One reason why the market for Real Time Locating Systems (RTLS) is growing rapidly to pass the billion dollar mark well within ten years is technology. It is improving rapidly, with new variants for the many new sub sectors of the market that are emerging.  Indeed, without new, affordable technologies to cover ranges from centimetres to kilometres and other parameters differing by many magnitudes, the predicted huge market for RTLS that is shown below will not be created.


Sharp improvements in UWB RTLS


Ultra Wide Band (UWB) RTLS usually gives the best accuracy and best immunity to interference in and out. That has come at a cost, limiting it to the quality end of the market. However, Time Domain has just announced a low cost version of its system and Ubisense has announced a system that ombines passive UHF and active UHF on automotive production lines. Ubisense already combines two signalling techniques Time of Arrival (TOA) and Angle of Arrival (AOA), that we explain below, for superlative performance. The functionality is also rapidly improving with advances in UWB such as the DecaWave chips that use Time Difference of Arrivals (TDOA) favoured by market leader WhereNet but have much added functionality such as mesh networking and much longer range than has previously been possible with UWB.


Hand held readers

Increasingly, the more sophisticated systems have more than a fixed infrastructure. For finding goods on foot, even outside the fixed reader network, hand held readers are increasingly offered as an extra facility. Indeed, at the bottom of the market, the Loc8tor hand held reader, used without fixed infrastructure, has had huge success in the last year. Although some may refer to this as primitive, its range and functionality exceeds that of some far more expensive fixed systems. It can set ring fencing alarms to protect assets and children etc. The tag can has an alarm button and flashing light and the hand held device vibrates, shows vectors and lights up. Indeed up to 25 tags can be programmed with a large menu driven screen. It is shown below.


Both active and passive RTLS have a place


Active RFID RTLS will not necessarily be replaced by the new passive tag RTLS. For instance, where sensing inputs must be recorded in the tag, active RFID is required and it is difficult to see how it can ever perform full mesh networking where tags talk to tags in scalable, fault tolerant systems. Active tags are also needed where there is a need to initiate a signal as with a nurses alarm pendant. Ubiquitous Sensor Networks (USN) are being researched in many places across the world. RTLS and USN are converging.


Energy harvesting

Energy harvesting is likely to be important for much RTLS and for USN. This is where photovoltaics or other methods are used to charge batteries during use. Indeed, there are now the painfully named supercabatteries in the laboratory that combine the virtues of both batteries and capacitors. In photovoltaics, there is rapid progress with various inorganic and composite formulations being printed reel to reel for low cost and easy use because they can be stuck to uneven surfaces like tags.


Choice of signal processing

There are different signal processing techniques used even at given frequencies and sometimes more than one is used in the same system. Indeed, to improve the poor performance of Cell ID (ie zonal RTLS), infrared has been used with the same tag and some systems also provide GPS or GPRS location. For active RFID RTLS, the main options are shown below. Cell ID is losing share because it is quite expensive yet has one of the poorest accuracies. It consists of having many readers with overlapping ranges. All other systems use beams of electromagnetic radiation, which is more precise.


Here TOA (Travel time trilateration against reference points also known as time of flight) using one frequency for metering, TDOA (Differential travel time triangulation against reference points using more than one frequency for metering), AOA (Travel time triangulation against reference points (AOA) using more than one receiver for metering). (TOF)


Zonal or cell ID refer to having many readers with overlapping ranges so the accuracy is poor, being simply the range of the reader. This is losing market share though some are sold with the enhancement and extra cost of infra red sensing. Received Signal Strength Indication (RSSI), a low cost method (eg Loc8tor) that is even used for some mid range systems (eg Awarepoint), when its problems accuracy and of metal and water disturbing the signal are overcome by high reader density, the system still being competitive on price. Indeed, with plug and play and self calibration due to ZigBee backhaul, the Awarepoint RTLS is highly rated and over 30 such systems have been sold in a short time.


Two conferences will give the latest news

Two impending conferences will give the latest news and analysis of the rapidly expanding RTLS technologies and applications. RFID Europe September 30-October 1 in Cambridge UK and Active RFID, RTLS and Sensor Networks November 5-6 in Dallas USA will both have many RTLS proponents and users speaking and attending.


The UK event will have Ekahau, Sonitor, Coronis. Essensium, Loc8tor, CST and other RTLS suppliers, many making new announcements and users and potential users the US Navy, Container Centralen, Lang ORourke, Marshall Aerospace and the UK National Health Service talking. Cambridge University will describe TINA, The Intelligent Airport - A Self-Organising, Wired/Wireless Converged Machine.


The US event will have RTLS suppliers Q-Track, Awarepoint, Sonitor, Loc8tor and others speaking and many end users. Indeed, it will be exclusively focussed on Active RFID, RTLS and Sensor Networks. Both events will have visits to local centers of excellence in the subject both users and suppliers.


For more information on Real Time Locating Systems please contact the author Peter Harrop at To find out more about RFID Europe 2008 please contact the Event Manager Corinne Jennings at, and for Active RFID, RTLS & Sensor Networks USA 2008 please contact the Event Manager Sarah Lee at