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Beamforming

The Experts below are selected from a list of 94173 Experts worldwide ranked by ideXlab platform

Jinho Choi – 1st expert on this subject based on the ideXlab platform

  • On generalized downlink Beamforming with NOMA
    Journal of Communications and Networks, 2017
    Co-Authors: Jinho Choi

    Abstract:

    Recently, nonorthogonal multiple access (NOMA) has been studied to increase the spectral efficiency of downlink in a multiuser system by exploiting the notion of superposition coding with successive interference cancellation (SIC). NOMA can be employed with downlink Beamforming for downlink transmissions from a base station (BS) equipped with an antenna array, which results in NOMA Beamforming. In this paper, we formulate a multiuser NOMA Beamforming problem as a semidefinite programming (SDP) problem and generalize it in order to include the conventional (multiuser) Beamforming. A low-complexity approach to decide SIC sets for the generalized NOMA Beamforming is studied using the correlation between channel vectors for better performance. From analysis and simulation results, we show that the (generalized) NOMA Beamforming can outperform the conventional Beamforming, especially under limited scattering environments.

  • Minimum Power Multicast Beamforming With Superposition Coding for Multiresolution Broadcast and Application to NOMA Systems
    IEEE Transactions on Communications, 2015
    Co-Authors: Jinho Choi

    Abstract:

    Multicast Beamforming with superposition coding (SC) is studied for multiresolution broadcast where both data streams of high priority (HP) and low priority (LP) are to be transmitted for a user close to a base station (BS), while only data stream of LP is to be transmitted to a user not close to the BS (e.g., a cell-edge user). Using SC, a minimum total transmission power Beamforming problem has been formulated to find Beamforming vectors and powers for both users. For given normalized Beamforming vectors, a closed-form expression for the optimal power allocation is derived from which an iterative algorithm is considered to find Beamforming vectors. The proposed multicast Beamforming with SC is applied to nonorthogonal multiple access (NOMA) systems to support multiple users as a two-stage Beamforming method.

  • ICC – Opportunistic Beamforming with Single Beamforming Matrix for Virtual Antenna Arrays
    2011 IEEE International Conference on Communications (ICC), 2011
    Co-Authors: Jinho Choi

    Abstract:

    Opportunistic Beamforming is a promising technique for downlink channels in cellular systems. When opportunistic Beamforming is to support multiple users at a time, beams should be formed to avoid interference and this requires the feedback of channel state information (CSI) from users to a base station (BS). With limited feedback, to minimize the impact of interference, the best Beamforming matrix can be selected from a set of multiple Beamforming matrices. Thus, when a different set of users are to be supported by a scheduler, a new Beamforming matrix has to be selected, which may require excessive complexity. To avoid this problem, in this paper, we propose an opportunistic Beamforming approach with single Beamforming matrix. In addition, we show that the proposed approach suits for a virtual antenna array where multiple BS units form a transmit antenna array.

Jiandong Li – 2nd expert on this subject based on the ideXlab platform

  • Hybrid Beamforming for Broadband Millimeter Wave Massive MIMO Systems
    IEEE Vehicular Technology Conference, 2018
    Co-Authors: Rui Chen, Hui Xu, Changle Li, Lina Zhu, Jiandong Li

    Abstract:

    MmWave systems with most prior work focused on its narrowband hybrid analog/digital precoding, however, will likely operate on wideband channels with frequency selectivity. Therefore, in this paper we investigate wideband angular Beamforming schemes for mmWave massive MIMO-OFDM systems. First, for the RF analog Beamforming, the optimal Beamforming of an unconstrained antenna array (UAA) is given as the performance benchmark. Then, the optimal angular Beamforming (OAB) and a simple dominant angular Beamforming (DAB) of a shared antenna array (SAA) are compared in received SNR and implementation cost. Second, for the baseband digital precoding, the space-frequency vector perturbation (SFVP) precoding is proposed to collect both spatial and multi-path diversity. Finally, analytical and simulation results show that: a) DAB is a cost- effective RF Beamforming scheme under LOS channel environment; b) the proposed hybrid DAB-SFVP Beamforming scheme achieves the array gain equaling the number of transmit antennas $N_t$ and diversity gain equaling the product of the number of RF chains $K$ and the number of temporal resolvable clusters ℒ.

Michele Zorzi – 3rd expert on this subject based on the ideXlab platform

  • EuCNC – Context information based initial cell search for millimeter wave 5G cellular networks
    2016 European Conference on Networks and Communications (EuCNC), 2016
    Co-Authors: Waqas Bin Abbas, Michele Zorzi

    Abstract:

    Millimeter wave (mmWave) communication is envisioned as a cornerstone to fulfill the data rate requirements for fifth generation (5G) cellular networks. In mmWave communication, Beamforming is considered as a key technology to combat the high path-loss, and unlike in conventional microwave communication, Beamforming may be necessary even during initial access/cell search. Among the proposed Beamforming schemes for initial cell search, analog Beamforming is a power efficient approach but suffers from its inherent search delay during initial access. In this work, we argue that analog Beamforming can still be a viable choice when context information about mmWave base stations (BS) is available at the mobile station (MS). We then study how the performance of analog Beamforming degrades in case of angular errors in the available context information. Finally, we present an analog Beamforming receiver architecture that uses multiple arrays of Phase Shifters and a single RF chain to combat the effect of angular errors, showing that it can achieve the same performance as hybrid Beamforming.

  • Context Information Based Initial Cell Search for Millimeter Wave 5G Cellular Networks
    arXiv: Information Theory, 2016
    Co-Authors: Waqas Bin Abbas, Michele Zorzi

    Abstract:

    Millimeter wave (mmWave) communication is envisioned as a cornerstone to fulfill the data rate requirements for fifth generation (5G) cellular networks. In mmWave communication, Beamforming is considered as a key technology to combat the high path-loss, and unlike in conventional microwave communication, Beamforming may be necessary even during initial access/cell search. Among the proposed Beamforming schemes for initial cell search, analog Beamforming is a power efficient approach but suffers from its inherent search delay during initial access. In this work, we argue that analog Beamforming can still be a viable choice when context information about mmWave base stations (BS) is available at the mobile station (MS). We then study how the performance of analog Beamforming degrades in case of angular errors in the available context information. Finally, we present an analog Beamforming receiver architecture that uses multiple arrays of Phase Shifters and a single RF chain to combat the effect of angular errors, showing that it can achieve the same performance as hybrid Beamforming.

  • towards an appropriate Beamforming scheme for initial cell discovery in mmw 5g cellular networks
    arXiv: Information Theory, 2016
    Co-Authors: Waqas Bin Abbas, Michele Zorzi

    Abstract:

    Beamforming is an essential requirement to combat high pathloss and to improve signal-to-noise ratio during initial cell discovery in future millimeter wave cellular networks. The choice of an appropriate Beamforming is directly coupled with its energy consumption. The energy consumption is even of more concern at a battery limited mobile station (MS). In this work, we provide an energy consumption based comparison of different Beamforming schemes while considering both a low power and a high power analog-to-digital converter (ADC) for a millimeter wave based receiver at the MS. We analyze both context information (CI) (GPS positioning based) and non context information based schemes, and show that analog Beamforming with CI (where mobile station’s positioning information is already available) can result in a lower energy consumption, while in all other scenarios digital Beamforming has a lower energy consumption than analog and hybrid Beamforming. We also show that under certain scenarios recently proposed phase shifters network architecture can result in a lower energy consumption than other Beamforming schemes. Moreover, we show that the energy consumption trend among different Beamforming schemes is valid irrespective of the number of ADC bits. Finally, we propose a new signaling structure which utilizes a relatively higher frequency sub-carrier for primary synchronization signals compared to other signaling, which allows a further reduction in initial cell search delay and energy consumption of the MS.