Yong-Serk Kim

Frequency-Domain Double-Talk Detection Based on the Gaussian Mixture Model

In this letter, we propose a novel frequency-domain approach to double-talk detection (DTD) based on the Gaussian mixture model (GMM). In contrast to a previous approach based on a simple and heuristic decision rule utilizing time-domain cross-correlations, GMM is applied to a set of feature vectors extracted from the frequency-domain cross-correlation coefficients. Performance of the proposed approach is evaluated through objective tests under various environments, and better results are obtained as compared to the time-domain method.

A voice trigger system using keyword and speaker recognition for mobile devices

Voice activity detection plays an important role for an efficient voice interface between human and mobile devices, since it can be used as a trigger to activate an automatic speech recognition module of a mobile device. If the input speech signal can be recognized as a predefined magic word coming from a legitimate user, it can be utilized as a trigger. In this paper, we propose a voice trigger system using a keyword-dependent speaker recognition technique. The voice trigger must be able to perform keyword recognition, as well as speaker recognition, without using computationally demanding speech recognizers to properly trigger a mobile device with low computational power consumption. We propose a template based method and a hidden Markov model (HMM) based method for the voice trigger to solve this problem. The experiments using a Korean word corpus show that the template based method performed 4.1 times faster than the HMM based method. However, the HMM based method reduced the recognition error by 27.8% relatively compared to the template based method. The proposed methods are complementary and can be used selectively depending on the device of interest.

Fast subpel motion estimation using selective motion vector accuracy of inter-mode decision for H.264/AVC

MPEG-4 Part-10 AVC/H.264 (H.264/AVC) is the newest video coding standard developed and finalized in March 2003 by the Joint Video Team (JVT) of ISO/IEC (MPEG) and ITU-T (VCEG). It includes many powerful features such as multiple reference pictures, variable block-size motion compensation, quarter-pel accuracy motion compensation, and so on. As a result, it achieves high coding performance but at the expense of huge computational complexity. To reduce the complexity while keeping the same coding performance, we propose a low complexity subpel motion estimation method using two content-aware decision criteria. Based on the criteria, four different levels of subpel motion estimation are proposed to achieve low complexity subpel motion estimation. Simulation results show that the proposed method reduces total encoding time by 55.53% on average and subpel motion estimation time by 82.2% on average.

Adaptive rate control for real-time video streaming over the mobile WiMAX

To achieve high video quality for real-time video streaming over the mobile WiMAX network, it is necessary to adaptively adjust the target bit rate of the video encoder based on verified network status. Since it is difficult to verify network congestion using only PHY-layer parameters, this paper proposes an algorithm for verifying network status by using a MAC-layer parameter implying PHY-layer information and then correspondingly adjusting the target bit rate. The results show that the proposed algorithm achieves a video quality 0.7 to 6.3 dB higher than that achieved with fixed target bit rates over the mobile WiMAX network.

A Globally Converging Blind Carrier Phase Offset Recovery Scheme for 8-VSB Signals

This paper presents a decision directed blind adaptive algorithm for carrier phase offset recovery of 8-VSB. The algorithm achieves phase recovery by minimizing the quadrature leakage into the in-phase component and removes undesirable local minima, which occur in most blind algorithms, by configuring the reliable leakage estimation region.

Development platform implementation and verification for UMTS UE MODEM

In this paper, we present the development platform (DP) of a user equipment (UE) baseband modem in compliance with 3GPP Release 99 FDD specification. The configuration of the development platform and a detailed explanation of test items are described. The functionality and performance of the UE modem and protocol stacks (layer 1 and layer 2/3) are confirmed by HW/SW co-verification using Seamless CVE and call tests using the Anritsu MD8480A base station simulator. Currently, the UMTS UE modem chip based on development platform is implemented in 0.18 /spl mu/m CMOS technology and tests on the chip are in progress.