● PRACH Timing & Ambiguity Viewer
LEO 600 · Cell Ø 200km
🖱️ Configure PRACH parameters to resolve ambiguity
📊 Cell Size 200 km
⏱️ 2×Max Diff Delay 2.616 ms
📈 RO Interval 2.000 ms
✅ Status ❌ AMBIGUITY!
2 UEs
5 UEs
RACH Capacity: 0 preambles/sec
PRACH Format0
RO Interval2.000 ms
2 × Max Diff Delay2.616 ms
Ambiguity❌ Yes
❌ Ambiguity! RO interval too small
RO interval < 2×MaxDiff
find a configuration that avoids ambiguity
🎯 Learning Outcome: This lab demonstrates the preamble ambiguity problem in NTN.
When the RO interval < 2 × Max Differential Delay, preambles from different ROs overlap.
📌 Ambiguity Scenario: ❌ GEO 1000km + PRACH Index 27 (RO=1ms) → 2×MaxDiff=12.88ms → AMBIGUITY!
✅ Solution: Use PRACH Index 0 (RO=160ms) or increase RO interval > 12.88ms.
✅ Solution: Use PRACH Index 0 (RO=160ms) or increase RO interval > 12.88ms.
📌 LEO Scenario: ✅ LEO 200km + PRACH Index 25 (RO=2ms) → 2×MaxDiff=2.616ms → NO AMBIGUITY
❌ LEO 200km + PRACH Index 27 (RO=1ms) → 2×MaxDiff=2.616ms → AMBIGUITY!
❌ LEO 200km + PRACH Index 27 (RO=1ms) → 2×MaxDiff=2.616ms → AMBIGUITY!
⚙️ Based on 3GPP TR 38.821 §7.2.1.1.1.2 · RO interval must be > 2 × Max Differential Delay