SRB

SRB0用于使用CCCH逻辑信道的RRC消息；

SRB1用于RRC消息（可能包括后向装载的NAS消息）以及SRB2建立之前的NAS消息，均使用DCCH逻辑信道；

SRB2用于NAS消息，全部使用DCCH逻辑通道。SRB2的优先级低于SRB1，在安全激活后总是由网络配置；

SRB3用于UE在EN-DC中时的特定RRC消息，均使用DCCH逻辑信道。

在EN-DC的情况下，SRB3可以被配置为经由NR无线电接口在UE和SgNB之间传输一些NR RRC消息。

默认SRB配置 RRC information elements SRB1/1S SRB2/2S SRB3 PDCP-Config t-Reordering RLC-Config CHOICE ul-RLC-Config sn-FieldLength t-PollRetransmit pollPDU pollByte maxRetxThreshold dl-RLC-Config sn-FieldLength t-Reassembly t-StatusProhibit logicalChannelIdentity LogicalChannelConfig priority prioritisedBitRate logicalChannelGroup Infinity AM size12 ms45 Infinity Infinity t8 size12 ms35 ms0 1 1 Infinity 0 Direction UE <-- NW UE --> NW UE <-- NW UE <-- NW Infinity AM size12 ms45 Infinity Infinity t8 size12 ms35 ms0 2 3 Infinity 0 Logical Channel BCCH DCCH DCCH PCCH Infinity AM size12 ms45 Infinity Infinity t8 size12 ms35 ms0 3 1 Infinity 0 RLC TM AM AM TM SRB N/A SRB1,SRB3 SRB1 N/A SRB映射到信令消息 Message MasterInformationBlock MeasurementReport MobilityFromNRCommand Paging RRCReestablishment RRCReestablishmentRequest RRCReconfiguration RRCReject RRCRelease RRCResume RRCResumeComplete RRCResumeRequest RRCResumeRequest1 RRCSetup RRCSetupComplete RRCSetupRequest RRCSystemInfoRequest SecurityModeCommand SecurityModeComplete SecurityModeFailure SIB1 SystemInformation UEAssistanceInformation UECapabilityEnquiry UECapabilityInformation ULInformationTransfer UE <-- NW UE --> NW UE <-- NW UE <-- NW UE <-- NW UE <-- NW UE --> NW UE --> NW UE --> NW UE <-- NW UE --> NW UE --> NW UE --> NW UE <-- NW UE --> NW UE --> NW UE <-- NW UE <-- NW UE --> NW UE <-- NW UE --> NW UE --> NW DCCH DCCH CCCH DCCH DCCH CCCH DCCH DCCH DCCH CCCH CCCH1 CCCH DCCH CCCH CCCH DCCH DCCH DCCH BCCH BCCH DCCH DCCH DCCH DCCH AM AM TM AM AM TM AM AM AM TM TM TM AM TM TM AM AM AM TM TM AM AM AM AM SRB1 SRB1 SRB0 SRB1,SRB3 SRB1,SRB3 SRB0 SRB1 SRB1 SRB1 SRB0 SRB0 SRB0 SRB1 SRB0 SRB0 SRB1 SRB1 SRB1 N/A N/A SRB1 SRB1 SRB1 SRB1,SRB2 RRCReestablishmentComplete UE --> NW RRCReconfigurationComplete UE --> NW