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« Atheros, Broadcom Say Draft N Chips Interoperable | Main | Wall Street Journal Runs Down the Problems with Draft N Gear »

June 1, 2006

More Rigorous Testing Shows Distance Drop with Draft N

By Glenn Fleishman

Tim Higgins of Tom’s Networking turned to industry testing gear to examine Draft N products: Higgins compared three Draft N devices (Buffalo, NetGear, and Linksys) against one based on Airgo’s third-generation chips (NetGear RangeMax 240), which don’t claim Draft N compliance and were released ahead of the merged draft. Two of the Draft N devices use Broadcom chips and one uses Marvell’s.

Higgins didn’t test for multipath performance, but he did some extensive comparison of speed and performance at simulated ranges with the Azimuth testing rig, which isolates devices from outside signals. This equipment is also used by manufacturers, so it’s a meaningful comparison of claimed performance rather than the real-world performance Higgins normally looks into (and found wanting).

One element that complicated testing is the constantly changing driver releases for this early equipment, which is not surprising. Higgins had difficulties with one of Buffalo’s products, found a newer driver in review equipment than in that he purchased from a retail channel or was on Buffalo’s site, and spotted the new drivers for download after he queried the company.

What Higgins found is that all three Draft N devices drop off in performance at far shorter distances than either the Airgo 3rd gen NetGear unit or plain old 802.11g. While G can’t hold a candle to throughput over shorter ranges, it continues at a decent speed for far greater simulated distances.

Higgins expects some criticism for not testing multipath performance in simulation, but the fact that the Airgo-based device performed substantially better than the Draft N equipment would seem to defuse that argument.

Higgins now advises against buying Draft N products at this time. He writes, “With high prices, immature drivers and firmware, no guarantee of upgrade to standard 11n when it’s released and now - shown for the first time - evidence that some current products doesn’t even perform better than 802.11g at lower signal levels, I can’t think of an upside that justifies the expense and hassle.”

He also continues to stand by his review from earlier this year of third-generation Airgo-based equipment as the latest firmware continues to have the bad neighbor problem for legacy B/G networks on 2.4 GHz channel 6.

Another part of this report will be posted soon.

Posted by Glennf at June 1, 2006 3:02 PM

Categories: Draft N


Is it true that he connected the antennas one to one, antenna #1 on the AP to antenna #1 on the card, ant #2 to ant #2 and so on? If this is the case this is a major mistake. You can not test a MIMO system this way.

[Editor's Note: I'm writing up his report in brief, but pointing you to his site where you can read Higgins's full methodology and critique it.--gf]

Posted by: Yuval at June 2, 2006 6:13 PM

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