GSM Network Component and Functions PPT File (https://drive.google.com/file/d/1zzRFNJGWDGuWL_kg-tb0iHPP0YHfWHyN/view?usp=sharing) Reference: Eng. Waleed El-Safoury Presentations

1. Chapter 2
GSM Network Architecture
Eng. Ahmed Khaled

2. SMS-C
MSC/VLR
HLR/AUC
GMSC
TRAU
BSC
EIR
ISDN/PSTN
Other
PLMNs
SSSOMS
BSS
MS
Base Transceiver Station Base Station Controller
BTS
GSM Network Architecture:

3. Mobile Station (MS):
Mobile Equipment (ME)
Subscriber Identity Module (SIM)
Mobile Station (MS)

4. Modes of Mobile station:
Modes of MS
Attached
Idle
Registration
LA Updating
Paging
Roaming
Active
Ongoing call
Handover
Monitoring power &
quality of its BTS
Monitoring power of
neighboring BTSs
Detached
IMSI de.
Implicit de.

5. • It is the terminal used by user
• Can be purchased from any store
• Without SIM no calls can be made
• It has an International Mobile Equipment Identity
(IMEI)
1- Mobile equipment (ME):

6. 490124 51 323897 0
TAC
(Type
Approval
Code)
FAC
(Final
Assemble
Code)
SNR
(Serial
Number)
SP
(Spare)
- - -
The IMEI:
• Is a 15-digit number.
• Verifies that the mobile station is type-approved and not stolen

7. 2- Subscriber identity module (SIM):
An electronic microchip for storing information.
Information Stored on SIM includes:
Subscriber Identification.
Charging.
Security.

8. 2- Subscriber identity module (SIM):

9. 2- Subscriber identity module (SIM):
Microprocessor
ROM
RAM
EEPROMI/O Control
Power
Ground
Clock
Reset
Input Output
CPU: Central Processing Unite – Microprocessor.
ROM: Read Only Memory (Non-Volatile).
EEPROM: Electrically Erasable Programmable Read Only Memory (Non-
Volatile).
RAM: Random Access Memory (Volatile).

10. GSM Identification Numbers:
• Mobile Station International Subscriber Dial-able NumberMSISDN
• International Mobile Subscriber IdentityIMSI
• Mobile Station Roaming NumberMSRN
• Temporary Mobile Subscriber Identity NumberTMSI

11. • Is the number dialed to reach a mobile Station.
• Has a Maximum of 15 digits.
The MSISDN:
46 705 123456
International
Prefix
CC
(Country
Code)
NDC
(National
Destination
Code)
SN (Subscriber
Number)
SWEDEN: - - -

12. 505 01 0987654321
MCC
(Mobile
Country
Code)
MNC
(Mobile
Network
Code)
MSIN (Mobile
Subscriber
Identity
Number)
AUSTRALIA: - -
The IMSI:
• The IMSI is the non-dial-able number for identifying a subscriber in the
GSM network.
• The IMSI is Stored on the SIM Card.

13. 33 007 987654
International
Prefix
CC
(Country
Code)
NDC
(National
Destination
Code)
SN (Subscriber
Number)
FRANCE: - - -
The MSRN:
The MSRN is used to route a call to the serving MSC/VLR Service area of the
called Subscriber.

14. The TMSI:
2463720
• Used instead of the IMSI within an MSC/VLR Service Area.
• Keeps the Subscriber’s IMSI Confidential.

15. The base station subsystem (BSS):
1. The Base Transceiver station (BTS)
BS contains the RF transmission equipment
It has an International cell global Identity (CGI)
It performs:
Power amplification
channel coding
ciphering
modulation

16. Base Station Transceiver (BTS):

17. The Base Station Subsystem (BSS):
2. The base station controller (BSC)
It carries out all control functions in the BSS as:
Paging
Channel allocation
Dynamic power control
Handover

18. The Base station Controller (BSC):
BTS
BTS
BSC
Remote BTS Co-located BTS

19. The base station controller (BSC):

20. The base station controller (BSC):

21. The base station controller (BSC):

22. The base station controller (BSC):

23. BSS Link Configuration – Cascaded:
BTS
BTS
BTS
BTS
BTS
BSC

24. BSS Link Configuration – Loop:
BTS BSC
BTS
BTS
BTS

25. BSS Link Configuration – Star:
BTS
BSC
BTS
BTS
BTS
BTS

26. The base station subsystem (BSS):
3. Transcoding and rate adaptation Unite (TRAU)
- It is used for speech compression/decompression
- Also adaptation of data to the requirement of the air
interface
VLR
MSC16161616
BSC
16
16
16
16
TRAU
64
64
64
64

27. The Mobile service switching center (MSC):
 It is an electronic computerized exchange provides the interface
between MS and the fixed network.
It will not contain any subscriber parameters
1. Switching
2. Charging
3. Call routing
4. Communication with HLR and VLR
5. Communication with other MSCs
6. Control of connected BSCs

28. Mobile Switching Centre (MSC):
The MSC is connected to:
HLR (Home location register)
VLR (Visitor location register)
AUC (Authentication Center)
EIR (Equipment identity register)
AUC
HLR EIR
MSC
VLR
GMSC
TRC
BSC
BTS (RBS)
PSTN
Cellular
Networks
PCS
Networks
OSS
SOG
BGW
Base Station System
Operation and Maintenance
Center
Switching
System

29. 1. HLR (Home location register):
The centralized database that stores and manages
all mobile subscription parameters
HLR contains :
Subscriber identification numbers (IMSI,MSISDN)
Subscriber current location information (MSC/VLR)
Subscriber authentication information
Charging
Billing method.

30. 2. VLR (Visitor location register):
A temporary storage location for subscription
information for MSs which are within MSC service area
VLR contains :
Mobile status (free, busy,…etc.)
Temporary MS identity (TMSI)
Temporary MS roaming number (MSRN)
Location areas
Supplementary service information

31. 3. Authentication:
It is a processor system that performs the authentication function
RAND
Database
IMSI, KI
𝑨 𝟑 𝑨 𝟖
RAND SRES 𝑲 𝒄
Triplet
Triplet
Request for
Triplet from
HLR, VLR
IMSI
Ki
AUC

32. 4. EIR (Equipment identity register):
As the subscriber and equipment are separate in GSM so we
use a separate authentication process for MS equipment
EIR is a centralized database for validation of international
mobile equipment identity (IMEI)
EIR contains 3 lists:
White list (for valid MS equipment)
Black list (for stolen or denied service MS)
Gray list (for mal-performance MS [e.g. faulty software] )
EIR
Check
IMEI
White
ListGray
List
Black
List

33. Geographic Network Areas:
The GSM Service area is the collection of PLMNs in which you can use
one mobile station

34. Geographic Network Areas:
A Public Land Mobile Network (PLMN) is:
 A group of MSC/VLR Service Area.
 The Largest geographical Area served by one network operator.

35. Geographic Network Areas:
An MSC/VLR Service Area is made up of several LA’s and is covered by
one MSC.

36. Location Area
Geographic Network Areas:

37. LAC (Location Area Code):
240 01 65412
MCC
(Mobile
Country
Code)
MNC
(Mobile
Network
Code)
LAC
(Location
Area
Code)
SWEDEN: - -
The MCC identifies the country.
The MNC identifies the PLMN.
The LAC identifies a Location Area within the PLMN network.

38. A cell is the smallest radio coverage area in the network.
Cell
Geographic Network Areas:

39. Cell Identity:
The MNC identifies the PLMN.
The LAC identifies a Location Area within the PLMAN.
The CI identifies a cell within the GSM Network.
262 02 4867 6832
MCC
(Mobile
Country
Code)
MNC
(Mobile
Network
Code)
LAC
(Location
Area Code)
CI
(Cell Identity)
Germany: - - -

40. Etisalat 2G Coverage: