first commit

app/services/path_loss.py

@@ -0,0 +1,36 @@
+from __future__ import annotations
+
+import math
+from typing import Literal
+
+from app.models.schemas import LinkBudget
+
+
+def fspl_db(distance_m: float, freq_mhz: float) -> float:
+  if distance_m <= 0:
+    return 0.0
+  return 20.0 * math.log10(distance_m / 1000.0) + 20.0 * math.log10(freq_mhz) + 27.55
+
+
+def compute_link_budget(
+  tx_power_dbm: float,
+  rx_sensitivity_dbm: float,
+  distance_m: float,
+  freq_mhz: float,
+) -> LinkBudget:
+  loss = fspl_db(distance_m, freq_mhz)
+  margin = tx_power_dbm - rx_sensitivity_dbm - loss
+  status: Literal["good", "marginal", "poor"]
+  if margin >= 20:
+    status = "good"
+  elif margin >= 10:
+    status = "marginal"
+  else:
+    status = "poor"
+
+  return LinkBudget(
+    tx_power_dbm=tx_power_dbm,
+    rx_sensitivity_dbm=rx_sensitivity_dbm,
+    margin_db=round(margin, 1),
+    status=status,
+  )