There's no shortage of hype in the world of 802.11g. A range of chipset technologies are lining up to offer speed boosts with theoretical figures on the box of 108 Mbit/s or 150 Mbit/s.
The actual figures are more like 40 to 60 Mbit/s. And as a previous article explains, without a standard, the IT manager should be careful of these in large Wi-Fi installations.
But what are the actual technologies on offer? .
This is the controversial option that includes "channel bonding". This opens two channels between the client and the access point, sending data along both, much as ISDN bonding uses two phone lines to get better throughput. This has been criticised by Broadcom and others as a poor neighbour, using up bandwidth and reducing the throughput available to other clients.
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, Super G "bonds" together Channel 6, half of Channel 1 and half of Channel 11, degrading nearby networks' performance.
Network tester Kevin Tolly of the Tolly Group has tested Super G products operating in 802.11g networks. The results, due out in April, but one data point issued to Network World, showed that when a Super G network was switched on it got 48.5 Mbit/s throughput, while an existing standard 802.11g network dropped back to 1.4 Mbit/s.
Although Atheros denies that Super G causes any problems in real world situations, it has produced a software download that lets users turn channel bonding off and on. The company claims to provide an impressive "real" 40 Mbit/s without channel bonding and 60 Mbit/s with channel bonding turned on - a mode it calls "Dynamic Turbo". The software actually scans other wireless channels and only turns on channel bonding if traffic levels are low.
Despite the criticisms, Super G has been a big success, driving Netgear's market share upwards -- and making up 30 percent of Netgear's sales. It is commercial reality that has brought D-Link into line. The two companies claim their Super G products will work together, but will not support them in combination.
Linksys claims to be within standards
Faced with the success of Super G, Cisco's home networking subsidiary Linksys promised to keep to standards -- and saw its market share dip from 56.6 percent in December 2003 to 53.1 percent in January 2004.
The company has had to come up with something, and that, eventually, has been SpeedBooster, based on Broadcom's AfterBurner technology that Linksys claims is "within the standards", using compression and other techniques to minimise the overhead in the wireless connection.
SpeedBooster can increase the overall throughput of a mixed 802.11b/g wireless network, by as much as 70 percent, says Linksys, and the techniques work on both 802.11b and 802.11g products, so there is an aggregate performance boost.
The 802.11 series of standards started out at 1Mbit/s using radio technology which has been improved on a lot. With faster data rates, and bigger frames of data, it makes sense to cut out some of the overhead which was put in to create a more reliable link in early versions of 802.11, says Linksys.
802.11g networks have a theoretical maximum throughput of 54 Mbit/s, but most users only see a total of about 20 to 25 Mbit/s. Tests on the Linksys SpeedBooster product have shown it to provide about 34 Mbit/s of real throughput. Paradoxically, this is better than normal 802.11g networks, though still short of the number on the product packaging.
Unlike other boosters, Linksys says this one actually helps other users on different protocols, by speeding its traffic and clearing the airwaves for other users. Even if only one client is using SpeedBooster, the whole network shows an improvement of about 20 percent, Linksys claims. The products are "good neighbours", to other 2.4GHz networks, staying on channel 6 and making minimal interference.
The technology uses standards-based techniques such as frame bursting, included in the Wi-Fi Alliance's upcoming 802.11e standard for quality of service. "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.
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 percent 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.
Make way for Agere
It isn't just Super G versus Afterburner, however, wireless chipmaker Agere has its own contender, Turbo G. The company has claimed 150 Mbit/s using software techniques similar to those in Afterburner, including frame bursting and 802.11e techniques to remove overhead.
Although the WaveLAN brand has a long history in the Wi-Fi business, Agere now only makes chips. You don't need to know the history of WaveLAN, but I'll feel better and you can impress your friends if I get it off my chest here. Some of the first 802.11 products in the 1990s, NCR's WaveLAN shifted by acquisition and reorganization to AT&T and then to Lucent, became its own business and finally, having been rebranded Orinoco, moved to ProximEnterasys, though it doesn't use Agere chips, as far as we know.
So who exactly is using WaveLAN chips? Its current 802.11b products are widely used in PCs and PC cards (Agere claims in four of the top five PC brands), but you can't buy any access points with Turbo G -- yet. "We are ramping into production on multimode systems, and haven't made a customer announcement yet," said Frank Ferro, Wi-Fi director for Agere systems.
Although Netgear, D-Link and Linksys seem settled with their current chip providers, he doesn't rule out the possibility of wooing them -- or another player like Buffalo -- away, with the promise of speed. "We've had a lot of retail manufacturers wanting to find out more about it," said Ferro. "150 Mbit/s on the box looks great."
Agere may carry on its focus on PCs, and could emerge in a specialised product. Consumer electronics products such as home video systems can control both ends of the link, Ferro points out, so manufacturers are free to take products from anyone.