1. GLOBAL SYSTEM
FOR
MOBILE COMMUNICATION
(GSM)
ARCHITECTURE
Vivek E.B

2. History & Evolution of Mobile Radio
1G Systems
2G Systems
3G Systems
4G Systems
1-Dec-18
Mobile communication

3. 1G Systems -Limitations
Analog technology
Limited capacity
Poor security against fraud
Little to offer in terms of advanced services.
1-Dec-18
Mobile communication

4. Second Generation Systems -2G
Use of digital technology
Advantages
Increased capacity
Greater security against fraud
More advanced services
1-Dec-18
Mobile communication

5. Second Generation Systems -2G
Limitation
They are not well suited to data communications
1-Dec-18
Mobile communication

6. 2.5 /2.75 Generation Systems GPRS EDGE CDMA 2000 1x 1-Dec-18
Mobile communication

7. GSM SPECIFICATIONS 1. Standard - ETSI. 2. Access Method - FDMA-TDMA.
3. Voice channels -8 chnls/carrier.
4. RF channel spacing(Channel BW) – 200 KHz.
5. Voice Coding Algorithm – RPE-LTP.
6. Voice Coding Rate – 13 Kbps.
7. Channel bitrate – Kbps.
8. Modulation Method- GMSK.

8. GSM SPECIFICATIONS
Therefore the frequencies for the uplink and the downlink are different ( Frequency Division Duplex - FDD) and the bandwidth of the GSM System is 25 Mhz..
Number of Channels – 124 channels pairs ( 25 Mhz/200 Khz )are available spaced at 200 KHz intervals
Due to interference to other systems, the very first carrier is not used.

9. GSM SPECIFICATIONS Cell To Mobile – Down Link 935-960 Mhz
Mobile to Cell – Up Link
Mhz
Mhz

10. FDMA/TDMA
Each channel pair serves eight ( Full Rate ) channels successively in a Timed Cycle.
In FDMA system each channel requires a transmitter and receiver
8 Voice channels, staggered in Time are transmitted via one carrier frequency
Each of the 124 FDMA linked carrier frequency is used to transmit 8 TDMA voice channels
Discontinuous nature of TDMA makes the entire 200 Khz bandwidth available to all 8 Voice channels.

11. Physical Channel The physical channel adopts FDMA and TDMA techs.1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
The physical channel adopts FDMA and TDMA techs.
On the time domain, a specified channel occupies the same timeslots in each TDMA frame, so it can be identified by the timeslot number and frame number.

12. GSM Various subsystems
12/1/2018
GSM Various subsystems
Mobile Station
Radio Subsystem
(Base Station Subsystem - BSS) includes the equipments and functions related to the management of the connections on the radio path.
Network & Switching Subsystem -NSS includes the equipments and functions related to end-to-end call.
Operations & Support subsystem- OSS includes the operation and maintenance of GSM equipment for the radio and network interface.

13. Mobile equipment or terminal.
Mobile Station
Mobile Station is really two distinct entities.
Mobile equipment or terminal.
SIM Card.
Mobile equipment, which is the actual Hardware, is anonymous.
SIM card, implemented as a smart card holds the subscriber information including a unique identifier called International Mobile Subscriber Identity (IMSI).
MS=ME+SIM

14. Functions of Mobile Station
Voice and data transmission
Frequency and time synchronization
Monitoring of power and signal quality of the surrounding cells
Provision of location updates even during inactive state
Equalization of multi path distortions

15. IMSI Used within the N/W to identify a mobile subscriber.
IMSI (International Mobile Subscriber Identity)
An unique identity which is used internationally.
Used within the N/W to identify a mobile subscriber.
The IMSI is fused in SIM by SIM manufacturer on the basis of information provided by the PLMN operator.
Stored within subscriber identity module(SIM), HLR, VLR,AC database.
The total number of digit in IMSI shall not be more than 15 digit.

16. GSM NETWORK ARCHITECTURE
2- Subscriber identity module (SIM)

17. SIM CARD A Smart Card That Identifies the Terminal
SIM provides personal mobility
SIM makes the terminal operational
User can have access to all subscribed services irrespective of both location of the terminal and the use of a specific terminal
SIM card may be protected against unauthorized use by a PIN (a Password)
Identified with IMSI

18. FUNCTIONS OF SIM CARD Acces control Customisation
Service personalisation
Network branding and advertising
Value addition in operator services
Roaming

19. IMEI is a serial number unique to each mobile
Each MS is identified by an International Mobile station Equipment Identity (IMEI) number which is permanently stored in the Mobile equipment.
TAC
FAC
SNR SP
TAC
FAC
SNR SP
= Type Approval Code
= Final Assembly Code
= Serial Number
= Spare

20. Base transceiver station
The base transceiver station, or BTS, contains the equipment for transmitting and receiving radio signals (transceivers), antennas, and equipment for encrypting and decrypting communications with the base station controller (BSC). Typically a BTS for anything other than apicocell will have several transceivers (TRXs) which allow it to serve several different frequencies and different sectors of the cell (in the case of sectorised base stations).

21. Base Transceiver station - BTS
FUNCTIONS
Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the antenna
Transcoding and rate adaption Functionality
Time and frequency synchronisation signals transmission.
Frequency hopping
Uplink radio channel measurements
Random access detection

22. Remote BTS BTS BTS BSC Co-located BTS GSM NETWORK ARCHITECTURE
The base station controller (BSC)
Remote BTS
BTS
BTS
BSC
Co-located BTS

23. BSC
The databases for all the sites, including information such as carrier frequencies, frequency hopping lists, power reduction levels, receiving levels for cell border calculation, are stored in the BSC

24. FUNCTION OF BSC It is connected to BTS and offloads MSC
Radio resource management
Inter-cell handover
Reallocation of frequencies
Power control
Performs traffic concentration to reduce the number of lines from BSC to MSC.
BSC performs call processing.

25. - Star BTS BTS BTS BTS BTS BSC GSM NETWORK ARCHITECTURE
BSS Link configuration
- Star
BTS
BTS
BTS
BTS
BTS
BSC

26. pppp GSM- NETWORK STRUCTURE GSM Area Location Area, MSC Area PLMN Area
CELL
Location Area,
MSC Area
PLMN Area

27. GSM Typical GSM Architecture
Data
HLR
VLR
MSC
AUC MS
EIR
PSTN
BTS
PSPDN
BSC
MSC
VLR Visited Location Register
HLR Home Location Register
EIR Equipment Identity Register
AUC Authentication Centre
MS Mobile Station
MSC Mobile Switching Centre
BTS Base Transceiver Station
BSC Base Station Controller

28. Network & Switching Subsystem
Manages the communication between the mobile users and other users. Provides all the functionality needed to handle a mobile subscriber such as: Registration Authentication Location updating Handovers and Routing to roaming subscribers.

29. Network & Switching Subsystem
Mobile Switching Center (MSC)
provides the services in conjunction with four intelligent databases.
Home Location Register (HLR)
Visitor Location Register (VLR)
Equipment Identity Register (EIR)
Authentication Centre (AuC)..

30. GSM MOBILE SWITCHING CENTER
Major functions:
Call setup,supervision and release
Digit collection and translation
Call routing
Billing information and collection
Mobility management(registration,location updating,handoff)
Paging and alerting
Management of radio resources during a call
Interrogation of appropriate registers(vlr/hlr)
Echo cancellation and manage connections to BSS,MSCs,PSTN

31. GSM Home Location Register…
Contains all administrative information of each subscriber registered in an GSM network. Logically there is one HLR per GSM. Can be implemented as a distributed database..

32. GSM Visitor Location Register….
VLR Contains selected administrative information from HLR needed for call control and provision of subscribed services for each mobile located in the geographical area controlled by it. .

33. GSM Authentication Centre…
The authentication center (AuC) stores the keys required for checking whether a mobile subscriber is authorized to access the PLMN.
-Used for security purposes. -A protected database -Subscriber authentication data ie.Authentication Keys Ki -Encryption data. -Used in association with random number, ciphering algorithms etc..

34. GSM Equipment Identity Register…
A database that contains a list of all valid mobile equipment of the network. Valid List, Suspect List & Fraudulent list through the use of International Mobile Equipment Identity (IMEI). Forbid calls from unauthorised terminals (non-standard terminals)..

35. Call Process MSC receives a dialing command from a calling subscriber.
MSC analyses the called number, send a command to the HLR of the called subscriber.
HLR query the database, and get the route information from the VLR that the called subscriber is existing in, namely MSRN.
MSC build a connection with the MSC that the called subscriber is existing in according to the MSRN.

36. 1.MSISDN 2. MSISDN 3. IMSI 4. MSRN 5. MSRN 6. MSRN
Call Process
PSTN MS
PSTN
GMSC
MSC/VLR
HLR MS 1 6 4 3 2 5
1.MSISDN 2. MSISDN 3. IMSI 4. MSRN
5. MSRN MSRN

37. IMSI
VLR
HLR
MSRN
MSRN
MSRN
MSC-1
MSC-2
TMSI MS MS

38. 2 3 5 4 6 9 8 7 1 10 MS MS Call Process HLR/AUC MSC/VLR MSC/VLR MS1

39. Mobile Originating CallMS
BSS
MSC
PSTN
CHANNEL REQUEST 1
VLR
Dialing
IMMEDIATE ASSIGNMENT 2
CM SERVICE REQUEST 2
CM SERVICE REQUEST 2
Authentication procedure 3
Ciphering procedure 3
Sending
Number
SETUP (basic) or
EMERGENCY 4
SETUP 4 5
IAM 6
CALL PROCEEDING 7
Ring
CALL PROCEEDING 7
Ringing
Assignment procedure 7
ACM 8
ALERTING 9
1- The MS originates the call by sending a CHANNEL REQUEST message (on RACH).
2- Immediate assignment: channel allocation with TCH / FACCH or SDCCH.
3- The VLR launches authentication (if required) and completes ciphering.
4- The MS initiates call establishment by sending a SETUP message (called party number) to the MSC.
5- The MSC in turn checks mobile subscriber capabilities with VLR for desired service.
6- If it agrees, the MSC relays the called number over an ISUP Initial Address Message.
7- The MSC also sends a CALL PROCEEDING message to the MS (assigning TCH / FACCH EA in case of Early Assignment).
8- Recipient PSTN switch rings the land telephone and returns an ISUP Address Complete Message to the MSC.
9- Upon receiving this message, the MSC alerts the MS with an ALERTING message.
10- The Called party goes off hook, and the PSTN sends an ISUP ANswer Message to the MSC. The MSC then connects the MS (assigning a TCH in case of OACSU).
11- The call is accepted (CONNECT/CONNECT ACK) and the conversation starts.
In case of Emergency MO Call, the SETUP message (basic call) is replaced by the EMERGENCY one.
Ringing
ANM 10
Path
Established
CONNECT 11
ACM = Address Complete Message
ANM = ANswer Message
IAM = Initial Address Message
CONNECT ACKnowledge 11

40. Thank You
1-Dec-18
CET