• Journal of information and communication convergence engineering
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• v.18 no.1
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• pp.1-7
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• 2020

This paper proposes a fast-processing and low-cost hardware multiple input multiple output (MIMO) channel emulator. The channel emulator is an important component of hardware-based simulation systems. The novelty of this work is the use of sharing and pipelining functions to reduce hardware resource utilization while maintaining a high sample rate. In our proposed emulator, the samples are created sequentially and interpolated to ensure the sample rate is equal to the base band rate. The proposed 4 × 4 MIMO requires low-cost hardware resource so that it can be implemented on a single field-programmable gate array (FPGA) chip. An implementation on Xilinx Virtex-7 VX980T was found to occupy 10.47% of the available configurable slice registers and 12.58% of the FPGA's slice lookup tables. The maximum frequency of the proposed emulator is 758.064 MHz, so up to 560 different paths can be processed simultaneously to generate 560 × 758 million × 2 × 32 bit complex-valued fading samples per second.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.149-156
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• 2011

MIMO-OFDM(Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) has been spotlighted as a solution of high-quality service for next generation's wireless communications. However, like OFDM, one of main problems of MIMO-OFDM is the high PAPR(Peak-to-Average Power Ratio). In this paper, an adaptive P-SLM(Partitioned-SeLetive Mapping) based on new phase sequence is proposed to reduce PAPR. The proposed method has better performance and lower complexity than conventional method due to the use of periodic multiplication and adaptability by fixed critical PAPR value. Simulation results show that the proposed method has better performance and lower complexity than conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.958-964
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• 2007

In this paper, we derive the relationship between the bit error probability (BEP) of maximum a posteriori (MAP) bit detection and the bit minimum mean square error (MMSE), that is, the BEP is greater than a quarter of the bit USE and less than a half of the bit MMSE. By using this result, the lower and upper bounds of the derivative of the mutual information are derived from the BEP and the lower and upper bounds are easily obtained in the multiple-input multiple-output (MIMO) communication systems with the bit-linear linear-dispersion (BLLD) codes in the Gaussian channel.

• Journal of Communications and Networks
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• v.16 no.6
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• pp.639-644
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• 2014

In low-density parity-check (LDPC) coded multiple-input multiple-output (MIMO) communication systems, probabilistic information are exchanged between an LDPC decoder and a MIMO detector. TheMIMO detector has to calculate probabilistic values for each bit which can be very complex. In [1], the authors presented a class of linear block codes named low-density MIMO codes (LDMC) which can reduce the complexity of MIMO detector. However, this code only supports the outer-iterations between the MIMO detector and decoder, but does not support the inner-iterations inside the LDPC decoder. In this paper, a new approach to construct LDMC codes is introduced. The new LDMC codes can be encoded efficiently at the transmitter side and support both of the inner-iterations and outer-iterations at the receiver side. Furthermore they can achieve the design rates and perform very well over MIMO channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.724-732
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• 2013

In this paper, we analyze a performance of multiuser massive multiple-input and multiple-output (MIMO) system. We derive the ergodic cell capacity based on a downlink frame structure and analyze the ergodic cell capacity with respect to the number of base station (BS) antennas and the number of users. This paper shows that the ergodic cell capacity is a concave function with respect to the number of BS antennas and the number of users, and also derives the optimal numbers of BS antennas and users for the maximum cell capacity. The simulation results verify the derived analyses and show that the derived numbers of BS antennas and users provide the maximum cell capacity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.712-723
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• 2013

Recent exploration of smart-phone user is fueling the deployment of long term evolution (LTE) service that offers higher data rates service over 3G HSPA networks. In particular, Korea, mobile powerhouse, recently launched the service of LTE-Advanced (LTE-A) which is the latest release in LTE standard. Multiple-input-multiple-output (MIMO) technology is the one of key enablers for LTE and LTE-A for achieving high data rate. MIMO technology has received much attention since it is possible to achieve channel capacity in proportion to the number of antennas without increasing frequency and power. In this paper, we overview of the theoretical background of MIMO technology regarding from single-user MIMO, multiuser MIMO, and massive MIMO and design considerations to implement the communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.338-343
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• 2005

MIMO(Multiple Input Multiple Output) systems are considered as one of the most promising systems for next generation mobile communication systems which require efficient frequency resource utilization as well as high data rate transmissions. BLAST-STTC is the MIMO system which transmits information from many of STTC encoder groups with two transmit antennas and cancels the interference from other groups in receiver. In this paper we propose a reverse-ordered iterative decoding scheme for BLAST-STTC systems which achieve full diversity gain for all groups and improve the performance of interference cancellation, and compare the error performance of the proposed scheme with general schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1239-1247
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• 2015

In frequency-division duplex (FDD) massive multiple-input multiple-output (MIMO) system, the computational complexity of downlink channel estimation is proportional to the number of antennas at a base station. Therefore, effective channel estimation techniques may have to be studied. In this paper, novel channel estimation algorithms using adaptive techniques such as Kalman and least mean square (LMS) filters are proposed in a channel model with temporal and spatial correlation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1113-1121
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• 2009

In this paper, the channel estimation and pilot sequence design technique of multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems in multi-cell environments are studied for situations in which the inter cell interference (ICI) is the dominant channel impairment. We design pilot sequence aiming at minimizing mean square error and propose the channel estimation technique correspond to the designed pilot sequences. The proposed pilot sequences employ the sequences with good correlation properties such as Chu sequence and through simulations, it is shown that channel estimation algorithm using designed pilot sequence is effective for mitigating the ICI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.341-349
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• 2010

In this paper, we studied on the optimization of the output power of Mobile WiMAX (IEEE 802.16) base station considering the technical condition of base station and wireless channel condition. The optimum power of base station can be estimated based on the link budget calculation of downlink and uplink in the Mobile WiMAX communication system. We investigated the optimum output power of base station in the case of 2Tx-2Rx base station with $2{\times}2$ MIMO(multiple input multiple output) technology, 2Tx-4Rx base station with improved receiver sensitivity, and 4Tx-4Rx base station with beamforming technology.