• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.9A
• /
• pp.776-783
• /
• 2011

In this paper, assuming that the transmitter can exploit imperfect channel state information (CSI), the diversity-multiplexing tradeoff (DMT) functions of three adaptive decode-and-forward (DF) relay protocols, each of which uses multiple-antennas at the destination node, at the relay node, or at the source node are derived. When the imperfect CSI qualities for the source-relay link, the relay-destination link, and the source-destination link are subject to asymptotic conditions, the additional diversity gains attainable by exploiting the imperfect CSI at the transmitter for those three adaptive DF relay protocols are investigated.

• Journal of electromagnetic engineering and science
• /
• v.11 no.2
• /
• pp.113-121
• /
• 2011

Multiple-input multiple-output with orthogonal frequency division multiplexing technology (MIMO-OFDM) is considered to be the ultimate solution for increasing system throughput and for enhancing communication reliability. In this paper, we propose to increase the uplink (UL) throughput by assigning the same UL resources to multiple single-antenna mobile stations. This leads to the loss of orthogonality among sub-carriers. Thus, at the base station (BS), MIMO-OFDM detection techniques are used to separate the streams of different users assigned the same UL resources. To obtain a realistic performance evaluation, different channel scenarios are applied with different correlation values among the antennas of the users. Simulation results show that the proposed MIMO-OFDM system linearly increases the uplink capacity of the OFDM system while maintaining a mobile station transmitter as simple as that used in a conventional OFDM system. For instance, when 4 users are assigned the same UL resources, the throughput of the proposed system is 3.07 times that achieved by a conventional single input single output OFDM system.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.4
• /
• pp.38-42
• /
• 2008

In this paper, we propose a new structure for spectrum sensing which employs multiples energy detectors in multiple antenna system in order to improve its reliability. The performance is analyzed by simulation and compared to that of the conventional energy detector. The simulation results shows that the performance of the proposed scheme is much better than that of the conventional one. Additionally, the performance of is described in terms of ROC curve.

• Journal of Communications and Networks
• /
• v.18 no.2
• /
• pp.173-181
• /
• 2016

In this paper, we address a new robust optimization problem in a multiuser multiple-input single-output broadcasting system with simultaneous wireless information and power transmission, where a multi-antenna base station (BS) sends energy and information simultaneously to multiple users equipped with a single antenna. Assuming that perfect channel-state information (CSI) for all channels is not available at the BS, the uncertainty of the CSI is modeled by an Euclidean ball-shaped uncertainty set. To optimally design transmit beamforming weights and receive power splitting, an average total transmit power minimization problem is investigated subject to the individual harvested power constraint and the received signal-to-interference-plus-noise ratio constraint at each user. Due to the channel uncertainty, the original problem becomes a homogeneous quadratically constrained quadratic problem, which is NP-hard. The original design problem is reformulated to a relaxed semidefinite program, and then two different approaches based on convex programming are proposed, which can be solved efficiently by the interior point algorithm. Numerical results are provided to validate the robustness of the proposed algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.6A
• /
• pp.624-631
• /
• 2007

This paper presents inter-cell cooperation methods with two transmit antennas for broadcast services in a coded OFDM cellular system. In the method, cells are divided into multiple cell groups and a coded packet is partitioned into the subparts. Then, a different cell group and antenna combination is assigned to each subpart for transmission of two orthogonal branches of the diversity code. For the method, we derive the bound on the pairwise error probability to predict the coded performance and verify the performance gain of the proposed method through the simulation using turbo code and analytically derived bound.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.29 no.11
• /
• pp.891-897
• /
• 2018

In this paper, we propose a blind estimation scheme for the antenna spacing of nonuniform linear array MIMO radar using distributed electronic sensors based on ESPRIT. We present a blind method to separate orthogonal waveforms of a MIMO radar based on the antenna spacing estimation. The estimated orthogonal waveforms of a MIMO radar can be used for disabling opponent MIMO radars.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.12B
• /
• pp.1752-1757
• /
• 2011

In a traditional phased array radar, closely spaced antenna elements transmit a scaled version of single waveform to maximize the signal energy. On the contrary, a multiple-input multiple-output (MIMO) radar consists of widely separated antennas and transmits an arbitrary waveform from each antenna element. These waveforms and spatial diversity enable superior capabilities compared with phased array radar. At high signal-to-noise ratio (SNR), the detection performance of the MIMO radar is better than the phased array radar due to the diversity gains. However, the phased array radar outperforms the MIMO radar at low SNR, due to the energy maximization. In this paper, we investigate the compromised scheme between the MIMO radar and the phased array radar. Employing the MIMO radar equipped with phased array elements, the compromised scheme achieves both array gain and diversity gain. Also, we compare the performance degradation when the steering direction is incorrect.

• Proceedings of the KIEE Conference
• /
• 2004.11c
• /
• pp.196-199
• /
• 2004

This paper presents a structure of the searcher using the space diversity in array antenna system operating in the DS/CDMA signal environments. The new technique exploits the fact that the In-phase and Quadrature components of interferers can respectively be viewed as independent Gaussian noise at each antenna element in most practical CDMA (Code Division Multiple Access) signal environments. The proposed PN acquisition scheme is a single dwell serial PN acquisition system consisting of two stage, that is, the searching stage and the verification stage. The searching stage correlates the received signals with the local PN oscilator for obtaining the synchronous energy at the entire uncertainty region. The verification stage compares the searching energy with the optimal threshold, which is pre-designed in the Lock-Detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the relationship of both diversity order and the mean acquisition time. In general, It is known that the mean acquisition time decreases significantly as the number of antenna elements increases. But, the enhancement of the performance is saturated in terms of PN acquisition scheme. Therefore, to decrease the mean acquisition time, we must design the optimal array antenna system by considering the operating SNR range of the receiver, the detection probability, and the false alarm probability. The performance of the proposed acquisition scheme is analyzed in frequency-selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on acquisition scheme is considered in terms of the detection probability, false alarm probability. and the mean acquisition time.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.2 s.344
• /
• pp.81-87
• /
• 2006

A small size broadband microstrip patch antenna with small ground plane has been fabricated using MEMS. Multiple layer substrates we used to realize small size and broadband characteristics. The microstrip patch is divided into 4 pieces and each patch is connected to each other using a metal microstrip line. The fabrication please process is simple and only one mask is needed. Two types of microtrip antennas are fabrication Type A is the microstrip antenna with metal lines and type B is the microstrip antenna without metal lines. The size of proposed microstip antenna is $8{\times}12{\times}2mm^3$ and the experimental results show that the antenna type A and type B have the bandwidth of 420MHz at 5.3 GHz and 480MHz at 5.66 GHz, respectively

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.1
• /
• pp.90-97
• /
• 2010

In this paper, we propose antenna topology and ground plane shape to improve the performance of PIFA (Planar Inverted F Antenna) which is built-in mobile phone. First, we designed the PIFA antenna consists of multiple radiators to provide multi-current paths. Then we designed U-shaped ground plane on the PCB under the antenna. The proposed antenna structure shows TRP/TIS improvement of 2.0 dB/3.7 dB for GSM and 2.2 dB/ 2.0 dB for DCS and 0.8 dB/1.5 dB for PCS and 1.3 dB/0.7 dB for WCDMA at the free space.