A Signaling Radio Bearer (SRB) is a radio bearer that carries DCCH signaling data. An SRB is used during connection establishment to establish the Radio Access Bearers (RABs) and then also to deliver signaling while on the connection (for example, to perform a handover, reconfiguration or release).
The test set supports three SRBs:
3.4k DCCH - see 3GPP TS 34.108 6.10.2.4.1.2
13.6k DCCH - see 3GPP TS 34.108 6.10.2.4.1.3
2.2k DCCH - this signaling radio bearer has the following properties:
More information Transport channel parameters, Downlink physical channel ...
Transport channel parameters | |
TrCH Type | DCH (DCCH) |
TB size | 100 |
TF 0 | 0 x 100 |
TF 1 | 1 x 100 |
TTI (ms) | 40 |
Coding type | Conv, 1/3 |
CRC | 12 bit |
Downlink physical channel | |
DTX Position | n/a |
TFCI | used |
Slot structure | 5 |
SF | 256 |
Uplink physical channel | |
Min. spreading factor | 256 |
DPCCH slot format | 0 |
TFCI | used |
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During connection establishment, an RRC Connection Setup procedure establishes the SRB. The SRB is then used to send all subsequent signaling to start the desired service and establish the radio bearers for the service. Establishment of the radio bearers is achieved using an RB Setup procedure. The RB Setup procedure configures how both the DCCH and DTCH will be carried on the radio bearers.
The RB Setup may specify a different DCCH RLC block size from the DCCH RLC block size that was being used when only an SRB was present. For example, the DCCH RLC block size for the default 3.4k DCCH SRB is 144 bits, but all RMCs (Reference Measurement Channels) call for a DCCH RLC block size of 96 bits. If the RB Setup specifies a change in the DCCH RLC block size from the stand-alone SRB configuration, the UE and network must change the DCCH RLC block size and then perform an RLC Re-establishment procedure to reset the RLC buffers. If your UE does not support changing the DCCH RLC block size during connection setup, you must establish the call using an SRB with a DCCH RLC block size that is equal to the DCCH RLC block size defined for the service you wish to establish.