A MODEL OF MARITIME VHF COMMUNICATION SYSTEM FOR DATA EXCHANGE BASED ON OFDM MODULATION

Razmjena podataka između brodova i kopnenih objekata od iznimne je važnosti za potrebe sigurnosti navigacije, kao i za potrebe komercijalnih usluga. Iz tog razloga, u ovome radu su detaljno analizirani postojeći pomorski komunikacijski sustavi za prijenos podataka, u svrhu određivanja smjernica za njihovu nadogradnju, odnosno zamjenu novim komunikacijskim sustavima. Kako u pomorskim VHF komunikacijama nema razvijenog sustava za potrebe prijenosa velikih količina podataka, nužno je primjenom novih tehnologija razviti nove sustave, koji bi modernizirali GMDSS sustav, značajno rasteretili komunikacijske kanale AIS sustava, te postavili smjernice za razvoj komunikacijske infrastrukture strategije IMO-a pod nazivom E-navigacija. Jednu od novih tehnologija predstavlja i digitalna OFDM modulacija, pomoću koje je moguće, korištenjem više valova nosilaca, postići velike brzine prijenosa podataka te visoku spektralnu učinkovitost. U ovome radu sustavno je analizirana navedena tehnologija te su određene prednosti i nedostaci komunikacijskih sustava s OFDM modulacijom u odnosu na sustave s jednim valom nosiocem. Nadalje, izrađeni su analitički i simulacijski modeli pomorskog VHF OFDM komunikacijskog sustava za prijenos podataka unutar pomorskih VHF komunikacijskih kanala. Navedeni komunikacijski kanali, odnosno pojave i fenomeni koji ih karakteriziraju modelirane su Rayleighevom i Riceovom razdiobom vjerojatnosti uz pojavu aditivnog bijelog Gaussovog šuma. Postignuta brzina prijenosa podataka, spektralna učinkovitost sustava te vjerojatnost ili učestalost pojave pogrešnih bitova predstavljaju kriterije na temelju kojih su vrednovani rezultati analitičkog i simulacijskog modela. Rezultati istraživanja pokazali su da se primjenom digitalne OFDM modulacije u pomorskim VHF komunikacijskim sustavima može unaprijediti dosadašnji GMDSS sustav, postizanjem većih brzina prijenosa, a samim time i prenošenjem veće količine podataka.Data exchange between ships and land facilities is of great importance for the safety of navigation and for commercial services. For this reason, a detailed analysis of existing maritime communications systems for data transmission is conducted within this paper in order to determine the guidelines for their upgrade or replacement by new communication systems. Since there is no system in maritime VHF communications for transmitting large amounts of data, it is necessary to employ new technologies and to develop new systems that would modernize the GMDSS system, significantly relieve the AIS communication channels, and set guidelines for development of the communication infrastructure of the IMO strategy called e- Navigation. The digital OFDM modulation is a new technology, by which it is possible, using multiple carrier waves, to achieve high data transmission rates and spectral efficiency. This technology is systematically analyzed, and the advantages and disadvantages of communication systems using OFDM modulation in comparison to single carrier systems are determined in this paper. Furthermore, analytical and simulation models of the maritime VHF OFDM communication system for data transmission within the maritime VHF communication channels are developed. These communication channels, i.e. appearances and phenomena within, are modeled by Rayleigh and Rice probability distributions with the the additive white Gaussian noise. The achieved data rate, the spectral efficiency of the system, and the bit error probability or rate represent the criteria on which the results of the analytical and simulation models are evaluated. The research results showed that the application of the digital OFDM modulation in maritime VHF communications systems can improve current communications within the GMDSS system, achieving higher data transmission rates, and thus enabling transmission of large amounts of data

A MODEL OF MARITIME VHF COMMUNICATION SYSTEM FOR DATA EXCHANGE BASED ON OFDM MODULATION

Razmjena podataka između brodova i kopnenih objekata od iznimne je važnosti za potrebe sigurnosti navigacije, kao i za potrebe komercijalnih usluga. Iz tog razloga, u ovome radu su detaljno analizirani postojeći pomorski komunikacijski sustavi za prijenos podataka, u svrhu određivanja smjernica za njihovu nadogradnju, odnosno zamjenu novim komunikacijskim sustavima. Kako u pomorskim VHF komunikacijama nema razvijenog sustava za potrebe prijenosa velikih količina podataka, nužno je primjenom novih tehnologija razviti nove sustave, koji bi modernizirali GMDSS sustav, značajno rasteretili komunikacijske kanale AIS sustava, te postavili smjernice za razvoj komunikacijske infrastrukture strategije IMO-a pod nazivom E-navigacija. Jednu od novih tehnologija predstavlja i digitalna OFDM modulacija, pomoću koje je moguće, korištenjem više valova nosilaca, postići velike brzine prijenosa podataka te visoku spektralnu učinkovitost. U ovome radu sustavno je analizirana navedena tehnologija te su određene prednosti i nedostaci komunikacijskih sustava s OFDM modulacijom u odnosu na sustave s jednim valom nosiocem. Nadalje, izrađeni su analitički i simulacijski modeli pomorskog VHF OFDM komunikacijskog sustava za prijenos podataka unutar pomorskih VHF komunikacijskih kanala. Navedeni komunikacijski kanali, odnosno pojave i fenomeni koji ih karakteriziraju modelirane su Rayleighevom i Riceovom razdiobom vjerojatnosti uz pojavu aditivnog bijelog Gaussovog šuma. Postignuta brzina prijenosa podataka, spektralna učinkovitost sustava te vjerojatnost ili učestalost pojave pogrešnih bitova predstavljaju kriterije na temelju kojih su vrednovani rezultati analitičkog i simulacijskog modela. Rezultati istraživanja pokazali su da se primjenom digitalne OFDM modulacije u pomorskim VHF komunikacijskim sustavima može unaprijediti dosadašnji GMDSS sustav, postizanjem većih brzina prijenosa, a samim time i prenošenjem veće količine podataka.Data exchange between ships and land facilities is of great importance for the safety of navigation and for commercial services. For this reason, a detailed analysis of existing maritime communications systems for data transmission is conducted within this paper in order to determine the guidelines for their upgrade or replacement by new communication systems. Since there is no system in maritime VHF communications for transmitting large amounts of data, it is necessary to employ new technologies and to develop new systems that would modernize the GMDSS system, significantly relieve the AIS communication channels, and set guidelines for development of the communication infrastructure of the IMO strategy called e- Navigation. The digital OFDM modulation is a new technology, by which it is possible, using multiple carrier waves, to achieve high data transmission rates and spectral efficiency. This technology is systematically analyzed, and the advantages and disadvantages of communication systems using OFDM modulation in comparison to single carrier systems are determined in this paper. Furthermore, analytical and simulation models of the maritime VHF OFDM communication system for data transmission within the maritime VHF communication channels are developed. These communication channels, i.e. appearances and phenomena within, are modeled by Rayleigh and Rice probability distributions with the the additive white Gaussian noise. The achieved data rate, the spectral efficiency of the system, and the bit error probability or rate represent the criteria on which the results of the analytical and simulation models are evaluated. The research results showed that the application of the digital OFDM modulation in maritime VHF communications systems can improve current communications within the GMDSS system, achieving higher data transmission rates, and thus enabling transmission of large amounts of data

A MODEL OF MARITIME VHF COMMUNICATION SYSTEM FOR DATA EXCHANGE BASED ON OFDM MODULATION

Razmjena podataka između brodova i kopnenih objekata od iznimne je važnosti za potrebe sigurnosti navigacije, kao i za potrebe komercijalnih usluga. Iz tog razloga, u ovome radu su detaljno analizirani postojeći pomorski komunikacijski sustavi za prijenos podataka, u svrhu određivanja smjernica za njihovu nadogradnju, odnosno zamjenu novim komunikacijskim sustavima. Kako u pomorskim VHF komunikacijama nema razvijenog sustava za potrebe prijenosa velikih količina podataka, nužno je primjenom novih tehnologija razviti nove sustave, koji bi modernizirali GMDSS sustav, značajno rasteretili komunikacijske kanale AIS sustava, te postavili smjernice za razvoj komunikacijske infrastrukture strategije IMO-a pod nazivom E-navigacija. Jednu od novih tehnologija predstavlja i digitalna OFDM modulacija, pomoću koje je moguće, korištenjem više valova nosilaca, postići velike brzine prijenosa podataka te visoku spektralnu učinkovitost. U ovome radu sustavno je analizirana navedena tehnologija te su određene prednosti i nedostaci komunikacijskih sustava s OFDM modulacijom u odnosu na sustave s jednim valom nosiocem. Nadalje, izrađeni su analitički i simulacijski modeli pomorskog VHF OFDM komunikacijskog sustava za prijenos podataka unutar pomorskih VHF komunikacijskih kanala. Navedeni komunikacijski kanali, odnosno pojave i fenomeni koji ih karakteriziraju modelirane su Rayleighevom i Riceovom razdiobom vjerojatnosti uz pojavu aditivnog bijelog Gaussovog šuma. Postignuta brzina prijenosa podataka, spektralna učinkovitost sustava te vjerojatnost ili učestalost pojave pogrešnih bitova predstavljaju kriterije na temelju kojih su vrednovani rezultati analitičkog i simulacijskog modela. Rezultati istraživanja pokazali su da se primjenom digitalne OFDM modulacije u pomorskim VHF komunikacijskim sustavima može unaprijediti dosadašnji GMDSS sustav, postizanjem većih brzina prijenosa, a samim time i prenošenjem veće količine podataka.Data exchange between ships and land facilities is of great importance for the safety of navigation and for commercial services. For this reason, a detailed analysis of existing maritime communications systems for data transmission is conducted within this paper in order to determine the guidelines for their upgrade or replacement by new communication systems. Since there is no system in maritime VHF communications for transmitting large amounts of data, it is necessary to employ new technologies and to develop new systems that would modernize the GMDSS system, significantly relieve the AIS communication channels, and set guidelines for development of the communication infrastructure of the IMO strategy called e- Navigation. The digital OFDM modulation is a new technology, by which it is possible, using multiple carrier waves, to achieve high data transmission rates and spectral efficiency. This technology is systematically analyzed, and the advantages and disadvantages of communication systems using OFDM modulation in comparison to single carrier systems are determined in this paper. Furthermore, analytical and simulation models of the maritime VHF OFDM communication system for data transmission within the maritime VHF communication channels are developed. These communication channels, i.e. appearances and phenomena within, are modeled by Rayleigh and Rice probability distributions with the the additive white Gaussian noise. The achieved data rate, the spectral efficiency of the system, and the bit error probability or rate represent the criteria on which the results of the analytical and simulation models are evaluated. The research results showed that the application of the digital OFDM modulation in maritime VHF communications systems can improve current communications within the GMDSS system, achieving higher data transmission rates, and thus enabling transmission of large amounts of data

ANALYSIS OF LAND DIGITAL COMMUNICATION SYSTEMS WITH EMPHASIS ON POSSIBLE APPLICATIONS IN THE MARITIME VHF BAND

Uslijed porasta broja korisnika i intenzivnog korištenja frekvencijskog VHF područja javila se potreba za povećanjem njegova kapaciteta. Također, javljaju se i potrebe za novim vrstama usluga, kao što je prijenos podataka, što postojeći analogni sustavi ne mogu uspješno podržati. Stoga su u ovome radu analizirana obilježja relevantnih kopnenih digitalnih komunikacijskih sustava s ciljem utvrđivanja mogućnosti primjene u pomorstvu. Ključni parametri prema kojima je provedena analiza odabrani su na temelju pretpostavke o važnosti istovremenog postojanja analognog i digitalnog načina rada na susjednim kanalima i mogućnosti postepenog uvođenja novog sustava. Analogni način rada potreban je za obavljanje komunikacija pogibelji, hitnosti i sigurnosti zbog njegove robusnosti i rasprostranjenosti. Za moguću primjenu u pomorskom VHF području predloženi su oni sustavi koji postižu visoku spektralnu učinkovitost i koji se uklapaju u postojeće komunikacijske kanale, čime bi se olakšalo njihovo uvođenje.Due to the increase in the number of users and the intensive usage of maritime VHF band, there has been a need to increase the system capacity. Moreover, there is a need for new types of services, such as data transmission, which cannot be supported efficiently by the existing analog systems. Therefore, in this paper the characteristics of relevant land digital communication systems have been analyzed with the aim of identifying possibilities of maritime applications. The key parameters, under which the analysis was conducted, were selected on the basis of the assumption on the importance of coexistence of analog and digital modes of operation on adjacent channels and the possibility for gradual introduction of a new system. The analog mode of operation should be maintained to perform the distress, urgency and safety communications due to its robustness and distribution/prevalence. The systems that achieve high spectral efficiency and fit into the existing communication channels, which would facilitate their introduction, are proposed for the possible application in the maritime VHF band

A Comparative Analysis of Maritime Universities Websites

Nowadays, the Internet, i.e. its leading services like the World Wide Web are unavoidable in communications, providing services and information sharing. Websites and a variety of Internet pages that make up the World Wide Web are the primary user interfaces for online business, providing information and promotional activities on the Internet. The rapid and progressive development of this medium has led to the fact that there is almost no maritime education institution without its own website, or at least a web page. The quality and success of the presentation via the Internet and the development of websites in a way to suit users’ needs still remain a problem, not only for designers and managers but also for owners, representing an incentive for the analysis and research in the field of maritime colleges. In evaluating user interfaces, including websites, different approaches and methods are used where the usability, due to its widespread use, is most often considered as the main factor of quality. In this paper, usability factors of websites are analyzed using the questionnaire method and available online tools for 20 maritime universities worldwide and the obtained results are presented as well as recommendations for further researches

Nature Inspired Metaheuristics for Optimizing Problems at a Container Terminal

Nowadays, maritime transport is the backbone of the international trade of goods. Therefore, seaports play a very important role in global transport. The use of containers is significantly represented in the maritime transport. Considering the increased number of container shipments in the global transport, seaport container terminals have to be adapted to a new situation and provide the best possible service of container transfer by reducing the transfer cost and the container transit time. Therefore, there is a need for optimization of the whole container transport process within the terminal. The logistic problems of the container terminals have become very complex and logistics experts cannot manually adjust the operations of terminal processes that will optimize the usage of resources. Hence, to achieve further improvements of terminal logistics, there is a need to introduce scientific methods such as metaheuristics that will enable better and optimized use of the terminal resources in an automated way. There is a large number of research papers that have successfully proposed the solutions of optimizing the container logistic problems with well-known metaheuristics inspired by the nature. However, there is a continuous emergence of new nature inspired metaheuristics today, like artificial bee colony algorithm, firefly algorithm and bat algorithm, that outperform the well-known metaheuristics considering the most popular optimization problems like travel salesman problem. Considering these results of comparing algorithms, we assume that better results of optimization of container terminal logistic problems can be achieved by introducing these new nature inspired metaheuristics. In this paper we have described and classified the main subsystems of the container terminal and its logistic problems that need to be optimized. We have also presented a review of new nature inspired metaheuristics (bee, firefly and bat algorithm) that could be used in the optimization of these problems within the terminal

ANALYSIS OF LAND DIGITAL COMMUNICATION SYSTEMS WITH EMPHASIS ON POSSIBLE APPLICATIONS IN THE MARITIME VHF BAND

Uslijed porasta broja korisnika i intenzivnog korištenja frekvencijskog VHF područja javila se potreba za povećanjem njegova kapaciteta. Također, javljaju se i potrebe za novim vrstama usluga, kao što je prijenos podataka, što postojeći analogni sustavi ne mogu uspješno podržati. Stoga su u ovome radu analizirana obilježja relevantnih kopnenih digitalnih komunikacijskih sustava s ciljem utvrđivanja mogućnosti primjene u pomorstvu. Ključni parametri prema kojima je provedena analiza odabrani su na temelju pretpostavke o važnosti istovremenog postojanja analognog i digitalnog načina rada na susjednim kanalima i mogućnosti postepenog uvođenja novog sustava. Analogni način rada potreban je za obavljanje komunikacija pogibelji, hitnosti i sigurnosti zbog njegove robusnosti i rasprostranjenosti. Za moguću primjenu u pomorskom VHF području predloženi su oni sustavi koji postižu visoku spektralnu učinkovitost i koji se uklapaju u postojeće komunikacijske kanale, čime bi se olakšalo njihovo uvođenje.Due to the increase in the number of users and the intensive usage of maritime VHF band, there has been a need to increase the system capacity. Moreover, there is a need for new types of services, such as data transmission, which cannot be supported efficiently by the existing analog systems. Therefore, in this paper the characteristics of relevant land digital communication systems have been analyzed with the aim of identifying possibilities of maritime applications. The key parameters, under which the analysis was conducted, were selected on the basis of the assumption on the importance of coexistence of analog and digital modes of operation on adjacent channels and the possibility for gradual introduction of a new system. The analog mode of operation should be maintained to perform the distress, urgency and safety communications due to its robustness and distribution/prevalence. The systems that achieve high spectral efficiency and fit into the existing communication channels, which would facilitate their introduction, are proposed for the possible application in the maritime VHF band

COMPARISON OF SIGNAL QUALITY OF PRESENT AND ALTERNATIVE MARITIME VHF COMMUNICATION SYSTEMS

U radu je provedena analiza postojećeg širokopojasnog i alternativnog uskopojasnog komunikacijskog sustava pomorskih VHF radiotelefonskih komunikacija, zasnovanih na simulacijskom modelu. Alternativni sustav predložen je od strane ITU organizacije kao jedno od mogućih rješenja problema nedostatka komunikacijskih kanala u pomorskom VHF području. Pomoću računalnih simulacijskih modela ispitan je utjecaj promjene modulacijskog postupka u pomorskim VHF radiotelefonskim komunikacijama na kvalitetu prenesene informacije, uvažavajući sve relevantne tehničke karakteristike pomorskih VHF radiotelefonskih uređaja. Postupak ocjenjivanja kvalitete govornih signala proveden je uz pomoć tehnologije objektivnog ocjenjivanja kvalitete upotrebom računalnog programa koji provodi PESQ (Perceptual Evaluation of Speech Quality Measurement) algoritam čime je osigurana usporedivost dobivenih rezultata s tradicionalnim subjektivnim načinom ocjenjivanja kvalitete signala. Postupak ocjenjivanja kvalitete proveden je upotrebom četiri standardizirana uzorka govornih signala s različitim utjecajem vanjskih smetnji na komunikacijski kanal. Analiza dobivenih rezultata potvrđuje mogućnost korištenja alternativnog komunikacijskog sustava.This paper presents an analysis, based on the simulation model, of the existing broadband and alternative narrowband maritime VHF radiotelephone communication systems. The alternative system proposed by the ITU organization is one of the possible solutions to the lack of communication channels in the maritime VHF bands. The influence of changes in the modulation process on the quality of information in the maritime VHF radiotelephone communications is examined using a computer simulation model taking into account all the relevant technical characteristics of maritime VHF radiotelephone equipment. The process of evaluating the quality of speech signals was carried out by means of an objective quality assessment technology using a computer program that implements PESQ algorithm which ensures the comparability of obtained results with the traditional method of subjective evaluation of signal quality. The process of quality assessment was conducted using four standardized sample voice signals with different influences of external interference on the communication channel. Analysis of the results confirms the possibility of using alternative communication systems

COMPARISON OF SIGNAL QUALITY OF PRESENT AND ALTERNATIVE MARITIME VHF COMMUNICATION SYSTEMS

U radu je provedena analiza postojećeg širokopojasnog i alternativnog uskopojasnog komunikacijskog sustava pomorskih VHF radiotelefonskih komunikacija, zasnovanih na simulacijskom modelu. Alternativni sustav predložen je od strane ITU organizacije kao jedno od mogućih rješenja problema nedostatka komunikacijskih kanala u pomorskom VHF području. Pomoću računalnih simulacijskih modela ispitan je utjecaj promjene modulacijskog postupka u pomorskim VHF radiotelefonskim komunikacijama na kvalitetu prenesene informacije, uvažavajući sve relevantne tehničke karakteristike pomorskih VHF radiotelefonskih uređaja. Postupak ocjenjivanja kvalitete govornih signala proveden je uz pomoć tehnologije objektivnog ocjenjivanja kvalitete upotrebom računalnog programa koji provodi PESQ (Perceptual Evaluation of Speech Quality Measurement) algoritam čime je osigurana usporedivost dobivenih rezultata s tradicionalnim subjektivnim načinom ocjenjivanja kvalitete signala. Postupak ocjenjivanja kvalitete proveden je upotrebom četiri standardizirana uzorka govornih signala s različitim utjecajem vanjskih smetnji na komunikacijski kanal. Analiza dobivenih rezultata potvrđuje mogućnost korištenja alternativnog komunikacijskog sustava.This paper presents an analysis, based on the simulation model, of the existing broadband and alternative narrowband maritime VHF radiotelephone communication systems. The alternative system proposed by the ITU organization is one of the possible solutions to the lack of communication channels in the maritime VHF bands. The influence of changes in the modulation process on the quality of information in the maritime VHF radiotelephone communications is examined using a computer simulation model taking into account all the relevant technical characteristics of maritime VHF radiotelephone equipment. The process of evaluating the quality of speech signals was carried out by means of an objective quality assessment technology using a computer program that implements PESQ algorithm which ensures the comparability of obtained results with the traditional method of subjective evaluation of signal quality. The process of quality assessment was conducted using four standardized sample voice signals with different influences of external interference on the communication channel. Analysis of the results confirms the possibility of using alternative communication systems

An Overview of Recent Changes in the Global Maritime Distress and Safety System Regarding Maritime Mobile Satellite Service

For a long time, Inmarsat satellite system was the only maritime mobile satellite service provider when Global Maritime Distress and Safety System (GMDSS) is concerned. This satellite system has different generations of its satellites providing a wide range of services and applications. In 2018, its services related to the GMDSS have migrated to a newer generation of satellites. This satellites’ services migration is systematically discussed and analysed in this paper in order to familiarize the readers with its effects on the safety of navigation. Furthermore, Inmarsat system announced a new service called Inmarsat Fleet Safety which will incorporate and provide all functional requirements for the GMDSS which are currently provided by Inmarsat-C and Inmarsat Fleet 77 terminals. However, in 2018 a new satellite system called Iridium has been recognized as a mobile satellite communication services provider in the GMDSS. Accordingly, this system and its capabilities are also introduced and briefly described in this paper. In addition, authors have discussed impacts of the introduction of the new satellite system as a service provider in the GMDSS and addressed several emphasized issues related to this GMDSS modernization