Digitally Assisted Analog Self-interference Cancellation for In-band Full-duplex Underwater Acoustic Communication

In-Band Full-Duplex (IBFD) Underwater Acoustic (UWA) communication technology can transmit and receive communication signals in the same frequency band at the same time. Theoretically, its frequency utilization efficiency can reach twice of the traditional half-duplex (HD) UWA communication systems. Therefore, it holds great research significance and application value for UWA communication where available spectrum resources are seriously limited. The main challenge in the implementation of IBFD-UWA communication system is to counteract the local self- interference (SI) signal. Generally, SI cancellation (SIC) can be divided into three main aspects, namely, SI suppression in space, SIC in analog domain and digital domain. Digitally Assisted Analog SIC (DAA-SIC) is concerned as it can deal with complexSI propagation channel. However, in the implementation process of the DAA-SIC scheme, its performance will be affected by hardware conditions, such as the effective number of bits of analog to digital converter (ADC) of auxiliary acquisition link, non-linear distortion of power amplifier (PA) and so on. To deal with the influence of hardware parameters on the performance of DAA-SIC scheme, this paper proposes a new analog SIC scheme. The core of this scheme is to reconstruct the output signal of PA and reduce the non-linear distortion of power amplifier and the influence of effective number of bits of auxiliary link through Memory Polynomial (MP) model and Digital Pre- Distortion (DPD) process. The performance of the existing scheme and the new DAA-SIC scheme is verified by numerical simulation. The simulation results show the effectiveness of the proposed scheme.