• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1827-1832
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• 2014

In this thesis, we use one by one each of the analog switch and a high-speed DAC instead of the DAC that two or more are used in transmitting and receiving antennas multiple systems, maintaining the advantages of the existing method, reducing design costs, physical to provide a method that can reduce the data converters from MIMO system can improve the economic efficiency and the size reduction of a basis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1502-1509
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• 2006

In this paper, we proposed reliability and capacity enhancement methods for IEEE 802.15.3 HDR-WPAN (High Data Rate-Wireless Personal Area Network) system which is currently getting an interest in home network technology adopting a MIMO technique. We also analyzed performance or the proposed system through a computer simulation. The HDR-WPAN system using V-BLAST algorithm, transmitting the different signal vector to each other's sub-channel, can get the transmission speed of more than 110Mbps using two Tx/Px antenna without bandwidth expansion in TCM-64QAM mode. Also the proposed system has reliability of 104 at $E_b/N_0=35dB$ under the Rayleigh fading channel in case of two Tx/Rx antenna with MMSE algorithm. The HDR-WPAN system adopting V-BLAST method has its drawback which is very complicated to determine the decision-ordering at the receiver. But, the proposed system enhances the transmission capacity and reliability without extra bandwidth expansion by sending data streams to multiple antennas.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.167-174
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• 2016

Underwater communication is difficult to increase the communication capacity because the carrier frequency is lower than that of radio communications on land. This is limited to the bandwidth of the signal under the influence of the characteristics of an ocean medium. As the high transmission speed and large transmission capacity have become necessary in the limited frequency range, the studies on MIMO (Multiple Input Multiple Output) communication have been actively carried out. The performance of the MIMO communication is lower than that of the SIMO (Single Input Multiple Output) communication because cross-talk occurs due to multiusers along with inter symbol interference resulting from the channel characteristics such as delay spread and doppler spread. Although the adaptive equalizer considering multi-channels is used to mitigate the influence of the cross-talk, the algorithm is normally complicated. In this paper, time reversal mirror technique with the characteristic of a self-equalization will be applied to simplify the compensation algorithm and relieve the cross-talk in order to improve the communication performance when the signal transmitted from two channels is received over interference on one channel in the same time. In addition, the performance of the MIMO communication based on the time reversal mirror is verified using data from the SAVEX15(Shallow-water Acoustic Variability Experiment 2015) conducted at the northern area of East China Sea in May 2015.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.86-93
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• 2009

We investigate lattice-reduction-aided precoding techniques for multi-user multiple-input multiple-output (MIMO) channels. When assuming full knowledge of the channel state information only at the transmitter, a vector perturbation (VP) is a promising precoding scheme that approaches sum capacity and has simple receiver. However, its encoding is nondeterministic polynomial time (NP)-hard problem. Vector perturbation using lattice reduction algorithms can remarkably reduce its encoding complexity. In this paper, we propose a vector perturbation scheme using Seysen's lattice reduction (VP-SLR) with simultaneously reducing primal basis and dual one. Simulation results show that the proposed VP-SLR has better bit error rate (BER) and larger capacity than vector perturbation with Lenstra-Lenstra-Lovasz lattice reduction (VP-LLL) in addition to less encoding complexity.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.89-103
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• 2018

A genius "Prince of Mathematician" Gaussian and "Father of Communication" Shannon comes up with the creative idea of motivation to meet each other? The answer is a coin leaf. Gaussian found some creative ideas in the matter of obtaining a sum of 1 to 100. This is the same as the probability distribution curve when a coin leaf is thrown. Shannon extended the Gaussian probability distribution to define the entropy, taking the source symbol and the reciprocal logarithm to obtain the weighted average. These where the genius Gaussian and Shannon meet in the same coin leaf. This paper focuses on this point, and easily proves Gaussian distribution and Shannon entropy. As an application example, we have obtained the capacity and transition probability of Jeongju seminal vesicle, and the Shannon channel capacity is 1 when the equivalent transition probability is 1/2.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1093-1105
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• 2012

We propose an interference space reuse (ISR) algorithm for the MU-MIMO design in 3-cell downlink interference channels. Also, we provide a strategy for the adoption of the ISR scheme in the cellular network. In the multicell interference channels, the cell edge users may undergo severe interferences and their signals should be protected from the interferers for reliable transmissions. However, the intra cell users do not only experience small interferences but also they require small transmission power for stable communication. We provide a vector design algorithm based on ISR, where intra cell users are served through reusing the cell edge users' interference space. The performance enhancement reaches 20% compared to the fractional frequency reuse (FFR) scheme combined with IA through the scheduling between the cell edge users and the intra cell users. Also, it can be used to enhance the cell edge throughput when the quality of service (QoS) requirements of the intra cell users are fixed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.444-451
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• 2017

In this paper, we have evaluated and analyzed OTFS(Orthogonal Time Frequency Space) modulation and OTFS-MIMO(Multiple Input Multiple Output) system. OTFS modulation can concisely compensate delay-Doppler spreading effect by using 2D(2-Dimension) iDFT (inverse Discrete Fourier Transform) and DFT(Discrete Fourier Transform) operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit all data streams without performance degradation on high Doppler frequency channel. As simulation results, we have confirmed that $1{\times}1$ OTFS system's achievable rate is a similar to each stream of $2{\times}2$ OTFS-MIMO system. That is, we have also confirmed that $2{\times}2$ MIMO system can completely achieve double achievable rate in comparison with OTFS system on high Doppler frequency channel.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.977-985
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• 2011

Recent works on multiuser transmission techniques have shown that the linear growth of capacity in single user MIMO system can be translated to the multiuser MIMO scenario as well. In this paper, we propose a method pursuing performance gain of vector perturbation in multiuser downlink systems. Instead of employing maximum number of mobile users for communication, we use small part of them as virtual users for improving reliability of users participating communication. By controlling parameters of virtual users including information and perturbation vector, we obtain considerable improvement in the effective SNR, resulting in large gain in bit error rate performance. Simulation results on the realistic multiuser downlink systems show that the proposed method brings substantial performance gain over the standard vector perturbation with marginal overhead in computations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.500-505
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• 2009

In this paper, We present a low complexity candidate list generation scheme in iterative MIMO receiver. Since QAM modulation can be decomposed into HP symbols and LP symbol and HP symbol is robust in error capability, we generate HP symbol list with simple ZF detector output and its corresponding neighbor HP symbols, Then, based on HP symbol list, the LP symbol list is generated by using the sphere decoder. From the second iteration, since apriori value from channel decoder is available, the candidate list is updated based on demodulated apriori value. Through the simulation, we observe that at the first iteration, the BER performance is worse than LSD. However, as the number of iteration is increased, the proposed scheme has almost same performance as LSD. Moreover, the proposed one has reduced candidate list generation time and lower number of candidate list compared with LSD.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.659-665
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• 2017

In this paper, a low complexity fast Fourier transform(FFT) processor is proposed for multiple input multiple output(MIMO) systems. The IEEE 802.11ac standard has been adopted along with the demand for a system capable of high channel capacity and Gbps transmission in order to utilize various multimedia services using a wireless LAN. The proposed scalable FFT processor can support the variable length of 64, 128, 256, and 512 for 8x8 antenna configuration as specified in IEEE 802.11ac standard with MIMO-OFDM scheme. By reducing the required number of non-trivial multipliers with mixed-radix(MR) and multipath delay commutator(MDC) architecture, the complexity of the proposed FFT processor was dramatically decreased. Implementation results show that the proposed FFT processor can reduced the logic gate count by 50%, compared with the radix-2 SDF FFT processor. Also, compared with the 8-channel MR-2/2/2/4/2/4/2 MDC processor and 8-channel MR-2/2/2/8/8 MDC processor, it is shown that the gate count is reduced by 18% and 17% respectively.