Fresh Field Mtc 001 Section 3

8/9/2019 Fresh Field Mtc 001 Section 3

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GSM SystemOverviewSection Three

GSM Air Interface


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2001 Freshfield Communications Limited.Company Confidential Slide 2

GSM Frequency Spectrum

Power Class Allocation Table

Channel Coding and Modulation

GSM TDMA Frame Structure

Advanced Features

Summary

Presentation Outline


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At the end of this course, attendees will: Understand frequency allocations in GSM

Have an appreciation of GSM air-interface burst structures

Have an understanding of idle mode processes

Have an appreciation of dedicated mode processes

Objectives


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BTS

Um Air-Interface

MS


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BS

Tx

DL

BS

RxUL


1990

1930

1910

1850

20 MHz

Guard Band

80 MHz

Separation

1880

1805

1785

1710

20 MHz

Guard Band

95 MHz

Separation

960

935

915

890

20 MHz

Guard Band

45 MHz

Separation

935

925

890

880

20 MHz

Guard Band

45 MHz

Separation

P-GSM900 E-GSM900 GSM1800 GSM1900


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Each system comprises two frequency bands Uplink band for mobile to fixed BTS communication

Downlink band for base station transmission to mobiles

Uplink always uses lower frequency band

lower band gives better radio propagation which is more criticalfor power-limited mobiles

Channel numbers assume guard bands of 200 KHz

GSM900 offers 124 channels

E-GSM900 offers 49 channels (not all mobiles support this)





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GSM Frequencies and Channel Numbering

In GSM, the channel numbering scheme is used moreoften than the actual MHz frequency.

Actual frequencies can be calculated from the ARFCN

as:

where

MHzxnnFul )(2.00.890)(

MHzFnFuldl

45)(

GSMPfornxARFCNn 1241,0,

GSMEfornxARFCNn 1023975,1024,


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2001 Freshfield Communications Limited.Company Confidential

Slide 8

GSM 900

GSM 1800

Multi-band Networks


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Slide 9

The use of multi-band techniques can provide a majorcapacity enhancement for GSM900 operators.

Available systems now support seamless switching

between GSM900 and GSM1800 layers.

Usually GSM1800 is used for capacity take-up andGSM900 is used for coverage

Inter-layer handover

Current systems support inter-layer handover using separatecontrol and traffic channels

Future systems will support inter-layer handover using one

control channel and separate traffic channels .

Multi-band Networks


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Slide 10

GSM900

0.85

24

53

82

20 (Deleted)1

Power O/P (Watts)Power ClassGSM1800 Mobile Station

0.252

11

Power O/P (Watts)Power Class


Most operators design their networks assuming 2W

and 0.8 W (GSM900) and 1W (GSM1800) only


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Slide 11

Eight classes of power levels for the BTS at macrocelllevel

Most operators employ a fixed range of BTS power

levels (10W-40W) for their networks.


PPoowweerrCCllaassss

GGSSMM990000 BBaasseeSSttaattiioonn PPoowweerrWWaattttss ((ddBBmm))

GGSSMM11880000 BBaasseeSSttaattiioonn PPoowweerrWWaattttss ((ddBBmm))

11 332200 WW ((5555)) 2200 WW ((4433))

22 116600 WW ((5522)) 1100 WW ((4400))

33 8800 WW ((4499)) 55 WW ((3377))44 4400 WW ((4466)) 22..55 WW ((3344))

55 2200 WW ((4433))

66 1100 WW ((4400))

77 55 WW ((3377))

88 22..55 WW ((3344))8


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Slide 12

Three classes of power levels for the BTS at microcell

level

Some manufacturers however provide microcell BTS

products with output powers of 1W.

PPoowweerr CCllaassss BBaassee SSttaattiioonn PPoowweerrWWaattttss ((ddBBmm))

MM11 00..2255 WW ((2244))

MM22 00..0088 WW ((1199))

MM33 00..0033 WW ((1144))88



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Slide 13

Modulation

CipheringBurstFormatting

BitInterleaving

ChannelCoding

Digitising &

SourceEncoding

13kbps

22.8kbps

33.8kbps

8 Timeslots

270.8kbps

Tx &

Antenna

Channel Coding & Modulation


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Slide 14

Class 2

70 bits

Class 1B

124 bits

Class 1A

50 bits

1A+15 most important from 1B

Cyclic Redundancy Check

Extra 8 Bits Produced

8 Repetition

Bits

244 bits

260 bits

Class 2

78 bits

Class 1B

132 bits

Class 1A

50 bits

EFR Speech Coding


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Slide 15

Class 2

78 bits

Class 1B

132 bits

Class 1A

50 bits

260 bits

456 bits

78 bits378 bits

132 4350

456 bitsConvolutional Coding

Tail Bits

Parity

Check Bits

Full-Rate Speech Coding


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Slide 16

240 bits

488 bits

4240 bits

Convolutional Coding

Tail Bits

456 bits

Code Puncturing

Data Encoding


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Slide 17

184 bits

456 bits

4224 bits

Convolutional Coding

Tail Bits

Fire coding adds 40

redundant bits

Signalling Coding


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Slide 18


GSM employs TDMA, TDD techniques

Each frequency channel is divided into eight different

time-slots numbered 0 to 7.

Each of the eight time slots is assigned to an

individual user.

In each cell one of the carriers, (the BCCH), does not

have all its 8 time slots free for traffic.

If a mobile is assigned time slot number 1, it transmitsonly in this time slot and stays idle for the remaining

seven time slots.


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Slide 19

3571261573

DataFlagTraining

SequenceFlagData TailTail

546 sec

1 burst period - 577 sec

TS6 TS7 TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0 TS1 TS2

Timeslot

577 sec

Frame 4.615 ms



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Slide 20


Bit rate of 270.83 kbits/s.

Bit duration of 3.69 us.

Time slot duration of 156.26 bits or 0.577 ms.

TDMA frame duration of 8 x 0.577 = 4.615 ms.

Front-end filter reduces GSM bandwidth requirements

to 200 kHz.


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Slide 21

GSM TDMA Frame Structures

In GSM a burst refers to one time slot and has a bit

duration of 156.25 bits.

GSM employs five different types of bursts for

communications between the BTS and the MS:

Normal Burst Frequency Correction Burst

Synchronisation Burst

Random Access Burst

Dummy Burst

These burst types are used for different functions for

conveying traffic and control signalling information.


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Slide 22

Control

Channels

Traffic

Channels

BSS

Broadcast

Control

Channel

Common

Control

Channel

Dedicated

Control

Channel

Voice

Channel

Data

Channel

Frequency

Correction

SynchronisationBroadcast Info

Paging

Access Request

Access Granting

Standalone Dedicated

Slow Associated

Fast Associated

Full Rate

Enhanced Full Rate

Half Rate

9.6 kb/s

4.8 kb/s

2.4 kb/s

MS

Channel Types


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Slide 23

Control

Channels

Broadcast Control

Channel (BCCH)

Common Control

Channel (CCCH)

Dedicated Control

Channel (DCCH)

FCCH BCCH

BCCH

RACH CBCH

PCH/AGCH

SDCCH SACCH

FACCH

Control Channel Groups


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Slide 24

148 bits all set to 0

Downlink

Frequency Correction Burst


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2001 Freshfield Communications Limited.

Company Confidential

Slide 25

339393

BSIC &

Frame No.Training

Sequence

64

BSIC &

Frame No.TailTail

Sync

Burst

Downlink

Synchronisation Burst


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Slide 26

Normal

Burst

Downlink

3571261573

ARFCNServing Cell

Neighbour Cells

Class Access

MS Tx Power

FlagTraining

SequenceFlag

MCC

MNC

LAC

Cell ID

TailTail

Broadcast Control Channel (BCCH)


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Slide 27

Normal

Burst

Downlink

3571261573

TMSI

or

IMSI

FlagTraining

SequenceFlag

TMSI

or

IMSI

TailTail

Paging Channel (PCH)


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Slide 28

Uplink

336418

Random

Identifier

&

Cause Value

Fixed bitsTailTail

Access

Burst

Guard Period

256 sec

321 sec

Random Access Burst


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Slide 29

Normal

Burst

Downlink

3571261573

Immediate

Assignment

Or

Reject

FlagTraining

SequenceFlag

Immediate

Assignment

Or

Reject

TailTail

Access Grant Channel


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Slide 30

Normal

Burst

Uplink & Downlink

3571261573

Layer 3 MessagesCall Setup

Location Area Update

SMS

FlagTraining

SequenceFlag

Layer 3 Messages

Call Setup


SMS

TailTail

Normal

Burst

Standalone Dedicated Control Channel


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Slide 31

Normal

Burst

Uplink & Downlink

57

Radio Link Maintenance

Timing Advance

Power Control

Rx Signal Strength

Quality

31261573

FlagTraining

SequenceFlag

Radio Link Maintenance

Timing Advance

Power Control

Rx Signal Strength

Quality

TailTail

Normal

Burst

Slow Associated Control Channel


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Slide 32

Normal

Burst

Downlink

3571261573

Cell Broadcast

MessageFlag

Training

SequenceFlag

Cell Broadcast

MessageTailTail

Cell Broadcast Channel


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Slide 33

When switched on, the MS synchronises itself in

frequency, in time and subsequently decodes

information from the BCCH.

Synchronisation in frequency is undertaken by:

scanning the operators GSM frequency allocation and selectingthe channel with the highest power level

detecting the FCCH at +67 kHz above the BCCH frequency

Synchronisation in time is undertaken by:

detecting the SCH after finding the FCCH

BCCH decoding is undertaken using the parameters

specified in the SCH.

Synchronisation With Network


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Slide 34

Channel MS BS

RACH Channel Request

AGCH Channel Assignment

SDCCH Request for location updating

SDCCH Authentication request from network

SDCCH Authentication response from the mobile station

SDCCH Request to transmit in ciphered mode

SDCCH Acknowledgement of ciphered mode

SDCCH Confirmation of the location updatng, ncluding thoptional assignment of a temporary identity

SDCCH Acknowledgement of the new location and the

temporary identity

SDCCH Channel release from network

The MS performs location updating to inform the network where it is. This

ensures that if calls arrive from the PSTN or any other MS, the network candirect paging messages via the PCH to a specific BTS.

Location updating is performed when the MS is switched on or when itmoves between location areas.

Location Updating


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Slide 35

Channel MS BS

PCH Paging of the mobile station

RACH Channel Request

AGCH Channel Assignment

SDCCH Answer to the paging from te network

SDCCH Authentication request from network

SDCCH Authentication response from the mobile station

SDCCH Request to transmit in ciphered mode

SDCCH Acknowledgement of ciphered mode

SDCCH Setup message for the incoming call

SDCCH ConfirmationSDCCH Assignment of a traffic channel

FACCH Acknowledgement of the traffic channelFACCH Alerting (caller gets ringing sound)FACCH Connect message when the mobile is off-hook

FACCH Acceptance of the connect message

TCH Exchange of user data (speech)

Call Establishment - Mobile Terminated


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Slide 36

Control Channel Configurations

FCH SCH BCCH 3 CCCH 4 SDCCHTS0 ARFCN 1

Combined Multiframe

FCH SCH BCCH 9 CCCHTS0 ARFCN 1

Non-Combined Multiframes (Minimum Configuration)

8 SDCCHTS1 ARFCN 1


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Slide 37

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

B

U

R

S

T

B

U

R

S

T

B

U

R

S

T

B

U

R

S

T

B

U

R

S

T

B

U

R

S

TB

U

R

S

T

B

U

R

S

T

Data Burst

Frame 0 Frame 1 Frame 2 Frame 3

Timeslot

DTMA Frame

Timeslots


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Slide 38

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

B

U

R

ST

B

U

R

ST

B

U

R

ST

B

U

R

ST

B

U

R

ST

B

UR

STB

U

R

ST

B

U

R

ST

Data Burst

Frame 0 Frame 1 Frame 2 Frame 3

0 1 2 3 4 5 6 78 9 10 11 12 13 14 15 16 17 6 718 19 20 21 22 23 24 25

SACCH IDLE

Multiframe 120 ms

Traffic Multiframe (26 TDMA frames)


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Slide 39

The 26-Multiframe Traffic Channel Structure

T T T T T T T T T T T T S T T T T T T T T T T T T I0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

T=TCH, S=SACCH, I=idle26 Frames = 120ms

The first 12 frames are used to transmit traffic data.

The next frame is an SACCH frame which is used to transmitsignal measurement information.

The next 12 frames are again used to transmit traffic data.

The last frames in the multiframe is idle and is used for

measurement of signal levels of the neighbouring cells by theMS

The total length of the multiframe is 26 x 4.615 ms = 120 ms.


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Slide 40

FCCH + SCH + CCCH + BCCH Logical Channel

Combination

This channel combination is used in cells with several carriersand a large amount of expected traffic on the CCCHs. It is

transmitted on slot 0 of the carrier designated the BCCH.

F S BCCH CCCH F S CCCH F S CCCH F S CCCH F S CCCH I0 1 2-5 6-9 10 11 12-19 20 21 22-29 30 31 32-39 40 41 42-49 50

Downlink F=FCCH, S=SCH, B=BCCH, C=CCCH (PCH,AGCH), I=idle51 Frames = 235.38 ms

R R R R R R R R R R R R R R R R R0 1 2-5 6-9 10 11 12-19 20 21 22-29 30 31 32-39 40 41 42-49 50

Uplink R=RACH51 Frames = 235.38 ms

The 51-Multiframe Signalling Structure


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Slide 41

The 51-Multiframe Signalling Structure

FCCH + SCH + CCCH + BCCH + SDCCH/4 + SACCH/4

Logical Channel CombinationF S BCCH CCCH F S CCCH F S SDCCH 0/1 F S SDCCH 2/3 F S SACCH 0/1 I0 1 2-5 6-9 10 11 12-19 20 21 22-29 30 31 32-39 40 41 42-49 50

F S BCCH CCCH F S CCCH F S SDCCH 0/1 F S SDCCH 2/3 F S SACCH 23 I0 2-5 6-9 10 11 12-19 20 21 22-29 30 31 32-39 40 41 42-49 50

Downlink F=FCCH, S=SCH, B=BCCH, C=CCCH (PCH,AGCH), I=idle51 Frames = 235.38 ms

S3 R A2 A3 R S0 S1 R S20-3 4-5 6-9 10-13 14-36 37-40 41-44 45-46 47-50

S3 R A0 A1 R S0 S1 4 S2

0-3 4-5 6-9 10-13 14-36 37-40 41-44 45-46 47-50

Uplink R=RACH, S=SDCCH/4 A=SACCH/451 Frames = 235.38 ms


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Slide 42

26- and 51-Multiframe Combinations

GSM employs superframe and hyperframe structures

to combine the 26 user data multiframe and the 51

signalling data multiframe.

A superframe consists of 26 x 51 TDMA frames or

1,326 frames and has a duration of 6.12s. A hyperframe consists of 2048 superframes.

Special counters, T1, T2 and T3 are used to number

TDMA frames in the superframe and hyperframe

structure.


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Slide 43

26- and 51-Multiframe Combinations

T1 counts super frames and has values between 0 and

2047.

T2 counts speech frames and has values between 0

and 25 in the 26-multiframe structure.

T3 counts signalling frames and has values between 0and 50 in the 51-multiframe structure.

These counter values are transmitted in the SCH and

assist the mobile in identifying the BCCH and system

information.


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Slide 44

BTS Tx

DL

3 TS

Offset

Time

BTS Rx

ULTime

Uplink and Downlink Timeslots


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Slide 45

Advanced Features

GSM Air-Interface


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Slide 46

Radio Tx/Rx

Time

Frequency Hopping


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Slide 47

Frequency Hopping at the BTS

Frequency hopping at the BTS can be implemented in

either one of two ways:

baseband hopping

synthesizer hopping

Baseband hopping means that each transmitter (TRX)

at the BTS operates on a fixed frequency. All bursts,

irrespective of which TCH connection they belong to

are routed to the transmitter of the proper frequencyat transmission.


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Slide 48

Baseband Hopping

TRX1 CONTROLLER transmitter

f0

TRX2 CONTROLLER transmitterf1 filter

combiner


f2


f3

bus for routing ofbursts


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Slide 49

Baseband Hopping

The advantage of this mode is that narrowband

tunable filter combiners can be used. With up to 16

inputs, it is possible to have as many frequencies in a

hopping set without having to connect several

combiners in cascade.

The disadvantage is that it is possible to use a larger

number of frequencies than there are transmitters.


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Slide 50


f0...fn hybrid

combiner


f0...fn hybrid

combiner


f0...fn hybrid

combiner


f0...fn

Synthesiser Hopping

S h i H i


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Slide 51

Transmitter tunes to the correct frequency at

transmission of each burst.

Number of frequencies that can be used for hopping

is not dependent upon the number of transmitters

available. Wide-band hybrid combiners must be used (insertion

loss of 2-3 dB).

Bursts are not routed via the bus as in the case of

baseband hopping.

Synthesiser Hopping

F H i P t


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Slide 52

ARFCN Allocation

Mobile Allocation (MA)

Starting ARFCN

Mobile Allocation Indication Offset (MAIO)

Hopping Sequence Number (HSN)

0 Cyclic

1-63 Pseudo Random

Frequency Hopping Parameters

P C t l


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Slide 53

High

Power

Low

Power

Power Control


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Slide 54

Power Control

RF power control refers to the mechanism by which the transmissionpower of the MS (and optionally the BTS) can be modified within a given

range mainly to reduce the level of interference to co-channel users

whilst maintaining the same communications quality.

0.25W

2W

1W

P C t l


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Slide 55

There are three primary reasons for power regulation

at the mobile: Reduction in battery power consumption and therefore longer talk time.

The receiver in the BTS has a limited dynamic range. This may cause

problems when the mobile is very close to a BTS. In this case the BTS

receiver might become saturated due to a very high received signalstrength from the mobile. A saturated receiver is temporarily blocked for

all timeslots. To avoid this power regulation is applied.

If the average output power of all mobile stations is reduced, the

interference in the network will be reduced since every mobile will radiate

less power into the air. Close to the BTS, the output power of mobiles isreduced. When mobiles move away from the BTS, the radiated power

has to be increased.

Power Control

P C t l


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Slide 56

In the GSM system, power regulation is performed in

steps of 2 dB with full power adjustment range of up

to 30 dB.

It is based upon the measurement reports of the

signal level (RXLEV) and the RXQUAL taken everySACCH multiframe, equivalent to an interval of 480

ms.Data Description Source

Uplink signal strength, full BTS

Uplink signal strength, sub BTS

Uplink quality, full BTSUplink quality, sub BTS

Power level used by MS MS

DTX used by mobile or not MS

Power Control

P C t l


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Slide 57

In uplink, MS power is estimated by BSC

Measurement data is averaged

Since the 2 dB regulation occurs every 60 ms, the

actual maximum power regulation range is 16 dB

during one SACCH period.

Power Control

M bil St t


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Slide 58

IMSI DetachPhone Switched Off Service Request/IMSI Attach

N

E

TW

O

R

K

IMSI AttachedPhone Idle


Dedicated Mode

Authentication

Encryption

Paging

Mobile terminated / originated call

Handover

Channel ReleaseMobile terminated / originated

Mobile States

C ll S l ti


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Slide 59

1st Time with SIM

Switch ON

Scan all DL Frequencies Scan all DL Frequencies

Yes No

Able to Decode BCCH ?

Calculate C1 Discard Frequency

Yes No

Form League Table of C! Results

Select League ChampionCell

Cell Selection

C ll S l ti F l


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Slide 60

Calculated by mobile for every cell detected

Mobile selects cell with biggest C1 value

C1=X-MAX(Y,0)

X = Rx levelminimum level in cellAccess burst Tx powermax mobile Tx power

For big C1 need big X, small Y

X big if level received is bigger than minimum

Y small if mobile easily capable of Tx AB

Cell Selection Formula

Cell Reselection


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Slide 61

Phase of mobile

Mobile moves

Recalculate C1

C2 Parameters being Txd

in new cells BCCH ?

1 2

Reselect into cell

with best C1

NO

Calculate C2

YES

Reselect into cell

With best C2

Cell Reselection

C2 Formula


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Slide 62

Calculated by mobile for every cell detected

Mobile reselects cell with biggest C2 valueCan control mobiles entry into cell

C1=(C1+ATTRACT VALUE)(REPEL VALUE x A)

Can make cell look good with big attract value

Can make cell look bad with big repel value

Can include time in cell with A value

A = 0 if mobile in cell longer than minimum

A = 1 if mobile not in cell for minimum time Major application in microcell underlay situation

C2 Formula

Cell Reselection Example


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Slide 63

Macro

Macro

Micro

Service

Large macros for fast movers Small micros for services

(slow/stationary)

Use C2 to keep fast movers

out of micro

Micro only used for people in

services for reasonable period

of time

Cell Reselection Example

Location Area Updates


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Slide 64

South

East Wales

Location

Area

Bristol

Location

Area

Periodic

Normal

Location Area Updates

Reselection Margin


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Slide 65

ZYW

X

LAC1 LAC2

Y to Z when

Zs C1/C2>Ys + Reselect Margin

W to X

when Xs C1/C2 > Ws

Reselection Margin

Dedicated Mode Processes


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Slide 66

Dedicated Mode Processes

Serving

BTS

UL Level &

Quality

DL Level & Quality

(Serving Cell)

DL Level (BCCH of

each Neighbour)

Mobile Cycle


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Slide 67

RetuneRxMeasureTxRetune TxRx

1 Frame=4.615 ms

Receive from server, measurelevel and quality

Transmit to server

Measure one neighbour BCCH

level

45 MHz

x MHzy MHz

Mobile Cycle

Co channel Interference


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Slide 68

Serving

Cell

Cell 15

BCCH

ARFCN 100

Cell 2

BCCH

BCCH

ARFCN 100

BCCH

BCCH

BCCHBCCH

Co-channel Interference

Decoding the BSIC


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Slide 69

BSIC is NCC and BCC

Sent in SCH in timeslot 0 of BCCH carrier

Mobile uses idle frame in 26 frame multi-frame

Listens to neighbour BCCH for whole frame

1 timeslot of frame must be timeslot zero:

May hit timeslot zero during SCH

May hit timeslot zero at different point in its 51 frame multi-

frame

If dont get SCH, try again next idle frame

Next idle frame corresponds to different point 51 frame multi-

frame

May take several attempts, but will get BSICReason for sliding effect (26 & 51 frames)

If BSIC not decoded, neighbour still in measurement report but

ignored by BTS

Decoding the BSIC

Measurement Reports


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Slide 70

SERVING CELL

Signal Strength Full = 100 measurements 100Signal Strength Sub = 12 measurements 12

Signal Quality Full = 100 measurements 100

Signal Quality Sub = 12 measurements 12

NEIGHBOUR CELLSignal Strength = y measurements y

BSIC

AFRCN

MOBILECurrent Timing Advance

Current TX Power

DTX Flag

Measurement Reports

Re Averaging


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Slide 71

Rx Signal

Strength

Time480 ms

Re-Averaging

Re-Averaging Parameters


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Slide 72

MR MR MR MR MR MR MR MR MR

Decision !!

Example:

hreqave = hreqt = 2

3x2x480 ms=2.88 sec warm-up480 ms

..480 ms later

MR MR MR MR MR MR MR MR MR

Decision !!

480 ms

Decision rolls forward

Re-Averaging Parameters

Voting


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Slide 73

Do at least 3 out of 4 exceed90 ?

Yes

Handover to the best adjacent cell

-83 -87 -85 -92 -96 -93 -93 -94 -93 -96 -92 -99

Example: P=3 N=4

Minimum acceptable receive level = -90 dBm

Voting

Handover


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Slide 74

Handover

BSC A BSC B

MSC

1

3

2

4

6

5

7

9

8

Handover Causes


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Slide 75

Handover Causes

Uplink Quality

Downlink Quality

Uplink Signal Level

Downlink Signal Level

Uplink Interference Downlink Interference

Distance

Power Level

Quality Measurements


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Slide 76

BSC A

Training

Sequence

Training

Sequence

Training

Sequence

BER:10x

7

6

5

4

3

2

1

0

DL Quality

Upper RXQUAL

DL

Lower RXQUALDL

18.1>12.87

9.056.4-12.86

4.533.2-6.45

2.261.6-3.24

1.130.8-1.63

0.570.4-0.82

0.280.2-0.41

0.14


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Slide 77

-110 dBm

-100 dBm

-90 dBm

-80 dBm

-70 dBm

-60 dBm

-47 dBm

Upper RxLev

Lower RxLev-4863

Signal Level (dBm)RxLev

Power Measurements

Interference


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Slide 78

3

-110 dBm

-100 dBm

-90 dBm

-80 dBm

-70 dBm

-60 dBm

-47 dBm

0

1

2

3

4

5

Rx PowerInterferer

Bands

BTS

ARFCN 100 ARFCN 120

-60dBm

-90dBm

Rx Power

0

-90dBm

Rx Quality

4

5

Interference

Timing Advance


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Slide 79

Timing Advance

The BTS performs measurements on the timing delay from mobiles and

commands those with bursts arriving too late at the base site to advance

burst transmissions. This feature is known as timing advance.

Timing advance figures: 0 to 63 corresponding to 0 to 0.252ms. Each

timing advance value corresponds to 1 bit duration (3.69 us).

0.1ms

0.01ms

0.2ms

Power Budget


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Slide 80

BTS

Serving

Cell

BTS

Neighbour

CellB

A

Power

Budget

10 km

Reported

Neighbour

Level

Reported

Server

Level

Power Budget

Power Budget


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Slide 81

Value = [min (MS Access Max Pwr)(MS Max Pwr)]-[RxLev Dl-PwrAdj Dl]

Power Budget Required for Handover = 10 dB

Serving Cell

MS Access Max Pwr = 20 dBm

MS Max Pwr =30 dBm

Rx Lev Dl =-83 dBm

Pwr Adj DL =-10dB

Neighbour Cell

MS Access Max Pwr = 20 dBmMS Max Pwr =30 dBm

Rx Lev Dl =-65 dBm

Pwr Adj DL =0dB

Value=[min(20)(30)]-[(-83)-(-10)]=93 dBm

Value=[min(20)(30)]-[(-65)-(0)]=85 dBm

Actual Power Budget=8 dB

Power Budget

Summary


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Summary

GSM air-interface is based upon a TDMA structure.

GSM relies upon the use of both control and traffic

signalling

Advanced features such as frequency hopping, DTX

and power control are employed in GSM GSM mobiles enter into various states for which

various network processes apply

Fresh Field Mtc 001 Section 3

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Transcript of Fresh Field Mtc 001 Section 3