Gi Hun Lee

Shell partition-based joint blind equalization for QAM systems

For quadrature amplitude modulation (QAM) systems, the joint blind equalization (JBE) algorithm, concatenation of the constant modulus algorithm (CMA) and the decision-directed (DD) algorithm, has been widely used. After initial equalization is accomplished by the CMA, the DD algorithm follows for fine equalization. This paper proposes a shell partition-based CMA (SPCMA), a multi-modulus CMA based on the equalizer output power, in which decision boundaries are obtained by maximum likelihood (ML) estimation. Unlike the DD algorithm, the SPCMA is independent of the carrier phase error and yields better results than the CMA, showing the optimum performance for QAM constellations. The proposed SPCMA is applied to the JBE algorithm, resulting in the JBE-SPCMA, in which the SPCMA follows the CMA. To compensate for the carrier phase error, the shell partition-based hybrid algorithm (SPHA) combining the SPCMA and a shell partition-based generalized Sato (1975) algorithm (SPGSA) is proposed and it is combined with the JBE, generating the JBE-SPHA. Computer simulation results for 16- and 64-QAM show the effectiveness of the proposed JBE algorithms.

Three-dimensional DCT/WT compression using motion vector segmentation for low bit-rate video coding

This paper proposes a method that combines 3-D compression with segmentation-based coding, in which 1-D temporal decomposition by the discrete cosine transform (DCT) and 1-D wavelet packet decomposition are employed. The proposed 1-D DCT/WT consists of a variable (2-, 3-, and 4-) point 1-D DCT for effective reduction of temporal redundancy and wavelet packet decomposition for adaptive selection of spatial frequency bands. Effectiveness of the proposed method is shown by computer simulation.

Modification of the reference signal for fast convergence in LMS-based adaptive equalizers

In adaptive equalizers based on least mean squares (LMS) algorithms, the convergence rate is determined by the correlation matrix of an input signal. When the eigenvalue spread of the correlation matrix is close to unity, the convergence rate is quite fast. In this paper, for fast convergence of LMS-based adaptive equalizers we propose a modified reference signal pertinent to the given statistical channel. From the theoretical analysis and computer simulations, it is shown that the proposed modification method is guile effective for fast convergence of LMS-based adaptive equalizers. >

Wavelet packet-based progressive image transmission by prioritized subband selection and multistage quantization

This paper proposes progressive image transmission (PIT) algorithms based on the wavelet packet transform. In the proposed methods quantization steps are optimized at each stage in an embedded manner for the given bit rate. After quantization selected subbands are ordered by their priorities for transmission. Subjective quality of the reconstructed image is improved by human visual system (HVS) weighting.

Hardware architectures of adaptive equalizers for the HDTV receiver

This paper proposes hardware architectures of adaptive equalizers applicable to both the quadrature amplitude modulation (QAM) and vestigial sideband modulation (VSB) systems. First, adaptive equalization algorithms for QAM and VSB systems are presented by modifying the constant modulus algorithm (CMA) and least mean squares (LMS) algorithm, and their hardware mapping procedure is described. The proposed digitization methods requiring a low hardware cost show performance comparable with that of the algorithm employing floating-point operations. To reduce the hardware cost of the high-definition television (HDTV) equalizers, we propose a pipelined architecture that processes some parallel parts sequentially. The synthesis results by very-high-speed integration circuit (VHSIC) hardware description language (VHDL) show that the proposed architecture reduces the hardware complexity by a factor of two, compared with the architecture designed directly from the equalization algorithms.

Joint blind equalization with a shell partition-based CMA for QAM signal constellations

For quadrature-amplitude modulation (QAM) systems, the joint blind equalization (JBE) algorithm, concatenation of two different equalization modes, has been widely used. After the eye is opened by the blind equalization mode, the decision-directed (DD) mode follows to improve the equalization performance with fast convergence. This paper proposes a shell partition-based constant modulus algorithm (CMA) (SPCMA) which acts as the DD mode in the JBE. Computer simulation results for 16-QAM show the effectiveness of the proposed JBE.

Efficient VLSI architechtures of adaptive equalizers for QAM/VSB transmission

This paper proposes hardware architectures of adaptive equalizers applicable to both the quadrature amplitude modulation (QAM) and vestigial sideband modulation (VSB) systems. This paper presents digitization methods for QAM and VSB systems requiring a low hardware cost with the performance comparable to that of the algorithm employing floating-point operations. To reduce the hardware cost of the high definition television (HDTV) equalizers, we also propose a pipelined architecture that processes some parallel parts sequentially.