• ETRI Journal
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• v.36 no.4
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• pp.625-634
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• 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.109-110
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• 2007

The sum-rate capacity of multi-antenna broadcast channels recently has attracted much research interests. However, those effort mainly has focused on a single-cell system. In this paper, we consider a multi-cell system where a transmitter uses zero-forcing beamforming with multiple antennas. We select a linear zero-forcing weight that maximizes the sum-rate when intercell interference exists. With numerical investigation, we will show the sum-rate gain achieved by the proposed method gets larger when the number of interfering cells increases.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.306-312
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• 2006

This paper studies theoretically the bit error rate (BER) performance of cooperative transmission using space-time block code (STBC) in a fully distributed manner. Specifically, we first propose a STBC-based cooperative signaling structure to make the cooperation of three single-antenna terminals possible. Then, we derive the closed-form BER expressions for both cooperation and noncooperation schemes under flat Rayleigh fading channel plus additive white Gaussian noise (AWGN). The validity of these expressions is verified by Monte-Carlo simulations. A variety of numerical and simulation results reveal that the cooperative transmission achieves higher diversity gain and better performance than the direct transmission for the same total transmit power.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.150-158
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• 2007

We consider channel-coded multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) transmission and obtain a condition on its signal for it to attain the maximum diversity and coding gain. As this condition may not be realizable, we propose a suboptimal design that employs an orthogonal transform and a space-frequency interleaver between the channel coder and the multi-antenna OFDM transmitter. We propose a corresponding receiving method based on block turbo equalization. Attention is paid to some detailed design of the transmitter and the receiver to curtail the computational complexity and yet deliver good performance. Simulation results demonstrate that the proposed transmission technique can outperform the conventional coded MIMO OFDM and the MIMO block single-carrier transmission with cyclic prefixing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.2
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• pp.143-155
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• 2013

A low-complexity dual-user multiplexing scheme is proposed for a pair of mobiles equipped with single antenna operating over frequency-selective fading channels. The proposed scheme employs OFDM transmission scheme with a modified version of a space-frequency code and a low-complexity PIC-SIC group detection is invoked at the corresponding receiver. The BER performances of the proposed scheme are studied using LTE-like parameters through simulations and are compared against those of conventional ZF and ML schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.2
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• pp.127-142
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• 2013

A dual-user multiplexing scheme for a pair of mobiles equipped with single antenna is proposed which incorporates time-delay diversity employing a rotation-based D-BLAST-like layered code. A low-dimension equivalent of the existing partial interference cancellation based group decoder is also proposed for the corresponding receiver. The BER performances of the proposed scheme and those of the ideal scheme are studied comparatively through Monte Carlo simulations.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.82-85
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• 1987

Electromagnetic waves from the satellite may be utilized to direct the tracking antenna toward the satellite. We design and fabricate the feed appropriate to the monopulse tracking technique which derive angle-error information on the basis of a single pulse. The feed consists of five cavity-backed turnstile elements mounted on a common ground plane. The turnstile dipole are connected to a set of five quadrature hybrids which convert the dual linear polarization into dual circular polarization. The five feed outputs are then processed in the monopulse comparator which is constructed in microstrip for compactness.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.226-233
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• 1999

A transmitting antenna mounted on the naval vessels can be easily exited by exogenous disturbances such as wave and impact. Gimbal system need for the controller to maintain the robust performance against various modeling uncertainties and disturbances. PI controller, however, cannot supply good robust performance under situation. Thus a robust $H_{\infty}$ control scheme is used to ensure a specified dynamic response under above conditions. Gimbal system controlled simplified as 2 DOF system that ignored coordinate co-relations of each direction and hydraulic system is linearly modelled. In this paper, we compared those of simulation to the results of experiment and H$_{\infty}$ controller, proposed, showed the good response and stability than PI controller.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.4
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• pp.467-474
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• 2019

Recently, optical phased array(OPA) based laser detection and ranging(LADAR) has gained great interest to replace the traditional mechanical light detection and ranging technique(LiDAR). In OPA-based LADAR, it is well known that phases of laser pulses traveling through each of channels should be the same to obtain a narrow free-space single beam without noise-like ripples in the far field. However, it is difficult to provide such ideal condition due to the fabrication errors. To tackle this problem, any algorithms should be necessary to compensate the initial random phases of each channel in OPA antenna. In this paper, we propose a hill-climbing based phase calibration algorithm and evaluate the performance of the proposed algorithm.

• Animal Systematics, Evolution and Diversity
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• v.37 no.4
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• pp.349-353
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• 2021

Scolelepis (Parascolelepis) papillosa (Okuda, 1937), originally described from a single incomplete individual from Jeju Island in Korea, was collected from the intertidal sandflats of Soan Island (Jeollanam-do province) in Korea. The examined specimens of S. (P.) papillosa agree well with the original description in having the papillae on the basal sheath of the palps, presence of occipital antenna, absence of notochaetae in chaetiger 1, branchiae completely fused with notopodial postchaetal lamellae at the anterior chaetigers, and neuropodial hooded hooks appearing from chaetiger 16. In this study, the sequences of partial mitochondrial cytochrome c oxidase subunit I (COI), 16S ribosomal DNA (16S rDNA), and the nuclear 18S ribosomal DNA (18S rDNA) of the species were determined. We also provide the detailed description and illustrations on this species based on the complete specimens newly collected in this study.