Environmental Information-Aided Electromagnetic Propagation Testbed for Maritime Communication

Maritime channel modeling can be affected by some key time-varying environmental factors.The ducting effect is one of the thorniest factors since it causes anomalous propagation enhancement and severe co-channel interference.Moreover,the atmospheric attenuation is much more severe in the ocean environment,resulting in shorter coverage distance and more link outage.In this paper,we propose an environmental information-aided electromagnetic propagation testbed.It is based on complex refractivity estimation and improved parabolic equation propagation model,taking into account both ducting effect and atmospheric attenuation.A large-scale temporal and spatial propagation measurement was conducted with meteorological acquisition.We consider practical path loss and ducting conditions to verify the testbed feasibility in these long-distance radio links.The simulation results are in good agreement with the measured data,which further reveal the basic temporal and spatial distribution of ducting effect at 3.5 GHz band.

Towards reinforcement learning in UAV relay for anti-jamming maritime communications

Maritime communications with sea surface reflections and sea wave occlusions are susceptible to jamming attacks due to the wide geographical area and intensive wireless communication services.Unmanned Aerial Vehicles(UAVs)help relay messages to improve communication performance,but the relay policy that depends on the rapidly changing maritime environments is difficult to optimize.In this paper,a reinforcement learning-based UAV relay policy for maritime communications is proposed to resist jamming attacks.Based on previous transmission performance,the relay location,the received power of the transmitted signal and the received jamming power,this scheme optimizes the UAV trajectory and relay power to save the energy consumption and decrease the Bit-Error-Rate(BER)of the maritime signals.A deep reinforcement learning-based scheme is also proposed,which designs a deep neural network with dueling architecture to further improve the communication performance and computational complexity.The performance bounds regarding the signal to interference plus noise ratio,energy consumption and the communication utility are provided based on the Nash equilibrium of the game against jamming,and the computational complexity of the proposed schemes is analyzed.Simulation results show that the proposed schemes improve the energy efficiency and decrease the BER compared with the benchmark.

Placement Optimization of Caching UAV-Assisted Mobile Relay Maritime Communication

Recently, due to the deployment flexibility of unmanned aerial vehicles(UAVs), UAV-assisted mobile relay communication system has been widely used in the maritime communication. However, the performance of UAV-assisted mobile relay communication system is limited by the capacity of wireless backhaul link between base station and UAV. In this paper, we consider a caching UAV-assisted decode-and-forward relay communication system in a downlink maritime communication. For the general case with multiple users, the optimal placement of UAV is obtained by solving the average achievable rate maximization problem through the one-dimensional linear search. For a special case with single user, we derive a semi closedform expression of the optimal placement of UAV. Simulation results confirm the accuracy of analytical results and show that the optimal placement of UAV and the average achievable rate significantly depend on the cache capacity at UAV. We also show the difference between the performances of the air-to-ground model and the air-to-sea model.

New Developments in Maritime Communications： a Comprehensive Survey

This paper summarizes the requirements for modem maritime wireless communication networks in the marine environments including the sea- to-sea and sea-to-shore communication scenarios. The existing maritime wireless communication sys- tems are presented and the development of the state-of-the-art maritime communication systems is surveyed. Furthermore, a hierarchical and integrated maritime network architecture is proposed to satisfy the increasing various classes of services which demand different Quality of Service （QoS）. Finally, the open issues for further development of maritime communications are identified.

NOMA-Based UAV Communications for Maritime Coverage Enhancement

The lack of communication infrastructure in the ocean inevitably leads to coverage blind zones.In addition to high-throughput marine satellites,unmanned aerial vehicles(UAVs)can be used to provide coverage for these blind zones along with onshore base stations.In this paper,we consider the use of UAV for maritime coverage enhancement.Particularly,to serve more ships on the vast oceanic area with limited spectrum resources,we employ non-orthogonal multiple access(NOMA).A joint power and transmission duration allocation problem is formulated to maximize the minimum ship throughput,with the constraints on onboard communication energy.Different from previous works,we only assume the slowly time-varying large-scale channel state information(CSI)to reduce the system cost,as the large-scale CSI is locationdependent and can be obtained according to a priori radio map.To solve the non-convex problem,we decompose it into two subproblems and solve them in an iterative way.Simulation results show the effectiveness of the proposed solution.

Energy-Efficient Full-Duplex UAV Relaying with Trajectory Optimization and Power Control in Maritime Communication Environments

This paper solves an energy-efficient optimization problem of a fixed-wing unmanned aerial vehicle(UAV) assisted full-duplex mobile relaying in maritime communication environments.Taking the speed and the acceleration of the UAV and the information-causality constraints into consideration,the energy-efficiency of the system under investigation is maximized by jointly optimizing the UAV’s trajectory and the individual transmit power levels of the source and the UAV relay nodes.The optimization problem is non-convex and thus cannot be solved directly.Therefore,it is decoupled into two subproblems.One sub-problem is for the transmit power control at the source and the UAV relay nodes,and the other aims at optimizing the UAV s flight trajectory.By using the Lagrangian dual and Dinkelbach methods,the two sub-problems are solved,leading to an iterative algorithm for the joint design of transmit power control and trajectory optimization.Computer simulations demonstrated that by conducting the proposed algorithm,the flight trajectory of the UAV and the individual transmit power levels of the nodes can be flexibly adjusted according to the system conditions,and the proposed algorithm can achieve signiflcantly higher energy efficiency as compared with the other benchmark schemes.

Spatial-Modulated Physical-Layer Network Coding Based on Block Markov Superposition Transmission for Maritime Relay Communications

As an alternative to satellite communications,multi-hop relay networks can be deployed for maritime long-distance communications.Distinct from terrestrial environment,marine radio signals are affected by many factors,e.g.,weather conditions,evaporation ducting,and ship rocking caused by waves.To ensure the data transmission reliability,the block Markov superposition transmission(BMST)codes,which are easily configurable and have predictable performance,are applied in this study.Meanwhile,the physical-layer network coding(PNC)scheme with spatial modulation(SM)is adopted to improve the spectrum utilization.For the BMST-SMPNC system,we propose an iterative algorithm,which utilizes the channel observations and the a priori information from BMST decoder,to compute the soft information corresponding to the XORed bits constructed by the relay node.The results indicate that the proposed scheme outperforms the convolutional coded SM-PNC over fast-fading Rician channels.Especially,the performance can be easily improved in high spatial correlation maritime channel by increasing the memory m.

Enabling Technologies for Agile Maritime Communication Networks

With the rapid development of maritime activities,there has been a growing demand for high data rate and ultra-reliable maritime communications.Traditionally,this is provided by maritime satellites.Besides,shore and island-based base stations(BSs)can be built to extend the coverage of terrestrial networks providing the fourth-generation(4G)or even the fifth-generation(5G)services.Unmanned aerial vehicles(UAVs)-aided and ship-borne BSs can also be exploited to serve as relaying nodes in maritime mesh/ad-hoc networks.Despite all these approaches,there are still open issues towards the establishment of an agile maritime communication network(MCN).

Enabling Technologies for Agile Maritime Communication Networks

With the rapid development of maritime activities, there has been a growing demand for high data rate and ultra-reliable maritime communications. Traditionally, this is provided by maritime satellites. Besides, shore and island-based base stations (BSs) can be built to extend the coverage of terrestrial networks providing the fourth-generation (4G) or even the fifth-generation (5G) services. Unmanned aerial vehicles (UAVs)-aided and ship-borne BSs can also be exploited to serve as relaying nodes in maritime mesh/ad-hoc networks. Despite all these approaches, there are still open issues towards the establishment of an agile maritime communication network (MCN). Different from terrestrial communications for urban or suburban coverage, the MCN faces several challenges due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications. To address all these challenges, conventional communications and networking theories and methods need to be tailored for maritime application scenarios or new ones should be explored. The goal of this feature topic is to present the state-of-the-art original research, and the latest advances and innovations in key theories, technologies, and innovative applications for agile MCNs, as well as identify emerging research topics and point out the future research directions. Extended versions of papers published in conferences, symposiums, or workshop proceedings are encouraged for consideration.

Enabling Technologies for Agile Maritime Communication Networks

With the rapid development of maritime activities, there has been a growing demand for high data rate and ultra-reliable maritime communications. Traditionally,this is provided by maritime satellites. Besides, shore and island-based base stations (BSs) can be built to extend the coverage of terrestrial networks providing the fourth-generation (4G) or even the fifth-generation (5G) services.

Packet Transport for Maritime Communications:A Streaming Coded UDP Approach

The maritime communication network(MCN)plays an important role in the 6th generation(6G)system development.In MCNs,packet transport over long-distance lossy links will be ubiquitous.Transmission control protocol(TCP),the dominant transport protocol in the past decades,have had performance issues in such links.In this paper,we propose a novel transport approach which uses user datagram protocol(UDP)along with a simple yet effective bandwidth estimator for congestion control,and with a proactive packet-level forward erasure correction(FEC)code called streaming code to provide low-delay loss recovery without data retransmissions at all.We show that the approach can effectively address two issues of the state-of-the-art TCP variants in the long-distance lossy links,namely 1)the low bandwidth utilization caused by the slow increase of the congestion window(CWND)due to long roundtrip time(RTT)and the frequent CWND drop due to random and congestion losses,and 2)the high endto-end in-order delivery delay when re-transmissions are incurred to recover lost packets.In addition,we show that the scheme’s goodput has good smoothness and short-term intra-protocol fairness properties,which are beneficial for multimedia streaming and interactive applications that are prominent parts of today’s wireless traffic.

Trajectory Design for UAV-Enabled Maritime Secure Communications:A Reinforcement Learning Approach

This paper investigates an unmanned aerial vehicle(UAV)-enabled maritime secure communication network,where the UAV aims to provide the communication service to a legitimate mobile vessel in the presence of multiple eavesdroppers.In this maritime communication networks(MCNs),it is challenging for the UAV to determine its trajectory on the ocean,since it cannot land or replenish energy on the sea surface,the trajectory should be pre-designed before the UAV takes off.Furthermore,the take-off location of the UAV and the sea lane of the vessel may be random,which leads to a highly dynamic environment.To address these issues,we propose two reinforcement learning schemes,Q-learning and deep deterministic policy gradient(DDPG)algorithms,to solve the discrete and continuous UAV trajectory design problem,respectively.Simulation results are provided to validate the effectiveness and superior performance of the proposed reinforcement learning schemes versus the existing schemes in the literature.Additionally,the proposed DDPG algorithm converges faster and achieves higher utilities for the UAV,compared to the Q-learning algorithm.

From Text to Field:Study on the Intercultural Communication of Music in Collection of Chinese Works and Translations by Matteo Ricci from the Perspective of Maritime Silk Road

In this paper,with Collection of Chinese Works by Matteo Ricci written by Zhu Weizheng and A summary Interpretation of Chinese literature of Matteo Ricci in Ming and Qing Dynasties written by Tang Kaijian as major research texts and historical basis,as well as intercultural communication as the major research method,the aesthetic adaptation of native music of traditional Chinese music,etiquette,sacrifice and religious customs under the description of Matteo Ricci is discussed and interpreted from the perspective of the spread of musical culture of the Maritime Silk Road,four stages of field investigation are planned,and related musical activities and local musical phenomena appearing in his literature have an on-site visit.In this way,the vital position and historical significance of Matteo Ricci’s cultural missionary activities in the music communication on the Maritime Silk Road are obtained.

Commercial Opportunities for Broadband Maritime Satellite Communications in the Era of HTS Satellites

Compared with the ever-changing development and changes of land communications,the development of maritime communications lags behind slightly,particularly on the offshore platform due to the complex and changeable environment,as well as the extremely difficult construction.However,the development of High Throughput Satellite(HTS)has changed the market pattern for traditional satellite communications,and its advanced technology concept ensures the rapid growth of maritime communications business.This article mainly analyzes the demand and current status of maritime satellite communications,discusses and expounds the commercial opportunities HTS satellites will bring to the era of maritime communications satellite.

Cross-cultural Communicative Competence Training in Maritime Spoken English Teaching

As a means of communication,English has been internationalized.Communication in English always happens among the seafarers from different cultures.If crews couldn’t deal with the cultural differences well,successful communication and shipboard safety,which are just what STCW (Standards on Training,Certificate and Watch -keeping) calls upon,are difficult to be arrived at. Therefore cross -cultural communicative competence training,or how to teach maritime spoken English is the problem or the challenge that we,English teachers,are facing.To show how the teaching can be made more efficient and practical so as to narrow the gap between the training of the seaman in China and the requirements of STCW,through the teaching process,including the syllabus design and the materials selecting,we must consider the notion of language function as the key point.

Fairness-Oriented Hybrid Precoding for Massive MIMO Maritime Downlink Systems with Large-Scale CSIT

Different from conventional cellular networks, a maritime communication base station(BS) has to cover a much wider area due to the limitation of available BS sites. Accordingly the performance of users far away from the BS is poor in general. This renders the fairness among users a challenging issue for maritime communications. In this paper, we consider a practical massive MIMO maritime BS with hybrid digital and analog precoding. Only the large-scale channel state information at the transmitter(CSIT) is considered so as to reduce the implementation complexity and overhead of the system. On this basis, we address the problem of fairness-oriented precoding design. A max-min optimization problem is formulated and solved in an iterative way. Simulation results demonstrate that the proposed scheme performs much better than conventional hybrid precoding algorithms in terms of minimum achievable rate of all the users, for the typical three-ray maritime channel model.

A Survey on Heliumspeech Communications in Saturation Diving

With the development of society and the progress of technology,more and more ocean activities are carried out.It results in booming of deep-sea diving.The use of helium-oxygen mixture(as a kind of breathing gas)solves the physiological problems of divers in saturated diving,but it brings about the Heliumspeech voice communication problem,the drop of speech intelligibility.There is no doubt that the effective speech communication must be provided for supporting the life and work of divers in deep-sea.This paper describes the mechanism of forming heliumspeech,discusses the effects of pressure and helium environment on the speech spectrum,compares the pros and cons of the time-domain and frequency-domain unscrambling techniques,shows the challenges in heliumspeech communications.Finally,it briefly introduces the deep learning,and points out that deep learning/machine learning may be a perfectly unscrambling technique.

Hybrid Satellite-UAV-Terrestrial Maritime Networks:Network Selection for Users on A Vessel Optimized with Transmit Power and UAV Position

The hybrid satellite-UAV-terrestrial maritime networks have shown great promise for broadband coverage at sea.The existing works focused on vessels collaboratively served by UAV-enabled aerial base station(ABSs)and terrestrial base stations(TBSs)deployed along the coast,and proved that data rate could be improved by optimizing transmit power and ABS’s position.In practice,users on a vessel can be collaboratively served by an ABS and a vesselenabled base station(VBS)in different networks.In this case,how to select the network for users on a vessel is still an open issue.In this paper,a TBS and a satellite respectively provide wireless backhaul for the ABS and the VBS.The network selection is jointly optimized with transmit power of ABS and VBS,and ABS’s position for improving data rate of all users.We solve it by finding candidates for network selection and iteratively solving transmit power and ABS’s position for each candidate.Simulation results demonstrate that data rate can be improved by collaborative coverage for users on a vessel.

Opportunistic Usage of Maritime VHF Band—Deployment Challenges for a New Regulatory Framework

Similarly to other domains, maritime community requests for broadband services have been significantly increasing. Worldwide navigation footprint and the lack of practical alternatives to Satellite Communications (SATCOM) empower VHF band as the natural choice to support most of those demands. Nevertheless, the major challenge for an implementation of maritime broadband VHF services is unquestionably the spectrum availability and management. Eventually, the solution must include spectrum sharing, using a Cognitive Radio (CR) based approach, but unfortunately current regulatory framework and spectrum management regime are not appropriate for such concepts and emerging technologies. To overcome such constraints, it is necessary to address a whole field of regulatory and standardization issues in order to prepare an evolution towards a more flexible and dynamic approach to spectrum management and a transition that would ensure incumbents live operations and legacy systems. The required paradigm change encompasses a new policy definition, an enforcement mechanism implementation and a comprehensive transition plan. The presented analysis pretends to address the regulatory feasibility of a framework change, discusses its evolving process and points some challenges related with practical aspects associated to Quality of Service (QoS) enforcement metrics definition, centering the arguments in maritime VHF band.

From General Maritime English to Specific Maritime English-Some Thought on the Revision to the 2009 Edition of IMO Maritime English Model Course 3.17

This paper expresses some thought on the revision to the 2009 edition of IMO Maritime English Model Course 3.17. It starts with the changes and challenges that have occurred with the amendments of the STCW Convention at Manila, and goes on with the observations and considerations of the possible principles for the revision. The paper argues that since the requirements and recommendations set in the newly amended convention are more specific, the course should be revised accordingly in correspondence with the specific requirements set and the methodology of the instruction should be adjusted with orientation toward communication competence and specific tasks and duties of the seafarers in English.