• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4759-4780
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• 2017

Full Dimension multiple input multiple output (FD-MIMO) architecture employs a planar array design at the Base Station (BS) to provide high order multi-user MIMO (MU-MIMO) via simultaneous data transmission to large number of users. With FD-MIMO, the BS can also adjust the beam direction in both elevation and azimuth direction to concentrate the energy on the user of interests while minimizing the interference leakage to co-scheduled users in the same cell or users in the neighboring cells. In a typical highly populated macrocell environment, modelling the elevation angular characteristics of three-dimensional (3D) channel is critical to understanding the performance limits of the FD-MIMO system. In this paper, we study the throughput performance of FD-MIMO system with varying elevation angular spread and inter-element spacing using a 3D spatial channel model. Our results show that for a typical urban scenario, horizontal beamforming with correlated antenna spacing achieves optimal performance but by restricting the spread of elevation angles of departure, elevation beamforming achieves high array gain with wide inter-element spacing. We also realize significant gains due to spatial array processing via modelling the elevation domain and varying the inter-element spacing for both the transmitter and receiver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1032-1037
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• 2016

In this paper, the method of isolation enhancement for the mobile phone MIMO antenna of LTE class 40(2300~2400MHz) was studied. Design of MIMO antenna was based on the hybrid antenna that operates both a monopole and an IFA(Inverted F Antenna). A structure for the isolation enhancement which controls induced electric field on the ground plane is located between MIMO antenna, and was not connected with the ground but apart 0.3mm. A MIMO antenna that operates on class 3~40(1710~2400MHz) of LTE service bands and a structure for the isolation enhancement at the class 10 band were designed. VSWR measurement of implemented antenna on the FR4 board showed within 3:1 at entire design bands, and isolation between antennas at the class 40 band was less than -30dB. Isolation was enhanced more than 20dB by the studied structure. ECC(Envelope Correlation Coefficient) for MIMO performance was under 0.1, and antenna average gain and efficiency measured in the anechoic chamber were -4.28~-1.40dBi and 37.32~72.36% respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.3
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• pp.22-30
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• 2010

This paper proposes a combination system of Adaptive Modulation and Coding (AMC) and Multiple Input Multiple Output (MIMO), which improves the throughput and has a better reliability. In addition, the system includes Precoding, Antenna Subset Selection and MIMO Mode Selection scheme. Finally, we make a performance analysis of the proposed system. The principal environmental parameters for the simulation experiment consist of a frequency non-selective rayleigh fading channel and a Spreading Factor (SF) of 16. Other parameters may be included in order to fulfill the requirements of the HSDP A Standard. The proposed system has a higher throughput and more reliability than the conventional system, which does not include MIMO Mode Selection scheme, Precoding or Antenna Subset Selection. According to the simulation results, the proposed system reaches the maximum throughput at 8dB, presentlng an improvement of 6dB and twice higher throughput, respect to the conventional system. Specifically, at the point of -6dB, the conventional system reaches 2.5Mbps, while the proposed system reaches 6.4Mbps at the same SNR. Also, at the point of 2dB, each system reaches 7.5Mbps (conventional system) and 15.3Mbps (proposed system), with near twice the difference. According to the results exposed above, we can conclude that the system proposed in this paper has, as the greatest contribution, the improvement of the throughput, especially, the average throughput.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.79-86
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• 2008

This paper presents to improve of isolation characteristics between personal communication service(PCS) antenna In mobile terminal and 2-channel multi input multi output(MIMO) antenna in the wireless broadband Internet(WiBro) band. In order to improve the isolation between each channel antenna, the proposed PCS antenna with an air space of 3 mm height is located on the projected ground plane($25{\times}12mm$) which is very small space$(0.19{\lambda})$ between the 2-channel WiBro-MIMO antenna. The proposed PCS antenna structure is a modified planar inverted F antenna (PIFA) of spiral type with shorting strip line(6${\times}$4 mm). The calculated Isolation values between the proposed PIFA with 3-dimensional structure and the MIMO antenna at Wibro band are about -20dB below and agree well with the measurement. Measured return loss, bandwidth, and gain o# the proposed antenna are -20dB at 1.8GHz, 110MHz(1.76${\sim}$1.87 GHz) band at -10dB below, and 0.05dBi, respectively, Moreover, we confirm that the proposed PCS antenna has no influence on performance and characteristics of the conversional 2-channel WiBro-MIMO antenna.

• ETRI Journal
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• v.35 no.2
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• pp.177-187
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• 2013

In this paper, we propose a dual-band multiple-input multiple-output (MIMO) antenna with high isolation for WLAN applications (2.45 GHz and 5.2 GHz). The proposed antenna is composed of a mobile communication terminal board, eight radiators, a coaxial feed line, and slots for isolation. The measured -10 dB impedance bandwidths are 10.1% (2.35 GHz to 2.6 GHz) and 3.85% (5.1 GHz to 5.3 GHz) at each frequency band. The proposed four-element MIMO antenna has an isolation of better than 35 dB at 2.45 GHz and 45 dB at 5.2 GHz between each element. The antenna gain is 3.2 dBi at 2.45 GHz and 4.2 dBi at 5.2 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1209-1216
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• 2008

In order to maximize spectrum efficiency and data rate MIMO(Multiple Input Multiple Output) is adopted to wireless system. OFDM-based WiMAX and LTE accommodate MIMO as mandatory technology. STC(Space Time Coding) and SM(Spatial Multiplexing) are used in downlink while in uplink C-MIMO(Collaborative MIMO) is used to improve data throughput. In this paper conventional pairing schemes, RPS(Random Pairing Scheduling) and DPS(Determinant Pairing Scheduling) are analyzed. From the analysis the performance of DPS algorithm is better than that of RPS because DPS measures orthogonal factor between paired users. However, there are potential problems such as hardware complexity and performance. To overcome the issues Power-Based Scheduling(PBS) algorithm is proposed for C-MIMO. PBS can provide higher performance compared to RPS and dramatically reduce hardware complexity compared to DPS

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.759-764
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• 2004

This paper proposes a method that estimates MIMO channel characteristics analytically using a 3D ray tracing propagation model. We calculate the discrete spatial correlation between sub-channels by considering phase differences of paths, and using this, estimate the mean capacity upper bound of MIMO channel by Jensen's inequality. This analysis model is a deterministic model that do not approach stochastically through measurement nor approach statistically through Monte-Carlo simulations, so this model has high efficiency for time and cost. And based on the electromagnetic theory, this model may analyze quantitatively the parameters which can affect the channel capacity - antenna pattern, polarization mutual coupling, antenna structure and etc. This model may be used for the development of an optimal antenna structure for MIMO systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.248-256
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• 2015

In this paper, a hybrid MIMO antenna for the metal phone with auxiliary slot for 4th generation mobile communication is designed and implemented. Auxiliary slot locates on the rear metal cover of the phone, and handles for LTE class 40 band. The auxiliary slot operates hybrid with a monopole antenna. Studied antenna satisfies under VSWR 3:1 for LTE class 13/ LTE class 14/ CDMA/ GSM/ DCS/ PCS/ W-CDMA/ LTE class 40 bands. ECC(Envelope Correlation Coefficient) value for MIMO characteristic is less than 0.2 over the whole design bands. Average gains and antenna efficiencies measured by MTG anechoic chamber were -5.57~-1.45 dBi and 27.75~71.6 %, respectively.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.634-646
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• 2015

Assuming perfect channel state information (CSI) at the transmitter and receiver, the optimization problem of maximizing the minimum Euclidean distance between two received signals by a linear precoder is considered for multiple-input multiple-output (MIMO) systems with arbitrary dimensions and arbitraryary quadrature amplitude modulation (QAM) input. A general precoding framework is first presented based on the Gram matrix, which is shown for 2-dimensional (2-D) and 3-dimensional (3-D) MIMO systems when employing the ellipse expanding method (EEM). An extended precoder for high-dimensional MIMO system is proposed following the precoding framework, where the Gram matrix for high-dimensional precoding matrix can be generated through those chosen from 2-D and 3-D results in association with a permutation matrix. A complexity-reduced maximum likelihood detector is also obtained according to the special structure of the proposed precoder. The analytical and numerical results indicate that the proposed precoder outperforms the other precoding schemes in terms of both minimum distance and bit error rate (BER).

• ETRI Journal
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• v.38 no.2
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• pp.280-290
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• 2016

To implement high-order multiuser multiple input and multiple output (MU-MIMO) for massive MIMO systems, there must be a feedback scheme that can warrant its performance with a limited signaling overhead. The interference-to-noise ratio can be a basis for a novel form of Codebook (CB)-based MU-MIMO feedback scheme. The objective of this paper is to verify such a scheme's performance under a practical system configuration with a 3D channel model in various radio environments. We evaluate the performance of various CB-based feedback schemes with different types of overhead reduction approaches, providing an experimental ground with which to optimize a CB-based MU-MIMO feedback scheme while identifying the design constraints for a massive MIMO system.