21. gNB發送AS層加密和完整性保護算法給UE。
SecurityModeCommand ::= SEQUENCE {
rrc-TransactionIdentifier RRC-TransactionIdentifier,
criticalExtensions CHOICE {
securityModeCommand SecurityModeCommand-IEs,
criticalExtensionsFuture SEQUENCE {}
}
}
SecurityModeCommand-IEs ::= SEQUENCE {
securityConfigSMC SecurityConfigSMC,
lateNonCriticalExtension OCTET STRING OPTIONAL,
nonCriticalExtension SEQUENCE{} OPTIONAL
}
SecurityConfigSMC ::= SEQUENCE {
securityAlgorithmConfig SecurityAlgorithmConfig,
...
}
22. UE確認對應的算法可用后發送確認給gNB，注意，此消息是有完整性保護但是沒有經過加密的，但是從此時開始后續的消息都是加密的。
SecurityModeComplete ::= SEQUENCE {
rrc-TransactionIdentifier RRC-TransactionIdentifier,
criticalExtensions CHOICE {
securityModeComplete SecurityModeComplete-IEs,
criticalExtensionsFuture SEQUENCE {}
}
}
SecurityModeComplete-IEs ::= SEQUENCE {
lateNonCriticalExtension OCTET STRING OPTIONAL,
nonCriticalExtension SEQUENCE{} OPTIONAL
}
23. gNB發送RRC Reconfiguration消息給UE，此消息典型攜帶信息包括Initial Context Setup Request（可能帶有Registration Accept）， 無線承載建立的相關參數，UE測量參數，如果有CA的話還會攜帶輔小區的相關信息。UE在收到此消息后會開始配置主小區組、無線輔小區組（如果有的話）、配置無線承載、基於收到的測量配置開始做測量、根據收到的NAS消息進行上下文和PDU Session（如果有的話）的相應操作。
RRCReconfiguration ::= SEQUENCE {
rrc-TransactionIdentifier RRC-TransactionIdentifier,
criticalExtensions CHOICE {
rrcReconfiguration RRCReconfiguration-IEs,
criticalExtensionsFuture SEQUENCE {}
}
}
RRCReconfiguration-IEs ::= SEQUENCE {
radioBearerConfig RadioBearerConfig OPTIONAL, -- Need M
secondaryCellGroup OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL, -- Need M
measConfig MeasConfig OPTIONAL, -- Need M
lateNonCriticalExtension OCTET STRING OPTIONAL,
nonCriticalExtension RRCReconfiguration-v1530-IEs OPTIONAL
}
RRCReconfiguration-v1530-IEs ::= SEQUENCE {
masterCellGroup OCTET STRING (CONTAINING CellGroupConfig) OPTIONAL, -- Need M
fullConfig ENUMERATED {true} OPTIONAL, -- Cond FullConfig
dedicatedNAS-MessageList SEQUENCE (SIZE(1..maxDRB)) OF DedicatedNAS-Message OPTIONAL, -- Cond nonHO
masterKeyUpdate MasterKeyUpdate OPTIONAL, -- Cond MasterKeyChange
dedicatedSIB1-Delivery OCTET STRING (CONTAINING SIB1) OPTIONAL, -- Need N
dedicatedSystemInformationDelivery OCTET STRING (CONTAINING SystemInformation) OPTIONAL, -- Need N
otherConfig OtherConfig OPTIONAL, -- Need M
nonCriticalExtension RRCReconfiguration-v1540-IEs OPTIONAL
}
RRCReconfiguration-v1540-IEs ::= SEQUENCE {
otherConfig-v1540 OtherConfig-v1540 OPTIONAL, -- Need M
nonCriticalExtension SEQUENCE {} OPTIONAL
}
MasterKeyUpdate ::= SEQUENCE {
keySetChangeIndicator BOOLEAN,
nextHopChainingCount NextHopChainingCount,
nas-Container OCTET STRING OPTIONAL, -- Cond securityNASC
...
}
關於Initial Context Setup Request所帶IE主要如下
或者
Registration Accept所帶主要IE如下
24. UE回復RRC Reconfiguration Complete來確認。
RRCReconfigurationComplete ::= SEQUENCE {
rrc-TransactionIdentifier RRC-TransactionIdentifier,
criticalExtensions CHOICE {
rrcReconfigurationComplete RRCReconfigurationComplete-IEs,
criticalExtensionsFuture SEQUENCE {}
}
}
RRCReconfigurationComplete-IEs ::= SEQUENCE {
lateNonCriticalExtension OCTET STRING OPTIONAL,
nonCriticalExtension RRCReconfigurationComplete-v1530-IEs OPTIONAL
}
RRCReconfigurationComplete-v1530-IEs ::= SEQUENCE {
uplinkTxDirectCurrentList UplinkTxDirectCurrentList OPTIONAL,
nonCriticalExtension SEQUENCE {} OPTIONAL
}
27. 通過上行直傳消息發送Registration Complete消息到AMF，至此注冊過程完成。
28&29. 可以使用對應的TEID來發送UL/DL data。