IEC TS 61334-5-5:2001

Distribution automation using distribution line carrier systems - Part 5-5: Lower layer profiles - Spread spectrum - fast frequency hopping (SS-FFH) profile

Is a technical specification describing the requirements of the spread spectrum-fast frequency hopping (SS-FFH) approach for distribution line carrier communication systems. It incorporates the primitives provided by the physical and MAC layer entities as well as the modulation and transmission methods.
This publication is of high relevance for Smart Grid.

General Information

• Status: Published
• Publication Date: 26-Sep-2001
• ICS: 33.200 - Telecontrol. Telemetering
• Technical Committee: TC 57 - Power systems management and associated information exchange
• Drafting Committee: WG 9 - TC 57/WG 9
• Current Stage: PPUB - Publication issued
• Start Date: 27-Sep-2001
• Completion Date: 15-Oct-2001

Overview

IEC TS 61334-5-5:2001 defines the Spread Spectrum – Fast Frequency Hopping (SS‑FFH) lower‑layer profile for Distribution Line Carrier (DLC) systems used in distribution automation. This IEC Technical Specification specifies the physical‑layer and MAC‑sublayer primitives, the modulation and transmission methods, and the timing/synchronization rules required to operate SS‑FFH over low‑voltage distribution networks (AC 230 V, 50/60 Hz). It is highly relevant for Smart Grid deployments that require robust, EMI‑friendly PLC/DLC communications.

Key topics and technical requirements

• Modulation method: Spread spectrum with fast frequency hopping (SS‑FFH) using time‑limited sinusoidal carrier “chips”; symbols are encoded as sequences of chips across different frequencies to increase robustness and reduce EMI concentration.
• Physical medium: Direct coupling to low‑voltage AC distribution wiring (single‑ or three‑phase, 230 V, 50/60 Hz).
• Receiver design: Soft‑decision demodulation where per‑frequency chip metrics are combined to select the most likely transmitted symbol (interoperability unaffected by specific internal receiver architectures).
• Synchronization and timing:
  • Basic timing anchored to mains zero‑crossings (basic timing unit t = 1/(6·fN), where fN is mains frequency).
  • Chip timing and symbol timing derived from the basic timing unit.
  • Frame synchronization via a defined preamble (eight symbols) preceding data frames.
• MAC services and primitives: Defines MAC layer services, frame encapsulation, routing repetition (hops) and repeater behavior to ensure reachability across DLC domains.
• Electrical and EMI considerations: Spreading energy across carriers improves electromagnetic compatibility compared to narrowband carriers.
• Interfacing: Specifies the logical interface between the physical layer and MAC sublayer including PDU structures and management services.

Practical applications

• Field‑tested method for reliable PLC in Smart Grid use cases:
  • Low‑voltage distribution automation (fault detection, control signalling).
  • Smart metering backhaul and control signalling over power lines where radio is unavailable or restricted.
  • Utility last‑mile communications and repeater‑assisted networks in rural/urban grids.
• Benefits include improved interference resilience and easier compliance with EMC limits versus narrowband FSK approaches.

Who should use this standard

• Utility communications engineers and planners
• Smart Grid equipment manufacturers (PLC modems, repeaters, concentrators)
• Protocol and firmware developers implementing DLC stacks
• Test laboratories and compliance engineers validating EMC and interoperability
• Standards and regulatory bodies harmonizing DLC deployments

Related standards

• IEC 61334‑5‑1 (S‑FSK profile) and IEC 61334‑5‑2 (FSK profile)
• IEC 61334‑4‑1, IEC 61334‑4‑32 (data link / reference model)
• IEC 61000‑3‑8 (EMC signalling on low‑voltage installations)
• ITU‑T V.42 (error correction procedures)

Keywords: IEC TS 61334‑5‑5, SS‑FFH, spread spectrum fast frequency hopping, distribution line carrier, DLC, distribution automation, Smart Grid, physical layer, MAC sublayer, PLC, EMI, synchronization.

Standards Content (Sample)

TECHNICAL IEC
SPECIFICATION
TS 61334-5-5
First edition
2001-09
Distribution automation using
distribution line carrier systems –
Part 5-5:
Lower layer profiles –
Spread spectrum-fast frequency
hopping (SS-FFH) profile
Reference number
IEC/TS 61334-5-5:2001(E)
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.
Consolidated editions
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edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
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TECHNICAL IEC
SPECIFICATION
TS 61334-5-5
First edition
2001-09
Distribution automation using
distribution line carrier systems –
Part 5-5:
Lower layer profiles –
Spread spectrum-fast frequency
hopping (SS-FFH) profile
 IEC 2001  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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U
International Electrotechnical Commission
For price, see current catalogue

– 2 – TS 61334-5-5  IEC:2001(E)
CONTENTS
FOREWORD . 3
INTRODUCTION .5
1 Scope and object . 6
2 Normative references. 6
3 Abbreviations and definitions . 7
3.1 Abbreviations. 7
3.2 Definitions . 7
4 Physical layer . 8
4.1 Purpose . 8
4.2 Electrical characteristics . 8
4.3 Modulation principle. 8
4.4 Receiver principle . 9
4.5 Synchronization . 9
4.6 Frequency sets . 10
4.7 Physical frame encapsulation. 10
4.8 Symbol, bit and byte encoding . 11
4.9 Important parameters. 11
4.10 Physical layer data services. 11
4.11 Physical layer management interface. 13
4.12 Physical layer states . 14
5 Medium access control sublayer . 16
5.1 Outline. 16
5.2 Repeater principle. 20
5.3 MAC layer data service definition. 20
5.4 MAC layer timeout values . 22
5.5 MAC sublayer management services . 23
5.6 MAC layer states . 27
Figure 1 – Time representation of M = 3 SS-FFH symbol. 8
Figure 2 – Coding of information symbols in sequence of carrier chips . 8
Figure 3 – Actual P_PDU representation . 11
Figure 4 – MAC services . 17
Figure 5 – Frame decomposition . 19
Figure 6 – MAC management services . 23
Figure 7 – Example segmentation of M_SDU. 29

TS 61334-5-5  IEC:2001(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DISTRIBUTION AUTOMATION USING
DISTRIBUTION LINE CARRIER SYSTEMS –
Part 5-5: Lower layer profiles –
Spread spectrum-fast frequency hopping (SS-FFH) profile
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this technical specification may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
IEC 61334-5-5, which is a technical specification, has been prepared by IEC technical
committee 57: Power system control and associated communications.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
57/489/CDV 57/518/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.

– 4 – TS 61334-5-5  IEC:2001(E)
The committee has decided that the contents of this publication will remain unchanged until
2004. At this date, the publication will be
transformed into an International Standard;
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.
A bilingual version of this publication may be issued at a later date.

TS 61334-5-5  IEC:2001(E) – 5 –
INTRODUCTION
This technical specification describes a new physical layer variant with respect to the already
defined modulation techniques FSK and S-FSK within the IEC 61334 series (IEC 61334-5-1
1)
and IEC 61334-5-2 ).
The SS-FFH profile outlined in this technical specification basically incorporates spread
spectrum modulation techniques. It offers the main advantages of very high robustness and
improved EMI characteristics without sharing classical spread spectrum drawbacks such as
exaggerated bandwidth demand or impractical realization.
The profile specifies the physical layer including the transmission methods and the services
provided by both the physical layer and medium access sublayer entities.
________
1)
IEC 61334-5-1, Distribution automation using distribution line carrier systems – Part 5-1: Lower layer profiles –
The spread frequency shift keying (S-FSK) profile
IEC 61334-5-2, Distribution automation using distribution line carrier systems – Part 5-2: Lower layer profiles –
Frequency shift keying (FSK) profile

– 6 – TS 61334-5-5  IEC:2001(E)
DISTRIBUTION AUTOMATION USING
DISTRIBUTION LINE CARRIER SYSTEMS –
Part 5-5: Lower layer profiles –
Spread spectrum-fast frequency hopping (SS-FFH) profile
1 Scope and object
This technical specification describes the requirements of the spread spectrum-fast frequency
hopping (SS-FFH) approach for distribution line carrier communication systems. It incor-
porates the primitives provided by the physical and MAC layer entities as well as the
modulation and transmission methods.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61334. For dated references, subsequent amend-
ments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this part of IEC 61334 are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of
IEC and ISO maintain registers of currently valid International Standards.
IEC 61000-3-8, Electromagnetic compatibility (EMC) – Part 3: Limits – Section 8: Signalling
on low-voltage electrical installations – Emission levels, frequency bands and electromagnetic
disturbance levels
IEC 61334-4-1, Distribution automation using distribution line carrier systems – Part 4: Data
communication protocols – Section 1: Reference model of the communication system
IEC 61334-4-32, Distribution automation using distribution line carrier systems – Part 4: Data
communication protocols – Section 32: Data link layer – Logical Link Control (UC)
ITU-T Recommendation V.42, Error-correcting procedures for DCEs using asynchronous-to-
synchronous conversion
TS 61334-5-5  IEC:2001(E) – 7 –
3 Abbreviations and definitions
For the purpose of this technical specification, the following abbreviations and definitions
apply.
3.1 Abbreviations
DA Destination_address
DLC Distribution Line Carrier
FFH Fast Frequency Hopping
LV Low Voltage
M_PDU MAC Layer Protocol Data Unit
M_SDU MAC Layer Service Data Unit
MAC, M, MA Medium Access Control
MV Medium Voltage
P_PDU Physical Layer Protocol Data Unit
P_SDU Physical Layer Service Data Unit
SC Service_class
SDU Service Data Unit
SS Spread Spectrum
3.2 Definitions
3.2.1
chip
sinusoidal carrier waveform of limited time duration. Sequences of four chips form one symbol
3.2.2
domain
logical section of a DLC network
3.2.3
hops
number of routing repetitions required for communication between the master and a specific
station
3.2.4
preamble
modulated signal sequence that precedes a data frame for synchronization purpose
3.2.5
routing repetition
re-sending a PDU with a modified protocol information field because the destination station
can not be reached directly by the source station. The routing repetition procedure concerns
only the protocol information field and is handled by the MAC sublayer
3.2.6
symbol
modulated signal that encodes two transmitted bits

– 8 – TS 61334-5-5  IEC:2001(E)
4 Physical layer
4.1 Purpose
This clause details the transmission method to transport data frames provided by the MAC
sublayer to and from peer MAC entities using the electrical low-voltage distribution network.
It also specifies the requirements for the logical interface between the physical layer and
the MAC sublayer.
4.2 Electrical characteristics
The physical layer interfaces directly with the low-voltage distribution wiring as transport
medium. The electrical characteristics of the distribution network are AC, 230 V, 50/60 Hz.
Network coupling may be either single- or three-phase.
4.3 Modulation principle
The modulation method is spread spectrum fast frequency hopping (SS-FFH) modulation.
The basis of SS-FFH are time-limited sinusoidal carrier waveforms of a certain time duration
T and different frequencies f i = 1 . M. These carrier bursts are called chips. The reciprocal
C i
of the chip time duration T is called chip rate R . An information symbol is encoded by a
C C
sequence of subsequential chips as seen in figure 1.
T
C
Time
IEC  1605/01
Figure 1 – Time representation of M = 3 SS-FFH symbol
Each frequency is used only once per sequence. For this reason, the number of symbols that
can be encoded this way is M.
An example for M = 4 is given in the following.
Symbol Bitmapping Chip 1 Chip 2 Chip 3 Chip 4
S 00 f f f f
1 1 2 3 4
S 01 f f f f
2 2 3 4 1
f f f f
S 10
3 3 4 1 2
S 11 f f f f
4 4 1 2 3
IEC  1606/01
Figure 2 – Coding of information symbols in sequence of carrier chips

TS 61334-5-5  IEC:2001(E) – 9 –
The mapping of symbols into two bit patterns is also shown in figure 2. The maximum number
of bits that can be encoded with M different symbols is ld M. Thus the data rate R given the
D
chip rate R is
C
R
C
R = × ld (M)
D
M
Spreading the information in the described way on numerous carriers has several advantages.
First-symbol detection is possible with only one carrier present which makes SS-FFH very
robust against interference. Second EMI regulations can be met more easily through the fact
that the signalling energy is not confined to a narrow spectral segment.
SS-FFH provides the robustness unique to spread spectrum systems without sharing the
drawbacks such as complicated synchronization or expensive system implementation.
4.4 Receiver principle
Demodulation and detection of symbols follows a soft decision algorithm. This means that
quasi-analogue values for the presence or non-presence of each chip of a symbol are used
for detection.
Four demodulated signals, one for each frequency j = 1 … 4, are used for symbol detection
for each of the subsequent chips k = 1 . 4. As an example of a receiver architecture the
receiver sums up the demodulated signals d for four possible symbols.
jk
DS = d + d + d + d
1 11 22 33 44
DS = d + d + d + d
2 21 32 43 14
DS = d + d + d + d
3 31 42 13 24
DS = d + d + d + d
4 41 12 23 34
Finally the symbol i with the largest sum DS is chosen.
i
NOTE Actual receiver realization has no influence on interoperability.
4.5 Synchronization
4.5.1 Bit timing
The basic timing unit is
t = 1/(6f )
B N
where f denotes the mains frequency, for example, 50 Hz or 60 Hz.
N
Shorter intervals for bit timing may be generated by subdividing the basic unit. The basic unit
itself is generated by dividing the time period between two voltage zero crossings of one
phase by three. The beginning of a basic timing unit is demarked by basic timing markers.
This procedure ensures synchronization of the basic timing units of any transmitter and
receiver within a three-phase low-voltage network.
NOTE 1 Transmission delays are negligible for the data rates and typical distances considered in this document.
NOTE 2 Without violating the synchronization condition, fixed phase shifts between zero crossings and basic
timing markers may be introduced. This phase shift must not be time variant and must be constant for the overall
system.
– 10 – TS 61334-5-5  IEC:2001(E)
4.5.2 Chip timing
The beginning of a chip sequence is demarked by the aforementioned bit timing.
Given a chip rate R , the symbol rate R is an integer multiple of R :
C S C
R = K × R
S C
4.5.3 Frame synchronization
Synchronization of frames is accomplished by preambles preceding the data frame. A pre-
defined sequence of eight symbols is used for this purpose. Acknowledging that accurate
preamble detection is mandatory for good overall system performance, two principles are
deployed:
• preamble chip rate is substantially lower than data chip rate;
1)
• a soft decision preamble detection algorithm is used.
The following binary sequence is used as a preamble.
Bit 100 101 110 010 001 1
Symbol S S S S S S S S
3 2 2 4 1 3 1 4
The suggested preamble chip rate is half the data chip rate, resulting in a signalling energy
which is two times higher for each transmitted symbol.
4.5.4 Enhanced bit synchronization
Synchronization may be enhanced by additionally using the preamble sequence for fine tuning
of the chip timing.
4.6 Frequency sets
Any frequency in the range 9 kHz to 95 kHz, which is a multiple of 2,4 kHz may be chosen for
signalling. Due to heavy interference at lower frequencies the upper end of this band is
preferable. Suggested frequencies are 52,8 kHz, 62,4 kHz, 72 kHz and 86,4 kHz.
4.7 Physical frame encapsulation (see table 1 and figure 3)
Each physical layer data frame (P_PDU) consists of the physical layer data unit (P_SDU) and
a preceding preamble (see 4.5.3).
Table 1 – P_PDU fields and rates
Preamble P_SDU
Length 8 symbols 26 octets
Chip rate 0,5 R R
C C
________
1)
The actual preamble detection algorithm does not affect compatibility.

TS 61334-5-5  IEC:2001(E) – 11 –
To ease implementation of the preamble detection algorithm, the very first symbol of the data
unit (P_SDU) has the time duration of a preamble symbol. Thus, the P_SDU has the following
actual structure.
Data
Preamble
IEC  1607/01
Figure 3 – Actual P_PDU representation
4.8 Symbol, bit and byte encoding
One byte is transmitted as a sequence of four symbols, each containing 2 bits (dibits). The LSB
(rightmost) dibit of a byte is transmitted first.
4.9 Important parameters
In order to achieve compatibility, the values of the parameters of the physical layer must be
agreed upon. Suggested parameters are
Signalling frequencies: 52,8 kHz, 62,4 kHz, 72 kHz and 86,4 kHz
Preamble symbols: 8
Preamble chip rate: 1 200 chip/s
Preamble bit sequence: 1001 0111 0010 0011
Data symbols: 13
Data chip rate: 2 400 chip/s
Gross bit rate: 1 200 bit/s
Phase shift zero crossing/basic timing markers: 90°
Transmitting signal voltage amplitude follows IEC 61000-3-8. Actual transmitting power is
strongly influenced by the input impedance of the power grid for the signalling frequencies.
For typical system implementation, amplitudes should be held stable in the range from under
1 Ω up to 10 Ω.
4.10 Physical layer data services
The physical layer data service primitives enable the MAC sublayers to transmit and receive
M_PDUs to and from peer MAC sublayers.
There are three basic service primitives:
• P_Data.request
• P_Data.confirm
• P_Data.indication
4.10.1 Interface data units
The data units used by Phy primitives are P_SDUs. Each P_SDU has a fixed length of 26 bytes.

– 12 – TS 61334-5-5  IEC:2001(E)
4.10.2 P_Data.request
4.10.2.1 Function
This primitive is used to request sending a P_SDU from the local Phy entity to one or several
peer Phy entities.
4.10.2.2 Structure
The semantics of the primitive are as follows:
P_Data.request(
P_SDU,
tscl
)
P_SDU is the data unit passed to the Phy layer interface.
tscl defines three different transmitter synchronization classes:
s_sync: physical frame transmission starts with basic timing marker
z_sync: physical frame transmission starts with zero crossing
no_sync: physical frame is sent out immediately
4.10.2.3 Use
The primitive is generated by the MAC sublayer entity.
Reception of a P_Data.request causes the physical layer entity to wait for the proper
synchronization moment (as defined by tscl), send out the preamble and the P_SDU.
4.10.3 P_Data.confirm
4.10.3.1 Function
The P_Data.confirm primitive provides an appropriate response to a P_Data.request primitive.
It indicates proper transmission of a P_SDU by the Phy layer entity.
4.10.3.2 Structure
The semantics are as follows:
P_Data.confirm(Transmission_Status)
Transmission_Status specifies whether the previously issued Phy_Data.request primitive was
executed successfully or not. The possible returned values are
P_OK: P_PDU was transmitted successfully
P_TU: Transmission failed due to temporarily unavailable resources at physical layer
P_HF: Hardware failure at the physical layer
P_SE: Syntax error
TS 61334-5-5  IEC:2001(E) – 13 –
4.10.3.3 Use
The primitive is generated in response to a previously issued P_Data.request.
It is assumed that the MAC sublayer has sufficient information to associate the confirmation
with the corresponding request.
4.10.4 P_Data.indication
4.10.4.1 Function
The primitive defines the transfer of data from the physical layer entity to the MAC sublayer entity.
4.10.4.2 Structure
The semantics of the primitive are as follow
...