Hello Srini,
ad hoc networking is when in a wireless lan two or more end user devices, PCs, form a network without using any access point, any infrastructure element.
This does not avoid that if one of the PCs has another network connection that it can share it with the other members of the ad hoc network.
Ad hoc networks are a security risk in enterprise networking.
The requirement is that all members use the same standard 802.11b or 802.11g or 802.11a
Without an access point I'm not sure you can mix 802.11b and 802.11g stations.
Ad hoc is however included in the 802.11 and 802.11b standards.
see the following link for a description
http://compnetworking.about.com/cs/wirelessfaqs/f/adhocwireless.htm
Hope to help
Giuseppe
