TTT

Time to Trigger is the patience timer on a measurement event. The event condition — say an A3 — has to stay true continuously for the whole TTT before the UE bothers to send the measurement report. If the condition blinks off partway through, the timer resets. It's a deliberate filter: it stops the network reacting to a momentary fade or a brief reflection that would otherwise fire a pointless handover.

The trade-off is the thing to internalise. A long TTT is great for a slow-moving pedestrian — it filters out transient peaks and cuts ping-pong — but it's dangerous for a UE on a highway, which may have driven out of usable coverage before the timer expires, giving you a too-late handover and a drop. That's exactly why TTT is one of the parameters MRO tunes per relation, and why fast-mobility scenarios often run shorter values. Typical configured values land somewhere in the few-hundred-millisecond range, but it's set per event and per relation, so don't assume one number fits the network.