Load Balancing Handover

The handovers triggered by load balancing are classified into two types: handovers between BSs (sectorcarriers) and handovers between zones.

Handover Between BSs (Sector Carriers)

The load balancing handover between BSs (sector carriers) is triggered in the following scenarios:

When the signal quality of the MSs connected to the network deteriorates and the load of asingle carrier reaches the value of HOSTARTTHRES, the BS selects some MSs with poor signal

quality and instructs them to perform scanning. Then, the MSs are handed over to the sectorcarrier with light load and good channel signal quality. In this way, the load of the single carrierdecreases.

In this scenario, the handover can be implemented between any two carriers such as intra-sectorcarriers and carriers between neighbor sectors or between neighbor BSs. Figure 1 shows thehandover scenario.

When most of online subscribers are implementing BE services and the number of onlinesubscribers implementing services increases gradually, load balancing handovers are triggeredfor BE subscribers if the BE satisfaction of the current carrier is lower than the value ofBESATISFACTIONTHRESH and the number of unsatisfactory BE connections is greater than

the value of BENUMFORLOADHO. In this scenario, the handover is implemented only within the

BS.

BESATISFACTIONTHRESH: BE satisfaction threshold for triggering load balancinghandovers for BE subscribers. The value ranges from 0 to 100, and the unit is %.

BENUMFORLOADHO: number of BE subscribers when load balancing handoverscan be triggered. The value ranges from 0 to 20.

NOTE:

When the ASN-GW does not support the forwarding of spare capability messages, the handover betweenBSs (sector carriers) can be implemented only between intra-BS carriers, and thus the MS cannot behanded over to the neighbor cell of the BS different from the BS to which the current serving carrier belongs.

Figure 1 Handover scenarios

Figure 2 shows the process of the handover between BSs (sector carriers).

Figure 2 Handover process

Select MSs for the load balancing handover.

Based on the QoS-required rates and MPRs, determine the priorities of the active MSs on thecarrier. Select the MSs with the highest priority. The total load of the selected MSs cannot belower than the amount by which the carrier load should decrease.

1.

Select a maximum of five carriers. Then, MSs perform scanning.

If multiple carriers function as serving carriers, another intra-sector carrier (whoseremaining resources should not be less than the resources requested for handover)is selected preferentially as the target carrier. If less than five carriers are selected,sort other carriers to find the carrier that has the most remaining resources underthe prerequisite that the remaining resources are not less than the resourcesrequired for MS handover. Then, this carrier is selected preferentially as a targetcarrier.

If the serving carrier is a single carrier, sort other carriers to find the five carrierswith the most remaining resources under the prerequisite that the remainingresources are not less than the required resources for MS handover. Then, thecarriers are selected preferentially as the target carriers.

NOTE:

In addition, the BE satisfaction difference between the target carrier and the serving carriermust be not lower than the value of BESATISFTDIFFETHRESHFORLOADHO so that load

balancing handovers can be triggered for BE subscribers.

BESATISFTDIFFETHRESHFORLOADHO: BE satisfaction difference threshold for triggeringload balancing handovers. The value ranges from 0 to 100, and the unit is %.

2.

Select target carriers for the handover and initiate the handover.

Based on scanning results, sort the downlink CINR values. Select the target carrier with thehighest downlink CINR value and compare the value with the downlink CINR value of the sourcecarrier.

If the highest CINR value of the target carrier is higher than the downlink CINR valueof the source carrier, this target carrier is selected for the handover.

If the highest CINR value of the target carrier is not higher than the downlink CINRvalue of the source carrier, compare the highest CINR value of the target carrier withthe default scanning threshold for handovers. Then, the handover is triggered onlywhen the highest CINR value of the target carrier is higher than the default scanningthreshold for handovers.

3.

Handover Between Zones

After the BS is configured with FFR, the load balancing handovers between zones are triggered if the loadof the zones is unbalanced. In this case, some MSs must be handed over to another zone, and thus the loadof multiple zones is distributed evenly.

In addition, during the inter-zone handover, an MS is handed over between PUSC 1/3 and PUSC with ALL.The load balancing handovers between zones are triggered in the following conditions:

When the load in PUSC 1/3 is higher than 80% and the load in PUSC with ALL is lower than

80%, the MS is handed over from PUSC 1/3 to PUSC with ALL.

When the load in PUSC with ALL is higher than 90% and the load in PUSC 1/3 is lower than70%, the MS is handed over from PUSC with ALL to PUSC 1/3.

Parent topic: Description of Load Balancing

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