• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.784-789
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• 2011

In this paper, a precoder based on limited phase feedback is proposed to maximize user's receive signal-to-interference-plus-noise ratio (SINR) in coordinated multi-point (CoMP) coordinated scheduling / coordinated beamforming (CS/CB) precoding matrix indicator (PMI) scenario. Most conventional precoding techniques based on limited phase feedback have been considered in a single-cell environment. However, considering neighboring cells in a multi-cell environment, we enhance the conventional preocoding. method. First, to maximize receive SINR, precoding matrices are designed to maximize the serving cell's signal and to minimize the coordinated cells' signal. Also, a precoder which can be used in a limited bit feedback condition is suggested. Finally, the proposed precoder's performance is evaluated and compared with some other precoding techniques by using simulation under the CoMP CS/CB PMI scenario.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.945-951
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• 2021

The SOQPSK-TG is a modulated signal for aeronautical telemetry with a very good bandwidth efficiency. In this paper, the frequency waveform filter of the SOQPSK-TG is linearly approximated and modeled with a duobinary precoder and a modified frequency waveform filter having a phase transition period of about 1T_b. In combination with the existing precoder, the SOQPSK-TG is modeled by a double duobinary MSK. Comparing the SOQPSK-TG signal and the newly modeled double duobinary MSK signal in time domain and frequency domain, it is confirmed that the two signals are almost identical and there is virtually no performance difference. Moreover, we can attain 0.1 dB BER performance improvement compared to the existing cosine filter when the filter of the IQ-detector is implemented with a cosine sum filter taking into account the change in the modulation index by the new double doubinary precoder.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.49-55
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• 2022

In the next generation mobile communication systems, hybrid massive multiple-input multiple output (MIMO) can be used to highly improve an achievable rate without increasing the number of RF chains. Recently, successive-interference-cancellation (SIC) based hybrid precoder design scheme was proposed to reduce the complexity. However, since this scheme uses simple diagonal matrix for baseband precoding, it cannot solve an interference problem between the transmitted streams. Also, there is a limitation for improving the data rate because of the use of one phase shifter for analog precoding. To solve these problems, in this paper we propose a digital precoding based on the SVD of the effective channel and an analog precoding using two phase shifters. Through simulation, we show that the proposed scheme has better achievable rate and SINR performances than the conventional one.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.2
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• pp.117-123
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• 2017

N-continuous orthogonal frequency division multiplexing (OFDM) is a precoding method for sidelobe suppression of OFDM signals and seamlessly connects OFDM symbols up to the high-order derivative for sidelobe suppression, which is suitable for suppressing out-of-band radiation. However, it severely degrades the error rate as it increases the continuous derivative order. Two schemes for orthogonal precoding of N-continuous OFDM have been proposed to achieve an ideal error rate while maintaining sidelobe suppression performance; however, the large size of the precoder matrices in both schemes causes very high computational complexity for precoding and decoding. This paper proposes matrix decomposition of precoder matrices with a large size in the orthogonal precoding schemes in order to reduce computational complexity. Numerical experiments show that the proposed method can drastically reduce computational complexity without any performance degradation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2616-2635
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• 2013

In this paper, we propose an iterative transceiver design in a multi-relay multi-user multiple-input multiple-output (MIMO) system. The design criterion is to minimize sum mean squared error (SMSE) under relay sum power constraint (RSPC) where only local channel state information (CSI)s are available at relays. Local CSI at a relay is defined as the CSI of the channel between BS and the relay in the $1^{st}$ hop link, and the CSI of the channel between the relay and all users in the $2^{nd}$ hop link. Exploiting BS transmitter structure which is concatenated with block diagonalization (BD) precoder, each relay's precoder can be determined using local CSI at the relay. The proposed scheme is based on sequential iteration of two stages; stage 1 determines BS transmitter and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. We verify that the proposed scheme outperforms simple amplify-and-forward (SAF), minimum mean squared error (MMSE) relay, and an existing good scheme of [13] in terms of both SMSE and sum-rate performances.

• ETRI Journal
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• v.34 no.1
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• pp.9-16
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• 2012

Precoding in the multiple-input multiple-output orthogonal frequency division multiplexing system is investigated. In conventional wideband precoding (WBP), only one precoder, obtained from the decomposition of the subcarrier independent channel matrix, is used for all subcarriers. With an investigation of the relationship between the subcarrier independent channel matrix and the temporal/frequency channels, an improved WBP scheme is proposed for practical scenarios in which a part of subcarriers are allocated to a user. The improved WBP scheme is a generalized scheme of which narrow-band precoding and conventional WBP schemes are special modes. Simulation results demonstrate that the improved WBP scheme almost achieves the optimum performance of a single precoder and outperforms the conventional WBP scheme in terms of the bit error ratio and ergodic capacity with slight complexity increase. The largest advantage of the improved WBP scheme on signal-to-noise ratio in simulation results is over 2.1 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.12-18
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• 2012

In this paper, we propose an improved analysis of transmission power of BTHP applied into the downlink multi-user (MU) multi-input multi-output (MIMO) system. On the contrary to the conventional analysis that adopts the strong interference assumption for every users in the system, the proposed analysis approximates the characteristics of the actual interference components so that provides more accurate approximation of the transmission power than that from the conventional analysis. By computer simulations, it is observed that the proposed approximation is more accurate than the conventional one, especially in the case of 4-QAM modulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.809-812
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• 2011

In this letter, in order to reduce the inter-channel interference at the transmitted side, we design the precoder based on Tomlinson-Harashima coding, which is well know for one kind of non-linear precoding schemes, for 3-user MIMO wireless systems. And its performance is also analyzed in comparison with that of the Dirty Paper Coding based precoder.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.552-559
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• 2013

In this paper, the multiple-input multiple-output (MIMO) system with a precoder is considered in the transmit-correlated Rayleigh channels. We specifically target the MIMO system employing the minimum mean square error receivers. Based on random matrix theory, we first present a direct and generalized formulation for deriving a probability density function (PDF) of the signal-to-interference-plus-noise ratio (SINR). Then, we derive the accurate closed-form SINR PDFs for a small number of transmit and receive antennas. Based on the SINR PDFs, tight closed-form approximations of the symbol error rate (SER) are derived. Our analysis suggests that the SER approximations can be used to accurately estimate the error probabilities or as a useful tool for the system design.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1A
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• pp.44-49
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• 2008

Recently, a so called orthogonal spatial multiplexing(OSM) scheme was presented which allows simple maximum likelihood decoding at the receiver with single phase feedback In this paper, by serially concatenating this scheme by a linear precoder, a new closed-loop SM scheme is proposed for two transmit arid two receive antennas. By computer simulation results, we show that the proposed scheme outperforms the conventional SM and OSM. For the proposed code, we also propose a new simple decoding algorithm which leads to a greatly reduced decoding complexity compared with the ML receiver without any loss of error performance.