Trouble of having iPad connected to ad-hoc with static IP

Question

I am having a problem with the iPad WiFi connection to ad-hoc (by Windows 7) with static IP.

The procedure:

1. Connect to the Internet with a wired local network connection (autoconfiguration, ip:192.168.1.100);
2. Enable the sharing of local network connection;
3. Setting the WiFi interface with static IP address: 192.168.2.1, netmask:255.255.255.0;
4. Create an ad-hoc WiFi network with WEP security, I have also tried open security;
5. iPad connect to the ad-hoc WiFi with the right password, with the static IP address:192.168.2.2, netmask:255.255.255.0, router:192.168.2.1, dns:8.8.8.8;
6. After 1 minute, the setting takes effect, the left-top WiFi icon is shown, but, iPad just couldn't access the Internet!

It's weird, I have no idea about how to solve it.

P.S.: I have tried ping 192.168.2.2(iPad) from 192.168.2.1 (Windows 7), some are ok, and some are timed out.