Evaluation of effects of multipath and co-channel interference on time reversal multiple-input/multiple-output in underwater acoustic channel

Abstract

The relationship between the performance of time-reversal-based multiple-input/multiple-output (MIMO) communication technique and the changes in the multipath environment is investigated quantitatively. In this study, the performance of adaptive time reversal (ATR)-MIMO is investigated by a parametric study approach. The ATR-MIMO communication technique is applied to the multipath-rich synthetic shallow sea acoustic dataset. We focused on discussing about the relationship among the changes in the multipath environment, the number of transmissions, the capability of ATR-MIMO to remove cochannel interference (CCI), and the efficiency of utilization of the energy of the multipath. The results reveal which characteristic of an acousticwavefield affects the performance of ATR-MIMO and how the performance saturates when the multipath environment changes. It is also demonstrated that ATR-MIMO can utilize the energy of the multipath as effectively as the passive-time-reversal-based single-input/multiple-output communication technique in a Gaussian-noise-dominant environment.

Investigation of the Variability Characteristics of Sound Waves Reflected on the Sea Surface Considering Surface Wavelength

“…nication that allows wireless information transmission in water [1][2][3][4] ; however, multipath waves and Doppler effect caused by sound wave propagation in seawater are obstacles against robust and highspeed acoustic communication. In this paper, the characteristics of sea surface reflected wave, which is the main cause of multipath wave, are examined.…”

Experimental demonstration on long-range time-reversal multiple-input/multiple-output underwater acoustic communication over tens of kbps in 12.5 km range

“…For MIMO communication, we utilize the ATR-DFE approach to decompose the signals from the intended transmitters. [15][16][17][18][19][20][21] In ATR, the estimated channel response is altered by an adaptive weight function calculated under the minimum-variance distortion-less response criteria to reduce the co-channel interference from other transmitters while the power from target transmitter is retained. 15,16) The ATR probe in the frequency domain w k ( f ) is given by:…”

“…In stationary condition, nearly ideal performances were demonstrated in past literatures. 20,21) Finally, the ATR process is followed by a single-channel DFE based on the recursive least square algorithm including a single feedback filter, a feedforward filter, and a 2nd order digital phase-locked loop (PLL). The role of the DFE in ATR-DFE scheme is to remove the interference caused by imperfect reciprocal focusing due to time variation and geometric restrictions.…”

“…In past studies, a single carrier system using a time-reversal based processing called adaptive time reversal (ATR) followed by a single channel DFE (ATR-DFE) have also been applied to SDM-MIMO UAC, [15][16][17][18][19][20][21] and their results give us some expectation to improve the communication rate. Specifically, the performance of the tank test for short range (about 20 m) using 5-channel 60 kHz centered transmitters show very high spectral efficiency of 16.7 bps Hz −1 at maximum throughput.…”

Suppression of effects of Doppler shifts of multipath signals in underwater acoustic communication

“…In this process, the signal-to-noise ratio (SNR) is improved by the effective usage of the energies of multipath signals [9]. Recently, applications for multiple-input/multiple-output (MIMO) and multiuser communication with time reversal have been studied [10][11][12][13][14].…”