## 3 Examples of Maritime Internet of Things Networks in Applications
The authors aim to monitor parameters such as water pressure, current velocity, water temperature, turbidity and salinity, and the presence of chlorophyll, among others. The system is composed of three clusters of sensors, where each cluster has a coordinator that collects data from the sensors via ZigBee. The coordinator node then transfers said data to a base station via a GPRS connection. There is also another node, isolated from the clusters, which communicates directly to the base station via GPRS. Fishery buoys floating on the ocean serve as a visual indication to fishermen of where their traps are located. Finding these buoys is performed with the naked eye and is made extremely difficult by adverse weather conditions and poor visibility. Consequently, in [44], the authors propose to facilitate this task by implementing a GPS locator in the buoys and relaying its location to the fishing vessel via a LoRaWAN connection. With the naked eye, fishermen can detect buoys at around 3 km. With the proposed system, the buoy can be reliably located 14 km away. The bibliography also contains several examples of proof-of-concept MIoT architectures, where varied wireless communication technologies are employed. In [48], the potential of 5G technology is demonstrated by the authors, who achieved a 1 Gbps data rate link from devices 1 km away from the shore through the use of a mobile 5G station on a ship. In [31], the authors test the use of several buoys interconnected via Zigbee which then have a coordinator that relays data via GSM to a coastal station. A flying wireless router approach is proposed in [45], where tethered balloons establish air-to-surface links via LTE and air-to-air (balloon-to-balloon) long-range communication via IEEE 802.11g protocol, relaying data from the surface to shore. A maritime LTE network is proposed in [30], with long-range and high-data-rate, ship-to-shore and ship-to-ship communication and the use of LTE routers in ships. A maritime wireless mesh network with the 802.16 protocol at 5.8 GHz is proposed in [49], and the use of 5.8 GHz 802.11 protocol is demonstrated in [51] to allow the establishment of a point-to-point (fishing ship to shore) 7 km link at 1 Mbps. The Iridium satellite network is also employed in [32] with data reception rates of 98.7%, demonstrating the reliability of this approach. Finally, non-RF communication technologies are also proposed in the bibliography, such as in [42], albeit in an embryonic state, as only simulations are presented. From the analysis of Table 3 and its discussion, it becomes clear that Zigbee is the protocol with the most adoption and potential for short-range communication between sensors and a central node, which coincides with the conclusion of Section 2.1, where Zigbee was singled out as a technology with significant strengths for employment in the ocean, of which mesh networking is key, and it is expected that it will be adopted more and more in upcoming years. In terms of long-range communications to the shore, the conclusions of Section 2.2 also hold up when the state of the art is analyzed. LTE is employed multiple times in the discussed works for shorter communication ranges, with LR Wi-Fi being used for longer ranges. Satellite networks are also employed with great results, and it is expected that the Starlink network will improve further upon the Iridium network, which is already deployed and operational.