NOKIA nokia.ppt/1 / 2015-11-19 Agenda. GSM900/DCS1800. The GSM Network & Air Interface. Technical...

NOKIA nokia.ppt/1 / 23/4/20

AgendaAgenda

. GSM900/DCS1800 . The GSM Network & Air Interface

. Technical Basics . Speech Coding . Types of Channel . Making a Phone Call


Global System for Mobile

( Groupe Special Mobile )

G S MG S M


1982 Groupe Special Mobile?is created within CEPT

1986 A Permanent Nucleus is set up

1987 Main radio transmission techniques are chosen, based on prototype evalution (1986)

1989 GSM becomes an ETSI technical committe

1990 The phase 1 GSM 900 specifications are finalized

1991 First systems are running

1992 All major European GSM 900 operators begin commercial operator

GSM Development HistoryGSM Development History


• Speech Services• Data Services• Short Message Services (SMS)

• Supplementary Services• Subscriber Identity Module (SIM)• Security Function

GSM / DCS1800 FunctionalitiesGSM / DCS1800 Functionalities


RF AspectsRF Aspects

• TDMA• 0.3GMSK Modulation• Burst Power Transmission• Neighbour Cells Measurement• Hopping• Uplink / Downlink DTx• BER & Receiver Testing


GSM900 GSM900 DCS1800 DCS1800 PCS1900Uplink 890 to 880 to 1710 to 1710 to 1850 to

915MHz 915MHz 1785MHz 1785MHz 1910MHzDownlink 935 to 925 to 1805 to 1805 to 1930 to

960MHz 960MHz 1880MHz 1880MHz 1990MHzARFCN range 1 to 124 0 to 124 and 512 to 885 512 to 885 512 to 810

975 to 1023TX/RX Spacing 45MHz 45MHz 95MHz 95MHz 80MHz(Freq.)TX/RX Spacing 3 Timeslots(Time)Modulation Data 270.833kbit/sRateFrame Period 4.615msTimeslot Period 576.9usBit Period 3.692usModulation 0.3GMSKChannel Spacing 200KHzTDMA Mux 8MS Max Power 20W( 8W is 8W 8W 1W 1W

max in use)MS Min Power 13dBm 5dBm 4dBm 0dBm 0dBmMS Power 5 to 19 0 to 15 0 to 15 30,31,0 to 15Control StepsVoice Coder Bit 13kbit/s 13kbit/s 13kbit/s 13kbit/s 13kbit/sRate 6.5kbit/s 6.5kbit/s

GSM900/DCS1800/PCS1900GSM900/DCS1800/PCS1900


GSM Frequency RangeGSM Frequency Range

• 890 - 915 MHz Uplink / MS Transmit

• 935 - 960 MHz Downlink / BS Transmit

• Duplex Offset 45 MHz

• Channel Spacing 200kHz

• Channel numbering 1 - 124

• Transmission Speed 270 Kbits


DCS1800 Frequency RangeDCS1800 Frequency Range

• 1710 - 1785 MHz Uplink / MS Transmit

• 1805 - 1880 MHz Downlink / BS Transmit

• Duplex Offset 95 MHz

• Channel Spacing 200kHz

• Channel numbering 512 - 885

• Transmission Speed 270 Kbits


GSM Primary BandGSM Primary Band

890 900 910 920 930 940 950 960 Freq

45 MHz

Uplink ( Mobile to Base )

Downlink ( Base to Mobile )


DCS1800 Primary BandDCS1800 Primary Band

1710 1735 1760 1785 1800 1825 1850 1875Freq

95 MHz

Uplink ( Mobile to Base )

Downlink ( Base to Mobile )


Carriers at the border of the GSM bandCarriers at the border of the GSM band

890.2 890.4 890.6 890.8

Freq

GSM band

200 kHz


Carriers at the border of the DCS1800 bandCarriers at the border of the DCS1800 band

1710.2 1710.4 1710.6 1710.8

Freq

DCS1800 band

200 kHz


GSM NetworksGSM Networks

BSC

BTS

BTS

BTSBSS

BSC

BTS

BTS

BTSBSS

MSC

MSC

OMCOMC

ADC NMC

VLR

VLRHLR

AUC

EIR

Interface to other network

MS


GSM NetworksGSM Networks

Terminology:MS- Mobile Station ( 移动台 )BSS- Base Station System ( 基站系统 )BTS- Base Transceiver Station ( 基站收发台 )BSC- Base Station Controller ( 基站控制器 )MSC- Mobile Switching Centre ( 移动业务交换中心 )OMC- Operations and Maintenance Centre ( 操作与维护中心 )NMC- Network Management Centre ( 网络管理中心 )AUC- Authentication Centre ( 鉴权中心 )HLR- Home Location Register ( 归属位置寄存器 )VLR- Visitors Location Register ( 来访位置寄存器 )

EIR- Equipment Identity Register ( 设备标识寄存器 )


MSCBSC

BSC

BSC

PSTNBTS

BTS

BTS

Air Interface Abis Interface SS#7 SS#7

GSM GSM InterfaceInterface

MS


GMSK ModulationGMSK Modulation

1 1 0 0 1 01 1 0 0 1 0

PSK

Guassian Filter

Spectrum < 200kHz


Fc Fc + 67.708KHzFc + 67.708KHz

+67.708KHz-67.708KHz Data Type ?0Data Type ?1

ModulationModulation


4 0

1

2

3

4

5

6

7

1 2 3 4 5 6

Frequency

Amplitude

ARFCN

Timeslot

Physical Channel isan ARFCN and Timeslot

TDMA and FDMATDMA and FDMA


TDMA and FDMATDMA and FDMA

Terminology:

FDMA - Frequency Division Multiple AccessTDMA - Time Division Multiple AccessARFCN - Absolute RF Channel NumberTS - TimeslotPhysical - The Combination of a TS number Channels and ARFCN.Logical - Are Mapped on Physical Channels Channels


10us

10us

10us

10us

8us 8us

3 31 157 5726

148 Active Bits, 546.42us

147 Useful Bits

542.8us

-70dB

-30dB

-6dB

+4dB

-6dB

-30dB

-70dB

Tol -1.0dB

Tol +1.0dB

GSM TDMA Power BurstGSM TDMA Power Burst


Power Time TemplatePower Time Template

542.8 us / 147 Bits 10 8 1010 8 10Time

Power

-70

0

dB

Upper Limit

Lower Limit

Actual

us

Normal Burst


Power Time TemplatePower Time Template

321.23 us / 87 Bits 10 8 1010 8 10Time

Power

-70

0

dB

Upper Limit

Lower Limit

Actual

us

Access Burst

87 bits


Uplink & DownlinkUplink & Downlink

Downlink / MS Receive

5 6 7 0 1 2 3 4 5 6 7 0 1 3 42

0 6 7 0 1 2 3 4 5 6 71 3 42

Uplink / MS Transmit

5


Uplink & DownlinkUplink & Downlink

ARFCN

0 2 4 7 3 6 01

3

5 06 1 4 72 5 31 2 64 5 7 2 4 60 3 5 713

210 4 5 6 7 0 1 2 3 4 5 6 7 0 0 3 4 5 6 7 0 1 2 3 4 51

ARFCN

UPLINK

DOWNLINK

45MHz

. Uplink Lags Downlink by 3 Timeslot periods

. Uplink and Downlink use same Timeslot Number

. Uplink and Downlink use same Channel Number (ARFCN)

. Uplink and Downlink use different bands(45MHz apart for GSM900)


Frequency HoppingFrequency Hopping

MOD

Coupler

Switch

Synth

Register

ControlUplink

BS 1 BS 2MonitoringRX LevRX Qual

Downlink 1

65

124

1

65

124

Home BS


20ms Blocks

Speech Coder

Bits Ordered

260 Bits

260 Bits

50 132 78

. RELP and LTP Coder RELP- Residual-Excited Linear Prediction Coder LTP- Long Term Prediction

. Converts Speech to Low Data Rate

. 20ms Speech makes 260Bits

. Output 13kbit/s

Very Important Bits Important Bits Other Bits

Speech CoderSpeech Coder


Error CorrectionError Correction

Type Ia 50 Type Ib 132 Type II 78

50 132 783

Type Ia CRC Type Ib Type II

Block Code

25 66 25663 4 78

Re-ordering

378 78

Half rate convolutional code

456 Bits from 20ms of Speech

Type Ia Type Ib Type Ib Type Ia Tail Type II

CRC

262 Bits

In

456 Bits

Out


Diagonal InterleavingDiagonal Interleaving

456 Bits from 20ms of Speech 456 Bits from 20ms of Speech

57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57 57

57 57 57 57 57 57 57 57

57

57 57 57 57TCH

Traffic Channel (TCH) Bursts Carry Two 57 Bits Blocks (114) Each120ms of Speech = 456x6 = 2736 bits2736/114 = 24 bursts I.e. 24frames(mobile transmits once per frame)Multiframe has 26 frames in 120msThere are 2 spare frames 厖 One SACCH, one Idle


Speech to Radio / Radio to SpeechSpeech to Radio / Radio to Speech

Channelcoding

Speech

Digitizing and Source coding

Interleaving

Burst formatting

Ciphering

Modulation

Channeldecoding

Speech

Source decoding

De-interleaving

Burst formatting

Deciphering

Demodulation


MS Camp on Flow ChartMS Camp on Flow Chart

MS Turn On

MS searches channelsand orders by signalstrength

MSStongest

BCCH

FCCH on BCCH and adjusts timebase

SCH on BCCH and fine tunes timebase & timing

Decode BCCH & store info

Is BCCHin PLMN ?

MSNext Stongest

BCCH

YES

NO

YES

NO

NO

Location =Previous Location?

YES

YES

MS camped on - listens for page, can request service

Using SACCH - adjust power, TA & report RX Qualetc

MS goes to the assigned SDCCH ( Freq., timeslot, ... )for authentication + location Update

MS sendsRACH

BS assigns SDCCH to MS using the CCCH


Orignated CallOrignated Call

BS pages MS usingthe CCCH MS sends RACH

BS ORIGINATED CALL

MS ORIGINATED CALL

MS responds withRACH

BS assigns MS to SDCCH

or TCH

MS transmits and receives speech on TCH

TCH

Using the FACCH onTCH authentication &location update

Using the SDCCH, authentication,call setup, and TCH assignment

Using the SACCH, BS commands MS to adust power + timing, MS

reports power + Rx quality of BCCH + adjacent BCCH

MS transmits + receives speechon TCH

Using the SACCH on TCH, MSreports power + Rx quality , BScommands MS to adjust power ,TA

During inactive timeslots, MS measures adjacent cells, BCCH

Call disconnected by MS or BS


Subscriber Identity Module ( SIM )Subscriber Identity Module ( SIM )

SIM contains ( at least ) following information :

• IMSI (International Mobile Subscriber Identification)

• MCC & MNC (Mobile Country Code and mobile Network Code)

• Any other user specific information


International Mobile Subscriber Identity ( IMSI )International Mobile Subscriber Identity ( IMSI )

IMSI = MCC + MNC + MSIN

NMSI

3 digits 2 digits

Not more than 15 digits

IMSI = International Mobile Subscriber Identity

MCC = Mobile Country Code

MNC = Mobile Network Code

MSIN = Mobile Station Identification Number

NMSI = National Mobile Subscriber Identity


International Mobile Equipment Identity ( IMEI )International Mobile Equipment Identity ( IMEI )

IMEI = International Mobile Equipment Identity

TAC = Type Approval Code

FAC = Final Assembly Code

SNR = Serial Number

SP = Spare

IMEI = TAC + FAC + SNR SP+

6 digits 2 digits 6 digits 1digit

NOKIA nokia.ppt/1 / 2015-11-19 Agenda. GSM900/DCS1800. The GSM Network & Air Interface. Technical...

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