Wireless Oom » rrc

RRC connection establishment

wirelessoom — Mon, 15 Mar 2010 19:19:03 +0000

What does RRC protocol do?

wirelessoom — Sun, 26 Jul 2009 13:59:23 +0000

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.

What types of SRBs exist?

wirelessoom — Fri, 19 Jun 2009 07:42:46 +0000

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 through DCCH.

SRB#1 uses unacknowledged mode and SRB#2 acknowledged mode

SRB#3 and SRB#4:

dedicated messages from NAS layer through DCCH with acknowledged mode

SRB#3 with high priority, SRB#4 with low priority

Additional SRBs up to 32 can be used for messages with transparent mode (e.g., through DCCH, PCCH or BCCH).

RRC connection vs RB

wirelessoom — Fri, 19 Jun 2009 07:32:53 +0000

RRC connection establishment is initiated by UE all the time.

RB established is initiated by CN all the time.

I'm confused! RRC connection, RB, SRB, signaling connection ?!

wirelessoom — Thu, 18 Jun 2009 18:18:29 +0000

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 messages. That is, messages are exchanged between UE and CN.

However, note that this NAS signal messages still use SRBs between UE and UTRAN!!

————–

RB:

The upper layer signalling messages (exchanged by the UE and the CN) may request the initiation of a user service (beloning to certain service class and with different requirements) .Then, RB will be established. RB is a user data.