Although transmission is limited to short range, with multiple receivers, UWB can be an effective technology for indoor positioning systems.
This article is an overview of Ultra Wideband (or "UWB" for short) in the context of indoor position tracking technology. Although Ultra Wideband was once considered a potentially suitable technology for personal area networks and an early competitor to WiFi, UWB has since transitioned to become a highly accurate, affordable, and low-energy solution to indoor positioning.
Although there are a multitude of technologies that are appropriate for use in indoor positioning applications, UWB's low-frequency and high-bandwidth mean that it can pass through both walls and other obstacles and that it can exist in harmony with other radio signals, such as those from cellular telephones. Taken together, this makes UWB ideal for indoor applications in multi-room environments, or in places like hospitals within which radio-frequency interference is a big concern.
Put simply, Ultra Wideband is a radio signal at a frequency greater than 500 MHz. In the US, the FCC has approved UWB for commercial use at a range of between 3.1 GHz and 10.6 GHz. Unlike most traditional radio signals, UWB does not use power, frequency, or phase modulation to encode the information that its signals carry. Instead, UWB uses frequent pulses at specific time intervals to carry information. This allows transmission across a wide bandwidth while avoiding interference with other radio signals in the same spectrum.
These characteristics allow UWB to transmit a large amount of data using relatively low power consumption. Although transmission is limited to a short range, with the use of multiple well-position receivers, UWB can be considered for most indoor position tracking applications.
The primary method used to determine location in Ultra Wideband systems is TDOA or Time Difference of Arrival. This means that in a UWB system, several networked receivers (a minimum of 3 for 2D location and 4 for 3D location) are placed at known locations throughout a space. The asset or assets to be tracked are outfitted with UWB transmitters, which emit an omnidirectional signal at a given interval. The signal arrives at nearby receiver units at differing times due to the distance from transmitter to receiver. A comparison of the varying times of arrival (and hence, distances) to each receiver is performed and the location of the transmitter is determined.
Ultra Wideband technology promises unparalleled accuracy, the ability to penetrate walls and other obstacles, and low power consumption all in one package. Although UWB is not as ubiquitous or inexpensive as other indoor tracking technologies (e.g. Bluetooth Low-Energy), in recent years UWB equipment has seen increased uptake and reduced cost of components. This makes UWB a technology to consider when planning any indoor location tracking project.