PhD Candidate Seung-Jun Yu

Committee: International Scientific Committee of Electronics and Communication Engineering
University: Sejong University
Department: Communication Research Institute
Research Fields: adaptive modulation, cooperative communication, CDD, OSTBC,

Publications

8 Adaptive Transmission Scheme Based on Channel State in Dual-Hop System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Jung-In Baik, Yong-Jun Kim

Abstract:

In this paper, a dual-hop relay based on channel state is studied. In the conventional relay scheme, a relay uses the same modulation method without reference to channel state. But, a relay uses an adaptive modulation method with reference to channel state. If the channel state is poor, a relay eliminates latter 2 bits and uses Quadrature Phase Shift Keying (QPSK) modulation. If channel state is good, a relay modulates the received symbols with 16-QAM symbols by using 4 bits. The performance of the proposed scheme for Symbol Error Rate (SER) and throughput is analyzed.

Keywords: relay, hierarchical modulation, adaptive transmission, channel state, dual-hop

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7 An Improved Transmission Scheme in Cooperative Communication System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Young-Min Ko

Abstract:

Recently developed cooperative diversity scheme enables a terminal to get transmit diversity through the support of other terminals. However, most of the introduced cooperative schemes have a common fault of decreased transmission rate because the destination should receive the decodable compositions of symbols from the source and the relay. In order to achieve high data rate, we propose a cooperative scheme that employs hierarchical modulation. This scheme is free from the rate loss and allows seamless cooperative communication.

Keywords: Cooperative Communication, high data rate, transmission scheme, hierarchical modulation

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6 Cooperative Scheme Using Adjacent Base Stations in Wireless Communication

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Chang-Bin Ha, Young-Min Ko

Abstract:

In a wireless communication system, the failure of base station can result in a communication disruption in the cell. This paper proposes a way to deal with the failure of base station in a wireless communication system based on OFDM. Cooperative communication of the adjacent base stations can be a solution of the problem. High performance is obtained by the configuration of transmission signals which is applied CDD scheme in the cooperative communication. The Cooperative scheme can be a e ective solution in case of the particular situation.

Keywords: OFDM, mimo, base station, CDD, diversity gain

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5 Cooperative CDD Scheme Based on Hierarchical Modulation in OFDM System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Yeong-Seop Ahn, Young-Min Ko

Abstract:

In order to achieve high data rate and increase the spectral efficiency, multiple input multiple output (MIMO) system has been proposed. However, multiple antennas are limited by size and cost. Therefore, recently developed cooperative diversity scheme, which profits the transmit diversity only with the existing hardware by constituting a virtual antenna array, can be a solution. However, most of the introduced cooperative techniques have a common fault of decreased transmission rate because the destination should receive the decodable compositions of symbols from the source and the relay. In this paper, we propose a cooperative cyclic delay diversity (CDD) scheme that use hierarchical modulation. This scheme is free from the rate loss and allows seamless cooperative communication.

Keywords: mimo, Cooperative Communication, CDD, hierarchical modulation

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4 Cooperative CDD Scheme Based On Adaptive Modulation in Wireless Communication System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Hwan-Jun Choi

Abstract:

Among spatial diversity scheme, orthogonal space-time block code (OSTBC) and cyclic delay diversity (CDD) have been widely studied for the cooperative wireless relaying system. However, conventional OSTBC and CDD cannot cope with change in the number of relays owing to low throughput or error performance. In this paper, we propose a cooperative cyclic delay diversity (CDD) scheme that use hierarchical modulation at the source and adaptive modulation based on cyclic redundancy check (CRC) code at the relays.

Keywords: Cooperative Communication, adaptive modulation, CDD, OSTBC

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3 A Novel Design for Hybrid Space-Time Block Codes and Spatial Multiplexing Scheme

Authors: Seung-Jun Yu, Jang-Kyun Ahn, Eui-Young Lee, Hyoung-Kyu Song

Abstract:

Space-time block codes (STBC) and spatial multiplexing (SM) are promising techniques that effectively exploit multipleinput multiple-output (MIMO) transmission to achieve more reliable communication and a higher multiplexing rate, respectively. In this paper, we study a practical design for hybrid scheme with multi-input multi-output orthogonal frequency division multiplexing (MIMOOFDM) systems to flexibly maximize the tradeoff between diversity and multiplexing gains. Unlike the existing STBC and SM designs which are suitable for the integer multiplexing rate, the proposed design can achieve arbitrary number of multiplexing rate.

Keywords: MIMO-OFDM, spatial multiplexing, Space-Time Block Codes

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2 A Novel Transmission Scheme for Reliable Cooperative Communication

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Won-Jun Choi, Jung-In Baik

Abstract:

Cooperative communication scheme can be substituted for multiple-input multiple-output (MIMO) technique when it may not be able to support multiple antennas due to size, cost or hardware limitations. In other words, cooperative communication scheme is an efficient method to achieve spatial diversity without multiple antennas. For satisfaction of rising QoS, we propose a reliable cooperative communication scheme with M-QAM based Dual Carrier Modulation (M-DCM), which can increase diversity gain. Although our proposed scheme is very simple method, it gives us frequency and spatial diversity. Simulation result shows our proposed scheme obtains diversity gain more than the conventional cooperative communication scheme.

Keywords: Diversity, cooperation, OFDM, M-DCM

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1 An Improved Lattice Reduction Aided Detection Scheme for MIMO-OFDM System

Authors: Seung-Jun Yu, Jang-Kyun Ahn, Eui-Young Lee, Hyoung-Kyu Song

Abstract:

This paper proposes an efficient lattice-reduction-aided detection (LRD) scheme to improve the detection performance of MIMO-OFDM system. In this proposed scheme, V candidate symbols are considered at the first layer, and V probable streams are detected with LRD scheme according to the first detected V candidate symbols. Then, the most probable stream is selected through a ML test. Since the proposed scheme can more accurately detect initial symbol and can reduce transmission of error to rest symbols, the proposed scheme shows more improved performance than conventional LRD with very low complexity.

Keywords: MIMO-OFDM, QRD-M, V-BLAST, Lattice reduction aided detection

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Abstracts

8 Adaptive Transmission Scheme Based on Channel State in Dual-Hop System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Jung-In Baik, Yong-Jun Kim

Abstract:

In this paper, a dual-hop relay based on channel state is studied. In the conventional relay scheme, a relay uses the same modulation method without reference to channel state. But, a relay uses an adaptive modulation method with reference to channel state. If the channel state is poor, a relay eliminates latter 2 bits and uses Quadrature Phase Shift Keying (QPSK) modulation. If channel state is good, a relay modulates the received symbols with 16-QAM symbols by using 4 bits. The performance of the proposed scheme for Symbol Error Rate (SER) and throughput is analyzed.

Keywords: relay, hierarchical modulation, adaptive transmission, channel state, dual-hop

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7 The Batteryless Wi-Fi Backscatter System and Method for Improving the Transmission Range

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Young-Min Ko, Seongjoo Lee

Abstract:

The Internet of things (IoT) system has attracted attention. IoT is a technology to connect all the objects to the internet as well as computer. IoT makes it possible for providing more data interoperability methods for an application purpose. Among the IoT technology, the research of devices so that they can communicate without power supply has been actively conducted. Batteryless system permits us to communicate without power supply devices. In this paper, batteryless backscatter system is used as a tag. And mobile devices which are embedded wireless fidelity (Wi-Fi) chipset are used as a reader. The backscatter tag can be obtained Internet connectivity from the reader. Conventional Wi-Fi backscatter system has limitation in the transmission range. In this paper, the proposed algorithm can be obtained improved reliability as well as overcoming the limitation about transmission range.

Keywords: RFID, IoT, Wi-Fi, backscatter, Ambient RF, Batteryless communication, Energy-harvesting, Tag

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6 An Efficient Strategy for Relay Selection in Multi-Hop Communication

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Jung-In Baik, Young-Min Ko

Abstract:

This paper proposes an efficient relaying algorithm to obtain diversity for improving the reliability of a signal. The algorithm achieves time or space diversity gain by multiple versions of the same signal through two routes. Relays are separated between a source and destination. The routes between the source and destination are set adaptive in order to deal with different channels and noises. The routes consist of one or more relays and the source transmits its signal to the destination through the routes. The signals from the relays are combined and detected at the destination. The proposed algorithm provides a better performance than the conventional algorithms in bit error rate (BER).

Keywords: OFDM, relay, multi-hop, relaying selection

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5 An Improved Transmission Scheme in Cooperative Communication System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Young-Min Ko

Abstract:

Recently developed cooperative diversity scheme enables a terminal to get transmit diversity through the support of other terminals. However, most of the introduced cooperative schemes have a common fault of decreased transmission rate because the destination should receive the decodable compositions of symbols from the source and the relay. In order to achieve high data rate, we propose a cooperative scheme that employs hierarchical modulation. This scheme is free from the rate loss and allows seamless cooperative communication.

Keywords: Cooperative Communication, hierarchical modulation, high data rate, transmission scheme

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4 Cooperative Scheme Using Adjacent Base Stations in Wireless Communication

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Chang-Bin Ha, Young-Min Ko

Abstract:

In a wireless communication system, the failure of base station can result in a communication disruption in the cell. This paper proposes a way to deal with the failure of base station in a wireless communication system based on OFDM. Cooperative communication of the adjacent base stations can be a solution of the problem. High performance is obtained by the configuration of transmission signals which is applied CDD scheme in the cooperative communication. The Cooperative scheme can be a effective solution in case of the particular situation.

Keywords: OFDM, mimo, base station, CDD, diversity gain

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3 Cooperative CDD Scheme Based On Hierarchical Modulation in OFDM System

Authors: Seung-Jun Yu, Yeong-Seop Ahn, Young-Min Ko and Hyoung-Kyu Song

Abstract:

In order to achieve high data rate and increase the spectral efficiency, multiple input multiple output (MIMO) system has been proposed. However, multiple antennas are limited by size and cost. Therefore, recently developed cooperative diversity scheme, which profits the transmit diversity only with the existing hardware by constituting a virtual antenna array, can be a solution. However, most of the introduced cooperative techniques have a common fault of decreased transmission rate because the destination should receive the decodable compositions of symbols from the source and the relay. In this paper, we propose a cooperative cyclic delay diversity (CDD) scheme that uses hierarchical modulation. This scheme is free from the rate loss and allows seamless cooperative communication.

Keywords: mimo, Cooperative Communication, CDD, hierarchical modulation

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2 Performance Improvement of Cooperative Scheme in Wireless OFDM Systems

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Ki-Ro Kim

Abstract:

Recently, the wireless communication systems are required to have high quality and provide high bit rate data services. Researchers have studied various multiple antenna scheme to meet the demand. In practical application, it is difficult to deploy multiple antennas for limited size and cost. Cooperative diversity techniques are proposed to overcome the limitations. Cooperative communications have been widely investigated to improve performance of wireless communication. Among diversity schemes, space-time block code has been widely studied for cooperative communication systems. In this paper, we propose a new cooperative scheme using pre-coding and space-time block code. The proposed cooperative scheme provides improved error performance than a conventional cooperative scheme using space-time block coding scheme.

Keywords: Cooperative Communication, space-time block coding, pre-coding

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1 Cooperative CDD scheme Based on Adaptive Modulation in Wireless Communiation System

Authors: Seung-Jun Yu, Hyoung-Kyu Song, Hwan-Jun Choi

Abstract:

Among spatial diversity scheme, orthogonal space-time block code (OSTBC) and cyclic delay diversity (CDD) have been widely studied for the cooperative wireless relaying system. However, conventional OSTBC and CDD cannot cope with change in the number of relays owing to low throughput or error performance. In this paper, we propose a cooperative cyclic delay diversity (CDD) scheme that use hierarchical modulation at the source and adaptive modulation based on cyclic redundancy check (CRC) code at the relays.

Keywords: Cooperative Communication, adaptive modulation, CDD, OSTBC

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