4 lte eran6.0 pci conflict detection & self-optimization issue1.00

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Page0Revision RecordDont Print This PageCourse CodeProductProduct VersionCourse Version ISSUEOEO107270LTEeRAN3.01.00Developer/ModifierTimeApproverNew/UpdateYuan Shuai2013-6Update from eRAN6.0Copyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-0Confidential Information of Huawei. No Spreading Without Permission LTE eRAN3.0 PCI Conflict & Self-Optimization www.huawei.comCopyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :40-47pt :26-30pt: :FrutigerNext LT Medium : Arial

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Copyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationConfidential Information of Huawei. No Spreading Without Permission P-1ObjectivesUpon completion of this course, you will be able to:Describe the working principle of PCI conflict detectionPerform PCI self-optimization in M2000Page2


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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-2Confidential Information of Huawei. No Spreading Without Permission ContentsFunction OverviewPCI Conflict Detection PCI Self optimization in M2000Page3


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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-3Confidential Information of Huawei. No Spreading Without Permission PCI Conflict PCI is contained in DL SS, used for UE cell search and synchronizationThere are 504 PCI totally, which are divided into 168 groups, each containing 3 PCIs.Page4


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Each E-UTRAN cell is allocated a PCI. When many cells exist in an LTE system, some cells must share one PCI. PCI conflict between neighboring cells may occur if PCIs are planned inappropriately or changed manually, or if neighboring cell parameters are modified.To solve this problem, Huawei developed the PCI conflict detection and self-optimization feature. This feature detects PCI conflict between neighboring cells and allocates appropriate PCIs to these conflicting cells by PCI self-optimization. This feature helps increase handover success rates, improve handover efficiency, and reduce service drop rates.

LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-4Confidential Information of Huawei. No Spreading Without Permission PCI Conflict TypePCI CollisionIf two intra-frequency cells use an identical PCI but they are poorly isolated, PCI collision occurs between them. In this case, UEs in the overlapping area of the two cells cannot implement signal synchronization or decoding.PCI ConfusionIf two or more neighbor cell have the same PCI configuration, then the eNodeB can not identify them while UE report, which cause handover call dropPage5PCI Collision

PCI ConfusionCopyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-5Confidential Information of Huawei. No Spreading Without Permission Structure of PCI Collision Detection & Optimization Page6

UUUUUEUEeNodeBeNodeBPCI self-OptimizationM2000OMOMPCI conflict detectionX2


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The following component are involved:UE: UEs report measurement results to eNodeBs during PCI conflict detection based on ANR. eNodeB: eNodeBs check for PCI conflict separately and report detected PCI conflict to the M2000. After PCI conflict is eliminated, eNodeBs also notify the M2000 of this information.M2000: The M2000 allocates new PCIs to cells experiencing PCI conflict and sends the PCIs to eNodeBs.

LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-6Confidential Information of Huawei. No Spreading Without Permission ContentsFunction OverviewPCI Conflict Detection PCI Self optimization in M2000Page7


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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-7Confidential Information of Huawei. No Spreading Without Permission Method of PCI Conflict DetectionPage8

UU

X2

MO ANR

X2 message interactModify ParameterCopyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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There 3 triggers of PCI conflict detection:PCI conflict detection triggered by eNodeB parameter adjustment: The trigger condition is that an eNodeB parameter is adjusted. The parameter may relate to the PCI, frequency, neighboring cell list (NCL), or neighbor relation table (NRT) of a cell.PCI conflict detection based on ANR: When the ANR function adds a neighboring cell or updates the PCI of a neighboring cell, the eNodeB performs PCI conflict detection if necessaryPCI conflict detection based on X2 messages: When the eNodeB receives an X2 message, which contains neighboring cell information, the eNodeB performs PCI conflict detection if necessary.LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-8Confidential Information of Huawei. No Spreading Without Permission Real Time PCI ConflictPCI conflict information can be observed in two ways:If PCI ConflictAlarmSwitch in on,the PCI conflict alarm can be show in alarm panelReal-time PCI conflict can be showed in PCI optimization task->PCI Collision information in M2000Page9


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Command to enable PCI conflict alarm reportLTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-9Confidential Information of Huawei. No Spreading Without Permission

PCI Conflict Detection Based on eNodeB Parameters ChangeThe following 2 scenarios data modification can trigger PCI conflict detection, function is controlled by license If the PCI or frequency of a local cell of any eNodeB changes, the eNodeB checks the PCI conflict between the local cell and its external cells If the parameter of NCL or NRT is changed ,the eNodeB checks the PCI conflict between and local cell and its external cells ,as well as the conflict between the neighbor cells belonging to the same local cell

Page10Copyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-10Confidential Information of Huawei. No Spreading Without Permission PCI Conflict Detection Based on Event ANRANR is a self-optimization function. It automatically complete and correct neighbor relationships, when neighboring cell information in NCL or NRT is changed by ANR, PCI Conflict detection will be triggered.Page11Copyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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The intra-RAT event-triggered ANR function can discover missing neighboring cells and triggers PCI collisions check between the local cells of an eNodeB and their neighboring cells. This function is controlled by the IntraRatEventAnrSwitch parameter. For details about this function, see ANR Management Feature Parameter Description.The eNodeB detects missing neighboring cells based on UE measurements for handovers: If a detected cell has a different ECGI from any configured neighboring cell of the serving cell, the eNodeB adds this detected cell to the NCL and NRT and starts checking for PCI conflicts.(there might be no PCI conflict) If a detected ECGI is the same as a configured ECGI but their PCIs are different, the eNodeB updates the PCI of the detected ECGI. This may lead to PCI conflict detection.The eNodeB detects missing neighboring cells based on UE history informationIf the target cell for a handover has a different ECGI from any configured neighboring cells of the serving cell, the eNodeB configures the target cell as a neighboring cell of the serving cell. This requires the eNodeB to check for PCI conflicts.LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-11Confidential Information of Huawei. No Spreading Without Permission PCI Conflict Detection Based on Active ANRActive PCI conflict detection is used to detect PCI confusions between configured and unconfigured neighboring cells Active PCI conflict detection based on ANR is controlled by the ActivePCIConflictSwitch parameter. After this switch is turned on, the eNodeB proactively checks for PCI conflicts over the period specified by StartTime and EndTime.

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In a detection period, the procedure for proactive PCI conflict detection based on ANR is as follows:The eNodeB chooses UEs that support ANR and initially access the network. Then, the eNodeB sends measurement configurations related to events A3 and A4, requesting the UEs to measure all E-UTRAN frequencies configured on the eNodeB.Each of the chosen UEs reports information about the neighboring cell with the highest handover priority to the eNodeB of the serving cell. This priority is determined by the RSRP and cell individual offset (CIO).The eNodeB sends a measurement configuration to the UE based on the received measurement report, requesting the UE to report the parameters of this best neighboring cell. These parameters include the ECGI, tracking area code (TAC), and public land mobile network (PLMN) ID list.The UE reports these parameters to the eNodeBThe eNodeB performs the following operations:If the ECGI of this best neighboring cell differs from the ECGI of the configured best neighboring cell of the serving cell, the eNodeB adds this best neighboring cell (with the measured PCI, ECGI, and frequency) to the NCL and adds the neighbor relation to the NRT. Then, the eNodeB starts checking for PCI conflict.If the ECGI of this best neighboring cell equals the ECGI of the configured best neighboring cell of the serving cell but the corresponding PCI is different from the configured one, the eNodeB updates the PCIs in the NCL and NRT. Then, the eNodeB starts checking for PCI conflict.LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-12Confidential Information of Huawei. No Spreading Without Permission Related CommandPage13


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Start time and Stop time can define the detect duration and moment. Its suggested to commit detection during busy hours to increase the possibility that users distribute in signal overlapping area, as a result to benefit active PCI conflict detection.

LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-13Confidential Information of Huawei. No Spreading Without Permission PCI conflict Detection Based on X2 MessageControlled by eNodeB license PCI collision detection based on X2 Setup Response X2Setup Request

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According to the picture, after eNodeB 2 receives the X2 Setup Request message, it checks whether its NCLs contain information about the cells belong to eNodeB 1. If the NCLs do not contain such information, eNodeB 2 adds the external cells to the corresponding NCLs and checks whether their PCIs collide with the PCIs of the local cells of eNodeB 2. After eNodeB 1 receives the X2 Setup Response message, it checks whether its NCLs contain information about the cells belong to eNodeB 2. If the NCLs do not contain such information, eNodeB 1 adds these external cells to the corresponding NCLs and checks whether their PCIs collide with the PCIs of the local cells of eNodeBLTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-14Confidential Information of Huawei. No Spreading Without Permission PCI conflict Detection Based on X2 Message (Cont.)When the parameter of one eNdoeB is changed ,the eNodeB will informs its neighboring eNodeBs, which contains the information of its local cells. On receiving X2 eNodeB Configuration Update message ,the eNdoeB may update the NCL NRT information ,therefore triggers PCI Conflict detection .

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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-15Confidential Information of Huawei. No Spreading Without Permission ContentsFunction OverviewPCI Collision Detection PCI Self optimization in M2000Page16


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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-16Confidential Information of Huawei. No Spreading Without Permission Basic ConceptionPage17CellACellBCellCFirst Order Neigboring CellFirst Order Neigboring CellSecond order Neighboring CellCellACellBBidirectional Neighboring CellCopyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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First-Order Neighboring CellEach eNodeB stores an NCL and NRTs. The NCL and NRTs contain information about the neighboring cells of the local cells of this eNodeB. These neighboring cells are the first-order neighboring cells. These cells may be intra-frequency, inter-frequency, or inter-RAT neighboring cells. RAT is short for radio access technology.Second-Order Neighboring CellThe first-order neighboring cells of the first-order neighboring cells of a cell are the second-order neighboring cells of this cell. Assume that cell B is a first-order neighboring cell of cell A and cell C is a first-order neighboring cell of cell B. Then, cell C is a second-order neighboring cell of cell A.Bidirectional Neighboring CellIf two cells are first- or second-order neighboring cells of each other, they are bidirectional neighboring cells.

LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-17Confidential Information of Huawei. No Spreading Without Permission Principle of Self - Optimization When new PCIs are reallocated, the following factors should be taken account:Consider 1st and 2nd bidirectional neighboring cells to avoid PCI collision and PCI confusionConsider blacklist, the new PCI can not be the same as blacklistConsider the relationship between PCI and DL RSConsider the relationship between PCI and primary synchronization signalPage18Copyright 2013 Huawei Technologies Co., Ltd. All rights reserved. :32-35pt : R153 G0 B0 :FrutigerNext LT Medium : Arial

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PCI self-optimization preferentially allocates an appropriate PCI to a cell with the highest conflict level and then (if necessary) performs a similar operation on another cell until all PCI conflict is eliminated or no further self-optimization can be performed. The conflict level of a cell is calculated by PCI self-optimization based on the number of cells whose PCIs conflict with the PCI of this cell. PCI self-optimization adheres to the following principles: A new PCI must be different from the PCI of any first-order or bidirectional second-order intra-frequency neighboring cell of the conflicting cell. If the new PCI is the same as the PCI of another cell, the two cells must be as far apart as possible, with as many eNodeBs as possible between the two cells.A new PCI must be different from the PCI of any blacklisted intra-frequency cell of the conflicting cell. If the conflicting cell is not in the intra- or inter-frequency cell blacklist of any of its first-order neighboring cells, the new PCI must be different from the PCI of any of these blacklisted cells.The PCIs of three cells with adjacent azimuths under an eNodeB must have different remainders after being divided by 3. In other words, these cells must have different primary synchronization signals.LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-18Confidential Information of Huawei. No Spreading Without Permission Operation in M2000Page19Setup PCI Optimization task

Using Modify button to fix the task mode


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Configuring PCI to any conflicting cell should not be in busy time. Because eNodeB will go through dative when PCI is reset. The time gap between PCI optimization analysis and PCI implementation should not be too large. Because its reasonable to configure the PCI to any conflicting cell according to the latest conflict information.Its important to avoid time overlap between PCI optimization analysis and PCI implementation

LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-19Confidential Information of Huawei. No Spreading Without Permission SummaryPCI conflict detection and self-optimization is a valid solution to maintain radio network works normally .This solution needs eNodeB and M2000 work together . eNodeB plays a role in detecting PCI conflict ,and there are many ways to trigger PCI conflict detection. M2000 handles all the conflict by the means of reallocating new PCIs to conflicting cells.PCI conflict can be observed in the form of logalarmand real-time display.When PCI conflict is solved ,the process of handover and synchronization will be improved , meanwhile, the real-time conflict message will decrease or disappear.Page20


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LTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-20Confidential Information of Huawei. No Spreading Without Permission Thank youwww.huawei.comLTE eRAN6.0 PCI Conflict Detection & Self-OptimizationP-21Confidential Information of Huawei. No Spreading Without Permission Downlink Synchronization Signals

cell

(1)

(2)

(1)

(2)

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NID = 3NID + NID

NID = 0,..167NID = 0, 1, or 2

Modify neighbor relations and trigger PCI conflict detection

Measurement report

eNodeB

UE

Measurement configuration

ECGI request

ECGI of the best detected cell

ENB CONFIGURATION UPDATE ACKNOWLEDGE

eNB1

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ENB CONFIGURATION UPDATE

4 lte eran6.0 pci conflict detection & self-optimization issue1.00

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