Hello there,source from sharetechnote :----
There can be many different scenario (combination) of Handover with Carrier Aggregation. I will start with the simplest case, but recently I am seeing various requirement to reduce the number of steps for Handover (e.g, PCC handover and adding SCC in a single RRC Connection Reconfiguration etc).
Case 1 : Remove SCC before Handover -> HO for PCC -> Add SCC
Probably one of the simplest case of scenario we can think of would be as follows (By 'the simplest case', I mean it is the simplest in logic (the easiest to understand/implement), it didn't mean that it is the simplest in terms of the number of protocol sequence. Actually, it requires the longest steps in terms of protocol sequence). As you see here, just PCC has been changed as final result of Handover. In this scenario, Network remove SCC first before Handover and perform PCC handover and then add SCC again.
Case 2 : Remove SCC and Handover for PCC in single step -> Add SCC
(2) RRC Connection Reconfiguration (for Handover to PCC2 and Release SCC1)
c1: rrcConnectionReconfiguration (4)
rrcConnectionReconfiguration
rrc-TransactionIdentifier: 0
criticalExtensions: c1 (0)
c1: rrcConnectionReconfiguration-r8 (0)
rrcConnectionReconfiguration-r8
mobilityControlInfo
targetPhysCellId: 10 // Physical Cell ID of PCC2
carrierFreq
dl-CarrierFreq: 2300 // DL Channel Number of PCC2
carrierBandwidth
dl-Bandwidth: n50 // Bandwidth of PCC2
t304: ms1000 (5)
newUE-Identity: 1032 [bit length 16, 0001 0000 0011 0010 decimal value 4146]
radioResourceConfigCommon
prach-Config
rootSequenceIndex: 64
prach-ConfigInfo
prach-ConfigIndex: 3
...0 .... highSpeedFlag: False
zeroCorrelationZoneConfig: 2
prach-FreqOffset: 19
pusch-ConfigCommon
pusch-ConfigBasic
n-SB: 1
hoppingMode: interSubFrame (0)
pusch-HoppingOffset: 0
.0.. .... enable64QAM: False
ul-ReferenceSignalsPUSCH
..0. .... groupHoppingEnabled: False
groupAssignmentPUSCH: 0
0... .... sequenceHoppingEnabled: False
cyclicShift: 0
pucch-ConfigCommon
deltaPUCCH-Shift: ds2 (1)
nRB-CQI: 4
nCS-AN: 6
n1PUCCH-AN: 0
ul-CyclicPrefixLength: len1 (0)
rach-ConfigDedicated
ra-PreambleIndex: 63
ra-PRACH-MaskIndex: 0
radioResourceConfigDedicated
physicalConfigDedicated
pusch-ConfigDedicated
betaOffset-ACK-Index: 9
betaOffset-RI-Index: 6
betaOffset-CQI-Index: 6
antennaInfo: explicitValue (0)
explicitValue
transmissionMode: tm1 (0)
ue-TransmitAntennaSelection: release (0)
release: NULL
schedulingRequestConfig: setup (1)
setup
sr-PUCCH-ResourceIndex: 41
sr-ConfigIndex: 27
dsr-TransMax: n32 (3)
securityConfigHO
handoverType: intraLTE (0)
intraLTE
.... 0... keyChangeIndicator: False
nextHopChainingCount: 0
nonCriticalExtension
nonCriticalExtension
nonCriticalExtension
sCellToReleaseList-r10: 1 item
Item 0
SCellIndex-r10: 1 // Serving Cell Index of SCC1
(7) RRC Connection Reconfiguration (for adding SCC1)
c1: rrcConnectionReconfiguration (4)
rrcConnectionReconfiguration
rrc-TransactionIdentifier: 0
criticalExtensions: c1 (0)
c1: rrcConnectionReconfiguration-r8 (0)
rrcConnectionReconfiguration-r8
radioResourceConfigDedicated
mac-MainConfig: explicitValue (0)
explicitValue
timeAlignmentTimerDedicated: infinity (7)
mac-MainConfig-v1020
physicalConfigDedicated
cqi-ReportConfig-r10
cqi-ReportAperiodic-r10: release
nomPDSCH-RS-EPRE-Offset: 0dB (0)
pucch-ConfigDedicated-v1020
pucch-Format-r10: channelSelection-r10 (1)
channelSelection-r10
n1PUCCH-AN-CS-r10: setup (1)
setup
n1PUCCH-AN-CS-List-r10: 2 items
Item 0
N1PUCCH-AN-CS-r10: 4 items
Item 0
N1PUCCH-AN-CS-r10 item: 101
Item 1
N1PUCCH-AN-CS-r10 item: 102
Item 2
N1PUCCH-AN-CS-r10 item: 103
Item 3
N1PUCCH-AN-CS-r10 item: 104
Item 1
N1PUCCH-AN-CS-r10: 4 items
Item 0
N1PUCCH-AN-CS-r10 item: 105
Item 1
N1PUCCH-AN-CS-r10 item: 106
Item 2
N1PUCCH-AN-CS-r10 item: 107
Item 3
N1PUCCH-AN-CS-r10 item: 108
nonCriticalExtension
nonCriticalExtension
nonCriticalExtension
sCellToAddModList-r10: 1 item
Item 0
SCellToAddMod-r10
sCellIndex-r10: 1
cellIdentification-r10
physCellId-r10: 400
dl-CarrierFreq-r10: 5790
radioResourceConfigCommonSCell-r10
nonUL-Configuration-r10
dl-Bandwidth-r10: n50 (3)
antennaInfoCommon-r10
antennaPortsCount: an1 (0)
phich-Config-r10
phich-Duration: normal (0)
phich-Resource: oneSixth (0)
pdsch-ConfigCommon-r10
referenceSignalPower: 18dBm
p-b: 1
radioResourceConfigDedicatedSCell-r10
physicalConfigDedicatedSCell-r10
nonUL-Configuration-r10
antennaInfo-r10
transmissionMode-r10: tm1 (0)
ue-TransmitAntennaSelection: release (0)
release: NULL
pdsch-ConfigDedicated-r10
p-a: dB0
Case 3 : Remove SCC before Handover -> Handover for PCC and Add SCC in a single step
Case 4 : Remove SCC , HO for PCC, Add SCC all in single step
Personally I haven't seen any real implementation for this case and haven't confirmed in 3GPP specification in detail, but just by logical point of view we can think of following scenario as well.
