You can try set static IP on your phone (menu > settings > wireless and network > wifi settings > menu > advanced), connect to your network, then un-set it and reconnect to your network see if this do the trick.
Thanks I tried this, it didn’t work.
The problem is my router+firewall has DHCP lease time which been set default to maximum.
In no time I can change and modify my router+firewall by changing DHCP lease time more shorten time. I put it as 3 minutes.
Then from my phone I disconnected it wait 4-5 minutes and connect again.
It will get new IP address.
But this is not good practical.
Smart phone support with IP address should have able to renew IP address.
Specially OS android with as we known powered by Linux.
Anyway if I use terminal by releasing IP address also denied.
It seems I should root my phone before doing SU privileges, to use function such renew IP address.
It will great someone can developed tools can do this