Gsm fundamental-uku

Uke Kurniawan Usman - 20051
GSM Fundamental
By
Uke Kurniawan Usman

Agenda
 Network Architecture
 Functional Layer of GSM
 Air Interface
 System Capacity
 Anti Interference Technology
 Network Planning
 Numbering arrangement

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

Equipment used by mobile service subscribers for
access to services.
Mobile Station
( MS )
Mobile Equipment
Subscriber Identity Module (SIM)
Mobile stations are not fixed to one subscriber.
A subscriber is identified with the SIM card.

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
GSM Network Entity
Base Transceiver Station
( BTS )

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.
Base Station Controller
( BSC )
GSM Network Entity

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).
GSM Network Entity
Mobile Service Switching Center
( MSC )

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
GSM Network Entity
Home Location Register
( HLR )

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
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
GSM Network Entity

Agenda
 Network Architecture
 Functional Layer of GSM
 Air Interface
 System Capacity
 Anti Interference Technology
 Network Planning
 Numbering arrangement

OAM
S ervice carrier
CM
MM
RR
Subscriber
Tran smission
Overview: Function Layers of GSM-1

CM
MM
RR
LAPDm
MS
RR
LAP Dm
Um
LAPD
BTSM
LAPD
Abis
RR
BTSM SCCP
MTP3
BS SAP
BTS BSC
MTP2
SCCP
MTP3
BS SAP
MTP2
CM
MM
MSC
A
Protocol Stack Structure of GSM

Agenda
Network Architecture
Functional Layer of GSM
Air Interface
System Capacity
Anti Interference Technology
Network Planning
Numbering arrangement

Concept:
channel is composed of a
series of timeslots of
periodicity. Different signal
energies are distributed into
different timeslots. The
adjacent channel interference
is restricted by connection
choosing from time to time. So
the useful signal is passed
only in the specified timeslot.
GSM adopts TDMA/FDMA mode
channel width: 200KHz
each channel has 8 timeslots
GSM adopts TDMA/FDMA mode
channel width: 200KHz
each channel has 8 timeslots
User 1
User 2
User 3
Frequency
time
TDMA

GSM Timeslot and Frame structure
time
Frequency
BP
15/26ms
200KHz
interval

Frequency Resource
GSM900 :
up: 890~915MHz
down: 935~960MHz
duplex interval: 45MHz
bandwidth: 25MHz ，
frequency interval: 200KHz
GSM1800 :
up: 1710-1785MHz
down: 1805-1880MHz
duplex interval: 95MHz ，
working bandwidth: 75MHz ，
EGSM900 :
up: 880~890MHz
down: 925~935MHz
duplex interval: 45MHz
bandwidth: 10MHz ，
GSM1900MHz:
up:1850~1910MHz
down:1930~1990MHz
duplex interval: 80MHz ，
working bandwidth:
60MHz ，

1800MHz
1900MHz
900MHzWhich one?
Single Band Network General Priority
High
Low
Reason
For SubscriberFor Operator
Propagation
Characteristic
New Operator
Frequency Resource

1800MHz
1900MHz
900MHz
Single Band Network
Single Band
Dual Band
Triple Band
In a sense, the network determines the handsets
can be selected.
But nowadays, most handsets support dual
band.
Frequency Resource

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

0 2045 2046 2047321 2044
3210 4947 48 50
0 24 251
1 super high frame = 2048 super frame = 2715648 TDMA frame
1 super frame = 1326 TDMA frame （ 6.12s ）
0 1 2524 504910
1 multiplex frame = 26 TDMA frames （ 120ms ） 1 multiplex frame = 51 TDMA frame
0 1 765432
1 TDMA frame = 8 timeslot （ 120/26 = 4.615ms ）
BCCH
CCCH
SDCHSACCH/TCH
FACCH
Timeslot and Frame structure

0 1 765432
8 9 151413121110
16 17 232221201918
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.
Physical Channel

channel
TCH
CCH
Voice CH
Data CH
FR Voice Traffic Channel (TCH/FS)
HR Traffic Channel (TCH/HS)
4.8Kbit/s HR TCH (TCH/H4.8)
9.6Kbit/s FR TCH(TCH/F9.6)
4.8Kbit/s FR TCH (TCH/F4.8)
BCH
FCCH (down)
SCH (down)
BCCH (down)
CCCH
RACH (up)
AGCH (down)
PCH (down)
DCCH
SDCCH
FACCH
SACCH
14.4Kbit/s FR TCH (TCH/F14.4)
Enhanced FR Traffic Channel (TCH/EFR)
Channel Type-Summary

Channel Type
Traffic Channel
Transmit voice and data
Signaling Channel
transmit the signaling and synchronous data between BTS and
MS.

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..)

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.

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

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

 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
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
Channel Assignment inside cells

Agenda
Air Interface
System Capacity
Network Planning

Cell Mode Layout
O
Omni-directional cell
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.

 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.
BTS Mode

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.
System capacity

Agenda
Air Interface
System Capacity
Network Planning

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.

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.

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
adequate isolation of transmissions.
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
Interference

 FH technology
 Dynamic power control (DPC)
 Discontinuous Transceiving
(DTX)
 Diversity receiving technique
Solution -Anti-interference

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
slots.
Frequency Hopping Technique

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

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.
Diversity Reception Technology

Agenda
Air Interface
System Capacity
Network Planning

“4 × 3” reuse mode:
one group includes 3 sectors /site ,12 frequency which
are distributed to 4 sites. Every site owns 3 frequency.
Frequency Reuse
A3
D2B1
C3
B2D1
D3
A2C1
B3
C2A1
B3
C2A1
A3
A1B1
D1
D3D2
C3
B2A1
C3D2
C3
C1
D2B1C2A1
A2C1
D3

A3
C2B1
B3
A2C1
C3
B2A1
A3
C2B1
B3
A2C1
B3
A1C1
A1
A3A2
C3
B2A1
A3A3
C3
C1
B2A1B2A1
A2C1
B3
Frequency Reuse
“3 × 3” reuse mode:
one group includes 3 sectors /site ,9 frequency which are
distributed to 3 sites. Every site owns 3 frequency.

Agenda
Air Interface
System Capacity
Network Planning

Numbering Arrangement
International Mobile Subscriber Identification number
(IMSI)
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
specific device and software and be stored into the HLR

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
inside each HLR
Mobile Subscriber ISDN Number （ MSISDN ）Mobile Subscriber ISDN Number （ MSISDN ）

International Mobile Equipment Identification code
(IMEI)
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

Mobile Subscriber Roaming Number
(MSRN)
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

Temporarily Mobile Subscriber Identification Number
(TMSI)
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.

Gsm fundamental-uku

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