• Journal of Korea Society of Industrial Information Systems
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• v.26 no.6
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• pp.1-9
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• 2021

In order to increase frequency transmission efficiency, single side band(SSB) transmission systems with the complex conjugate symmetry characteristics on a frequency domain have been studied. In addition, orthogonal block codes(space-time or space-frequency block code(SFBC)) for the diversity performance gain of transmission systems have been widely researched. In this paper, we implement a 3/4-rate SFBC SSB single-carrier(SC) frequency division multiple access(FDMA) system with 4 transmit antennas. It can be shown from the simulation results that the proposed SFBC SSB SC FDMA system using the 3/4-rate 4×4 orthogonal block code outperforms the conventional SSB SC FDMA system and the 2×2 SFBC SSB SC FDMA system with 2 transmit antennas.

• Korea Real Estate Review
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• v.24 no.1
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• pp.7-14
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• 2014

This study, as the temporal and spatial data for the real price apartment in Seoul from January 2006 to June 2013, empirically compared and analyzed the estimation result of apartment price using OLS by hedonic price model for the problem of space-time correlation, temporal autoregressive model (TAR) considering temporal effect, spatial autoregressive model (SAR) spatial effect and spatiotemporal autoregressive model (STAR) spatiotemporal effect. As a result, the adjusted R-square of STAR model was increased by 10% compared that of OLS model while the root mean squares error (RMSE) was decreased by 18%. Considering temporal and spatial effect, it is observed that the estimation of apartment price is more correct than the existing model. As the result of analyzing STAR model, the apartment price is affected as follows; area for apartment(-), years of apartment(-), dummy of low-rise(-), individual heating (-), city gas(-), dummy of reconstruction(+), stairs(+), size of complex(+). The results of other analysis method were the same. When estimating the price of real estate using STAR model, the government officials can improve policy efficiency and make reasonable investment based on the objective information by grasping trend of real estate market accurately.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1042-1050
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• 2014

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Turbo Equalization method based on layered Space Time Codes has improved performance compared to conventional UWA communication.

• Journal of Broadcast Engineering
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• v.9 no.3
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• pp.225-235
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• 2004

In this paper, we propose a new stereoscopic video coding approach for heterogeneous consumer devices by exploiting the concept of spatio-temporal scalability. The proposed method uses MPEG-2 standard for coding the left or main sequence and an enhanced compatible coding scheme for predicting the P- and B-type of frames of the right or auxiliary sequence. The enhanced compatible coding scheme predicts matching block by interpolating both two forward and backward motion predicted macroblocks and disparity predicted macroblock. To provide flexible stereo video service, we define both a temporally scalable layer and a spatially scalable layer for each eye-view. The experimental results show the efficiency of proposed coding scheme by comparison with already known methods and the advantages of disparity estimation in terms of scalability overhead. According to the experimental results, we expect the proposed functionalities will play a key role in establishing highly flexible stereo video service for ubiquitous computing environment where devices and network connections are heterogeneous.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.479-486
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• 2010

In this paper, we propose a novel low-complexity Alamouti coded orthogonal frequency division multiplexing (OFDM) scheme for asynchronous cooperative communications. Exploiting the combination of OFDM symbols at the source node and simple operations including sign change and complex product at the relay node, the proposed scheme can achieve cooperative diversity gain without use of time-reversion and shifting operations that the conventional scheme proposed by Li and Xia needs. In addition, by using the cyclic prefix (CP) removal and insertion operations at the relay node, the proposed scheme does not suffer from a considerable degradation of bit-error-rate (BER) performance even though perfect timing synchronization is not achieved at the relay node. From the simulation results, it is demonstrated that the BER performance of the proposed scheme is much superior to that of the conventional scheme in the presence of timing synchronization error at the relay node. It is also shown that the proposed scheme obtains two times higher diversity gain compared with the conventional scheme at the cost of half reduction in transmission efficiency.

• The Journal of the Acoustical Society of Korea
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• v.25 no.8
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• pp.356-361
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• 2006

We present the performance of differential space-time block decoders. which does not require the channel state information. We suggest the structure of the multiple blocks differential space time decoders. which does not require the channel state information, and analyze the Performances. In quasi-static flat fading channels. the Performance of multiple blocks differential detection (MD-STC) outperforms that of 2 blocks(D-STC) by 1.5dB. But in the time-selective fading channels due to Doppler frequency $(f_d)$, the performance of MD-STC degrades as the vehicular speed is greater than 200km/hr in 802.16e systems, where the data transmission rate is 144kbps.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.07a
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• pp.26-27
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• 2015

본 논문에서는 대역폭 효율을 향상시키는 공간 변조(spatial modulation) 다중 안테나 시스템을 제안한다. 기존의 공간 변조 다중 안테나 시스템은 다중 송신 안테나 중 하나의 안테나를 사용하여 채널 간에 간섭을 피할 수 있어서 다중 경로가 많은 실내 환경에서 적합하다. 그러나 심벌 전송 구간마다 한 개의 안테나만을 선택하여 전송하므로 다중 안테나의 최대 부호 이득을 얻을 수 없다. 이를 극복하기 위하여 시공간블록부호화 방식을 적용한 공간 변조 다중 안테나 시스템은 두 개의 안테나를 사용하여 수신 성능을 향상시키지만 대역폭 효율이 향상되지 않는 단점이 있다. 본 논문에서는 Hybrid STBC 시스템을 적용한 공간 변조를 제안하여 공간 변조 다중 안테나 시스템의 대역폭 효율을 개선한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.611-614
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• 2012

Space-Time Block Code (STBC) is a simple transmit diversity scheme mitigating detrimental effects of fading channel. However, STBC receivers require channel knowledge and suffer from inaccurate channel estimation. Differential Space-Time Modulation (DSTM) renders the receiver a choice of coherent detection or non-coherent detection, depending on the availability of the channel information. Based on the simulated BER performances of these two schemes over various normalized Doppler frequency scenarios using LTE-like parameters, a benefit of adaptively switching the receiver type is investigated.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.106-112
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.109-114
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• 2007

A new space-time cooperative communication relaying strategy with assistant or management terminals is proposed in multi-hop wireless communication systems. More than one relaying terminals are included in one cooperative group to share the state information such as frame error rate and channel information. Among the cooperative group, the best ones are selected to send bit information using space-time codes. An implementation for the proposed scheme is also presented using a TDMA cooperative protocol. Receive signal to transmit signal ratio($E_r/E_s$) and computer simulation show the strategy outperform the conventional cooperative system.