1. Modes Mobile Station ( MS )
MS Switched Off
can not receive incoming paging messages.
can not make outgoing call.
No dedicated channel is associated with it.
MS Switched On And in Idle Mode
can receive incoming paging messages.
can make outgoing call.
No dedicated channel is associated with it.
MS in Dedicated Mode
MS is in conversation
A dedicated traffic channel TCH is associated with it.

2. Technical Terms Used w.r.t. MM(Mobility Management)
IMSI International Mobile Subscriber Identity
MSISDN -Mobile Subscriber ISDN Number
TMSI Temporary Mobile Subscriber Identity
MSRN -Mobile Subscriber Roaming Number
IMEI - International Mobile Equipment Identity
LAI Local Area Identity
A Authentication Algorithm
A Ciphering Algorithm
A Kc(Ciphering Key) Generation Algorithm

3. MSISDN (Mobile subscriber ISDN Number)
Technical Terms Used in GSM
MSISDN
MSISDN (Mobile subscriber ISDN Number)
A number assigned to the mobile subscriber
Registered in Telephone Directory
Used by the calling party for dialing
MSISDN is used
by the caller to set up a connection to this GSM mobile subscriber.
by the MSC/GMSC to address the HLR when interrogating the visitor location of the GSM mobile subscriber.
By the system to access the database of the GSM mobile subscriber in the HLR.
Stored as semi permanent data in HLR

4. MSISDN format CC – Country Code NDC – National Destination Code CC NDCSN
3 DIGITS
2 DIGITS
10 DIGITS
CC – Country Code
NDC – National Destination Code
- uniquely identifies the PLMN in a country
-Max No of digits 15 as per ITU recommendation.

5. Technical Terms Used in GSM
IMSI (International Mobile Subscriber Identity)
A unique identity allocated to each MSISDN.
Known only to the operator
To ensure confidentiality to the subscriber.
IMSI is used
By VLR to address the HLR while updating the location of the GSM subscriber.
To access the database of the GSM subscriber in the HLR, VLR and AuC
Stored as
permanent data in SIM,
Semi permanent data HLR,
Transient data in VLR.

6. IMSI MCC MNC MSIN MCC – Mobile Country Code
3 DIGITS
2 DIGITS
<= 10 DIGITS
MCC
MNC
MSIN
15 DIGITS OR LESS
MCC – Mobile Country Code
To Identify the home country of the PLMN
MNC – Mobile Network Code
To identify a GSM PLMN in a country
MSIN – Mobile Station Identification Number
Uniquely identifies a subscriber within a home PLMN.
2 DIGITS DIGITS
HLRID SN

7. Technical Terms Used in GSM
TMSI (Temporary Mobile Subscriber Identity)
Identity which guarantees the integrity of mobile subscriber on the radio interface.
Uses only over the radio path
Assigned by VLR to each mobile subscriber entering the VLR area
Stored in SIM of MS and in VLR
TMSI is used
To address the GSM subscriber in the BSS
To address the GSM subscriber data in the VLR
Consists of Four Octets, coded using a full hexadecimal representation

8. LMSI (Local Mobile Subscriber Identification)
Allocated by VLR and sent to HLR
LMSI is the address at which GSM subscriber are stored in VLR database
HLR includes it together with IMSI to speed up the search for subscriber data to in VLR.
Comprises of 4 Octets.

9. MSRN (Mobile Subscriber Roaming Number)
Required by GMSC to route an incoming call to a MS that is not currently under the gateway’s control
It is a temporary number used
To set up the voice connection from the originating MSC/GMSC to the VMSC
To address the GSM subscriber data in VLR.
HLR knows the current MSC/VLR service area for a mobile subscriber
HLR requests the current MSC/VLR to allocate a MSRN to the called subscriber and return to it.
After receiving MSRN, HLR returns the same to GMSC, which can route the call to current MSC/VLR exchange.
Format:--- MSRN=CC+NDC+SN
CC=Country code.
NDC=Network Destination Code.
SN=Subscriber Number.

10. IMEI (International Mobile Equipment Identity Number)
Identifies the mobile equipment
TAC
FAC
SNR
6 CHAR
2 CHAR
TAC – Type Approval Code
Allows approved types to be distinguished
from Non approval types.
FAC – Final Assembly Code
Identifies the place of manufacture
SNR – Serial Number issued by manufacturer.

11. All the cells in a Location area are served by single VLR.
Location area consist of one or more than one cell which may be served by one or more BSC s.
All the cells in a Location area are served by single VLR.

12. Location Area SS 7 HLR BSC LA 1 BSC VLR 1 LA 2 BSC LA 3 BSC BTS BTS
MSC1
LA 1
BTS
BSC
BTS
VLR 1
LA 2
SS 7
BTS
HLR
BSC
MSC2
BTS
LA 3
BTS
BSC
VLR 2
Location Area

13. Location Area
Each location area in a GSM PLMN is identified by a Location Area Identity ( LAI ).
LAI = MCC + MNC + LAC
MCC - Mobile Country Code.
MNC - Mobile Network Code.
LAC - Location Area Code .
MCC
MNC
LAC
3 digits
2 digits
2 octets max
LAI
( 16 bits )
Maximum length of LAC is 16 bits.
Thus there can be maximum of 65,536 Location Areas defined in one GSM PLMN.
Stored as semi permanent data in VLR
Stored in SIM of MS

14. Subscriber Data at MSC/HLR
Data related to identification and numbering ( IMSI, MSISDN).
Data related to MS Subscription type.
Authentication and Ciphering Data.
MS VLR number

15. Subscriber Data at MSC/VLR
Data related to identification and numbering ( IMSI, MSISDN,MSRN and TMSI ).
Data related to MS subscription type.
Authentication and Ciphering Data.
MS status data, Location Area
Hand-over data,

16. Authentication is used to check the validity of a mobile subscriber.
At MS
At N/W Ki Ki
RAND( 128 bits ) A3 A3
SRES
SRES
( 32 bits ) =?
AUTHENTICATION

17. Ki ( 128 bits) : Identification Key
- Purpose : Ki is used to calculate SRES and Kc.
- Ki is stored in SIM and HLR.
- Ki is never transmitted over signaling network.
RAND ( 128 bits ):Random Number
- Purpose : RAND is used to calculate SRES and Kc.
Kc ( 64 bits ) : Ciphering Key
- Purpose : Kc is used to encrypt data over radio interface.
SRES ( 32 bits) :Signed Response

18. A5 A5 S1 S2 S1 S2 114 bits BTS MS Kc. FRAME NO. Kc 64bits FRAME NO.
CIPHERING
DECIPHERING
DECIPHERING
CIPHERING
BTS MS

19. Ciphering is used to encrypt data on radio interface.
RAND Ki
Kc generation is done at the time of Authentication. A8
Frame No. (22 bits )
Kc ( 64 bits) A5
Ciphering Stream
Ciphered Bits
XOR
Information Bits ( 114 bits )
CIPHERING

20. LOCATION UPDATE SCENARIO - I
Request For Service
Old MSC/ VLR
New MSC/ VLR
HLR /AUC MS
BSS
Channel Request 1
RACH
SDCCH Assignment 2
AGCH
Location Update Request ( TMSI , LAI 0 ) 3
SDCCH
Request IMSI
( TMSI ) 4
Send IMSI

21. LOCATION UPDATE SCENARIO - II Authentication and Ciphering
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS 5
Get Authentication Parameters
( IMSI )
Authentication Parameters
Authenticate MS ( RAND )
( RAND,Kc,SRES )
SDCCH 6
Authentication Response ( SRES )
SDCCH
Cipher Radio Channel 7
( Kc )
Cipher Up Link Channel
SDCCH

22. LOCATION UPDATE SCENARIO - III Authentication and Ciphering
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Up Link Ciphered 8
SDCCH
BSS Ciphers Down link Channel . 9
Ciphering Complete

23. LOCATION UPDATE SCENARIO - IV Update HLR/VLR & TMSI Reallocation
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Update Location 10
De Register Mobile 11
Mobile De-registered 12
Location Updated
Location Updated Accept TMSI 13
SDCCH

24. LOCATION UPDATE SCENARIO - V Update HLR/VLR & TMSI Reallocation
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Location Updated Complete 14
SDCCH 15
Clear Signaling Connection
Clear Complete 16
Release Radio Signaling Channel
SDCCH

25. SETUP PHASE - CALL SETUP - CALL RELEASE
Mobile To Land Call Set-up Scenario
SETUP PHASE
- REQUEST FOR SERVICE ( CHANNEL ) BY MS
- AUTHENTICATION
- CIPHERING
- EQUIPMENT VALIDATION ( EIR CHECK )
- VALIDATION AT VLR
- CALL SETUP
- HAND OVERs
- CALL RELEASE

26. Service Request (TMSI,LAI)
MOBILE TO LAND CALL - I
Request For Service
MSC/VLR
BSS MS
Channel Request 1
RACH
SDCCH Assignment 2
AGCH
Service Request (TMSI,LAI) 3
SDCCH
Authentication
Ciphering
Equipment validation

27. Equipment Validation
A process by which a specific ME can be identified to prevent the use of stolen, unauthorized or malfunctioning equipment in the network.
Each equipment is uniquely identified by an International Mobile Equipment Identity (IMEI) code.
IMEI is incorporated into ME by the manufacturer
IMEI Consists of three components
Type approval code (TAC)
Final Assembly Code (FAC)
Serial Number (SNR)
IMEI is stored in EIR

28. Equipment Validation EIR
MSC/VLR
BSS
EIR MS
IMEI Request 1
SDCCH
IMEI Response (IMEI) 2
SDCCH
Check IMEI 3
IMEI Check results 4

29. MOBILE TO LAND CALL - II Call Setup
MSC/VLR
BSS MS
Call Setup Request 5
SDCCH
Call Proceeding 6
SDCCH
Assign Trunk and radio
Assign TCH 7
SDCCH
Radio Assignment Complete
SDCCH
Trunk and Radio Assignment Complete

30. MOBILE TO LAND CALL - III
Call Setup
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Network Setup ( Dialed Digits ) 8
Network Alerting
Alerting 9
FACCH
Connect
Start Billing 10
Connect
FACCH
Connect Acknowledge 11
FACCH

31. MOBILE TO LAND CALL - IV Call Release
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Disconnect 12
Network Release
Release 13
FACCH
Release Complete 14
FACCH
Clear Command 15
Channel Release
FACCH
Release Complete

32. Land To Mobile Call Set-up Scenario
Phases of Land To Mobile Call
( Mobile Terminating - MT Call )
Routing Analysis
Paging
Authentication
Ciphering
Call-Setup
Call Release

33. Fixed to Mobile Call Routing
VLR
PSTN
MSC
HLR
BSS
MSRN
MSISDN
IMSI/TMSI
IMSI/TMSI
MSISDN
MSISDN
MSRN
IMSI/TMSI

34. Fixed to Mobile Call Routing
VLR
PSTN
MSC
HLR
BSS
(VISITED)
(HOME)
MSRN
MSISDN
MSISDN
MSRN
MSRN
IMSI/TMSI
MSISDN
IMSI/TMSI
MSRN
IMSI/TMSI

35. Routing Analysis LAND TO MOBILE CALL - I HLR MSC/VLR GMSC PSTN
Incoming Call 1
( MSISDN )
Get Route 2
Get Route
( MSISDN ) 3
( IMSI )
Routing Information 4
( MSRN )
Routing Information
( MSRN )
Incoming Call 5
( MSRN )

36. Paging LAND TO MOBILE CALL - II BSS MS MSC (TMSI) PCH ( RACH )
Perform Page
Page
(TMSI) 6
PCH
Channel Request 7
( RACH ) 8
Access Granted
( AGCH )
Paging Response
( TMSI, LAI ) 9
SDCCH
Page Response

37. LAND TO MOBILE CALL - III
Call Set-up
BSS
MSC MS
Call Set Up 10
SDCCH
Call Set Up Confirm 11
SDCCH
Assign Trunk & Radio Channel
Assign Radio Channel 12
SDCCH
Radio Channel Assigned
Trunk and Radio Channel Assignment Complete
SDCCH

38. LAND TO MOBILE CALL - IV Call Setup
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Mobile Alerting 13
FACCH
Network Alerting
Connect ( off-hook ) 14
FACCH
Connect
Connect Acknowledge 15

39. LAND TO MOBILE CALL - V Call Release
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Network Release
Disconnect 16
FACCH
Release 17
Release Complete
FACCH
Release Complete 18
FACCH
Clear Command 19
Clear Channel
Clear Complete
FACCH

40. Mobile To Mobile Call Set-up Scenario
Phases of Mobile To Mobile Call
Request for service.
Authentication
Mobile Originating
Ciphering
Call-Setup
Call Release
Routing Analysis
Paging
Mobile Terminating
Authentication
Ciphering
Call-Setup
Call-Release

41. CHANNELS USED IN GSM PHYSICAL CHANNELS LOGICAL CHANNELS
Traffic channels
Control channels

42. CONTROL CHANNELS BROADCAST CONTROL CHANNEL COMMON CONTROL CHANNEL
DEDICATED CONTROL CHANNEL

43. BROADCAST CONTROL CHL BCCH---BroadCast CHannel
FCCH---Frequency Correction CHannel
SCH------Synchronisation CHannel

44. COMMON CONTROL CHL PCH-----Paging CHannel RACH---Random Access CHannel
AGCH---Access Grant CHannel

45. DEDICATED CONTROL CHL SDCCH---Standalone Dedicated Control CH
SACCH---Slow Associated Control CH
FACCH---Fast Associated Control CH