Wireless-N upgrade

[hmphargh]

I'm an occasional reader and posted some a couple of years back. I received good advice and help then, so I figured you guys might be able to help me again. I did a search and could not find anything useful due to the fact that my search terms were too common.

I have an X61s (type: 7668CTO) with an Atheros a/b/g card, I believe it is an ath5k card. I recently upgraded my home network to a/b/g/n with the help of a Linksys WRT 610N, and I would like to do the same with my laptop. I know that Thinkpads often have special issues when upgrading wireless devices, so I wanted to know if there are any drop-in replacements that won't require me to flash my computer with a hacked bios. I went to the Lenovo site and could not find any a/b/g/n cards that are specifically supported by the 7668CTO.

Do any a/b/g/n cards exist that will work as drop-in replacements?

Thank you in advance for any help or suggestions.

[Batavian]

I think this will work.

http://www.google.com/products/catalog? ... ps-sellers

You will need a third wire too.

[hmphargh]

Can anyone tell me about the 3rd wire situation? Do I just need to buy a certain wire and route it the same way the other 2 are? Sorry for my naivety, this is the first time I've ventured into the whole wireless upgrade arena.

[EOMtp]

Given that you want to stay with a standard BIOS, as you state, then you cannot use any "standard" Intel 4965 card -- you must use the Lenovo-branded "flavor" of the Intel 4965, i.e., FRU #42T0865. You may also use the Atheros-based card, named ThinkPad 11a/b/g/n, FRU #42T0825.

The third antenna (white) mounts inside the LCD case. You would need to remove the LCD bezel to install the third antenna, which is part of the WLAN MIMO antenna kit: FRU #93P4540 (if you have the regular LCD screen) or FRU #93P4541 (if you have the UltraLight LCD screen).

[bill bolton]

so I wanted to know if there are any drop-in replacements that won't require me to flash my computer with a hacked bios.

A Lenovo 4965AGN (that is, one with a Lenovo FRU on the label) will drop right into an X61.

There is one here... http://cgi.ebay.com/IBM-Lenovo-Thinkpad ... 76867141QQ

Give it a try with two antennas and see how it works for you, before going to the trouble of fitting the third antenna.

Cheers,

Bill B.

[hmphargh]

Thanks for the reply, out of curiosity, does anyone know what performance gains, if any I will get by upgrading to wireless N with 2 antennae?

[EOMtp]

The performance gains depend on whether the device is using 20MHz channels or 40MHz channels. The Intel 4965AGN card supports 802.11n standard 40MHz channels only in the 5GHz spectrum in order to minimize negative impact to legacy devices/networks. So if the device can "see" 801.11g transmitters within range, then the device will revert to 20MHz channels.

As you can see from the chart below, the throughput is double with 40MHz channels vs. 20MHz channels, at just about every signal-to-noise ratio (SNR) at which the devices can operate (the horizontal axis in the chart represents SNR).
http://www.deviceforge.com/files/articl ... 041_g3.gif

The primary advantage provided by a 2x3-20MHz implementation over the 2x2-20MHz implementation is improved SNR.

Consequently, with only 2 antennas, one can see anything from 0% to 100% improvement in throughput, depending on the operating environment. As you can see from the chart, far more important than 3 or 4 antennas is whether or not the device is "permitted" to operate in the 5GHz spectrum -- an unlikely situation in densely populated urban areas, but most probable in low density population areas.

[hmphargh]

The performance gains depend on whether the device is using 20MHz channels or 40MHz channels. The Intel 4965AGN card supports 802.11n standard 40MHz channels only in the 5GHz spectrum in order to minimize negative impact to legacy devices/networks. So if the sevice can "see" 801.11g transmitters within range, then the device will revert to 20MHz channels.

As you can see from the chart below, the throughput is double with 40MHz channels vs. 20MHz channels, at just about every signal-to-noise ratio (SNR) at which the devices can operate (the horizontal axis in the chart represents SNR).
http://www.deviceforge.com/files/articl ... 041_g3.gif

Consequently, with only 2 antennas, one can see anything from 0% to 100% improvement in throughput, depending on the operating environment.

Thank you, obviously no one can tell without trying it out, but I just wanted to make sure that running the card with only 2 antennae wasn't completely futile from the start

[EOMtp]

The following is no way "obvious" -- note the AES encryption requirement for "N" speeds:
http://www-307.ibm.com/pc/support/site. ... MIGR-67113

[hmphargh]

Thanks for that, incidentally, I already run AES only because Apple products in my household seem to poop their pants when given the option between TKIP and AES.

[bill bolton]

whether or not the device is "permitted" to operate in the 5GHz spectrum -- an unlikely situation in densely populated urban areas, but most probable in low density population areas.

Operation in the 5GHz spectrum is the preferred mode for densely populated urban areas.... more bandwith to start with so more channels available etc etc.

Propogation in the 5GHz channel is going to be less favourable inside buildings than for the 2.4GHz band, however this is balanced by the better chance of getting a "interference free" channel to operate in. For operation over modest distances (up to 7 metres or so) from an internal access point, the propogation difference between the bands are probably not significant (depending on the construction materials used in the the building), but for operation over longer distances from the access point, the differences are likely to be more significant.

Cheers,

Bill B.

[EOMtp]

Operation in the 5GHz spectrum is the preferred mode for densely populated urban areas....

That is true, and will be the mode of operation in an ideal world devoid legacy hardware. However, in densely populated areas in the real world, it may be necessary for N devices to self-"downshift".

[bill bolton]

However, in densely populated areas in the real world, it may be necessary for N devices to self-"downshift"

Your meaning here is completely unclear to me.

Can you please explain it using other words.

Cheers,

Bill B.

[EOMtp]

Can you please explain it using other words.

The following has the clarity and detail that lacked in my cryptic comment:
http://www.enterasys.com/company/litera ... 11n-wp.pdf

[bill bolton]

The following has the clarity and detail that lacked in my cryptic comment:
http://www.enterasys.com/company/litera ... 11n-wp.pdf

Hmmm... there's one only mention of downshift in the whole document, and its in context its about mixed-mode operation in the 2.4GHz WiFi band (though the document doesn't make that clear).

For the 5Ghz WiFi band, unless there is significant 802.11a traffic (which is only likely in a few commercial facilties in North America), mixed-mode operation is not going to be present, so the "downshifting" referred to is just not going to occur.

Cheers,

Bill B.