Jong Yeol Ryu

Korea Advanced Institute of Science and Technology , Sŏul, Seoul, South Korea

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Publications (7)6.23 Total impact

  • Jong Yeol Ryu, Wan Choi, Dong In Kim
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    ABSTRACT: For a decode-and-forward (DF)-based multiple-input-multiple-output (MIMO) relaying system, we propose a novel partial-information relaying scheme that adaptively controls the number of streams to be forwarded to the destination. In the first transmission phase, a source node broadcasts data streams that consist of nonforwarding and forwarding streams. In the second transmission phase, a relay node forwards only forwarding streams to the destination, and a destination node decodes both nonforwarding and forwarding streams by successive interference cancellation. We consider two possible scenarios according to the availability of the channel-state information (CSI) at the source. The first scenario is that no CSI is available at the source, and therefore, a source node broadcasts data streams with equal power allocation. In this scenario, the number of data streams to be forwarded by the relay is determined according to the available CSI at the relay. For the second scenario, where the perfect CSI is available at the source, we propose a linearly combined precoding matrix for rate maximization. We also propose suboptimal schemes to reduce the complexity of the precoding design. Our analytical and numerical results show that the proposed scheme achieves a substantially higher rate than both the conventional relaying scheme, which forwards all the received streams, and the direct transmission scheme without relaying, regardless of CSI availability at the source.
    IEEE Transactions on Vehicular Technology 01/2013; 62(1):205-218. · 2.06 Impact Factor
  • Jong Yeol Ryu, Wan Choi
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    ABSTRACT: A novel user relaying scheme based on bit concatenation is proposed for multiple-input multiple-output (MIMO) broadcast channels. In a broadcasting phase, a part of information for a destination user is concatenated to data for a relaying user and transmitted to the relaying user. The destination user receives the part of information via the relaying user in a relaying phase in addition to the data in the broadcasting phase. An achievable rate region for the proposed scheme is derived and an algorithm to characterize the boundary of the rate region is proposed. Our analysis shows that the proposed user relaying in a MIMO BC expands the achievable rate region for the zero-forcing dirty paper coding (ZF-DPC) in the MIMO BC without relaying. It is also shown that the proposed user relaying scheme always outperforms a superposition coding (SC) based user relaying scheme. Optimal and suboptimal user pair scheduling algorithms are investigated for a two-user MIMO BC and the proposed suboptimal user pair scheduling scheme is shown to approach the optimal scheduling when the relaying channel gain is large.
    IEEE Transactions on Communications 01/2012; 60(8):2208-2220. · 1.75 Impact Factor
  • Jong Yeol Ryu, Eun Young Ahn, Wan Choi
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    ABSTRACT: A novel user relaying scheme based on bit concatenation is proposed for a two-user multiple input multiple output(MIMO) broadcast channel (BC). In broadcasting phase, a part of information for a destination user is concatenated to data for a relaying user and transmitted to a relaying user. The destination user receives the part of information via the relaying user in relaying phase in addition to the data in broadcasting phase. Achievable rate region of the proposed scheme is derived and an algorithm to characterize the boundary of the rate region is proposed. Our analysis and simulations show that the proposed user relaying in a MIMO BC expands the achievable rate region of a zero-forcing dirty paper coding (ZF-DPC) in a MIMO BC without relaying.
    Proceedings of the Global Communications Conference, GLOBECOM 2011, 5-9 December 2011, Houston, Texas, USA; 01/2011
  • Jong Yeol Ryu, Wan Choi
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    ABSTRACT: This paper proposes a linear precoding technique for multiple-input multiple-output (MIMO) decode-and-forward (DF) based relay communications. The proposed precoder is constructed by linearly combining two independently designed precoders that maximize data rates at relay and destination, respectively. Contrary to conventional precoding in DF relay communications, the proposed precoding balances direct and relay links and maximize the achievable rate of the overall system. We also propose a distributed precoder design method using limited information. The proposed algorithms are shown to significantly reduce computation complexity of precoder design. The numerical results show that the proposed precoders with full information and limited information achieve significantly higher data rates than conventional precoding neglecting a direct link and comparable data rate to the optimal precoding even when the coefficients for linear combining are restricted to real numbers.
    IEEE Transactions on Wireless Communications 01/2011; 10:2390-2400. · 2.42 Impact Factor
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    Jong Yeol Ryu, Wan Choi, Dong In Kim
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    ABSTRACT: This paper proposes a novel partial decode-and-forward (DF) relaying strategy with multiple antennas. In the first phase, the source broadcasts data streams consisting of non-forwarding and forwarding data streams. In the second phase, a relay node forwards only forwarding data streams to a destination node, and a destination node decodes both non-forwarding and forwarding data streams by successive interference cancellation (SIC). We provide an analytical framework of achievable rate and design a linearly combined precoding matrix for rate maximization. Our results show that the proposed partial DF relaying with a linearly combined precoding matrix achieves substantially higher rate than a conventional DF relaying scheme.
    Vehicular Technology Conference Fall (VTC 2010-Fall), 2010 IEEE 72nd; 10/2010
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    Jong Yeol Ryu, Wan Choi
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    ABSTRACT: We propose a simple linear precoding scheme to cancel interference in downlink multiuser cellular relay networks where the available information is asymmetric between the base station and the relay node. The interference signal from the relay is eliminated by linear pre-pocessing at the base station without any cooperation between the base station and the relay. In the information asymmetric environment, our mathematical and numerical analysis shows that the proposed scheme outperforms a conventional time division multiple access (TDMA) scheme and approaches an ideal scheme based on dirty paper coding (DPC) in terms of capacity.
    Wireless Communications and Networking Conference (WCNC), 2010 IEEE; 05/2010
  • Jong Yeol Ryu, Wan Choi
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    ABSTRACT: This paper proposes a beamforming technique for multiple-input single-output (MISO) decode-and-forward (DF) based relay communications. The proposed beamformer is constructed by linearly combining two independently designed beamformers that maximize data rates at relay and destination, respectively. Contrary to conventional beamforming in DF relay communications, the proposed beamformer balances direct and relay links and maximize the achievable rate of the overall system. It is shown that the proposed beamforming scheme achieves significantly higher data rates than conventional beamforming neglecting a direct link.
    Circuits, Systems and Computers, 1977. Conference Record. 1977 11th Asilomar Conference on 01/2010;