Needless to say, the wireless connection is the one that’s more convenient, as the car automatically detects the mobile device, so you don’t have to keep any cables around.On the other hand, many prefer a wired connection because when Android Auto is running on the car’s display, the phone is also recharged. So technically, you get an extra charge whenever you jump behind the wheel.But what’s sometime confusing for many is that despite using a wired connection, Bluetooth is still required for Android Auto to run. In other words, despite running Android Auto on your car’s screen using a USB cable, the device still needs to be paired with the vehicle’s head unit via Bluetooth as well.And it’s all because of the way Android Auto was developed in the first place.Technically, Bluetooth lacks the necessary bandwidth to offer both audio and video for Android Auto, so what Google did was restrict the use of Bluetooth for phone calls via the Hands Free Protocol, also known as HFP. So despite most of Android Auto running through the cable, the Bluetooth is used for phone calls.As a matter of fact, all head units installed in a car must support audio over USB because Android Auto sends the music audio over USB. At the same time, phone call audio is sent over Bluetooth. The difference between the two is made by the audio quality. The music that Android Auto sends to the HU features a higher quality, typically CD quality, so it needs more bandwidth to work properly.The drawback is that when having Android Auto running on the car’s screen, no other device can connect to Bluetooth, even if technically the system runs over USB. And of course, there’s no way to disable phone calls via Bluetooth to leave it open for other devices.