Uwb Technology And Its New Direction

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					This paper introduces the basic features of UWB technology, as well as
ultra-wideband technology scenarios and analysis of ultra wideband technology,
regulation and standardization status, the challenges of UWB technology, and finally
introduced the ultra-broadband technology developments.

 ? I. Introduction When the design of future short-range wireless communication
system, we have to consider the general characteristics and B3G communication
referred to "any person, any time, any place" connectivity. This requires the new
wireless world is the present and future wireless communication systems integration,
including WANs, WSP? Column = news & key = LANtarget = _blank class =
qqx_gjz> LANs, WPANs, and AdHoc and household LAN, you can connect a variety
of devices , including computers and entertainment equipment. To achieve this goal,
we need a new wireless technology.

  UWB technology started in 1960 as a military radar technology development, early
radar technology used; in 1972 UWB pulse detector for a U.S. patent; in 1978
appeared the first UWB communication system; 1984 UWB system successfully in a
10 km test; 1990 Defense Advanced Projects Agency (DARPA) began UWB
technology for authentication. February 2002, FCC approved UWB technology for
civilian use.

  UWB technology slowly reasons: prior to 1994 mainly restricted to military use,
limited third-party development support UWB hardware and software; because UWB
uses many special band, FCC approval of the UWB technology slow progress; UWB
interference caused by UWB also hindered the pace of development; And, because
UWB technology could replace the current use of all wireless technologies, including
PAN, WLAN (802.11a, 802.11b, 802.11g) and wireless WAN (such as GPRS,
1XRTT), so, many companies will resist the technology business.

 2, UWB spectrum efficiency In short distance communications, UWB-RT to the
current spectrum management and wireless systems engineering provides the answer
to most problems. In the UWB-RT, the new approach is to share available spectrum,
rather than seeking a new band. This view was US Control Board approval. Europe
and Asia have begun work in this area, especially in Japan and Singapore. UWB-RT
will be multi-media home networking and entertainment market with great impact, it
allows the implementation of intelligent networks and devices, can achieve
user-centered world of wireless communications.

  FCC's initial report and the industrial sector of the UWB device is defined as: a
relative bandwidth of the transmitted signal is greater than 0.2, or at least 500MHz
bandwidth of transmission equipment. Relative bandwidth is defined as 2 (fH-fL) /
(fH + fL), where fH and fL-10dB respectively, when the upper frequency and lower
bound frequency. In the physical layer, UWB communications extend a few EIRP,
under the FCC's definition, less than 0.56mW compared to its center frequency,
through a wide frequency band. This can be calculated from the power spectral
density in the 3.01 ~ 10.6GHz, as 75nW/MHz. This definition of UWB is not only a
high time resolution, but also lower than the decline of the marginal band system.

  UWB devices can be divided into many categories, such as imaging systems,
automotive radar systems, communications, measurement systems. They all need very
high spectral efficiency, through the use of appropriate technical standards, UWB can
use existing wireless devices to use spectrum without causing interference, which can
make better use of spectrum. In WBAN / WPAN network nodes, application AdHoc
concepts such as the use of multihop routing, UWB devices can reduce the
transmission power and coverage, making it in the same area, can have a lot of
equipment operation, greatly increased spectrum efficiency and capacity. Since the
maximum transmission range of a system with the rate inversely proportional to at
any time, any place covered, the cost will increase as the data rate. Therefore, the
short-range wireless system coverage area is small, technology based on UWB-RT
will be the future high-capacity network space an option.

  3, UWB's advantages Compared with other wireless communication technology,
UWB has many advantages. Table 1, the UWB technology and other wireless LAN
technologies are compared. UWB technology features include: high transfer rate,
system capacity, anti-multipath capability, low power consumption and low cost.
UWB pulse by changing the magnitude, distance or duration to transmit information.
And narrow-band transceiver and Bluetooth transceiver, compared, UWB does not
produce sinusoidal carrier signal, can directly launch impulse pulse sequence, which
has a very wide spectrum and very low average power, is conducive to co-exist with
other systems to improve spectrum efficiency.

  UWB need sine wave modulation and the upper and lower frequency, does not
require local oscillators, amplifiers and mixers, etc., so small, the system is relatively
simple structure. UWB signal processing is relatively simple, just use a small RF or
microwave devices, radio frequency design is simple, the system's frequency adaptive
ability. Pulse transmitter and receiver can be integrated into a front-end chip, and the
time-based and controller, it can constitute a UWB communications equipment.
Therefore, it can significantly reduce the cost.

 As UWB signal using time hopping spread spectrum, the RF bandwidth of up to
1GHz or above, its transmit power spectral density is low, the signal hidden in the
environmental noise and other signals, and use the conventional receiver can not
reception and recognition, must be consistent with the originator pulse spreading code
can be demodulated, thereby increasing the security of the system.

 UWB signal the decline of low, there is a strong anti-multipath fading capability.
UWB signal bandwidth brought great system capacity, due to UWB impulse radio
signals emitted very low pulse duty cycle, the system has high gain and strong
multipath resolution, so that the system capacity than the other Wireless technology is
high.

 As spread spectrum UWB signal processing gain relatively large, even with low-gain
omnidirectional antenna can also use the less than 1mW transmit power to achieve a
few kilometers of communication. Such a low power transmitter power to extend the
system's use of time, very suitable for mobile communications equipment. Research
has shown that the use of ultra-broadband phone standby time can be up to 6 months,
and the low radiation power to avoid excessive electromagnetic radiation on the
human body injury.

 4, UWB-RT applications

 UWB-RT as the start of commercial use, the technology to support high-speed
applications and low intelligence
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