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4G/LTE - LTE Advanced

Handover

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

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

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.