RRC is the main AS control protocol.
RRC performs
1. establishment, modification and release of RRC conncetions
RRC connections are used to transfer RRC signal messages and be used to transport higher layer NAS protocol messages.
2. establishment, modification and release of RAB (radio access bearer ), user plane data connection.
3. radio mobility functions, etc.
RRC messages are transferred by the lower layers through SRBs, which specify the characteristics of the logical, transport and physical channels.
SRB#0 : when establishing a RRC connection
1. uses CCCH logical channel
2. uses the RACH transport channel in the uplink
3. uses the FACH transport channel in the downlink
SRB#1 and SRB#2:
dedicated message generated at RRC layer [...]
RRC connection establishment is initiated by UE all the time.
RB established is initiated by CN all the time.
Now I got the idea!!!
RRC connection:
To transfer RRC messages (messages generated at RRC layer itself and NAS messages) between UE and UTRAN.
RRC messages are transferred by the lower layers through Signaling Radio Bearers (SRBs).
Thus, establishment of RRC connections mean establishments of different SRBs.
Only a single connection.
———-
Signal connection:
Establishment is needed in order to transfer NAS signal [...]
