Basic GSM Call Flows

With traces from Huawei MSOFT

BASIC Call Flow Basic Call Flow

1. Location Update2. MOC TDM3. MOC IP4. MTC TDM5. MTC IP

Basic Call Flow

Location Update (LOC UP)

Location Update

LOC Up: Identity Response

LOC UP: Authentication

LOC UP: AUC Internal Structure

IMSI Ki

RANDOM number

generatorRAND

SRES

Kc

Ki

MSCHLR

AUC

IMSIIMSI

A3

triplet triplet

A8

LOC UP: Authentication

LOC UP: Authentication

MSC RAND SRES

Kc

RAND

SIM

RAND

Ki

A3

A8

SRES

SRES

Kc

SRES = SRES?

LOC UP: Authentication Request

LOC UP: Authentication Response

LOC UP: Update Location Req

LOC UP: Insert Subscriber Data

LOC: IMEI receive

LOC UP: Ciphering

LOC UP: TMSI Reallocation

Basic Call Flow

Mobile Originating Call (MOC)

MOC: Complete call Trace

CM Service Request

MOC : “Setup” MessageSetup message contains the dialed number from the Mobile station (MS)

MOC: (SRI) Send Routing Information

MOC: Reply from HLR

Assignment Request

MOC: IAM – Initial Address Message

MOC: ACM – Address Complete Message

MOC: Connect & Release

Basic Call Flow

Mobile Terminating Call (MTC)

MTC: Complete Trace

MTC: Provide Roaming Number (PRN)

MTC: PRN Response

MTC: IAM

Paging Request

Paging Response

Set UP

IP CALL

Call Flow through IP( MOC)

BICC TYPE IAM

TO BICC TYPE APM

FROM BICC TYPE APM

Call Flow through IP( MTC)

PRN

PRN Response

BICC TYPE IAM

Set UP

TO BICC TYPE APM

FROM BICC TYPE APM

Assignment Request

ALERT AND BICC TYPE ACM

CONNECT AND BICC TYPE ANM

DISCONNECT AND RELEASE

THANK YOU