Ultrawideband(2)
Applications
In its current state of development, UWB is aimed at high data rates for personal-area networks, which have an effective operating radius of approximately 10 meters or less. Though similar to the current capabilities of Bluetooth, it uses a very different technology. UWB transmissions trade distance for bandwidth, so the greater the range, the lower the final data rate. Range can be extended up to perhaps a kilometer by using high-gain antennas and reducing performance.
One of UWB’s defining characteristics is that it requires very little electrical power——one source says it uses 0.001% as much power as a cell phone——and thus is virtually undetectable by conventional radios, which see the UWB signal as just very quiet background noise. Thus, a UWB telephone would use so little power that it could remain on for weeks without needing to be recharged. And because it uses all available spectra, UWB may well be cheaper to design and manufacture than conventional radios that require careful tuning to a specific frequency.
A UWB transmitter and receiver must be closely coordinated and synchronized to send and receive pulses with an accuracy of trillionths of a second. The receiver responds only to a familiar pulse sequence. This makes UWB very secure, which explains why it was once used for clandestine communications by military and espionage agencies. UWB's broad frequency range includes the ultralow frequencies the U.S. Navy uses to communicate with submerged submarines.
UWB products will include radar and electronic location and positioning devices in addition to radios. UWB radar can see right through walls, ceilings and floors that would block or reflect other types of radio signals. As an electronic measuring technology, UWB is more accurate than Global Positioning System satellites, and it can be used indoors. The Navy reportedly plans to put UWB markers on almost everything it ships overseas, just to track materiel and keep it from being stolen.
Eventually, UWB networks are expected to run at speeds up to a gigabit per second and therefore should be able to handle all of the phone, television, and Internet traffic for a home or small business.
UWB, Bluetooth and IEEE 802.15.3
Ultrawideband will not replace Bluetooth for short-range communications, because Bluetooth is a complete, end-to-end communications standard, whereas UWB is merely a radio technology that can be used as part of an overall standard. Bluetooth defines how data is managed, formatted and physically carried over a wireless personal-area network (WPAN). However, designers expect that future Bluetooth implementations will be built on top of UWB signals.
802.15.3 is the IEEE standard for a high-data-rate WPAN designed to provide sufficient quality of service for the real-time distribution of content such as video and music. It is ideally suited for a home multimedia wireless network. The original standard uses a traditional carrier-based 2.4-GHz radio as the physical transmission layer.
802.15.3a, a follow-on standard still in the formative stages, will define an alternative 0layer. Current proposals based on UWB will provide more than 110Mbit/sec. at a distance of 10 meters and 480Mbit/sec. at 2 meters.(The End)
超宽带无线技术(2)
应用
在目前的开发状态下，UWB旨在提供个人区域网中的高数据传输率，它的有效范围大致在10米或更短一些的半径内。虽然它与蓝牙当前的能力相近，但它采用完全不同的技术。UWB发射是以带宽换距离，距离越长，最终的数据率就越低。利用高增益天线和降低性能，可以把距离延长到一公里。
UWB的显著特点之一就是要求极低的电功率——有消息称它使用的功率只有手机的0.001%，所以常规的无线电设备实际上是检测不到UWB的，因为它把UWB看成极低的背景噪声。因此，UWB电话使用极小的功率，不需要充电就可以使用数周。由于UWB使用可资利用的所有频谱，所以它比设计和制造需要仔细调谐到指定频率的常规无线电设备更便宜。
UWB发射机和接收机必须紧密配合和同步，以便发送和接收精度为万亿分之一秒的脉冲。接收机只响应熟悉的脉冲序列。这使UWB非常安全，这就解释了为什么UWB一度由军方和谍报部门用于秘密通信。UWB宽阔的频率范围包括了极低频率，美国海军将它用于与水中潜艇的通信。
UWB产品除了无线电外还包括雷达和电子定位设备。UWB雷达可以穿透墙壁、天花板和地板，而其他类型的无线电信号会被这些东西挡住或反射。作为一项电子测量技术，UWB比全球定位系统卫星更精确，它可以在室内使用。有报道称，美国海军计划在运到海外去的几乎所有东西都装上UWB标志，以便跟踪它们，防止被偷。
最终，UWB网络有望运行在高达每秒千兆位的速度上，因此能处理电话、电视以及家庭和小公司的因特网流量。
UWB、蓝牙和 IEEE 802.15.3
超宽带不会代替用于短距离通信的蓝牙，因为蓝牙是一个完整的、端到端的通信标准，而UWB只是一种无线电技术，只能作为一个完整标准的一部分。蓝牙定义了数据是如何管理和格式化、以及在无线个人区域网上是如何承载的。但是，设计人员希望将来蓝牙可基于UWB来实现。
802.15.3是IEEE的高速率WPAN（无线个人区域网）标准，设计旨在为视频和音乐等内容的实时分发提供足够的服务质量。它非常适合家庭多媒体无线网络。最初的标准使用传统的基于载波的2.4GHz无线电作为物理传输层。
802.15.3a是一个后来的标准，还在形成之中，它将定义一个可替代的物理层。最新的建议就是基于UWB，它将提供在10米的距离上超过110兆位/秒和在2米距离上480兆位/秒。这将允许媒体服务器和高分辨率监视器之间的高分辨视频流，以及服务器和便携设备之间极快的文件传输。（全文完）
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