Ultra Wide Band.doc (Size: 82.5 KB / Downloads: 173)
The average person has a small home, but a huge appetite for entertainment. All of us would want to zap video images from digital camcorders to our hard drives without tripping over the cables that connect them. As home entertainment systems become more sophisticated, u will have flat panel displays. You could hang them like paintings on your wallÂ¦..Now who would want cables to dangle from those beauties
So you think - big dealÂ¦. We have Bluetooth and 802.11 wireless technologies to solve this problem. They do a decent job of linking our pcâ„¢s and digital gadgets in the home and office. However, more bandwidth and speed is always welcome. Its here that UWB makes its grant entrance.
UWB can handle more bandwidth intensive applications â€œ such as streaming video â€œ than any 802.11 or Bluetooth technology. It has a data rate of roughly 100 Mbps. Compare that with the maximum speeds of 11 Mbps for 802.11b, called Wireless Fidelity or Wi-Fi, which is the technology currently used in WLANs (wireless LANs). Bluetooth has a data rate of about 1 Mbps. UWB is expected to reach around 500 Mbps by 2004.
Propagation environments place fundamental limitations on the performance of wireless communications systems. The existence of multiple propagation paths (multipath), with different time delays, gives rise to complex, time-varying transmission channels. A line-of-site path between the transmitter and receiver seldom exists in indoor environments, because of natural or man-made blocking, and one must rely on the signal arriving via multipath.
UWB gives us these extremely high data rates at lower costs and lower levels of power consumption, which makes it ideally suitable for handhelds and mobiles.
What is Ultra Wideband technology
Ultra Wideband is a revolutionary wireless technology for transmitting digital data over a wide spectrum of frequency bands with very low power. It can transmit data at very high rates (for wireless local area network applications). The approach employed by UWB devices is based on sharing already occupied spectrum resources, rather than looking for still available but possibly unsuitable new bands. Within the power limit allowed under current FCC regulations, Ultra Wideband can not only carry huge amounts of data over a short distance at very low power, but also has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. At higher power levels, UWB signals can travel to significantly greater ranges. Instead of traditional sine waves, ultra wideband broadcasts digital pulses that are timed very precisely on a signal across a very wide spectrum at the same time. Transmitter and receiver must be coordinated to send and receive pulses with an accuracy of trillionths of a second.
UWB is not a new technology. Dr. Gerald F Ross had demonstrated its potential in radar and communications in the early 1970s itself. However, its usage for wireless applications, particularly for WLANs and WPANs, began only in the late 1990s with several players like XtremeSpectrum, Time Domain, Multispectral Solutions, Aether Wire, Fantasma Network, IBM, Intel and Motorola.
UWB was also used in espionage agencies in both the United States of America and the former Soviet Union. The research of military radar technicians led to the Ëœultra wideband synthetic aperture radarâ„¢, used by spy planes and satellites to see through dense ground cover to locate enemy troops and camouflaged equipment on the ground. It works by showering the target with rapid pulses of broad, low frequency signals that punch their way through solid objects. UWB works in a similar fashion.
How secure is UWB
UWB promises to be highly secure. Itâ„¢s very difficult to filter a pulse signal out of the flood of background electronic noise with traditional RF scanners. Besides, vendors such as Time Domain are encrypting the zeros and ones being transmitted by the pulses.
If an intruder could find the signal in the noise floor, maintaining precise synchronization with a series of pseudo-random pulses of energy present less than 10% of the time and less than 500 picoseconds in duration is a monumental engineering challenge.
BACK TO BASICS
Normal radio waves are sine waves or smoothly fluctuating waves. Traditionally, radio communications stay within the allocated frequency band. We normally use a carrier wave to transmit data. The carrier wave is imprinted with data by modulating any of the followingâ€ amplitude, frequency or phase of the carrier wave. Three common ways of modulating a sine wave are AM (Amplitude Modulation), FM (Frequency Modulation) and PM (Pulse Modulation).
What happens when you listen to news from an AM radio station, say an All India Radio medium wave station The sine wave of the announcerâ„¢s voice is combined with the transmitterâ„¢s sine wave (carrier wave) to vary its amplitude, and then transmitted. In AM, the amplitude of the sine wave or rather its peak-to-peak voltage changes. FM stations and other wireless technologies including cordless phones, cell phones and WLANs use FM, where based on the information signal, the transmitterâ„¢s sine wave frequency changes slightly. In PM, the carrier or sine wave is turned on and off to send data. In its simplest form, it can be a kind of Morse code. (See diagrams for a basic idea of how narrow-band communications work). The receiver in each case is specially tuned to decode information in the carrier wave.
Usage of a carrier wave within a narrow band effectively means limiting amount of data that can be imprinted on to it. Hence the importance of UWB.
UWB uses a kind of pulse modulation. To transfer data, a UWB transmitter emits a single sine wave pulse (called a monocycle) at a time. This monocycle has no data in it. On the contrary, it is the timing between monocycles (the interval between pulses) that determines whether data transmitted is a 0 or a 1. A UWB pulse typically ranges between .2 and 1.5 nanoseconds. If a monocycle is sent early (by 100 pico seconds), it can denote a 0, while a monocycle sent late (by 100 pico seconds) can represent a 1. Now, one pico second = one trillionth of a second. Hence, the quantity of data transmitted is on the high side
Spacing between monocycles changes between 25 to 1000 nanoseconds on a pulse-to-pulse basis, based on a channel code. A channel code allows data to be detected only by the intended receiver. Since pulses are spaced and timing between pulses depends on the channel, itâ„¢s already in encrypted form and is more secure than conventional radio waves. Through several million monocycles, it uses a wide range of frequencies to transmit large amounts of data in one go.
Only a receiver specifically tuned to the transmitter can receive transmitted data. Hence, it is a comparatively more secure channel for data transmission. Moreover, by using some amount of modulation, sharp spiking and subsequent noise interference with other narrow band devices are reduced to minimal levels. Any other device into whose band UWB pulses might spill over, will at most, feel it as background noise as energy levels of the pulse are low.
APPLICATIONS OF UWB TECHNOLOGY
Â¢ Radar Applications
1. Disaster rescue: UWB technology has been used for some time in Ground Penetrating Radar (GPR) applications and is now being developed for new types of imaging systems that would enable police, fire and rescue personnel to locate persons hidden behind a wall or under debris in crises or rescue situations. By bouncing UWB pulses, rescuers can detect people through rubble, earth or even walls using equipment similar to radar. Construction and mineral exploration industries may also benefit.
2. Radars: The US military has already been using this technology for military radars and tracking systems for the last 15 years.
3. Collision avoidance: UWB technology can make intelligent auto-pilots in automobiles and other crafts a reality one day.
4. Construction safety: UWB imaging devices also could be used to improve the safety of the construction and home repair industries by locating steel reinforcement bars (i.e., re-bar) in concrete, or wall studs, electrical wiring and pipes hidden inside walls.
5. Automotive safety: UWB devices could improve automotive safety with collision avoidance systems and air bag proximity measurement for safe deployment
6. Medical Application: Potential medical uses include the development of a mattress-installed breathing monitor to guard against Sudden Infant Death Syndrome and heart monitors that measure the heart's actual contractions
7. Home safety: Some potential home safety uses include intrusion detection systems that are less susceptible to false alarms, and space heaters that turn themselves off when a child comes nearby.
Â¢ Communications Applications
1. UWB devices can be used for a variety of communi-cations applications involving the transmission of very high data rates over short distances without suffering the effects of multi-path interference. (Multipath is the propagation phenomenon that results in signals reaching the receiving antenna by two or more paths, usually due to reflections of the transmitted signal. The ability to time-gate the receiver would allow it to ignore signals arriving outside a prescribed time interval, such as signals due to multipath reflections.)
2. UWB communication devices could be used to wirelessly distribute services such as phone, cable, and computer networking throughout a building or home. These devices could also be utilized by police, fire, and rescue personnel to provide covert, secure communications devices
3. It can emerge as a competitor to cellular services that currently use CDMA and TDMA technologies
Â¢ Positioning Applications
1. Personnel tracking: Security personnel can use it to tag employees and visitors inside high security areas, give or deny permission to access certain areas etc. The US Navy is testing prototypes of this system to track its possessions overseas. UWB devices can be used to measure both distance and position. UWB positioning systems could provide real time indoor and outdoor precision tracking for many applications. Some potential uses include locator beacons for emergency services and mobile inventory, personnel and asset tracking for increased safety and security, and precision navigation capabilities for vehicles and industrial and agricultural equipment.
ADVANTAGES OF UWB TECHNOLOGY
Low power usage - Its significance lies in the fact that it transmits several times the data possible over current wireless technologies, using very low levels of power (in the order of a few milliwatts).Making it ideal for use in battery powered devices such as camcorders and cell phones. Wi-Fi , in contrast, is limited to PCs and things that u can plug into the wall.
The low power pulse can penetrate obstacles like doors, walls, metal etc, and suffers little or no interference from other narrow band frequencies. Hence, it is useful in densely built-up areas
It doesnâ„¢t require allocation of Ëœpreciousâ„¢ or Ëœpaid forâ„¢ narrow-band spectrum in use now.
Its electro-magnetic noise is only as much as that of a hair dryer or electric fan, and it doesnâ„¢t interfere with or hamper other RFs.
Best of all, it costs a fraction of current technologies like Blue-tooth, WLANs and Wi-Fi.
Minimal Noise Generation - UWB doesnâ„¢t suffer from multi-path interference (where signals reach the receiver after traveling through two or more paths). Something similar happens when your car is at an intersection surrounded by tall buildings. Your radio might not give a clear reception as itâ„¢s receiving both direct signals and those that have bounced off the buildings. Often, the static disappears when you move ahead or backwards. Hence, it can be used in densely built-up places, or where number of users are more than what is supported by Wi-Fi, Blue-tooth etc.
Some players have come out with UWB prototypes. XtremeSpectrum claims to have created a chipset codenamed Trinity that offers 100 Mbps data rates and consumes only 200 milliwatts of power. Trinity will be priced around $ 20 per piece in groups of 100,000. Commercial production is expected in the first half of 2003.
So far, while some players have given it a wide berth, others are lobbying hard for it. Those who have worked on competing technologies like 2.5 G and 3 G are against it.
They claim that since UWB is spread across the spectrum, it could theoretically interfere with other electromagnetic waves and essential services dependent on these, like air traffic communications, mobile services, GPS, radio and TV signals. Also, rivals like Synad Technologies have developed the Mercury5G chipset that can operate on both 802.11a WLAN and 802.11b (Wi-Fi) standards and offers reasonably high throughputs.
Where does this leave UWB It is undoubtedly a niche technology which holds promise in a wide area. But, its success depends on scoring against a handful of rival technologies in which companies have invested billions. Those whoâ„¢ve invested their money will not hasten to consider an upstart rival, even if it offers better services. It seems that UWB will most probably succeed in WPANs as a means of delivering data-intensive applications like video. Imagine downloading the latest blockbuster on your portable player while tanking up at the petrol pump! But, this dream will take at least a year to materialize at the current pace of things.
Now, visualize what happens when you heave a large rock into a small pond. It splashes out the water in one go (as seen with our naked eyes). If captured as a still photo, weâ„¢ll see the millions of water droplets that splash out in a fraction of a second and make the splash we see. If ripples are like normal transmission of data between wireless devices (as in blue-tooth or Wi-Fi), UWB promises to be the Ëœhuge rockâ„¢ in data transmission
IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 48, NO. 4, APRIL 2000
IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS MONTREAL, CANADA, JUNE 1997
BACK TO BASICS
APPLICATIONS OF UWB TECHNOLOGY
ADVANTAGES OF UWB TECHNOLOGY
Ultra Wide Bandwidth (UWB) can handle more bandwidth intensive applications â€œ such as streaming video â€œ than either 802.11 or Bluetooth because it can transmit data 10 times faster than the typical DSL line, cable modem or 802.11b. It has a data rate of roughly 100 Mbps, with speeds up to 500 Mbps. Compare that with the maximum speeds of 11 Mbps for 802.11b, called Wi-Fi, which is the technology currently used in most wireless LANs. Bluetooth has a data rate of about 1 Mbps.
UWB gives us these extremely high data rates at lower cost and lower levels of power consumption. This makes it ideally suited for handhelds and mobiles. According to one estimate, 20,000 people could talk on UWB cellphones within one square block with no interference
I extend my sincere thanks to Prof. , Head of the Department for providing me with the guidance and facilities for the Seminar.
I express my sincere gratitude to Seminar coordinator
Mr. , Staff in charge, for his cooperation and guidance for preparing and presenting this seminar.
I also extend my sincere thanks to all other faculty members of Electronics and Communication Department and my friends for their support and encouragement.
ultra wide band technology.ppt (Size: 1.98 MB / Downloads: 298)
ULTRA WIDEBAND TECHNOLOGY CREATING A WIRELESS WORLD
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, todayâ„¢s wireless LAN and WPAN technologies cannot meet the needs of tomorrowâ„¢s connectivity of such a host of emerging electronic devices that require high bandwidth.
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.
Regarding Bandwidth and Frequency:
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) fashionâ€can gain access to the UWB spectrum under the rules.
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.
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.
The UWB transmitter and the receiver are tightly coupled by means of an acknowledgement scheme where the transmitter waits for the receiverâ„¢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.
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.
In the current Multiband OFDM Alliance's proposal, bands 1â€œ3 are used for Mode 1 devices (mandatory mode), while the other remaining channels (2â€œ5) 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.
Wi-Fi Vs. UWB:
Wi-Fi has a significant problem: the lack of whatâ„¢s known in the industry as Quality of Service or Quos.
Instead, Wi-Fi uses a contention â€œ based access scheme which is exactly what it sounds like, everybody thatâ„¢s trying to use the network musty fight for it. That works okay for data but its death for video.
Since most wireless routers arenâ„¢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.
Application Areas of UWB:
Wireless Home Networks
High-Definition TV (HDTV) and video game console.
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.
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.
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.
Characteristics/Advantages of UWB:
High Data Rates
Low Power Consumption
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.