# Cooperative Downlink Listening for Low-Power Long-Range Wide-Area Network
## 1 Introduction  
Over the last decades, rapid advances in low-cost low-power wireless communication technologies have accelerated the development of the Internet of Things (IoT) applications and services. These wireless technologies are generally based on short range communication such Bluetooth low energy (BLE), IEEE 802.15.4, and Wi-Fi (IEEE 802.11). However, the range limitation of IoT applications based on these communication technologies has made communication links unreliable and thus it has led to the degradation of communication reliability. Therefore, the demand for wide communication coverage is increased. Finally, these strong demands have led to the advent of low-power, long-range wireless communication systems, called low-power wide-area network (LPWAN). Various research groups are developing new LPWAN systems based on the new standards. These include long-range wide-area network (LoRaWAN) [1] by the LoRa Alliance, Long Term Evolution for machine to machine (LTE-m) [2] and Narrow Band Internet of Things (NB-IoT) [3] by 3 GPP, ultra-narrow band communication by Sigfox [4], etc. Among these new technologies, LoRa is widely being accepted as the most promising LPWAN technologies in terms of power efficiency, low-cost chipset, and regional ISM bands. One of the key technologies of LoRa is to use chirp spread spectrum (CSS) for modulation, while the legacy low-power communications are based on frequency shift keying (FSK) to achieve low-power. For decades, the CSS modulation has been used in specific areas such as space communications or the military, since it has advantages of long communication capability and robustness to interference. That is, the LoRaWAN has long-range characteristics while maintaining robustness to interference. Due to its advantages, interesting applications [5; 6; 7] are already being introduced based on LPWAN; the LoRaWAN has also attracted many researchers. [PERSON] et al. [8] revealed thecapabilities and limitations of LoRaWAN. In particular, they emphasized that the following challenges should be addressed: new multiple access mechanism and energy efficient multi-hop solution. [PERSON] et al. (2017) presented the results of an analysis of LoRaWAN in terms of uplink throughput and data transmission time. According to the results, LoRaWAN duty-cycle-based Medium Access Control (MAC) scheme may increase packet collision probability and delay. In addition, they also showed that LoRaWAN has critical drawbacks in reliability and delay, especially in terms of downlink traffic. [PERSON] et al. (2017) pointed out some problems of LoRa gateway capability, and proposed new data transmission network architecture for long-range sensor networks, which are based on a hybrid approach combining LoRa infrastructure and sensor networks. [PERSON] et al. (2016) proposed the hybrid network architecture of LoRaWAN and 802.11 ah, and [PERSON] et al. (2016) also proposed LoRaWAN use for smart grid network instead of RF mesh networks (Wi-SUN). [PERSON] et al. (2016) proposed a Markov chain model of the OTAA. They analyzed the impact of several parameters on traffic conditions, duty cycles, and channel availability. [PERSON] et al. (2017) studied the indoor performance of LoRaWAN based on health and well-being monitoring equipment. The authors also studied the coverage of LoRaWAN [PERSON] et al. (2017). According to the results, the maximum communication range is over 15 km on ground and close to 30 km on water. [PERSON] et al. (2017) designed a low-cost DIY LoRa gateway which has a number of functionalities. Even though LoRaWAN has several advantages including low-power and long-range capability, it also has some limitations and problems as already discussed in several literatures ([PERSON] et al., 2016; [PERSON] et al., 2017; [PERSON] et al., 2017). In particular, a key problem arises from the class A for the low-power operation of end device.