owo113030 wcdma ran11 handover algorithm and parameters issue102

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WCDMA Handover Algorithm and Parameters
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Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Foreword
The mobility of UE
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Handover is a basic function of the cellular mobile network. The purpose of handover is to ensure that a UE in CELL_DCH state is served continuously when it moves.
With the development of WCDMA network, more and more users join in the system. Using Handover can achieve load balance between carriers and fully utilizes system resources.
HCS: Hierarchical Cell Structure.
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Confidential Information of Huawei. No Spreading Without Permission
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References
3GPP TS 23.122: Non Access Stratum functions related to Mobile Station (MS) in idle mode
3GPP TS 24.008: Mobile radio interface layer 3 specification; Core Network Protocols - Stage 3
3GPP TS 25.304: UE Procedures in Idle Mode and Procedures for Cell Reselection in Connected Mode
3GPP TS 25.331: RRC Protocol Specification
3GPP TS 23.060: General Packet Radio Service (GPRS); Service description
3GPP TS 25.931: UTRAN Functions, Examples on Signalling Procedures
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Objectives
Upon completion of this course, you will be able to:
Explain the features of each handover
Describe the procedures of each handover
Perform the parameters setting of each handover
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Active set
Monitored set
Detected set
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Active set: A set of cells simultaneously involved in a specific communication service between the UE and the UTRAN.
Monitored set: A set of cells included in the CELL_INFO_LIST, but do not belong to the active set.
Detected set: A set of cells detected by the UE, and do not included in the CELL_INFO_LIST.
RL: Radio link between NodeB and UE.
RLS: All radio links from the same NodeB consist of a radio link set.
Combination way: For soft handover, the uplink signals are combined in RNC. The RNC will select one best signal to process. We call this selective combination. For softer handover, the uplink signals are combined in the RAKE receiver of NodeB. It is maximum ratio combination.
Soft handover gain: Please refer to the WCDMA Coverage Planning course.
PCPICH: Primary Common Pilot Channel. UE measures the signal strength of PCPICH for handover decision.
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Contents
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Contents
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Intra-Frequency Handover Types
The carrier frequencies of the current cell and target cell are the same:
Intra-frequency soft handover
Intra-frequency hard handover
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Intra-frequency handover is of the following two types:
Intra-frequency soft handover: means that multiple radio links are connected to the UE at the same time.
Intra-frequency hard handover: means that only one radio link is connected to the UE at the same time.
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Item
Several
One
Can be happened in Intra-frequency cells or Inter-frequency cells
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The maximum number of RL in the active set is 3 by default. And This parameter can be changed in the RNC. But this function need the UE to support. Normally, the active set supported by UE is fixed 3 and can not be changed.
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Intra-NodeB soft handover (also known as softer handover)
Intra-RNC inter-NodeB soft handover
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Intra-frequency soft handover is characterized by the function that the UE can be connected to multiple Universal Terrestrial Radio Access Network (UTRAN) access points at the same time. Addition and/or release of radio links are controlled by the ACTIVE SET UPDATE procedure.
The HO_INTRA_FREQ_SOFT_HO_SWITCH parameter in the SET CORRMALGOSWITCH command is used to determine whether to enable both soft handover and softer handover. By default, this switch is set to ON, indicating that both soft handover and softer handover are enabled.
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Scenario
When the UE is in the overlapped coverage area of two neighboring cells of a NodeB with combined RLs
When the UE is in the overlapped coverage area of two neighboring cells of different NodeBs
Uplink signal
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During softer handover, the uplink signaling are combined in NodeB by maximum ratio combination, but during soft handover they are combined in RNC by selective combination.
Compare to later one, the maximum ratio combination can get more gain. So the performance of maximum ratio combination is better.
Since softer handover is completed in NodeB, it do not consume more transport resource of Iub.
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Soft handover fails
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Compared with soft handover, intra-frequency hard handover uses fewer resources. The scenarios of intra-frequency hard handover are as follows:
No Iur interface is present between RNCs. In this scenario, intra-frequency hard handover instead of soft handover can be performed between two RNCs.
The Iur interface is congested between RNCs. In this scenario, also intra-frequency hard handover instead of soft handover can be performed between two RNCs.
There is a high-speed Best Effort (BE) service. Compared with soft handover, intra-frequency hard handover is used to save downlink bandwidth for a high-speed BE service.
The intra-frequency soft handover fails and intra-frequency hard handover is allowed. When intra-frequency soft handover fails because of a congestion problem of the target cell, the RNC tries an intra-frequency hard handover with a lower service bit rate.
The HO_INTRA_FREQ_HARD_HO_SWITCH parameter in the SET CORRMALGOSWITCH command is used to determine whether to enable intra-frequency hard handover. By default, this switch is set to ON.
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Contents
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The intra-frequency handover procedure is divided into three phases: handover measurement, handover decision, and handover execution.
After the UE transits to the CELL_DCH state in connected mode during a call, the RNC sends a MEASUREMENT CONTROL message to instruct the UE to take measurements and report the measurement event results. Upon the reception of an event report from the UE, the RNC makes a handover decision and performs the corresponding handover.
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Contents
Neighboring Cell Combination Algorithm
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Event trigger threshold
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L3 filtering formula:
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A: measurement value of the physical layer
B: measurement value obtained after layer-1 filtering. The value is weighted by the layer 3 filtering coefficient.
C: measurement value obtained after layer 3 filtering. This value is controlled by the higher layer. Filtering coefficient C is applicable to event reports and periodic reports.
C': another measurement value. C' and C are measured in the same way.
D: measurement report message of Uu.
Parameters (a) include the layer 3 filtering system and Parameters (b) include the measurement report configuration.
L3 filtering formula:
Fn: measurement value obtained after the nth filtering
Fn-1: measurement value obtained after the (n-1)th filtering
Mn: measurement value of the nth physical layer
α = 1/2(k/2): k is determined by the parameter which is the layer 3 filtering coefficient of intra-frequency handover measurement
When α is set to 1, k = 0 and layer 3 filtering is not performed.
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Recommended value: CPICH_EC/NO
Recommended value: D3, namely K=3
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IntraFreqMeasQuantity
Value range: CPICH_EC/NO, CPICH_RSCP
FilterCoef
Content: This parameter specifies the intra-frequency measurement L3 filter coefficient. The larger the value of this parameter, the stronger the smoothing effect and the higher the anti-fast-fading capability, but the lower the signal tracing capability and the greater the possibility of call drops. If the value of this parameter is too small, unnecessary soft handover or the ping-pong handover may occur.
Value range: D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D11, D13, D15, D17, D19
Physical value range: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 15, 17, 19
Set these parameters through SET INTRAFREQHO/ADD CELLINTRAFREQHO/MOD CELLINTRAFREQHO.
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Event
Description
1A
A primary CPICH enters the reporting range. This indicates that the quality of a cell is close to the quality of the best cell in the active set. A relatively high combined gain can be achieved when the cell is added to the active set.
1B
A primary CPICH leaves the reporting range. This indicates that a cell has a lower quality than the best cell in the active set. The cell has to be deleted from the active set.
1C
A non-active primary CPICH becomes better than an active primary CPICH. This indicates that the quality of a cell is better than the quality of the worst cell in the active set. The RNC replaces a cell in the active set with a cell in the monitored set.
1D
1J
RAN10.0 provides the solution to the issue of how to add an HSUPA cell in a DCH active set to an E-DCH active set. Event 1J is added to the 3GPP protocol. This event is triggered when a non-active E-DCH but active DCH primary CPICH becomes better than an active E-DCH primary CPICH.
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1A event
Event 1A is triggered on the basis of the following formula:
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MNew is the measurement value of the cell in the reporting range.
CIONew is equal to the sum of CIO and CIOOffset, which adjusts the cell boundary in the handover algorithms. To facilitate handover in neighboring cell configuration, the parameter is set as a positive value; otherwise, the parameter is set as a negative value.
W represents Weighted factor, which is determined by the parameter Weight. The total quality of the best cell and the active set is specified by W.
Mi is the measurement value of a cell in the active set.
NA is the number of cells not forbidden to affect the reporting range in the active set. The parameter CellsForbidden1A indicates whether adding the cell to the active set affects the relative threshold of event 1A.
MBest is the measurement value of the best cell in the active set.
R1a is the reporting range or the relative threshold of soft handover. The threshold parameters of the CS non-VP service, VP service, and PS service are as follows:
IntraRelThdFor1ACSVP
IntraRelThdFor1ACSNVP
IntraRelThdFor1APS
H1a represents 1A hysteresis, the hysteresis value of event 1A.
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Intra-Frequency Handover Measurement Events (Cont.)
A: signal quality curve of the best cell in the active set
B: signal quality curve of a cell in the monitored set
C: curve of Th1A
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The above figure shows the triggering of event 1A. In this procedure, the default parameter values are used.
If the signal quality of a cell that is not in the active set is higher than Th1A for a period of time specified by TrigTime1A (that is, Time to trigger in the figure), the UE reports event 1A.
Th1A = (CPICH Ec/No of the best cell in the active set) - (reporting range for event 1A)
If Weighted factor > 0, then Th1A = (general signal quality of all the cells in the active set) - (reporting range for event 1A).
Reporting range for event 1A is equal to the value of IntraRelThdFor1ACSVP, IntraRelThdFor1ACSNVP, or IntraRelThdFor1APS.
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CIO
Recommended value: 0, namely 0dB
CIOOffset
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CIO
Content: This parameter works with the Neighboring cell oriented CIO. It is used for intra- or inter-frequency handover decisions. The larger the sum, the higher the handover priority of the neighboring cell. The smaller the sum, the lower the handover priority of the neighboring cell. Usually it is configured to 0.
Value range: -20~20
Physical unit: dB
CIOOffset
Content: This parameter defines the neighboring cell oriented cell individual offset. The set value functions in combination of the cell oriented CIO. Their sum is added to the measurement quantity before the UE evaluates whether an event has occurred. In handover algorithms, this parameter is used for moving the border of a cell.
Value range: -20~20
Physical unit: dB
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IntraRelThdFor1ACSNVP
Parameter name: CS non VP service 1A event relative THD
IntraRelThdFor1ACSVP
IntraRelThdFor1APS
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IntraRelThdFor1ACSNVP/IntraRelThdFor1ACSVP/IntraRelThdFor1APS
Content: These parameters specify the CS non-VP/VP and PS services relative threshold of event 1A. The higher the threshold is, the more easily the target cell joins the active set, the harder the call drops, the larger the ratio of the UE involved in soft handover is, but the more the use of forward resources is. The lower the threshold is, the more difficult the target cell joins the active set. Thus the communication quality and the smooth handover cannot be guaranteed.
Value range: 0~29
Physical unit: dB
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Hystfor1A
TrigTime1A
Recommended value: D320, namely 320ms
Weight
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Hystfor1A
Content: This parameter specifies the hysteresis value for event 1A. The value of this parameter correlates with slow fading. The larger the value of this parameter, the less possibility of ping-pong effect or wrong decision. But the event might not be triggered in time.
Value range: 0~15
Physical unit: dB
TrigTime1A
Content: This parameter specifies the time delay to trigger event 1A. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower the incorrect decision probability, but the slower the response of the event to measurement signal change.
Value range: D0, D10, D20, D40, D60, D80, D100, D120, D160, D200, D240, D320, D640, D1280, D2560, D5000
Physical value range: 0, 10, 20, 40, 60, 80, 100, 120, 160, 200, 240, 320, 640, 1280, 2560, 5000
Physical unit: ms
Weight
Content: This parameter is used to define the soft handover relative threshold based on the measured value of each cell in the active set. The greater the parameter value, the higher the soft handover relative threshold. When this value is set to 0, the soft handover relative threshold is determined only by the best cell in the active set.
Value range: 0~20
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1A event report mode:
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The report mode of 1A is event trigger report.
Generally the event 1A is reported only once. However, to avoid measurement report loss, the event 1A reporting can be turned to periodical reporting.
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ReportIntervalfor1A
PeriodMRReportNumfor1A
Recommended value: D16
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ReportIntervalfor1A
Content: This parameter specifies the reporting period of event 1A. That is, event 1A is reported at each reporting interval. Usually, event 1A is reported only once. Nevertheless, if the cell, where event 1A is reported, does not join the active set in a specified period of time, the UE can change the reporting of event 1A into periodical mode to avoid missing of measurement reports. The event 1A of this cell is reported for PeriodMRReportNumfor1A times with the reporting interval as the set value.
Value range: NON_PERIODIC_REPORT, D250, D500, D1000, D2000, D4000, D8000, D16000
Physical value range: NON_PERIODIC_REPORT, 250, 500, 1000, 2000, 4000, 8000, 16000
Physical unit: ms
PeriodMRReportNumfor1A
Content: This parameter specifies the number of reporting times of event 1A for periodical reporting. When the actual reporting times exceeds the set value, the periodical reporting ends.
Value range: D1, D2, D4, D8, D16, D32, D64, INFINITY
Physical value range: 1, 2, 4, 8, 16, 32, 64, INFINITY
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1B event
Event 1B is triggered on the basis of the following formula:
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MOld is the measurement value of the cell that becomes worse.
CIOOld is equal to the sum of CIO and CIOOffset, which is the offset between the cell in the reporting range and the best cell in the active set.
W represents Weighted factor, used to weight the quality of the active set. The total quality of the best cell and the active set is specified by the parameter Weight.
Mi is the measurement value of a cell in the active set.
NB is the number of cells not forbidden to affect the reporting range in the active set. The parameter CellsForbidden1B indicates whether adding the cell to the active set affects the relative threshold of event 1B.
R1b is the reporting range or the relative threshold of soft handover. The threshold parameters of the CS non-VP service, VP service, and PS services are as follows:
IntraRelThdFor1BCSVP
IntraRelThdFor1BCSNVP
IntraRelThdFor1BPS
H1b is the hysteresis value of event 1B, which is determined by the parameter Hystfor1B.
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B: signal quality curve of the worst cell in the active set
C: curve of Th1B
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The above figure shows the triggering of event 1B. In this procedure, the default parameter values are used.
If the signal quality of a cell in the active set is lower than Th1B for a period of time specified by TrigTime1B (Time to trigger in the figure), the UE reports event 1B.
Th1B = (CPICH Ec/No of the best cell in the active set) - (reporting range for event 1B)
If Weight > 0, then Th1B = (general signal quality of all the cells in the active set) - (reporting range for event 1B).
Reporting range for event 1B is equal to the value of IntraRelThdFor1BCSVP, IntraRelThdFor1BCSNVP, or IntraRelThdFor1BPS.
Configuration rule and restriction:
The value of IntraRelThdFor1BCSNVP has to be larger than that of IntraRelThdFor1ACSNVP.
The value of IntraRelThdFor1BCSVP has to be larger than that of IntraRelThdFor1ACSVP.
The value of IntraRelThdFor1BPS has to be larger than that of IntraRelThdFor1APS.
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IntraRelThdFor1BCSNVP
Parameter name: CS non VP service 1B event relative THD
IntraRelThdFor1BCSVP
IntraRelThdFor1BPS
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IntraRelThdFor1BCSNVP/IntraRelThdFor1BCSVP/IntraRelThdFor1BPS
Content: These parameters specify the CS non-VP/VP and PS services relative threshold of event 1B. The lower the threshold is, the more easily the event 1B is triggered. The higher the threshold is, the harder the event 1B is triggered.
Value range: 0~29
Physical unit: dB
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Hystfor1B
TrigTime1B
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Hystfor1B
Content: This parameter specifies the hysteresis value for event 1B. The value of this parameter correlates with slow fading. The larger the value of this parameter, the less possibility of ping-pong effect or wrong decision. But the event might not be triggered in time.
Value range: 0~15
Physical unit: dB
TrigTime1B
Content: This parameter specifies the time delay to trigger event 1B. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower the incorrect decision probability, but the slower the response of the event to measurement signal change.
Physical unit: ms
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1C event
Event 1C is triggered on the basis of the following formula:
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MNew is the measurement value of the cell in the reporting range.
CIONew is the cell individual offset value of the cell in the reporting range. It is equal to the sum of CIO and CIOOffset, which is the offset between the cell in the reporting range and the best cell in the active set.
MInAS is the measurement value of the worst cell in the active set.
H1c is the hysteresis value of event 1C, which is determined by the parameter Hystfor1C.
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B: signal quality curve of a cell in the active set
C: signal quality curve of the worst cell in the active set
D: signal quality curve of a cell in the monitored set
E: curve of Th1C
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The above figure shows the triggering of event 1C. In this procedure, the default parameter values are used.
If the signal quality of a cell not in the active set is higher than Th1C for a period of time specified by TrigTime1C (Time to trigger in the figure), the UE reports event 1C, as shown in the figure.
Th1C = (CPICH Ec/No of the worst cell in the active set) + (Hystfor1C/2)
The UE reports event 1C for qualified cells after the number of cells in the active set reaches the maximum value. The maximum number of cells in the active set can be set by the MaxCellInActiveSet parameter.
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Hystfor1C
TrigTime1C
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Hystfor1C
Content: This parameter specifies the hysteresis value for event 1C. The value of this parameter correlates with slow fading. The larger the value of this parameter, the less possibility of ping-pong effect or wrong decision. But the event might not be triggered in time.
Value range: 0~15
Physical unit: dB
TrigTime1C
Content: This parameter specifies the time delay to trigger event 1C. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower the incorrect decision probability, but the slower the response of the event to measurement signal change.
Physical unit: ms
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1C event report mode:
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The report mode of 1C is event trigger report.
Generally the event 1C is reported only once. However, to avoid measurement report loss, the event 1C reporting can be turned to periodical reporting.
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ReportIntervalfor1C
PeriodMRReportNumfor1C
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ReportIntervalfor1C
Content: This parameter specifies the number of reporting times of event 1C for periodical reporting. That is, event 1C is reported at each reporting interval. Usually, event 1C is reported only once. Nevertheless, if the cell, where event 1C is reported, does not join the active set in a specified period of time, the UE can change the reporting of event 1C into periodical mode to avoid missing of measurement reports. The event 1C of this cell is reported for PeriodMRReportNumfor1C times with the reporting interval as the set value.
Physical unit: ms
PeriodMRReportNumfor1C
Content: This parameter specifies the number of reporting times of event 1C for periodical reporting. When the actual reporting times exceeds the set value, the periodical reporting ends.
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1D event
Event 1D is triggered on the basis of the following formula:
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MNotBest is the measurement value of a cell that is not the best cell.
CIONotBest is equal to the sum of CIO and CIOOffset, which is the offset between the cell in the reporting range and the best cell in the active set.
CIOBest is the cell individual offset value of the best cell. This parameter is not used for event 1D.
H1d is the hysteresis value of event 1D, which is determined by the parameter Hystfor1D.
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B: signal quality curve of a cell in the active set or the monitored set
C: curve of Th1D
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The above figure shows the triggering of event 1D. In this procedure, the default parameter values are used.
If the signal quality of a cell not in the active set is higher than Th1D for a period of time specified by TrigTime1D (Time to trigger in the figure), the UE reports event 1D.
Th1D = (CPICH Ec/No of the best cell in the active set) + (Hystfor1D/2)
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Hystfor1D
TrigTime1D
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Hystfor1D
Content: This parameter specifies the hysteresis value for event 1D. The value of this parameter correlates with slow fading. The larger the value of this parameter, the less possibility of ping-pong effect or wrong decision. But the event might not be triggered in time.
Value range: 0~15
Physical unit: dB
TrigTime1D
Content: This parameter specifies the time delay to trigger event 1D. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower the incorrect decision probability, but the slower the response of the event to measurement signal change.
Physical unit: ms
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1J event
Event 1J is triggered on the basis of the following formula:
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MNew is the measurement result of the cell not in the E-DCH active set but in the DCH active set.
CIONew and CIOInAS refer to the offset of each cell.
MInAS is the measurement result of the cell in the E-DCH active set with the lowest measurement result.
H1J is the hysteresis parameter for event 1J and is determined by Hystfor1J.
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A: signal quality curve of a cell in the E-DCH active set
B: signal quality curve of the worst cell in the E-DCH active set
C: signal quality curve of a cell not in the E-DCH active set but included in DCH active set
D: signal quality curve of a cell not in the E-DCH active set but included in DCH active set
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The above figure shows the triggering of event 1J. In this procedure, the hysteresis and the cell individual offsets for all cells equal 0.
If the signal quality of a cell not in the E-DCH active set is higher than Th1J for a period of time specified by TrigTime1J (Time to trigger in the figure), the UE reports event 1J.
Th1J = (CPICH Ec/No of the worst cell in the active set) + (Hystfor1J/2)
The first measurement report is sent when primary CPICH D becomes better than primary CPICH B. The "cell measurement event result" of the measurement report contains the information of primary CPICH D and CPICH B.
On the assumption that the E-DCH active set has been updated after the first measurement report (E-DCH active set is now primary CPICH A and primary CPICH D), the second report is sent when primary CPICH C becomes better than primary CPICH A. The "cell measurement event result" of the second measurement report contains the information of primary CPICH C and primary CPICH A.
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The characteristics of 1J event:
3GPP define the maximum DCH active set size is 6 and the maximum E-DCH active set size is 4.
The DCH active set covers the E-DCH active set or they are the same.
The best cell in E-DCH active set should be the same as that in DCH active set.
Uplink channel type of UE is decided by the best cell in DCH active set:
Uplink channel is E-DCH if the best cell in DCH active set supports HSUPA.
Uplink channel is DCH if the best cell in DCH active set can NOT support HSUPA.
Processing procedure of 1J event:
The UE reports 1J event if it find a non-active E-DCH but active DCH cell PCICH becomes better than an active E-DCH PCIPCH.
RNC will add the target cell into E-DCH active set if the E-DCH active set is NOT full.
RNC will perform replace procedure if the E-DCH active set is full.
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Hystfor1J
TrigTime1J
MaxEdchCellInActiveSet
Parameter name: Max number of cell in EDCH active set
Recommended value: 3
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Hystfor1J
Content: This parameter specifies the hysteresis value for event 1J. The value of this parameter correlates with slow fading. The larger the value of this parameter, the less possibility of ping-pong effect or wrong decision. But the event might not be triggered in time.
Value range: 0~15
Physical unit: dB
TrigTime1J
Content: This parameter specifies the time delay to trigger event 1J. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower probability of incorrect decision, but the slower the response of event to the change of measured signals.
Physical unit: ms
MaxEdchCellInActiveSet
Content: This parameter determines the maximum number of links in the EDCH active set. When the RNC acts as the SRNC, the number of links in the EDCH active set for all the UEs under the RNC cannot exceed the parameter value. If the parameter value is too large, a lot of resources on the RAN side will be occupied as the same data is transferred over multiple EDCH links in macro diversity, thus affecting the system performance. If this parameter value is too small, insufficient combination gain can be achieved in macro diversity by the EDCH, which causes excessive retransmissions and affects the UE speed.
Value range: 1~4
Set this parameter through SET HOCOMM.
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1J event report mode:
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The report mode of 1J is event trigger report.
Generally the event 1J is reported only once. However, to avoid measurement report loss, the event 1J reporting can be turned to periodical reporting.
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ReportIntervalfor1J
PeriodMRReportNumfor1J
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ReportIntervalfor1J
Content: This parameter specifies the number of reporting times of event 1J for periodical reporting. That is, event 1J is reported at each reporting interval. Usually, event 1J is reported only once. Nevertheless, if the cell, where event 1J is reported, does not join the EDCH active set in a specified period of time, the UE can change the reporting of event 1J into periodical mode to avoid missing of measurement reports. The event 1J of this cell is reported for PeriodMRReportNumfor1J times with the reporting period as the set value.
Physical unit: ms
PeriodMRReportNumfor1J
Content: This parameter specifies the number of reporting times of event 1J for periodical reporting. When the actual reporting times exceeds the set value, the periodical reporting ends.
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Contents
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The intra-frequency handover decision and execution procedure depends on the different measurement events that the RNC receives:
1A Event
1B Event
1C Event
1D Event
1J Event
Course Name
Course Name
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Event
1A
When receiving an event 1A report, the RNC decides whether to add a cell. For event 1A, the UE can report more than one cell in the event list in one measurement report. These cells are in the list of the MEASUREMENT CONTROL message, and they are sequenced in descending order of measurement quantity. For the cells in the list, the RNC adds the radio link to the active set only if the number of cells in the active set does not reach the maximum value. This operation is not required if the number of cells in the active set reaches a specified value.
1B
When receiving an event 1B report, the RNC decides whether to delete a cell. For event 1B, if there is more than one radio link in the active set, the RNC decides whether to delete a radio link. This operation is not required if there is only one radio link in the active set.
1C
When receiving an event 1C report, the RNC decides whether to change the worst cell. For event 1C, the UE reports a list that contains good cells and the cells to be replaced, and sequences the cells in descending order by measurement quantity. After receiving the list from the UE, the RNC replaces the bad cells in the active set with the good cells in the list.
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1D
As stipulated in related protocols, an event 1D report includes information about only one cell. This cell can be listed in an active set or a monitored set. The RNC learns that the quality of this cell is better than that of the serving cell and takes one of the following actions: If the reported cell is in the active set, the RNC decides whether to change the best cell or reconfigure measurement control. If the reported cell is in the monitored set, then: If the number of cells in the active set has not reached the maximum value, the RNC adds the cell to the active set. If the number of cells in the active set has reached the maximum value, the RNC replaces the worst cell in the active set with the reported cell. The best cell is changed to the reported cell. The RNC determines whether the intra-frequency hard handover scenarios are applicable. If any scenario is applicable, the RNC performs an intra-frequency hard handover.
1J
When receiving an event 1J report with information about the good cells and the cells to be replaced, the RNC proceeds as follows: If the current number of cells in the E-DCH active set is smaller than the value of MaxEdchCellInActiveSet, the uplink of the cell where event 1J is triggered is reconfigured to E-DCH. If the current number of cells in the E-DCH active set is equal to the value of MaxEdchCellInActiveSet, the RNC searches the measurement report for the non-serving E-DCH with the lowest measured quality in the E-DCH active set. Then, the uplink of the cell where event 1J is triggered is reconfigured from DCH to E-DCH.
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MaxCellInActiveSet
Recommended value: -24, namely -24dB
Course Name
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MaxCellInActiveSet
Content: This parameter specifies the maximum number of cells in the active set. This parameter can achieve the balance between the signal quality in the SHO area and the performance of the system. The more cells the active set contains, the larger macro diversity gain the user obtains in the SHO area, and the smaller the intra-frequency interference is. But in this case, the user occupies resources of several cells, which increases the amount of data to be processed by the system and lowers the system performance.
Value range: 1~6
SHOQualmin
Content: When the RNC receives events 1A, 1C and 1D, the target cell can be added to the active set only when CPICH Ec/No of the target cell is higher than this absolute threshold.
Value range: -24~0
Physical unit: dB
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Rate Reduction After an SHO Failure
If the radio link addition for a soft handover fails, the rate reduction is triggered for R99 NRT (Non Real Time) services to increase the probability of a successful soft handover
1A,1C,1D is received by RNC
Execute admission control in target cell
Admission succeed?
Execute Handover
Rate Reduction
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If the RNC receives a 1A, 1C, or 1D measurement report, the RNC tries to add the corresponding cell to the active set. If the addition fails, the RNC performs the estimation procedure for rate reduction.
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Step 1:
The RNC evaluates whether the measurement quantity of the cell failing to be admitted meets the condition of rate reduction.
If the condition is met, the RNC performs a rate reduction process for the access service immediately, as described in the next page Procedure of Rate Reduction Execution.
If the condition is not met, the RNC performs the step 2.
The condition of rate reduction is as follows: Mnew > Mbest_cell - RelThdForDwnGrd
Mnew is the CPICH Ec/No measurement value of the cell failing to be admitted.
Mbest_cell is the CPICH Ec/No measurement value of the best cell in the active set.
RelThdForDwnGrd is configured through the parameter Relative threshold of SHO failure.
Step 2:
The RNC evaluates whether the number of SHO failures in the cell exceeds the Threshold number of SHO failure.
If the number of SHO failures in the cell is smaller than the ShoFailNumForDwnGrd:
If the timer has not been started, the RNC starts it.
If the timer has been started, the RNC increments the SHO failure counter by one.
The timer length is set through the parameter ShoFailPeriod.
The SHO failure counter of a cell is used to record the number of SHO failures in this cell. For each UE, the RNC records the number of SHO failures in three cells at most. For SHO failures in any other cells, the RNC does not record the number.
Before the SHO failure evaluation timer expires, no action is taken and the RNC waits for the next measurement report period.
When the SHO failure evaluation timer expires, the RNC sets the SHO failure counter of the corresponding cell to 0 and ends the evaluation.
If the number of SHO failures in the cell is larger than or equal to the parameter ShoFailNumForDwnGrd, the RNC performs a rate reduction process for the access service.
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RelThdForDwnGrd
ShoFailPeriod
Recommended value: 60, namely 60s
ShoFailNumForDwnGrd
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RelThdForDwnGrd
Content: This parameter specifies the threshold of immediate rate reduction after the soft handover failure.
Value range: -29~29
Physical unit: dB
ShoFailPeriod
Content: This parameter specifies the maximum evaluation period of the soft handover failure. When the rate reduction evaluation is performed on a cell that fails to join the active set, the evaluation timer is started. If the cell cannot fulfill the condition of rate reduction before the timer expires, the evaluation and rate reduction retry on the cell will not be performed.
Value range: 0~120
Physical unit: s
ShoFailNumForDwnGrd
Content: This parameter specifies the threshold number of the soft handover failures. This parameter determines the reporting times of the events from the cell that fails to join the active set in soft handover, to trigger the rate reduction of the active set and the attempt to join the active set.
Value range: 0~63
Set these parameters through SET INTRAFREQHO.
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Course Name
Course Name
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The RNC performs a rate reduction process for the access service. The method of determining the access rate after the rate reduction is the same as that described in rate negotiation of load control course.
After the rate reduction succeeds, the RNC immediately attempts to add this cell to the active set without measurement:
If the cell succeeds in admitting the UE, the RNC adds the radio link and sets the SHO failure counter of the cell to 0 and ends the execution.
If the cell fails to admit the UE, the RNC starts the Period of penalty timer for SHO failure after down rate to avoid an increase in the rate triggered by DCCC within the period. Also in this period, the RNC sets the SHO failure counter of the cell to 0 and ends the execution.
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DcccShoPenaltyTime
Parameter name: Period of penalty timer for SHO failure after down rate
Course Name
Course Name
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DcccShoPenaltyTime
Content: This parameter defines the length of penalty timer for SHO failure after rate reduction in the active set. When the rate reduction in the active set is performed which triggers the increase of SHOs in the target cell, if the target cell fails to join the active again, the RNC starts the penalty timer for SHO failure. This parameter defines the length of the penalty timer. Before the timer expires, the rate increasing in the active set is prohibited, but rate reduction is not prohibited.
Value range: 0~255
Physical unit: s
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After that, the neighboring cells of cell B are added.
Finally, the neighboring cells of cell C are added.
Cell A, Cell B and Cell C are in active set. Cell A is the best cell. Cell B Ec/No is greater than Cell C.
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After the active set is updated, the RNC updates the neighboring cell list by using the neighboring cell combination algorithm according to the status of the active set. This list includes the new intra-frequency, inter-frequency, and inter-RAT neighboring cells. The combination methods of intra-frequency handover, inter-frequency handover, and inter-RAT handover are the same.
The neighboring cell combination result is contained in the MEASUREMENT CONTROL message and sent to the UE, which instructs the UE to perform intra-frequency, inter-frequency, and inter-RAT measurement and handover procedures.
The number of inter-frequency neighboring cells is configured as follows:
A maximum of 32 intra-frequency neighboring cells are configured.
A maximum of 32 single-carrier inter-frequency neighboring cells are configured.
A maximum of 64 multi-carrier inter-frequency neighboring cells are configured.
A maximum of 32 inter-RAT neighboring cells are configured.
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HO_MC_NCELL_COMBINE_SWITCH is the neighboring cell combination switch.
If the switch is set to ON, measurement objects are chosen from the neighboring cells of all the cells in the active set.
If the switch is set to OFF, measurement objects are chosen from the neighboring cells of the best cell.
Neighboring cell combination procedure:
After obtaining the intra-frequency neighboring cells of each cell in the active set, the RNC calculates the union neighboring cell set of the intra-frequency cells, which is referred as Sall, by using the following method. This method can also be used to generate the Sall of inter-frequency or inter-RAT cells.
The intra-frequency, inter-frequency, and inter-RAT neighboring cells of each cell in the current active set are obtained.
The RNC sequences the cells in the active set in descending order of CPICH Ec/No according to the latest measurement report (event 1A, 1B, 1C, or 1D) from the UE. The best cell is based on event 1D, whereas other cells are based on the latest measurement report.
The cells in the active set are added to Sall.
The neighboring cells of the best cell in the active set are added to Sall. NprioFlag (the flag of the priority) and Nprio (the priority of the neighboring cell), which are set for each neighboring cell, are used to change the order of adding the neighboring cells to Sall.
The neighboring cells of other cells in the active set are added to Sall in descending order by CPICH Ec/No values of these cells in the active set. The neighboring cells of the same cell in the active set are added according to Nprio and the number of repeated neighboring cell is recorded.
If there are more than 32 intra-frequency neighboring cells in Sall, delete the repeated neighboring cells whose number in Sall is less. The top 32 neighboring cells are grouped into the final Sall.
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HO_MC_NCELL_COMBINE_SWITCH
Recommended value: ON
Recommended value: FALSE
Recommended value: None
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HO_MC_NCELL_COMBINE_SWITCH
Content: When the switch is on, the neighboring cell combined algorithm is used during the delivery of the objects to be measured. When the switch is off, the best cell algorithm is used.
Value range: ON, OFF
Set this parameter through SET CORRMALGOSWITCH.
NprioFlag
Content: Priority identifier of neighboring cells. TRUE indicates that the neighboring cell priority is valid in the algorithm of neighboring cell combination. FALSE indicates that the neighboring cell priority is invalid, and, in the algorithm of neighboring cell combination, the cell with invalid priority is the last one to be considered as the measurement object.
Value range: FALSE, TRUE
Nprio
Content: Priority of neighboring cells. The lower the priority, the easier it is for the neighboring cell to be delivered as the measurement object. For example, it is more possible for a neighboring cell of priority 1 than a cell of priority 2 to be delivered as the measurement object.
Value range: 0~30
Set the upper two parameters through ADD INTRAFREQNCELL/MOD INTRAFREQNCELL / ADD INTERFREQNCELL/MOD INTERFREQNCELL / ADD GSMNCELL/MOD GSMNCELL.
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Contents
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There are five types of signaling procedures for intra-frequency handover:
Intra-NodeB Intra-Frequency Soft Handover
Inter-RNC Intra-Frequency Soft Handover
Inter-RNC Intra-Frequency Hard Handover
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Inter-Frequency Handover Types
The carrier frequency of the current cell and target cell are different
Based on the triggering causes of handover, inter-frequency handover can be categorized into two types:
Coverage-based inter-frequency handover
Load-based inter-frequency handover
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Coverage-based inter-frequency handover:
If a moving UE leaves the coverage of the current frequency, the RNC needs to trigger the coverage-based inter-frequency handover to avoid call drops.
QoS-based inter-frequency handover:
According to the Link Stability Control Algorithm, the RNC needs to trigger the QoS-based inter-frequency handover to avoid call drops.
Load-based inter-frequency blind handover:
To balance the load between inter-frequency con-coverage cells, the RNC chooses some UEs and performs the inter-frequency blind handover according to user priorities and service priorities.
Speed-based inter-frequency handover:
When the Hierarchical Cell Structure (HCS) applies, the cells are divided into different layers according to coverage. The macro cell has a larger coverage and a lower priority, whereas the micro cell has a smaller coverage and a higher priority.
Inter-frequency handover can be triggered by the UE speed estimation algorithm of the HCS. To reduce frequent handovers, the UE at a higher speed is handed over to a cell under a larger coverage, whereas the UE at a lower speed is handed over to a cell under a smaller coverage.
The InterFreqHOSwitch parameter in the ADD CELLHOCOMM command is used to chooses the inter-frequency measurement control parameters to implement handover measurement based on coverage, QoS and speed.
The HO_INTER_FREQ_HARD_HO_SWITCH parameter in the SET CORRMALGOSWITCH command is used to determine whether to allow load-based inter-frequency handover.
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Inter-Frequency anti-Ping-Pong
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In the triggering phase:
The RNC requests the UE to measure through an inter-frequency measurement control message. If the CPICH Ec/No or CPICH RSCP of the current cell is lower than the corresponding threshold, the UE reports event 2D.
In the measurement phase:
The RNC sends an inter-frequency measurement control message to the UE, requesting the NodeB and UE to start the compressed mode. The RNC also requests the UE to perform the inter-frequency measurement.
In this phase, the method of either periodical measurement report or event-triggered measurement report can be used.
In the decision phase:
After the UE reports event 2B, the RNC performs the handover. Otherwise, the UE periodically generates measurement reports, and the RNC makes a decision after evaluation.
In the execution phase:
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Triggering event:
2D event:
The estimated quality of the currently used frequency is below a certain threshold
2F event:
The estimated quality of the currently used frequency is above a certain threshold
Course Name
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When the estimated quality or strength of the currently used frequency is below a certain threshold, 2D event will be triggered. Then RNC will initiate the compressed mode to start inter-frequency measurement.
During compressed mode, if the estimated quality of the currently used frequency is above a certain threshold, 2F event will be triggered. Then RNC will stop the compressed mode.
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Measure the inter-frequency cell or inter-RAT cell under FDD mode
Categories
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Compressed mode control is a mechanism whereby certain idle periods are created in radio frames during which the UE can perform measurements on other frequencies. The UE can carry out measurements in the neighboring cell, such as GSM cell and FDD cell on other frequency. If the UE needs to measure the pilot signal strength of an inter-frequency WCDMA or GSM cell and has one frequency receiver only, the UE must use the compressed mode.
Each physical frame can provide 3 to 7 timeslots for the inter-frequency or inter-RAT cell measurement, which enhances the transmit capability of physical channels but reduces the volume of data traffic.
In DL, during compressed mode, UE receiver can test signal from other frequency. In order to avoid the effect cause by UE transmitter, compressed mode is also used in UL.
The compressed mode includes two types, spreading factor reduction (SF/2) and high layer approaches. The usage of type of compressed mode is decided by the RNC, according to spreading factor used in uplink or downlink.
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2D event:
Event 2D is triggered on the basis of the following formula:
QUsed ≤ TUsed2d - H2d/2
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QUsed is the measured quality of the used frequency.
TUsed2d is the absolute quality threshold of the cell that uses the current frequency. Based on the service type and measurement quantity, this threshold can be configured through one of the following parameters:
InterFreqCSThd2DEcN0
InterFreqR99PsThd2DEcN0
InterFreqHThd2DEcN0
InterFreqCSThd2DRSCP
InterFreqR99PsThd2DRSCP
InterFreqHThd2DRSCP
H2d is the event 2D hysteresis value set through the parameter HystFor2D.
After the conditions of event 2D are fulfilled and maintained until the TimeToTrig2D is reached, the UE sends the event 2D measurement report message.
Any of the Ec/No and RSCP measurement result can trigger the 2D event.
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InterFreqR99PsThd2DEcN0
InterFreqHThd2DEcN0
Course Name
Course Name
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InterFreqCSThd2DEcN0
Value range: -24~0
Physical unit: dB
Value range: -24~0
Physical unit: dB
Value range: -24~0
Physical unit: dB
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Recommended value: -95, namely -95dBm
InterFreqR99PsThd2DRSCP
InterFreqHThd2DRSCP
Course Name
Course Name
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Value range: -115~-25
Physical unit: dBm
Physical unit: dBm
Physical unit: dBm
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HystFor2D
TimeToTrig2D
Course Name
Course Name
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HystFor2D
Content: Hysteresis value for the event 2D. The value of this parameter correlates with slow fading. The larger the value of this parameter, the smaller probability of ping-pong effect or wrong decision, but event 2D might not be triggered in time.
Value range: 0~29
Physical unit: dB
TimeToTrig2D
Content: Time delay to trigger event 2D. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower probability of incorrect decision, but the slower the response of event 2D to the change of measured signals.
Physical unit: ms
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2F event
Event 2F is triggered on the basis of the following formula:
QUsed ≥ TUsed2f + H2f/2
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QUsed is the measured quality of the used frequency.
TUsed2f is the absolute quality threshold of the cell that uses the current frequency. Based on the service type and measurement quantity, this threshold can be configured through one of the following parameters:
InterFreqCSThd2FEcN0
InterFreqR99PsThd2FEcN0
InterFreqHThd2FEcN0
InterFreqCSThd2FRSCP
InterFreqR99PsThd2FRSCP
InterFreqHThd2FRSCP
H2f is the event 2F hysteresis value set through the parameter HystFor2F.
After the conditions of event 2F are fulfilled and maintained until the parameter TimeToTrig2F is reached, the UE reports the event 2F measurement report message.
Any of Ec/No and RSCP measurement result can trigger the 2F event.
Conditions of event 2F are as follows: TUsed2d - H2d/2 < TUsed2f + H2f/2, for example, (InterFreqCSThd2DEcN0–HystFor2D/2) < (InterFreqCSThd2FEcN0+ HystFor2F/2).
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InterFreqR99PsThd2FEcN0
InterFreqHThd2FEcN0
Course Name
Course Name
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Value range: -24~0
Physical unit: dB
Value range: -24~0
Physical unit: dB
Value range: -24~0
Physical unit: dB
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InterFreqR99PsThd2FRSCP
InterFreqHThd2FRSCP
Course Name
Course Name
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Physical unit: dBm
Physical unit: dBm
Physical unit: dBm
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HystFor2F
TimeToTrig2F
Course Name
Course Name
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HystFor2F
Content: Hysteresis value for the event 2F. The value of this parameter correlates with slow fading. The larger the value of this parameter, the smaller probability of ping-pong effect or wrong decision, but event 2F might not be triggered in time.
Value range: 0~29
Physical unit: dB
TimeToTrig2F
Content: Time delay to trigger the event 2F. The value of this parameter correlates with slow fading. The larger the value of this parameter, the lower probability of incorrect decision, but the slower the response of event 2F to the change of measured signals.
Physical unit: ms
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Measurement control:
UE
RNC
Measurement control (Ec/No)
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When the UE enters the compress mode, RNC will trigger the inter-frequency handover measurement by two additional measurement control signaling, so as to request UE test inter-frequency neighbor cell.
In this Measurement control message, RNC should inform the UE inter-frequency measurement parameter, including neighbor list and reporting mode as well.
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Measurement report:
Measurement report
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The measurement report mode of inter-frequency handover is configured through the parameter InterFreqReportMode. By default, periodically reporting is recommended.
The advantage of periodical measurement report is that if the handover fails, the RNC reattempts the handover to the same cell after receiving the periodical measurement report from the UE. This increases the probability of the success of inter-frequency handover.
Based on the measurement control message received from the RNC, the UE periodically reports the measurement quality of the target cell. Then, based on the measurement report, the RNC makes the handover decision and performs handover.
If the reporting mode is periodically reporting: UE test the Inter-frequency neighbor RSCP and Ec/No.
If the reporting mode is event trigger reporting: UE test the Inter-frequency neighbor RSCP and Ec/No, and current cell Ec/No or RSCP.
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InterFreqReportMode
Recommended value: Periodical reporting
InterFreqMeasTime
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InterFreqReportMode
Value range: PERIODICAL_REPORTING(Periodical reporting), EVENT_TRIGGER(Event trigger)
Physical value range: Periodical reporting, Event trigger
PrdReportInterval
Physical value range: NON_PERIODIC_REPORT, 250, 500, 1000, 2000, 3000, 4000, 6000, 8000, 12000, 16000, 20000, 24000, 28000, 32000, 64000
Physical unit: ms
Content: Timer length for inter-frequency measurement. After inter-frequency measurement starts, if no inter-frequency handover is performed when this timer expires, the inter-frequency measurement and the compressed mode (if started) are stopped. The value 0 indicates the timer is not to be enabled.
Value range: 0~512
Physical unit: s
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The coverage-based inter-frequency handovers are categorized into two types according to the following two measurement report modes:
periodical measurement report mode
event-triggered measurement report mode
Each mode corresponds to a different decision and execution procedure
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owo113030 wcdma ran11 handover algorithm and parameters issue102

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