Real-time locating standards: Difference between revisions

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According to ISO/IEC FDIS 19762-5 an RTLS (real-time locating system) is a combination of hardware and software that is used to continuously determine and provide the real-time position of assets and resources equipped with devices designed to operate with the system. Standardization is mainly covered by ISO/IEC 24730 pl. Some of these standards are under discussion and not yet published. Real-time locating is described in detail on the respective page Real-time locating systems. This page here specially addresses the aspects of systems varieties with respect to the actual status of ISO/IEC standardization concerning RTLS. Standardization concerning the communications basics covered with IEEE and IETF ist not referred.

Components of an RTLS

RTLS systems layout may follow very different designs. The only communality is: there are

Moving nodes and
Residing nodes,

whereas the moving nodes shall be located and the residing nodes support this requirement.

Beyond this segregation, there may be additionally

Central units and
Server units

with more old fashioned designs, where staggered centralism helps to reduce the hardware required at the expense of wired and/or wireless communication links.

The more advanced designs reduce the variety of nodes and units to nodes only, which belong to the following classes, all of which are transponders:

RTLS tags not capable to locate themselves but to measure cooperatively
RTLS anchors just capable to restore and report its known coordinates and to measure cooperatively
RTLS assistants capable to compute their own location with local resources after cooperative metering of distances
RTLS gateways that help to start a network with information from a data base.

Each of these are transponders receiving and transmitting and all of these may be either moving or residing.

However, there is no mandatory requirement that any time synchronization or any computing facility must extend this collection.

Standardization of RTLS systems solutions

Real-time locating systems (RTLS) are a newly defined segregation from other mobile GNSS or similar navigation services and a special extension beyond the capabilities of RFID systems. Basically, the term RTLS describes any approach of Far-Field Electromagnetic Ranging (FFER). The basic issues of RTLS are yet readily standardized with ISO/IEC , the International Organisation for Standardization (www.iso.org) and the International Electrotechnical Commission (www.iec.ch), both in Geneve, Switzerland, under the tree of ISO/IEC 24730. In this series of standards the basic standard ISO/IEC 24730-1 identifies the basic terms describing a certain form of RTLS utilized by a set of vendors, but not encompassing the full scope of RTLS technology as commonly recognized by the market.

Currently several standards are published or under discussion:

ISO/IEC FDIS 19762-5 Information technology AIDC techniques — Harmonized vocabulary, Part 5 — Locating systems
ISO/IEC 24730-1:2006 Information technology real-time locating systems (RTLS) Part 1: Application program interface (published).
ISO/IEC 24730-2:2006 Information technology real-time locating systems (RTLS) Part 2: 2,4 GHz Air interface protocol (published, WhereNet/Zebra approach)).
ISO/IEC WD 24730-5 Information technology real-time locating systems (RTLS) Part 5: (drafted ISO/IEC standard out for balloting in 2008, Nanotron approach)).

The other proposals ISO/IEC 24730-3 and ISO/IEC 24730-4 had never left the stage of intention.

These standards do neither stipulate any special method of computing locations nor the method of measuring locations. This may be defined in sound system specifications for either lateration, trilateration, multi-lateration, angulation, triangulation or multi-angulation or any hybrid approaches to trigonometric computing for planar or spherical models of a terrestrial area.

However, many earlier approaches to RTLS (multiple circumscriptions of this term are in common use) have appeared and surely numerous future approaches to a sound solution may appear beyond or apart from this standard.

Identifying as an inherent function with RTLS

In a cooperative approach, other but with simple scanning ranging procedures, locating in an ad hoc networking concept requires appropriate identification of the nodes involved. This may be primarily performed on the MAC layer by exchanging MAC addresses. But for operational purposes there may be need for an independent but as well hierarchical identification scheme. This is formally envisaged with the ISO/IEC standard 24730-1. Such identification is the minimum requirement bridging to functionalities of resident or portable RFID and generally to MIIM. Respective precautions must be set forth with the special implementations and therefore may refer to standardized numbering concepts as with ISO/IEC 15459-2 and according subsets in a numbering hierarchy.

For an RTLS to function, the location of tagged items must be determined either by cumputing in a central processor or by an autonomous mobile computing facility. Locating is generally accomplished with the following:

Mobile and / or fixed nodes disclose membership to communities and invite other nodes to communicate.
Mobile and / or fixed nodes exchange communication parameters to facilitate communication with each other.
Mobile and / or fixed nodes exchange enrollment data to establish a proper communications link with the community.
Mobile and / or fixed nodes exchange identification data and perform encrypted communications.
Mobile and / or fixed nodes perform metering and exchange metered distances.
Mobile and / or fixed nodes autonomously perform locating based on subsequently obtained distance information.
Mobile and / or fixed nodes forward sensor data and other data for application purposes.
Mobile and / or fixed nodes relay sensor data and other data for application purposes to and fro other nodes.

In case on an asymmetric system layout, cooperativeness still remains a prerequisite, but the functions may be shared with certain specialization of various classes off nodes.

Nomenclature

In addition to the ISO/IEC standards on interfacing as referred above, another basing standard was published end of 2007 as a final discussion document on terms and definitions.However, it could not yet be disclosed, which special breed of systems operates with the named types of transponders. Probably further discussion of the standards proposal will lead to a more universally valid glossary or transponder type zoo.

ISO/IEC FDIS 19762-5: Information technology AIDC techniques, Harmonized vocabulary, Part 5 – Locating systems.

This discussion paper is published on the website of subcommittee SC31 of ISI technical committee 122 on the website of www.autoid.org. This emerging standard now names the following items as components in an RTLS:

infrastructure(RTLS): System components existing between the air interface protocol and the RTLS server API
exciter(RTLS): Device that transmits a signal that alters the behavior of an RTLS transmitter.
interrogator(RTLS): This term is used in the context, however not yet defined. Probably it may the very same type of unit as a reader. Typically an interrogator actively reads and 'readers' are always active unit in this context.
reader(RTLS): Device that receives signals from an RTLS transmitter.
server(RTLS): Computing device that aggregates data from the readers and determines location of transmitters.
transmitter(RTLS): Active radio devices that utilize the specified RTLS protocols.

However, no requirement is set that any of these device types must be apart from any of the other types, hence combinations are also conformal to these definitions.

Standardization of RTLS communications

The communications between RTLS nodes is not defined with the air interface standardization of an RTLS system. Not all of the RTLS systems standardized or in process of standardization is subject of standardization as well. In detail

ISO/IEC 24730-1 does not address a special RTLS system, but the communality of RTLS system.
ISO/IEC 24730-2 refers to a strongly proprietary communications system. This system is designed for good coexistence with other wireless services in the 2.45 GHz ISM band.
ISO/IEC 24730-5 will refer to the standardized communications according to IEEE 802.15.4aCSS. This system is designed for good coexistence with other wireless services, especially with IEEE 802.11 b/g in the 2.45 GHz ISM band.

All other offered RTLS systems do currently not comply with any standard for RTLS, but mandatorily must ensure good coexistence with other wireless services in their respective ISM bands, i.e. 433 MHz, 2.45 GHz, 5.8 GHz.

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