Among all the battles over wireless standards, the high speed personal area networking sector has been one of the most fraught, with the long drawn out fight over UltraWideBand platforms still affecting progress, with new options like 60GHz Personal Area Networks (Pans) coming into play. The WiMedia Alliance may have won the 2005 war to set the main UWB standard ‘ though only by abandoning the IEEE body and going to ECMA instead ‘ but it is now fighting to justify its performance promises, with independent Pulse~Link snapping at its heels, while facing a possible new challenge in 60GHz.
The Alliance – originally led by Intel and Texas Instruments and advocating a UWB over multiband OFDM approach ‘ has so far demonstrated disappointing data rates, even though its technology has been adopted to be the basis of future standards including Wireless USB and a high data rate extension of Bluetooth. It is now advocating that unlicensed spectrum should be carved up into sections, each dedicated to a different application that particularly suits the properties of that frequency. This would support WiMedia’s ambition to provide unifying base technology for multiple short range standards in different bands, including 60GHz, rather than setting up in opposition to other standards like Bluetooth and ZigBee.
“There’s a tendency to bolt into a new place and hope for the best, but as an industry we need to do an analysis,” said WiMedia chief, Intel’s Stephen Wood. “We suspect the industry needs to divvy up applications into the various unlicensed bands.’ The Alliance has already approached one university to research the issue.
Doubts were recently cast over whether WiMedia UWB – which works within regulatory limits that significantly restrict the potential performance of unfettered UWB ‘ is living up to its performance claims. An independent testing lab, Octoscope, claims the UWB products that are currently shipping have average throughput of only 20Mbps over 15 feet, rather than the 480Mbps peak that is promised. “We are finding throughput is quite disappointing,” said wireless test expert Fanny Mlinarsky. “There is nothing above 50Mbps maximum, and the average is 20Mbps. Everyone thought this was going to be the short range Gbit network.’
The lab tested systems from Belkin and IO Gear, using chips from Alereon, Freescale, Intel and NEC. The chipmakers refused to participate directly in the tests, pointing out that they are sponsored by a UWB company promoting its own implementation rather than WiMedia ‘ Pulse~Link. The two vendors said the poor results were down to inefficiencies in the MAC chips and software drivers, but these flaws were being fixed for the next products ‘ an explanation that Mlinarsky found unconvincing given the low PHY data rates.
Wood claims the external devices tested were aimed at relatively low end applications, and that 50Mbps would be adequate for printers and scanners ‘ also that external devices carry overhead because they must translate a wired USB signal to wireless and back again to a wired link. Systems with wireless USB on mini-PCI cards embedded in notebooks don’t face that hurdle and thus hit rates as high as 160Mbps in recent public demonstrations, he said, adding that when devices at both end of a link use native, embedded chips, rates will go as high as 220Mbps. He also thinks the Wireless USB protocols slow down the underlying capabilities of UWB radios and are not “friendly for wireless’.
The WiMedia Alliance and USB Implementors’ Forum say they will address the performance issues by replacing the adapters, for both the host PC and the peripheral device, that Wireless USB currently uses to complete the wireless link. The implementation is known as the HWA/DWA (Host Wire Adapter/Device Wire Adapter) and these will be replaced over time with native implementations whose signals do not need to cross multiple protocol stacks. The USB-IF says that, with native devices, it will achieve 70Mbps for a host adapter to native device; 160Mbps for a native host to DWA device ; 220Mbps for a native to native data transfer .
The Bluetooth SIG maintains that it is ‘optimistic’ that, for its own WiMedia-based implementation, it will hit the targeted 100Mbps rate for Bluetooth version 3.0 at 6GHz and above. Three chipmakers showed data rates of 175Mbps or more at 6GHz and above at a Bluetooth SIG meeting in Beijing in September, said Wood, and UWB start-up WiQuest has showed data rates up to 375Mbps using a proprietary protocol geared for video.
Global spectrum availability is also an issue for the WiMedia Alliance, which has defined six band groups in a range from 3GHz to 10GHz, with certified Wireless USB products focusing on band 1 (3GHz). However, in Europe and Asia regulators want UWB products to implement a ‘detect and avoid’ protocol when they are in the presence of fixed broadband signals such as WiMAX or radar ‘ but are unlikely to define what these protocols will be until the end of next year. Some WiMedia members believe that the best route to market in these regions will be to move to one of the higher band groups in the 6GHz range where detect and avoid is not an issue, but this would fragment the market between different products for different territories.
The WiMedia Alliance is working with the ECMA standards group to finish a specification for WiMedia on 60GHz radios by next summer, which could bring the group into conflict again with the IEEE, which has accepted submissions for its own 60GHz Pan standard, 802.15.3c. 60GHz systems will be geared mainly to very fast in-home networks and to carrying uncompressed video as fast as current wireline HDMI systems. Chip companies like IBM and Toshiba are just succeeding in implementing 60GHz systems in low cost CMOS, whereas in the past it has only been practical in expensive gallium arsenide.
Wood is keen to divide the home media market between the various flavours of WiMedia, with the 60GHz systems handling uncompressed and current UWB networks focused on compressed video ‘ thus squeezing out Wi-Fi video and also other potential 60GHz implementations, many of these coming out of Japan.
Meanwhile, Pulse~Link – which promotes its own UWB technology optimized for video and HDTV, Lan distances and wireless/wireline delivery ‘ has stayed outside the IEEE and ECMA/WiMedia activities and is now claiming validation of its claims that its CWave chipset has the highest wireless data rate available at 1.35Gbps over the air or 890Mbps for application layer throughput. The test was also carried out by octoScope which said that ‘CWave throughput held at around 500Mbps at up to eight feet of wireless range. CWave sustained throughput of 115Mbps up to 40 feet.’ The chipset also measured sustained TCP/IP throughputs of 500Mbps across 450 feet of coaxial cable.
Other high speed, low power options are starting to emerge. As well as pioneering work from SiBeam, IBM, Toshiba and others in 60GHz radios, other start-ups like NewLans are innovating in this area, where the IEEE is to commence a standards process for personal area networks next year. Now Motorola has joined the race, having failed to dominate UWB with the technology, DS-UWB, that it created when it still owned Freescale. Motorola Labs has a joint development agreement with Colorado-based Phiar, and the partners have succeeded in using metal insulator electronics instead of semiconductors for 60GHz WPAN devices. Motorola says its semiconductor-free radio will be a direct challenge to the products under development by IBM, which will use its silicon germanium BiCMOS radios. Metal insulator electronics are low cost and can be fabricated on standard CMOS lines on top of ultra-cheap plastic substrates. Motorola also said the prototype Phiar-based devices have higher performance than their benchmark devices, and conform to the preliminary specifications laid down by the IEEE’s 802.15.3c 60GHz standards working group.
Other companies developing 60GHz WPAN chipsets include the WirelessHD consortium (LG Electronics, Matsushita/Panasonic, NEC, Samsung, SiBeam, Sony and Toshiba); STMicro; Bridgeway Systems and TeraBeam.
Alternative approaches come from specialists like Amimon and Radiospire. The former uses a souped-up variant of 802.11n to provide a wireless high definition interface for HDTV, running at 1.5Gbps, while Radiospire uses tweaked versions of WiMAX and Wi-Fi. Its chips operate in the 3.1GHz-4.8GHz range to avoid interference with 802.11.
Some Wi-Fi enthusiasts are also starting to lobby regulators on plans for very high frequency bands, notably 275GHz to 1THz. AT&T has criticized European Union plans to exclude Wi-Fi from such bands. “The best terahertz spectrum is being carved up among science, satellite and amateur radio interests. The giveaway of this precious spectrum is unexpected, capricious and irreconcilable with the evolution of future broadband wireless networks,” David Britz of AT&T said in his presentation to the IEEE study group. Phiar and other start-ups are already working on terahertz receivers.