Jianguo Huang

Diffusion adaptation over networks with kernel least-mean-square

Distributed learning over networks has become an active topic of research in the last decade. Adaptive networks are suitable for decentralized inference tasks, e.g., to monitor complex natural phenomena or infrastructure. Most of works focus on distributed estimation methods of linear regression models. However, there are many important applications that deal with nonlinear parametric models to be fitted, in a collaborative manner. In this paper, we derive functional diffusion strategies in reproducing kernel Hilbert spaces.

Robust sparse spectral fitting in element and beam spaces for Directions-Of-Arrival and power estimation

In this paper, we propose a robust sparse spectrum fitting method (RSpSF) for Directions-Of-Arrival (DOA) and power estimation in the presence of general form of modeling errors in the array manifold matrix. By exploiting the group sparsity between the power spectrum and the modeling errors, RSpSF formulates the estimator as a convex optimization program. Then, in order to reduce its computational complexity, we apply a beam-space technique to RSpSF and obtain another convex estimator, the beam-space RSpSF (BMRSpSF). Simulation examples are presented to demonstrate the robustness of the proposed methods to off-grid DOAs and to random array calibration errors.

Single-carrier block transmission in time reversal shortened underwater acoustic channels

The single-carrier block transmission (SCBT) method has been considered for bandwidth efficiency in underwater acoustic (UWA) communication recently. The cyclic prefix (CP) in the SCBT method should be longer than the multipath spread, but a long CP reduces the data rate of SCBT UWA communications in significant multipath channels. The proposed scheme in this paper includes two parts: i) modified passive time reversal processing is used to shorten the large delay multipath channel, thus reducing the CP length; and ii) a hybrid time-frequency domain equalizer (HTFDE) is used to obtain spatial diversity and to remove the residual inter-symbol interference (ISI). The results of a lake experiment are presented to verify the efficiency of the proposed method.

Single carrier with multi-channel time-frequency domain equalization for underwater acoustic communications

Single-carrier with frequency domain equalization (SC-FDE) has been considered for bandwidth efficiency underwater acoustic (UWA) communication recently due to its reduced computational complexity and low peak-to-average power ratio. A multi-channel time-frequency domain equalization method for pseudurandom noise (PN) based SC-FDE is proposed in this paper. The proposed equalizer includes a multi-channel frequency domain equalizer followed by a low order multi-channel adaptive time domain decision feedback equalizer (DFE). The proposed algorithm is applied to the real data receiving from a lake test conducted in November 2011. It is demonstrated that the uncoded error-free data rates of around 1500 and 3000 bps are achieved using one transmitter and six-channel receiving hydrophone array at a distance of 1.8 km. Experiment results shows that the performance can be enhanced by 4.5-5.5 dB in terms of output signal-to-noise ratio (SNR).

Convergence analysis of the augmented complex klms algorithm with pre-tuned dictionary

Complex kernel-based adaptive algorithms have been recently introduced for complex-valued nonlinear system identification. These algorithms are built upon the same framework as complex linear adaptive filtering techniques and Wirtingers calculus in complex reproducing kernel Hilbert spaces. In this paper, we study the convergence behavior of the augmented complex Gaussian KLMS algorithm. Simulation results illustrate the accuracy of the analysis.

DOA estimation in monostatic MIMO array based on sparse signal reconstruction

In this paper, a novel method for direction arrival (DOA) estimation in monostatic multiple-input multiple output (MIMO) array is presented. By using the sparse signal reconstruction of monostatic MIMO array measurements with an overcomplete basis, the singular value decomposition (SVD) of the received data matrix can be penalties based on the l1-norm. The optimization problem can be solved exploiting the second-order cone programming framework. The proposed method for monostatic MIMO array could achieve more accurate DOA estimation than the traditional DOA estimation methods. The simulation examples are presented to demonstrate the effective of the proposed method in monostatic MIMO array.

Multiuser underwater acoustic communication using cyclic shift keying

A novel code division multiple access (CDMA) using cyclic shift keying (CSK) signaling, namely CSK-CDMA, has been proposed for multiuser underwater acoustic communication. The proposed method uses the cyclic correlation characteristic of spread spectrum signals and time reversal processing to increase the data rate each user and to reduce the complexity of the receiver. In CSK-CDMA system, multiple bits information is represented by the cyclically shifted version of the basic spread spectrum waveform at the transmitter. Therefore, the CSK scheme provides a higher data rate than conventional direct sequence spread spectrum. At the receiver, the peak position of the cyclic correlator output is estimated to recovery information. Multiuser communications are demonstrated with lake experimental recorded data. The data rate is 40 bits/s/user for 4 users with zeros error bits and 20 bits/s/user for 8 users with BER around 10-2 at low signal-to-noise ratio (-3 dB), given 4 kHz bandwidth, respectively.

Multi-channel iterative FDE for single carrier block transmission over underwater acoustic channels

Recently, single carrier block transmission (SCBT) has received much attention in high-rate phase-coherent underwater acoustic communication. However, minimum-mean-square-error (MMSE) linear FDE may suffer performance loss in the severely time dispersive underwater acoustic channel. To combat the channel distortion, a novel multi-channel receiver with maximum ratio combining and a low complex T/4 fractional iterative frequency domain equalization (FDE) is investigated to improve diversity gain and the bit error rate (BER) performance. The proposed method has been verified by the real data from a lake underwater acoustic communication test in November 2011. At 1.8 km, the useful data rates are around 1500 and 3000 bits/ s for BPSK and QPSK respectively. The results show the improvements of system performance. Compared with MMSE FDE system, the output SNR improvement is 6.9 dB, and the BER is from 10-3 to no error bits for BPSK. The output SNR improvement is 5.3 dB, and the BER is from 1.91×10-2 to 2.2×10-4 for QPSK.

Fast MUSIC algorithm for joint DOD-DOA estimation based on Gibbs Sampling in MIMO array

Multiple signal classification (MUSIC) algorithm has been used for joint Direction of Departure (DOD) and Direction of Arrival (DOA) estimation in Multiple Input Multiple Output (MIMO) array. It has shown excellent angle estimation performance. However, the two dimensional angle peaks searching of MIMO MUSIC algorithm renders high computational complexity. In order to resolve this problem, a fast MIMO MUSIC algorithm for joint DOD-DOA Estimation based on Gibbs Sampling is proposed. The proposed algorithm combines Markov Monte Carlo method with MIMO MUSIC estimator. Firstly, the power of the MIMO MUSIC spectrum function is regarded as the target distribution up to a constant scalar, then the Gibbs sampler sample from the scalar, and the joint DOD-DOA estimation can be achieved from the linger position. Simulation results show that the proposed method not only keeps the similar DOA estimation performance which is achieved by the MIMO MUSIC algorithm, but also reduces the computational complexity.

Performance analysis of self interference cancellation in bidirectional relaying underwater acoustic communication(BiRUAC) system

Due to the underwater acoustic channel is more complexity than the wireless communication channel. It has more multipath interference and larger attenuation, so the rate of transmission in the underwater acoustic channel is lower and the probability of error is larger. Aim to those problems, we proposed a bidirectional relaying underwater acoustic communication system and analysis the performance of this algorithm. The algorithm utilized the self interference cancellation model to remove the self interference. In the performance analysis part, we set the different size of self interference cancellation model. The simulations show that our proposed algorithm has lower SER and higher rate of transmission.