• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.295-302
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• 2011

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.

• Korean journal of communication and information
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• v.61
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• pp.28-51
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• 2013

The present study analyzed the effects of brand extension on the existing parent brand by applying the media brand extension model which previous studies had suggested based on consumer based brand equity model. Based on previous studies, the present study constructed a research model in which pre-brand extension parent brand evaluation, brand portfolio quality variance, perceived number of brand extensions, perceived fit between parent brand and brand extended channel, and brand extended channel evaluation are supposed to affect post-brand extension brand extension evaluation, and tested the media brand extension feedback effects model through structural equation modeling. The analysis results show that pre-brand extension parent brand evaluation, brand portfolio quality variance, perceived fit, and brand extended channel evaluation affect post-brand extension parent brand evaluation while the effect of perceived number of brand extensions is not significant.

• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.44-51
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• 2002

This paper describes the performance evaluation and analysis of an Orthogonal Frequency-Division Multiplexing (OFDM) system having the least Inter Symbol Interference (ISI) in a multi-path fading channel environment. Wireless Local Area Network (W-LAN) in accordance with IEEE 802.11a and IEEE 802.11b provides high-speed transmission to universities, businesses and other various places. In addition, service providers can offer a public W-LAN service on restricted areas such as a subway. The proliferation of W-LAN has led to greater W-LAN service demands, but problems are also on the rise in offering a good W-LAN service. In particular, urban areas with high radio wave interference and many buildings are vulnerable to deteriorated QoS including disconnected data and errors. For example, when high-speed data is transmitted in such areas, the relatively high frequency generates ISI between Access Points (AP) and Mobile Terminals (such as a notebook computer), leading to a frequency selective fading channel environment. Consequently, it is difficult to expect a goodW-LAN service. The simulation proves that the OFDM system enables W-LAN to implement QoS in high-speed data transmission in a multi-path fading channel environment. The enhanced OFDM performance with 52 sub-carriers is verified via data modulation methods such as BPSK, QPSK and 16QAM based on IEEE 802.11a and punched convolutional codes with code rate of 1/2 and 3/4 and constraint length of 7. Especially, the simulation finds that the OFDM system has better performance and there is no data disconnection even in a mobile environment by applying a single tap equalizer and a decision feedback equalizer to a mobile channel environment with heavy fading influence. Given the above result, the OFDM system is an ideal solution to guarantee QoS of the W-LAN service in a high-speed mobile environment.

• Journal of Broadcast Engineering
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• v.10 no.2
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• pp.210-220
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• 2005

This paper presents and analyzes laboratory test results of Equalization Digital On-Channel Repeater (EDOCR) using ATSC(Advanced Television Systems Committee) terrestrial digital TV broadcasting system. The EDOCR laboratory test, which is done at CRC(Communications Research Centre) Canada, is classified to receiver test, transmitter test, and synchronization test between transmission and reception frequencies. The receiver part includes feedback signal, random noise, single echo, multi-path ensemble, and NTSC/DTV interference test. The transmitter part includes out-of channel emission, quality of transmitting signal, and phase noise test. By the field test results, the receiver part of the EDOCR eliminates average 5.5 dB of feedback or single echo signal in range of 0 to 11 ${\mu}s$ and has average 18.6 dB at TOV(Threshold of Visibility) under random noise environment. Also, the transmitter part of the EDOCR satisfies the specification of US FCC(Federal Communications Commission), and frequency difference between transmitter and receiver is zero.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2353-2362
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• 2015

In this paper, we employ the single channel full duplex radio for wireless local area network (WLAN) systems, and design digital interference cancellers using adaptive signal processing. When the full duplex scheme is used for WLAN systems with multiple transmit and receive antennas, some interference is caused through the feedback of transmit signals from multiple antennas. To remove the feedback interference, we derive the least mean square (LMS), normalized LMS (NLMS), and recursive least squares (RLS) algorithms based on adaptive signal processing techniques. In addition, we analyze the theoretical convergence of the proposed LMS and RLS methods. The channel capacity of full duplex radios increases by two times than that of half duplex radios, when the packet error rate (PER) performances for the two systems are identical. Through numerical simulations in WLAN systems, it is shown that the full duplex method with the proposed interference cancellers has a similar PER performance with the conventional half duplex transmission scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1299-1305
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• 2017

In this paper, we consider a beamforming game between the transmitters in a two-user multiple-input single-output interference channel using limited feedback and investigate how each transmitter is able to find a modified strategy from the quantized channel state information (CSI). In the beamforming game, each of the transmitters (i.e., a player) tries to maximize the achievable rate (i.e., a payoff function) via a proper beamforming strategy. In our case, each transmitter's beamforming strategy is represented by a linear combining factor between the maximum ratio transmission (MRT) and the zero forcing (ZF) beamforming vectors, which is the Pareto optimal achieving strategy. With the quantized CSI, the transmitters' strategies may not be valid because of the quantization errors. We propose a modified solution, which takes into account the effects of the quantization errors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.1959-1975
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• 2011

Adaptive Bit Loading (ABL) in Multiple-Input Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM) is often used to achieve the desired Bit Error Rate (BER) performance in wireless systems. In this paper, we discuss some of the bit loading algorithms, compare them in terms of the BER performance, and present an effective and concise Adaptive Grouped Loading (AGL) algorithm. Furthermore, we propose a "weight factor" for loading algorithm to converge rapidly to the final solution for various data rate with variable Signal to Noise Ratio (SNR) gaps. In particular, we consider the bit loading in near optimal Singular Value Decomposition (SVD) based MIMO-OFDM system. While using SVD based system, the system requires perfect Channel State Information (CSI) of channel transfer function at the transmitter. This scenario of SVD based system is taken as an ideal case for the comparison of loading algorithms and to show the actual enhancement achievable by our AGL algorithm. Irrespective of the CSI requirement imposed by the mode of the system itself, ABL demands high level of feedback. Grouped Loading (GL) would reduce the feedback requirement depending upon the group size. However, this also leads to considerable degradation in BER performance. In our AGL algorithm, groups are formed with a number of consecutive sub-channels belonging to the same transmit antenna, with individual gains satisfying predefined criteria. Simulation results show that the proposed "weight factor" leads a loading algorithm to rapid convergence for various data rates with variable SNR gap values and AGL requires much lesser CSI compared to GL for the same BER performance.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.31-39
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• 2012

DVC(Distributed Video Coding) techniques have been attracting a lot of research works since these enable us to implement the light-weight video encoder and to provide good coding efficiency by introducing the feedback channel. However, the feedback channel causes the decoder to increase the decoding complexity and requires very high decoding latency because of numerous iterative decoding processes. So, in order to reduce the decoding delay and then to implement in a real-time environment, this paper proposes several parity bit estimation methods which are based on the temporal correlation, spatial correlation and spatio-temporal correlations between LDPCA frames on each bit plane in the consecutive video frames in pixel-domain Wyner-Ziv video coding scheme and then the performances of these methods are compared in fast DVC scheme. Through computer simulations, it is shown that the adaptive spatio-temporal correlation-based estimation method and the temporal correlation-based estimation method outperform others for the video frames with the highly active contents and the low active contents, respectively. By using these results, the proposed estimation schemes will be able to be effectively used in a variety of different applications.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.25-28
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• 2010

The need for multiband RF front-end in modern communication system is growing rapidly. For example, satellite system always uses a complex arrangement of frequency plans and consequently needs filters for each communication channel and it will be ideal to have a single filter module that does jobs of all those channel filters to reduce the size and payload of the system. In this paper, a new method to transform four-port self-feedback balanced dual-band bandpass filter into two-port is proposed. The two-port balanced dual-band bandpass filter which has baluns at the input and output ports and the fundamental frequency at 2.5 GHz and the first harmonic frequency at 5.7 GHz is fabricated and measured. Good agreement between measured and simulated results was achieved.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.9
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• pp.37-43
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• 2010

An Interference Cancellation Wireless Repeater transmitts directly amplified the RF signal input to extend the coverage of the base station. Such a repeater inevitably suffers from the feedback interferences due to the environment and the adaptive Interference Cancelling System(ICS) is necessary. In this paper, the Variable Stepsize Complex Sign -Sign(VSCSS) LMS algorithm for ICS is presented. The algorithm can be implemented without multiplication/division arithmetic operation so that the required logic resources can be dramatically reduced in FPGA implementation. The performance of the proposed algorithm was analyzed in comparison with CSS-LMS algorithm and the learning curves obtained from simulation showed an excellent agreement with the theorical prediction. The simulation result with ICS in fading feedback channel environment showed the performance of the proposed algorithm is competible with NLMS algorithm.