Can't control connection bit rate using iwconfig with Atheros TL-WN821N (AR7010)
By Sophia Vance
I'm trying to reduce the connection bit rate on my Atheros TP-Link TL-WN821N v3 usb wifi adapter due to frequent instability issues (reported connection speed goes down to 1Mb/s and I have to physically reconnect the adapter to regain a connection). I know this is a common problem with this device, and I have tried everything I can think of to fix it, including using drivers from linux-backports; compiling and installing a custom firmware (following instructions on ) and (as a last resort) using ndiswrapper.
When using ndiswrapper, the wifi adapter is stable and operates in g mode at 54Mb/s (whilst when using the default ath9k_htc module, the adapter connects in n mode and the bit rate fluctuates constantly). Unfortunately, with this setup I have to run my processor using only one core, since using SMP with ndiswrapper causes a kernel oops on my system.
So I want to lock my bit rate to 54Mb/s (or less, if need be) for connection stability, using the ath9k_htc module.
I've tried 'sudo iwconfig wlan0 rate 54M'; the command runs with no error but when I check the bit rate with 'sudo iwlist wlan0 bitrate' the command returns:
wlan0 unknown bit-rate information. Current Bit Rate:78 Mb/sAny ideas? Here's some info (hopefully relevant) on my setup:
Xubuntu (12.04.3) 64bit (kernel 3.2.0-55.85-generic) using Network Manager. My Router is from Virgin Media, the VMDG480.
lshw -C network : *-network description: Wireless interface physical id: 1 bus info: usb@1:4 logical name: wlan0 serial: 74:ea:3a:8f:16:b6 capabilities: ethernet physical wireless configuration: broadcast=yes driver=ath9k_htc driverversion=3.2.0-55 firmware=1.3 ip=192.168.0.9 link=yes multicast=yes wireless=IEEE 802.11bgnlsusb -v:
Bus 001 Device 003: ID 0cf3:7015 Atheros Communications, Inc. TP-Link TL-WN821N v3 802.11n [Atheros AR7010+AR9287]
Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 255 Vendor Specific Class bDeviceSubClass 255 Vendor Specific Subclass bDeviceProtocol 255 Vendor Specific Protocol bMaxPacketSize0 64 idVendor 0x0cf3 Atheros Communications, Inc. idProduct 0x7015 TP-Link TL-WN821N v3 802.11n [Atheros AR7010+AR9287] bcdDevice 2.02 iManufacturer 16 ATHEROS iProduct 32 UB95 iSerial 48 12345 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 60 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0x80 (Bus Powered) MaxPower 500mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 6 bInterfaceClass 255 Vendor Specific Class bInterfaceSubClass 0 bInterfaceProtocol 0 iInterface 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x01 EP 1 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x82 EP 2 IN bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x83 EP 3 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0040 1x 64 bytes bInterval 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x04 EP 4 OUT bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0040 1x 64 bytes bInterval 1 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x05 EP 5 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0 Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x06 EP 6 OUT bmAttributes 2 Transfer Type Bulk Synch Type None Usage Type Data wMaxPacketSize 0x0200 1x 512 bytes bInterval 0
Device Qualifier (for other device speed): bLength 10 bDescriptorType 6 bcdUSB 2.00 bDeviceClass 255 Vendor Specific Class bDeviceSubClass 255 Vendor Specific Subclass bDeviceProtocol 255 Vendor Specific Protocol bMaxPacketSize0 64 bNumConfigurations 1
Device Status: 0x0000 (Bus Powered)iwlist wlan0 scanning:
wlan0 Scan completed : Cell 01 - Address: C4:3D:C7:3A:1F:5D Channel:1 Frequency:2.412 GHz (Channel 1) Quality=37/70 Signal level=-73 dBm Encryption key:on ESSID:"my essid" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s 24 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s Mode:Master Extra:tsf=00000070cca77186 Extra: Last beacon: 5588ms ago IE: Unknown: 0007756E69636F726E IE: Unknown: 010882848B962430486C IE: Unknown: 030101 IE: Unknown: 2A0100 IE: Unknown: 2F0100 IE: IEEE 802.11i/WPA2 Version 1 Group Cipher : TKIP Pairwise Ciphers (2) : CCMP TKIP Authentication Suites (1) : PSK IE: Unknown: 32040C121860 IE: Unknown: 2D1AFC181BFFFF000000000000000000000000000000000000000000 IE: Unknown: 3D1601080400000000000000000000000000000000000000 IE: Unknown: DD7E0050F204104A0001101044000102103B00010310470010F99C335D7BAC57FB00137DFA79600220102100074E657467656172102300074E6574676561721024000631323334353610420007303030303030311054000800060050F20400011011000743473331303144100800022008103C0001011049000600372A000120 IE: Unknown: DD090010180203F02C0000 IE: WPA Version 1 Group Cipher : TKIP Pairwise Ciphers (2) : CCMP TKIP Authentication Suites (1) : PSK IE: Unknown: DD180050F2020101800003A4000027A4000042435E0062322F00iwconfig:
lo no wireless extensions.
wlan0 IEEE 802.11bgn ESSID:"my essid" Mode:Managed Frequency:2.412 GHz Access Point: C4:3D:C7:3A:1F:5D Bit Rate=78 Mb/s Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=36/70 Signal level=-74 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0,2 Answers
I don't have this hardware so I am unable to test, however, it appears that the rate is decided by the firmware. There's patched firmware here that should work with kernel 3.2.0-55.85-generic and perhaps later kernels as well.
Quoting befinitiv
You find a pre-compiled firmware that uses MCS3 (26mbit/s) as an injection rate under patches/AR9271/firmware/htc_9271.fw. Copy this file to /lib/firmware and re-insert the card to use the modified firmware. If you want to compile the firmware with a different injection rate you can take look at the patch that I supplied. The easiest way is to replace the first line in the list with a copy of the wanted injection rate. Instructions for compiling the firmware for Linux are given in the firmware repo.
After installing the firmware, simply re-plug the USB Adapter to use it.
Sources:
Edit: As @pandalion98 points out in this comment the patch under discussion can be found here.
7Use iw instead:
iw wlan0 set bitrates legacy-2.4 9before establishing the connection
