Kyung-Taek Lee

Pilot-Aided Iterative Frequency Offset Estimation for Digital Video Broadcasting (DVB) Systems

The main disadvantage of orthogonal frequency division multiplexing (OFDM) systems is its sensitivity to carrier frequency offset and timing offset. This paper proposes a simple way of improving the performance of the integer frequency offset (IFO) estimator in OFDM-based digital video broadcasting (DVB) system. By modifying the conventional maximum likelihood (ML) estimator to have multi-stage estimation strategy, two IFO estimators are derived. Simulations indicate that the proposed IFO estimators work robustly with reduced computational burden when compared to ML estimator.

The efficacy of portal vein embolization prior to right extended hemihepatectomy for hilar cholangiocellular carcinoma: A retrospective cohort study

BACKGROUND/PURPOSE Preoperative portal vein embolization was introduced to minimize complications after extended hepatectomy. This retrospective cohort study was conducted to compare outcomes with and without portal vein embolization before hepatectomy for hilar cholangiocellular carcinoma. METHODS This study was conducted with 35 patients who underwent right extended hemihepatectomy for hilar cholangiocellular carcinoma from 2001 to 2008. Preoperative portal vein embolization was performed in 14 patients (embolization group) and not performed in 21 patients (non-embolization group). RESULTS The groups did not differ in terms of sex, age, operative time, transfusion, postoperative serum bilirubin level, prothrombin time, and length of intensive care unit (ICU) stay. Although blood loss was higher in the embolization group than in the non-embolization group (P = .009), no major complications were observed between embolization and resection. At presentation, future liver remnant was smaller in the embolization group (19.8%, range 16-35%) than in non-embolization group (28.3%, 15-47%; P = .001). After embolization, the volume of the future liver remnant increased significantly to 27.2% (range, 23-42%; P = .001). Future liver remnants just before operation were similar in both groups (P > .99). There was no significant difference in terms of the rate of morbidity and in-hospital mortality. No statistically significant differences were observed in disease-free survival (P = .52) and overall survival (P = .30). CONCLUSIONS Portal vein embolizations do not increase the rate of morbidity, in-hospital mortality, local recurrence and system metastasis. Therefore it can be considered safe and effective for patients with small future liver remnants. Embolization can lessen postoperative liver failure and widen the indication of the surgical resection, especially in patients with marginal future liver remnants.

Development of Portable T-DMB Receiver for Data Services

In December 2005, Korea launched terrestrial DMB (T-DMB) services for the first time in the world, making multimedia broadcasting services available in the mobile environment. In addition to high-quality digital radio (audio) and television (video), diverse data services, such as traffic and travel information, BIFS, and visual radio, are currently being serviced. At the moment, there are no mobile/portable T-DMB terminals in the market that can support all the data services available. In this paper, we present a low-power portable T-DMB receiver, which can decode not only T-DMB video services but also various data services. In particular, it can simultaneously decode DMB video and data services within the same ensemble.

Digital tuner implementation using FM tuner for DRM plus receivers

The DRM Plus standard is being considered by many as a digital replacement of analog FM broadcasting. In this paper, an implementation of the DRM Plus tuner is described using the existing FM tuner and a digital signal processor (DSP). Performance of the proposed tuner is verified with satisfactory results.

Pilot-aided frequency offset tracking scheme for OFDM-based DVB-T

The main disadvantage of orthogonal frequency division multiplexing (OFDM) systems is its sensitivity to carrier frequency offset and timing offset. This paper proposes a simple way of improving the performance of a residual frequency offset (RFO) estimator in OFDM-based digital video broadcasting (DVB) system. To demonstrate the efficiency of the proposed RFO estimator, comparisons are made with conventional estimator in terms of mean square error (MSE) performance, estimation range, and complexity.

Exploiting Ambient Light Sensor for Authentication on Wearable Devices

Wearable devices are computationally rich, portable and wearable to suit users in various needs and situations. Still, users of wearable devices suffer from lack of efficient input methods and proper feedback modality. In this paper, we design and implement a novel input method exploiting readily available ambient light sensor on wearable devices. We present concepts and implementation results of re-purposing the light sensor for user input and processing UI events. Furthermore, a PIN entry application based on the proposed input method is implemented to demonstrate a device authentication scenario for wearables.

A new binary tree algorithm implementation with Huffman decoder on FPGA

Compression is useful technique in digital system, as it reduces the channel bandwidths and storage size. This paper presents new Huffman decoder based on binary tree method for improving usage of memory and speed. It is shown through experiment result related to computational speed that the propose method is superior to other predecessor. The customized Huffman hardware decoder comparison is presented at different speed on various FPGAs.

Accurate Pilot-Aided Sampling Frequency Offset Estimation Scheme for DRM Broadcasting Systems

In this paper, we propose an improved sampling frequency offset (SFO) estimation scheme for orthogonal frequency division multiplexing (OFDM) based digital radio mondiale (DRM) broadcasting systems. To demonstrate the performance of the proposed frequency estimator, analytical expression of the mean square error (MSE) is derived and performances are compared with conventional pilot-assisted estimators. Based on the simulation and theoretical analysis, our proposed estimator shows an improved estimation performance compared to the conventional estimators.

Detection method for digital radio mondiale plus in hybrid broadcasting mode

In this paper, we propose a detection method for Digital Radio Mondiale (DRM) Plus suitable for hybrid mode broadcasting of both DRM Plus and analog FM (Frequency Modulation) within the same frequency band. The guard-interval correlation method of Orthogonal Frequency Division Multiplexing (OFDM) is good for DRM Plus signal detection, but the false alarm possibility increases when FM signal is received. The proposed method includes a reference block in the guard-interval correlation which increases the identification rate of weak DRM Plus signals and decreases the false alarm possibility when analog FM is received. The performance of the proposed method is verified through simulations1.

Synchronization Receiver for OFDM-Based FM Broadcasting Systems

The digital radio mondiale (DRM) consortium is now preparing to test and verify the design of DRM plus, prior to standardization, produce a revision to the existing DRM system specification. This paper presents an overview of the OFDM-based DRM system, planned to operate in FM bands, utilizing important receiver aspects, such as timing and frequency synchronization, which can provide benefits to the overall system performance. In particular, algorithms are devised or selected for the sequential estimation of symbol timing and carrier frequency offsets by exploiting the structure of the data and pilot. The performance of using the proposed algorithms is demonstrated via several examples in the channel models for FM bands.