Upper Layer Signaling
Moray Rumney · 2013
The access stratum (AS) contains the functionality associated with access to the radio network and the control of active connections between a UE and the radio network. The AS consists of a user plane and a control plane. There is an important L1/L2 control protocol called the downlink control information (DCI) that resides in the physical layer. The remainder of the AS covers four protocols: the medium access control (MAC); the radio link control (RLC); the packet data convergence protocol (PDCP); and the radio resource control (RRC). MME is the control plane entity that implements the procedures used for EPS mobility management (EMM) and EPS session management (ESM) in the evolved packet system (EPS). The non-access stratum (NAS) contains all the functions and protocols used directly between the UE and the core network.