Full-Duplex Cognitive Underwater Acoustic Communications: Concept and Challenges

Full-duplex cognitive underwater acoustic communication (FDCUAC) research has not been accessed so far, but has the merits between cognitive underwater acoustic communications (CUACs) and full-duplex underwater acoustic communications (FDUACs). Broadly speaking, FDCUACs employ the full duplex and spectral sensing method mainly, which improve the performance of the CUACs and FDUACs. However, it will also meet some challenges, such as how to achieve spectrum sensing over the non-Gaussian behaviour of ocean background noise, the hardware imperfection and power constraint of the underwater acoustic communication facilities, stochastic communication among sea creatures, and uncertain conditions underwater acoustic communications. Above all, this paper will introduce new ideas with great potential for the FDCUACs, especially in available enough spectrum but no influence on marine environment and system enhancements, and identify key future research challenges.