An Adaptive Multi-Mode Underwater Acoustic Communication System Using OSDM and Direct Sequence Spread Spectrum Modulation

Lanjun Liu,Hui Ren,Jialin Chen,Junfeng Wang,Jiong Niu,Hao Zhao

doi:10.1109/access.2021.3071416

Abstract

Dynamic underwater acoustic network is a research hotspot. Due to the complexity and time-varying of underwater acoustic channel, the performance of single-mode underwater acoustic communication system is often limited by the worst channel situation. Orthogonal signal division multiplexing (OSDM) is a new signal modulation technology, which can be regarded as a bridge between single carrier modulation and orthogonal frequency division multiplexing (OFDM) modulation. In order to improve the channel adaptive ability of underwater acoustic communication system and obtain a unified architecture of different carrier modulation, an adaptive multi-mode underwater acoustic communication system based on OSDM and direct sequence spread spectrum modulation (AMMUAC/OS) is proposed in this paper. Combined with spread spectrum modulation, the system can realize single carrier time domain spread spectrum (SC-TDSS), single carrier system with cyclic prefix (SC-CP), OSDM, multicarrier frequency domain spread spectrum (MC-FDSS), and OFDM communication system by adjusting the vector length M of OSDM. The addition of a variety of digital mapping methods enables the system to achieve multi-mode communication with a unified architecture. Based on the relationship between the OSDM vector length M and the underwater acoustic channel delay, a joint adaptive decision criterion based on the maximum channel delay and the channel signal-to-noise ratio (SNR) is proposed. Firstly, the OSDM vector length M is determined according to the maximum channel delay, and then the system communication mode is selected according to the channel SNR. Orthogonal matching pursuit (OMP) channel estimation algorithm is used to obtain channel information and minimum mean square error (MMSE) channel equalization algorithm is used for channel compensation. An adaptive multi-mode data frame structure is designed for the interaction between the sender and the receiver. The simulation results show that the proposed AMMUAC/OS can adapt to underwater acoustic channels with different channel delay and SNR.

Highlights

Underwater acoustic communication (UAC) plays a more and more important role in marine environment monitoring, underwater detection, disaster prevention and so on [1], [2]
Considering the development advantages of multi-mode adaptive underwater acoustic communication and the architecture advantages of Orthogonal signal division multiplexing (OSDM) modulation technology, an adaptive multi-mode underwater acoustic communication system based on OSDM and direct sequence spread spectrum (DSSS) modulation (AMMUAC/OS) is proposed in this paper
Based on the performance limitation of single-mode underwater acoustic communication system and the incompatibility of different carrier systems, a series of studies combined with link adaptive method are carried out in this paper

Summary

INTRODUCTION

Underwater acoustic communication (UAC) plays a more and more important role in marine environment monitoring, underwater detection, disaster prevention and so on [1], [2]. The main contribution are as follows: 1) Using the joint modulation of OSDM and DSSS, a novel multi-mode adaptive underwater acoustic communication system with a unified architecture is proposed. Combined with spread spectrum modulation, the system can realize single carrier time domain spread spectrum (SC-TDSS), single carrier system with cyclic prefix (SC-CP), OSDM, multicarrier frequency domain spread spectrum (MC-FDSS), and OFDM modulation modes by adjusting the vector length M of OSDM It meets the requirements of adaptive multi-mode communication of underwater network. The signal modulation mode suitable for the current channel is selected by using the measured channel information and the adaptive decision criterion, which can be described as the appropriate digital mapping, the spread spectrum code length and the OSDM modulation vector length. The digital modulation mapping mode, spread spectrum code length and OSDM vector length can be adjusted to adapt to the current underwater acoustic channel. Where, τ0, τk is the first and the last path delay, respectively

CHANNEL EQUALIZATION

DOPPLER ESTIMATION

CONCLUSION