RRC connection
exists
when a UE went through the connection establishment procedure and has been allocated resources in the UTRAN and a U-RNTI.
With RRC connection, some SRBs are allocated.
RB (Radio Bearer)
is a layer 2 connection between the UE and the RNC.
It is used for both control signaling and user data.
RB used for signaling is called an SRB.
various types of connections that the UE will have with the network:
1. RL
2. RB
3. RAB
4. SRB
5. PDP
6. RRC connection
RL (UE-Node B)
RB (UE-Node B-RNC)
RAB (UE-Node B-RNC-SGSN)
PDP context (UE-Node B-RNC-SGSN-GGSN)
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 [...]
Layer 2 provides upper layers with information transmission between the UE and UTRAN by means of Radio Bearers (RBs) and Signaling Radio Bearers (SRBs).
RBs are for transmission of user data.
SRBs are for transmission of control information that can be originated either in the RRC or in upper layers.
RB specifies the configuration and the parameters of [...]
Radio interface protocol structure:
Note that RB vs. SRB
At the UTRAN side, RLC and above protocols are located at RNC.
MAC protocols: some functionalities are at Node B, others are at RNC.
The AS provides the NAS with a service of information transfer between UE and the CN in what is named a Radio Access Bearer (RAB).
RAB consists of two:
1. Radio bearer (RB) between the UE and RNC
2. Iu Bearer between RNC and CN
RB is only for user data either in CS or PS mode.
RB is [...]
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 [...]
