Cooperative intelligent transport systems (C-ITS) -- Guidelines on the usage of standards

This document serves as a guideline explaining the concept of hybrid communications and support functionalities for Cooperative ITS services deployed in conformance with the ITS station architecture and related Cooperative ITS standards.

Systèmes de transport intelligents coopératifs (C-ITS) - Lignes directrices sur l'utilisation des normes

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TECHNICAL ISO/TR
REPORT 21186-2
First edition
2021-02
Cooperative intelligent transport
systems (C-ITS) — Guidelines on the
usage of standards —
Part 2:
Hybrid communications
Systèmes de transport intelligents coopératifs (C-ITS) - Lignes
directrices sur l'utilisation des normes —
Partie 2: Communications hybrides
Reference number
ISO/TR 21186-2:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TR 21186-2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 21186-2:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 5

5 Motivations for hybrid communications support .............................................................................................................. 5

5.1 Connected and cooperative mobility ................................................................................................................................... 5

5.2 Examples of use cases requiring a diversity of access technologies ......................................................... 7

5.2.1 Road hazard notification (use case 1) ........................................................................................................... 7

5.2.2 Emergency call (use case 2) ................................................................................................................................... 8

5.2.3 Public transport (use case 3) ................................................................................................................................ 8

5.3 Hybrid communication technologies................................................................................................................................... 9

5.4 Unified communication and data management architecture ......................................................................... 9

5.4.1 Requirements for the unified communication and data management

architecture .......................................................................................................................................................................... 9

5.4.2 Supporting a diversity of applications with diverging communication needs ........10

5.4.3 Supporting a diversity of communication paths ...............................................................................10

5.4.4 Supporting a diversity of access technologies and protocols.................................................11

6 The ITS station architecture and functionalities in support of hybrid communications ......12

6.1 Origins of the ITS station architecture ............................................................................................................................12

6.2 Detailed ITS station architecture .........................................................................................................................................14

6.3 Design principles of the ITS station architecture ...................................................................................................16

6.4 ITS station functionalities in support for hybrid communications ........................................................17

6.5 ITS station management entity ..............................................................................................................................................18

6.6 ITS station capabilities ..................................................................................................................................................................19

6.7 ITS station service managed entity (ITS-S MSE) ....................................................................................................20

6.8 Management of data flow types (ITS-S flow type) ................................................................................................22

6.9 Management of communication paths (ITS-S path) ............................................................................................22

6.10 Management of communication profiles (ITS-SCP) .............................................................................................22

6.11 Management of communication handovers ...............................................................................................................24

6.12 Management of globally unique identifiers ................................................................................................................24

6.13 Standards necessary in support of hybrid communications ........................................................................24

7 How to develop ITS application standards .............................................................................................................................25

7.1 Generic development principle .............................................................................................................................................25

7.2 Specifying ITS-S application process ................................................................................................................................25

7.3 Defining data flow communication requirements ................................................................................................25

7.4 Registering communication requirements ..................................................................................................................26

7.5 Transmitting data ..............................................................................................................................................................................26

Bibliography .............................................................................................................................................................................................................................27

© ISO 2021 – All rights reserved iii
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ISO/TR 21186-2:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems, in

collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC

278, Intelligent transport systems, in accordance with the Agreement on technical cooperation between

ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 21186 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
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ISO/TR 21186-2:2021(E)
Introduction

This document is part of a family of deliverables from Standard Development Organizations (SDOs)

for Cooperative Intelligent Transport Systems (C-ITS), which is a subset of standards for Intelligent

Transport Systems (ITS).
ITS aims to improve surface transportation in terms of:
— safety
e.g. crash avoidance, obstacle detection, emergency calls, dangerous goods;
— efficiency

e.g. navigation, green wave, priority, lane access control, contextual speed limits, car sharing;

— comfort
e.g. telematics, parking, electric vehicle charging, infotainment;
— sustainability
by applying information and communication technologies (ICT).

In the European Union, the legal framework is given by the European Commissions Mandate M/453

[53] [52]

on C-ITS , the European Commission Directive 2010/40 , and the European Commission Mandate

[54]
M/546 .

The whole set of standards for deployment of C-ITS is difficult to understand by developers of equipment

and software, especially ITS application software, and thus guidelines explaining a beneficial choice

of standards (C-ITS Release), the purpose and interaction of standardized features, beneficial

implementation approaches and guidance in developing ITS applications are a prerequisite for a fair

and open market allowing early deployment of interoperable and future-proof solutions.

The ISO 21186 series provides necessary guidelines in multiple parts, each dedicated to a specific

purpose:
[14]
— Part 1: Standardization landscape and releases ;
— Part 2: Hybrid communications (this document);
15]
— Part 3: Security .
This document can be complemented by further parts as required, for example:

— Usage of the service announcement protocol specified, for example, in ISO 22418;

— Dynamically extendable data and protocol parameters ("Information Object Classes" and

"Information Object Sets"; based on ASN.1 type CLASS);
— Usage of the GTDM framework specified in ISO/TS 21184 .

The purpose of this document is thus to inform about relevant standards and to describe the

functionalities of the ITS station architecture defined in support for hybrid communication

technologies. It is intended to serve as a guideline to structure the development of new C-ITS standards

and to harmonize the deployment of C-ITS services relying on the use of hybrid communication

technologies. It also intends to give support to the developers of standards defining C-ITS services and

to the developers of C-ITS solutions and ITS applications complying with the ITS station architecture

and its set of functionalities supporting hybrid communications.
1) Under preparation. Stage at the time of publication: ISO/PRF TS 21184:2021.
© ISO 2021 – All rights reserved v
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ISO/TR 21186-2:2021(E)

At time of writing this document, no applicable Intellectual Property Rights (IPR) issues were known

related to this document. However, this document references standards, for which IPRs are known.

Information on such IPRs is expected to be provided in those respective standards, which might be

from any one of the Standards Development Organisations working on ITS or C-ITS.

Referencing other SDOs and their respective deliverables in no way is to be understood as an

endorsement, but rather as an informative piece of information.

More details on the C-ITS domain can be found in the Brochure cited in Reference [58].

vi © ISO 2021 – All rights reserved
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TECHNICAL REPORT ISO/TR 21186-2:2021(E)
Cooperative intelligent transport systems (C-ITS) —
Guidelines on the usage of standards —
Part 2:
Hybrid communications
1 Scope

This document serves as a guideline explaining the concept of hybrid communications and support

functionalities for Cooperative ITS services deployed in conformance with the ITS station architecture

and related Cooperative ITS standards.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
access technology
technology employed in a communication interface to access a specific medium
[SOURCE: ISO 21217:2020, 3.1]
3.2
communication adaptation layer
CAL

set of protocols and functions to adapt access technologies to the ITS-S networking and transport

layer (3.20)
[SOURCE: ISO 21217:2020, 3.3]
3.3
hybrid communications

composition of multiple access technologies and communication protocols combined to provide

complementary or redundant communication channels
[SOURCE: ISO 21217:2020, 3.7]
3.4
hybrid communication support

feature of an ITS station used to combine multiple access technologies and protocols

[SOURCE: ISO 21217:2020, 3.8]
© ISO 2021 – All rights reserved 1
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ISO/TR 21186-2:2021(E)
3.5
hybrid ITS service
ITS service that relies on hybrid communications (3.3)
[SOURCE: ISO 21217:2020, 3.9]
3.6
ITS station
ITS-S

functional entity comprised of an ITS-S facilities layer (3.13), ITS-S networking and transport layer (3.20),

ITS-S access layer (3.7), ITS-S management entity, ITS-S security entity and ITS-S applications (3.9) entity

providing ITS services

Note 1 to entry: From an abstract point of view, the term "ITS station" refers to a set of functionalities. The

term is often used to refer to an instantiation of these functionalities in a physical unit. Often, the appropriate

interpretation is obvious from the context. The proper name of the physical instantiation of an ITS-S is ITS

station unit (ITS-SU).
[SOURCE: ISO 21217:2020, 3.15]
3.7
ITS-S access layer

protocol layer in the ITS-S reference architecture containing the OSI physical and data link layer

protocols for ITS communications
[SOURCE: ISO 21217:2020, 3.16]
3.8
ITS-S access technology
access technology (3.1) dedicated to operation in an ITS station (3.6)
[SOURCE: ISO 21217:2020, 3.20]
3.9
ITS-S application
ITS-S application process (3.10) residing in the ITS-S application entity
[SOURCE: ISO 21217:2020, 3.21]
3.10
ITS-S application process

element in an ITS station (3.6) that performs information processing for a particular application and

uses ITS-S services to transmit and receive information
[SOURCE: ISO 21217:2020, 3.22]
3.11
ITS-S capability

uniquely addressable protocol or functionality that is part of an ITS-S managed service entity (3.19)

Note 1 to entry: Examples of ITS-S capabilities in the ITS station (3.6) facilities layer are generic ITS-S facilities

layer (3.13) services specified in ISO/TS 17429 (Communication Profile Handler, Facilities Services Handler,

Content Subscription Handler), the position and time service defined in ISO/TS 21176, the security services

defined in ISO/TS 21177; examples of ITS-S capabilities in the ITS-S networking and transport layer (3.20) are

IPv6 functionalities defined in ISO 21210 (IPv6 neighbour discovery, IPv6 forwarding, IPv6 mobility support,

etc.), the fast service announcement protocol defined in ISO 22418, etc.
[SOURCE: ISO 21217:2020, 3.24]
2 © ISO 2021 – All rights reserved
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ISO/TR 21186-2:2021(E)
3.12
ITS-S communication profile
ITS-SCP

parameterized ITS-S communication protocol stack (set of protocols composing all the ITS station (3.6)

layers) that allows communication end points to communicate with one another
[SOURCE: ISO 21217:2020, 3.25, modified.]
3.13
ITS-S facilities layer

layer in the ITS-S reference architecture containing OSI layers 5, 6 and 7 that connects applications to

the ITS-S networking and transport layer (3.20)
[SOURCE: ISO 21217:2020, 3.31]
3.14
ITS-S flow

identifiable sequence of packets of a given ITS-S flow type (3.16) transmitted between a source node

and a destination node.
[SOURCE: ISO 21217:2020, 3.36]
3.15
ITS-S flow identifier

identifier, being unique within an ITS station (3.6) unit, that identifies an ITS-S flow (3.14)

[SOURCE: ISO 24102-6:2018, 3.9]
3.16
ITS-S flow type
set of characteristics describing a data flow
[SOURCE: ISO 21217:2020, 3.37]
3.17
ITS-S flow type identifier

identifier being unique within the ITS station (3.6) that identifies an ITS-S flow type (3.16)

[SOURCE: ISO 24102-6:2018, 3.11]
3.18
ITS-S host

ITS-S node (3.21) comprised of ITS-S functionalities other than the functionalities of an ITS-S router

(3.23), ITS-S border router, ITS-S mobile router, or an ITS-S gateway
[SOURCE: ISO 21217:2020, 3.39]
3.19
ITS-S managed service entity
MSE

uniquely addressable entity in an ITS-S layer comprised of a set of related ITS-S capabilities

Note 1 to entry: Examples of ITS-S managed service entities are: a communication module in the ITS-S access

technologies layer (M5, cellular, etc.), a protocol suite in the ITS-S networking & transport layer (IPv6, FNTP,

GeoNetworking, 6LoWPAN, etc.), the generic facilities at the ITS-S facilities layer (3.13) (COH, FSH, CSH).

[SOURCE: ISO 21217:2020, 3.42]
© ISO 2021 – All rights reserved 3
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ISO/TR 21186-2:2021(E)
3.20
ITS-S networking and transport layer

layer in the ITS-S reference architecture containing OSI layers three and four that connects the ITS-S

facilities layer (3.13) to the ITS-S access layer (3.7)
[SOURCE: ISO 21217:2020, 3.46]
3.21
ITS-S node

node comprised of a set of functionalities in an ITS station (3.6) unit that is connected to the ITS station-

internal network or comprises an entire ITS station unit
[SOURCE: ISO 21217:2020, 3.47]
3.22
ITS-S path

directed sequence of nodes connected by links starting at a source node, traversing a communication

interface of the source ITS-S, an ITS-S ingress anchor node and an ITS-S egress anchor node, ending at a

destination node
[SOURCE: ISO 21217:2020, 3.48]
3.23
ITS-S router

ITS-S node (3.21) comprised of routing functionalities of an ITS station (3.6) unit used to connect two

networks and to forward packets not explicitly addressed to itself
[SOURCE: ISO 21217:2020, 3.49]
3.24
localized communications

communications with nearby stations without involving support of an infrastructure network

[SOURCE: ISO 21217:2020, 3.53]
3.25
networked communications
communications using support of an infrastructure network
[SOURCE: ISO 21217:2020, 3.60]
3.26
urban WiFi

short-range networked communications (3.25) WiFi access technology (3.1) used mostly in urban

environments and in personal devices such as smartphones, tablets and laptops

Note 1 to entry: An example of urban WiFi is IEEE 802.11 Basic Service Set (BSS) for WLAN access used in 2,4 GHz

or 5,4 GHz frequency range.
3.27
vehicular WiFi

short-range localized communications (3.24) WiFi access technology (3.1) specifically designed for

vehicular localized communications

Note 1 to entry: An example of vehicular WiFi is IEEE 802.11 operating outside the context of a Basic Service

[51]

(OCB), also known as IEEE 802.11p , used in the 5,9 GHz frequency range reserved for ITS services with profile

standards named ITS-G5 (ETSI) in Europe and Australia, and US-DSRC in North America and their harmonization

at ISO ( ITS-M5).
4 © ISO 2021 – All rights reserved
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ISO/TR 21186-2:2021(E)
4 Symbols and abbreviated terms
CAM cooperative awareness message
C-ITS cooperative intelligent transport systems
CPH communication profile handler
CSH content subscription handler
DENM decentralized environmental notification message
DSRC dedicated short-range communication
ETSI European Telecommunication Standards Institute
FSH facilities service handler
IEEE Institute of Electrical and Electronics Engineers
IPv6 internet protocol version 6
ITS intelligent transport systems
ITS-SU ITS station unit
LDM local dynamic map
LiFi light fidelity
LoRA long range
LTE-V2X long term evolution based vehicle-to-everything
OCB outside the context of a basic-service set
OSI open systems interconnection
PVT position, velocity and time
SDO standards development organization
US-DSRC american dedicated short range communication
V2X vehicle-to-vehicle and vehicle-to-roadside
WiFi wireless fidelity
WSMP wave short message protocol
5 Motivations for hybrid communications support
5.1 Connected and cooperative mobility

Intelligent transport systems (ITS) services are traditionally ranged into three categories: road traffic

safety, traffic efficiency and comfort (infotainment, value added services, etc.).

ITS services were initially deployed either in the roadside infrastructure (variable message signs, etc.),

in vehicles (telematics) or nomadic devices (navigation, traffic alerts, etc.) with little or no interaction

between the vehicles, other road users and the roadside infrastructure. With the advent of short-range

communication technologies, ITS services using the exchange of data between vehicles and the roadside

© ISO 2021 – All rights reserved 5
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ISO/TR 21186-2:2021(E)
[2],[36]-[38] [3]

infrastructure then started to appear (electronic fee collection , electric-vehicle charging ,

[39]

emergency call , etc.). These ITS services are specified to operate in a very controlled environment,

with a very specific radio technology, and for a very specific purpose.

While recent generations of vehicles are deployed with built-in communication systems providing

connectivity to remote platforms providing services (navigation, software update, telematics, electric

vehicle charging, emergency call, etc.), the forthcoming generation of vehicles will cooperate with

their surrounding environment (other vehicles, other road users, roadside infrastructure and urban

infrastructure). This localized exchange of data improves road safety (crash avoidance, obstacle

detection, etc.) and traffic efficiency (traffic information, green wave, lane access control, contextual

speed limit, etc.).

Cooperative ITS (C-ITS) services, i.e. ITS services for connected and cooperative mobility that rely on

the data exchanged between vehicles (cars, trucks, buses, etc.), other road users (pedestrians, cyclists,

etc.), the roadside and urban infrastructure (traffic lights, road tolls, etc.) and control and services

centres in the cloud (traffic control centre, service providers, map providers, etc.), and especially on the

sharing of data amongst service domains and applications of the same service domain, are thus being

developed. See Figure 1.
Figure 1 — Connected and Cooperative Mobility

However, distinct C-ITS services have diverging communication requirements (distribution area,

amount of data, delivery delay, privacy, confidentiality, etc.). No single communication technology is

able to fulfil all of these requirements at once.

Many communication technologies are available today on the market (cellular 3G/4G, infrared, LiFi,

satellite, urban WiFi, vehicular WiFi, LoRA, etc.) and new promising technologies appear regularly. They

6 © ISO 2021 – All rights reserved
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ISO/TR 21186-2:2021(E)

have very different characteristics (radio coverage range, bandwidth, propagation delay, reliability,

price, transmission power), and are more or less prone to security threats (denial of service, intrusion,

impersonation, observation). Each of these access technologies has its own benefits and drawbacks

with respect to the type of service that is to be delivered.

Due to their diverging characteristics, their geographic penetration, and regional regulations, the

combination of several access technologies and protocols is beneficial or even necessary for ensuring

reliability, interoperability and sustainable development of C-ITS services. This requires a common

approach to the way security, communications and data are handled.

Before requirements for this common approach are discussed in 5.3, subclause 5.2 presents examples

illustrating the need to combine a diversity of access technologies.
5.2 Examples of use cases requiring a diversity of access technologies
5.2.1 Road hazard notification (use case 1)

Road hazards present road safety risks that could be leveraged using localized communications (using

vehicular WiFi in the 5,9 GHz frequency band, for example) and networked communications (using

3G/4G cellular technology, for example). A typical example is black ice on the road as illustrated on

Figure 2.

A vehicle equipped with sensors can detect black ice. If it is equipped with localized communications

capabilities it can inform subsequently following vehicles so that they reduce speed in due time and

take other automatic actions to ensure safety. All equipped vehicles can relay this alert from vehicle to

vehicle, but at some point, there will not be any vehicle able to relay this message further. Consequently,

an approaching vehicle still kilometres away will not be informed.
[64]
Figure 2 — Black ice notification using hybrid communications (FP7 GeoNet )

To ensure wide transmission of the alert, vehicles that detect the hazard could transmit a road hazard

alert to the road traffic control centre, either directly using networked communications, or through a

nearby roadside ITS station unit ("RSU" on Figure 2) using localized communications. The road traffic

© ISO 2021 – All rights reserved 7
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ISO/TR 21186-2:2021(E)

control centre can thus take necessary actions, like sending a patrol vehicle to secure the area, and

inform road users.

In turn, the road traffic centre could inform vehicles approaching the risk area through a roadside

ITS station unit located on the road upstream of the risk area that would repetitively broadcast the

alert using localized communications or display the hazard through a variable message sign board.

Alternatively, the road traffic centre could directly inform each of the vehicles subscribed to a road

hazard alert service through networked communications. Such notification could be used to advise

vehicles on alternative itineraries.

This example shows the value of using both localized and networked communications to inform

vehicles and the control centres about road hazards so that the road hazard alert can be transmitted

more widely and effectively. Localized communications are used to inform about an immediate time-

critical danger, whereas networked communications are used to inform about dangers upstream of

time and location.
5.2.2 Emergency call (use case 2)

A new series of vehicles are now placed on the market with an "emergency call" service which alerts

public safety services in case of an accident.

At the time of writing this document, this road safety service relies on a 2 generation cellular

technology with limited capabilities and limited coverage. However, there will continuously be

geographical areas not covered by the cellular network, either because there is no base station in the

vicinity or because the service is disrupted or overloaded. In such a situation, the emergency call cannot

be issued, although access technologies al
...

TECHNICAL ISO/TR
REPORT 21186-2
First edition
Cooperative intelligent transport
systems (C-ITS) — Guidelines on the
usage of standards —
Part 2:
Hybrid communications
PROOF/ÉPREUVE
Reference number
ISO/TR 21186-2:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO/TR 21186-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TR 21186-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Motivations for hybrid communications support .............................................................................................................. 2

5.1 Connected and cooperative mobility ................................................................................................................................... 2

5.2 Examples of use cases requiring a diversity of access technologies ......................................................... 5

5.2.1 Road hazard notification (use case 1) ........................................................................................................... 5

5.2.2 Emergency call (use case 2) ................................................................................................................................... 6

5.2.3 Public transport (use case 3) ................................................................................................................................ 6

5.3 Hybrid communication technologies................................................................................................................................... 7

5.4 Unified communication and data management architecture ......................................................................... 7

5.4.1 Requirements for the unified communication and data management

architecture .......................................................................................................................................................................... 7

5.4.2 Supporting a diversity of applications with diverging communication needs ........... 8

5.4.3 Supporting a diversity of communication paths .................................................................................. 8

5.4.4 Supporting a diversity of access technologies and protocols.................................................... 9

6 The ITS station architecture and functionalities in support of hybrid communications ......11

6.1 Origins of the ITS station architecture ............................................................................................................................11

6.2 Detailed ITS station architecture .........................................................................................................................................12

6.3 Design principles of the ITS station architecture ...................................................................................................14

6.4 ITS station functionalities in support for hybrid communications ........................................................15

6.5 ITS station management entity ..............................................................................................................................................16

6.6 ITS station capabilities ..................................................................................................................................................................17

6.7 ITS station service managed entity (ITS-S MSE) ....................................................................................................18

6.8 Management of data flow types (ITS-S flow type) ................................................................................................20

6.9 Management of communication paths (ITS-S path) ............................................................................................20

6.10 Management of communication profiles (ITS-SCP) .............................................................................................20

6.11 Management of communication handovers ...............................................................................................................22

6.12 Management of globally unique identifiers ................................................................................................................22

6.13 Standards necessary in support of hybrid communications ........................................................................22

7 How to develop ITS application standards .............................................................................................................................23

7.1 Generic development principle .............................................................................................................................................23

7.2 Specifying ITS-S application process ................................................................................................................................23

7.3 Defining data flow communication requirements ................................................................................................23

7.4 Registering communication requirements ..................................................................................................................24

7.5 Transmitting data ..............................................................................................................................................................................24

Bibliography .............................................................................................................................................................................................................................25

© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO/TR 21186-2:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems, in

collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC

278, Intelligent transport systems, in accordance with the Agreement on technical cooperation between

ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 21186 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/TR 21186-2:2020(E)
Introduction

This document is part of a family of deliverables from Standard Development Organizations (SDOs)

for Cooperative Intelligent Transport Systems (C-ITS), which is a subset of standards for Intelligent

Transport Systems (ITS).
ITS aims to improve surface transportation in terms of
— safety
e.g. crash avoidance, obstacle detection, emergency call, dangerous goods;
— efficiency

e.g. navigation, green wave, priority, lane access control, contextual speed limits, car sharing;

— comfort
e.g. telematics, parking, electric vehicle charging, infotainment;
— sustainability,
by applying information and communication technologies (ICT).

In the European Union, the legal framework is given by the European Commissions Mandate M/453

[51] [50]

on C-ITS , the European Commission Directive 2010/40 , and the European Commission Mandate

[52]
M/546 .

The whole set of standards for deployment of C-ITS is difficult to understand by developers of equipment

and software, especially ITS application software, and thus guidelines explaining a beneficial choice

of standards (C-ITS Release), the purpose and interaction of standardized features, beneficial

implementation approaches and guidance in developing ITS applications are a prerequisite for a fair

and open market allowing early deployment of interoperable and future-proof solutions.

The ISO 21186 series provides necessary guidelines in multiple parts, each dedicated to a specific

purpose:
— Part 1: Standardization landscape and releases;
— Part 2: Hybrid communications (this document);
— Part 3: Security.
This document can be complemented by further parts as required, for example:
— Usage of the service announcement protocol specified, e.g. in ISO 22418;

— Dynamically extendable data and protocol parameters ("Information Object Classes" and

"Information Object Sets"; based on ASN.1 type CLASS);
— Usage of the GDTM framework specified in ISO/TS 21184.

The purpose of this document is thus to inform about relevant standards and to describe the

functionalities of the ITS station architecture defined in support for hybrid communication

technologies. It is intended to serve as a guideline to structure the development of new C-ITS standards

and to harmonize the deployment of C-ITS services relying on the use of hybrid communication

technologies. It also intends to give support to the developers of standards defining C-ITS services and

to the developers of C-ITS solutions and ITS applications complying with the ITS station architecture

and its set of functionalities supporting hybrid communications.

At time of writing this document, no applicable Intellectual Property Rights (IPR) issues were known

related to this document. However, this document references standards, for which IPRs are known.

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Information on such IPRs is expected to be provided in those respective standards, which might be

from any one of the Standards Development Organisations working on ITS or C-ITS.

Referencing other SDOs and their respective deliverables in no way is to be understood as an

endorsement, but rather as an informative piece of information.
[56]

More details on the C-ITS domain can be found in the Brochure produced by the CEN/TC 278 Project

Team PT 1605.
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TECHNICAL REPORT ISO/TR 21186-2:2020(E)
Cooperative intelligent transport systems (C-ITS) —
Guidelines on the usage of standards —
Part 2:
Hybrid communications
1 Scope

This document serves as a guideline explaining the concept of hybrid communications and support

functionalities for Cooperative ITS services deployed in conformance with the ITS station architecture

and related Cooperative ITS standards.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 21217, Intelligent transport systems — Station and communication architecture

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 21217 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
ITS-S flow identifier

identifier, being unique within an ITS station unit, that identifies an ITS-S flow

[SOURCE: ISO 24102-6:2018, 3.9]
3.2
urban WiFi

short-range networked communications WiFi access technology used mostly in urban environments

and in personal devices such as smartphones, tablets and laptops

Note 1 to entry: An example of urban WiFi is IEEE 802.11 Basic Service Set (BSS) for WLAN access used in 2,4 GHz

or 5,4 GHz frequency range.
3.3
vehicular WiFi

short-range localized communications WiFi access technology specifically designed for vehicular

localized communications

Note 1 to entry: An example of vehicular WiFi is IEEE 802.11 operating outside the context of a Basic Service

[49]

(OCB), also known as IEEE 802.11p , used in the 5,9 GHz frequency range reserved for ITS services with profile

standards named ITS-G5 (ETSI) in Europe and Australia, and US-DSRC in North America and their harmonization

at ISO ( ITS-M5).
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4 Symbols and abbreviated terms
CAM cooperative awareness message
C-ITS cooperative intelligent transport systems
CPH communication profile handler
CSH content subscription handler
DENM decentralized environmental notification message
DSRC dedicated short-range communication
ETSI European Telecommunication Standards Institute
FSH facilities service handler
IEEE Institute of Electrical and Electronics Engineers
IPv6 internet protocol version 6
ITS intelligent transport systems
ITS-S ITS station
ITS-SU ITS station unit
LDM local dynamic map
LiFi light fidelity
LoRA long range
LTE-V2X long term evolution based vehicle-to-everything
OCB outside the context of a basic-service set
OSI open systems interconnection
PVT position, velocity and time
SDO standards development organization
US-DSRC american dedicated short range communication
V2X vehicle-to-vehicle and vehicle-to-roadside
WiFi wireless fidelity
WSMP wave short message protocol
5 Motivations for hybrid communications support
5.1 Connected and cooperative mobility

Intelligent transport systems (ITS) services are traditionally ranged into three categories: road traffic

safety, traffic efficiency and comfort (infotainment, value added services, etc.).

ITS services were initially deployed either in the roadside infrastructure (variable message signs, etc.),

in vehicles (telematics) or nomadic devices (navigation, traffic alerts, etc.) with little or no interaction

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between the vehicles, other road users and the roadside infrastructure. With the advent of short-range

communication technologies, ITS services using the exchange of data between vehicles and the roadside

[2],[34]-[36] [3]

infrastructure then started to appear (electronic fee collection , electric-vehicle charging ,

[37]

emergency call , etc.). These ITS services are specified to operate in a very controlled environment,

with a very specific radio technology, and for a very specific purpose.

While recent generations of vehicles are deployed with built-in communication systems providing

connectivity to remote platforms providing services (navigation, software update, telematics, electric

vehicle charging, emergency call, etc.), the forthcoming generation of vehicles will cooperate with

their surrounding environment (other vehicles, other road users, roadside infrastructure and urban

infrastructure). This localized exchange of data improves road safety (crash avoidance, obstacle

detection, etc.) and traffic efficiency (traffic information, green wave, lane access control, contextual

speed limit, etc.).

Cooperative ITS (C-ITS) services, i.e. ITS services for connected and cooperative mobility that rely on

the data exchanged between vehicles (cars, trucks, buses, etc.), other road users (pedestrians, cyclists,

etc.), the roadside and urban infrastructure (traffic lights, road tolls, etc.) and control and services

centres in the cloud (traffic control centre, service providers, map providers, etc.), and especially on the

sharing of data amongst service domains and applications of the same service domain, are thus being

developed. See Figure 1.
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ISO/TR 21186-2:2020(E)
Key
1 satellite broadcast 8 vehicle-to-vehicle
2 terrestrial broadcast 9 localized communications (e.g. 5 GHz, 60 GHz, IR)
3 GPS/GALILEO 10 roadside-to-roadside
4 cellular 11 roadside-to-vehicle
5 portable-to-vehicle 12 centre-to-roadside
6 vehicle-to-centre 13 internet
7 hot-spot
Figure 1 — Connected and Cooperative Mobility

However, distinct C-ITS services have diverging communication requirements (distribution area,

amount of data, delivery delay, privacy, confidentiality, etc.). No single communication technology is

able to fulfil all of these requirements at once.

Many communication technologies are available today on the market (cellular 3G/4G, infrared, LiFi,

satellite, urban WiFi, vehicular WiFi, LoRA, etc.) and new promising technologies appear regularly. They

have very different characteristics (radio coverage range, bandwidth, propagation delay, reliability,

price, transmission power), and are more or less prone to security threats (denial of service, intrusion,

impersonation, observation). Each of these access technologies has its own benefits and drawbacks

with respect to the type of service that is to be delivered.

Due to their diverging characteristics, their geographic penetration, and regional regulations, the

combination of several access technologies and protocols is beneficial or even necessary for ensuring

reliability, interoperability and sustainable development of C-ITS services. This requires a common

approach to the way security, communications and data are handled.
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Before requirements for this common approach are discussed in 5.3, subclause 5.2 presents examples

illustrating the need to combine a diversity of access technologies.
5.2 Examples of use cases requiring a diversity of access technologies
5.2.1 Road hazard notification (use case 1)

Road hazards present road safety risks that could be leveraged using localized communications (using

vehicular WiFi in the 5,9 GHz frequency band, for example) and networked communications (using

3G/4G cellular technology, for example). A typical example is black ice on the road as illustrated on

Figure 2.

A vehicle equipped with sensors can detect black ice. If it is equipped with localized communications

capabilities it can inform subsequently following vehicles so that they reduce speed in due time and

take other automatic actions to ensure safety. All equipped vehicles can relay this alert from vehicle to

vehicle, but at some point, there will not be any vehicle able to relay this message further. Consequently,

an approaching vehicle still kilometres away will not be informed.
Key
1 V2V GeoBroadcast
2 RSU 1
3 vehicle A to control centre
4 internet IPv6
5 control centre
6 control centre to vehicles in GeoArea
7 RSU 2
8 roadside unit to vehicles in GeoArea
[54]
Figure 2 — Black ice notification using hybrid communications (FP7 GeoNet )
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To ensure wide transmission of the alert, vehicles that detect the hazard could transmit a road hazard

alert to the road traffic control centre, either directly using networked communications, or through a

nearby roadside ITS station unit ("RSU" on Figure 2) using localized communications. The road traffic

control centre can thus take necessary actions, like sending a patrol vehicle to secure the area, and

inform road users.

In turn, the road traffic centre could inform vehicles approaching the risk area through a roadside

ITS station unit located on the road upstream of the risk area that would repetitively broadcast the

alert using localized communications or display the hazard through a variable message sign board.

Alternatively, the road traffic centre could directly inform each of the vehicles subscribed to a road

hazard alert service through networked communications. Such notification could be used to advise

vehicles on alternative itineraries.

This example shows the value of using both localized and networked communications to inform

vehicles and the control centres about road hazards so that the road hazard alert can be transmitted

more widely and effectively. Localized communications are used to inform about an immediate time-

critical danger, whereas networked communications are used to inform about dangers upstream of

time and location.
5.2.2 Emergency call (use case 2)

A new series of vehicles are now placed on the market with an "emergency call" service which alerts

public safety services in case of an accident.

At the time of writing this document, this road safety service relies on a 2 generation cellular

technology with limited capabilities and limited coverage. However, there will continuously be

geographical areas not covered by the cellular network, either because there is no base station in the

vicinity or because the service is disrupted or overloaded. In such a situation, the emergency call cannot

be issued, although access technologies alternatives are available that could replace or complement the

cellular network.

A case in which localized communications technologies could be useful is a situation in which a vehicle

has driven off the road and has fallen into a canyon. The passengers are still alive, but unable to get out

of the vehicle. There is no cellular coverage, so the emergency call cannot be transmitted. However,

the vehicle is not far from the road and is in radio coverage using localized communications. If the

emergency call could be supplied over that localized communications link in addition to the cellular

network, passing-by vehicles could get the emergency call and relay it to public safety services as soon

as they are in cellular radio coverage, or when they reach a roadside ITS station unit ("RSU").

[37]
A first related standard on "eCall via an ITS station" is CEN/TS 17182 .
5.2.3 Public transport (use case 3)

Recent fleets of buses are deployed with communication technologies providing different types of

services: buses are usually equipped with tracking capabilities to monitor the progress of the bus on

the itinerary and inform passengers waiting at bus stops. They are also often equipped with a video

capability in order to inform the control centre in an emergency situation; and sometimes with a

system allowing priority of buses at crossroads. The newest generations of buses would of course also

be equipped with with road safety services (see 5.2.1) and with emergency call (see 5.2.2).

As a consequence, buses are equipped with multiple communication systems. Each service is deployed

using its own antenna, radio technology, hardware, software and screen, and has its own proprietary

or standardized data format. These frequently duplicate one another, as there could be several

communication systems deployed using the same access technology, e.g. cellular. This is not efficient

in terms of cost, complexity and reliability. Overall, all of these communication systems are unable to

exchange data between one another. An emergency call can thus not be transmitted using an alternative

access technology if one fails or if the bus is out of cellular network coverage.

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In this situation, a common reference communication architecture is needed to share data between the

various communication systems and to combine multiple access technologies and protocols to provide

more reliable and efficient services.
5.3 Hybrid communication technologies

As highlighted in the use cases described in 5.2, connected and cooperative mobility services cannot be

achieved by a single type of communication technology. Multiple access technologies and protocols are

needed and are preferably combined, for several reasons, including:
— to offer extended connectivity to an ITS service;
— to offer complementary or redundant communication channels;
— to address a diverse range of ITS services with varying communications needs;
— to allow future-proof development of specifications;
— to sustain environments with varying connectivity quality.

Combining multiple access technologies and communication protocols into a unified communication

system (possibly duplicated for redundancy, or spread in multiple communication units complying to

the same communication architecture) is sometimes referred to as "hybrid communications".

The term "hybrid communications" so far has no strict standardized definition and may be interpreted

differently from different groups of stakeholders. Some views are:

— It merely means the combination of inter-changeable flavours of short-range access technologies

used for localized communications with medium-range communication technologies used for

connectivity to the cloud into a single communication system.

— It means the ability to deploy the same C-ITS services either using localized communications in

some vehicles or cellular-based networked communications in other vehicles.

— It means having two independent systems integrated into a single platform, one with short range

communications for a limited set of services (time critical road safety) and one with long-range

communication capabilities for another limited set of services (infotainment, telematics, non-time

critical road safety).

More generally, a hybrid communication system can be defined as a communication system combining

various access technologies and protocols, used to support a range of applications with different and

varying communications requirements.

In the context of C-ITS, the term hybrid communications is defined as multiple access technologies and

protocols dynamically managed (combined) to provide complementary or redundant communication

channels.
5.4 Unified communication and data management architecture

5.4.1 Requirements for the unified communication and data management architecture

Combining multiple access technologies and communication protocols as advocated in the previous

sections requires a common approach on how communications and data are managed in a secure way,

i.e. a unified communication architectu
...

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