ISO 17515-3:2019

Intelligent transport systems - Evolved-universal terrestrial radio access network - Part 3: LTE-V2X

This document provides specifications related to the ITS-S access layer for a communication interface (CI) named "ITS-LTE-V2X". ITS-LTE-V2X CIs are based on the evolved-universal terrestrial radio access (E-UTRA) vehicle-to- everything (LTE-V2X) technology standardized at 3GPP. This document enables usage of the LTE-V2X technology as an ITS access technology in an ITS station by reference to respective specifications from 3GPP, and by specifying details of the "Communication Adaptation Layer" (CAL) and the "Management Adaptation Entity" (MAE) of communication interfaces specified in ISO 21218.

Systèmes de transport intelligents — Réseau d'accès à la radio terrestre universelle évoluée (E-UTRAN) — Partie 3: LTE-V2X

General Information

• Status: Published
• Publication Date: 04-Aug-2019
• ICS: 03.220.20 - Road transport
• ICS: 35.240.60 - IT applications in transport
• Technical Committee: ISO/TC 204 - Intelligent transport systems
• Drafting Committee: ISO/TC 204/WG 16 - Communications
• Current Stage: 9060 - Close of review
• Completion Date: 04-Mar-2030

Overview

ISO 17515-3:2019 - "Intelligent transport systems - E-UTRA - Part 3: LTE-V2X" specifies how LTE-V2X (E-UTRA vehicle-to-everything) is used as an ITS access technology. The standard defines the ITS-LTE-V2X communication interface (CI) for ITS stations, referencing 3GPP LTE/V2X specifications and specifying the Communication Adaptation Layer (CAL) and the Management Adaptation Entity (MAE) required by ISO 21218. ISO 17515-3 enables LTE features - including cellular, device-to-device (D2D) and V2X modes - to be integrated into ITS station units to support cooperative and localized ITS services.

Key topics and technical requirements

• Scope & intent: Defines ITS-S access layer behavior for ITS-LTE-V2X and how LTE-V2X is applied in ITS stations.
• Reference to 3GPP: Uses 3GPP LTE and LTE-V2X specifications (e.g., E-UTRA, RRC, V2X architecture) as the radio and protocol baseline.
• CAL and MAE: Specifies the Communication Adaptation Layer and Management Adaptation Entity functions required by ISO 21218, including management parameters, MI-COMMANDs and MI-REQUESTs.
• Protocol stack: Covers physical and data link layer expectations, data link addresses (layer‑2 ID), and higher‑layer identification.
• Operational modes: Supports operation with network infrastructure (eNB/Uu) and without infrastructure (PC5/D2D sidelink) per 3GPP V2X.
• Procedures & behavior: Includes transmit/receive procedures, CI connection, CI state management, cross-CI prioritization and MAC address mapping.
• Conformance & testing: Defines conformance clauses and test method references; normative annexes provide CI parameters, ASN.1 definitions, and command/request schemas.

Applications and users

ISO 17515-3 is intended for practical deployment of LTE-V2X in Intelligent Transport Systems:

• Vehicle OEMs and suppliers implementing ITS station units and onboard units (OBUs).
• Roadside and infrastructure vendors integrating V2I services.
• Mobile network operators and V2X service providers deploying V2N and V2X-enabled services.
• Systems integrators and test laboratories validating CAL/MAE behavior, conformance and interoperability.
• Standards bodies and regulators aligning ITS deployments with 3GPP and ISO ITS architecture.

Use cases include Cooperative ITS, urban traffic management, safety-critical V2V alerts, V2P pedestrian protection, and hybrid communications combining LTE and other ITS access technologies.

Related standards

• ISO 21217 (CALM architecture) and ISO 21218 (Hybrid communications - Access technology support)
• ISO 24102 series (ITS station management)
• 3GPP specifications (e.g., TS 36.300, TS 36.331, TS 23.285, TS 24.386)
• ISO/IEC ASN.1 standards referenced for message encoding

Keywords: ISO 17515-3:2019, ITS-LTE-V2X, LTE-V2X, E-UTRA, CAL, MAE, ITS station, V2X, D2D, 3GPP.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17515-3
First edition
2019-08
Intelligent transport systems —
Evolved-universal terrestrial radio
access network —
Part 3:
LTE-V2X
Systèmes intelligents de transport) — Réseau d'accès à la radio
terrestre universelle évoluée (E-UTRAN) —
Partie 3: LTE-V2X
Reference number
©
ISO 2019
© ISO 2019
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms . 2
5 Usage of LTE in ITS . 3
5.1 LTE features used in ITS . 3
5.2 General access to the Internet . 3
5.3 Device-to-device communications (D2D) . 4
5.4 Vehicle-to-everything communications (V2X) . 4
5.5 Implementation guidelines . 5
6 General requirements . 5
6.1 LTE basics . 5
6.1.1 LTE-V2X . 5
6.1.2 Supported LTE modes of operation . 5
6.2 ITS station . 6
6.2.1 Station and communication architecture . 6
6.2.2 Service access points . 8
6.2.3 Hybrid communications support . 8
7 Communication interface protocol stack . 8
7.1 Physical layer . 8
7.2 Data link layer . 9
7.2.1 Basic behaviour . 9
7.2.2 Data link layer communication addresses . 9
7.2.3 Identification of higher layer protocols. 9
7.3 Communication adaptation sub-layer .10
8 Communication interface management .11
8.1 General management.11
8.2 Management adaptation entity.11
8.2.1 LTE-V2X parameters and I-Parameters .11
8.2.2 LTE-V2X management commands and MI-SAP commands and requests .11
9 Procedures .12
9.1 Communication interface procedures .12
9.1.1 Transmit procedure .12
9.1.2 Receive procedure .12
9.2 Management procedures .12
9.2.1 Cross-CI prioritization .12
9.2.2 Operational mode .13
9.2.3 LTE-V2X MAC address mapping.13
9.2.4 CI connection procedure .14
9.2.5 CI state management .14
10 Conformance .14
11 Test methods .15
Annex A (normative) Communication interface parameters .16
Annex B (normative) MI-COMMANDs .19
Annex C (normative) MI-REQUESTs .20
Annex D (normative) ASN.1 definitions .21
Annex E (informative) CI state transitions .24
Bibliography .26
iv © ISO 2019 – All rights reserved

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.
A list of all parts in the ISO 17515 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.
Introduction
Localized communications are an essential component of hybrid communications in Intelligent
Transport Systems (ITS). Various access technologies are suited for localized communications. An
increasing interest of ITS stakeholders for "Cooperative ITS" and "Urban ITS" is in the access technology
known under the acronym of LTE. LTE refers to a packet switched cellular network technology specified
by 3GPP. Beside the "traditional" features of cellular networks, LTE also supports device-to-device
communications, e.g. for public safety applications, and vehicle-to-everything communications (LTE-
V2X) especially designed for ITS.
This document provides complements to LTE-V2X specifications from 3GPP needed to operate it as an
ITS access technology in an ITS station unit specified in ISO 21217. An implementation of this document
is referred to as an ITS-LTE-V2X communication interface (CI).
ITS-LTE-V2X CIs are able to
— operate with support of an LTE base station, and
— operate without support of an LTE base station, e.g. outside LTE coverage areas
as specified by 3GPP.
vi © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 17515-3:2019(E)
Intelligent transport systems — Evolved-universal
terrestrial radio access network —
Part 3:
LTE-V2X
1 Scope
This document provides specifications related to the ITS-S access layer for a communication interface
(CI) named "ITS-LTE-V2X".
ITS-LTE-V2X CIs are based on the evolved-universal terrestrial radio access (E-UTRA) vehicle-to-
everything (LTE-V2X) technology standardized at 3GPP.
This document enables usage of the LTE-V2X technology as an ITS access technology in an ITS station
by reference to respective specifications from 3GPP, and by specifying details of the “Communication
Adaptation Layer” (CAL) and the “Management Adaptation Entity” (MAE) of communication interfaces
specified in ISO 21218.
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 8824-1:2015, Information technology — Abstract Syntax Notation One (ASN.1): Specification of
basic notation — Part 1
ISO/IEC 8825-2:2015, Information technology — ASN.1 encoding rules: Specification of Packed Encoding
Rules (PER) — Part 2
ISO 21217, Intelligent transport systems — Communications access for land mobiles (CALM) — Architecture
ISO 21218, Intelligent transport systems — Hybrid communications — Access technology support
ISO 24102-1, Intelligent transport systems — ITS station management — Part 1: Local management
ISO 24102-3,Intelligent Transport Systems — ITS station management — Part 3: Service access points
3GPP TS 23.285, 3rd Generation Partnership Project; Technical Specification Group Services and System
Aspects; Architecture enhancements for V2X services (Release 14)
3GPP TS 24.334, 3rd Generation Partnership Project; Technical Specification Group Core Network and
Terminals; Proximity-services (ProSe) User Equipment (UE) to ProSe function protocol aspects; Stage 3
(Release 14)
3GPP TS 24.386, 3rd Generation Partnership Project; Technical Specification Group Core Network and
Terminals; User Equipment (UE) to V2X control function; protocol aspects; Stage 3 (Release 14)
3GPP TS 36.300, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network;
Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access
Network (E-UTRAN); Overall description; Stage 2 (Release 14)
3GPP TS 36.331, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network;
Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification
(Release 14)
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 http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
layer-2 ID
identifier at the OSI layer 2 functionally similar to an IEEE 802 MAC address
3.2
V2X application server
server hosting ITS applications within the LTE networks as specified by 3GPP
4 Symbols and abbreviated terms
CI Communication Interface
[SOURCE: ISO 21217]
eNB Evolved Node B (Fixed station of a mobile network that directly interacts with
UEs); generally called a "cell tower"
E-UTRA Evolved Universal Terrestrial Radio Access
E-UTRAN Evolved Universal Terrestrial Radio Access Network
ITS-SU ITS station unit
[SOURCE: ISO 21217]
LGW Local Gateway
LTE Long Term Evolution
LTE-D2D LTE Device-to-Device
LTE-V2X LTE Vehicle-to-Everything communication
ITS-LTE-V2X Name of the communication interface specified in this document
eMBMS Evolved Multimedia Broadcast Multicast Service
MBMS Multimedia Broadcast Multicast Service
n.a. not applicable
PC5 ProSe communication 5
PDN GW Packet Data Network Gateway
PPPP ProSe Per-Packet Priority
2 © ISO 2019 – All rights reserved

ProSe Proximity-based Service
SC-PTM Single-cell Point-to-Multipoint
UE (LTE) User Equipment (mobile LTE device)
Uu Radio interface between the UE (user equipment) and the eNB
V2I Vehicle-to-Infrastructure
(3GPP definition. In ITS terms this means vehicle-to-roadside)
V2N Vehicle-to-Network
(3GPP definition. In ITS terms this means vehicle-to-central office)
V2P Vehicle-to-Pedestrian (3GPP definition. In ITS terms this means vehicle-to-person-
al device)
V2V Vehicle-to-Vehicle
V2X Vehicle-to-everything
[SOURCE: 3GPP TS 24.386]
VCI Virtual CI
[SOURCE: ISO 21218]
NOTE Some of the terms used in this document are ambiguous in a global context due to the fact that different
SDOs use different definitions. For the purpose of this document, definitions from ISO TC 204 are applicable.
5 Usage of LTE in ITS
5.1 LTE features used in ITS
The LTE network is a packet-switched cellular network specified by 3GPP. It provides features that may
be used in ITS station units (ITS-SUs) as:
— general access to the Internet as described in 5.2;
— device-to-device communications (D2D) as described in 5.3;
and provides features that are dedicated to ITS:
— vehicle-to-everything communications (V2X) as described in 5.4.
NOTE Usage of IPv6 in the context of an ITS station (ISO 21217), used, e.g. for accessing the Internet and for
[7]
localized communications, is specified in ISO 21210 .
Implementation guidelines are presented in 5.5. An LTE mobile device is referred to as User Equipment
(UE) in 3GPP. This term is used in this document if the ITS term CI is not appropriate, e.g. for LTE
management communications.
5.2 General access to the Internet
General access to the Internet is supported with the LTE-Uu based architecture reference model
specified in 3GPP TS 23.285. In this reference model, a UE accesses the Internet via the PDN GW or LGW
using IPv4 or IPv6. Detailed operational procedures for connection establishment and management
[20]
over LTE-Uu are specified in 3GPP TS 23.401 .
Details on how to establish general access to the Internet in an ITS-SU via an LTE interface are specified
[3]
in ISO 17515-1 .
5.3 Device-to-device communications (D2D)
[4]
Details on how to perform LTE-D2D communications in an ITS-SU are specified in ISO 17515-2 .
5.4 Vehicle-to-everything communications (V2X)
V2X communications in LTE (LTE-V2X) are possible via two different LTE interfaces:
— the LTE PC5 communications interface, and
— the LTE Uu communications interface.
The initial primary purpose of LTE-V2X communications identified so far by 3GPP is dissemination of
[17] [16]
ITS information from an ITS-SU to other ITS-SUs, see e.g. 3GPP TR 22.885 and 3GPP TR 22.185 ,
where these ITS-SUs can be either vehicle ITS-SUs, roadside ITS-SUs, central ITS-SUs, or personal ITS-
SUs as specified in ISO 21217.
NOTE 1 The 3GPP definitions of "Vehicle-to-Infrastructure (V2I)", "Vehicle-to-Network (V2N)", and "Vehicle-
to-Pedestrian (V2P)" differ from those used in ITS, see e.g. ISO 21217. The ITS meaning of "3GPP V2I" is "vehicle-
to-roadside station", of "3GPP V2N" is "vehicle-to-central station", and of "3GPP V2P" is "vehicle-to-personal
station".
In PC5 communications (see 6.1.2.2) information dissemination goes directly from a vehicle station
to other stations; unicast sessions are not supported for V2X. In Uu communications (see 6.1.2.3)
information dissemination goes from a vehicle to a V2X application server via the LTE network acting
as a kind of "relay", and from there to other vehicle stations.
NOTE 2 The Uu interface also supports unicast communications.
NOTE 3 The V2X application server is not part of the LTE network.
NOTE 4 The V2X application server is selected by the LTE network. Consequently, there can be only one single
V2X application server for the indicated ITS application selected by the network at a specific location of the UE,
i.e. provision of this service by various service providers is not possible using LTE-V2X Uu communications.
PC5 communications is also referred to as SideLink communications. Two operational modes of
SideLink communications exist:
— operator managed;
— with dynamic scheduling of resources;
— without dynamic scheduling of resources;
— non-operator managed.
The non-operator managed mode is applicable in case the LTE network cannot be reached, and thus
pre-configured communication resources apply.
In the operator managed mode an LTE base station manages allocation of communication resources,
which adds flexibility in resource allocation. In operator managed mode.
— the eNB may dynamically schedule communication resources for SideLink communications, and
thus collisions in the subsequent scheduled communications are avoided;
— otherwise communication resources are taken from a resource pool configured by the eNB.
NOTE 5 Currently there are no globally applicable means for harmonized resource pool allocation in scenarios
without network coverage.
4 © ISO 2019 – All rights reserved

NOTE 6 At time of writing the present document no 3GPP rules were identified on the issue of resource pool
information created by an LTE network in a given regulatory domain, whilst respective SideLink communications
are being performed in a different regulatory domain.
In Uu communications, ITS packets are encapsulated in IP packets for forwarding from UE to the V2X
application server like ordinary IP traffic, and from the V2X application server to UE.
5.5 Implementation guidelines
Both PC5 and Uu communications are designed for time-critical applications with requirements for very
low latency. PC5 communications without dynamic scheduling of resources preferably are to be selected
for time-critical applications with requirements for very low latency, whilst PC5 communications with
scheduling of resources and Uu communications may be used for applications that are not as time-
critical. However, this is not a requirement and the guideline may be revised once better knowledge
about the operational facts is available.
The medium-specific I-Parameter OperationalMode of ASN.1 type OperationalMode specified in
ISO 21218 is used to indicate the currently valid operational mode of LTE-V2X. The LTE-specific details
of OperationalMode are given by the ASN.1 type LTE-OperationalMode specified in D.2, i.e. a named
Integer variable with the following identified named values:
— 0: unknown operational mode;
— 1: SideLink communication;
— 2: Uu communication.
[3] [4]
Further modes may be specified, e.g. in ISO 17515-1 and ISO 17515-2 .
6 General requirements
6.1 LTE basics
6.1.1 LTE-V2X
An implementation of an ITS-LTE-V2X communication interface is based on relevant specifications
from 3GPP.
NOTE 3GPP specifications related to LTE-V2X are e.g. [19], [21], [22], [23], [24], [25], [26], [27], [28], [29].
6.1.2 Supported LTE modes of operation
6.1.2.1 Overview
Either one or both of the following two modes of operation shall be supported by an LTE-V2X CI, see
also 5.4 and 5.5:
a) PC5 interface communications (SideLink communication):
— operator managed;
— non-operator managed;
b) Uu interface communications with
— unicast uplink (UE to eNB);
— unicast downlink (eNB to UE);
— broadcast downlink with
i) Multimedia Broadcast Multicast Service (MBMS),
ii) Single-cell Point-to-Multipoint (SC-PTM).
6.1.2.2 PC5 interface communications
In the operator-managed mode, the UE may either use resources scheduled by the LTE network or
select autonomously resources from resource pools which are configured by the LTE network; these
resources are for data communications of the LTE-V2X CI.
In the non-operator managed mode, the UE may on its own select resources from resource pools which
are pre-configured.
6.1.2.3 Uu interface communications
The data to be transmitted by an LTE-V2X CI is firstly delivered to the eNB (base station of the
LTE network) in unicast mode, where the eNB forwards the data to an V2X application server. This
V2X application server then forwards the originally received data, or the pre-processed data to the
appropriate eNB, which itself unicasts or broadcasts the data via Multimedia Broadcast Multicast
Service (MBMS) or Single-cell Point-to-Multipoint (SC-PTM) specified by 3GPP to the respective UE
within coverage of this eNB.
6.2 ITS station
6.2.1 Station and communication architecture
The ITS station architecture specified in ISO 21217 is presented in Figure 1. The ITS-LTE-V2X CI is
allocated in the ITS-S access layer of the ITS station architecture.
Figure 1 — ITS station architecture
6 © ISO 2019 – All rights reserved

Figure 2 shows the architecture diagram of an ITS-LTE-V2X CI communications interface (CI) embedded
in the general ITS station architecture.
Figure 2 — LTE-V2X CI architecture
As 3GPP also specified the network and transport layer of LTE, related parts of the LTE-V2X
specifications might be provided in the ITS-S networking & transport layer as illustrated in Figure 3.
Details are out of scope of this document.
Figure 3 — LTE-V2X functionality in an ITS station
The communication protocol layers of the ITS-LTE-V2X CI specified by 3GPP are:
a) Physical layer (PHY);
b) Data link layer (DLL).
An ITS-LTE-V2X CI as specified in this document is an ITS wireless CI
[1]
— of MedType c-ITSatt-iso17515 specified in ISO 17419 ;
— of CI class CIC-l6 specified in ISO 21218 for one-to-many communications either with support of a
base station of a cellular network or without support of the base station;
— of CI access class CIAC-3 specified in ISO 21218.
An ITS-LTE-V2X CI provides the functionality of the IN-SAP specified in ISO 21218, and uses the
functionality of an MI-SAP, and an SI-SAP specified in ISO 24102-3.
NOTE 1 Service primitive functions for the SI-SAP are not identified so far.
NOTE 2 Multiple ITS-LTE-V2X 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.
6.2.2 Service access points
6.2.2.1 General
NOTE As Service Access Points (SAPs) per definition describe functional behaviour only, SAPs can be
implemented in different ways. Requirements set up in this document to support SAPs and the related service
primitives thus mean to support the functionality. This support can be implemented either in a strict meaning,
i.e. using the ASN.1 definitions of the service primitives as "PDU" definitions, or in an abstract meaning, allowing
for proprietary solutions.
6.2.2.2 Communications service access points
An ITS-LTE-V2X CI shall support the IN-SAP functionality specified in ISO 21218.
6.2.2.3 Management service access points
An ITS-LTE-V2X CI shall support the MI-SAP functionality of ISO 24102-3 with details specified in
ISO 21218.
6.2.2.4 Security service access points
An ITS-LTE-V2X CI shall support the SI-SAP functionality of ISO 24102-3 with details specified in
ISO 21218.
NOTE So far no service primitives are identified for the SI-SAP.
6.2.3 Hybrid communications support
An ITS-LTE-V2X CI for an ITS-SU supporting hybrid communications shall be compliant with ISO 21218
[9]
and ISO 24102-1. It is suggested that path and flow management as specified in ISO 24102-6 is applied.
7 Communication interface protocol stack
7.1 Physical layer
The basic behaviour of the LTE-V2X CI physical layer shall be as specified in the respective LTE
standards from 3GPP, see 6.1.1.
8 © ISO 2019 – All rights reserved

7.2 Data link layer
7.2.1 Basic behaviour
The basic behaviour of the LTE-V2X CI data link layer shall be as specified in the respective LTE
standards from 3GPP, see 6.1.1.
7.2.2 Data link layer communication addresses
LTE-V2X SideLink communication does not use 48 bit MAC addresses, but uses 24 bit Layer-2 Identifiers
(Layer-2 ID) for identifying source and destination, see 3GPP TS 36.300.
LTE-V2X Uu unicast communication does not use Layer-2 IDs, as communication is always from the UE
to the available LTE base station.
7.2.3 Identification of higher layer protocols
LTE-V2X uses the concept of a "Layer-3 protocol data unit types" and the concept of "V2X message
family" specified in 3GPP TS 24.386 for identifying the type of payload. This information is contained in
LTE-V2X frames.
"Layer-3 protocol data unit types" and corresponding EtherType values are presented in Table 1.
Table 1 — LTE-V2X Layer-3 protocol data unit type
Value Protocol type EtherType
a
0 IPv6 0x86.DD
IPv4 0x08.00
1 Allocation and retention priority n.a.
2 PC5 signaling n.a.
3 Non-IP "V2X message family"; see the LTE-V2X Non-
IP Header
4 - 7 Reserved n.a.
a
IPv4 and IPv6 can both be supported by Uu communications whilst IPv4 is not supported for SideLink communications
so far. Selection of the appropriate EtherType value at the CAL requires inspection of the IP header. Details on the usage of
[7]
IPv6 in ITS are specified in ISO 21210 .
If "Non-IP" is indicated in "Layer-3 protocol data unit types", further details are presented in the field
"Non-IP Header". The non-IP protocol types (indicated in the "Non-IP Header" and corresponding
EtherType values are presented in Table 2.
Table 2 — LTE-V2X Non-IP Header of "V2X message family"
Value Non-IP protocol type EtherType
0 Reserved n.a.
[13]
1 WSMP specified in IEEE 1609.3 0x88.DC
[11]
2 FNTP specified in ISO 29281-1 0x89.50
[14]
3 GeoNetworking specified in ETSI EN 302 636 0x89.47
4 – 255 Reserved n.a.
NOTE 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) specified in IEEE Std 802™, 2014. Allocations of EtherType values are published at http:
//standards .ieee .org/develop/regauth/ethertype/eth .txt. Values in the range 0 through 1 535 (0x05.FF) are not
allowed as EtherType addresses, as these numbers provide length information.
7.3 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-LTE-V2X CIs in accordance with ISO 21218 shall use an EtherType value in the IN-UNITDATA service
primitives to identify the applicable ITS-S networking & transport layer protocol. Thus the information
on type of payload presented in 7.2 shall be converted into an Ethertype in support of ISO 21218.
In other implementation contexts, the EtherType value shall be used in the applicable service access
point primitives that exchange service data units between ITS-LTE-V2X 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. The relation between user priority and LTE ProSe Per-Packet Priority
(PPPP) for LTE-V2X SideLink communication shall be a linear mapping as illustrated in Tables 3 and 4.
The value zero of User Priority means "lowest priority", whilst the value zero of PPPP means "highest
priority".
Table 3 shows the mapping of user priority values to PPPP values on the basis of the PPPP definition
in 3GPP TS 24.334 as applied in the transmit path. Once the number range of PPPP changes, the linear
mapping shall be adapted in the spirit illustrated in Table 3.
Table 3 — Mapping of user priority values to PPPP values
a
User priority PPPP
— 0 (not used)
255 - 224 1 (highest priority used)
223 - 192 2
191 - 160 3
159 - 128 4
127 - 96 5
95 - 64 6
63 - 32 7
31 - 0 8 (lowest priority used)
— 9 - 255 (not used)
a
Although PPPP is specified as a one octet unsigned Integer, only the values 1 through 8 are used in 3GPP TS 24.334.
Table 4 shows the mapping of PPPP values to user priority values on the basis of the PPPP definition
in 3GPP TS 24.334 as applied in the receive path. Once the number range of PPPP changes, the linear
mapping shall be adapted in the spirit illustrated in Tables 4.
Table 4 — Mapping of PPPP values to user priority values
a
PPPP User priority
0 (not used) —
1 (highest priority used) 255
2 223
3 191
4 159
5 127
6 95
a
Although PPPP is specified as a one octet unsigned Integer, only the values 1 through 8 are used in 3GPP TS 24.334.
10 © ISO 2019 – All rights reserved

Table 4 (continued)
a
PPPP User priority
7 63
8 (lowest priority used) 31
9 - 255 (not used —
a
Although PPPP is specified as a one octet unsigned Integer, only the values 1 through 8 are used in 3GPP TS 24.334.
8 Communication interface management
8.1 General management
The basic management of an LTE-V2X CI shall be as specified in the respective LTE standards from
3GPP, see 6.1.1.
8.2 Management adaptation entity
8.2.1 LTE-V2X parameters and I-Parameters
In implementations in accordance with ISO 21218, the following rules apply:
— LTE-V2X parameters that have an equivalent I-Parameter defined in ISO 21218 shall be mapped on
I-Parameters as specified in Annex A.
— LTE-V2X parameters which are relevant for ITS-LTE-V2X 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-LTE-V2X but cannot be mapped on an LTE-V2X parameters
shall be implemented in the MAE as specified in ISO 21218 with details specified in Annex A.
8.2.2 LTE-V2X management commands and MI-SAP commands and requests
In implementations in accordance with ISO 21218 and ISO 24102-3, the following rules apply:
— LTE-V2X management commands that have an equivalent MI-COMMAND/MI-REQUEST defined in
ISO 24102-3 shall be mapped on these MI-COMMAND/MI-REQUEST as specified in Annex B and
Annex C.
— LTE-V2X management commands that are relevant for an implementation of ITS-LTE-V2X and do
not have an equivalent MI-COMMAND/MI-REQUEST defined in ISO 24102-3 shall be made accessible
in an implementation specific way.
— MI-COMMANDs/MI-REQUESTs which are relevant for ITS-LTE-V2X but cannot be mapped on LTE-
V2X management commands are implemented in the MAE as specified in ISO 24102-3 with details
specified in Annex B and Annex C.
9 Procedures
9.1 Communication interface procedures
9.1.1 Transmit procedure
Upon reception of a transmission request service primitive, i.e. an IN-UNITDATA.request service
primitive specified in ISO 21218, CAL shall
a) use the operational mode as indicated in the I-Parameter "Operational Mode",
b) perform settings of LTE-V2X transmit parameters as being applicable,
c) for LTE-V2X SideLink communications, determine the LTE-V2X PPPP value from the user priority
presented in the parameter "priority" of the IN-UNITDATA.request service primitive as specified in
Table 3,
NOTE 1 For LTE-V2X Uu communications usage of user priority is not defined; priority values are defined
[18]
in 3GPP TS 23.203 .
d) create the LTE-V2X "Non-IP Header" and the "LTE-V2X Layer-3 protocol data unit type" according
to the EtherType value presented in the parameter "nt_protocol_id" of the IN-UNITDATA.request
service primitive,
e) request transmission of the resulting frame (ITS-APDU specified in ISO 21217) to the destination
presented in the parameter "destination_address" of the IN-UNITDATA.request service primitive
considering the determined PPPP.
9.1.2 Receive procedure
Upon reception of a frame, CAL shall
a) calculate the user priority from the PPPP value associated with the received SideLink frame as
specified in Table 4,
NOTE 1 Usage of PPPP and the related user priority at higher layers is not defined; priority values are
[18]
defined in 3GPP TS 23.203 .
NOTE 2 Usage of user priority at higher layers is not defined for Uu communications; priority values are
[18]
defined in 3GPP TS 23.203 .
b) derive the EtherType value from the LTE-V2X Layer-3 protocol data unit type and from the LTE-
V2X Non-IP Header,
c) present the received packet (ITS-NTPDU) to the ITS-S networking & transport layer, i.e. using the
IN-UNITDATA.indication service primitive specified in ISO 21218.
9.2 Management procedures
9.2.1 Cross-CI prioritization
A basic "Cross-CI prioritization procedure" is specified in ISO 21218. For ITS-LTE-V2X operating in
the frequency band 5 800 MHz ± DSRC , with DSRC = 200 MHz the option "CI protection" shall be
BW BW
applied for all implementations with a CEN MDR-DSRC OBU, or HDR-DSRC OBU, (5,8 GHz backscatter
technology) being part of the ITS station unit.
NOTE The value of the single-sided protection bandwidth DSRC depends on the result of investigations on
BW
mitigation techniques for avoiding harmful interference on MDR-DSRC and HDR-DSRC.
12 © ISO 2019 – All rights reserved

9.2.2 Operational mode
Any change of the operational mode by the LTE network shall be stored in the I-Parameter
"OperationalMode". Any change of the value of the I-Parameter "OperationalMode" not requested
by the ITS station management shall be notified to the ITS station management with MI-REQUEST
{Event21218Notification {E21218-5} } specified in ISO 21218.
9.2.3 LTE-V2X MAC address mapping
9.2.3.1 LTE-V2X SideLink communication
LTE-V2X SideLink communication uses Layer-2 identifiers of size 24 bits instead of 48 bit MAC
addresses; distinction is made between a source Layer-2 ID and destination Layer-2 ID, see 7.2.
1) Destination Layer-2 ID:
i) In the 3GPP Release 14 of LTE-V2X it is indicated that an LTE-V2X SideLink destination Layer-2
ID points to an ITS service. It is further suggested that this service identified by a registered
[1]
value of the ITS application identifier ITS-AID. ITS-AID is specified in ISO 17419 . The mapping
of ITS-AIDs on LTE-V2X destination Layer-2 ID is not yet standardized.
ii) If this concept of generating an LTE-V2X SideLink destination Layer-2 ID is precisely specified,
the applicable value of ITS-AID can be provided as "transmit access parameter" in the "access
parameters" parameter of the IN-UNITDATA.request service primitive specified in ISO 21218.
2) Source Layer-2 ID:
An LTE-V2X SideLink source Layer-2 ID is self-assigned. An initial value may be provided by the
LTE network.
The LTE-V2X SideLink source Layer-2 ID is managed as a pseudonym, i.e. values are locally assigned
and replaced by new values upon request by the ITS station management. So far no specific update rate
or update condition is specified. It shall be possible to change LTE-V2X SideLink source Layer-2 ID upon
request by the ITS station management with MI-COMMAND {ChangePseudonymMACaddress}.
For IP based communications the LTE-V2X CI auto-configures a link local IPv6 source address (prefix:
fe80::/10) as specified in TS 23.303, clause 4.5.3; privacy regulations may require change of the IP
source address simultaneously with the change of the source Layer-2 ID.
The mapping of LTE-V2X Layer-2 IDs onto the EUI-64 format used in Link-ID (LocalCIID and Remote
CIID) specified in ISO 21218 shall use the basic format for encapsulation of identifiers specific to ITS
specified in ISO 21218:2018, C.3:
1) LocalCIID:
As specified in ISO 21218, i.e. the LTE-V2X SideLink source Layer-2 ID is mapped to the
"VCISerialNumber" value zero in combination with "UC/GC" set to '000000' .
2) RemoteCIID:
As specified in ISO 21218, i.e. the LTE-V2X SideLink source Layer-2 ID is mapped to the
"VCISerialNumber" value 65535 in combination with "UC/GC" set to '111111' , i.e. indication
broadcast communications.
NOTE The VCISerialNumber is not necessarily subject to privacy regulations, as it is designed as a station-
internal number. Thus changing the pseudonym LTE-V2X source Layer-2 ID does not necessarily result in a
change of Link-ID. Applying IPv6 communications, the Link-ID can appear in the wireless link.
9.2.3.2 LTE-V2X Uu communication
Either LTE-V2X Uu CIs and VCIs are identified by a 48 bit MAC address assigned by the vendor of the CI,
or the LTE-V2X Uu CI and VCI identification shall be as follows, see also ISO 21218:
1) LocalCIID: Same as for LTE-V2X SideLink communication, see 9.2.3.1.
2) RemoteCIID:
i) The "VCISerialNumber" 65535 in combination with "UC/GC" set to '000000' is used to identify
unicast communications to the LTE base station.
ii) The "VCISerialNumber" 65535 in combination with "UC/GC" set to '111111' is used to identify
broadcast communications from the LTE base station.
iii) The rules for the fields "ITS-SCU-ID", and "MedID" are as specified in ISO 21218.
9.2.3.3 Overview
Table 5 summarizes the LTE-V2X MAC address mapping specified in 9.2.3.1 and 9.2.3.2.
Table 5 — LTE-V2X MAC address mapping
UC/GC VCISerialNumber Comment
MSB LSB
0 0 0 0 0 0 0 LocalCIID identifying local CI (SideLink and Uu communications)
0 0 0 0 0 0 65535 RemoteCIID identifying unicast communications to the LTE base
station (Uu communications)
1 1 1 1 1 1 65535 RemoteCIID identifying broadcast communications from the
LTE base station (Uu communications), and SideLink broadcast
communications.
9.2.4 CI connection procedure
When the CI state is “active” and I-Parameter Connect is set to “automatic” (0), or upon reception of
the MI-COMMAND “CIstateChange” with
...