ISO/IEC 24730-22:2012

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

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 24730-22:2012 is the mode of ISO/IEC 24730-2 transmitters operating with multiple spread codes and employing a quadrature phase shift keying (QPSK) data encoding and Walsh offset QPSK (WOQPSK) spreading scheme.

Technologies de l'information — Systèmes de localisation en temps réel — Partie 22: Protocole d'interface d'air à 2,4 GHz d'étalement de spectre à séquence directe (DSSS): Émetteurs fonctionnant avec des codes d'étalement multiples et utilisant un codage de données QPSK et un schéma d'étalement Walsh offset QPSK (WOQPSK)

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 24730-22
First edition
2012-06-01

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
Technologies de l'information — Systèmes de localisation en temps réel
(RTLS) —
Partie 22: Protocole d'interface d'air à 2,4 GHz d'étalement de spectre à
séquence directe (DSSS): Émetteurs fonctionnant avec des codes
d'étalement multiples et utilisant un codage de données QPSK et un
schéma




Reference number
ISO/IEC 24730-22:2012(E)
©
ISO/IEC 2012

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ISO/IEC 24730-22:2012(E)

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©  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,
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ISO/IEC 24730-22:2012(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Symbols and abbreviated terms . 4
5  Requirements . 4
5.1  Frequency range . 4
5.2  2,4 GHz spread spectrum air interface attributes . 4
5.3  Compliance requirements . 5
5.4  Manufacturer tag ID . 5
5.5  Physical layer parameters . 5
6  Mandatory air interface protocol specification . 7
6.1  General . 7
6.2  Physical layer specification . 9
Annex A (informative)  Reader synchronization by the RTLS reference tag . 17
Bibliography . 19

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ISO/IEC 24730-22:2012(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 24730-22 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 24730-22, together with ISO/IEC 24730-2 and ISO/IEC 24730-21, 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 5: Chirp spread spectrum (CSS) at 2,4 GHz air interface
 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
The following parts are under preparation:
 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
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ISO/IEC 24730-22:2012(E)
Introduction
ISO/IEC 24730 defines a single application program interface (API) for real-time locating systems (RTLs) for
use in asset management and is intended to allow for compatibility and to encourage interoperability of
products for the growing RTLS market. ISO/IEC 24730 also defines three air interface protocols, as follows:
ISO/IEC 24730-2, based on a direct sequence spread spectrum (DSSS), ISO/IEC 24730-5, based on a chirp
spread spectrum (CSS) technique, and ISO/IEC 24730-6 Ultra Wide Band Air Interface protocol.
This part of ISO/IEC 24730, the direct sequence spread spectrum (DSSS) 2,4 GHz air interface protocol,
establishes a technical standard for real-time locating systems that operate at an internationally available
2,4 GHz frequency band and is intended to provide approximate location with frequent updates (for example,
several times a minute). In order to be compliant with this part of ISO/IEC 24730 compliance with
ISO/IEC 24730-1 is also required.
Real-time locating systems are wireless systems with the ability to locate the position of an item anywhere in a
defined space (local/campus, wide area/regional, global) at a point in time that is, or is close to, present time.
Position is derived by measurements of the physical properties of the radio link.
This part of ISO/IEC 24730 specifies the air interface for a system that locates an asset in a controlled area,
e.g. warehouse, campus, airport (area of interest is instrumented) with accuracy to 3 m or less.
There are two additional methods of locating an object which are really RFID rather than RTLS:
 locating an asset by virtue of the fact that the asset has passed point A at a certain time and has not
passed point B;
 locating an asset by virtue of providing a homing beacon whereby a person with a handheld device can
find an asset.
The method of location is through identification and location, generally through multi-lateration. The different
types are
 time of Arrival (ToA) / Time of Flight Ranging Systems,
 amplitude / Received Signal Strength Triangulation,
 time Difference of Arrival (TDoA), and
 angle of Arrival (AoA).
This part of ISO/IEC 24730 defines the air interface protocol needed for the creation of an RTLS system.
Although there are many types of location algorithms that could be used, one example of a location algorithm
is provided in Annex A of ISO/IEC 24730-21.
This part of ISO/IEC 24730 also defines the physical layer for compliant RTLS transmitters operating with
multiple spread codes and employing a QPSK data encoding and Walsh offset QPSK (WOQPSK) spreading
scheme, and defines the air interface protocol needed for the reader synchronization essential for the location
method based on timing information, such as Time Difference of Arrival (TDOA).
Although there are many types of reader synchronization methods that could be used, an example of RTLS
reader synchronization is provided in Annex A.

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INTERNATIONAL STANDARD ISO/IEC 24730-22:2012(E)

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
1 Scope
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.
This part of ISO/IEC 24730 is the mode of ISO/IEC 24730-2 transmitters operating with multiple spread codes
and employing a quadrature phase shift keying (QPSK) data encoding and Walsh offset QPSK(WQPSK)
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 24730-1, Information technology — Real-time locating systems (RTLS) — Part 1: Application
program interface (API)
ISO/IEC 24730-2, Information technology — Real-time locating systems (RTLS) — Part 2: Direct Sequence
Spread Spectrum (DSSS) 2,4 GHz air interface protocol
ISO/IEC 18000-4:2008, Information technology — Radio frequency identification for item management —
Part 4: Parameters for air interface communications at 2,45 GHz
ISO/IEC 19762-1, Information technology — Automatic identification and data capture (AIDC) techniques —
Harmonized vocabulary — Part 1: General terms relating to AIDC
ISO/IEC 19762-3, Information technology — Automatic identification and data capture (AIDC) techniques —
Harmonized vocabulary — Part 3: Radio frequency identification (RFID)
ISO/IEC 15963, Information technology — Radio frequency identification for item management — Unique
identification for RF tags
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ISO/IEC 24730-22:2012(E)
ISO/IEC 8802-11:2005, Information technology — Telecommunications and information exchange between
systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) specifications
TM
IEEE Std 1451.7 -2010, IEEE Standard for A Smart Transducer Interface for Sensors and Actuators —
Transducers to Radio Frequency Identification (RFID) Systems Communication Protocols and Transducer
Electronic Data Sheet Formats
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19762-1, ISO/IEC 19762-3 and
the following apply.
3.1
air interface
wireless communications protocol and signal structure used to communicate data between RTLS transmitters
and other RTLS devices
3.2
host applications
customer’s management information systems
3.3
RTLS infrastructure
system components existing between the air interface protocol and the RTLS server API
3.4
real-time locating system
set of radio frequency receivers and associated computing equipment used to determine the position of a
transmitting device relative to the placement of the aforementioned receivers that is capable of reporting that
position within several minutes of the transmission used for determining the position of the transmission
NOTE Refer to Figure 1 for clarity regarding elements of RTLS infrastructure.

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ISO/IEC 24730-22:2012(E)
RTLS
reference
tags
RTLS RTLS RTLS host
transmitters infrastructure server applications
exciter
RTLS
transmitters
optional mandatory application
air air program
interface interface interface

Figure 1 — Elements of RTLS infrastructure

3.5
RTLS server
computing device that aggregates data from the readers and determines location of transmitters
3.6
RTLS transmitter
battery powered radio device that utilizes the protocols specified in ISO/IEC 24730-2
NOTE The term transmitter is used interchangeably with the term tag.
3.7
RTLS reader
device that receives signals from an RTLS transmitter or reference tag
3.8
open field
path from transmitter to receiver is LOS (Line Of Sight)
[ANS T1.523-2001]
3.9
exciter
device that transmits a signal that alters the behaviour of an RTLS transmitter
3.10
upconvert
change a baseband signal to a higher frequency signal
3.11
tag blink
radio frequency transmission(s) from an RTLS transmitter that may consist of one or multiple duplicate
messages
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ISO/IEC 24730-22:2012(E)
3.12
sub-blink
message that is transmitted one or multiple times in a "blink"
3.13
RTLS reference tag
always on powered radio device that utilizes the protocols specified in ISO/IEC 24730-2, mainly for the RTLS
reader synchronization
4 Symbols and abbreviated terms
For the purposes of this document, the symbols and abbreviated terms given in ISO/IEC 19762-1,
ISO/IEC 19762-3 and the following apply.
AEXB Exciter Blink
BPSK Binary Phase Shift Keying
CRC Cyclic Redundancy Check
DBPSK Differential Binary Phase Shift Keying
DSSS Direct Sequence Spread Spectrum
EB Event Blink
EIRP Equivalent Isotropically Radiated Power
EXB EXciter Blink
FSK Frequency Shift Keying
MSB Most Significant Bit
OOK On-Off Keying
PN Pseudo Noise
QPSK Quadrature Phase Shift Keying
RSS Received Signal Strength
RTLS Real-Time Locating Systems
TIB Timed Interval Blink
WOQPSK Walsh Offset Quadrature Phase Shift Keying
5 Requirements
5.1 Frequency range
This part of ISO/IEC 24730 addresses real-time locating systems (RTLS) operating in the 2,400 GHz to
2,4835 GHz frequencies.
5.2 2,4 GHz spread spectrum air interface attributes

The minimum feature set shall include the following:
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ISO/IEC 24730-22:2012(E)
– RTLS transmitters and reference tags shall autonomously generate a direct sequence spread
spectrum radio frequency beacon.
– Transmission shall be at a power level that can facilitate reception at ranges of at least 300 m open-
field separation between the transmitter and receiver when operating within the parameters described
in Table 1 of ISO/IEC 24730-21 and in from Table 1 to Table 2 of ISO/IEC 24730-22.
– RTLS transmitters and reference tags shall be fully compliant with local regulatory requirements.
– Class 1 RF transmissions are low power and electro-magnetically compatible with and shall not
interfere (not cause any measurable difference in throughput) and co-exist with existing standardized
ISO/IEC 8802-11:2005 wireless communication networks. They are also systems that co-exist with
ISO/IEC 18000-4:2008, and shall not exceed the maximum power of 10 dBm EIRP and the
requirements of the local regulatory agencies.
– Class II RF transmissions shall not exceed the maximum power requirements of the local regulatory
agencies.

5.3 Compliance requirements

The beacon transmitters specified in this part of ISO/IEC 24730 shall transmit at a power level that can
facilitate reception at ranges of at least 300 m LOS separation between the transmitter and receiver. Such
RTLS transmitters shall be fully compliant with local radio frequency regulatory requirements. Each receiver
shall be capable of receiving and processing data from a minimum of 120 beacon transmissions per second.
The nominal location data provided by the RTLS shall be within a 3 m or less radius of the actual location of
the RTLS transmitter. The RF transmissions are low power, compatible with, and shall not interfere with
existing standardized ISO/IEC 8802-11:2005 wireless communication networks, and systems compliant with
ISO/IEC 18000-4:2008.
To be fully compliant with this part of ISO/IEC 24730, RTLS shall also comply with ISO/IEC 24730-1.
5.4 Manufacturer tag ID
The manufacturer’s tag identification (ID) number identifies a particular manufacturer and consists of 16 bits. A
manufacturer may have more than one ID number. As reported from the RTLS server to the API, the first
16 bits are designated for the manufacturer’s identification number. As reported from the Data Link Layer to
the API, the remaining 16 bits establish a numbering system made unique by the initial manufacturer ID
number. The manufacturer’s identification number is a registration in accordance with ISO/IEC 15963. The
16-bit manufacturer’s identification number shall be assigned in accordance with ISO/IEC 15963, Allocation
Class 16h.
5.5 Physical layer parameters
The parameter definitions in Table 1 to Table 2 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.
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 WOQPSK DSSS
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ISO/IEC 24730-22:2012(E)
Parameter name Description
Data encoding QPSK encoded
Data bit rate 119,226 kb/s
Packet error rate 0,01%
PN chip rate 30,521875 MHz ± 25 ppm
PN code length 512 (zero padded)
9 8 5 4
PN polynomial f(x) = X + X + X + X + 1
I/Q orthogonal codes Walsh codes with a period of 512 chips
Data packet lengths Option 1:     72 bits
Option 2:     88 bits
Option 3:    104 bits
Option 4:    168 bits
10 9 5 4
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 150 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 2 — RTLS reference tag DSSS link parameters
Parameter name Description
Operating frequency range 2400 MHz–2483,50 MHz
Operating frequency accuracy ± 0,5 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 WOQPSK DSSS
Data encoding QPSK encoded
Data bit rate 119,226 kb/s
Packet error rate 0,01%
PN chip rate 30,521875 MHz ± 0,5 ppm
PN code length (zero padded) 512
9 8 5 4
PN polynomial f(x) = X + X + X + X + 1
I/Q orthogonal codes Walsh codes with a period of 512 chips
Data packet lengths 60 bits
10 9 5 4
Message CRC polynomial G(x) = X + X + X + X + X + 1
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ISO/IEC 24730-22:2012(E)
Parameter name Description
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 150 ms ± 16 ms maximum
Maximum frequency drift < ± 0,2 ppm over the duration of the entire message
Phase noise < 0,5 degrees when the noise is integrated from 100 Hz to
100 kHz

6 Mandatory air interface protocol specification
ISO/IEC 24730-22 defines the air interface protocols for RTLS DSSS spread-spectrum transmissions and the
command/data level air interface communication protocols, operating over the frequency range from
2,400 GHz to 2,4835 GHz. The DSSS air interface shall have the main characteristic that the
ISO/IEC 24730-22 transmitters operate with multiple spread codes and employ a QPSK data
encoding/WOQPSK spreading scheme. The transmitters spread a QPSK signal for each sub-blink using a
randomly selected spread code among pre-defined code pairs. These protocols facilitate communication
between a compliant RTLS transmitter and a compliant infrastructure. ISO/IEC 24730-22 follows the optional
protocols in clause 7 of ISO/IEC 24730-21 which facilitate communication between the RTLS transmitter and
the programming device or exciter device respectively. The timing parameters and signal characteristics for
the protocols are defined in the physical link specification in clause 5.

6.1 General
6.1.1 Functional classification
Beacon type RTLS system architecture consists of RTLS transmitters that “blink” a DSSS signal, fixed position
reference tags that also “blink” a DSSS signal, and fixed position RTLS readers that receive those signals.
The position of the RTLS transmitter (also called the tag) is to be located and tracked, and the reference tag is
used to calibrate synchronization errors among readers. The system 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.

The RTLS transmitter module is typically a compact internally-powered radio frequency device that is a part 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 ID of the RTLS transmitter. 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 through 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 parts of a multiple level anti-interference system; time diversity, spatial diversity, processing
gain, code diversity. The combination of these multiple sub-blinks, multiple receiving antennas and spread
spectrum correlation also allow multiple RTLS transmitters to blink simultaneously while still being received.

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ISO/IEC 24730-22:2012(E)
The format of the DSSS transmission from the RTLS transmitter is shown in Figure 2. 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 22-bit preamble, 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.


Figure 2 — 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 3.
Note: For Figure 3 and all future figures, solid lines denote required features and dotted lines denote optional
features.
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ISO/IEC 24730-22:2012(E)

Figure 3 — 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.
6.1.2 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.
6.2 Physical layer specification

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ISO/IEC 24730-22:2012(E)
The RTLS system architecture consists of RTLS transmitters that “blink” a DSSS signal, fixed position RTLS
reference tags that also “blink” a DSSS signal, and fixed position RTLS readers that receive those signals.
QPSK scheme shall be used to encode data for both RTLS transmitters and reference tags. The RTLS
transmitters may employ multiple spread code pairs to spread the encoded data. Employing multiple spread
code pairs mitigates the packet collision problem so that a small number of sub-blinks be used, thereby
significantly reducing tag power consumption. In case of employing multiple spreading code pairs, a spread
code pair should be randomly selected for each sub-blink among pre-defined code pairs. The maximum
number of code pairs for RTLS transmitters is 4, and the number of code pairs shall be programmable. The
spread code pair for reference tags is fixed and has a low cross correlation with those of RTLS transmitters.
Since a reader does not know which code pair was used for a
...