Research On Routing Approach For Underwater Optical Wireless Communication Networks

Marine resources are extremely rich but to be explored.Communication is an essential link in all kinds of underwater operations.Underwater optical wireless communication(UOWC)technology has attracted more and more attention due to its low energy consumption,high bandwidth,strong anti-interference and other advantages over recent years.However,study on UOWC are mostly focused on physical layer issues but rarely involves the network layer.Routing protocols are crucial in addressing network layer issues in UOWC system.Compared with traditional terrestrial routing protocols,new challenges have been brought because of the special aquatic channel conditions(such as absorption,scattering,ocean turbulence,etc.)and the directional transmission and reception of underwater optical nodes.In addition to modifying the process of route discovery or route maintenance,selecting an appropriate routing metric can also effectively improve routing protocols.Therefore,the routing approach for UOWC is studied in this paper.The major work of the article is as follows:(1)A novel routing metric based on expected transmission count(ETX)which suits the needs of UOWC is proposed,and traditional routing protocol is modified in ns-3 simulator.Comparative simulations using three different routing metrics are designed to analyze the network performance of UOWC networks.Simulation results show that the performance of UOWC network using the novel routing method is significantly improved in terms of throughput,packet delivery rate and end-to-end delay compared with using hop-count or traditional ETX as routing metric.(2)The physical interference model for UOWC is established in ns-3 to simulate underwater environment.Specifically,the underwater attenuation of optical signal is modeled using Beer-Lambert's law,and directing property of optical node is considered as well.Besides,network performance of omnidirectional communication and directional communication in underwater scene is compared and analyzed using ns-3 simulator.The simulation results show that the system performance considering the directivity of optical communication nodes is dramatically improved.