• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.29-34
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• 2011

In this paper, we propose and analyze the equalizer schemes, zero-forcing (ZF) and minimum mean square error (MMSE) in power line communication (PLC) system for automatic meter reading (AMR). For efficient implementation of AMR system with PLC, effects of impulsive noise and multipath channel should be mitigated. To overcome these effects, the above equalizer schemes are employed. System performance is evaluated in term of bit error rate. From simulation results, it is confirmed that the equalizer can significantly improve bit error rate (BER) performance in PLC system, and MMSE equalizer provides better performance than ZF scheme. The results of this paper can be applied to AMR system as well as various smart grid services using PLC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.928-938
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• 1994

We designed and implemented (3.3) tap Decision Feedback Equalizer using Zero Forcing algorithm for 64 QAM RF MODEM (155Mbps) in SDH STM-1, Before we designed DFE, simulate 11 tap linear equalizer and (3.3) tap DFE. Then we get results that performance of DFE is better than linear equalizer by 5dB in fading. Practically, implemented DFE have good performance equalizing signal in 20dB fading depth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1577-1582
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• 2013

In this paper, we have analyzed the performance of MIMO (Multi-Input Multi-Output) underwater acoustic communication by using the acquired data via the experiments in water tank. First of all, in the pursuit of this aim, we have measured the channel transfer characteristics at several transceiver locations. The transmitted signal was modulated by QPSK(Quadrature Phase Shit Keying) and the received signal was recovered through the detector that contains the zero forcing equalizer. A maximum 30~40 ms delay was appeared because of physically closed water tank environment that has the harsh multi-path transmission conditions. In result of experiment, even though the bit error rate showed comparatively large when $2{\times}2$ MIMO system with two transmitters and receivers was considered. However, we confirmed it has approximately 15% enhanced performance compared with SISO (Single-Input Single-Output) system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.405-408
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• 2013

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Space-time code, Turbo code, and Zero forcing techniques is shown that improved performance than conventional UWA communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7A
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• pp.623-631
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• 2010

In this paper, various of pilot-assisted channel estimation techniques for 3GPP LTE downlink are tested under multipath Rayleigh fading channel. At first, the conventional channel estimation techniques are applied with linear zero-forcing (ZF) equalizer, such as one dimensional least square (1-D LS) linear interpolation, two dimensional (2-D) wiener filter, the time and frequency dimension separate wiener filter and maximum likelihood estimator (MLE). Considering the practical implementation, we proposed two channel estimation techniques by combining time-dimension wiener filter and MLE in two manners, which showed a good tradeoff between system performance and complexity when comparing with conventional techniques. The nonlinear decision feedback equalizer (DFE) which can show a better performance than linear ZF equalizer is also implemented for mitigating inter-carrier interference (ICI) in our system. The complexity of these algorithms are calculated in terms of the number of complex multiplications (CMs) and the performances are evaluated by showing the bit error rate (BER).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5513-5529
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• 2016

Doppler Effect is a prominent obstacle in vehicular networks, which dramatically increase the Bit-Error-Rate (BER). This problem is accompanied with the presence of the Orthogonal Frequency Division Multiplexing (OFDM) systems in which the Doppler shift interrupts the subcarriers orthogonality. Additionally, Inter-Symbol Interference (ISI) and high Peak-to-Average Power Ratio (PAPR) are likely to occur which corrupt the received signal. In this paper, the single-carrier combined with the frequency domain equalizer (SC-FDE) is utilized as an alternative to the OFDM over the IEEE 802.11p uplink vehicular channels. The Minimum Mean Squared Error (MMSE) and Zero-Forcing (ZF) are employed in order to study the impact of these equalization techniques along with the SC-FDE on the propagation medium. In addition, we aim to enhance the BER, improve the transmitted signal quality and achieve ISI and PAPR mitigation. The proposed schemes are investigated and we found that the MMSE outperforms the ZF equalization under different Doppler shift effects and modulations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.1-7
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• 2013

We perform simulation. It is that LED panels is fixed and moving the terminal with PD in order to analyze the performance of visible-light wireless communication system based on MIMO under variety of the interference environment. And, based on the technology MIMO, we analyzed whether the interference caused by external light to give what effect changes in the quality of the communication channel. The distortion due to time delay in channel transmission must be compensated by using the equalizer. Especially, use of equalizer is need absolutely as data rate becomes high speed. Therefore, in this paper, the system VLC, were analyzed BER performance using channel equalization.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.402-404
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• 2013

The wireless communication channel different speed by depth of water or salt and it is influenced by multi-path according underwater. In the paper, MIMO(Multi-input-Multi-Output) system used turbo Equalizer combining Equalizer with Turbo codes for data rates by multi-path channel. we proposed and simulated that the Decision-Directed method used for phase offset. The simulation of proposed method show that the bit-error rate performance can be severely affected by phase errors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.305-310
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• 2012

This paper proposes a selection combined hybrid sequential deconvolution and single carrier modulation with a zero forcing frequency domain equalizer for single carrier transmission system in order to enhance performance. Selection combining method is an algorithm of antenna space diversities, the receiver can choose the best channel environment only with the increase of the number of antennas, but a baseband structure is the same as the traditional receiver architecture. Simulation results show that the proposed algorithm has a better performance rather than the traditional single carrier transmission with a frequency domain equalizer.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.985-988
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• 2009

본 논문에서는 3GPP-LTE 상향링크 기술인 SC-FDMA에서 적응형 등화기 성능에 대해 알아보았다. SC-FDMA의 등화기에서 계산량을 줄여 효율성을 높이는 방법으로 ZF(Zero Forcing)과 MMSE(Minimum Mean Square Error)를 이용한 스위칭 기법을 제안하고, 제안한 시스템에서의 성능을 비교 분석하고자 한다. 제안한 스위칭 기법을 사용함으로써 SNR이 낮을 때는 MMSE를 이용하여 잡음에 대한 영향을 최소화 시켜주고, SNR이 높을 때는 ZF을 써서 상대적으로 복잡도가 적은 등화 기법을 통해 전체적인 시스템 복잡도를 줄여 효율성을 높이고자 한다.