“…Conversely, range-based schemes usually have better accuracy. They measure the time of arrival (ToA) [2, 3], time difference of arrival (TDoA) [4–6], angle of arrival (AoA) [2, 4, 15, 17, 18, 20, 21, 27], and received signal strength indicator (RSSI) [3, 7–14, 16, 20, 21] to estimate the distances or angles between pairs of nodes, which in turn are used to calculate the locations of nodes. Most kinds of measurement are taken with extra auxiliary hardware.…”