# Tracking and Monitoring System Based on LoRa Technology for Lightweight Boats
## 2 Related Work  
As stated previously, different communication alternatives usually employed in IoT deployments have been applied to maritime scenarios. These technologies include WSN, such as IEEE 802.15.4-based architectures, cellular systems, e.g., GSM (Global System for Mobile communications), 3G, and 4G, or VHF/UHF-based solutions [2]. However, very few works have addressed the use of LP-WAN technologies in these scenarios. In the following, an overview of different recent efforts performed for establishing maritime communications with these technologies is presented. Regarding WSN, they have been used for many applications due to their energy efficiency that permits end-nodes to be alive during years without battery replacement. Thus, works in [14; 15] proposed employing Zigbee-based WSNs for maritime surveillance and safety monitoring. However, both papers adopted different approaches. The first one [14] presented a simulation-based framework for developing a maritime sensor network. With the aim of implementing a system for acquiring information about ship dynamic states, marine environmental protection, etc., the authors introduced the needed architecture and communication protocols based on WSN. In turn, the work in [15] showed the real deployment of a long-term hazard monitoring system installed in a harbor. The nodes composing the WSN made use of an energy-saving smart algorithm and data encryption for securing the Zigbee link between them and the gateway. Although less energy efficient, WiFi technology has been proposed too in other real deployments [16; 17]. In turn, Mobile Ad hoc NETworks (MANET) have also been explored in maritime scenarios [18; 19]. Work in [18] proposed a Nautical Ad hoc NETwork (NANET) in the VHF band in order to improve the range of the individual links. Depending on the distance of the nodes to the shore, the authors proposed to employ terrestrial nodes for enabling the communications in coastal areas and the use of P2P (ad hoc) links in further areas to the shore. From a different perspective, the authors of [19] studied the impact of typical maritime traffic patterns on the performance of different MANET routing protocols. The results showed that, in some scenarios, a boat chain can be established for transporting information from a far node to the gateway on land in a multi-hop fashion, but, in other cases, some boats are isolated with no communication capabilities. In order to solve the issue of temporally isolated nodes due to frequent disconnections, the use of Delay Tolerant Networks (DTN) have been proposed as well [20; 21]. Work in [20] explored the use of WiMAX-based technology for over the horizon ship-to-ship communications following a DTN scheme. The results, attained by means of computing simulation, showed superior performance of DTN-oriented routing protocols in comparison with traditional MANET routing algorithms. In turn, the authors of [21] also made use of simulation tools to demonstrate that DTN are a viable option, but, even more important, that as vessel mobility patterns can be well-known beforehand, the upcoming network topology changes can be accurately predicted. Considering this fact, more efficient routing algorithms can be developed within the context of DTN. As discussed later, cellular networks are not the best option for constrained devices because of the associated high power consumption of the communication module; despite this, they have been employed in maritime scenarios due to their longer range in comparison with WSN technologies. As a typical usage example, the authors of [22] used GSM and 3G links to connect a set of Autonomous Underwater Vehicles (AUV) and wavy drifter buoys with monitoring purposes to the data collector. Other works [2] have identified cellular technologies to be more appropriate in the case of large boats or ships because they do not present energetic restrictions and may employ high-gain antennas in order to extend the link with the base station on land.