WLAN n-mode dramatically slower than g-mode on T61p

[sequoia6488]

I run a WLAN with mixed mode (802.11 a/b/g/n).

My TP61p is blessed with an Intel 4965 AGN chip which should be able to communicate nicely in n-mode.
The Wireless Network Connection Icon in the sys tray says I have a 130 Mbps connection.


In fact, the speed is limited to a lousy trickle, as evidenced by the
speedtest.net (internet download) reading, which gives me just 920 kbps.

If I disable the n-mode in the intel driver's settings (thus downgrading to g-mode) the speed dramatically INCREASES to
8500 kbps, which is what I usually get from my USP.

It seems that the driver cannot really handle n-mode, and therefore shifts down to a low speed.

I have downloaded the latest drivers, and the router runs the latest firmware.

Where should I start to look?

DAVId

[bill bolton]

The Wireless Network Connection Icon in the sys tray says I have a 130 Mbps connection.

What brand and model of 802.11n router/access point are you connecting to?

Unless your router/access point supports operation on the 5Ghz WiFi band, you will not get more than 130Mpbs link level connection speed from a truly 802.11n Draft 2 compliant device such as the 4965AGN.

In fact, the speed is limited to a lousy trickle, as evidenced by the speedtest.net (internet download) reading, which gives me just 920 kbps.

You should also check that you are running WPA2 + AES on the 802.11n connection, as running anything else will definitely impact throughput.

It seems that the driver cannot really handle n-mode, and therefore shifts down to a low speed.

Using a 4965AGN with a LinkSys WRT600N router connected to a ~30 Mbps HFC Internet connection, I can achieve Speedtest.net measured throughputs of over 20,000 kbps across the 802.11n link, so its nothing to do with the driver.

Cheers,

Bill B.

[sequoia6488]

Thanks, Bill.

The router is a linksys WRT150N .
The settings are:
- Network mode: mixed
- Radio band: auto
- Wide channel: auto
- Standard channel: auto

On the link level, thinkvantage connections says I get 130 Mbps.

I tried whe WPA2/AES encryption, and indeed it improved the throughput a little:
from 900 kbps to 1100 kbps - but still far from the 8000 kbps I get when I disable the n-capability on the radio chip.

The 8000 kbps is btw exactly the speed I get on a (only g-capable) T60 notebook.

Regards DAVID

[beGi]

Try to change your channel, maybe there is someone nearby that uses the same as you do, that can cause interference.

[sequoia6488]

Thanks for the idea.

I just scanned the neighborhood radios and made sure that
my channel does not interfere with anyone in the neighborhood.

Unfortunately this did not work, n-performance is still about 900 kbps, while g-performance is 9000 kbps.

DAVID

[runbuh]

Which client are you using - PROset or WZC? Which OS are you running, and at what service pack level?

Can you set your AP for 802.11n only? Do you have a "wide" and "standard" channel setting? You should select "wide".

I realize you want/need to run a mixed mode network, but try making it n-only (both on the card, and on the AP) to see what happens

[sequoia6488]

Which client are you using - PROset or WZC?
- Sorry, I do not understand.

Which OS are you running, and at what service pack level?
- XP SP3

Can you set your AP for 802.11n only?
- Yes, I have tried that. No improvement

Do you have a "wide" and "standard" channel setting? You should select "wide".
- Yes, I have tried that. Speed improves only from 900 kbps to 1100 kbps......

I realize you want/need to run a mixed mode network, but try making it n-only (both on the card, and on the AP) to see what happens
- Yes, tried that. Result: 900 to 1100 kbps download speed.

Regards

DAVID

[bill bolton]

The router is a linksys WRT150N .

The WRT150N operates only on the 2.4GHz WiFi band, so 130 Mbps is the best you will get from a 4965AGN/5100AGN/5300AGN etc (which were all designed to be 802.11n Draft 2 compliant) when using it.

You need a WRT610N (or similar) to get 270 Mbps link level connections (using the 5 GHz WiFi band).

I tried whe WPA2/AES encryption, and indeed it improved the throughput a little: from 900 kbps to 1100 kbps - but still far from the 8000 kbps I get when I disable the n-capability on the radio chip.

802.11n in the 2.4GHz band requires wide channels (40Mhz) to be available and traffic free. Its possible that in your locality you can find a traffic free single 20MHz channel but not a traffic free 40 MHz wide channel.

In the 2.4GHz Wi Fi band there are only three 20 MHz channels that don't overlap at all, so bonding two of those together to get a 40 Mhz wide channel means that you will be sitting over two thirds of the available 2.4 GHz WiFi band channel space...... so the chances of interference from 802.11b/g traffic on other networks is quite significant in urban areas.

Traffic contention in the 2.4 GHz band has proved such a problematic issue out in the field for the 802.11n standards group, that since the 802.11n Draft 2 spec, the major push for 802.11n has been to get traffic off the 2.4 GHz WiFi band and onto the 5GHz WiFi band... where there is much more bandwidth so multiple wide channels can be made available.

Cheers,

Bill B.