1.1.1 ZWF21-03-050 Handover Optimization in Weak Coverage

Benefits

This feature supports the performance enhancement for handover, and

increases the handover success rate, decrease call drop rate, and improve the

RAN network performance and the service experience.

Description

This feature includes the following improvements:

(1) When UE is in weak-coverage area, even if it reports intra-frequency

measurement event(such as 1a,1c) and indicates that some new radio links

should be added to the active set, but the quality of these new radio link may be

not good enough, and then to avoid these poor quality radio links are added to

active set, RNC need to evaluate their quality. When their quality is above the

pre-configured threshold, these radio links will be added to the active set.

(2) In the soft-handover procedure, after RNC send Active Set Update message

to UE, if it does not receive the Active Set Update Complete message in control

plane from UE when waiting timer is expired, but the user plane in RNC

confirms that UE has received the Active Set Update message by RLC ACK,

then RNC can do the subsequent processing as it has received the Active Set

Update Complete message from UE, therefore the success rate of

soft-handover operation can be increased, and the call drop rate can be

decreased.

(3) When UE is in weak-coverage area, the quality of target cell in HSPA

Serving cell change may be not good even if it meet the condition of

measurement event report, such as 1d, if the HSPA Serving cell change to this

cell, firstly maybe the call drop will happen due to the weak-coverage, Secondly

the Serving Cell change does not bring benefit for service because of the target

cell’s poor quality, for this reason, the HSPA Serving cell change in the above

situation should be avoided as far as possible. For this purpose, a quality

threshold for target cell of HSPA serving cell change is introduced, the threshold

is configurable, and only when the candidate target cell quality is above the

threshold, the HSPA Serving cell change processing will be initiated by RNC.