Wi-Fi "booster" products that claim to provide business with over 100Mbit/s in reality only provide a fifth of that, new tests have shown.

While many small businesses are buying products to get more out of their wireless systems, thanks to network overhead, a lack of agreed tests and companies who put "theoretical maximum" speeds on their product packages, the reality is that they give about only 24Mbit/s of usable bandwidth.

All networks deliver a bit less than their stated data rate, as some of the raw data-rate is used for overheads such as packet headers. In Wi-Fi, the nature of the radio link makes this overhead greater. While 100Mbit/s wired Ethernet gives about 85 Mbit/s throughput, the actual throughput of "11Mbit/s" 802.11b turns out to be about 4 or 5Mbit/s.

The gap appears to be widening with successive generations, to the extent that boosted 802.11g networks, which use non-standard techniques to get their claimed link rate of more than 100Mbit/s, actually deliver only a fifth of that speed.

While 802.11g (stated speed 54Mbit/s, actual throughput about 18Mbit/s) is still becoming established, vendors are already offering faster, non-standard technologies. The two main contenders, Super G (found in products from D-Link and Netgear) and Afterburner (found in Belkin, Linksys US Robotics and Buffalo). Both offer between 22Mbit/s and 24Mbit/s throughput, according to tests.

The speed boost is real enough for users who want to move big files fast, says Becky Waring of PC World, who carried out the tests: "They can be a boon to users who need to transfer large files from one computer to another wirelessly or to stream high-quality multimedia files," she says. However, since most SoHo users or teleworkers will have a broadband connection less than 1Mbit/s between them and the Internet or their office network, most users will see no improvement.

In any case, people who pay the extra for an apparently double-quick WLAN may not even get the 30 percent it actually can offer, because the setup routines are too fiddly, says Waring: "I fiddled for hours with advanced router settings and card drivers before I got them humming at their top speeds," she says. "The job would have taken only a few minutes had better setup utilities been provided. I suspect that many users, after paying a price premium, will simply get the routers working and will never know that they are not performing in high-speed mode."

Read the full feature Tests of both Super G and Afterburner, in this report.

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