Wireless Curriculum Development Section Wireless Curriculum Development Section ISSUE ISSUE 3.2 3.2 GSM Fundamentals GSM Fundamentals
Oct 27, 2014
Wireless Curriculum Development SectionWireless Curriculum Development SectionWireless Curriculum Development SectionWireless Curriculum Development Section
ISSUEISSUE 3.23.2
GSM FundamentalsGSM FundamentalsGSM FundamentalsGSM Fundamentals
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
Service Area and Number Planning
GSM Network Components
Channels on The Air Interface
Radio Technologies
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
ObjectivesObjectives
Name the two different cell types and understand why and when each would be used.
Get the concept of frequency reuse.
Name the frequency spectrum used in GSM
Name the two different cell types and understand why and when each would be used.
Get the concept of frequency reuse.
Name the frequency spectrum used in GSM
On completion of this section you will be able to:
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CELLCELL
Omni
1
120degree
1
23
Omni-Directional CellsOmni-Directional Cells
120 Degree Sectors120 Degree Sectors
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Cell conceptCell concept
HighwayHighway
TownTownSuburbSuburb
RuralRural
• Flexible network planning based on location nature Flexible network planning based on location nature
• Smooth Handover (no service degradation while subscriber moves)Smooth Handover (no service degradation while subscriber moves)
• Frequency reuse (same group of frequencies used in different cells)Frequency reuse (same group of frequencies used in different cells)
Signal Signal strengthstrength
distancedistance
• Cell : basic service area that can be efficiently managed by the network
• One base station (equipment to switch, transmit and receive calls) per cell for comm. between MS and the network
• Cell boundaries are defined by BS signal strength
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25 MHz Uplink (MS to BS)
25 MHz Downlink (BS to MS)
f
200 KHz
915 MHz890 MHz
……
960 MHz935 MHz
45 MHz duplex spacing
Frequency Spectrum GSM 900Frequency Spectrum GSM 900
……
For DCS1800: uplink from 1710 to 1785MHz, downlink is from 1805 to 1880MHz 75Mhz each / 374 RF carriers . 95MHz duplex spacing.
t
f
200 KHz
……
200 KHz x 125 = 25 MHz
1 TDMA frame = 0.577 m
s x 8 TS
……
915 MHz
890 MHz
Physical channelsPhysical channels
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Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
Service Area and Number Planning
GSM Network Components
Channels on The Air InterfaceChannels on The Air Interface
Radio Technologies
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Understand the structure of multiframes
On completion of this section you will be able to:
ObjectivesObjectives
Name the 4 most commonly used channel combinations
Identify the types of physical channels and logical channels
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Logical channels Logical channels
Logical ChannelsLogical ChannelsLogical ChannelsLogical Channels
CCHCCHCCHCCHTCHTCHTCHTCH DATADATADATADATASPEECHSPEECHSPEECHSPEECH
TCH/HRTCH/HR7kbps7kbps
TCH/HRTCH/HR7kbps7kbps
TCH/FRTCH/FR13kbps13kbps
TCH/FRTCH/FR13kbps13kbps
2.4/4.8kbps2.4/4.8kbps((FR&HR)FR&HR)2.4/4.8kbps2.4/4.8kbps((FR&HR)FR&HR) 9.6kbps 9.6kbps FRFR9.6kbps 9.6kbps FRFR
Logical traffic channelsLogical traffic channels
logical channels consist of the information carried over the physical channel.logical channels consist of the information carried over the physical channel.
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Logical control channelsLogical control channels
CCHCCHCCHCCH
BCHBCHBCHBCHDCHDCHDCHDCH CCCHCCCHCCCHCCCH
SCHSCHSCHSCH
FCCHFCCHFCCHFCCHPCHPCHPCHPCH AGCHAGCHAGCHAGCH RACHRACHRACHRACHSDCCHSDCCHSDCCHSDCCH
BCCHBCCHBCCHBCCH
•Power Control indicator•cell ID , LAI , PLMN code •List of neighboring cells
SACCHSACCHSACCHSACCH
Power & timing controlRSSI & link quality
FACCHFACCHFACCHFACCH
Auth. and HO.
- Frequency-correction channel, used for MS frequency correction.- Frequency-correction channel, used for MS frequency correction.- Synchronization channel, used for MS frame synchronization and BS - Synchronization channel, used for MS frame synchronization and BS identification.identification.
Broadcast control channel, used to send cell information.Broadcast control channel, used to send cell information.-Random access channel, for dedicated channels assignment requestRandom access channel, for dedicated channels assignment request-Access grant channel, used to assign dedicated control channels for the MSAccess grant channel, used to assign dedicated control channels for the MS-Paging channel : used to page (alert) MS Paging channel : used to page (alert) MS -Standalone dedicated channel : Supports the transfer of data during connection Standalone dedicated channel : Supports the transfer of data during connection setupsetup-Slow/Fast associated control channels : carrying information associated with the Slow/Fast associated control channels : carrying information associated with the process being carried out on either the SDCCH or the TCH.process being carried out on either the SDCCH or the TCH.
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Timeslots and TDMA FramesTimeslots and TDMA Frames
Higher Capacity Cell / more than 1 RF carriermore than 1 RF carrier
Broadcast TrafficDedicated
Traffic00 1 2 3 4 5 6 7
00 1 2 3 4 5 6 7
Low Capacity Cell / 1 RF carrier 1 RF carrier
Combined Traffic
0 1 2 3 4 5 6 7
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GSM Logical ChannelGSM Logical Channel
Channel Combination
• Main BCH combination – BCCH + CCCH
• DCH combination – SDCCH8 + SACCH8
• Combined Channel Combination – BCCH + CCCH
+SDCCH4 + SACCH4
• TCH combination – TCH8/FACCH + SACCH
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Structure of Logical Channel Combination Frame-Main BCCH
Structure of Logical Channel Combination Frame-Main BCCH
1 multi-frame (51TDMA Frames) 235.38ms Downlink
Group Group1 Group2
Group3,4
(same as
Group2)
Grpup5
Channel F S BX4 CX4 F S CX4 CX4 …… F S CX4 CX4 I
Frame
Number0 1 2-5 6-9 10 11 12-15 16-19 20-39 40 41 42-45 46-49 50
1 multi-frame (51TDMA Frames) 235.38ms Uplink
Channel R R R R R R R R R R R R R R……R R R R R
Frame
Number0 1 2 3 4 5 6 7 8 9 10 11 12 13-46 47 48 49 50
F:FCCH; S:SCH; B:BCCH; C:CCCH; I:IDLE; R:RACH
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Structure of Logical Channel Combination Frame-Main SDCCH
Structure of Logical Channel Combination Frame-Main SDCCH
1 multi-frame (51TDMA Frames) 235.38ms Downlink
Channel D0×4 D1×4 D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A0×4 A1×4 A2×4 A3×4 I I I
Channel D0×4 D1×4 D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A4×4 A5×4 A6×4 A7×4 I I I
Frame
Number0-3 4-7 8-11 12-15 16-19 20-23 24-27 28-31 32-35 36-39 40-43 44-47 48 49 50
1 multi-frame (51TDMA Frames) 235.38ms Uplink
ChannelA5×
4A6×4 A7×4 I I I D0×4
D1×
4D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A0×4
ChannelA1×
4A2×4 A3×4 I I I D0×4
D1×
4D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A4×4
Frame
Number0-3 4-7 8-11 12 13 14
15-
18
19-
2223-26
27-
3031-34 35-38 39-42 43-46 47-50
F:FCCH; S:SCH; B:BCCH; C:CCCH; I:IDLE; R:RACH
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Structure of Logical Channel Combination Frame-Combined BCCH
Structure of Logical Channel Combination Frame-Combined BCCH
1 multi-frame (51TDMA Frames) 235.38ms Downlink
Group Group1 Group2 Group3 Group4 Grpup5
Channel F SB×
4
C×
4F S
C×
4
C×
4F S
D0
×4
D1
×4F S
D2
×4
D3
×4F S
A0
×4
A1
×4I
Channel F SB×
4
C×
4F S
C×
4
C×
4F S
D0
×4
D1
×4F S
D2
×4
D3
×4F S
A2
×4
A3
×4I
Frame
Number0 1 2-5 6-9 10 11
12-
15
16-
1920 21
22-
25
26-
2930 31
32-
35
36-
3940 41
42-
45
46-
4950
1 multi-frame (51TDMA Frames) 235.38ms Uplink
Channel D3×4 R R A2×4 A3×4 R……R D0×4 D1×4 R R D2×4
Channel D0×4 R R A0×4 A1×4 R……R D0×4 D1×4 R R D2×4
Frame
Number0-3 4 5 6-9 10-13 14-36 37-40 41-44 45 46 47-50
F:FCCH; S:SCH; B:BCCH; C:CCCH; I:IDLE; R:RACH
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Structure of Logical Channel Combination Frame-TCH
Structure of Logical Channel Combination Frame-TCH
T:TCH; I:IDLE ; A:SACCH
1 multi-frame (26TDMA Frames) 120ms
Channel T T T T T T T T T T T.A…T T T T T I
Frame Number 0 1 2 3 4 5 6 7 8 910-12 -
2021 22 23 24 25
.The FACCH is not showed in the diagram as it does not receive its own time allocation. The FACCH steals a time period from the TCH when required. .The 13th frame is used by the SACCH which carriers link control information to and from the mobile and BTS.
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Frames hierarchy Frames hierarchy
The hyper frame lasts for over 3 hours, after which ciphering and FH algorithms are restarted.The hyper frame lasts for over 3 hours, after which ciphering and FH algorithms are restarted.
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
Service Area and Number PlanningService Area and Number Planning
GSM Network Components
Channels on The Air InterfaceChannels on The Air Interface
Radio Technologies
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Service AreaService Area
PLMN service area
......
System area
PLMN service area
MSC service area...
Location area...
Base station area...
Radio cell
...... ......
MSC service area...
Location area...
Base station area...
Radio cell
PLMN service area
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LAILAI
Location Area Identification
The LAI is the international code for a location area.
MCC : Mobile Country Code , It consists of 3 digits . For example: The MCC of China is "460"MNC : Mobile Network Code , It consists of 2 digits . For example: The MNC of China Mobile is "00"LAC : Location Area Code , It is a two bytes BCD
code(hex). The value 0000 and FFFF is invalid.For example: 460-00-0011
MCC : Mobile Country Code , It consists of 3 digits . For example: The MCC of China is "460"MNC : Mobile Network Code , It consists of 2 digits . For example: The MNC of China Mobile is "00"LAC : Location Area Code , It is a two bytes BCD
code(hex). The value 0000 and FFFF is invalid.For example: 460-00-0011
MCC MNC LAC
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
CGICGI
The CGI is a unique international identification for a cell
The format is LAI+CI
LAI: Location Area Identification
CI : Cell Identity. This code uses two bytes BCD
code(hex) to identify the radio cells within an LAI.
For example : 460-00-0011-0001
The CGI is a unique international identification for a cell
The format is LAI+CI
LAI: Location Area Identification
CI : Cell Identity. This code uses two bytes BCD
code(hex) to identify the radio cells within an LAI.
For example : 460-00-0011-0001
CGI: Cell Global Identification
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
CC : Country Code. For example: The CC of China is "86".NDC : National Destination Code. For example: The NDC of
China Telecom is 139, 138, 137, 136, 135.SN : Subscriber Number. Format:H0 H1 H2 H3 ABCDExample: 86-139-0666-1234
CC : Country Code. For example: The CC of China is "86".NDC : National Destination Code. For example: The NDC of
China Telecom is 139, 138, 137, 136, 135.SN : Subscriber Number. Format:H0 H1 H2 H3 ABCDExample: 86-139-0666-1234
MSISDNMSISDN
CC NDC SN
National (significant)Mobile number
Mobile station internationalISDN number
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MCC : Mobile Country Code , It consists of 3 digits . For example: The MCC of China is "460" 。MNC : Mobile Network Code , It consists of 2 digits . For example: The MNC of China Telecom is "00" 。MSIN : Mobile Subscriber Identification Number. H1H2H3 S
ABCDEF For example: 666-9777001NMSI : National Mobile Subscriber Identification , MNC and MSIN
form it together. For Example of IMSI : 460-00-666-9777001
MCC : Mobile Country Code , It consists of 3 digits . For example: The MCC of China is "460" 。MNC : Mobile Network Code , It consists of 2 digits . For example: The MNC of China Telecom is "00" 。MSIN : Mobile Subscriber Identification Number. H1H2H3 S
ABCDEF For example: 666-9777001NMSI : National Mobile Subscriber Identification , MNC and MSIN
form it together. For Example of IMSI : 460-00-666-9777001
Not more than 15 digits
3 digits 2 digits
IMSI
MCC MNC MSIN
NMSI
IMSI IMSI
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The TMSI is assigned only after successful subscriber authentication.
TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret.
The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the telecom operator.
The TMSI is assigned only after successful subscriber authentication.
TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret.
The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the telecom operator.
TMSITMSI
TMSI: Temporary Mobile Subscriber Identification)
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IMEIIMEI
TAC FAC SNR SP
IMEI
TAC : Type approval code. It is administered by the type approval center.
FAC : Final assembly code.It is administered by the manufacturer.
SNR : Serial number.It is issued by the manufacturer of the MS.
SP : Not used.
TAC : Type approval code. It is administered by the type approval center.
FAC : Final assembly code.It is administered by the manufacturer.
SNR : Serial number.It is issued by the manufacturer of the MS.
SP : Not used.
IMEI: International Mobile Station Equipment Identification
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
Service Area and Number PlanningService Area and Number Planning
GSM Network ComponentsGSM Network Components
Channels on The Air InterfaceChannels on The Air Interface
Radio Technologies
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
PSTNPSTN
OtheOther r
GSM GSM
OMCOMC
GSM network architectureGSM network architecture
Permanent data:Permanent data:
-IMSIIMSI
-Suppl. service info .Suppl. service info .
-Authentication key Authentication key
-Roaming & billing info Roaming & billing info
Temporary data:Temporary data:
-MSC/VLR address-MSC/VLR address
Temporary data:Temporary data:
-copy of most of data for -copy of most of data for active subscribers in VLR active subscribers in VLR coverage coverage
-Mobile status-Mobile status
-LAI-LAI
-TMSI-TMSI
Mobile Station : - Mobile Equipment contains IMEI for ME identification Mobile Station : - Mobile Equipment contains IMEI for ME identification - Subscriber Identity module contains IMSI,TMSI,LAI,Auth. key - Subscriber Identity module contains IMSI,TMSI,LAI,Auth. key
Base Transceiver Station : the first access point for mobile stations to access the Base Transceiver Station : the first access point for mobile stations to access the network. The BTS is a radio equipment (transceivers & antennas) needed to serve network. The BTS is a radio equipment (transceivers & antennas) needed to serve each cell in the network. each cell in the network.
Base Station Controller : controls one or more BTSs and interfaces BSS to NSS. It is Base Station Controller : controls one or more BTSs and interfaces BSS to NSS. It is a high capacity switch that provides handover, cell configuration data. a high capacity switch that provides handover, cell configuration data. Mobile Switching Center : controls one or more BSCs and manages switching Mobile Switching Center : controls one or more BSCs and manages switching
White list :White list :
Valid mobiles Valid mobiles
Black list :Black list :
Stolen or forbidden Stolen or forbidden
Gray list :Gray list :
Faulty mobilesFaulty mobiles
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Subscriber Identity Module – SIMSubscriber Identity Module – SIM
NSS MS
Authentication Process
Air interface
HLR AUC SIM
BSS
Authentication Algorithms
Authentication Algorithms
Authentication Algorithms
Authentication Algorithms
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Transcoder and submultiplexerTranscoder and submultiplexer
30 x 64k voice channels = 120 x 16k compressed/combined = 2Mbps PCM link
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Mobile to Landline callMobile to Landline call
MS BSS MSC VLR HLR CHANNEL REQUEST <RACH>
<AGCH>DCCH ASSIGN
<SDCCH>
SIGNALING LINK ESTABLISHED
REQ. FOR SERVICECR
CC
AUTHENTICATION
SET Cipher MODE
SET-UP <SDCCH>
Call Info EQUIP. ID REQ.
COMPLETE CALL
CALL PROCEEDING <SDCCH>
PSTN
SFOC
services Auth.
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Mobile to Landline callMobile to Landline call
ASSIG. COMMAND<SDCCH>
ASSIG. COMPLETE
Address Complete(ACM)
Alerting
<FACCH>
Answer (ANS)Connect
TCH connect
<TCH>
Initial and Final Address Message (IAM)
MS hears ring tone from land phone
<FACCH>
Ring tone stops
MS BSS MSC VLR HLR PSTN
Connect Acknowledge<FACCH>
BILLINGBILLING
ISUP (IAM)ISUP (IAM)
(ACM) (ACM)
+ alerting + alerting
ANSANS
Conn.
Conn. ack
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Contents Contents
Basic Concepts of Cellular Mobile SystemBasic Concepts of Cellular Mobile System
Service Area and Number PlanningService Area and Number Planning
GSM Network ComponentsGSM Network Components
Channels on The Air InterfaceChannels on The Air Interface
Radio TechnologiesRadio Technologies
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
On completion of this section you will be able to know about the following radio technologies :
VAD, DTX, DRX
Diversity
Frequency Hopping
ObjectivesObjectives
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Battery LifeBattery Life
Power ControlPower Control
Voice Activity Detection – VAD
Discontinuous Transmission – DTX
Discontinuous Reception – DRX
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VAD & DTXVAD & DTX
Encoding the speech silences at a rate of 500 bit/s rather than the full 13Kb/s.
If the mobile does not transmit during ‘silence’ there is a reduction in the overall power output requirement
Without DTX
With DTX
Comfort Noise
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DRXDRX
PCH is structured so that MS knows when it needs to check for a paging signal. In the time between paging signals, the mobile can go into sleep mode, when almost no power is used.
P P P P P P BCCH P P
BCCH Multiframe P = Paging Channel
MS Being paged
MS in listen mode
MS receive System
information
MS in listen mode
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DiversityDiversity
When diversity is implemented two antennas are situated at the receiver. These antennas are placed several wavelengths apart to ensure minimum correlation between the two receive paths.
The two signals are then combined, this ensures that a low signal strength is less likely to occur.
Compare oradd signals
Resultant Signal
Approx. 10 wavelengths
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Frequency HoppingFrequency Hopping
Synthesizer Hopping:each timeslot on a given transceiver can transmit at a different frequency
Baseband Hopping: each transceiver stays at the same frequency and the data is switched to the appropriate transceiver.
Each time the BTS or mobile transmits a burst, it does so on a different RF carrier frequency.
time
frequency
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Security Level: InternalConfidential Information of Huawei. No Spreading without Permission.
Subscriber Identity Module – SIMSubscriber Identity Module – SIM