# A Systematic Literature Review of LoRaWAN: Sensors and Applications  
[PERSON]  
1 Departamento de Informatica y Ciencias de la Computacion, Escuela Politecnica Nacional, Quito 170525, Ecuador12 Smart Lab, Escuela Politecnica Nacional, Quito 170525, Ecuador2  
[PERSON]  
1 Departamento de Informatica y Ciencias de la Computacion, Escuela Politecnica Nacional, Quito 170525, Ecuador12 Smart Lab, Escuela Politecnica Nacional, Qufocuses on energy efficiency and offers wide global coverage but with a slower data rate. Sigfox's network architecture allows messages from one end device to be received by multiple base stations [3]. Narrow-band IoT (NB-IoT), also called LTE Cat NB1, is a 3 GPP-standard-based narrow-band radio technology that was published in 2016. It is a low-speed and low-power network that offers higher security and data transmission speed in comparison with Sigfox. However, NB-IoT requires existing cellular infrastructure and can be more expensive to implement [4]. LoRaWAN, or long-range wide-area network, is an LPWAN network technology that uses spread spectrum technology to enable data transmission over long distances. LoRaWAN offers high energy efficiency and wide coverage, as well as the ability to send data through obstacles such as buildings and walls. Furthermore, LoRaWAN is an open network, which means that it is not controlled by a single provider and can be used by multiple companies and organizations [5]. Among the aforementioned options, LoRaWAN is an attractive choice due to its high energy efficiency, wide coverage, and ability to send data through obstacles. In addition, since LoRaWAN is an open and flexible network, it can be used by companies and organizations without any kind of restrictions, which makes it the most accessible and affordable option for many applications. LoRaWAN is primarily designed for being used with sensors, which are expected to exchange information with a server at a low transmission rate and relatively long intervals of time where a transmission can take place every hour or even days apart [6]. LoRaWAN is used globally, and its use is constantly expanding, which makes it a very attractive solution for future IoT-based applications [6]. LoRaWAN operates with tree main components: end devices, gateways, and back-end servers (a back-end server has a network server (NS), join server (JS), and application server (AS)) [7]. LoRaWAN has three classes of end devices:  
* Class A: Bidirectional devices with the highest latency among the three classes. These devices are in sleep mode until they receive an uplink message which opens two reception windows and enables a downlink [4]. * Class B: Like class A, these are bidirectional devices. These devices open additional reception windows at scheduled times in addition to the two default windows [4]. * Class C: The reception windows of this class keep open continuously; due to this, these devices consume the greatest amount of energy of the three classes [4]. LoRaWAN incorporates robust security mechanisms to protect data integrity and confidentiality. For encryption purposes, LoRaWAN uses AES-128 in CTR mode, whereas a message authentication code (MAC) is used for integrity [7]. This technology supports two activation methods: activation by personalization (ABP) and over-the-air activation (OTAA). ABP is a straightforward method where device parameters, such as DevEUI, AppEUI, and AppKey, are pre-configured in the end node, AS, NS, and JS for joining and sending messages. This could be insecure since the session keys are always the same. On the other hand, OTAA is a more robust and secure activation method. The end devices in OTAA mode start a join procedure with DeviceEUI, Join EUI, NwkKey, and AppKey. With these parameters, dynamic session keys are generated and exchanged every session [7]. With this background, the present work seeks to provide a complete and updated overview of the areas in which LoRaWAN long-range communication technology has been used in the last 5 years.