ETSI TR 103 576-2 V1.1.1 (2020-02)

TECHNICAL REPORT
Intelligent Transport Systems (ITS);
Pre-standardization study on ITS architecture;
Part 2: Interoperability among heterogeneous
ITS systems and backward compatibility

2 ETSI TR 103 576-2 V1.1.1 (2020-02)

Reference
DTR/ITS-00276-2
Keywords
architecture, ITS
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ETSI
3 ETSI TR 103 576-2 V1.1.1 (2020-02)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 Challenges in a heterogeneous ITS environment . 8
5 Regulatory environment . 9
6 Interoperability . 9
6.1 Context . 9
6.2 Definition . 9
7 Backward Compatibility. 10
7.1 Context . 10
7.2 Definition . 10
8 Implementation options . 10
8.1 Context . 10
8.2 Background of 5,9 GHz ITS band . 11
8.3 Evaluation criteria . 11
8.4 Baseline options . 12
8.4.1 Single radio technology in 5,9 GHz ITS band (Base#1) . 12
8.4.1.1 Description of the option . 12
8.4.1.2 Observation and analysis of the option . 12
8.4.2 Single radio technology with its future iterations in 5,9 GHz ITS band (Base#1b) . 13
8.4.2.1 Description of the option . 13
8.4.2.2 Observation and analysis of the option . 13
8.4.3 Different radio technologies in distinct ITS-Ss (Base#2) . 14
8.4.3.1 Description of the option . 14
8.4.3.2 Observation and analysis of the option . 14
8.5 Interoperability options . 15
8.5.1 Multiple technologies for all ITS-Ss (MTA) . 15
8.5.1.1 Description of the option . 15
8.5.1.2 Observation and analysis of the option . 16
8.5.2 Duplicated transmission via cellular interface (DTC). 17
8.5.2.1 Description of the option . 17
8.5.2.2 Observation and analysis of the option . 18
8.6 Interoperability and Backward compatibility options . 18
8.6.1 General . 18
8.6.2 Multiple technologies for later deployed ITS-Ss (MTL) . 19
8.6.2.1 Description of the option . 19
8.6.2.2 Observation and analysis of the option . 19
8.6.3 Multiple technologies and duplicated transmission for later deployed ITS-Ss (MTL-DT) . 20
8.6.3.1 Description of the option . 20
8.6.3.2 Observation and analysis of the option . 21
8.6.4 Infrastructure Based Conversion (IBC) . 21
8.6.4.1 Description of the option . 21
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4 ETSI TR 103 576-2 V1.1.1 (2020-02)
8.6.4.2 Observation and analysis of the option . 24
9 Analysis and Conclusion . 25
9.1 Summary of analysis . 25
9.2 Conclusion . 27
History . 28

ETSI
5 ETSI TR 103 576-2 V1.1.1 (2020-02)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables 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 (https://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.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Intelligent Transport Systems (ITS).
The present document is part 2 of a multi-part deliverable covering the Intelligent Transport Systems (ITS);
Pre-standardization study on ITS architecture, as identified below:
Part 1: "Architecture for communications among ITS stations with multiple access layer technologies";
Part 2: "Interoperability among heterogeneous ITS systems and backward compatibility".
Modal verbs terminology
In the present document "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
There are a number of candidate wireless communications technologies to address ITS requirements, including ITS-G5,
TM
IEEE 802.11bd [i.24], LTE-V2X PC5, NR-V2X, mmWave, mobile cellular systems (Uu-Interface), etc. The
available band, such as the 5,9 GHz ITS band, could be occupied by several distinct ITS technologies, and those
technologies are likely to operate simultaneous at the same time and location. It is thus needed to clarify the inherent
challenges in this situation and discover possible solutions to overcome the challenges.

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6 ETSI TR 103 576-2 V1.1.1 (2020-02)
1 Scope
The present document presents the results of the investigation for achieving interoperability and backward
compatibility, two principles of ITS Directive [i.2], when implementing the ITS architecture with multiple
communication interfaces according to the existing ETSI ITS specifications. The present document elaborates the
definitions of interoperability and backward compatibility.
The requirements for functional safety according to ISO 26262 [i.12] and IEC 61508 [i.13], as well as privacy and
security requirements are not addressed in detail in the present document.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
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
referenced 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.
th
[i.1] M/453 (6 October 2009) Standardication Mandate addressed to CEN, CENELEC and ETSI in the
field of information and communication technologies to support the interoperability of
co-operative systems for intelligent transport in the European Community.
[i.2] Directive 2010/40/EU of the European Parliament and of the Council of 7 July 2010 on the
framework for the deployment of Intelligent Transport Systems in the field of road transport and
for interfaces with other modes of transport.
[i.3] Commission Decision 2008/671/EC of 5 August 2008 on the harmonised use of radio spectrum in
the 5875 - 5905 MHz frequency band for safety-related applications of Intelligent Transport
Systems (ITS) (notified under document number C(2008) 4145).
[i.4] CEPT/ECC Decision (08)01: "The harmonised use of the 5875-5925 MHz frequency band for
Intelligent Transport Systems (ITS)", approved 14 March 2008, Amended 3 July 2015.
[i.5] ETSI TS 136 300: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved
Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (3GPP
TS 36.300)".
[i.6] ETSI EN 302 663: "Intelligent Transport Systems (ITS); ITS-G5 Access layer specification for
Intelligent Transport Systems operating in the 5 GHz frequency band".
[i.7] ETSI TR 102 962: "Intelligent Transport Systems (ITS); Framework for Public Mobile Networks
in Cooperative ITS (C-ITS)".
[i.8] ETSI TS 103 613: "Intelligent Transport Systems (ITS); Access layer specification for Intelligent
Transport Systems using LTE Vehicle to everything communication in the 5,9 GHz frequency
band".
ETSI
7 ETSI TR 103 576-2 V1.1.1 (2020-02)
[i.9] ETSI TS 123 401 (V10.5.0): "LTE; General Packet Radio Service (GPRS) enhancements for
Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (3GPP TS 23.401
version 10.5.0 Release 10)".
[i.10] ETSI TS 125 300: "Universal Mobile Telecommunications System (UMTS); Universal Terrestrial
Radio Access Network (UTRAN); General description; Stage 2 (3GPP TS 25.300)".
[i.11] ETSI TS 138 300: "5G; NR; Overall description; Stage-2 (3GPP TS 38.300)".
[i.12] ISO 26262: "Road vehicles -- Functional safety".
[i.13] IEC 61508: "Functional safety of electrical/electronic/programmable electronic safety-related
systems".
[i.14] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.15] EC COM(2016) 766 final (30th November 2016): "Communication from the Commission to the
European Parliament, the Council, the European economic and social committee and the
committee of the regions -- A European strategy on Cooperative Intelligent Transport Systems, a
milestone towards cooperative, connected and automated mobility".
[i.16] European Commission C-ITS Platform reports I, January 2016.
NOTE: Available at https://ec.europa.eu/transport/sites/transport/files/themes/its/doc/c-its-platform-final-report-
january-2016.pdf.
[i.17] European Commission C-ITS Platform reports II, September 2017.
NOTE: Available at https://ec.europa.eu/transport/sites/transport/files/2017-09-c-its-platform-final-report.pdf.
[i.18] ETSI TS 101 539-1 (V1.1.1): "Intelligent Transport Systems (ITS); V2X Applications;
Part 1: Road Hazard Signalling (RHS) application requirements specification".
[i.19] ETSI TS 101 539-2 (V1.1.1): "Intelligent Transport Systems (ITS); V2X Applications;
Part 2: Intersection Collision Risk Warning (ICRW) application requirements specification".
[i.20] ETSI TS 101 539-3 (V1.1.1): "Intelligent Transport Systems (ITS); V2X Applications;
Part 3: Longitudinal Collision Risk Warning (LCRW) application requirements specification".
[i.21] Bijlsma, Tjerk & Hendriks, T & Vissers, J & Elshof, L & Jansen, T & Krosse, B. (2016):
"In-Vehicle Architectures for Truck Platooning: The Challenges to reach SAE Automation
Level 3".
[i.22] Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014 on the
harmonisation of the laws of the Member States relating to the making available on the market of
radio equipment and repealing Directive 1999/5/EC.
[i.23] Directive (EU) 2018/1972 of the European Parliament and of the Council of 11 December 2018
establishing the European Electronic Communications Code.
TM
[i.24] Description of IEEE 802.11bd , C2C Journal page 21ff.
NOTE: Available at https://www.car-2-car.org/fileadmin/downloads/PDFs/car-2-car-journal/Journal_23_C2C-
CC_Oct_2019_web.pdf.
TM
[i.25] IEEE 802.11 -2016: "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".
ETSI
8 ETSI TR 103 576-2 V1.1.1 (2020-02)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI EN 302 665 [i.14], ETSI EN 302 663 [i.6] and ETSI
TS 103 613 [i.8] apply.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
rd
3GPP 3 Generation Partnership Project
th
5G 5 generation of cellular mobile communications
CEN Comité Européen de Normalisation (European Committee for Standardization)
CENELEC Comité Européen de Normalisation Électrotechnique (European Committee for Electrotechnical
Standardization)
DTC Duplicated transmission via cellular interface
GW GateWay
IBC Infrastructure Based Conversion
ITS Intelligent Transportation System
ITS-G5 Access layer technology
NOTE: As defined in ETSI EN 302 663 [i.6].
ITS-S ITS Station
LTE Long Term Evolution
LTE-V2X Long Term Evolution based Vehicle-to-Everything
NOTE: As defined in ETSI TS 103 613 [i.8].
MAC Media Access Control
MEC Multi-access Edge Computing
MTA Multiple technologies for all ITS-Ss
MTL Multiple technologies for later deployed ITS-Ss
MTL-DT Multiple technologies and duplicated transmission for later deployed ITS-Ss
NGV Next Generation V2X
NR New Radio
PC5 Proximity-based Communication (Interface) 5
V2N Vehicle-to-Network
V2X Vehicle-to-Everything
4 Challenges in a heterogeneous ITS environment
There are a number of candidate wireless communications technologies to address ITS requirements, including in
particular 3GPP LTE-V2X (Releases 14 and 15) specified in ETSI TS 103 613 [i.8], ITS-G5 specified in ETSI
EN 302 663 [i.6], and 3GPP cellular technologies specified in ETSI TS 125 300 [i.10], ETSI TS 136 300 [i.5], ETSI
TS 138 300 [i.11] and ETSI TR 102 962 [i.7] for short and long-range communications. Furthermore, it is expected that
communication standards evolve; for example, 3GPP has a work item on an evolution of the existing LTE-V2X
solution towards 5G New Radio (NR) technology, which aims to comprise a new system design, including a new access
layer and aims to support interoperability and backward compatibility on system level with the existing LTE-V2X
systems. Also, IEEE is developing IEEE 802.11bd [i.24] which aims to provide a next generation V2X access layer that
aims to be interoperable and backward compatible with the existing ITS-G5 (IEEE 802.11p [i.25] - based access layer)
on system level and radio access technology level.
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9 ETSI TR 103 576-2 V1.1.1 (2020-02)
Since it is possible that distinct short-range access layer technologies may be operated in the 5,9 GHz ITS band at the
same time and location, interoperability and backward compatibility are addressed in the present document.
Other challenges, e.g. coexistence of different short-range communication technologies and potential architecture
enhancement for ITS-Ss with multiple access layer technologies, are addressed by other work within ETSI.
5 Regulatory environment
To guide the investigation of interoperability and backward compatibility on utilizing multiple access layer technologies
for Cooperative ITS, the related regulatory environments are summarized in this clause. The ITS Directive
2010/40/EU [i.2] is the umbrella legislation for ITS services. M/453 [i.1] was subsequently adopted to ensure that the
addressed standardization bodies are taking their role in developing the standards. Those standards provide a basis for
the effective provision of Cooperative ITS priority services.
The interoperability and backward compatibility aspects for heterogeneous communication systems are considered
based on the definitions of interoperability and backward compatibility in the ITS Directive 2010/40/EU [i.2]. With
regards to the regulatory framework, at least the following additional regulations and reports exist:
• COM(2016) 766 [i.15].
• European Commission C-ITS Platform reports I [i.16] and II [i.17].
• European spectrum regulation, EC Decision 2008/671/EC [i.3], Directive 2014/53/EU [i.22] and Directive
(EU) 2018/1972 [i.23].
6 Interoperability
6.1 Context
Multiple ITS access layer technologies have been developed independently of each other or are currently in
development, e.g. ITS-G5 specified in ETSI EN 302 663 [i.6], LTE-V2X specified in ETSI TS 103 613 [i.8], and
cellular technologies specified in ETSI TS 125 300 [i.10] for 3G, ETSI TS 136 300 [i.5] for 4G and ETSI
TS 138 300 [i.11] for 5G. Some access layer technologies for ITS services are fundamentally different and thus not
interoperable at the physical and MAC layers. For example, an LTE-V2X PC5 radio is not able to process ITS-G5
signals nor vice versa. However, interoperability of C-ITS services between devices using different access layer
technologies might be supported via other means such as those described in subsequent clauses of the present
document.
NOTE: Some other access layer technologies in development aim to be interoperable and backward compatible
with each other, for example IEEE 802.11p [i.25] access technology and its evolvement
IEEE 802.11bd [i.24].
6.2 Definition
The Article 4 in the Directive 2010/40/EU [i.2] defines interoperability as follows:
• interoperability: capacity of systems and the underlying business processes to exchange data and to share
information and knowledge.
The Annex II in the Directive 2010/40/EU [i.2] provides a related principle and definition as follows:
• deliver interoperability: ensure that systems and the underlying business processes have the capacity to
exchange data and to share information and knowledge to enable effective ITS service delivery.
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10 ETSI TR 103 576-2 V1.1.1 (2020-02)
7 Backward Compatibility
7.1 Context
As various short-range ITS access technologies designed to operate in the 5,9 GHz ITS band as well as long-range
cellular technologies supporting ITS applications have been developed and are continuing to evolve, it is important to
consider how a new iteration of a technology can operate with previous iterations of that technology. In practice, this
often leads to the following approach that earlier generation features are maintained by later generation equipment;
however, later generation equipment include additional innovations, services and features.
NOTE: Where updates of existing equipment are needed to obtain backward compatibility it should be noted that
updates in the field, when possible, might imply recalls for ITS equipment where a 100 % update rate
would be unrealistic to guarantee.
7.2 Definition
The article 4 in the Directive 2010/40/EU [i.2] defines compatibility as follows:
• compatibility: general ability of a device or system to work with another device or system without
modification.
The Annex II in the Directive 2010/40/EU [i.2] defines the support of backward compatibility as follows:
• support backward compatibility: ensure, where appropriate, the capability for ITS systems to work with
existing systems that share a common purpose, without hindering the development of new technologies.
NOTE: Incumbent technologies are not considered here and are treated according to frequency regulation.
8 Implementation options
8.1 Context
The context and terminology explanation for the interoperability and backward compatibility have been introduced in
previous clauses. The objective of clause 8 is to introduce candidate solutions, which allow vehicular wireless
communications equipment of distinct short-range communication technologies interact with each other.
The background of 5,9 GHz ITS band is described in clause 8.2, the evaluation criteria used to evaluate implementation
options are listed in clause 8.3, and the baseline implementation options which do not take into account the
interoperability and backward compatibility are described in clause 8.4 for the purpose of comparison. The
implementation options supporting interoperability are described in clause 8.5, and those supporting interoperability and
backward compatibility are described in clause 8.6.
NOTE 1: For technologies which support interoperability and backward compatibility via their access layer design,
the implementation options providing interoperability and backward compatibility via higher layer design
described in clauses 8.5 and 8.6 are not needed.
Coexistence of access layer technologies is out of scope of the present document. Co-channel and adjacent channel
coexistence between the two existing C-ITS technologies are covered by other work in ETSI. For the scope of the
present document, it is assumed that different technologies use separate channels, but coexistence studies may
overcome this assumption.
NOTE 2: It is essential to know how long products equipped with ITS-Ss will be supported. For vehicles it is
typical for 10 years after end of production. For a typical vehicle model, typical development time is
3-5 years, production time is 5-8 years and lifetime is more than 10 years with guaranteed support. In
contrast, the typical lifetime of consumer communication equipment is 2-3 years.
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11 ETSI TR 103 576-2 V1.1.1 (2020-02)
8.2 Background of 5,9 GHz ITS band

Figure 1: European 5,9 GHz channel layout
According to Commission Decision 2008/671/EC [i.3] and ECC Decision (08)01 [i.4], the 5,9 GHz ITS band in Europe
consists of three 10 MHz frequency channels for safety-related ITS applications, as shown in Figure 1.
8.3 Evaluation criteria
The following criteria are considered in the present document to support applications for the road safety and traffic
efficiency, and are used to evaluate the implementation options described in clauses 8.4 to 8.6.
1) Interoperability: as defined in clause 6.2.
2) Backward compatibility: as defined in clause 7.2.
3) Latency: time it takes to transfer a given piece of information from a transmitting ITS-S to a receiving ITS-S
at the facilities layer, more specifically time from the moment that a given piece of information is passed to the
facilities layer at the transmitting ITS-S to the moment that the given piece of information is passed from the
facilities layer to its upper layer of the receiving ITS-S.
NOTE 1: Implementation options with higher latencies above C-ITS safety services requirements are not suitable.
Latency requirements for several C-ITS services are found in ETSI TS 101 539-1 [i.18], ETSI
TS 101 539-2 [i.19], ETSI TS 101 539-3 [i.20] and [i.21].
4) Efficiency of spectrum usage: the efficiency of spectrum usage is defined in the present document as the
effective and efficient spectrum usage. The efficiency of spectrum usage is considered as high when duplicated
message transmission is not needed regardless of the radio technology, and as low when duplicated message
transmission is needed to transmit a same ITS message.
5) Radio access impartiality: the radio access impartiality is defined in the present document that the system
design neither imposes nor discriminates in favour of the use of a particular type of radio access technology.
6) Technology evolution acceptability: the technology evolution acceptability is defined in the present
document as not hindering the development of new technologies.
7) Implementation complexity: required hardware and software costs, package volume in vehicles.
8) Infrastructure required: whether or not an implementation option properly works only in an infrastructure
coverage.
NOTE 2: The goal of the criteria 3) to 8) is to evaluate the qualitative cost that each implementation option needs
for supporting the interoperability and backward compatibility compared to other options.
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12 ETSI TR 103 576-2 V1.1.1 (2020-02)
8.4 Baseline options
8.4.1 Single radio technology in 5,9 GHz ITS band (Base#1)
8.4.1.1 Description of the option
This option is defined with the following assumptions:
• Only a single iteration of a single radio technology is used in the 5,9 GHz ITS band.
• All ITS-Ss are equipped with the single iteration of that radio technology.
• All ITS-Ss transmit and receive ITS messages via the single radio technology.
Figure 2 illustrates an example of the solution described above.

NOTE: ITS-Ss can be vehicle or roadside ITS-Ss.

Figure 2: Example architecture for Base#1
8.4.1.2 Observation and analysis of the option
• Interoperability: The interoperability between ITS-Ss equipped with distinct radio technologies is not
addressed in this option because only a same iteration of one single radio technology is considered. The
interoperability among all ITS-Ss in this option is supported the highest among all options, since all ITS-Ss are
equipped with a same iteration of the same radio technology.
• Backward compatibility: Not applicable because only a single iteration of a single radio technology is
considered.
• Latency: Lowest among all options.
NOTE 1: The latency of this option is considered the lowest no matter which radio technology is used since this
option does not need additional latency for supporting interoperability and/or backward compatibility.
The latency of this option can be referred when evaluating the latency of other options.
• Efficiency of spectrum usage: Highest among all options.
NOTE 2: The spectrum usage of this option is considered the highest no matter which radio technology is used
since this option does not need additional spectrum usage for supporting interoperability and/or backward
compatibility. The spectrum usage of this option can be referred when evaluating the spectrum usage of
other options.
• Radio access impartiality: Not applicable by the definition of this option because only a single iteration of a
single radio technology is considered.
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13 ETSI TR 103 576-2 V1.1.1 (2020-02)
• Technology evolution acceptability: Not applicable by the definition of this option because only a single
iteration of a single radio technology is considered.
• Implementation complexity: Lowest among all options.
NOTE 3: The implementation complexity of this option is considered the lowest no matter which radio technology
is used since this option does not need additional implementation complexity for supporting
interoperability and/or backward compatibility. The implementation complexity of this option can be
referred when evaluating the implementation complexity of other options.
• Infrastructure required: No.
8.4.2 Single radio technology with its future iterations in 5,9 GHz ITS band
(Base#1b)
8.4.2.1 Description of the option
This option is defined with the following assumptions:
• Multiple iterations of a single radio technology, which are interoperable and backward compatible with each
other at the physical and MAC layers, are used in the 5,9 GHz ITS band. No distinct channels are needed and
all iterations can work in the same channel. All later iterations can receive and interpret messages from earlier
iterations.
• All ITS-Ss are equipped only with one of the technology iterations.
• All ITS-Ss transmit and receive ITS messages via a single radio technology. Neither for transmission nor for
reception multiple radios are necessary.
Figure 3 illustrates an example of the solution described above.

NOTE: ITS-Ss can be vehicle or roadside ITS-Ss.

Figure 3: Example architecture for Base#1b
8.4.2.2 Observation and analysis of the option
• Interoperability: The interoperability between ITS-Ss equipped with distinct radio technologies is not
addressed in this option. However, the interoperability among all ITS-Ss in this option is supported because all
ITS-Ss can communicate with others within the same or older iteration of the same radio technology.
• Backward compatibility: Supported.
• Latency: Same as that of Base#1, i.e. lowest among all options.
• Efficiency of spectrum usage: Same as that of Base#1, i.e. highest among all options.
• Radio access impartiality: Not applicable by the definition of this option because only iterations of a single
radio technology are considered.
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14 ETSI TR 103 576-2 V1.1.1 (2020-02)
• Technology evolution acceptability: Limited as only one technology's backward compatible iterations are
considered.
• Implementation complexity: On a system level similar to that of Base#1. For a given ITS Station the
iterations of technology might increase complexity, but should be lower than multi-radio technology
implementations.
• Infrastructure required: No.
8.4.3 Different radio technologies in distinct ITS-Ss (Base#2)
8.4.3.1 Description of the option
This option is defined with the following assumptions:
• Multiple different radio technologies are not interoperable with each other at the physical and MAC layers. It
is assumed for simplicity of the present document that the different radio technologies use distinct 10 MHz
channels of the 5,9 GHz ITS band. It is assumed that the number of distinct radio technologies is equal or less
than the number of available 10 MHz channels.
NOTE: Practical deployments may use different channels for different services using one radio technology.
• Each ITS-S is equipped with a single radio technology among the multiple radio technologies.
• Each ITS-S transmits and receives ITS messages via the equipped radio technology and does not communicate
with the ITS-Ss equipped with the other radio technology.
Figure 4 illustrates an example of the solution described above.

NOTE: ITS-Ss can be vehicle or roadside ITS-Ss. It is assumed that different radio resources are used by the
different technologies.
Figure 4: Example architecture for Base#2
8.4.3.2 Observation and analysis of the option
• Interoperability: Not supported because ITS-Ss equipped with distinct radio technologies cannot
communicate with each other.
• Backward compatibility: Not supported because ITS-Ss equipped with distinct radio technologies cannot
communicate with each other.
• Latency: Same as that of Base#1, i.e. lowest among all options.
• Efficiency of spectrum usage: Same as that of Base#1, i.e. highest among all options because no message is
duplicated compared to Base#1.
ETSI
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NOTE: Even though the spectrum usage of this option is same as that of Base#1, all options, including this
option, assuming multiple radio technologies are used in distinct channels need additional channel
assignment compared to the Base#1 and it reduces the number of channels available for other use cases.
In case of high channel utilization and uneven distribution of technology deployment, it prevents load
balancing over multiple channels: a channel is blocked even by a limited number of users of the minority
technology.
• Radio access impartiality: Initially supported but limited by the number of available channels, since each
technology is using a distinct channel. Later deployed technologies have a smaller number or no channel
available.
• Technology evolution acceptability: Supported but limited by the number of available channels, since each
technology uses a distinct channel. Later deployed technologies have a smaller number or no channel
available.
• Implementation complexity: Same as that of Base#1, i.e. lowest among all options.
• Infrastructure required: No.
8.5 Interoperability options
8.5.1 Multiple technologies for all ITS-Ss (MTA)
8.5.1.1 Description of the option
An ITS message is transmitted via one of multiple radio technologies in the 5,9 GHz ITS band which cannot directly
communicate with each other at the radio level. To ensure that ITS messages can be received and processed by ITS
applications at the receiving ITS-Ss regardless of the radio technology used for the transmission, this option is defined
with the following assumptions:
• Multiple different radio technologies are not interoperable with each other at the physical and MAC layers. It
is assumed for simplicity of the present document that the different radio technologies use distinct 10 MHz
channels of the 5,9 GHz ITS band. It is assumed that the number of distinct radio technologies is equal or less
than the number of available 10 MHz channels.
NOTE: Practical deployments may use different channels for different services using one radio technology.
• Each ITS-S is equipped with all the multiple radio technologies and implements the identical and standardized
ETSI ITS upper layer protocol stack. In this option, each ITS-S is assumed to be updatable so that each ITS-S
will be equipped with all the multiple radio technologies including any new technologies.
• Each ITS-S transmits and receives ITS messages via any single radio technology of the equipped multiple
radio technologies and can communicate with any other ITS-Ss. Multiple radio technologies are equally
considered in this solution. ITS-Ss have the freedom to select the transmitting technology.
Figure 5 illustrates an example of the solution described above.
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16 ETSI TR 103 576-2 V1.1.1 (2020-02)

NOTE: ITS-Ss can be vehicle or roadside ITS-Ss.

Figure 5: Example architecture for MTA
8.5.1.2 Observation and analysis of the option
• Interoperability: Supported because each ITS-S can communicate with any other ITS-Ss.
• Backward compatibility: Not supported since an earlier deployed ITS-S needs a modification to be equipped
with additional radio technology.
NOTE 1: Lack of backward compatibility might influence the interoperability, e.g. interoperability with earlier
deployed equipment only supporting one technology is not supported.
• Latency: Same as that of Base#1, i.e. lowest among all options.
• Efficiency of spectrum usage: Same as that of Base#1, i.e. highest among all options.
• Radio access impartiality: Initially supported but limited by the number of available channels, since each
technology is using a distinct channel. Later deployed technologies have a smaller number or no channel
available.
NOTE 2: This option does not discriminate in favour of the use of a particular type of technology, but does impose
requirements to be able to receive messages via all technologies.
• Technology evolution acceptability: Supported but limited by the number of available channels, since each
technology uses a distinct channel. Later deployed technologies have a smaller number or no channel
available.
• Implementation complexity: Higher than that of Base#1 to support more than one radio technology and
might need update in the field.
• Infrastructure required: No.
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8.5.2 Duplicated transmission via cellular interface (DTC)
8.5.2.1 Description of the option
Transmission of data packets on the cellular interface can be a way to enable the interoperability between the ITS-Ss
which cannot directly communicate with each other at the radio level. This option is defined with the following
assumptions:
• Multiple different radio technologies are not interoperable with each other at the physical and MAC layers. It
is assumed for simplicity of the present document that the different radio technologies use distinct 10 MHz
channels of the 5,9 GHz ITS band. It is assumed that the number of distinct radio technologies is equal or less
than the number of available 10 MHz channels.
NOTE: Practical deployments may use different channels for different services using one radio technology.
• Each ITS-S is equipped with a single short-range radio technology among the multiple radio technologies.
• All ITS-Ss are also equipped with a cellular radio technology, e.g. LTE-V2N Uu with a valid subscription to
be able to participate in this scenario.
• Each ITS-S transmits and receives ITS message via the equipped single short-range radio
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