5 EQUIP. ID REQ.

MS BSS MSC VLR HLR PSTN

Mobile Originated SequenceMobile Originated Sequence

Signaling Link request

Signaling Link Granted

Call setup is in Process

Setup Voice Call

Dailed digits …+91 40 66235307

Channel request

<

MS BSS MSC VLR HLR PSTN

7 ASSIG. COMMAND

ASSIG. COMPLETESwitch from Signaling Mode to Voice

8.Initial and Final Address Message (IFAM)

Alerting MS hears ring tone from land phone

Address Complete(ACM)

9 Answer (ANS)Connect

Ring tone stops

10 Connect Acknowldge

BILLING STARTSSpeech Started

Called Subscriber Answered

Switch Informs

Call Answered

Acknowledge Call Answered received

Hi RK

Ring Alert

Passed to Mobile

Switch routes the call to PSTN

PSTN indicates to Switch

Called Subscriber Informed Via Ring

+91 40 66235307

Mobile Originated SequenceMobile Originated Sequence

<

MSISDN+91 9885 xxxxxx

IMSI404 13 xxxxxxxxxx

MSRN

LAI & TMSI)TMSI)TMSI)

PCH>

MSRN MSRN

MSRN

Initial and Final 1 Address Message

2 Send Routing Info

3 Routing Info Ack

Initial and Final Address Message

4 Send Info For I/C Call Setup

5 PagePaging Request

MS BSS MSC VLR HLR GMSC GMSC

MSISDN+91 9885 xxxxxx

091 9885 xxxxxx (roaming number)

091 9885 xxxxxx (roaming number)

LAI – 404 13 location Area Code

Mobile Terminated SequenceMobile Terminated Sequence

AP Vodafone AP Airtel

MS BSS MSC VLR HLR GMSC GMSC

Billing starts

7 Connect

Connect ACK ANS

Ringing stops at Other Mobile

Subscriber picks up

Hello...

6 Assignment Command

Assignment Complete

AlertRingtone Alert Acknowledge

Ring Tone at the Other

Mobile

Address Complete

Speech Started

Mobile Subscriber Answered

Mobile Terminated SequenceMobile Terminated Sequence

AP Vodafone AP Airtel

Call Setup Request

Call Setup Confirmed

Radio tower

Base Station

Radio tower

Mobile Switching Station

Regional Switch Office Regional Switch Office

Trunk

5. Destination switch officereceives call, and forwardsto Mobil Switching Station

4. Regional Switch Officeforwards calls

Radio tower Base Station

Radio tower

Mobile Switching Station

1. Cell phone transmits tolocal towers

2. Towers are serviced bya local base station

3. Basestations areservices by MobilSwitching Station

5. Mobile SwitchingStation forwards to Base

Station

6. Base Station forwardsto local towers.

7. Local towers completethe loop

Mobile-to-Mobile Long DistanceMobile-to-Mobile Long Distance

Mobile is in RoamingMobile is in Roaming

2.Receiving Mobile on Roaming2.Receiving Mobile on Roaming

3. Both Mobiles are on Roaming3. Both Mobiles are on Roaming

International Roamer terminated callInternational Roamer terminated call

Location AreaCode

Global Cell Identification

CountryCode404

NetworkCode

49

CellIdentity

BSC3BSC2BSC1

MSC B MSC A

404 49 100 53

404 49 100 54

404 49 100 55

404 49 100 51

404 49 100 52

404 49 089 20

404 49 089 21

404 49 089 22

404 49 100 50

Location Area-100Location Area-089

INDIA-AP-AirtelMCC-MNC404 -49(INA49)

HandoverHandover

Questions ?