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With the recent media attention on UWB and the announcements of 22 UWB based Wireless-USB (W-USB) products being certified by the WiMedia Alliance, the time has come to evaluate this exciting new wireless technology and see if it has delivered on the promise of transporting hundreds of megabits per second while delivering superior QoS.
This test was organized with the cooperation of WirelessNetDesignline and EE Times and sponsored by Pulse~LINK, a vendor of UWB silicon. Our plan was to have a group of UWB companies collectively sponsor the test to promote their recently announced UWB products. UWB silicon providers and system vendors were invited to participate or to co-sponsor the test.
Based on the wave of recent WiMedia certifications, we anticipated that the latest and greatest WiMedia reference designs would be submitted for the test. However, none of the WiMedia vendors chose to participate and we had to use off-the-shelf commercially available WiMedia W-USB products. This left Pulse~LINK as the only sponsor.
The Pulse-LINK CWave implementation focuses on video distribution and embodies the complete point-to-point and point-to-multipoint communication system with TCP/IP throughput of over 500 Mbps and reaching 890 Mbps at close range. By comparison, the top throughput measured over the WiMedia links was an order of magnitude lower—around 50 Mbps at close range.
Background
The initial public awareness of Ultra Wide Band (UWB) came about in February 2002 when the FCC allocated 7.5 GHz of spectrum—3.1 to 10.6 GHz—or use by UWB devices, enabling this previously classified military technology to be commercialized, as had happened with CDMA years before.
Click here for Figure 1
Figure 1: UWB operates in the noise floor of traditional wireless applications and is able to share the already allocated spectrum with other services while only negligibly raising their noise floor.
The unique benefit of UWB signaling— its ability to operate at the noise floor—enables UWB devices to peacefully co-exist and share spectrum with traditional wireless services (Figure 1).
The low transmit power authorized by the FCC (Table 1) curtailed the range of UWB links to about 10 meters limiting this technology to Wireless Personal Area Networking (WPAN) applications. This range is not a fundamental limitation of UWB technology itself. If transmit power limits were increased the range of UWB would increase as well.
Click here for Table 1
Table 1: Indoor UWB emission limits in the US.
The FCC approved the UWB spectrum allocation and transmit power limit but did not specify an air interface, modulation or Media Access Controller (MAC) " specifications that were undertaken by the IEEE 802.15 committee in December of 2002 and abandoned in January of 2006. For more information, see the sidebar article IEEE 802.15 Standardization of UWB .
Today, UWB implementations are not constrained to any particular MAC or PHY and have the flexibility of using any MAC and PHY layers as long as they comply with the FCC spectrum mask limits.
Many of the companies originally working on the IEEE 802.15 standard joined the WiMedia Alliance creating their own specification of UWB based on OFDM PHY and a distributed USB-like MAC.
This WiMedia specification was published as the European Computer Manufacturers Association ECMA-368 standard. Pulse-LINK developed and enhanced their original impulse-based UWB signaling and implemented their solution based on the IEEE 802.15.3b MAC.
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