What is a signal? What is the function of signals?

Signaling is a control signal in wireless communication system, which not only transmits user information, but also ensures the normal communication in order to make the whole network work in order.

Signaling function: call establishment, supervision, dismantling, information needed by distributed application processes (query/response between processes or user-to-user data) and network management information.

Signaling notes:

Random access: to achieve uplink synchronization between the terminal and the base station, involving the physical layer (primary), AS layer and NAS layer.

Attachment: mobile phone access to the core network, registered into the network, involving the NAS layer; Random access must be performed before the attachment process.