UWB is a wireless technology that transmits binary dataâ€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 15â€100 m. It doesnâ„¢t use carrier wave to transmit data.
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.
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
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.
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 Ëœ1â„¢ is differentiated from a Ëœ0â„¢ either by the size of the signal or when it arrives in time â€œ but all the pulses are the same shape. A more efficient approach, bi-phase ultra-wideband, is also being deployed. Bi-phase differentiates a Ëœ1â„¢ with a Ëœright-side-upâ„¢ pulse and a Ëœ0â„¢ with an Ëœupside-downâ„¢ 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)â€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)â€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)â€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.
Â¢ PULSE POSITION MODULATION (PPM)
Encodes information by modifying the position of the pulse
Â¢ PULSE AMPLITUDE MODULATON (PAM)
Determines whether a pulse is a Ëœ1â„¢ or Ëœ0â„¢ based on the size of the pulse.
Â¢ ON-OFF KEYING
Determines a Ëœ0â„¢ by the absence of a pulse and Ëœ1â„¢ by the presence of a pulse
Reads forward and backward pulses as either Ëœ0â„¢or Ëœ1â„¢
Why is UWB so Effective
The Hartley-Shannon Law â€œ
C =B log 2(1+S/N)
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.
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.
Â¢ 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.
Â¢ 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.
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.
Doesnâ„¢t suffer from multi-path interference.
High data carrying capacity.
It need only low power.
Low energy density.
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.
UWB is not a long â€œrange 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.
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.
1. IEEE Communications Magazine, July 2003
2. Everyday Practical Electronics, January 2003
3. Nikkei Electronics Asia, April 2003
4. Digital Communication, J Proakis
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 seminars.
I also thank all the other faculty members of AEI department and my friends for their help and support.
Â¢ INTRODUCTION 1
Â¢ ULTRA WIDE BAND 3
Â¢ INNER WORKINGS 9
Â¢ APPLICATION 13
Â¢ ADVANTAGES 15
Â¢ DISADVANTAGES 16
Â¢ CONCLUSION 17
Â¢ REFERENCES 18