rt2500pci with BeBox (Thomson ST 780WL)

Live forum: http://rt2x00.serialmonkey.com/viewtopic.php?t=4609


09-02-2008 12:57:27

I have a small home network with 4 wireless nodes and one of them is the rt2500pci. Two of the others are Intel PRO devices and the last is an Apple. The problem I face with the Ralink device is that it seems to have a detrimental effect on the AP itself (specially with BitTorrent). iwconfig usually shows excellent link conditions (54Mbps, 88/100 link quality) but the interface speed on the AP itself (a Thomson SpeedTouch 780WL) drops to 1 or 2Mbps soon after a torrent is started on the Ralink node. I think it is fair to assume that BT is not the culprit since it works just fine from any of the other 3 nodes.

I have had this issue for quite some time (more than 6 months). Does anyone have any idea on how I can go about troubleshooting this problem? I am currently running Fedora 8 with the kernel. modinfo gives me the following

filename: /lib/modules/
license: GPL
description: Ralink RT2500 PCI & PCMCIA Wireless LAN driver.
version: 2.0.14
author: http://rt2x00.serialmonkey.com
srcversion: 1230A1910F10F35934D00F7
alias: pci:v00001814d00000201sv*sd*bc*sc*i*
depends: rt2x00pci,rt2x00lib,eeprom_93cx6
vermagic: SMP mod_unload

Thanks in advance.


09-02-2008 13:30:03

You should set the rate manually

iwconfig wlan0 rate 54M

after that it shouldn't drop to 1Mbit anymore.


09-02-2008 13:43:55

That may not help if the problem is the AP reducing the rate (but it is worth trying to help identify the cause of the problem). The TX and RX rate are independent and setting the rate at the Ralink end will only affect it's Tx rate. When there have been problems with rt2x00 I have often seen my RT73 transmit at 54M but the AP only reply to it at 1M.

To find out if that is the case it would be useful if the OP can run of his iwlwifi devices in monitor mode with wireshark and see if there are lots of retries from the AP. It would be useful if possible to confirm that the problem only affects the rt2x00 driver and goes away if using the legacy driver.


09-02-2008 14:47:04

As Adam pointed out, the TX rate on the rt2500 device remains at 54M. It is the TX rate of the AP that drops down to 1/2M. The interesting thing here is that this problem seems to be triggered by BT traffic only. I can do 9M rate downloads (e.g. with yum) over http without any problems.

I'll try getting packet dumps from the Intel devices later. Could someone tell me which modules I need to unload (other than the obvious rt* ones) before I can try the legacy drier?



09-02-2008 14:52:02

just rmmoding rt2500pci is enough, that will put rt2x00pci and rt2x00lib out of use (you could rmmod them if you want but is not required).


09-02-2008 16:48:45

I've tried capturing on one of the iwl3945 interfaces (with an active torrent session running on the rt2500pci) using wireshark (promiscuous + monitor) but the only frames I got there were the beacons.

I also tried to use the legacy driver but I could not associate with the AP with it (WEP - no errors in dmesg).

While trying out different encryption methods (None/WEP/WPA2), I discovered that the problem does not seem to manifest when encryption on the AP is set to "none". Perhaps the issue is in the rt2x00 driver's encryption related code?