By following below steps. One time setup via usb cable will be required though.
Source: Sync your iPhone, iPad, or iPod using iTunes on your computer
"Sync your content using Wi-Fi
After you set up syncing with iTunes using USB, you can set up iTunes to sync to your device with Wi-Fi instead of USB. Here's how:
- Connect your iOS device to your computer with a USB cable, then open iTunes and select your device.
- Click Summary on the left side of the iTunes window.
- Select "Sync with this [device] over Wi-Fi."
- Click Apply.
When the computer and the iOS device are on the same Wi-Fi network, the iOS device appears in iTunes. The iOS device syncs automatically whenever it's plugged in to power and iTunes is open on the computer."