Those who are having Wi-Fi connection share a common problem. If you stay in the room having the Wireless router, you will get decent signal but on moving away a bit from there you will experience network connection problems. To fix such problems you need to do Wireless site survey which is defined as the process of planning and designing a wireless network, to provide a wireless solution that will deliver the required wireless coverage, data rates, network capacity, roaming capability and Quality of Service. Mac has an in-built Wi-Fi Diagnostics program which is somewhat hidden user settings and sort of expertise is needed to make use of that. For common users, NetSpot Team has launched a new free app called NetSpot for sorting out such problems easily.
To get a complete idea of how to make use of this software you need to see this video.
The features of the program asdescribed in their website can be seen below.
As I don’t have a Mac, I want to suggest you to read this review for better understanding about the software.
If you have any problem using it or want more features, you can login to their forum.