IEC 62106-1:2018

Radio data system (RDS) - VHF/FM sound broadcasting in the frequency range from 64,0 MHz to 108,0 MHz - Part 1: Modulation characteristics and baseband coding

IEC 62106-1:2018 defines the basic layer of the Radio Data System (RDS) intended for application to VHF/FM sound broadcasts in the range 64,0 MHz to 108,0 MHz, which can carry either stereophonic (pilot-tone system) or monophonic programmes (as stated in ITU‑R Recommendation BS.450-3 and ITU-R Recommendation BS.643-3).
IEC 62106-1:2018 together with IEC 62106-2, IEC 62106-3, IEC 62106-4, IEC 62106-5 and IEC 62106-6, cancels and replaces IEC 62106:2015, and constitutes a technical revision.
This edition includes the following significant technical changes with respect to IEC 62106:2015:
• Provision has been made to carry RDS on multiple data-streams (RDS2).

General Information

• Status: Published
• Publication Date: 09-Oct-2018
• ICS: 33.160.40 - Video systems
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Drafting Committee: MT 62106 - TC 100/TA 1/MT 62106
• Current Stage: PPUB - Publication issued
• Start Date: 10-Oct-2018
• Completion Date: 02-Oct-2018

Relations

• Replaces: IEC 62106:2015 - Specification of the radio data system (RDS) for VHF/FM sound broadcasting in the frequency range from 87,5 MHz to 108,0 MHz
• Effective Date: 05-Sep-2023

Overview

IEC 62106-1:2018 specifies the basic layer of the Radio Data System (RDS) for VHF/FM sound broadcasting in the 64.0 MHz to 108.0 MHz band. This Part 1 standard focuses on modulation characteristics and baseband coding used to carry RDS data over FM broadcasts (stereo or mono as per ITU‑R Recommendation BS.450-3 and BS.643-3). The 2018 edition introduces support for carrying RDS on multiple data‑streams (RDS2) and forms the foundational technical specification for RDS transmission and receiver design.

Key topics and technical requirements

The standard defines the core technical building blocks of RDS and RDS2, including:

• Subcarrier generation and precise data‑stream subcarrier frequencies for the FM multiplex (including the traditional 57 kHz RDS subcarrier and additional RDS2 subcarriers).
• Subcarrier phase and level requirements to ensure compatibility between transmitters and receivers.
• Data‑stream modulation requirements, including clock frequency, data rate, and differential coding on all streams.
• Baseband coding structure and error protection mechanisms (including a modified shortened cyclic code described in informative annexes).
• Data‑channel spectrum shaping, symbol timing and symbol phase shifts across multiple data‑streams to minimize interference with audio services.
• Synchronization of blocks and groups across all streams, with defined offset words for group/block sync and implementation guidance.
• Normative and informative annexes that cover encoder/decoder theory, shift‑register implementations, and synchronization algorithms.

Practical applications and who uses this standard

IEC 62106-1 is essential for stakeholders involved in FM broadcast data services and device interoperability:

• Broadcasters and network operators implementing RDS/RDS2 services to deliver program information, traffic messages, and additional data services.
• Transmitter and encoder manufacturers designing compliant RDS modulators and FM multiplexers.
• Receiver and automotive electronics vendors ensuring accurate demodulation, decoding and presentation of RDS and RDS2 data on infotainment systems and consumer radios.
• Regulators and standards bodies defining national broadcast profiles and frequency planning.
• Software developers and ODA (Open Data Application) creators who rely on a stable baseband and message layer for delivering apps and metadata over FM.

Related standards

• IEC 62106 series (Parts 2–6): message formats, ODA usage, code tables, device marking, public technical specs.
• ITU‑R Recommendation BS.450‑3 and BS.643‑3: relevant stereophonic and monophonic FM broadcasting references.
• RDS Forum specifications for RDS2 extension and application-level features.

Keywords: IEC 62106-1, RDS, RDS2, Radio Data System, VHF/FM, 57 kHz, modulation characteristics, baseband coding, FM multiplex, subcarrier, FM broadcasting.

Standards Content (Sample)

IEC 62106-1 ®
Edition 1.0 2018-10
INTERNATIONAL
STANDARD
Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range
from 64,0 MHz to 108,0 MHz –
Part 1: Modulation characteristics and baseband coding

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IEC 62106-1 ®
Edition 1.0 2018-10
INTERNATIONAL
STANDARD
Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range

from 64,0 MHz to 108,0 MHz –
Part 1: Modulation characteristics and baseband coding

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.40 ISBN 978-2-8322-6066-1

– 2 – IEC 62106-1:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 8
3.3 Notation and conventions . 8
3.3.1 Hexadecimal notation . 8
3.3.2 Nomenclature for group types . 8
3.3.3 Capitalized RDS terms. 8
4 Modulation characteristics of the data channels . 8
4.1 General . 8
4.2 Subcarrier generation . 9
4.3 Data-stream subcarrier frequencies for all possible streams . 10
4.4 Subcarrier phase requirements . 11
4.5 Subcarrier level requirements . 11
4.6 Data-stream modulation requirements . 11
4.7 Clock-frequency and data-rate . 11
4.8 Differential coding on all data-streams . 11
4.9 Data-channel spectrum shaping on all data-streams . 12
4.10 Symbol phase shifts of data across data-streams . 15
5 Baseband coding . 16
5.1 Data-stream baseband coding structure . 16
5.2 Data-stream error protection . 16
5.3 Synchronization of blocks and groups across all streams . 17
6 Transmission options on data-streams 1, 2 and 3 . 18
Annex A (normative) Offset words to be used for group and block synchronization . 19
Annex B (informative) Theory and implementation of the modified shortened cyclic
code . 20
B.1 General . 20
B.2 Encoding procedure . 20
B.2.1 Theory . 20
B.2.2 Shift-register implementation of the encoder . 22
B.3 Decoding procedure . 23
B.3.1 Theory . 23
B.3.2 Implementation of the decoder . 24
Annex C (informative) Implementation of group and block synchronization using the
modified shortened cyclic code . 26
C.1 Theory . 26
C.1.1 Acquisition of group and block synchronization . 26
C.1.2 Detection of loss of synchronization . 26
C.2 Shift register arrangement for deriving group and block synchronization
information . 26
Bibliography . 29

Figure 1 – Block diagram of data-stream 0 radio-data equipment at the transmitter . 9
Figure 2 – Block diagram of a typical data-stream 0 radio-data receiver/decoder . 10
Figure 3 – Subcarriers for RDS data-stream 0 and additional RDS2 data-streams 1, 2
and 3 . 10
Figure 4 – Amplitude response of the specified transmitter or receiver data-shaping filter . 13
Figure 5 – Amplitude response of the combined transmitter and receiver data-shaping
filters . 14
Figure 6 – Spectrum of biphase coded radio-data signals . 14
Figure 7 – Time-function of a single biphase symbol . 15
Figure 8 – 57 kHz modulated data-signal . 15
Figure 9 – Structure of the baseband coding . 16
Figure B.1 – Generator matrix of the basic shortened cyclic code in binary notation . 21
Figure B.2 – Shift-register implementation of the encoder . 22
Figure B.3 – Parity-check matrix of the basic shortened cyclic code . 24
Figure B.4 – Shift-register implementation of the decoder . 25
Figure C.1 – Group and block synchronization detection circuit. 27

Table 1 – Encoding rules . 12
Table 2 – Decoding rules . 12
Table 3 – Phase shifts of data across data-streams 1-3 with respect to data-stream 0 . 16
Table A.1 – Offset word codes . 19
Table B.1 – Offset word syndromes using matrix of Figure B.3 . 24
Table C.1 – Offset word syndromes for group and block synchronization . 28

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RADIO DATA SYSTEM (RDS) –
VHF/FM SOUND BROADCASTING IN THE FREQUENCY
RANGE FROM 64,0 MHz TO 108,0 MHz –

Part 1: Modulation characteristics and baseband coding

FOREWORD
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62106-1 has been prepared by technical area 1: Terminals for
audio, video and data services and contents, of IEC technical committee 100: Audio, video
and multimedia systems and equipment.
This first edition, together with IEC 62106-2, IEC 62106-3, IEC 62106-4, IEC 62106-5 and
IEC 62106-6, cancels and replaces IEC 62106:2015, and constitutes a technical revision.
This edition includes the following significant technical changes with respect to
IEC 62106:2015:
• Provision has been made to carry RDS on multiple data-streams (RDS2).

The text of this International Standard is based on the following documents:
CDV Report on voting
100/2907/CDV 100/3055/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62106 series, published under the general title Radio data
system (RDS) – VHF/FM sound broadcasting in the frequency range from 64,0 MHz to
108,0 MHz, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC 62106-1:2018 © IEC 2018
INTRODUCTION
Since the mid-1980s a fascinating development has taken place. Most of the multimedia
applications and standards have been created or redefined significantly. Hardware has
become extremely powerful with dedicated software and middleware. In the mid-1980s,
Internet as well as its protocols did not exist. Navigation systems became affordable in the
late 1990s, and a full range of attractive smartphones now exist. The computing power of all
these new products is comparable with that of the mainframe installations in that era.
Listener expectations have grown faster than the technology. Visual experience is now very
important, like the Internet look and feel. Scrolling text or delivering just audio is nowadays
perceived as insufficient for FM radio, specifically for smartphone users. New types of radio
receivers with added value features are therefore required. RDS has so far proven to be very
successful.
FM radio with RDS is an analogue-digital hybrid system, which is still a valid data
transmission technology and only the applications need adaptation. Now the time has come to
solve the only disadvantage, the lack of sufficient data capacity. With RDS2, the need to
increase the data capacity can be fulfilled.
RDS was introduced in the early 1980s. During the introductory phase in Europe, the car
industry became very involved and that was the start of an extremely successful roll-out.
Shortly afterwards, RDS (RBDS) was launched in the USA [1, 2, 3, 4, 5].
The RDS Forum has investigated a solution to the issue of limited data capacity. For RDS2,
both sidebands around the RDS 57 kHz subcarrier can be repeated a few times, up to three,
centred on additional subcarriers higher up in the FM multiplex still remaining compatible with
the ITU Recommendations.
The core elements of RDS2 are the additional subcarriers, which will enable a significant
increase of RDS data capacity to be achieved, and then only new additional data applications
will have to be created, using the RDS-ODA feature, which has been part of the RDS standard
IEC 62106 for many years.
In order to update IEC 62106:2015 to the specifications of RDS2, IEC 62106 has been
restructured as follows:
Part 1: Modulation characteristics and baseband coding
Part 2: RDS message format, coding and definition of RDS features
Part 3: Usage and registration of Open Data Applications ODAs
Part 4: Registered code tables
Part 5: Marking of RDS and RDS2 devices
Part 6: Compilation of technical specifications for Open Data Applications in the public domain
The following future parts are planned:
Part 7: RBDS
Part 8: Universal Encoder Communication Protocol UECP
The original specifications of the RDS system have been maintained and the extra
functionalities of RDS2 have been added.
Obsolete or unused functions from the original RDS standard IEC 62106:2015 have been
deleted. The presentation in Parts 1, 2 and 3 follows the OSI basic reference model for
information processing systems [6].
_______________
Numbers in square brackets refer to the Bibliography.

RADIO DATA SYSTEM (RDS) –
VHF/FM SOUND BROADCASTING IN THE FREQUENCY
RANGE FROM 64,0 MHz TO 108,0 MHz –

Part 1: Modulation characteristics and baseband coding

1 Scope
This part of IEC 62106 defines the basic layer of the Radio Data System (RDS) intended for
application to VHF/FM sound broadcasts in the range 64,0 MHz to 108,0 MHz, which can
carry either stereophonic (pilot-tone system) or monophonic programmes (as stated in
ITU-R Recommendation BS.450-3 and ITU-R Recommendation BS.643-3).
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.
IEC 62106 (all parts), Radio Data System (RDS) – VHF/FM sound broadcasting in the
frequency range from 64,0 MHz to 108,0 MHz
ITU-R Recommendation BS.450-3, Transmission standards for FM sound broadcasting at
VHF
ITU-R Recommendation BS.643-3, Radio data system for automatic tuning and other
applications in FM radio receivers for use with pilot-tone system
3 Terms, definitions and abbreviated terms
3.1 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 http://www.iso.org/obp
3.1.1
data-stream
data modulated on any RDS subcarrier

– 8 – IEC 62106-1:2018 © IEC 2018
3.2 Abbreviated terms
AM Amplitude Modulation
FM Frequency Modulation
MF Medium wave broadcasting Frequency band
NOTE 1 MF applies to ITU, all Regions.
LF Long wave broadcasting Frequency band
NOTE 2 LF applies to ITU, Region 1 only.
VHF Very High Frequency broadcasting band
NOTE 3 VHF applies only to ITU.
RDS Radio Data System
NOTE 4 RDS is the generic term for Radio Data System. It designates also the legacy RDS
system of all previous editions of IEC 62106, but it uses only the basic stream 0 on subcarrier
57 kHz.
RDS2 Radio Data System 2
NOTE 5 RDS2 is the generic term for Radio Data System 2. It designates Radio Data System
comprising data-stream 0 on a 57 kHz subcarrier and one or more additional data-streams
(1, 2, 3) on higher frequency subcarriers.
RBDS Radio Broadcast Data System
NOTE 6 RBDS is a variant of RDS, see [5].
3.3 Notation and conventions
3.3.1 Hexadecimal notation
C notation “0x” designates hex (base 16) numbers.
NOTE This notation is used throughout this standard.
3.3.2 Nomenclature for group types
Group types A and B are referenced by a number 0…15 and a version A or B. Group type C
is referenced by a header byte and 7 data bytes
3.3.3 Capitalized RDS terms
To align with general usage, some technical terms are capitalized throughout the IEC 62106
series, such as "Radio Data System" and "Radio Broadcast Data System".
4 Modulation characteristics of the data channels
4.1 General
The Radio Data System is intended for application to VHF/FM sound broadcasting
transmitters in the range from 64,0 MHz to 108,0 MHz, which carry stereophonic (pilot-tone
system) or monophonic sound broadcasts specified in ITU-R Recommendation BS.450-3.
The data-streams are carried on up to four subcarriers, which are added to the stereo
multiplex signal (or monophonic signal, as appropriate) at the input of the VHF/FM transmitter.
Block diagrams of the data source equipment at the transmitter and a typical receiver
arrangement are shown for RDS in Figure 1 and Figure 2, respectively.

4.2 Subcarrier generation
During stereo broadcasts, the subcarrier frequencies are derived from and phase-locked to
the 19 kHz pilot-tone. The tolerance of the subcarriers is directly related to the tolerance of
the 19 kHz pilot-tone, which is ± 2 Hz (ITU-R Recommendation BS.450-3).
During monophonic broadcasts, the frequency of the data-stream 0 subcarrier is
57 kHz ± 6 Hz. RDS2 data-stream 1, 2 and 3 subcarriers are locked to the data-stream 0
subcarrier.
Data-stream 0 subcarrier is required for RDS and RDS2 while data-stream 1, 2 and 3
subcarriers are optional and are only applicable to RDS2.

Figure 1 – Block diagram of data-stream 0 radio-data equipment at the transmitter

– 10 – IEC 62106-1:2018 © IEC 2018

a
The overall data-shaping in this decoder comprises the filter F1 and the data-shaping inherent in the biphase
symbol decoder. The amplitude/frequency characteristic of filter F1 is therefore not the same as that given in
Figure 4.
Figure 2 – Block diagram of a typical data-stream 0 radio-data receiver/decoder
4.3 Data-stream subcarrier frequencies for all possible streams
The data-stream subcarriers are as in Figure 3.
Data-stream 0: 57,0 kHz (3 × pilot-tone)
Data-stream 1: 66,5 kHz
Data-stream 2: 71,25 kHz
Data-stream 3: 76,0 kHz (4 × pilot-tone)
The theoretically possible 61,75 kHz data-stream subcarrier is not used.

Figure 3 – Subcarriers for RDS data-stream 0 and
additional RDS2 data-streams 1, 2 and 3

4.4 Subcarrier phase requirements
During stereo broadcasts, the subcarrier for data-stream 0 shall be locked either in phase or
in quadrature to the 19 kHz pilot-tone. The tolerance on this phase angle is ± 10°, measured
at the modulation input to the FM transmitter. The subcarriers for data-streams 1, 2 and 3
shall be locked in phase to the subcarrier for data-stream 0, so that all subcarriers periodically
have 0 phase at the same time, nominally repeating every 4/19 ms.
4.5 Subcarrier level requirements
The maximum permitted deviation due to the composite multiplex signal is ± 75 kHz. In order
to support additional subcarriers, the deviation will have to be reduced on other elements in
the multiplex MPX spectrum to keep within the maximum deviation requirement.
The minimum recommended deviation for data-stream 0 subcarrier is 1,5 kHz. Optimal
performance is achieved at 2 kHz of deviation for data-stream 0.
The number of subcarriers utilized and their relative levels may be adjusted in order to meet
the desired output deviation and subcarrier coverage area.
The ITU has recommendations for the amount of deviation to use for elements of the MPX
spectrum. The overall transmission shall meet the ITU requirements.
NOTE With the 2 kHz injection level of the subcarrier, the level of each sideband of the subcarrier corresponds to
half the nominal peak deviation level of 2 kHz for an all-zeroes message data-stream (i.e. a continuous bit-rate
sine-wave after biphase encoding).
4.6 Data-stream modulation requirements
Each subcarrier is amplitude-modulated by the shaped and biphase coded data signal
(see 4.9). The subcarrier itself is suppressed. This method of modulation may alternatively be
thought of as a form of two-phase phase-shift-keying (PSK) with a phase deviation of ±90°.
4.7 Clock-frequency and data-rate
The clock-frequency for data-stream 0 subcarrier 57 kHz is obtained by dividing the
transmitted subcarrier frequency by 48. Consequently, the basic data-rate for data-stream 0
(see Figure 1) is 1 187,5 bit/s ± 0,125 bit/s.
The frequencies for the data-stream 1-3 subcarriers can be calculated by addition of the
¼ pilot frequencies: 19/4 = 4,75 kHz. The first position, 61,75 kHz is not used to protect the
basic subcarrier of 57 kHz on existing receivers.
This results in subcarrier frequencies as shown in 4.3 and Figure 3. The data rate for data-
streams 1, 2 and 3 are the same as for data-stream 0.
4.8 Differential coding on all data-streams
The source data at the transmitter are differentially encoded according to the following rules,
see Table 1.
– 12 – IEC 62106-1:2018 © IEC 2018
Table 1 – Encoding rules
Previous output New input New output
(at time t ) (at time t ) (at time
...