Gsm fundamentals
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Transcript of Gsm fundamentals
INTRODUCTIONINTRODUCTION
,
GSM-FUNDAMENTALS PRESENTED TO NIGERIAN
SOCIETY OF ENGINEERS- ELECTRICAL DIVISION(
NIGERIAN INSTITUTION OF ELECTRICAL AND
2
ELECTRONICS ENGINEERS-NIEEE) BY
Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
GSM Network Components
Terrestrial Interface
3
Engr
Terrestrial Interface
Service Area and Number Planning
Channels on The Air Interface
GSM 900GSM 900
EGSM GSM EGSM GSM
The Frequency SpectrumThe Frequency Spectrum
4
Engr
Duplex Separation: 45MHz
Channel Bandwidth: 200KHz
880 890 915 925 935 960MHz
Base Station Receive Base Station Transmit
DCS 1800DCS 1800
The Frequency SpectrumThe Frequency Spectrum
5
Engr
Duplex Separation: 95MHz
Channel Bandwidth: 200KHz
1710 1785 1805 1880MHz
Frequency Re-UseFrequency Re-Use
Because frequency resource of mobile system is very limited,
What is Frequency Re-Use?What is Frequency Re-Use?
6
very limited,
different Subscribers must use the same frequency in different place.
Of course, the quality of communication must be ensured.
Frequency Re-UseFrequency Re-Use
How can we reuse frequency?How can we reuse frequency?
7(Site)X 1(Cell)
2
7
Engr
7(Site)X 1(Cell) Re-use 2
1
3
4
5
6
7
Frequency Re-UseFrequency Re-Use
4(Site)X 3(Cell)
Re-use
5
1
9 6
2
7
3
8
Engr
10
2
7
3
115
9
1
10
212
8
4
11
3
9
5
1
6
CELLCELL
Omni
1Omni-Directional CellsOmni-Directional Cells
9
Engr
120degree
1
23
120 Degree Sectors120 Degree Sectors
Contents Contents
Basic Concepts of Cellular Mobile System
GSM Network ComponentsGSM Network Components
Terrestrial Interface
10
Terrestrial Interface
Service Area and Number Planning
Channels on The Air Interface
Radio Technologies
The Future Development
AUCAUC
OMCOMC
HLRHLR
OSS
NSS
EIREIR
GSM Network ComponentsGSM Network Components
11
Engr
MEMESIMSIM
MSC/VLRMSC/VLR
BTSBTS BSCBSC
PSTN
MS BSS
Mobile Station—MSMobile Station—MS
International Mobile EquipmentIdentity (IMEI)
MS=ME+SIMMS=ME+SIM
12
Engr
Identity (IMEI)– Mobile Equipment
International Mobile SubscriberIdentity (IMSI)
– Subscriber Identity Module
Subscriber Identity Module – SIMSubscriber Identity Module – SIM
International Mobile SubscriberIdentity (IMSI)
Temporary Mobile SubscriberIdentity (TMSI)
International Mobile SubscriberIdentity (IMSI)
Temporary Mobile SubscriberIdentity (TMSI)
13
Engr
Identity (TMSI) Location Area Identity (LAI) Subscriber Authentication Key
(Ki) Mobile Station International
Standard Data Network (MSISDN),it is optional.
Identity (TMSI) Location Area Identity (LAI) Subscriber Authentication Key
(Ki) Mobile Station International
Standard Data Network (MSISDN),it is optional.
The Base Station
Controller – BSC
The Base Transceiver
The Base Station
Controller – BSC
The Base Transceiver BSS
MSC
Base Station Subsystem – BSSBase Station Subsystem – BSS
14
Engr
The Base Transceiver
Station – BTS
The Trans-coder – TC
and Sub multiplexer
(SM)
The Base Transceiver
Station – BTS
The Trans-coder – TC
and Sub multiplexer
(SM)
BTSBTS
BSCBSC
TC/SMTC/SMBSS
AUCAUCHLRHLR
PSTN
NSS
EIREIROMCECEC
The Network Switching SystemThe Network Switching System
15
Engr
Mobile Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC Inter-Working Function – IWFEcho Cancellor – EC
Mobile Switching Center – MSC Home Location Register – HLR Visitor Location Register – VLR Equipment Identity Register – EIR Authentication Center – AUC Inter-Working Function – IWFEcho Cancellor – EC
MSC/VLRMSC/VLR
BSS
IWFIWF
Mobile Service Switching Center – MSC Mobile Service Switching Center – MSC
Call Processing
Operations and Maintenance
Support
Call Processing
Operations and Maintenance
Support
16
Engr
Inter-network & Inter-working
Billing
Inter-network & Inter-working
Billing
Home Location Register – HLR Home Location Register – HLR
Subscriber ID (IMSI and MSISDN)
Current subscriber VLR (current location)
Supplementary service information
Subscriber ID (IMSI and MSISDN)
Current subscriber VLR (current location)
Supplementary service information
17
Engr
Supplementary service information
Subscriber status (registered/deregistered)
Authentication key and AuC functionality
Supplementary service information
Subscriber status (registered/deregistered)
Authentication key and AuC functionality
Visitor Location Register – VLR Visitor Location Register – VLR
Mobile Status(IMSI detached/ attached)
Location Area Identity(LAI)
Temporary Mobile Subscriber Identity(TMSI)
Mobile Status(IMSI detached/ attached)
Location Area Identity(LAI)
Temporary Mobile Subscriber Identity(TMSI)
18
Engr
Mobile Station Roaming Number(MSRN) Mobile Station Roaming Number(MSRN)
IMEIIs Checked against White List
If NOT found,
•White List•Black List•Grey List
Equipment Identity Register – EIR Equipment Identity Register – EIR
19
Engr
IMEIIs Checked against Black/Grey List
If NOT found, checked against Grey/Black List
If NOT found, checked against White List indications
If found, returns a Black or Grey List indicator
OSS(NMC)
Operation and Maintenance Sub SystemOperation and Maintenance Sub System
20
Engr
OMCOMC
OMC
Region2
Region 1
Region 3
Operation and Maintenance Center – OMC Operation and Maintenance Center – OMC
OMC – R: OMC assigned specifically tothe Base Station Subsystem
21
Engr
OMC – S: OMC assigned specifically tothe Network Switching Subsystem
OMC Functional ArchitectureOMC Functional Architecture
MMI
Event/AlarmManagement
SecurityManagement
22
Engr
OS
MMI
DB
ConfigurationManagement
Performance Management
Fault Management
HLR
VLR
EIR
AUCVLR
B
H
F
GC
D
GSM InterfaceGSM Interface
23
Engr
MSC
EC IWF
TC
MSC
IWF EC
BTS BSCMS
A
E
Um Abis
HLR
MSC/VLR
EIRAUCOMC
MSC/VLR
IWF
SigL1: 2MBps TrunksSigL1: 2MBps Trunks
24
Engr
EC
TC
EC
BSC PSTN
BTS BTS
Typical Configuration
TS 0 TS 1-15 TS16 TS 17-31
2MBps Trunks2MBps Trunks
25
Engr
TS = Time slot
TS# Used for
0
1-15
16
17-31
Frame Alignment /Error Checking /Signaling
Traffic
CCS7 Signaling (Other TS may also the used)
Traffic
Contents Contents
Basic Concepts of Cellular Mobile System
GSM Network Components
Terrestrial Interface
26
Engr
Terrestrial Interface
Service Area and Number Planning
Channels on The Air InterfaceChannels on The Air Interface
Radio Technologies
The Future Development
The physical channel is the medium over whichthe information is carriedThe logical channels consist of the informationcarried over the physical channel
The physical channel is the medium over whichthe information is carriedThe logical channels consist of the informationcarried over the physical channel
Physical and Logical ChannelsPhysical and Logical Channels
27
Engr
00 1 2 3 4 5 6 7
TDMA FRAME
Timeslot
The information carried in one time slot is called a “burst”
The information carried in one time slot is called a “burst”
Traffic ChannelTraffic Channel
TCHTraffic Channels
Normal Burst
28
Engr
Speech
TCH/FS
Data
TCH/HSTCH/9.6 TCH/2.4
TCH/4.8
TCH Traffic ChannelTCH/FS Full rate Speech Channel TCH/HS Half rate Speech Channel TCH/9.6 Data Channel 9.6kb/sTCH/4.8 Data Channel 4.8kb/sTCH/2.4 Data Channel 2.4Kb/s
CCH Control Channels
DCCH BCCH
ACCH
Control ChannelControl Channel
29
Engr
FCCHSCH
SDCCHBCCH Synch. CH.
ACCH
SACCHFACCH CCCH
RACHCBCH
PCH/AGCH
Broadcast Control Channel – BCCHCommon Control Channel – CCCHDedicated Control Channel – DCCHAssociated Control Channel – ACCH
CCH
BCCHdownlink only
The information carried on the
BCCH is monitored by the mobile
periodically when it is switched
on and not in a call
The information carried on the
BCCH is monitored by the mobile
periodically when it is switched
on and not in a call
Broadcast Control Channel – BCCHBroadcast Control Channel – BCCH
30
Engr
BCCH Synch.
Channels
SCH FCCH
BCCH:Broadcast Control Channel
FCCH: Frequency Correction
Channel
SCH: Synchronization Channel
BCCH:Broadcast Control Channel
FCCH: Frequency Correction
Channel
SCH: Synchronization Channel
CCH
CCCH
The CCCH is responsible fortransferring control informationbetween all mobiles and theBTS.
RACH: Random Access Control
The CCCH is responsible fortransferring control informationbetween all mobiles and theBTS.
RACH: Random Access Control
Common Control Channel – CCCHCommon Control Channel – CCCH
31
Engr
RACHuplink
CBCH downlink
PCH/AGCHdownlink
RACH: Random Access ControlChannel
PCH: Paging Channel
AGCH: Access Grant ControlChannel
CBCH:Cell Broadcast Channel
RACH: Random Access ControlChannel
PCH: Paging Channel
AGCH: Access Grant ControlChannel
CBCH:Cell Broadcast Channel
CCH
DCCH
DCCH is assigned to a singlemobile connection for call setupor for measurement and handoverpurpose.SDCCH: Standalone DedicatedControl Channel
DCCH is assigned to a singlemobile connection for call setupor for measurement and handoverpurpose.SDCCH: Standalone DedicatedControl Channel
Dedicated Control Channel – DCCH Dedicated Control Channel – DCCH
32
Engr
SDCCH
FACCH SACCH
Control ChannelACCH: Associated ControlChannelSACCH: Slow Associated ControlChannelFACCH:Fast Associated ControlChannel
Control ChannelACCH: Associated ControlChannelSACCH: Slow Associated ControlChannelFACCH:Fast Associated ControlChannel
ACCH
Search for frequency correction pulse
Search for synchronous pulse
Unscramble system information
Snoop into paging message
FCCH
SCH
BCCH
PCH
Power-off state
Idle state
How to use these channel?How to use these channel?
33
Engr
Snoop into paging message
Send access pulse
Allocate signaling channel
Set up the call
Allocate voice channel
Conversation
Release the call
PCH
RACH
AGCH
SDCCH
FACCH
TCH
FACCH
Dedicated mode
Idle state
TDMA Frames
0 1
0 1 102 3 4 5 6 7 2 3 5 764
GSM MultiframeGSM Multiframe
34
Engr
0 1 2 43 46 47 48 5049
51 – Frame Multiframes
CONTROL CHANNELS
Timeslots and TDMA FramesTimeslots and TDMA Frames
Higher Capacity Cell
Broadcast TrafficDedicated
00 1 2 3 4 5 6 7
35
Engr
Dedicated
Traffic00 1 2 3 4 5 6 7
Low Capacity Cell
Combined Traffic00 1 2 3 4 5 6 7
GSM MultiframeGSM Multiframe
TDMA Frames
0 1
0 1 102 3 4 5 6 7 2 3 5 764
36
Engr
0 1 2 43 21 22 23 2524
26 – Frame Multiframes
TRAFFIC CHANNELS
Contents Contents
Basic Concepts of Cellular Mobile System
GSM Network Components
Terrestrial Interface
37
Engr
Terrestrial Interface
Service Area and Number Planning
Channels on The Air Interface
Radio TechnologiesRadio Technologies
Modulation TechniquesModulation Techniques
Amplitude Modulation (AM)
Frequency Modulation (FM)
Phase Modulation (PM)
38
Engr
– phase modulation can be implemented easilyfor digital signals, this is the method used forthe GSM air interfaces. Phase Modulation isknown as Phase Shift Keying when applied todigital signals
– phase modulation can be implemented easilyfor digital signals, this is the method used forthe GSM air interfaces. Phase Modulation isknown as Phase Shift Keying when applied todigital signals
1 0 0 1 1 GaussianDigital Filter
Phase Modulator
Gaussian Minimum Shift Keying (GMSK) Gaussian Minimum Shift Keying (GMSK)
39
Engr
Digital FilterModulator
Battery LifeBattery Life
Power ControlPower Control
Voice Activity Detection – VAD
40
Engr
Voice Activity Detection – VAD
Discontinuous Transmission – DTX
Discontinuous Reception – DRX
Power ControlPower Control
8WBoth Uplink and Downlinkpower settings can becontrolled independentlyand individually.
41
Engr
Saves radio battery powerReduces co-channel andadjacent channel interference
0.8W
5W
VAD & DTXVAD & DTX
Encoding the speechsilences at a rate of500 bit/s ratherthan the full 13Kb/s.
Without DTX
42
Engr
than the full 13Kb/s.
If the mobile doesnot transmit during‘silence’ there is areduction in theoverall poweroutput requirement
With DTX
Comfort Noise
DRXDRX
DRX allows the mobile station to effectively “switch off”during times when reception is deemed unnecessary.
BCCH Multiframe P = Paging Channel
43
Engr
P P P P P P BCCH P P
MS Being paged
MS in listen mode
MS receive System
information
MS in listen mode
Multipath FadingMultipath Fading
•Diversity
•FrequencyHopping
44
Engr
Hopping
Time Dispersion
DiversityDiversity
When diversity is implementedtwo antennas are situated atthe receiver. These antennasare placed severalwavelengths apart to ensure
Approx. 10 wavelengths
45
Engr
wavelengths apart to ensureminimum correlation betweenthe two receive paths.
The two signals are thencombined, this ensures that alow signal strength is less likelyto occur.
Compare oradd signals
Resultant Signal