Yosemite Wi-Fi Enhancements
Taken together, this information can help you sort out network difficulties. If you always see 20 MHz in the Channel line, but the PHY (physical protocol mode) is 802.11ac, you have other networks in the vicinity on the same or adjacent channels that are forcing the base station and client to negotiate a slower rate; moving the base station or forcing a different channel could help.
If your noise value is very high (like -30 dBm instead of -90 dBm), there’s interference from other devices, Wi-Fi or otherwise, in the same band, and you again may need to move the base station or pick a different channel.
