What is AS (Access Stratum)?

It is a functional layer in the protocol stack of UMTS and LTE technology. The protocol stack acts between the user equipment and the radio network. Access stratum is responsible for transporting data over the wireless connection. Access stratum is also responsible for managing the radio resources. The radio network is called the access network and the Access stratum contains the functionality associated with access to the radio network and the control of active connections between the UE and the radio network. Security that acts in the Access stratum part is known as the AS security.