User Agent Group redirect mobile website

Hi
I want to use the User Agent Group to redirect to my mobile website in subdomain for every visit from a mobile device.

I add the user agent and the subdomain of my mobile website (http://mobile.site.com)

The only problem is that it redirect to the root of the website (/) and not to the specific post if user came from.

example:
from http://www.site.com/?p=1234 it redirect to http://mobile.site.com/ instead of http://mobile.site.com/?p=1234

Any solution?

http://wordpress.org/plugins/w3-total-cache/