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Maritime Communications: A Survey on Enabling Technologies, Opportunities, and Challenges
Fahad S. Alqurashi, Abderrahmen Trichili, Nasir Saeed, Boon S. Ooi, Mohamed-Slim Alouini
TL;DR
Reliable high-speed maritime connectivity remains challenging across vast oceans and diverse propagation environments. This survey synthesizes RF, optical, satellite, aerial, and maritime IoT technologies, then identifies open challenges and future directions.
Problem
Reliable and high-speed communication remains difficult at sea despite growing oceanic activity and expanding maritime applications.
Method
The paper presents a state-of-the-art survey covering maritime technologies, channel models, modulation and coding, resource management, coverage, capacity, energy efficiency, and IoT use cases.
Results
The survey synthesizes RF, optical, satellite, aerial, and maritime IoT technologies while identifying open challenges and future research directions.
Takeaways & Limitations
Coverage and capacity are improving, while deep-sea broadband, on-board THz and visible-light communication, and data-driven channel modeling remain future directions.
Abstract
from arXiv · showhide
Water covers 71% of the Earth's surface, where the steady increase in oceanic activities has promoted the need for reliable maritime communication technologies. The existing maritime communication systems involve terrestrial, aerial, and satellite networks. This paper presents a holistic overview of the different forms of maritime communications and provides the latest advances in various marine technologies. The paper first introduces the different techniques used for maritime communications over the RF and optical bands. Then, we present the channel models for RF and optical bands, modulation and coding schemes, coverage and capacity, and radio resource management in maritime communications. After that, the paper presents some emerging use cases of maritime networks, such as the Internet of Ships (IoS) and the ship-to-underwater Internet of things (IoT). Finally, we highlight a few exciting open challenges and identify a set of future research directions for maritime communication, including bringing broadband connectivity to the deep sea, using THz and visible light signals for on-board applications, and data-driven modeling for radio and optical marine propagation.
I. INTRODUCTION
Maritime communication is increasingly important as oceanic activity expands, yet reliable high-speed connectivity at sea remains difficult. This survey addresses that gap by synthesizing maritime technologies, communication building blocks, applications, and research directions.
- Growing shipping, offshore energy, fishing, tourism, and other ocean activities increase the need for reliable maritime communication.
- Existing maritime systems use terrestrial, aerial, and satellite platforms, while conventional MF, HF, VHF, and UHF links mainly support basic applications.
- A. Related Surveys: Prior surveys address selected topics, including network architectures, RF channels, autonomous marine systems, video scheduling, and maritime IoT.
- B. Contributions: The survey provides a holistic treatment of maritime communication technologies, their building blocks, and emerging maritime IoT applications.
- The paper covers RF, optical, and hybrid communication for ship-to-ship, ship-to-shore, satellite-ship, and on-board links.
A. RF Technologies for Maritime Communications
RF maritime communication supports essential voice, identification, messaging, and broadband functions across several frequency bands. Systems extend range and capability through digital protocols, unused spectrum, aerial relays, and multihop networking.
- Maritime VHF supports voice calls, digital selective calling, AIS, and text messaging, including distress communication and vessel identification.
- AIS uses GMSK/FM at 9.6 kbps and SOTDMA to coordinate synchronized data transmission among vessels.
- Helikites provide radio relays from land or sea platforms, including operation under windspeeds of 100 km/hr.
- Unused VHF and UHF television channels can support long-range line-of-sight maritime transmission.
- Multihop relaying extends maritime radio coverage using air-air IEEE 802.11g links and air-sea UMTS or LTE links.
2) Satellites-Based Maritime Communication System:
Satellite, aerial, and on-board systems broaden maritime connectivity beyond conventional shore-based radio. Their deployment combines wide-area coverage and high-altitude relays with channel models tailored to sea-surface and ship-interior propagation.
- Satellite systems provide wider maritime coverage than standard microwave techniques, with Inmarsat offering near-global L-band connectivity up to 50 Mbps.
- Aerial networks use UAVs and HAPS for relay, sensing, search-and-rescue, and broad coverage; HAPS connectivity has reached up to 140 km.
- B. On-board Communications: On-board channels require dedicated modeling because steel ship structures produce propagation conditions unlike conventional indoor environments.
- B. On-board Communications: On-board measurements report RMS delay spreads of 70–90 ns and path-loss gradients from 1/2 to unity across 800 MHz–2.6 GHz.
- B. On-board Communications: A broader study found sub-6 GHz path-loss exponents of 1.21, 1.14, and 1.36, versus 1.9 for mmWave communications.
C. FSO and Hybrid RF/FSO for Maritime Communications
FSO maritime links offer secure, high-capacity optical communication, including passive modulating retro-reflector designs and long-range demonstrations. Hybrid RF/FSO schemes are emerging, while maritime networks continue to face bandwidth, range, and satellite-related constraints.
- FSO maritime links: FSO links are difficult to intercept and immune to jamming, supporting military and civil maritime applications.These properties contrast with RF signals and motivate optical deployment in maritime communication.
- FSO maritime links: 300 Mbps uncompressed video was transmitted over 17.5 km for 10 hours without disruptions or delay between naval vessels.The demonstration used FSO systems installed on two naval vessels during the 2006 Trident Warrior exercise.
- FSO maritime links: Up to 7.5 Gbps FSO communication was demonstrated between moving ships, while ship-to-shore rates of 1–2 Gbps were reported beyond 25 km.The ship-to-shore terminal operated for 14 hours; voice communication extended beyond 35 km and messages reached 45 km line-of-sight distance.
- MRR-based FSO: An MRR-based FSO modulates laser light at a passive retro-reflector and reflects the modulated beam back to an optical receiver.The MRR combines a corner-cube retro-reflector with a modulator and emits no optical power of its own.
- MRR-based FSO: MRR maritime experiments included 100–500 Mbps over a 32.4 km folded round trip and a 32 km round-trip link using a 1550-nm laser.Other trials used five quantum-well MRRs for shore-to-boat communication over 2 km, reaching up to 5 Mbps.
- Hybrid RF/FSO and challenges: Hybrid RF/FSO links are being investigated for ship-to-ship and ship-to-shore communication, but maritime research remains at an early stage.The survey identifies hybrid RF/FSO schemes as requiring further research alongside broader maritime communication challenges.
A. Channel Models (RF/FSO/Hybrid Systems)
Maritime channel models account for sparsity, wave-induced instability, ducting, and link-specific propagation across RF, FSO, and hybrid systems. The survey describes two-ray, finite-scattering, three-ray, duct-based, and satellite/air-to-ship models, while also noting FSO trials and on-board channel modeling.
- Maritime channels differ from terrestrial channels because sparsity, wave-induced instability, and ducting affect ship-to-ship, air-to-ship, shore-to-ship, and satellite-to-ship links.
- RF-based Channel Models: Evaporation ducting forms when atmospheric refractivity varies with height, trapping signals in a near-surface layer that typically ranges from 10 to 20 m.The duct height can reach a maximum of 40 m.
- RF-based Channel Models: Short-range shore-to-ship and ship-to-ship links are modeled primarily with two-ray propagation that includes direct and sea-surface-reflected components.Reflection amplitude depends on factors including surface roughness, while phase difference can be estimated geometrically using a curved-Earth approximation.
- RF-based Channel Models: Three-ray and finite-scattering models extend short-range channel descriptions when local scattering or additional multipath components cannot be neglected.The finite-scattering model combines a specular component with a diffusion component represented by complex Gaussian terms.
- RF-based Channel Models: For long-range propagation, duct-based links can provide beyond-line-of-sight communication, with parabolic equations solved using split-step Fourier, finite-difference, or finite-element methods.The appropriate numerical strategy depends on the scenario and the numerical model used to solve the parabolic equation.
- RF-based Channel Models: Satellite/air-to-ship links experience line-of-sight and reflected paths, with experiments identifying the Rician model as suitable and 3D simulations providing more realistic sea-surface modeling than 2D simulations.Three-dimensional formulations require high computational power.
2) FSO Channel Modeling:
Maritime FSO channel modeling accounts for attenuation from weather and scattering, as well as turbulence-induced scintillation and beam wandering. Models use visibility, wavelength, and particle-size distributions, but terrestrial turbulence models do not directly describe marine propagation.
- Propagation impairments: Weather attenuates maritime optical beams, while turbulence causes millisecond-scale scintillation and beam wandering.Beam wandering is the random movement of the incoming laser beam on the receiver plane.
- Attenuation models: FSO power attenuation follows Beer’s law, with wavelength-dependent loss combining absorption and scattering.For maritime FSO wavelengths in non-absorption atmospheric windows, absorption can be neglected; scattering includes Rayleigh, Mie, and non-selective components.
- Scattering models: Mie-scattering models parameterize the scattering coefficient using visibility, a reference wavelength, and particle-size distribution.The Kruse model uses visibility-dependent values of q across visibility ranges, while the Kim model provides higher accuracy at low visibility.
- Scattering models: Rain and snow scattering can be modeled empirically from precipitation intensity and model-specific coefficients.The cited formulations express rain and snow scattering coefficients as functions of precipitation intensity and snowfall rate, respectively.
- Turbulence models: The refractive-index structure parameter C^2_n measures fluctuation strength and ranges from 10^-13 for strong turbulence to 10^-17 for weak turbulence.Stochastic terrestrial models include lognormal, negative exponential, Gamma-Gamma, and generalized Málaga distributions for different turbulence regimes.
- Turbulence models: Terrestrial FSO turbulence models cannot directly represent maritime propagation because turbulence behaves differently over water.Marine refractive-index fluctuations differ from inland conditions, mainly because of significant humidity variations; marine-specific theoretical and experimental models have therefore been developed.
3) Hybrid Models:
Hybrid maritime links exploit different RF and FSO responses to weather. Measurements show that RF maintained high availability while rain degraded RF and fog severely attenuated FSO.
- Weather-dependent link behavior: FSO is highly sensitive to fog and snow but resilient to rain, whereas RF is resilient to fog and snow but severely degraded by rain.The contrasting weather responses motivate hybrid links that combine FSO with RF backup.
- Experimental observations: The RF link achieved more than 99% availability during measurements and was mainly degraded by rain.The measurements were collected alongside weather observations to correlate hybrid-link behavior with environmental conditions.
- Experimental observations: The FSO link operating at 850 nm was primarily affected by fog, causing severe attenuation especially during daytime.The study also reported maximum and average Fried-parameter values for the measured optical link.
B. Modulation and Coding Schemes
Maritime communication studies address modulation and coding at the physical layer for both RF and FSO-based systems.
- Scope: The survey organizes maritime modulation and coding techniques into RF-based and FSO-based systems.It introduces RF techniques first, followed by FSO techniques.
1) RF-based schemes:
RF maritime schemes adapt transmission to channel conditions, while optical systems use direct-detection or coherent architectures with distinct modulation options. Reported maritime links and network designs also target capacity, coverage, and resource allocation.
- RF-based schemes: Adaptive coding and modulation changes the VHF-based VDES modulation format and coding rate according to experienced SNR.This adaptation addresses weaker received signals when ships are far from shore.
- FSO-based schemes: FSO systems use either IM/DD, which supports unipolar modulation, or coherent detection, which enables information encoding with complex multilevel signals.IM/DD directly detects laser intensity, whereas coherent systems use a local oscillator for phase tracking.
- FSO-based schemes: A 5.62 Gbps homodyne FSO transmission was conducted between two Canary Islands in 2005.Homodyne detection matches local-oscillator and laser frequencies; heterodyne detection mixes them into the microwave region.
- FSO-based schemes: DPSK with repetition coding provided a compromise between long distance and system capacity in BER simulations against PPM, PAM, OOK, and QPSK.Repetition coding sends the same message multiple times to exploit time diversity, and DPSK can resolve BPSK phase ambiguity.
- FSO-based schemes: An MRR-based FSO system modulates the laser beam at a modulator and reflects it to the receiver through a passive retro-reflector.MRRs have also been used in terrestrial and Earth-satellite laser communication for link characterization and ranging.
- Coverage and capacity: Higher-frequency maritime RF links improve capacity, with Korean LTE-maritime demonstrating 100 km coverage and data rates of a few Mbps.Evaporation ducts have also supported 10 Mbps over a 78 km, 10.6 GHz link and demonstrated additional links of 109, 63, and 87 km.
- Radio resource management: Maritime radio-resource management optimizes bandwidth at a cluster head to serve naval-fleet cluster nodes while reducing resource-exhaustion risk.The described MANET uses LTE nodes, with ships represented as cluster nodes and a shipmaster as cluster head.
E. Energy Efficiency
Maritime networks pursue energy efficiency through software-defined networking, aerial architectures, and self-powered devices. IoT deployments also use renewable energy harvesting, while mobility and connectivity constraints shape collection methods.
- SDN can reduce network latency and energy consumption while preserving network flexibility.
- Self-powered marine networks use buoys that harvest energy from ocean-wave movement to operate communication units.
- Deployment and simulation results showed that wave-powered buoy systems could produce more energy than needed for operation.
- Internet-of-Ships: IoS coordinates ship and buoy nodes through core-network virtualization using machine learning and artificial intelligence.
- Maritime IoT: Maritime IoT projects use solar-powered buoys and UAV-assisted collection, but mobile collection heads can complicate routing and UAV operation is constrained by battery lifetime.
- Maritime IoT: Maritime IoT applications include smart ports, weather prediction, pollution control, and oil-platform monitoring.
C. Internet of Underwater Things
The Internet of Underwater Things connects underwater sensor networks to surface sinks and control centers for scientific and industrial monitoring. Acoustic, optical, and magnetic-induction links offer different trade-offs, while energy harvesting addresses persistent powering needs.
- Ships, buoys, and ASVs act as sinks that collect underwater sensor data and forward it to control centers via radio waves.
- IoUT uses acoustic, optical wireless, magnetic-induction, and hybrid communication technologies.
- Acoustic links support long distances but have limited bandwidth, limited stealth, and reliability challenges.
- Underwater optical links offer broad bandwidth around 400-500 nm but are strongly affected by turbulence from temperature and salinity variations.
- Magnetic-induction communication provides better transmission stability than optical and acoustic links at the air-water interface.
- IoUT devices can harvest energy from solar light, ocean waves, wind, or underwater currents to reduce battery-replacement demands.
V. CHALLENGES AND FUTURE RESEARCH DIRECTIONS
Maritime communications face unreliable data, costly or delayed offshore connectivity, absent cybersecurity standardization, and limited broadband reach. Proposed directions include hybrid UAV architectures and on-board optical communication.
- Ship mobility and limited sea coverage can make maritime data inadequate, imprecise, untrustworthy, dropped, or interrupted.
- Satellite communication remains common far offshore but is costly and incurs significant delays from long propagation distances.
- Safety and Security: Maritime transportation lacks a standardized cybersecurity strategy despite severe potential consequences for accidents and supply chains.
- Deep-Sea Broadband: Terrestrial cellular broadband commonly reaches only 20-25 km offshore, while GEO satellite connectivity causes at least 240 ms latency.
- Deep-Sea Broadband: UAVs could provide on-demand maritime coverage by connecting coastal terrestrial stations and using satellites for far-offshore backhaul.
- On-Board Communication: VLC can support on-board maritime communication while remaining immune to electromagnetic interference with RF terminals.
D. A Room for THz Communication?
THz communication is suited to high-rate on-board applications rather than relatively long-range maritime links because atmospheric water vapor strongly absorbs THz signals. The survey also identifies machine learning and inter-medium relaying as research directions for maritime networks.
- THz Applications: THz spans 0.1 THz to 10 THz and is unsuitable for relatively long-range ship-to-ship or shore-to-ship links because water vapor strongly absorbs its signals.
- THz Applications: THz can support high-rate on-board communication, chemical and biological sensing, and high-accuracy localization with small-footprint antennas.
- Data-Driven Modeling: Machine learning can assist maritime channel modeling and estimation when RF or optical channels are partially or completely unknown.
- Data-Driven Modeling: Deep learning has been used to optimize coding and modulation end to end, suggesting applications for RF and optical maritime links.
- Inter-Medium Communication: Decode-and-forward relays can bridge air-water links by changing communication technology between media.
- Future Directions: The survey identifies broadband deep-sea connectivity, visible light and THz on-board applications, and machine-learning-based modeling as open research problems.