Proposal of interference power occupancy estimation method using chirp demodulation

Abstract

In recent years, Low Power Wide Area (LPWA) has been attracting attention as being suitable for utilizing the Internet of Things (IoT). In Japan, LPWA has been standardized as a specific low power radio that uses the 920MHz band, and is a communication standard that enables long-distance communication with low power consumption. In the specific low power radio of the 920MHz band, since multiple radio standards share the same frequency, communication interruption due to the same frequency interference Co-Channel Interference (CCI) becomes a serious problem. Long Range (LoRa), which is one of LPWA, uses chirp modulation (spread spectrum technology) to suppress CCI. This modulation method is resistant to CCI because it expands the desired signal power after demodulation by wideband gain. However, when operating LoRa, it is necessary to determine the necessity of frequency sharing suitable for Signal to Interference Ratio (SIR) in consideration of interference from other systems, and to set the required diffusion rate. The authors have proposed a method for estimating desired signal power and interference power using chirp demodulation. In this paper, we have established a method for estimating the occupancy rate, which is the access ratio of other systems, with high accuracy from the probability distribution of interference power and noise power.