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Purpose
The following tables display and discuss the parameter settings that are relevant for the Inter-RAT Handover of a Circuit Switched call from UMTS to GSM.
measurementQuantityInterRATHHO
The following table displays the settings for the parameter “Measurement quantity for Inter-RAT HO trigger condition”:
Subparameters Recommendation Explanation
RSCP Boundary cells When going away from the center of the UMTS
cell, the RSCP level may lower, whereas the Ec/No may stay constant. In this situation, Ec/No measurements will not be a suitable basis for Inter-RAT trigger conditions.
ECN0 Central cells When going towards the center of the UMTS
cell, the RSCP level may stay constant, whereas the noise level may change significantly. In this situation, RSCP measurements will not be a suitable basis for Inter-RAT trigger conditions.
RSCP_ECN0 Default setting In most cases, the measurements of both, RSCP
and Ec/No measurements will be a suitable basis for Inter-RAT trigger conditions.
umts2GsmQTriggerMAHO
The following table displays the settings for the parameter “MAHO Trigger Condition”:
Subparameters Too low values Too high values
rSCPThreshold/ eCN0Threshold
Handover is triggered too late.
Call quality may get unacceptably bad. Call may drop.
The value should be chosen higher than required for minimal call quality of a static call. This is necessary to regard for the time that is required to execute the handover to GSM and the movement of the UE.
Handover is triggered too early. A handover to GSM is performed although the quality of the UMTS signal is sufficient, i.e. the UE is still inside the UMTS area.
UTRAN key performance indicators
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Subparameters Too low values Too high values
timeToTrigger Handover is triggered too early.
Measurement report is sent even if the trigger condition is only fulfilled for a very short time. Such fast time fading may be caused for example by
interference and should not cause a handover to GSM.
Handover is triggered too late. Call will drop
In case of bad quality the UE has to wait for the time to trigger before sending the measurement report. This time in conjunction with the time for the execution of the handover to GSM, the UE may have already moved out of coverage of the UMTS area and is not able to receive the handover command from the UMTS network.
weight Quality of the strongest cell has higher
influence than the estimated quality of the active set.
weight: 0 means that the strongest
cell of the Active Set is taken into account, only.
weight: <1 means that the quality of
the strongest cell is taken into account with higher preference than the other cells of the Active Set.
Quality of the strongest cell has less influence than the estimated quality of the active set.
weight: 1 means that all cells of the
Active Set are taken account with the same preference.
weight: >1 means that the quality of
the strongest cell is taken into account with lower preference than the other cells of the Active Set.
umts2GsmQActCM2D
The following table displays the settings for the parameter “Compressed Mode Activation”:
UTRAN key performance indicators Parameter discussion
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Subparameters Too low values Too high values
rSCPThreshold/ eCN0Threshold
Compressed mode will be activated too late.
Call may drop before IRAT PMs can be performed.
Call may drop before HO to GSM is initiated.
Set value to the same or higher value than the HO threshold
(umts2GsmQTriggerMAHO.threshold).
The time of activated CM is reduced to a minimum if both thresholds are equal at a constant TTT. A higher threshold for CM activation may be required to regard for further quality degradation during the time the UE performs IRAT PMs.
Compressed mode is activated earlier than required.
CM active although quality of UMTS signal is sufficient, IRAT HO not to be considered at this time.
CM has negative impact on throughput and/or cell capacity and it should be avoided to activate compressed mode if not required,
timeToTrigger Compressed mode will be activated
earlier than required.
Measurement report is sent even if the trigger condition is only fulfilled for a very short time.
Fast time fading may be caused due to interference and should not trigger the activation of CM.
Compressed mode will be activated too late.
Call may drop due to following scenario: In case of bad quality UE has to wait for the time to trigger before sending the PM report. Further time is required to activate CM, perform IRAT PMs and execute the HO to GSM. During this time the UE may already have moved out of UMTS coverage area, and the call drops.
umts2GsmQDeactCM2F
The following table displays the settings for the parameter “Compressed Mode Deactivation”:
UTRAN key performance indicators Parameter discussion
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Subparameters Too low values Too high values
rSCPThreshold/ eCN0Threshold
Frequent toggling of the compressed mode
Compressed mode is deactivated after a previous activation if the UMTS quality raises only by a small amount. High signalling load
Negative effect on the call quality.
Compressed mode is kept activated very long.
CM active although quality of UMTS signal is sufficient, IRAT HO not to be considered at this time.
CM has negative impact on throughput and/or cell capacity and it should be avoided to keep CM activated if not required.
timeToTrigger Compressed mode will be deactivated
earlier than required.
Measurement report is sent even if the trigger condition is only fulfilled for a very short time.
Fast time fading may be caused due to interference and should not trigger the deactivation of CM.
Compressed mode will be deactivated too late.
UTRAN key performance indicators Parameter discussion
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