Information technology -- Radio frequency identification for item management -- Methods for localization of RFID tags

This document defines how to use the RFID air interface standards of the ISO/IEC 18000 series that are based on backscatter technology for localization of RFID tags, specifically tags which are ISO/IEC 18000‑4, ISO/IEC 18000‑61, ISO/IEC 18000-62, ISO/IEC 18000-63 and ISO/IEC 18000-64 compliant. This document specifies the physical and logical requirements for localization. The system comprises interrogators, also known as readers, and tags, also known as labels. An interrogator receives information from a tag by transmitting a modulated RF signal to the tag and the tag responds by modulating the reflection coefficient of its antenna, thereby backscattering an information signal to the interrogator. The modulated RF signal for data exchange is based on the relevant part of the ISO/IEC 18000 series and, in addition, there is a superimposed modulated RF signal with the same or different carrier frequency intended for localization. This document describes the signals required for localization, the method to derive localization information from the signals received by the interrogator and the requirements onto tags and interrogators.

Technologies de l'information -- Identification par radiofréquence (RFID) pour la gestion d'objets -- Méthodes pour la localisation d'étiquettes RFID

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Status
Published
Publication Date
29-Sep-2019
Current Stage
6060 - International Standard published
Start Date
27-Aug-2019
Completion Date
30-Sep-2019
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ISO/IEC 22243:2019 - Information technology -- Radio frequency identification for item management -- Methods for localization of RFID tags
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INTERNATIONAL ISO/IEC
STANDARD 22243
First edition
2019-09
Information technology — Radio
frequency identification for item
management — Methods for
localization of RFID tags
Technologies de l'information — Identification par radiofréquence
(RFID) pour la gestion d'objets — Méthodes pour la localisation
d'étiquettes RFID
Reference number
ISO/IEC 22243:2019(E)
ISO/IEC 2019
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ISO/IEC 22243:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 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: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2019 – All rights reserved
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ISO/IEC 22243:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Conformance ............................................................................................................................................................................................................. 2

4.1 Claiming conformance ...................................................................................................................................................................... 2

4.2 Interrogator conformance and obligations .................................................................................................................... 2

4.3 Tag conformance and obligations ........................................................................................................................................... 2

5 Symbols and abbreviated terms ........................................................................................................................................................... 2

6 Ranging requirements .................................................................................................................................................................................... 4

6.1 Overview of the ranging method ............................................................................................................................................. 4

6.2 Description of operating procedure ..................................................................................................................................... 4

6.3 Ranging requirements for ISO/IEC 18000-63 based systems ....................................................................... 8

6.3.1 Tag requirements ............................................................................................................................................................ 8

6.3.2 Interrogator requirements ...................................................................................................................................11

6.3.3 Multiple interrogators ..............................................................................................................................................12

6.4 Ranging requirements for ISO/IEC 18000-4, ISO/IEC 18000-61, ISO/IEC 18000-62

and ISO/IEC 18000-64 based systems ............................................................................................................................12

Annex A (normative) Codes for localization results ..........................................................................................................................13

Bibliography .............................................................................................................................................................................................................................15

© ISO/IEC 2019 – All rights reserved iii
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ISO/IEC 22243:2019(E)
Foreword

ISO (the International Organization for Standardization) and IEC (the International Electrotechnical

Commission) form the specialized system for worldwide standardization. National bodies that

are members of ISO or IEC participate in the development of International Standards through

technical committees established by the respective organization to deal with particular fields of

technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other

international organizations, governmental and non-governmental, in liaison with ISO and IEC, also

take part in the work.

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 document 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 and IEC 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) or the IEC

list of patent declarations received (see http: //patents .iec .ch).

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 Joint Technical Committee ISO/IEC JTC 1, Information technology,

Subcommittee SC 31, Automatic identification and data capture techniques.

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.
iv © ISO/IEC 2019 – All rights reserved
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ISO/IEC 22243:2019(E)
Introduction

Technology progress continuously achieves longer read ranges for RFID and in particular UHF RFID.

With increasing communication ranges, the actual possible location of a tag around an interrogator

gets larger and larger and there is often demand for more precise details on the tag location around the

interrogator.

This document addresses tag localization by additionally superimposing a wideband localization signal

to the communication between interrogator and tag.

In order to ensure interoperable systems, this document addresses the physical layer, logical layer and

details on systems.

The International Organization for Standardization (ISO) and International Electrotechnical

Commission (IEC) draw attention to the fact that it is claimed that compliance with this document may

involve the use of patents, including concerning “Method and System for Locating Objects” given in 6.1

and 6.2.

ISO and IEC take no position concerning the evidence, validity and scope of these patent rights. The

holders of these patent rights have assured ISO and] IEC that they are willing to negotiate licences

under reasonable and non-discriminatory terms and conditions with applicants throughout the world.

In this respect, the statements of the holders of these patent rights are registered with ISO and IEC.

Information may be obtained from:
Technische Universität Wien
Research & Transfer Support
Karlsplatz 13
1040 Vienna, Austria
Impinj, Inc.
400 Fairview Ave N, # 1200
Seattle, WA 98109 USA

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights other than those identified above. ISO and IEC shall not be held responsible for identifying

any or all such patent rights.
© ISO/IEC 2019 – All rights reserved v
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INTERNATIONAL STANDARD ISO/IEC 22243:2019(E)
Information technology — Radio frequency
identification for item management — Methods for
localization of RFID tags
1 Scope

This document defines how to use the RFID air interface standards of the ISO/IEC 18000 series

that are based on backscatter technology for localization of RFID tags, specifically tags which are

ISO/IEC 18000-4, ISO/IEC 18000-61, ISO/IEC 18000-62, ISO/IEC 18000-63 and ISO/IEC 18000-64

compliant.

This document specifies the physical and logical requirements for localization. The system comprises

interrogators, also known as readers, and tags, also known as labels. An interrogator receives

information from a tag by transmitting a modulated RF signal to the tag and the tag responds by

modulating the reflection coefficient of its antenna, thereby backscattering an information signal

to the interrogator. The modulated RF signal for data exchange is based on the relevant part of the

ISO/IEC 18000 series and, in addition, there is a superimposed modulated RF signal with the same or

different carrier frequency intended for localization. This document describes the signals required for

localization, the method to derive localization information from the signals received by the interrogator

and the requirements onto tags and interrogators.
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 18000-63, Information technology — Radio frequency identification for item management —

Part 63: Parameters for air interface communications at 860 MHz to 960 MHz Type C

ISO/IEC 18047-6, Information technology — Radio frequency identification device conformance test

methods — Part 6: Test methods for air interface communications at 860 MHz to 960 MHz

ISO/IEC 19762, Information technology — Automatic identification and data capture (AIDC) techniques —

Harmonized vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 19762 and the

following 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
information-bit
single bit of information sent from the tag to the interrogator

Note 1 to entry: Depending on the selected modulation of the backscatter link, an information-bit is represented

by multiple modulation-bits.
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ISO/IEC 22243:2019(E)
3.2
modulation-bit
smallest unit in a binary modulated backscatter communication

Note 1 to entry: Depending on the type of modulation, an information-bit is represented by multiple

modulation-bits.

Note 2 to entry: In case of ISO/IEC 18000-63 modulations, each modulation bit has the length of Tpri/2.

3.3
Query
command from interrogator-to-tag
Note 1 to entry: This term is explained in more detail in ISO/IEC 18000-63.
4 Conformance
4.1 Claiming conformance

An interrogator or tag shall comply with all relevant clauses of this document, except those marked as

“optional”.
4.2 Interrogator conformance and obligations

An interrogator shall implement the mandatory commands defined in this document and conform to

ISO/IEC 18000-63.

An interrogator may implement any subset of the optional commands defined in this document.

The interrogator shall not
— implement any command that conflicts with this document, or

— require the use of an optional, proprietary or custom command to meet the requirements of this

document.
4.3 Tag conformance and obligations

A tag shall implement the mandatory commands defined in this document for the supported types and

conform to ISO/IEC 18000-63.

A tag may implement any subset of the optional commands defined in this document.

A tag shall not
— implement any command that conflicts with this document, or

— require the use of an optional, proprietary or custom command to meet the requirements of this

document.
5 Symbols and abbreviated terms

The main symbols and abbreviated terms used in this document are detailed in ISO/IEC 19762. Symbols,

abbreviated terms and notation specific to this document are as follows:
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ISO/IEC 22243:2019(E)
BLF backscatter-link frequency
CW continuous wave

Δs (τ) difference waveform between the averaged waveforms Δs (τ) − Δs (τ). This wave-

avg avg,1 avg,0
form serves as the basis for calculation the ToF between interrogator and tag

averaged delta voltage between the tag’s two different modulation states (complex

ΔIQ
valued)
Δ delta radar cross section
RCS
DUT device under test
FT frequency tolerance (of the backscatter link)
G gain of the receiving antenna
G gain of the transmitting antenna
I in-phase component (real-part of complex value)
average IQ voltage during modulation state m and bit number k
km,
k index of the backscatter modulation-bits, k = 0, 1, 2…
P minimum power allowing the DUT tag activation
I,min
Q quadrature-phase component (imaginary-part of complex value)
R=>T interrogator-to-tag
RCS radar cross section of tag
RX receive(d)

s (τ) averaged waveform of the RX waveforms, realigned in time, s′ (τ) of “0”-modulation-bits

avg,0 RX,k

s (τ) averaged waveform of the RX waveforms, realigned in time, s′ (τ) of “1”-modulation-bits

avg,1 RX,k
S (τ) cyclic ranging signal in time-domain (one period)
RRSEQ

s (τ) part of the RX-signal due to leakage and reflections with the length of one period of the

leakage,RX,k
ranging signal, received in time-slot k
s′ (τ) part of the RX-signal due to leakage and reflections cyclically rotated
leakage,RX,k

s (τ) part of the RX-signal from the active tag with the length of one period of the ranging

tag.RX,k
signal, received in time-slot k
s′ (τ) part of the RX-signal from the active tag cyclically rotated
tag,RX,k

s (τ) RX-signal with the length of one period of the ranging signal, received in time-slot k

RX,k
s′ (τ) RX-signal cyclically rotated
RX,k
t length of a single period of the ranging signal
RSEQ
T k-th time-segments of the tag’s backscattered modulation-bits
T=>R tag-to-interrogator
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ISO/IEC 22243:2019(E)
ToF time of flight

τ time within a signal of the length of a ranging signal’s single period 0 ≤ τ < t

RSEQ
TX transmit(ted)
6 Ranging requirements
6.1 Overview of the ranging method

The ranging principle is intended to be used in backscatter-based RFID systems. It uses a wideband-

signal, superimposed onto the interrogator’s signal during tag-to-interrogator (also known as reader)

(T=>R) communication. The interrogator uses signal processing on the received signal to determine the

distance between tag and interrogator when interrogating the tag. The tag may implement commands

and/or operational modes, enhancing the accuracy of the ranging. Ranging in general works with

regular tags as e.g. tags compliant to ISO/IEC 18000-63, however some tag designs can have limitations

in range and accuracy. The requirements within this document ensure a certain minimum ranging

performance for different tag- and interrogator vendors.
6.2 Description of operating procedure

The ranging is based on ToF measurements of the round-trip time from interrogator to tag and back

to interrogator. As typical RFID tags work with rather low link data rates (e.g. up to 640 kBits/s for

ISO/IEC 18000-63 tags) and allow timing variations of several microseconds, ToF cannot be used

directly. Using a wideband interrogator signal and measuring the delay of the received echo does

not give usable results either, as the echo is dominated by multiple other contributions (e.g. antenna

coupling, other tags).

Figure 1 shows an example for the ranging signal, being transmitted after a ISO/IEC 18000-63 Query

command during the time a response from the tag is expected.
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ISO/IEC 22243:2019(E)
Key
1 ranging signal
2 Query sequence
3 response from tag expected
Figure 1 — Superimposed ranging signal

The superimposed periodic signal S (τ) shall have a periodicity not longer than the time of a single

RRSEQ

modulation-bit of the tag’s backscatter signal. Due to data encoding, a modulation-bit can have a shorter

length than an information-bit, depending on the chosen T=>R modulation. Additionally, the timing

tolerance of the modulation-bit has to be taken into account. Figure 2 shows an example of the

backscattered information bit-sequence “01” with Miller 4-encoding applied. Here, each information-bit

consists of 8 modulation-bits. For ISO/IEC 18000-63 tags, the maximum length of one period of the

1− fT

ranging signal S (τ), denoted by the time t , can be expressed by t ≤ , with f as the

RRSEQ RSEQ BL
RSEQ
2 fBL

backscatter-link frequency (BLF) and f as the tag’s allowed frequency tolerance (FT) defined by

ISO/IEC 18000-63.
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