# Feasibility of LoRa for Smart Home Indoor Localization
## 2 Literature Review
### Long Range (LoRa)  
LoRa is a low-power wide-area network (LPWAN), and it is the physical layer of the LoRa communication technology [63]. long-range wide area network (LoRaWAN) is the media access control (MAC) layer of the LoRa [64; 26]. It defines the communication protocol and system architecture for LoRa. LoRaWAN determines the battery lifetime, communication range, and the quality of service. LoRaWAN utilizes long-range star architecture instead of the more common mesh network architecture. In the star topology, the individual nodes need not forward the data from other nodes, which preserves the energy and increase the battery lifetime. The battery of some end instruments could work for more than ten years [6]. Since LoRa uses the chirp spread spectrum (CSS) modulation, which provides resilience against interfering and multipath effects, and broadens the communication range significantly [17], the maximum reception range would reach fifteen km in suburban and five km in urban areas [25; 26]. The LoRaWAN specification also defined that LoRa transmits over the industrial scientific medical (ISM) bands [47; 65], which are license-free bands. It reduces the implementation cost of LoRa. Moreover, the cheap nodes, end devices, and infrastructure further lower the implementation threshold. Another advantage of LoRa is the lower center frequency compared to WiFi, BLE, and UWB. Signal attenuation increases with increasing center frequency [66], in both free space and through objects. Lower center frequency allows LoRa signals to penetrate through heavy objects of buildings (such as walls, floors, furniture, and electronic devices) [67] which is not possible with other sensing technologies. The capability to penetrate objects causing NLOS combined with the long-range reading makes LoRa a viable sensing technology for robust localization in large indoor spaces with various NLOS situations using a small number of static anchors. More specifically, a study on vehicle tracking in a large indoor parking garage (180 m \(\times\) 80 m) shows promising localization results with only three anchors [68]. Since buildings commonly have various objects blocking the signals, using other sensing technologies that do not penetrate objects well would require several anchors installed to make sure a certain number of anchors are seen from all the localizations in the building. Even though UWB with a large frequency bandwidth has the highest accuracy and precision in LOS, the performance of UWB can be significantly reduced by various objects in smart homes causing NLOS conditions. Additionally, a large frequency bandwidth requires using a larger center frequency which can drastically impact the maximum range and penetration of UWB signals through various objects. Similarly, WiFi and BLE cannot achieve high communication range and high penetration compared to LoRa. Another research study shows that LoRa has better localization accuracy (0.7 m-3.72 m) than BLE (1.53 m-26.46 m) and WiFi (0.5 m-4.06 m) in indoor environments [25]. Beyond the accuracy and coverage (maximum range), LoRa has lower power consumption than WiFi and UWB, and similar power consumption as RFID and BLE [69; 70]. LoRa outperforms RFID in maximum range of communication, mainly because of the difference in their modulations. RFID is not specifically designed for long-range communication nor localization. Because of the strengths in penetration, long-distance, low-cost, and energy-efficient transmission, LoRa can be used for the development of robust indoor localization systemsresilient against changes. An indoor localization system using sensing technology without LoRa's penetration capability requires careful installation of several anchors considering the building configuration and objects in the building to make sure all the locations in the building are in LOS situation. Furthermore, locations of anchors need to be adjusted to cope with slight changes of configuration of the space, such as placement of furniture and electronic devices.