Events

SHO

Reporting event 1A for adding cells to the active set

Reporting event 1A is controlled with the following parameters:

Active Set Weighting Coefficient (ActiveSetWeightingCoefficient) Addition Time (AdditionTime) Addition Window (AdditionWindow).

CPICH Ec/No Offset (AdjsEcNoOffset) Maximum Active Set Size (MaxActiveSetSize)For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

Reporting event 1A is used for adding cells in the active set. The UE sends the event 1A-triggered measurement report when a cell enters the reporting range as defined by the following formula:

Figure: Formula for calculating the UE measurement report on event 1AThe variables in the formula are defined as follows:

Table: Variables for measurement report on event 1AVariableDescription

MNewMeasurement result of the cell entering the reporting range

MiMeasurement result of a cell in the active set, not forbidden to affect the reporting range

NANumber of cells not forbidden to affect the reporting range in the current active set

MBestMeasurement result of the strongest cell in the active set, not forbidden to affect the reporting range and not taking into account any cell individual offset

WActive Set Weighting Coefficient (ActiveSetWeightingCoefficient) parameter sent from the RNC to the UE

RAddition Window (AdditionWindow) parameter sent from the RNC to the UE

H1aHysteresis, which is zero for event 1A

CIOnewCPICH Ec/No Offset (AdjsEcNoOffset) parameter of the neighbour cell entering the reporting range

A time-to-trigger mechanism can be used to modify the measurement reporting behaviour of event 1A. If the time-to-trigger mechanism is used, the cell must continuously stay within the reporting range for a given period of time before the UE can send the event 1A-triggered measurement report to the RNC. The length of this period is controlled by the RNP parameter Addition Time (AdditionTime).

Measurement event 1A can be triggered by monitored set cells and detected set cells. Detected set cells are only taken into account if detected set reporting is enabled in one or more of the active set cells.Reporting event 1B for deleting cells from the active set

Reporting event 1B is controlled with the following parameters:

Active Set Weighting Coefficient (ActiveSetWeightingCoefficient) Drop Time (DropTime) Drop Window (DropWindow) CPICH Ec/No Offset (AdjsEcNoOffset)For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

Reporting event 1B is used for deleting cells in the active set. The UE sends the event 1B-triggered measurement report when a cell leaves the reporting range as defined by the following formula:

Figure: Formula for calculating the UE measurement report on event 1B

The variables in the formula are defined as follows:

Table: Variables for measurement report on event 1B

VariableDescription

MOldMeasurement result of the cell leaving the reporting range

MiMeasurement result of a cell in the active set, not forbidden to affect the reporting range

NANumber of cells not forbidden to affect the reporting range in the current active set

MBestMeasurement result of the strongest cell in the active set, not forbidden to affect the reporting range and not taking into account any cell individual offset.

WActive Set Weighting Coefficient (ActiveSetWeightingCoefficient) parameter sent from RNC to UE

RDrop Window (DropWindow) parameter sent from RNC to UE

H1bHysteresis, which is zero for the event 1B

CIOnewCPICH Ec/No Offset (AdjsEcNoOffset) parameter of the neighbour cell entering the reporting range

A time-to-trigger mechanism can be used to modify the measurement reporting behaviour of event 1B. If the time-to-trigger mechanism is used, the cell must continuously stay outside the reporting range for a given period of time before the UE can send the event 1B-triggered measurement report to the RNC. The length of this period is controlled by theDrop Time (DropTime) RNP parameter.

Note

The RNC does not remove a cell from the active set if it is the only cell in the active set which has uplink physical layer synchronisation.

Reporting event 1C for replacing cells in the active set

Reporting event 1C is controlled with the following parameters:

Maximum Active Set Size (MaxActiveSetSize) Replacement Time (ReplacementTime) Replacement Window (ReplacementWindow).

CPICH Ec/No Offset (AdjsEcNoOffset)For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

Reporting event 1C is used for replacing cells in the active set. The UE sends the event 1C-triggered measurement report when the number of cells in the active set is equal to the Maximum Active Set Size (MaxActiveSetSize) parameter and a cell that is not included in the active set becomes better than a cell in the active set as defined by the following formula:

Figure: Formula for calculating the UE measurement report on event 1C

Table: Variables for measurement report on event 1C

VariableDescription

MNewMeasurement result of the cell not included in the active set

MInASMeasurement result of a cell in the active set which has the lowest measurement result in the active set

H1cReplacement window parameter sent from the RNC to the UE

CIONewCPICH Ec/No Offset (AdjsEcNoOffset) parameter of the cell not included in the active set

CIOinASCPICH Ec/No Offset (AdjsEcNoOffset) parameter of the cell in the active set

In the following figure, cells 1, 2 and 3 are in the active set, but cell 4 is not (yet) in the active set.

Figure: A cell that is not in the active set becomes better than a cell in a full active set

A time-to-trigger mechanism can be used to modify the measurement reporting behaviour of event 1C. If the time-to-trigger mechanism is used, the cell must continuously stay within the triggering condition for a given period of time before the UE can send the event 1C-triggered measurement report to the RNC. The length of this period is controlled by the Replacement Time (ReplacementTime)RNP parameter.

The cell (not included in the active set) leaves the triggering condition if it again becomes worse than the cells in the active set as defined by the following formula:

Figure: Formula for calculating the UE measurement report on event 1C

Measurement event 1C can be triggered by monitored set cells and detected set cells. Detected set cells are only taken into account if detected set reporting is enabled in one or more of the active set cells.

Note

The RNC does not replace a cell in the active set if it is the only cell in the active set which has uplink physical layer synchronisation.

Event-triggered periodic intra-frequency measurement reporting

The reporting period is controlled with the following parameters:

Addition Reporting Interval (AdditionReportingInterval) Replacement Reporting Interval (ReplacementReportingInterval) Drop Reporting Interval (DropReportingInterval)For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

When a cell enters the reporting range and triggers event 1A, 1B or 1C, the UE transmits a MEASUREMENT REPORT message to the RNC to update the active set.

The UE reverts to periodical measurement reporting if the RNC does not update the active set after the transmission of the measurement report. The RNC can be unable to add the cell to the active set due to capacity shortage, for example. If the reported cell is not added to or removed from the active set, the UE continues reporting by changing to periodical measurement reporting. This is illustrated in Figure Periodic reporting triggered by event 1A below.

During periodical reporting, the UE transmits measurement report messages to the RAN at pre-defined intervals. The reports include information on the active, monitored and detected (if applicable) cells in the reporting range.

Figure: Periodic reporting triggered by event 1A

Event-triggered periodic measurement reporting is terminated either when there are no more active, monitored or detected (if applicable) cell(s) within the reporting range or when the RNC has updated the active set so that it includes the optimal cells.

Time-to-trigger mechanism for modifying measurement reporting behaviour

The value of the time-to-trigger is controlled separately for each event with the following parameters:

Addition Time (AdditionTime) Drop Time (DropTime) Replacement Time (ReplacementTime)For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

A time-to-trigger parameter can be connected with reporting events 1A, 1B and 1C.

When the time-to-trigger mechanism is applied, the report is triggered only after the conditions for the event have existed for the specified time. In the following example, cell 3 enters the reporting range (event 1A), but it is not reported until it has been within the range for the time indicated by the Addition Time (AdditionTime) parameter.

Figure: Time-to-trigger limits the number of measurement reports

Identification of an intra-frequency cell

Handover control identifies an intra-frequency cell which is reported in the RRC: MEASUREMENT REPORT message by comparing the scrambling code of the Primary CPICH of the reported cell with:

1. the primary CPICH scrambling code of the cells included in the combined intra-frequency cell list

2. the primary CPICH scrambling code of those intra-frequency neighbour cells of the active set cells that have been left out from the full combined intra-frequency cell list

3. the primary CPICH scrambling code of additional intra-frequency neighbour cells of the active set cells

When detected set reporting based soft handover is enabled in one or more active set cells, handover control proceeds step-by-step in the identification process from the 1st step to the 3rd step until it identifies the reported cell. Handover control does not execute the steps 2 and 3 if detected set reporting or the detected set reporting based soft handover is disabled in all active set cells.

The reported intra-frequency cell can be an active, monitored or detected set cell:

1. an active set cell included in the combined intra-frequency cell list

2. a monitored set cell included in the combined intra-frequency cell list

3. an intra-frequency neighbour cell defined in the RNW database object ADJS which has been left out from the full combined intra-frequency cell list

4. an additional intra-frequency neighbour cell which is defined in the RNW database object ADJD and not included in the intra-frequency cell list

If the scrambling code of the Primary CPICH of the reported cell matches with more than one relevant intra-frequency neighbour cells, handover control associates the reported neighbour cell to the active set cell with the higher CPICH Ec/No measurement result. If the scrambling code of the Primary CPICH of the reported cell does not match with any relevant intra-frequency cell, the reported intra-frequency cell remains an unidentified cell.

Soft handover based on detected set reporting

Detected set reporting is based on a 3GPP feature that allows the UE to measure and report any intra-frequency cell which is outside the intra-frequency cell list of the UE. This capability removes the limitation on the length of the intra-frequency cell list. In addition to the active and monitored set cells that are included in the intra-frequency cell list of the UE, the UE can include any detected intra-frequency cell in the event evaluation and reporting:

The UE sends an event 1A/1C triggered measurement report to the RNC when a cell, that is not included in the intra-frequency cell list of the UE, enters the reporting range.

The Primary CPICH scrambling code identifies the detected set cell that has triggered the event 1A/1C measurement report.

The RNC adds the detected set cell into the active set if it is possible to identify the detected set cell, that is the primary CPICH scrambling code of the detected set cell equals to the primary CPICH scrambling code of an intra-frequency neighbour cell. The RNC is not able to identify the detected set cell during anchoring. Detected set reporting is available for all supported bearer services.

The Soft Handover based on Detected Set Reporting feature needs to be enabled on RNC level. For more information on license management see License Management Principles.

When the feature is enabled on RNC level, it can be activated and deactivated on a cell-by-cell basis by modifying the value of the parameter FMCS - DSRepBasedSHO.

Handover control activates the detected set reporting for an RRC connection if the Soft Handover Based on Detected Set Reporting feature is enabled on RNC level and either of the following conditions is true:

Detected set reporting is enabled in one or more active set cells by the parameter FMCS - DSRepBasedSHO (value of the parameter is 1).

Detected set reporting based soft handover is enabled in one or more active set cells by the parameter FMCS - DSRepBasedSHO (value of the parameter is 2).

Note that the E-DCH active set does not affect the procedure.

In the handover decision process, handover control handles detected set cells according to the value of the parameter FMCS - DSRepBasedSHO:

Detected set cells are excluded from the decision when the value of parameter FMCS - DSRepBasedSHO is 0 (DSR is not allowed) or 1 (DSR is enabled but SHO to detected cell is not allowed).

Detected cells are taken into account in addition to the active and monitored set cells when the value of parameter FMCS - DSRepBasedSHO is 2 (DSR based SHO is enabled). This applies to detected cells which are defined in the ADJS object but are left out from the full combined intra-frequency cell list.

Unknown reported cells are excluded from the handover decision process.

If a detected set cell is added to the active set as a result of the handover decision procedure, handover control adds this new active set cell (ex-detected set cell) and its neighbouring cells into the combined intra-frequency cell list which is sent to the UE in the RRC: MEASUREMENT CONTROL message.

If an inter-RNC soft/softer handover is not possible, the handover control initiates an inter-RNC intra-frequency hard handover to the detected set cell as soon as the measurement results of the detected set cell satisfy the required conditions.

Cell individual offsets for modifying measurement reporting behaviour

Individual offsets can be controlled with the CPICH Ec/No Offset (IntraFreqNcellEcNoOffset) parameter.

For a description of the parameter, see WCDMA Radio Network Configuration Parameters.

The individual offset mechanism can be used to change the reporting of an individual cell, and as a result, to move the cell border. For each cell that is monitored, an offset value can be defined which the UE adds to the measurement result (CPICH Ec/No) of the neighbour cell before it compares the Ec/No value with the reporting criteria. The offset can be either positive or negative.

In the following example, an offset is added to the measurement result of cell 3, and the dotted curve is used in evaluating if an event occurs. Measurement reports from the UE to the RNC are therefore triggered when the cell including the corresponding offset (the dotted curve) leaves and enters the reporting range.

When positive offset is used, as in the following example, the UE sends measurement reports as if the cell (CPICH) is offset x dB better than what it really is. Therefore, cell 3 is included in the active set earlier than should have been the case without the positive offset. The cell in question can reside in an area where it often becomes good very quickly (due to street corners, for instance).

Figure: A positive offset is applied to cell 3 before event evaluation in the UE

Mechanism for forbidding a cell to affect the reporting range

The mechanism for forbidding cells to affect the reporting range is controlled with the following parameter:

Disable Effect on Reporting Range (AdjsDERR) indicates whether or not the neighbour cell is forbidden to affect the reporting range (addition/drop window) calculation, if it belongs to the active set.

For a description of the parameter, see WCDMA Radio Network Configuration Parameters.

The Addition Window (AdditionWindow) and Drop Window (DropWindow) parameters affect reporting events 1A and 1B. The reporting ranges of events 1A and 1B are relative to the measurement results of those cells in the active set which are not forbidden to affect the reporting range.

In the following figure, cell 3 is forbidden to affect the reporting range, for example, because it is very unstable in a specific area.

Figure: Cell 3 is forbidden to affect the reporting range

Note

The UE ignores the mechanism if all cells in the active set are forbidden to affect the reporting range.

Reporting events 6F and 6G for deleting cells from the active set

UE Rx-Tx time difference measurement is controlled with the following parameters:

Upper Rx-Tx Time Difference Threshold (UpperRxTxTimeDiff) determines the upper threshold which is used by the UE to trigger the reporting event 6F due to UE Rx-Tx time difference.

Lower Rx-Tx Time Difference Threshold (LowerRxTxTimeDiff) determines the lower threshold which is used by the UE to trigger the reporting event 6G due to UE Rx-Tx time difference.

For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

When the UE Rx-Tx time difference for a cell included in the active set becomes larger than the threshold defined by the parameter Upper Rx-Tx Time Difference Threshold (UpperRxTxTimeDiff), the UE sends an event 6F-triggered measurement report message to the RNC and the RNC deletes the cell from the active set. Similarly, the RNC deletes the cell from the active set if the UE sends an event 6G-triggered measurement report message to the RNC when the UE Rx-Tx time difference for the cell has become smaller than the threshold defined by the Lower Rx-Tx Time Difference Threshold (LowerRxTxTimeDiff)parameter.

Function in abnormal conditions

This section describes the functioning of the RNC in case of an unsuccessful soft handover and radio link failure. In abnormal conditions, the RNC can release the RRC connection or order the UE to move to CELL_FACH state to avoid excessive uplink interference. If the conditions for the RRC connection release and the intra-frequency hard handover are met simultaneously, the hard handover has the higher priority.

RRC connection release due to unsuccessful soft handover

When an intra-frequency neighbour cell enters the reporting range and triggers either event 1A (cell addition) or event 1C (cell replacement), the UE transmits a measurement report to the RNC to add the neighbour cell to the active set. If the soft handover branch addition is unsuccessful, the RNC may release the RRC connection or order the UE to move to CELL_FACH state. This is to avoid excessive uplink interference due to non-optimum fast closed loop power control as the UE is not linked to the strongest cell any more when the requested handover branch is clearly the strongest branch or would become the strongest branch. The RRC connection release and state transition to CELL_FACH due to unsuccessful branch addition procedure are performed according to the following rules:

emergency calls: The RNC does not release emergency call in any case.

AMR + NRT PS multi services: The RNC releases the NRT DCH and retries the branch addition for the AMR service immediately after the NRT DCH is mapped to DCH/DCH 0/0 kbit/s. If there are several NRT DCHs, the RNC releases one NRT DCH and retries the branch addition for the AMR service and the remaining NRT PS data services. If the retry is unsuccessful, the RNC aborts the ongoing branch addition procedure. The RNC can start another branch addition immediately after the reception of the next event 1A/1C triggered measurement report.

NRT PS data services: The RNC may order the UE to move to CELL_FACH state when the requested handover branch is clearly the strongest branch. The EnableRRCRelease parameter of the intra-frequency handover path indicates whether the state transition to CELL_FACH state is allowed due to non-optimum fast closed loop power control. In case of RT/NRT multi services, the RNC uses the HOPS parameter set which is defined for real time (RT) radio bearers.

CS AMR or data services and AMR + RT PS data multi services: the RNC may release the RRC connection when the requested handover branch is clearly the strongest branch. The EnableRRCRelease parameter of the intra-frequency handover path indicates whether the RRC connection release (excluding emergency calls) is allowed due to non-optimum fast closed loop power control.

The parameters related to handling of RRC connection release because of an unsuccessful soft handover are:

CPICH Ec/No Averaging Window (EcNoAveragingWindow) determines the number of event triggered periodic intra-frequency measurement reports from which the RNC calculates the averaged CPICH Ec/No values.

Enable RRC Connection Release (EnableRRCRelease) determines whether RRC connection release (excluding emergency calls) is allowed in situations when soft handover branch addition (or replacement) fails.

Release Margin for Average Ec/No (ReleaseMarginAverageEcNo) determines the maximum allowed difference between the averaged CPICH Ec/No of the neighbour cell and the averaged CPICH Ec/No of the best cell in the active set in situations when the RNC is not able to perform a soft handover between these cells. If the difference between the averaged CPICH Ec/No values exceeds the value of the parameter, the RNC releases the RRC connection or orders the UE to move to CELL_FACH state (in case of streaming and NRT PS data services) in order to avoid excessive uplink interference due to non-optimum fast closed loop power control.

Release Margin for Peak Ec/No (ReleaseMarginPeakEcNo) determines the maximum allowed difference between the CPICH Ec/No of the neighbour cell and the CPICH Ec/No of the best cell in the active set in situations when the RNC is not able to perform a soft handover between these cells. If the difference between CPICH Ec/No values exceeds the value of the parameter, the RNC releases the RRC connection or orders the UE to move to CELL_FACH state (in case of streaming and NRT PS data services) in order to avoid excessive uplink interference due to non-optimum fast closed loop power control.

For a description of the parameters, see WCDMA Radio Network Configuration Parameters.

The UE proceeds to the periodic measurement reporting if the RNC cannot add the requested cell into the active set. If the forced RRC connection release or state transition to CELL_FACH is allowed, the RNC makes the decision on the release or state transition to CELL_FACH on the basis of the CPICH Ec/No of the best cell in the active set, the CPICH Ec/No of the requested neighbour cell and the Release Margin for Average Ec/No and Release Margin for Peak Ec/No control parameters.

The RRC connection release or state transition to CELL_FACH is required when the measurement results of the requested neighbour cell satisfies one of the following equations:

AveEcNoDownlink + ReleaseMarginforAveEc/No (n) < AveEcNoNcell (n)or

EcNoDownlink + ReleaseMarginforPeakEc/No (n) < EcNoNcell (n)The measurement results in the equations are defined as follows:Table: Criteria for enabling the RRC connection release

VariableDescription

AveEcNoDownlinkaveraged CPICH Ec/No of the best cell in the active set

AveEcNoNcell(n)averaged CPICH Ec/No of the neighbouring cell

EcNoDownlinkCPICH Ec/No of the best cell in the active set

EcNoNcell(n)CPICH Ec/No of the neighbouring cell

The RNC calculates the averaged values from a specified number of periodic intra-frequency measurement reports. Averaging is controlled with the CPICH Ec/No Averaging Window (EcNoAveragingWindow) parameter.

Radio link failure

When a radio link in the active set loses uplink physical layer synchronisation, the RNC deletes the radio link (cell) from the active set if the uplink physical layer remains out of synchronisation for a period of time which is specified by an internal constant. After the radio link deletion procedure, the UE can start sending reporting event 1A to the RNC to return the cell back to the active set.

If all radio links in the active set lose uplink synchronisation, the RNC initiates either an RRC Connection Re-establishment or an RRC Connection Release procedure. For more information, see RNC Packet Data Transfer States.

Restart of intra-frequency CPICH Ec/No measurement without detected set reporting

If the handover control receives an RRC: MEASUREMENT CONTROL FAILURE message from the UE upon the request to report detected set cells, the handover control restarts the intra-frequency CPICH Ec/No measurement without the detected set reporting.

ISHO

Inter-frequency handover because of CPICH Ec/No

The IFHO caused by CPICH Ec/No (GSMcauseCPICHEcNo) RNP parameter indicates whether an inter-system handover to GSM caused by low measured absolute CPICH Ec/No is enabled or not. When the inter-frequency handover is enabled, the RNC sets up an intra-frequency measurement to monitor the absolute CPICH Ec/No value. The measurement reporting criteria for the intra-frequency CPICH Ec/No measurement is controlled by the following parameters:

CPICH Ec/No HHO Threshold (HHoEcNoThreshold) determines the absolute CPICH Ec/No threshold which is used by the UE to trigger the reporting event 1F.

CPICH Ec/No HHO Time Hysteresis (HHoEcNoTimeHysteresis) determines the time period during which the CPICH Ec/No of the active set cell must stay worse than the threshold HHoEcNoThreshold before the UE can trigger the reporting event 1F.

CPICH Ec/No HHO Cancellation (HHoEcNoCancel) determines the absolute CPICH Ec/No threshold which is used by the UE to trigger the reporting event 1E.

CPICH Ec/No HHO Cancellation Time (HHoEcNoCancelTime) determines the time period during which the CPICH Ec/No of the active set cell must stay better than the threshold HHoEcNoCancel before the UE can trigger the reporting event 1E.

CPICH Ec/No Filter Coefficient (EcNoFilterCoefficient) controls the higher layer filtering (averaging) of physical layer CPICH Ec/No measurements before the event evaluation and measurement reporting is performed by the UE. The UE physical layer measurement period for intra-frequency CPICH Ec/No measurements is 200 ms.

If the CPICH Ec/No measurement result of an active set cell becomes worse than or equal to the HhoEcNoThreshold absolute threshold/parameter, the UE sends the event 1F-triggered measurement report to the RNC. The UE cancels event 1F by sending an event 1E-triggered measurement report to the RNC if the CPICH Ec/No measurement result of the active set cell increases again and becomes better than or equal to the threshold HHoEcNoThreshold (event 1F is valid for all active set cells simultaneously), the RNC starts the inter-system (GSM) measurement as described in Measurement procedure for inter-frequency handover.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant control parameters, as described in Handover decision procedure for quality reason inter-frequency handover.

Note

The RNC does not break off ongoing inter-system measurement even if the measured CPICH Ec/No of one or more active set cells increases again above the reporting threshold HHoEcNoCancel and the UE sends the corresponding event 1E triggered intra-frequency measurement report to the RNC.

Inter-System handover cancellation

Inter-system measurements and thereby the inter-system handover / network initiated cell reselection for PS services in the UE can be cancelled when the radio conditions in the current WCDMA layer improve during the inter-system measurement phase. This function enables the call to be retained in the current WCDMA network. Thus the end-users are benefited as the inter-system handover is always a hard handover which causes the users to experience a small disconnection in their call. Typically about one-fourth of the inter-system handovers can be interrupted. The individual figure depends on radio network planning and the traffic conditions.

Inter-System Handover Cancellation is supported during anchoring if the inter-system measurements have been previously started during anchoring by the Support for I-HSPA Sharing and Iur Mobility Enhancements feature.

The RNC can cancel the inter-system handover by deactivating compressed mode and instructing the UE to cancel the ongoing inter-system measurements for the following quality and/or coverage based trigger conditions:

UE transmission power

start: Measurement event 6A

stop: Measurement event 6B

Received Signal Code Power (RSCP) or CPICH Ec/No measurement result for a primary CPICH (active set cell)

start: Measurement event 1E stop: Measurement event 1F

Downlink DPCH power

start: DL DPCH Tx Pw increasing beyond the maximum threshold

stop: DL DPCH Tx Pw falls below the maximum threshold

In addition, inter-system measurements are cancelled due to active set update in the UE because of cell addition/replacement.

Inter-System measurement cancellation is performed in the UE only if the measurement reports for the cancellation events are received before the last inter-system measurement report that starts the inter-system handover (RANAP) signalling procedure. If the cancellation triggers are received after the handover decision has taken place, they are ignored and the handover process continues.

Inter-System measurements are related to one individual quality or coverage related handover criteria even if more than one trigger for inter-system measurements due to quality and/or coverage reasons are received simultaneously. Inter-System measurement cancellation, however, is only performed if it is ensured that none of the quality and coverage based inter-system handover causes still persist for the corresponding UE.

If for example event 1F and event 6A triggered measurement reports are received by the RNC for a corresponding UE, inter-system measurements are only stopped if the corresponding cancellation events 1E and 6B are both received.

If IMSI based inter-system handover is enabled in an active set cell, the RNC selects only those GSM neighbour cells into the inter-system neighbour cell list whose PLMN identifiers are either included in the relevant WANE list or which have the same PLMN identifier as the subscriber. Inter-System measurement cancellation is performed in the same manner as that of the other quality and coverage reasons inter-system handover scenarios. For more information on IMSI based handover see Functionality of IMSI-based handover.

Inter-System handover cancellation is available for all the CS and PS services for which quality and coverage based inter-system handover is supported. The cancellation mechanism applies to emergency calls during inter-system measurements due to quality and coverage reasons.

Cancellation of inter-system handover due to event 1EThe RNC stops inter-system measurements when event 1E occurs for at least one cell of the active set. Event 1E can be configured for the following measurements on the Primary CPICH:

CPICH RSCP: received signal code power (RSCP)

CPICH Ec/No: received energy per chip divided by the power density in the band, that is CPICH RSCP/UTRA Carrier RSSI

The parameters ISHOClcauseCPICHEcNo and/or ISHOClcauseCPICHrscp indicate whether inter-system measurement cancellation in the UE is enabled or not for situations when a primary CPICH (active set cell) increases beyond the absolute threshold (Event 1E).

Inter-System handover cancellation due to measurement event 1E can be performed only when all of the following conditions are met:

The Inter-System Handover Cancellation feature is enabled by the ISHOCancellation parameter.

The ISHOClcauseCPICHEcNo or ISHOClcauseCPICHrscp parameter has been set to enabled for one or more cells in the active set.

The number of inter-system cancellations that have been performed for the corresponding UE with the current active set is less than the value specified for the MaxNumISHOClPerAS parameter.

Inter-System measurements were started in the UE due to event 1F (for CPICH Ec/No or CPICH RSCP) triggered measurement report.

Event 1E triggered measurement report was received during inter-system measurement phase.

For information on the cancellation procedure see Inter-System measurement cancellation procedure with CM.

Cancellation of inter-system handover due to event 6B

The ISHO Cancellation caused by UE TX Power (ISHOClcauseTxPwrUL) RNP parameter indicates whether an inter-system handover cancellation caused by the UE transmission power (measurement event 6B) is enabled or not.

Inter-System handover cancellation due to measurement event 6B can be performed only when all of the following conditions are met:


The ISHOClcauseTxPwrUL parameter has been set to enabled for one or more cells in the active set.


Inter-System measurements were started in the UE due to measurement event 6A, that is the UE transmission power increases beyond the threshold.

The event 6B triggered measurement report was received during the inter-system measurement phase.


Cancellation of inter-system handover due to downlink DPCH power

When the downlink DPCH transmission power decreases below the threshold as indicated by the corresponding NBAP/RNSAP dedicated measurement report, the RNC stops the inter-system measurements in the UE. The ISHO Cancellation caused by DL DPCH TX Power (ISHOClcauseTxPwrDL) RNP parameter indicates whether an inter-system handover cancellation caused by a low measured downlink DPCH transmission power level is enabled or not.

Inter-System handover cancellation due to downlink DPCH power can be performed only when all of the following conditions are met:


Tthe ISHOClcauseTxPwrDL parameter has been set to enabled for the cell(s) for which the NBAP/RNSAP:DEDICATED MEASUREMENT REPORT was received.

The number of inter-system measurement cancellations that have been performed for the corresponding UE with the current active set must be less than the value of MaxNumISHOClPerAS.

Inter-System measurements were started in the UE because the downlink DPCH power increased beyond a threshold as indicated by the NBAP/RNSAP:DEDICATED MEASUREMENT REPORT.

The NBAP/RNSAP:DEDICATED MEASUREMENT REPORT which indicates that the downlink DPCH transmission power decreases below the threshold was received during the inter-system measurement. Inter-System handover cancellation can be performed only if an individual NBAP/RNSAP report has been received indicating that the DL DPCH Pwr has now decreased below the threshold for all the radio links an NBAP/RNSAP: Dedicated Measurement Report was received before indicating that the DL DPCH Tx Pwr had increased above the threshold.

The downlink code power of a single radio link satisfies the following equation:

DL_CODE_PWR - PowerOffsetDLdpcchPilot < CPICH_POWER + MAX_DL_DPCH_TXPWR + DL_DPCH_TXPWR_THRESHOLD + DL_DPCH_TXPWR_CANCEL_OFFSETTable: Variables for inter-system handover cancellation

VariableDescription

DL_CODE_PWRindicates the measured downlink code power

PowerOffsetDLdpcchPilotis a constant that defines the power offset for the pilot fields of the DPCCH, expressed as a relative value with respect to the DPDCH power

CPICH_POWERindicates the transmission power of the primary CPICH of an active set cell

MAX_DL_DPCH_TXPWRindicates the maximum transmission power level of the DPDCH symbols a base station can use on the DPCH, expressed as a relative value (dB) with respect to the primary CPICH power (dBm)

DL_DPCH_TXPWR_THRESHOLDis controlled with the following inter-system measurement control parameters, depending on the service type:

DL DPCH TX Power Threshold for RT PS (GsmDLTxPwrThrRtPS ) determines the downlink DPCH transmission power threshold for a real time packet-switched data connection.

DL DPCH TX Power Threshold for NRT PS (GsmDLTxPwrThrNrtPS) determines the downlink DPCH transmission power threshold for a non-real time packet switched data connection.

DL DPCH TX Power Threshold for CS (GsmDLTxPwrThrCS) determines the downlink DPCH transmission power threshold for a circuit-switched data connection.

DL DPCH TX Power Threshold for AMR (GsmDLTxPwrThrAMR) determines the downlink DPCH transmission power threshold for a circuit-switched voice connection.

The downlink DPCH transmission power thresholds are relative (dB) to the allocated maximum transmission power of the DPCH.

In case of a multiservice, the RNC selects the lowest threshold value for the calculation (e.g. when the alternative threshold values are -1dB and -3dB, the RNC selects the -3dB threshold value). Downlink transmission power shall not be used as a handover cause for a service type if the value of the corresponding threshold parameter is 'not used'.

DL_DPCH_TXPWR_CANCEL_OFFSETis a constant that is used to reduce the DL_DPCH_TXPWR_THRESHOLD by a fixed value so that the measured code power of the radio link is compared with a slightly lower threshold (2 to 3db lesser)

It is controlled by the DLDPCHTxPwrClOffset inter-system measurement cancellation parameter.


Cancellation of inter-system handover due to active set update

An active set update during the inter-system handover procedure can be triggered by:

Intra-Frequency measurement event 1A when a primary CPICH enters the reporting range. Upon successful resource allocation in the target cell, the RNC adds the corresponding cell to the active set of the UE.

Intra-Frequency measurement event 1C when the number of cells in the active set is equal to the Maximum Active Set Size (MaxActiveSetSize) parameter and a cell that is not included in the active set becomes better than a cell in the active set. If the resources are successfully reserved in the corresponding monitored cell, this cell replaces the cell in the active set.

Inter-System handover cancellation due to active set update can be performed only when all of the following conditions are met:


Either the ISHOClcauseCPICHEcNo or the ISHOClcauseCPICHrscp parameter has been set to enabled for one or more cells in the active set depending on which of the handover causes (CPICH Ec/No or CPICH RSCP) started inter-system handover measurements in the UE.


Inter-System measurements were started in the UE due event 1F (CPICH Ec/No) or event 1F (CPICH RSCP).

The active set in the UE was updated due to event 1A or event 1C during the inter-system measurement.

Upon completion of the active set update due to event 1A or event 1C, the CPICH EcNo/CPICH RSCP measurement results of the cell that is new in the active set is compared against the threshold for measurement event 1E (CPICH Ec/No) or event 1E (CPICH RSCP). The active set update causes inter-system handover cancellation in the UE if the CPICH Ec/No or the CPICH RSCP of this cell is found to be greater than or equal to the threshold for event 1E.


Inter-System measurement cancellation procedure with CM

Inter-System measurements are cancelled in two steps:

1. In the BTS, compressed mode is deactivated by sending an NBAP:COMPRESSED MODE COMMAND message. The command deactivates all ongoing transmission gap pattern sequences. If the transport channel parameters have been modified by compressed mode, the NBAP:RADIO LINK RECONFIGURATION procedure is performed to deactivate compressed mode.

2. In the UE, compressed mode is deactivated and inter-system measurements are cancelled. The cancellation is initiated for the corresponding UE by sending an RRC:MEASUREMENT CONTROL REQUEST message. If the transport channel parameters have been modified by compressed mode, the RRC:TRANSPORT CHANNEL RECONFIGURATION procedure is triggered.

While the cancellation procedure is ongoing, new trigger for inter-system handover due to quality and coverage reasons can be received. These measurement results are stored and the cancellation process continues. When the measurement interval expires and the trigger conditions are still valid, compressed mode is started. For more details on deactivation of compressed mode see Compressed mode.

Inter-System measurement cancellation procedure without CM

Inter-System measurements configured in the corresponding UE are cancelled by sending an RRC:MEASUREMENT CONTROL REQUEST message.

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