So a few days ago I just bought a new MacBook Pro Retina Early 2015 and at first it was all good. 2-3 days ago I noticed strange problem – Wi-Fi keeps going down like every 10-30 seconds or so and it's not router's problem, because on my other PCs the Wi-Fi is working perfectly fine. For example right now I was downloading 35MB file (500KB/s download speed) and the speed went to 0KB/s like 5 times or so, so I had to turn off Wi-Fi on MBP and turn it on again. Then the speed went to 0 and I had to do the same. Same problem occurs when I'm browsing – out of nowhere Safari stops loading pages and I need to wait for like 30 seconds until the wi-fi starts working again or I need to turn off and on wi-fi on MBP.
What I tried:
Turning off wi-fi and deleting these files:
com.apple.airport.preferences.plist
com.apple.network.identification.plist
com.apple.wifi.message-tracer.plist
NetworkInterfaces.plist
preferences.plist
from /Library/Preferences/SystemConfiguration/
It didn't help. I also tried to forget the network I was currently on and connect to it again, but that didn't work either. Atm I don't have a possibility to check how my MBP works on other Wi-Fi networks. I've installed the latest version of Yosemite.
Best Answer
Usually when the WiFi connection is still active but no data is flowing indicates Chanel crowding (to many devices/users on same channel).
If the WiFi is disconnecting that could be number of other reasons. But since you are talking about the speed going down...
When the MCS index is zero (0) then the channel crowding is a issue. The MCS needs to be at least 3 or more.
To see yours hold the "alt" key and click on the WiFi icon. (this is what I have)
Easiest test (fix) is to change the Chanel on the router.
You could also do a WiFi channel analysis to find out and then choose a less crowded Channel.
To change the Wifi channel on Pirelli DRG A125G router: