Efficient communication over highly spread underwater acoustic channels

Abstract

In this paper we propose a novel method for communication over underwater acoustic channels for which the product of delay-spread and Doppler-spread is large, such as those pertaining to the surf zone. In particular, we propose the use of pulse-shaped multicarrier modulation to convert the doubly dispersive channel into an inter-carrier interference (ICI) channel with small ICI spread. We then propose a novel joint ICI-estimation/data-detection strategy which performs near optimally yet at low complexity, due to the use of an efficient tree search algorithm and the ability to leverage sparseness in the delay-power profile. The delay-power profile, which itself varies in time, can be readily tracked via pilots. Numerical simulations show that our technique gives performance close to genie-aided bounds over highly spread channels.

Efficient Multicarrier Communication for Highly Spread Underwater Acoustic Channels

“…In this paper, we propose a turbo JED receiver, building on our earlier work [20], [24], that operates in a pulse-shaped MCM framework and which takes full advantage of sparsity in the channel delay profile. Our approach uses a sparse Fourier BEM to model frequency-domain channel variation and a fast tree-search to compute the soft noncoherent equalizer outputs.…”

Equalization of Time-Varying Channels

“…The method in Zhang, Fitz, and Gelfand [ZFG97] can be considered as using the T-algorithm to obtain symbol-MAP fixed-lag metrics for the same channel. For a doubly selective channel modeled by a generic BEM, Hwang and Schniter proposed PSP-based noncoherent M-algorithm tree-searches that accomplish approximate MLSD, in [HS07a], and approximate MAP bit detection, in [HS07b]. The latter, with complexity O(KM 2 I 2 ), was combined with soft decoding in a turbo receiver.…”

Partial FFT Demodulation: A Detection Method for Doppler Distorted OFDM Systems

“…It thus enables a low complexity implementation, where only a few additional FFTs are required at the receiver front-end. The signal after combining can be processed in a standard manner, without dedicated ICI suppression such as banded equalization [12]. Clearly, partial FFT demodulation can also be combined with ICI equalization; however, our goal at the moment is to investigate its performance as a stand-alone alternative.…”