通信工程 毕业设计外文文献翻译：超宽带系统的数据通信文档格式.docx

1、10240 Flanders Ct. San Diego CA 92121E-mail: gopal.racherla, jason.ellis, susan.lin, david.furuno Website: luwbABSTRACTUltra-Widebandt （UWB） is a radio transmission scheme that uses extremely low power pulses of radio energy spread across a wide spectrum of frequencies. UWB has several advantages ov

2、er conventional continuous wave radio communications including potential support for high data rates, robustness to multipath interference and fading. We present an overview of UWB technology and its use in data communications and networking. We look at design considerations for UWB based networks a

3、t various layers of the protocol stack.1. INTRODUCTIONUltra-Wideband 1-6一 also known as baseband or impulse radio 一 is a carrier- free radio transmission that uses narrow, extremely low power pulses of radio energy spread across a wide spectrum of frequencies. UWB has recently gained a great deal of

4、 interest due to the recent Federal Communications Commission （FCC） Report and Order which allocates the UWB band 一 7.5 GHz of unlicensed spectrum for indoor and outdoor communication applications. UWB communications are required to have a -10 dB fractional bandwidth of more than 20% or a -10 dB ban

5、dwidth of more than500 MHz 7. It is important to note that the FCC has not defined a specific modulation scheme to be used. UWB systems offer the promise of high data rate, low susceptibilityto multipath fading, high transmission security low prime power requirements, low cost, and simple design 1,2

6、,5,6.UWB has been used in military applications for the past several years for ground-penetrating precision radar applications and secure communications 3,8. For the past few years, UWB has been developed for commercial applications 1,2,5,6. With the recent FCC 7 report and order for theuse of UWB t

7、echnology, there has been an added impetus to this endeavor. Other notable UWB applications include collision avoidance radar, tagging/identification; geolocation 9 and data communications in personal area networks （PAN） and local area network （LAN） environments.UWB presents a great opportunity for

8、data communications for todays media- rich consumer electronics and home entertainment systems that run on battery powered handheld devices. It can form the basis of a low cost, low power and very high data rate solution as a wireless cable replacement technology for computer-to- peripherals, periph

9、erals-to-peripherals and digital home networking applications. A very useful attribute of UWB technology is its ability to perform precision geo- location which can aid in ad-hoc or mesh networking where the operations of the mobile hosts benefit by knowing the location of the other hosts. UWB techn

10、ology promises to fill the void left by established standards like Bluetooth and 802.11a/b/g.There are several future challenges to the wide adoption of UWB for wireless data communications including the infancy of the technology in the commercial arena, lack of reliablechannel models, the early sta

11、ges of standardization effort and lack of low-cost system on chip （SoC） implementations. In this paper, we look at UWB technology for data communications and inside a UWB physical （PHY） layer characteristics. We also briefly introduce other related wireless standards such as 802.11 10, 802.15.3 11-1

12、3 Bluetooth 14, HomeRF 15 and HIPERLAN 16 and present a brief synopsis of the regulatory effort worldwide with special emphasis on the FCC. We also present the design considerations for UWB based data networking.2. ULTRA-WIDEBAND TECHNOLOGYThe basic waveform that employed in a UWB system is an appro

13、ximation to an impulse, such as that shown in Fig. 1. The short duration of the pulse is associated with large inherent bandwidth; hence, the nomenclature Ultra-Wideband. Typical attributes of UWB waveforms are summarized in Table 1.Fig. 1. UWB waveform example.The high spectral content of the UWB w

14、aveform gives rise to one of the primary advantages UWB operation for communications where a UWB system is robust against multipath fading17 and narrowband interference 18. In multipath fading, where the transmitted radio frequency （rt） signal can reflect off objects in its transmission path and can

15、 cause destructive interferences at the receiver, a loss of reception can occur. ThisTable 1: Characteristics of Typical UWB Systems Fractional Bandwidth 20%Pulse Width 0.1-2 asPulse Repetition Frequency 1 kHz-2 GHz Average Transmitted Power1mWeffect is particularly problematic indoors where there are many reflecting surfaces. In the frequency domain, multipath is shown as frequency selective fading. Because UWB communications systems spreads the transmitted data over a broad frequency band if d