• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.456-458
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• 2006

Power line communication: PLC which easy to install at anywhere near outlet for electric machine. PLC uses transmission line for voltage of which is 60 Hz. Signals don't affect to electric machine in PLC because they are very small voltage. One of the important thing is the processes of adding signal to power line and extracting the signal from power line, the other is to choose the strong modulation method which sends signals long distance without loosing in PLC channel. but PLC channel have very high and variable noise and attenuation and then it is very hard to transmit optimally between the transmitter and the receiver. After all, impedance and noise problems of PLC channel must be overcame. Noises of 2 kinds which are AWGN abd impulse noise and attenuation are orated. To overcome the noise. Recently, Multi-carrier Modulation: MCM methods like as OFDM and DMT which are divide the channel into many sub-channel have been studied. those are powerful communication methods in PLC. In this paper, PLC channels made up of 3 numbers of noise and attenuation are simulated for getting BER by Matlab simulink.

• ETRI Journal
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• v.35 no.5
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• pp.739-747
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• 2013

This paper investigates the multifarious nature of the long-term evolution (LTE) scheme and that of the modified LTE scheme for symbol timing synchronization (STS). This investigation allows us to propose a new replica correlation-based STS scheme to overcome the inherent weaknesses of the other two schemes. The proposed STS signal combines a gold sequence and a half sine wave in the time domain, whereas conventional STS signals specify either binary sequences or complex sequences in the time domain or in the frequency domain. In the proposed scheme, a sufficient correlation property is realized by the gold sequence, and robustness against the frequency offset (FO) is achieved through the sine wave. Compared to the existing LTE-related schemes, the proposed scheme can better achieve immunity to FO and reduction in detector complexity, as well as a low peak-to-average power ratio and a low detection error rate. Performance evaluations through analysis and simulation are provided in the paper to demonstrate these attributes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3672-3688
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• 2016

The nonorthogonality between the real and imaginary FBMC/OQAM modulated signals complicates the channel estimation (CE) process, and conventional OFDM CE methods cannot be directly applied to FBMC/OQAM. The conventional preamble-based CE schemes in FBMC/OQAM systems are mainly based on the interference approximation method (IAM) to improve the estimation performance. In this paper, we develop a novel preamble structure to improve the CE performance. We exploit the symmetry pattern to cancel interference and take into account the interference weights in this symmetric structure. The conventional preamble and the proposed preamble are compared via simulations in the IEEE 802.22, 3GPP Vehicular A and Pedestrian A channels. Numerical simulation results demonstrate that the proposed preamble can achieve better bit error ratio (BER) and mean squared error (MSE) performance under the three channel models considered.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.610-628
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• 2012

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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.301-303
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• 2016

This paper proposes a method providing diversity gain using small base stations in a cell coverage in order to improve diversity gain. The small base stations and the conventional base station consist a virtual MIMO array by using the cooperative communication scheme. Also, transmission diversity scheme is applied. A mobile user can receive the signals having the improved reliability by the applied transmission diversity scheme and the cooperative communication scheme.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1002-1003
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• 2006

Power line communication: PLC which easy to install at anywhere near outlet for electric machine. PLC uses transmission line for voltage of which is 60 Hz. One of the important thing is the processes of adding signal to power line and extracting the signal from power line, another is to choose the strong modulation method which sends signals to long distance without loosing in PLC channel. but PLC channel have very high and variable noise and attenuation and then it is very hard to transmit optimally between the transmitter and the receiver. AWGN, impulse noise and attenuation are created. To overcome the noise and attenuation. Multi-carrier Modulation methods like as OFDM and DMT which divide the channel into many sub-channel are powerful communication methods for PLC. In this paper, PLC channels are simulated for getting BER by Matlab simulink

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.93-101
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• 2019

This paper presents a software design and implementation of software-defined radio based IEEE 802.11ac encoder using Texas Instruments TMS320C6670 digital signal processor (DSP) platform. In this paper, the implemented encoder has the capability of generating all the signals consisting of preamble field and data field under different modulation & coding scheme in the IEEE 802.11ac standard. Moreover, the flexibility in choosing different rate, bandwidth, or mode can also be achieved by software reconfiguration using the DSP. As a result, by utilizing the computing power provided by multi-cores as well as the FFT coprocessors in the DSP, the required maximum throughput 78Mbps can be fully reached within 4 ㎲ for each OFDM symbol in the case of 20MHz bandwidth of IEEE 802.11ac.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.973-976
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• 2000

This paper proposes a new polarization diversity scheme for OPFDM (Orthogonal Polarization and Frequency Division Multiplexing). OPFDM is an extension of OFDM (Orthogonal Frequency Division Multiplexing) in conjunction with polarization multiplexing in order to ensure the orthogonality amongst subcarriers. Since OPFDM uses two orthogonally polarized channels, it can easily employ the polarization diversity. In order to get the diversity gain effectively in a frequency selective fading channel, the proposed scheme combines the signals in subcarrier-by-subcarrier basis. The computer simulation results confirm that the proposed scheme is superior to conventional one in the two orthogonally polarized two-ray Rayleigh fading channels with cross-talk between the two channels.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.60-68
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• 2019

In this paper, we propose the adaptive beamforming algorithm for the MIMO (Multi-Input Multi-Out)-OFDMA(Orthogonal Frequency Division Multiplexing Access)system to improve the performance. The performance of MIMO-OFDMA systems is greatly decreased in the wireless channel environment with multiusers, because the received signals are much distorted by a cochannel interference (CCI) during the space-time decoding. The proposed approach can track the DOA of each signal from the multiple antennas of the desired user without being greatly dependent on the impinging angle. And beams are directed toward the multiple transmitters of the desired user while null beams are directed toward interference directions. Therefore, we can can effectively cancel CCI and mitigate the impairment of delay spread while preserving the STC(space time code) diversity. BER performance improvement is investigated through computer simulation by applying the proposed approach to MIMO-OFDMA system in a multipath fading channel with CCI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.4
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• pp.424-432
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• 2016

World's leading countries are developing next generation digital broadcasting system specifications to support UHDTV (ultra-high definition television) contents and other various services. In order to maximize the transmission capacity by using the bandwidth efficiently, most broadcasting systems adopt MIMO-OFDM. In distributed-MIMO systems, multiple transmit antennas are spatially separated and therefore result in multiple timing offsets. To overcome this problem, this paper proposes a technique using a null symbol to detect each individual signal from distributed transmit antennas. By inserting null symbols before preambles, the receiver can distinguish the signals between each transmit antennas and perform frame synchronization. When the reception time difference is shorter than 500 samples, the proposed method outperforms the conventional method.