• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.378-381
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• 2006

This paper proposes the method of a channel estimation for MIMO-OFDM with ISI. The proposed method uses a new special training sequence to obtain a constant PAR in OFDM and to remove the effect of ISI on channel estimation. Using this training sequence, we are able to avoid a singular problem in matrix. As a result of simulation, we are able to assure that the proposed system inclosed the performance in MSE of estimated channel by more than 30dB than a conventional method if SNR is high.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.494-499
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• 2009

In this paper, we provide an efficient method of user selection for achieving the maximum system throughput in downlink multiuser Multiple-Input Multiple-Output (MIMO) systems. A proposed method is for selecting a fine user set only with powers of each user channel and angles between them. This algorithm is simpler than SUS because there is no considering about the optimal value of correlation. The proposed method finds the user set toward maximizing system throughput, so it has high performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12A
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• pp.1006-1013
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• 2009

This paper proposes a data stream allocation technique for fair capacity performance in multiuser multiple-input multiple-output (MIMO) systems using block diagonalization (BD) algorithm. Conventional studies have been focused on maximum sum capacity. Thus, there is a very large difference of capacity among users, since user capacity unfairly distributed according to each user channel environment. In additional, poor channel user has very small capacity, since base station allocates the power by using water-filling technique. Also, almost studies limited itself to obtain the additional gain by using the same number of data streams for all users. In this paper, we propose the technique for maximizing sum capacity under the fair performance constraint by allocating data stream according to user channel environment. Also, proposed algorithm has more gain of sum capacity and transmit power than conventional equal allocation via computer simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.747-752
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• 2009

In this paper, the MIMO(Multi-Input Multi-Output) channel characteristics for Rx antenna spacing are described in the real environment, which has LOS(Ling of Sight) and NLOS (Won-Line of Sight). We developed $2\times2$ MIMO channel measurement system at 2.3GHz Wibro Band. MIMO antenna evaluation parameters such as received power, channel capacity and spatial correlation are evaluated for standard dipole antenna with 0.25, 0.5, 0.75 and 1.0 wavelength spacing at 2-position for LOS and 4-position for NLOS. The spatial correlation is distributed more than 0.9 in most LOS case which might be intricate to operate MIMO communication. MIMO antenna design need to be focused on getting spatial diversity and reducing spatial correlation in LOS case.

• Journal of Broadcast Engineering
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• v.17 no.5
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• pp.864-875
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• 2012

In this paper, we propose a carrier frequency offset estimation method for single-carrier MIMO systems. In the proposed method, phase rotated PN (Pseudo-Noise) sequences are transmitted to prevent a cancelling out of partial PN sequences. After removing a modulation of received PN sequences by multiplying of complex conjugated PN Sequences which are locally generated in receiver, a CFO (Carrier Frequency Offset) is accurately estimated by employing L&R method which is a kind of ML (Maximum Likelihood) estimation algorithm and uses multiple auto-correlatos. In addition, the frequency offset estimation scheme by using channel state information is proposed for accurate CFO estimation in time-varying Rayleigh channel. By performing computer simulations, MSE (Mean Square Error) performance of proposed method is almost same as MSE performance of SISO systems in AWGN channel. Moreover, MSE Performance of proposed method with using channel information is higher than MSE performances of SISO system and conventional method in time-varying Rayleigh channel.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.640-650
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• 2004

Channel estimation schemes are proposed for Multiple Input-Multiple output Orthogonal Frequency Division Multiplexing(MIMO-OFDM) systems based on the physical layer specification of the IEEE 802.1 la. By combining the space-time block coding(STBC)/ space-frequency block coding(SFBC) techniques with the transform domain interpolation, the proposed algorithms achieve more accurate channel coefficients for the MIMO channels such that improve the BER performance. The performance improvements of the proposed algorithms are evaluated by simulations under the various multipath fading channel environments and various transmission rates.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2791-2797
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• 2010

In recent years, the goal of providing high speed wireless data services has generated a great amount of interest among the research community. Several researchers have shown that the capacity of the system, in the presence of flat Rayleigh fading, improves significantly with the use of combined MIMO and LDPC. To feed the soft values to LDPC decoder, the soft values must be calculated from multiple transmitter and receiver antennas in Rayleigh fading channel. It requires high computational complexity to get the soft symbols by increasing number of transmitter and receiver antennas. Therefore, this thesis proposed on effective algorithm for calculation of soft values from multiple antennas based on LLR. As result, This thesis shows that maximum 61% of computational complexity is reduced with a little loss of performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.3
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• pp.216-221
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• 2013

In this paper, wireless channel characteristics of massive MIMO system is analyzed by comparing angular spread, cross polarization discrimination(XPD) and delay spread of dual polarized 4 and 128 transmit array antenna systems, by using 3D rat-tracing simulator, Wireless Insite in microcell environments. The analysis shows that increasing the number of transmit antennas results in the smaller angular spread and delay spread, and the higher value of XPD.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.119-125
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• 2015

In this paper, we introduce a Hadamard matrix interstream transmission based blind channel estimation for multi-cells multiple-input and multiple-output (MIMO) networks. The proposed scheme is based on a network with mobile stations (MS) which are deployed with multi cells. We assume that the MS have the signals from both cells. The signal from near cell are considered as desired signal and the signals from the other cells are interference signal. Since the channel is blind, so that we transmit Hadamard matrix pattern pilot stream to estimate the channel; that gives easier and fast channel estimation for large scale MIMO channel. The computation of Hadamard based system takes only complex additions, and thus the complexity of which is much lower than the scheme with Fourier transform since complex multiplications are not needed. The numerical analysis will give perfection of proposed channel estimation.