On-channel Repeater Research Articles

Implementation and test results of on‐channel repeater for ATSC 3.0 systems

Despite the successful launch of Advanced Television Systems Committee (ATSC) 3.0 broadcasting worldwide, broadcasters are facing obstacles in constructing void-less large-scale single-frequency networks (SFNs). The bottleneck is the absence of decent on-channel repeater (OCR) solutions necessary for SFNs. In the real world, OCRs suffer from the maleficent feedback interference (FI) problem, which overwhelms the desired input signal. Moreover, the undesired multipaths between studio-linked transmitters and the OCR deteriorate the forward signals' quality as well. These problems crucially restrict the feasibility of conventional OCR systems, arousing the strong need for cost-worthy advanced OCR solutions. This paper presents an ATSC 3.0-specific solution of advanced OCR that solves the FI problem and refines the input signal. To this end, the FI canceler and channel equalizer functionalities are carefully implemented into the OCR system. The presented OCR system is designed to be fully compliant with the ATSC 3.0 specifications and performs a fast and efficient signal processing by exploiting the specific frame structure. The real product of ATSC 3.0 OCR is fabricated as well, and its feasibility is verified via field and laboratory experiments. The implemented solution is installed at a commercial on-air site and shown to provide substantial coverage gain in practice.

Integrated Inter-Tower Wireless Communications Network for Terrestrial Broadcasting and Multicasting Systems

This paper describes systems, devices, and methods to implement a bi-directional integrated inter-tower wireless communications network (IITWCN). The described technology can be implemented in combination with the Broadcast Core Network (BCN) in next generation broadcast eco-system and, therefore, support new business cases for broadcast operators such as the delivery of flexible datacasting services or support broadcast or point-to-point Internet services. The introduced bi-directional inter-tower communications network (ITCN) extends the previous unidirectional in-band distribution links (IDL) and adopts the on-channel repeater (OCR) as a simplified backhaul solution in single frequency networks (SFN). The concept of the coordinated ITCN is also presented, aiming at future broadcast Internet services. The ITCN provides a scalable and configurable network solution embedded in a broadcast system, which becomes independent from any non-broadcasting telecommunication infrastructure. The described technology partially relies on the infrastructure of the underlying broadcast/multicast network, using the allocated service channels without requiring additional frequency bands or a separate frequency band. The bi-directional inter-transmitter communication links are therefore referred to as integrated transmission links and the corresponding network as an integrated network.

Using Layered Division Multiplexing for Wireless In-Band Distribution Links in Next Generation Broadcast Systems

To meet the ever increasing demand for better service quality and availability, the next generation digital TV (DTV) broadcast, a.k.a., the ATSC 3.0, is developed with new capabilities to deliver 4K ultra-high-definition (4K-UHD) services to fixed receivers, robust HD-quality services to mobile receivers, as well as non-broadcast services (e.g., broadband), including Internet of Things (IoT), Connected Vehicles, etc. To realize these capabilities, it becomes necessary to evolve the existing single-transmitter high-power-high-tower (HPHT) network to multi-transmitter low-power-low-tower single-frequency-networks (SFN), which requires installing new transmitters. Each new transmitter needs a feederlink to receive the service data from the broadcast gateway (BG) for transmission. This feederlink contributes to a significant portion of installation and operational costs of the new transmitters. This paper proposes a wireless in-band distribution link (WIDL) technology, where the distribution data is delivered to the newly deployed transmitters from the existing DTV towers wirelessly sharing the same TV band with the broadcast services. The distribution signal is multiplexed with service signal in the same ATSC 3.0 waveform. Layered division multiplexing (LDM) technology is proposed to achieve more efficient transmission of the distribution signal. The WIDL offers better performance and more robust operation than the on-channel repeater (OCR) technologies. More importantly, it offers the possibility of delivering backhaul data for future applications over the DTV infrastructure, such as IoT and connected vehicles. Therefore, the proposed WIDL is one enabling technology to achieve convergence of broadcast services with broadband and other wireless services on the DTV spectrum.

대역확산 기법을 사용한 단일 채널 중계기 개발

This paper describes the elimination of feedback signals to implement a stable on-channel repeater regardless of input signals in the frequency bandwidth desired by the user. Toward this objective, the spread spectrum technique is applied to an adaptive filter, in which the least mean square algorithm removes the frequency characteristics of input signals. OCRs have been commercialized using adaptive filters based on the LMS algorithm in existing mobile communication services, including in GSM, CDMA, WCDMA, and LTE. However, in current mobile communication networks, various services with different signal characteristics can become mixed in the user’s frequency band, and bands with no signals may also exist. If the integrated bandwidth and the occupied bandwidth do not coincide, a bandpass filter cannot completely suppress other bands. Because the LMS algorithm is affected by the frequency characteristics of input signals as well as the feedback path of the object to be removed, feedback signals cannot be canceled for the entire band. Therefore, in this paper, the SS technique is applied to the existing LMS method to remove the frequency characteristics of input signals, thereby eliminating feedback signals in a more stable manner. The performance of the proposed scheme is verified through simulation and experiments.

Design Criteria for FIR-Based Echo Cancellers

The most relevant impairment experienced by on-channel repeaters (OCRs) in single frequency networks scenarios is the presence of a coupling-channel between the transmitting and receiving antennas, that generates unwanted echoes. This phenomenon causes a degradation of the repeated signal and, above all, could lead to the instability of OCRs, owing to the positive feedback that could result. For this reason, OCRs are usually equipped with echo canceller units, aimed at removing the coupling contributions. In this paper, we consider a realistic OCR setup and we analytically derive proper design criteria for echo-cancellers, showing the role of system parameters and implementation aspects on their performance. Here, in particular, we investigate the joint effect of the estimation noise and the finite precision arithmetic of digital systems, the system sensitivity to different design parameters and the relation between the echo-cancelling performance and the probability of instability.

귀환 채널 추정 및 RFP 성능을 개선한 간섭 제거 기반의 동일 채널 중계기

#$%&'()*+,-./01102345, 678 9:1; >?@*0AB:CD>?EFG H(5*IDAB(Digital Audio Broadcasting)I :JHK, *:ATSC(Advanced Television Systems Committee)GLM&NIO. J (P=>>?/O>?QRST &'U*VW XCY, *&Z[ =\U, ]^_`EFG9Rabc?>?de*fbgGhi*jkHlV O.AbstractIn this paper, Method for the phase distortion compensation timing offset and DC eliminator for the pilot component estimation and removal, transmitted and received signal correlation in the delay scheme DAB interference cancellation based on the same channel for using for estimating the feedback signal based on a between for removal for the timing offset compensation It proposes a repeater. This was applied to the ATSC system. The on-channel repeater of the proposed interference cancellation based on the interference removing capability is improved in interference signal is 20dB greater than the primary transmission signal environment via the return channel estimation and improve performance RFP. Accordingly, it was confirmed by simulation that good signal is sent out with the improvement of the ability of the repeater.Keywords : ATSC system, on-channel repeater, interference cancellation

Performance Analysis of an LMS Based Adaptive Feedback Canceller for On-Channel Repeaters

Performance Analysis of an LMS Based Adaptive Feedback Canceller for On-Channel Repeaters

Performance and Stability Analysis of Echo Cancellers Based on Training Sequences

We analyze a two-stage echo cancellation technique for on-channel repeaters (OCRs) based on the reconstruction of the coupling channel impulse response via digital filtering. The estimation of the coupling channel between the transmitting and the receiving antennas is achieved through the injection in the repeated signal of locally generated low-power pseudo-noise sequences or trains of short pulses. The analytical model developed in this paper permits the investigation of some important performance figures, such as the mean rejection ratio, the echo suppression and the echo suppression at nominal position. In addition, a new analytical framework dealing with canceller stability issues, arising due to the non perfect echo cancellation, is derived. Specifically, an upper bound on the probability of instability of the canceller is provided. As shown in the numerical results, this framework permits the identification of the main OCR design guidelines. Finally, we will validate our analytical models by showing their accordance with the experimental measurements realized with the OCR prototypes we developed.

Dynamic Gain Management for On-Channel Repeaters

Stability and output signal quality are always two major concerns with the deployment of on-channel repeaters. This paper proposes a gain management scheme and evaluates the performance of the proposed gain management technique for on-channel repeaters. The gain manager uses a loop gain metric as an indication of stability and output signal quality (SNR) of the repeater to continuously and accurately monitor the repeater status, and adjust the repeater gain accordingly. The repeater output SNR and stability can thus be tightly controlled. It is demonstrated that the proposed gain management ensures the safe and robust operation of the repeater against the dynamics of the environment.

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.

Equalisation digital on‐channel repeater with a feedback interference canceller for the advanced television systems committee terrestrial digital television system

In this study, the authors propose a novel equalisation digital on-channel repeater (EDOCR) with a feedback interference canceller (FIC) for a single frequency network of the advanced television systems committee terrestrial digital television system. The proposed EDOCR with an FIC not only has high output power by the cancellation of feedback signals caused by insufficient antenna isolation through the FIC, but also shows better quality of output signals than conventional digital on-channel repeaters (DOCRs) by removing multipath signals existing between the main transmitter and DOCR, as well as residual feedback signals through an equaliser. Computer simulation results are provided to demonstrate the superior performance of the proposed EDOCR with an 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.

FPGA Design and Performance Evaluation of a Pulse-Based Echo Canceller for DVB-T/H

The main design issues and performance characterization of an echo canceller for digital on-channel repeaters (OCRs) applicable to multiple standards for communications and broadcasting are addressed. In particular, in this paper we focus on a DVB-T/H scenario. The low-complexity channel cancellation technique here described is based on the introduction of a negative feedback loop capable to counterbalance the coupling effects between the OCR antennas (echoes). In the initial phase, locally generated pulse trains are transmitted to estimate the coupling channel between the transmitting and the receiving antennas. This first echo estimation is used to set-up the canceling unit, whose purpose is to generate a properly filtered replica of the repeated DVB-T/H signal compensating the echoes. After the initial set-up of the system, efficient tracking of the echoes can be performed through conventional least mean square (LMS) techniques. After developing a proper theoretical model, we introduce and discuss some important performance figures such as mean rejection ratio (MRR) and echo suppression at nominal position (ESNP). Then, a detailed description of our implementation of the echo canceller on a field programmable gate array (FPGA) board is reported. Finally, the performance of our prototype is evaluated and the measurement results are compared with those derived by the analytical model.

Path Loss Model for Coupling Loop Interference with Multiple Reflections over Single Frequency Network

Path loss models are important for predicting coverage area and for performance analysis in simulation and design of radio systems including an on-channel repeater (OCR). In this paper, an analytical path loss model for the coupling loop path is proposed to evaluate the performance of an OCR in a single frequency network (SFN). Since the receive antenna and the transmit antenna in the OCR are electrically coupled, the coupling loop interference (CLI) between the transmitting and receiving antennas at the OCR must be suppressed in order to avoid signal distortion and oscillation. Although numerous publications exist for path loss models, the assumption is commonly that transmit and receive antennas are fully separated. Therefore, an important step toward designing and installing an OCR station in an SFN is to model the actual propagation characteristics of CLI. Based on the ellipses model, an analytical path loss model in which the receiver and the transmitter are co-located is developed according to reflection distance.

지상파방송 난시청 해소를 위한 특정소출력 DTV 중계기(II): 구현 및 현장시험

In this paper, low power on-channel DTV repeater is implemented to improve the fringe area of terrestrial DTV broadcasting services and its effectiveness is verified by field trials. System requirements of on-channel repeater are drive from received signal model and gain transfer model. Implemented on-channel DTV repeater has coverage of about 1km with 10mW/MHz output power. Experimental results show that implemented system can effectively improve small/medium size DTV fringe areas in Korea.

Correlation Canceling-Type Feedback Canceler Based on Decision-Directed Pilot Symbols for T-DMB Repeaters

This paper presents a novel correlation canceling-type feedback canceler based on decision-directed pilot symbols for a terrestrial digital multimedia broadcasting (T-DMB) on-channel repeater (OCR). In order to guarantee an additional isolation of the OCR, two types of the feedback cancelers have been investigated: a correlation canceling (CC)-type feedback canceler and a frequency-domain channel estimation (FDCE)-type feedback canceler. While both of the feedback cancelers suppress the feedback signal effectively, they can operate complementarily each other with their own respective advantages. To achieve these complementary properties of the two types of feedback cancelers, we adopt a CC-type feedback canceling structure based on the frequency-domain estimated pilot symbols. The proposed feedback canceler improves the feedback channel estimation accuracy of the conventional CC-type feedback canceler as well as increases the channel estimation speed of the conventional FDCE-type feedback canceler. Simulation results show that the proposed feedback canceler has better feedback canceling performance and tracking ability for dynamic feedback channels.

Channel Estimation and Interference Cancellation of Feedback Interference for DOCR in DVB-T System

This paper considers a problem of unwanted feedback interferences caused by coupling from the transmit antenna to the receive antenna in the digital video broadcasting-terrestrial (DVB-T) digital on-channel repeater (DOCR) system. We model the DVB-T DOCR system and propose a feedback interference cancellation method based on the linear minimum mean square error (LMMSE) estimation of the feedback interference channel. Since the accurate estimation of the feedback interference channel is an important factor that determines the performances of the feedback interference cancellation, the channel estimation by averaging the estimated channel and iterative decision feedback cancellation method are proposed. Simulation results of signal-to-noise ratio (SNR) relation between the reference SNR and the processed SNR are presented and the theoretical analysis is performed to verify the simulation results. The proposed methods are compared to the conventional method on the typical urban 6 channels with maximum Doppler frequencies of 0 Hz and 3 Hz in terms of SNR, bit error rate and various transmission modes in the DVB-T system. Simulation results and the theoretical results show that the proposed method outperforms the conventional method.

VSB-Based Digital On-Channel Repeater with Interference Cancellation System

This paper investigates the design and performance of a digital on-channel repeater (DOCR) for use in Advanced Television Systems Committee (ATSC) digital television (DTV) broadcasting. The main drawback of a DOCR is the echo interference caused by coupling between transmitter and receiver antennas, which induces system instability and performance degradation. In order to overcome this problem, an echo canceller based on the adaptive echo channel estimation (ECE) technique has been researched and applied for a DOCR. However, in the case of ATSC, the pilot signal, which is used for carrier synchronization, may cause a DC offset error and reduce the isolation performance of the echo canceller for a DOCR in an ATSC network. Moreover, since the multipath fading effect of a radio channel usually occurs in a real environment, it should be minimized to improve the overall performance of a DOCR. Therefore, due to the limited isolation performance of echo canceller and the multipath fading effect, an interference cancellation system (ICS) is proposed for a DOCR in an ATSC network. The performance of the proposed DOCR with an ICS is evaluated by software simulation and hardware test results.

VSB-Based Digital On-Channel Repeater with Interference Cancellation System

VSB-Based Digital On-Channel Repeater with Interference Cancellation System

Techniques for High-Performance DAB and DVB-T On-Channel Repeaters

On-channel repeaters are able to receive and re-transmit a broadcast signal on the same frequency and thus can facilitate network expansion, particularly in an SFN, and network repair following the introduction of strong adjacentchannel transmissions. For effective operation, systems must incorporate excellent RF design and high-performance signal processing in order to remain stable and re-radiate a clean, decodable signal. This paper describes the operation of on-channel repeaters designed for DAB and DVB-T signals by BBC R, and goes on to outline a number of key techniques, including correlation compensation for controlling unwanted out-of-band products due to part-Nyquist signal occupancy and adaptive null-steering for pre-echo rejection in a DAB SFN. The former is now a field-proven technique whilst the latter is in development and awaiting a full engineering realisation. Keywords: Active deflector, DAB, DVB-T, on-channel repeater, SFN, transposer, Residual Correlation, Pre-Echoes, Twin-Antenna Reception, steering vector