My Iphone does not sync over my Wi Fi Network

I have an I phone 4 S which is up to date as far as IOS 5.xx. Yet it does not sync over my Wi Fi Network??? I also have an I pad which also does not snyc over my Wi Fi net work.

I have followed the I Tunes instructions, as far as plugging in my devices to power and making sure they are on my Wi Fi network, they still do not sync over thge network.

Can someone please help me trouble shoot this problem.

Thanks

I phone 4S

I pad 2.0

Windows 7 64 bit system

Outlook 2010