Jong-Seob Baek

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 fast array architecture for block matching algorithm

The block-matching motion estimation is the most popular method for motion-compensated coding of image sequence. Based on two dimensional systolic array, VLSI architecture for an implementation of full-search block matching algorithm is described. The proposed architecture has the following advantages: (1) it allows serial data inputs to save pin counts but performs parallel processing. (2) It is flexible in adaptation to the dimensional change of search window with simple control logic. (3) It has no idle time during the operation. (4) It can operate in real time for videoconference application and EDTV application. (5) It is modular and regular in design, and thus suitable for VLSI implementation.<<ETX>>

MIMO-OFDM Transceivers With Dual-Polarized Division Multiplexing and Diversity for Multimedia Broadcasting Services

This brief paper presents multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with dual-polarized division multiplexing (PDM) and diversity for multimedia broadcasting services. In particular, the polarized diversity is realized by transmitting two independent and distributed space-frequency coded signals through two sets of dual-polarized transmit antennas. In the corresponding polarized receptions, MIMO zero-forcing (ZF) detection and ZF detection combined with a group-wise or a symbol-wise successive cancelation (SIC) are used to minimize a depolarization effect caused by a cross-polarization discrimination (XPD). Furthermore, we analyze the output signal-to-interference-plus-noise ratio (SINR) of such MIMO detections in terms of the XPD effect. It is shown that the output SINR of MIMO ZF detection increases as the absolute XPD value increases. It is also shown that the output SINR of ZF-SIC detection converges to that of ZF detection as the absolute XPD value increases. Finally, we compare the performances of uni-polarized and dual-polarized MIMO-OFDM systems over a multipath Rician channel with XPD. From simulation results, we conclude that as the absolute XPD value increases, the polarized MIMO-OFDM systems provide a lower symbol error rate than uni-polarized MIMO-OFDM systems.

Cooperative Networks with Amplify-and-Forward Multiple-Full-Duplex Relays

In this paper, we present a cooperative system with amplify-and-forward (AF) multiple-full-duplex relays (FDRs) that receives and transmits signals simultaneously. In the first, we propose a new concept of delayed M-FDR relaying (M-D-FDR) scheme being able to achieve the full spatial diversity. At this time, we consider each delayed FDR receives a signal from source, adjacent relays and its delayed loop interference signal from its transmit antenna. In the second, we propose an efficient iterative successive interference cancellation (SIC) technique at destination that gradually cancels a delayed signal in order to fully obtain link diversity generated from M-D-FDR. Then, we investigate the various properties of the proposed M-D-FDR network by analyzing the pairwise-error-probability (PEP) analysis, especially in terms of signal-to-noise ratios (SNRs) between source to relays and source to destination links, respectively. Finally, we accomplish the performance evaluations to verify the analysis results and to compare with a non-delayed M-FDR (M-N-FDR) network.

Efficient Pilot Patterns and Channel Estimations for MIMO-OFDM Systems

In this paper, we present the efficient pilot patterns and channel estimations for a high-rate multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system. In particular, we propose the scattered pilot (SP), edge pilot (EP), and continuous pilot (CP) by exploiting a basic orthogonal property of a unitary matrix. From the orthogonal property, we then propose the efficient channel frequency response (CFR) and channel impulse response (CIR) estimations. Finally, we evaluate the efficiency of the proposed schemes by comparing with a multi-input single-output OFDM (MISO-OFDM) system.

Physical Layer Time Interleaving for the ATSC 3.0 System

This paper presents optimized time interleaving which has been adopted for the Advanced Television System Committee 3.0 system as a physical layer tool to mitigate the effects of burst errors. The adopted time interleaver (TI) is very flexible and can have different configurations according to the number of physical layer pipes (PLPs) and service type, i.e., fixed, portable, and mobile. Notably, for single-PLP mode a sheer convolutional TI (CTI) is used, whereas for the multiple-PLP mode a hybrid TI (HTI) composed of cell interleaver, twisted block interleaver, and a convolutional delay-line is used. Optionally, the CTI and the HTI can be used in conjunction with extended time interleaving and a cell interleaver (only for HTI) to further improve robustness over long burst error lengths at the expense of latency.

Effective Symbol Timing Recovery Based on Pilot-Aided Channel Estimation for MISO Transmission Mode of DVB-T2 System

This paper proposes an effective symbol timing recovery (STR) based on a pilot-aided channel impulse response (CIR) estimation for multi-input single-output (MISO) transmission mode of DVB-T2 system. In particular, this paper focuses on fine STR capable of resolving an ambiguity effect of the CIR which is caused by an inaccurate coarse symbol timing offset (STO). In the proposed fine STR, the CIR of the MISO channel is estimated after performing coarse STR. Then, the ambiguity of the CIR is investigated by categorizing it into four regions under the assumption of an inaccurate STO. Finally, accurate STO is estimated by changing the fast Fourier transform (FFT) window with respect to the ambiguity categorization. Performance evaluations are accomplished by comparing the proposed STR with the conventional STR in large delay channels.

Improved CIR-Based Receiver Design for DVB-T2 System in Large Delay Spread Channels: Synchronization and Equalization

This paper proposes to implement an improved orthogonal frequency division multiplexing (OFDM) receiver by utilizing a channel impulse response (CIR)-based synchronization and sparse equalization for DVB-T2 system operating in both the single-input single-output (SISO) and multi-input single-output (MISO) transmission modes. First, the proposed OFDM receiver performs a pilot-aided CIR estimation after a coarse symbol timing recovery (STR). Then, the proposed CIR-based fine STR compensates for a false symbol timing offset (STO). In particular, the fine STR resolves an ambiguity effect of CIR, which is the main problem caused by a false coarse STO in exploiting the CIR. Upon the completion of the fine synchronization, the proposed CIR-based sparse equalization is performed in order to minimize the noise and interference effects by shifting or selecting a basic frequency interpolation (FI) filter according to an echo delay (phase) or maximum delay spread, respectively. Performance evaluations are accomplished in large delay spread channels in which the maximum delay spread is less or longer than a guard interval (GI). It is shown that the proposed receiver is not only capable of estimating the fine STO but also minimizing effectively the noise effects. In particular, the performance gain in a single pre-echo channel being longer than GI is remarkable as compared with a conventional receiver.

Efficient design of block adaptive equalization and diversity combining for space-time block-coded single-carrier systems

In this paper, a weighted space-time block-coding (STBC)-like matrix-wise block adaptive frequency-domain equalization (WSB-FDE), which has a flexibility over the STBC-like matrix-wise block length as compared to a normalized least-mean-square (NLMS)-FDE and a recursive-least-square (RLS)-FDE, is proposed for the cyclic-prefixed STBC single-carrier systems equipped with a diversity combining. In the WSB-FDE, the STBC-like matrix-wise block is first formulated from received blocks. The correction terms of the equalizer coefficients in each block are then updated so as to minimize a weighted squared-norm of the a posteriori error vector for the formulated block. Moreover, a square-root adaptive algorithm based on an unitary Givens rotation is proposed to achieve the numerical stability and computational efficiency in update procedure of the WSB-FDE. The theoretic convergence and the steady-state excess mean-square error (EMSE) of the WSB-FDE are analyzed, where it is observed that the EMSE decreases as the STBC-like matrix-wise block length and the number of antenna increase. Finally, the performance evaluation shows in a typical urban (TU) channel that the bit-error-rate (BER) performance of the WSB-FDE is superior to that of the RLS-FDE as the STBC-like matrix-wise block length increases.

Efficient Iterative SIC and Detection for Two-Path Cooperative Block Transmission Relaying

In this paper, we present a block transmission for an amplify-and-forward two-path relaying in frequency-selective block fading channel. In particular, this paper focuses on an efficient and yet robust iterative successive interference cancellation (SIC) incorporating various diversity detections, after performing a complete interrelay interference (IRI) cancellation at destination. The performance results are provided to verify the superiority of the proposed iterative SIC and detections compared to a conventional SIC and detection.