## 4 Architecture of the Maritime Internet of Things  
The MIoT has the potential to be a game changer in fields such as water quality monitoring, fishery, aquaculture, and vessel communication [5; 36; 44; 47]. Due to the heterogeneity of possible applications, the types of data sent in an MIoT network can greatly vary. For example, in weather monitoring systems, several variables can be monitored, such as air temperature and pressure, wind speed and direction, and relative humidity, among others. In water quality monitoring, water temperature and salinity are important factors, along with measurements of chlorophyll, nitrates, phosphates, and so on [52]. Data from these applications must then be relayed to a base station for processing and analysis. In fishery, the GPS coordinates of fishing buoys are used to allow fishermen to locate their buoys more accurately and efficiently [44].  
As illustrated above, the MIoT must be capable of dealing with data from many different sources and direct it either to shore or vessels. Considering, for example, an application where we want to monitor several parameters of water quality, we can define an adequate architecture for an MIoT that reliably collects data from many sensors and sends it to base stations onshore for storage and processing.  
The sensor nodes should comprise four modules: power, sensing, processing, and wireless communications [52]. The first can be a battery, or an energy harvester, or a combination of both for an extended lifetime. The processing unit controls the entire node, collects data from the sensors and directs them to the wireless communication module, which then relays the information in the network until it reaches the base station (onshore or on a vessel).  
Wireless communications can be employed in several technologies, such as ZigBee, Bluetooth, Wi-Fi, and GPRS, among others. Nevertheless, as it is envisioned that many sensor nodes may be required for high-spatial-resolution monitoring, that their lifetime should be extended for as long as possible, and that the cost of operation should be minimized, shorter-range and low-power communication protocols such as ZigBee are desired. With this technology, the sensor nodes can create a mesh network for increased communication reliability and range through multihopping. To maximize sensor lifetime, all data can be aggregated in a central node, called a coordinator, which is composed of three modules--power, processing, and wireless communications--where the latter has a ZigBee module to receive data from the sensor nodes and a long-range communication method to relay the data to a base station, which can be through satellite communication or GPRS, for example. This way, it is possible to create several independent clusters of sensors, or subnetworks, to ensure a low-cost and high-resolution monitoring [5].  
From the conclusions drawn in this work, we propose the hypothetical implementation of a wireless communication network presented in Figure 3 that is suitable for monitoring, for example, water quality parameters over a large ocean area. This proposed network uses a short-range wireless communication protocol such as Zigbee to aggregate sensor data from shallow- and deep-water monitoring systems in monitoring stations, which then relay these data to a collecting station via a long-range protocol, for example, LR Wi-Fi or via satellites.