ath9k bluetooth coexistence#
This page documents howbluetooth coexistence is supported by ath9k.
Supported Coexistence Schemes#
Enabling bluetooth coexistence#
Bluetooth coexistence has to be manually enabled when loading ath9k bysetting thebtcoex_enable module parameter.
modprobe ath9k btcoex_enable=1
Cards supporting BTCOEX#
2-wire (two-chip cards with separate WLAN and BT)#
* WB197 ( AR9287 + AR3011 )
3-wire (two-chip cards with separate WLAN and BT)#
* WB195 ( AR9285 + AR3011 )* WB225 ( AR9485 + AR3012 )
MCI (SoC-type cards with integrated WLAN and BT)#
* WB222 ( based on AR9462 )* WB335 ( based on AR9565 )
3-wire scheme details#
Some Atheros cards in both the AR9002 and AR9003 family use this schemein which WLAN and Bluetooth time-shares their usage of the 2.4 GHz band.Three pins are used in this scheme.
PIN | Driven by | Details |
|---|---|---|
BT_ACTIVE | BT | Signals that Bluetooth device is expecting TX or RX activity. Provides WLAN with information about when the antenna is being used by Bluetooth. |
BT_PRIORITY | BT | At the start of BT_ACTIVE, it is asserted to indicate the priority of the Bluetooth activity. Then, this pin indicates the TX/RX status of the Bluetooth activity. |
WLAN_ACTIVE | WLAN | Indicates when WLAN has taken the antenna. |
PTA (Packet Traffic Arbitration ) Algorithm#
BT weights and WLAN weights are programmed in the hardware by thedriver. Hardware infers the Bluetooth activity by sampling the BT_ACTIVEsignal. Whenever there’s Bluetooth activity, hardware compares theassigned weight of Bluetooth traffic and the current WLAN traffic. IfBluetooth traffic has a lower priority, hardware will continue WLANtraffic, thus stomping on the Bluetooth side (and possible interferenceon WLAN side as well). If Bluetooth traffic has a higher priority,hardware will abort WLAN traffic and treat it as if there’s collisionon-air.