worked on signal-strength-estimation

add this information to grid nodes
evaluate this information
new test-cases

sensors/radio/model/LogDistanceModel.h

@@ -0,0 +1,47 @@
+#ifndef LOGDISTANCEMODEL_H
+#define LOGDISTANCEMODEL_H
+
+#include <cmath>
+
+class LogDistanceModel {
+
+public:
+
+	/** convert from RSSI to a distance (in meter) */
+	static float rssiToDistance(const float txPower, const float pathLoss, const float rssi) {
+		return pow(10, (txPower - rssi) / (10 * pathLoss));
+	}
+
+	/** convert from a distance (in meter) to the expected RSSI */
+	static float distanceToRssi(const float txPower, const float pathLoss, const float distance_m) {
+		if (distance_m <= 1) {return txPower;}
+		return (txPower - (10 * pathLoss * std::log10(distance_m)));
+	}
+
+};
+
+#include <vector>
+
+class LogDistFastModel {
+
+private:
+
+	std::vector<float> lut;
+
+public:
+
+	LogDistFastModel() {
+		lut.resize(2000);
+		for (int i = 0; i < 2000; ++i) {
+			lut[i] = std::log10(i/10.0f);
+		}
+	}
+
+	float distanceToRssi(const float txPower, const float pathLoss, const float distance) const {
+		if (distance <= 1) {return txPower;}
+		return (txPower - (10 * pathLoss * lut[ (int) (distance*10) ]));
+	}
+
+};
+
+#endif // LOGDISTANCEMODEL_H