Editing Ultra-wideband (section)

==Characteristics==
Ultra-wideband is a technology for transmitting information across a wide bandwidth (>500&nbsp;[[Hertz|MHz]]). This allows for the transmission of a large amount of signal energy without interfering with conventional [[narrowband]] and [[carrier wave]] transmission in the same frequency band. Regulatory limits in many countries allow for this efficient use of radio bandwidth, and enable high-data-rate [[personal area network]] (PAN) wireless connectivity, longer-range low-data-rate applications, and the transparent co-existence of radar and imaging systems with existing communications systems.

Ultra-wideband was formerly known as ''pulse radio'', but the FCC and the [[International Telecommunication Union]] Radiocommunication Sector ([[ITU-R]]) currently define UWB as an antenna transmission for which emitted signal bandwidth exceeds the lesser of 500&nbsp;MHz or 20% of the arithmetic center frequency.<ref>[http://www.itu.int/dms_pubrec/itu-r/rec/sm/R-REC-SM.1755-0-200605-I!!PDF-E.pdf Characteristics of ultra-wideband technology]</ref> Thus, pulse-based systems—where each transmitted pulse occupies the UWB bandwidth (or an aggregate of at least 500&nbsp;MHz of a narrow-band carrier; for example, [[orthogonal frequency-division multiplexing]] (OFDM))—can access the UWB spectrum under the rules.

=== Theory ===
A significant difference between conventional radio transmissions and UWB is that conventional systems transmit information by varying the power level, frequency, or phase (or a combination of these) of a sinusoidal wave. UWB transmissions transmit information by generating radio energy at specific time intervals and occupying a large bandwidth, thus enabling [[Pulse-position modulation|pulse-position]] or time modulation. The information can also be modulated on UWB signals (pulses) by encoding the polarity of the pulse, its amplitude and/or by using orthogonal pulses. UWB pulses can be sent sporadically at relatively low pulse rates to support time or position modulation, but can also be sent at rates up to the inverse of the UWB pulse bandwidth. Pulse-UWB systems have been demonstrated at channel pulse rates in excess of 1.3 billion pulses per second using a continuous stream of UWB pulses (Continuous Pulse UWB or [[C-UWB]]), while supporting forward error-correction encoded data rates in excess of 675&nbsp;Mbit/s.<ref>{{cite web|title=Wireless HD video: Raising the UWB throughput bar (again)|url=https://www.eetimes.com/document.asp?doc_id=1273536|access-date=17 April 2018|website=EETimes}}</ref>

A UWB radio system can be used to determine the "time of flight" of the transmission at various frequencies. This helps overcome [[multipath propagation]], since some of the frequencies have a [[Line-of-sight propagation|line-of-sight]] trajectory, while other indirect paths have longer delays. With a cooperative symmetric two-way metering technique, distances can be measured to high resolution and accuracy.<ref>[https://www.researchgate.net/profile/Milos_Drutarovsky/publication/224341251_Efficient_Method_of_TOA_Estimation_for_Through_Wall_Imaging_by_UWB_Radar/links/02e7e52e63c5733233000000/Efficient-Method-of-TOA-Estimation-for-Through-Wall-Imaging-by-UWB-Radar.pdf Efficient method of TOA estimation for through wall imaging by UWB radar]. International Conference on Ultra-Wideband, 2008.</ref>