Outdoor RSSI Measurements Using Open-Source Hardware-Based 3D Positioning Device

Accurate positioning information is necessary, for example, to build a radio map and assess radio performance. Although the global navigation satellite system (GNSS) is primarily used outside, its accuracy decreases in places with a high concentration of buildings and it is not suitable for use there. In this paper, we evaluate the wireless performance by using a 3D positioning device that can correctly specify a position with an accuracy on the order of millimeters. In particular, we use a LoRa module that uses 920 MHz to measure the received power in a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$50\ \text{cm}\times 50\ \text{cm}$</tex>. area at equal intervals. By comparing this received power distribution with the Nakagami-Rice fading distribution, the characteristic of the distribution (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$K$</tex>-factor) is estimated. This process is performed at intervals as short as 1 m to confirm that different distributions are obtained. The above results show that the 3D positioning device is also effective in obtaining detailed distributions under conditions where the channel characteristics change with slight movement.