Seung-Won Kim

Equalization digital on-channel repeater in the single frequency networks

Digital On-Channel Repeater (DOCR) can be used for Single Frequency Networks (SFNs). It is much simple and low cost compared to Distributed Transmitter which needs Studio to Transmitter Link (STL). However, traditional DOCR has one of those defects such as a power limit, a long time system processing delay or a poor output signal quality. In order to overcome all of those defects, we introduce Equalization DOCR (EDOCR) which regenerates the original 8-VSB output signal with relatively short time system processing delay. Lab. and Field test results show that the EDOCR can eliminate the loop-back signal up to 5.5 dB with 5.5 /spl mu/s system processing delay. By using EDOCR, we can save spectrum resources and extend coverage areas.

A Design of Equalization Digital On-Channel Repeater for Single Frequency Network ATSC System

This paper presents a guideline for designing an Equalization Digital On-Channel Repeater (EDOCR) and proposes an efficient method to implement it. The major concerns in the design of an EDOCR are shortening the system delay, maintaining synchronization between a main transmitter and an EDOCR, obtaining high signal to noise ratio (SNR) output, and enabling operation in an environment of adjacent channel interference. The short system delay is achieved adopting a demodulation scheme without an additional lowpass filter to remove harmonics, an intelligent slicer of a trellis decoder with a trace back depth of 1 for equalization, and an equi-ripple filter for the 8-VSB pulse shaping filter. To maintain the synchronization, the frequency offset information extracted from the received signal is reflected on a re-transmitting signal. Distinguished features of the EDOCR are adaptive equalization with the intelligent slicer which corrects symbol errors caused by on-air interface including the signal loopback, and the signal processing scheme which demodulates the received signal to a baseband symbol and re-modulates the symbol. Hence, the EDOCR can produce an exact replica of the main transmitters signal with high SNR although there may be adjacent channels and input signal is distorted by multipath and noise. Finally, the performance evaluation of the designed EDOCR in both simulation and laboratory tests are presented and implementations of single frequency networks employing EDOCRs are discussed

Performance analysis of error propagation effects in the DFE for ATSC DTV receivers

The paper analyzes the error propagation phenomenon in the decision feedback equalizer (DFE) for the receivers of Advanced Television Systems Committee (ATSC) digital television (DTV) and presents the performance upper-limits of the DFE by comparing various error propagation cases and the no-error propagation case. As one approach to the performance limit, we consider a blind DFE, adopting a trellis decoder with a trace-back depth of 1 as a decision device. Through simulation, we show how much the DFE performance in ATSC DTV receivers is affected by error propagation. We found that while blind equalization is preferable to decision-directed (DD) equalization at signal-to-noise ratio (SNR) values less than 18 dB, DD equalization is superior to blind equalization at SNR values greater than 18 dB. In addition, symbol error rate curves quantitatively show that the performance difference in the DFE caused by error propagation becomes clearer at the trellis decoder following the DFE. The analysis results presented are very informative for developing equalization algorithms for ATSC DTV receivers.

Blind decision feedback equalization for VSB-based DTV receivers

We present a novel blind decision feedback equalization algorithm for VSB-based DTV receivers by modifying a stop-and-go dual-mode algorithm to improve the performance of convergence speed and residual MSE. Considering VSB modulation and RF-band effects with the baseband-equivalent VSB channel model raises the reliability of our results for practical applications.

Enhanced-xVSB system development for mobile/portable reception

The paper describes an enhanced-xVSB system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. The proposed system is fully backward compatible with the current ATSC 8-VSB standard. For mobile and portable reception support, the E-xVSB system adopts a reduced constellation method as well as an enhanced trellis-coded modulation scheme.

Enhanced-xVSB system development for improving ATSC terrestrial DTV transmission standard

This paper describes advanced dual stream system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. E-xVSB system can transmit a mixture of normal (8-VSB) stream and enhanced (robust) stream. The robust stream has a higher threshold of visibility (TOV) compared to the standard stream, and legacy receivers ignore the robust packets. Thus, Enhanced-xVSB system is fully backward compatible with a current ATSC standard. For more robust transmission support, E-xVSB system adopts a reduced constellation method as well as enhanced trellis-coded modulation scheme. E-xVSB system supports a variety of enhanced modulation schemes: Pseudo-2VSB, Enhanced-4VSB, modified Enhanced-8VSB and Hybrid-VSB. Proposed system has been tested in the Lab, and the testing results are shown in this paper.

An adaptive carrier synchronization technique for robust 8-VSB DTV reception

In this paper, an adaptive digital frequency phase locked loop (FPLL) algorithm is proposed to improve the carrier recovery performance of 8-VSB receiver. The proposed carrier synchronization technique not only provides a robust 8-VSB DTV reception in fixed and indoor environments, but also makes it possible to watch the HDTV in portable environment. This is because the proposed technique dramatically reduces tracking jitter and acquisition time and enlarges acquisition range by adopting a sign detector, pilot extract filter bank, adaptive lock detector, mode selector, and loop filter bank to the conventional FPLL algorithm.

Field Test Results of the E-VSB System in Korea

This paper presents and analyses field test results of the Enhanced-VSB (E-VSB) system proposed by Zenith/ATI and adopted as an Advanced Television Standard Committee (ATSC) standard. The possibility of successful reception at outdoor and indoor test points according to types of antennas, noise margin, and ease of reception are measured to analyse performance improvement of the E-VSB system. Verification of backward compatibility between the E-VSB and conventional 8-VSB systems, selection of test points, and configurations of the transmitter and the test vehicle are also presented. The field test results show that the E-VSB system does not only outperform the 8-VSB system at severe multipath environment such as indoor reception, but also is fully backward compatible with it

Frequency-domain equalization for distributed terrestrial DTV transmission environments

This paper presents a frequency-domain direct-inversion equalization method for DTV receivers to deal with 0 dB ghosts. To secure the existence of a channel inverse, channel-matched filtering and noncausal filtering are performed prior to equalization. Simulation results show that the proposed method has a comparable performance to the ideal DFE

Robust decision-feedback equalization with a noncausal filter for ATSC DTV receivers

This paper presents a robust decision-feedback equalization method for 8-VSB DTV receivers under severe channel environments where a 0-dB ghost exists. Noncausal filtering is employed to make a severe channel be mild. Simulation results show that the proposed method has more stable convergence than existing decision-feedback equalization schemes.