What is Ultra-Wide Band (UWB) Technology?

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- everything RF

Jul 15, 2021

Ultra-Wide Band (UWB) Technology is an ultra-low power, short range wireless technology that can be used to transmit data and capture accurate location and directional information. It can provide a data rate of up to 1Gbit/s within a 10-meter radius for wireless personal area communications. UWB can provide cm-level location information between a transmitter and receiver within a short range (10-15 meters). Its positioning and direction-finding capabilities are significantly more accurate than Bluetooth and Wi-Fi which has resulted in companies like Apple and Samsung incorporated UWB technology into their latest products. For example, the Apple AirTags are based on UWB technology.

UWB Technology operates over a wide frequency range from 3.1 to 10.6 GHz and has channel bandwidths over 500 MHz. It uses a pulse pattern based radio technology that sends out short pulses with widths of a few nanoseconds. Because of the wide spectrum available to the technology, pulsed data can be sent very quickly. The wide bandwidth also allows it to have a low power spectral density which minimizes interference with other technologies operating in the same frequency band. The spectral density has been restricted to -41dBm/MHz by regulators like the FCC. This low power density is often lower than the spurious emissions from other electronic devices which have been certified by the FCC and other certification bodies.

Low power spectral density coupled with pulse-based transmission minimizes interference with other technologies operating in the same frequency band. This low power density is often lower than the spurious emissions from other electronic devices which have been certified by the FCC and other certification bodies. Another advantage of the low power spectral density is that transmissions using UWB technology are secure as they are very difficult to detect.

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Conventional wireless transmissions encode data by changing the power, frequency, and/or phase of a signal rather than emitting simple pulses. UWB implements Pulse Position Modulation (PPM), Bipolar Signalling (BPSK), Pulse Amplitude Modulation (PAM), On/Off Keying (OOK) and Pulse-Shape Modulation techniques.

UWB can also use Orthogonal Frequency Division Multiplexing (OFDM) for data transmission by subdividing the total UWB bandwidth into a set of broadband channels. This method exploits the spectrum very efficiently and delivers better performance and data throughput. However, the hardware required for this method is more complex and power-consuming.

Ultra-Wideband Technology can achieve data rates of up to 1 Gbps, which is much higher than NFC (424 Kbps) and Bluetooth (2.1 Mbps). However, it falls short of the data rates provided by the latest Wi-Fi standards of up to 9.6 Gbps with Wi-Fi 6/6E.

Though UWB can also be used for data transmission, most current use cases are around indoor positioning as there was a technology gap in the market for this type of application. Wi-Fi and Bluetooth can provide this functionality however, they are not as accurate and consumes significantly more power (at least Wi-Fi). Battery charged devices can use UWB technology for long periods of time without requiring a recharge.

How does UWB Work?

Think of UWB as a radar technology, that can lock on to the position of a device (receiver) and send/receive data to/from it. It does so by sending out short pulses of about 2 ns across its wide channel bandwidth (usually greater than 500 MHz). The short pulses carry the information and provide accurate location information.

UWB uses Time of Flight (ToF) to accurately determine the distance between the transmitter and receiver. Time-of-Flight is a method for measuring the distance between a transmitter and receiver based on the time difference between when the signal was transmitted and when a reflected version of the same signal is received by the transmitter after being reflected by the receiver. On top of this UWB uses the Received Signal Strength Indicator (RSSI) and Angle-of-Arrival (AoA) simultaneously to determine the location of a receiver.

The technique used to implement ToF can differ according to the application and environment. The most common techniques to implement UWB include - Time Difference of Arrival (TDoA) and Two Way Ranging (TWR).

Time Difference of Arrival (TDoA): This method of implementation requires UWB anchors which are installed in fixed locations throughout the space where devices are to be located. These fixed anchors should be running on the same clock and synchronized to provide accurate and reliable data. The transmitting UWB devices can communicate with multiple anchors in its communication range. The signals received by the anchors are time stamped and sent to a central RTLS, where data from each anchor is analyzed to determine the differences in arrival times to each anchor and calculate the device’s coordinates/location.

This method of implementation also allows the creation of a virtual map of the indoor environment and enables visualization of the devices on the map for better representation.

Two Way Ranging: In TWR, the transmitting and receiving devices communicate directly with each other, without the need for fixed anchors. When two UWB devices are in close proximity to one another, they will start ranging to determine their relative positions. Ranging refers to the calculation the time of flight (ToF) between the two devices. TWR process can only use one ranging partner to locate the device at a time.

Ultra Wideband technology can also be used to track device movements in real time to figure out motion and relative position. This has many applications, as it can tell if a user is moving towards a door or away from a door or if a user is inside the house or outside the house. This way if a user is walking towards the door from outside the house, it can open the door and if the user is walking away from the door outside the house it can lock the door.

UWB can operate both in LOS (Line of Sight) and Non-LOS (No Line of Sight) conditions, though it is more accurate in LOS conditions. The fact that it can operate in Non-LOS conditions makes it ideal for indoor location applications where there are doors and walls.

Another advantage of UWB is that it has a physical layer (PHY) based on the IEEE 802.15.4z specification. This layer uses enhanced security that can prevent unauthorized users from accessing the data.

The History of Ultrawide Band Technology

Ultra-wideband’s invention dates back to the early 1900s. However, its use cases at the time were limited. The military started using this technology in the 1960s for both radars and communication applications. There are even patents on UWB developments in the 1970s. In 1974, a scientist named Morey designed a UWB radar system that could penetrate the ground, which became a commercial success at Geophysical Survey Systems Inc. (GSSI). This technology was sort of restricted for government/military use till the 1990s.

In 2002, the U.S. Federal Communication Commission (FCC) allowed the unlicensed use of UWB systems in radar, public safety, and data communication applications. When the awareness of UWB started to grow, strict rules on permissible frequencies power limits and disagreements between market players delayed the IEEE standardization of the technology. It was not until 2019, that companies like Apple and Samsung started evaluating the technology for integration into various devices.