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DS-UWB enables convergence

By Ian Gifford, special to Network World
June 14, 2004 12:06 AM ET
This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.

Network World - The PC, consumer electronics and cellular markets are in a state of convergence as mobile communications devices are being used to carry an array of datastreams such as photographs and streaming video. But current wireless technologies don't offer sufficient data rates to support the multimedia-intensive applications in development for multifunctional devices. Ultrawideband (UWB) might provide the missing link.

UWB is an emerging wireless technology for personal-area networks (PAN) that link wireless IP devices such as mobile phones, media players, digital cameras, camcorders and other consumer electronic and network gear in the home and office. UWB can provide seamless, low-cost, highly reliable video, audio and data connectivity for such devices.

The IEEE is considering more than one wireless standards solution, but two events have propelled UWB to the forefront. First, the FCC has permitted commercial UWB communication devices to operate in the 3.1GHz to 10.6GHz spectrum. And second, the IEEE 802.15.3a task group is crafting a physical layer for next-generation PANs, and UWB is an ideal candidate for the physical layer.

While all the proposed technologies are designed to provide optimal performance, only Direct Sequence UWB (DS-UWB) uses a combination of a single-carrier spread-spectrum design and wide coherent bandwidth. Developed by the UWB Forum, an industry organization focused on UWB design and application, the DS-UWB approach provides low-fading, optimal interference characteristics, inherent frequency diversity and precision ranging capabilities.

Unlike conventional wireless systems, which use narrowband modulated carrier waves to transmit information, DS-UWB transmits data by pulses of energy generated at very high rates: in excess of 1 billion pulses per second, providing support for data rates of 28M, 55M, 110M, 220M, 500M, 660M and 1320M bit/sec. A fixed UWB chip rate in conjunction with variable-length spreading code words enables this scalable support.

DS-UWB provides four key advantages over legacy wireless technologies: quality of service; high data rates that scale to 1G bit/sec or more; lower cost; and longer battery life. These attributes mean DS-UWB is well suited to be the physical layer for PANs.

By using the widest possible bandwidth to produce the shortest possible pulses, DS-UWB supports robust, high-data-rate links in a high multipath environment and offers precise spatial resolution for location detection of UWB devices. (A multipath environment is one in which radio waves bounce off many objects, resulting in ghosts and fades that tend to break other approaches.)

By capitalizing on coherent processing over the entire frequency band, DS-UWB allows the best theoretically possible performance in high multipath environments, such as homes.

And by generating continuous smooth white noise at lower levels than competing approaches, DS-UWB will minimize interference. It does not cause any harmful interference to existing spectrum users, a key concern of worldwide regulators.

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