Mobile underwater acoustic communication with orthogonal signal division multiplexing under inter-carrier interference larger than a guardband

Abstract

Underwater acoustic (UWA) communication is a key technology providing wireless communication, but using UWA channels is challenging due to the existence of large Doppler and delay spreads. UWA channels also have long but sparse reverberation tails. To address these issues simultaneously, we have proposed Doppler-resilient orthogonal signal division multiplexing using compressed sensing (D-OSDM-CS). The optimization of compressed sensing (CS) under a large Doppler spread remains difficult since noise induced by inter-carrier interference (ICI) is present in the received signal. Herein, we mathematically clarify the effect of ICI-induced noise on the received signal, and we propose an advanced D-OSDM-CS method that can measure ICI-induced noise and optimize the regularization parameter of CS. We also evaluate the performance of the advanced D-OSDM-CS in simulations and experiments. The obtained results suggest that the advanced D-OSDM-CS achieves better communication quality than the existing D-OSDM-CS under a large-Doppler-spread environment.

Underwater acoustic communication using orthogonal signal division multiplexing with windowing

“…Table III shows the number of error-free data blocks of D-OSDM with and without windowing and of advanced D-OSDM-CS (previous study). 49) D-OSDM with and without windowing has 671 and 430 error-free data blocks when the Tx-Rx distance is 50-600 m, respectively; the number with windowing is thus 56% larger than that without. When the distance is 50-100 m, there are 334 and 182 error-free blocks with and without windowing.…”

“…The Tx transmits a message as follows. Note that signal processing procedures 1-3 in the Tx and 2-3 in the Rx are the same as in the previous D-OSDM 43,[45][46][47][48][49][50] and that processing procedure 1 in the Rx is newly introduced in this study.…”

“…The simulation system is the same as that used in our previous studies. 48,49) Figure8 shows the simulation environment, which is a shallow-water field whose depth is 40 m. The Tx and RX are set at depths of 2 m and 12 m, respectively. The Rx is fixed and the Tx moves at a velocity of 2 m s −1 between the Tx and Rx, the distance between which becomes 50-600 m. The Rx uses two hydrophones (R = 2).…”

“…The experimental data are the same as those used in our previous studies. 48,49) Figure 10 shows the experimental environment and apparatus. The experimental environment is almost the same as the simulation environment in Sect.…”

“…48) Moreover, in 2021 we proposed an advanced D-OSDM-CS that can improve communication quality by optimizing the regularization parameter of CS even when the Doppler spread is larger than the guardband (an unused part of the signal spectrum between a pilot and message signals to prevent them from interfering with each other). 49) However, the communication quality of D-OSDM has room for improvement, as follows. In D-OSDM, the UWA channel is modeled by the basis expansion model (BEM), where the effects of delay and Doppler spreads are expressed by discrete matrices.…”