Ultra wideband

From Free net encyclopedia

Ultra-wideband (also UWB, and ultra-wide-band, ultra-wide band, etc.) may be used to refer to anything with a very large bandwidth (e.g.: a type of sampling rate in the Speex speech codec). This article discusses the meaning in radio communications.

1 Overview
2 Possible Applications
3 See also
4 External links
- 4.1 Chip manufacturers
5 Software Providers

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Overview

Ultra-wideband usually refers to a radio communications technique based on transmitting very-short-duration pulses, often of duration of only nanoseconds or less, whereby the occupied bandwidth goes to very large values. This allows it to deliver data rates in excess of 100 Mbit/s, while using a small amount of power and operating in the same bands as existing communications without producing significant interference. However it is not limited to wireless communication, UWB can also use mains-wiring, coaxial cable or twisted-pair cables to communicate - with potential to deliver data faster than 1 gigabit per second.

UWB is fundamentally different from all other radio frequency communications. It is unique in that it achieves wireless communications without using a sine-wave RF carrier. Instead it uses modulated high frequency low energy pulses of less than one nanosecond in duration. Since the actual transmission is physically a wavelet, some authorities consider it to be true modulated-wavelet radio.

There are two major methods used to modulate waveforms: Time-modulation pulse-position modulation and pulse polarity-modulation pulse-amplitude modulation [1], although orthogonal waveforms may also be employed. By long-established practice, UWB is considered to occupy a fractional bandwidth of 20% or greater, or a bandwidth of 500 MHz or more, of spectrum. The U.S. Federal Communications Commission (FCC) restricts UWB to fractional bandwidth of 20% or greater, or bandwidths of 500 MHz or more. In December 2004 the FCC effectively eliminated this minimum bandwidth requirement as to the 5925-7250 MHz and 16.2-17.7 GHz frequency bands.

The processing gain of UWB, defined as the ratio of occupied bandwidth relative to the modulation bandwidth, is similar to spread spectrum for transmission. Reception of UWB is usually based on time-correlation of pulses for pulse transmissions, and waveform correlation for direct sequence type modulations. Additionally, pulse-UWB has difficult-to-realise synchronization requirements (for semiconductor companies) due to the very low Duty cycle pulses employed. Direct-sequence type UWB on the other hand is relatively easy to detect and receive. One way to effectively detect types of transmissions is by using a massively parallel DSP front end operating at more than 2.4 teraflops/second. There is at least one company successfully using this approach for its first-generation silicon. Other companies make effective use of high speed analogue to digital converters to simply and easily directly sample the RF and provide a low-power consuming solution that is effective for data rates in the gigabit per second range.

On February 14 2002 [FCC15 2002] the FCC approved a spectral mask for operation of UWB devices. The major part of it lies between 3.1 and 10.6 GHz (from the middle of S band through to the middle of X band) with allowed effective isotropically radiated power (EIRP) of -41.3 dBm/MHz. It has been proposed that impulse radio systems (that transmit very narrow pulses) are good candidates to satisfy these constraints. OFDM-based technologies also meet FCC bandwidth requirements by aggregating more than a 100 narrow band carriers. In March 2005 the FCC granted a waiver that benefits both so-called multiband OFDM (MB-OFDM), which "hops" a 500+ MHz wide OFDM symbols from one band to another, and gated direct sequence ultra-wideband (DS-UWB), which occupies a much wider switch of spectrum but switches on and off while in operation. The waiver allows both technologies to take their measurements for compliance with the -41.3 dBm/MHz limit in their normal operating mode -- i.e., with the hopping or gating turned on. The practical effect is to boost the useful operating power by several dB.

While there are a number of competing standards which risk to make universally compatible UWB products problematic in the short-term, Wireless USB - certified by the USB Implementors Forum (USB-IF) - has selected WiMedia (MB-OFDM) as its underlying radio. 1394 on the other hand has not standardized either the DS-UWB solution or the WiMedia (MB-OFDM) radio. Bluetooth stakeholders have selected WiMedia Alliance's MB-OFDM for integration with current Bluetooth wireless technology. UWB signaling is a candidate for the alternate physical layer protocols for the high data rate IEEE 802.15.3a standard (where a DS-UWB and an MB-OFDM solution have been proposed) as well as the low data rate IEEE 802.15.4a "ZigBee" wireless personal area network (WPAN) standards where a DS-UWB pulsed-type system is being developed. The IEEE 802.15.4a standard aims at providing a physical layer wireless communication protocol with ranging capabilities for low-power applications such as sensor networks. The narrow duration of the direct sequence modulated UWB pulses enables achievement of the stringent ranging accuracy (<1m) requirements.

Unfortunately, in early 2006 an industry working group announced that it would disband because two competing factions could not agree on a single UWB standard [2] [3] [4]. Therefore consumers will once again face a "VHS-versus-Beta" format war until one faction gains a clear lead.

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Possible Applications

Due to its extremely short range, UWB is unfortunately limited to the same sort of devices that Bluetooth is used for. The main advantage to using Ultra-wideband as opposed to Bluetooth is, as the name implies, bandwidth speed. Excepting any interference, a UWB device could theoretically achive transfer speeds of up to 1 Gbps. The range of applications for these kinds of speeds are staggering even given the range limitations of UWB.

As mentioned above, UWB will debut in the same manner that Bluetooth did. Manufactuers will undoubtedly incorporate this into cell phones for uses such as wireless headsets and distributing Internet connectivity to nearby devices like PDAs (aka Personal Digital Assistant). Simpler applications are also concievable. UWB could be incorporated into wireless mice, keyboards, gamepads, speakers and more.

However, the true promise in UWB lies in eliminating the cable altogether. For example, wireless monitors would be possible, eliminating another bulky cable from the typical PC desktop. UWB enabled digital camcorders would be able to transmit high-definition video streams in real time to a UWB HDTV or PC, acting as a mobile wireless VCR. Getting back to the cell phone example used above, a UWB cell phone could transmit a video signal to a wireless video headset, allowing a user to view incoming calls, answer them, write emails, and book appointments without even touching the phone.

A few more examples:

An office worker could put a mobile PC on a desk and instantly be connected to a printer, scanner and Voice over IP (VoIP) headset.
All the components for an entire home entertainment center could be set up and connected to each other without a single wire.
A portable MP3 player could stream audio to high-quality surround-sound speakers anywhere in the room.
A mobile computer user could wirelessly connect to a digital projector in a conference room to deliver a presentation.
Digital pictures could be transferred to a photo print kiosk for instant printing without the need of a cable.

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External links

The Networking with UWB Group of the University of Rome "La Sapienza" is active in the UWB research field since the end of 1999, and has many available papers on UWB. They also published the book "Understanding Ultra Wide Band Radio Fundamentals", which combines the theory and practice for the understanding and design of Ultra Wide Band (UWB) communication networks.
The Ultra-Wideband Radio Laboratory at the University of Southern California has many publications including "Low noise amplifier design for ultra-wideband radio" by Jongrit Lerdworatawee, Won Namgoong, 2003
UWB Radio Technology Primer on UWB
UWB Forum The UWB Forum is dedicated to ensuring that standards-based Ultra-Wideband products from multiple vendors are truly interoperable – from mobile phones to set-top boxes, from computers to televisions to digital camcorders and more.
WiMedia Alliance The WiMedia Alliance is an open, non-profit industry association dedicated to collaboratively developing and administering specs from the physical layer up; enabling connectivity and interoperability for multiple industry-based protocols sharing the MBOA-UWB spectrum.
UWB Info and resources

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Chip manufacturers

Intel Corp.
Pulse-Link, a fabless semiconductor providing UWB solutions at Gbit/s rates on-air and over wired media
Time Domain is a fabless semiconductor company, and is a UWB pioneer providing time-modulated pulse based UWB solutions
Freescale Semiconductor Manufacturer of DS-UWB chips sets and evaluation kits demonstrating FCC certified 114 Mb/s radios
Alereon Inc. is a fabless semiconductor company providing complete solutions for Certified Wireless USB and WiMedia ultra-wideband (UWB) applications.
FOCUS Enhancements
Staccato Communications
TZero
Artimi, a fabless semiconductor company providing complete WiMedia-based UWB systems solutions with Low Band and High Band capability in a single device for Certified Wireless USB and Bluetooth over WiMedia UWB Applications.
WiQuest
Wisair
General Atomics