Joint power allocation for multiple nodes in serial relaying networks over underwater wireless optical channels

Abstract

Underwater wireless optical communications (UWOC) suffer from severe path loss and limited communication range due to the multifarious oceanic channel impairments. Serial relaying could expand the end-to-end transmission distance, while its joint power allocation for multiple nodes is an intractable problem. To this end, this paper proposes a fitting-based joint power allocation algorithm for multiple nodes in serial relaying UWOC, which consists of two phases including the fitting-based global pre-allocation and bisection search method-based partial optimization. Specifically, the serial relaying for UWOC is modeled, where the combined effects of absorption, scattering, and oceanic turbulence are all taken into account. The joint power allocation algorithm for multiple nodes is formulated to minimize the outage probability under the constraint of total transmitted power. To solve this problem, a fitting-based scheme is proposed to pre-allocate the power for all nodes, which could implement the global pre-allocation. Subsequently, to further reduce the outage probability, we design a partial optimization scheme, where a bisection search method is proposed to optimize the partial two-hop links. Simulation results demonstrate that the proposed scheme achieves better performance in the decrease of the outage probability compared with the existing schemes for the serial relaying UWOC.