INTER-FREQUENCY LOAD BALANCINGFunctional Overview

Inter-Frequency Load balancing feature handles uneven distribution of traffic in the Shared RAN network.For cells that have load relations established, the high-level behavior is:(every 15 seconds)

1. Determine own cell load status2. Exchange and compare load status

with target relations3. If own cell has higher load than

target, select offload candidate UEs4. If target has good RSRP, then send

UEs to target to balance load5. New own cell load status

Every load balancing cycle, each cell determines its load statusThe ratio load based is based on total sum of qciSubscriptionQuanta over cellSubscriptionCapacity

Load Status

– Subscription quanta is weighted based on QCI and represents a generic cost of eachbearer.› The value for each QCI is configured with the parameter qciSubscriptionQuanta(QciProfilePredefined / QciProfileOperatorDefined).

– Cell subscription capacity represents an estimate of the total cell capacity.› The value for each cell is configured with the parameter cellSubscriptionCapacity(EUtranCellFDD / EUtranCellTDD).› Average subscription ratio is observed with the counters pmLbSubRatioSumand pmLbSubRatioSamp (EUtranCellFDD / EUtranCellTDD)

Info exchange

Source and target exchange load info and the difference in load are checked against minimum and maximum offload thresholds

If the difference in load (subscriptionRatio) is grater than lbThreshold the load balancing Load_Balance_Magnitude is calculated. This then determine the amount of UE’s to load balance. The maximum amount of UE’s is limited by lbCeiling.› UEs are randomly selected and requested to reconfigure for a A4 Measurement report.› The following checks are performed before the UE is requested to perform the A4 Measurement report.• Not in an emergency call *• Not in bad coverage in the source cell #• Support the frequency of the target cell• UE is not restricted by the Handover Restriction List (HRL) to measure the target

frequency.

› IF the UE successfully reports the A4 Measurement, a final check is done to see if load balancing amount has been met before the UE is then sent for IFHOUE’s that report the A4 Measurement have acceptable coverage in the target cell

Candidate Selection

If the UE has reported the target cell as the best server and has met all checks. The UE will be sent for a normal Inter-Frequency Handover to the target cell. - A UE can only be balance to its reported best server.The cell will continue the load balancing process until the 15sec lbCycle has finished. At this time, the cell will have its new load balancing status and the new lbCycle will start.

Load Balance Action

Configuration

Parameter

pmLbSubRatioSumRecords the subscription ratio as the result of the traffic load assessment at every load balancing cycle. Those values are accumulated each ROP, allowing the average subscription ratio to be presented for each period.MOC: EUtranCellFDD / EUtranCellTDD

pmLbSubRatioSampThe number of load balancing cycles during the ROP. This together with the counter pmAvSubRatioSum can be used to calculate an average subscription ratio.MOC: EUtranCellFDD / EUtranCellTDD

Counter Description - 1

pmLbMeasuredUe› Records the number of UEs selected for measurements qualifying for load balancing action towards cells on the related frequency. Those values are accumulated each ROP. Used to calculate the LB measurement success rate for the related cells.› MOC: EUtranFreqRelation

pmLbQualifiedUe› Records the number of UEs qualified for load balancing action towards the related cell. Those values are accumulated each ROP. Used to calculate the LB measurement success rate for the related cell.› MOC: EUtranCellRelation

Counter Description - 2

pmHoPrepAttLteInterFLb› The number of attempts to start outgoing intra LTE inter frequency handover preparation due to load balancing.› Sub-counter to pmHoPrepAttLteInterF (legacy)› MOC: EUtranCellRelation

› pmHoPrepSuccLteInterFLb› The number of successful outgoing intra LTE inter frequency handover preparations that was performed for load balancing reasons.› Sub-counter to pmHoPrepSuccLteInterF (legacy)› MOC: EUtranCellRelation

Counter Description - 3

pmHoExeAttLteInterFLb› The number of outgoing intra LTE inter frequency handover execution attempts due to load balancing.› Sub-counter to pmHoExeAttLteInterF (legacy)› MOC: EUtranCellRelation

pmHoExeSuccLteInterFLb› The number of successful outgoing intra LTE inter frequency handovers that was performed for load balancing reasons.› Sub-counter to pmHoExeSuccLteInterF (legacy)› MOC: EUtranCellRelation

Counter Description - 4