mounir34
2017-06-07, 02:10 AM
1. Parameter settings on feature enabling
MLB is divided into the following steps: MLB algorithm trigger, candidate neighboring cell and target frequency selection, UE selection, load transfer
【 Step 1 】 MLB algorithm trigger
Switch configuration:
CellAlgoSwitch.MlbAlgoSwitch.UtranMlbSwitch - 1.
EnodebAlgoSwitch.HoModeSwitch.UtranPsHoSwitch - 1.
When the switchs are enabled,
The eNodeB starts MLB for UL-sync UEs if the following conditions are met continuously for 5s:
The cell PRB usage ≥ (CellMLB.InterRatMlbThd + CellMLB.LoadOffset)
Uplink and gaits user of ≥ (CellMLB.InterRatMlbUeNumThd + CellMLB.InterRatMlbUeNumOffset)
The cell PRB including
Uplink GBRPRB usage
Downlink GBRPRB usage
Uplink TotalPRB efficiency (uplink GBRPRB rate + Uplink Non-GBRPRB utilization)
Downlink TotalPRB rate (The GBRPRB rate + Downlink Non-GBRPRB utilization)
GBR PRB usage takes priority over total PRB usage in triggering. MLB is triggered by total PRB usage.The eNodeB will transfer non-GBR services.
【 Step 2 】 target cell/frequency selection
After MLB triggered, eNB selects target cells within period of CellMLB.InterRatLoadEvalPrd.
If CellAlgoSwitch.MlbAlgoSwitch.MlbLoadInfoSwitch is on, eNB will get load information of UTRANNCELLs through RIM procedure. If load information can't be gotten successfully for RIM is not configured correctly or other reasons, eNB take actions as the neighbour cell is in lowload.
The eNodeB filters out the cells from the UTRAN neighboring relation table (NRT) to generate a list of candidate cells
Congested or overloaded cells
Cells for which the UtranNCell.NoHoFlag parameter is set to FORBID_HO_ENUM(Forbid Ho)
The selection policy of target cells for MLB by transferring UL-Sync UEs is determined by CellMLB.FreqSelectStrategy, complies with the following rules:
If CellMLB.FreqSelectStrategy is FAIRSTRATEGY, select all UTRAN frequency as the target cell frequency.
If CellMLB.FreqSelectStrategy is PRIOR IT YBASED, the eNodeB selects the frequencies (one or more frequencies) with the highest priority defined by UtranNFreq.MlbFreqPriority as target frequencies..
【 steps 3 】 UE Selection
The eNodeB preferentially selects non-CA UEs over CA UEs.
According to CellMLB.InterRatMlbUeSelStrategy complies with the following rules:
1) CellMLB.InterRatMlbUeSelStrategy choose for PRBRATIOHIGHMODE, Each of the seleced UEs must meet all the following conditions:
PRB usage of the UE in the direction (uplink or downlink) where MLB is triggered >2%
Total PRB usage of all UEs to be transferred in the same direction <CellMLB.LoadDiffThd/2
PRB usage of the UE in the opposite direction ≤ 2%
e.g. If the MLB is triggered by UL PRB USAGE, the opposite direction is DL PRB USAGE.
2.) CellMLB.InterRatMlbUeSelStrategy choose for PRBRATIOLOWMODE, Each of the seleced UEs must meet all the following conditions:
PRB usage of the UE in the load balancing triggering direction< CellMLB.InterRatMlbUeSelPrbThd
【 steps 4 】 load transfer
There are two methods of transferring UL-Sync UEs that support inter-RAT handover: blind handover and measurement-based handover. Measurement - based handover:
measurement-based handover
eNB will send LOAD -BASED B1 measurement control to UE, when UE reports the event, eNB trigger the load - based handover, the threshold is based on configurations as follows:
RSCP: indicates the InterRatHoUt RAN Group. LdSvBasedHoUtranB1ThdRscp
ECN0. InterRatHoUt RAN Group. LdSvBasedHoUtranB1ThdEcn0
Blind handover
When CellAlgoSwitch.MlbHoMode.InterRatMlbBlindHo switch is selected, UE will transfered by blind handover. If the UE does not support inter-rat handover,it will be transfered by blind redirection.
When the InterRatMlbBlindHo is off, and the UE does not support inter-rat handover,it will be transfered by redirection ; If PS-HO switch off, redirection switch is on, the UE will transfered by redirection.
【 testing methods 】 for function presentation only,not be the same with live network, pls obtain required version testing cases from official before demos , the following parameters settings only for reference,
For testing,the parameters related each step can be changed as follows to make the conditions more tractable, for example,
1.The cell MLB.InterRatMlbThd and CellMLB.LoadOffset set lower value to make the MLB is easy to trigger.
2. CellMLB.InterRatMlbUeNumThd set to 99 (represent the actual user of 2) or 100 (represent the actual user constant 1). Note that if this parameter is set to 1 ~ 98, it means the actual user Number of 10 ~ 980;
CellMLB.InterRatMlbUeNumOffset should be set to 0, if UEs for testing is not enough.
3.When the CellMLB.InterRatMlbUeSelStrategy is PRBRATIOHIGHMODE, make the target cell with no UEs on service while properly increase CellMLB.LoadDiffThd to enable the UEs easy to be selected.
4.When CellMLB.InterRatMlbUeSelStrategy is set to PRBRATIOLOWMODE, it is appropriate higher CellMLB.InterRatMlbUeSelPrbThd should be set.
5. If the restrictions on UE download rate is enable, limit the UE's dpwnload speed to make the UE's PRB usage less than CellMLB.InterRatMlbUeSelPrbThd; If the restrictions on UE download rate is unable, CellMLB.LoadDiffThd or CellMLB.InterRatMlbUeSelPrbThd should be set reasonably according to the number of testing UEs. .e.g there're 3 testing UEs, not limit download speed, then it is ensures that there's at least one UE's PRB usage is less than 33 %, so set CellMLB.LoadDiffThd to 70 or CellMLB.InterRatMlbUeSelPrbThd to 35 will ensure there is at least one UE can meet the selected conditions.
6. Decrease the InterRatHoUTRANGroup. LdSvBasedHoUtranB1ThdRscp, or InterRatHoUTRAN Group. LdSvBasedHoUtranB1ThdEcn0, to make UE easier to report handover event.
7. Pay attention to the following items, avoid coverage - based inter-rat handover threshold is set too lowto amke the UE has transfered by coverage-based handover before it can be transfered by load-based handover.
8.At the start of testing, open S1 / UU trace andthe MLB monitoring in U2000 (CellPerformanceMon IT oring > MLB Monitoring) in order to monitor whether MLB is triggered, MLB's unsuccesful reason can be found diredtly by the record of MLB monitoring, parameter specific meaning see U2000 online help.
9. By observation of S1AP_HANDOVER_REQUIRED with cause reduc- load- in-serving-cell and RRC_MOBILITY_FROM_EUTRAN _COMMAND to confirm MLB handover is triggered.
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MLB is divided into the following steps: MLB algorithm trigger, candidate neighboring cell and target frequency selection, UE selection, load transfer
【 Step 1 】 MLB algorithm trigger
Switch configuration:
CellAlgoSwitch.MlbAlgoSwitch.UtranMlbSwitch - 1.
EnodebAlgoSwitch.HoModeSwitch.UtranPsHoSwitch - 1.
When the switchs are enabled,
The eNodeB starts MLB for UL-sync UEs if the following conditions are met continuously for 5s:
The cell PRB usage ≥ (CellMLB.InterRatMlbThd + CellMLB.LoadOffset)
Uplink and gaits user of ≥ (CellMLB.InterRatMlbUeNumThd + CellMLB.InterRatMlbUeNumOffset)
The cell PRB including
Uplink GBRPRB usage
Downlink GBRPRB usage
Uplink TotalPRB efficiency (uplink GBRPRB rate + Uplink Non-GBRPRB utilization)
Downlink TotalPRB rate (The GBRPRB rate + Downlink Non-GBRPRB utilization)
GBR PRB usage takes priority over total PRB usage in triggering. MLB is triggered by total PRB usage.The eNodeB will transfer non-GBR services.
【 Step 2 】 target cell/frequency selection
After MLB triggered, eNB selects target cells within period of CellMLB.InterRatLoadEvalPrd.
If CellAlgoSwitch.MlbAlgoSwitch.MlbLoadInfoSwitch is on, eNB will get load information of UTRANNCELLs through RIM procedure. If load information can't be gotten successfully for RIM is not configured correctly or other reasons, eNB take actions as the neighbour cell is in lowload.
The eNodeB filters out the cells from the UTRAN neighboring relation table (NRT) to generate a list of candidate cells
Congested or overloaded cells
Cells for which the UtranNCell.NoHoFlag parameter is set to FORBID_HO_ENUM(Forbid Ho)
The selection policy of target cells for MLB by transferring UL-Sync UEs is determined by CellMLB.FreqSelectStrategy, complies with the following rules:
If CellMLB.FreqSelectStrategy is FAIRSTRATEGY, select all UTRAN frequency as the target cell frequency.
If CellMLB.FreqSelectStrategy is PRIOR IT YBASED, the eNodeB selects the frequencies (one or more frequencies) with the highest priority defined by UtranNFreq.MlbFreqPriority as target frequencies..
【 steps 3 】 UE Selection
The eNodeB preferentially selects non-CA UEs over CA UEs.
According to CellMLB.InterRatMlbUeSelStrategy complies with the following rules:
1) CellMLB.InterRatMlbUeSelStrategy choose for PRBRATIOHIGHMODE, Each of the seleced UEs must meet all the following conditions:
PRB usage of the UE in the direction (uplink or downlink) where MLB is triggered >2%
Total PRB usage of all UEs to be transferred in the same direction <CellMLB.LoadDiffThd/2
PRB usage of the UE in the opposite direction ≤ 2%
e.g. If the MLB is triggered by UL PRB USAGE, the opposite direction is DL PRB USAGE.
2.) CellMLB.InterRatMlbUeSelStrategy choose for PRBRATIOLOWMODE, Each of the seleced UEs must meet all the following conditions:
PRB usage of the UE in the load balancing triggering direction< CellMLB.InterRatMlbUeSelPrbThd
【 steps 4 】 load transfer
There are two methods of transferring UL-Sync UEs that support inter-RAT handover: blind handover and measurement-based handover. Measurement - based handover:
measurement-based handover
eNB will send LOAD -BASED B1 measurement control to UE, when UE reports the event, eNB trigger the load - based handover, the threshold is based on configurations as follows:
RSCP: indicates the InterRatHoUt RAN Group. LdSvBasedHoUtranB1ThdRscp
ECN0. InterRatHoUt RAN Group. LdSvBasedHoUtranB1ThdEcn0
Blind handover
When CellAlgoSwitch.MlbHoMode.InterRatMlbBlindHo switch is selected, UE will transfered by blind handover. If the UE does not support inter-rat handover,it will be transfered by blind redirection.
When the InterRatMlbBlindHo is off, and the UE does not support inter-rat handover,it will be transfered by redirection ; If PS-HO switch off, redirection switch is on, the UE will transfered by redirection.
【 testing methods 】 for function presentation only,not be the same with live network, pls obtain required version testing cases from official before demos , the following parameters settings only for reference,
For testing,the parameters related each step can be changed as follows to make the conditions more tractable, for example,
1.The cell MLB.InterRatMlbThd and CellMLB.LoadOffset set lower value to make the MLB is easy to trigger.
2. CellMLB.InterRatMlbUeNumThd set to 99 (represent the actual user of 2) or 100 (represent the actual user constant 1). Note that if this parameter is set to 1 ~ 98, it means the actual user Number of 10 ~ 980;
CellMLB.InterRatMlbUeNumOffset should be set to 0, if UEs for testing is not enough.
3.When the CellMLB.InterRatMlbUeSelStrategy is PRBRATIOHIGHMODE, make the target cell with no UEs on service while properly increase CellMLB.LoadDiffThd to enable the UEs easy to be selected.
4.When CellMLB.InterRatMlbUeSelStrategy is set to PRBRATIOLOWMODE, it is appropriate higher CellMLB.InterRatMlbUeSelPrbThd should be set.
5. If the restrictions on UE download rate is enable, limit the UE's dpwnload speed to make the UE's PRB usage less than CellMLB.InterRatMlbUeSelPrbThd; If the restrictions on UE download rate is unable, CellMLB.LoadDiffThd or CellMLB.InterRatMlbUeSelPrbThd should be set reasonably according to the number of testing UEs. .e.g there're 3 testing UEs, not limit download speed, then it is ensures that there's at least one UE's PRB usage is less than 33 %, so set CellMLB.LoadDiffThd to 70 or CellMLB.InterRatMlbUeSelPrbThd to 35 will ensure there is at least one UE can meet the selected conditions.
6. Decrease the InterRatHoUTRANGroup. LdSvBasedHoUtranB1ThdRscp, or InterRatHoUTRAN Group. LdSvBasedHoUtranB1ThdEcn0, to make UE easier to report handover event.
7. Pay attention to the following items, avoid coverage - based inter-rat handover threshold is set too lowto amke the UE has transfered by coverage-based handover before it can be transfered by load-based handover.
8.At the start of testing, open S1 / UU trace andthe MLB monitoring in U2000 (CellPerformanceMon IT oring > MLB Monitoring) in order to monitor whether MLB is triggered, MLB's unsuccesful reason can be found diredtly by the record of MLB monitoring, parameter specific meaning see U2000 online help.
9. By observation of S1AP_HANDOVER_REQUIRED with cause reduc- load- in-serving-cell and RRC_MOBILITY_FROM_EUTRAN _COMMAND to confirm MLB handover is triggered.
40551