https://blog.csdn.net/shij19/article/details/52946517

本節主要介紹小區重選過程，再次強調 重選過程發生在IDLE狀態下

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LTE小區重選分為同系統內的同頻、異頻重選以及異系統重選。

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LTE小區同頻重選沒有優先級的概念。異頻和異系統重選有高優先級的小區重選和低優先級的小區重選

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向高優先級的小區重選時，只要高優先級的小區門限超過一定門限，不管本小區信號如何，終端都要向高優先小區進行重選

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向低優先級的小區重選時，需要本小區的信號低于一定門限值，低優先級的小區高于一定門限值才能發生重選。

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小區重選的步驟：啟動測量->計算、評估->排序->重選

同頻小區重選：

對于同頻測量：主要參數在SIB1和SIB3中

啟動測量：

??如果滿足Srxlev > SIntraSearchP 且Squal >SIntraSearchQ時，UE可以選擇不進行intra_freq測量

??????否則開始進行測量同頻小區

相關的參數有：

TreselectionRAT ?測量時間

SIntraSearchP ?用于啟動同頻測量的RSRP信號電平門限值

SIntraSearchQ ?用于啟動同頻測量的RSRQ信號質量門限值

2011 Jul 22 14:27:32.497? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.3.0

Radio Bearer ID = 0, Physical Cell ID = 11

Freq = 5230

SysFrameNum = 990, SubFrameNum = 5

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 22

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

?message c1 : systemInformationBlockType1 :

???? ============================================

?????? cellSelectionInfo

?????? {

???????? q-RxLevMin -60, //最小接入電平值-60*2=-120dBm

???????? q-RxLevMinOffset 4 //q-RxLevMinOffset=4*2=8dB

?????? },

???? ?

???????? {

?????????? si-Periodicity rf8,

?????????? sib-MappingInfo

?????????? {

???????????? sibType3//--->SIB3消息

?????????? }

???????? }

?????? },

??? ?

?2011 Jul 22 14:27:32.533? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.3.0

Radio Bearer ID = 0, Physical Cell ID = 11

Freq = 5230

SysFrameNum = 994, SubFrameNum = 1

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 7

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

? message c1 : systemInformation:

???? {

?????? criticalExtensions systemInformation-r8 :

???????? {

?????????? sib-TypeAndInfo

?????????? {

???????????? sib3 :

?????????????? {

???????????????? cellReselectionInfoCommon

???????????????? {

?????????????????? q-Hyst dB2------------->=2dB

???????????????? },

???????????????? cellReselectionServingFreqInfo

???????????????? {

?????????????????? s-NonIntraSearch 7,====SnonIntraSearchP”

?????????????????? threshServingLow 5,

?????????????????? cellReselectionPriority 5

???????????????? },

???????????????? intraFreqCellReselectionInfo ==同頻測量信息

???????????????? {

?????????????????? q-RxLevMin -60,

?????????????????? s-IntraSearch 31,//同頻測量門限，SIntraSearchP

?????????????????? presenceAntennaPort1 TRUE,

?????????????????? neighCellConfig '01'B,

?????????????????? t-ReselectionEUTRA 2==時間 2s

???????????????? }

?????????????? }

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從LOG中可以看到：

同頻小區的測量：

Srxlev = Qrxlevmeas – (Qrxlevmin + Qrxlevminoffset)– Pcompensation

????? = Qrxlevmeas-(-60*2+4*2)-0= Qrxlevmeas+112< SintraSearchP=31

Qrxlevmeas<31-112=-81dBm時，啟動測量

當鄰區的Rn 大于服務小區的Rs時，即可進行小區重選。

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異頻/異系統重選

高優先級：

????? EUTRAN or UTRAN RAT/ frequency ： Squal > ThreshX, HighQ

????? GERAN or CDMA2000 RAT/ frequency ： Srxlev > ThreshX, HighP

也就是說，只要鄰小區高于一個門限值，不論當前小區門限值是多少，則都執行重選

ThreshX, HighQ---在SIB5~SIB8中

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低優先級：

????? EUTRAN or UTRAN RAT/ frequency ：

??????????????????? Squal-serving < ThreshServing, LowQ 且Squal-neighbor > ThreshX, LowQ

ThreshServing, LowQ---在SIB3中

ThreshX, LowQ---在SIB5~SIB8中

????? GERAN or CDMA2000 RAT/ frequency ：

??????????????????? Squal-serving < ThreshServing, LowQ and Srxlev-neighbor >ThreshX, LowP

?也就是說，當前小區低于一個門限值，鄰小區高于一個門限值，則進行重選

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若沒有提供threshServingLowQ則所有的都是用Srxlev來進行判別

小區使用R準則進行排序：

??????Rs = Qmeas,s +QHyst???

??????Rn = Qmeas,n - Qoffset

LOG=====

2013 Aug 14 02:59:42.869? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

cellSelectionInfo

?????? {

???????? q-RxLevMin -53

?????? },

SIB3:

cellReselectionServingFreqInfo

???????????????? {

?????????????????? threshServingLow 0,

?????????????????? cellReselectionPriority 4—當前小區優先級=4

???????????????? },

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2013 Aug 14 02:59:42.966? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.10.0

Radio Bearer ID = 0, Physical Cell ID = 0

Freq = 900

SysFrameNum = 132, SubFrameNum = 3

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 17

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

? message c1 : systemInformation:

???? {

?????? criticalExtensions systemInformation-r8 :

???????? {

?????????? sib-TypeAndInfo

?????????? {

???????????? sib5 :

?????????????? {

???????????????? interFreqCarrierFreqList //異頻小區信息

???????????????? {

?????????????????? {

???????????????????? dl-CarrierFreq 650,

???????????????????? q-RxLevMin -53,

???????????????????? t-ReselectionEUTRA 0,

???????????????????? threshX-High 10,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority 5,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? },

?????????????????? {

???????????????????? dl-CarrierFreq 1150,

???????????????????? q-RxLevMin -53,===最小接入電平-106

???????????????????? t-ReselectionEUTRA 0,時間為0

???????????????????? threshX-High 10,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority4,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? }

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同頻同優先級重選，使用R準則：

Rs = Qmeas,s + Qhyst=-90+0=-90

Rn = Qmeas,n - Qoffset =-85-0=-85

所以選擇到鄰小區PCI=3的小區上！

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2013 Aug 14 03:00:06.289? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.10.0

Radio Bearer ID = 0, PhysicalCell ID = 3

Freq = 1150

SysFrameNum = 674, SubFrameNum = 1

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 7

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

? message c1 : systemInformation:

???? {

?????? criticalExtensions systemInformation-r8 :

???????? {

?????????? sib-TypeAndInfo

?????????? {

???????????? sib3 :

?????????????? {

???????????????? cellReselectionInfoCommon

???????????????? {

?????????????????? q-Hyst dB0====0

???????????????? },

???????????????? cellReselectionServingFreqInfo

???????????????? {

?????????????????? threshServingLow 0,

?????????????????? cellReselectionPriority 4

???????????????? },

???????????????? intraFreqCellReselectionInfo

???????????????? {

?????????????????? q-RxLevMin -53,

?????????????????? presenceAntennaPort1 FALSE,

?????????????????? neighCellConfig '01'B,

?????????????????? t-ReselectionEUTRA 0

???????????????? }

?????????????? }

?????????? }

???????? }

???? }

}

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?

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2013 Aug 14 03:00:06.630? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.10.0

Radio Bearer ID = 0, Physical Cell ID = 3

Freq = 1150

SysFrameNum = 708, SubFrameNum = 3

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 17

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

? message c1 : systemInformation:

???? {

?????? criticalExtensions systemInformation-r8 :

???????? {

?????????? sib-TypeAndInfo

?????????? {

???????????? sib5 :

?????????????? {

???????????????? interFreqCarrierFreqList

???????????????? {

?????????????????? {

???????????????????? dl-CarrierFreq 900,

???????????????????? q-RxLevMin -53,

???????????????????? t-ReselectionEUTRA 0,

???????????????????? threshX-High 2,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority 4,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? },

?????????????????? {

???????????????????? dl-CarrierFreq 650,

???????????????????? q-RxLevMin -53,==最小接入點評-106

???????????????????? t-ReselectionEUTRA 0,==重選時間0秒

???????????????????? threshX-High 10,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority 5,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? }

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從優先級=4重選到優先級=5的高優先級小區上時，只需要鄰小區的信號

EUTRAN or UTRAN RAT/ frequency ： Squal> ThreshX, HighQ

也就是Squal = Qqualmeas – (Qqualmin +Qqualminoffset)= Qqualmeas-（-53*2+0）>10*2

Qqualmeas>-86dBm就會重選過去
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sib3 :

?????????????? {

???????????????? cellReselectionInfoCommon

???????????????? {

?????????????????? q-Hyst dB0

???????????????? },

???????????????? cellReselectionServingFreqInfo

???????????????? {

?????????????????? threshServingLow 10,====== ThreshServing, LowQ

?????????????????? cellReselectionPriority 5

???????????????? },

???????????????? intraFreqCellReselectionInfo

???????????????? {

?????????????????? q-RxLevMin -53,

?????????????????? presenceAntennaPort1 FALSE,

?????????????????? neighCellConfig '01'B,

?????????????????? t-ReselectionEUTRA 0

???????????????? }

?????????????? }

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2013 Aug 14 03:00:10.315? [00] 0xB0C0? LTE RRC OTA Packet --? BCCH_DL_SCH

Pkt Version = 2

RRC Release Number.Major.minor = 9.10.0

Radio Bearer ID = 0, Physical Cell ID = 6

Freq = 650

SysFrameNum = 452, SubFrameNum = 3

PDU Number = BCCH_DL_SCHMessage,??? MsgLength = 17

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Interpreted PDU:

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value BCCH-DL-SCH-Message ::=

{

? message c1 : systemInformation:

???? {

?????? criticalExtensions systemInformation-r8 :

???????? {

?????????? sib-TypeAndInfo

?????????? {

???????????? sib5 :

?????????????? {

???????????????? interFreqCarrierFreqList

???????????????? {

?????????????????? {

???????????????????? dl-CarrierFreq 900,

???????????????????? q-RxLevMin -53,

???????????????????? t-ReselectionEUTRA 0,

???????????????????? threshX-High2,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority 4,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? },

?????????????????? {

???????????????????? dl-CarrierFreq 1150,

???????????????????? q-RxLevMin -53,

???????????????????? t-ReselectionEUTRA 0,

???????????????????? threshX-High 2,

???????????????????? threshX-Low 1,

???????????????????? allowedMeasBandwidth mbw50,

???????????????????? presenceAntennaPort1 FALSE,

???????????????????? cellReselectionPriority 4,

???????????????????? neighCellConfig '01'B,

???????????????????? q-OffsetFreq dB0

?????????????????? }

從優先級=5重選到優先級=4的低優先級小區上時，需要本小區信號質量：

低優先級：

????? EUTRAN or UTRAN RAT/ frequency ：

??????????????????? Squal-serving < ThreshServing, LowQ and Squal-neighbor >ThreshX, LowQ

也就是：

Squal = Qqualmeas – (Qqualmin + Qqualminoffset)=Qqualmeas-(-106+0)<10*2

Qqualmeas<-86dBm

臨小區小區質量：Squal-neighbor > ThreshX, LowQ=Qqualmeas-(-106+0)>1*2

Qqualmeas>-104dBm
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作者：時九19 ?
來源：CSDN ?
原文：https://blog.csdn.net/shij19/article/details/52946517 ?
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