This document provides an overview of the fundamental concepts of GSM networks. It discusses the network architecture including entities like the BTS, BSC, MSC, HLR, VLR and AUC/EIR. It describes the air interface including TDMA frame structure and physical channels. It also covers topics like frequency allocation, channel types, and channel assignment within cells. The document serves as an introduction to GSM network concepts, components, and operations.

1. GSM Fundamental
By
Uke Kurniawan Usman
1 Uke Kurniawan Usman - 2005

2. Agenda
 Network Architecture
 Functional Layer of GSM
 Air Interface
 System Capacity
 Anti Interference Technology
 Network Planning
 Numbering arrangement
2 Uke Kurniawan Usman - 2005

3. GSM Network Structure
OMC
MSC/VLR
BSC
E
BIE
Abi A PSTN
BTS s MSC/VLR ISDN
BSS PSPDN
C
Um F H
HLR/
AUC EIR SC/VM
MS
MSS
3 Uke Kurniawan Usman - 2005

4. Mobile Station
( MS )
Equipment used by mobile service subscribers for
access to services.
Mobile Equipment
Subscriber Identity Module (SIM)
Mobile stations are not fixed to one subscriber.
A subscriber is identified with the SIM card.
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5. GSM Network Entity
Base Transceiver Station
( BTS )
Base Transceiver Station (BTS)
Wireless transmission
Wireless diversity
Wireless channel encryption
Conversion between wired and wireless signals
Frequency Hopping
BaseBand Unit:
voice and data speed adapting and channel coding
RF Unit:
modulating/demodulating, transmitter and receiver
Common Control Unit:
BTS operation and maintenance
5 Uke Kurniawan Usman - 2005

6. GSM Network Entity
Base Station Controller
( BSC )
Managing Wireless network-BSS
Monitoring BTS
Controls:
Wireless link distribution between MS and BTS
Communication connection and disconnection
MS location, handover and paging
Voice encoding, transecoding (TC), rate, adaptation,
The operation and maintenance functions of BSS.
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7. GSM Network Entity
Mobile Service Switching Center
( MSC )
holds all the switching functions
manages the necessary radio resources,
updating the location registration
carrying out the inter-BSC and inter-MSC tender
Inter-working with other networks (IWF).
7 Uke Kurniawan Usman - 2005

8. GSM Network Entity
Home Location Register
( HLR )
Manages the mobile subscribers database
 subscriber information
 part of the mobile location information
 3 identities essential
the International Mobile subscriber Identity
the Mobile station ISDN Number
the VLR address
8 Uke Kurniawan Usman - 2005

9. GSM Network Entity
Visitor Location Register
( VLR )
dynamically stores subscriber information needed to handle
incoming/outgoing calls
Mobile Station Roaming Number
When a roaming mobile enters an MSC area. This MSC
warns the associated VLR of this situation; the mobile
enters a registration procedure through which it is
assigned a mobile subscriber roaming number (MSRN)
Temporary Mobile Subscriber Identity, if applicable
The location area in which the mobile has been
registered
Data related to supplementary service parameters
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10. GSM Network Entity
AUC/EIR
Authentication Center(s) (AUC)
Providing the authentication key used for
authorizing the subscriber access to the
associated GSM PLMN.
Equipment Identity Register(s) (EIR)
Handling Mobile Station Equipment Identity
10 Uke Kurniawan Usman - 2005

11. Agenda
 Network Architecture
 Functional Layer of GSM
 Air Interface
 System Capacity
 Anti Interference Technology
 Network Planning
 Numbering arrangement
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12. Overview: Function Layers of GSM-1
S ervice carrie r
O AM Subsc riber
CM
MM
RR
Tran smissi on
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13. Protocol Stack Structure of GSM
MS BTS BSC M SC
CM CM
MM MM
RR BS SAP BS SAP
RR RR
BTSM BTSM SCCP SCCP
MT P3 MTP3
L APDm LAP Dm LAPD LAPD
MT P2 MTP2
Um Abis A
13 Uke Kurniawan Usman - 2005

14. Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement
14 Uke Kurniawan Usman - 2005

15. TDMA
time
Concept:
User 3 channel is composed of a
series of timeslots of
User 2
periodicity. Different signal
User 1 energies are distributed into
different timeslots. The
Frequency
adjacent channel interference
is restricted by connection
GSM adopts TDMA/FDMA mode choosing from time to time. So
channel width: 200KHz the useful signal is passed
each channel has 8 timeslots only in the specified timeslot.
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16. GSM Timeslot and Frame structure
Frequency
200KHz
BP time
15/26ms
interval
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17. Frequency Resource
GSM900 : EGSM900 :
up: 890~915MHz up: 880~890MHz
down: 935~960MHz down: 925~935MHz
duplex interval: 45MHz duplex interval: 45MHz
bandwidth: 25MHz ， bandwidth: 10MHz ，
frequency interval: 200KHz
frequency interval: 200KHz
GSM1800 : GSM1900MHz:
up: 1710-1785MHz up:1850~1910MHz
down: 1805-1880MHz down:1930~1990MHz
duplex interval: 95MHz ， duplex interval: 80MHz ，
working bandwidth: 75MHz ， working bandwidth:
frequency interval: 200KHz 60MHz ，
17 frequency interval: Usman - 2005
Uke Kurniawan 200KHz

18. Frequency Resource
Single Band Network General Priority
Which one?
900MHz High
1800MHz
1900MHz Low
New Operator
Reason
Propagation
Characteristic
For Operator For Subscriber
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19. Frequency Resource
Single Band Network
Single Band 900MHz
Dual Band 1800MHz
Triple Band 1900MHz
In a sense, the network determines the handsets
can be selected.
But nowadays, most handsets support dual
19 band. Uke Kurniawan Usman - 2005

20. Frequency Resource
Single Band Network
Cell coverage radius :
We know
Propagation characteristic
The higher the propagation
frequency 900MHz
1800MHz
The higher the propagation loss
1900MHz
The smaller the cell coverage radius.
20 Uke Kurniawan Usman - 2005

21. Timeslot and Frame structure
1 super high frame = 2048 super frame = 2715648 TDMA frame
0 1 2 3 2044 2045 2046 2047
BCCH
1 super frame = 1326 TDMA frame （ 6.12s ） CCCH
SACCH/TCH SDCH
FACCH 0 1 2 3 47 48 49 50
0 1 24 25
1 multiplex frame = 26 TDMA frames （ 120ms ） 1 multiplex frame = 51 TDMA frame
0 1 24 25 0 1 49 50
1 TDMA frame = 8 timeslot （ 120/26 = 4.615ms ）
0 1 2 3 4 5 6 7
21 Uke Kurniawan Usman - 2005

22. Physical Channel
0 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.
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23. Channel Type-Summary
14.4Kbit/s FR TCH (TCH/F14.4)
9.6Kbit/s FR TCH(TCH/F9.6)
Data CH 4.8Kbit/s FR TCH (TCH/F4.8)
TCH 4.8Kbit/s HR TCH (TCH/H4.8)
FR Voice Traffic Channel (TCH/FS)
Voice CH Enhanced FR Traffic Channel (TCH/EFR)
HR Traffic Channel (TCH/HS)
channel FCCH (down)
SCH (down)
BCH BCCH (down)
RACH (up)
CCH CCCH AGCH (down)
PCH (down)
SDCCH
DCCH FACCH
SACCH
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24. Channel Type
Traffic Channel
Transmit voice and data
Signaling Channel
transmit the signaling and synchronous data between BTS and
MS.
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25. Channel Type
BCH :
Frequency Correction CHannel （ FCCH ）
-- for MS error correction
Synchronous Channel （ SCH)
-- for MS frame synchronization and BTS recognization
Broadcasting Control CHannel （ BCCH ）
-- broadcasting information(cell selection information, etc..)
25 Uke Kurniawan Usman - 2005

26. Channel Type
DCCH
Self-help Dedicated Control Channel （ SDCCH ）
for channel distribution information transmission
Slow Associated Control Channel （ SACCH ）
combined with one traffic channel or SDCCH, to transmit some
specific information of user information
Fast Associated Control Channel （ FACCH ）
combined with one traffic channel, taking the same signal as
SDCCH. It occupies the service channel to transmit signaling
information.
26 Uke Kurniawan Usman - 2005

27. Structure of 51-frame Control CH
51 Frame
BCCH+CCCH
F S B C F S C C F S C C F S C C F S C C I
(Downlink)
BCCH+CCCH
RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR
(uplink)
(a) FCCH+SCH+BCCH+CCCH
8 SDCCH/8
D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A3 I I I
(Downlink)
D0 D1 D2 D3 D4 D5 D6 D7 A4 A5 A6 A7 I I I
8 SDCCH/8
A1 A2 A3 I I I D0 D1 D2 D3 D4 D5 D6 D7 A0
(uplink)
A5 A6 A7 I I I D0 D1 D2 D3 D4 D5 D6 D7 A4
(b) SDCCH/8(0,...,7)+SACCH/C8(0,...,7)
BCCH+CCCH+
F S B C F S C C F S D0 D1 F S D2 D3 F S A0 A1 I
4SDCCH/4
(Downlink) F S B C F S C C F S D0 D1 F S D2 D3 F S A2 A3 I
BCCH+CCCH+
D3 RR A2 A3 RRRRRRRRRRRRRRRRRRRRRRR D0 D1 F S D2
4SDCCH/4
(uplink) D3 RR A0 A1 RRRRRRRRRRRRRRRRRRRRRRR D0 D1 F S D2
(c) FCCH+SCH+CCCH+SDCCH/4(0,...,3)+SACCH/C4(0,...,3)
F：FCCH S：SCH
B：BCCH C：CCCH(CCCH=PCH+AGCH+RACH)
R：RACH D：SDCCH
27 A：SACCH/C I： idle Uke Kurniawan Usman - 2005

28. Channel Combination Type
Several logic channels combine together in some way to form
some specific types of channel to transmit user data or signaling
information. They are called combined channels. One combined
channel can be mapped to a physical channel.
There are the following combined channels:
a TCH/F + FACCH/F + SACCH/TF
b TCH/H(0,1) + FACCH/H(0,1) + SACCH/TH(0,1)
c TCH/H(0,0) + FACCH/H(0,1) + SACCH/TH(0,1) + TCH/H(1,1)
d FCCH + SCH + BCCH + CCCH
e FCCH + SCH + BCCH + CCCH + SDCCH/4(0...3) + SACCH/C4(0...3)
f BCCH + CCCH
g SDCCH/8(0 ..7) + SACCH/C8(0 .. 7)
CCCH = PCH + RACH + AGCH
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29. Channel Assignment inside cells
 Small capacity cell with only 1 TRX
TN0: FCCH+SCH+CCCH+BCCH+SDCCH/4(0,_,3)+SACCH/C4(0,_,3);
TN1-7: TCH/F+FACCH/F+SACCH/TF
 The medium-size cell with 4 TRXs
1TN0 group: FCCH+SCH+BCCH+CCCH;
2 SDCCH/8(0,_,7)+SACCH/C8(0,_,7);
29 TCH/F+FACCH/F+SACCH/TF
29 Uke Kurniawan Usman - 2005

30. Channel Assignment inside cells
 Large-size cell with 12 TRXs
1 TN0 group: FCCH+SCH+BCCH+CCCH;
1 TN2 group, 1 TN4 group and 1 TN6 group: BCCH+CCCH;
5 SDCCH/8(0,_,7)+SACCH/C8(0,_,7);
87 TCH/F+FACCH/F+SACCH/TF
30 Uke Kurniawan Usman - 2005

31. Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement
31 Uke Kurniawan Usman - 2005

32. Cell Mode Layout
Omni-directional cell
O
Adopt omni-directional antenna ，
the overall directional propagation
characteristic is the same.
Directional cell
In general, cell with multi-sector is in
common use. Every directional cell
adopts directional antenna.
32 Uke Kurniawan Usman - 2005

33. BTS Mode
 Capacity
When the traffic is very low, and no possibility for quick
increment, Omni-directional cell is used in common.
Otherwise, we suggest to adopt the sector cell.
Note: TRX-transceiver,each TRX handles 1 frequency.
 Coverage Area
Sector cell is often used to enlarge the cell coverage
radius because of the higher antenna gain.
For special coverage ,such as road coverage, two-sector
cell is adopted firstly.
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34. System capacity
Erlang :
the traffic intensity of a totally occupied channel (i.e.
the call hour of a unit hour or the call minute of a unit
minute). For example, the traffic of a channel occupied
for 30 minutes in an hour is 0.5 Erlang)
GOS:
defined as the probability of call blocking or the
probability when the call delay time is longer than a
given queuing time.
34 Uke Kurniawan Usman - 2005

35. Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement
35 Uke Kurniawan Usman - 2005

36. Reasons for Interference
The transmission path is very complex, ranging
from the simple line-of-sight transmission to
encountering such terrain as buildings, hills and
trees. Wireless channels are extremely
unpredictable.
Abrupt drop, or fading, of signal strength in the
land mobile wireless channel is quite common. The
fading feature of the mobile channel depends on the
radio wave propagation environment.
36 Uke Kurniawan Usman - 2005

37. Reasons for interference
Environmental factors:
• Terrain (mountains, hills, plains, water bodies, etc.);
• The quantity, heights, distribution and materials of
buildings;
• The vegetation of the region;
• Weather conditions;
• Natural and artificial electromagnetic noises;
• Frequency;
• How MS is moved.
37 Uke Kurniawan Usman - 2005

38. Interference
Co-Channel Interference
Conception:
the interference among the signals of co-
channel cells is called co-channel interference.
Result from :
Frequency reuse
Reduction method:
co-channel cells must physically be
spaced at a minimum interval to ensure
38 adequate isolation of transmissions. Usman - 2005
Uke Kurniawan

39. Interference
 Adjacent Channel Interference
Conception:
The signal interference from the frequency
adjacent to that of the signal used is called
adjacent channel interference.
Reduction method:
accurate filtering and channel allocation
(maximizing channel intervals of the
cell). Interval of frequency reuse inter-cell
interference, such as C/I, C/A
39 Uke Kurniawan Usman - 2005

40. Solution -Anti-interference
 FH technology
 Dynamic power control (DPC)
 Discontinuous Transceiving
(DTX)
 Diversity receiving technique
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41. Frequency Hopping Technique
Reason:
 counteract Rayleigh Fading
 scatter interference among multiple calls
Types:
 Base band frequency hopping
keeps the transmission and receiving frequency of each
carrier unit unchanged, but merely sends FU transmission
data to different carrier units at different FN moments.
 radio frequency hopping
controls the frequency synthesizer of each transceiver,
making it hop according to different schemes in different time
41 slots. Uke Kurniawan Usman - 2005

42. Discontinuous Speech Transmission (DTX)
Two aims can be achieved by adopting DTX mode:
•lower the total interference electric level in the air
•save transmitter power.
TRAU BTS
BTS MS
480 ms
comfort noise frame
Speech frame
42 Uke Kurniawan Usman - 2005

43. Diversity Reception Technology
The multi-path propagation of radio signals causes
magnitude fading and delay time.
 Space Diversity (antenna diversity)
 Polarization Diversity
orthogonal polarization diversity.
horizontal polarization and vertical polarization.
 Frequency Diversity
The working principle of this technology is that
such fading won’t take place on the frequency
outside the coherence bandwidth of the channel.
43 Uke Kurniawan Usman - 2005

44. Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement
44 Uke Kurniawan Usman - 2005

45. Frequency Reuse
D3 A1 C2 C3 B1 D2
C1 A2 A3 D1 B2 B3 C1
C3 B1 D2 D3 A1 C2 C3
A1 B2 B3 C1 A2 A3 D1
D2 A1 C2 C3 B1 D2
A1 D3
“4 × 3” reuse mode:
one group includes 3 sectors /site ,12 frequency which
are distributed to 4 sites. Every site owns 3 frequency.
45 Uke Kurniawan Usman - 2005

46. Frequency Reuse
B3 A1 B2 B3 A1 B2
C1 A2 A3 C1 A2 A3 C1
C3 B1 C2 C3 B1 C2 C3
A1 B2 B3 A1 B2 B3 A1
A3 C1 A2 A3 C1 A2
A1 A3
“3 × 3” reuse mode:
one group includes 3 sectors /site ,9 frequency which are
distributed to 3 sites. Every site owns 3 frequency.
46 Uke Kurniawan Usman - 2005

47. Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement
47 Uke Kurniawan Usman - 2005

48. Numbering Arrangement
International Mobile Subscriber Identification number
(IMSI)
It identifies a unique international universal number of a
mobile subscriber, which consists of MCC+MNC+MSIN.
1) MCC: country code, 460
2 ） MNC: network code, 00 or 01
3 ） MSIN: subscriber identification, H1H2H3H4
9XXXXXX,
H1H2H3H4: subscriber registering place
H1H2: assigned by the P&T Administrative Bureau
(operator )to different provinces, to each province
H3H4: assigned by each province/city
the IMSI of user will be written into the SIM card by
48 specific device and software and be stored into the HLR - 2005
Uke Kurniawan Usman

49. Numbering Arrangement
Mobile Subscriber ISDN Number （ MSISDN ）
It is the subscriber number commonly
used. China uses the TDMA independent
numbering plan:
CC+NDC+ H1H2H3H4 +ABC
CC: country code, 86
NDC: network code, 135—139, 130
H1H2H3H4: HLR identification code
ABCD: mobile subscriber number
49 inside each HLR Uke Kurniawan Usman - 2005

50. Numbering Arrangement
International Mobile Equipment Identification code
(IMEI)
It will uniquely identify a mobile station. It is a
decimal number of 15 digits. Its structure is:
TAC+FAC+SNR+SP
TAC=model ratification code, 6 digits
FAC=factory assembling code, 2 digits
SNR=sequence code, 6 digits
SP=reserved, 1 digit
50 Uke Kurniawan Usman - 2005

51. Numbering Arrangement
Mobile Subscriber Roaming Number
(MSRN)
The MSRN is temporarily distributed to the
subscriber by the VLR according to the request
by the HLR when this subscriber is called. The
MSRN is released and can be assigned to other
subscriber later.
CC + NDC + 00 + M1M2M3 + ABC
CC: country code, 86
NDC: mobile network code, 135—139,
130
M1M2: same as the H2H3 of MSISDN
ABC: 000 -- 999
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52. Numbering Arrangement
Temporarily Mobile Subscriber Identification Number
(TMSI)
To insure the IMSI security, the VLR will
assign an unique TMSI number for the
accessed subscriber. It is used locally only
and is a 4-byte TMSI number BCD code.
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