• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.59-68
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• 2017

The flower and woman are beautiful but Euler's theorem and the symmetry are the best. Shannon applied his theorem to information and communication based on Euler's theorem. His theorem is the root of wireless communication and information theory and the principle of today smart phone. Their meeting point is $e^{-SNR}$ of MIMO(multiple input and multiple output) multiple antenna diversity. In this paper, Euler, who discovered the most beautiful formula($e^{{\pi}i}+1=0$) in the world, briefly guided Shannon's formula ($C=Blog_2(1+{\frac{S}{N}})$) to discover the origin of wireless communication and information communication, and these two masters prove a meeting at the Shannon limit, It reveals something what this secret. And we find that it is symmetry and element-wise inverse are the hidden secret in algebraic coding theory and triangular function.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1022-1030
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• 2004

The next generation cellular radio systems require high data rate transmission and large system capacity In order to meet these requirements, multiple antennas can be used at the base and mobile stations, forming MIMO(multiple-input, multiple-output) channels This paper considers a downlink MIMO system assuming a large number of base station antennas, a small number of mobile station antennas, and rich-scattering, quasi-stationary, and flat-fading channel environments When the channel state information is given at the base station in a single user system, a MIMO technique with SVD(singular value decomposition) and water-filling can achieve the maximal downlink channel capacity. In multi-user environments, however, SDMA(space division multiple acces) technique can be used to further increase the total channel capacity supported by the base station This paper proposes a MIMO SDMA technique which can transmit parallel data streams to each of multiple users. The proposed method. can achieve higher total channel capacity than SVD-based MIMO techniques or conventional SDMA using smart antennas.

• ETRI Journal
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• v.25 no.2
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• pp.65-72
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• 2003

To achieve cost and size reductions, we developed a low cost manufacturing technology for RF substrates and a high performance passive process technology for RF integrated passive devices (IPDs). The fabricated substrate is a conventional 6" Si wafer with a 25${\mu}m$ thick $SiO_2$ surface. This substrate showed a very good insertion loss of 0.03 dB/mm at 4 GHz, including the conductive metal loss, with a 50 ${\Omega}$ coplanar transmission line (W=50${\mu}m$, G=20${\mu}m$). Using benzo cyclo butene (BCB) interlayers and a 10 ${\mu}m$ Cu plating process, we made high Q rectangular and circular spiral inductors on Si that had record maximum quality factors of more than 100. The fabricated inductor library showed a maximum quality factor range of 30-120, depending on geometrical parameters and inductance values of 0.35-35 nH. We also fabricated small RF IPDs on a thick oxide Si substrate for use in handheld phone applications, such as antenna switch modules or front end modules, and high-speed wireless LAN applications. The chip sizes of the wafer-level-packaged RF IPDs and wire-bondable RF IPDs were 1.0-1.5$mm^2$ and 0.8-1.0$mm^2$, respectively. They showed very good insertion loss and RF performances. These substrate and passive process technologies will be widely utilized in hand-held RF modules and systems requiring low cost solutions and strict volumetric efficiencies.

• Journal of Digital Contents Society
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• v.9 no.1
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• pp.1-6
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• 2008

In traditional wireless communication systems the main power consumption is due to the actual transmissions power. Therefore, energy-constrained wireless networks have gained considerable research attention in recent years. Multiple-input-multiple-output (MIMO) structure, or multiple antenna communication is one of the techniques that has gain considerable importance in wireless systems and networks. In this paper, BER and throughput performance of MISO system with Go-back-N ARQ(Automatic Repeat Request) technique in wireless networks are analyzed and the energy consumption of MISO-based wireless networks is compared with conventional SISO-based wireless networks. Obtained results show the applicability of MISO system with Go-back-N ARQ technique in wireless networks with smart system design.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.4
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• pp.212-220
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• 2014

The current cellular communications are optimized for low mobility users, meaning that their performance is degraded at high speed. Therefore, passengers in a high-speed train experience very poor radio link quality due to the significantly large number of simultaneous handovers. In addition, wireless data traffic is expanding exponentially in trains, subways and buses due to the widespread use of smartphones and mobile devices. To solve the inherent problem of cellular communication networks and meet the growing traffic demand, this paper proposes the mobile hotspot network of a millimeter-wave communication system as a mobile wireless backhaul. This paper describes the physical layer design of uplink and downlink in the proposed system, and the performances of uplink and downlink are evaluated under Rician fading channel conditions. The implemented baseband prototype of the proposed millimeter-wave communication modem is presented. This system can provide a Gbps data rate service in high-speed trains carrying hundreds of wireless Internet users.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.61-67
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• 2004

The next generation cellular wireless communication systems require high data rate transmissions and large system capacities. In order to meet these requirements, multiple antennas can be used at the base and mobile stations, forming MIMO(Multiple Input Multiple Output) channels. This paper proposes a MIMO SDMA(Space Division Multiple Access) technique with dynamic slot allocation which allows the transmitter to efficiently transmit parallel data streams to each of multiple receivers. The proposed technique can increase system capacities significantly by transmitting a larger number of data streams than conventional MIMO techniques while minimizing the performance degradation due to the beamforming dimension reduction.

• Journal of IKEEE
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• v.18 no.4
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• pp.495-501
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• 2014

In this paper, we designed a diversity modem hardware architecture for IEEE802.11p WAVE and tested the modem on the road with car attached shark antenna. One of the dual channel modem and the diversity single modem with maximum ratio combining algorithm can be selected on the designed architecture. The designed modem have been implemented on the Xillinx Kintex7 FPGA. We tested the modem performance on the smart highway experience road. As experimental results, we can verify the performance of the diversity modem on real road and the enlarged communication range by more than 30%.

• ETRI Journal
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• v.38 no.6
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• pp.1052-1063
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• 2016

We propose a millimeter wave (MMW)-based mobile hotspot network (MHN) system for application in high-speed railways that is capable of supporting a peak backhaul link throughput of 1 Gbps per train at 400 km/h. The MHN system can be implemented in subways and high-speed trains to support passengers with smart devices and provide access to the Internet. The proposed system can overcome the inherent high path loss in MMW through system designs and high antenna gains. We present a simulation of the system performance that shows that a fixed beamforming strategy can provide high signal-to-interference-plus-noise-ratio similar to those of an adaptive beamforming strategy, with the exception of 15% of the train path in which the network can use link adaptation with low-order modulation formats or trigger a handover to maintain the connection. We also demonstrate the feasibility of the MHN system using a test bed deployed in Seoul subway line 8. The backhaul link throughput varies instantaneously between 200 Mbps and 500 Mbps depending on the SNR variations while the train is running. During the field trial, the smartphones used could make connections through offloading.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.248-257
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• 2006

There will come someday when UAUs can fly into the airspace of manned aircraft in the near future because of the increasing number of operational UAUs together with technologies development. Since pilots of UAVs are on the gound, the equipment for sensing and avoiding obstacles in front is indispensable. In this paper, we analyze functions and interfaces of TCAS II, a collision avoidance device for manned aircraft, then find out whether it is suitable for the collision avoidance device for UAV and problems associated with it, if any. It turns out to be that the onboard directional antenna of TCAS II does not provide a precise directional information, and that the TCAS II is not assumed to be installed alone, but used as supplementary with other device which provides the better precision.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.4
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• pp.258-264
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• 2015

The first 77 GHz transceiver that applies a heterodyne structure-based linear frequency modulation-frequency shift keying (LFM-FSK) front-end module (FEM) is presented. An LFM-FSK waveform generator is proposed for the transceiver design to avoid ghost target detection in a multi-target environment. This FEM consists of three parts: a frequency synthesizer, a 77 GHz up/down converter, and a baseband block. The purpose of the FEM is to make an appropriate beat frequency, which will be the key to solving problems in the digital signal processor (DSP). This paper mainly focuses on the most challenging tasks, including generating and conveying the correct transmission waveform in the 77 GHz frequency band to the DSP. A synthesizer test confirmed that the developed module for the signal generator of the LFM-FSK can produce an adequate transmission signal. Additionally, a loop back test confirmed that the output frequency of this module works well. This development will contribute to future progress in integrating a radar module for multi-target detection. By using the LFM-FSK waveform method, this radar transceiver is expected to provide multi-target detection, in contrast to the existing method.