A lot of people have report problem with their weak Wi-Fi signal. Some of the people have experience a significant drop in signal using iPad comparing to signal on computers or iPhones held in the same location relative to the same access point.
Here are some possible solutions you can try to fix the weak wi-fi signals on ipad:
1. Use an AirPort Extreme.
2. Return a problem device back to Apple store for a replacement.
3. Turn off WIFI and back on again seems to fix for some people.
4. On the modem router set to 802.11G only and set be connected continously.
5. The iPad has problems if you use a dual-channel router (one that supports both 802.11a and 802.11n at the same time) if the networks use the same name. Change the SSID to different names.
6. "I use 3 different routers in my home; FIOS Actiontec, Linksys WRT54GS (w/DD-WRT) and Verizon/Westell Router. I (now) connect no problem to all 3 and Speedtest shows consistently 15-20Mbps D/L and pretty consistent 10-15Mbps U/L . Each has a unique SSID but the password, security settings, etc are exactly the same. I had issues with weak connectivity until I changed all to hide SSID, WP2-Personal, MAC Address filtering. All 3 SSID's, password set up in iPad. Rebooted all routers and iPad. Also in iPad network settings "forget" all neighbors networks, bluetooth off, brightness medium, http proxy off or auto works . Again hope it helps."
7. On iPad go to the Wi-Fi setting, Swipe on it to bring up all the settings. Then change http proxy from (default) off to Auto.