When exactly we go for event A2 during Handover?

Question

Hi Folks,

Can you explain me when we will prefer A2 and A3 events for measurement report?
And is there any relation between the events?
What are these Ms,Hys,Thresh,Ofn,Ocn,Mn and how ENb will set these values in the meas config?

Thanks ,

Naveen.

Answer 1

A2: This event is triggered to indicate eNodeB that UE detects serving cell strength worst than the configured threshold. In other words, UE is going far way from cell centre or the event is triggered when the following condition is true:

MEAsserv + Hyst < Threshold 

Triggering of the event is subsequently cancelled when the following condition is true.

MEAsserv - Hyst > Threshold 
The hysteresis can be configured with a value between 0 and 30 dB.

A3: The LTE Event A3 is triggered when a neighbouring cell becomes better than the serving cell by an offset. The offset can be either positive or negative. The event is triggered when the following condition is true:

MEASneigh + Oneigh,freq + Oneigh,cell - Hyst > MEASserv + Oserv,freq + Oserv,cell + Offset 

MEASneigh + Oneigh,freq + Oneigh,cell + Hyst < MEASserv + Oserv,freq + Oserv,cell + Offset

Answer 2

This is dependent on how the handover algorithm is implemented. generally people use a2, a5 and a3 events against the rsrp and rsrq thresholds. also it depends on whether the handover algorithm is also addressing inter-frequency or not.