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Linksys boosts WLAN speeds

Mar 15, 20047 mins
Cellular NetworksUnified Communications

SpeedBooster products call into question competitors' use of proprietary technologies in 802.11 standard.

Linksys this week announced a line of 802.11g gear that the company says significantly boosts wireless LAN speeds without the use of proprietary technology.

Linksys this week announced a line of 802.11g gear that the company says significantly boosts wireless LAN speeds without the use of proprietary technology. SpeedBooster, an extension of the 802.11g standard, increases performance by 35% on a SpeedBooster-only network, and up to 20% when used with standard 802.11g products, Linksys says.

The move is in response to the success small office/home office network rivals Netgear and D-Link Systems are having with Super G, a wireless chip technology developed by Atheros. Super G uses a proprietary technique called “channel bonding” to achieve 108M bit/sec-rated speeds when used with similar equipment.

Netgear and D-Link started selling Super G gear last year; Netgear says Super G makes up about 30% of its 802.11g equipment sales. Touting a standards-only approach, Linksys has resisted and seen a slight drop in WLAN market share – from 56.59% in December 2003 to 53.13% in January 2004 – to sales of competitor’s faster equipment.

Chip vendors such as Atheros and Conexant have developed higher-speed wireless products powered by a mix of standards-based technology and proprietary techniques such as packet bursting, hardware encryption, and most notably, channel bonding. The development is because the IEEE’s 802.11n standard, which is expected to get 100M bit/sec speeds, is at least a year away and to meet the performance demands of emerging entertainment networks.

However, such products only achieve higher speeds when they communicate with other similar products, which flies in the face of the Wi-Fi Alliance’s push to ensure all Wi-Fi products interoperate. The group has certified products using Super G and others for interoperability, but only in standard 54M bit/sec mode. The Wi-Fi Alliance says it will not certify any vendor’s 108 mode or any proprietary mode.

D-Link and Netgear use the same Atheros Super G chip, but whether their products interoperate isn’t clear. D-Link says they do. Netgear says its customers say they do but Netgear won’t support interoperability with D-Link Super G. Atheros says they interoperate; rival Broadcom, which developed the technology on which SpeedBooster is based, says they do not.

But the biggest problem with Super G isn’t the lack of interoperability: It’s the use of channel bonding. Network World columnist Kevin Tolly of The Tolly Group conducted tests (which Broadband commissioned) in December that showed standard 802.11g networks suffer severe performance degradation when near a Super G network. 802.11g has 11 channels, but only three are non-overlapping, which means you can operate three wireless networks in the same area without interference, so long as they are set to channels 1, 6 and 11, respectively. To achieve higher throughput, the technique “bonds” together Channel 6, half of Channel 1 and half of Channel 11, degrading nearby networks’ performance.

Last week, Tolly’s team completed a new round of tests, extending the range between Super G and standard 802.11g networks to 30, 50, 100 and 150 feet. Tolly also tested an Atheros Super G network against an Atheros standard 802.11g network. These tests address claims that the first tests placed the networks too close together and that testing Super G against Broadcom standard 802.11g equipment created a bias.

Although the results won’t appear on Tolly’s Web site until April, he gave Network World a sneak peek. In testing a Netgear Super G network against a Netgear standard 802.11g network positioned 30 feet apart, the mean was 48.5M bit/sec for the Super G network, but 1.4M bit/sec for the standard network.

“The new results don’t show anything that contradicts what we found previously,” Tolly says. “Even at 30 and 50 feet we found significant interference, which represents what users in condos and apartments could experience through walls, ceilings and floors. Many lots aren’t 50 feet wide, and there are plenty of places where you don’t have 50 feet between you and your neighbor’s DSL connections.”

Tolly’s tests also found that placing two Super G networks near each other degrades performance because both must use Channel 6, of particular significance to users who buy a second to expand the network.

Fast and friendly

With its SpeedBooster line, Linksys has incorporated several standards-based, speed-enhancing techniques such as frame bursting that are taken from the Wi-Fi Alliance’s upcoming 802.11e standard for quality of service. SpeedBooster products will begin shipping next month. The Wireless-G Router with SpeedBooster will cost $130; PC Card adapter and PCI card each will cost $99.

“Because the 2.4-GHz band is so crowded, people need to use all 11 channels to coexist with other wireless networks. And the fact that Super G tramples over every other wireless signal we found is just unacceptable,” says Mike Wagner, director of marketing at Linksys.

SpeedBooster is based on a new Broadcom wireless chip technology called Afterburner. Afterburner increases WLAN efficiency by reducing the amount of overhead transmitted with the data packets. 802.11 was developed to transmit data at 1M and 2M bit/sec, which means the protocol spent 80% of the time transmitting data and 20% transmitting overhead. With the higher speeds of 802.11g, the protocol spends more time transmitting overhead packets than data packets: That’s why 54M bit/sec-rated speed translates into less than half that in actual data throughput.

Afterburner is an improvement over Broadcom’s earlier speed-enhancing chip Express, announced last July. Afterburner increases efficiency even further by shortening the header packets by 50% and by concatenating, or chaining and transmitting five packets together for each header packet sent out.

“What’s important for end users is that Afterburner is a friendly overlay on top of 802.11g,” says Jeff Abramowitz, senior director of WLAN at Broadcom. He adds that its PC OEM customers – Acer, Apple, Dell, Fujitsu, Gateway and HP – are interested in using Afterburner, as are the company’s broadband modem manufacturers Efficient and Motorola. Buffalo Technology also says it will ship products using Afterburner in May.

Smart radios

Although Atheros, D-Link and Netgear continue to defend Super G, all three are working to find ways to decrease interference that channel bonding causes.

D-Link says it will release a firmware update to its Super G router in April that will let the radio automatically detect the presence of another 802.11g network and prevent channel bonding.

Netgear says it is working with Atheros to develop “adaptive network radio” technology, which will let a wireless router check which channels other wireless networks are using and avoid them. According to Netgear’s Vivek Patela, senior director of product management/marketing, a client PC using adaptive network radio can wander far enough from the access point that it enters the range of a neighboring network, yet maintain its connection. In other words, the technology lets the router communicate only with its clients, avoiding signals from neighboring networks. Netgear plans to release details next month, but it appears the company will release a new product line, rather than a firmware update existing Super G products.

Atheros, which created the technology, is in a quiet period since going public Feb. 12. However, Colin Macnab, the company’s vice president of marketing and business development, says the FCC calls this approach “cognitive radio” and is discussing whether to give “spectral advantages” to companies that use radio spectrum in a more intelligent manner. One such advantage could be being granted an increase in the amount of power products transmit. Today, the power for wireless gear is capped at 1 watt, but most operate at about 100 milliwatts.