An Underwater Acoustic Implementation of DFT-Spread OFDM

Yonghuai Zhang,Weijie Shen,En Cheng,Haixin Sun

doi:10.1155/2010/572453

Abstract

This paper presents a design of DFT-spread OFDM system applied to an underwater acoustic channel. It does not only combine all the advantages of a conventional OFDM system but also reduces the peak-to-average power ratio of the transmit signal. Besides, the scheme spreads the information over several subcarriers as a result of the application of an additional DFT operation and leads to a diversity gain in a frequency-selective fading channel, which is one of the many challenges of communicating data through an underwater acoustic channel. Simulation results show that our proposal possesses good bit-error-rate performance. The system has been tested in a real underwater acoustic channel—the experimental pool in Xiamen University. The experimental results show that the DFT-spread OFDM system can achieve better results than a simple OFDM system in a benign underwater channel.

Highlights

Underwater acoustic channels are considered to be “quite possibly nature’s most unforgiving wireless medium” [1]
This paper presents a design of DFT-spread orthogonal frequency division multiplexing (OFDM) system applied to an underwater acoustic channel
The OFDM system suffers a number of drawbacks, one of them is high peak-to-average power ratio, since the OFDM systems transmit signal resulting from the superposition of a large number of independent data symbols [5, 6]

Summary

Introduction

Underwater acoustic channels are considered to be “quite possibly nature’s most unforgiving wireless medium” [1]. Compared with conventional OFDM systems, the DFT-spread OFDM leads to a diversity gain in frequencyselective channel, and it combines the advantages of singlecarrier transmission, like constant signal envelope, simple clock, and frequency synchronization [15]. As such it has already been selected as the uplink modulation scheme for the upcoming Long-Term Evolution of 3G systems under the work item of Evolved-UTRA by 3GPP [16]. Simulation results of the DFT-spread OFDM and OFDM systems under Rayleigh fading channel conditions are given in Section 4, as well as the experiment results in experimental pool of Xiamen University, China

System Model

Channel Estimation

Simulation and Experiment Results

Conclusions