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Wireless Channel Models for Over-The-Sea Communication: a Comparative Study

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applied sciences Review Wireless Channel Models for Over-the-Sea Communication: A Comparative Study Arafat Habib and Sangman Moh * Department of Computer Engineering, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea; [email protected] * Correspondence: [email protected]; Tel.: +82-62-230-6032 Received: 18 December 2018; Accepted: 21 January 2019; Published: 28 January 2019 Abstract: Over the past few years, the modeling of wireless channels for radio wave propagation over the sea surface has drawn the attention of many researchers. Channel models are designed and implemented for different frequencies and communication scenarios. There are models that emphasize the influence of the height of the evaporation duct in the marine environment, as well as models that deal with different frequencies (2.5, 5, and 10 GHz, etc.) or the impact of various parameters, such as antenna height. Despite the increasing literature on channel modeling for the over-the-sea marine environment, there is no comprehensive study that focuses on key concepts that need to be considered when developing a new channel model, characteristics of channel models, and comparative analysis of existing works along with their possible improvements and future applications. In this paper, channel models are discussed in relation to their operational principles and key features, and they are compared with each other in terms of major characteristics and pros and cons. Some important insights on the design and implementation of a channel model, possible applications and improvements, and challenging issues and research directions are also discussed. The main goal of this paper is to present a comparative study of over-the-sea channel models for radio wave propagation, so that it can help engineers and researchers in this field to choose or design the appropriate channel models based on their applications, classification, features, advantages, and limitations. Keywords: over-the-sea communication; radio wave propagation; wireless channel; channel model; wireless channel characterization 1. Introduction Wireless channels for the radio wave propagation over the sea surface are different from the usual channels used in ground-to-ground wireless communication due to the unique nature of the marine environment. For example, neither the refraction of wave propagation, nor the effect of the evaporation duct is present in the ground-to-ground scenarios. Existing approaches to the modeling of over-the-sea channels vary with frequencies, technology used, and implementation scenario. While some approaches used millimeter waves and wide band technology, others used frequencies such as 1.9, 2, and 10 GHz, etc. Some approaches considered vessel-to-vessel mobile communication on the sea. Ship-to-ship and ship-to-shore wireless communication scenarios were also considered and implemented. So far, there are two preliminary minor approaches [1,2], that briefly describe a few models of channels for over-the-sea communication; however, with inadequate analysis and limited discussion on various models, applications, future improvements, and research directions. Readers can prompt references [1,2] for further details. Typically, the over-the-sea wave propagation environment can be divided into two types: One is “near the sea surface” and the other is “hundreds of meters above Appl. Sci. 2019, 9, 443; doi:10.3390/app9030443 www.mdpi.com/journal/applsci Appl. Sci. 2019, 8, x FOR PEER REVIEW 2 of 32 Appl. Sci. 2019, 9, 443 2 of 32 Appl. Sci. 2019, 8, x FOR PEER REVIEW 2 of 32 sea surface or higher.” In the near the sea surface environment, the transceiver platform remains close seatothe the surface sea sea surface surface.or higher.” or higher.” For In example, the In near the nearthecommunication sea the surface sea surface environment, between environment, a ship the transceiverand the a transceiver base platform station platform isremains maintained remains close toashore.close the tosea Figure the surface. sea 1 surface. shows For suchexample, For example,a scenario communication communication when communication between between a shipoccurs a ship and near and a baseathe base sea station station surface. is is maintained maintained ashore. Figure 1 shows such a scenario when communication occurs near the sea surface. ashore. Figure1 shows such a scenario when communication occurs near the sea surface. Figure 1. Radio wave propagation near the sea surface. FigureFigure 1. 1. RadioRadio wave wave propagation propagation near near the the sea sea surface. surface. 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Two- Two- of andthe and paper. three-ray three-ray models models of waveof wave propagation propagation will will be furtherbe further discussed discussed in thein theupcoming upcomingIn a scenario sections sections where of theof wireless the paper. paper. transmission takes place hundreds of meters above the sea surface, the transceiverInIn a a scenario scenario is wheredeployed where wireless wireless on an transmission transmission airborne device takes takes or pl place aceplatforms, hundreds hundreds such of of metersas meters unmanned above above the theaerial sea sea vehiclessurface, surface, the(UAVs)the transceiver transceiver or any otheris is deployed deployed aircrafts. on on It an anis airbornepossible airborne fordevice device the elevatedor or platforms, platforms, duct suchin such the as astroposphere unmanned unmanned regionaerial aerial tovehicles vehicles cause (UAVs)an(UAVs) attenuation or any otherotherof the aircrafts.aircrafts. signal It Itand isis possiblepossible affect for forair-to-ground the the elevated elevated ductcommunication duct in in the the troposphere troposphere through region regionthe tosea to cause causewave an anpropagation.attenuation attenuation of The theof elevated signalthe signal and duct affect andis an air-to-ground affectatmospheric air-to-ground communicationcanal that communication consists through of a layer thethrough seawith wave highly the propagation. sea dense wave air propagation.[4].The It elevated starts and The duct remains elevated is an atmospheric at highduct altitudesis an canal atmospheric and that mainly consists canal affects of that a layer transmission consists with of highly a withlayer
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