Study of the immunity of the GSM-R against electromagnetic … · Characterisation and Analysis of...

Railcom final conference, UIC, Paris, 21 april 2009

Virginie Deniau, INRETS, France virginie [email protected]

R. Adriano, S. Dudoyer, N. Ben Slimen, J. Rioult, P. Massy, B. Meyniel, M. Berbineau, A. Raux and E. Smulders

Study of the immunity of the GSM-R against electromagnetic disturbances present on moving

trains

mailto:[email protected]


Outline

•

The GSM-R system•

Characterisation and Analysis of the disturbances received by GSM-R antennas

•

Impact of the supply voltage on the disturbances•

Estimation of the impact of the transient disturbances on the BER of GSM-R communications

•

Immunity testing on GSM-R communications in laboratory

•

Detection of transients disturbances for diagnostic in-situ

•

Conclusion, future works


ERTMS and GSM-R

ERTMS: European Rail Traffic Management SystemHarmonised signaling standards throughout Europe

GSM-R

GSM-R

Data and voicetransmissions

GSM-R : Global System for Mobiles-RAILWAYSradio system for providing voice and data communication between the track and the train


GSM-R PCRD 6STREP

The GSM-R is based on the standard GSM Phase 2+the modulation type is GMSK (Gaussian Minimum Shift Keying).

Specific frequencies:876-880 MHz for the up-link (trains → base stations) 921-925 MHz for the down-link (base stations → trains)200 kHz frequency spacing between each channel

+ Advanced functions specifically developed for rail.group calls, ads

or calls broadcast,

location-based

connections, call pre-emption

in case of emergency…

Base Transceiver

Station (BTS) close to the tracksThe distance between

base stations ≈

3-4 km

GSM-R antennas on the roof of the trains


GSM-R PCRD 6STREP

The GSM-R is a “Time Division Multiple Access” (TDMA) system

For each carrier frequency (physical channel)

-

data are organized per periodic TDMA frame, with a period of 4.615

ms.

-

each TDMA frame is divided into 8 time intervals of 577

μs

long called "Time Slots"

Each “Time Slot” (logical channel)

-

includes 156 bits which 148 bits of information. The one bit transmission duration is about 3.7 µs.


burst

3.7 µsbit time

GSM-R PCRD 6STREP

Time

user

2us

er 1

user

4

user

3

user

7us

er 8

user

6

user

5

TDMA frame= 4.6

ms

user

2us

er 1

user

4

user

3

user

7us

er 8

user

6

user

5

8 logical channels

924.8 MHz

924.6 MHz

921.2 MHz

921.4 MHz

200 kHz

Carrier frequenciesphysical channels

Freq

uenc

y

Time slot577

μs


Characterisation and Analysis of the disturbances received by GSM-R antennas


The disturbances

received

by GSM-R antennas

Main potential EM disturbances for the GSM-R:•

Public GSM, UMTS 900 on frequency channels adjacent to the GSM-R frequency bands⇔ «

permanent

»

disturbances• Transients coming from the catenary -

pantograph sliding contact

On-board

measurements:

1.

To characterise the coverage levels of the permanent disturbances2.

To characterise the level of noise produced by the transients in

the GSM-R frequency bands

3.

To characterise the time characteristics and the repetition rate

of the transients


Pow

er (d

Bm

)300 MHz

Pow

er (d

Bm

)F.F.T

S11-antenna1 GHz

≈

-35 dBm

≈

-35 dBm

GSM-R frequencies are systematically

covered

•

Characterisation of the noise levels produced by the transients in the GSM-R frequency bands:

Analysis

of transient

disturbances

received

by GSM-R antennas


• Characterisation

of the time characteristics

of the transients

:

90%

10%

AA

100%

50%

time timeDuration Rise time

Time caracteristics

of the transient disturbances


2 4 6 8 10x 10

-10

0

0.5

1

1.5

2

2.5

3x 109

Rise time (s)

Pro

babi

lity

Den

sity

Fun

ctio

n

Rise Time

experimental distributionempirical distribution

0 0.5 1 1.5 2x 10

-8

0

5

10

15

x 107

Duration (s)

Pro

babi

lity

Den

sity

Fun

ctio

n

Duration

experimental distributionempirical distribution

• Statistical study with about 20000 collected transients on trains:

Duration

(s) Rise time (s)

20 ns 1 ns

Typical

duration

= 5 ns Typical

rise

time = 0.4 ns

Time caracteristics



• Characterisation

of the repetition

rate «

Rr »

of the transients

:

Analysis

of transient

disturbances received

by GSM-R antennas

Measurements

performed

in 400 µs time windowsObjective: to establish distributions of the time delays between the transients according to the operating conditions

0 1 2 3 4x 10

-4

-0.4

-0.2

0

0.2

0.4

0.6

Time (s)

Am

plitu

de (V

) Time delay

400 µs

Very

variable Rr according

to the trains operating conditions -0 1

-0.05

0

0.05

0.1

0.15

400 µs

1 transient/ 5µs

0 1 2 3 4-1

-0.5

0

0.5

1

Am

plitu

de (V

)

1 transient/ 10 µs

400 µs


• Number

of transients

in each

400 µs time window

:

Analysis

of transient

disturbances received

by GSM-R antennas

1568 recorded files

Number of transient

disturbances

0 200 400 600 800 1000 1200 1400 16000

10

20

30

40

50

60

70

80

90

file order

9080706050403020100

≈

4.5 µs medium time delay betweentwo successive transients

400 µs Time Window Loading

Time

Over a 1500 s

Measurements duration :1568

recorded files ==> 0,95 s

Time duration of the measurements process+ = ~ 1 s

Measurement equipment was continuously detecting transients

0 200 400 600 800 1000 1200 1400 1600Successive time windows


Impact of the supply

voltages on the time characteristics

of the transients

1500 Vcc

25000 Vcc

About 300 transient

disturbances

collected

under

1500 Vcc

and 25000 Vac

Comparison

of the rise

times

0 50 100 150 200 250 3000

0.5

1

1.5

2x 10-9

0 50 100 150 200 250 3000

0.5

1

1.5

2x 10-9 Rise Time

Time (ns)

Typicalrise

time

= 0.4 ns

= 0.4 ns



voltages on the noise levels

over the GSM-R channels

About 300 transient

disturbances

collected

under

1500 Vcc

and 25000 Vac

0 50 100 150 200 250 300-80

-70

-60

-50

-40

0 50 100 150 200 250 300-80

-70

-60

-50

-40Maximal Amplitude 921 MHz - 925 MHz

FFT of the 300 transients

and post pocess

to extract

the maximal noise level

over the GSM-R frequency

bands

1500 Vcc

25000 Vcc

921 MHz-925 MHz : Down-link

GSM-R



voltages on the peak values

About 300 transient

disturbances

collected

under

1500 Vcc

and 25000 Vac

1500 Vcc

25000 Vcc

0 50 100 150 200 250 3000

0.5

1

1.5

2

0 50 100 150 200 250 3000

0.5

1

1.5

2Peak Amplitude

0 50 100 150 200 250 300-80

-70

-60

-50

-40

0 50 100 150 200 250 300-80

-70

-60

-50

-40Maximal Amplitude 921 MHz - 925 MHz

Peak

valueF.F.T

921 MHz-925 MHz

Pow

er (d

Bm

)


Estimation of the impact of the transient disturbances on the BER of GSM-R communications


Transient disturbances and BER on GSM-R transmissions

Hypothesis :

• Transients duration <<

duration

of one bit→ approximated by a punctual event,•

Transients produce high levels of interference in the GSM-R band, •

Transients produce an arbitrary decision in a bit inside the burst (worst case?).

S

r

RRBER ⋅=

21

Rs is the symbol rate of the communication systemRr represents the repetition rate of the transients

GSM burst


Immunity testing on GSM-R communications in laboratory


Immunity testing on GSM-R communications

CMU 200924.8 MHz

Combiner

GSM-RMobile

Spectrum analyzerCalibration of the power levels

-40dB

Loop back

Signal generator

Directional

combiner

Amplifier

SMIQGSM Public925.2 MHz

CM

U 2

00

SM

IQ

50 Ω

load

combiner

Erroneous

bits * 100%total number

of bitsBER =

Over 1200 speech frames

• Test set-up

:


GSM-R Mobile

Spectrum analyzer

CMU 200

SMIQ

Arbitrary signal

generator

Oscilloscope

combiners



Combiner


Signal generator

GSM-RMobile

load

CMU 200924.8 MHz

• Power calibration based

on the preliminary

on-board

measurements:

?Transients:analysis

by applying

FFT

→ Maximum level

≈

-35 dBm

?

GSM-R :measurement

campaign

for

coverage

levels

and specifications→ -90 dBm < GSM-R < -25 dBm

?

GSM public:measurement

campaign

for

measurements

of coverage

levels→ Maximum level

≈

-25 dBm



3 -

Normalization

to 1V peak

to peak

4 –

Variation of the repetition

rate

• Wave

form

of the transients

based

on the statistical

distributions:

1 –

“Double exponential model”• duration = 5 ns• rise time = 0.4 ns

Combiner


Signal generator

GSM-RMobile

load

CMU 200924.8 MHz

2 –

Application of“Bandpass

numerical filter”

or modulation with a sinus


-100

-90

-80

-70

-60

-50

-40

920 922 924 926 928 930Frequency (MHz)

Pow

er (d

Bm) without transients

GS

M-R

GS

M

CMU 200924.8 MHz

Combiner

Transient

GSM-RMobile

50 Ω

GSM Public925.2 MHz

Spectrum analyzerMaxhold

combiner



Time interval

-100

-90

-80

-70

-60

-50

-40

920 922 924 926 928 930Frequency (MHz)

Pow

er (d

Bm)

4 µs time interval10 µs time interval20 µs time interval1.7 ms time intervalwithout transients

CMU 200924.8 MHz

Combiner

Transient

GSM-RMobile

50 Ω

GSM Public925.2 MHz

Spectrum analyzerMaxhold

combiner


Time interval

≥

10 µsfor the immunity

tests


BER and RXQUAL

Quality level i

Rxqual: parameter

employed

to control the quality

of the service in situ

Range of valuesTypical values

of BER


Immunity tests -

Results


- 17/23 -

Impact of public GSM signals

1 2 3 4 5 6

GSM-R FREQUENCY

GSM-R POWER (dBm)

GSM public FREQUENCY

GSM public POWER (dBm)

Measured

BER (%)

RXQUAL

924.8 MHz -70 925.2 MHz -70 0.004 0

-52 0.011 0

-30 0.01 0

-17 0.086 0

-15 0.137 1

-12 0.44 2

+ 55 dBm

GSM-R924.8 MHz

GSM-RMobile

GSM Public925.2 MHz

Combiner


0.0

0.4

0.8

1.2

1.6

2.0

-60 -50 -40 -30 -20 -10 0GSM public power (dBm)

Transients with TI = 90 µsTransients with TI = 150 µsTransients with TI = 550 µsBER without Transient

Rxqual

= 1

Rxqual

= 3

Impact of the transient disturbances in presence of public GSM

BER (%)


BER induced

by two

different

collected transients

GSM-R924.8 MHz

GSM-RMobile

Combiner

Signal generator

Transients

collectedon board

0.00.20.40.60.81.01.21.41.61.82.0

0 400 800 1200 1600Transients time interval (µs)

BER

(%)

Recorded transient D=6.1 ns and RT= 0.35 nsRecorded transient D=6.75 ns and RT= 0.4 ns

GSM-R power = -70 dBm


GSM-R924.8 MHz

GSM-RMobile

Combiner

Signal generator

S

r

RRBER ⋅=

21

Comparisons

between

measured

and estimated

BER

Transient

collected

on boardRT= 0.35 ns, D= 6.1 ns

GSM-R power = -70 dBm

0.3

0.2

0.1

0

‐0.1

‐0.2

‐0.3

Temps (µs)0 0.1 0.2 0.3 0.4

(V)

Variable Time interval

Time

V

( ) ( )tRTt

FTtAtV γ⎟⎟

⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛−−⎟

⎠⎞

⎜⎝⎛−= expexp

Double exponential

ModelRT= 0.4 ns and D= 5 ns

Prediction

of the BER


Comparisons

between

measured

and estimated

BER

0.0

0.4

0.8

1.2

1.6

2.0

0 200 400 600 800 1000 1200 1400 1600Intervalle de temps entre les transitoires (µs)

BER (%)

estimation du BER (%)

transitoire réel

modèle de transitoire

0.3

0.2

0.1

0

‐0.1

‐0.2

‐0.3

Temps (µs)0 0.1 0.2 0.3 0.4

(V)

( ) ( )tRTt

FTtAtV γ⎟⎟

⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛−−⎟

⎠⎞

⎜⎝⎛−= expexp

RsRrBER ⋅=

21

Double exponential

ModelRT= 0.4 ns and D= 5 ns

Time interval

between

transients

GSM-R power = -70 dBmS/N=1 over the duration of the transient


Detection of transient disturbances for diagnostic in-situ


Characterisation

of the noise level

0 50 100 150 200 250 300-80

-70

-60

-50

-40

Maximal Amplitude 921 MHz - 925 MHz

Over 300 transients

Noise level

varies between-40 dBm and -70 dBm

GSM-R Reception

level

canVary

between

About -20 dBm and -92 dBm

The definition

of a maximum level

of noise is

not adapted to this

application

We

propose to control the recurrence


and to compare it

with

the Rxlevel

of the GSM-

R signal


Minimum GSM-R power level

to keep

a BER inferior

to 1.13 %

GSM-R924.8 MHz

GSM-RMobile

Combiner

Signal generator

Variable GSM-R power

-80

-78

-76

-74

-72

-70

-68

-66

-64

0 400 800 1200 1600Transients time interval (µs)

Req

uire

d G

SM-R

Pow

er (d

Bm)

With Collected transient D=6.1 ns, RT = 0.35 ns

With Collected transient D=6.75 ns, RT = 0.4 ns

BER>1.13 %

BER<1.13 %


Detection

of the transient

disturbancesMethod

employed

during

the project

is

to «

count

»

the transient

is

too

«

heavy

»

for a diagnostic methodology

in situ

-50

-40

-30

-20

-10

0

300 400 500 600 700 800 900 1000Frequency (MHz)

|Sii|

(dB

)|S11|- straight antenna|S11|- oblique antenna

850 MHzFree channel

Reflexion

S-parameters

of the GSM-R antennas

EMI Test ReceiverIn zero spanMeasures 1point/3.7 µs

Approach

proposed


-80

-70

-60

-50

-40

-30

-20

0.0 0.5 1.0 1.5 2.0Time (ms)

Pow

er (d

Bm

)

Detection

of the transient

disturbances

Approach

proposed

-

Results

70 µs 200 µs

Model transient

Real transient

Test sequence

Arbitrary

waveform

generator EMI Test Receiver

70 µs 200 µs

Advantage: we

collect

1 point by transient

disturbance


Conclusion

•

Complete characterisation

of the time characteristics


produced

by the catenary-pantograph

sliding

contact

•

Proposition of a laboratory

testing

method

to control the immunity

of the GSM-R communications against

EM disturbances

representative

of the in

situ conditions (+ permanent and transient

disturbances

simultaneously)

•

Proposition of a prediction

method

of the BER induced

by the transients observed

on board

as a function

of the repetition

rate of the transients

!Characterisation with a GSM-R antenna → the bandwidth of the antenna can impact the rise time distribution obtained

•

Proposition of a methodology to preliminary verify the conditions required to guarantee the quality of the communications

Study of the immunity of the GSM-R against electromagnetic … · Characterisation and Analysis of...

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