Resource Allocation for Cognitive Underwater Acoustic Downlink OFDMA System With a Practical Spectrum Sensing Scheme

In response to the increasing demand for marine data transmission, underwater acoustic (UWA) communication is widely recognized as a key technology to support various applications of the Internet of Underwater Things (IoUT). However, due to the narrow bandwidth shared by multiple acoustic systems and the constrained energy of the underwater nodes, it is an urgent problem to design an energy-efficient resource allocation scheme which can avoid interference simultaneously. In this article, we establish a cognitive orthogonal frequency-division multiple access (OFDMA) UWA communication system, where dynamic resource allocation relies on the feedback channel state information (CSI) and spectrum usage of interference. In order to detect interference, a spectrum sensing scheme applicable to the underwater environment is proposed and experimentally verified. Subsequently, the resource allocation problem is mathematically modeled with energy efficiency (EE) as the reasonable optimization objective in UWA communication systems. In order to reduce the computational complexity, the original problem is decomposed into two subproblems and a low-complexity algorithm named acrlong BOSC- acrlong TLI is developed for feasible solutions. Simulation and sea experiment results show that the proposed algorithm outperforms the existing underwater resource allocation schemes.