Introduction to Indoor Positioning

Ultra-wide Band (UWB)

Although there are numerous 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. Altogether, this makes UWB ideal for indoor positioning applications in multi-room environments, or in places like hospitals within which radio-frequency interference is a big safety concern.

What Is Ultra-Wideband?

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 ranges between 3.1 GHz and 10.6 GHz. Unlike most traditional radio signals, UWB doesn’t 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.

How Does UWB Track Location?

The primary method used to determine location in Ultra-Wideband systems is Time Difference of Arrival or TDOA. 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. You would then compare the varying times of arrival (and hence, distances) to each receiver and determine the location of the transmitter.

Conclusion

Ultra-Wideband technology promises unparalleled accuracy, the ability to penetrate walls and other obstacles, and low power consumption—all in one package. Although UWB isn’t 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.