Time-varying wideband underwater acoustic channel estimation for OFDM communications

Josso, Nicolas; Zhang, J. J.; Fertonani, D.; Papandreou-Suppappola, Antonia; Duman, Tolga M.

doi:10.1109/icassp.2010.5495257

Cited by 14 publications

(13 citation statements)

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“…As the UWA communications channel is highly time-varying, it can cause undesirable distortions, such as multipath and Doppler scaling, under certain conditions [5][6][7]. Existing UWA communications schemes do not fully exploit matching the UWA channel characteristics to signaling schemes and often have to compensate for that at the receiver.…”

Section: Motivation and Relation To Prior Workmentioning

confidence: 98%

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Hyperbolic frequency modulation for multiple users in underwater acoustic communications

Zhou

Zhang

Papandreou-Suppappola

2014

2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

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Nonlinear frequency-modulated signals have been effectively applied in multiple-user communication schemes. In this paper, we propose to implement a multiple-user communication scheme using hyperbolic frequency-modulated (HFM) signals for underwater acoustic communications. We derive constraints on the HFM parameters to optimally reduce multiple access interference (MAI) at the transmission side. Additional constraints on the frequency-modulation (FM) rate reduce the underwater channel effects of multipath and scaling. The proposed signaling scheme is compared to an HFM-based code-division multiple-access (HFM-CDMA) scheme to demonstrate improved error performance. MOTIVATION AND RELATION TO PRIOR WORKUnderwater acoustic (UWA) communications methods, such as orthogonal frequency-division multiplexing (OFDM) and code-division multiple access (CDMA), have been widelyused for multiple users [1][2][3][4]. As the UWA communications channel is highly time-varying, it can cause undesirable distortions, such as multipath and Doppler scaling, under certain conditions [5][6][7]. Existing UWA communications schemes do not fully exploit matching the UWA channel characteristics to signaling schemes and often have to compensate for that at the receiver. In [1], the distorted OFDM signal due to Doppler is compensated at the receiver using resampling, and any remaining Doppler is removed using inter-carrier interference reduction techniques. A multiple resampling OFDM receiver front-end is designed in [2] such that each resampling branch deals with a different Doppler factor. Adaptive multi-user detection techniques are applied in [3], but their assumed UWA channel model does not include multiple Doppler paths at the receiver. A spread spectrum hyperbolic frequency modulation scheme in [8] can potentially match the UWA channel but only assumes one Doppler scale path and does not compensate for multiple time delay paths that can distort any potential scale diversity. In [9], we design an HFM scheme to match the This work is funded by the National Science Foundation grant NSF-ECCS 1102357.UWA communications channel. The HFM scheme is integrated with the use of a discrete time-scale canonical model, which represents the received signal from a wideband channel as a linear superposition of discrete time shifts and Doppler scalings of the transmitted signal, weighted by the wideband spreading function (WSF) [10]. We demonstrate an inherent joint multipath-scale diversity using this scheme, and we combine it with direct sequence CDMA for use in multi-user UWA communications. The different users are distinguished by a unique pseudo-noise (PN) sequence [9]. As we demonstrate, the scheme can successfully resolve information bits at the receiver side, but the performance degrades as the number of users increases.A nonlinear frequency-modulated signaling scheme is developed in [11] by deriving constraints on the nonlinear phase function of the transmit signal to achieve orthogonality; the scheme, combined with frequency-hopping CDMA, is use...

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Section: Motivation and Relation To Prior Workmentioning

confidence: 98%

“…Note that we assume that the UWA channel WSF coefficients are estimated a priori; methods for estimating the WSF coefficients can be found in [6,7].…”

Section: Multi-user Uwa Hfm Signalingmentioning

confidence: 99%

Hyperbolic frequency modulation for multiple users in underwater acoustic communications

Zhou

Zhang

Papandreou-Suppappola

2014

2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

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“…where is the filter taps representing the estimate of the timeinvariant channel impulse response over the duration of the th block (22) The output of the FIR filter bank in response to the original watermark is used at the receiver for replica correlation. The watermark signal is divided into equal length blocks…”

Section: Watermark Replica Generation By Channel Compensationmentioning

confidence: 99%

“…Estimating the acoustic channel with Doppler has been covered for sparse channels [21], OFDM [18], [22], and CDMA [23]. More recent approaches involve compressive sensing [24], joint delay-Doppler and amplitude estimation [17], and time-reversal [25].…”

Section: Watermark Replica Generation By Channel Compensationmentioning

confidence: 99%

Information Embedding in Sonar by Modifications of Time-Frequency Properties

Mobasseri

Lynch

2016

IEEE J. Oceanic Eng.

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In the crowded underwater acoustic channels, the ability to recognize sonar transmissions based on an identifying signature is quite valuable. In this work, we propose an algorithm to embed a watermark in the time-frequency coefficients of a sonar waveform and produce a watermarked sonar. The watermark, which is a digital signature, is used to authenticate the sonar by verifying the source that is broadcasting the waveform. The embedding rule is modeled after spread spectrum modulation and driven by two secure keys. The first key consists of the spreading code that is unique to each source. The second key is an embedding mask used to select and additively modify the selected time-frequency cells of the sonar. The mask is chosen based on the frequency response of the acoustic channel (primarily, its time and frequency coherence) and the signal energy distribution in the time-frequency plane. The detector is modeled after a matched filter receiver performing a replica correlation with the spread watermark passed through the channel model. A successful detection needs access to both the spreading code and the embedding mask. Watermark detection performance is extensively evaluated based on range; watermark energy; watermark placement; ambient noise; number of multipaths; and other ocean parameters, such as depth, surface, and bottom models.

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“…However because of the complex time-space variability and dynamic properties [8,9] inherent in underwater acoustic channels, a blind equalizer which can be successfully used in an underwater acoustic channel may be inefficient or even invalid in another channel, just as shown in [11,12]. How to improve the blind equalization algorithm's adaptability to different channels is an important problem for practical underwater acoustic communications.…”

Section: Introductionmentioning

confidence: 99%

Self-adjusting decision feedback equalizer for variational underwater acoustic channel environments

Luo

Liu

et al. 2014

J. of Syst. Eng. Electron.

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Aimed at the abominable influences to blind equalization algorithms caused by complex time-space variability existing in underwater acoustic channels, a new self-adjusting decision feedback equalization (DFE) algorithm adapting to different underwater acoustic channel environments is proposed by changing its central tap position. Besides, this new algorithm behaves faster convergence speed based on the analysis of equalizers' working rules, which is more suitable to implement communications in different unknown channels. Corresponding results and conclusions are validated by simulations and spot experiments.

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Time-varying wideband underwater acoustic channel estimation for OFDM communications

Cited by 14 publications

References 10 publications

Hyperbolic frequency modulation for multiple users in underwater acoustic communications

Hyperbolic frequency modulation for multiple users in underwater acoustic communications

Information Embedding in Sonar by Modifications of Time-Frequency Properties

Self-adjusting decision feedback equalizer for variational underwater acoustic channel environments

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