Inside Mac OS X 10.7 Lion: New Wi-Fi Diagnostics tool
http://www.appleinsider.com/articles/11/03/15/inside_mac_os_x_1
WiFi Dropping in OS X Lion? Here are Some Wireless Troubleshooting Solutions
http://osxdaily.com/2011/07/22/wifi-dropping-in-os-x-lion-fixes
