# LoRa Technology Propagation Models for IoT Network Planning in the Amazon Regions
## 2 LoRa Overview  
LoRa is a technology belonging to the physical layer of LPWAN (low-power wide-area network) technology, featuring wireless modulation that offers an attractive combination of long-range capability, low energy consumption, and security in data transmission [5; 25]. Created by Semtech and promoted by the LoRa Alliance, LoRa is the physical layer that establishes the long-range communication link. LoRaWAN is the communication protocol based on the ALOHA [26] communication system architecture. This protocol and the star-type architecture influence the battery life, network capacity, security, and quality of service of applications connected to the network. The LoRa network architecture comprises the end devices or end nodes, gateways, network servers, and application servers. Figure 1 shows the LoRa network architecture. End devices communicate with LoRa gateways via the LoRaWAN protocol. Gateways serve as bidirectional packet converters, transmitting packets from end devices to the network and vice versa. The communication between end devices and the network involves uplink and downlink. Transmitting packets from end devices to the network is the uplink message, and sending packets from the network to end devices is the downlink message. The LoRaWAN protocol is responsible for defining the communication and architecture of a system specifically designed for network sensors. It employs low data rates and extended time for communication, impacting network capacity, node lifetime determination, service quality, security, and various connected applications. Figure 1: LoRa network architecture [25]. This protocol facilitates communication between a large chain of peripheral devices and a single gateway by enabling medium access control (MAC). However, the end nodes are not tied to a specific gateway, which may lead to data loss. To mitigate this, multiple gateways can receive the data, thereby increasing the range of communication between devices and the gateway. For the network layers of LoRa technology and the LoRaWAN protocol, the definition is generally structured into three layers: the physical layer, the data link layer, and the application layer. The LoRa layer combines the physical layer (wireless communication and signal modulation) with the radio frequency layer, containing the frequency bands the technology operates in. The data link layer encompasses the LoRaWAN protocol classes and the LoRaWAN protocol itself, while the application layer represents all the end applications that can be realized using the LoRaWAN protocol. According to the LoRa Alliance, communication between layers of LoRa technology is shown in Figure 2.  
There are two layers of protection for data security in LoRa: the network layer and the application layer. Network layer security ensures the authenticity of the node in the network, while application layer security ensures that the network operator cannot access the end user's application data. LoRa end devices can be categorized into three classes: A, B, and C. These classes represent the trade-off between network downlink communication and battery life. Class A devices require the least amount of system power and support bidirectional communication, both uplink and downlink. Class B devices are also bidirectional, but the gateway can be programmed to receive specific signals. On the other hand, Class C devices have downlink latency and cannot send and receive packets simultaneously. While Class A is fundamental, Classes B and C are optional. In this study, we utilized LoRa end device Class B [25]. Due to its unique characteristics and capabilities, LoRa technology has great potential for scientific research and a wide range of applications. Key points to consider are the following:  
1. Long-range, low-power communication: LoRa's spread spectrum modulation and chirp spread spectrum techniques enable communication over long distances, making it ideal for scenarios where low power consumption is crucial, making it suitable for applications like IoT. 2.