Android 9 introduces the ability for devices to operate in STA and AP mode concurrently. For devices supporting Dual Band Simultaneous (DBS), this feature opens up new capabilities such as not disrupting STA Wi-Fi when a user wants to enable hotspot (softAP).
Examples and source
Wi-Fi STA/AP concurrency is supported in the default AOSP Android framework
code. It is also supported by the reference HAL implementation described in
Wi-Fi HAL. The
WIFI_HIDL_FEATURE_DUAL_INTERFACE build-time flag described in the
Implementation section below enables an interface concurrency specification
indicating concurrent support for STA and AP.
To implement Wi-Fi STA/AP concurrency on your device:
Turn on a build-time flag to enable support for two interfaces in the HAL. The flag is located in
- WIFI_HIDL_FEATURE_DUAL_INTERFACE := true
Expose two network interfaces:
- wlan0 and wlan1
WIFI_HIDL_FEATURE_DUAL_INTERFACE flag is ignored if the
flag is specified. For more information, see
Wi-Fi multi-interface concurrency.
To validate that the feature is working as intended, run both an integration test (ACTS) and a manual test.
The ACTS file,
WifiStaApConcurrencyTest.py, located in
tools/test/connectivity/acts/tests/google/wifi, contains a set of tests which
bring up different combinations of STAs and APs.
To manually validate this feature, turn the STA and AP interfaces on and off independently from UI.
If both AP and STA are on the same subnet, routing issues on the device-under-test (DUT) may occur. To avoid collisions, try moving the AP to a different subnet.
Some Wi-Fi chip vendors place the radio in time-sharing mode if STA and AP are on the same band but on different channels. This leads to a severe drop in performance. To address this issue, the chip can use Channel Switch Avoidance (CSA) to either:
- Move the AP to the same channel as the STA
- Move the AP to a different band from the STA