Self-interference channel modeling for in-band full-duplex underwater acoustic modem

Abstract

In-band full-duplex (IBFD) underwater acoustic (UWA) communication can significantly improve the throughput of UWA communication networks. In this paper, we focus on the self-interference (SI) channel modeling which is essential for SI cancellation in an IBFD modem. The SI consists of direct self-loop interference (SLI) and self multi-path interference (SMI) due to reflections from water surface and bottom. Therefore, we first propose a simplified finite element model for SLI in an IBFD UWA modem. Then we model the underwater vertical channel to obtain the SMI path loss and propagation delays. Simulation results show that the SLI signal is composed of diffraction and scattering components, and it is greatly affected by the modem housing material and shape. The SLI channel has a long (several tens of ms) impulse response. To verify the proposed model, based on the IBFD UWA communication modem developed by our team, we conducted a lake experiment in December 2019 at Qiandao Lake in Hangzhou, China. The simulated results match well with the experimental results in time/frequency features and transmission loss. This study reveals the complexity of SI channel in IBFD UWA communication.