# A Survey on LoRaWAN Architecture, Protocol and Technologies
## 2 LoRa & LoRaWAN Technologies
### Physical Layer-LoRa
LoRa is a sub-GHz technology and it has many application areas, authors [26] aim to analyze fading and path loss of the technology for smart animal tracking. LoRa is a Chirp Spreading Spectrum (CSS) technology that provides LoRa to be resistant to interference, this feature is analyzed by the paper [27] to illustrate how the gain of the chirps can be set independently with the number of orthogonal chirps. Also, it is shown that orthogonal CSS is more flexible for various applications. Since IoT deployments are increasing both urban sub-urban areas, LoRa deployed IoT-nodes will face high interference. [PERSON] et al. [28] take attention to the issue and aim to analyze protocol performance. It is shown that even high interference scenarios LoRa provides robust communication links. [PERSON] et al. [29] present a work to validate channel orthogonality within different SF values using testbed experiments. Also, LoRa GFSK mutual interference is evaluated by the study. Also, interference studies carried out for different regions in North America--915 MHz and it is proven that 915 MHz in North America can achieve higher throughput than EU 863-870 MHz [30]. ISM frequency bands give researchers, hobbyists and makers flexibility to use and develop RF protocols. This advantage brings a downside to co-existing communication technologies for interference. [PERSON] et al. [31] inspect the IEEE 802.15.4 and LoRa for cross-technology interference using different BW and SFs. Respectively LPWAN and other sub-GHz radio technologies operating at the near frequency can cause interference to each other these issues addressed by works of the authors [32; 33]. Performance of the LoRa technology is analyzed for different types of application scenarios such as Smart Grids. [PERSON] et al. [34] evaluate LoRa for rural smart grid application for network coverage and path losses. According to the study, it is reported that the packet success ratio ranges from 0.9-0.95 which is a feasible technology in most Smart Grid applications. An interesting signal measurement is performed by [PERSON] et al. [35], where authors track human movements (mainly walking) within an area with LoRa. According to the study, it is not feasible to track a person on the streets in an Urban area. Unlike the theoretical range 25 km, the authors claim that 200 m is the successful packet reception range and packet loses start at 600 m.  
A prorogation analysis presented by [PERSON] et al. [36] using LoRa for underground soils and, the electrical conductivity of soil is evaluated. It is shown that rain has effects on the successful packet reception ratios and also, the performance of the system decreases during heavy rains. A spread spectrum analysis performed at 2.45 GHz using LoRa modulation by [PERSON] et al. [37]. 868 MHz & 915 MHz require 8.1 cm and 7.9 cm long antenna to have proper signal reception and transmission. Researchers address this issue to provide compact [38], wearable [39; 40] and electrically configurable patch [41] antenna solutions. \(\mu\)PnP is a plug and plug system for IoT platforms.Ramachandran et al. [42] aim to add LoRa technology to provide sensor based IoT platform. While a large number of studies focus communication range in LoRa, indoor performance analysis is a fact that to be considered. Researchers [PERSON] et al. [43] and [PERSON] [44] address this issue and provides LoRa metrics for indoor use cases for various indoor scenarios. [PERSON] et al. [45] evaluates indoor signal propagation and it is shown that packet loses increase when the building or structures get complicated. Radio-based wake receivers are evaluated by [PERSON] et al. [46] to eliminate idle listening. Authors present a scheme to solve latency and power consumption and analytical results show that 3000 times energy savings. Since LoRa modulation is patented this resulted in the search of alternative modulation methods to replace LoRa [47]. Thus, the authors offer a FSK mathematical model that aligns with LoRa which is intended to be an open alternative.