• Journal of the Korean Society for Railway
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• v.11 no.4
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• pp.364-370
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• 2008

In this paper, we proposed new sensor network architecture with autonomous robots based on beacon mode and implemented real time monitoring system in real test-bed environment. The proposed scheme offers beacon based real-time scheduling for reliable association process with parent nodes and dynamically assigns network address by using NAA (Next Address Assignment) mechanism. For the large scale multi-sensor processing, our real-time monitoring system accomplished the intelligent database processing, which can generate not only the alert messages to the civilians but also process various sensing data such as fire, air, temperature and etc. Moreover, we also developed mobile robot which can support network mobility. Though the performance evaluation by using real test-bed system, we illustrate that our proposed system demonstrates promising performance for emergence monitoring systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1395-1401
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• 2004

In The objective of this paper is to apply blind minimum output energy multiuser detection method to multicarrier direct sequence code division multiple access system. The performance of MC/DS-CDMA is reduced due to multiple access. To increase the performance of system, we need to cancel multiple user components. Blind interference canceller is able to detect the desired's information with the only minimal information of the desired user. We evaluate the performance of the proposed receiver under Gaussian channel. Simulation results show that the proposed receiver has about 6［dB］ gain of signal to noise ratio without multiple user interference and has about 3［dB］ gain of SNR with multiple user interference. Also, the result of comparing the capacity of the active users shows that the proposed method has about 2 times capacity more than conventional method. As a conclusion, simulation results show that the proposed method has better performs better than conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.517-525
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• 2009

We propose a quality guaranteed scalable video streaming service over the Internet using a new rate adaptation algorithm. Because video data requires much more bandwidth rather than other types of service, therefore, quality of video streaming service should be guaranteed while providing friendliness with other service flows over the Internet. To successfully provide this, we propose a framework for providing quality-guaranteed streaming service using two-channel transport layer and rate adaptation of scalable video stream. In this framework, baseline layer for scalable video is transmitted using TCP transport for minimum qualify service. Enhancement layers are delivered using TFRC transport with layer adaptation algorithm. The proposed framework jointly uses the status of playout buffer in the client and the encoding rate of layers in media contents. Therefore, the proposed algorithm can remarkably guarantee minimum quality of streaming service rather than conventional approaches regardless of network congestion and the encoding rate variation of media content.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12C
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• pp.1014-1020
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• 2008

Storage devices such as memories are widely used in various electronic products. They require high-density memory and currently the data has been stored in multi-level format, that results in high error rate. In this paper, we apply error correction schemes that are widely used in communication system to the storage devices for satisfying low bit error rate and high code rate. In A WGN channel with average BER $10^{-5}$ and $5{\times}10^{-6}$, we study error correction schemes for 4-1evel cell to achieve target code rate 0.99 and target BER $10^{-11}$ and $10^{-13}$, respectively. Since block codes may perform better than the concatenated codes for high code rate, and it is important to use less degraded inner code even when many bits are punctured. The performance of concatenated codes using general feedforward systematic convolutional codes are worse than the block code only scheme. The simulation results show that RSC codes must be used as inner codes to achieve good performance of punctured convolutional codes for high code rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1167-1176
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• 2014

In this paper, a relay communication scheme for enhancing the WiMedia network performance by device's mobility is proposed. WiMedia protocol is suitable for the application that supports the real-time multimedia service in Ship Area Network since it supports high speed data transfer. However, the device's mobility is caused the dramatic change of link state and network topology, and is occurred the degradation of network performance. Therefore, a relay communication scheme for WiMedia network is proposed in this paper. The proposed technique can intelligently treat the change of link state, and solve the degradation of network performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1159-1166
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• 2014

In this paper, a resource management scheme for enhancing the network connectivity and reliability in wireless USB system is proposed. Wireless USB protocol is suitable for the application that supports the real-time multimedia service in Ship Area Network since it supports high speed data transfer. However, the device's mobility is caused the dramatic change of link state and network topology, and is occurred the degradation of network performance. Therefore, a resource management scheme for wireless USB system is proposed in this paper. The proposed technique can intelligently treat the change of link state, and solve the degradation of network performance. The simulation results show that proposed protocol can enhance the throughput and delay performance by selecting relay device with better link state.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.396-397
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• 2011

This paper has proposed a multi-channel low pass filter (LPF) for LTE-Advanced systems. The proposed LPF is an active-RC 5th chebyshev topology with three cut-off frequencies of 5 MHz, 10 MHz, and 40 MHz. A 3-bit tuning circuit has been adopted to prevent variations of each cut-off frequency from process, voltage, and temperature (PVT). To achieve a high cut-off frequency of 40 MHz, an operational amplifier used in the proposed filter has employed a PMOS cross-connection load with a negative impedance. A proposed filter has been implemented in a $0.13-{\mu}m$ CMOS technology and consumes 20.2 mW with a 1.2V supply voltage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2B
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• pp.59-68
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• 2008

In order to activate the digital broadcasting in Korea, the analog broadcasting will have been closed down until 2012. Recently IPTV(Internet Protocol TV) thorough internet has been regarded as the fourth media following the terrestrial, satellite, and cable for the digital broad casting. And it has been the important medium for the communication and broadcasting system. However IP is not easy to replace the entire broadcasting system with the digital - type broadcasting system. For the digital broadcasting, we should replace all TV sets, install the settop-boxes to receive the various IP media, solve problems about time delaying when changing channels, and support communication and broadcasting consolidation service for such as PVR and Network CCTV. IPMG is the digital converter that is able to solve these problems. In this paper, I'll develop and analyze IPMG converter's performance which sends and receives both the analogue and digital broadcasting signals through various media gives the Network PVR service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.12
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• pp.1093-1105
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• 2012

We propose an interference space reuse (ISR) algorithm for the MU-MIMO design in 3-cell downlink interference channels. Also, we provide a strategy for the adoption of the ISR scheme in the cellular network. In the multicell interference channels, the cell edge users may undergo severe interferences and their signals should be protected from the interferers for reliable transmissions. However, the intra cell users do not only experience small interferences but also they require small transmission power for stable communication. We provide a vector design algorithm based on ISR, where intra cell users are served through reusing the cell edge users' interference space. The performance enhancement reaches 20% compared to the fractional frequency reuse (FFR) scheme combined with IA through the scheduling between the cell edge users and the intra cell users. Also, it can be used to enhance the cell edge throughput when the quality of service (QoS) requirements of the intra cell users are fixed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.243-252
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• 2008

In this paper, we propose the next-generation broadband wireless access network architecture, which is based on the wavelength division multiplexing-passive optical network(WDM-PON), and efficient mobility management scheme to support quality-of-service(QoS) of multimedia services in the next-generation wireless network. By adapting WDM-PON technology to wireless access network, the proposed scheme can realize broadband wireless access network. In addition, We utilize newly proposed local channels between optical network units(ONUs) or subnets in order to support the fast and efficient local data and handoff data transmission. We evaluate the performance of the proposed scheme in terms of handoff delay and packet loss thru computer simulation. Thru various computer simulation results, we verified the superior performance of the proposed scheme by comparing with the results of other schemes.