Introduction: Real Time Locating Systems (RTLS)
Real Time Locating Systems (RTLS) are RFID enabled solutions, which continually monitor the location of assets and personnel. RTLS solutions not only can identify assets/personnel but can also locate these assets/personnel in a physical space on a real-time basis. Real Time Locating Systems (RTLS) are electronic systems that are intended to locate small electronic devices on people or things at any time.
There are many application areas for RTLS, particularly now that it has become affordable and the mobile devices that are sensed have, in many cases, become small and convenient. Mieloo & Alexander have implemented various supply chain solutions based on RTLS, among which the largest RTLS site in the world.
Forecast of global RTLS market (source IDTechEx 2006)
Frequencies and standards
RTLS solutions are currently provided in 3 frequency ranges: WIFI, 2.4 GHz. and 433 MHz. The advantage of RTLS solutions based on WIFI, besides being a worldwide standard, are the alleged lower infrastructure investments required to deploy such solutions. Very often the RTLS systems do however require additional infrastructure (access points) in order to be able to provide the required locate accuracy. RTLS solutions based on 2.4 GHz. operate directly next to WIFI on a separate band. These solutions do require specific infrastructure but have the advantage of a dedicated band with limited interference. The 433 MHz. solutions operate on a narrow band, with a lower read range. The operating frequency range and choice of infrastructure is very much dependent on the application and the environment in which the solution will operate.
TDOA vs. RSSI
The locating of the RTLS solution is done using two techniques, i.e. TDOA and RSSI. TDOA stands for Time Difference Of Arrival and it is the time difference between signals that reach the location sensors. RSSI stands for Received Signal Strength Indication and is the strength of the signal from the device as measured by the access point. Generally speaking one could say that, RSSI is useful in (indoor) walled areas such as hospitals and warehouses and TDOA finds application in outdoor environments like finished vehicle compounds, ports and shipyards.
Application of RTLS solutions
The main applications of RTLS will be in manufacturing, automotive industry (OEM and finished vehicle logistics), military, healthcare, transportation and logistics but with increased interest from most other sectors including retail and the entertainment industry.
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