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Robert W. Heath - One of the best experts on this subject based on the ideXlab platform.

  • EUSIPCO - Base station cluster patterns for semi-static multi-Cell cooperation in irregular network topologies
    2015 23rd European Signal Processing Conference (EUSIPCO), 2015
    Co-Authors: Jeonghun Park, Robert W. Heath
    Abstract:

    This paper proposes a clustering strategy for semi-static mul-tiCell cooperation. Semi-static multiCell cooperation exploits multiple predefined base station (BS) cluster patterns for improving Cell-Edge User throughput. The proposed clustering guarantees that every User communicates with their two closest BSs, so that Users are protected from the dominant interferer. The key idea of the proposed clustering is to use the 2nd-order Voronoi region to form BS clusters. Each of the formed BS clusters is mapped into a particular cluster pattern by exploiting the Edge-coloring in graph theory. Through simulations, the performance is compared to that of other conventional strategies. Our major finding is that the proposed clustering provides performance gains for Cell-Edge Users compared to that of the conventional strategies.

  • Base station cluster patterns for semi-static multi-Cell cooperation in irregular network topologies
    2015 23rd European Signal Processing Conference (EUSIPCO), 2015
    Co-Authors: Jeonghun Park, Robert W. Heath
    Abstract:

    This paper proposes a clustering strategy for semi-static mul-tiCell cooperation. Semi-static multiCell cooperation exploits multiple predefined base station (BS) cluster patterns for improving Cell-Edge User throughput. The proposed clustering guarantees that every User communicates with their two closest BSs, so that Users are protected from the dominant interferer. The key idea of the proposed clustering is to use the 2nd-order Voronoi region to form BS clusters. Each of the formed BS clusters is mapped into a particular cluster pattern by exploiting the Edge-coloring in graph theory. Through simulations, the performance is compared to that of other conventional strategies. Our major finding is that the proposed clustering provides performance gains for Cell-Edge Users compared to that of the conventional strategies.

Jeonghun Park - One of the best experts on this subject based on the ideXlab platform.

  • EUSIPCO - Base station cluster patterns for semi-static multi-Cell cooperation in irregular network topologies
    2015 23rd European Signal Processing Conference (EUSIPCO), 2015
    Co-Authors: Jeonghun Park, Robert W. Heath
    Abstract:

    This paper proposes a clustering strategy for semi-static mul-tiCell cooperation. Semi-static multiCell cooperation exploits multiple predefined base station (BS) cluster patterns for improving Cell-Edge User throughput. The proposed clustering guarantees that every User communicates with their two closest BSs, so that Users are protected from the dominant interferer. The key idea of the proposed clustering is to use the 2nd-order Voronoi region to form BS clusters. Each of the formed BS clusters is mapped into a particular cluster pattern by exploiting the Edge-coloring in graph theory. Through simulations, the performance is compared to that of other conventional strategies. Our major finding is that the proposed clustering provides performance gains for Cell-Edge Users compared to that of the conventional strategies.

  • Base station cluster patterns for semi-static multi-Cell cooperation in irregular network topologies
    2015 23rd European Signal Processing Conference (EUSIPCO), 2015
    Co-Authors: Jeonghun Park, Robert W. Heath
    Abstract:

    This paper proposes a clustering strategy for semi-static mul-tiCell cooperation. Semi-static multiCell cooperation exploits multiple predefined base station (BS) cluster patterns for improving Cell-Edge User throughput. The proposed clustering guarantees that every User communicates with their two closest BSs, so that Users are protected from the dominant interferer. The key idea of the proposed clustering is to use the 2nd-order Voronoi region to form BS clusters. Each of the formed BS clusters is mapped into a particular cluster pattern by exploiting the Edge-coloring in graph theory. Through simulations, the performance is compared to that of other conventional strategies. Our major finding is that the proposed clustering provides performance gains for Cell-Edge Users compared to that of the conventional strategies.

Kenichi Higuchi - One of the best experts on this subject based on the ideXlab platform.

  • Investigations on Power Allocation among Beams in Non-Orthogonal Access with Random Beamforming and Intra-Beam SIC for Cellular MIMO Downlink
    2013 IEEE 78th Vehicular Technology Conference (VTC Fall), 2013
    Co-Authors: Yuta Hayashi, Yoshihisa Kishiyama, Kenichi Higuchi
    Abstract:

    We propose an enhancement to the power allocation among multiple beams in our previously reported non-orthogonal access with random beamforming and intra-beam successive interference canCeller (SIC) for Cellular multiple-input multiple-output (MIMO) downlink. By equally allocating transmission power among multiple beams, the average User throughput within a Cell can be enhanced due to the effective use of spatial multiplexing. The throughput of Users at the Cell Edge may be improved by allocating non-equal transmission power among beams since the inter-beam interference is decreased and the received signal power is increased from the viewpoint of the main beam to which most of the transmission power is allocated. Aiming at further enhancement of the system efficiency and Cell-Edge User experience in our previous non-orthogonal access scheme, we propose coordinated frequency block-dependent inter-beam power allocation and inter-frequency block power allocation based on fractional frequency reuse (FFR) for inter-Cell interference coordination. Based on simulation results, we show that the proposed power allocation method effectively enhances the tradeoff between the average and Cell-Edge User throughput.

  • Enhancing User fairness in non-orthogonal access with successive interference canCellation for Cellular downlink
    2012 IEEE International Conference on Communication Systems (ICCS), 2012
    Co-Authors: Junpei Umehara, Yoshihisa Kishiyama, Kenichi Higuchi
    Abstract:

    Aiming at a better tradeoff between the system frequency efficiency measured by the mean User throughput and the User fairness measured by the Cell-Edge User throughput, we propose applying fractional frequency reuse (FFR) and weighted proportional fair (PF)-based multiUser scheduling to non-orthogonal access with a successive interference canCeller (SIC) in the Cellular downlink. We also propose a frequency block access policy for Cell-interior and Cell-Edge User groups in FFR, which are appropriate for non-orthogonal access with the SIC. The optimum power is allocated to the non-orthogonally multiplexed Users in conjunction with the weighted multiUser PF scheduler. Extensive simulation results show that the proposed non-orthogonal access scheme with the SIC significantly enhances the system frequency efficiency and User fairness at the same time compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems.

  • VTC Fall - Enhanced User Fairness Using Non-Orthogonal Access with SIC in Cellular Uplink
    2011 IEEE Vehicular Technology Conference (VTC Fall), 2011
    Co-Authors: Tomohiro Takeda, Kenichi Higuchi
    Abstract:

    This paper investigates the enhancement of Cell-Edge User throughput by using non-orthogonal access with a successive interference canCeller (SIC) in the Cellular uplink compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems. Since both the total User throughput and Cell-Edge User throughput are important in a real system, we compare the Cell-Edge User throughput, while subject to the same total User throughput. The optimum resource allocation such as bandwidth and transmission power for each User is assumed for the respective access schemes based on the instantaneous channel conditions. Based on the evaluation results, we show that non-orthogonal access with a SIC can significantly enhance the Cell-Edge User throughput (thus User fairness) compared to the orthogonal access while achieving the same total User throughput in the context of the Cellular uplink, which can yield some insights regarding the direction of the wireless access scheme for the systems beyond IMT-Advanced.

  • ISPACS - Non-orthogonal access with SIC in Cellular downlink for User fairness enhancement
    2011 International Symposium on Intelligent Signal Processing and Communications Systems (ISPACS), 2011
    Co-Authors: Shun Tomida, Kenichi Higuchi
    Abstract:

    This paper investigates the enhancement of Cell-Edge User throughput by using non-orthogonal access with a successive interference canCeller (SIC) in the Cellular downlink compared to orthogonal access, which is widely used in 3.9 and 4G mobile communication systems. Since both the total User throughput and Cell-Edge User throughput are important in a real system, we compare the Cell-Edge User throughput while subject to the same total User throughput. The optimum resource allocation in terms of bandwidth and transmission power for each User is assumed for the respective access schemes based on the instantaneous channel conditions. The evaluation results show that non-orthogonal access with a SIC significantly enhances the Cell-Edge User throughput (thus User fairness) compared to orthogonal access while achieving the same total User throughput in the context of the Cellular downlink, which can yield some insights regarding the direction of the wireless access scheme for the systems beyond IMT-Advanced.

  • ISPACS - Efficient adaptive frequency partitioning in OFDMA downlink with fractional frequency reuse
    2011 International Symposium on Intelligent Signal Processing and Communications Systems (ISPACS), 2011
    Co-Authors: Yohei Umeda, Kenichi Higuchi
    Abstract:

    This paper investigates an adaptive frequency and transmission power partitioning method between Cell-interior and Cell-Edge Users in the downlink orthogonal frequency division multiple access (OFDMA) with fractional frequency reuse (FFR). In the conventional FFR method, the frequency and transmission power partitioning between Cell-interior and Cell-Edge Users is fixed and this results in limited system-level performance in terms of the average and Cell-Edge User throughput. This paper presents enhancements to a previously proposed partitioning algorithm to improve the system-level performance. The computer simulation results show that the enhanced method increases both the average and Cell-Edge User throughput compared to the conventional FFR and the previous method.

Beongku An - One of the best experts on this subject based on the ideXlab platform.

  • Improving the Performance of Cell-Edge Users in NOMA Systems Using Cooperative Relaying
    IEEE Transactions on Communications, 2018
    Co-Authors: Tri Nhu Do, Daniel Benevides Da Costa, Trung Q. Duong, Beongku An
    Abstract:

    In this paper, we study the performance improvement methods for a Cell-Edge User of two-User non-orthogonal multiple access (NOMA) systems in downlink scenarios. To this end, we propose two cooperative relaying schemes, namely ON/OFF-full-duplex relaying (ON/OFF-FDR) and ON/OFF-half-duplex relaying (ON/OFF-HDR) schemes. More specifically, in order to improve the performance of the Cell-Edge User, we consider a Cell-center User as a relay, where either FDR or HDR can be employed to assist the direct NOMA transmission from a base station (BS) to the Cell-Edge User. An ON/OFF mechanism is proposed to decide whether the cooperative relaying transmission is necessary or not. The ON/OFF relaying decision is made based on the quality of the direct and relaying links from the BS to the Cell-Edge User. The performance of the two proposed schemes is investigated in terms of outage probability and sum throughput. Numerical results reveal that the proposed schemes not only provide essential outage performance improvements for the Cell-Edge User, but also are able to improve the sum throughput of the two-User NOMA systems. The advantages and drawbacks of each proposed scheme are highlighted and insightful discussions are provided.

  • Optimal sum-throughput analysis for downlink cooperative SWIPT NOMA systems
    2018 2nd International Conference on Recent Advances in Signal Processing Telecommunications & Computing (SigTelCom), 2018
    Co-Authors: Tri Nhu Do, Beongku An
    Abstract:

    In this paper, we investigate the sum-throughput of Cell-center and Cell-Edge Users in downlink scenarios of cooperative simultaneous wireless information and power transfer (SWIPT) non-orthogonal multiple access (NOMA) systems. Specifically, we consider a two-User NOMA system, in which the Cell-center User acts as a power-splitting (PS)-based SWIPT relay aiming to improve the performance of the Cell-Edge User. In order to evaluate the performance of the considered system, we first derive a closed-form expression for the outage probability (OP) of the Cell-center User and a closed-form approximate expression for the OP of the Cell-Edge User. Adopting the gradient decent method, we then propose an algorithm that finds the optimal value of the PS coefficient, which results in a maximum sum-throughput of the system. With the obtained optimal PS coefficient, we show that the optimal SWIPT NOMA system provides essential throughput improvement for the Cell-Edge User while the use of SWIPT-based relaying transmission does not jeopardize the sum-throughput of the system compared to that of non-cooperative NOMA systems.

  • Improving the Performance of Cell-Edge Users in MISO-NOMA Systems Using TAS and SWIPT-Based Cooperative Transmissions
    IEEE Transactions on Green Communications and Networking, 2018
    Co-Authors: Tri Nhu Do, Daniel Benevides Da Costa, Trung Q. Duong, Beongku An
    Abstract:

    In this paper, we study the performance of a Cell-Edge User in a two-User multiple-input single-output nonorthogonal multiple access (MISO-NOMA) system. Since the outage performance and fairness data rate of Cell-Edge Users are essential issues in NOMA systems, we focus on how to resolve such problems. To this end, we propose three cooperative downlink transmission schemes utilizing hybrid simultaneous wireless information and power transfer (SWIPT) and transmit antenna selection (TAS) protocols. Particularly, in each scheme, a Cellcenter User acts as a relay to assist the Cell-Edge User and its relaying operation is powered by a hybrid time-switching/powersplitting SWIPT protocol. Additionally, each scheme employs a different TAS criterion to exploit the spatial diversity gain of a multiple antennas base station. In particular, we derive tight closed-form approximate expressions for the outage probabilities (OPs) and the corresponding asymptotic OPs to provide significant insights into the impact of our proposed schemes on the system performance. Our numerical results demonstrate the achievable performance improvements of the proposed schemes in comparison to that of the orthogonal multiple access and non-cooperative NOMA systems. In addition, the proposed schemes achieve various level of diversity gains accompanying with different complexity requirements.

Quanzhong Li - One of the best experts on this subject based on the ideXlab platform.

  • Stochastic Optimal Control for Buffer-Aided Cooperative Relaying Systems Using Nonorthogonal Multiple Access
    Mobile Information Systems, 2019
    Co-Authors: Zhishan Deng, Qianyun Gong, Quanzhong Li
    Abstract:

    In this paper, a multiple-cluster downlink multiple-input single-output (MISO) nonorthogonal multiple access (NOMA) system is considered. In each cluster, there are one central User and one Cell-Edge User. The central User has a data buffer with finite storage units, which will decode the Cell-Edge User’s message and store it at the data buffer. To enhance the performance of the Cell-Edge User, the central User operates as a relay and helps forward the message to the Cell-Edge User. Our objective is to maximize the long-term average sum rates for the Cell-Edge Users by designing the beamforming vectors and online power control, under the constraints of the data buffer causality, required information rates for central Users, and transmit power at the base station and central Users. Based on the current buffer state and the channel state information, we propose a low-complexity online Lyapunov optimization algorithm combined with a constrained concave-convex procedure (CCCP) to solve the causal and nonconvex problem. Furthermore, we verify the asymptotic optimality of the proposed online Lyapunov optimization algorithm. Simulation results demonstrate that our proposed scheme performs better than the greedy algorithm and the orthogonal multiple access (OMA) scheme.

  • Cooperative Non-Orthogonal Multiple Access in Multiple-Input-Multiple-Output Channels
    IEEE Transactions on Wireless Communications, 2018
    Co-Authors: Yiqing Li, Qi Zhang, Miao Jiang, Quanzhong Li
    Abstract:

    Cooperative non-orthogonal multiple access (NOMA) systems inherit advantages of the NOMA protocol and the cooperative relay. In this paper, we propose cooperative NOMA systems in multiple-input-multiple-output channels. The whole transmission is divided into two phases. In the first phase, the base station broadcasts signals using the NOMA protocol to a central User and a Cell-Edge User. In the second phase, the central User helps the base station cooperatively relay signals intended for the Cell-Edge User. Our objective is to maximize achievable rate from the base station to the Cell-Edge User under transmit power constraints and achievable rate constraint from the base station to the central User. The difficulty of this problem is the joint beamforming of the base station and the central User in the second phase. We propose a constrained convex-concave procedure (CCCP)-based algorithm. To reduce computational complexity, we also propose a closed-form search-based suboptimal algorithm. Simulation results demonstrate that our proposed cooperative NOMA system with CCCP-based algorithm outperforms the conventional NOMA scheme. When achievable rate constraint to the central User is low, our proposed cooperative NOMA system with the closed-form search-based suboptimal algorithm outperforms the NOMA scheme.

  • Secure Beamforming in Downlink MIMO Nonorthogonal Multiple Access Networks
    IEEE Signal Processing Letters, 2017
    Co-Authors: Miao Jiang, Qi Zhang, Yiqing Li, Quanzhong Li
    Abstract:

    In this letter, we consider a Cellular downlink multiple-input-multiple-output nonorthogonal multiple access (NOMA) secure transmission network, which consists of a base station, a central User, and a Cell-Edge User. The base station and two Users are all equipped with multiple antennas. The central User is an entrusted User and the Cell-Edge User is a potential eavesdropper. We focus on secure beamforming optimization problem, which maximizes achievable secrecy rate of the central User subject to transmit power constraint at the base station and transmission rate requirement at the Cell-Edge User. The optimization problem is nonconvex. We employ majorization-minimization method to iteratively optimize a sequence of valid surrogate functions for the nonconvex optimization problem. Furthermore, in each iteration, we derive the semi-closed form solution to optimize the valid surrogate functions. Simulation results demonstrate that our proposed NOMA scheme outperforms the zero-forcing-based NOMA scheme and conventional orthogonal multiple access scheme.

  • Secure Beamforming in Downlink MISO Nonorthogonal Multiple Access Systems
    IEEE Transactions on Vehicular Technology, 2017
    Co-Authors: Yiqing Li, Qi Zhang, Miao Jiang, Quanzhong Li
    Abstract:

    In this paper, we consider a Cellular downlink multiple-input-single-output (MISO) nonorthogonal multiple access (NOMA) secure transmission system, where Users are grouped as multiple clusters. Each cluster consists of a central User and a Cell-Edge User. The central User is an entrusted User, and the Cell-Edge User is a potential eavesdropper. We focus on the secure beamforming and power allocation design optimization problem which maximizes the sum achievable secrecy rate of central Users subject to the transmit power constraint at the base station and transmission rate requirements at Cell-Edge Users. The problem is nonconvex because of coupling optimization variables in the considered fractional quadratically constrained quadratic programming. We propose an alternating optimization-based solution and a constrained concave-convex procedure-based solution to the considered problem. Simulation results demonstrate that our proposed NOMA schemes outperform the conventional orthogonal multiple access scheme.