WLAN Test Leads to Adapter Agita

Analysis: eWEEK Labs hits some snags while testing the interoperability of wireless LAN gear based on the draft 802.11n spec.

Im deep in the process of testing the interoperability of wireless LAN gear based on the draft 802.11n spec. Ive been performing tests using a pair of brand-new Lenovo ThinkPad T60 laptops, each featuring the latest Centrino wireless adapter—the Intel Pro/Wireless 3945ABG. I had intended to use the Centrino adapters as 802.11g clients in my test matrix, but Ive encountered a few problems that may require me to look elsewhere.

While preparing the laptops for my tests, by loading up the latest Windows patches and drivers, I noticed that the Centrino adapters consistently crashed my new home network access point, a Netgear RangeMax 240 based on Airgo Networks True MIMO Gen3.

A little research uncovered that this is a known problem—the Netgear router reboots frequently when it receives null QOS (quality-of-service) frames emitted by the 3945ABG. As a temporary workaround, I disabled the clients QOS support to keep the router functional.

Unfortunately, my problems with the 3945ABG may have extended more broadly to the 802.11n tests. Early results have shown incredibly poor results when using the 3945ABG in conjunction with a draft 802.11n router operating in 40MHz mode. I would expect this pairing to operate at 802.11g speeds (about 22M bps of real throughput), but instead Ive seen as little as 6M bps.

Ill be investigating this mystery as testing continues, and I will perform the same tests with other 802.11g client adapters to see if this problem indicates an issue specific to the Centrino card or a more pervasive backward-compatibility issue with the draft 802.11n products under test.


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