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  • Comparative Studies. Non-European Languages/Literatures  (22)
  • 1
    Online Resource
    Online Resource
    Dual-channel orthogonal modulation differential pattern time delay shift coding underwater acoustic communication method
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 134, No. 5_Supplement ( 2013-11-01), p. 4112-4112
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 134, No. 5_Supplement ( 2013-11-01), p. 4112-4112
    Abstract: Information is carried by the time delay between adjacent code elements in differential pattern time delay shift coding system. It has an ability of anti inter-symbol interference and the Doppler effects. In order to obtain higher communication rate and reduce the interference between channels, this paper proposes a dual-channel orthogonal modulation differential pattern time delay shift coding underwater acoustic communication method and selects the balance Gold sequence as Patterns. At the transmitter end, divide input bits into two channels to differential pattern time delay shift encode and modulate orthogonally. Then add the encoded signal of two channels together to transmit. At the receiver end, demodulate the received signal orthogonally, search the correlation peak position of patterns. And estimate time delay to restore the original input information. Dual parallel channel transmission mode effectively improves communication rate of differential Pattern time delay shift coding and the orthogonal modulation method greatly reduces the interference between channels. Simulation research is carried on for the method, at transmission data 2x104bit and SNR -5dB, information is recovered at a communication rate 205 bit/s with very low bit error rate.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4831102
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
    detail.hit.zdb_id: 1461063-2
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  • 2
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    Study on Doppler effects estimate in underwater acoustic communication
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 133, No. 5_Supplement ( 2013-05-01), p. 3463-3463
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 133, No. 5_Supplement ( 2013-05-01), p. 3463-3463
    Abstract: Two estimate methods of the Doppler effects in mobile underwater acoustic communication have been proposed. For the first method the Doppler coefficients are obtained by estimating frequency change of CW impulse signal with notch filter. For the other method the Doppler coefficients are obtained by estimating chirp rate change of LFM signal with fractional Fourier transform (FRFT). And the performance of the Doppler effects estimation method based on notch filter or the FRFT are compared by the computer simulation. The advantages, shortcoming and the application occasion of the two methods are elaborated. The effectiveness and robustness of the two methods have been proved. Key Word: Notch Filter, Fractional Fourier transform, Doppler Effects, Underwater Acoustic Communication
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4806168
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
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  • 3
    Online Resource
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    Underwater acoustic communication in time-varying channel environment based on passive time reversal
    Acoustical Society of America (ASA) ; 2016
    In:  Journal of the Acoustical Society of America Vol. 139, No. 4_Supplement ( 2016-04-01), p. 2084-2084
    Details
    In: Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 139, No. 4_Supplement ( 2016-04-01), p. 2084-2084
    Abstract: Channels estimated from probe signal or training symbols will mismatch with the true channels in passive time reversal (TR) underwater acoustic (UWA) communication when the ocean environment is time-varying, leading to poor channel equalization performance. In order to solve this problem, this paper studies Block-based TR processing structure. The received data are divided into small blocks and the channel estimated from previously decoded symbols is used to match filter the current block to suppress the channel mismatch. Decision feedback equalizer (DFE) is also combined with Block-based TR to remove the residual inter symbol interference (ISI) and Doppler effect (Block-based TR-DFE). Mobile UWA communication experiment was conducted near Xiao Changshan island, Dalian in July, 2015. Though the received data are preprocessed by resampling, residual Doppler effect still exists due to ununiform motion between the receiver and transmitter, making the channel time-varying fastly. Block-based TR realized effective tracking and compensation for time-varying channels. The output signal-to-noise ratio (SNR) after equalization is greatly improved and the bit error rate (BER) is significantly reduced.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4950189
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2016
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  • 4
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    Active average intensity based on single vector sensor
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 132, No. 3_Supplement ( 2012-09-01), p. 2015-2015
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 132, No. 3_Supplement ( 2012-09-01), p. 2015-2015
    Abstract: Code divided multiple access underwater communication based on single vector sensor is studied in this paper. The most common methods to estimate azimuth with self-directivity of single vector sensor are average sound intensity method and complex sound intensity method, however, for the same frequency band multi-users, theoretical limitation for these methods is only two users.Spread spectrum communication is featured with strong anti-multipath, anti-interference, secret-keeping and communication web composing ability. Active average intensity method, which measures azimuths of multi-users simultaneously with the excellent correlative characteristics of pseudo-random code in spread spectrum communication, is proposed in this paper. Simulation and experiment for same frequency band spread spectrum multi-user communication testify the feasibility and utility of active average sound intensity method. With the estimated azimuth, vector combination can be generated to adjust the directivity of vector sensor, achieve multi-user beam communication, inhibit multi-path interference, and enhance processing gain and lower error rate. Key words: underwater acoustic communication; CDMA; single vector sensor; active acoustic intensity average
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4755456
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
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  • 5
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    Vorticity-involved acoustic damping performance of an in-duct orifice with a bias flow
    Acoustical Society of America (ASA) ; 2016
    In:  Journal of the Acoustical Society of America Vol. 139, No. 4_Supplement ( 2016-04-01), p. 2066-2066
    Details
    In: Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 139, No. 4_Supplement ( 2016-04-01), p. 2066-2066
    Abstract: Acoustic damping performance of an in-duct perforated orifice with a bias flow in terms of power absorption and reflection coefficients are evaluated in this work. For this, experimental measurements of a cold-flow pipe system with a diameter of 2b with an in-duct perforated plate implemented are conducted first. It is shown that the maximum power absorption Δmax and reflection coefficients χmax are approximately 80% and 90%, respectively. In addition, Δ and χ are periodically changed with the forcing frequency. To simulate the experiments and gain insights on the damping performance of the orifice with a diameter of 2a, a 1D theoretical model embodying vorticity-involved damping mechanism is developed. It is based on the modified form of the Cummings equation describing unsteady flow through an orifice and the Cargill equation describing acoustically open boundary condition at the end of the downstream duct. It is shown that Δ and χ are strongly related to (1) the mean flow Mach number, (2) forcing frequency ω, and (3) porosity η = a/b, and (4) the downstream pipe length Ld. Theoretical predictions are found to agree well with experimental measurements. This confirms that the model has the potential to predict the acoustic damping performance of in-duct orifices.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4950126
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2016
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  • 6
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    Experimental demonstration of multiband underwater acoustic transmissions based on single carrier communication
    Acoustical Society of America (ASA) ; 2015
    In:  Journal of the Acoustical Society of America Vol. 137, No. 4_Supplement ( 2015-04-01), p. 2214-2214
    Details
    In: Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 137, No. 4_Supplement ( 2015-04-01), p. 2214-2214
    Abstract: In a recent shallow water experiment, multiband transmissions were carried out using a vertical array with six sensors uniformly spaced every 0.5 m. The entire frequency band (2–8 kHz) was divided into two sub-bands, each of which is about 2.55 kHz in width. Time reversal processing is first used to compress severe multipath spread, following by a single channel decision feedback equalizer (DFE) to remove residual inter-symbol-interference (ISI). Using experimental data, this paper demonstrates that multiband transmissions are very beneficial to improve the throughput of underwater acoustic communications, achieving a data rate of 6k bits/s using QPSK modulation with almost error free performance.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4920063
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2015
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  • 7
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    Group sparse underwater acoustic channel estimation with impulsive noise: Simulation results based on Arctic ice cracking noise
    Acoustical Society of America (ASA) ; 2019
    In:  The Journal of the Acoustical Society of America Vol. 146, No. 4 ( 2019-10-01), p. 2482-2491
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 146, No. 4 ( 2019-10-01), p. 2482-2491
    Abstract: Many underwater acoustic (UWA) channels exhibit impulsive noise, thereby severely degrading the performance of traditional channel estimation algorithms. This paper presents two channel estimation algorithms for impulsive noise, namely (i) the variable forgetting factor l1,0 recursive least sign algorithm (VFF-l1,0-RLSA) and (ii) the variable forgetting factor l2,0 recursive least sign algorithm (VFF-l2,0-RLSA), both of which exploit the group sparse multipath structure and maintain robustness under impulsive noise. By using the l1 norm of the estimation error as part of the cost function, RLSAs are better at detecting and rejecting impulsive noise than the recursive least squares algorithms. A mixed l1,0 or l2,0 norm is incorporated with a RLSA to achieve better performance in group sparse UWA channel estimation. The time-varying forgetting factor and regularization parameter in the two proposed algorithms help to improve their performance. Simulation results based on Arctic ice cracking noise demonstrate the robustness and superiority of the two proposed algorithms.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5129056
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2019
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  • 8
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    Iterative channel estimation-based soft successive interference cancellation for multiuser underwater acoustic communications
    Acoustical Society of America (ASA) ; 2021
    In:  The Journal of the Acoustical Society of America Vol. 150, No. 1 ( 2021-07-01), p. 133-144
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 150, No. 1 ( 2021-07-01), p. 133-144
    Abstract: This paper presents a single-carrier multiuser receiver in underwater acoustic communications with strong multiple access interference (MAI) combining passive time-reversal (PTR) and direct-adaptation-based turbo equalization. The receiver works in an iterative block by block manner. In the first iteration, when the symbols of all users are detected by successive interference cancellation (SIC) in the block, the channel impulse response (CIR) of each user is then updated by post-SIC signal to achieve more accurate MAI reconstruction and PTR combination for the next block. In the following iterations, the a priori mean of symbol in the current block is available and used to further improve the accuracy of reconstructed MAI and the updated CIR. The proposed receiver is demonstrated using experimental data collected at Songhua Lake, China, in 2019. The results show that single-carrier nine-user communication data with quadrature phase-shift keying can be successfully recovered, with an average data rate of 1.67 kbps for each user.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/10.0005476
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2021
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  • 9
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    Blind beamforming-based strong interference suppression in underwater acoustic direct-sequence code-division multiple-access systems
    Acoustical Society of America (ASA) ; 2022
    In:  The Journal of the Acoustical Society of America Vol. 152, No. 4 ( 2022-10-01), p. 2128-2139
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 152, No. 4 ( 2022-10-01), p. 2128-2139
    Abstract: In an underwater acoustic direct-sequence code-division multiple-access (DS-CDMA) system, the performance of the conventional receiver is severely limited by the strong multiple-access interferences, which is due to the near-far effect. In this paper, a time-frequency-time with eigendecomposition-based blind beamformer (TFT-EBB) method is proposed for a distant user to suppress strong interference from a nearby user in DS-CDMA underwater acoustic communications. When the interference level is moderately higher than that of the desired signal, the TFT-EBB method can estimate the composite steering vector of all multipath components of the weak desired user signal via the eigendecomposition of the array covariance matrix at each frequency bin. Then the proposed energy detection-based RAKE receiver is cascaded to achieve multipath diversity, in which it requires less prior information compared with the conventional RAKE receiver. The proposed method is evaluated by using both simulated and field experimental data, which verifies its effectiveness.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/10.0014598
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2022
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  • 10
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    Application of differential amplitude and phase-shift keying in underwater acoustic communication based on orthogonal frequency division multiplexing
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 133, No. 5_Supplement ( 2013-05-01), p. 3463-3463
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 133, No. 5_Supplement ( 2013-05-01), p. 3463-3463
    Abstract: With the increase of of marine resource and underwater users, developing a high-bit-rate underwater acoustic communication has become a hot topic. Amplitude and phase-shift keying (APSK) is a modulation technique having high efficiency in spectrum utilization, it attracts more and more attention in high-bit-rate underwater acoustic communication. Differential APSK (DAPSK) is modulated using differential amplitude and phase code in time domain, and it has higher bandwidth efficiency and be easier to realize the system than APSK. A transmission system based on DAPSK modulation and OFDM is presented to solve the problems of effectiveness and reliability in high-bit-rate underwater acoustic communication. Simulation results show that the system using DAPSK modulation has a better performance than those using APSK and QAM modulation.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4806167
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
    detail.hit.zdb_id: 1461063-2
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