完成py_plan.md

sim/radio/propagation.py

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+"""Radio propagation model."""
+
+import math
+import random
+from sim import config
+
+
+def calculate_distance(x1: float, y1: float, x2: float, y2: float) -> float:
+    """Calculate Euclidean distance between two points."""
+    return math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
+
+
+def calculate_rssi(tx_power: float, distance: float) -> float:
+    """
+    Calculate RSSI using free-space path loss model.
+
+    RSSI = TX_POWER - 10*n*log10(d) + Gaussian_noise
+
+    Args:
+        tx_power: Transmit power in dBm
+        distance: Distance in meters
+
+    Returns:
+        RSSI in dBm
+    """
+    if distance < 1.0:
+        distance = 1.0  # Avoid log(0)
+
+    # Path loss
+    path_loss = 10 * config.PATH_LOSS_EXPONENT * math.log10(distance)
+
+    # Gaussian noise
+    noise = random.gauss(0, config.NOISE_SIGMA)
+
+    rssi = tx_power - path_loss + noise
+    return rssi
+
+
+def can_receive(rssi: float) -> bool:
+    """Check if packet can be received based on RSSI threshold."""
+    return rssi >= config.RSSI_THRESHOLD
+
+
+def calculate_link_penalty(rssi: float) -> float:
+    """
+    Calculate link penalty for routing.
+
+    penalty = max(0, (RSSI_THRESHOLD - RSSI) / SCALE)
+
+    Args:
+        rssi: Received signal strength
+
+    Returns:
+        Link penalty (higher = worse link)
+    """
+    return max(0.0, (config.RSSI_THRESHOLD - rssi) / config.LINK_PENALTY_SCALE)
+
+
+def is_link_viable(rssi: float) -> bool:
+    """Check if link is viable for communication."""
+    return can_receive(rssi)