ISO 21215:2018

INTERNATIONAL ISO
STANDARD 21215
Second edition
2018-06
Intelligent transport systems —
Localized communications — ITS-M5
Systèmes intelligents de transport — Communications localisées — M5
Reference number
ISO 21215:2018(E)
©
ISO 2018

---------------------- Page: 1 ----------------------
ISO 21215:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 21215:2018(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 General requirements . 2
5.1 IEEE 802.11 . 2
5.2 Architecture . 2
5.3 Hybrid communications support . 4
5.4 Path and flow management support . 4
5.5 MI-SAP support . 4
6 Communication interface protocol stack . 4
6.1 Physical layer . 4
6.2 Medium access control sub-layer. 5
6.3 Logical link control sub-layer . 5
6.4 Communication adaptation sub-layer . 6
7 Communication interface management . 7
7.1 General management. 7
7.2 Management adaptation entity. 7
7.2.1 802.11 parameters and I-Parameters . 7
7.2.2 802.11 commands and MI-SAP commands and requests . 7
7.2.3 802.11 management frames . 8
8 Procedures . 8
8.1 Communication interface procedures . 8
8.1.1 Transmit procedures . 8
8.1.2 Receive procedures . 8
8.2 Management procedures . 9
8.2.1 MAC address conflict . 9
8.2.2 Pseudonym MAC address change . 9
8.2.3 Cross-CI prioritization . 9
8.2.4 Communication range reference . 9
9 Conformance . 9
10 Test methods . 9
Annex A (normative) Communication interface parameters .10
Annex B (normative) MI-COMMANDs .13
Annex C (normative) MI-REQUESTs .14
Annex D (normative) ASN.1 definitions .15
Annex E (normative) Path and flow management support .18
Annex F (informative) Frequency allocations .19
Annex G (normative) Implementation conformance statement proforma .23
Bibliography .27
© ISO 2018 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 21215:2018(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 on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
This second edition cancels and replaces the first edition (ISO 21215:2010) which has been technically
revised.
The following main changes have been made since the last edition:
— document restructured in support of different regulatory regions;
— requirements applicable for usage in the European Union added;
— LDP/SNAP replaced by EPD;
— ASN.1 aligned with latest developments in ISO/TC 204;
— provisioning for path and flow management added;
— normative annex related to conformance testing, that contains the PICS proforma, added;
— editorial improvements.
iv © ISO 2018 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 21215:2018(E)

Introduction
Localized communications is an essential component of hybrid communications in Intelligent Transport
Systems (ITS). Various access technologies are suited for localized communications. A major focus of
ITS stakeholders for "Cooperative ITS" and "Urban ITS" is on the access technology originally specified
by IEEE in the standard IEEE Std 802.11™-2016. For usage in ITS, IEEE specified the operational mode
"Outside the Context of a BSS" (OCB), also known under the acronym of 802.11p.
This document primarily provides complements to IEEE Std 802.11™-2016 OCB needed to operate as
an ITS access technology in the various regions of the world, and optionally also supports ordinary
WiFi operation, i.e. not applying OCB. An implementation of this document is referred to as an ITS-M5
communication interface (CI).
ITS-M5 CIs are capable of
— interoperating with IEEE WAVE devices, and
— receiving messages from ETSI ITS-G5 devices.
This document supports usage of ITS-M5 in various station contexts. Precise specifications are
provided for the context specified in ISO 21217 and ISO 21218. Optional support for "Path and Flow
[8]
Management" specified in ISO 24102-6 is also provided.
© ISO 2018 – All rights reserved v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 21215:2018(E)
Intelligent transport systems — Localized communications
— ITS-M5
1 Scope
This document provides specifications of a communication interface (CI) named "ITS-M5". The name
"ITS-M5" indicates microwave frequency bands in the range of 5 GHz.
ITS-M5 CIs are based on the wireless LAN technology standardized at IEEE. This document specifies
the additions to and deviations from IEEE Std 802.11™-2016 required to make ITS-M5 CIs compatible
with the ITS station and communication architecture specified in ISO 21217.
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/IEC 8825-2, Information technology — ASN.1 encoding rules: Specification of Packed Encoding
Rules (PER)
ISO 21217, Intelligent Transport Systems — Communications access for land mobiles (CALM) — Architecture
ISO 21218, Intelligent Transport Systems — Hybrid communications — Access technology support
ETSI EN 301 893, 5 GHz RLAN; Harmonised Standard covering the essential requirements of article 3.2 of
Directive 2014/53/EU
ETSI EN 302 571, Intelligent Transport Systems (ITS); Radiocommunications equipment operating in the 5
855 MHz to 5 925 MHz frequency band; Harmonised Standard covering the essential requirements of article
3.2 of Directive 2014/53/EU
IEEE Std 802™, IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture
IEEE Std 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
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:
— IEC Electropedia: available at https: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
EtherType
2-octet unsigned Integer number with allowed values ≥1 536 (0x06.00), assigned by the IEEE Registration
Authority and used in data link layer frames, which identifies the protocol in the ITS networking &
transport layer able to parse and process the ITS-NTPDU contained in the data link layer frame
© ISO 2018 – All rights reserved 1

---------------------- Page: 6 ----------------------
ISO 21215:2018(E)

4 Symbols and abbreviated terms
I-Parameter Parameter of a CI or virtual CI (VCI) specified in ISO 21218.
M5-parameter Parameter of an ITS-M5 CI / VCI specified in this document.
, Commas within numbers are used as decimal points.
e.i.r.p. Equivalent isotropic radiated power
NPDU Network PDU
EPD EtherType protocol discrimination
ITS-SU ITS station unit (composed of one or several ITS-SCUs)
ITS-SCU ITS station communication unit
LLC Logical link control (sub-layer of the data link layer)
LPD LLC protocol discrimination
LPDU Link PDU
SNAP Sub-network access protocol
ITS-NTPDU ITS networking & transport layer PDU
PDU Protocol data unit
RLAN Radio LAN
BRAN Broadband radio access network
LAN Local area network
OCB Outside the context of a BSS
BSS Basic service set (specified in IEEE Std 802.11™-2016)
PHY Physical (layer)
MAC Medium access control (sub-layer of the data link layer)
5 General requirements
5.1 IEEE 802.11
An ITS-M5 implementation shall be compliant with IEEE Std 802.11™-2016, with restrictions and
amendments as specified in this document.
5.2 Architecture
The ITS station architecture specified in ISO 21217 is presented in Figure 1. The ITS-M5 CI is allocated
in the ITS-S access layer of the ITS station architecture.
2 © ISO 2018 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 21215:2018(E)

Figure 1 — ITS station architecture
Figure 2 shows the architecture diagram of an ITS-M5 communications interface (CI) embedded in the
general ITS station architecture.
Figure 2 — ITS-M5 CI architecture
The communication protocol layers of the ITS-M5 CI are
a) Physical layer for microwave communications (PHY), and
b) Medium access control sub-layer (MAC).
© ISO 2018 – All rights reserved 3

---------------------- Page: 8 ----------------------
ISO 21215:2018(E)

An ITS-M5 CI as specified in this document is an ITS wireless CI of CI class CIC-l1 for general
simultaneous bi-directional communications with multiple peer-stations as specified in ISO 21218. An
implementation may also be configured as an ITS wireless CI of CI class CIC-I3 (groupcast transmitter),
and CI class CIC-I4 (receiver only).
An ITS-M5 CI provides the functionality of the IN-SAP specified in ISO 21218, and uses the functionality
[6]
of the MI-SAP, and the SI-SAP, as specified in ISO 24102-3 .
NOTE 1 Service primitive functions for the SI-SAP are not identified so far.
NOTE 2 Multiple ITS-M5 CIs per ITS station unit (ITS-SU) are possible, regardless of whether the CIs belong to
the same ITS-SCU or to different ITS-SCUs of the same ITS-SU; see ISO 21217 for the specifications of ITS-SU and
ITS-SCU.
5.3 Hybrid communications support
An ITS-M5 CI shall support the hybrid communications functionality of ISO 21218, and may implement
this functionality in a strict way compliant with ISO 21217, but also in different ways supporting other
station architectures.
5.4 Path and flow management support
[8]
Support of path and flow management specified in ISO 24102-6 is optional.
Details of path and flow management applicable for the ITS-S access layer are specified in ISO 21218.
Path and flow management uses MI-COMMAND and MI-REQUEST service primitive functions presented
in Annex B and in Annex C, respectively. Specific behaviour of ITS-M5 upon reception of such MI-
COMMANDs, and the procedures to present MI-REQUESTs beyond the requirements set up in ISO 21218
are specified in Annex E.
5.5 MI-SAP support
[6]
An ITS-M5 CI shall support the MI-SAP functionality of ISO 24102-3 with details specified in
ISO 21218, and may implement this functionality in a strict way compliant with ISO 21217, but also in
different ways supporting other station architectures.
6 Communication interface protocol stack
6.1 Physical layer
An ITS-M5 implementation shall be compliant with the specification of
— Orthogonal frequency division multiplexing (OFDM) specified in IEEE Std 802.11™-2016, Clause 18.
Other PHY specifications from IEEE Std 802.11™-2016 are not applicable for ITS-M5.
According to regional requirements an ITS-M5 implementation shall
— support applicable congestion control mechanisms, and
— support applicable mitigation techniques enabling coexistence with nearby other services, e.g.
[21]
mitigation techniques specified in ETSI TS 102 792 .
EXAMPLE Coexistence with the European "Electronic Toll Collection" (ETC) services based on 5,8 GHz
backscatter communications is essential in Europe.
An ITS-G5 implementation shall support self-interference mitigation techniques, e.g. cross-CI
prioritization specified in ISO 21218, if self-interference mitigation techniques are applicable for a given
implementation.
4 © ISO 2018 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 21215:2018(E)

Radio frequency parameters such as centre frequency, channel spacing, (default) data rates, TX power
(density) limits, channel usage are as required by regional regulation.
6.2 Medium access control sub-layer
The "Frame body" field of data frames specified in IEEE Std 802.11™-2016, Figure 9-1 contains the
ITS-M5 LPDU (Link Protocol Data Unit) as illustrated in Figure 3.
Figure 3 — 802.11 data frame
6.3 Logical link control sub-layer
IEEE Std 802.11™-2016 does not specify a logical link control sub-layer protocol. Related functionality
is part of the communication adaptation sub-layer specified in 6.4.
[26]
The Length/Type field specified in IEEE 802.3-2015 contains a 2-octet unsigned Integer number.
Dependent on the value, the field provides either length information or EtherType information. If the
value contained in this field is equal to or larger than 1 536 = 0x06.00, the field contains an EtherType
address. Ethertype addresses are assigned by the IEEE Registration Authority, and are used to identify
the protocol employed directly above the ITS-S access layer. This method of addressing is named
"EtherType Protocol Discrimination" (EPD). An ITS-M5 CI shall support EPD specified in IEEE Std 802™.
[9]
EXAMPLE ISO FNTP specified in ISO 29281-1 is identified by the EtherType 0x89.50. IPv6 is identified by
[20]
the EtherType 0x86.DD. GeoNetworking specified in the ETSI multi-part standard EN 302 636 is identified by
[24]
the EtherType 0x89.47. The IEEE WSMP specified in IEEE 1609.3 is identified by the EtherType 0x88.DC.
NOTE 1 Allocations of EtherType values are published at http: //standards .ieee
.org/develop/regauth/ethertype/eth .txt.
NOTE 2 EPD replaces LLC Protocol Discrimination (LPD). ETSI ITS-G5 is the only known ITS access technology
still using LPD.
Different to the information in IEEE Std 802.11™-2016, 5.1.4, EPD is applicable in all frequency bands
as long as dot11OCBActivated is set to true, i.e. activating the operation mode "outside the context of a
BSS" (OCB).
The ITS-M5 LPDU illustrated in Figure 4 contains the ITS-NTPDU introduced in ISO 21217, preceded by
the EtherType field.
Figure 4 — ITS-M5 LPDU
NOTE 3 Values in the range 0 through 1 535 (0x05.FF) are not allowed to occur in the EtherType field, as these
numbers provide length information.
On the basis of "best effort" an ITS-M5 CI may also support reception of 802.11 data frames with a
frame body field supporting SNAP (SubNetwork Access Protocol) addressing rather than EtherType
addressing. SNAP addressing is illustrated in Figure 5. Discrimination between SNAP and EPD is
possible as long as the value 0xAA.AA is not used as an EtherType address.
© ISO 2018 – All rights reserved 5

---------------------- Page: 10 ----------------------
ISO 21215:2018(E)

Figure 5 — SNAP addressing
NOTE 4 SNAP is an extension of the deprecated IEEE 802.2 Logical Link Control (LLC) standard, still
[25]
available as ISO/IEC 8802-1:2001 . Currently the only know implementation of SNAP in ITS is standardized in
[19]
ETSI EN 302 663 for ETSI ITS-G5.
NOTE 5 The normative support of EPD enables interoperability with IEEE WAVE devices (e.g. for road safety
messages from the BSM message set). The SNAP support in receive mode allows reception of messages from ITS
station units conformant with ETSI EN 302 663 (e.g. broadcast road safety messages such as CAM and DENM).
6.4 Communication adaptation sub-layer
The communication adaptation sub-layer (CAL) is introduced in ISO 21218. The major task of CAL is
to provide the IN-SAP. ASN.1 details of the IN-SAP IN-UNITDATA service primitives are specified in
ISO 21218.
ITS-M5 CIs being compliant with ISO 21218 shall use an EtherType value in the IN-UNITDATA service
primitives to identify the applicable ITS-S networking & transport layer protocol.
In other implementation contexts, the EtherType value shall be used in the applicable service access
point primitives that exchange service data units between ITS-M5 and the network layer entity; details
are outside the scope of this document.
The IN-SAP service primitives of DL-UNITDATA contain the parameter "priority", which is the user
priority specified in ISO 21218. In implementations being compliant with ISO 21218 the relation
between user priority and IEEE 802.11 access category shall be as specified in Tables 1 and 2.
Table 1 — User priorities and IEEE access categories for TX
User priority Access category Data traffic UP in Data traffic type in IEEE
(AC) type IEEE 802.1D 802.1D
224 – 255 AC_VO Voice 7 Network control (NC)
192 – 223 6 Voice (VO)
160 – 191 AC_VI Video 5 Video (VI)
128 – 159 4 Controlled load
96 – 127 AC_BE Best effort 3 Excellent effort (EE)
64 – 95 0 Best effort (BE)
32 – 63 AC_BK Background 2 Spare (-)
0 – 31 1 Background (BK)
Table 2 — User priorities for RX
TID unknown 1 2 0 3 4 5 6 7
User priority 0 31 63 95 127 159 191 223 255
6 © ISO 2018 – All rights reserved

---------------------- Page: 11 ----------------------
ISO 21215:2018(E)

7 Communication interface management
7.1 General management
The ITS-M5 management shall be compliant with IEEE Std 802.11™-2016, with restrictions and
amendments as specified in this document.
The default value of the MIB parameter dot11OCBActivated specified in IEEE Std 802.11™-2016 shall be
true, enabling OCB communication, i.e. communication outside the context of a "Basic Service Set" (BSS).
Other modes of operation specified in IEEE Std 802.11™-2016 may also be implemented, e.g. ordinary
WiFi mode with dot11OCBActivated set to false. However for ordinary WiFi, LPD is required instead of
EPD, see IEEE Std 802.11™-2016, 5.1.4.
[20]
Operation in some frequency bands, e.g. the RLAN/BRAN band in Europe , requires transmit power
control (TPC), a procedure for dynamic frequency selection (DFS) and uniform spreading, in order
to detect signals from radar systems and to avoid co-channel interference. This functionality is not
supported in IEEE Std 802.11™-2016 if the MIB parameter dot11OCBActivated is set to true. In order
to optionally enable operation outside of a BSS in such bands, appropriate mechanisms enabling
compliance with regulatory requirements on TPC and DFS shall be implemented in a way not necessarily
being conformant with IEEE Std 802.11™-2016, if this optional mode of operation is to be supported by
an implementation.
ITS-M5 shall transmit data using EDCA as defined in IEEE Std 802.11™-2016, 9.19.2. With the MIB
parameter dot11OCBActivated being set to true, EDCA default values are static and not negotiated before
transmission. Default values are found in IEEE Std 802.11™-2016, table 8-106. The ITS station manager
may update these parameters using information from a trusted source, e.g. applying remote ITS station
[5]
management specified in ISO 24102-2 . Specific settings may be requested e.g. for roadside-to-vehicle
[3] [28]
communications initiated with service advertisement as specified in ISO 24102-5 and ISO 16460 .
7.2 Management adaptation entity
7.2.1 802.11 parameters and I-Parameters
In implementations compliant with ISO 21218, the following rules apply:
— IEEE 802.11 parameters that have an equivalent I-Parameter defined in ISO 21218 shall be mapped
on I-Parameters as specified in Annex A.
— IEEE 802.11 parameters which are relevant for ITS-M5 and do not have an equivalent I-Parameter
defined in ISO 21218 shall be made visible to the ITS station management by means of medium-
specific I-Parameters as specified in Annex A.
— I-Parameters which are relevant for ITS-M5 but cannot be mapped on an IEEE 802.11 parameters
shall be implemented in the MAE as specified in ISO 21218 with details specified in Annex A.
7.2.2 802.11 commands and MI-SAP commands and requests
[6]
In implementations compliant with ISO 21218 and ISO 24102-3 , the following rules apply:
— IEEE 802.11 management commands that have an equivalent MI-COMMAND/MI-REQUEST defined
[6]
in ISO 24102-3 shall be mapped on these MI-COMMAND/MI-REQUEST as specified in Annex B and
Annex C.
— IEEE 802.11 management commands that are relevant for an implementation of ITS-M5 and do not
[6]
have an equivalent MI-COMMAND/MI-REQUEST defined in ISO 24102-3 shall be made accessible
in an implementation specific way.
© ISO 2018 – All rights reserved 7

---------------------- Page: 12 ----------------------
ISO 21215:2018(E)

— MI-COMMANDs / MI-REQUESTs which are relevant for ITS-M5 but cannot be mapped on an
[6]
IEEE 802.11 management commands are implemented in the MAE as specified in ISO 24102-3
with details specified in Annex B and Annex C.
7.2.3 802.11 management frames
An ITS-M5 CI may support transmission of management frames requested by the ITS station
management with the MI-COMMAND "MacManagementFrameTX" of ASN.1 type UnitData specified
in ISO 21218.
An ITS-M5 CI may support forwarding of received management frames to the ITS station management
with the MI-REQUEST "MacManagementFrameRX" of ASN.1 type UnitData specified in ISO 21218.
The ASN.1 type UnitData contains a component with name "parameter" of ASN.1 type
MframeParameter, that is a medium-specific parameter used to indicate details of the 802.11
management frame, e.g. subtype BEACON/ACTION. For ITS-M5 MframeParameter contains the
component "parameter" of ASN.1 type M5-MgmtSubTypes, and is select
...