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ppt.... paper presentation on mobile communication...


Posted Date: 03-Jul-2009  Last Updated:   Category: Education    
Author: Member Level: Bronze    Points: 15






ABSTRACT



Mankind has come across many stages right from ancient Stone Age to the modern wireless age. In every stage it developed its own unique method of communication to suit its requirements. These methods range from Graham Bell’s cabled telephones to today’s wireless mobile handsets. But if there could be a technology such that the waves could surpass any obstacles like hard walls or the hard earth etc… isn’t it wonderful like a dream?

It isn’t a dream anymore!!! The new technology called ULTRA WIDE BAND has brought all our dreams come true with many features to add.

It has

• A band width extending 25%of the center frequency
• Speeds of 1Giga bits per second
• See through capability
• Less power requirement
• Superior performance over all the existing technologies.

And many more…

This paper discusses what this technology is and how it is capable of all these features. Further it discusses wide range of applications in communication field and how it is yet to revolutionize the Mobile Communications.





INTRODUCTION

Mobile communications field has tremendously revolutionized in the past few decades. Day- by- day many new features are getting added. Today one is able to view running images on the small screen of the mobile handset. Such features demand for very high speeds showing way to the emergence of new and capable technologies. Ultra wide band has been described as one of the most promising technologies of our times. Early Ultra wide band systems were developed mainly as a military surveillance tool because they could see through trees and beneath ground surfaces. UWB is true digital radio communication, a series of very short electrical pulses (billionths of a second) that exist not on any particular frequency, but on ALL frequencies simultaneously. It is just a blast of electrical noise. In order to hear the information in that code, a UWB receiver has to know exactly WHEN to listen in order to hear. This makes UWB very secure. UWB is pretty much immune to eavesdropping, interference or jamming.
UWB requires ultra low power, often one ten thousandth as much as a cell phone, and because of that low power it is undetectable by conventional radios, looking to them just like very quiet noise. Besides UWB has important friends companies like Intel, IBM, Motorola and Texas Instruments that are committed to making UWB chipsets or have invested in uwb startups. A UWB phone uses so little power it can remain on for weeks without recharging and UWB will ultimately be cheaper to make than conventional radios since it is built entirely of commercial grade computer chips and requires no tuning. These are some of the unique characteristics posed by this new technology. Because of this it is completely irresistible to put this technology to use.



Prevalent Technologies:

WiFi, WiMax, 802.20, woznet etc are the prevalent technologies leading the wireless field today. Let us look at this table comparing these technologies in speed, coverage, their advantages and disadvantages.




Main Disadvantage:
The main disadvantage of the above mentioned technologies is that of
security.
The new technology that is coming as a solution to the disadvantages of all these prevalent technologies is the base band, Zero carrier ULTRA WIDE BAND technology that can drive data at the rates of 1Giga bits per second. UWB emits background noise as harmless as the static produced by laptop PCs. It operates at one-millionth of the power of a cell phone and many more…

ULTRA WIDE BAND- A new technology with thousands of potential applications
UWB is an impulse, base band or zero carrier technology transmitting very short duration pulses often of duration of nanoseconds or even less. UWB systems transmit signals across a much wider frequency than conventional systems and are usually very difficult to detect.
The bandwidth of UWB signal is at least 25% of center frequency. The minimum bandwidth of a UWB signal centered at 4GHz would be 1GHz. This allows it to deliver data rates in excess of 100Mbps using a small amount of power and operating in the same bands as existing communications without producing significant interference.

Unique characteristics:

• Extremely difficult to intercept
• High data rate capability for communications
• Fine range resolution capability for radar
• Multi path immunity
• Common architecture for communications, radar & positioning
• Low cost, nearly “all-digital architectures”

Advantages of UWB:
• Very low transmit power
• Data rates in excess of 100Mega-bits per second
• Does not cause interference to other radio system
• UWB devices can be co-located with GPS and PCS systems
• UWB receivers can use range information to reduce interference further, optimize network configuration and traffic flow.
• UWB’s strong resolution capability also improves the performance of the radio

Ultra Wide Band- A descriptive overview:-

UWB technology offers very effective solutions for various communications and sensing applications, but its uncommon approach of using narrow pulses, or impulses, as a basic signal structure rather than generating and modulating a sinusoidal carrier results in an unusually wide emission bandwidth. Since such a wide signal covers many radio bands and services, the conditions under which it can operate without causing undue interference must be determined before UWB systems are allowed to proliferate.
The use of a carrier signal by nearly all existing services that share the radio spectrum helps ensure that the bandwidth of the emissions of those signals can be kept as narrow as possible for any given application, i.e. the bandwidth required to transmit the information of interest or perform the necessary sensing functions. This approach allows for effective and efficient spectrum management and frequency assignment procedures for sharing of the radio spectrum among diverse applications and users.
UWB is alternately referred to as impulse, base band or zero-carrier technology. Ultra-wideband systems operate coherently across a wide range of frequency spectrum relative to the center frequency. This wide relative bandwidth governs how immune the radio will be to multi path interference while simultaneously penetrating walls or other material. A UWB signal can be typified by a series of low-power derivative-of-Gaussian pulses.
Each pulse is extremely short in duration, typically much shorter than the interval corresponding to a single bit. This pulse shape is similar to the unintentional emissions generated by consumer electronics devices. The radiated signal is often less than a PC is allowed to radiate unintentionally. Because of the short duration of the pulses, the frequency spectrum of a UWB signal can be many gigahertz wide, overlaying the bands used by existing narrowband systems.

How security problem is solved:

It is just a blast of electrical noise. The key to turning that noise into communication lies in the timing of the pulses that beat out a code. But in order to hear the information in that code, a UWB receiver has to know the exact pulse sequence used by the transmitter. In other words, with UWB you have to know exactly WHEN to listen in order to hear. This makes UWB very secure.
Figure below shows examples; (a) is a narrow impulse about 1.5 ns in length from one of the UWB


Figure(a) : An example of a short UWB pulse

Figure(b) is a longer, very complex pulse shape about 15 ns in length from a different device. The former occupies about 3.5 GHz of spectrum and the latter about a fifth or sixth of that.


Figure (b): An example of a long UWB pulse

Although some devices generate an impulse like that shown above in 1(a), when radiated by an antenna, the impulse may be changed quite dramatically. Figure 1(c) shows what the pulse shown in (a) is like after being radiated by an antenna designed to radiate UWB signals.


Figure (c): The shape of the pulse shown in (a) radiated in space


As a result of UWB’s distribution of energy, the spectral density is extremely low. A UWB radio will probably less than 75 nano watts of power per Megahertz of frequency bandwidth. This will be equivalent to an aggregated power of 0.26 milli watts in contrast to 1mW to 1W for Bluetooth radios.

Disadvantages of UWB:
• Range is limited to around one kilometer UWB trades bandwidth for distance, so longer links are slower.
• UWB will raise the noise threshold for the radio astronomers.
Major UWB Application Areas:-

• Surveillance Systems
• Medical Systems
• Through-wall Imaging Systems
• Wall Imaging Systems
• Ground Penetrating Radar Systems

In my View:-

As it can be seen - the ultra wide range applications of Ultra Wide Band among wireless communications, it is an open secret that this technology can come as a threat to the existing technologies within near future. Though the coverage range is only one kilometer, this is only the beginning. It is surprising that a no carrier base band signal can travel so fast (1Giga bits per second) and still cover one kilometer. Revolutionary changes can be expected in the field of Mobile communications with the dream speeds coming true some day.

• Using a narrow band carrier for the signal modulation may increase the coverage range without compromising with the large bandwidth it poses.
• UWB is not restricted only to wireless communications. It can also travel through cables and wires yielding 1Giga bits per second- data rate
So, this may lead us back to older wire-communications, but at faster speeds.


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