A3 Interface

The A3 interface carries coded user information (voice/data) and signaling information between the Selection / Distribution unit function and the channel element component of the BTS (Base Transceiver System). The A3 interface is composed of two parts, Signaling and User Traffic. The signaling information is carried across a separate logical channel from the user traffic channel, and controls the allocation and use of channels for transporting user traffic. The user traffic is transported in traffic channels.