[openairinterface5g] RRC NR resolution (I)

1. RRC Source location

RRC(Radio Resource Control) It is called radio resource control , yes 5G The core module of the system , Its main function is to give the lower layer (PHY,MAC,RLC,PDCP) Control or configure all wireless resources , To ensure that UE Communicate with the base station .
OAI RRC Module in openair2\RRC Next , There is NR,LTE,NR UE Wait for a few source directories , We only analyze NR.

2. File function

RRC The main documents of the module are as follows ：

file name	function
rrc_gNB.c	RRC Core program , Include RRC Message receiving and processing
rrc_gNB_NGAP.c	NGAP Message generation and sending
rrc_gNB_UE_context.c	UE Context generation , Acquisition and deletion, etc
rrc_gNB_reconfig.c	Coreset0, search space ,BWP,rb And so on
rrc_gNB_GTPV1U.c	GTPV1U relevant
nr_rrc_config.c	Rlc,mac cellgroup Wait for some parameters to be initialized to 0
nr_rrc_common.c	Some global parameters are initialized

3. The functionality

rrc_gNB.c yes RRC The core source code file of the module , all RRC Messages are received here , All processes are initiated from here ,rrc_gnb_task() amount to RRC Modular Main The main function .

function	describe
rrc_gnb_task	Receive other modules and send them to RRC Modular msg, by the advices ID Enter different processing branches
rrc_gNB_decode_dcch	dcch decode
nr_rrc_gNB_decode_ccch	ccch decode
rrc_gNB_generate_RRCSetup	Generate RRC Setup
rrc_gNB_generate_RRCSetup_for_RRCReestablishmentRequest	Generate for RRC Reconstructed RRC SETUP
rrc_gNB_generate_RRCReject	Generate RRC Reject
rrc_gNB_process_RRCSetupComplete	Handle RRC setupComplete
rrc_gNB_generate_defaultRRCReconfiguration	Generate RRC Reconfiguration command
rrc_gNB_process_RRCReconfigurationComplete	Handle RRC Reconfiguration completion command
rrc_gNB_generate_RRCReestablishment	Generate RRC Rebuild command
rrc_gNB_process_RRCConnectionReestablishmentComplete	Handle RRC Rebuild complete command
rrc_gNB_generate_SecurityModeCommand	Generate encryption mode command
rrc_gNB_generate_UECapabilityEnquiry	Generate UE Capability query
rrc_gNB_generate_RRCRelease	Generate RRCRelease
init_NR_SI	MIB,SIB1 code

4. Main function flow

itti_receive_msg（） Main receiver function , As mentioned in the previous article . adopt ITTI_MSG_ID(msg_p) Get message ID, from switch Transfer to each processing branch process , Decode the data .
nr_rrc_gNB_decode_ccch()： be responsible for CCCH decode , Incoming data calls uper_decode() Conduct per decode , Get the news ID, The main messages include rrcSetupRequest and rrcReestablishmentRequest Two article .
rrc_gNB_decode_dcch()： be responsible for DCCH decode , Incoming data calls uper_decode() Conduct per decode , Get the news ID, Include rrcSetupComplete,rrcReconfigurationComplete,ulInformationTransfer,securityModeComplete,securityModeFailure,ueCapabilityInformation,rrcReestablishmentComplete.
The other branches are mainly NGAP Related messages , Including down NAS,PDU Session establishment and release ,UE Context Creation and release .