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System Model:
AUC
HLR EIR
SS
BSS
MSC
BTS
MS
NMC and OMC
Switching System
Signaling transmissionCall connections and
signaling transmission
Base Station System
Othernetworks
BSC
GMSC
VLR
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Network elements in GSM:
MS
PLMN
PSTN
ISDN
AUC
EIRHLR
VLR
MSC
BSC
BTS
GMSC
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SA2
MSC
VLR
MSCMSC
VLR
BSC
BSC BSC
BSC
LA1LA2
GMSC
MSC
BTS
SA1
HLR
AUC
EIR
SA - Service AreaLA - Location AreaBTS - Base Transceiver StationBSC - Base Station Controller
MSC - Mobile Switching CenterVLR - Visitor Location RegisterGMSC - Gateway MSCEIR - Equipment Identity RegisterAUC - Authentication Center
HLR - Home Location Register
Mobile identity
SIM card
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Base Station System:
Base Station System
BSC
BTS
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BSS in Ericssons GSM Systems:
MSC TRC BSC
BSSSS
RBS
BSC/TRC RBS
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Transmission Rates in BSS:
MSC/VLR
TRC
BSC
RBS
BSC/TRC
RBS
RBS
RBSRBS
RBS RBS
RBS
BSC
RBS
RBSRBS
RBS
MSC/VLR
BSC
RBSRBS
64 kbits/s
per call
16 Kb/s
full-rate33.8 Kb/s per full-rate call
16 Kb/s
full-rate
16 Kb/s
full-rate
16 Kb/sfull-rate
64 kbits/sper call
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Switching System:
SS
MSC/VLR
EIR
ILR
GMSC
DTI
AUC
HLR
SMS-GMSCSMS-IWMSC
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VLR-HLR Interaction:
HLR
UpdateDe
lete
MSC/VLR MSC/VLR
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Mobile Station:
ME
MobileEquipment
SIM
SubscriberIdentityModule
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GSM interfaces:
MS BTS BSC MSC HLR
VLR
MSC
EIR
VLR
Um Abis A
B
C
E
F
D
G
AUC
H
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A Cell:
Cell
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Macro, Mini, Micro and Indoor Cells:
Antenna positions
Macro
Mini
MicroPico
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MSC Service Area:
cell 6
cell 1 cell 5
cell 4 cell 2 cell 3
MSC
LA1LA3
LA5
LA4
VLR
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Relation Between Areas in GSM:
GSM Service Area
PLMN Service Area(one per operator)
MSC Service Area
Location Area
Cell
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"Hardware" view of a Sample Network:
HLR
EIR
AUC
GMSC
ILR
MSC/VLR 1PSTN
MSC Service Area 2MSC Service Area 1
LEGEND
MSC BoundaryBSC BoundaryPCM LinksBase Station
MSC/VLR 2
BSC 1B
BSC 1C
BSC 2B
BSC 1A
BSC 2A
BSC 2C
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"Software" view of a Sample Network:
LA 1-B
LA 1-A
LA 2-D
LA 2-ACell 2-A-25
LA 2-B
HLR
EIR
AUC
GMSC
ILR
MSC/VLR 1PSTN
MSC Service Area 2
MSC Service Area 1
LEGEND
MSC BoundaryBSC BoundaryPCM LinksBase Station
MSC/VLR 2
LA 2-C
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Authentication Procedure:
MSC/VLR
1. RAND
3. SRES
MS2. MS calculates SRES using RAND + Ki
(SIM-card) throug A3 and Kc using RAND+Kithrough A8.
4. Compare SRES received from
MS with SRES in triplet. If theyare equal access is granted.
MSC/VLR Mobile service Switching CenterMS Mobile Station
RAND Random numberSRES Signed Response
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Authentication in GSM:
VLR
MSC
HLRAUC
Subscriber number (IMSI)Code key (Ki)
Random number (RAND)
Signal response (SRES)
RAND / SRES
RAND
SRES
Figure D.6.4
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Equipment Identification:
MSC/VLR
MS
EIR3. Check IMEI
4. Access/barring info
1. IMEI request
2. IMEI
IMEI International Mobile station Equipment IdentityEIR Equipment Identity RegisterMSC/VLR Mobile services Switching Center
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OSS CNA
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OSS Provides Central Supervision of all Network:
OMC OMC
HLR
AUC/EIR
TRC
MSC
BSC
BTS
Operation and
Support System
NMC
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SOG and BGW:
Gateway productsfor billing informationand service
GSM Modes:
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GSM Modes:
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Operation Overview:
Attached (On)
Detached (Off)
Idle
Busy
Roaming
Paging
Handover
Mr. Bond!!
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Roaming:
MSC/VLR
MSC/VLR
LA 1
LA 2
Th RBS Li t i f Ch l R t d
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The RBS Listening for Channel Requests andMeasuring the Uplink on an Established Connection:
Signal strength!
Quality!Timing!
Access
burst!MS
MS
MS MS
RBS
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Monitoring BCCH Carriers:
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GSM Frequency Bands:
0.8GHz 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0
GSM 900 GSM 1800 GSM 1900
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Frequency bands for the different GSM-based
networks (Values within brackets refer to E-GSM):
Network type
GSM 900 (880)890-915/(925)935-960 MHz GSM 900
GSM 1800 1710 - 1785/1805 -1880 MHz GSM 1800
GSM 1900 1850 - 1910/1930 -1990 MHz GSM 1900
EricssonsImplementations
Frequency bandUL/DL
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Uplink and Downlink on a Radio Channel:
Uplink
Downlink
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System Parameters:
up link down link
f
Carrier spacing Bandwidth spacing
Duplex spacing
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Duplex Distance:
890 960915 935MHz
Uplink Downlink
Duplex Distance (45 MHz)
Bandwidth (2 x 25 MHz)
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Duplex distances for different frequency bands:
Standard GSM 900 GSM 1800 GSM 1900
Duplex dist. 45 MHz 95 MHz 80 MHz
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Carrier Separation:
Carrier Separation (200 KHz)
895.4 895.6MHz
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Neighboring Cells Cannot Have the Same
Frequency (Simplified):
B
G
A
C
G
AD
F
F
E
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TDMA:
0
Frequency 1
1 2 3 4 5 6 7
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Basic TDMA frame, timeslot, and burst structures
0 1 2 3 4 5 6 7
4.615 ms
3 57 1 26 1 57 3
Burst
148 Bits
156.25 Bits0.577 ms
DataTrainingData
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Analog Signal:
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Digital Signal:
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A/D Conversion:
Analog
A/D Conversion
Digital
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Analog Signal Sampling:
t
Analogue signal
t
Sampling
Ts
t
Sampled signal
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Regeneration of Digital Signal:
Transmitted Received Regenerated
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Quantization:
q7
q6
q5
q4
q3
q2
q1
q0
Ts 2Ts 3Ts 4Ts 5Ts 6Ts 7Ts 8Tstime
}
Sampledvalue
Quantizedvalue
D = Quantized error
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Parameters that are important for GSM:
Path loss
Shadowing
Rayleigh fading
Signal strength
Time dispersion
Time Alignment
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Problems Solution Fading:
Distance Eventually leading to handover
Shadowing Make a better coverage of the cell or smaller cells
Rayleigh Antenna diversity- two antennas on the BS, 5-6 m apart
Repeated change of frequencies after each frame
Sh d i
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Shadowing:
R Si l St th
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Rx Signal Strength:
Fadingmargin
SS (dB)
Distance (meters)
Global mean value
Fading dip (Rayleigh)
Receiver sensitivity
R Sig l St gth V Di t
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Rx Signal Strength Versus Distance:
log (distance)
Signallevel(
dB)
Path loss ( )
Rayleigh fading (-)
Log normalfading ( )
Rayleigh Fading:
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Rayleigh Fading:
Reuse distance and carrier-to-interference ratio:
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S (dB)
S(A,f1) S(B,f1)
Reuse distance for f1 Distance from A
>18 dB in analog systems>7 dB in digital systems
C
I
I C
A B
Figure D.5.4
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Co-channel interference:
f1
f1
B
A
Acceptable
Speech quality
Figure D.5.3
Time Dispersion:
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Time Dispersion:
1
1
1.
0
0
2.
1
1
3.
1
0
The Time Alignment Problem:
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The Time Alignment Problem:
A. Close to BTSBTS
TDMA-frameB. Far away
from BTSA.
B.
TS0 TS1 TS2
Intermodulation in a 900 MHz cellular system:
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Intermodulation in a 900 MHz cellular system:
890 900 910 920 930 940 950 960 MHz
RX band
Duplex distance (D)
TX band
Allocated RX band (B)(10 MHz inthis example)
Allocated TX band (B)(10 MHz in this example)
IM7 IM5 IM3
Intermodulation (IM) in cellular systems:
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( ) y
System
GSM900
DCS1800
PCS1900
NMT450
Duplexdistance,D, (MHz)
45
95
80
10
IM3
22.5
47.5
40.0
5.0
IM5
15.0
31.7
26.7
3.3
IM7
11.3
23.8
20.0
2.5
IM9
9.0
19.0
16.0
2.0
Maximum band, B, (MHz) to avoid IM order:
Definitions:IM3, IM5, etc.=Intermodulation products of 3rd, 5th, etc.,D = Duplex distance (MHz)B = Allocated band (MHz)Worst case = IM from the lowest and
the highest frequencies in the allocated band
Worst-case relationsIM3 in Rx band if D/B < 2IM5 in Rx band if D/B < 3IM
7
in Rx band if D/B < 4IM9 in Rx band if D/B < 5
Co-Channel Interference:
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CarrierInterference
Distance
f1 f
1dB
C I
Adjacent Channel Interference:
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AC
CarrierAdjacent
Distance
f1 f2
dB f2
= f1
+ 200 kHz
-9 dB3 dB
Locating the BTS close to the reflecting object to
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Locating the BTS close to the reflecting object to
combat ISI:
D2
D0
D1
Pointing the antenna away from the reflecting object
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Pointing the antenna away from the reflecting object
to combat ISI:
Mountain Site with antenna
pointing away
Channel Coding:
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g
Blockcoder
50 Very important bits
132 Important bits
78 Not so important bits
1:2Convolutional
Coder
456
4 Tail bits
53 bits 378 bits
Space Diversity:
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p y
TxRx (B)Rx (A)
AntennaDiversity
DiversitySystemOutput
ReceiverSensivity
Level
ReceivedSignalLevel
A, B combined
Receiver A
Receiver B
No Diversity
Tx Rx
Interleaving:
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g
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4
message blocks
interleaving
interleavedmessage blocks
Received Interleaved Message Blocks:
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g
1 X 3 4 1 X 3 4 1 X 3 4 1 X 3 4
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Timing Advance:
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0 1 2 3 4 5 6 7
Time
0 1 2 3 4 5 6 7
Synchronization time
StartSending
Segmentation and Speech Coding:
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01100011000111110011100
Speech Code
20 ms
Speech Signal
Interleaving of 20 ms of Encoded Speech:
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191725I
IIIIII
IIIII
449
210III
IIIIII
IIIII
450
311III
IIIIII
IIIII
451
412III
IIIIII
IIIII
452
513III
IIIIII
IIIII
453
614III
IIIIII
IIIII
454
715III
IIIIII
IIIII
455
816III
IIIIII
IIIII
456
8 blocks
57 bits
Speech Frame:
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20 ms speech
456 bits = 8x57
A
20 ms speech
456 bits = 8x57
B
20 ms speech
456 bits = 8x57
C
20 ms speech
456 bits = 8x57
D
Second Level of Interleaving:
A/8
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A/8
A/8
A/8
A/8
B/8 A/8
B/8 A/8
B/8 A/8
B/8 A/8
C/8 B/8
C/8 B/8
C/8 B/8
C/8 B/8
D/8 C/8
D/8 C/8
D/8 C/8
GSM Transmission Process:
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33.8 kbit/s
22.8 kbit/s
13 kbit/s
8 kHz13 bits
Transmitting part
Receiving part
Speaker
ReceiverDemodulator
AdaptiveEqualization
De-ciphering
De-interleaving
Channel decoding
Speech decoding
D/A-conversion
TransmitterModulator
Burst formatting
CipheringInterleaving
Channel coding
Speech coding
Segmentation
A/D-conversion
Microphone
13 kbit/s
Transmitting part
Receiving part
TransmitterModulator
Burst formatting
CipheringInterleaving
Channel coding
D/D-conversion
8 kHz8 bits
64 kbit/s PCM
ReceiverDemodulator
AdaptiveEqualization
De-ciphering
De-interleaving
Channel Decoding
GSM Network
Mobile equipment
GPRS Logical Architecture:
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Traffic and signaling
Signaling
TE Terminal EquipmentMT Mobile TerminalMS Mobile Station
BSS Base Station SystemBTS Base Transceiver StationBSC Base Station ControllerGMSC Gateway Mobile Services Switching
CenterMSC Mobile services Switching CenterVLR Visitor Location RegisterHLR Home Location RegisterAUC Authentication Center
EIR Equipment Identity RegisterSGSN Serving GPRS Support NodeGGSN Gateway GPRS Support NodeUm Air InterfaceA, Abis Interfaces (GSM)Gx Interfaces (GPRS)
ExternalIP Network(CorporateLAN)
Gi
TE MT
MS
BSC
GMSC
MSC/VLR
SGSN
EIR
HLR
AUC
GGSNIP-Backbone
Network
ExternalIP Network(Internet)
External
X.25 Network
GsGf
Gr
BTS
Gb
UmISDN/PSTN
Gn
A
OtherPLMN
Gp
BSS Abis
Recommended