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-hand circular polarization.
3.15
D5a — cross-polarization
ellipticity of polarization
antenna designed to transmit left-hand circular waves, which can transmit some right-hand circular
waves in addition
Note 1 to entry: Cross-polar discrimination (XPD) is defined as the ratio between left- and right-hand circular
power, P /P , when the total power transmitted is P + P . XPD is related to the ellipticity of polarization.
LHC RHC LHC RHC
3.16
D6 — modulation
keying of the carrier wave by coded data
EXAMPLE Amplitude shift keying (ASK), phase shift keying (PSK), frequency shift keying (FSK) and linear
amplitude modulation (AM).
3.17
D6a — modulation index
ratio of the variation of the modulation parameter (frequency, amplitude, phase) caused by the
modulation signal (data signal)
EXAMPLE Given the minimum and maximum values V and V of the envelope amplitude V of the
max min
modulated signal, the amplitude modulation index m is defined as:
VV−
maxmin
m= .
VV+
maxmin
3.18
D7 — data coding
downlink base band signal presentation, i.e. a mapping of logical bits to physical signals
EXAMPLE Bi-phase schemes (Manchester, FM0, FM1, differential Manchester), NRZ and NRZI. NRZI: No
transition at beginning of "1" bit, transition at beginning of "0" bit, no transition within bit.
3.19
D8 — bit rate
number of bits per second, independent of the data coding
3.20
D8a — tolerance of bit clock
maximum downlink deviation of the bit clock resulting from any cause, expressed in ppm
EXAMPLE 100 ppm of 500 kbit/s allows for the bit clock to be in the range of 500 kHz ± 50 Hz.
3.21
D9 — bit error ratio for communication
maximum allowed bit error ratio valid within the dynamic range of the receiver as defined by D11a and
D11b
3.22
D10 — wake-up trigger for OBU
signal which:
a) indicates to the OBU that it is within a communication zone, i.e. that it can now communicate with
an RSU;
b) switches the OBU main circuitry from sleep mode to the active mode
Note 1 to entry: This is a feature to allow the OBU to save battery power. It is not mandatory for an OBU to use a
wake-up process.
3.23
D10a — maximum start time
maximum time between the reception of the wake-up trigger and the time when the OBU has switched
to the active mode
3.24
D11 — communication zone
spatial region within which the incident power of the OBU has a dynamic range as defined by D11a and
D11b
3.25
D11a — power limit for communication (upper)
upper level of incident power referred to a lossless isotropic antenna (0 dB) in front of the OBU
Note 1 to entry: This is the level below which, subject to D11b, communication is guaranteed with a specified
bit error ratio. Communication can take place above this limit, but is not guaranteed. Together with D11b it also
specifies the minimum dynamic range of the OBU receiver. Power values are measured without any additional
losses due to rain or misalignment.
3.26
D11b — power limit for communication (lower)
lower level of incident power referred to a lossless isotropic antenna (0 dB) in front of the OBU
Note 1 to entry: This is the level above which, subject to D11a, communication is guaranteed with a specified
bit error ratio. Communication can take place below this limit, but is not guaranteed. Together with D11a it also
specifies the minimum dynamic range of the OBU receiver. Power values are measured without any additional
losses due to rain or misalignment
3.27
D12 — cut-off power level of OBU
incident power that is lower than the specified cut-off power level that does not result in communication
3.28
D13 — preamble
specific downlink layer 1-bit pattern
Note 1 to entry: Preamble is the bit pattern transmitted immediately before a frame.
3.29
D13a — preamble length
length of the downlink preamble measured in number of bits
3.30
D13b — preamble wave form
signal shape of the preamble
3.31
D13c — trailing bits
sequence of bits transmitted after the end flag of the data link layer
3.32
downlink
communication channel on which the fixed equipment transmits its information
3.33
downlink communication
communication from the RSU to the OBU
4 © ISO 2021 – All rights reserved

3.34
equivalent isotropically radiated power
E.I.R.P.
signal power fed into an ideal lossless antenna radiating equally in all directions that generates the
same power flux at a reference distance as the one generated by a signal fed into the antenna under
consideration in a predefined direction within its far field region
3.35
fixed equipment
fixed communication facility with one or more downlink channels and, optionally, one or more uplink
channels
Note 1 to entry: Normally the fixed equipment is installed at a fixed location, but it may be installed on a mobile
platform.
3.36
interlayer management
assembly of communication parameters of all protocol layers such that a consistent communication
protocol is provided
3.37
link identifier
LID
unique address used for addressing the mobile equipment
3.38
mobile equipment
mobile communication facility capable of receiving information from the fixed equipment on the
downlink and, optionally, also capable of transmitting information to the fixed equipment on the uplink
Note 1 to entry: The mobile equipment normally corresponds to the vehicle’s communication unit.
3.39
on-board unit
OBU
physical assembly that is located and operated in or on the vehicle to transmit and/or receive SDTC
signals
Note 1 to entry: An OBU may be in a form that is removable from the vehicle, or mountable in or on any part of
the vehicle structure, or bonded to a part of the vehicle, or an integral part of a vehicle component, such as a
windscreen, bumper or licence plate. In this document, parameters that refer to an OBU relate to the form that
the OBU takes as it is supplied to the vehicle manufacturer or constructor.
Note 2 to entry: An OBU is an alternative descriptor to Mobile Equipment.
3.40
roadside unit
RSU
SDTC equipment usually residing by the side of the road or overhead the road
Note 1 to entry: An RSU is an alternative descriptor to Fixed Equipment.
3.41
SDTC channel
frequency band for SDTC indicated by reference to the downlink centre frequency of one of up to four
frequency bands with 5 MHz width each
3.42
SDTC profile
consistent and standardized set of cross layer parameters controlling the behaviour of the SDTC
3.43
service access point
SAP
interface point between data link layer and application layer, that has a unique link identifier and that
allows layers to communicate
3.44
smart digital tachograph communication
SDTC
CEN DSRC applied for the Smart Digital Tachograph (SDT)
[23]
Note 1 to entry: This is as identified by Regulation 2016/799 of the European Union .
3.45
termination
procedure used to terminate communication between an RSU and an OBU
3.46
U1 — sub-carrier frequencies
number and values of the uplink sub-carrier frequencies, i.e. the frequency separation from the centre
of the uplink side band to the centre of the corresponding downlink band
3.47
U1a — tolerance of sub-carrier frequencies
maximum deviation of the sub-carrier frequency resulting from any cause
EXAMPLE 1 % of 1,5 MHz sub-carrier allows for the sub-carrier frequency to be in the range of
1,5 MHz ± 15 kHz.
Note 1 to entry: Normally this is expressed in percentage (%) or in parts per million (ppm) of the sub-carrier
frequency.
Note 2 to entry: Terms prefixed with U present uplink parameters; uplink parameters apply to transmission of
data from OBU to RSU.
3.48
U1b — use of side bands
specification of the use of the uplink side bands
Note 1 to entry: Data can be modulated on the upper side band only, or the lower side band only, or on both side
bands. In principle, different data can be modulated on the two side bands.
3.49
U2 — OBU transmitter spectrum mask
maximum allowed power emitted by the OBU transmitter within a defined frequency band
3.50
U4 — maximum single side band E.I.R.P. (bore sight)
maximum E.I.R.P. transmitted by the OBU within a single side band, measured at the maximum incident
power defined by D11a
Note 1 to entry: For a non-isotropic OBU antenna the single side band E.I.R.P varies with the direction of the
incident power and the direction in which the emitted power is measured.
3.51
U4a — maximum single side band E.I.R.P. (bore sight)
measurement when the incident power is in bore sight and the emitted power is measured in bore sight
3.52
U4b — maximum single side band E.I.R.P. (35°)
measurement when the incident power is in bore sight and the emitted power is measured at any angle
not less than 35° away from bore sight
6 © ISO 2021 – All rights reserved

3.53
U5
uplink parameter indicating the uplink polarization
3.54
U5 — cross-polarization
uplink parameter indicating the cross-polarization
3.55
U6 — sub-carrier modulation
keying of the sub-carrier wave by coded data
EXAMPLE Amplitude shift keying (ASK), phase shift keying (PSK), and frequency shift keying (FSK).
Note 1 to entry: U6b is not used.
3.56
U6b — duty cycle
ratio of the length of high or low pulses to the duration of a complete cycle
Note 1 to entry: In NRZI a sequence of zero bits results in a pulse of alternating high- and low-level sections. A
low-level section and the adjacent high-level section constitute a cycle of the pulse. The nominal duration of such
a single section is equal to the bit duration. The cycle duration is twice the bit duration. The duty cycle is the ratio
of the duration of the high-level section to the cycle duration.
3.57
U6c — modulation on carrier
keying of the carrier wave by the modulated sub-carrier
3.58
U7 — data coding
uplink base band signal presentation, i.e. a mapping of logical bits to physical signals
3.59
U8 — bit rate
number of bits per second, independent of the data coding
3.60
U8a — tolerance of symbol clock
maximum uplink deviation of the bit clock resulting from any cause, expressed in ppm
3.61
U9 — bit error ratio for communication
maximum allowed bit error ratio valid within the dynamic range of the receiver
3.62
U11 — communication zone
spatial region within which the OBU is situated such that its transmissions are received by the RSU
with a bit error ratio of less than a specified value
3.63
U12 — conversion gain
difference between OBU E.I.R.P. within one side band and the carrier incident power on OBU
3.64
U13 — preamble
specific uplink layer 1-bit pattern
3.65
U13a — preamble length
length of the uplink preamble
Note 1 to entry: Preamble length is measured either in multiples of symbols or in seconds.
3.66
U13b — trailing bits
sequence of bits transmitted after the end flag of the data link layer
3.67
uplink
communication channel on which mobile equipment transmits its information
3.68
uplink communication
communication from the OBU to the RSU
3.69
vehicle service table
VST
data structure transmitted by the OBU to indicate available services
3.70
window
period of time during which the physical medium is allocated either to the fixed equipment or to the
mobile equipment
4 Abbreviated terms and symbols
2-PSK binary phase shift keying
ACK acknowledge
ACn acknowledged command with sequence bit n
ADU application data unit
AM amplitude modulation
APDU application protocol data unit
ASDU application service data unit
ASK amplitude shift keying
C/R command/response
CEN European Committee for Standardization
CEPT European Conference of Postal and Telecommunications Administrations
CW continuous wave
DLL data link layer
DSRC dedicated short-range communication
EC European Commission
8 © ISO 2021 – All rights reserved

EDTC European digital tachograph communication
EFC electronic fee collection
EN European Standard
ERC European Radiocommunications Committee
ERM electromagnetic compatibility and radio spectrum matters
ETSI European Telecommunications Standards Institute
F final
FCS frame check sequence
FE fixed equipment
FM0 / FM1 bi-phase coding scheme, bit inverse to FM1 / FM0
FSK frequency shift keying
HDLC high-level data link control
ISM industrial, scientific, medical
L1 layer 1 of SDTC (physical layer)
L2 layer 2 of SDTC (data link layer)
L7 layer 7 of SDTC (application layer)
LLC logic link control
LPDU link layer protocol data unit
LSB least significant bit
LSDU link layer service data unit
M modifier function bit
MAC medium access control
ME mobile equipment
MSB most significant bit
NRZ non-return to zero
NRZI non-return to zero inverted
OSI open systems interconnection
P poll
P/F poll/final
PICS protocol implementation conformance statement
PDU protocol data unit
PPDU physical layer protocol data unit
PSDU physical layer service data unit
ppm parts per million
PSK phase shift keying
R response
R&TTE radio and telecommunications terminal equipment
RR response request
RTTT road transport and traffic telematics
TDMA time division multiple access
TSS&TP test suite structure and test purposes
UI unnumbered information
V receive state variable (LLC)
rx
V transmit state variable (LLC)
tx
XPD cross-polar discrimination
5 Digital tachograph interrogation
5.1 General
A regulatory device such as a smart tachograph needs to offer an interface for interrogation by
authorized officers. Such an interface may be carried through a physical connector, or via a wireless
communication interface. When the second option is chosen, stringent requirements of confidentiality
and, in general, security, arise.
A DSRC helps in satisfying these security requirements because of its localized nature and because of
the experience already gained in securing this type of links. This is one of the reasons the specification

of the application for digital tachograph interrogation in ISO 15638-9 is based on this type of
communication mechanism.
Some legislations require that a radio link shall be available in smart tachograph devices, such as in
[21]
Europe, where Regulation 165/2014 requires that "In order to facilitate targeted roadside checks by
the competent control authorities, tachographs installed in vehicles … shall be able to communicate to those
authorities while the vehicle is in motion".
The right to allocate frequencies for DSRC and to determine suitable protocols for interrogation
applications is left to regional legislation.
In Europe the frequency band of 5,8 GHz has been in use for EFC applications for example for many
years. The communication and application layers defined for EFC are also suitable for other types of
short range radio interrogations, such as that for the digital tachograph, and that which is required in
[22]
Annex 14 of the Smart Tachograph Implementing Regulation of the EU . The requirements on lower
layers for the European digital tachograph are thus expressed in 5.2 and 5.3.
10 © ISO 2021 – All rights reserved

5.2 SDTC protocol stack
5.2.1 Simplified OSI layered
SDTC is based on a simplified OSI layered model presented in Figures 1 and 2. The OSI Layers 3 (Network)
and 4 (Transport) do not exist, as SDTC concerns localized communications, i.e. not providing routing
of packets through a network.
NOTE The definition of "localized communications" can be found in ISO 21217. However, ISO 21217 is not
needed for the understanding of this document, or for an interoperable implementation of SDTC.
Functionality of OSI Layers 5 (Session), 6 (Presentation) and 7 (Application) is provided in the SDTC
Layer, application layer (L7).
The OSI Layer 1 maps to the SDTC Layer, physical layer (L1), and the OSI Layer 2 maps to the SDTC
Layer, data link layer (L2).
Details of the digital tachograph application, which resides on top of L7, are out of the scope of this
document. For details of the SDTC Layers, see 5.2.2, 5.2.3, 5.2.4 and 5.3.
5.2.2 SDTC L1
The SDTC physical layer specifications for the required 5,8 GHz DSRC shall be as specified in Annex A of
this document.
5.2.3 SDTC L2
The SDTC data link layer procedures shall be as specified in Annex B of this document.
5.2.4 SDTC L7
The SDTC application layer to be used as a support for the digital tachograph interrogation shall be as
specified in Annex C of this document.
5.3 SDTC profiles
The specification of SDTC L1, L2 and L7 allows for different implementations. To avoid ambiguity
and non-interoperable implementations, a choice of options referred to as "SDTC profiles" shall be as
specified in Annex D of this document.
6 Test methods
The exact specification of conformance testing procedures is left to national regulations. However,
it is worthwhile noting here that the following conformance testing standards are available for all
requirement standards listed in Clause 5, and in Annex A, Annex B, Annex C, and Annex D, and can be
used in national certification procedures:
a) For the physical layer, including testing Layer 1 requirements specified in the profiles in Annex D:
[12]
1) ETSI EN 300 674-1 for the general test procedures and test environment setup;
[13]
2) ETSI EN 300 674-2-1 for the roadside unit;
[14]
3) ETSI EN 300 674-2-2 for the roadside unit.
b) For the data link layer, including testing Layer 2 requirements specified in the profiles in Annex D:
[15]
1) ETSI TS 102 486-1-1 for the protocol implementation conformance statement (PICS);
[16]
2) ETSI TS 102 486-1-2 for the test suite structure and test purposes (TSS&TP);
[17]
3) ETSI TS 102 486-1-3 for the abstract test suite and partial PIXIT proforma.
c) For the application layer, including testing Layer 7 requirements specified in the profiles in
Annex D:
[18]
1) ETSI TS 102 486-2-1 for the protocol implementation conformance statement (PICS);
[19]
2) ETSI TS 102 486-2-2 for the test suite structure and test purposes (TSS&TP);
[20]
3) ETSI TS 102 486-2-3 for the abstract test suite and partial PIXIT proforma.
12 © ISO 2021 – All rights reserved

Annex A
(normative)
SDTC physical layer
A.1 Overview and relation to CEN EN 12253
This annex:
— specifies the physical layer at 5,8 GHz for SDT Communications (SDTC); and
— provides requirements for the communication medium to be used for exchange of information
between roadside units (RSUs) and on-board units (OBU);
[1]
It provides specifications equivalent to those published in CEN EN 12253 and as used in the
specification for the Digital Tachograph; see ISO 15638-9, Reference [21] and Reference [22].
The terms "SDTC" and "DSRC" used in this annex are synonymous in terms of their applicability for the
SDT.
A.2 SDTC link parameters
A.2.1 General
This clause defines relevant downlink and uplink parameters of the SDTC OSI Layer 1 (physical layer).
The values to be used shall be set in accordance with SDTC profiles defined in Annex D.
OSI Layer 1 parameters are measured for free space propagation. Attention is drawn to the definition
of an OBU in 3.38, which means that measurements are taken in the absence of a windscreen or other
obscuring material unless it forms part of the manufactured OBU assembly.
A.2.2 Downlink parameters
Table A.1 shows downlink parameters.
Table A.1 — Downlink parameters
Item
Parameter Value(s) Remark
No.
D1 Carrier frequencies Two downlink channels at: Other 10 MHz bands within the
same ISM band allocated for RTTT
Downlink channel 1: 5,797 5 GHz
on a national basis:
Downlink channel 2: 5,802 5 GHz
Downlink channel 3:
5,807 5 GHz
Downlink channel 4:
5,812 5 GHz
These channels are defined
in accordance with
[10]
ECC/DEC(02)01 .
The selection of carrier frequencies
is outside the scope of this docu-
ment.
Table A.1 (continued)
Item
Parameter Value(s) Remark
No.
D1a Tolerance of carrier fre- Within ±5 ppm
quencies
D2 RSU transmitter spec- 1) Out band power:
[12]
trum mask see ETSI EN 300 674-1
2) In band power: ≤ +33 dBm
3) Unwanted emission for
unmodulated carrier wave shall
be less than:
Co-channel uplink at 1,5 MHz:
≤ -27 dBm in 500 kHz.
Co-channel uplink at 2,0 MHz:
≤ -27 dBm in 500 kHz.
Adjacent channel uplinks:
≤ -47 dBm in 500 kHz.
Equipment conforming with the
4) For in-band unwanted emission
different classes results in different
with modulated carrier wave,
re-use distances.
three different requirement
[12]
See ETSI EN 300 674-1 for more
classes are defined:
details
Class A: Class A is originally specified in the
respective CEN European Norm,
Co-channel uplink at 1,5 MHz:
indicating that this Class A should
≤ -7 dBm in 500 kHz.
not be used in new installations.
Co-channel uplink at 2,0 MHz: Further on, it is not considered for
≤ -27 dBm in 500 kHz. the European Digital Tachograph.
Adjacent channel uplinks:
≤ -30 dBm in 500 kHz.
Class B:
Co-channel uplink at 1,5 MHz:
≤ -17 dBm in 500 kHz.
Co-channel uplink at 2,0 MHz:
≤ -27 dBm in 500 kHz.
Adjacent channel uplinks:
≤ -37 dBm in 500 kHz.
Class C:
Co-channel uplink at 1,5 MHz:
≤ -27 dBm in 500 kHz.
Co-channel uplink at 2,0 MHz:
≤ -27 dBm in 500 kHz.
Adjacent channel uplinks:
≤ -47 dBm in 500 kHz.
D3 OBU Minimum Frequency 5,795 GHz – 5,815 GHz
Range
D4 Maximum E.I.R.P. +33 dBm
D4a Angular E.I.R.P. mask Θ ≤ 70°: ≤ +33 dBm
Θ > 70°: ≤ +18 dBm
D5 Polarization Left-hand circular
14 © ISO 2021 – All rights reserved

Table A.1 (continued)
Item
Parameter Value(s) Remark
No.
D5a Cross-polarization XPD:
In bore sight: RSU ≥ 15 dB
t
OBU ≥ 10 dB
r
At -3 dB area: RSU ≥ 10 dB
t
OBU ≥ 6 dB
r
D6 Modulation Two level amplitude modulation.
D6a Modulation index 0,5 - 0,9
D7 Data coding FM0
"1" bit has transitions only at the be-
ginning and end of the bit interval.
"0" bit has an additional transition
in the middle of the bit interval com-
pared to the "1" bit.
D8 Bit rate 500 kbit/s
D8a Tolerance of bit clock Better than ±100 ppm
-6
D9 Bit error ratio for commu- ≤ 10 when incident power at OBU is
nication in the range given by [D11a to D11b].
D10 Wake-up trigger for OBU OBU shall wake up on receiving any No special wake-up pattern is
frame with 11 or more octets (includ- necessary.
ing preamble).
OBU may wake up on receiving a
frame with less than 11 octets.
D10a Maximum start time ≤ 5 ms
D11 Communication zone Spatial region within which a
bit error ratio according to D9 is
achieved.
D11a Power limit for communi- Incident power: Implemented values are subject
cation (upper) to profiles and sets defined in
D11a-0: -24 dBm
Annex D.
D11a-1: -17 dBm
D11b Power limit for communi- Incident power:
cation (lower)
-43 dBm
D12 Cut-off power level of OBU -60 dBm Applicability of this parameter is
subject to profiles and sets defined
in Annex D.
D13 Preamble Preamble is mandatory.
D13a Preamble length 16 bits ± 1 bit
D13b Preamble wave form An alternating sequence of low level
and high level with pulse duration of
2 µs.
The tolerance is given by D8a.
D13c Trailing bits The RSU is permitted to transmit a
maximum of 8 bits after the end flag.
An OBU is not required to take these
additional bits into account.
A.2.3 Uplink parameters
Table A.2 shows uplink parameters.
Table A.2 — Uplink parameters
Item
Parameter Value(s) Remark
No.
U1 Sub-carrier frequencies An OBU shall support 1,5 MHz and Selection of sub-carrier frequency
2,0 MHz. (1,5 MHz or 2,0 MHz) depends on
profile indicated by the RSU.
An RSU shall support 1,5 MHz or
2,0 MHz or both. For interoperability with existing
installations it is recommended
U1-0: 1,5 MHz
that a 1,5 MHz sub-carrier frequen-
U1-1: 2,0 MHz
cy is used wherever possible.
U1a Tolerance of sub-carrier Within ±0,1 %
frequencies
U1b Use of side bands Same data on both sides.
U2 OBU transmitter spec- 1) Out band power: Information on the choice of val-
[12]
trum mask see ETSI EN 300674-1 ues can be found, for example, in
Annex D.
2) In band power:
≤ [U4a] dBm in 500 kHz
3) Emission in any other uplink
channel:
U2(3)-0 = -39 dBm in 500 kHz
U2(3)-1 = -35 dBm in 500 kHz
U4a Maximum single side band U4a-0: -14 dBm Information on the choice of val-
E.I.R.P. (bore sight) U4a-1: -21 dBm ues can be found, for example, in
Annex D.
U4b Maximum single side band -17 dBm Applicability of this parameter is
E.I.R.P. (35°) subject to profiles and sets defined
in Annex D.
U5 Polarization Left-hand circular transmitted when
left-hand circular received.
U5a Cross-polarization XPD:
In bore sight: RSU ≥ 15 dB
r
OBU ≥ 10 dB
t
At -3 dB: RSU ≥ 10 dB
r
OBU ≥ 6 dB
t
U6 Sub-carrier modulation 2-PSK
Encoded data synchronized with
sub-carrier: Transitions of encoded
data coincide with transitions of
sub-carrier.
U6b Duty cycle 50 % ± α, α ≤ 5 %
U6c Modulation on carrier Multiplication of modulated sub-car-
rier with carrier.
U7 Data coding NRZI
U8 Bit rate 250 kbit/s
U8a Tolerance of bit clock Within ±1 000 ppm
-6
U9 Bit error ratio for commu- ≤ 10
nication
U11 Communication zone The spatial region within which the
OBU is situated such that its trans-
missions are received by the RSU
with a bit error ratio of less than that
given by U9.
16 © ISO 2021 – All rights reserved

Table A.2 (continued)
Item
Parameter Value(s) Remark
No.
U12a Conversion gain (lower 1 dB for each side band Greater or equal to the specified
limit) value for each side band within a
Range of angle:
circular cone around bore sight of
Circularly symmetric between bore
±35° opening angle.
sight and ±35°.
U12b Conversion gain (upper 10 dB for each side band Less than the specified value for
limit) each side band within a circular
cone around bore sight of ±35°
opening angle.
Applicability of this parameter is
subject to sets and profiles defined
in Annex D.
U13 Preamble Preamble is mandatory.
U13a Preamble length and 32 µs to 36 µs modulated with
pattern sub-carrier only, then 8 bits of NRZI
coded "0" bits.
U13b Trailing bits The OBU is permitted to transmit a
maximum of 8 bits after the end flag.
An RSU is not required to take these
additional bits into account.
Annex B
(normative)
SDTC data link layer
B.1 Overview and relation to CEN EN 12795
This annex specifies the data link layer (DLL) of SDTC. The DLL of SDTC:
— is positioned with respect to other related standards by the layers defined in the OSI basic reference
model specified in ISO/IEC 7498-1, as adopted for SDTC;
— supports broadcast and half-duplex transmission modes;
— supports a variety of fixed equipment configurations;
— supports configurations where one instance of a fixed equipment communicates with one instance
of a mobile equipment, as well as configurations where one instance of a fixed equipment can
communicate with several instances of a mobile equipment;
— takes into account that the mobile equipment communicates with the fixed equipment while passing
through a communication zone with limited size;
— defines parameters to be used in negotiation procedures taking place between fixed equipment and
mobile equipment.
By defining two distinct sublayers of the DLL, namely the "Medium Access Control" (MAC) sublayer and
the "Logical Link Control" (LLC) sublayer, this annex defines:
a) MAC procedures for the shared physical medium;
b) addressing rules and conventions;
c) data flow control procedures;
d) acknowledgement procedures;
e) error control procedures;
f) services provided to the application layer.
The MAC sublayer is specific to SDTC. The LLC services offered are unacknowledged and acknowledged
connectionless services based on ISO/IEC 8802-2.
[2]
This annex provides specifications equivalent to those published in CEN EN 12795 and as used in the
specification for the Digital Tachograph; see ISO 15638-9, Reference [21] and Reference [22].
The terms "SDTC" and "DSRC" used in this annex are synonymous in terms of their applicability for the
SDT.
B.2 Frame format
B.2.1 Frame structures and bit streams
All SDTC transmissions are in frames, and each frame conforms to the structure shown in Figure B.1.
18 © ISO 2021 – All rights reserved

Figure B.1 — Frame structure
Frames containing no LPDU form a special case; see Figure B.2.
Figure B.2 — Frame structure, no LPDU
The physical bit stream can also comprise a preamble and/or trailing bits; see Figure B.3.
Figure B.3 — Physical layer bit stream
B.2.2 Flags
All frames shall start and end with a flag. A flag is a 0-bit followed by six 1-bits followed by a 0-bit
(0111 1110). When in receiving state, all stations shall continuously check on a bit-by-bit basis for this
sequence. A transmitter shall send only complete flags with eight bits.
The flag which ends a frame shall not be used as the start flag for the next frame.
In order to achieve transparency, the flag is prevented from accidentally occurring in the link address
field
...