Understanding A1 & A2 Events: Monitoring and Optimizing Serving Cell Performance
Before diving into handover decision-making, let’s first understand how LTE networks continuously monitor the serving cell to ensure a stable connection.
Understanding A1 & A2 Events
A1 Event – Strong Coverage, No Action Needed
The network monitors the Reference Signal Received Power (RSRP) of the serving cell.
If the RSRP is above the A1 threshold (e.g., -85 dBm), the connection remains stable, and no mobility action is required.
A2 Event – Weak Coverage, Handover Preparation
When RSRP falls below the A2 threshold (e.g., -100 dBm), it indicates poor signal strength.
This triggers the network to prepare a handover to a better cell to avoid call drops or degraded user experience.
Technical Insight: Why A1 & A2 Matter?
A1 prevents unnecessary handovers by ensuring the UE stays with a strong-serving cell.
A2 triggers handover preparation early, allowing a proactive switch before connection issues arise.
Real-World Scenario
Imagine you’re on a video call while walking from an open area into a building:
Outside → Your phone stays on the same serving cell (A1 active).
Inside, moving deeper → The signal weakens as obstacles block coverage (A2 triggered).
Network responds → Prepares a handover to another cell with better signal strength.
Graph: RSRP vs. Time with A1/A2 Events
Blue Line: RSRP values over time.
Green Line (A1 Threshold -85 dBm): Above this level, no action needed.
Red Line (A2 Threshold -100 dBm): Below this level, handover preparation starts.
Shaded Zone: Area where signal weakens, prompting mobility actions.
Optimization Tip:
Tuning A1/A2 thresholds based on mobility patterns can improve handover performance, reducing call drops and data interruptions.
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