I have 12.04 installed on my Samsung laptop with RTL8111/8168B PCI Express Gigabit Ethernet controller. But I can't connect to or create a Ad-hoc network. Whether I need to install any additional drivers for enabling Ad-hoc network?
Unfortunately, your card is a wired card. It does not have any sort of transmitter or antenna. You can, however, use a cable, to connect to another computer or a router. An alternative is to buy a wireless adapter. You may install it inside your computer. IT, however, should have an adapter already installed, being a laptop.
Should you try to set up a wired network, you need at least one device to run a DHCP server(many routers do that) or manually assign an IP address to every device.