Jingwei Yin

A Kalman Filter-Based Blind Adaptive Multi-User Detection Algorithm for Underwater Acoustic Networks

An underwater acoustic Kalman filter-based blind adaptive multi-user detection algorithm, suitable for underwater acoustic communication networks, is proposed in this paper. The algorithm can be employed to effectively improve the system capacity of multi-user communication in underwater acoustic sensor networks, reduce transmitting power and costs on power control, extend the multi-user communication distance, weaken or eliminate intersymbol interference, multiple access interference and near-far effect, thus effectively utilizing limited underwater frequency band resource. First, the dynamic model of underwater acoustic multi-user communication system and the optimal filter equation of the proposed algorithm are found. Second, computation complexity is analyzed, and convergence analysis is carried out in terms of excess mean output energy. Finally, pool, river, sea, and under-ice asynchronous communication experiments have been carried out for both the scalar and the vector hydrophones. Good experimental results verify the effectiveness of the proposed algorithm.

Depth classification of underwater targets based on complex acoustic intensity of normal modes

In order to solve the problem of depth classification of the underwater target in a very low frequency acoustic field, the active component of cross spectra of particle pressure and horizontal velocity (ACCSPPHV) is adopted to distinguish the surface vessel and the underwater target. According to the effective depth of a Pekeris waveguide, the placing depth forecasting equations of passive vertical double vector hydrophones are proposed. Numerical examples show that when the sum of depths of two hydrophones is the effective depth, the sign distribution of ACCSPPHV has nothing to do with horizontal distance; in addition, the sum of the first critical surface and the second critical surface is equal to the effective depth. By setting the first critical surface less than the difference between the effective water depth and the actual water depth, that is, the second critical surface is greater than the actual depth, the three positive and negative regions of the whole ocean volume are equivalent to two positive and negative regions and therefore the depth classification of the underwater target is obtained. Besides, when the 20 m water depth is taken as the first critical surface in the simulation of underwater targets (40 Hz, 50 Hz, and 60 Hz respectively), the effectiveness of the algorithm and the correctness of relevant conclusions are verified, and the analysis of the corresponding forecasting performance is conducted.

An application of the differential spread-spectrum technique in mobile underwater acoustic communication

A direct sequence/binary differential phase-shift keying underwater acoustic communication technique based on differential coherent demodulation is proposed. Differential coherent demodulation is adopted at the receiving terminal to overcome the difficulty of estimating the carrier in underwater acoustic communication and overcoming the frequency and phase error resulting from carrier frequency drift. Anti-multipath, anti-Doppler, low-error-rate, effective and robust features for a complex underwater acoustic channel were verified in a lake experiment.

Sea trial research on multi-source underwater acoustic image measurement technology based on the sparse array

The underwater acoustic image measurement technology is a technology of passive acoustic localization in near field, which can get the track of moving target by measuring the main noise sources of the target through large scale array. Because of the complexity of underwater environment, it is difficult to lay a large high-accuracy half-wavelength array. Thus it is more convenient to use a sparse array in underwater acoustic image measuring. The sea trial research on the underwater acoustic image measurement based on the sparse array has been done to verify the feasibility of the method. The experiment result shows that using sparse array would lead to a series of interference fringes appearing in the image, but the interference fringes can be removed by frequency-division integrated technology. Three tracks measurement results of a catamaran are given. The results prove that the method is feasible.

Null subcarriers based Doppler scale estimation for multicarrier communication over underwater acoustic non-uniform Doppler shift channels

The Doppler scale estimation based on Null subcarriers in underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) communication is investigated, which is an optimization problem for finding extremum. The cost function constructed of the total energy of null subcarriers in ultra-wideband UWA channels is proposed. The frequencies of null subcarriers are calculated according to non-uniform Doppler shifts at each tentative scaling factor. Then it is shown that the cost function can be fitted as a quadratic polynomial near the global minimum. So an accurate Doppler scale estimation is achieved by location of the global minimum through polynomial interpolation with several samples around the global minimum, without the conflict between precision and computation complexity. In order to locate the global minimum roughly to take samples, a Doppler scale coarse estimating method is developed based on the delay change between two pilots. The data from a shallow water experiment is used to demonstrate the performance. Excellent performance results are obtained in ultra-wideband underwater acoustic channels with a relative bandwidth of 67%, when the transmitter and the receiver are moving at a relative speed of 5kn, which validates the method proposed.

Space-division multiple access for CDMA multiuser underwater acoustic communications

Time reversal mirror(TRM) can use the physical characteristics of the underwater acoustic(UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity(AASI) detector can estimate all azimuths of users with the same frequency band at the same time in order to achieve directional communication by vector combination.Space-division multiple access(SDMA) based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access(CDMA) UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.

Null subcarriers based Doppler scale estimation with polynomial interpolation for multicarrier communication over ultrawideband underwater acoustic channels

This paper addresses the extremal problem of the null subcarriers based Doppler scale estimation in underwater acoustic(UWA) orthogonal frequency division multiplexing(OFDM) communication. The cost function constructed of the total energy of null subcarriers through discrete Fourier transform(DFT) is proposed.The frequencies of null subcarriers are identified from non-uniform Doppler shift at each tentative scaling factor. Then it is proved that the cost function can be fitted as a quadratic polynomial near the global minimum. An accurate Doppler scale estimation is achieved by the location of the global scarifying precision and increasing the computation minimum through polynomial interpolation,without complexity. A shallow water experiment is conducted to demonstrate the performance of the proposed method. Excellent performance results are obtained in ultrawideband UWA channels with a relative bandwidth of 67%, when the transmitter and the receiver are moving at a relative speed of 5 kn, which validates the proposed method.

An analysis on fractional Fourier transform in Doppler and multipath mobile underwater acoustic channel.

Fractional Fourier transform is a kind of time‐frequency analysis method, which combines the information of signals in time domain and frequency domain. FRFT has chirp‐based decomposition characteristics, for a given chirp signal, there is a fraction which gathers the energy of linear frequency‐modulated signals to a maximum, which provides a basis for the detection of chirp signal with Doppler frequency offset and can also be used in the synchronization detection of mobile communication in underwater acoustic and the channel parameter estimation. This paper describes the theoretical basis of FRFT and its characteristics analysis, then by the computer simulation, performance analysis of FRFT and correlation detection in the conditions of Doppler and multipath are worked out, and the facts are verified that fractional Fourier transform is more suitable than copy correlator for Doppler frequency offset and multipath underwater acoustic channel.

Study of underwater acoustic communication based on vector Pattern time delay shift coding

The vector sensor is proposed to apply to the field of the underwater acoustic communication based on Pattern time delay shift coding scheme. The underwater acoustic communication based on the pattern time delay shift coding communication system is a kind of pulse position modulation (PPM), in which the time delay shift values of the Pattern are used to encode the digital information. The azimuth estimation of the information source based on broad band synchronization signal and information code signal, combined decoding system based on sound pressure and particle velocities joint processing, modeling for vector field of isotropic noise, and the applications of the vector sensor in the field of underwater acoustic communication are studied in this paper. In this system, vector processing gain in the anti-isotropic interference field can be obtained, longer communication distance and lower bit error rate can be achieved as well, the multiple access interference at different positions can be eliminated, last but most important is azimuth variation quantity of moving source can be adjusted real-time by information code continued to come one after another. Simulation experiments testify the feasibility and reliability of the vector underwater acoustic communication based on Pattern time delay shift coding system.

Multitarget Tracking Algorithm Using Multiple GMPHD Filter Data Fusion for Sonar Networks

Multitarget tracking algorithms based on sonar usually run into detection uncertainty, complex channel and more clutters, which cause lower detection probability, single sonar sensors failing to measure when the target is in an acoustic shadow zone, and computational bottlenecks. This paper proposes a novel tracking algorithm based on multisensor data fusion to solve the above problems. Firstly, under more clutters and lower detection probability condition, a Gaussian Mixture Probability Hypothesis Density (GMPHD) filter with computational advantages was used to get local estimations. Secondly, this paper provided a maximum-detection capability multitarget track fusion algorithm to deal with the problems caused by low detection probability and the target being in acoustic shadow zones. Lastly, a novel feedback algorithm was proposed to improve the GMPHD filter tracking performance, which fed the global estimations as a random finite set (RFS). In the end, the statistical characteristics of OSPA were used as evaluation criteria in Monte Carlo simulations, which showed this algorithm’s performance against those sonar tracking problems. When the detection probability is 0.7, compared with the GMPHD filter, the OSPA mean of two sensor and three sensor fusion was decrease almost by 40% and 55%, respectively. Moreover, this algorithm successfully tracks targets in acoustic shadow zones.