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A Survey of Ultra Wideband Technology

by Pragnesh Patel (Author) Hardik Modi (Author)

Research Paper (undergraduate) 2015 5 Pages

Communications - Miscellaneous

Excerpt

Ultra Wideband Technology: Overview

Pragnesh V Patel and Hardik K Modi

Abstract— Ultra wideband technology has great potentials to enhance the wireless technologies as compared to conventional narrow band technology. Because of this fact researchers are attracted towards this band. A report in February 2002 by Federal Communication Commission was issued which was a major breakthrough for UWB Technology. FCC had approved the band of 3.1 GHz to 10.6 GHz for unlicensed use for indoor and outdoor applications in the USA. Our paper gives brief introduction in section 1 followed by reasons for using this technology in section 2. Section 3 describes the spectral mask implemented by various countries and section 4 describes the application of this technology. Section 5 discusses the types of ultra wideband communication systems and Section 6 concludes the paper.

Index Terms— Narrow Band Technology, Ultra Wideband Technology, Power Spectral Density, Bandwidth.

I. INTRODUCTION

The frequency regulatory agency in United States, Federal Communications Committee (FCC) has defined Ultra Wideband Systems according to the bandwidth occupied. If absolute bandwidth of any communication system is greater than 500 MHz with center frequency above 2.5 GHz qualify as Ultra Wideband System (UWB). Also if we take fractional bandwidth of communication system into consideration, a system can be called as UWB System only if the fractional bandwidth is greater than 0.2 and at the same time central frequency is less than 2.5 GHz.5

Mathematically, Fractional bandwidth is defined as

illustration not visible in this excerpt

Where B is bandwidth of Ultra Wideband System and is central frequency.

[illustration not visible in this excerpt]is also defined mathematically as [illustration not visible in this excerpt]

Where [illustration not visible in this excerpt] are high and low frequency where the power spectral density is - 10 db below to that of [illustration not visible in this excerpt]

On substituting [illustration not visible in this excerpt] we get the below equation

illustration not visible in this excerpt

It is pictorially explained in figure below

Pragnesh V Patel is a Graduate student at San Diego State University, 92115 CA. He is working as Research Assistant of Dr. MahaSweta Sarkar at San Diego State University.(e-mail : pvpvrp@gmail.com)

Dr. Hardik Modi is working as Associate Professor at Charotar University of Science and Technology, Gujarat, India. He has Phd degree in Electrical Engineering from the same university (CHARUSAT, Changa). (e-mail: hardikmodi.ec@charusat.ac.in)

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Figure 1 Lower, Central and Higher Frequency for any communication system10

There are several constraints on Transmitter power level of Ultra Wideband Communication systems imposed by Federal Communication Committee in order avoid any interference caused to existing communication systems. A huge bandwidth of 7.5 GHz having lower frequency at 3.1 GHz and higher frequency at 10.6 GHz was made available unlicensed. This made it easy for industry and researchers to develop products. Thus Ultra Wideband technology has great potentials to free people from wires and have wireless links between multiple devices for video, audio and other bandwidth hungry applications exchange.

II. REASONS FOR USING UWB TECHNOLOGY

Ultra Wideband has frequency from range of 3.1 GHz to 10.6 GHz. Examining at the basic relation between antenna size and wavelength we can give the very first reason for using Ultra Wideband Technology.

The relation between frequency and wavelength is [illustration not visible in this excerpt] . Thus increase in f, the value of [illustration not visible in this excerpt] goes down as c is constant and [illustration not visible in this excerpt] and f are inversely related to each other. The length of dipole is [illustration not visible in this excerpt] and thus low value of results in smaller size of antenna. Ultra Wideband Communication systems do not require any carrier frequencies. Thus this reduces the complexity of transmitter and receiver operating in Ultra Wideband frequency range. This further reduces the die size. Ultra wideband communication systems are highly immune to multipath fading and are best choice for indoor applications. Moreover Ultra Wideband Communication systems occupy 500 MHz of bandwidth around the center frequency as compared to very less bandwidth of narrow band communication systems.

There exists a relationship between bandwidth occupied by channel and data rate / channel capacity. This relationship is defined by Shannon Hartley theorem given as

illustration not visible in this excerpt

Where C is channel capacity, B is bandwidth and is average signal to noise ratio.

Thus from the theorem we can state that Ultra Wideband systems have higher data rate as compared to narrow band technology. Any increase in [illustration not visible in this excerpt] will also cause increase in channel capacity C. But the increase will not be significant as there exists logarithmic relation between them. But increase in B will have more effect as C and B are related directly to each other. Thus Ultra Wideband communication system is more effective in providing high data rate for short range communication.[2,3]

III. REGULATIONS WORLDWIDE

Among all the natural renewable resources that we humans have its only radio spectrum where we face a lot of scarcity. Scarcity faced is not uniform across the globe. Demand rises in certain areas where as there are places where demand is low. To meet up this scarcity there are various organizations that play vital role in management of radio resource spectrum. The masks for Ultra Wideband changes from country to country which is explained later in this section.

Although Ultra Wideband has very large bandwidth but it does not come for free. We have to take care that this large bandwidth radio systems does not interfere with existing narrow band systems. To make sure there are many organizations working worldwide. All organizations have set up their standards and regulations according to their needs. In United States, FCC regulates the frequency spectrum and rules for Ultra Wideband communication systems are decided by them which are discussed in earlier part of the paper.

1. European Regulations

Regional organizations of Europe are mainly responsible for efficient management of Radio Spectrum. The major organizations across Europe are CEPT (European Conference of Postal and Telecommunications Administration) and ECC (Electronic Communications Committee). ECC works to make sure that radio frequencies are used harmonically.

illustration not visible in this excerpt

Figure 2: Ultra Wideband Mask in Europe4

The 3.1 GHz to 10.6 GHz band is divided into two parts based on indoor and outdoor applications. The indoor applications can use frequency band from 3.4 GHz to 4.8 GHz with mean power density restriction equal to - 41.3 dBm / MHz EIRP. The frequency band from 6 GHz to 8.5 GHz can be used for both indoor and outdoor applications. The mean power density restriction is same as - 41.3 dBm / MHz EIRP which is also same as FCC regulations. The 3.4 GHz to 4.8 GHz band has to be used with certain mitigation techniques finalized by ECC.

2. Japanese and Korean Regulations

The band from 3.1 GHz to 3.4 GHz is allocated to Robotics and Automation Society of Japan. Band from 3.4 GHz to 4.2 GHz is used by Satellite communications operator and can be used for UWB communication systems by using mitigation techniques. Also the band from 4.2 GHz to 4.8 GHz is reserved for 4G communications but UWB systems can use that band after using mitigation techniques. If no mitigation techniques are applied then the transmitting power has to be as low as - 70 dBm/MHz. The band for 6 GHz to 7.25 GHz is allocated to TV news gathering and hence it is not used.6

illustration not visible in this excerpt

Figure 3 Japanese UWB Mask6

For South Korea, the band from 6 GHz to 7.2 GHz is reserved for licensed service. For operations in 3.1 GHz to 4.8 GHz Detect and Avoid mitigation technique is needed.

illustration not visible in this excerpt

Figure 4 Korean Regulations6 ]

3. United States Regulations

In United States, FCC approved band from 3.1 GHz to 10.6 GHz in 2001. The figure below shows the mask approved by FCC for indoor applications. The mean power is limited to - 41.3 dBm/MHz. [6,14]

illustration not visible in this excerpt

Figure 5 UWB Mask in USA7

IV. APPLICATIONS OF UWB TECHNOLOGY

According to8, the major application of Ultra Wideband technology is classified into three parts namely Communications and sensors, Position location19 and tracking and radar.

illustration not visible in this excerpt

Figure 6 Power Spectral Density of Ultra Wideband Signals 9

It can be concluded from the figure that the power spectral density of UWB signals is almost equal to that of noise. Thus with such low power spectral density UWB systems can operate with narrow band communication systems without causing any undue interference.

Infrared and Ultrasonic Technology covers most of the indoor applications market today. Problem with infrared is Line of sight and Ultrasonic has less penetration depth. Computer hardware such as mouse, keyboard, printer etc can be connected to each other wirelessly using UWB signals. Similarly UWB signals can also be used for wireless sensor area networks. In10 such a network was implemented which is shown in figure below

illustration not visible in this excerpt

Figure 7 Wireless sensor network using UWB technology 10

UWB technology stands to be best technology for WBAN applications. This is because the transmitter has very less complexity and thus uses less power giving extended battery life. A UWB sensor network of electrocardiogram, Oxygen saturation sensor, Temperature sensor etc can be used to develop a smart healthcare system 13. Large video screen that stream videos wirelessly from internet can be benefited from UWB Technology. One such product is shown in figure is from Samsung Electronics made specifically for Asia Pacific region.

illustration not visible in this excerpt

Figure 8 Samsung Product for wireless multimedia transfer 11

There are several radar applications of short pulse UWB techniques such as range measurement and resolution, increased detection for certain targets that fall under certain class and ability to detect minor changes such as breathing the air or pumping of heart [10, 13, 14]. UWB signals have ability to penetrate wide range of materials such as plastic, wood, concrete etc. Also UWB technology is major candidate in micro air vehicles applications.12 There are many other field where this technology is investigated. Wide Body Area Networks would be most benefited field from these communication technology when it gets deployed fully. There are many group across United States and other countries that are working in these field.15

UWB Technology finds application for human imaging too. It has competition from narrow band microwave radar17, acoustic infrared along with UWB Microwave radar [18-19]. The comparison for all technology is listed in the table with the parameters for comparison as resolution, wall penetration, motion tracking and day/night operation.

illustration not visible in this excerpt

Table 1 Comparison of Technology16

illustration not visible in this excerpt

Figure 7 Wireless sensor network using UWB technology10

V. ULTRA WIDEBAND PULSE GENERATION

In general, all wireless communication systems either work on single band or multi band. Single band systems are the systems that work on single parameter mostly frequency. The wireless system connecting our TV remotes with TV sets is simplest example of it. Some wireless systems work on multi band that apply multiple frequencies to complete the communication. Similarly Ultra wideband systems are also classified into two kinds of systems which are discussed above. Irrespective of the band used the central frequency must have bandwidth of 500 MHz.

The single band communication systems generate UWB signals using very short low power electrical pulses. Due to carrier less characteristics of UWB systems we don’t need to generate sine waves in order to modulate information.20 This property of UWB signals gives UWB system new names like carrier less system or Impulse based Radio. The transmitter circuit is less complex as compared to narrow band communication system as carrier signal is not required. Thus RF devices needed in front end design is less compared to conventional narrow band systems.21 There is no need of local oscillator to generate UWB pulses at transmitter side. Mostly Gaussian monocycle and its derivative are used. For single band communication system the receiver also has simple circuit as we don’t need local oscillator and IF Mixer circuits.

For multi band communication systems, there are two methods carrier less and carrier based. Carrier based systems are UWB OFDM systems in which bandwidth is divided into many sub bands. Depending upon the multi band or single band communication system, the needs for the antenna is decided. The antenna used in multi band communication system needs to have flat gain over entire band as compared to linear phase. Linear phase enjoys same priority as that of gain in single band communication systems. Thus choosing of antenna depends completely on what kind of systems it is.22 For multiband communication systems, the receiver is complex as it has to sweep whole frequency range to detect signal. After detection of signal, extra circuitry is needed to transfer the incoming signal to Intermediate Frequency so that further processing can be made easy.

VI. CONCLUSION

For varieties of wireless applications, Ultra Wideband Technology can be termed as leading technology. For BAN applications this technology is best suit as it is very power efficient. Applications for commercial as well as government purposes can be develop easily. In these paper the world wide UWB regulations were discussed and thus it shows that product of one country can be used in other countries only under certain conditions.

[...]


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Available: http://uwbegypt.tripod.com/appendix_a.html

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10 Lower, Central and Higher Frequency for any communication system

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Pages
5
Year
2015
ISBN (eBook)
9783656953647
File size
866 KB
Language
English
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v298801
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Title: A Survey of Ultra Wideband Technology