2. 1. Network Subsystem includes the equipments
and functions related to end-to-end call.
2. Radio Subsystem includes the equipments and
functions related to the management of the
connections on the radio path.
3. Operations and Maintenance subsystem
includes the operation and maintenance of
GSM equipment for the radio and network
interface.
2

3. 3
B
T
S
MSC VLR
HLR
PSTN
ISDN
Data
Networks
(
Air interface
OSS
B
T
S
B
T
S
MSC VLR
BSCBSC

4.  GSM Service Area
 PLMN Service Area
 MSC Service Area
 Location Area
 Cells
4

5. 5
V
MSC
MSC
MSC
MSC
VLR
VLR
VLR
I II
IVII
I
I

6. 6
MSC
VLRLA1
LA2
LA3
LA6LA4 LA5

7. 7
MSC
VLRLA1
LA2
LA3
LA6LA4 LA5
C1 C2 C3
C6 C5
C4
C=CELL

8. 8
Location Area
Cell
Area served by a BTS
Location Area
MSC Service Area
PLMN Service Area
GSM Service Area

9. 9
MCC
LAI
LACMNC
3 digit 3 digit 2 Octets

10.  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
10

11.  Portable, vehicle mounted, hand held
 MS identified by unique IMEI
 Shall display at least last ten received,
dialed and missed calls
 Minimum talk time of 1hr 30 min. and
standby time of 80 hrs
 160 characters long SMS
11

12. 12
Power
Class
Max. Peak
Power
Tolerance (dB)
Normal Extreme
1 20W
(43 dBm)
+/- 2 +/- 2.5
2 8W
(39 dBm)
+/- 2 +/- 2.5
3 5W
(37 dBm)
+/- 2 +/- 2.5
4 2W
(33 dBm)
+/- 2 +/- 2.5
5 0.8W
(29 dBm)
+/- 2 +/- 2.5

13.  SIM Module
 Unique Subscriber’s ID IMSI and ISDN
 PIN
 Key Ki, Kc and A3,A5 and A8
algorithms
 SIM has CPU, ROM, RAM and EPROM
13

14.  IMEI
 MSISDN
 IMSI
 TMSI
 MSRN
14

15.  Mobile Subscriber’s ISDN Number
 The MSISDN is registered in the telephone
directory and used by the calling party for
dialing.
15
CC NDC SN
1 to 3 digits Variable Variable
MSISDN : not more than 15 digits
N(S)N

16.  International mobile subscriber’s Identity
 The IMSI is an unique identity which is
used internationally and used within
the network to identify the mobile
subscribers.
 The IMSI is stored on the subscriber
identity module (SIM), the HLR, VLR
and AC database.
16

17. 17
MCC MNC MSIN
3 digits 3 digits Not more than 9 digits
NMSI
IMSI : Not more than 15 digits

18.  Temporary Mobile subscriber’s
Identity
 The TMSI is an identity which guarantees
the integrity of the mobile subscribers on
the radio interface.
 The VLR assigns a TMSI to each mobile
subscribers entering the VLR area.
18

19. Mobile Station Roaming
Number
 The MSRN is used in the GMSC to set
up a connection to the visited
MSC/VLR.
19

20.  International Mobile Equipment Identity
 The IMEI is an unique code allocated
to each mobile equipment. It is
checked in the EIR.
 IMEI check
White List
Grey List
Black List
20

21. 21
RADIO SUB SYSTEM (RSS)
n BTS n BTS
BSC
BSC
BSC
MSC/VLR
RSS

22.  Encodes, encrypts, multiplexes,
modulates and feeds the RF signals to
the antenna
 Transcoding and rate adaption
Functionality
 Time and frequency synchronization
signals transmission.
 11 power classes from .01 watts
(Micro cell) to 320 watts (Umbrella
cell)
22

23.  Frequency hopping
 Random access detection
 Uplink radio channel measurements
 BTS mainly consists of a set of
transceivers (TRX). Can accommodate
1 to 7 TRX per Sector
23

24.  It is connected to BTS and offloads MSC
 Radio resource management
 Inter-cell handover
 Reallocation of frequencies
 Power control
24

25.  Time delay measurement of the received
signals from MS with respect to BTS
clock.
 Performs traffic concentration to reduce
the number of lines from BSC to MSC.
 Provide interface TCP/IP X.25 to the OMS
25

26.  BSC performs call processing
 TRAU are generally located at the site of MSC.
 BSC- BTS configurations as per requirement.
 Data from OMC and can be down loaded to
BSC
26

27. 27
BTS
BTS
BTS
BTS BTS
BTS
A-bis
BSC
BSS
Configuration -6
Multi - cell site
= multi--BTS
site
Many single
cell sites
BSS
MSC
BTS
A
A
A
Single - cell site
Configuration -1
Multi - cell site (sector Cells
Configuration -5
MCC: Mobile Switching Centre
BSS: Base Station System
BSC: Base Station Controller
BTS: Base Transceiver Station
A-bis

28. 28
MSC
(PSTN)
VLR
HLR AUC
EIR
D
C
SS7 Signalling
Traffic Path
F
(BSS)
A
E
Other
MSC

29.  Manages communication between GSM &
other network
 Call setup functions, basic switching are
done
 MSC takes into account the RR allocation in
addition to normal exchange functions
 MSC does gateway function while its
customers roams to other network by using
HLR /VLR
29

30.  Paging, specifically call handling
 Location updation
 Handover management
 Billing for all subscribers based in its area
 Reallocation of frequencies to BTSs in its
area to meet heavy demands
30

31.  Echo canceller operation control
 Signaling interface to databases like HLR, VLR.
 Gateway to SMS between SMS centers and
subscribers
 Handle interworking function while working as
GMSC
31

32.  It controls those mobiles roaming in its area.
 VLR reduces the number of queries to HLR
 One VLR may be incharge of one or more LA.
 VLR is updated by HLR on entry of MS its area.
 VLR assigns TMSI which keeps on changing.
 IMSI detach and attach operation
32

33.  IMSI & TMSI
 MSISDN
 MSRN.
 Location Area
 Supplementary service parameters
 MS category
 Authentication Key
33

34.  Reference store for subscriber’s parameters,
numbers, authentication & Encryption values.
 Current subscriber status and associated VLR.
 Both VLR and HLR can be implemented in the
same equipment in an MSC.
 one PLMN may contain one or several HLR.
34

35.  Permanent data in HLR
 Data stored is changed only by man-machine.
 IMSI, MS-ISDN number.
 Category of MS ( whether pay phone or not )
 Roaming restriction ( allowed or not ).
 Supplementary services like call forwarding
35

36.  Temporary data in HLR
 The data changes from call to call & is
dynamic
 MSRN
 RAND /SRES and Kc
 VLR address , MSC address.
 Messages waiting data used for SMS
36

37.  AUC is a separate entity and physically
included in HLR
 Protect against intruders in air interface
 Authentication (Ki) and ciphering (Kc) key are
stored in this data base.
 Keys change randomly with each call
 Keys are never transmitted to MS on air Only
calculated response are sent.
37

38.  AUC
38
Database
Generation
of Random
Number
RAND
RAND
IMSI1
IMSI3
IMSI2
ki1
ki2
ki3
RANDSRESKc
Algorithm for
Ciphering
A8
Algorithm
for
Authenticati
on
A3
Kc
64 bits
SRES
32 bits
HLR

39.  This data base stores IMEI for all registered
mobile equipments and is unique to every ME.
 Only one EIR per PLMN.
 White list : IMEI, assigned to valid ME.
 Black list : IMEI reported stolen
 Gray list : IMEI having problems like faulty
software, wrong make of equipment etc.
39

40. 40
The centralized operation of the various
units in the system and functions needed to
maintain the subsystems.
Dynamic monitoring and controlling of the
network
Separate OMC-S and OMC-R for NSS and
RSS
Operations and Maintenance
Centre OMC

41. 41
functions
-O&M data function
-Configuration management
--Fault report and alarm handling
-Performance supervision/management
-Storage of system software and data
-Support GUI for operation and
Maintenance
Functions Of OMC

42.  Four basic security services provided
by GSM
 Anonymity : TMSI Assignment
 Authentication
 Encryption:
 PIN
42

43. 43
Encryption
Process
KEY
Plain Text
Cipher-text

44. 44
A3 A3
Ki Ki
RAND
RAND
Compare
SRES
SRES
Response
IMSI
IMSI
Yes/No
Radio Path

45.  AUC
45
Database
Generation
of Random
Number
RAND
RAND
IMSI1
IMSI3
IMSI2
ki1
ki2
ki3
RANDSRESKc
Algorithm for
Ciphering
A8
Algorithm
for
Authenticati
on
A3
Kc
64 bits
SRES
32 bits
HLR

46. 46
ARC
HLR
SRES=
SRESc
A3
Sim
Card
Key Pad
A8
Store
Kc
Access
Granted
RAND
Yes
MSC/VLR
RAND Ki
SRESc
(128)
SRES
(32)
Kc
Cipher
Key Transfer Kc to
BTS
no

47. 47