Connectivity Analysis of Underwater Optical Wireless Sensor Networks: A Graph Theoretic Approach

摘要

As an alternative to low rate and high latency acoustic systems, underwater optical wireless sensor network (UOWSN) is a promising technology to enable high speed and low latency underwater communications. However, the aquatic medium poses significant challenges for underwater optical wireless communications (UOWC) such as higher absorption, scattering, ambient noise, and turbulence impairments of seawater. These severe impairments yield very limited transmission ranges and necessitate multihop transmissions to expand communication ranges and enhance the network connectivity. Therefore, one needs to take some crucial design parameters into account in order to achieve a fully connected multihop UOWSN (MH-UOWSN). Unlike the omnidirectional wireless network, one of the most distinctive features of UOWSN is transmission occurs only within a directed beam sector. Therefore, we model an MH-UOWSN as a randomly scaled sector graph where connection among the nodes is established by point-to-point directed links. Thereafter, the probability of network connectivity is analytically derived as a function of communication range, network density, and beam-width. Throughout the extensive simulations, we demonstrate that the probability of an obscured/isolated node strongly depends on these three parameters and the upper bound for network connectivity is achieved at larger beam-widths and dense deployments. The proposed work provides a practical method for effective selection of the physical layer design parameters of MH- UOWSNs.