WiFi Signal Booster?

My father recently got WiFi for the house but because it’s an old house and in the country side it has very thick walls which cut the Wireless signals area to very small. He wants to be able to connect a laptop from a caravan about 7~12ish meters away from the router. He wants a cheap but good wireless signal booster, like the ones that recieve the packets and resend them so you can increase signal or would a bigger antenna be better?

Related posts:

1. How can a Wifi antenna booster increase the wireless connection performance?
2. NEW High Power USB Wifi Adaptor – Long Range Signal Booster
3. Can I Get A Wifi Booster That Will Work With My Ps3 and Laptop?
4. What is the best way to pick up a wifi signal between homes?
5. Cable Antenna Signal Amplifier TV Broadband Booster