Feasibility Analysis of Line of Sight (LOS) Underwater Wireless Optical Communications (UWOCs) via Link Budget

Abstract

Optical Wireless Communications (OWCs) are capable of handling large data rate in the Internet of Underwater Things (IoUT) at low latency to be suitable for real time image and video applications. This paper presents communication link feasibility via link budget to determine the link communication range for three types of line-of-sight link configurations: point to point, diffused and modulating retro reflector link. The main aim of this paper studies a more realistic power link budget which is developed to take into account the following: LED Photo Source Lambertian radiation model, Beer Lambert pass loss model that includes absorption and scattering effects of water types, Spherical wave propagation model, photo detector which is modeled by active area model, transmitter projection optics (PO) gain and receiver collection optics (CO) gain. Moreover, this paper considers the effects of aquatic channels ‘scattering and absorption by using IM-DD OOK intensity modulation direct detection, LED and LD –PS based transmitter and SiPM-PD based receiver. The impact of different underwater environment, transmitter and receiver parameters will be investigated on the communication link range. Its range on the order of tens of meters could be achieved by the three link configurations. It is concluded from the analysis; line of sight point to point provides more communication range than diffused line of sight. Diffused line of sight is used when it is required to multicast from a node to several nodes. Modulating retro reflector provides moderate communication range and it is used when one party has more resources than the other one on the communication link. For medium distances, is determined by up to a hundred meter by placing multiple relay nodes between source node and destination node. The communication range is increased as increasing the active physical area of photodetector and transmitted power. The communication range in both clear sea water and clear ocean water is higher turbid water which is less since optical water suffers from higher attenuation. By using the multi hop concept, extended communication link range can be achieved.