• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.607-613
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• 2004

The future wireless communication systems will use spatial multiplexing with Multiple Input Multiple Output(MIMO) system to take advantage of high spectral efficiencies. In such systems it will be desirable to select a sub-set of available transmit or receive antennas to reduce cost and complexity. In this paper we propose a novel transmit antenna selection schemes for MIMO systems which is suitable for multipath environment. The proposed transmit antenna selection schemes offer better BER performance than that of MIMO systems without antenna selection and with traditionally proposed antenna selection schemes.

• Journal of Communications and Networks
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• v.5 no.2
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• pp.116-123
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• 2003

In this paper, we address the problem of designing multirate codes for a multiple-input and multiple-output (MIMO) system by restricting the receiver to be a successive decoding and interference cancellation type, when each of the antennas is encoded independently. Furthermore, it is assumed that the receiver knows the instantaneous fading channel states but the transmitter does not have access to them. It is well known that, in theory, minimummean- square error (MMSE) based successive decoding of multiple access (in multi-user communications) and MIMO channels achieves the total channel capacity. However, for this scheme to perform optimally, the optimal rates of each antenna (per-antenna rates) must be known at the transmitter. We show that the optimal per-antenna rates at the transmitter can be estimated using only the statistical characteristics of the MIMO channel in time-varying Rayleigh MIMO channel environments. Based on the results, multirate codes are designed using punctured turbo codes for a horizontal codedMIMOsystem. Simulation results show performances within about one to two dBs of MIMO channel capacity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1425-1440
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• 2017

In wireless communications, antenna selection (AS) is a widely used method for reducing comparable cost of multiple RF chains in MIMO systems. As is well known, most of literatures on combining AS with MIMO techniques concern linear modulations such as phase shift keying (PSK) and quadrature amplitude modulation (QAM). The combination of CPM and MIMO has been considered an optimal choice that can improve its capacity without loss of power and spectrum efficiency. The aim of this paper is to investigate joint transmit and receive antenna selection (JTRAS) in CPM MIMO systems. Specifically, modified incremental and decremental JTRAS algorithms are proposed to adapt to arbitrary number of selected transmit or receive antennas. The computational complexity of several JTRAS algorithms is analyzed from the perspective of channel capacity. As a comparison, the performances of bit error rate (BER) and spectral efficiency are evaluated via simulations. Moreover, computational complexity of the JTRAS algorithms is simulated in the end. It is inferred from discussions that both incremental JTRAS and decremental JTRAS perform close to optimal JTRAS in BER and spectral efficiency. In the sense of practical scenarios, adaptive JTRAS can be employed to well tradeoff performance and computational complexity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.8
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• pp.301-306
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• 2003

This paper proposes a novel detection scheme using a radial basis function (RBF) network in a multi-input multi-output (MIMO) environment. In order to evaluate the performance of the proposed MIMO-RBF receiver, simulations are performed over the rich-scattering fading channel. Simulation results confirm that the proposed scheme shows the similar bit-error rate (BER) performance of a maximum likelihood detection (MLD) and outperforms Vertical-Bell Laboratories Layered Space-Time using minimum-mean-square-error nulling (VBLAST-MMSE) as well as VBLAST using zero-forcing nulling (VBLAST-ZF). Moreover, we investigate the effect on the performance of the number of RBF center with two modulation formats (BPSK and QPSK) and different number of transmit and receive antennas. The performance of the proposed detector is verified with respect to an initialization-rate of RBF centers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.8
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• pp.3054-3067
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• 2015

The phenomena of higher channel cross polarization discrimination (XPD) is mainly observed for future wireless technologies such as small cell network and massive multiple-input multiple-output (MIMO) system. Therefore, utilization of high XPD is very important and space-polarization division multiple access (SPDMA) with dual-polarized MIMO system could be a suitable solution to high-speed transmission in high XPD environment as well as reduction of array size at base station (BS). By SPDMA with dual-polarized MIMO system, two parallel data signals can be transmitted by both vertically and horizontally polarized antennas to serve different mobile stations (MSs) simultaneously compare to conventional space division multiple access (SDMA) with single-polarized MIMO system. This paper analyzes the performance of SPDMA for maximum ratio transmission (MRT) in time division duplexing (TDD) system by proposed dual-polarized MIMO spatial channel model (SCM) compare to conventional SDMA. Simulation results indicate that how SPDMA utilizes the high XPD as the number of MS increases and SPDMA performs very close to conventional SDMA for same number of antenna elements but half size of the array at BS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.8
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• pp.3589-3605
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• 2018

In this paper, we investigate an individual channel estimation problem for multiple-input multiple-output (MIMO) two-way amplify-and-forward (AF) relay networks. To avoid self-interference during the estimation of the individual MIMO channels, a novel blind interference cancellation (BIC) approach is proposed based on an orthogonal preceding framework, where a pair of orthogonal precoding matrices is utilized at the source nodes. By designing an optimal decoding scheme, we propose to decompose the bidirectional transmission into a pair of unidirectional transmissions. Unlike most existing approaches, we make the practical assumption that the nonreciprocal MIMO channel and the mutual interference of multiple antennas are both taken into consideration. Under the precoding framework, we employ an orthogonal superimposed training strategy to obtain the individual MIMO channels. However, the AF strategy causes the noise at the terminal to be the sum of the local noise and the relay-propagated noise. To remove the relay-propagated noise during the estimation of the second-hop channel, a partial noise-nulling method is designed. We also derive a closed-form expression for the total mean square error (MSE) of the MIMO channel from which we compute the optimal power allocation. The simulation results demonstrate that the analytical and simulated curves match fully.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.121-129
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• 2008

This paper presents the spatial multiplexing MIMO system to increase data rate to double in MB-OFDM UWB system, which is ECMA standards, and compares BER performance of various receiver structures. The complexity and BER performance of various types of spatial multiplexing receivers are compared and analyzed using diagonal and horizontal encoding techniques for $2{\times}2$\;and\;2{\times}3$ antennas systems. Computer simulations exhibit that $2{\times}2$ MML and $2{\times}3$ ZF method show better BER performance than that of SISO system with simple complexity.

• 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 Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.80-85
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• 2010

In this paper, a MIMO antenna is proposed for LTE/DCSl800/USPCSl900 handset applications. The proposed antenna is based on the IFA and its wide bandwidth is obtained by using a stagger tuning technique. To improve the isolation, a suspended line is connected to the shorting points in two antennas, and capacitors and inductors are added to the connected suspended line. Two identical antennas of which dimension is 2.8cc($40{\times}10{\times}7mm$) are mounted on the two end lines of the system ground plane($40{\times}60mm$). Analysis of the antenna performance and optimization is performed using CST Microwave Studio. The bandwidths are satisfied for LTE band class 13(746-787MHz), class 14(758-798MHz) and DCSl800/USPCSl900 band (1710-1990MHz). The isolations between two antennas are about -12dB for LTE band and -10dB for DCSl800/USPCSl900 band. And the radiation efficiency of each antenna is about for LTE band 33% and 45% for DCSl800/USPCSl900 band respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.84-90
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• 2012

Since the major cellular data service providers in U.S, Japan as well as in Korea started the LTE (Long Term Evolution) service, there has been more strong need for the methods that can accurately measure the MIMO (Multi Input-Multi Outout) OTA (Over The Air) performance of LTE handsets because the performance of the MIMO antenna determines the packet data rates in the downlink and therefore the higher system throughput of the network. In this regard, there has been a lot discussions in 3GPP on the candidate MIMO OTA test solutions. In this paper, a faire comparison has been done for the conventional method, the Envelop Correlation Coefficient (ECC) measurements, and the anechoic chamber based MIMO OTA test solution, one of the candidate system being discussed in 3GPP. The evaluations and the comparisons are conducted by numerically and experimentally.