Jong-Ho Paik

An Enhanced DFT-Based Channel Estimation Using Virtual Interpolation with Guard Bands Prediction for OFDM

In this paper, we investigate the conventional windowed DFT-based channel estimation for OFDM systems with guard bands. The conventional method suffers from the edge effect and the pilot position mismatch. In order to solve the problems, we propose an enhanced DFT-based channel estimation using virtual interpolation with guard bands prediction, where linear minimum mean square error (LMMSE) smoothing/prediction and circular frequency shifting are employed. This technique can efficiently mitigate the edge effect caused by the DFT of the truncated channel impulse response and compensate the pilot position mismatch that pilot symbols are not allocated at the first and the last subcarriers in a useful band. Simulation results show that the proposed method has about 5 dB SNR gain at BER=10-3 compared to the conventional method and is as good as the frequency-domain LMMSE method

DFT-based PSA channel estimation using linear prediction for OFDM systems with virtual carriers

This paper proposes an improved discrete Fourier transform-based and pilot-symbol-aided channel estimation (DFT-based PSA CE) for coherent orthogonal frequency division multiplexing (OFDM) systems. Conventional DFT-based PSA CE suffers from the dispersive distortion of an estimated channel impulse response (CIR) caused by virtual carriers. The proposed method estimates an equal-spaced channel frequency response (CFR) in a virtual carrier region by using forward and backward linear prediction (FBLP). Simulation results show that the proposed method outperforms the conventional one with slightly increased complexity and provides a performance similar to the frequency domain linear minimum mean square error (LMMSE) channel estimation with significantly reduced complexity.

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.

Iterative Detection and ICI Cancellation for MISO-mode DVB-T2 System with Dual Carrier Frequency Offsets

In the DVB-T2 system with a multiple-input single-output (MISO) transmission mode, Alamouti coded orthogonal frequency division multiplexing (OFDM) signals are transmitted simultaneously from two spatially separated transmitters in a single frequency network (SFN). In such systems, each transmit-receive link may have a distinct carrier frequency offset (CFO) due to the Doppler shift and/or frequency mismatch between the local oscillators. Thus, the received signal experiences dual CFOs. This not only causes dual phase errors in desired data but also introduces inter-carrier interference (ICI), which cannot be removed completely by simply performing a CFO compensation. To overcome this problem, this paper proposes an iterative detection with dual phase errors compensation technique. In addition, we propose a successive-iterative ICI cancellation technique. This technique successively eliminates ICI in the initial iteration by exploiting pre-detected data pairs. Then, in subsequent iterations, it performs a fine interference cancellation using a priori information, iteratively fed back from the channel decoder. In contrast to previous works, the proposed techniques do not require estimates of dual CFOs. Their performances are evaluated via a full DVB-T2 simulator. Simulation results show that the DVB-T2 receiver equipped with the proposed dual phase errors compensation and the successive-iterative ICI cancellation techniques achieves almost the same performance as ideal dual CFOs-free systems, even for large dual CFOs.

Implementation of a global mobile TV system

This paper presents an implementation of a multi-standard global mobile TV system. Audio, video, and data services provided by the different digital broadcasting mobile TV standards available today are decoded on a single, unified platform.

An effective frame detection and FFT window point tracking algorithm for Digital Radio Mondiale receivers

Digital Radio Mondiale (DRM) is an OFDM-based digital radio broadcasting system for the frequency bands below 30MHz. ODFM systems are sensitive to synchronization errors, which cause inter-carrier interference (ICI). In this paper, a frame detection algorithm and FFT window point tracking method for low-power portable DRM receivers are presented.

Optimal Compensation of Dual Carrier Frequency Offsets for MISO-mode DVB-T2

Dual carrier frequency offsets (CFOs) occur in multiple-input single-output (MISO)-mode DVB-T2 systems, where signals are transmitted simultaneously from two distributed transmitters in a single frequency network (SFN). In this paper, we first derive an optimal compensation frequency for dual CFOs. We also propose an algorithm that optimizes the compensation frequency for the MISO-mode DVB-T2 application. Its performance is compared with the conventional scheme by using a full DVB-T2 simulator.

Reducing IP packet loss in ATSC-M/H multiplexer

In Advanced Television Systems Committee — Mobile/Handheld (ATSC-M/H) transmission system, the output data rate of the encoder may overflow, resulting in IP packet loss at the receiver side. In this paper, we present a method to reduce IP packet loss in ATSC-M/H multiplexer using an IP stream buffer.

A Time-Domain ICI Canceller Using Modulation Order Increasing and Repetition Coding in OFDM

In this paper, an enhanced time-domain cancellation method is proposed for inter-carrier interference (ICI) reduction in OFDM systems. The conventional time-domain cancellation does not work well in deep fades. In order to supplement the conventional method, the simple repetition (de-)coding and the modulation order increasing are employed in the time-domain cancellation. The approximated repetition decoding provides reliable symbols in the regeneration operation, and the increased modulation order maintains the spectral efficiency. Simulation results indicate that the proposed method using 16QAM significantly improves the BER performance compared to the conventional method using QPSK, while maintains the spectral efficiency. Moreover, the proposed method using 64QAM concurrently improves both the BER performance and the spectral efficiency.

Interactive services for ATSC mobile DTV based on BWS

This paper presents an interactive data service system for Advanced Television Systems Committee — Mobile/Handheld (ATSC-M/H) digital mobile broadcasting. The system is based on the Broadcast Website (BWS) and Internet is used as a back channel to support interactivity. The system can be considered as an alternative application framework for ATSC-M/H.