SEMINAR REPORT on Ultra Wide Band(UWB)

A SEMINAR REPORT ON

RF transmission based on Microwave UWB Submitted in partial fulfilment of the requirements for the award of the degree of

BACHELOR OF TECHNOLOGY In

ELECTRONICS AND COMMUNICATION ENGINEERING

Submitted by

VINOD V: 07402144 DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING SREE CHITRA THIRUNAL COLLEGE OF ENGINEERING THIRUVANANTHAPURAM 695 018 NOVEMBER 2010

SREE CHITRA THIRUNAL COLLEGE OF ENGINEERING, THIRUVANANTHAPURAM - 695 018. DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING.

CERTIFICATE Certified that seminar work entitled “RF transmission based on Microwave UWB” is a bonafide work carried out in the seventh semester by “VINOD V (07402144)” in partial fulfilment for the award of Bachelor of Technology in “ELECTRONICS AND COMMUNICATION ENGINEERING” from University of Kerala during the academic year 2010-2011, who carried out the seminar work under the guidance and no part of this work has been submitted or published any where earlier for the award of any degree.

SEMINAR CO-ORDINATOR

HEAD OF THE DEPARTMENT

SUBHA V Lecturer, Department of ECE SCT College of Engineering Thiruvananthapuram-18

S.VAIDYANATHAN Professor, Department of ECE SCT College of Engineering Thiruvananthapuram-18

ACKNOWLEDGEMENT I owe a great many thanks to a great many people who helped and supported us during the making of this seminar. My deepest thanks to Ms Subha.V, lecturer in Electronics and Communication Engineering, Sree Chitra Thirunal College of Engineering, Trivandrum, the seminar co-ordinator for guiding and correcting various documents with attention and care. They have taken pain to go through the seminar and make necessary corrections as and when needed. I gratefully obliged to thank Prof. S.Balachandran, Principal, Sree Chitra Thirunal College of Engineering, Trivandrum and Prof. S.Vaidyanathan, Head of the Department, Department of Electronics & Communication Engineering for their timely assistance during the course of this seminar. I would like to thank our institution and our faculty members without whom this seminar would have been a distant reality. I also extend our heartfelt thanks to our families and well wishers. Last but not the least I would like to express our gratitude to God almighty. Vinod V

ABSTRACT Ultra-wideband (UWB) transmission has recently received great attention in both academia and industry for applications in wireless communications. It was among the CNN’s top 10 technologies to watch in 2004. A UWB system is defined as any radio system that has a 10-dB bandwidth larger than 20% of its center frequency, or has a 10-dB bandwidth equal to or larger than 500 MHz, The recent approval of UWB technology by Federal Communications Commission (FCC) of the United States reserves the unlicensed frequency band between 3.1 and 10.6 GHz (7.5 GHz) for indoor UWB wireless communication systems. It is expected that many conventional principles and approaches used for short-range wireless communications will be reevaluated and a new industrial sector in short-range (e.g., 10 m) wireless communications with high data rate (e.g., 400 Mbps) will be formed. Further, industrial standards IEEE 802.15.3a (high data rate) and IEEE 802.15.4a (very low data rate) based on UWB technology have been introduced. The design and implementation rules are outlined and described in http://www.wimedia.org/ & http://www.uwbforum.org/

TABLE OF CONTENTS LIST OF FIGURES

i

LIST OF TABLES

ii

CHAPTER TITLE

1.0

PAGE NO:

INTRODUCTION

1

1.1.

History and Background

2

1.2.

FCC Emission limits

3

1.3.

UWB Concepts

4

1.4.

UWB Signals

5

2.0

WHY UWB

7

3.0

BAND-PASS UWB

11

3.1

11

Filter Technologies

4.0

MULTIBAND-OFDM APPROACH

14

5.0

IR-UWB vs. MB-OFDM

19

6.0

LNA ARCHITECTURE

20

7.0

UWB ANTENNAS

22

8.0

UWB VS. SPREAD SPECTRUM

24

9.0

UWB APPLICATIONS

25

9.1

UWB Radar

27

9.1.1 Measuring method

28

9.1.2 UWB radar over NB radar

29

9.1.3 Position Estimation Techniques

30

10.

CHALLENGES TO UWB

33

11.

CONCLUSION

34

REFERENCES

35

APPENDIX

36

LIST OF FIGURES FIGURE

NAME

PAGE NO:

FIG. 1.1

UWB History

2

FIG. 1.2

FCC Emission limits

3

FIG. 1.3

UWB and Narrowband

4

FIG. 1.4(a)

UWB Wavelet

5

FIG. 1.4(b)

Wavelet generation

6

FIG.2.1

Coexistence with NB

7

FIG. 3

Band-pass UWB

11

FIG. 3.1(a)

UWB Filter response

12

FIG. 3.1 (b)

Micro-strip filter

13

FIG. 3.1 (c)

UWB Notch filter

13

FIG. 4 (a)

DS-UWB 3.1 to 5 GHz

15

FIG. 4 (b)

DS-UWB 6 to 10.6 GHz

15

FIG. 4 (c)

MB-OFDM

16

FIG. 4 (d)

MB-OFDM Generation

17

FIG. 4(e)

MB-OFDM with CR

18

FIG. 6(a)

LNA Architecture

20

FIG. 6 (b)

Impedance matching

20

FIG. 6 (c)

Interference suppression

21

i

FIG. 7

UWB Antennas

23

FIG. 8

UWB vs. Spread Spectrum

24

FIG. 9

OPPN

26

FIG. 9.1

SRR

27

FIG. 9.1.3 (a)

UWB position estimation

30

FIG. 9.1.3 (b)

UWB position estimation- Setup

31

LIST OF TABLES TABLE

NAME

PAGE NO:

TABLE.1.3

UWB, WB & NB

4

TABLE.4

MB-OFDM Generator

17

TABLE.5

MB-OFDM vs. DS-UWB

19

TABLE.7

Antenna design

23

TABLE.10

UWB Interference

33

ii

1. INTRODUCTION Every radio technology allocates a specific part of the spectrum; for example, the signals for TVs, radios, cell phones, and so on are sent on different frequencies to avoid interference to each other. As a result, the constraints on the availability of the RF spectrum become more and stricter with the introduction of new radio services. Ultra-wideband (UWB) technology offers a promising solution to the RF spectrum drought by allowing new services to coexist with current radio systems with minimal or no interference. This coexistence brings the advantage of avoiding the expensive spectrum licensing fees that providers of all other radio services must pay. This seminar provides a comprehensive overview of ultra-wideband Communications.

1

1.1 History and Background

FIG. 1.1 UWB History

Ultra-wideband communications is not a new technology; in fact, it was first employed by Guglielmo Marconi in 1901 to transmit Morse code sequences across the Atlantic Ocean using the spark gap radio transmitters. However, the benefit of a large bandwidth and the capability of implementing multiuser systems provided by electromagnetic pulses were never considered at that time. Approximately fifty years after Marconi, modern pulse-based transmission gained momentum in military applications in the form of impulse radars. Some of the pioneers of modern UWB communications in the United States from the late 1960s are Henning Harmuth of Catholic University of America and Gerald Ross and K. W. Robins of Sperry Rand Corporation. From the 1960s to the 1990s, this technology was restricted to military and Department of Defense (DoD) applications under classified programs such as highly secure communications. However, the recent advancement in micro processing and fast switching in semiconductor technology has made UWB ready for commercial applications. Therefore, it is more appropriate to consider UWB as a new name for a long-existing technology. As interest in the commercialization of UWB has increased over the past several years, developers of UWB systems began pressuring the FCC to approve UWB for commercial use. In February 2002, the FCC approved the First Report and Order (R&O) for commercial use of UWB technology under strict power emission limits for various devices. 2

1.2 Fcc Emission Limits

FIG. 1.2- UWB FCC Emission In order to protect existing radio services from UWB interference, the FCC has assigned conservative emission masks between 3.1 GHz and 10.6 GHz for commercial UWB devices. The maximum allowed power spectral density for these devices—that is,–41.3 dBm/MHz, or 75 nW/MHz—places them at the same level as un-intentional radiators (FCC Part 15 class) such as televisions and computer monitors. The spectral mask for outdoor devices is 10 dB lower than that for indoor devices, between 1.61 GHz and 3.1 GHz, as shown in above Figure 1.2. According to FCC regulations, indoor UWB devices must consist of handheld equipment, and their activities should be restricted to peer-to-peer operations inside buildings. The FCC’s rule dictates that no fixed infrastructure can be used for UWB communications in outdoor environments. Therefore, outdoor UWB communications are restricted to handheld devices that can send information only to their associated receivers.

3

1.3 Uwb Concepts

FIG. 1.3- UWB & Narrowband

TABLE.1.3 – UWB, Wide band, & Narrow Traditional narrowband communications systems modulate continuous waveform (CW) RF signals with a specific carrier frequency to transmit and receive information. A continuous waveform has well-defined signal energy in a narrow frequency band that makes it very vulnerable to detection and interception. Above Figure 1.3 represents both narrowband & wideband signals in the time and frequency domains. UWB systems use carrier-less, short-duration (picoseconds to nanosecond) pulses with a very low duty cycle (less than 0.5 percent) for transmission and reception of the information.

4

Low duty cycle offers a very low average transmission power in UWB communications systems. The average transmission power of a UWB system is on the order of microwatts, which is a thousand times less than the transmission power of a cell phone! However, the peak or instantaneous power of individual UWB pulses can be relatively large, but because they are transmitted for only a very short time, the average power becomes considerably lower. Consequently, UWB devices require low transmit power due to this control over the duty cycle, which directly translates to longer battery life for handheld equipment. Since frequency is inversely related to time, the short-duration UWB pulses spread their energy across a wide range of frequencies—from near DC several gigahertz (GHz)—with very low power spectral density (PSD). The wide instantaneous bandwidth results from the time-scaling property of theoretical Fourier transforms.

1.4 Uwb Signals

FIG. 1.4(a) - UWB Wavelet

UWB modulates an impulse-like waveform (WAVELET) with Data. A typical baseband UWB pulse, also called mono-pulse, such as the Gaussian first derivative pulse can be used. UWB signals must have bandwidths of greater than 500MHz or a fractional bandwidth larger than 20 percent at all times of transmission. Fractional (relative) bandwidth is a factor used to classify signals as narrowband, wideband, or ultra-wideband and is defined by the ratio of bandwidth at –10 dB points to center frequency. 5

where fh and f1 are the highest and lowest cutoff frequencies (at the –10 dB point) of a UWB pulse spectrum, respectively. A UWB signal can be any one of a variety of wideband signals, such as Gaussian, chirp, wavelet, or Hermite-based shortduration pulses. Above Figure 1.4(a) represents a Gaussian monocycle as an example of a UWB pulse.

Wavelet Generation

FIG. 1.4(b) - Wavelet Generation

The development of laser-actuated semiconductor fast-acting switches that can produce impulses or short duration waveforms of one or several cycles has been of interest for UWB. The traveling wave tube (TWT) can be used. It can be excited with a narrow impulse, but its energy is limited by the peak power of the TWT.

6

2. WHY UWB? The nature of the short-duration pulses used in UWB technology offers several advantages over narrowband communications systems. Next, we discuss some of the key benefits that UWB brings to wireless communications.

2.1 Ability to Share the Frequency Spectrum

FIG. 2.1-Coexistence with Narrow band

UWB systems reside below the noise floor of a typical narrow-band receiver and enables UWB signals to coexist with current radio services with minimal or no interference as illustrated in FIG. 2.1.

2.2 Large Channel Capacity

One of the major advantages of the large bandwidth for UWB pulses is improved channel capacity. Channel capacity, or data rate, is defined as the maximum amount of data that can be transmitted per second over a communications channel.

7

The large channel capacity of UWB communications systems is evident from Hartley-Shannon’s capacity formula. Where C represents the maximum channel capacity, B is the bandwidth, and SNR is the signal-to-noise power ratio. As shown in Equation, channel capacity C linearly increases with bandwidth B. Therefore, having several gigahertz of bandwidth available for UWB signals, a data rate of gigabits per second (Gbps) can be expected. However, due to the FCC’s current power limitation on UWB transmissions, such a high data rate is available only for short ranges, up to 10 meters. This makes UWB systems perfect candidates for short-range, high-data-rate wireless applications such as wireless personal area networks (WPANs). The trade-off between the range and the data rate makes UWB technology ideal for a wide array of applications in military, civil, and commercial sectors.

2.3 Ability to Work with Low Signal-To-Noise Ratios The Hartley-Shannon formula for maximum capacity also indicates that the channel capacity is only logarithmically dependent on signal-to-noise ratio (SNR).Therefore, UWB communications systems are capable of working in harsh communication channels with low SNRs and still offer a large channel capacity as a result of their large bandwidth.

2.4 Low probability of intercept and detection Because of their low average transmission power, UWB communications systems have an inherent immunity to detection and intercept. With such low transmission power, the eaves-dropper has to be very close to the transmitter (about 1 meter) to be able to detect the transmitted information. In addition, UWB pulses are time modulated with codes unique to each transmitter/receiver pair. The time modulation of extremely narrow pulses adds more security to UWB transmission, because detecting picoseconds pulses without knowing when they will arrive is next to impossible. Therefore, UWB systems hold significant promise of achieving highly

8

secure, low probability of intercept and detection (LPI/D) communications that is a critical need for military operations.

2.5 Resistance to Jamming Processing gain (PG) is a measure of a radio system’s resistance to jamming and is defined as the ratio of the RF bandwidth to the information bandwidth of a signal. The frequency diversity caused by high processing gain makes UWB signals relatively resistant to intentional and unintentional jamming, because no jammer can jam every frequency in the UWB spectrum at once. Therefore, if some of the frequencies are jammed, there is still a large range of frequencies that remains untouched. However, this resistance to jamming is only in comparison to narrowband and wideband systems. Hence, the performance of a UWB communications system can still be degraded, depending on its modulation scheme, by strong narrow-band interference from traditional radio transmitters coexisting in the UWB receiver’s frequency band.

2.6 High performance in multipath channels The phenomenon known as multipath is

unavoidable in wireless

communications channels. It is caused by multiple reflections of the transmitted signal from various surfaces such as buildings, trees, and people. The straight line between a transmitter and a receiver is the line of sight (LOS); the reflected signals from surfaces are non-line of sight (NLOS). The effect of multipath is rather severe for narrowband signals; it can cause signal degradation up to –40 dB due to the out-of-phase addition of LOS and NLOS continuous waveforms. On the other hand, the very short duration of UWB pulses makes them less sensitive to the multipath effect. Because the transmission duration of a UWB pulse is shorter than a nanosecond in most cases, the reflected pulse has an extremely short window of opportunity to collide with the LOS pulse and cause signal degradation. 9

2.7 Superior penetration properties Unlike narrowband technology, UWB systems can penetrate effectively through different materials. The low frequencies included in the broad range of the UWB frequency spectrum have long wavelengths, which allows UWB signals to penetrate a variety of materials, including walls. This property makes UWB technology viable for through-the-wall communications and ground-penetrating radars (GPRs). However, the material penetration capability of UWB signals is useful only when they are allowed to occupy the low-frequency portion of the radio spectrum.

2.8 Simple transceiver architecture UWB transmission is carrier-less, meaning that data is not modulated on a Continuous waveform with a specific carrier frequency, as in narrowband and wideband technologies. Carrier-less transmission requires fewer RF components than carrier-based transmission. For this reason UWB transceiver architecture is significantly simpler and thus cheaper to build. The transmission of low-powered pulses eliminates the need for a power amplifier (PA) in UWB transmitters. Also, because UWB transmission is carrier-less, there is no need for mixers and local oscillators to translate the carrier frequency to the required frequency band; consequently there is no need for a carrier recovery stage at the receiver end. In general, the analog front end of a UWB transceiver is noticeably less complicated than that of a narrowband transceiver. This simplicity makes an all- CMOS implementation of UWB transceivers possible, which translates to smaller form factors and lower production costs.

10

3. BAND-PASS UWB

FIG. 3-Band-pass UWB Low energy, short duration UWB pulses modulates Input data. Microwave Spectrum controlled by impulse response of BPF in FIG. 3. Modulation scheme may be among PPM, OOK, or BPSK.

3.1 Filter Technologies UWB band-pass filter is a key component of UWB system. It must have an ultra wide pass-band, but also needs high selectivity to reject signals from existing systems such as 1.6 GHz global positioning systems (GPS) and 2.4 GHz Bluetooth systems. In addition, in some cases, the UWB band pass filter needs to introduce steeply notched frequency bands (FIG 3.1(a)) in order to reduce interference from existing NB radio systems located within the UWB pass-band. These requirements increase the challenges for the UWB filter designer.

11

However, since conventional filter theory is based on the narrowband assumption and cannot be used to design UWB band pass filters, novel techniques and technologies need to be developed for UWB band pass filter design.

FIG. 3.1(a)-UWB Filter response

12

Micro-strip Filter

FIG. 3.1(b)-Micro-strip Filter

Micro strip filters only become practical above 300MHz. It is a size issue. The inductance and capacitance of the micro strip line PCB traces to form the filter, rather than discrete inductors and capacitors.

FIG. 3.1(c)-UWB Notch Filter

13

4. MULTIBAND-OFDM APPROACH The ability of UWB technology to provide very high data rates for short ranges (less than 10 meters) has made it an excellent candidate for the physical layer of the IEEE 802.15.3a standard for wireless personal area networks (WPANs). However, two opposing groups of UWB developers are battling over the IEEE standard. The two competing technologies are single band and multiband. The single-band technique, backed by Motorola/XtremeSpectrum, supports the idea of impulse radio that is the original approach to UWB by using narrow pulses that occupy a large portion of the spectrum. The multiband approach divides the available UWB frequency spectrum (3.1 GHz to 10.6 GHz) into multiple smaller and non overlapping bands with bandwidths greater than 500 MHz to obey the FCC’s definition of UWB signals. The multiband approach is supported by several companies, including Staccato Communications, Intel, Texas Instruments, General Atomics, and Time Domain Corporation. To date, several proposals from both groups have been submitted to the IEEE 802.15.3a working group, and the decision is yet to be made because both technologies are impressive and have technical credibility. The following subsections discuss the two leading candidates for the 802.15.3a standard: direct-sequence UWB (DS-UWB) and multiband orthogonal Frequency division multiplexing (OFDM)

14

Direct-Sequence Uwb

FIG. 4(a)-DS-UWB 3.1 to 5 GHz

Above figure 4(a) shows DS-UWB with 3.1-to 5-GHz range band plan. And the below figure 4(b) shows DS-UWB with 6-to 10.6-GHz band plan

FIG. 4(b) - DS-UWB 6 to 10.6

Direct-sequence UWB is a single-band approach that uses narrow UWB pulses and time-domain signal processing combined with well-understood DSSS techniques to transmit and receive information. Data representation in this approach is based on simple bi-phase shift keying (BPSK) modulation, and rake receivers are used to capture the signal energy from multiple paths in a multipath channel. According to the proposals sent to the IEEE 802.15.3a standardization committee by the proponents of this technology, the DS-UWB technique is scalable and can achieve data rates in excess of 1 Gbps. The technical reason behind using DS15

UWB is the propagation benefits of ultra-wideband pulses, which experience no Rayleigh fading. In contrast, narrowband transmissions degrade significantly due to fading.

Multiband OFDM

FIG. 4(c)-MB-OFDM The multiband UWB approach uses the 7500 MHz of the RF spectrum available to UWB communications in a way that differs from traditional UWB techniques. The UWB frequency band is divided into multiple smaller bands with bandwidths greater than 500 MHz (FIG. 4(c)). This approach is similar to the narrowband frequency-hopping technique. Dividing the UWB spectrum into multiple frequency bands offers the advantage of avoiding transmission over certain bands, such as 802.11a at 5 GHz, to prevent potential interference. In the multiband approach, UWB pulses are not as narrow as in traditional UWB techniques; therefore, synchronization requirements are more relaxed. A variety of modulation techniques have been proposed by industry leaders for the multiband approach; however, OFDM, which was initially proposed by Texas Instruments, offers improved performance for high-data rate applications. In fact, both technologies are technically valid and impressive. Supporters of DS-UWB criticize the multiband OFDM systems for their complexity, which results from using complex Fast Fourier Transforms (FFTs). On the other side, advocates of multiband OFDM believe that their technique offers better coexistence with other radio services, and they disapprove of DS-UWB because of possible interference concerns. 16

The debate will likely continue until the IEEE 802.15.3a standardization committee reaches a decision.

Mb-OFDM Generation Method

FIG. 4(d)-MB-OFDM generation

PLL provides center frequencies for first three Groups “A” bands.

TABLE.4-MB-OFDM Generator

17

Integration of Multiband and Cognitive Radio (CR)

FIG. 4(e)-MB-OFDM with CR Cognitive Radio (CR) is an emerging approach for a more flexible usage of the precious radio spectrum resources. By investigations on the radio spectrum usage, it has been observed that some frequency bands are largely unoccupied most of the time, some other frequency bands are only partially occupied, and the remaining frequency bands are heavily used. A CR terminal can sense its environment and location and then adapt some of its features allowing to dynamically reusing valuable spectrum. This could lead to a multidimensional reuse (dynamical usage) of spectrum in space, frequency and time, exceeding the severe limitations in the spectrum and bandwidth allocations (FIG. 4(e)).

18

5. IR-UWB VS. MB-OFDM

TABLE.5-MB-OFDM vs. IR-UWB

19

6. LNA ARCHITECTURE Due to the wide bandwidth, classical narrow band LNA design techniques cannot be used. Feedback amplifier architecture, described in Figure 6(a), has been considered as a good candidate for wideband amplification due to its relative simplicity to provide flat gain and good 50 Ohms matching with respect to low noise.

FIG. 6(a)-LNA (Low Noise Amplifier)

Wideband Input Impedance Matching The main challenge in UWB designs is to extend matching to the wide frequency range of 3.1-10.6 GHz. The LNA has to exhibit good input impedance as in FIG. 6(b).

FIG. 6(b)-Impedance matching 20

NB interference suppression

FIG. 6(c)-NB Interference

A tunable center frequency RF “roofing filter” applied to the UWB NB interference mitigation problem as in FIG. 6(c). This filter will introduce significant group delay distortion in the pass band, and so spectral shaping of the transmitted waveform out of the interference band will also be required to minimize the resulting degradation in system performance. In the second case, an accurate estimation of the frequency, phase, and amplitude of the jammer is required to significantly reduce the interference level.

21

7. UWB ANTENNAS Antennas are particularly challenging aspect of UWB. If an impulse is fed to an antenna, it tends to ring, severely distorting the pulse and spreading it out in time. Also have poor matching and large reflections. Conventional wideband antennas such as the log-periodic and the spiral are wideband in amplitude, but not in phase; they distort the UWB signal. The best antennas for UWB are arrays of TEM horns. The higher the frequency the antennas can be equally small (FIG. 7). In UWB systems, antenna design is one of key technologies and has been widely investigated by both academia and industry. The antenna design considerations are strongly dependent on the modulation scheme, which the UWB systems are using, and applications. In general, MB-OFDM UWB wireless communication systems require the antennas which should have broadband response in terms of return loss, gain at the directions of interest, and /or polarization. Such requirements are almost the same as the designs for conventional broadband wireless systems but a required extremely broad bandwidth of 50% to 100% with a consistent gain response. However, additional attention must be paid for pulse-based UWB systems where the UWB antenna usually function as a band pass filter and tailor the spectra of the radiated/received pulses so that the waveforms distorted.

22

of radiated/received pulses are

TABLE.7-UWB Antenna design

FIG. 7-Antenna shapes

23

8. Uwb Vs Spread Spectrum

FIG. 8-UWB & SS

Although UWB and spread-spectrum (SS) techniques share the same advantage of expanded bandwidth as evident from FIG. 8, the method of achieving the large bandwidth is the main distinction between the two technologies. In conventional spread-spectrum techniques, the signals are continuous-wave sinusoids that are modulated with a fixed carrier frequency. In UWB communications, on the other hand, there is no carrier frequency; the short duration of UWB pulses directly generates an extremely wide bandwidth. Another distinguishing factor in UWB is the very large bandwidth. Spread-spectrum techniques can offer megahertz of bandwidth, while UWB pulses provide several gigahertz of bandwidth. Above figure 8 shows the time and frequency domain representation of narrowband, wideband, and UWB signals. The low transmission power could be a disadvantage for UWB systems, because the information can travel only short distances. Therefore, for long-range applications, spread-spectrum techniques are still more appropriate. 24

9. UWB APPLICATIONS The trade-off between data rate and range in UWB systems holds great promise for a wide variety of applications in military, civilian, and commercial sectors.

The FCC

categorizes UWB applications as radar,

imaging,

or

communications devices. Radar is considered one of the most powerful applications of UWB technology. The fine positioning characteristics of narrow UWB pulses enables them to offer high-resolution radar (within centimeters) for military and civilian applications. Also, because of the very wide frequency spectrum band, UWB signals can easily penetrate various obstacles. This property makes UWB-based ground-penetrating radar (GPR) a useful asset for rescue and disaster recovery teams for detecting survivors buried under rubble in disaster situations. In the commercial sector, such radar systems can be used on construction sites to locate pipes, studs, and electrical wiring. The same technology under different regulations can be used for various types of medical imaging, such as remote heart monitoring systems. In addition, UWB radar is used in the automotive industry for collision avoidance systems. Moreover, the low transmission power of UWB pulses makes them ideal candidates for covert military communications. UWB pulses are extremely difficult to detect or intercept; therefore, unauthorized parties will not get access to secure military information. Also, because UWB devices have simpler transceiver circuitry than narrowband transceivers, they can be manufactured in small sizes at a lower price than narrowband systems. Small and inexpensive UWB transceivers are excellent candidates for wireless sensor network applications for both military and civilian use. Such sensor networks are used to detect a physical phenomenon in an inaccessible area and transfer the information to a destination. A military application could be the detection of biological agents or enemy tracking on the battlefield. Civilian applications might include habitat monitoring, environment observation, health monitoring, and home automation.

25

The precise location-finding ability of UWB systems can be used in inventory control and asset management applications, such as tagging and identification systems—for example, RFID tags. Also, the good performance of UWB devices in multipath channels can provide accurate geo-location capability for indoor and obscured environments where GPS receivers won’t work. The high-data-rate capability of UWB systems for short distances has numerous applications for home networking and multimedia-rich communications in the form of WPAN applications. UWB systems could replace cables connecting camcorders and VCRs, as well as other consumer electronics applications, such as laptops, DVDs, digital cameras, and portable HDTV monitors. No other available wireless technologies—such as Bluetooth or 802.11a/b—are capable of transferring streaming video.

UWB Outdoor Peer-To-Peer Network (OPPN)

FIG. 9-UWB OPPN Downloading of video movie purchase or rental, for example, is a very dataintensive activity that could be enabled by UWB.

26

9.1 Uwb Radar (Short-Range Radar (SRR))

FIG. 9.1-UWB SRR The wide bandwidth of UWB signals implies a fine time resolution that gives them a potential for high-resolution positioning applications /Localization and tracking (LT)/ranging, provided that the multipath are dealt with. As of Short Pulse Width we can Resolve Multipath Components. Above Figure 9.1 demonstrates external views of this UWB radar model. The major specifications of the prototype are given be • Operation range 8 m; • Pulse power 10 mW; • Average power 80 ~W; • Width of the antenna’s pattern: 8° x 8°; and • Duration of radiated radio pulses 2 ns.

27

9.1.1 The Measuring Method of Uwb Radar While constructing UWB radars, as with constructing conventional narrowband radars, we use the property of electromagnetic waves to be scattered from a boundary of two media with different parameters. The short electromagnetic pulses radiated by radar are scattered by a moving object. The oscillation frequency within the pulse and the repetition frequency of pulses are changed owing to the Doppler Effect. The sign of these variations depends on the direction of target movement relative to the radar and the variation value depends on the object's radial velocity. According to this direction, the signal spectrum is going wider or narrower and moves toward high or low frequency areas. The radars work in conditions of high level of passive noise - the signals, reflected from walls and stationary objects, which will have large amplitude and will disguise useful signals. Time slots, opening the receiver at the moment of input of signal reflected from object at distance defined are formed in receiving path to eliminate interfering pulses. This task in radar design is executed by a time discriminator, being gated. It consists of fast-acting electronic switches. The switching time is on the order of 200-300 picoseconds. The switches connect the receiving antenna to the UWB amplifier at the moment of signal input. These moments are defined by a delay magnitude of the control signal at a softwarecontrolled delay line. All of the rest of the time, the receiver is closed. The signals received at time slots are detected and amplified in integrating amplifier and the signal, carrying data of target motion is selected at its output. The time constant of integration of integrating amplifier is chosen Independently of the bandwidth of the desired signal. For example, measuring a person's vital signs, the bandwidth of the desired signal is near 40 - 50 Hz, that corresponds to an accumulation of 10 - 30 thousands of pulses, approximately. The accumulation permits us to decrease the average radiated power of the transmitter and increase the signal-to-noise ratio at the input of the amplifier.

28

The selected and amplified low-frequency signal enters the analog-digital converter (ADC). The microprocessor-controlled unit directs the work of the radar on given algorithms, monitors the state of major units and modules, and provides data output for further digital processing in the computer. The selection of moving targets, fast Fourier transform, and digital filtration are software-programmable at the computer.

9.1.2 UWB Radar over NB Radar •

Higher range resolution and accuracy .Ultra High

Range

Resolution

(UHRR) •

enhanced target recognition

•

immunity to passive “interference”

•

immunity to co-located radar transmissions

•

signals scattered by separate target elements do not interfere

•

operational security because of the extremely large spectral spreading

•

ability to detect very slowly moving or stationary targets

•

Multiple targets can be resolved

•

With a long pulse NB radar waveform, changes in the target aspect cause a change only in the amplitude of the echo signal. With UWB signals, the echo signal will change, which makes efficient signal processing.

•

NB signal processing in radar almost always utilizes the envelope. With UWB waveforms, either the envelope or the RF signal can be used.

•

In indoor and dense urban environments the GPS signal is typically unavailable.

29

9.1.3 Position Estimation Techniques

FIG. 9.1.3(a) - Target in piconet

In the below set-up FIG. 9.1.3(b) Short-pulse RF emissions from the tags are subsequently received by either all, or a subset, of these sensors and processed by the central hub CPU.

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FIG. 9.1.3(b)-UWB position estimation

A set of three or more receivers (four receivers are typically used) are positioned at known coordinates within, or about the periphery of, the area to be monitored as in FIG 9.1.3(a). In order to comprehend the high-precision positioning capability of UWB signals, position estimation techniques should be investigated first. Position estimation of a node in a wireless network involves signal exchanges between that node (Called the target_ node; i.e., the node to be located) and a number of reference nodes (FIG. 9.1.3(b)). A central unit that gathers position information from the reference nodes and then estimates the position based on those signal parameters. Signal parameters, such as TOA (time-of-arrival), angle-of-arrival (AOA), TDOA (Time Difference of Arrival), RTD (Round Trip Delay) and/or received signal 31

strength (RSS) are estimated. Short-pulse RF emissions from the tags are subsequently received by receivers and processed by the central hub CPU. A typical tag emission consists of a short burst, which includes synchronization preamble, tag identification (ID), optional data field (e.g., tag battery indicator), and FEC bits. Time differences of arrival (TDOA) of the tag burst at the various receiver sites are measured and sent back to the central processing hub for processing. Calibration is performed at system startup by monitoring data from a reference tag, which has been placed at a known location.

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10. CHALLENGES TO UWB ► suspicious about the NB interference as shown in TABLE.10 ► extreme antenna bandwidth requirements ► very accurate timing synchronization need for correlation -based receiver ► Complex RAKE-type receiver to cope with significant amount of energy in the multipath ► filter matching accuracy ► timely approval from the regulatory bodies ► lack of an universal standard

TABLE.10-Systems degraded by UWB

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11. CONCLUSION With the recent advances in semiconductor device technology and the FCC’s approval of the unlicensed use of ultra-wideband systems, UWB development has moved from research labs and classified military projects to the commercial sector. UWB technology brings many opportunities as well as challenges to the world of wireless communications. UWB is a promising technology for the Next Generation Wireless Systems! Home audio systems and PCs without the confusing and messy cables, and even more tech savvy cell phones are the promise of UWB. Some people question whether UWB really will impact consumer life. A better question is when? There is a definite demand for the applications that can be developed using UWB. UWB also has a unique edge over competing technologies in its low cost and low power model. Unfortunately early regulatory division has split UWB implementers down the middle. Countries around the world have been reluctant to release radio spectrum for UWB use. The consequential lack of a universal standard must be addressed so consumers can reap the benefits of UWB.

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APPENDIX

AWICS BToUWB- Bluetooth over Ultra Wideband

DRACO IEEE 802.15.3a IEEE 802.15.4a

IEEE 802.15.6 ORION Precision Asset Location (PAL) System QUPID- QUick response Perimeter Intrusion Detection SPIDER UROOF UWB Endoscope UWB-MIMO

UWB SATCOM

UWB UMV Wireless USB

UWB Aircraft Inter communications system Bluetooth connection’s data over a software implemented UWB Medium Access Control (MAC) and simulated Physical (PHY) layer radio channel UWB Network Transceiver UWB HDR WPAN UWB LDR WSN Sensor, positioning, and identification network (SPIN) UWB Wearable LDR WBAN L-band UWB Transceiver UWB for detection of on-board items inside vehicles UWB radar used for guarding of objects in the room. GPR used as a backup sensor for a large mining vehicle UWB Radio Over Optical Fiber for UWB Network extension real-time diagnosis with high resolution images by UWB UWB-based Virtual-MIMO system for cellular network to provide better spatial diversity and higher system capacity UWB signals are radiated from satellites to the earth by which new satellite applications can be developed UWB UnManned Vehicle employing Vehicular collision avoidance by SRR UWB as the technology to achieve high data rates up to 480 Mbps

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