cen dsrc / itscen dsrc / its-g5 coexistence...-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40...
TRANSCRIPT
World Class Standards
CEN DSRC / ITS G5CEN DSRC / ITS-G5 coexistencecoexistence
Basic RF properties
Dieter Smely© ETSI 2011. All rights reserved
Workshop; July 2011 | Ispra
Workshop, Coexistence between CEN DSRC and ITS-G5
Workshop; July 2011 | Ispra
World Class Standards
Index
Signal properties
Interference mechanismInterference mechanism
Coexistence considerations
Coexistence methods
Power coexistence
Time sharing coexistence
Mitigation area identification
Example: Isolation estimation
Workshop, Coexistence between CEN DSRC and ITS-G5 2
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Signal PropertiesSignal Properties
Workshop, Coexistence between CEN DSRC and ITS-G5 3
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CEN DSRC features
Used for road tolling and access applications
Small low price retrofit onboard units (OBU)Small low price retrofit onboard units (OBU)
Roadside units (RSU) with defined antenna footprint( ) p
Workshop / Coexistence between CEN DSRC and ITS-G5 4
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CEN DSRC signal propertiesRSU
The RSU is using amplitude shift keying (ASK) with a data rate of 500 kBit/s to modulate the down link (DL) (2 µs per bit).( ) ( µ p )
1 0
0.0
1.0
2.0
x10-3
-2.0
-1.0
20181614121086420µs
OBUThe OBU acts as a variable reflector to a constant DL (passive back scatter technology). By changing the phase of the reflected signal the uplink (UL) isBy changing the phase of the reflected signal the uplink (UL) is generated. The modulation type of this UL is phase shift keying with two states (2-PSK) and a data rate of 250 kBit/s.In addition either a 1 5 MHz or a 2 MHz sub carrier PSK modulation is
Workshop / Coexistence between CEN DSRC and ITS-G5 5
In addition, either a 1.5 MHz or a 2 MHz sub carrier PSK modulation is used to shift the UL in frequency.
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CEN DSRC signal in frequency domainDSRC frequency utilization for 1 5 MHz sub-carrier frequency (U1-0 CEN EN 12253 )
DSRC frequency utilization for 1,5 MHz sub-carrier frequency (U1-0, CEN EN 12253 )
7950
GH
z
8000
GH
z
8050
GH
z
8100
GH
z
8150
GH
z
7975
GH
z
8025
GH
z
8075
GH
z
8125
GH
z
8030
GH
z
8040
GH
z
8020
GH
z
8010
GH
z
7960
GH
z
7970
GH
z
7980
GH
z
7990
GH
z
8080
GH
z
8090
GH
z
8070
GH
z
8060
GH
z
8130
GH
z
8140
GH
z
8120
GH
z
8110
GH
z
Channel 1 Channel 2 Channel 3 Channel 4
5. 5. 5. 5. 5.5. 5. 5. 5.5. 5.5.5.5. 5. 5. 5. 5. 5.5.5. 5. 5.5.5.
UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
DSRC frequency utilization for 2 MHz sub-carrier frequency (U1-1, CEN EN 12253 )
5.79
50 G
Hz
5.80
00 G
Hz
5.80
50 G
Hz
5.81
00 G
Hz
5.81
50 G
Hz
5.79
75 G
Hz
5.80
25 G
Hz
5.80
75 G
Hz
5.81
25 G
Hz
5.80
30 G
Hz
5.80
45 G
Hz
5.80
20 G
Hz
5.80
05 G
Hz
5.79
55 G
Hz
5.79
70 G
Hz
5.79
80 G
Hz
5.79
95 G
Hz
5.80
80 G
Hz
5.80
95 G
Hz
5.80
70 G
Hz
5.80
55 G
Hz
5.81
30 G
Hz
5.81
45 G
Hz
5.81
20 G
Hz
5.81
05 G
Hz
Channel 1 Channel 2 Channel 3 Channel 4
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UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
UL
DL
DL
Car
rier
UL
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Overlapping of CEN DSRC DL in MLFF
Lane Width
Multilane free flow (MLFF)Several, but not all, MLFF implementations use one RSU
10m Tolling Zone
pper lane with overlapping antenna footprints and synchronised modulation.
CEN DSRC RSU CEN DSRC RSU
yTo avoid signal cancellation in the overlap region, different carrier frequencies are used in
10mTolling Zone
qadjacent lanes.The OBU uses a broadband envelop detector. Therefore it
Lane Width
pcan demodulate the sum signal of several RSUs.
Workshop / Coexistence between CEN DSRC and ITS-G5 7
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ITS-G5 signal propertiesAll ITS-G5 stations use the physical layer described in IEEE 802.11p which is currently in the progress of being merged with all other IEEE 802.11 standards.Signal properties ValueChannel bandwidth 10 MHzCarrier spacing 156,25 kHzNumber of used carriers 52 (including 4 pilots) (OFDM)Symbol duration 8 µs (including 1 6 µs cyclic prefix)Symbol duration 8 µs (including 1,6 µs cyclic prefix)Modulation 2 PSK, 4 PSK, 16 QAM and others
1.0
0.0
-1.0
x10-3
Workshop / Coexistence between CEN DSRC and ITS G5 8
876543210µs
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ITS –G5 Signal in frequency domain (from ES 202 663 )Channel Centre frequency IEEE 802.11 Channel Default data rate TX power limit TX powerChannel
typeCentre frequency IEEE 802.11
CH numberChannel spacing
Default data rate TX power limit TX power density limit
G5CC 5 900 MHz 180 10 MHz 6 Mbit/s 33 dBm EIRP 23 dBm/MHzG5SC2 5 890 MHz 178 10 MHz 12 Mbit/s 23 dBm EIRP 13 dBm/MHzG5SC1 5 880 MHz 176 10 MHz 6 Mbit/s 33 dBm EIRP 23 dBm/MHzG5SC3 5 870 MHz 174 10 MHz 6 Mbit/s 23 dBm EIRP 13 dBm/MHzG5SC4 5 860 MHz 172 10 MHz 6 Mbit/s 0 dBm EIRP -10 dBm/MHzG5SC5 As required in EN 302 571 for the
band 5 470 MHz to 5 725 MHzseveral dependent on channel
spacing30 dBm EIRP (DFS master) 17 dBm/MHz23 dBm EIRP (DFS slave) 10 dBm/MHz
NOTE: With respect to emission limits (power limit / power density limit), the more stringent requirement applies.
Workshop / Coexistence between CEN DSRC and ITS-G5 9
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Interference mechanismInterference mechanism
ITS_WG4#13, Coexistence between CEN DSRC and ITS-G5 10
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Different possible interference scenariosDifferent possible interference scenarios
ITS-G5 transmitter to CEN DSRC OBU receiver
ITS-G5 transmitter to CEN DSRC RSU receiver
CEN DSRC RSU transmitter to ITS-G5 receiver
Workshop / Coexistence between CEN DSRC and ITS-G5 11
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Interference from ITS-G5 to CEN DSRC OBUThe CEN DSRC DL and the interfering ITS-G5 signal sum up in the CENThe CEN DSRC DL and the interfering ITS G5 signal sum up in the CEN DSRC OBU receiver. Since the OBU uses an envelope detector, the interference signal is treated as additional noise.
2.0
-2.0
-1.0
0.0
1.0
0
x10-3
RSU DL
86420µs
1.0
0.010-3
ITS signal-1.0
x
876543210µs
g
-2
0
2
x10-3
sum signal
Workshop / Coexistence between CEN DSRC and ITS-G5 1286420
µs
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Interference from ITS-G5 to CEN DSRC RSU
BlockingThe CEN DSRC UL and the interfering ITS-G5 signal sum up in the CEN DSRC RSU receiverRSU receiver. The RSU sensitivity at the antenna for a left hand circular polarised CEN DSRC UL is about -110 dBm to -120 dBm. Therefore the input low noise amplifier or the input mixer can be saturated by a much stronger interference p p y gsignal even it is not in the CEN DSRC UL frequency band.The interference level that causes this so called blocking, strongly depends on the CEN DSRC implementation.
Spurious and unwanted emissionsIf the ITS-G5 unwanted emissions in the CEN DSRC UL frequencyIf the ITS G5 unwanted emissions in the CEN DSRC UL frequency band exceed -120dBm, interference to the CEN DSRC UL will start to happen.
Workshop / Coexistence between CEN DSRC and ITS G5 13
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Interference from CEN DSRC RSU to ITS-G5
In theory blocking and interference by unwanted emissions of the CEN DSRC RSU can also happen to ITS-G5 stations.
But...... since the antenna food print of the CEN DSRC stations is very small, the
ibl i t f d t th ITS G5 i ti illpossible interference area compared to the ITS-G5 communication range will be very small.... since the input sensitivity of the ITS-G5 station is only in the order of -80 to -90 dBm it will be less sensitive to interference signals compared to CEN-90 dBm it will be less sensitive to interference signals compared to CEN DSRC.... measurements showed no interference from CEN DSRC to ITS-G5.
Interference from the CEN DSRC OBU to an ITS-G5 station has no practical relevance because of the low output power level of the passive backscatter technology used in the OBUpassive backscatter technology used in the OBU.
Workshop / Coexistence between CEN DSRC and ITS G5 14
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Coexistence considerationsCoexistence considerations
ITS_WG4#13, Coexistence between CEN DSRC and ITS-G5 15
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Power coexistence limits evaluated by STF 395
Within a CEN DSRC Tolling Zone the electric field strength of a fi d ITS G5 t ti h ll t
Lane Width (*)
fixed ITS-G5 station shall not exceed 0,11V/m (-52 dBm).
10m Tolling Zone (**)
At the CEN DSRC RSU antenna the field strength of a fixed ITS-G5 station shall not exceed 0 21 V/m
CEN DSRC RSU CEN DSRC RSU
station shall not exceed 0,21 V/m (-46 dBm).
10mTolling Zone (**)
Lane Width*) The width of the CEN DSRC tolling zone is given by the number of parallel lanes. Usually one RSU is used per lane.
(*)
**) Mobile enforcement vehicles will not have a fixed Tolling
Workshop, Coexistence between CEN DSRC and ITS-G5 16
) gZone position or RSU position.
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How to achieve coexistence
Detect Identify the position of the mitigation areaDetect
A
Identify the position of the mitigation area
And
Avoid Avoid interference by a set of Coexistence Methodsy
Workshop, Coexistence between CEN DSRC and ITS-G5 17
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Coexistence MethodsCoexistence Methods
Workshop, Coexistence between CEN DSRC and ITS-G5 18
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CEN DSRC RSU
Fixed tolling stationCEN DSRC RSUmounted ongantry
RTTT
mobileITS-G5 RTTT
OBUstation
Interference can only happen when the CEN DSRC OBU is inside the tolling zone.
Workshop, Coexistence between CEN DSRC and ITS-G5 19
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CEN DSRC RSU
Power coexistence mitigation areas40
CEN DSRC RSUmounted ongantry
35
30
dBm
EIR
P
25 dB
33 dBm17
0 m
Pathloss coefficient n=1.8
25
20
15ut p
ower
lim
it / d 25 dBm
70 m
B is
olat
ion
B is
olat
ion
mum
mum
mobileITS-G5 RTTT15
10
5
ITS-
G5
Out
p
10 dBm 75 d
B
82 d
Bm
inim
min
imstationRTTTOBU
0
-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200Distance to CEN DSRC tolling station / m
schematically - not true scale!
Workshop, Coexistence between CEN DSRC and ITS-G5 20
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Power coexistence mitigation areas40
35
30
dBm
EIR
P
25 dB
33 dBm17
0 m
Pathloss coefficient n=1.8
( ) 6 8-10-dlog18P ⋅=25
20
15ut p
ower
lim
it / d 25 dBm
70 m
B is
olat
ion
B is
olat
ion
mum
mum
( ) 6.810dlog18PTX =
15
10
5
ITS-
G5
Out
p
10 dBm 75 d
B
82 d
Bm
inim
min
im
0
-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200Distance to CEN DSRC tolling station / m
10 dBm ITS-G5 output power level assures coexistence (Non interference mode).
Higher power levels are possible at more than 20 m distance to the tolling station or when a time sharing method is used alternatively
Workshop, Coexistence between CEN DSRC and ITS-G5 21
station or when a time sharing method is used alternatively.
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Principles of time sharing coexistenceTime sharing can work when ITS-G5 is in Low Duty Cycle (LDC) operation.R
SU
RX
/ TX
TX RX TX X retry RX ....
Additionally to the channel load, ITS-G5 channel usage timing constraints g gmust be specified.
ITS-
G5
activ
ity ....(*)
STF 411 is dealing with LDC methods.
STF 420 on ITS-G5 channel configurationX
2520151050
STF 420 on ITS-G5 channel configuration could consider this topic.
OB
U
RX
/ TX XTXRX TXRX ....
*) Interference will usually happen in CEN DSRC down link.2520151050
Workshop, Coexistence between CEN DSRC and ITS-G5 22
time / ms) Interference will usually happen in CEN DSRC down link.
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Proposed LDC operation35
Bm
30
25
20
ower
lim
it / d
B
tati
15
10
5
-G5
outp
ut p
o
Additionally to the channel load, the maximum ITS-G5 channel activity time ta
0ITS-
time
and the minimum idle time ti should be specified.
Because of CSMA/CS, an ITS-G5 station monitors the channel continuously. This can be used to determine whether the channel was idle for at least time tThis can be used to determine whether the channel was idle for at least time ti
or active for time ta. The experiments here at JRC will help to find out whether CSMA/CS sensitivity is sufficient to ensure coexistence.
Workshop, Coexistence between CEN DSRC and ITS-G5 23
During idle time, the channel can still be used with a power level of less than 10 dBm.
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Mitigation area identification
Part 1
Workshop, Coexistence between CEN DSRC and ITS-G5 24
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90
Isolation estimation methods - principle85
80
75
70
65isol
atio
n / d
B Pathloss coefficient n=1.8Fading margin +/- 6dB
( )dlog189.47 ⋅+=Isolation
60
55
( )g
50
-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180 200Distance to beacon / m
Due to fading the isolation can vary by ±6 dB around its expected valueDue to fading, the isolation can vary by ±6 dB around its expected value.
To ensure coexistence, the worst case minimum isolation is essential.
The use of an RF signal detector can directly estimate this minimum isolation
Workshop, Coexistence between CEN DSRC and ITS-G5 25
The use of an RF signal detector can directly estimate this minimum isolation.
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Example: CEN DSRC signal detectorExpected maximum(*) isolation to a CEN DSRC signal while passing the RSUExpected maximum(*) isolation to a CEN DSRC signal while passing the RSU
CEN DSRC RSUmounted ongantryg y
95
90
85
Pathloss coefficient n=1.8Fading margin +6dB
80
75
70latio
n / d
B
70
65
60
55
iso
2001901801701601501401301201101009080706050403020100Distance to beacon / m
55
50
Workshop , Coexistence between CEN DSRC and ITS-G5 26
*) Because of fading, the isolation between detector and RSU might differ from the isolation to the victim.
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Example: CEN DSRC signal detectorThe TX power level and the antenna characteristics of CEN DSRC are standardised*.
CEN DSRC RSUmounted ongantry
The TX power level and the antenna characteristics of CEN DSRC are standardised .
g y
65
-60
-55
d / d
Bm
B is
olat
ion
mum
B is
olat
ion
mum
detector RX level threshold
-75
-70
-65
tect
or th
resh
old
Pathloss coefficient n=1.8Fading margin +6dB
75 d
B
min
im82
dB
min
im-72 dBm
-85
-80
75
CEN
DSR
C d
e Fading margin +6dBpolarization margin +3dB
mm
-79 dBm
-90
2001901801701601501401301201101009080706050403020100
Distance to beacon / m
170
m
70 m
Workshop, Coexistence between CEN DSRC and ITS-G5 27
*) Outside the main lobe of the RSU antenna the TX power level is 18 dBm EIRP.
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Example: CEN DSRC signal detectorExample of combination with power coexistence areas (*)
CEN DSRC RSUmounted ongantry
Example of combination with power coexistence areas
g y
65
-60
-55
d / d
Bm
70
60
50
ITS
B is
olat
ion
mum
B is
olat
ion
mum
detector RX level threshold ITS-G5 TX power limit
-75
-70
-65
tect
or th
resh
old 50
40
30
TX power lim
it /
Pathloss coefficient n=1.8Fading margin +6dB
33 dBm75
dB
min
im82
dB
min
im-72 dBm
-85
-80
75
CEN
DSR
C d
e 30
20
10
/ dBm
EIRP
Fading margin +6dBpolarization margin +3dB
m
25 dBm
m
10 dBm
-79 dBm
-90
2001901801701601501401301201101009080706050403020100
Distance to beacon / m
0170
m
70 m
Workshop, Coexistence between CEN DSRC and ITS-G5 28
*) As another option LDC could be combined with a CEN DSRC signal detector.
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SummaryNon interference mode with 10 dBm ITS-G5 TX power level
no identification of CEN DSRC Toll Station needed
Non interference mode can also be implemented by use of the proposed LDC operation.
no identification of CEN DSRC Toll Station needed
Combination of power coexistence method and time sharingCombination of power coexistence method and time sharing coexistence (LDC) is possible in one device, but also can coexist from a system view perspective.
The actual isolation from the victim can be directly estimated by use of an RF detector (no indirect position based estimation).
Workshop, Coexistence between CEN DSRC and ITS-G5 29
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Thank you for your attentionThank you for your attention
Workshop, Coexistence between CEN DSRC and ITS-G5 30
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AbbreviationsCEN Comité Européen de NormalisationCSMA/CA Carrier Sense Multiple Access with Collision AvoidanceCH ChannelCVIS Cooperative Vehicle-Infrastructure SystemsDAA Detect And AvoidDL Down LinkDSRC Dedicated Short Range CommunicationEIRP Equivalent Isotropic Radiated PowerEN European NormETC Electronic Toll CollectionETSI E T l i ti St d d I tit tETSI European Telecommunication Standard InstituteIEEE Institute of Electrical and Electronics EngineersITS Intelligent Transport SystemITS-G5 acronym for the 5,9 GHz vehicular adhoc network PHY LDC Low Duty CycleLHCP Left Hand Circular PolarizedLHCP Left Hand Circular PolarizedMLFF Multi Lane Free FlowOBU OnBoard UnitOFDM Orthogonal Frequency Division MultiplexPHY PHYsical (OSI layer)RF Radio FrequencyRF Radio FrequencyRSU RoadSide UnitRX ReceiveTS Technical SpecificationTX TransmitUL UpLinkUL UpLink
Workshop / Coexistence between CEN DSRC and ITS-G5 31