Research On The Relationship Between GMDSS Modernization And E-Navigation Strategy Based On The Requirements Of Video Transmission

The e-Navigation strategy is one of the most important strategy of the International Maritime Organization.Its aim is to improve the safety of maritime navigation.e-Navigation puts forward higher requirements for collecting,sharing,integrating and displaying data on marine safety.Its key is information technology.Global Maritime Distress and Safety System(GMDSS)provides plans in case of distress,emergencies,safety and standard communication.It is the main communication platform used for ship-shore and ship-ship information sharing.In order for it to co-evolve with the e-Navigation strategy,the International Maritime Organization established the GMDSS Review and Modernization manual in April of 2008.This study aims to analyze the e-Navigation strategy's developmental needs,to clearly state the bottlenecks that hinder this strategy's development and to explore the direction in which the GMDSS will modernize.Bandwidth is a measurement of quality for the transmission channels used for ship-shore and ship-ship long-distance information sharing.A broad bandwidth is the main developmental bottleneck of e-Navigation strategy.Video transmission is widely used in many fields such as in the safety of maritime navigation,in the security of such navigation and in treating medical emergencies during such navigation.It also has significant meaning for the e-Navigation strategy.Video transmission has the advantage of being timely,being able to offer a rich amount of information and being able to let the receiver be aware of the surroundings.At the same time,its big occupied bandwidth and its need for a high signal-to-noise ratio.To overcome past studies'problems of failing to highlight key issues and having unclear lines,among others,we began by studying video transmission's need for a broad bandwidth.We further narrowed our focus down to studying the relationship between the signal-to-noise ratio and bit error rate as well as people's perception of information under different signal-to-noise ratios.The aim is to transmit standard high definition videos.It was determined that the information source uses a 720P video file compressed by the H.265 encoding standard.Based on the video the Matlab platform obtained after reading the code,the video was converted into a code stream format and was transmitted.Considering the characteristics of the environment under which information is shared at sea,the channel model was used to simulate sea surface diffuse reflection,the Gaussian channel model was used simulate noise interference and the Doppler frequency shift model was used to simulate ship motion.Finally,the binary convolutional code was used to complete channel coding to enhance the signal's error correction capabilities.After the compressed file is transmitted using a model that simulates information sharing at sea,it was decoded by the Viterbi decoding method.By using the method of finding the maximum likelihood path,the error correction capability was increased by a certain extant.Based on Matlab simulation platform's count of code errors during video transmission,we compared the quality between the video from the information source end and the video from the receiving end.The relationship between signal-to-noise ratio and the bit error rate was graphed.Based on the graph,the portion of signal-to-ratios with a bit error rate between 10-4-10-5 was selected and the signal-to-noise accuracy was improved.30 trusted people were then instructed to offer their subjective opinion based on the SPSS statistical analysis platform's calculations of the signal-to-noise ratio interval of videos of various qualities.Study shows,in marine environment,when the bit error rate is zero,the information channel's signal-to-noise rate is greater than 21.6dB;when the bit error rate is around 10'5,the signal-to-noise ratio is around 20dB;the selected people were more willing to accept if the signal-to-noise ratio is greater than 19.4dB.The current GMDSS modernization can transmit a video up to 451×803 pixels.When the Ka band is enabled in the Inmarsat and Iridium systems,the channel requirements previously estimated can be met.That is,the 720P video transmission at sea is completed with a 19.4dB signal-to-noise ratio,From studying the requirements of wireless long-distance video transmission,the following conclusion was made:GMDSS should include follow stage:primary-modernization of GMDSS,quasi-modernization of GMDSS,ultimate-modernization of GMDSS.Currently,the modernization is of the primary stage,meaning that,it can only support the e-Navigation strategy at a low level.With the quasi-modernization phase of GMDSS,the e-Navigation strategy's demand will be satisfied.Along with many others,the concepts of GMDSS system distress alert and double-set equipment need to be abandoned.A more diversified communication strategy needs to be found for ships sailing near shorelines,near the coastal regions and in the open oceans.The ultimate modernization of GMDSS is a constantly evolving process,and it will resolve the problem of having to use a broad bandwidth,which will gradually resolve the issue of information transmission delay and gradually increase the reliability of transmitted information and transmission channels.All of this will provide support for the development of smart ships.