MacBook Pro can't actually connect to Wi-Fi with Self-Assigned IP

Question

Hi there
I have a 15 inch MacBook Pro and it can connect to Wi-Fi but have no actual data coming in. And it says self-assigned IP.
This only happens to my home Wi-Fi, however, I can connect and use Wi-fi at school or anywhere else perfectly. In the mean time, my Android phone and my flatmates' Windows have no problem using the Wi-Fi. The problem has been going on and off for a month, sometimes it works again and sometimes it goes wrong like this again.
During this time I mostly use my other MacBook Pro 13 inch Retina. Until today, this problem happens on my 13 Retina mac for the first time, and the 15 Pro again as well. A few days ago, my 15 Pro started working again, and today they just gone wrong together at the same time.
I just found out that my 15 pro can still work if connected to ethernet, but I can't just work in the living room, where the router is. And as you know Retina doesn't support Ethernet.
I've check on the Internet and found many people have the same problem as I do. I also tried lots of ways to fix it with the information I found online. And nothing works. I even suspect that it's actually my flatmate blocks me out with some setting on the router (Is it possible?)
Anyways, can someone please help me fix it thoroughly... Please and thanks.

Answer 1

Each country regulates wireless networking differently. Wi-Fi devices are restricted to certain frequencies and power levels. The client devices try to find out where they are and configure themselves accordingly. Since a wireless access point (WAP) usually does not move across national boundaries, the Wi-Fi regulatory domain (country code) is set by querying the first one to respond when the client initializes itself. You don't have any direct control over it on the client. If your device is picking up the wrong country code, and is therefore locked out of using some Wi-Fi channels or operating at full power, the only lasting solution is to fix or remove the misconfigured WAP.
To find out which WAP's are broadcasting a wrong country code, do as follows.
Triple-click anywhere in the line below on this page to select it:
/S*/*/P*/*/*/*/*/airport -s | open -ef
Copy the selected text to the Clipboard by pressing the key combination command-C.
Launch the built-in Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window by pressing command-V.
The command may take a noticeable amount of time to run. Wait for a new line ending in a dollar sign ($) to appear.
A TextEdit window will open with the output of the command. The first line should look like this:
SSID BSSID RSSI CHANNEL HT CC SECURITY (auth/unicast/group)
Each line below that one represents a WAP within range. Compare the two-letter code in the column headed "CC" with the ISO code for your country. The code "X0" means that the country couldn't be determined. If a WAP with a wrong code is not under your control, try restarting the computer as close as possible to your own router.