ultra wide band technology

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ULTRA WIDEBAND TECHNOLOGY CREATING A WIRELESS WORLD By A.GEETHA

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Introduction: The need for wireless connectivity has extended well beyond the business world and has entered the consumer market, which in itself has brought new challenging demands to current Devices and technology. Soon there will be a demand for PCs, MP3 players/recorders, HDTVs, digital cameras, set-top boxes, cell phones, PDAs. “However, today’s wireless LAN and WPAN technologies cannot meet the needs of tomorrow’s connectivity of such a host of emerging electronic devices that require high bandwidth”.

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Ultra-wideband (UWB) technology is Cost effective & brings the convenience and mobility of wireless communications to high-speed interconnects in devices throughout the digital home and office. UWB is Designed for short-range, wireless personal area networks (WPANs), UWB is the leading technology for freeing people from. UWB, short-range radio technology, complements other longer range radio technologies such a Wi-Fi , Wi-MAX and cellular wide area communications.

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It delivers data over 15 to 100 meters and does not require a dedicated radio frequency, so is also known as carrier-free, impulse or base-band radio. UWB radio transmissions can legally operate in the range from 3.1 GHz up to 10.6 GHz, at a limited transmit power of -41dBm/MHz. Consequently, UWB provides dramatic channel capacity at short range that limits interference. Thus, pulse-based systems wherein each transmitted pulse instantaneously occupies the UWB bandwidth or an aggregation of at least 500 MHz worth of narrow band carriers. for example in orthogonal frequency-division multiplexing (OFDM) fashion—can gain access to the UWB spectrum under the rules. Regarding Bandwidth and Frequency:

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Pulse repetition rates may be either low or very high. Pulse-based radars and imaging systems tend to use low repetition rates, typically in the range of 1 to 100megapulses per second. Each pulse in a pulse based UWB system occupies the entire UWB bandwidth, thus reaping the benefits of relative immunity to multipath fading (but not to inter symbol interference) unlike carrier-based systems that are subject to both deep fades and inter symbol interference.

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How UWB Works: UWB broadcasts short digital pulses, which are timed very precisely on a carrier signal across a very wide spectrum (number of frequency channels) at the same time. The duration of the short pulse is generally less than 1 nanosecond. Transmitter and receiver must be coordinated to send and receive pulses with an accuracy of a trillionth of a second. In a multiple access system, a user has a unique “pseudo-random” (PN) code. A receiver operating with the same PN code can decode the transmission. The UWB receiver consists of a highly accurate clock oscillator and a correlator to convert the received RF signal into a baseband digital or analog output signal.

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The UWB transmitter and the receiver are tightly coupled by means of an acknowledgement scheme where the transmitter waits for the receiver’s response for a specific time period (approx. 10 seconds). Modern UWB systems use other modulation techniques, such as Orthogonal Frequency Division Multiplexing (OFDM), to occupy these extremely wide bandwidths. With the formation of the Multi-Band OFDM Alliance (MBOA) in June 2003, OFDM for each sub band was added to the initial multiband approach in order to develop the best technical solution for UWB. In the Multiband OFDM approach, the available spectrum of 7.5 GHz is divided into several 528-MHz bands.

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Band Plan for MB-OFDM Method The band plan for the MBOA proposal has five logical channels (see Figure). Channel 1,Which contains the first three bands, is mandatory for all UWB devices and radios. Multiple groups of bands enable multiple modes of operation for Multiband OFDM devices.

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In the current Multiband OFDM Alliance's proposal, bands 1–3 are used for Mode 1 devices (mandatory mode), while the other remaining channels (2–5) are optional. There are up to four time-frequency codes per channel, thus allowing for a total of 20 piconets with the current MBOA Proposal. In addition, the proposal also allows flexibility to avoid channel 2 when and if U-NII (Unlicensed-National Information Infrastructure) interference, such as from 802.11a, is present.

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Wi-Fi Vs. UWB:   Wi-Fi has a significant problem: the lack of what’s known in the industry as Quality of Service or Quos. Instead, Wi-Fi uses a contention – based access scheme which is exactly what it sounds like, everybody that’s trying to use the network musty fight for it. That works okay for data but its death for video. Since most wireless routers aren’t smart enough to prioritize data streams the more devices that are connected the slower the connection speed for all those devices. With video, the issue is particularly vexing since any data loss during transmission of these large files leads to image stuttering or worse.

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Application Areas of UWB: Wireless Home Networks PC, MP3 player, Digital camera, Printer, Scanner, High-Definition TV (HDTV) and video game console.

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Radar in Automotive Industry It is ideally suited for collision avoidance, detecting the movement and location of objects near a vehicle, improving airbag activation and suspension settings.

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Security Applications Applications such as ground penetrating radar (GPR), through-wall surveillance, appear attractive given today's focus on detection, but are best handled by established systems companies. Tracking Applications Applications involving the tracking of children, personnel, equipment and inventory, to an accuracy of less than one inch, are attractive, especially as UWB can work indoors unlike GPS.

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Characteristics/Advantages of UWB: High Data Rates Low Power Consumption Interface Immunity High Security Reasonable Range Low Complexity, Low Cost Ultra wideband (UWB) has been described by some as one of the most promising technologies of our times. Recently, however, UWB technology focused on consumer electronics communications. We can fully appreciate the potential of UWB in these applications.

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References http://whitepapers.techrepublic.com.com/abstract.aspx?docid=304800 http://www.xchangemag.com/articles/hotspotinterrupted.html http://www.ausairpower.net/AC-0900.html http://www.deviceforge.com/articles/AT8171287040.html