• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.730-734
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• 2003

A beamforming method is a kind of spatial filter that focus the amy's signal capturing abilities in a desired direction. In this paper, we detect the location of a source under reflective condition using the multi-dimensional MUSIC algorithm then, we can iud the image source locations from the experimental geometry, and we reconstruct the partial fields for direct wave and reflected wave by using Adaptive nulling algorithm. Numerical simulations are performed to verify its performance under various conditions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.24-31
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• 2009

In this paper, the new technique combing power control with Pre-FFT beamforming is proposed for MIMO(multi-input multi-output)-OFDM(orthogonal frequency division multiplexing) system. As combining the proposed power control with beamforming, we can iteratively control the transmittingpower and update the weight of beamformer together. And then, the beam is formed toward the desired direction and SNIR of each subcarrier is converged to target SNIR. Therefore, the performance of MIMO-OFDM system is very improved. BER performance improvement of the proposed approach is investigated through computer simulation by combining power allocation algorithm with MIMO-OFDM system using Pre-FFT beamformer

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.1-9
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• 2006

In this paper, we propose a MIMO-OFDMA (Multi Input Multi Output-Orthogonal Frequency Division Multiple Access) system based on beamforming for performance improvement of downlink real-time traffic transmission in harsh channel conditions with low CIR (Carrier-to-Interference Ratio). In the proposed system, we first consider the M-GTA-SBA (Modified-Grouped Transmit Antenna-Simple Bit Allocation) using effective CSI (Channel State Information) calculation procedure based on spatial resource grouping, which is adequate for the combination of MRT (Maximum Ratio Transmission) in the transmitter and MRC (Maximum Ratio Combining) in the receiver. In addition, to reduce feedback information for the beamforming, we also apply QEGT (Quantized Equal Gain Transmission) based on quantization of amplitudes and phases of beam weights. Furthermore, considering multi-user environments, we propose the P-SRA (Proposed-Simple Resource Allocation) algorithm for fair and efficient resource allocation. Simulation results reveal that the proposed MIMO-OFDMA system achieves significant improvement of spectral efficiency in low CRI region as compared to a typical open-loop MIMO-OFDMA system using pseudo-orthogonal space time block code and H-ARQ IR (Hybrid-Automatic Repeat Request Incremental Redundancy).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.588-599
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• 2007

This paper presents the coexistence issues between M-WiMAX TDD and WCDMA FDD systems. To improve the M-WiMAX system performance and to reduce the adjacent channel interference to WCDMA FDD system, transmit and receive beamforming techniques are applied in the base stations of M-WiMAX system. Furthermore, we propose an adjacent channel interference modeling methodology, which captures the effect of transmit beamforming on the adjacent channel interference. Besides, we verify the performance improvement in the uplink of WCDMA system due to the transmit beamforming in M-WiMAX downlink based on the proposed adjacent channel interference modeling methodology. We also verify the performance enhancement due to the receive beamforming in the uplink of M-WiMAX system through system level Monte Carlo simulations, considering random user position, the effect of shadowing and multi-path fading channel. Discussions on the gain of applying transmit and receive beamforming in M-WiMAX system comparing the case of SISO system are also included. Furthermore, we present the performance of cosited M-WiMAX and WCDMA systems, considering commercial deployment, additional channel filter at base stations and the effects of TxBF and RxBF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1133-1139
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• 2012

In this paper, hybrid mode beamforming (HMB) which allows simultaneous transmission of joint beamforming and disjoint beamforming is proposed. HMB is proven to be asymptotically optimal beamforming for sum rate growth. Extensive simulations show that HMB achieves nearly the same performance as joint encoding (JE) in symmetric interference channel. It is also shown that it outperforms JE in a more realistic asymmetric interference channel environment, though it still experiences some performance degradation due to power inefficiency of joint beamforming in asymmetric channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.17-26
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• 2004

This paper proposes JBSTBC (Joint Beamforming Space-Time Block Coding) scheme for MIMO (Multi-Input Multi-Output) communication systems. To enhance the order of spatial diversity in presence of deteriorative fading correlations as well as inter-substream interferences, the proposed JBSTBC method employs joint eigen-beamforming technique together with the BOLD (block-ordered layered detector) for MIMO-STBC. In order to confirm superiority of the proposed JBSTBC method, the computer simulations are conducted in highly correlated fading situations with providing detailed mathematical derivations for clarifying functionality of the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2298-2304
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• 2015

In this paper, we provide a new approach which optimizes the vertical tilting angle of the base station for multi-cell multiple-input single-output (MISO) downlink active antenna systems (AAS). Instead of the conventional optimal algorithm which requires an exhaustive search, we propose simple and near optimal algorithms. First, we represent a large system approximation based vertical beamforming algorithm which is applied to the average sum rate by using the random matrix theory. Next, we suggest a signal-to-leakage-and-noise ratio (SLNR) based vertical beamforming algorithm which simplifies the optimization problem considerably. In the simulation results, we demonstrate that the performance of the proposed algorithms is near close to the exhaustive search algorithm with substantially reduced complexity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.29-34
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• 2017

This paper considers hybrid beamforming for millimeter wave system in uplink transmission where multiple users send their data streams simultaneously. Hybrid beamforming has low-cost and low power consumption features compared to conventional digital beamforming schemes. We assume that each user uses one transmit antenna and sends one data stream, while the base station has multiple receive antennas and multiple radio frequency chains. Therefore, hybrid beamforming is performed only at the base station. We also assume that each user does not know instantaneous channel side information (CSI), while the base station is able to estimate the CSI from all users accurately. Under this channel assumption, the outage probability is not zero. We evaluate the outage probability of the considered hybrid beamforming as a performance metric through computer simulations. We show that the outage probability of hybrid beamforming approaches that of digital beamforming in some cases.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.128-135
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• 2007

A combined opportunistic multiple beamforming method is presented that the first beam is designed with an aid of channel state information using uplink mid-amble and other beams are orthogonally generated to the first beam sequentially. The power allocation with SINR feedback increases overall throughput for the decentralized systems. The advantages of the proposed scheme is that the first beam is not interfered by other beams guaranteeing quality of service (QoS) and other orthogonal beams are operated opportunistically to obtain multi user diversity. The computer simulation demonstrates that the proposed scheme is effective at a small number of users, which is common in cellular systems, and outperforms conventional spatial division multiple access (SDMA) opportunistic beamforming methods.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.53-60
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• 2013

In this paper, the new multi-beamforming is proposed for Multiple-input multiple-output (MIMO) Multicarrier-Code division multiple access(MC-CDMA) systems to overcome the decrease of performance due to multiuser interference and multiple-antenna interference. Installing the number of multi-beamformer which is equal to the number of multi-transmitter antennas and exploiting the proposed approach at the receiver of MIMO MC-CDMA, the multi-beams are formed toward each multi-antenna of desired user and null beam are formed to other interference. Therefore, the performance of MIMO MC-CDMA system is improved as removing the interference signal. BER performance improvement is investigated through computer simulation by the proposed approach to MIMO MC-CDMA system.