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22-01-2010, 03:31 PM
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ultra wide band technology full report

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ABSTRACT
UWB is a wireless technology that transmits binary data”the 0s and 1s that are the digital building blocks of modern information systems. It uses low-energy and extremely short duration (in the order of pico seconds) impulses or bursts of RF (radio frequency) energy over a wide spectrum of frequencies, to transmit data over short to medium distances, say about 15”100 m. It doesn™t use carrier wave to transmit data.
Ultra Wide Bandwidth (UWB) can handle more bandwidth intensive applications “ such as streaming video “ 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.

INTRODUCTION
Ultra Wide Band (UWB) is a revolutionary technology with incomparable potential in terms of throughput, performance and low cost implementation. The uniqueness of UWB is that it transmits across extremely wide bandwidth of several GHz, around a low center frequency, at very low power levels.
UWB is fundamentally different from existing radio frequency technology. For radios today, picture a guy watering his lawn with a garden hose and moving the hose up and down in a smooth vertical motion. You can see a continuous stream of water in an undulating wave. Nearly all radios, cell phones, wireless LANs and so on are like that: a continuous signal that's overlaid with information by using one of several modulation techniques.
Now picture the same guy watering his lawn with a swiveling sprinkler that shoots many, fast, short pulses of water. That's typically what UWB is like: millions of very short, very fast, precisely timed bursts or pulses of energy, measured in nanoseconds and covering a very wide area. By varying the pulse timing according to a complex code, a pulse can represent either a zero or a one: the basis of digital communications.
UWB is almost two decades old, but is used mainly in limited radar or position-location devices. Only recently has UWB been applied to business communications. It's a different type of transmission that will lead to low-power, high-bandwidth and relatively simple radios for local- and personal-area network interface cards and access points. At higher power levels in the future, UWB systems could span several miles or more.
Wireless technologies such as 802.11b and short-range Bluetooth radios eventually could be replaced by UWB products that would have a throughput capacity 1,000 times greater than 802.11b (11M bit/sec). Those numbers mean UWB systems have the potential to support many more users, at much higher speeds and lower costs, than current wireless LAN systems. Current UWB devices can transmit data up to 100Mbps, compared to the 1Mbps of Blue-tooth and the 11Mbps of 802.11b. Best of all , it costs a fraction of current technologies such as Blue-tooth, WLANs and Wi-Fi.

ULTRA WIDE BAND
This concept doesn't stand for a definite standard of wireless communication. This is a method of modulation and data transmission which can entirely change the wireless picture in the near future. The diagram given below demonstrates the basic principle of the UWB:

The UWB is above and the traditional modulation is below which is called here Narrow Band (NB), as opposed to the Ultra Wideband. On the left we can see a signal on the time axis and on the right there is its frequency spectrum, i.e. energy distribution in the frequency band. The most modern standards of data transmission are NB standards - all of them work within a quite narrow frequency band allowing for just small deviations from the base (or carrier) frequency. Below on the right you can see a spectral energy distribution of a typical 802.11b transmitter. It has a very narrow (80 MHz for one channel) dedicated spectral band with the reference frequency of 2.4 GHz. Within this narrow band the transmitter emits a considerable amount of energy necessary for the following reliable reception within the designed range of distance (100 m for the 802.11b). The range is strictly defined by FCC and other regulatory bodies and requires licensing. Data are encoded and transferred using the method of frequency modulation (control of deviation from the base frequency) within the described channel.
Now take a look at the UWB - here the traditional approach is turned upside down. In the time space the transmitter emits short pulses of a special form which distributes all the energy of the pulse within the given, quite wide, spectral range (approximately from 3 GHz to 10 GHz). Data, in their turn, are encoded with polarity and mutual positions of pulses. With much total power delivered into the air and, therefore, a long distance of the reliable reception, the UWB signal doesn't exceed an extremely low value (much lower than that of the NB signals) in each given spectrum point (i.e. in each definite licensed frequency band). As a result, according to the respective FCC regulation, such signal becomes allowable although it also takes spectral parts used for other purposes:

So, the most part of energy of the UWB signal falls into the frequency range from 3.1 to 10.6 GHz. Below 3.1 GHz the signal almost disappears. The more ideal the form of a pulse formed with the transmitter, the less the energy goes out of the main range. The spectral range lower than 3.1 GHz is avoided not to create problems for GPS systems. However, UWB is accurate to within 10 centimeters -- much better than the Global Positioning System satellites and because it spans the entire frequency spectrum (licensed and unlicensed), it can be used indoors and underground, unlike GPS. UWB could replace communications of all types, ending forever our dependence on wires and making worthless the ownership of radio frequencies.
The total energy of the transmitter which can fit into this band is defined by the area of the spectral characteristic (see filled zones on the previous picture). In case of the UWB it's much greater compared to the traditional NB signals such as 802.11b or 802.11a. So, with the UWB we can send data for longer distances, or send more data, especially if there are a lot of simultaneously working devices located close to each other. Here is a diagram with the designed maximum density of data transferred per square meter:

Density of transferred data able to coexist on the same square meter is much higher for the UWB compared to the popular NB standards. That is, it will be possible to use the UWB for the intrasystem communication or even for an interchip communication within one device!
In case of the NB a frequency and width of the dedicated spectral range for the most part (though the real situation is much more complicated) defines a bandwidth of the channel, and the transmitter's power defines a distance range. But in the UWB these two concepts interwine and we can distribute our capabilities between the distance range and bandwidth. Thus, at small distances, for example, in case of an interchip communication, we can get huge throughput levels without increasing the total transferred power and without cluttering up the air, i.e. other devices are not impeded. Look at how the throughput of data transferred in the UWB modulation depends on distance:

While the traditional NB standard 802.11a uses an artificially created dependence of throughput on distance (a fixed set of bandwidths discretely switched over as the distance increases), the UWB realizes this dependence in a much more natural way. At short distances its throughput is so great that it makes our dreams on the interchip communication real, but at the longer distances the UWB loses to the NB standard. On the one hand, a theoretical volume of the energy transferred, and therefore, the maximum amount of data, is higher. On the other hand, we must remember that in a real life information is always transferred in large excess. Beside the amount of energy, there is the design philosophy which also has an effect. For example, a character of modulation, i.e. how stably and losslessly it is received and detected by the receiver. Let's compare the classical:

... and UWB transceivers:

The classical transceiver contains a reference oscillator (synth) which, as a rule, is stabilized with some reference crystal element (Ref Osc). Further, in case of reception this frequency is subtracted from the received signal, and in case of transmission it is added to the data transferred. For the UWB the transmitter looks very unsophisticated - we just form a pulse of a required shape and send it to the antenna. In case of reception we amplify the signal, pump it through the band filter which selects our working spectrum range and... that's all - here is our ready pulse.
A comparison table of the characteristics:
Distance range, m Frequency Channel width Throughput
UWB Up to 50 (at present) 3.1 to 10.6 GHz The same Hundreds of Mbit
802.11b 100 2.4 GHz 80 MHz Up to 11 Mbit
802.11a 50 5 GHz 200 MHz Up to 54 Mbit
BlueTooth 10 2.4 GHz Up to 1 Mbit

INNER WORKINGS
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.
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.
Modulation Methods
Several modulation techniques can be used to create UWB signals, some more efficiently than others. In its formative years, some of the most popular methods to create UWB pulse streams used mono-phase techniques such as pulse amplitude (PAM), pulse position (PPM), or on-off keying (OOK). In these techniques, a ˜1™ is differentiated from a ˜0™ either by the size of the signal or when it arrives in time “ but all the pulses are the same shape. A more efficient approach, bi-phase ultra-wideband, is also being deployed. Bi-phase differentiates a ˜1™ with a ˜right-side-up™ pulse and a ˜0™ with an ˜upside-down™ pulse and works by reading pulses both backwards and forwards, irrespective of time. Multi-phase UWB is not being deployed today as it is too cost-prohibitive for the consumer and enterprise markets.
Mono-phase Ultra-wideband: In this approach, all pulses are right side up, meaning they all look alike. Using pulses in time to create the desired ultra-wideband waveform, mono-phase ultra-wideband technologies are currently used in select military applications under a special license from the FCC. All of these deployed systems are much higher in power and much lower in frequency than the limits published by the FCC in their recent UWB approval guidelines.
The three most popular mono-phase ultra-wideband approaches include:
1. Pulse amplitude (PAM)”PAM works by separating the tall and the short waves. By varying the amplitude (height of pulse) the receiver can tell the difference between 1 and 0, thereby encoding data in the signal.
2. Pulse position (PPM)”In PPM, all the pulses (both 1s and 0s) are the same height. The receiver distinguishes between a 1 or a 0 by when it arrives in time, or the time lag between pulses. In this case, a long time lag could mean a 1 and a short time lag could mean a 0.
3. On-Off Keying (OOK)”In OOK, a 1 is a pulse and an absence of a pulse is a 0.
Bi-phase Ultra-wideband: In this approach, the pulses can be sent right side up or upside down, which determines whether the pulse is a 1 or a 0, so pulses can be sent at a much higher rate.

¢ PULSE POSITION MODULATION (PPM)
Encodes information by modifying the position of the pulse
0 1

¢ PULSE AMPLITUDE MODULATON (PAM)
Determines whether a pulse is a ˜1™ or ˜0™ based on the size of the pulse.
¢ ON-OFF KEYING
Determines a ˜0™ by the absence of a pulse and ˜1™ by the presence of a pulse

¢ BI-PHASE
Reads forward and backward pulses as either ˜0™or ˜1™

Why is UWB so Effective
The Hartley-Shannon Law “
C =B log 2(1+S/N)
Where:
C = Max Channel Capacity (bits/sec)
B = Channel Bandwidth (Hz)
S = Signal Power (watts)
N = Noise Power (watts)
C grows linearly with B, but only logarithmically with S/N. Since B is very high C also becomes very high.

APPLICATION
Ultra Wideband (UWB) devices can be used for precise measurement of distances or locations and for obtaining the images of objects buried under ground or behind surfaces. UWB devices can also be used for wireless communications, particularly for short-range high-speed data transmissions suitable for broadband access to the Internet.
¢ Communication Applications
UWB devices can be used for a variety of communications applications involving the transmission of very high data rates over short distances without suffering the effects of multi-path interference. UWB communication devices could be used to wirelessly distribute services such as phone, cable, and computer networking throughout a building or home.
¢ Positioning Applications
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.
¢ 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.

ADVANTAGES
Doesnâ„¢t suffer from multi-path interference.
High data carrying capacity.
It need only low power.
Low energy density.
Minimum complexity.
Low cost.
Highly secure.
Apart from low-power usage, inherent security and 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 numbers of users are more than what is supported by Wi-Fi, Blue-tooth etc.

DISADVANTAGES
UWB is not a long “range system.
Frequency sharing with existing users is a problem.
The technology too is at an early stage of development and standardization is incomplete.
KEY ISSUES FOR UWB
UWB technology is attracting as an ultra fast interface for digital appliances. A number of technical issues involved in getting UWB up and running in homes and offices have been uncovered .
They can be broken down into five groups namely
1. Reducing interference with other radio systems,
2. Complying with electromagnetic regulations of many nations,
3. Minimizing erroneous transmissions caused by reflections from walls and objects (multi-path),and
4. Assuring continuous communication between multiple pieces of equipment (multi-access),
5. Reducing implementation cost of UWB radio circuitry.
6. All of these issues will be vital to the success of UWB.

CONCLUSION
Ultra wide band has the potential to become a viable and competitive technology for short-range high-rate WPANs as well as lower-rate and low-power consuming low-cost devices and networks with the capability to support a truly a pervasive user-centric and thus personal wireless world.
UWB 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.
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.

REFERENCES
1. IEEE Communications Magazine, July 2003
2. Everyday Practical Electronics, January 2003
3. Nikkei Electronics Asia, April 2003
4. Digital Communication, J Proakis
5. http://www.techonline.com
6. http://www.pcquest.com
7. http://www.uwbplanet.com


ACKNOWLEDGEMENT
I extend my sincere gratitude towards Prof . P.Sukumaran Head of Department for giving us his invaluable knowledge and wonderful technical guidance
I express my thanks to Mr. Muhammed kutty our group tutor and also to our staff advisor Ms. Biji Paul for their kind co-operation and guidance for preparing and presenting this seminar.
I also thank all the other faculty members of AEI department and my friends for their help and support.

CONTENTS
¢ INTRODUCTION 1
¢ ULTRA WIDE BAND 3
¢ INNER WORKINGS 9
¢ APPLICATION 13
¢ ADVANTAGES 15
¢ DISADVANTAGES 16
¢ CONCLUSION 17
¢ REFERENCES 18

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18-03-2010, 07:15 AM
Post: #2
RE: ultra wide band technology full report

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INTRODUCTION
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 wall¦..Now who would want cables to dangle from those beauties
So you think - big deal¦. We have Bluetooth and 802.11 wireless technologies to solve this problem. They do a decent job of linking our pc™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 “ such as streaming video “ 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 following” 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.
WORKING PRINCIPLE
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
¢ 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.
¢ 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
¢ 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.
Inherent security
CONCLUSION
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
REFERENCES
http://www.thinkdigit.com
http://www.uwbplanet.com
http://www.nasatech.com
http://www.entecollege.com
IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 48, NO. 4, APRIL 2000
IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS MONTREAL, CANADA, JUNE 1997
http://www.pcquest.com
CONTENTS
INTRODUCTION
BACK TO BASICS
WORKING PRINCIPLE
APPLICATIONS OF UWB TECHNOLOGY
ADVANTAGES OF UWB TECHNOLOGY
CONCLUSION
REFERENCES
ABSTRACT
Ultra Wide Bandwidth (UWB) can handle more bandwidth intensive applications “ such as streaming video “ 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
ACKNOWLEDGEMENT
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.




.ppt  ultra wide band technology.ppt (Size: 1.98 MB / Downloads: 309)

ULTRA WIDEBAND TECHNOLOGY CREATING A WIRELESS WORLD

Presented By
A.GEETHA


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, 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) fashion”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 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.





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 “ 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 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
PC,
MP3 player,
Digital camera,
Printer,
Scanner,
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.



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.





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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30-03-2010, 11:30 PM
Post: #3
RE: ultra wide band technology full report
UWB (Ultra Wideband) Communication System


Presented By:
PREETHI R

Outline
UWB invented
Introduction to ULTRA WIDE BAND.
What is UltraWideBand
Different types of UWB devices.
Block Diagram of TM-UWB Transceiver.
Advantages-Disadvantages Of UWB.
What are some of the applications for UWB technology
Different from others.

UWB
When was UWB invented and by whom
In the late 1960â„¢s
Dr. Gerald F. Ross
Dr. Gerry

Introduction to ULTRA WIDE BAND the Next-Generation Wireless Connection
Overview: Transitioning to the Real World
Digital Home Requirements
Why is UWB considered by many to be the next "big thing" in the wireless space It allows for high data throughput with low power consumption for distances of less than 10 meters, or about 30 feet, which is very applicable to the digital home requirements. The fastest data rate publicly shown over UWB is now an impressive 252 Mbps, and a rate of 480 Mbps is expected to be shown in the not-too-distant future.


Wider Applications of UWB
Some of the more notable applications that would operate on top of the common UWB platform would be wireless universal serial bus (WUSB), IEEE 1394, the next generation of Bluetooth, and Universal Plug and Play (UPnP). You can see a diagram of this vision in Figure 1.
What is IEEE 802.15.3 and 802.15.3a
802.15.3 is the IEEE standard for high data rate WPAN designed to provide Quality of Service (QoS). The original standard uses a "traditional" carrier-based 2.4 GHz radio as the physical layer (PHY).
A follow-on standard, 802.15.3a, is still in the formative stages. It will define an alternative PHY, current candidate proposals are based on UWB, that will provide in excess of 110 Mbps at a 10m distance and 480 Mbps at 2m.
What is UltraWideBand

The term "ultra-wideband," comes from the fundamental physics benefits of radios designed to use coherent wide-relative-bandwidth propagation.
UWB is defined as any radio technology having a spectrum that occupies a bandwidth greater than 20 percent of the center frequency, or a bandwidth of at least 500 MHz

Federal Communications Commission
The definition from FCC:
Why is UWB attractive
Simplicity: itâ„¢s essentially a base-band system (carrier-free), for which the analog front-end complexity is far less than for a traditional sinusoidal radio.
High spatial capacity (bps/m2)
Low power
(Bluetooth:1Mbps,10m,1mW UWB: 1Mbps,10m,10)
4. Low cost, simple implementation
5. Immune to multipath fading as well as multi-user interference

Do we really need another wireless technology
unwired.
Plus it's low power.
The current technologies, like WLAN just aren't fast enough.
Unlike conventional radio systems, which operate within a relatively narrow bandwidth, ultra-wideband operates across a wide range of frequency spectrum by transmitting a series of extremely narrow (10 - 1000ps) and low power pulses.
Information Modulation
Pulse length <1ns; Energy concentrated in 2-6GHz band; Power < 10uW
Pulse Position Modulation (PPM)

Pulse Amplitude Modulation (PAM)

On-Off Keying (OOK)

Bi-Phase Modulation (BPSK)

Different types of UWB devices
There are a number of different types of UWB devices, based broadly on the application to which they are likely to be put. In this consultation document, we have grouped the devices into two categories:
Generic devices that might be used for a wide range of applications such as personal area networks (PANs).
Specific devices used for ground probing radar, 'through the wall' imaging and a number of other specialist applications.


Two main data modulation schemes used for UWB systems
Time hopping pulse position modulation (TH-PPM)

Direct spread code division multiple access (DS-CDMA)


Block Diagram of TM-UWB Transceiver

A traditional UWB transmitter works by sending billions of pulses across a very wide spectrum of frequency several GHz in bandwidth.
The corresponding receiver then translates the pulses into data by listening for a familiar pulse sequence sent by the transmitter.
Multipath and Propagation
Modern UWB systems
Frequency Division Multiplexing (OFDM) Orthogonal
MultiBand OFDM (M-OFDM)
In the MultiBand OFDM approach, the available spectrum of 7.5 GHz is divided into several 528-MHz bands.
CONT¦.
The band plan for the MBOA proposal has five logical channels.
Channel 1, mandatory
channels (2“5) , optional
Advantages Of UWB
Lower power.
Low probability of detection (LPD).
Low probability of jamming (LPJ).
Ability to penetrate wall.
Higher immunity to multi-path fading effects.
Availability of precise location information.
Low interference to existing radio services.
High processing gains.

Disadvantages of UWB
Under current FCC regulations, it is limited to 10, or a few 10s of meters, depending on the desired data rate.
What are some of the applications for UWB technology
There are numerous application areas in which UWB technology can provide significant performance and cost advantages.
CONT¦.applications for UWB technology
Full Duplex UWB Handheld Transceivers.
CONT¦.applications for UWB technology
UWB Wireless Intercom Communications System (WICS).
CONT¦.applications for UWB technology
UWB License Plate (Tag + Collision Avoidance Radar).
CONT¦.applications for UWB technology
Military/Government:
Tactical Handheld & Network Radios
Groundwave Communications
Obstacle Avoidance Radar
Tags
Intrusion Detection Radars
Precision Geolocation Systems
UAV/UGV Datalinks
Proximity Fuzes
Wireless Intercom Systems
CONT¦.applications for UWB technology
Commercial:
High Speed (20+ Mb/s) LAN/WANs
Altimeter/Obstacle Avoidance Radars
(commercial aviation)
Collision Avoidance Sensors
Tags (Intelligent Transportation
Systems, Electronic Signs, Smart
Appliances)
Intrusion Detection Radars
Precision Geolocation Systems
Industrial RF Monitoring Systems
How different Ultra-wideband from other WLAN/WPAN technologies
UWB is the only technology today that can achieve data rates significantly in excess of 54Mbps at power consumption levels and price points amenable to battery-powered consumer appliances, i.e. digital cameras, flat panel displays, etc. In addition, UWB presents some astonishing properties in terms of coexistence, multipath immunity for indoor environments, and security.
What about Bluetooth
Bluetooth, like UWB is a wireless personal area networking technology. The data rates delivered are significantly different and therefore the application spaces addressed by each technology are different. Like other application-specific technologies, it is likely that UWB and Bluetooth could both be integrated into end-devices to serve these different application spaces
Product
UWB “ A Broader Outlook
Challenges:

Noise and interference due to other signals in the same bandwidth
Efficient pulse generation
Pulse reception (with dispersion)
Wideband antenna design
Development of efficient coding techniques in order to control spectral characteristics
of the signal, allowing optimum usage of bandwidth as per FCC regulations
Synchronization (esp. for the time hopping case)
FCC compliance

Work done so far
Investigation into the nature of ultra wideband antenna
Analytical studies on UWB propagation, channel modeling, BER studies
Implementation of simple UWB transceiver prototypes
Development of localizers for positioning systems


Attached File(s)
.ppt  UWB-Ultra Wideband Communication System.PPT (Size: 1.65 MB / Downloads: 218)

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29-03-2011, 12:29 PM
Post: #4
RE: ultra wide band technology full report

.docx  uwt.docx (Size: 134.09 KB / Downloads: 85)
ABSTRACT
Wireless connectivity has enabled a new mobile lifestyle filled with conveniences for mobile computing users. Consumers will soon demand the same conveniences throughout their digital home, connecting their PCs, personal digital recorders, MP3 recorders and players, digital camcorders and digital cameras, high-definition TVs (HDTV’s), set-top boxes (STBs), gaming systems, personal digital assistants (PDAs), and cell phones, to connect to each other in a wireless personal area network (WPAN) in the home. But today’s wireless LAN and WPAN technologies cannot meet the needs of tomorrow’s connectivity of such a host of emerging consumer electronic devices that require high bandwidth. A new technology is needed to meet the needs of high-speed WPANs.
Ultra-wideband (UWB) technology offers a solution for the bandwidth,
cost, power consumption, and physical size requirements of next-generation consumer electronic devices. UWB enables wireless connectivity with consistent high data rates across multiple devices and PCs within the digital home and the office. This emerging technology provides the high bandwidth that multiple
digital video and audio streams require throughout the home. With the support of industry workgroups, such as the wireless universal serial bus (USB) workgroup, and technology leaders, like Intel, UWB technology promises to make it easy to create high speed WPANs that can connect devices throughout the home.
This document describes UWB technology and presents potential applications for UWB technology for use in WPANs in the digital home.
INTRODUCTION
The benefits of an increasingly mobile lifestyle introduced by wireless technologies in cell phones and home PCs have resulted in greater demand for the same benefits in other consumer devices. Consumers enjoy the increased convenience of wireless connectivity. They will soon demand it for their video recording and storage devices, for real-time audio and video (AV) streaming, interactive gaming, and AV conferencing services as the need for digital media becomes more predominate in the home.
Many technologies used in the digital home, such as digital video and audio streaming, require high-bandwidth connections to communicate. Considering the number of devices used throughout the digital home, the bandwidth demand for wireless connectivity among these devices becomes very large indeed.
The wireless networking technologies developed for wirelessly connecting PCs, such as Wi-Fi* and Bluetooth* Technology, are not optimized for multiple high-bandwidth usage models of the digital home. Although data rates can reach 54 Mbps for Wi-Fi, for example, the technology has limitations in a consumer electronics environment, including power consumption and bandwidth. When it comes to connecting multiple consumer electronics (CE) devices in a short-range network, or WPAN, a wireless technology needs to support multiple high data rate streams, consume very little power, and maintain low cost, while sometimes fitting into a very small physical package, such as PDA or cell phone. The emerging UWB wireless technology and silicon developed for UWB applications offer a compelling solution.
The Case for UWB
The emerging digital home environment is made up of many different CE devices (e.g., digital video and audio players), mobile devices (e.g., cellular phones and PDAs), and personal computing devices (e.g., mobile notebook PCs) that will support a multitude of applications. These devices fall into three general overlapping categories (Figure 1):
• PC and the Internet
• Consumer electronics and the broadcast system
• Mobile and handheld devices
These devices have traditionally been kept in different rooms and used for different functions. Increasingly, however, owners expect them to interact—MP3 players exchanging files with PCs, digital video recorders communicating with STBs, etc.
This convergence of device segments calls for a common wireless technology and radio that allows them to easily interoperate and delivers high throughput to accommodate multiple, high speed applications. Currently, these segments utilize different interfaces and content formats.
The next generation of PC, consumer electronics, and mobile applications demand connectivity speeds beyond the 1 Mbps peak data rate of Bluetooth Technology, which is used by many devices to create WPANs today. But many CE devices cannot support the cost and power required by the higher speed 802.11a/g radios for Wi-Fi networking. While Wi-Fi is much faster than Bluetooth Technology, it still does not deliver sufficient performance to effectively allow streaming of multiple simultaneous high-quality video streams.
UWB technology provides the throughput required by the next generation of converged devices. Plus, the support of industry initiatives, such as the WiMedia* Alliance, will help ensure interoperability across multiple protocols, including IEEE 1394, USB, and Universal Plug and Play (UPnP*), making UWB a broad technology solution for creating high-speed, low-cost, and low-power WPANs.
31-03-2011, 04:48 PM
Post: #5
RE: ultra wide band technology full report
PRESENTED BY:
S.sravya
T.Sandhya


.doc  Ultra-Wideband Technology for Short- or Medium-Range .doc (Size: 193.5 KB / Downloads: 68)
Abstract:
Ultra-Wideband (UMB) technology is loosely defined as any wireless transmission scheme that occupies a bandwidth of more than 25% of a center frequency, or more than 1.5GHz. The Federal Communications Commission is currently working on setting emissions limits that would allow UWB communication systems to be deployed on an unlicensed basis following the Part 15.209 rules for radiated emissions of intentional radiators, the same rules governing the radiated emissions from home computers, for example. This rule change would allow UWB-enabled devices to overlay existing narrowband systems, which is currently not allowed, and result in a much more efficient use of the available spectrum.
A breakdown, of how this paper is organized: The first section looks at UWB technology from the high-level perspective of how this technology compares with other current and future wireless alternatives. Next, we describe the current state of the regulatory process, where UWB transmissions are under consideration for being made legal on an unlicensed basis. Then, some implementation advantages of UMB systems are discussed that distinguish UWB transceiver architectures from more conventional “narrowband” systems. After this, we illustrate the throughput vs. distance characteristics for an example UWB system. Finally, we conclude with a summary of the benefits of UWB and suggest some future challenges that are currently being investigated.
Introduction:
Ultra-Wideband (UWB) technology has been around since the 1980s, but it has been mainly used for radar-based applications until now, because of the wideband nature of the signal that results in very accurate timing information. However, due to recent developments in high-speed switching technology, UWB is becoming more attractive for low-cost consumer communications applications (as detailed in the “Implementation Advantages” section of this paper).
Although the term Ultra-Wideband (UMB) is not very descriptive, it does help to separate this technology from more traditional “narrowband” systems as well as newer “wideband” systems typically referred to in the literature describing the future 3G cellular technology. There are two main differences between UMB and other “narrowband” or “wideband” systems. First, the bandwidth of UMB systems, as defined by the Federal Communications Commission (FCC), is more than 25% of a center frequency or more than 1.5GHz. Clearly, this bandwidth is much greater than bandwidth used by any current technology for communication. Second, UWB is typically implemented in a carrier-less fashion. Conventional “narrowband” and “wideband” systems use Radio Frequency (RF) carriers to move the signal in the frequency domain from baseband to the actual carrier frequency where the system is allowed to operate. Conversely, UWB has a very sharp rise and fall time, thus resulting in a waveform that occupies several GHz of bandwidth. Although there are other methods for generating a UWB waveform (using a chirped signal, for example), in this paper, we focus on the impulse-based UWB waveform -- due to its simplicity.
The high data rates afforded by UWB systems will tend to favor applications such as video distribution and/or video teleconferencing for which Quality of Service (QoS) will be very important. So, in addition to describing the physical layer attributes of UWB systems, it’s important to keep in mind the Medium Access Control (MAC) layer as well. Therefore, we have devoted a section to describing the current mechanisms that exist to support the required QoS for these high-rate applications.
WIRELESS ALTERNATIVES
In order to understand where UWB fits in with the current trends in wireless communications, we need to consider the general problem that communications systems try to solve. Specifically, if wireless were an ideal medium, we could use it to send
1. a lot of data,
2. very far,
3. very fast,
4. for many users,
5. all at once.
Unfortunately, it is impossible to achieve all five attributes simultaneously for systems supporting unique, private, two-way communication streams; one or more have to be given up if the others are to do well. Original wireless systems were built to bridge large distances in order to link two parties together. However, recent history of radio shows a clear trend toward improving on the other four attributes at the expense of distance. Cellular telephony is the most obvious example, covering distance of 30 kilometers to as little as 300 meters. Shorter distances allow for spectrum reuse, thereby serving more users, and the systems are practical because they are supported by an underlying wired infrastructure-the telephone network in the case of cellular. In the past few years, even shorter range systems, from 10 to 100 meters, have begun emerging, driven primarily by data applications. Here, the Internet is the underlying wired infrastructure, rather than the telephone network. Many expect the combination of short-range wireless and wired Internet to become a fast-growing complement to next-generation cellular systems for data, voice, audio, and video. Four trends are driving short-range wireless in general and ultra-wideband in particular:
1. The growing demand for wireless data capability in portable devices at higher bandwidth but lower in cost and power consumption than currently available.
2. Crowding in the spectrum that is segmented and licensed by regulatory authorities in traditional ways.
3. The growth of high-speed wired access to the Internet in enterprises, homes, and public spaces.
4. Shrinking semiconductor cost and power consumption for signal processing.
Trends 1 and 2 favor systems that offer not just high-peak bit rates, but high special capacity as well, where spatial capacity is defined as bits/sec/square-meter. Just as the telephone network enabled cellular telephony, Trend 3 makes possible high-bandwidth, in-building service provision to low-power portable devices using short range wireless standards like Bluetooth and IEEE 802.11. Finally, Trend 4 makes possible the use of signal processing techniques that would have been impractical only a few years ago. It is this final trend that makes Ultra-Wideband (UWB) technology practical.
When used as intended, the emerging short- and medium- range wireless standards vary widely in their implicit spatial capacities. For example:
• IEEE 802.11b has a rated operating range of 100 meters. In the 2.4GHz ISM band, there is about 80MHz of useable spectrum. Hence, in a circle with a radius of 100 meters, three 22MHz IEEE 802.11b systems can operate on a non-interfering basis, each offering a peak over-the-air speed of 11Mbps. The total aggregate speed of 33Mbps, divided by the area of the circle, yields a spatial capacity of approximately 1000 bits/sec/square-meter.
• Bluetooth, in its low-power mode, has a rated 10-meter range and a peak over-the-air speed of 1Mbps. Studies have shown that approximately 10 Bluetooth “piconets” can operate simultaneously in the same 10-meter circle with minimal degradation yielding an aggregate speed of 10Mbps. Dividing this speed by the area of the circle produces a spatial capacity of approximately 30,000 bits/sec/square-meter.
• IEEE 802.11a is projected to have an operating range of 50 meters and a peak speed of 54Mbps. Given the 200MHz of available spectrum within the lower part of the 5GHz U-NII band, 12 such systems can operate simultaneously within a 50-meter circle with minimal degradation, for an aggregate speed of 648Mbps. The projected spatial capacity of this system is therefore approximately 83,000 bits/sec/square-meter.
• UWB systems vary widely in their projected capabilities, but on UWB technology developer has measured peak speed of over 50Mbps at a range of 10 meters and projects that six such systems could operate within the same 10-meter radius circle with only minimal degradation. Following the same procedure, the projected spatial capacity for this system would be over 1000000 bits/sec/square-meter.
As shown in Figure 1, other standards now under development in the Bluetooth Special Interest Group and IEEE 802 working groups would boost the peak speeds and spatial capacities of their respective systems still further, but none appear capable of reaching that of UWB. A plausible reason is that all systems are bound by the channel capacity theorem, as shown in Figure 2. Because the upper bound on the capacity of a channel grows linearly with total available bandwidth, UWB systems, occupying 2GHz or more, have greater room for expansion than systems that are more constrained by bandwidth.
Thus, UWB systems appear to have great potential for support of future high-capacity wireless systems. However, there are still several important challenges ahead for this technology before it can be realized. Not the least of these challenges is finding a way to make the technology legal without causing unacceptable interference to other users that share the same frequency space. This is addressed in the next section.
REGULATORY AND STANDARDS ISSUES:
The Federal Communications Commission (FCC) is in the process of determining the legality of Ultra-Wideband (UWB) transmissions. Due to the wideband nature of UWB emissions, it could potentially interfere with other licensed bands in the frequency domain if left unregulated. It’s a fine line that the FCC must walk in order to satisfy the need for more efficient methods of utilizing the available spectrum, as represented by UWB, while not causing undo interference to those currently occupying the spectrum, as represented by those users owning licenses to certain frequency bands. In general, the FCC is interested in making the most of the available spectrum as well as trying to foster competition among different technologies.
The FCC first initiated a Notice of Inquiry (NOI) in September of 1998, which solicited feedback from the industry regarding the possibility of allowing UWB emissions on an unlicensed basis following power restrictions described in the FCC Part l5 rules. The FCC Part l5 rules place emission limits on intentional and unintentional radiators in unlicensed bands. These emission limits are defined in terms of microvolts per meter (uV/m), which represent the electric field strength of the radiator. In order to express this in terms of radiated power, the following formula can be used. The emitted power from a radiator is given by the following:
Where Eo represents the electric field strength in terms of V/m, R is the radius of the sphere at which the field strength is measured, and η is the characteristic impedance of a vacuum where η = 377 ohms. For example, the FCC Part 15.209 rules limit the emissions for intentional radiators to 500u V/m measured at a distance of 3 meters in a 1MHz bandwidth for frequencies greater than 960MHz. This corresponds to an emitted power spectral density of -41.3dBm/MHz.
In May of 2000, the FCC issued a Notice of Proposed Rule Making (NPRM), which solicited feedback from the industry on specific rule changes that could allow UWB emitters under the Part l5 rules. More than 500 comments have been filed since the first NOI, which shows significant industry interest in this rule-making process. Figure 3 below shows how the current NPRM rules would limit UWB transmitted power spectral density for frequencies greater than 2GHz.
The FCC is considering even lower spectral density limits below 2GHz in order to protect the critical Global Positioning System (GPS) even more, but currently no upper boundary has been defined. Results of a National Telecommunications and Information Administration (NTIA) report analyzing the impact of UWB emissions on GPS, which operate at 1.2 and 1.5GHx, was recently published and suggests that an additional 20-35dB greater attenuation, beyond the power limits described in the FEE Part l5.209, may be needed to protect the GPS band. However, placing proper spectral density emission limits in the bands that may need additional protection wile still allow UWB systems to be deployed in a competitive and useful manner while not causing an unacceptable amount of interference on other useful services sharing the same frequency space. This report, and others, will be carefully considered by the FCC prior to a final ruling.
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