Real-time locating standards

Articleissues
copyedit=May 2008

According to ISO/IEC FDIS 19762-5 [ [http://www.autoid.org/SC31/sc31.htm] (ISO Subcommittee SC31)] 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.

Hence, real time locating first is not mandatorily a cooperative approach (the term "to operate with" does not require responses)and not any detection system. And thus the current layout of this ISO standardization workprogramme by definition "does not cover all types of discontinuous locating", e.g. with simple RFID concepts. However, discontinuous locating is one of the other options. On the contrary, classical RADAR by definition is no real time locating system, whereas modern TCAS may be classified as such. The early planning to include satellite based locating concept into the scope of standardization is currently not subject of work with the ISO work group, just the number ISO/IEC 24730-4 shows a spare place for this overriden planning [ [http://www.autoid.org/sc31/wg5.htm] (ISO JTC1 SC31 WG5 RTLS scope of work)] .

Standardization of various systems is mainly covered by ISO/IEC 24730 pl [ [http://www.iso.org/iso/search.htm?qt=24730&published=on&active_tab=standards] (Search results with ISO in ISO/IEC 24730)] . 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 standards and IETF RFC and draft documents is not referred in this context.

Components of an RTLS

RTLS systems layout may follow very different designs. The only communality is: there are two classes
* Moving nodes or mobile tags, i.e. responders or transponders with unknown location and
* Residing nodes, anchor nodes or any or fix mounted , i.e. responders or transponders with known locationwhereas the moving nodes shall be located and the residing nodes support this requirement.

For both of these classes, there is no limitation to any concept of signalling, that leads to alternatively
* Nodes beaconing all time with a certain repetition rate
* Nodes responding on demand after receiving a polling request from another node and i.e. performing a wake up cycle
* Nodes surveying their ambience by polling other nodes according to a certain strategy and reflecting detection events
* Nodes actively exploring their location by polling other nodes according to a certain strategy while moving
* Nodes relaying just the information transmitted from other nodes to serve for a coherent networking.Each concept in standards will address the special choice.

Real time locating is defined when autonomous systems come to age, especially with networking sensors. However, earlier designs refer to the concepts of common wireless illuminations and local centralized computing. Hence, beyond this segregation of distributed components, there may be additionally
* Central units and
* Server unitswith more or less old fashioned designs, where staggered centralism helps to reduce the hardware required at the expense of wired and/or wireless communication links and loads.

The more advanced distributive designs reduce the variety of nodes and units to autonomous 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 transponders are receiving and transmitting and all of these may be either moving or residing according to local distribution concepts in the operational area.

However, there is no mandatory requirement that any concept of time synchronization or any computing facility must extend this collection. Many systems work with a synchronization concepts, but other just operate on individual clocking schemes and compensate time sync errors by operational technology.

Standardization of RTLS systems solutions

Real-time locating systems (RTLS) are a newly defined segreation 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 Organization 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 [ [http://www.autoid.org/2002_Documents/TC%20122_WG%207/N026_RFIDStds_Updt_20010123.ppt] (ISO JTC1 SC31 WG5 work programme)] :
* ISO/IEC FDIS 19762-5 Information technology AIDC techniques — Harmonized vocabulary, Part 5 — Locating systems [ [http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50718 ISO/IEC FDIS 19762-5] ( RTLS standardized definition)]
* 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. For copies of these documents see references.

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.

See also

* Locating engine
* Real-time locating
* RTLS implementing
* RTLS communications

All additional references within Wikipedia and external references on the Internet may be found on the RTLS page.

External links and references

* [http://www.iec.ch/ International Standardization in Engineering]
* [http://www.iso.org/ International Standardization in Industry and Science]
* [http://www.iso.org/iso/search.htm Search Page for ISO standards concerning RTLS]
* [http://www.ieee.org/ International Standardization in Electrical Engineering]
* [http://www.ietf.org/ International Standardization in Communications]
* [http://www.aimglobal.org/ International Lobbying in Automatic Identification]
* [http://www.aimusa.org/ US American Lobbying in Automatic Identification]
* [http://www.aimglobal.org/technologies/rtls/ Statement of International Lobbying on Real Time Locating]
* [http://www.autoid.org/SC31/wg5.htm/ ISO JTC1 (TC122) SC31 WG5 Homepage on RTLS]
* [http://www.autoid.org/sc31/MIIM/MIIMn0061_MtgRpt_20071030-31.doc/ ISO JTC1 (TC122) SC31 WG5 Inaugural Meeting on MIIM]
* [http://www.qed.org/ Company driving international standardization on e.g. RFID and RTLS in US]
* [http://www.autoid.org/SC31/wg5.htm Schedule and actual scope of RTLS standardisation in ISO JTC1, TC122 and SC31]
* [http://www.car-to-car.org/ Car-to_Car communications programme funding of the European Union]

Standards

* Real-time locating standards
* [http://www.iso.org/iso/home.htm International Organization for Standardization]
* [http://www.autoid.org/SC31/sc31.htm ISO/IEC 19762-5 Information technology -- Automatic identification and data capture (AIDC) techniques -- Harmonized vocabulary -- Part 5: Locating systems ]
* [http://www.iso.org/iso/search.htm?qt=iso+24730-1&searchSubmit=Search&sort=rel&type=simple&published=on Real-Time Locating with ISO/IEC 24730]
* [http://www.autoid.org/sc31/wg5.htm Standardization for Real-Time Locating in ISO JTC1 / TC122 SC31 WG5 with www.autoid.org]
* [http://www.autoid.org/sc31/sc31.htm Standardization for Automatic Identification in ISO JTC1 / TC122 SC31 WG5 with www.autoid.org]
* [http://www.autoid.org/2002_Documents/TC%20122_WG%207/N026_RFIDStds_Updt_20010123.ppt www.AutoID.org on Real-Time Locating]

Literature

* Indoor Geolocation Using Wireless Local Area Networks (Berichte aus der Informatik), Michael Wallbaum, Shaker Verlag , Aachen (2006), ISBN-10 3-8322-4838-2
* Location-Based Services: Fundamentals and Operation, Axel Küpper, Wiley, New York, 2005, ISBN-13 978-0470092316
* Local Positioning Systems: LBS applications and services, Krzysztof Kolodziej & Hjelm Johan, CRC Press Inc (2006), ISBN-13 978-0849333491
* Ortsbezogene Anwendungen und Dienste, 4. GI/ITG KuVS Fachgespräch, Roth, Küpper Linnhoff-Popien (Ed.), Verlag Dr. Hut, München 2007, ISBN-13 978-3-89963-591-1
* Praxis der GPS-Navigation, Martin Friedrichs, Delius Klasing Verlag, Bielefeld (2006), ISBN-13 978-3-7688-1773-8