worked on signal-strength-estimation

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

sensors/radio/WiFiGridNode.h

@@ -0,0 +1,123 @@
+#ifndef WIFIGRIDNODE_H
+#define WIFIGRIDNODE_H
+
+#include <cstdint>
+#include "AccessPoint.h"
+
+/**
+ * rssi model-estimation for one AP, denoted by its index [among all APs present within the map]
+ * the signal strength is stored as uint8_t and allows a granularity of 0.25 dB between -40 and -103 dB
+ */
+struct WiFiGridNodeAP {
+
+private:
+
+	static const int UNUSED_IDX = 255;
+
+private:
+
+	/** access-point index -> max 255 APs/Map */
+	uint8_t idx;
+
+	/** access-point rssi */
+	uint8_t rssi;
+
+public:
+
+	/** empty ctor */
+	WiFiGridNodeAP() : idx(UNUSED_IDX), rssi(0) {;}
+
+	/** ctor */
+	WiFiGridNodeAP(const int idx, const float rssi) : idx(idx), rssi(stretch(rssi)) {;}
+
+
+	/** is this entry valid/used? */
+	bool isValid() const {return idx != UNUSED_IDX;}
+
+	/** set AP and its signal strength */
+	void set(const int apIdx, const float rssi) {
+		this->idx = apIdx;
+		this->rssi = stretch(rssi);
+	}
+
+	/** get the predicted signal-strength */
+	float getRSSI() const {return unstretch(rssi);}
+
+	/** get the access-point's index */
+	int getAPIdx() const {return idx;}
+
+private:
+
+	/** [-40:-103] -> [0:252] => this allows 0.25 steps */
+	static inline int8_t stretch(float rssi) {
+		if (rssi > -40) {rssi = -40;}
+		if (rssi < -103) {rssi = -103;}
+		return std::round((-rssi - 40) * 4);
+	}
+
+	/** [0:252] -> [-40:-103] */
+	static inline float unstretch(const float rssi) {
+		return -(rssi / 4.0f + 40.0f);
+	}
+
+};// __attribute__((packed));
+
+
+/**
+ * base-class for grid-nodes that contain wifi signal-strength estimations.
+ * such estimations are calculated offline and added to each node.
+ * this also allows for using very complex signal-strength estimation models
+ */
+template <int maxAccessPoints> struct WiFiGridNode {
+
+
+	/** contains the 10 strongest APs measureable at this position */
+	WiFiGridNodeAP strongestAPs[maxAccessPoints];
+
+
+	/** ctor */
+	WiFiGridNode() {;}
+
+
+
+	/** shared vector of all accesspoints the are present within the map. the IDX referes to this vector */
+	static std::vector<AccessPoint>& getMapAPs() {
+		static std::vector<AccessPoint> list;
+		return list;
+	}
+
+	/** get the maximum number of APs each node is able to store */
+	int getMaxAPs() const {return maxAccessPoints;}
+
+	/**
+	 * get the RSSI for the given AP
+	 * returns 0 if unknown
+	 */
+	float getRSSI(const std::string& mac) const {
+		return getRSSI(MACAddress(mac));
+	}
+
+	/**
+	 * get the RSSI for the given AP
+	 * returns 0 if unknown
+	 */
+	float getRSSI(const MACAddress mac) const {
+		for (const WiFiGridNodeAP ap : strongestAPs) {
+			if (!ap.isValid()) {break;}			// reached the end
+			if (getMapAPs()[ap.getAPIdx()].mac == mac) {return ap.getRSSI();}
+		}
+		return 0;
+	}
+
+	/** get the number of access-points visible at this node */
+	int getNumVisibleAPs() const {
+		for (int i = 0; i < getMaxAPs(); ++i) {
+			if (!strongestAPs[i].isValid()) {return i;}
+		}
+		return getMaxAPs();
+	}
+
+
+};// __attribute__((packed));
+
+#endif // WIFIGRIDNODE_H