ISO 21217:2010

INTERNATIONAL ISO
STANDARD 21217
First edition
2010-04-15


Intelligent transport systems —
Communications access for land mobiles
(CALM) — Architecture
Systèmes intelligents de transport — Accès aux communications des
services mobiles terrestres (CALM) — Architecture





Reference number
ISO 21217:2010(E)
©
ISO 2010

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ISO 21217:2010(E)
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ISO 21217:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Conformance .1
3 Normative references.1
4 Terms, definitions and abbreviated terms.1
4.1 Terms and definitions .1
4.2 Abbreviated terms .4
5 Requirements.4
5.1 Principles for CALM-related International Standards.5
5.2 ITS viewpoint .5
5.3 Handover .6
5.4 ITS subsystems and ITS-Ss.8
5.5 Communication scenarios and classes.11
5.6 ITS-S architecture.14
5.7 CALM communications kernel.20
5.8 Services.20
5.9 Details related to the access layer.21
5.10 Details related to the networking and transport layer .23
5.11 Details related to facilities layer.24
5.12 Details related to ITS-S applications .25
5.13 Management elements.25
5.14 Security.26
6 Declaration of patents and intellectual property.26
Annex A (informative) CALM standards reference.30
Annex B (informative) Examples of details of communication scenarios .31
Annex C (informative) Implementations .34
Bibliography.38

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ISO 21217:2010(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 21217 was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
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ISO 21217:2010(E)
Introduction
This International Standard is part of a family of International Standards based on the communications access
for land mobiles (CALM) concept. These International Standards specify a common architecture, network
protocols and communication interface definitions for wired and wireless communications using various
access technologies including cellular 2nd generation, cellular 3rd generation, satellite, infra-red, 5 GHz micro-
wave, 60 GHz millimetre-wave and mobile wireless broadband. These and other access technologies that can
be incorporated are designed to provide broadcast, unicast and multicast communications between mobile
stations, between mobile and fixed stations and between fixed stations in the intelligent transport systems
(ITS) sector.
This International Standard describes the common architectural framework around which CALM-compliant
communication entities called ITS stations (ITS-Ss) are instantiated, and provides the architectural reference
for use by the CALM family of International Standards, including the lower layer service access point
specifications described in ISO 21218, network protocol specifications described in ISO 21210 (IPv6
networking) and ISO 29281 (non-IP networking), and the ITS-S management specifications described in
ISO 24102.
The relationship between the members of the CALM family of International Standards is shown in Figure A.1.
The numbers in the boxes are references to the International Standard in which the indicated functionality is
specified.
The functional requirements for information transmission in the ITS sector over large distances using wireless
access technologies may be very different from the requirements for, for example, European dedicated short
range communication (DSRC). In ITS, large volumes of data are required for purposes such as safety, traffic
information and management, video downloads to mobile stations for tourist information and entertainment
and navigation-system-updates. In order to support such services, mobile stations need to be able to
communicate over longer ranges with fixed stations, and the system must be able to hand over sessions from
one fixed station to another. Thus, the CALM family of International Standards is explicitly designed to enable
quasi-continuous communications, communications of protracted duration, and short messages and sessions
of high priority with stringent time constraints.
CALM-complaint systems provide the ability to support handover of different types. One of the essential
features of the CALM concept is the ability to support media independent handover (MIH), also referred to as
heterogeneous handover, between the various access technologies supported by CALM, e.g. cellular, satellite,
microwave, mobile wireless broadband, infra-red, DSRC. With this flexibility, CALM-complaint systems
provide the ability to use the most appropriate access technology for message delivery. Selection rules that
are supported include user preferences and access technology capabilities in deciding which access
technology to use for a particular session, and when to handover between access technologies or between
service providers on the same access technology. It is also important to note that communication between
ITS-Ss is peer-to-peer, regardless of the networks providing the connectivity. This provides flexibility in
designing applications for the ITS sector. While this flexibility is very important in providing quasi-continuous
connectivity, applications may be restricted to specific access technologies and operational frequency bands,
if required.
A fundamental advantage of the CALM concept over traditional systems is that applications are abstracted
from the access technologies that provide the wireless connectivity and the networks that transport the
information from the source to the destination(s). With reference to Figure A.1, this means that ITS-Ss are not
limited to a single access technology and networking protocol, and can implement any of those supported; it
also means that the ITS-S management can make optimal use of all these resources. To exploit this flexibility,
CALM-complaint systems provide the ability to support handover of different types, including those involving a
change of communication interface (which may or may not involve a change of access technology, since
ITS-Ss may have multiple communication interfaces using the same access technology), those involving
reconfiguration or change of the network employed to provide connectivity, and those involving both a change
in communication interface and network reconfiguration.
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ISO 21217:2010(E)
The architecture specified within this International Standard makes provision for rapid session initialization,
where this is required, e.g. for road safety applications.
The architecture specified within this International Standard supports a variety of different ITS-S
implementations, ranging from “simple single-box implementations” up to “complex distributed
implementations” where the complete ITS-S functionality is distributed in several physical boxes
interconnected with wired or wireless local networks. The instantiation of access technologies used for these
local station-internal networks follows the same principles as the instantiation of access technologies used to
connect to external networks.

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INTERNATIONAL STANDARD ISO 21217:2010(E)

Intelligent transport systems — Communications access for
land mobiles (CALM) — Architecture
1 Scope
This International Standard specifies the architectural communications framework of intelligent transport
systems (ITS) for the family of CALM-related International Standards. The architecture is described in an
abstract way with several graphical views and examples. The graphical representations partly follow the ISO
Open Systems Interconnection (OSI) principles. In addition to the requirements specified within this
International Standard, a number of notes and examples are provided to illustrate the CALM concept.
Wherever practicable, this International Standard has been developed by reference to suitable extant
International Standards, adopted by selection. The architecture provides for regional variations where
regulations differ in different countries and regions.
2 Conformance
Conformance declarations for the various parts of a CALM-compliant system shall be based on the relevant
CALM-related International Standards.
3 Normative references
The following referenced documents are indispensable for the application 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 21210, Intelligent transport systems — Communications access for land mobiles (CALM) — IPv6
Networking
ISO 21218, Intelligent transport systems — Communications access for land mobiles (CALM) — Medium
service access points
ISO 24102, Intelligent transport systems — Communications access for land mobiles (CALM) — Management
4 Terms, definitions and abbreviated terms
4.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1.1
access technology
technology employed in a communication interface to access a specific medium
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ISO 21217:2010(E)
4.1.2
CALM-aware application
ITS-S application which is capable of supporting features specific to CALM
NOTE CI selection management is an example.
4.1.3
central ITS-S
central ITS station
implementation of an ITS-S in a central ITS subsystem
4.1.4
FA interface
interface between the facilities layer and the ITS-S applications entity
NOTE The FA interface is presented in Figure 14.
4.1.5
geo-networking
geo-routing
network layer protocol using addresses in the form of geo-coordinates which identify target areas of possible
destination stations
4.1.6
heterogeneous handover
process by which a communication link is switched from one virtual communication interface to another one of
a different medium type
4.1.7
homogeneous handover
process by which a communication link is switched from one virtual communication interface to another one of
the same medium type
4.1.8
IN interface
interface between the access layer and the networking and transport layer
NOTE The IN interface is presented in Figure 14.
4.1.9
ITS service
service provided by a set of ITS-S applications
4.1.10
ITS-S
ITS station
entity in a communication network, comprised of application, facilities, networking and access layer
components specified in this International Standard that operate within a bounded secure management
domain
4.1.11
ITS-S application
functionality in an ITS-S that uses ITS-S services to connect to one or more other ITS-S application
4.1.12
ITS-S gateway
gateway functionality provided in the facilities layer of an ITS-S
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ISO 21217:2010(E)
4.1.13
ITS-S host
application and facilities functionality provided in an ITS-S together with a minimum communication
functionality to connect to the ITS-S internal network
4.1.14
ITS-S router
routing functionality provided in an ITS-S
4.1.15
ITS-S service
communication functionality offered by an ITS-S to an ITS-S application
4.1.16
MA interface
interface between the communication and station management entity and the ITS-S applications entity
NOTE The MA interface is presented in Figure 14.
4.1.17
medium
any entity upon which a signal is impressed or from which a signal is received, e.g. wireless or on a wire, radio
waves or light, low or high frequency band, modulation scheme
4.1.18
MF interface
interface between the communication and station management entity and the facilities layer
NOTE The MF interface is presented in Figure 14.
4.1.19
MI interface
interface between the communication and station management entity and the access layer
NOTE The MI interface is presented in Figure 14.
4.1.20
MN interface
interface between the communication and station management entity and the networking and transport layer
NOTE The MN interface is presented in Figure 14.
4.1.21
MS interface
interface between the communication and station management entity and the security entity
NOTE The MS interface is presented in Figure 14.
4.1.22
network-based multi-hopping
multi-hopping from ITS-S to ITS-S performed by a networking protocol
4.1.23
NF interface
interface between the networking and transport layer and the facilities layer
NOTE The NF interface is presented in Figure 14.
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ISO 21217:2010(E)
4.1.24
personal ITS-S
personal ITS station
implementation of an ITS-S in a personal ITS subsystem
4.1.25
roadside ITS-S
roadside ITS station
implementation of an ITS-S in a roadside ITS subsystem
4.1.26
SA interface
interface between the security entity and the ITS-S applications entity
NOTE The SA interface is presented in Figure 14.
4.1.27
SF interface
interface between the security entity and the facilities layer
NOTE The SF interface is presented in Figure 14.
4.1.28
SI interface
interface between the security entity and the access layer
NOTE The SI interface is presented in Figure 14.
4.1.29
SN interface
interface between the security entity and the networking and transport layer
NOTE The SN interface is presented in Figure 14.
4.1.30
vehicle ITS-S
vehicle ITS station
implementation of an ITS-S in a vehicular ITS subsystem
4.2 Abbreviated terms
API application programming interface
CAL communication adaptation layer
CALM communications access for land mobiles
CCK CALM communications kernel
CI communication interface
DSRC dedicated short range communication
ECU electronic control unit
HMI human-machine interface
IPv6 Internet protocol version 6
ITS intelligent transport systems
LLC logical link control
PDA personal digital assistant
SAP service access point
VMS vehicle motion sensor
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ISO 21217:2010(E)
5 Requirements
5.1 Principles for CALM-related International Standards
CALM-related International Standards shall focus on specifying open interfaces with regard to the
functionalities required for all relevant layers of the OSI reference model.
CALM-related International Standards shall not specify implementation aspects, except in situations where
such specification is deemed essential to interoperability of the interface protocol.
5.2 ITS viewpoint
5.2.1 Wireless links
Figure 1 illustrates the global ITS scope to be considered by the set of CALM-related International Standards.
It shows several types of access technologies for wireless communication links between individual ITS-Ss and
between ITS-Ss and legacy stations which can be expected to be present in ITS environments.
NOTE The CALM concept is not limited to the access technologies presented in Figure 1.


Figure 1 — Examples of wireless links employing various access technologies
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ISO 21217:2010(E)
5.2.2 Access technologies
The access technologies shown in Figure 1 with an asterisk are each fully specified by a CALM International
Standard, e.g. M5 (ISO 21215), IR (ISO 21214) and MM (ISO 21216). These access technologies have been
developed with a specific focus on ITS deployment.
The other access technologies shown in Figure 1 are examples of legacy access technologies. Legacy access
technologies are specified by reference to the standards according to which they operate (see, for example,
ISO 25111). For these legacy access technologies, an adaptation as specified in ISO 21218 can be required
in order to fit to the communication and station management entity, to the security entity and to the networking
and transport layer; see Figure 14.
Regionally specified DSRC systems may be supported in ITS-Ss as specified in ISO 24103 and ISO 29281.
Applications based on the DSRC standards ISO 15628:2007 or EN 12795:2003 can be supported in the ITS
environment as specified in ISO 29281.
Positioning data from satellite networks such as GPS, GALILEO or GLONASS may be received and provided
to the related applications, e.g. via the ITS station-internal network presented in Figure 2.
5.2.3 Communication interface
An implementation of an access technology is called a communication interface (CI). The concept of a CI and
its virtual communication interfaces (VCIs) are specified in ISO 21218.
5.2.4 Logical channel types
Logical communication channels are a key element of CALM's abstraction of ITS-S applications from the
physical communication channels used to transport the information. ITS-S applications communicate through
logical channels which are mapped by the ITS-S management to physical channels in CIs. Automatic mapping
of ITS-S applications on specific CIs, referred to as “CI selection management”, is specified in ISO 24102.
Definitions of logical channel types are provided in ISO 21218.
5.3 Handover
5.3.1 General
The essential feature of the CALM concept that distinguishes it from traditional communication systems is that
applications are abstracted from the access technologies that provide the wireless connectivity and the
networks that transport the information from the source to the destination(s). ITS-Ss are not limited to a single
access technology and networking protocol and can implement any of those supported, and the ITS-S
management can make optimal use of all these resources. To exploit this flexibility, CALM-compliant systems
provide the ability to support handover of different types including
⎯ those involving a change of CI (which may or may not involve a change of access technology, since
ITS-Ss may have multiple communication interfaces using the same access technology,
⎯ those involving reconfiguration or change of the network employed to provide connectivity, and
⎯ those involving both a change in communication interface and network reconfiguration.
The following examples illustrate the various types of handover that are possible.
⎯ Homogeneous handover:
Maintaining a session between an ITS-S application in a vehicular ITS subsystem and an ITS-S
application in a central ITS subsystem using subsequent roadside ITS-Ss along the road of the same
roadside subsystem, using the same access technology in the various ITS-Ss.
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ISO 21217:2010(E)
⎯ Heterogeneous handover:
Maintaining a session between an ITS-S application in a vehicular ITS subsystem and an ITS-S
application in a central ITS subsystem by switching from a dedicated CALM access technology, e.g. M5
or IR, to a public cellular network.
5.3.2 Network domains
The top-level point of view of networking supported by ITS is presented in Figure 2.

Figure 2 — Top-level networking view
Two domains are distinguished, i.e.
⎯ the ITS domain, and
⎯ the generic domain.
Possible networks in the ITS domain are
⎯ the ITS station-internal network,
⎯ the ITS ad-hoc network, and
⎯ the ITS access network.
NOTE 1 The concept of an ITS-S is presented in Figure 14.
NOTE 2 The ITS station-internal network may be realized simultaneously with different access technologies, both wired,
e.g. Ethernet, or wireless, e.g. Bluetooth. See also ISO 21210 and ISO 29281.
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ISO 21217:2010(E)
Possible networks in the generic domain are
⎯ the local data network (typically a private network),
⎯ the public access network,
⎯ the private access network, and
⎯ the core networks.
The boundary of an ITS-S is indicated in Figure 2. The ITS-S connects to the local proprietary data network
via an ITS-S gateway, as presented in Figure 15, i.e. the vehicle gateway in Figure 4, the roadside gateway in
Figure 5 and the central gateway in Figure 7. The ITS-S connects to the access networks via ITS-S border
routers, as presented in Figure 17, i.e. the routers presented in Figures 5 and 7.
5.4 ITS subsystems and ITS-Ss
5.4.1 Peer-to-peer communication
Figures 4, 5, 6 and 7 present four ITS subsystems, i.e. vehicular ITS subsystem, roadside ITS subsystem,
personal ITS subsystem and central ITS subsystem.
The essential element in every ITS subsystem is the ITS-S compliant with the ITS-S reference architecture
presented in Figures 13 and 14. ITS-S subsystems are introduced for the sole purpose of illustrating the
different implementation possibilities of ITS-Ss. All communications between ITS-Ss is peer-to-peer, as
illustrated in Figure 3, regardless of the ITS-S locations relative to the networks involved in the connection.


Figure 3 — ITS subsystems and peer-to-peer communications
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ISO 21217:2010(E)
Figures 4, 5, 6 and 7 distinguish ITS-S hosts and ITS-S routers in accordance with Figure 16, although this
functionality is completely covered by the concept of an ITS-S. This distinction illustrates that in an
implementation, the overall functionality of an ITS-S may be provided in several distinct physical units, where
several physical units with the same functionality may also exist.
ITS-S gateways in accordance with Figure 15 and ITS-S border routers in accordance with Figure 17 are
presented in order to show that the interconnection with proprietary and public networks is not CALM
compliant.
5.4.2 Vehicular ITS subsystem
The vehicular ITS subsystem presented in Figure 4 contains a vehicle ITS-S. The vehicle ITS-S may be
physically split into ITS-S hosts, ITS-S routers and the CALM-compliant part of the vehicle ITS-S gateway. A
passenger may use a personal ITS-S, as presented in Figure 6, which uses an HMI and forms an integral part
of the vehicular ITS-S.
The vehicle ITS-S gateway supports functionality in order to connect to the ITS-S host and the ITS-S router
via the ITS station-internal network presented in Figure 2. The part of the vehicle ITS-S gateway which
connects to the proprietary in-vehicle network and the ECUs is outside the scope of this International
Standard.

Figure 4 —Vehicular ITS subsystem
5.4.3 Roadside ITS subsystem
The roadside ITS subsystem presented in Figure 5 contains a roadside ITS-S. The roadside ITS-S may be
physically split into ITS-S hosts, ITS-S routers and the CALM-compliant parts of roadside ITS-S gateways and
ITS-S border routers. In this context, the ITS-S router is also called access router.
The roadside ITS-S gateway supports functionality in order to connect to the ITS-S hosts, the ITS-S routers
and the ITS-S border routers via the ITS station-internal network presented in Figure 2. The part of the
roadside ITS-S gateway which connects to the proprietary roadside network and the roadside components
such as VMS, inductive loops, etc., is outside the scope of this International Standard.

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ISO 21217:2010(E)

Figure 5 — Roadside ITS subsystem
5.4.4 Personal ITS subsystem
The personal ITS subsystem presented in Figure 6 provides the ITS-S functionality in consumer electronic
devices such as PDAs and mobile phones. It contains a personal ITS-S. Portable devices, e.g. PDAs, cellular
phones, with ingress connectivity (provided by Bluetooth, for example), in addition to connectivity to public
wireless network services, may be used as egress access technologies for ITS-Ss. Portable devices, e.g.
laptops and media p
...