Equalization Digital On-channel Repeater Research Articles

ATSC DTV 방송용 중계기 궤환간섭 제거 성능 개선

본 논문에서는 ATSC DTV 시스템에서 독립적인 궤환간섭 제거기(Feedback Interference Canceller: FIC)를 가지는 등화형 디지털 동일채널 중계기(Equalization Digital On-Channel Repeater: EDOCR)의 궤환간섭 제거 성능 향상을 위한 새로운 구조의 FIC를 제안한다. FIC는 기준신호와 궤환되는 신호의 상관관계를 이용하여 궤환채널을 추정하는데, ATSC DTV 방송 신호는 신호의 상관관계 특성을 저해하는 DC 파일럿을 포함하고 있으므로 FIC로 하여금 정확한 궤환채널 추정을 수행하지 못하게 한다. 이러한 문제를 해결하기 위해, EDOCR과 FIC의 결합 구조에 기반하여 EDOCR에서 신호 재변조 시 DC 파일럿을 포함하지 않는 기준신호를 추가적으로 생성하여 궤환채널 추정에 사용하는 DC 파일럿 없는 기준신호 기반 FIC와 디지털 신호처리를 통해 입력신호들을 백색화하여 DC 파일럿을 제거한 후 궤환채널을 추정하는 백색화된 신호 영역 FIC를 제안한다. 모의실험을 통해, 제안된 두 FIC 구조 모두 기존의 상관관계 제거형 FIC에 비해 우수한 궤환간섭 제거 성능을 가짐을 보인다. We propose two feedback interference cancellers(FICs) to improve the performance of the equalization digital on-channel repeater(EDOCR) with the FIC for the ATSC DTV broadcasting system. The FIC estimates the feedback channel between Tx. and Rx. antennas of the repeater by cross-correlating the reference signal and the feedback signal. Since there is a DC pilot which ruins the white property of the ATSC DTV signals, the FIC cannot estimate the feedback channel accurately. To solve the problem, the structural method which uses an additional DC pilot free reference for feedback channel estimation and the algorithmic method based on the digital signal processing which whitens the ATSC DTV signals and performs the feedback cancellation in the whitened signal domain. Simulation results show that the proposed two FICs show better feedback cancellation performance than the conventional FIC.

A Novel Distributed Translator for an ATSC Terrestrial DTV System

This paper presents a new design and implementation method of distributed translator (DTxR), termed the equalization DTxR (EDTxR), for distributed translator network in ATSC systems. EDTxR has a simple structure and does not require any devices to be added to studio or transmitter facilities already deployed. EDTxRs which retransmit the same transmitter signal can have identical output symbol streams among them without additional synchronization information by utilizing the structure of the equalization digital on-channel repeater (EDOCR). Moreover, they can synchronize output frequency among them without global positioning system (GPS) clock receivers by adopting a crystal oscillator for each translator and compensating the frequency offset of the each crystal oscillator through the carrier and timing recovery. To verify the proposed method, multiple EDTxRs are implemented and tested in the laboratory and in the field. Through the tests, it is confirmed that EDTxR is a simple and economic distributed translator for distributed transmission system which does not need additional synchronization devices. Therefore, EDTxR can be a promising translator for coverage extension of digital terrestrial television broadcasting under spectrum deficient situations.

Interference Cancellation On-Channel Regenerative Repeater for the Single Frequency Network of ATSC Terrestrial Broadcasting

In this paper we consider technological requirements to broadcast digital television signals using single frequency networks(SFN) in the Advanced Television Systems Committee(ATSC) transmission systems and propose Interference Cancellation Digital On Channel Regenerative Repeater(IC-DOCR) thar overcomes the limitation of EDOCR(Equalization Digital On Channel Repeater) proposed by ETRI. The proposed IC-DOCR maintains the benefits of EDOCR that have good output signal quality removing multi-path, additive white Gaussian noise(AWGN). In additional, since the Interference Cancellation algorithm using the 8-VSB symbol demodulation of received signal removes the Interference of feedback signal, IC-DOCR improve the weakness of EDOCR that have low isolation between receive and transmit antenna so that can overcome the limitation of output signal power. we did analysis and verification of the proposed system performance using computational simulation.

ATSC 지상파 DTV 시스템을 위한 궤환간섭 제거기를 가지는 EDOCR

In this paper, we propose an equalization digital on-channel repeater (EDOCR) with a feedback interference canceller (FIC) for single frequency network of the ATSC terrestrial DTV system. The proposed EDOCR with FIC does not have only high output power by cancelling feedback signals caused by insufficient antenna isolation through the FIC, but also shows better quality of output signals than the conventional on-channel repeaters (OCRs) by removing multipath signals existing between the main transmitter and the OCR, and residual feedback signals through an equalizer. In addition, computer simulations are provided to figure out the superior performance of the proposed EDOCR with FIC.

Modulation and Pre-Equalization Method to Minimize Time Delay in Equalization Digital On-Channel Repeater

This paper presents novel modulation and pre-equalization methods to minimize a signal processing time delay in the equalization digital on-channel repeater (EDOCR) for the ATSC terrestrial digital TV system. The proposed modulation method uses equi-ripple (ER) filter for vestigial side bands (VSB) pulse shaping instead of conventional square root raised cosine (SRRC) filter. And the proposed pre-equalization method calculates pre-equalizer filter coefficients by comparing a baseband signal as a reference signal and a demodulated repeater output signal, and then creates new VSB pulse shaping filter coefficients by the convolution of the ER filter and the pre-equalizer filter coefficients. The new VSB pulse shaping filter minimizes the time delay of EDOCR by adjusting the number of its pre-taps and also compensates the linear distortions due to the use of the ER filter and mask filter.

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

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> 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 transmitter's 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. </para>

Equalization Digital On-Channel Repeater in the Single Frequency Networks

Digital On-Channel Repeater (DOCR) can be used for Single Frequency Networks (SFN's). 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.