Last week I gave OpenBSD a second chance. And after a few minutes searching the Internet I found a post to the Android issue. It seems that OpenBSD 5.2 did not support the energy saving features used by many mobile devices. However, they improved OpenBSD in the meanwhile and the update to 5.3 solved the issue.
Unfortunately, one point is still open. The connection hangs when Android awakes from sleep and the Wi-Fi sleep policy (keep Wi-Fi on during sleep) is set to "always".
Set it to 'never'. With that setting Android turns Wi-Fi of if it goes to sleep and automatically reconnects to the access point after wake-up. This way my Android tablet works fine with OpenBSD 5.3.
See also:
- Wireless Access Point Using OpenBSD
- OpenBSD Issue with Android and the Atheros Driver
- Set Wi-Fi Sleep Policy to Never
- Save Battery Keeping Wi-Fi Alive (don't do that when using an OpenBSD access point)