A Centralized Cross-Layer Protocol for Joint Power Control, Link Scheduling, and Routing in UWSNs

The characteristics of volatile ocean environments and complex acoustic communication channels have posed great difficulties to the design of real-time data transmission in underwater wireless sensor networks (UWSNs). In this article, we develop a centralized cross-layer protocol that mitigates network interference and maximizes concurrent transmissions to reduce end-to-end delay. Instead of optimizing individual layers separately, we blend the traditional layered architecture and combine the physical layer, medium access control (MAC) layer, and network layer functions together. Specifically, we optimize the power control in the physical layer, link scheduling in the MAC layer, and routing in the network layer jointly to achieve a global optimization of end-to-end delay. First, the joint design problem is formulated as a mixed-integer linear programming (MILP) problem, which is an NP-hard problem and hard to solve mathematically. Then, we propose a bio-inspired-algorithm-based solution, namely, the discrete improved artificial bee colony (DIABC) algorithm, aiming at finding an approximate optimal cross-layer scheduling scheme. To further reduce end-to-end delay, we optimize the uplink frame structure and routing metric in the centralized cross-layer framework. The simulation results show that the proposed protocol achieves network performance improvement in terms of end-to-end delay, service rate, and energy consumption.