“…Currently, there exist two types of wireless localization methods: range-based localization [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ] and range-free localization [ 18 , 19 , 20 ], according to whether there is actually the distance or angle of measured nodes in the localization process. The range-based localization mechanisms determine the localization of unknown nodes by measuring the actual point-to-point distance or angle information between nodes and using the trilateration, triangulation or maximum likelihood estimation methods, based on the time of arrival (TOA) [ 11 ], time difference of arrival (TDOA) [ 12 , 13 ], angle of arrival (AOA) [ 14 ], signal-based signature distance [ 15 ], received signal strength indicator (RSSI) [ 16 , 17 ], and so on. In the above four algorithms, TOA, TDOA and AOA require additional hardware devices, while RSSI does not because the interface of most nodes has the function of receiving radio frequency (RF) signals [ 21 ] and can test the signal strength.…”