ISO/IEC 24730-21:2012

Information technology — Real time locating systems (RTLS) — Part 21: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol: Transmitters operating with a single spread code and employing a DBPSK data encoding and BPSK spreading scheme

ISO/IEC 24730-2 is comprised of a main document and two additional parts, ISO/IEC 24730-21 and ISO/IEC 24730-22, and defines a networked location system that provides X-Y coordinates and data telemetry. The system utilizes real-time locating systems (RTLS) transmitters that autonomously generate a direct sequence spread spectrum radio frequency beacon. These devices can be field programmable and support an optional exciter mode that allows modification of the rate of location update and location of the RTLS device. ISO/IEC 24730-2 defines these modes, but does not define the means by which they are accomplished. ISO/IEC 24730-21:2012 specifies transmitters operating with a single spread code and employing a differential binary phase shift keying (DBPSK) data encoding and binary phase shift keying (BPSK) spreading scheme.

Technologies de l'information — Systèmes de localisation en temps réel (RTLS) — Partie 21: Protocole d'interface d'air à 2,4 GHz d'étalement de spectre à séquence directe (DSSS): Émetteurs fonctionnant avec un code d'étalement unique et utilisant un codage de données DBPSK et un schéma d'étalement BPSK

General Information

• Status: Published
• Publication Date: 30-May-2012
• ICS: 35.040 - Information coding
• ICS: 35.040.50 - Automatic identification and data capture techniques
• Technical Committee: ISO/IEC JTC 1/SC 31 - Automatic identification and data capture techniques
• Drafting Committee: ISO/IEC JTC 1/SC 31/WG 4 - Radio communications
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 11-Jun-2023

Relations

• Revised: ISO/IEC 24730-2:2012 - Information technology — Real time locating systems (RTLS) — Part 2: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol
• Effective Date: 24-Apr-2010
• Revises: ISO/IEC 24730-2:2006 - Information technology — Real-time locating systems (RTLS) — Part 2: 2,4 GHz air interface protocol
• Effective Date: 24-Apr-2010

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 24730-21
First edition
2012-06-01

Information technology — Real time
locating systems (RTLS) —
Part 21:
Direct Sequence Spread Spectrum
(DSSS) 2,4 GHz air interface protocol:
Transmitters operating with a single
spread code and employing a DBPSK
data encoding and BPSK spreading
scheme
Technologies de l'information — Systèmes de localisation en temps réel
(RTLS) —
Partie 21: Protocole d'interface d'air à 2,4 GHz d'étalement de spectre à
séquence directe (DSSS): Émetteurs fonctionnant avec un code
d'étalement unique et utilisant un codage de données DBPSK et un
schéma d'étalement BPSK




Reference number
ISO/IEC 24730-21:2012(E)
©
ISO/IEC 2012

---------------------- Page: 1 ----------------------
ISO/IEC 24730-21:2012(E)

COPYRIGHT PROTECTED DOCUMENT


©  ISO/IEC 2012
All rights reserved. Unless otherwise specified, 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 either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland

ii © ISO/IEC 2012 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/IEC 24730-21:2012(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. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
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.
ISO/IEC 24730-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 31, Automatic identification and data capture techniques.
This first edition of ISO/IEC 24730-21, together with ISO/IEC 24730-2 and ISO/IEC 24730-22, cancels and
replaces the first edition of ISO/IEC 24730-2:2006, which has been technically revised.
ISO/IEC 24730 consists of the following parts, under the general title Information technology — Real time
locating systems (RTLS):
 Part 1: Application program interface (API)
 Part 2: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol
 Part 21: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol: Transmitters operating
with a single spread code and employing a DBPSK data encoding and BPSK spreading scheme
 Part 22: Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol: Transmitters operating
with multiple spread codes and employing a QPSK data encoding and Walsh offset QPSK (WOQPSK)
spreading scheme
 Part 5: Chirp spread spectrum (CSS) at 2,4 GHz air interface
 Part 6: Ultra Wide Band Air Interface protocol
 Part 61: Low rate pulse repetition frequency Ultra Wide Band (UWB) air interface
 Part 62: High rate pulse repetition frequency Ultra Wide Band (UWB) air interface
© ISO/IEC 2012 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO/IEC 24730-21:2012(E)
Introduction
ISO/IEC 24730-21 defines the physical layer for compliant RTLS transmitters operating with a single spread
code and employing a DBPSK data encoding and BPSK spreading scheme.

iv © ISO/IEC 2012 – All rights reserved

---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO/IEC 24730-21:2012(E)

Information technology — Real time locating systems (RTLS) —
Part 21:
Direct Sequence Spread Spectrum (DSSS) 2,4 GHz air interface
protocol: Transmitters operating with a single spread code and
employing a DBPSK data encoding and BPSK spreading
scheme
1 Scope
ISO/IEC 24730-2 is comprised of a main document and two additional parts and defines a networked location
system that provides X-Y coordinates and data telemetry. The system utilizes RTLS transmitters that
autonomously generate a direct sequence spread spectrum radio frequency beacon. These devices can be
field programmable and support an optional exciter mode that allows modification of the rate of location
update and location of the RTLS device. ISO/IEC 24730-2 defines these modes, but does not define the
means by which they are accomplished.
This part of ISO/IEC 24730 specifies transmitters operating with a single spread code and employing a
differential binary phase shift keying (DBPSK) data encoding and binary phase shift keying (BPSK) spreading
scheme.
2 Normative references
The following referenced documents are indispensable for the application 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 24730-2:2011, Information technology — Real time locating systems (RTLS) — Part 2: Direct
Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol
ISO/IEC 24730-22:2011, Information technology — Real time locating systems (RTLS) — Part 22: Direct
Sequence Spread Spectrum (DSSS) 2,4 GHz air interface protocol: Transmitters operating with multiple
spread codes and employing a QPSK data encoding and Walsh offset QPSK (WOQPSK) spreading scheme
3 Terms and definitions
For the purposes of this document, the terms and definitions provided in ISO/IEC 24730-2 apply.
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviated terms provided in ISO/IEC 24730-2 apply.
© ISO/IEC 2012 – All rights reserved 1

---------------------- Page: 5 ----------------------
ISO/IEC 24730-21:2012(E)
5 Requirements
5.1 Frequency range
For the purposes of this document, the frequency range provided in ISO/IEC 24730-2 applies.
5.2 2,4 GHz spread spectrum air interface attributes
For the purposes of this document, the 2,4 GHz spread spectrum air interface attributes provided in
ISO/IEC 24730-2 apply.
5.3 Compliance requirements
For the purposes of this document, the compliance requirements provided in ISO/IEC 24730-2 apply.
5.4 Manufacturer tag ID
For the purposes of this document, the manufacturer tag ID provided in ISO/IEC 24730-2 applies.
5.5 Physical layer parameters
The parameter definitions in Table 1 apply. These parameters are referenced by parameter name. These
operating parameters are to be defined for the temperature range of –30 degrees Celsius to 50 degrees
Celsius.
An optional mode is defined for utilization in Japan. This allows the operation in conformance with local radio
regulations in Japan. This mode shall be used for systems that will be operated in Japan. Link parameters for
this mode are defined in Table 2a.
Table 3 and Table 4 specify the parameters for the optional air interfaces that may be implemented.
Table 1 — RTLS transmitter DSSS link parameters
Parameter name Description
Operating frequency range 2400 MHz–2483,50 MHz
Operating frequency accuracy ± 25 ppm maximum
Centre frequency 2441,750 MHz
Occupied channel bandwidth 60 MHz
Transmit power Class 1: 10 dBm EIRP max.
Class 2: Maximum in accordance to local regulations
Spurious emission, out of band The device shall transmit in conformance with spurious
emissions requirements defined by the country’s regulatory
authority within which the system is operated.
Modulation BPSK DSSS
Data encoding Differentially encoded
Data bit rate 59,7 kb/s
Bit error rate 0,001%
PN chip rate 30,521875 MHz ± 25 ppm
PN code length 511
PN spread code 0x1CB
2 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 6 ----------------------
ISO/IEC 24730-21:2012(E)
Parameter name Description
Data packet lengths Option 1: 56 bits
Option 2: 72 bits
Option 3: 88 bits
Option 4: 152 bits
12 11 3 2
Message CRC polynomial G(x) = X + X + X + X + X + 1
CRC polynomial initialized value 0x001
Blink interval Programmable, 5 s minimum
Blink interval randomization ± 638 ms maximum
Number of sub-blinks Programmable, 1 - 8
Sub-blink interval randomization 125 ms ± 16 ms maximum
Maximum frequency drift < ± 2 ppm over the duration of the entire message
Phase accuracy < 0,50 radians within any 33 s period
Phase noise < 15 degrees when the noise is integrated from 100 Hz to
100 kHz
Table 2a — RTLS transmitter DSSS link parameters for Japan Mode
Parameter name Description
Operating frequency range 2400 MHz–2483,50 MHz
Operating frequency accuracy ± 25 ppm maximum
Centre frequency 2441,750 MHz
Occupied channel bandwidth 26 MHz
Transmit power Class 1: 10 dBm EIRP max.
Class 2: Maximum in accordance to local regulations
Spurious emission, out of band The device shall transmit in conformance with spurious
emissions requirements defined by the country’s regulatory
authority within which the system is operated.
Modulation BPSK DSSS
Data encoding Differentially encoded
Data bit rate 59,7 kb/s
Bit error rate 0,001%
PN chip rate 15,260938 MHz ± 25 ppm
PN code length 511
PN spread code 0x8D
Data packet lengths Option 1: 56 bits
Option 2: 72 bits
Option 3: 88 bits
Option 4: 152 bits
12 11 3 2
Message CRC polynomial G(x) = X + X + X + X + X + 1
CRC polynomial initialized value 0x001
Blink interval Programmable, 5 s minimum
Blink interval randomization ± 638 ms maximum
© ISO/IEC 2012 – All rights reserved 3

---------------------- Page: 7 ----------------------
ISO/IEC 24730-21:2012(E)
Parameter name Description
Number of sub-blinks Programmable, 1 - 8
Sub-blink interval randomization 125 ms ± 16 ms maximum
Maximum frequency drift < ± 2 ppm over the duration of the entire message
Phase accuracy
< 0,50 radians within any 33 s period
Phase noise < 15 degrees when the noise is integrated from 100 Hz to
100 kHz

Table 3 — RTLS transmitter OOK link parameters
Parameter
Number Parameter Name Description
O 1a Carrier frequency 2400 MHz - 2483,5 MHz
O 1b Operating frequency accuracy ± 25 ppm maximum
O 1c Centre frequency 2441,750 MHz
O 2a Data encoding Differentially encoded
Data packet lengths Option 1: 88 bits
O 2b
Option 2: 184 bits
16 12 5
O 2c Message CRC polynomial G(x) = X + X + X + 1
O 2d CRC polynomial initialized value 0x0001
Transmit power Class 1: 10 dBm EIRP max.
O 3
Class 2: Max. per local radio regulations
Transmit spurious emissions, out of
O 4 Within local radio regulations
band
O 5 Modulation OOK/FSK, using 2 tones @ 376,8 kHz /535,5 kHz
O 5a Logic “0” 19 cycles at a 377 kHz rate of 2,44652 GHz on/off
O 5b Logic “1” 27 cycles at a 535 kHz rate of 2,44652 GHz on/off
O 6 Data rate 19,83 kb/s
O 7 Duty cycle 50%
O 8 Data error rate 0,001% max.

4 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 8 ----------------------
ISO/IEC 24730-21:2012(E)
Table 4 — RTLS transmitter magnetic link parameters
Parameter
Number Parameter Name Description
M 1 Signalling frequencies 114,688 kHz and 126,976 kHz
M 2 Field strength Regulatory/application dependent
M 3 Bit data rate 2,048 kb/s
M 4 Symbol period 244,14 ms
M 5 Data error rate 0,001%
Start sync. 3 symbol periods @ 114,688 kHz followed by 3 symbol
M 6
periods @ 126,976 kHz
End sync. 3 symbol periods @ 126,976 kHz followed by 3 symbol
M 7
periods @ 114,688 kHz
Data bit 0 1 symbol period @ 126,976 kHz followed by 1 symbol
M 8
period @ 114,688 kHz
Data bit 1 1 symbol period @ 114,688 kHz followed by 1 symbol
M 9
period @ 126,976 kHz
Programmer packet lengths Option 1: 10 bits
Option 2: 48 bits
Option 3: 64 bits
M 10a
Option 4: 68 bits
Option 5: 144 bits
Option 6: 160 bits
Exciter packet lengths Option 1: 10 bits
Option 2: 28 bits
M 10b
Option 3: 44 bits
Option 4: 144 bits
M 11 Data encoding Manchester encoding
Programmer message CRC
12 11 3 2 1
M 12a G(X) = X + X + X + X + X + 1
polynomial
8 4 3 2
M 12b 28-bit exciter CRC polynomial G(X) = X + X + X + X + 1
12 11 3 2 1
M 12c 44-bit exciter CRC polynomial G(X) = X + X + X + X + X + 1
10-bit programmer / exciter CRC 4 1
M 12d G(X) = X + X + 1
polynomial

6 Mandatory air interface protocol specification
6.1 General
ISO/IEC 24730-21 defines the 2,400 GHz to 2,4835 GHz RTLS spread-spectrum transmissions and the
command/data level air interface communication protocols. These protocols facilitate communication between
a compliant RTLS transmitter and a compliant infrastructure. The optional protocols in clause 7 facilitate
communication between an RTLS transmitter and a programming device and also an exciter device
respectively. The timing parameters and signal characteristics for the protocols are defined in the physical link
specification in clause 5.
© ISO/IEC 2012 – All rights reserved 5

---------------------- Page: 9 ----------------------
ISO/IEC 24730-21:2012(E)
6.2 Introduction
Beacon type RTLS system architecture consists of RTLS transmitters that “blink” a Direct Sequence Spread
Spectrum (DSSS) signal, and fixed position RTLS readers that receive those signals. The system then
determines the x, y location of the RTLS transmitters. Location of tagged assets can be determined with better
than 3 m accuracy in most environments, indoors and out. Once the location of the RTLS transmitter is
determined, the location information and any other information are passed to the host application.
Additionally, an option that provides the ability to transmit telemetry data is defined.
6.3 Functional Description and Specification
The RTLS transmitter module is typically a compact internally powered radio frequency device that is a
component of the RTLS system. The RTLS system is designed to track and locate items with attached RTLS
transmitters. Each locatable transmission is a pulse of direct sequence spread spectrum radio signal. The
RTLS infrastructure receives these signals, or blinks. The blink is a short ID-only message or a longer
telemetry message also containing the RTLS transmitters ID. Each transmission also contains a status data
word that provides information on the RTLS transmitter configuration, battery status and other data. The RTLS
transmitter’s ID, status data word, and location are provided to the host by the RTLS Infrastructure. Multiple
RTLS transmitters may be present in typical installations allowing a large number of items to be tracked and
located in real time.
Anti-collision synchronization protocols are not required. Each “blink” is comprised of multiple sub-blinks. The
sub-blinks are part of a multiple level anti-interference system; time diversity, spatial diversity, processing gain.
The combination of these multiple sub-blinks, multiple receiving antennas and spread spectrum correlation
also allow multiple RTLS transmitters to blink simultaneously and still be received.
The RTLS transmitter data shall be binary encoded with the MSB (Most Significant Bit) transmitted first in all
messages. It is differentially encoded using the example circuit of Figure 1. The output of the encoder shall be
initialized to "1". It shall be exclusively OR’d with the output of the PN (Pseudo Noise) generator, modulated
using a BPSK (Bi-Phase Shift Keyed) format and upconverted using a single sideband upconverter. The
signal is then amplified and transmitted to the RTLS infrastructure.
SET
D Q
Data Out
Data In
CLR Q
Clock

Figure 1 — Example of differential encoding circuit
6 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 10 ----------------------
ISO/IEC 24730-21:2012(E)
An example of the RTLS transmitter PN Generator is shown in Figure 2.

Figure 2 — RTLS transmitter PN generator
An example of the RTLS transmitter PN Generator for Japan mode is shown in Figure 3a.
PN-
code
D 8
1
B C
SET
SET SET SET SET SET SET SET SET
D Q
D Q D Q D Q D Q D Q D Q D Q D Q
Q
CLR Q Q Q Q Q Q Q Q
CLR CLR CLR CLR CLR CLR CLR CLR
D1 D2 D3 D4 D5 D6 D7 D8 D9
PN generator
output
Figure 3a — RTLS transmitter PN generator for Japan Mode
© ISO/IEC 2012 – All rights reserved 7

---------------------- Page: 11 ----------------------
ISO/IEC 24730-21:2012(E)
Data encoding and transmission process is shown below in Figure 4.

Figure 4 — RTLS transmitter data encoding and transmission process
The format of the DSSS transmission from the RTLS transmitter is shown in Figure 5. Each DSSS
transmission from the RTLS transmitter contains a “blink” packet containing N sub-blinks. Each set of sub-
blinks can be one of four message lengths. All sub-blinks within a “blink” shall be identical to provide time
diversity. Each sub-blink includes the RTLS transmitter’s 32-bit ID, 5-bit of status data, CRC data, and optional
telemetry data depending on the type of message. The “blink” packet occurs at the beginning of the blink
interval. Sub-blinks shall be separated by an interval, which is not user configurable. The number of sub-blinks
per blink and the blink interval are configurable.
Blink containing N sub-blinks
Sub-blink

Blink interval

Figure 5 — DSSS air interface
Three classes of DSSS blinks are defined; Timed Interval Blink (TIB), EXciter Blink (EXB), and Event Blink
(EB). A TIB shall transmit at a pre-programmed rate. An EB shall be caused by a switch event or external
stimulus. A state diagram showing the different operational states of the RTLS transmitter is shown below in
Figure 6.
Note: For Figure 6 and all future figures, solid lines denote required features and dotted lines denote optional features.
8 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 12 ----------------------
ISO/IEC 24730-21:2012(E)
Set blink
rate=off.
Initial power-on
Program mode
Timed Interval
Programmer
Completion of
signal
Blink (TIB) mode
blink
Sec 6.3.3.4
Completion of
programming
Sec 6.3.3.1
Interval
Sleep mode
timer
Exciter
message
Completion of
blink
External
Exit exciter
input
mode
EXciter Blink
Event Blink (EB)
(EXB) mode
mode
Sec 6.3.3.3
Set blink
Sec 6.3.3.2
rate=off.

Figure 6 — RTLS transmitter state diagram
The DSSS carrier frequency is fixed at 2441,75 MHz and the chip rate shall be fixed at 30,521875 MHz.
6.4 RTLS transmitter radiated power
Two classes of RTLS transmitters exist with respect to the output power level they are capable of delivering.
The Equivalent Isotropically Radiated Power (EIRP) of a Class 1 RTLS transmitter is less than 10 mW
(10 dBm). Class 1 RTLS transmitters are intended for applications with moderate to dense infrastructures and
minimal obstructions.
The EIRP of a Class 2 RTLS transmitter is greater than 10 mW (10dBm) and less than the maximum allowed
by local radio regulations. Class 2 RTLS transmitters are intended for sparse infrastructures where RTLS
readers may be located greater than 300 meters from the RTLS transmitter or environments with major
obstructions.
The antenna of the RTLS transmitter should provide a pattern that is as omni-directional as possible within the
constraints of the RTLS transmitter packaging requirements. This will ensure near equivalence with regard to
orientation performance of individual transmitters within the system. The RF EIRP of a tag shall not vary more
than 10 dB peak to peak in a spherical pattern in free space. It shall not vary more than 10 dB in a semi-
spherical pattern around a tag mounted directly to a metallic plate of 1 sq. meter in order to achieve the
required system performance.
© ISO/IEC 2012 – All rights reserved 9

---------------------- Page: 13 ----------------------
ISO/IEC 24730-21:2012(E)
6.5 DSSS message specifications
The message specifications are provided below.
6.5.1 DSSS message encoding
The PN Spreading Code shall be 0x1CB. The PN Generator is initialized with a “1” in register D9 and “0”’s in
all other registers.
The beginning of the blink interval shall be randomized by a maximum of ±638 ms to avoid repeatedly
colliding with blinks from other RTLS transmitters. The beginning of each successive sub-blink shall also be
randomized. The interval between each sub-blink shall be 125 ms randomized by a maximum of ±16 ms from
the beginning of the previous sub-blink.
6.5.2 DSSS message structures
There are four different message formats determined by the length of the message in bits: the 56-bit message,
the 72-bit message, the 88-bit message, and the 152-bit message. An RTLS transmitter shall be capable of
transmitting at least one of these message formats. The 56-bit and 72-bit message format is intended for
transmitting the RTLS transmitter ID, the 72 and 88-bit messages are intended for transmitting the RTLS
transmitter ID and exciter information, and the 152-bit message format is intended for transmitting limited
amounts of telemetry information. The structure of each of these message formats is shown in more detail in
the following sections.
Each message type contains an 8-bit preamble of 0x01.
Each message type contains a 4-bit RTLS transmitter status as defined in the message definitions.
72- and 88-bit messages may carry an exciter ID. An exciter ID is comprised of 16 bits. The MSB designates
whether the RTLS transmitter has entered or left an exciter field.
Each message type contains a CRC generator polynomial defined by X12 + X11 + X3 + X2 + X + 1. The
preamble is not included in this polynomial.
Each message contains a 32-bit RTLS transmitter ID. These ID’s are defined in the range 1 to 4 294 967 296
(0x00000001 to 0xFFFFFFFF).
Unique data to the each message type is shown.
6.5.2.1 DSSS 56-bit message format
The DSSS 56-bit message format for the RTLS transmitter is shown in Table 5. The 56-bit message format
consists of the 8-bit preamble, the 4-bit RTLS transmitter status field, a 32-bit field containing the RTLS
transmitter ID, and the 12-bit CRC field for a total message length of 56 bits. The 56-bit message shall have
transmission duration of 937.5 μs.
Table 5 — DSSS 56-bit message format
Preamble RTLS transmitter status RTLS transmitter ID CRC
8 "0" S2 S1 B 32 12
8 "1" Reserved 32 12
Bit 55 to bit 48 Bit 47 to bit 44 Bit 43 to bit 12 Bit 11 to bit 0

For S1 and S2 a value of "1" shall equal a set condition. For B, (the battery bit), a value of "1" shall equal a
notification of a battery alarm.
10 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 14 ----------------------
ISO/IEC 24730-21:2012(E)
6.5.2.2 DSSS 72-bit message format
The DSSS 72-bit message format for the RTLS transmitter is shown in Table 6. The 72-bit message format
consists of the 8-bit preamble, the 4-bit RTLS transmitter status field, a 32-bit field containing the RTLS
transmitter ID, a 16-bit payload field, and the 12-bit CRC field for a total message length of 72 bits. The 72-bit
message can be used for communicating the RTLS transmitter’s 32-bit ID and either data or an exciter
address or an extended RTLS transmitter ID as payload. The status field determines the content format of the
payload field. The 72-bit message shall have transmission duration of 1.205 ms.
Table 6 — DSSS 72-bit message format
Preamble RTLS transmitter status RTLS transmitter ID Payload CRC
8 "0" S2 S1 B 32 Extended ID 12
8 "1" "0" "0" "0" 32 Exciter ID 12
8 "1" X X X 32 Indexed Data 12
Bit 71 to bit 64 Bit 63 to bit 60 Bit 59 to bit 28 Bit 27 to bit 12 Bit11 to bit 0

6.5.2.3 DSSS 88-bit message format
The DSSS 88-bit message format for the RTLS transmitter is shown in Table 7. The 88-bit message format
consists of an 8-bit preamble, a 4-bit RTLS transmitter status field, a 32-bit field containing the RTLS
transmitter ID, a 16-bit exciter field, an additional 16-bit address field, and a 12-bit CRC field for a total
message length of 88 bits. The 88-bit message format can be used for communicating the RTLS transmitter’s
32-bit ID and an extended RTLS transmitter ID and either an exciter address or data as the payload. The
status field determines the content format of the payload field. The 88-bit message shall have transmission
duration of 1,473 ms.
Table 7 — DSSS 88-bit message format
RTLS RTLS Extended
Preamble Payload CRC
transmitter status transmitter ID address
Reserved "0" S2 S1 B Reserved Reserved Reserved Reserved
8 "1" "0" "0" "0" 32 16 Exciter ID(16) 12
8 "1" X X X 32 16 Indexed data(16) 12
Bit 87 to bit 80 Bit 79 to bit 76 Bit 75 to bit 44 Bit 43 to bit 28 Bit 27 to bit 12 Bit11 to bit 0

6.5.2.4 DSSS 152-bit message format
The DSSS 152-bit message format for the RTLS transmitter is shown in Table 8. The 152-bit message format
consists of an 8-bit preamble, a 4-bit RTLS transmitter status field, a 32-bit field containing the RTLS
transmitter ID, a 96-bit data field, and a 12-bit CRC field for a total message length of 152 bits. The 152-bit
message shall have transmission duration of 2,544 ms.
Table 8 — DSSS 152-bit message format
RTLS RTLS
Preamble Payload CRC
transmitter status transmitter ID
8 X S2 S1 B 32 96 12
8 X S2 S1 B 32 60-DF 16 ext ID 72 12
Bit 107 to Bit 99 to Bit 83 to
Bit 151 to bit 144 Bit 143 to bit 140 Bit 139 to bit 108 Bit 11 to bit 0
bit 100 bit 84 bit 12
© ISO/IEC 2012 – All rights reserved 11

---------------------- Page: 15 ----------------------
ISO/IEC 24730-21:2012(E)
6.5.3 DSSS message modes
There are multiple message modes. These modes allow the system to be matched to the application
requirements, by providing the ability to: minimize airtime, transmit exciter ID's, transmit event notifications, or
transmit telemetry data.
6.5.3.1 Timed Interval Blink (TIB) mode
Timed Interval Blink mode transmits one of four message types transmitted over the DSSS link. The following
parameters may be configurable in conformance with the specifications provided.
6.5.3.1.1 Number of sub-blinks
The number of sub-blinks transmitted by the RTLS transmitter during a TIB may be configurable. If the
number of sub-blinks is configurable, they shall be configurable from 1 to 8 sub-blinks per blink.
6.5.3.1.2 Blink interval
The blink interval of TIB transmissions may be configurable. The minimum blink interval shall be 5 s. A
command to set the blink interval to 0 shall disable an RTLS transmitter.
6.5.3.1.3 152-bit blink repetition rate
The 152-bit blink repetition rate shall define the TIB repetition rate for 152-bit messages. Available intervals
th th
shall be every 8 blink, every 64 blink, always or never.
6.5.3.2 Event Blink (EB) mode
Events are defined as pushbutton activation, slide switch toggles, or other external inputs. Event blinks shall
occur only after an event is detected. After an event is detected, the RTLS transmitter shall blink from 1 to 15
times as programmed. The minimum blink interval shall be 5 s. An EB shall be 56, 72, or 152 bits in length.
If the transmitter is disabled an event shall not cause a blink.
6.5.3.2.1 Number of event blinks
The number of EBs for the RTLS transmitter should be configurable from 0 to 15 blinks per event.
6.5.3.2.2 Event blink interval
The event blink Interval shall be 5 s or greater.
6.5.3.2.3 Event blink re-trigger time
The event blink re-trigger interval is defined as the time to ignore the same event input after the last blink. The
event blink re-trigger interval period shall be 5 s or greater.
6.5.3.3 EXciter Blink (EXB) mode
If supported, EXciter Blink Mode allow the system to modify the RTLS transmitter blink rate to provide a
different blink rate or a finer level of location by providing a locate function with regard to the exciter.
6.5.3.4 Program mode
If supported, Program mode allows an RTLS transmitter to have operational parameters programmed. The
RTLS transmitter may also be turned on and off in this mode.
12 © ISO/IEC 2012 – All rights reserved

---------------------- Page: 16 ----------------------
ISO/IEC 24730-21:2012(E)
7 Optional air interfaces
7.1 General
The RTLS transmitter may support the use of a programmer and an exciter. If the RTLS transmitter does
support the use of these devices, then it shall comply with the following clauses.
7.2 RTLS transmitter OOK/FSK message specifications
If the RTLS transmitter does support the use of a programmer, then it shall respond to the programmer with
OOK/FSK messages as defined below.
7.2.1 OOK/FSK blink message description
The RTLS transmitter may include a method to respond to a programming device.
If the RTLS transmitter includes this capability, the transmitter shall receive commands transmitted using
magnetic FSK and use OOK/FSK transmissions to respond to the programming device. The programming
device may be used to write and read configuration information, load data registers, and/or read the identity
from the RTLS transmitter.
If external programming and/or data load is supported, there shall be two different message lengths, 88-bit
and 184-bit. The structure of the 88-bit message shall
...