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1、Review This paper explores the state-of-the-art research and development of UWB applications in many sectors, including the construction industry. This paper will provide insights into the technology for the un-initiated reader without involving detailed technological and arithmetic aspects of UWB.

2、To do so, this paper first introduces the key concepts behind UWB and provides a brief historical perspective. It then summa-sizes the UWBs technical features which enable it so popular in industry.Finally, a number of UWB application examples in many sectors, including construction, are presented t

3、o analyze and highlight the impact on the industry performance. UWB technology is expected to become a very important component and have profound impact in ubiquitous computing in the near future.INRTODUCTIONThis paper provides an introduction to UWB technology. It presents UWB systems principles wh

4、ich characterize the function and composition of UWB system and brief history of UWB technology. Moreover, the UWBs technical features are summarized to facilitate profound understanding UWBs popularity. Specific emphasis is given to the UWB technologys applications in various industries including t

5、he construction industry.Definition of use of UWB systemsUWB wireless communications offers a radically distinct approach to wireless communication compared to traditional narrow band systems. According to the FCC, UWB is any signal that has a fractional bandwidth equal to or greater than0.20 or has

6、 a bandwidth equal to or greater than 500 MHz （Breed 2005）.UWB technologies can transmit extremely short and low power electro-magnetic pulses. The radio spectrum spreads over a very wide bandwidth （Shen et al.2008）. Due to its short pulse radio frequency （RF） waveforms and large bandwidth, UWB prov

7、ides fine time resolution and provides good potential for application in ranging and positioning and well immunity to multipath effects.The tags in UWB tracking system decide the localization dimensionality, reception by three or more receivers permits accurate 2D localization, while reception by fo

8、ur or more receivers allows for pre-cise 3D localization. If only one or two receivers can receive a tag transmission,proximity detection can also be readily accomplished （Khoury et al. 2009）.Commercially existing ultrawide band systems （see principle layout illustrated in Fig. 1） include the follow

9、ing （Teizer etal. 2008; Giretti et al. 2009）: Processing computer and hub including a graphical user interface; Minimum of four UWB receivers at different height levels to record real-time three-dimensional signal data in a field of view of 90 （mid-gain）, 60 （high gain）, and omni-directional;CAT-5es

10、hieldedwires（wires potentially to be replaced with a wireless signal transmission）; Low-and high -powered UWB tags （approved for safe use by FCC: 5mW, 1 W） with different emitting signal refresh rates of 1, 15, 30, or60 Hz, including one reference tag.The UWB system operates as follows:a set of 3 or

11、 more receivers are positioned at known coordinates about the periphery of the area to be monitored.Short-pulse RF emissions from tags are subsequently received by either all, ora subset, of these sensors and processed by the central hubs CPU. A typical tag emission consists of a short burst,include

12、d a set of data for ID purposes,repeated at given frequency（limited between 1 and 60 Hz）. Time differences of arrival （TDOA） of the tag burst at the various receivers are measured and sent back to the central processing hub. Calibration （i.e. signal speed measuring） is performed at system start up b

13、y monitoring data from a reference tag, which has been placed at the known location. Everyreceiver obtains its power from the central processing hub via standard CAT-5cables, which are also used to carry data back to the hub for subsequent processing （Giretti et al. 2009）A brief history of UWBAlthou

14、gh recently concerned extensive research interest, UWB technologys origin can date back to work in the early1960s on time-domain electromagnetic wave propagation. Bennett and Rosssummarized UWBs early application in a seminal paper （Bennett et al. 1978）.Ross was the first researcher to demonstrate a

15、n UWB communication system in1986. The first （1973） fundamental landmark patent on UWB communications systems simply referred to the techno-logy as “base-band pulse” （Ross 1973;Barrett 2000）. The term “UWB” originated with the Defense Advanced Research Projects Agency （DARPA） in a radar study undert

16、aken in 1990, serving as a convenient means for discriminating between conventional radar and those utilizing short-pulse waveforms having a large fractional bandwidth （Fontana 2004）.The early UWB systems were designed for military, low probability of detection radar, and communications applications

17、（Fontana 2004）. Until 1994, the majority of the work was performed under US government programs. With the rulings of the FEDERAL Communications Commission （FCC） under the U.S. government,after 1994, there has been an increase in nongovernmental related research and an increase in the number of UWB g

18、overnment agencies and companies that are greatly accelerating the development of UWB technology （Breed 2005） （Teizer et al. 2007）. In 2002, the FCC approved the unrestricted use of low-powered UWB systems and tags 5 milliwatts （mW）. By far, as one of the earliest civilian applications of UWB, Fonta

19、na et al. （Fontana et al. 2003） utilized UWB for accurate assets localization. First time of arrival（TOA） measurement was adopted to achieve the position accuracy of better than one foot. Other early research included Fontana （Fontana 2004） and Park et al （Park et al. 2004）. Fontana discussed recent

20、 techniques for the generation and reception of short-pulse electromagnetic waveforms and examined a number of recently developed UWB systems in the communications, radar, and precision-positioning fields. Park et al developed a UWB GPR system for detecting small objects buried under ground.Owing to

21、 the consideration about potential interference to existing and future planned services, the process of establishing rules of UWB frequency range is usually time-consuming. At present few countries and areas, such as USA, Euro-pe, have established the rules, however in many other countries, UWB devi

22、ce shave yet to be approved （Allen et al.2005; Teizer et al. 2008）.In the U.S.A., the Federal Communications Commission （FCC） has mandated that UWB radio transmission can legally operate in the range from 3.1 GHz to 10.6GHz （Fontana 2004） （FCC NEWS）（Ingram et al. 2004）.In the U.S.A., the Federal Com

23、munications Commission （FCC） has mandated that UWB radio transmission can legally operate in the range from 3.1 GHz to 10.6 GHz （Fontana 2004） （FCC NEWS）（Ingram et al. 2004）.UWBs technical featuresThere are some distinctive advantages of short-range high-bandwidth UWB which are summarized below （Ben

24、sky 2004）（Fontana et al. 2003; Teizer et al. 2008;Giretti et al. 2009） （Khoury et al. 2009）:high immunity to interference from other radio systems;high multipath immunity,due to the use of very short UWB pulses, capable of discriminating between direct and time-orthogonal reflected waves;high data r

25、ate;high localization accuracy（for both 2D and 3D）, due to the reliability of the TDOA （time difference of arrival） algorithm implemented;extremely low duty cycles,which translates into low average prime power requirements allowing tags to work autonomously for year, ideal for battery-operated equip

26、ment and without frequent recharging needs;can track multiple resource at the same time, real time and three-deimensionally;can work in indoor and outdoor environments at the same time, reducing the installation cost of multiple sen-sing units to a minimum;longer indoor range than other high rate co

27、mmunications systems, due to the high peak-to-average power ratio;lighter weight,the weight for each tag is less than 12 g;update rate of RF signal of each tag can be up to 60 Hz;need nt calibration.Applications of UWB in industrySince UWB technology has shown to possess unique advantages for precis

28、ion localization applications, a number of scientific and technical domains have benefited from UWBs successful application, such as military affairs, medical treatment and engineering.UWB technology is very useful for military application. Because a very short duration pulse implies a large band, t

29、he power is spread over numerous frequencies instead of being concentrated. The resultant power spectral density is very low and the probability of detection and interception is very low.In the field of high power UWB technology （electromagnetic detection） for military application, an impulse UWB ra

30、dar have the following features:Ability to detect through obstacles and in dense media;Improvement of the radar ranger solution;Improved clutter rejection;Improved detection of low flying targets;Improved detection of （stealth or not） target;Improved recognition （or even identification） of targets;T

31、arget imagery made possible,using a Synthetic Aperture Radar mode （SAR）, which gives a high cross-range resolution added to the high ranger solution;Access to low pulse repetition frequency mode without range-velocity ambiguity.An experimental UWB radar was developed, called PULSAR, to assess the be

32、nefit of UWB concerning the detection of targets masked by vegetation, or anti-tank mines.In the field of low power UWB technology for military application, wireless communications and localization-identification are two major application fields. Two technical approaches canbe investigated in wireless communications. The first approach is utilizing UWB as radio link between body and weapon/head devices to transmit data or video between the camera on theweapon system and