LTE HO event A3 and A5 comparison

[incoincov]

Hi guys,

Could anybody give me some reason why LTE event A5 HO is better than event A3 in bad coverage conditions?

thanks

[AA20]

Event A3 - Neighbor becomes offset better than serving
Event A5 - Serving becomes worse than threshold1 & neighbor becomes better than threshold2

In bad coverage conditions, Event A5 makes sure that the target cell is better than a certain value of RSRP. For Event A3, you can't regulate the target's absolute value. Its value is relative to the serving cell.

For the sake of explanation, let's assume that the A3 parameters are set up such that the neighbor needs to be 5dB better than the serving & for A5, threshold1 = -100 dBm & threshold2 = -95
For event A3, when the serving is at -105 dBm. In this case the target cell has to be -100 dBm or stronger. Similarly if the UE reaches poor coverage, it could still HO to a cell with weak coverage as long as the target is 5dB stronger than the serving.
But the parameters for A5 define the minimum level for the target cell. So in bad coverage conditions, the UE is forced to look for a target stronger than threshold2.

The threshold values will need to be optimized for the region they are being applied to.