A3 Interface

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 – 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. User traffic – the user traffic is transported in traffic channels.