• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7C
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• pp.715-723
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• 2009

In this paper, we propose a new detection method called dual-cell combining (DCC) detection for the acquisition in time of spread spectrum codes in the presence of residual frequency offset (RFO). When the RFO exists, the correlation peak used for detection during the acquisition process is split into two neighboring peaks with smaller amplitudes, resulting in considerable degradation in the overall acquisition performance of conventional methods. In the DCC detection method, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the RFO can be alleviated. Numerical results show that the DCC detection method can offer better mean-time-to-synchrouization performance than the conventional method based on the cell-by-cell detection.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.1-8
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• 2012

In this paper, we consider an efficient protocol for the multi-hop relay transmission on a sensor network which can be utilized in a ubiquitous environment. More specifically, we propose an efficient relaying protocol for the distance and position recognition on the proposed sensor network which performs with the differentially bi-orthogonal chirp spread spectrum (DBO-CSS) in the industrial, scientific and medical (ISM) bands. For an efficient networking access, we design and implement four different packet structures, zone information packet, hop information packet, tag information packet, and application serial packet. Additionally, we also propose an efficient position recognition algorithm. Finally, for verification of our proposed protocol's efficiency, we build the testbed system which consists of $15m{\times}15m$ multi-cell and 10 hops in the network.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.242-248
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• 2017

Recently, Population has been concentrated in cities due to rapid economic growth. As a result, urban buildings are becoming more dense, high-rise, and diversified. The shape of these urban buildings increases the risk of fire, accidents and crime. The narrow living space has the characteristic of the unchanged floor. In case of a fire, the living space of the narrow residence is large in the damage because the smoke diffusion rate is fast. The radio wave transmittance and transmission distance of wireless communication used in fire fighting operations vary depending on the type of building materials and buildings. Therefore, this paper analyzes the building materials and structural characteristics of the narrow residential space for efficient fire fighting operations. We have developed a communication environment solution for a narrow residential space for the optimal fire fighting operation through the measurement of the radio wave transmittance and the transmission distance of the wireless communication.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.97-100
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• 2013

최근 4세대(4G) 통신망으로의 전환의 가속화와 스마트 모바일 기기의 확산으로 인하여 무선 통신망에서 데이터 트래픽이 급증하고 있다. 이러한 급증하는 데이터 트래픽을 분산시키기 위하여 2개의 주파수 밴드를 사용하는 멀티 캐리어 기술이 선보이고 있다. 방송 디스크는 서버가 데이터베이스에 저장된 모든 데이터를 연속적으로 다수의 모바일 클라이언트에게 방송하고, 클라이언트는 방송 채널을 감시하여 원하는 데이터가 방송될 경우 방송 채널로부터 데이터를 수신하는 통신 구조이다. 이런 관점에서 방송 채널은 클라이언트가 데이터를 액세스할 수 있는 디스크의 역할을 담당한다. 본 논문에서는 무선 통신망이 멀티 캐리어를 지원할 경우, 클라이언트에서 실행되는 읽기 전용 트랜잭션의 정확성을 보장하기 위한 동시성 제어 기법(Dual-Channel based Concurrency Control: DCC)을 제안한다. 기존에 동시성 제어 기법들은 단일 방송채널에서 트랜잭션의 철회률을 줄이기 위하여 추가적인 제어 정보들을 방송하거나 방송 데이터의 타임스탬프 필드를 이용하고 있다. 클라이언트에서 실행되는 트랜잭션은 단일 방송 사이클이 아니라 여러 방송 사이클에 걸쳐서 실행된다. 이러한 방송 디스크 환경의 특징은 클라이언트 트랜잭션이 디스크에서 방송 인덱스를 판독하여 방송 프로그램 상에서 트랜잭션에 필요한 데이터가 방송 될 때까지 기다리게 된다. 이와는 달리 DCC는 주력 망과 보조 망에서 방송되는 방송 프로그램의 순서를 서로 다르게 하여 데이터 판독에 필요한 대기 시간을 줄일 수 있다. 보조망의 방송 프로그램의 순서는 주력망의 방송 프로그램 순서의 역순서로 방송함으로써 보조 망 또는 주력 망에서 실행되고 있는 트랜잭션이 다른 방송 채널의 방송 인덱스를 판독하지 않아도 방송 프로그램 순서를 예측할 수가 있다. 그 결과, DCC는 방송 디스크의 데이터 판독에 요구되는 대기시간을 줄여 읽기 전용 트랜잭션의 철회률을 줄일 수 있다는 장점을 갖는다.

• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.761-770
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• 2004

The multicarrier direct sequence code-division (MC-DS/CDMA) is a well-known multiple access and data transmission scheme that is applicable for various mobile and wireless communications. Particularly for modern, smart vehicles equipped with multiple sensors, MC-DS/CDMA is one of the possible means for giving the sensors to get connected one another for sending and receiving messages and control information. For intra-vehicalur communicaiton and networking applications, we have proposed a novel MC-DS/CDMA multiple access and data transmission scheme incorporating a new idea of inserting sub-symbol based cyclic prefixes for compromising inter-symbol interference. In the performance investigation of our MC-DS/CDMA, we have looked into system performances related to bandwidth utiltzation, coding gain, and multiple number of sensors. Since the channel delay is comparatively shorter inside of vehicle than any other general mobile channels, the proposed scheme can be a successful candidate for networking wireless sensors simultaneously operting in an intelligent vehicle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.4
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• pp.830-837
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• 2009

In this thesis, Multi-code/Multi-carrier CDMA(MC/MC CDMA) system which is combination of Multi-code CDMA and Multi-carrier CDMA is analyzed. This system is suitable fur multi-rate services that use multi-codes and high data rate transmission that employ multi-carriers. In addition, the MC/MC CDMA system is robust against frequency selective fading, is good for narrowband interference rejection, and has higher spectral efficiency. In this paper, The users are assigned OVSF codes as a spreading code according to their data rates and divides the active users having different representative code split into a number of groups for effective cancellation. At the receiver, The code grouping interference canceller performs cancellation between the groups. The proposed receiver does not require any information about interference users, such as code, data and amplitude, and has relatively low complexity. The results show the large improvement in performance that can be attained by cancellation scheme.

• Journal of Korea Port Economic Association
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• v.29 no.4
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• pp.135-155
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• 2013

With the application enlargement of RFID technology in the field of logistics, it is needed to analyze the relation adoption factors of RFID with logistics performance. That is, this study aims at analyzing how RFID adoption would give an effect to logistics performance in logistics company, stating its implications. More specifically, this study tests empirical relation of CEO's support, technical competence, trading partner, compatibility, relative advantage and logistics performance of applying RFID in logistics company. Based on previous studies which are related to RFID in the field of SCM, logistics, distribution and manufacturing, this study established research model and hypothesis, and surveyed employees of logistics company. To analyze the data, exploratory factor analysis, reliability analysis, confirmatory factor analysis and structural equation model were applied. The results are follows. Applying RFID in logistics, CEO's support and trading partner gives significantly positive effect to logistics performance. But compatibility and relative advantage do not give meaningful effect to logistics performance. Additionally, though technical competence does not have statistical significance to logistics performance, it is necessary to consider it can have meaningful influence on logistics performance substantially.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.333-340
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• 2003

In this paper, we propose a new turbo-coded orthogonal frequency division multiplexing (OFDM) transmission scheme that can improve greatly the performance by making all the turbo-coded symbols have the same reliability for OFDM transmission over a frequency selective fading channel. The same reliability, that is, the same fading can be accomplished through multiplexing of turbo-coded symbols using distinct orthogonal codes and spreading over the whole effective subcarriers (hereafter, called as the orthogonal code multiplexing (OCM)). As for the orthogonal code selection, we choose the set of the discrete Fourier transform (DFT) basis sequences, since the code set holds the orthogonality irrespective of the length and also has the equal energy property. We perform computer simulations using the Log-maximum-a-posteriori (Log-MAP) algorithm for iterative decoding in order to assess the performance of the proposed transmission scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.694-701
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• 2003

In this paper, we present a hardware structure and new features of a smart antenna BTS (Base Transceiver Station) for CDMA2000 1X system. The proposed smart antenna BTS is a composite system consisting of many subsystems, i.e., array antenna element, frequency up/down converters, AD (Analog-to-Digital) and DA (Digital-to-Analog) converters, spreading/despreading units, convolutional encoder/Viterbi decoder, searcher, tracker, beamformer, calibration unit etc. Through the experimental tests, we found that the desired beam-pattern in both uplink and downlink communications is provided through the calibration procedure. Also it has been confirmed that the adaptive beamforming algorithm adopted to our smart antenna BTS is fast and accurate enough to support 4 fingers to each user. In our experiments, commercial mobile terminals operating PCS (Personal Communication System) band have been used. It has been confirmed that the smart antenna BTS tremendously improves the FER (Frame Error Rate) performance compared to the conventional 2-antenna diversity system.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.5
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• pp.152-161
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• 2017

The CBTC(Communication based Train Control) system employed on 2.4GHz ISM band adopt the IEEE802.11.x standard. Therefor communication time delay, distortion and data losses will be produced. To overcome these problems, CPSK(Continuous Phase shift keying) modulated DS/SS(Direct Sequence Spread Spectrum) transmitter with 908MHz carrier frequency is proposed. Through the eye diagram and scatter diagram the performance is analysed. And the phase noise characteristic of the local oscillator is measured about 60dBc/Hz, this means that the phase noise performance is very good compared to the signal. Reference frequency suppression of the 2nd local oscillator is 50dB below compared to the signal. Through the polarities of the complementary signal equally probable, the line spectrum of the output spectrum is eliminated. The nonlinear effects which introduce the spectral spreading or spectral regeneration is reduced remarkably.