Ultra-wideband (UWB), a 132-year-old communication, is now being revitalized for wirelessly connecting devices over short distances. Many industry observers claim UWB could prove more successful than Bluetooth because it has superior speed, is cheaper, uses less power, is more secure, and provides superior location discovery and device ranging.
Companies such as Intel, Time Domain, Apple, Huawei, Samsung, Xiaomi, NXP, Sony, Bosch, and Xtreme Spectrum are researching and investing in UWB technology. In fact, Apple already provides UWB chips in its iPhone 11 enabling superior positioning accuracy and ranging through “Time of Flight” measurement.
In this article, we'll cover the basics of ultra-wideband technology, including its origins, benefits, and a high-level look at transmission methods.
What Is UWB?
Ultra-wideband (UWB) is a short-range wireless communication protocol—like Wi-Fi or Bluetooth—uses radio waves of short pulses over a spectrum of frequencies ranging from 3.1 to 10.5 GHz in unlicensed applications.
The term UWB is used for a bandwidth (BW) that is larger or equal to 500 MHz or a fractional bandwidth (FBW) greater than 20% where FBW = BW/fc, where fc is the center frequency.
History of UWB
The history of UWB technology dates back to the time of the first man-made radio when Marconi used spark-gap (short electrical pulses) transmitters for wireless communication.
In 1920, UWB signals were banned from commercial use. UWB technology was restricted to defense applications under highly classified programs for secure communication. It was not until 1992 that UWB started receiving noticeable attention in the scientific community.
Developments in high-speed microprocessors and fast switching techniques have made UWB commercially viable for short-range, low-cost communication. Early applications include radar systems, communication, consumer electronics, wireless personal area networks, localization, and medical electronics. Since that time, detailed knowledge of UWB electromagnetics, components, and system engineering have been developed.
In 2002, the US Federal Communication Commission (FCC) was the first organization worldwide to release UWB regulations allowing the unlicensed use of the allocated spectrum. However, the allowable power limit was set very low to avoid interference with other technologies that operate in this frequency band such as WiFi, Bluetooth, etc.
The low spectral density of UWB signals is attractive, making UWB less susceptible to in-band interference from other narrowband signals and very secure as they are difficult to detect due to low power density.
The Advantages of Ultra-Wideband Technology
The very wide bandwidth of UWB signals enables superior indoor performance over traditional narrow-band systems.
Some of this bandwidth's features are highlighted below:
- The wide bandwidth provides immunity against the channel effect in a dense environment and enables very fine time-space resolutions for highly accurate indoor positioning of the UWB nodes, e.g., the new iPhone 11.
- The low spectral density, below environmental noise, ensures a low probability of signal detection and increases the security of communication.
- High data rates can be transmitted over a short distance using UWB.
- UWB systems can co-exist with already-deployed narrowband systems.
UWB Transmission
Two different approaches are adopted for data transmission:
- Ultra-short pulses in the picosecond range, which covers all frequencies simultaneously (also called impulse radios)
- Subdividing the total UWB bandwidth into a set of broadband Orthogonal Frequency Division Multiplexing (OFDM) channels
The first approach is cost-effective at the expense of degraded signal to noise ratio. In general, impulse radio transmission does not require the use of a carrier, which means reduced complexity compared to traditional narrowband transceivers (i.e., simpler transceiver architecture) as the signal is directly radiated via the UWB antenna. Gaussian monocycle or one of its derivatives is an example of a UWB pulse that's easy to generate.
The second approach exploits the spectrum more efficiently and offers better performance and data throughput at the expense of increased complexity (i.e., requires signal processing), and power consumption.
The choice between the two approaches depends on the applications.
