1. Key Technologies of the Maritime Internet of oThings

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 Sensor technology (ST)

The MIoT is a system based on ST which is used for monitoring and collecting marine environmental data. Sensors are installed in various locations and devices in the ocean to sense different parameters and conditions ^[3][45]. These parameters can include ocean temperature, salinity, pressure, water quality, light, and more ^[4][46]. At the same time, ocean sensors have a variety of types and functions for monitoring and collecting marine environmental data. Here are some common ocean sensor types and their features:

The role and advantages of ABSs in the MIoT

• ABSs can be used as wireless communication BSs to provide stable networking connectivity for MIoT devices. By incorporating radio equipment and antennas, they enable efficient communication with IoT devices far from shore ^[44][86].
• Temperature sensor: Used to measure the temperature distribution of the ocean ^[5][47]. Common STs include resistive temperature sensors and thermal conductivity sensors.
• Salinity sensor: Measures the salinity distribution of the ocean. A conductivity sensor is one of the commonly used salinity STs ^[6][48].
• Pressure sensor: Used to measure the depth and pressure distribution of water in the ocean. Pressure sensors are widely used in marine scientific research and marine engineering.
• Light sensor: Measures light intensity and spectral distribution in the ocean. This is important for understanding phytoplankton distribution, photosynthesis, and ecosystem function ^[7][49].
• Water quality sensor: Used to monitor dissolved oxygen, chemical concentration, nutrients, toxic substances, etc., in water. They help to assess the state of marine water quality and environmental health ^[8][50].
• Sonar sensor: Uses sound waves to measure and detect marine life, seafloor terrain, and obstacles. These sensors are commonly used in marine ecological research and ocean navigation ^[9][51].
• Oxygen sensors: Used to measure the amount of dissolved oxygen in the ocean, which is essential for biological survival and biogeochemical processes ^[10][52].
• Video and image sensors (VAISs): Video and images in the ocean are recorded using camera equipment for monitoring marine life, the marine substrate, and human activities ^[11][53].

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 Communication technology (CT)

With the increasing frequency of maritime activities, the development of maritime CT has an important strategic position ^[12][54]. However, due to the complex and variable marine environment, inconsistent standards of communication systems, and other factors, the development of marine communication lags behind land-based communication systems. Therefore, in order to adapt the marine communication to different environments and communication characteristics, different CTs are usually adopted. At the same time, the CT of the MIoT plays a crucial role in transmitting sensor data and realizing the functions of the MIoT. Below, rwesearchers introduce the communication protocols and technologies used for the MIoT.

• Cellular network: A cellular network is a wireless CT that enables communication with the internet by connecting MIoT devices to BSs on land. This communication can use different communication protocols such as 2G, 3G, 4G, and 5G. Cellular networks feature wide coverage and high-speed data transmission for a wide range of MIoT applications ^[13][55].
• SC: SC is a CT widely used in maritime dense communication environments. MIoT devices can communicate with networks on land via satellite. SC has wide area coverage and global characteristics, suitable for MIoT applications far from land and ocean navigation.
• Radio-frequency identification (RFID): RFID technology uses radio-frequency signals to identify and communicate with items or devices. In MIoT, RFID tags can be attached to goods, equipment, or individuals to transmit relevant information to data collection systems by interacting with RFID readers ^[14][56]. This CT is widely used in supply chain management (SCM), ship tracking, and item security ^[15][57].
• Wireless sensor network (WSN): A WSN is a technology that enables the widespread deployment of sensor devices in the MIoT. The WSN uses wireless communication protocols such as Wi-Fi or Bluetooth to connect sensor devices to a network for communication and data transmission among devices. These sensor devices can self-organize into networks that transmit data via repeaters to BSs or data collection systems.
• Submarine optical cable (SOC): An SOC is a CT that enables communication among devices by transmitting optical signals in an undersea cable. This CT is characterized by a high data transmission speed and reliability, and is suitable for MIoT applications that require large bandwidth and long-distance communication. SOCs are commonly used to connect MIoT devices to terrestrial networks and enable data transmission and remote control ^[16][58].

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 Data processing and storage

Data acquisition, processing, and storage in the MIoT are complex and critical processes. MIoT systems typically consist of sensors and devices that monitor and collect various maritime environmental data, such as meteorological conditions, marine life, vessel status, etc. ^[17][59].

Data collection is the first step in the process. Sensors and equipment measure and monitor environmental parameters at sea and transmit these data to a central data processing system ^[18][60]. These sensors can be mounted on boats, buoys, pontoons, and even marine organisms to enable comprehensive data collection ^[19][61].

Once the data has been collected, the next step is data processing. This includes cleaning, validating, converting, and correcting the original data. The cleansing process helps remove noise and outliers from the data, ensuring the data’s accuracy and reliability ^[20][62]. The checksum remediation process is used to handle erroneous data caused by sensor failure or other problems. The conversion process may include data format conversion, unit conversion, and data standardization for further analysis and application.

Once data processing is complete, the next step is data storage. Data in the MIoT are often large-scale and real-time, requiring robust storage systems to house and manage these data ^[21][63]. Cloud computing platforms and distributed storage systems are among the commonly used solutions, which can provide highly scalable storage and processing power ^[22][64]. In addition, data backup and redundancy mechanisms are also indispensable to ensure the security and durability of data ^[23][65].

In MIoT systems, data collection, processing, and storage need to consider factors such as resource constraints, data transmission, and security. In order to achieve effective data utilization, data analysis, and mining, visualization and monitoring operations are also needed ^[24][66]. The combination of these steps can help to achieve a comprehensive understanding of the offshore environment and support decisions.

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 Security and hidden dangers

When it comes to the MIoT, security and privacy issues are important issues to be seriously considered. The following lists some challenges and privacy issues that may be faced in the MIoT and provides some solutions, which can be seen in Table 1 ^[25][67].

Table 1. Security risks and solutions in the air-to-sea (A2S) integrated MIoT.

Security risks and solutions in the A2S integrated MIoT.

Security Risks	Solutions

(a)

 Security challenges:

• Authentication and device security: Ensure that only authorized devices can connect to the network and take appropriate measures to prevent unauthorized access.
  Solution: Adopt strong authentication mechanisms, such as two-factor authentication, and use data encryption to secure devices and communications ^[26][68].

Identity authentication and device security	Advanced encryption technologies and two-factor authentication can be employed to ensure the secure and reliable transmission of data and communication between devices.
Physical security

• Data integrity and confidentiality: Ensure that data are not tampered with or stolen during transmission ^[27][

Tamper-resistant sensors and physical security infrastructure can be deployed to ensure the resilience and reliability of the A2S integrated MIoT in real-world environments.

• Solution: Provide appropriate physical protection, such as security facilities and monitoring measures, to ensure the physical security of equipment and infrastructure
• ^[
• ²⁸
  ^][70].

(b)

 Privacy issues:

• Personal privacy: Ensure that data collected, transmitted, and stored do not reveal personally identifiable or sensitive information ^[29][71].
  Solution: Use data masking techniques to minimize the collection of personally identifiable information, and take appropriate access control and privilege management measures.

• 69
• ].
• Location tracking and behavior monitoring: Tracking and recording an individual’s location and behavior can be a privacy violation ^[30][72].

Personal privacy
Robust privacy regulations and the implementation of anonymization techniques can be enforced to ensure effective protection of individual information during data collection and transmission processes.
Location tracking and behavior monitoring	Differential privacy techniques can be implemented to protect location information privacy, based on which the compliant data collection and usage standards can be adhered to ensure lawful and transparent behavior monitoring.
Data sharing

• Solution: Use end-to-end encryption to protect the data transmission and implement effective data-integrity checking mechanisms.

Secure data sharing protocols and decentralized blockchain techniques can be adopted to ensure trustworthy and efficient data exchange and collaboration.

• Solution: Clearly inform users that data are being collected and provide users with options to opt in, such as authorizing or disabling location tracking.

75]. Channel modeling plays a crucial role in this context by studying the mathematical models of signal transmission processes to optimize channel transmission performance, enhance data transfer reliability, and adapt to changes in diverse environments ^[34][76].

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 Classification:

• Mobile communication BS: This is the most common type of ABS used to provide mobile communication services. It connects the aircraft’s mobile communications equipment with ground BS or SC networks, enabling passengers and crew to make voice calls, send text messages, and use the internet during flight, among other things ^[37][79].
• Physical security: Protect the device from malicious damage, physical intrusion, or damage to the device.
• Data sharing: Ensure that data collected from the MIoT is only shared where necessary and with appropriate anonymization and security safeguards in place ^[31][73].
  Solution: Establish clear data sharing policies and legal frameworks, limit the collection and use of data, and ensure that data sharing complies with privacy regulations.

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Channel modeling

In the A2S integrated MIoT, channel modeling is important for network deployment and the accurate prediction of wireless conditions, especially considering the existence of aerial nodes ^[32][74]. Specifically, the A2S integrated MIoT represents an advanced network architecture that tightly integrates the realms of the sky and the ocean. The successful implementation of such networks requires establishing reliable communication connections in different environments ^[33][

• Satellite communication BS: This BS provides air communication connection through a satellite network. SC installs satellite dishes and terminal equipment on the aircraft for communication with satellite communication systems, thus enabling long-distance communication in flight ^[39][81].
• UAV communication BS: UAVs can also be equipped with communication BSs for communication and control with ground control stations or other UAVs. This BS enables two-way communication between the drone and the operator, and supports DT and sensor information sharing ^[40][82].

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 Application of ABSs in various fields:

• Commercial aviation: ABSs play an important role in commercial aviation. They enable passengers to maintain mobile phone signals during the flight, make voice calls, send text messages, and use the internet. This provides a better passenger experience and communication connectivity, while also providing value-added communication services for airlines.
• Military and security applications: ABSs play a key role in the military and security fields. ABSs on military aircraft provide military communications capabilities, support command and control, and share battlefield information. This is essential for coordination and decision-making in military operations.

• First, channel modeling in A2S integrated MIoT contributes to understanding and analyzing the channel characteristics in the atmosphere and the ocean. The atmospheric and oceanic environments exert unique influences on the propagation of electromagnetic waves, involving phenomena such as multi-path propagation, fading, and scattering. By establishing accurate channel models, researchers can better comprehend the propagation characteristics of signals in these complex environments, providing robust theoretical support for network design.
• Second, channel modeling aids in optimizing the communication system parameters of A2S integrated MIoT. Through simulation and analysis of channel transmission performance, the optimal parameters for modems, power control strategies, and spectrum allocation schemes can be determined, enhancing the efficiency and performance of the communication system. This optimization ensures that the network maintains high-quality communication connections under different atmospheric and oceanic conditions.
• Third, channel modeling is crucial for the security of A2S integrated MIoT. By modeling the propagation paths of signals, potential sources of interference and security threats can be identified. This helps in designing and implementing effective security protocols and protection mechanisms, ensuring that the network remains stable and reliable in the face of malicious attacks.

2. Air-to-2Sea Integrated Technology

• Other dedicated ABSs: In addition to mobile communication BSs, there are also some ABSs specifically designed for specific purposes. For example, military aircraft may be equipped with military communication BSs for military command and control communications; public safety BSs on aircraft may be used for emergency communications and rescue operations ^[38][80].
• Emergency rescue and disaster relief: ABSs provide critical communications support during emergency rescue and relief operations. They allow rescuers to maintain contact with ground command centers and share rescue information. This helps to improve rescue efficiency and the safety of rescue operations ^[41][83].
• Air-based warfare can provide greater coverage. Their height and flexibility allow them to provide the signal coverage over a wider range than land BSs or SCs. As a result, more MIoT devices can be connected, enabling a wider range of data transmission and communication.
• Air-based warfare also offers the advantages of rapid deployment and flexibility. They can move from one place to another at a relatively fast pace, providing communication support in different areas at sea depending on demand ^[45][87]. This flexibility can play an important role in situations of emergency, temporary assignment, or specific needs ^[46][88].
  UAV applications: ABSs are also widely used in UAV applications. The BS equipped with the UAV can realize the communication and control between the UAV and the ground control station, as well as the collaborative operation among UAVs. This allows UAVs to play an important role in surveillance, logistics, agriculture, security, and other fields ^[42][84].
• Satellite communications: ABSs are used in conjunction with SC systems to provide long-range communication connectivity in aviation services. Through SC, ABS can realize broadcasting, DT, and remote control on a global scale to meet the communication needs of aircraft and passengers ^[43][85].

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3. Air-to-2Sea Integrated Maritime Internet of Things IoT Architecture

Figure 1.

A2S integrated MIoT architecture.

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 Perception layer: The perception layer refers to sensor nodes and IoT devices. Sensor nodes include various environmental detectors, position and attitude sensors, cameras, etc., which are connected to the MIoT through IoT devices and collect data and upload the data to the next layer of the network. It consists of various sensor devices deployed in the air, on the ground, and at sea, such as meteorological sensors, ocean sensors, position sensors, etc. These sensor devices transmit the collected data to the data center via wireless communication ^[48][90].

(2)

 Transport layer: The transport layer refers to the interaction of various communication networks. Including satellite positioning system, SC of the wireless network, etc., used to connect the various components. These communication networks provide reliable data transmission channels that support real-time marine environmental awareness and data exchange ^[49][91].

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Processing layer: The marine environmental data obtained from the perception layer are centrally stored and processed for cloud computing. A cloud-based service enablement platform is used to manage and operate the entire MIoT system ^[50][92]. The platform provides the equipment management, data management, and other functions, and supports the real-time monitoring, analysis, and sharing of the marine environmental data. At the same time, the IoT platform can also be integrated with other systems, such as shipborne navigation systems, maritime supervision systems, etc. Data centers are typically equipped with HPCAS devices and utilize data processing algorithms to analyze, mine, and visualize ocean data.

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 Application layer: This refers to various specific application scenarios and business requirements, such as smart ports, marine environmental monitoring, ship safety, fisheries resource management, etc., which exchange data and share information through the MIoT. Based on the MIoT, various marine environment application services, such as marine early warning, marine resource management, route planning, etc. These application services use the marine environmental data provided by the IoT platform to provide decision support and information services for users in maritime, fisheries, energy, tourism, and other fields ^[51][93].

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 Space segment: This segment aims to establish a security monitoring system, real-time monitoring of the security status and abnormal conditions of the IoT system, security protection and privacy protection, and timely warning and appropriate protective measures ^[52][94].

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 Specific cases: Through the A2S integrated MIoT architecture, researcherswe can achieve comprehensive perception and monitoring of the marine environment, improve the safety and efficiency of maritime transportation, promote the sustainable development and utilization of marine resources, and provide decision-making support and services for relevant industries and government departments ^[53][95].