Digital Self-Interference Cancellation for Asynchronous In-Band Full-Duplex Underwater Acoustic Communication

Abstract

To improve the throughput of underwater acoustic (UWA) networking, the In-band full-duplex (IBFD) communication is one of the most vital pieces of research. The major drawback of IBFD-UWA communication is Self-Interference (SI). This paper presents a digital SI cancellation algorithm for asynchronous IBFD-UWA communication system. We focus on two issues: one is asynchronous communication dissimilar to IBFD radio communication, the other is nonlinear distortion caused by power amplifier (PA). First, we discuss asynchronous IBFD-UWA signal model with the nonlinear distortion of PA. Then, we design a scheme for asynchronous IBFD-UWA communication utilizing the non-overlapping region between SI and intended signal to estimate the nonlinear SI channel. To cancel the nonlinear distortion caused by PA, we propose an Over-Parameterization based Recursive Least Squares (RLS) algorithm (OPRLS) to estimate the nonlinear SI channel. Furthermore, we present the OPRLS with a sparse constraint to estimate the SI channel, which reduces the requirement of the length of the non-overlapping region. Finally, we verify our concept through simulation and the pool experiment. Results demonstrate that the proposed digital SI cancellation scheme can cancel SI efficiently.

Digital Self-Interference Cancellation for Full-Duplex Underwater Acoustic Systems

“…To maximise the capacity of the acoustic links, we consider full-duplex (FD) communications, when a transceiver simultaneously transmits and receives data in the same frequency band [3]- [5]. The main challenge of achieving FD communication is the strong self-interference (SI) introduced by the near-end transmission [6]- [11]. Due to the high transmission power of the near-end data, we expect to deal with a high level of SI, which can be 100 dB higher than the noise floor in some communication scenarios.…”

“…This design achieves around 30 dB of digital SI cancellation with a multipath SI channel model. The recent work [11] proposes a sparse adaptive algorithm for estimation of the SI channel and PA nonlinearity, but the cancellation performance is limited. One approach to dealing with the PA nonlinearity without developing a high complexity digital SI canceller is to use the PA output as a reference signal [20].…”

A Novel Self-Interference Cancellation Method Using an Optimized LMS Algorithm in CCFD Systems for a 5G Communication Network

“…The main mathematical principle of RF cancellation in a CCFD system is the composition of vectors [31]. The following notation is utilized in developing a mathematical model for the problem of SI cancellation in the RF domain addressed in this paper: s(t) is the near-end transmitting signal, s i (t) is the same phase component as s(t), s q (t) is the orthogonal component obtained by s i (t) through a 90 degree phase shifter, r 1 (t) is the estimated SI signal, r(t) is the near-end receiving signal, and e(t) is the error signal.…”

Adaptive Filtering for Full-Duplex UWA Systems with Time-Varying Self-Interference Channel

“…For FD UWA systems, due to the lower frequencies of acoustic signals, high resolution ADCs are available. Thus, digital cancellation can be considered as the main practical approach for SI cancellation in FD UWA systems [8], [9].…”

“…A general approach to deal with the PA non-linearity is to estimate the non-linear distortion, e.g. using the Hammerstein model and its extensions, and then compensate it in the received signal [5], [8], [11]. To accurately model the non-linearity, high order basis functions are required.…”