ETSI TS 102 792 V1.1.1 (2012-10)

Technical Specification
Intelligent Transport Systems (ITS);
Mitigation techniques to avoid interference between European
CEN Dedicated Short Range Communication (CEN DSRC)
equipment and Intelligent Transport Systems (ITS)
operating in the 5 GHz frequency range

2 ETSI TS 102 792 V1.1.1 (2012-10)

Reference
DTS/ITS-0040013
Keywords
DSRC, ITS, radio, RTTT
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ETSI
3 ETSI TS 102 792 V1.1.1 (2012-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Symbols and abbreviations . 8
3.1 Symbols . 8
3.2 Abbreviations . 9
4 General overview . 10
4.1 Introduction to coexistence. 10
4.2 Restrictions and mitigation methods overview. 10
4.2.1 Power restrictions and muting of ITS-G5A/B stations . 10
4.2.2 Duty cycle restrictions (DCR) of ITS-G5A/B stations . 11
4.2.3 Additional coexistence measure for mobile ITS stations . 11
4.2.3.1 Additional coexistence measure introduction . 11
4.2.3.2 Detect and Avoid principle . 11
4.2.3.3 Detection of tolling stations . 11
4.2.3.3.1 Radio Identification of the tolling station . 11
4.2.3.3.2 Beaconing . 12
4.2.3.3.3 Static and dynamic Map-based identification . 12
4.2.4 Implementation guide of basic coexistence measures. 12
4.2.4.1 Coexistence measures for fixed ITS-G5A/B stations . 12
4.2.4.2 Coexistence measures for mobile ITS-G5A/B stations . 12
4.3 Summary of limits and methods for interference free operation of ITS-G5A/B and CEN DSRC . 13
4.4 Document structure . 14
5 Coexistence measures and limits . 14
5.1 Coexistence scenarios . 14
5.2 Field strength limits within the Tolling Zone . 15
5.3 Duty cycle limits for ITS-G5A/B stations . 15
6 Coexistence measures for mobile ITS-G5A/B stations . 16
6.1 Tolling Zone radio detection methods . 16
6.1.1 Introduction to radio detection and power regulation methods . 16
6.1.2 Detection of CEN DSRC radio signals . 16
6.2 Methods to avoid interference . 17
6.2.1 ITS muting . 17
6.2.1.1 Introduction to ITS muting . 17
6.2.1.2 Direct interface to a CEN DSRC OBU to invoke ITS muting . 18
6.2.1.3 Use of RF detection unit to invoke ITS muting . 18
6.2.2 Output power regulation . 19
6.2.2.1 Basic requirements of the output power regulation . 19
6.2.2.2 Use of RF detection unit to control the ITS-G5A/B output power level . 19
6.2.3 Duty Cycle Restriction (DCR) mode . 20
7 Coexistence measures for fixed ITS-G5A/B stations . 21
7.1 Coexistence by field strength and duty cycle limitation . 21
7.2 Coexistence by CEN DSRC MAC synchronization with ITS . 21
Annex A (informative): Recommendations for interference limits of CEN DSRC receivers . 22
A.1 CEN DSRC RSU receiver blocking capability . 22
ETSI
4 ETSI TS 102 792 V1.1.1 (2012-10)
A.2 CEN DSRC OBU receiver blocking capability . 22
Annex B (informative): Calculations and examples . 23
B.1 Examples of coexistence scenarios . 23
B.1.1 Overview of coexistence scenario examples . 23
B.1.2 Example of interference to a CEN DSRC RSU . 23
B.1.3 Example of interference to a CEN DSRC OBU . 24
B.2 Path loss model . 24
B.3 Calculation of the coexistence limit for the CEN DSRC down link . 25
B.3.1 Calculation outline . 25
B.3.2 CEN DSRC OBU receiver structure . 25
B.3.3 Calculation of the CEN DSRC receiver threshold value . 25
B.3.4 Calculation of the OFDM signal statistics . 26
B.3.5 Maximum output power of an interfering ITS station being in a CEN DSRC communication zone . 28
B.3.5.1 Example of cars driving in adjacent lanes . 28
B.3.5.2 Example of cars driving behind each other . 28
B.3.6 Maximum output power level of an interfering ITS station after leaving a CEN DSRC communication
zone . 29
B.3.7 Idle time T as function of the number of interferes. 30
off
B.4 Calculation of CEN DSRC detector sensitivity . 31
B.5 CEN DSRC uplink blocking . 32
B.5.1 Measurement setup for the determination of CEN DSRC RSU blocking characteristics . 32
B.5.2 Measurement results of CEN DSRC RSU blocking characteristics . 33
B.5.3 CEN DSRC RSU blocking: Summary and conclusions . 34
B.5.4 CEN DSRC RSU blocking: Example . 34
B.6 Calculation of maximum CEN DSRC receive power level at ITS-G5 mobile station . 34
B.7 Examples of coexistence scenarios with fixed ITS stations . 34
B.8 Implementation example of a mobile ITS-G5A/B station with power regulation and radio
detection of CEN DSRC RSU . 36
Annex C (informative): CEN DSRC station types . 38
C.1 CEN DSRC basics . 38
C.2 Toll plazas and access applications . 38
C.3 Multilane free flow tolling . 38
C.4 Mobile enforcement . 38
Annex D (informative): Ranking of coexistence options . 39
D.0 Ranking criteria and summary . 39
D.1 CEN DSRC Detector . 39
D.2 DCR method . 40
D.3 ITS beacon . 40
D.4 Dynamic geographic database of all CEN DSRC stations . 40
D.5 CEN DSRC MAC synchronization with fixed ITS stations . 41
D.6 Transition for road tolling technology from CEN DSRC to ITS . 41
History . 42

ETSI
5 ETSI TS 102 792 V1.1.1 (2012-10)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport System (ITS).
Introduction
Without the use of special mitigation techniques, European CEN Dedicated Short Range Communication (DSRC)
equipment operating in the frequency range from 5 795 MHz to 5 815 MHz might suffer from harmful interference
caused by Intelligent Transport Systems (ITS) using adjacent frequency bands. The present document specifies methods
to ensure coexistence of both systems.
ETSI
6 ETSI TS 102 792 V1.1.1 (2012-10)
1 Scope
As shown in TR 102 654 [i.10] and TR 102 960 [i.16] previously, interference from ITS-G5 A/B to CEN DSRC might
occur in close proximity to ETC zones if no mitigation techniques are applied. The present document deals in detail
with different techniques to ensure coexistence of ITS-G5A/B and CEN DSRC.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
[1] CEN EN 12253: "Road transport and traffic telematics - Dedicated short-range communication -
Physical layer using microwave at 5,8 GHz".
[2] ETSI EN 300 674 (parts 1, 2-1 and 2-2): "Electromagnetic compatibility and Radio spectrum
Matters (ERM); Road Transport and Traffic Telematics (RTTT); Dedicated Short Range
Communication (DSRC) transmission equipment (500 kbit/s / 250 kbit/s) operating in the 5,8 GHz
Industrial, Scientific and Medical (ISM) band".
[3] ISO 21218: "Intelligent transport systems - Communications access for land mobiles (CALM) -
Medium service access points".
[4] ISO 24102: "Intelligent transport systems - Communications access for land mobiles (CALM) -
Management".
[5] IEEE 802.11: "IEEE Standard for Information Technology - Telecommunications and information
exchange between systems Local and metropolitan area networks - Specific requirements;
Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
[6] ETSI EN 302 571: "Intelligent Transport Systems (ITS); Radiocommunications equipment
operating in the 5 855 MHz to 5 925 MHz frequency band; Harmonized EN covering the essential
requirements of article 3.2 of the R&TTE Directive".
[7] ETSI ES 202 663: "Intelligent Transport Systems (ITS); Access layer specification for Intelligent
Transport Systems operating in the 5 GHz frequency band".
[8] ETSI TS 102 724: "Intelligent Transport Systems (ITS); Harmonized Channel Specifications for
Intelligent Transport Systems operating in the 5 GHz frequency band".
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] CVIS project: "CVIS COMM Interference measurements test report", February 2010.
ETSI
7 ETSI TS 102 792 V1.1.1 (2012-10)
[i.2] CEN EN 12795: "Road transport and traffic telematics - Dedicated Short Range, Communication
(DSRC) - DSRC data link layer: medium access and logical link control".
[i.3] CEN EN 12834: "Road transport and traffic telematics - Dedicated Short Range Communication
(DSRC) - DSRC application layer".
[i.4] CEN EN 15509: "Road transport and traffic telematics - Electronic fee collection; Interoperability
application profile DSRC".
[i.5] CEPT ECC Report 127: "The impact of receiver parameters on spectrum management".
[i.6] L. Cheng, B. E. Henty, F. Bai, and D. D. Stancil: "Highway and rural propagation channel
modeling for vehicle-to-vehicle communications at 5.9 GHz" in Proc. IEEE Antennas Propagation
Soc. Int. Symp., July 2008, pp. 1-4.
[i.7] J. Kunisch and J. Pamp: "Wideband car-to-car radio channel measurements and model at 5.9 GHz"
in Proc. IEEE Veh. Technol. Conf. 2008 fall, September 2008.
[i.8] J. Karedal, N. Czink, A. Paier, F. Tufvesson, and A. F. Molisch: "Pathloss Modeling for
Vehicle-to-Vehicle Communications", to appear in IEEE Transactions on Vehicular Technology,
2010.
[i.9] L. Bernadó, T. Zemen, N. Czink, P. Belanovic: "Physical Layer Simulation Results for IEEE
802.11p using Vehicular non-Stationary Channel Model", IEEE International Communications
Conference (ICC) 2010 Workshop on Vehicular Connectivity, Cape Town, South Africa, May
23-27, 2010.
[i.10] ETSI TR 102 654: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Road
Transport and Traffic Telematics (RTTT); Co-location and Co-existence Considerations regarding
Dedicated Short Range Communication (DSRC) transmission equipment and Intelligent Transport
Systems (ITS) operating in the 5 GHz frequency range and other potential sources of interference".
[i.11] CEN/ISO EN 14906: "Road transport and traffic telematics; Electronic fee collection; Application
interface definition for dedicated short-range communication".
[i.12] CEN/ISO TS 14907-1: "Road transport and traffic telematics - Electronic fee collection - Test
procedures for user and fixed equipment - Part 1: Description of test procedures".
[i.13] CEN/ISO TS 14907-2: "Road transport and traffic telematics - Electronic fee collection - OBU
conformance test procedures".
[i.14] ETSI TS 102 486: "Intelligent Transport Systems (ITS); Road Transport and Traffic Telematics
(RTTT); Test specifications for Dedicated Short Range Communication (DSRC) transmission
equipment".
[i.15] CEN EN 15876: "Electronic fee collection - Conformity evaluation of on-board unit and roadside
equipment to EN 15509".
[i.16] ETSI TR 102 960: "Intelligent Transport Systems (ITS); Mitigation techniques to avoid
interference between European CEN Dedicated Short Range Communication (RTTT DSRC)
equipment and Intelligent Transport Systems (ITS) operating in the 5 GHz frequency range;
Evaluation of mitigation methods and techniques".
[i.17] ETSI TR 100 028-2: "ETSI TR 100 028 -2: "Electromagnetic compatibility and Radio spectrum
Matters (ERM); Uncertainties in the measurement of mobile radio equipment characteristics;
Part 2".
ETSI
8 ETSI TS 102 792 V1.1.1 (2012-10)
3 Symbols and abbreviations
3.1 Symbols
For the purposes of the present document, the following symbols apply:
A Coefficient for T definition
off
α opening angel of CEN DSRC OBU antenna
a CEN DSRC signal level "high"
a CEN DSRC signal level "low"
a CEN DSRC decision threshold
thresh
B Coefficient for T definition
off
BP break point parameter: lower limit for T
Toff off
BP break point parameter: lower limit for T
Ton on
C Coefficient for T definition
off
c speed of light in vacuum (2,99792458 ⋅ 10 )
d distance
d reference distance for path loss model (1 m)
d distance to CEN DSRC RSU when approaching the Tolling Zone
a
d distance to CEN DSRC RSU when leaving the Tolling Zone
l
d separation of two lanes
lane
d minimum effective distance
min
(max)
maximum OFDM signal electrical field strength at the CEN DSRC OBU antenna
E
OFDM
f CEN DSRC carrier frequency
D
f ITS-G5 A/B carrier frequency

O
F (t) impulse response of LP filter
LP
i power index for CEN DSRC power level (either 1 or 2)
I Isolation from interferer to ensure coexistence (path loss)
PL
L antenna loss due to polarization or windscreen
ant
l detection distance margin
c
l detection distance
d
l minimum distance to CEN DSRC OBU
m
m modulation index
N number of interferers
n path loss coefficient
P CEN DSRC average power level
P CEN DSRC power level for the "high" signal
P CEN DSRC power level for the "low" signal
P CEN DSRC detector sensitivity
Dsens
P maximum CEN DSRC RSU EIRP output power level
DSRC
P CEN DSRC power level for power index i
i
PL free space path loss
PL free space path loss in 1 m distance
(max)
P maximum OFDM signal power level at the CEN DSRC OBU antenna
OFDM
(norm)
normalisation power level (1 W)
P
OFDM
P receive power level
Rx
P receive power level at ITS-G5 A/B antenna
RX_ITS
P CEN DSRC OBU RX sensitivity
sens
P transmit power level
Tx
P maximum transmit power level
TXmax
σ fading loss for path loss model
ETSI
9 ETSI TS 102 792 V1.1.1 (2012-10)
s(t) time domain signal at CEN DSRC receiver
(max)
maximum OFDM signal power density at the CEN DSRC OBU antenna
S
OFDM
s (t) imaginary part of complex ITS-G5 A/B baseband signal
I
s (t) time domain CEN DSRC signal for power index i
i DSRC
s (t) time domain CEN DSRC signal
DSRC
s (t) time domain signal after LP filter
LP
s (t) time domain ITS-G5 A/B signal after LP filter
LP-OFDM
(peak)
s peak value of time domain ITS-G5 A/B signal after LP filter
LP−OFDM
s (t) time domain ITS-G5 A/B signal
OFDM
s (t) real part of complex ITS-G5 A/B baseband signal
R
t time
T Minimum time between two transmissions in the DCR method
off
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ADC Analog Digital Converter
BER Bit Error Ratio
CDMA Code Division Multiple Access
CEN Comité Européen de Normalisation
CH Channel
CVIS Cooperative Vehicle-Infrastructure Systems
DAA Detect And Avoid
DCR Duty Cycle Restrictions
DENM Decentralised Environmental Notification Message
DL Down Link
DSRC Dedicated Short Range Communication
ECC Electronic Communications Committee
EFC Electronic Fee Collection
EIRP Equivalent Isotropic Radiated Power
EN European Norm
ETC Electronic Toll Collection
ETSI European Telecommunication Standard Institute
GNSS Global Navigation Satellite System
IEEE Institute of Electrical and Electronics Engineers
IPR Intellectual Property Rights
ISO International Standardisation Organisation
ITS Intelligent Transport System
ITS-G5 5,9 GHz vehicular adhoc network PHY
ITS-G5A/B vehicular adhoc network PHY for the frequency range 5 855 MHz to 5 925 MHz
ITS-S ITS Station
ITU International Telecommunication Union
LDM Local Dynamic Map
LHCP Left Hand Circular Polarized
LoS Line of Sight
LP Low Pass (filter) or Linear Polarized
MAC Medium Access Control
MLFF MultiLane Free Flow
OBU OnBoard Unit
OFDM Orthogonal Frequency Division Multiplex
PHY PHYsical (OSI layer)
RF Radio Frequency
RSU RoadSide Unit
RX Receive
ETSI
10 ETSI TS 102 792 V1.1.1 (2012-10)
SA Spectrum Analyzer
TS Technical Specification
TX Transmit
UL UpLink
4 General overview
4.1 Introduction to coexistence
To ensure coexistence between CEN DSRC and ITS-G5A/B stations, the transmission behaviour of the ITS-G5A/B
station shall fulfil restrictions related to the transmission power level, to the transmission duty cycle, or to both,
depending on the separation distance to the Tolling Zone and the number of interfering ITS-G5A/B stations. The
present document specifies the limits and methods that shall be applied to ensure coexistence. Additionally, the
technical specification on ITS-G5A/B Channel configuration [8] defines how these limits and methods shall be used
under DCC control.
The complexity of the coexistence measure depends on the ITS-G5A/B output power level, the actual spatial density of
the ITS-G5A/B stations and the actual separation distance between the IT-G5A/B station and the potential victim tolling
station. The higher the actual maximum output power level and the more ITS-G5A/B stations are actually in range of
the potential victim tolling station, the more sophisticated coexistence measures are necessary.
Different possible coexistence measures and the corresponding limits are specified in clauses 4.2, 4.3, 5, and 6.2, their
applicability is summarized in table 4.1.
As shown in table 4.1, the applicable coexistence measure depends mainly on the actual maximum output power range
and the ITS-G5A/B antenna type used by the mobile ITS station. Which coexistence measure shall be applied in some
special cases with alternative ITS-G5A/B antenna types not included in Table 4.1 is specified by electrical field strength
limits given in clause 5.2.
Clauses 4.2.3.3 and 6.1 describe how the Tolling Zone can be detected and identified in case additional mitigation
techniques are needed that adapt the ITS-G5A/B transmission power level and/or the transmission duty cycle to the
separation distance to the Tolling Zone.
Methods to ensure coexistence of fixed ITS-G5A/B stations and CEN DSRC devices (OBU or RSU) are given in
clause 7. Examples how these limits can be met are given in clause B.7.
An implementation example for mobile ITS-G5A/B stations is given in clause B.8.
4.2 Restrictions and mitigation methods overview
4.2.1 Power restrictions and muting of ITS-G5A/B stations
An ITS-G5A/B station can restrict the TX power level to a value where no harmful interference will occur to a CEN
DSCR victim tolling station. The maximum allowed TX power level is in general dependent on the radio isolation
between the interferer (ITS-G5A/B station) and the victim (tolling station). The lower the isolation and thus the distance
between the two systems the lower the maximum allowed TX power level for the ITS-G5A/B system. For different
isolation values and thus distances between the two systems the maximum TX power levels can be evaluated, see
clauses 6.2.2.1 and B.7.
For ITS-G5A/B installations where the transmit antenna has no fixed position, e.g. hand held devices, or where the
ITS-G5A/B antenna is mounted very close to the CEN DSRC OBU, the ITS-G5A/B transmit signal shall be muted
during a CEN DSRC toll transaction. Alternatively the ITS-G5A/B device can transmit short bursts of data with long
pauses in between to avoid harmful interference. The timing of these bursts and pauses is specified by the duty cycle
restrictions (DCR).
ITS-G5A/B installations with a fixed transmit antenna position that is more than 1,5 m away from the CEN DSRC OBU
and that transmit with a power level of up to 10 dBm will not generate any interference to the CEN DSRC tolling
system. Closer distances to the CEN DSRC OBU are possible if the field strength limit at the CEN DSRC OBU is not
exceeded as described in clause 6.2.1.1.
ETSI
11 ETSI TS 102 792 V1.1.1 (2012-10)
4.2.2 Duty cycle restrictions (DCR) of ITS-G5A/B stations
The basic coexistence investigation and evaluation are based on the assumption that an ITS-G5A/B system is
continuously transmitting a signal, thus having a duty cycle of 100 %. Since the CEN DSRC protocol is based on a
packet communication, a restriction of the duty cycle of the ITS-G5A/B system will lead to a significantly lower
potential of harmful interference to the CEN DSRC system even the maximum allowed TX power level is exceeded.
Based on exhaustive simulations, a duty cycle restriction can be defined which can guarantee coexistence between the
two systems without the risk of harmful interference generated from ITS-G5A/B to CEN DSRC (see clause 5.3).
This restriction shall been taken into account in the G5A/B channel configuration specification [8].
4.2.3 Additional coexistence measure for mobile ITS stations
4.2.3.1 Additional coexistence measure introduction
In case an ITS-G5A/B station needs to operate outside the limits (TX power, Duty Cycle, separation distance), which
are given for an interference free operation, additional coexistence techniques shall be implemented based on the actual
situation and distance to the tolling station.
The additional coexistence measures can essentially be split into two main operations:
• Tolling Zone detection operation
• Interference avoidance operation
Therefore, this additional measure is called "Detect and Avoid" (DAA). In the first step the need for an interference
avoidance operation will be identified by detecting the presence of a CEN DSRC tolling station in the near vicinity. As
a result of this detection process, if required the suitable interference avoidance operation will then be taken.
In the present document a Tolling Zone detection method and the appropriate interference avoidance operations are
specified.
In annex D a ranking of different detection methods is summarized.
4.2.3.2 Detect and Avoid principle
Detect and Avoid is a combination between a victim identification operation and an interference avoidance operation. In
general, the detection of the victim to be protected can be performed by doing any feasible identification method.
E.g. the detection process can be done by evaluating the isolation between the ITS-G5A/B station and the CEN DSRC
tolling station based on radio measurements, by beaconing information, or by geographical information contained in
static or dynamic maps (see clause 4.2.3.3).
Based on the result of the isolation evaluation the interference avoidance can then apply and configure the required
coexistence mechanism process (e.g. TX power reduction, duty cycle restriction, …).
4.2.3.3 Detection of tolling stations
4.2.3.3.1 Radio Identification of the tolling station
The radio identification of a CEN DSRC tolling station is based on a signal strength measurement of the CEN DSCR
RSU signal at the position of the potentially interfering ITS-G5A/B station. Based on the actual measured signal
strength and the known EIRP level of the CEN DSCR RSU the ITS-G5A/B station can estimate the isolation towards
the possible victim tolling station (see clause 6.1). In the present document three isolation zones are given as example in
clause B.8 to protect the CEN DSRC tolling stations. The corresponding requirements are in clause 6.2.2.1. For
isolation values above 85 dBm the TX power restriction of 33 dBm as already specified in [6] is sufficient.
ETSI
12 ETSI TS 102 792 V1.1.1 (2012-10)
4.2.3.3.2 Beaconing
The ITS-G5A/B system could implement a message that commands a specific behaviour of the ITS-G5A/B station in a
defined geographical area around a potential victim. In the scope of the present document this victim is a CEN DSCR
tolling station. The message could include control parameter for the cross layer DCC Management entity overwriting
the standard settings for the DCC control. The ITS beacon would be installed close to the potential victim tolling station
and would send out the beaconing message in fixed periodicity. This message and the corresponding applications need
to be specified elsewhere and are out of scope of the present document.
4.2.3.3.3 Static and dynamic Map-based identification
In a map based identification approach the geographical positions of the potential victim station would be stored in the
ITS-G5A/B station entirely, or they would be transferred to the ITS-G5A/B station for a specific region when needed.
The actual position of the vehicle could be compared to the stored positions and based on the evaluated distance the
required mitigation method could be applied. No further investigations of this detection method have been performed.
The topic is for further studies and is not specified in the present document.
4.2.4 Implementation guide of basic coexistence measures
4.2.4.1 Coexistence measures for fixed ITS-G5A/B stations
Since fixed ITS-G5A/B stations cannot move through the Tolling Zone, the maximum transmit power level that avoids
harmful interference to CEN DSRC can be evaluated from the isolation distance to the victim tolling station. If the
maximum transmit power level is exceeded, either duty cycle restrictions shall be applied or the CEN DSRC signal
shall be synchronised with the ITS-G5A/B transmission in a way that they are communicating in different time slots.
4.2.4.2 Coexistence measures for mobile ITS-G5A/B stations
Since CEN DSRC OBUs and mobile ITS-G5A/B stations can be mounted in the same vehicle, the distance between the
two devices can be short. Especially handheld ITS-G5A/B stations can be mounted only some centimetres away from
the OBU, therefore these devices shall mute their transmission at least temporally while passing a toll station (see
clause 4.2.1). Other mobile ITS-G5A/B stations need to have coexistence measures implemented only when they are
transmitting with more than 10 dBm output power level.
The present document specifies following mitigation techniques and combinations that can avoid harmful interference
to CEN DSRC under the restrictions listed in table 4.1:
• Only DCR:
Duty cycle restrictions (DCR) in combination with a transmit power control are used continuously without
detection of the Tolling Zone (see clause 6.2.3). In this case DCR applies to transmissions with a transmit
power level above 10 dBm only.
• Muting with DCR:
Duty cycle restrictions in combination with a transmit power control are used continuously without detection
of the tolling zone (see clause 6.2.3). In this case DCR applies to all transmissions (no transmissions are
possible during T ).
off
• DAA + power regulation:
Detection of the distance to the Tolling Zone and control of the ITS-G5A/B transmit power level accordingly
(see clause 6.2.2).
• DAA + DCR:
Detection of the distance to the Tolling Zone and application of DCR (see clause 6.2.3) to all transmissions
that exceed the ITS-G5A/B transmit power levels specified in clause 6.2.2.1. Usually this also includes an
ITS-G5A/B transmit power control as supplement to DCR.
• DAA + muting:
Detection of the Tolling Zone and muting of the ITS-G5A/B transmission while a CEN DSRC transaction is
performed or while the Tolling Zone is passed (see clause 6.2.1).
ETSI
13 ETSI TS 102 792 V1.1.1 (2012-10)
• DAA + muting and power regulation:
Detection of the Tolling Zone and muting of the ITS-G5A/B transmission while a CEN DSRC transaction is
performed or while the Tolling Zone is passed (see clause 6.2.1). Outside the Tolling Zone the transmit power
levels are controlled according to the detected distance to the Tolling Zone as specified in clause 6.2.2.1.
• DAA + muting with DCR:
Detection of the distance to the Tolling Zone and application of DCR (see clause 6.2.3) to all transmissions
that exceed the ITS-G5A/B transmit power levels specified in clause 6.2.2.1. Within the Tolling Zone or while
a CEN DSRC transaction is performed, DCR is applied to all ITS-G5A/B transmissions. Usually this
combination also includes an ITS-G5A/B transmit power control as supplement to DCR.
Table 4.1 summarises the applicability of these coexistence measures.
Table 4.1: Summary of coexistence measures for mobile ITS stations (for details see clause 6.2)
ITS-G5A/B antenna type
External vehicle antenna Internal antenna
and (included in the ITS station)
ITS-G5A/B output power range
field strength limit at CEN or
DSRC OBU for P = 10 dBm field strength limit at CEN DSRC
Tx
OBU for P = 10 dBm exceeded
not exceeded Tx
Muting with DCR
No coexistence measures or
≤ 10 dBm
DAA + muting
Only DCR
Muting with DCR
or
or
> 10 dBm ≤ 33 dBm DAA + power regulation
DAA + muting and power regulation
or
or
DAA + DCR
DAA + muting with DCR
Calculations, measurements, and further examples of coexistence measures of mobile ITS-G5A/B stations are given in
clauses B.3 and B.5.
4.3 Summary of limits and methods for interference free
operation of ITS-G5A/B and CEN DSRC
In general the following limits and methods apply to an ITS-G5A/B system for an interference free operation toward a
CEN DSRC tolling station:
TX power limitation: For ITS-G5A/B station with a TX power level equal or below 10 dBm no interference towards a
CEN DSRC tolling system will occur if the ITS-G5A/B antenna is mounted in a fixed position more than 1,5 m away
from the CEN DSRC OBU (e.g. on the rooftop of the car). In this case no additional limitations related to the duty cycle
are required.
TX power level muting: In case of handheld devices with no fixed mounting positions, or fix mounted ITS antennas in
close vicinity to the OBU mounting position, the transmission shall be at least temporarily muted within the CEN
DSRC Tolling Zone. The duty cycle of the muting is defined by the Duty Cycle Restrictions (DCR).
Duty Cycle Restrictions: For ITS-G5A/B station with a maximum packet burst duration of 5 ms and a minimum
packet burst spacing of T according to equation (5.1) in clause 5.3 no harmful interference will occur toward a CEN
off
DSRC tolling system. The ITS-G5A/B TX power level influences the number of interferers N and thereby has an
impact on the outcome of equation (5.1). Depending on whether ITS muting (clause 6.2.1) applies, the transmission
shall be stopped (muted) or can be continued with a TX power level of up to 10 dBm during T . The highest possible
off
transmission duty cycle can be reached when no other ITS-G5A/B station is exceeding the electric field strength limit at
the victim CEN DSRC OBU. In this case of a single interferer a 5 ms transmission burst shall be followed by a 50 ms
transmission pause, resulting in 9,1 % duty cycle.
Separation distance: Assuming the limitation of 33 dBm to the TX power level of an ITS-G5A/B station. No harmful
interference will occur toward a CEN DSRC tolling system form an ITS-G5A/B station operating in a distance of more
than 170 m away.
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14 ETSI TS 102 792 V1.1.1 (2012-10)
In the ITS-G5A/B channel configuration specification [8] these limits have been taken into account to define a proper
operation of the ITS-G5A/B system under DCC control.
4.4 Document structure
The present document is structured in the following way:
Clause 5 summarises all normative limits and specifications to define appropriate techniques to ensure
coexistence of CEN DSRC [1] and [2], ITS-G5A/B [6] and [7] devices.
Clause 6 describes the coexistence measures for mobile ITS stations in detail.
Clause 6.1 defines Tolling Zone detection methods.
Clause 6.2 defines methods to avoid interference.
Clause 7 specifies the coexistence measures for fixed ITS stations.
Annex A recommends interference limits of CEN DSRC receivers (RSU and OBU).
Annex B contains calculations and examples.
Clause B.1 shows examples of coexistence scenarios.
Clause B.2 outlines the path loss model used for calculation of all coexistence limits.
Clause B.3 provides a thorough calculation and examples of the interference to CEN DSRC OBUs by
ITS-G5A/B stations.
Clause B.4 contains the calculation of the CEN DSRC detector sensitivity, necessary to invoke interference
avoidance methods.
Clause B.5 shows measurement results of CEN DSRC uplink blocking.
Clause B.6 describes the interference from CEN DSRC to ITS-G5 mobile stations.
Clause B.7 shows examples of coexistence scenarios with fixed ITS stations.
Clause B.8 gives an implementation example of a mobile ITS-G5A/B station with power regulation and radio
detection of CEN DSRC RSU.
Annex C is a summary of CEN DSRC and EFC basics.
Annex D compares different coexistence options.
5 Coexistence measures and limits
5.1 Coexistence scenarios
Some examples of coexistence scenarios are given in clause B.1. These examples show scenarios where techniques for
coexistence are necessary, because the electrical field strength limits defined for coexistence of CEN DSRC devices
(OBU or RSU) and ITS-G5A/B are exceeded (see clause 5.2).
The most important scenario is the passage of a CEN DSRC Tolling Zone by a mobile ITS-G5A/B station, where
interference
...