Young-Woo Suh

Interference Cancellation Techniques for Digital On-Channel Repeaters in T-DMB System

Digital on-channel repeater (DOCR) is regarded as a desirable solution to effectively build a wide-area network of mobile terrestrial-digital multimedia broadcasting (T-DMB) services. On the other hand, the DOCR mainly suffers from interference effects caused by a strong feedback signal and a time-varying channel dispersion. In this paper, we propose a novel DOCR for use in the T-DMB system in order to mitigate effectively both interference effects. First, we present an energy equalizer using the scarce pilot structure of T-DMB system to estimate a channel state information on every OFDM symbol. An optimum frequency domain channel estimation (FDCE) algorithm is then derived for the energy equalizer. In addition, a moving average filter (MAF) is employed to mitigate the phase distortion of truncated equalizer coefficients in deep null channel. Finally, in the performance evaluations, it is shown that the optimum FDCE outperforms a perfect FDCE. It is also shown that the DOCR equipped with the proposed interference cancellation can solve the problems caused by a limited channel information update, a phase distortion of the equalizer, and a residual feedback signal.

A novel integrated measurement and analysis system for digital broadcasting

To analyze numerous field test data of digital broadcasting systems efficiently, field measurement systems have been integrated and become more intelligent. In this paper, we present the Integrated Measurement and Analysis System (IMAS) which manages DTV and TDMB (Terrestrial Digital Multimedia Broadcasting) test data very efficiently. This system can measure various parameters of DTV, T-DMB as well as analog TV (ATV) and FM broadcasting in fixed or mobile measurement mode. All the test equipments are connected through the local area network and managed by the system controller with an open device interface. Every test result can be converted into specific standard formats and stored in the main data base which can be accessed with a web graphical user interface through the intranet.

Echo Canceller for On-Channel Repeaters in T-DMB System

In this paper, a new adaptive algorithm applied to echo canceller for on-channel repeaters is proposed. At each repeater in a single frequency network (SFN) for T-DMB, there are unwanted echo signals caused by the coupling from the transmit antenna to receive antenna. Gradient adaptive lattice (GAL) can be used as an adaptive filter to cancel out those echo signals. In comparison with other adaptive algorithms, the orthogonalization properties of the GAL algorithm provide a compromise in computational complexity. This paper shows computer simulation results of rate of convergence (ROC) of mean square error (MSE) compared to other adaptive algorithms.

Adaptive HPA Linearization Technique for Practical ATSC DTV System

In the digital television (DTV) broadcasting system, high power amplifier (HPA) is the most essential device to expand the service availability and coverage. However, as the input power level of HPA increases, the HPA is driven into the saturation mode and HPA output signal suffers nonlinear distortion. HPA nonlinearity is potentially responsible for adjacent channel interference and inter-symbol interference (ISI). To prevent these negative effects, digital pre-distortion (DPD) is one of the most widely used techniques for the HPA linearization. In order to estimate the HPA nonlinearity, DPD technique requires a feedback signal, which needs to be appropriately down converted and digitized from HPA output. However, since the feedback signal might be generally influenced by offset error, it is important to reduce the offset error in order to improve HPA linearization. In this paper, an adaptive DPD technique based on iterative look-up table (LUT) update and adaptive acquisition is proposed. The proposed DPD technique is validated on the advanced television systems committee (ATSC) terrestrial DTV broadcasting system by computer simulation and laboratory test.

Network Design and Field Application of ATSC Distributed Translators

In this paper, a design method for a distributed translator network considering the equalization window of commercial receivers is presented and compared with the field application results with three distributed translators in an urban area of Seoul, Korea. Proper transmission timing to minimize pre-ghost can be derived from the proposed design method. With designed timing information and the measured TxID (Transmitter Identification) information, the transmission timings of translators can be adjusted. Three types of receivers with different chipset generations were used for this field test. Several combinations of translators were applied for the analysis of the effect of operating multiple translators. Field test results are analyzed and discussed for the evaluation of the target distributed translator network and its design method.

A novel receive power analysis system for DTV broadcasting network

This paper presents a receive power analysis system for DTV broadcasting networks. This system measures the receive power and channel information simultaneously, analyzes the receive power of the measured multipath components and constructs 360 degree receive power profile by repeating analysis in all antenna directions. The proposed receive power analysis algorithm is proved by laboratory tests with two distributed translators. Field test results are briefly introduced and discussed for the evaluation of the proposed system.

An improved LUT based DPD technique for nonlinear HPA in ATSC DTV system

It is well known that high power amplifier (HPA) induces nonlinear distortion around its saturation region. It causes the inter-modulation distortion (IMD) and spectrum re-growth problems. Thus, the digital pre-distortion (DPD) technique is used to improve the linearity of HPA. This paper proposes the adaptive DPD technique, which is composed of a look-up table (LUT) based adaptive update algorithm, for the compensation of HPA nonlinearity. From the simulation results, the proposed technique shows the better convergence speed and spectrum re-growth suppression compared with conventional LUT technique.

A novel TxID insertion system for ATSC DTV auxiliary data transmission

This paper presents a new TxID (Transmitter Identification) data insertion system for ATSC DTV auxiliary data transmission. Because the functional description of TxID was not included in the early ATSC transmission standard, most of the conventional DTV transmitters and translators cannot transmit TxID signal which should be generated during 8-VSB (Vestigial Side Band) symbol generation process. The proposed system generates RF signal of TxID and then combines it synchronously with the RF signal of the legacy ATSC transmitter. This combination enables the conventional DTV transmitters and translators to transmit TxID signal with auxiliary data based on RF watermark technique. The proposed system is implemented and its performance is evaluated through laboratory tests.

A new synchronous watermark data insertion method for ATSC transmission systems

In this paper, a new synchronous insertion method of the uniquely assigned RF watermark data into ATSC transmitters and translators is proposed. Watermark data is generated, VSB filtered and up-converted to the same IF or RF frequency with the target transmission system. Frequency and timing of the generated RF watermark data are synchronized with the target system by extracting synchronization information from the exciter module of the target system. The generated synchronized RF watermark signal is combined with the output signal of the exciter of target transmitter at the level of the designated bury ratio. Performance of the proposed method is evaluated and compared with the conventional RF watermark insertion method through computer simulations.

An interference cancellation technique for digital on-channel repeaters in T-DMB system

In this paper, a feedback interference cancellation scheme for digital on-channel repeaters (DOCRs) in terrestrial-digital multimedia broadcasting (TDMB) system is introduced. In order to mitigate the feedback signal in DOCR, an interference cancellation scheme using proportionate normalized least mean squares (PNLMS) algorithm is proposed. Simulation results confirm the RFP performance improvement at the DOCR and the BER performance improvement of T-DMB in time-varying typical urban channel.