There are two types of blind handover:
1. Emergent blind handover
Emergent blind handover is triggered by 1F event that indicates the used frequency becomes worse. The UE must perform emergent handover to avoid call drops.
2. Non-emergent blind handover
this handover may be triggered by LDR, DRD, or HCS speed estimation.For details about LDR and DRD.
The parameter BlindHoFlag is configured for neighboring cells and determines whether a blind
handover to this cell is allowed.The parameter BlindHOPrio indicates the blind handover priority of the cell. The value 0 represents the highest priority.Currently, Huawei does not support inter-RNC blind handovers (R14).
Triggering of Event 1F
After the conditions of event 1F are fulfilled and maintained until the parameter TrigTime1F is reached, the UE reports the event 1F measurement report message. Event 1F is triggered on the basis of the following formula:
10LogMOld ≤ T1f - H1f/2
Where,
10LogMOld ≤ T1f - H1f/2
Where,
- MOld is the measurement value of the cell that becomes worse.
- T1f is an absolute threshold. It is set through the parameter IntraAblThdFor1FRSCP or intratraAblThdFor1FecNo.
- H1f is the event 1F hysteresis value set through the parameter Hystfor1F.
Blind Handover Based on Event 1F
When there is only one cell in the active set, the RNC performs inter-frequency blind handover after receiving event 1F.
1. The RNC gets the actual best cell from event 1F. If the quality of the best cell meets the blind
handover condition, that is the quality of the best cell is larger than or equal to
BlindHORSCP1FThreshold, the RNC gets neighboring cells for blind handover of the best cell, and
filtrates the cells that belong to the frequency bands that UEs do not support. If the quality of the best
cell is lower than BlindHORSCP1FThreshold, the UE is at the edge of the network coverage and
the blind handover is not allowed.
1. The RNC gets the actual best cell from event 1F. If the quality of the best cell meets the blind
handover condition, that is the quality of the best cell is larger than or equal to
BlindHORSCP1FThreshold, the RNC gets neighboring cells for blind handover of the best cell, and
filtrates the cells that belong to the frequency bands that UEs do not support. If the quality of the best
cell is lower than BlindHORSCP1FThreshold, the UE is at the edge of the network coverage and
the blind handover is not allowed.
2. If there are multiple neighboring cells for blind handover, the RNC chooses the cell must support all
the current services of UE. When there are multiple such cells, the RNC choose the neighboring cell
for blind handover randomly.
If any inter-frequency cell does not meet the above conditions, then the RNC chooses the inter-RAT cells
with the highest priority of blind handover. The blind handover priority of the cell is specified by the
parameter BlindHOPrio.
