• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.7
• /
• pp.6-12
• /
• 2009

In this paper, we propose the opportunistic channel state information feedback scheme for eigen based scheduling in multiuser MIMO systems. According to 3GPP SMC channel model, the system capacity of MU-MIMO systems is severly degraded, since the antennas are highly correlated in urban macro cell. Although the eigen based scheduling scheme mitigates the adverse effect of the antenna correlation, it achieves only small amount of the multiuser diversity gain. Since the opportunistic channel state information scheme can achieve sufficient multiuser diversity gain, the system capacity of MU-MIMO systems can be improved. The system capacity improvement is verified by the computer simulation results.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.2
• /
• pp.219-224
• /
• 2020

In this paper, we studied the compact MIMO(: Multi-Input Multi-Output) antenna for multi-beam pattern generation and control in narrow space. The characteristics and performance of the basic Dipole SPA and Monopole SPA structures are shown. We implemented a monopole SPA antenna and measured its performance in an 802.11g system. When the average transmission rate was measured using the SPA antenna, the SPA antenna improved the best performance by 8.7 times compared to commercial antenna.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.3A
• /
• pp.223-231
• /
• 2011

It has been shown that the performance of multiple-input multiple-output (MIMO) spatial multiplexing systems is significantly degraded when spatial correlation exists between transmit and receive antenna pairs. In this paper, we investigate designs of a new statistical precoder for spatial multiplexing systems with maximum likelihood (ML) receiver which requires only correlation statistics at the transmitter. Two kinds of closed-form solution precoders based on rotation and power allocation are proposed by means of maximizing the minimum E tlidean distance of joint symbol constellations. In addition, we extend our results to linear receivers for correlated channels. We provide a method which yields the same profits from the proposed precoders based on a simple zero-forcing (ZF) receiver. The simulation shows that 2dB and 8dB gains are achieved for ML and ZF systems with two transmit antennas, respectively, compared to the conventional systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.2C
• /
• pp.86-92
• /
• 2011

This paper details the downlink performance analysis of an multiple antennas system that combines adaptive beamforming and spatial multiplexing (SM) Multiple Input Multiple Output (MIMO). The combination of MIMO signal processing with adaptive beamforming is applied to WiBro, the South Korean Orthogonal Frequency Division Multiple Access (OFDMA) system that follows the IEEE 802.16e standard. Performance analysis is based on the results of experiments and simulations obtained from a fixed-point simulation testbed. Simulations demonstrate that the MIMO Beamforming OFDMA system improves the required signal to noise ratio (SNR) over the conventional MIMO OFDMA system by 3 dB (QPSK) / 2.5 dB (16-QAM) for the frame error rate (FER) of 1% in the WiBro signal environments. From the implementation of the fixed-point simulation testbed and its experimental results, we verify the feasibility of the MIMO Beamforming technology for realizing a practical WiBro base station.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.12
• /
• pp.1113-1119
• /
• 2013

In this letter, a new approach is proposed for the design of a multi antenna for MIMO wireless devices. The proposed antenna covers various LTE(Long Term Evolution) service bands: band 17(704~746 MHz), band 13(746~787 MHz), band 5(824~894 MHz), and band 8(880~960 MHz). The proposed main antenna consists of a conventional monopole antenna with an inverted L-shaped slit for wideband operation. The proposed the LTE sub antenna is based on a switch loaded loop antenna structure, with a resonance frequency that can be controlled by capacitance of a logic circuit. The tuning technique for the LTE Rx antenna uses a RF MEMS(Micro-Electro mechanical system) to match the impedances to realize the bands of interest. Because the two proposed antennas are polarized orthogonally to each other, the ECC(Envelope Correlation Coefficient) characteristic between two antennas was measured to be very low (below 0.06) with an isolation characteristic below -20 dB between the two antennas in the operating overall LTE bands. The proposed antenna is particularly attractive for mobile devices that integrate LTE multiple systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.7
• /
• pp.552-559
• /
• 2013

In this paper, the multiple-input multiple-output (MIMO) system with a precoder is considered in the transmit-correlated Rayleigh channels. We specifically target the MIMO system employing the minimum mean square error receivers. Based on random matrix theory, we first present a direct and generalized formulation for deriving a probability density function (PDF) of the signal-to-interference-plus-noise ratio (SINR). Then, we derive the accurate closed-form SINR PDFs for a small number of transmit and receive antennas. Based on the SINR PDFs, tight closed-form approximations of the symbol error rate (SER) are derived. Our analysis suggests that the SER approximations can be used to accurately estimate the error probabilities or as a useful tool for the system design.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.4
• /
• pp.17-25
• /
• 2013

In this paper, a coding algorithm is proposed for multi-user multi-input multi-output (MU-MIMO) systems to improve the reception performance in fading conditions without reducing the bandwidth efficiency. The space division multiple access (SDMA) scheme that is one of the commonly used for MU-MIMO systems is vulnerable to the fading. The space time block code (STBC) scheme that is used to overcome the fading has a disadvantage of reduced throughput. The proposed MU-MIMO system first encodes transmitted symbols by linear dispersion code (LDC) which is less vulnerable to the fading and increases the throughput in proportional to the number of transmit antennas. Then, the LDC coded symbols are pre-coded by the result of singular value decomposition (SVD) of the estimated channel gain. We evaluate the performance of the proposed scheme compared with the conventional algorithms by computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.9
• /
• pp.817-825
• /
• 2013

The UHDTV system, which provides realistic service with ultra-high definite video and multi-channel audio, has been studied as a next generation broadcasting service. Since the conventional digital terrestrial transmission system is not capable to cover the increased transmission data rate of the UHDTV service, there are great necessity of researches about increase of data rate. Accordingly, the researches has been studied to increase the transmission data rate of the DVB-T2 system using dual-polarized MIMO technique and high order modulation. In order to optimize the MIMO DVB-T2 system where irregular LDPC codes are used, it is necessary to study the design of the bit mapper that matches the LDPC code and QAM symbols in MIMO channel. However, the research related to the design of the bit mapper has been limited to the SISO system. Therefore, this paper defines a new parameter that indicates the VND distribution of MIMO DVB-T2 system and performs the performance analysis according to the parameter which will be helpful for designing a MIMO bit mapper.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.4
• /
• pp.983-990
• /
• 2010

In this paper, we designed and implemented the MIMO antenna for LTE(Long Term Evolution), supposed to be a next generation communications network, DCS1800, DCS1900 and WCDMA. Using conventional monopole antenna with MD material results in good characteristics, miniaturization for LTE band and as well as broadbanding for DCS, WCDMA band. The performance of the proposed MIMO antenna shows VSWR < 2, under -10 dB of isolation and the gain is -1.66 ~ 1.33 dBi for LTE(Long Term Evolution), DCS1800, DCS1900 and WCDMA, which has omnidirectional radiation pattern.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37B no.11
• /
• pp.1072-1081
• /
• 2012

For Ka-band satellite communication system, a new flexible payload technologies which can compensate rain attenuation have to be developed. The Ka-band satellite output power control technology enables to adjust downlink output power of satellite payload in Ka-band (19.8 ~ 22.2 GHz). In this paper, we introduce multi-beam antenna with multi-port amplifiers for Ka-band flexible output power allocation system. We have designed multi-beam antenna with array-fed reflector to form 8 beams on the Korean Peninsula. The target EIRP per beam is more than 59 dBW. The system is designed to present 6 dB boost beams for rainfall areas. Individual beams were optimized by the excited amplitude and phase of feed elements of the feed cluster. The multi-port amplifier(MPA) is one of effective approaches for flexible power allocation in combination with multi-beam antenna. In case of using MPA in multi-beam system, the inter-port isolation characteristic of MPA is important parameter to avoid interference among the output ports. In this paper, we propose a new MPA structure that consists of two $4{\times}4$ Buttler matrixes and phase/amplitude controllable power amplifier modules.