When i try to connect through WIFI i can see the carambola device in my tab but when i try to connect, the tab is trying to get the IP from the carambola device but it can't get the IP. Please help me i am waiting for your valuable replay.

presuming the board acts as AP bridged as

[DSLrouter - main DHCP server]---[carambola2 AP mode](--- ---)[your tablet]

look at your main DHCP server and find the IP lease assigned to carambola2, if any. If so, ssh/telnet to that IP and check /etc/config network and wireless config files.
If no lease was assigned you probably could re-flash the board, unless you have some recovery IP address.