参考资料：3GPP 38.300、3GPP 38.331
1. 名词缩写
缩写 | 全称 | 描述 |
SI | System Information | 系统信息 |
MIB | Master Information Block | 主信息块 |
SIB | System Information Block | 系统信息块 |
RMSI | Remaining Minimum SI | 剩余最小SI，即除MIB外的最小SI |
SSB | Synchronization Signal Block | 同步信息块 |
PSCell | Primary SCG Cell | |
BWP | Bandwidth Part |
2. 系统消息
SI包括一个MIB和多个SIB。SI分为最小SI 和其它SI。
（1）最小SI ：包括了初始接入和如何获取其它SI的基本信息。
- MIB：包含了如何获取SIB1的信息，以及其它。
★★ 携带的消息：systemFrameNumber、subCarrierSpacingCommon、 ssb-SubcarrierOffset、dmrs-TypeA-Position、pdcch-ConfigSIB1、cellBarred 、 intraFreqReselection（是否允许同频重选）。
★★ MIB消息在BCH上周期性重复广播，周期为80ms。重复次数由SSB的周期决定。 - SIB1：包括了初始接入需要的信息以及其它SI的调度信息。
★★ 携带的消息： cellSelectionInfo 、cellAccessRelatedInfo 、connEstFailureControl、si-SchedulingInfo、 servingCellConfigCommon、ims-EmergencySupport、eCallOverIMS-Support 、ue-TimersAndConstants 、uac-BarringInfo、useFullResumeID。
★★ SIB1也叫RMSI，剩余最小SI，即除MIB外的最小SI。
★★ SIB1在DL-SCH上周期性重复广播，周期为160ms。在每个周期内重复广播的次数是不固定的，其取决于具体实现。默认是8次。
★★ 当UE处于RRC_CONNECTED态时，可通过周期广播，或者通过RRCReconfiguration消息获取SIB1。
★★ SIB1指示其它SI是周期性广播，还是按需提供。若按需提供其它SI，则SIB1还需包括UE执行SI请求的信息。
（2）其它SI：不包括在最小SI的其余所有系统消息。
- 获取其它SI的方式：
① 周期性广播，其广播信息由SIB1中携带的si-SchedulingInfo决定；
② 按需广播（ RRC_IDLE、RRC_INACTIVE），或者通过RRCReconfiguration发送给特定UE（ RRC_CONNECTED）； - SIB2：包括了小区重选公共信息（同频、异频、RAT间），服务小区小区重选信息、同频小区重选信息。
SIB2 ::= SEQUENCE {
cellReselectionInfoCommon SEQUENCE {
nrofSS-BlocksToAverage INTEGER (2..maxNrofSS-BlocksToAverage) OPTIONAL, -- Need R
absThreshSS-BlocksConsolidation ThresholdNR OPTIONAL, -- Need R
rangeToBestCell RangeToBestCell OPTIONAL, -- Need R
q-Hyst ENUMERATED {
dB0, dB1, dB2, dB3, dB4, dB5, dB6, dB8, dB10,
dB12, dB14, dB16, dB18, dB20, dB22, dB24},
speedStateReselectionPars SEQUENCE {
mobilityStateParameters MobilityStateParameters,
q-HystSF SEQUENCE {
sf-Medium ENUMERATED {dB-6, dB-4, dB-2, dB0},
sf-High ENUMERATED {dB-6, dB-4, dB-2, dB0}
}
} OPTIONAL, -- Need R
...
},
cellReselectionServingFreqInfo SEQUENCE {
s-NonIntraSearchP ReselectionThreshold OPTIONAL, -- Need R
s-NonIntraSearchQ ReselectionThresholdQ OPTIONAL, -- Need R
threshServingLowP ReselectionThreshold,
threshServingLowQ ReselectionThresholdQ OPTIONAL, -- Need R
cellReselectionPriority CellReselectionPriority,
cellReselectionSubPriority CellReselectionSubPriority OPTIONAL, -- Need R
...
},
intraFreqCellReselectionInfo SEQUENCE {
q-RxLevMin Q-RxLevMin,
q-RxLevMinSUL Q-RxLevMin OPTIONAL, -- Need R
q-QualMin Q-QualMin OPTIONAL, -- Need S
s-IntraSearchP ReselectionThreshold,
s-IntraSearchQ ReselectionThresholdQ OPTIONAL, -- Cond RSRQ
t-ReselectionNR T-Reselection,
frequencyBandList MultiFrequencyBandListNR-SIB OPTIONAL, -- Need S
frequencyBandListSUL MultiFrequencyBandListNR-SIB OPTIONAL, -- Need R
p-Max P-Max OPTIONAL, -- Need R
smtc SSB-MTC OPTIONAL, -- Need R
ss-RSSI-Measurement SS-RSSI-Measurement OPTIONAL, -- Need R
ssb-ToMeasure SSB-ToMeasure OPTIONAL, -- Need R
deriveSSB-IndexFromCell BOOLEAN,
...,
[[
t-ReselectionNR-SF SpeedStateScaleFactors OPTIONAL -- Need N
]]
},
...
}
RangeToBestCell ::= Q-OffsetRange- SIB3：包括了同频邻区信息和同频黑名单小区信息，用于同频小区重选。
SIB3 ::= SEQUENCE {
intraFreqNeighCellList IntraFreqNeighCellList OPTIONAL, -- Need R
intraFreqBlackCellList IntraFreqBlackCellList OPTIONAL, -- Need R
lateNonCriticalExtension OCTET STRING OPTIONAL,
...
}
IntraFreqNeighCellList ::= SEQUENCE (SIZE (1..maxCellIntra)) OF IntraFreqNeighCellInfo
IntraFreqNeighCellInfo ::= SEQUENCE {
physCellId PhysCellId,
q-OffsetCell Q-OffsetRange,
q-RxLevMinOffsetCell INTEGER (1..8) OPTIONAL, -- Need R
q-RxLevMinOffsetCellSUL INTEGER (1..8) OPTIONAL, -- Need R
q-QualMinOffsetCell INTEGER (1..8) OPTIONAL, -- Need R
...
}
IntraFreqBlackCellList ::= SEQUENCE (SIZE (1..maxCellBlack)) OF PCI-Range- SIB4：包括了异频小区重选信息，异频邻区信息，以及异频黑名单小区信息，用于异频小区重选。
SIB4 ::= SEQUENCE {
interFreqCarrierFreqList InterFreqCarrierFreqList,
lateNonCriticalExtension OCTET STRING OPTIONAL,
...
}
InterFreqCarrierFreqList ::= SEQUENCE (SIZE (1..maxFreq)) OF InterFreqCarrierFreqInfo
InterFreqCarrierFreqInfo ::= SEQUENCE {
dl-CarrierFreq ARFCN-ValueNR,
frequencyBandList MultiFrequencyBandListNR-SIB OPTIONAL, -- Cond Mandatory
frequencyBandListSUL MultiFrequencyBandListNR-SIB OPTIONAL, -- Need R
nrofSS-BlocksToAverage INTEGER (2..maxNrofSS-BlocksToAverage) OPTIONAL, -- Need R
absThreshSS-BlocksConsolidation ThresholdNR OPTIONAL, -- Need R
smtc SSB-MTC OPTIONAL, -- Need R
ssbSubcarrierSpacing SubcarrierSpacing,
ssb-ToMeasure SSB-ToMeasure OPTIONAL, -- Need R
deriveSSB-IndexFromCell BOOLEAN,
ss-RSSI-Measurement SS-RSSI-Measurement OPTIONAL,
q-RxLevMin Q-RxLevMin,
q-RxLevMinSUL Q-RxLevMin OPTIONAL, -- Need R
q-QualMin Q-QualMin OPTIONAL, -- Need S,
p-Max P-Max OPTIONAL, -- Need R
t-ReselectionNR T-Reselection,
t-ReselectionNR-SF SpeedStateScaleFactors OPTIONAL, -- Need S
threshX-HighP ReselectionThreshold,
threshX-LowP ReselectionThreshold,
threshX-Q SEQUENCE {
threshX-HighQ ReselectionThresholdQ,
threshX-LowQ ReselectionThresholdQ
} OPTIONAL, -- Cond RSRQ
cellReselectionPriority CellReselectionPriority OPTIONAL, -- Need R
cellReselectionSubPriority CellReselectionSubPriority OPTIONAL, -- Need R
q-OffsetFreq Q-OffsetRange DEFAULT dB0,
interFreqNeighCellList InterFreqNeighCellList OPTIONAL, -- Need R
interFreqBlackCellList InterFreqBlackCellList OPTIONAL, -- Need R
...
}
InterFreqNeighCellList ::= SEQUENCE (SIZE (1..maxCellInter)) OF InterFreqNeighCellInfo
InterFreqNeighCellInfo ::= SEQUENCE {
physCellId PhysCellId,
q-OffsetCell Q-OffsetRange,
q-RxLevMinOffsetCell INTEGER (1..8) OPTIONAL, -- Need R
q-RxLevMinOffsetCellSUL INTEGER (1..8) OPTIONAL, -- Need R
q-QualMinOffsetCell INTEGER (1..8) OPTIONAL, -- Need R
...
}
InterFreqBlackCellList ::= SEQUENCE (SIZE (1..maxCellBlack)) OF PCI-Range- SIB5：包括了E-UTRA小区重选信息、E-UTRA小区信息，E-UTRA黑名单小区信息，用于RAT间小区重选。
SIB5 ::= SEQUENCE {
carrierFreqListEUTRA CarrierFreqListEUTRA OPTIONAL, -- Need R
t-ReselectionEUTRA T-Reselection,
t-ReselectionEUTRA-SF SpeedStateScaleFactors OPTIONAL, -- Need S
lateNonCriticalExtension OCTET STRING OPTIONAL,
...
}
CarrierFreqListEUTRA ::= SEQUENCE (SIZE (1..maxEUTRA-Carrier)) OF CarrierFreqEUTRA
CarrierFreqEUTRA ::= SEQUENCE {
carrierFreq ARFCN-ValueEUTRA,
eutra-multiBandInfoList EUTRA-MultiBandInfoList OPTIONAL, -- Need R
eutra-FreqNeighCellList EUTRA-FreqNeighCellList OPTIONAL, -- Need R
eutra-BlackCellList EUTRA-FreqBlackCellList OPTIONAL, -- Need R
allowedMeasBandwidth EUTRA-AllowedMeasBandwidth,
presenceAntennaPort1 EUTRA-PresenceAntennaPort1,
cellReselectionPriority CellReselectionPriority OPTIONAL, -- Need R
cellReselectionSubPriority CellReselectionSubPriority OPTIONAL, -- Need R
threshX-High ReselectionThreshold,
threshX-Low ReselectionThreshold,
q-RxLevMin INTEGER (-70..-22),
q-QualMin INTEGER (-34..-3),
p-MaxEUTRA INTEGER (-30..33),
threshX-Q SEQUENCE {
threshX-HighQ ReselectionThresholdQ,
threshX-LowQ ReselectionThresholdQ
} OPTIONAL -- Cond RSRQ
}
EUTRA-FreqBlackCellList ::= SEQUENCE (SIZE (1..maxEUTRA-CellBlack)) OF EUTRA-PhysCellIdRange
EUTRA-FreqNeighCellList ::= SEQUENCE (SIZE (1..maxCellEUTRA)) OF EUTRA-FreqNeighCellInfo
EUTRA-FreqNeighCellInfo ::= SEQUENCE {
physCellId EUTRA-PhysCellId,
q-OffsetCell EUTRA-Q-OffsetRange,
q-RxLevMinOffsetCell INTEGER (1..8) OPTIONAL, -- Need R
q-QualMinOffsetCell INTEGER (1..8) OPTIONAL -- Need R
}- SIB6：ETWS主通知。
- SIB7：ETWS辅通知
- SIB8：CMAS告警通知
- SIB9：GPS和UTC相关信息。UE可根据SIB9获取GPS、UTC以及本地时间。
3. UE获取系统消息
（1）UE何时需要获取系统消息？
- 小区选择（刚开机）、小区重选、从未覆盖的区域到有覆盖的区域、从其它RAT进入到当前RAT、收到系统消息变更的指示、收到PWS通知、存储的SI已过期、after reconfiguration with sync completion。
（2）UE如何获取系统消息？
- 获取MIB和SIB1：
★★ 当UE获取MIB和SIB1消息失败时，则认为该小区禁止接入。
★★ 处于RRC_IDLE或 RRC_INACTIVE的UE，根据38.213协议所述，在BCCH信道上获取MIB消息；
★★ 处于RRC_IDLE、 RRC_INACTIVE，或已激活BWP，searchSpaceSIB1 和pagingSearchSpace配置了公共搜索空间且被指示系统消息已变更RRC_CONNECTED的UE，根据MIB消息，在DL-SCH信道上获取SIB1。 - 获取其它SI：
（3）UE存储系统消息
4. 系统消息的有效性
本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
