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What is Ultra Wideband (UWB) ?
| UWB Technology | Comparison with Other Wireless Applications |
UWB Technology
UWB is a wireless communication technology that was originally developed for the US military, and was disclosed for public use in 2002. In general, data communication, particularly those using radio waves, is performed by modulating the assigned "channel" (a bandwidth centered around a "carrier wave" frequency) with the data (baseband) being transmitted. With UWB, the baseband can be transmitted in extremely short impulses, and by using an extremely wide frequency range instead of the carrier wave (hence the name, Ultra Wide Band). UWB communications use a frequency range of 3.1 GHz to 10.6 GHz.
- Uses a wide frequency range of 3.1 GHz to 10.6 GHz, with transmission power at or below the system noise level.
- High-speed data transfer (110 MHz @ 10 m, 480 MHz @ 3 m).
- Aimed to be low-cost and license-free (regulations are currently under consideration in each country).
With UWB, signals are transmitted over a wide frequency range, but over a short distance, and at an output level so low that it would be considered as noise for any other wireless communication method. The reduced output level may seem like an obstacle for data communication, but by detecting, correcting, and combining phase differences in signals received via multiple receivers, the "multi-path" interference can theoretically be eliminated completely, and interference with other transmissions and channels can also be avoided. Since the method does not depend on detecting the strongest signal with a single receiver, the transmission power can be suppressed.
Several implementations of UWB have been devised to avoid interference with existing wireless communication (in particular, the 5 GHz range of IEEE 801.11a). Wireless USB uses the MB-OFDM method recommended by WiMedia.
The MB-OFDM method divides the frequency range between 3.1 GHz and 10.6 GHz into 14 "bands," which are then grouped into 5 "channels."
With the MB-OFDM method, the wide frequency range is first split into "bands" with a width of 528 MHz. Three consecutive bands are then grouped into a "channel." Each channel consists of 128 narrow subcarriers. For improved stability, the same data is transmitted simultaneously over each of these subcarriers. This is called "multiplexing." The name FDM (Frequency Division Multiplexing) comes from dividing the subcarriers by frequency.
Normally, adjacent channels have overlapping frequencies, so a band of unused frequencies is provided as a "guard band" to prevent the overlap. OFDM is a method that allows for a more efficient use of frequencies by using "orthogonality" to prevent the interference between adjacent subcarriers. The OFDM method is also used for wireless LAN.
UWB also reduces transmission power by periodically switching between bands within a channel. Power consumption by UWB communication is less than 1/100,000 of that by wireless LAN.
Comparison with Other Wireless Applications
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When Wireless USB was first conceived, discussion ensued on how it could be differentiated from existing wireless connectivity solutions. Ultra Wide Band (UWB), the wireless technology adopted for Wireless USB, offers similar range and transfer rate to that of the existing wired USB 2.0 standard (maximum communication distance of 5 m, maximum transfer rate of 480 Mbps).