By Alan S. Kay Special to The Washington Post
Sunday, April 20, 2003; Page H09
How fast is fast enough? Manufacturers of wireless networking gear tend to have a simple answer: "Whatever we just put on sale." But the picture is always more complicated.
On one hand, WiFi networks send data faster than can any cable or digital-subscriber-line Internet connection, which can make even slow WiFi feel fast to the uninitiated. On the other hand, WiFi never runs as fast as advertised. And so the reality may not come clear until after a long period of tweaking and puzzlement.
We spent two weeks putting three forms of WiFi -- 802.11b, the kind most people use, and two faster versions, 802.11a and 802.11g -- through their paces, testing eight access points and receiver cards.
The reviewed hardware included two 802.11b devices (Netgear's MR814 access point and MA401 card), three 802.11g units (Apple's AirPort Extreme base station and card, and Netgear's WG602 access point), two tri-mode a/b/g components (Linksys's WPC55AG access point and Netgear's WAG511 card) and one dual-mode 802.11a/b access point (D-Link's DI-764).
We set up basic WiFi networks and timed how long each took to transmit a 40.8-megabyte file.
The test environment was a two-story wood-frame house, vintage 1935. Why is this relevant? WiFi signals weaken not just over distance but also as they pass through physical objects such as walls, ceilings and fireplaces. In our tests, those obstructions outweighed distance in attenuating a WiFi signal. When the connection gets sufficiently weak -- in our tests, 20 percent of the original strength -- the WiFi hardware will give up on it.
Our benchmark was a wired network built on 100Mbps Ethernet technology, the traditional way to link computers. That moved the test file in 12 seconds every time -- a speed of about 27 million bits per second.
(Networks, wired or not, are amazingly inefficient for many reasons, including the overhead of their communications protocols. As a rule of thumb, real-world performance of half the promised speed is extraordinarily good, and day-to-day reality is likely to be half of that.)
Standard 802.11b WiFi offers a theoretical peak rate of 11Mbps; with access point and receiving laptop in the same room, the file transfer took slightly less than 80 seconds, for a speed of 4Mbps.
Moving that access point one floor away slowed the transfer time to 107.4 seconds (3.2Mbps). At 25 feet and two walls and a floor away, the signal began to fail. WiFi is supposed to work up to 150 feet away, but without an amplified antenna or open ground between access point and receiver, you will probably never see that range.
