ISO 4426:2021

INTERNATIONAL ISO
STANDARD 4426
First edition
2021-07
Intelligent transport systems —
Lower layer protocols for usage in the
European digital tachograph
Systèmes de transport intelligents - Protocoles de couche basse pour
utilisation dans le cadre du chrono tachygraphe numérique européen
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms and symbols . 8
5 Digital tachograph interrogation .10
5.1 General .10
5.2 SDTC protocol stack .11
5.2.1 Simplified OSI layered .11
5.2.2 SDTC L1 .11
5.2.3 SDTC L2 .11
5.2.4 SDTC L7 .11
5.3 SDTC profiles .11
6 Test methods .11
Annex A (normative) SDTC physical layer .13
Annex B (normative) SDTC data link layer .18
Annex C (normative) SDTC application layer .53
Annex D (normative) SDTC profiles .56
Bibliography .65
Foreword
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This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
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iv © ISO 2021 – All rights reserved

Introduction
This document is designed to encompass communication requirements in support of the Smart Digital
[23]
Tachograph (SDT) as identified by Regulation 2016/799 of the European Union .
This document specifies SDT Communications (SDTC). SDTC is the application of CEN Dedicated Short
Range Communication (DSRC) for SDT. See the following:
— EN 12253, Road transport and traffic telematics — Dedicated short-range communication — Physical
[1]
layer using microwave at 5,8 GHz
— EN 12795, Road transport and traffic telematics — Dedicated Short Range Communication (DSRC) —
[2]
DSRC data link layer: medium access and logical link control
— EN 12834, Road transport and traffic telematics — Dedicated Short Range Communication (DSRC) —
[3]
DSRC application layer
— EN 13372, Road transport and traffic telematics — Dedicated short-range communication — Profiles
[4]
for RTTT applications
Complementing the standardized specifications and descriptions, several private documents describe
this dedicated short range semi-passive communication technology in an informative manner, providing
additional detailed explanations and implementation hints. See for example:
[24]
— DSRC tutorial published by ESF GmbH in July 2003 (publicly available) ;
[25]
— GSS industry specification published in August 2003 (no longer available from the authors;
essential content is now available in ISO 15509);
It is to be noted that the abovementioned private documents provide information that can be essential
to easily achieving interoperability with existing DSRC equipment and optimum performance.
[1]
EN 12253 deals with the physical layer of the DSRC protocol stack presented in Figure 1; i.e. it
comprises requirements for Open Systems Interconnection (OSI) Layer 1 at 5,8 GHz for DSRC.
Figure 1 — DSRC protocol stack
[1]
EN 12253 does not include associated measurement procedures for verification of the requirements.
[12] [13]
Test methods for conformity are provided in ETSI EN 300674-1 , ETSI EN 300674-2-1 and ETSI
[14]
EN 300674-2-2 .
[1]
EN 12253 caters for on-board units based on transponder technologies. Furthermore, it allows for
mixed time, frequency and space division multiple access approaches.
[1]
EN 12253 is conceived for the 10 MHz part (i.e. 5,795 GHz to 5,805 GHz) of the ISM band at 5,8 GHz
[10]
which is recommended by ECC/DEC(01)01 . An additional sub-band (5,805 GHz - 5,815 GHz) may be
allocated on a national basis. National restrictions on the usage of these frequency bands can apply
[11]
according to CEPT/ERC REC 70-03 .
[2]
EN 12795 gives the architecture and services offered by the DSRC data link layer.
[3]
EN 12834 and the almost identical ISO 15628 give the architecture and services offered by the DSRC
application layer.
[4]
EN 13372 deals with the interlayer management of the DSRC protocol stack.
Figure 2 illustrates the global data flow between the elements of the SDTC stack, (physical layer, data
link layer and application layer) and the SDT application.
Figure 2 — Architecture and data flow of the SDTC stack
vi © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 4426:2021(E)
Intelligent transport systems — Lower layer protocols for
usage in the European digital tachograph
1 Scope
This document specifies communication requirements in support of the Smart Digital Tachograph
[23]
(SDT) as identified by Regulation 2016/799 of the European Union .
The specification covers:
— the physical layer at 5,8 GHz for SDT communications (SDTC);
— the data link layer (DLL) of SDTC;
— the application layer of SDTC;
— SDTC profiles which provide coherent sets of communication tools for applications based on SDTC.
This document provides further information beneficial for the design and development of SDTC
equipment.
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 15628, Intelligent transport systems — Dedicated short range communication (DSRC) — DSRC
application layer
ISO/IEC 13239, Information technology — Telecommunications and information exchange between
systems — High-level data link control (HDLC) procedures
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
adjacent channel
neighbouring SDTC channel for use by two or more emissions
Note 1 to entry: It is possible that a SDTC channel has either one of two adjacent channels.
3.2
antenna bore sight direction
direction of maximum antenna gain
3.3
application
set of processes including related functions and structured data that uses the services offered by the
SDTC communication stack
3.4
beacon service table
BST
data structure transmitted by the fixed equipment indicating available services
3.5
bit error ratio
averaged number of erroneous bits relative to the total number of transmitted bits
3.6
co-channel
refers to the use of the same SDTC channel by two or more emissions
3.7
communication initialization
procedure used to establish communication between an RSU and a newly arrived OBU
Note 1 to entry: Terms prefixed with D present downlink parameters; downlink parameters apply to transmission
of data from RSU to OBU.
3.8
D1 — carrier frequencies
number and values of the downlink carrier frequencies, which are equal to the frequencies of the CW,
transmitted by the RSU and used by transponder OBUs for uplink communication
Note 1 to entry: Each carrier frequency is the centre frequency of a downlink channel.
3.9
D1a — tolerance of carrier frequencies
maximum deviation of the carrier frequency resulting from any cause
Note 1 to entry: It is expressed in parts per million (ppm)
EXAMPLE ±1 ppm of a 5,8 GHz carrier allows for the carrier frequency to be in the range of 5,8 GHz ± 5,8 kHz.
3.10
D2 — RSU transmitter spectrum mask
maximum allowed power within a defined frequency band emitted by the RSU transmitter
3.11
D3 — OBU minimum frequency range
minimum range of frequencies that has to be received by the OBU receiver
3.12
D4 — maximum E.I.R.P.
maximum allowed value of E.I.R.P.
3.13
D4a — angular E.I.R.P. mask
E.I.R.P. as a function of the angle Θ, where Θ indicates the angle relative to a vector perpendicular to the
road surface, pointing downwards
2 © ISO 2021 – All rights reserved

3.14
D5 — polarization
locus of the tip of the vector of the electrical field strength in a plane perpendicular to the transmission
vector
EXAMPLE Horizontal and vertical linear polarization and left- and right-h
...