Have Oleg's fw installed in ASUS.
Set ASUS for client/station mode:
System Setup | Operation Mode - Home Gateway
Wireless | Bridge > AP Mode - WDS Only
Wireless | Advanced > Extended Mode - Station
Then You set the rest of the wireless part (SSID .... ) as an adapter = the same config as used in Your AP/Senao. Use a channel above 6.
I use WEP, haven't tried WPA.
How to handle IP depends on your need. DHCP or fixed.
If DHCP is handled from Senao, set Senao LAN to 192.168.1.1 and for ASUS set Lan to 192.168.1.2, WAN to Automatic IP and Enable DHCP server= No