Root - no need to use USB cable - Only Rooted devices!!!
No Root - USB cable Required to switch on Wi-Fi Mode

ADB - (Android Debug Bridge) for android developers
"Wi-Fi ADB" is an application that allows your device to be connected to your computer through Wi-Fi connection.

Test and debug your applications via Wi-Fi connection
Quick access to Wi-Fi hotspots
Indicator of Wi-Fi network connection
Automatic detection of IP-addresses
Pop-up notifications to show of the network status
Quick access to developer tools
Support for Android devices from version Android 2.3.3 and up


Activate Wi-Fi Mode with Wi-Fi ADB and run on your PC command:
adb connect device_ip