HFM spread spectrum modulation scheme in shallow water acoustic channels

Lan, Zhang; Xu, Xiaomei; Feng, Wei; Chen, Yougan

doi:10.1109/oceans.2012.6404896

Cited by 17 publications

(11 citation statements)

References 9 publications

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“…The UWA channel parameters and the HFM signal parameters remain the same as in the first figure. For these cases, for each value of K, we selected D symb and D user to satisfy both conditions (4) and (8) are satisfied for the given time-bandwidth product of T = 0.1 and 5 kHz maximum bandwidth. It can be observed that the BER performance decreases as the number of users increases.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…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.…”

Section: Motivation and Relation To Prior Workmentioning

confidence: 99%

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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: Simulation Resultsmentioning

confidence: 99%

Section: Motivation and Relation To Prior Workmentioning

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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“…HFM signal is a kind of non-linear frequency modulation signal whose instantaneous frequency is a hyperbolic function of time, which can be expressed as [16]:…”

Section: Hfm Signalmentioning

confidence: 99%

“…HFM signal is a preferable training signal in UWA communication as the frequency shifts caused by Doppler effects can be treated as a time shift [16,17]. Thus the Doppler effects and time delay can be simultaneously estimated by analyzing the time-frequency characteristics of the signal.…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach for the Estimation of Doubly Spread Acoustic Channels Based on Wavelet Transform

Zhang

Song

et al. 2018

Applied Sciences

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Abstract:In this paper, the estimation of doubly spread underwater acoustic (UWA) channels is investigated. The UWA channels are characterized by severe delay spread and significant Doppler effects, and can be well modeled as a multi-scale multi-lag (MSML) channel. Furthermore, exploiting the sparsity of UWA channels, MSML channel estimation can be transformed into the estimation of parameter sets (amplitude, Doppler scale factor, time delay). Based on this, the orthogonal matching pursuit (OMP) algorithm has been widely used. However, the estimation accuracy of OMP depends on the size of the dictionary, which is related with both delay spread and Doppler spread. Thus it requires high computational complexity. This paper proposes a new method, called wavelet transform (WT) based algorithm, for the UWA channel estimation. Different from OMP algorithm which needs to search in both time domain and Doppler domain, WT-based algorithm only needs to search in time domain by using the Doppler invariant characteristic of hyperbolic frequency modulation (HFM) signal. The performance of the proposed algorithm is evaluated by computer simulations based on BELLHOP. The simulation results show that WT-based algorithm performs slightly better than OMP algorithm in low signal to noise ratio (SNR) while can greatly reduce computational complexity.

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“…The traditional processing in the receiver is matched filter, namely correlation processing [6], see in Fig. 1.…”

Section: A the Traditional Synchronization Processingmentioning

confidence: 99%

Frequency-hopping acoustic communication in shallow water: Synchronization with time-reversal and united frame structure

et al. 2014

Oceans 2014 - Taipei

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Owing to the special economic position and environment protection requirements for shallow water, shallow water acoustic communication becomes a hot research area in recent years. The frequency-hopping (FH) technique being considered as one robust and reliable communication plays a vital role in communication system design, because of the characteristics of shallow water channel, e.g., strong multipath, large fluctuation and fast time-varying. Synchronization processing is a key factor of FH system. In this paper, we introduce a real-time FH-MFSK acoustic communication system; adopt the passive time reversal approach to process synchronization for suppressing the multipath interference of underwater acoustic propagation. The united frame structure which contains passive time-reversal synchronization signal is proposed to reduce the impact of time-varying channel on the communication system. Also Convolutional coding is used to future improve the reliability performance of the system. In addition to experimental studies, we used TMS320C6713 DSP for system design. The laboratory pool tests and a sea trial at Wuyuan Bay, Xiamen were carried out. The experimental results demonstrate that the proposed scheme is particularly suitable for FH acoustic communication in shallow water where the channel characterizes as strong multipath, time-varying, fluctuation and random signal variations.

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HFM spread spectrum modulation scheme in shallow water acoustic channels

Cited by 17 publications

References 9 publications

Hyperbolic frequency modulation for multiple users in underwater acoustic communications

Hyperbolic frequency modulation for multiple users in underwater acoustic communications

A Novel Approach for the Estimation of Doubly Spread Acoustic Channels Based on Wavelet Transform

Frequency-hopping acoustic communication in shallow water: Synchronization with time-reversal and united frame structure

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