Linux Wireless

This page documents how antenna diversity is supported by ath9k.

Adrian Chadd's excellent, detailed notes.

• HB95 (AR9285)
• HB125 (AR9485)

There are 3 types of WB335-based cards. 1-ANT cards share a LNA between WLAN/BT. 2-ANT cards have dedicated LNA for BT and WLAN and have antennae in both slots (MAIN and ALT), but WLAN RX diversity is disabled for some cards (based on vendor requirements).

2-ANT cards supporting WLAN RX diversity.

CUS252 (AR9565 + xLNA)

To enable WLAN RX diversity using the ALT antenna, use the module parameter bt_ant_diversity. The Bluetooth interface has to be disabled when this feature is enabled in ath9k. Also, BTCOEX should be disabled, so the driver must not be loaded with btcoex_enable=1.

modprobe ath9k bt_ant_diversity=1

This can also be turned on/off using the debugfs file bt_ant_diversity.

echo 1 > /sys/kernel/debug/ieee80211/phy0/ath9k/bt_ant_diversity
echo 0 > /sys/kernel/debug/ieee80211/phy0/ath9k/bt_ant_diversity

The debugfs file antenna_diversity can be used to see how the LNA combining algorithm is performing.

cat /sys/kernel/debug/ieee80211/phy*/ath9k/antenna_diversity

Current MAIN config : LNA1
Current ALT config  : LNA2
Average MAIN RSSI   : 40
Average ALT RSSI    : 16

Packet Receive Cnt:
-------------------
                          MAIN            ALT
TOTAL COUNT   :          30932             63
LNA1          :          30932              0
LNA2          :              0             63
LNA1 + LNA2   :              0              0
LNA1 - LNA2   :              0              0

LNA Config Attempts:
--------------------
                          MAIN            ALT
LNA1          :              5              0
LNA2          :              0              5
LNA1 + LNA2   :              0              0
LNA1 - LNA2   :              0              0