Hu Guangrui

A new speech enhancement method

The paper proposes a speech enhancement method in the wavelet domain, that is, using a soft thresholding to remove noise components from the wavelet coefficients of noisy speech. To prevent the quality degradation of the unvoiced sounds during the denoising process, we first separate unvoiced region from noisy speech and then apply the thresholding method in a different way from other regions. Simulation results demonstrate that the method has good performance. Considering the simplicity of the proposed algorithm, this method is proven to be very promising.

Improved robust speaker identification in noise using auditory properties

The paper presents a novel approach to improve speaker identification in noise with the aid of auditory properties. The redundancy of auditory representation of speech helps to introduce the missing data technique to robust speaker identification and the auditory masking threshold is used to detect the missing parts of speech features.

Interference rejection in direct-sequence spread spectrum communication systems based on higher-order statistics and genetic algorithm

A new higher order statistics (HOS) and genetic algorithm (GA)-based interference rejection filter is introduced. When a reference signal, which is highly correlated with the interference, is available, the new method uses GA to update the adaptive filter coefficients after the HOS of the primary and reference signal are computed. Compared with the adaptive filters based on second-order statistics, the HOS and GA-based filter can reject the interference more efficiently and is independent of uncorrelated Gaussian noise. The HOS and GA-based adaptive filter tends to converge to the optimum and is much less sensitive to the choice of the step size parameter than the adaptive filters based on the gradient algorithm. Computer simulations show that the method can reject narrowband interference efficiently.

Application of scan-to-scan integration-correlation to detection of small fast-moving target on sea surface

Conventional scan-to-scan integration correlation (SIC) algorithms can detect small and stationary targets. However, they are ineffective in detecting small and fast-moving targets. This paper presents an improved SIC algorithm together with clutter suppression measures that remove or decrease sea clutter. The algorithm divides the scan-to-scan integration (SI) into two branches, one provides optimum clutter attenuation by means of SI weighting while the other ensures that targets are detected even if they are fast-moving. Sea clutter suppression can lower detection thre-sholds and, at the same time, increase signal-to-clutter ratio. Simulation results show that the proposed approach greatly improves the detection capability for warship radar.

Adaptive biorthogonal local discrete cosine transform for interference excision in direct sequence spread spectrum communications

A novel time-frequency domain interference excision technique is proposed. The technique is based on adaptive biorthogonal local discrete cosine transform (BLDCT). It uses a redundant library of biorthogonal local discrete cosine bases and an efficient concave cost function to match the transform basis to the interfering signal. The main advantage of the algorithm over conventional transform domain excision algorithms is that the basis functions are not fixed but can be adapted to the time-frequency structure of the interfering signal. It is well suited to transform domain compression and suppression of various types of interference. Compared to the discrete wavelet transform (DWT) that provides logarithmic division of the frequency bands, the adaptive BLDCT can provide more flexible frequency resolution. Thus it is more insensitive to variations of jamming frequency. Simulation results demonstrate the improved bit error rate (BER) performance and the increased robustness of the receiver.

Immune RBF network and its application in the modulation-style recognition of radar signals

Based on Immune Programming(IP), a novel Radial Basis Function (RBF) network designing method is proposed. Through extracting the preliminary knowledge about the width of the basis function as the vaccine to form the immune operator, the algorithm reduces the searching space of canonical algorithm and improves the convergence speed. The application of the RBF network trained with the algorithm in the modulation-style recognition of radar signals demonstrates that the network has a fast convergence speed with good performances.

ESTIMATION OF HMM PARAMETERS BASED ON GRADIENTS

Based on the matrix representation, a new method is proposed to calculate the partial derivatives of the likelihood probability of an HMM with respect to its parameters. Experimental results are presented and a comparison is made with other methods.

Improved DSE-CMA Error Function for Blind Multiuser Interference Suppression in DS/CDMA Systems

This paper presents an improved error function of dithered signed-error constant modulus algorithm (IDSE-CMA) for blind multiuser interference suppression in DS/CDMA systems. It uses a different error function to replace the former one in sign operation of the DSE-CMA and compares their performance in multiple access interference (MAI) suppression ability. Simulations indicate that the new algorithm has better performance than the similar CMA in terms of convergence speed and steady-state performance.

Space-time multiuser detection for DS-CDMA communication in MIMO systems

Space-time signal processing based on multiple-input multiple-output(MIMO) systems is an active research field in which interfering signals are cancelled and multiuser detection is achieved using space diversity. In a Rayleigh fading channel, space-time block codes using multiple transmitting antennas can improve system performance and reduce bit-error-rate for multiuser detection. In this paper, several antenna configurations are designed for DS-CDMA communication in MIMO systems. Space-time linear multiuser detection and space-time serial interference cancellation multiuser detection are simulated. Bit-error-rate and computation complexities of the two methods are compared. Conclusions are given in the end.

A new generalized complex orthogonal space-time block codes

Recent research challenges in the wireless communication include the usage of diversity and efficient coding to improve data transmission quality and spectral efficiency. Space diversity uses multiple transmitting and/or receiving antennas to create independent fading channels without penalty in bandwidth efficiency. Space-time block coding is an encoding scheme for communication over Rayleigh fading channels using multiple transmitting antennas. Space-time block codes from complex orthogonal designs exist only for two transmitting antennas. This paper generalizes a new complex orthogonal space-time block code for four transmitting antennas, whose decoding complexity is very low. Simulations show that the generalized complex orthogonal space-time block code has low bit error rate, full rate and possibly large diversity.