Slide 1* © Nokia Siemens Networks BSS13 Release Content / TAL & PJD / 05 2008
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BSS20974 Radio Link Timeout parameter for AMR HR
S13 Features :
BSS20776 AMR Progressive Power Control
BSS20872 Robust AMR Signalling (FACCH/SACCH)
BSS20485 Separate UL&DL AMR Link Adaption Thresholds
RG10 Features :
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Objective:
Prevent AMR packing and upacking during bad RxLevel condition
This feature enables new triggers to be added to the Packing and Unpacking algorithms:
DL: Packing RxLevel Threshold (PRLT) & Unpacking RxLevel Threshold (URLT)
UL: Packing UL RxLevel Threshold (PURLT) & Unpacking UL RxLevel Threshold (UURLT)
These new parameters (and their values) are managed via UTPFIL (Unit Type Associated Parameter File) and are effective at the BSC level.
Packing and Unpacking functions are then implemented in the following manner:
• AMR Packing is triggered when (Downlink RxLev ≥ PRLT) AND (Uplink RxLev ≥ PURLT) AND (Downlink and Uplink RxQual ≤ IHRF1) are fulfilled.
• AMR Unpacking is triggered when (Downlink RxLev ≤ URLT) OR (Uplink RxLev ≤ UURLT) OR (Downlink or Uplink RxQual ≥ IHRH2) are fulfilled.
1 The existing parameter IHRF - Intra HO Threshold Rx Qual AMR FR.
2 The existing parameter IHRH - AMR Handover HR Intra Threshold DL Rx Qual.
Expected Result & Verification:
OSS Measurement : improved AMR HR utilisation and Reduced drop call rate during AMR packing and unpacking
Application SW
5. AMR Unpacking Optimisation
New AMR quality and handover parameters to avoid useless unpacking in intra-cell FR/HR handovers.
Two new parameters are introduced in the HO algorithm.
1. Lower RX level thresholds for quality based intra cell handovers
If RX level is below this threshold then AMR unpacking, packing and interference handovers (the new type) are not allowed.
2. Lower quality threshold to prevent interference and AMR intra cell handovers
If the quality is on that level or worse then intra-cell quality based handovers are not started.
CAPEX savings & improved network quality by reducing drop call rate
Application SW
Rapid field drop quality drops AMR unpacking handovers.
If dropping too strongly too quickly the mobile cannot decode the HO assignment
Rapid interference increase Failed SACCH decoding
Normally radio link time out timer controls the time how long the mobile can be unreachable before the TCH is deactivated and the call is seen as a drop.
This can be e.g. 16 seconds
But for HO a fixed 6s timer is used before the BSC deactivates TCH call drop
So without an intra cell handover the MS have about 10 seconds more time to get out off bad coverage.
With this feature
HO algorithm will prevent AMR unpacking and interference based intra cell handovers when Rx Level and/or Rx Quality conditions are very bad.
Functional Description
Expected Result
By means of the new quality and level threshold feature allows to avoid risky packing/unpacking HOs. Therefore the main benefit should be observed in terms of Call Drop Rate reduction.
Feature blocks certain amount of unpacking HOs. It means that more calls stay in HR longer.
More HR calls => lower blocking.
5. AMR Unpacking Optimisation
There is no impact of different values of intra HO lower rx quality limit AMR (named on the picture as RxQualLimit) on UL FER degradation. Furthermore FER improvement was observed for intra HO lower rx level limit AMR HR (named as RxLevelLimits) values of -80 and -70dBm. This was caused by the fact that for the both cases these thresholds forced some users to be kept in HR, reducing the interference.
FER degradation was not observed for different values of intra HO lower rx quality limit AMR (called RxQualLimit). Moreover an improvement was achieved for RxQualLimit of 5. For different values of intra HO lower rx level limit AMR HR (named as RxLevelLimits) a huge FER improvement was observed for RxLevelLimits values of -80 and -70dBm. Here the same as in UL it is caused by the fact that for the both cases these thresholds forced some users to keep in HR, reducing the interference in the network.
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5. AMR Unpacking Optimisation
BSS21120
In this configuration packing HO is triggered if RxQual is below 2. However in case signal level is below -100dBm it is not initiated to avoid the risk that the procedure will end up with the dropped call.
Unpacking HO is triggered with RxQual above 3 but it is prohibited in the very bad radio conditions (RxQual 7). Moreover even if the cal is in RxQual range triggering HO from FR to HR it will be not started if RxLev is below -100dBm or above -48dBm.
Obviously the quality threshold to trigger packing and unpacking HO depends on the radio condition in the network and the operator strategy for HR usage. For this reason it varies from network to network. Anyway in very bad radio condition (bad RxQual or poor signal strength) it is recommended not to trigger packing or unpacking HO since there is high probability that this procedure will lead to the call drop. For this reason it is recommended to set intra HO lower rx quality limit AMR to 6 and intra HO lower rx level limit AMR HR to -100dBm.
Moreover in specific configuration where the unpacking quality threshold is below interference quality threshold, HO from AMR HR to AMR FR would be triggered before interference HO. In order to avoid unnecessary AMR HR-> AMR FR-> AMR HR handovers (for more details see above) it is recommended to use higher RxLev limit for AMR unpacking handovers threshold to prevent needless HOs. In any other configuration this parameter should be set to default (-47dBm) what means that unpacking HO would never be prevented due to very good signal strength as it is impossible to receive signal level above – 47dBm.
For both level threshold the range is from -47dBm to 110dBm. Setting the parameter intra HO upper rx level limit AMR HR to -47dBm means that that unpacking will never be blocked due to this threshold. On the other hand value -110 would mean that unpacking would always be prohibited due to level.
For the parameter intra HO lower rx level limit AMR HR it is other way around: value -47 dBm means that unpacking and interference based intra cell handovers are not allowed and value -110 dBm means that these types of HO will never be forbidden due to this threshold.
If the parameter intra HO lower rx quality limit AMR is equal to the quality threshold for unpacking (intra HO Threshold Rx Qual AMR HR) or interference (amrHoHrThrDlRxQual or amrHoHrThrUlRxQual) these two types of handovers will never be triggered.
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BSS21120 AMR Unpacking Optimization
Third Trial
Fourth Trial
BSS20485 Separate UL&DL AMR Link Adaption Thresholds
Fitth Trial
EFL = efeective frequency load
DCR = drop call rate
* © Nokia Siemens Networks BSS13 Release Content / TAL & PJD / 05 2008
Confidential