# A Visitor Assistance System Based on LoRa for Nature Forest Parks
## 1 Introduction  
Ecotourism, according to the World Economic Forum [1], is an economic activity that strongly contributes to income generation and distribution, especially in underdeveloped countries. In addition to helping to reduce poverty, ecotourism helps to preserve endangered ecosystems. Indeed, Environmental Conservation Units, such as parks and forest reserves, are extremely important because they promote environmental education and integrate the society with nature. Nonetheless, the natural environment presents inherent risks. Inside tropical forests, those mainly include getting lost, getting hurt, being in an unfamiliar environment, and the occurrence of natural disasters, such as flash flooding or forest fires. Efficiently responding to the occurrence of lost visitors requires their geolocation, in addition to means of communication--or the search and rescue operation may take too long. The use of global navigation satellite systems (GNSS), such as the GPS, would make the task of determining the visitor's position straightforward. The problem is, it is not possible to rely on a GNSS within conservation units, for example, inside dense forests or canyons. In these situations, alternative techniques need to be explored. This work describes the project of a visitor assisting system where the localization is done collaboratively, using a low power wide range wireless network, and a DTN (Delay and disruption Tolerant Network) communication model. LoRa [2; 3; 4] is the wireless technology chosen, being the one that provided the largest range inside the tropical forest. Only the LoRa physical layer is used once our communication scenario does not justify the use of LoRaWAN [5; 6]. Our main requirements for the mobile terminal, which will be carried by the user (a bracelet, ideally), are lightweight, very low energy consumption, and long-range communication. As such, we can consider this terminal as an Internet of Things (IoT) device. As a consequence, we also have some constraints: low memory, low processing capacity, and low data transmission rates. The aim is to keep the project simple and inexpensive to facilitate its implementation in different conservation units. The goal is to maximize wireless network coverage while reducing infrastructure. This minimizes the cost of the project and also the environmental impacts that may be caused to fauna and flora. The architecture of the proposed visitor assistance system has mobile and fixed nodes, which implement a security application. The mobile nodes are the visitor terminals and the fixed ones are the totems, an infrastructure to forward traffic to the application servers. The security application provides monitoring of visitors' location, whether alone or in a group, and additionally allows help requests. To support the application, we design a protocol for exchanging location messages. As the application is designed to run directly above the LoRa physical layer, an alternate method to control access to the medium is developed. In a nutshell, the contributions of our work are:  
* The proposal of a specific medium access control protocol for the LoRa network, which connects user terminals to totems and among themselves. A lightweight variation of CSMA (Carrier-Sense Multiple Access) is implemented using the different spreading factors of the LoRa PHY layer;
* A protocol for the collaborative localization of visitors inside the park, which builds upon the one proposed in the CenWits project [7]. The proposed protocol includes visitor's active requests for rescue and dynamic group creation. Groups allow to optimize terminal memory and battery utilization, as well as reducing the load offered to the network. This work is organized as follows. Section 2 presents the main contributions of this work, and Section 3 shows existing related work in the literature. Section 4 briefly analyzes radio propagation in the forest environment. Section 5 details the visitor assistance system proposed, including architecture, protocol, and application.