Speed-Boosted Wi-Fi isn't all that fast
Worth doing if you have a specific need.
By Becky Waring, PC World | PC World | Published: 00:00, 09 June 2004
While public hotspots and most enterprise networks are still moseying along with pokey old 11 Mbit/s 802.11b Wi-Fi network cards and routers, SOHO users have moved to the faster 802.11g standard and are already being offered a new generation of products promising rip-roaring speeds of 108 Mbit/s or 125 Mbit/s.
Informal testing shows that the real-world throughput of these souped-up devices is actually more like 22 to 24 Mbit/s. This sounds disappointing, but is still significantly faster than the real-world performance you get with basic 54 Mbit/s 802.11g cards - around 18 Mbit/s.
The high speed modes have been criticised for being nonstandard. In order to get the promised speed increases, you have to use both cards and access points that have the same type of speed-boosting technology, currently selling in two competing flavours: 108 Mbit/s and 125 Mbit/s.
The 108 Mbit/s Super G technology, which came out last autumn, is based on Atheros chip sets and is used by D-Link and NetGear, among others. The 125 Mbit/s Afterburner technology, which shipped this spring, is based on Broadcom chip sets and is found in products from Belkin, Buffalo, Linksys, and US Robotics, among others.
I tried three of these new high-speed routers (and their companion adapters) to see how they stacked up:
- Buffalo Technology's AirStation 125 High-Speed Mode wireless cable/DSL router with AOSS (WHR3-G54)
- Cisco Systems' Linksys Wireless-G Router with SpeedBooster.
- D-Link Systems' AirPlus XtremeG DI-624.
Do they work together?
Though all these devices are certified Wi-Fi G compatible, that simply means they will perform in the standard 54 Mbit/s 802.11g mode with G cards and routers from other vendors. So if you have a 108 Mbit/s card and a 125 Mbit/s router, the whole thing will run at a maximum of 54 Mbit/s, negating the advantages of the speed-boosting technologies. Similarly, if you have a mixed network of high-speed and regular 802.11g devices, performance will drop when the regular devices are connected.
However, if you are just setting up wireless in your home and can buy matching equipment, either of these technologies will do the job about 33 percent faster than basic 802.11g equipment - for about 30 percent more money.
Just how do the Super G and Afterburner modes work? Super G gets part of its speed increase from "bonding" data from two non-overlapping wireless channels together (normal Wi-Fi uses only 1 out of the 11 channels in the 2.4-GHz range). This channel bonding, though, increases the potential for troublesome interference with microwave ovens, with cell phones and with other Wi-Fi networks (see our feature comparing the different speed boost technologies).
In particular, Super G has been criticised in the past for using so much of the Wi-Fi band that other networks in the vicinity, which normally would automatically seek out and use non-overlapping channels to avoid interference problems, could be severely impacted. During my week of tests, I experienced no noticeable drop in performance in either network when I used the D-Link 108 Mbit/s router in the same house with the Linksys 125-Mbit/s router.
By contrast, the 125-Mbit/s Afterburner technology uses just one channel. Instead of bonding two channels of data together, it squeezes more data through a single channel by reducing overhead and aggregrating smaller packets of data into larger ones. Some of this technology will be used in the upcoming 802.11e wireless multimedia enhancements standard, which is designed to improve delivery of streaming audio and video.
The 125 Mbit/s Afterburner vendors claim that their products are all interoperable in high-speed mode, while Super G products may not be. In a separate test, I found that D-Link and NetGear Super G products were in fact compatible in the 108-Mbit/s mode; however, such compatibility may not be true of products from all Super G vendors.
Real speed - the file transfer test
In my informal tests of file transfers from a local server to a wireless client - performed with encryption off, 4 feet from the router - the two technologies provided similar real-world performance, ranging from 22 to 24 Mbit/s in wireless throughput. That's still significantly slower than their 108-Mbit/s and 125-Mbit/s monikers would lead you to believe.
The fact is that real Wi-Fi speeds, measured in terms of file transfers, have always been slower than the claimed data rate. This is because headers, handshakes and other overhead take up a substantial amount of the available bandwidth. Here are the real file transfer speeds I measured with each class of WLAN product:
- 802.11b, nominally 11 Mbit/s, actual throughput 4.5Mbit/s
- 802.11g, nominally 54 Mbit/s, actual throughput 18 Mbit/s
- Boosted G, nominally 108 Mbit/s or 125 Mbit/s, actual throughput 22 to 24 Mbit/s
Despite the shortfall, both models boost speeds well above 802.11g and 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.
However, they will make no difference to web-surfing or other Internet activities, as most broadband services connect at well under 1 Mbit/s. Paradoxically, the users who might benefit, in offices with high-speed Internet connections, won't be using speed-boosted Wi-Fi, because of the sensible conservatism of IT managers (see The fast Wi-Fi paradox).
All three shipping routers were easy to connect to the Internet, and all of them have very good router and firewall features, such as MAC address filtering and WPA (Wi-Fi Protected Access) encryption. The D-Link and Buffalo routers also include WDS (wireless distribution system), a convenient way to link multiple routers wirelessly to cover a larger area.
Speed boosts are hard to get working
The Linksys product had the best setup utility and documentation. However, all three routers and adapters were difficult to get working together in high-speed mode - I fiddled for hours with advanced router settings and card drivers before I got them humming at their top speeds. 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.
Such users should probably not be buying these routers in the first place, though. If all you need is reliable and compatible Wi-Fi service for typical broadband connections, an inexpensive 802.11g router will provide all the speed you require. But if you really need the performance boost that these new routers provide, then by all means step up.
D-Link Systems AirPlus XtremeG DI-624
Excellent performance, stout firewall features, and wireless distribution system support.
Buffalo Technology AirStation 125 High-Speed Mode Wireless Cable/DSL Router with AOSS (WHR3-G54)
Great performance, compatibility.
Cisco Systems Linksys Wireless-G Router with SpeedBooster
Admirable performance and compatibility, great setup utility.