ETSI TS 102 792 V1.2.1 (2015-06)

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

RTS/ITS-00438

General Information

• Status: Published
• Publication Date: 17-Jun-2015
• Technical Committee: ITS WG4 - Media and Medium related
• Current Stage: 12 - Completion
• Due Date: 10-Jul-2015
• Completion Date: 18-Jun-2015
• Mandate: M/453

Standards Content (Sample)

ETSI TS 102 792 V1.2.1 (2015-06)






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

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2 ETSI TS 102 792 V1.2.1 (2015-06)



Reference
RTS/ITS-00438
Keywords
DSRC, ITS, radio, RTTT
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3 ETSI TS 102 792 V1.2.1 (2015-06)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions, symbols and abbreviations . 6
3.1 Definition . 6
3.2 Symbols . 7
3.3 Abbreviations . 7
4 General overview . 8
4.1 Introduction . 8
4.2 Field strength thresholds for coexistence . 10
4.3 ITS output power thresholds for coexistence . 10
4.4 Duty cycle limits . 10
4.5 Procedures . 10
5 Interference mitigation mechanisms. 11
5.1 Introduction and basic requirements. 11
5.2 Protected zone . 11
5.2.1 Protected zone definition . 11
5.2.2 Protected zone centre position . 11
5.2.2.1 Protected zone centre position overview . 11
5.2.2.2 Temporary protected zone centre positions . 12
5.2.2.3 Protected zone centre position list . 12
5.2.3 Protected zone radius . 12
5.2.4 Protected zone database . 13
5.2.5 Short range protected zone radio detection . 14
5.3 Normal mode . 14
5.4 Coexistence mode. 14
5.5 Procedures . 15
5.5.1 Mobile and personal ITS stations . 15
5.5.2 Fixed ITS stations . 16
5.6 Additional requirements . 16
5.6.1 Personal equipment . 16
Annex A (informative): Calculations and examples . 17
A.1 Idle time Toff as function of the number of interferers . 17
A.2 Implementation example of a mobile ITS station with power level adjustment . 18
Annex B (informative): Recommendations . 20
B.1 Mobile ITS station antenna mounting . 20
Annex C (informative): Bibliography . 21
History . 23

ETSI

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4 ETSI TS 102 792 V1.2.1 (2015-06)
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 Systems
(ITS).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The band 5 795 MHz to 5 815 MHz has been harmonized for the use by Transport and Traffic Telematics (TTT), also
called CEN DSRC, by the EC decision 2013/752/EU [i.12] and the ECC recommendation ECC/REC/70-03 [i.13],
which is primarily used for road charging systems in Europe and elsewhere.
By issuing the Directive 2004/52/EC [i.14] of the European Parliament and of the Council and Commission Decision
2009/750/EC [i.15] the European Union has pointed to TTT to be used for road charging systems in Europe.
By issuing ECC/DEC/(08)01 [i.2] and ECC/REC/(08)01 [i.3] ECC has allocated the band 5 855 MHz to 5 925 MHz to
be used for Intelligent Transport Systems (ITS). In addition, the band 5875 MHZ to 5905 MHz has been harmonized for
the use in the EU by the EC decision 2008/671/EC [i.2]. These documents recommend ITS systems to be designed and
to be operated in a way to avoid harmful interference to TTT.
The present document specifies necessary measures to avoid such harmful interference.
ETSI

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5 ETSI TS 102 792 V1.2.1 (2015-06)
1 Scope
Radio transmissions in the ITS-G5A/B/D frequency bands (see ETSI EN 302 571 [i.5]) interfere with CEN DSRC using
the TTT band (see EC Decision 2013/752/EC [i.12]) when equipment from both systems are close to each other.
This was shown in ECC Report 101 [i.1], ECC Report 228 [i.8], ETSI TR 102 960 [i.7] and ETSI TR 102 654 [i.6].
The present document specifies requirements to ensure coexistence between ITS stations using the frequency bands
ITS-G5A/B/D and CEN DSRC using the TTT band. It is intended to be used as a basis for product development and for
development of suitable testing procedures to prove conformance to regulations.
2 References
2.1 Normative 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.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 302 637-2: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 2: Specification of Cooperative Awareness Basic Service".
[2] ETSI TS 102 894-2 (V1.2.1) (2014-09): "Intelligent Transport Systems (ITS); Users and
applications requirements; Part 2: Applications and facilities layer common data dictionary".
[3] CEN EN 12253: "Road transport and traffic telematics - Dedicated short-range communication -
Physical layer using microwave at 5,8 GHz".
[4] CEN EN 12795: "Road transport and traffic telematics - Dedicated Short Range, Communication
(DSRC) - DSRC data link layer: medium access and logical link control".
[5] ETSI ES 200 674-1 (V2.4.1): "Intelligent Transport Systems (ITS); Road Transport and Traffic
Telematics (RTTT); Dedicated Short Range Communications (DSRC); Part 1: Technical
characteristics and test methods for High Data Rate (HDR) data transmission equipment operating
in the 5,8 GHz Industrial, Scientific and Medical (ISM) band".
2.2 Informative 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.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
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] ECC Report 101: "Compatibility studies in the band 5855- 5925 MHz between Intelligent
Transport Systems (ITS) and other systems".
[i.2] ECC/DEC/(08)01: "ECC Decision of 14 March 2008 on the harmonised use of the 5875-5925
MHz frequency band for Intelligent Transport Systems (ITS) (2008/671/EC)".
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6 ETSI TS 102 792 V1.2.1 (2015-06)
[i.3] ECC/REC/(08)01: "Use of the band 5855-5875 MHz for intelligent transport systems (ITS)".
[i.4] 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".
[i.5] 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".
[i.6] 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.7] 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.8] ECC Report 228: "Compatibility studies between intelligent transport systems (ITS) in the band
5855- 5925 MHz and other systems in adjacent bands".
[i.9] ETSI EN 302 637-3: "Intelligent Transport Systems (ITS); Vehicular Communications; Basic Set
of Applications; Part 3: Specifications of Decentralized Environmental Notification Basic
Service".
[i.10] ETSI TS 101 539-1: " Intelligent Transport Systems (ITS); V2X Applications; Part 1: Road
Hazard Signalling (RHS) application requirements specification".
[i.11] ETSI TS 101 539-3: "Intelligent Transport Systems (ITS); V2X Applications; Part 3: Longitudinal
Collision Risk Warning (LCRW) application requirements specification".
[i.12] EC Decision 2013/752/EC: "COMMISSION IMPLEMENTING DECISION of 11 December
2013 amending Decision 2006/771/EC on harmonisation of the radio spectrum for use by short-
range devices and repealing Decision 2005/928/EC"; Band No. 62.
[i.13] ECC Recommendation ECC/REC/70-03:'Relating to the Use of Short Range Devices (SRD)',
Tromsø 1997, amended February 2014.
[i.14] Directive 2004/52/EC: "Directive of the European Parliament and of the Council of 29 April 2004
on the interoperability of electronic road toll systems in the Community".
[i.15] 2009/750/EC: "Commission Decision of 6 October 2009 on the definition of the European
Electronic Toll Service and its technical elements".
[i.16] EC Decision 2008/671/EC;"COMMISSION DECISION of 5 August 2008 on the harmonised use
of radio spectrum in the 5 875-5 905 MHz frequency band for safety-related applications of
Intelligent Transport Systems (ITS)".
[i.17] ETSI EN 302 636-4-1: "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 4: Geographical addressing and forwarding for point-to-point and point-to-
multipoint communications; Sub-part 1: Media-Independent Functionality".
3 Definitions, symbols and abbreviations
3.1 Definition
For the purposes of the present document, the following terms and definitions apply:
CEN DSRC: dedicated short range communication as specified in CEN EN 12253 [3], CEN EN 12795 [4] and
ETSI EN 300 674 [i.4]
ETSI

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7 ETSI TS 102 792 V1.2.1 (2015-06)
coexistence mode: operational mode of an ITS station that avoids harmful interference to CEN DSRC installations
default ITS radio parameters: ITS transmit power level of 23 dBm EIRP and unwanted ITS emissions in the
frequency range from 5 795 MHz to 5 815 MHz not exceeding -33 dBm/MHz EIRP
default protected zone radius: protected zone radius for ITS stations with default ITS radio parameters, it is either
stored in the protected zone database, or it can be received in a CAM from a roadside ITS station
ITS station: station transmitting in the frequency bands ITS-G5A, ITS-G5B or ITS-G5D
NOTE 1: This definition is more restrictive than in other related documents.
NOTE 2: ITS-G5A, ITS-G5B and ITS-G5D are defined in ETSI EN 302 571 [i.5].
mitigation mechanism: set of rules that an ITS station applies to operate in coexistence mode
protected zone: circular area defined by its centre and radius where mitigation mechanisms are be applied
official protected zone database: database published by an international consortium of toll operators, which contains
the positions and protected zone radii of tolling installations
vehicle station type: station types with value range from 3 to 11
NOTE: See ETSI TS 102 894-2 [2].
3.2 Symbols
For the purposes of the present document, the following symbols apply:
d distance
d reference distance for path loss model (1 m)
0
L antenna loss due to polarization or windscreen
ant
N number of interfering ITS stations
N number of ITS stations within the protected zone radius
ITS
n path loss coefficient
PL free space path loss
PL free space path loss in 1 m distance
0
P receive power level
Rx
P transmit power level
Tx
P maximum transmit power level
TXmax
σ fading loss for path loss model
T Minimum time between two transmissions
off
T Minimum time between two transmissions in coexistence mode C
off(C)
T Minimum time between two transmissions in coexistence mode D
off(D)
T Maximum length of a transmission
on
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
CEN Comité Européen de Normalisation
CVIS Cooperative Vehicle-Infrastructure Systems
NOTE: CVIS was a European project.
C-ITS Cooperative Intelligent Transport Systems
DEC Decision
DENM Decentralised Environmental Notification Message
DSRC Dedicated Short Range Communication
ECC Electronic Communications Committee
EIRP Equivalent Isotropic Radiated Power
EN European Norm
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8 ETSI TS 102 792 V1.2.1 (2015-06)
ERM Radio spectrum Matters
ETSI European Telecommunication Standard Institute
HDR High Data Rate
NOTE: DSRC communication conforming to ETSI ES 200 674-1 [5].
IEEE Institute of Electrical and Electronics Engineers
IPR Intellectual Property Rights
ISO International Standardization Organization
ITS Intelligent Transport System
ITS-S ITS station
ITU International Telecommunication Union
MAC Medium Access Control
OBU On Board Unit
PHY PHYsical (OSI layer)
REC Recommendation
RSU RoadSide Unit
RTTT Road Transport and Traffic Telematics
RX Receive
TS Technical Specification
TTT Transport and Traffic Telematics
NOTE: TTT is a more recent denomination for RTTT.
TX Transmit
4 General overview
4.1 Introduction
Cooperative ITS (C-ITS) uses wireless communication between ITS stations in the frequency bands ITS-G5A/B/D
according to ECC/DEC/(08)01 [i.2], ECC/REC/(08)01 [i.3] and ETSI EN 302 571 [i.5].
ITS stations can be:
• fixed, mounted at a fixed geographical position, often close to a road or street (roadside ITS stations);
• mobile, mounted in vehicles (vehicle ITS stations); or
• personal, integrated in smart phones or other personal equipment.
Deployment of C-ITS is expected to start in 2015 with a gradually increasing penetration. Considering this, almost
every road vehicle is expected to be equipped with ITS-G5 technology and fixed stations are expected to be installed in
great numbers. Deployment of personal ITS stations is also expected.
C-ITS is considered essential to support different European policies intended to reduce road accidents.
CEN DSRC stations operate in the band 5 795 MHz to 5 815 MHz according to ETSI EN 300 674 [i.4]. Fixed
installations with one or many road side units (RSUs) are mainly located at road charging points. On board units
(OBU), which are only active in close vicinity of the fixed stations, are installed in a significant fraction of the vehicle
population in Europe and other regions.
CEN DSRC communication is very local in nature. The area where communication takes place is often referred to as
the tolling zone. The tolling zone can be approximated by a box with 10 m length measured from the RSU position
opposite the driving direction and a width that includes all lanes of one direction (see figure 4.1). The height of this box
is from ground up to 3 m. Even though the CEN DSRC communication zone is limited, interference from radio sources
even outside this area may harm CEN DSRC communication when the field strength limits specified in clause 4.2 are
exceeded.
ETSI

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9 ETSI TS 102 792 V1.2.1 (2015-06)
Because of the small frequency separation between the bands 5 795 MHz to 5 815 MHz and 5 855 MHz to 5 925 MHz
and the fact that both systems operate in the road traffic environment, there is a significant potential for interference. In
ECC Report 101 [i.1], ECC Report 228 [i.8], ETSI TR 102 654 [i.6] and ETSI TR 102 960 [i.7] it has been concluded
that:
• CEN DSRC transmissions do not cause any significant interference to ITS stations.
• Some mitigation techniques that are specified in the present document degrade the performance of ITS
stations.
• The transmit signal from ITS stations can cause blocking at the receiver in a CEN DSRC RSU.
• Unwanted emissions from ITS stations can cause interference at the receiver in a CEN DSRC RSU.
• The transmit signal from ITS stations can cause interference at the receiver in a CEN DSRC OBU in vehicles.
Therefore, technical solutions are required to minimize interference to tolling CEN DSRC RSU and OBU and to
minimize the performance degradation of ITS.
For ITS stations, this can be achieved either by always complying with some transmit restrictions (coexistence mode,
see clause 5.4) or by receiving and processing information on the position of CEN DSRC tolling stations and complying
to transmit restrictions in the immediate vicinity of the CEN DSRC tolling station (protected zone, see clause 5.2). The
goal is to restrict the unwanted emissions of an ITS station within the vicinity of a CEN DSRC tolling zone.
CEN DSRC stations may enhance their adjacent channel rejection (blocking) capabilities such that the interference from
the ITS stations is reduced.
NOTE: The mitigation mechanisms specified in the current document may help reducing interference to road
tolling systems based on high data rate (HDR) DSRC used in Italy (specified in ETSI ES 200 674-1 [5]),
which shares the same frequency range as CEN DSRC. At the time of publication of the present
document no studies were available that could prove that these mechanisms are also capable to avoid
harmful interference to HDR DSRC tolling.
Lane Width
Tolling Zone
CENDSRCRSU
CENDSRCRSU
Tolling Zone
Lane Width

Figure 4.1: Example of tolling zone geometry
ETSI
0 m
1
1
0 m

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10 ETSI TS 102 792 V1.2.1 (2015-06)
4.2 Field strength thresholds for coexistence
A continuous interfering signal within the frequency band from 5 855 MHz to 5 925 MHz (ITS-G5A/B/D band) does
not cause harmful interference to the CEN DSRC downlink from the RSU to the OBU, when the electric field strength
of this signal within the tolling zone does not exceed 0,11 V/m (-51,6 dBm).
A continuous linear polarized interfering signal within the frequency band from 5 855 MHz to 5 925 MHz
(ITS-G5A/B/D band) does not cause harmful interference to the CEN DSRC uplink from the OBU to the RSU, when
the electric field strength of this signal at the CEN DSRC RSU antenna does not exceed 0,21 V/m (-46 dBm).
A continuous linear polarized interfering signal within the frequency band from 5 795 MHz to 5 815 MHz (CEN DSRC
band) does not cause harmful interference to the CEN DSRC uplink from the OBU to the RSU, when the power density
of this signal at the CEN DSRC RSU antenna does not exceed -129 dBm/MHz.
The strictest requirement of these three is taken as a basis for the interference mitigation mechanisms in clause 5.
For non-continuous signals, all these field strength limits can be exceeded for a time span of up to 7 ms under the
conditions described in clause 5.4.
NOTE: Values are derived from ECC Report 228 [i.8], ETSI TR 102 654 [i.6] and ETSI TR 102 960 [i.7].
4.3 ITS output power thresholds for coexistence
Taking the field strength thresholds for coexistence at the CEN DSRC OBU antenna and RSU antenna from clause 4.2
into account, the TX power thresholds for ITS transmitters can be calculated for typical use cases. These calculation
results are summarized in this clause and requirements based on them are given in clause 5.4.
Mobile ITS stations transmitting a continuous signal with less than or equal to +10 dBm linear polarized EIRP, and
having unwanted emissions with an EIRP density of less than or equal to -65 dBm/MHz into the 5 795 MHz
to 5 815 MHz frequency band, do not interfere with a receiving CEN DSRC RSU in tolling zones.
When the ITS-G5 antenna is mounted not higher than 2 m above ground (e.g. in a passenger car), this upper unwanted
EIRP emission limit in the 5 795 MHz to 5 815 MHz frequency band is -60 dBm/MHz (see ECC Report 228 [i.8]).
When the antenna is mounted inside the vehicle cabin (e.g. personal devices) or closer than 1,5 m to the CEN DSRC
OBU, an ITS station fulfilling these requirements may still interfere with a CEN DSRC OBU in the same vehicle (see
also clause 5.4, clause B.1, and clause 5.6.1).
4.4 Duty cycle limits
CEN DSRC is based on a packet communication. Typical frames have a duration of 0,5 ms to 2,5 ms. Inter frame time
is implementation specific but often in the range 5 ms to 10 ms. The time of a payment transaction may vary between
25 ms and 1 s.
C-ITS is also based on packet communication. Typical frames have a duration T of less than 1 ms at a data rate of
on
6 Mbit/s, while frames of maximum allowed size have a duration of 2 ms.
Early C-ITS deployment is expected to use a typical inter frame time T of more than 100 ms (see ETSI
off
EN 302 637-2 [1]). Later implementations for additional services may require significantly shorter times.
Even if the field strength limits in clause 4.2 and clause 4.3 are exceeded, duty cycle limitations can decrease the risk of
interference to negligible levels. T
...