###### Abstract  
In terms of low power consumption and long-range communication--low-power wide-area networks (LPWAN) are suitable for wireless sensor networks. Long-range (LoRa) wireless communication is one of the standards of LPWAN. LoRa shares common frequency spectrum bands with both multiple transmitters, which are the sensors in the LoRa system (and those in the other system). Therefore, co-channel interference (CCI) degrades the packet delivery rate. To avoid CCI, the CCI power and the occurrence probability of CCI in the target channel are estimated, then the sensor decides whether to use the channel and where the occurrence probability of CCI is defined as the channel occupancy ratio (COR). If a large signal power is obtained at the receiver, the received signal can be demodulated because of the capture effect. The desired signal power must also be estimated for the capture effect. In this study, we propose an estimation scheme based on chirp modulation of LoRa under spectrum sharing among other systems. The proposed scheme estimates the desired signal power, CCI power, and COR. From the computer simulation results, we clarify the advantages of the proposed scheme in terms of estimation accuracy and packet delivery rate. LoRa; chirp modulation; LPWAN; co-channel interference 20  
frequency of CCI is useful for exploiting a channel with zero or few CCIs [8], where it is referred to as the channel occupancy ratio (COR) [9]. Channel selection based on the estimated COR improves the throughput performance [10]. If the powers of the CCI and desired signals are estimated, successful demodulation--even in the presence of CCI--is expected, which is referred to as the capture effect [11]. Exploiting the channel with no CCI and demodulating the packet owing to the capture effect could realize frequency sharing among the other systems and improve the usage efficiency of the frequency spectrum. To estimate the power of the desired signal, the construction of a communication link is necessary; however, the accuracy of estimating the power of the desired signal degrades owing to the CCI. Therefore, an estimation scheme (for the power of CCI, the power of the desired signal, and the COR with robustness to the CCI) is essential. LoRa employs chirp modulation, which is a spread spectrum technique, to ensure robustness to the CCI [12]. Chirp modulation alters the frequency sweep pattern of the carrier wave (depending on the digital data). If the frequency components of the transmitted signal are detected by a period shorter than the sweeping period of the carrier wave, they are separated into two components: the frequency components occupied and unoccupied by the carrier wave, where the former and latter are referred to as the partially occupied bands (POD) and partially unoccupied bands (PUD), respectively. POD includes the components of the desired signal, CCI, and noise, and PUD includes that of the CCI and noise. If the residual components are ignored, POD minus PUD causes the components of the desired signal; thus, the power of the desired signal can be estimated. Because the residual components have a tendency similar to that of noise, they can be compressed by the averaging process. The components of the POD are switched between the component of the noise and that of the noise plus the CCI by the occurrence of the CCI, where the CCI occurrence is decided by the access of the other system sharing common frequency bands. The average occurrence probability of CCI is determined by the COR of the other system [13]. Packet access from each sensor to the data center is assumed, where the packet comprises multiple modulated symbols. When the components of POD are estimated from various packets with different arrival times, the estimated component sets are the mixed data between the noise components and noise plus CCI components.