Yong-Jun Kim

Publications

4 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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3 Improved Wi-Fi Backscatter System for Multi-to-Multi Communication

Authors: Hyoung-Kyu Song, Dong-Hyun Ha, Chang-Bin Ha, Yong-Jun Kim

Abstract:

The conventional Wi-Fi backscatter system can only process one-to-one communication between the Wi-Fi reader and the Wi-Fi tag. For improvement of throughput of the conventional system, this paper proposes the multi-to-multi communication system. In the proposed system, the interference by the multi-to-multi communication is effectively cancelled by the orthogonal multiple access based on the identification code of the tag. Although the overhead is generated by the procedure for the multi-to-multi communication, because the procedure is processed by the Wi-Fi protocol, the overhead is insignificant for the entire communication procedure. From the numerical results, it is confirmed that the proposed system has nearly proportional increased throughput in according to the number of the tag that simultaneously participates in communication.

Keywords: Wi-Fi, backscatter, multi-to-multi communication, orthogonality

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2 Improved Performance of Cooperative Scheme in the Cellular and Broadcasting System

Authors: Hyoung-Kyu Song, Bit-Na Kwon, Yong-Jun Kim, Hyun-Jee Yang

Abstract:

In the cooperative transmission scheme, both the cellular system and broadcasting system are composed. Two cellular base stations (CBSs) communicating with a user in the cell edge use cooperative transmission scheme in the conventional scheme. In the case that the distance between two CBSs and the user is distant, the conventional scheme does not guarantee the quality of the communication because the channel condition is bad. Therefore, if the distance between CBSs and a user is distant, the performance of the conventional scheme is decreased. Also, the bad channel condition has bad effects on the performance. The proposed scheme uses two relays to communicate well with CBSs when the channel condition between CBSs and the user is poor. Using the relay in the high attenuation environment can obtain both advantages of the high bit error rate (BER) and throughput performance.

Keywords: OFDM, cooperative communications, diversity gain, interworking system

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1 Efficient Variable Modulation Scheme Based on Codebook in the MIMO-OFDM System

Authors: Hyoung-Kyu Song, Chang-Bin Ha, Yong-Jun Kim, Jae-Hyun Ro

Abstract:

Because current wireless communication requires high reliability in a limited bandwidth environment, this paper proposes the variable modulation scheme based on the codebook. The variable modulation scheme adjusts transmission power using the codebook in accordance with channel state. Also, if the codebook is composed of many bits, the reliability is more improved by the proposed scheme. The simulation results show that the performance of proposed scheme has better reliability than the the performance of conventional scheme.

Keywords: MIMO-OFDM, variable modulation, codebook, channel state

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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 Improved Performance Using Adaptive Pre-Coding in the Cellular Network

Authors: Hyoung-Kyu Song, Chang-Bin Ha, Yong-Jun Kim, Jae-Hyun Ro

Abstract:

This paper proposes the cooperative transmission scheme with pre-coding because the cellular communication requires high reliability. The cooperative transmission scheme uses pre-coding method with limited feedback information among small cells. Particularly, the proposed scheme has adaptive mode according to the position of mobile station. Thus, demand of recent wireless communication is resolved by this scheme. From the simulation results, the proposed scheme has better performance compared to the conventional scheme in the cellular network.

Keywords: CDD, pre-coding, SPC, cellular network

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6 Reduced Complexity of ML Detection Combined with DFE

Authors: Hyoung-Kyu Song, Chang-Bin Ha, Yong-Jun Kim, Jae-Hyun Ro

Abstract:

In multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems, many detection schemes have been developed to improve the error performance and to reduce the complexity. Maximum likelihood (ML) detection has optimal error performance but it has very high complexity. Thus, this paper proposes reduced complexity of ML detection combined with decision feedback equalizer (DFE). The error performance of the proposed detection scheme is higher than the conventional DFE. But the complexity of the proposed scheme is lower than the conventional ML detection.

Keywords: Detection, MIMO-OFDM, DFE

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5 Efficient Variable Modulation Scheme Based on Codebook in the MIMO-OFDM System

Authors: Hyoung-Kyu Song, Chang-Bin Ha, Yong-Jun Kim, Jae-Hyun Ro

Abstract:

Because current wireless communication requires high reliability in a limited bandwidth environment, this paper proposes the variable modulation scheme based on the codebook. The variable modulation scheme adjusts transmission power using the codebook in accordance with hannel state. Also, if the codebook is composed of many bits, the reliability is more improved by the proposed scheme. The simulation results show that the performance of proposed scheme has better reliability than the the performance of conventional scheme.

Keywords: MIMO-OFDM, variable modulation, codebook, channel state

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4 Improved Wi-Fi Backscatter System for Multi-to-Multi Communication

Authors: Hyoung-Kyu Song, Dong-Hyun Ha, Chang-Bin Ha, Yong-Jun Kim

Abstract:

The conventional Wi-Fi back scatter system can only process one-to-one communication between the Wi-Fi reader and the Wi-Fi tag. For improvement of throughput of the conventional system, this paper proposes the multi-to-multi communication system. In the proposed system, the interference by the multi-to-multi communication is effectively cancelled by the orthogonal multiple access based on the identification code of the tag. Although the overhead is generated by the procedure for the multi-to-multi communication, because the procedure is processed by the Wi-Fi protocol, the overhead is insignificant for the entire communication procedure. From the numerical results, it is confirmed that the proposed system has nearly proportional increased throughput in according to the number of the tag that simultaneously participates in communication.

Keywords: Wi-Fi, backscatter, multi-to-multi communication, orthogonality

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3 Inter-Cell-Interference Mitigation Scheme in Wireless Communication System

Authors: Eui-Hak Lee, Hyoung-Kyu Song, Yong-Jun Kim, Jae-Hyun Ro

Abstract:

Mobile communication has been developing very rapidly since it appeared. However, although mobile communication market has been rapidly developing, many mobile users are not offered good quality of service (QoS) due to increment of the amount of data traffic. Recently, femtocell is very hot issue in mobile communication because femtocell can solve the problems of data traffic and offer better QoS to mobile users. However, the deployment of femtocell in existing macrocell coverage area is not so simple due to the influence of inter-cell-interference (ICI) with existing macrocell. Thus, this paper proposes femtocell scheme which is able to reduce the influence of ICI to deploy femtocell easily.

Keywords: OFDM, Interference, CDD, femtocell, macrocell

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2 Advanced CoMP Scheme for LTE-based V2X System

Authors: Hyoung-Kyu Song, Su-Hyun Jung, Yong-Jun Kim, Young-Su Ryu

Abstract:

In this paper, a highly efficient coordinated multiple-point (CoMP) scheme for vehicular communication is proposed. The proposed scheme controls the transmit power and applies proper transmission scheme for the various situations. The proposed CoMP scheme provides comparable performance to the conventional dynamic cell selection (DCS) scheme. Moreover, this scheme provides improved power efficiency compared with the conventional joint transmission (JT) scheme. Simulation results show that the proposed scheme can achieve more enhanced performance with the high power efficiency and improve the cell capacity.

Keywords: V2V, V2I, LTE-A, CoMP, V2X

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1 Improved Performance of Cooperative Scheme in the Cellular and Broadcasting System

Authors: Hyoung-Kyu Song, Bit-Na Kwon, Yong-Jun Kim, Hyun-Jee Yang

Abstract:

In the cooperative transmission scheme, both the cellular system and broadcasting system are composed. Two cellular base stations (CBSs) communicating with a user in the cell edge use cooperative transmission scheme in the conventional scheme. In the case that the distance between two CBSs and the user is distant, the conventional scheme does not guarantee the quality of the communication because the channel condition is bad. Therefore, if the distance between CBSs and a user is distant, the performance of the conventional scheme is decreased. Also, the bad channel condition has bad effects on the performance. The proposed scheme uses two relays to communicate well with CBSs when the channel condition between CBSs and the user is poor. Using the relay in the high attenuation environment can obtain both advantages of the high bit error rate (BER) and throughput performance.

Keywords: OFDM, cooperative communications, diversity gain, interworking system

Procedia PDF Downloads 408