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Ohsoon Shin - One of the best experts on this subject based on the ideXlab platform.

  • a novel spectral efficient Resource allocation approach for noma based full duplex systems
    Global Communications Conference, 2019
    Co-Authors: Hieu V Nguyen, Vandinh Nguyen, Octavia A Dobre, Diep N Nguyen, Eryk Dutkiewicz, Ohsoon Shin
    Abstract:

    This paper investigates the coexistence of non- orthogonal multiple access (NOMA) and full-duplex (FD), where the NOMA successive interference cancellation technique is applied simultaneously to both uplink (UL) and downlink (DL) transmissions in the same time-Frequency Resource block. Specifically, we jointly optimize the user association (UA) and power control to maximize the overall sum rate, subject to user-specific quality-of-service and total transmit power constraints. To be spectrally-efficient, we introduce the tensor model to optimize the UL users' decoding order and the DL users' clustering, which results in a mixed-integer non- convex problem. For solving this problem, we first relax the binary variables to be continuous, and then propose a low-complexity design based on the combination of the inner convex approximation framework and the penalty method. Numerical results show that the proposed algorithm significantly outperforms the conventional FD-based schemes, FD-NOMA and its half-duplex counterpart with random UA.

  • joint antenna array mode selection and user assignment for full duplex mu miso systems
    IEEE Transactions on Wireless Communications, 2019
    Co-Authors: Hieu V Nguyen, Vandinh Nguyen, Octavia A Dobre, Ohsoon Shin
    Abstract:

    This paper considers a full-duplex (FD) multiuser multiple-input single-output system where a base station simultaneously serves both uplink (UL) and downlink (DL) users on the same time-Frequency Resource. The crucial barriers in implementing FD systems reside in the residual self-interference and co-channel interference. To accelerate the use of FD radio in future wireless networks, we aim at managing the network interference more effectively by jointly designing the selection of half-array antenna modes (in the transmit or receive mode) at the base station with time phases and user assignments. The first problem of interest is to maximize the overall sum rate subject to quality-of-service requirements, which is formulated as a highly non-concave utility function followed by non-convex constraints. To address the design problem, we propose an iterative low-complexity algorithm by developing new inner approximations, and its convergence to a stationary point is guaranteed. To provide more insights into the solution of the proposed design, a general max–min rate optimization is further considered to maximize the minimum per-user rate while satisfying a given ratio between UL and DL rates. Furthermore, a robust algorithm is devised to verify that the proposed scheme works well under channel uncertainty. The simulation results demonstrate that the proposed algorithms exhibit fast convergence and substantially outperform existing schemes.

  • joint antenna array mode selection and user assignment for full duplex mu miso systems
    arXiv: Signal Processing, 2019
    Co-Authors: Hieu V Nguyen, Vandinh Nguyen, Octavia A Dobre, Ohsoon Shin
    Abstract:

    This paper considers a full-duplex (FD) multiuser multiple-input single-output system where a base station simultaneously serves both uplink (UL) and downlink (DL) users on the same time-Frequency Resource. The crucial barriers in implementing FD systems reside in the residual self-interference and co-channel interference. To accelerate the use of FD radio in future wireless networks, we aim at managing the network interference more effectively by jointly designing the selection of half-array antenna modes (in the transmit or receive mode) at the BS with time phases and user assignments. The first problem of interest is to maximize the overall sum rate subject to quality-of-service requirements, which is formulated as a highly non-concave utility function followed by non-convex constraints. To address the design problem, we propose an iterative low-complexity algorithm by developing new inner approximations, and its convergence to a stationary point is guaranteed. To provide more insights into the solution of the proposed design, a general max-min rate optimization is further considered to maximize the minimum per-user rate while satisfying a given ratio between UL and DL rates. Furthermore, a robust algorithm is devised to verify that the proposed scheme works well under channel uncertainty. Simulation results demonstrate that the proposed algorithms exhibit fast convergence and substantially outperform existing schemes.

Ove Edfors - One of the best experts on this subject based on the ideXlab platform.

  • The World's First Real-Time Testbed for Massive MIMO: Design, Implementation, and Validation
    IEEE Access, 2017
    Co-Authors: Steffen Malkowsky, Ian C. Wong, Karl Nieman, Nikhil Kundargi, Joao Vieira, Paul Harris, Fredrik Tufvesson, Viktor Öwall, Liang Liu, Ove Edfors
    Abstract:

    This paper sets up a framework for designing a massive multiple-input multiple-output (MIMO) testbed by investigating hardware (HW) and system-level requirements such as processing complexity, duplexing mode and frame structure. Taking these into account, a generic system and processing partitioning is proposed which allows flexible scaling and processing distribution onto a multitude of physically separated devices. Based on the given HW constraints such as maximum number of links and maximum throughput for peer-to-peer interconnections combined with processing capabilities, the framework allows to evaluate modular HW components. To verify our design approach, we present the LuMaMi (Lund University Massive MIMO) testbed which constitutes the first reconfigurable real-time HW platform for prototyping massive MIMO. Utilizing up to 100 base station antennas and more than 50 Field Programmable Gate Arrays, up to 12 user equipments are served on the same time/Frequency Resource using an LTE-like Orthogonal Frequency Division Multiplexing time-division duplex-based transmission scheme. Proof-of-concept tests with this system show that massive MIMO can simultaneously serve a multitude of users in a static indoor and static outdoor environment utilizing the same time/Frequency Resource.

  • Massive MIMO Performance Evaluation Based on Measured Propagation Data
    IEEE Transactions on Wireless Communications, 2015
    Co-Authors: Xiang Gao, Fredrik Rusek, Ove Edfors, Fredrik Tufvesson
    Abstract:

    Massive MIMO, also known as very-large MIMO or large-scale antenna systems, is a new technique that potentially can offer large network capacities in multi-user scenarios. With a massive MIMO system, we consider the case where a base station equipped with a large number of antenna elements simultaneously serves multiple single-antenna users in the same time-Frequency Resource. So far, investigations are mostly based on theoretical channels with independent and identically distributed (i.i.d.) complex Gaussian coefficients, i.e., i.i.d. Rayleigh channels. Here, we investigate how massive MIMO performs in channels measured in real propagation environments. Channel measurements were performed at 2.6 GHz using a virtual uniform linear array (ULA), which has a physically large aperture, and a practical uniform cylindrical array (UCA), which is more compact in size, both having 128 antenna ports. Based on measurement data, we illustrate channel behavior of massive MIMO in three representative propagation conditions, and evaluate the corresponding performance. The investigation shows that the measured channels, for both array types, allow us to achieve performance close to that in i.i.d. Rayleigh channels. It is concluded that in real propagation environments we have characteristics that can allow for efficient use of massive MIMO, i.e., the theoretical advantages of this new technology can also be harvested in real channels.

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

  • A Novel Dynamic Full Frequency Reuse Scheme in OFDMA Cellular Relay Networks
    2011 IEEE Vehicular Technology Conference (VTC Fall), 2011
    Co-Authors: Jian Liang, Haokai Chen, Zhongnian Li
    Abstract:

    In this paper, a novel dynamic full Frequency reuse scheme is proposed to improve the spectral efficiency in orthogonal Frequency division multiple access (OFDMA) cellular relay networks. Different from the conventional full Frequency reuse scheme which only allows the base station (BS) reusing the subcarriers in the specific regions, we proposed an improved full Frequency reuse scheme to allow the BS reusing all the subcarriers in the whole BS coverage region to exploit more multiuser diversity gain. In order to dynamically reuse the Frequency Resource among the BS and relay stations (RSs) to further improve the spectral efficiency, the adaptive subcarrier scheduling is introduced into the improved full Frequency reuse scheme, which forms the proposed novel dynamic full Frequency reuse scheme. Simulation results show that the proposed scheme can obtain high spectral efficiency, fine fairness and low outage probability.

Thomas L Marzetta - One of the best experts on this subject based on the ideXlab platform.

  • joint unicast and multi group multicast transmission in massive mimo systems
    arXiv: Information Theory, 2019
    Co-Authors: Meysam Sadeghi, Erik G. Larsson, Emil Bjornson, Chau Yuen, Thomas L Marzetta
    Abstract:

    We study the joint unicast and multi-group multicast transmission in massive multiple-input-multiple-output (MIMO) systems. We consider a system model that accounts for channel estimation and pilot contamination, and derive achievable spectral efficiencies (SEs) for unicast and multicast user terminals (UTs), under maximum ratio transmission and zero-forcing precoding. For unicast transmission, our objective is to maximize the weighted sum SE of the unicast UTs, and for the multicast transmission, our objective is to maximize the minimum SE of the multicast UTs. These two objectives are coupled in a conflicting manner, due to their shared power Resource. Therefore, we formulate a multiobjective optimization problem (MOOP) for the two conflicting objectives. We derive the Pareto boundary of the MOOP analytically. As each Pareto optimal point describes a particular efficient trade-off between the two objectives of the system, we determine the values of the system parameters (uplink training powers, downlink transmission powers, etc.) to achieve any desired Pareto optimal point. Moreover, we prove that the Pareto region is convex, hence the system should serve the unicast and multicast UTs at the same time-Frequency Resource. Finally, we validate our results using numerical simulations.

  • Joint Unicast and Multi-group Multicast Transmission in Massive MIMO Systems.
    IEEE Transactions on Wireless Communications, 2018
    Co-Authors: Meysam Sadeghi, Erik G. Larsson, Emil Bjornson, Chau Yuen, Thomas L Marzetta
    Abstract:

    We study the joint unicast and multi-group multicast transmission in massive multiple-input multiple-output systems. We consider a system model that accounts for channel estimation and pilot contamination and derive achievable spectral efficiencies (SEs) for unicast and multicast user terminals (UTs) under maximum ratio transmission and zero-forcing precoding. For unicast transmission, our objective is to maximize the weighted sum SE of the unicast UTs, and for the multicast transmission, our objective is to maximize the minimum SE of the multicast UTs. These two objectives are coupled in a conflicting manner, due to their shared power Resource. Therefore, we formulate a multiobjective optimization problem (MOOP) for the two conflicting objectives. We derive the Pareto boundary of the MOOP analytically. As each Pareto optimal point describes a particular efficient tradeoff between the two objectives of the system, we determine the values of the system parameters (uplink training powers, downlink transmission powers, and so on) to achieve any desired Pareto optimal point. Moreover, we prove that the Pareto region is convex, and hence, the system should serve the unicast and multicast UTs at the same time–Frequency Resource. Finally, we validate our results using numerical simulations.

  • Massive MU-MIMO downlink TDD systems with linear precoding and downlink pilots
    2013 51st Annual Allerton Conference on Communication, Control, and Computing, Allerton 2013, 2013
    Co-Authors: Hien Quoc Ngo, Erik G. Larsson, Thomas L Marzetta
    Abstract:

    We consider a massive MU-MIMO downlink time-division duplex system where a base station (BS) equipped with many antennas serves several single-antenna users in the same time-Frequency Resource. We assume that the BS uses linear precoding for the transmission. To reliably decode the signals transmitted from the BS, each user should have an estimate of its channel. In this work, we consider an efficient channel estimation scheme to acquire CSI at each user, called beamforming training scheme. With the beamforming training scheme, the BS precodes the pilot sequences and forwards to all users. Then, based on the received pilots, each user uses minimum mean-square error channel estimation to estimate the effective channel gains. The channel estimation overhead of this scheme does not depend on the number of BS antennas, and is only proportional to the number of users. We then derive a lower bound on the capacity for maximum-ratio transmission and zero-forcing precoding techniques which enables us to evaluate the spectral efficiency taking into account the spectral efficiency loss associated with the transmission of the downlink pilots. Comparing with previous work where each user uses only the statistical channel properties to decode the transmitted signals, we see that the proposed beamforming training scheme is preferable for moderate and low-mobility environments.

Fredrik Tufvesson - One of the best experts on this subject based on the ideXlab platform.

  • The World's First Real-Time Testbed for Massive MIMO: Design, Implementation, and Validation
    IEEE Access, 2017
    Co-Authors: Steffen Malkowsky, Ian C. Wong, Karl Nieman, Nikhil Kundargi, Joao Vieira, Paul Harris, Fredrik Tufvesson, Viktor Öwall, Liang Liu, Ove Edfors
    Abstract:

    This paper sets up a framework for designing a massive multiple-input multiple-output (MIMO) testbed by investigating hardware (HW) and system-level requirements such as processing complexity, duplexing mode and frame structure. Taking these into account, a generic system and processing partitioning is proposed which allows flexible scaling and processing distribution onto a multitude of physically separated devices. Based on the given HW constraints such as maximum number of links and maximum throughput for peer-to-peer interconnections combined with processing capabilities, the framework allows to evaluate modular HW components. To verify our design approach, we present the LuMaMi (Lund University Massive MIMO) testbed which constitutes the first reconfigurable real-time HW platform for prototyping massive MIMO. Utilizing up to 100 base station antennas and more than 50 Field Programmable Gate Arrays, up to 12 user equipments are served on the same time/Frequency Resource using an LTE-like Orthogonal Frequency Division Multiplexing time-division duplex-based transmission scheme. Proof-of-concept tests with this system show that massive MIMO can simultaneously serve a multitude of users in a static indoor and static outdoor environment utilizing the same time/Frequency Resource.

  • Massive MIMO Performance Evaluation Based on Measured Propagation Data
    IEEE Transactions on Wireless Communications, 2015
    Co-Authors: Xiang Gao, Fredrik Rusek, Ove Edfors, Fredrik Tufvesson
    Abstract:

    Massive MIMO, also known as very-large MIMO or large-scale antenna systems, is a new technique that potentially can offer large network capacities in multi-user scenarios. With a massive MIMO system, we consider the case where a base station equipped with a large number of antenna elements simultaneously serves multiple single-antenna users in the same time-Frequency Resource. So far, investigations are mostly based on theoretical channels with independent and identically distributed (i.i.d.) complex Gaussian coefficients, i.e., i.i.d. Rayleigh channels. Here, we investigate how massive MIMO performs in channels measured in real propagation environments. Channel measurements were performed at 2.6 GHz using a virtual uniform linear array (ULA), which has a physically large aperture, and a practical uniform cylindrical array (UCA), which is more compact in size, both having 128 antenna ports. Based on measurement data, we illustrate channel behavior of massive MIMO in three representative propagation conditions, and evaluate the corresponding performance. The investigation shows that the measured channels, for both array types, allow us to achieve performance close to that in i.i.d. Rayleigh channels. It is concluded that in real propagation environments we have characteristics that can allow for efficient use of massive MIMO, i.e., the theoretical advantages of this new technology can also be harvested in real channels.