Thinkpads Forum

Just wanted to relate my experiences setting up for wireless N, using a Linksys broadband ABGN router and the Intel adapter in my T61p. Short story - I could only get an N band link using WPA2 with AES encryption. The website FAQ for Intel says that the 4965 will not link up in N band with WPA1 enabled - they were right. They also say that it will work with WPA2 in either TKIP or AES mode - not true for my situation. If I switch to TKIP, the link immediately falls back to G band (54 Mbps). Switch back to AES, links back at N band (130 Mbps). I also have a Linksys ABGN pc-card adapter, and it links in N band with either WPA1 or WPA2, TKIP or AES, at speeds up to 270 Mbps. Especially odd, since the pc-card just has a little 1/4" coil antenna, compared to the T61p built in above the LCD. The Intel FAQ says that N links using WPA1 are not allowed in the Draft N specs, so their driver doesn't allow it. Wonder who wrote that part of the draft? Anyway, I just thought this info might save other 'padders some time in getting it to work. I would be interested in other experiences with N band and the T61 built-in adapter. The performance drop of the Intel card from the higher speed and flexibility of the Linksys pc-card adapter could be related to the Linksys router, also.

kernelpanic wrote:Wonder who wrote that part of the draft?

The IEEE 802.11 Technical Standard Working Group! See... http://standards.ieee.org/wireless/index.html

kernelpanic wrote:The performance drop of the Intel card from the higher speed and flexibility of the Linksys pc-card adapter could be related to the Linksys router, also.

802.11n is still a DRAFT standard. It is clear that there are a wide variety of responses from commercial suppliers to Draft 2 as it stands (and seemingly somewhat dependent on how they implemented the earlier draft), and that some are reacting more promptly than others to the real implications of Draft 2. This is particularly in respect of achieving 270Mpbs connectivity in 802.11g 2.4Ghz environments where there is existing congestion due to channel contention from multiple 802.11g network instances.

LinkSys (and several other vendors) initially achieved 270Mbps link connectivity with their own branded "pre-N" cards solely in the 2.4GHz band, through aggregating several 802.11b/g channels to provide the required "wide" channel bandwidth, but this is not a sustainable strategy in terms of urban 802.11 environments and this is reflected in the Draft 2 specification.

The Intel 4965 card requires the Draft 2 the 5GHz channel to be available to achieve 270Mbps link performance and the LinkSys WRT3XXN routers apparently do not have 5GHz hardware!

Linksys has recently released their WRT600N router model which has a significantly higher level of Draft 2 compliance than the WRT3xxN models and is able to achieve 270Mpbs link connectivity with an Intel 4965 card (RF propogation conditions permitting).

In terms of the 4965 card in a ThinkPad, it will achieve ~130Mbps link connectivity with any Draft 2 compliant access point solely off the two 2.4GHz antennas.... that is with the 5GHz antenna entirely disconnected (or missing), which indicates that the 4965 card is implementing the primary intent of the Draft 2 specification.

Cheers,

Bill B. (a member of several IEEE Technical Standards Committees)

Thanks Bill - your post really cleared up a lot of the questions that I had. You are absolutely correct, the Linksys 300N router I am using does not have 5GHz channels, and is working through 2 2.5 Ghz (max) channels, providing a wide bandwidth of 40 Mhz. I thought that Linksys was probably providing some "home cooking" for its own branded cards. The Intel at 130 Mbps is more than enough, probably, since the actual throughput will be much lower, anyway. I have some legacy stuff, though that does not have WPA2 enabled, so it is kind of a bummer to have to set the router to WPA2 to service N-band connections. Thanks for the link, also. That is what I love about this forum - you have people who actually know stuff... lots of stuff.