David Gesbert

Institut de France, Lutetia Parisorum, Île-de-France, France

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Publications (289)234.32 Total impact

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    ABSTRACT: In this paper we propose a novel robust channel estimation algorithm exploiting path diversity in both angle and power domains, relying on a suitable combination of the spatial filtering and amplitude based projection. The proposed approach is able to cope with a wide range of system and topology scenarios, including those where interference channel may overlap with desired channels in terms of multipath angles of arrival (AoA) or exceed them in terms of received power. We establish the analytical conditions under which the proposed channel estimator is fully decontaminated.
    Full-text · Conference Paper · Mar 2016
  • Mingbo Dai · Bruno Clerckx · David Gesbert · Giuseppe Caire
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    ABSTRACT: In a multiuser MIMO broadcast channel, the rate performance is affected by the multiuser interference when the Channel State Information at the Transmitter (CSIT) is imperfect. To tackle the detrimental effect of the multiuser interference, a Rate-Splitting (RS) approach has been proposed recently, which splits one selected user's message into a common and a private part, and superimposes the common message on top of the private messages. The common message is drawn from a public codebook and should be decoded by all users. In this paper, we generalize the idea of RS into the large-scale array regime with imperfect CSIT. By further exploiting the channel second-order statistics, we propose a novel and general framework Hierarchical-Rate-Splitting (HRS) that is particularly suited to massive MIMO systems. HRS simultaneously transmits private messages intended to each user and two kinds of common messages that can be decoded by all users and by a subset of users, respectively. We analyse the asymptotic sum rate of RS and HRS and optimize the precoders of the common messages. A closed-form power allocation is derived which provides insights into the effects of system parameters. Finally, simulation results validate the significant sum rate gain of RS and HRS over various baselines.
    No preview · Article · Dec 2015
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    ABSTRACT: In multiuser massive MIMO systems, it is not clear whether users should feed back the channel or the precoder when they can exchange the channel state information (CSI). This paper compares the precoder feedback scheme with the channel feedback scheme. It is found that when there are sufficient number of bits for CSI exchange, the precoder feedback scheme can reduce the interference leakage to 1/(K − 1) of the channel feedback scheme, where K is the number of users. Moreover, the interference leakage under the precoder feedback scheme decreases faster than the channel feedback scheme when the number of feedback bits increases.
    Full-text · Conference Paper · Nov 2015
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    DESCRIPTION: We address the problem of noise and interference corrupted channel estimation in massive MIMO systems. Interference, which originates from pilot reuse (or contamination), can in principle be discriminated on the basis of the distributions of path angles and amplitudes. In this paper we propose novel robust channel estimation algorithms exploiting path diversity in both angle and power domains, relying on a suitable combination of the spatial filtering and amplitude based projection. The proposed approaches are able to cope with a wide range of system and topology scenarios, including those where, unlike in previous works, interference channel may overlap with desired channels in terms of multipath angles of arrival or exceed them in terms of received power. In particular we establish analytically the conditions under which the proposed channel estimator is fully decontaminated. Simulation results confirm the overall system gains when using the new methods.
    Full-text · Research · Sep 2015
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    DESCRIPTION: We address the problem of noise and interference corrupted channel estimation in massive MIMO systems. Interference, which originates from pilot reuse (or contamination), can in principle be discriminated on the basis of the distributions of path angles and amplitudes. In this paper we propose novel robust channel estimation algorithms exploiting path diversity in both angle and power domains, relying on a suitable combination of the spatial filtering and amplitude based projection. The proposed approaches are able to cope with a wide range of system and topology scenarios, including those where, unlike in previous works, interference channel may overlap with desired channels in terms of multipath angles of arrival or exceed them in terms of received power. In particular we establish analytically the conditions under which the proposed channel estimator is fully decontaminated. Simulation results confirm the overall system gains when using the new methods.
    Full-text · Research · Sep 2015
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    ABSTRACT: In this paper, the problem of joint design of Spectrum Sensing (SS) and receive beamforming (BF), with reference to a Cognitive Radio (CR) system, is considered. The aim of the proposed design is the maximization of the achievable average uplink rate of a Secondary User (SU), subject to an outage-based Quality-of-Service (QoS) constraint for primary communication. A hybrid CR system approach is studied, according to which, the system either operates as an interweave (i.e., opportunistic) or as an underlay (i.e., spectrum sharing) CR system, based on SS results. A realistic Channel State Information (CSI) framework is assumed, according to which, the direct channel links are known by the multiple antenna receivers (RXs), while, merely statistical (covariance) information is available for the interference links. A new, closed form approximation is derived for the outage probability of primary communication, and the problem of rate-optimal selection of SS parameters and receive beamformers is addressed for hybrid, interweave and underlay CR systems. It is proven that our proposed system design outperforms both underlay and interweave CR systems for a range of system scenarios.
    Preview · Article · Sep 2015
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    ABSTRACT: In this paper, the operation of a Licensed Shared Access (LSA) system is investigated, considering downlink communication. The system comprises of a Multiple-Input-Single-Output (MISO) incumbent transmitter (TX) - receiver (RX) pair, which offers a spectrum sharing opportunity to a MISO licensee TX-RX pair. Our main contribution is the design of a coordinated transmission scheme, inspired by the underlay Cognitive Radio (CR) approach, with the aim of maximizing the average rate of the licensee, subject to an average rate constraint for the incumbent. In contrast to most prior works on underlay CR, the coordination of the two TXs takes place under a realistic Channel State Information (CSI) scenario, where each TX has sole access to the instantaneous direct channel of its served terminal. Such a CSI knowledge setting brings about a formulation based on the theory of Team Decisions, whereby the TXs aim at optimizing a common objective given the same constraint set, on the basis of individual channel information. Consequently, a novel set of applicable precoding schemes is proposed. Relying on statistical coordination criteria, the two TXs cooperate in the lack of any instantaneous CSI exchange. We verify by simulations that our novel coordinated precoding scheme outperforms the standard underlay CR approach.
    Preview · Article · Aug 2015
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    Mingbo Dai · Bruno Clerckx · David Gesbert · Giuseppe Caire
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    ABSTRACT: In a multiuser MIMO broadcast channel, the rate performance is affected by the multiuser interference when the Channel State Information at the Transmitter (CSIT) is imperfect. To tackle the interference problem, a Rate-Splitting (RS) approach has been proposed recently, which splits one user's message into a common and a private part, and superimposes the common message on top of the private messages. The common message is drawn from a public codebook and should be decoded by all users. In this paper, we propose a novel and general framework, denoted as Hierarchical Rate Splitting (HRS), that is particularly suited to FDD massive MIMO systems. HRS simultaneously transmits private messages intended to each user and two kinds of common messages that can be decoded by all users and by a subset of users, respectively. We analyse the asymptotic sum rate of HRS under imperfect CSIT. A closed-form power allocation is derived which provides insights into the effects of system parameters. Finally, simulation results validate the significant sum rate gain of HRS over various baselines.
    Full-text · Article · Jul 2015
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    ABSTRACT: We address the problem of noise and interference corrupted channel estimation in massive MIMO systems. Interference , which originates from pilot reuse (or contamination), can in principle be discriminated from the desired channels upon observing the distributions of path angles and amplitudes. In this paper we propose novel robust channel estimation algorithms exploiting path diversity in both angle and amplitude domains, relying on a suitable combination of a subspace projection and MMSE estimation. The proposed estimator improves on past methods in a wide range of system and topology scenarios.
    Full-text · Conference Paper · Jun 2015
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    Rajeev Gangula · Deniz Gündüz · David Gesbert
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    ABSTRACT: We determine the achievable distortion region when the correlated source samples are transmitted by two energy harvesting (EH) sensor nodes to the destination over orthogonal fading channels. A time slotted system is considered in which the energy and the source samples arrive at the beginning of each time slot (TS), and both the correlation between source samples at the two nodes and fading coefficients change over time but remain constant in each TS. Assuming non-causal knowledge of these time-varying source statistics, energy arrivals and the channel gains, i.e., under the offline optimization framework, we obtain the optimal transmission and coding schemes that achieve the points on the Pareto boundary of the total distortion region. An iterative directional 2D waterfilling algorithm is proposed to obtain two specific points on this boundary.
    Full-text · Conference Paper · Jun 2015
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    Sandeep Kottath · David Gesbert · Eric Hardouin

    Preview · Article · Jun 2015
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    Qianrui Li · David Gesbert · Nicolas Gresset
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    ABSTRACT: This paper considers the problem of coordinated multi-point transmission from transmitter devices that acquire noisy and partial channel state information (CSI) estimates from local feedback links. As cooperative multi-antenna transmission often relies on the availability of global channel estimates, we propose a novel decentralized algorithm that produces MMSE-optimal channel estimates on the basis of combining local feedback and inter-transmitter communications. To this end, we assume the devices are equipped with rate-limited bi-directional communication links over which they exchange a finite number of CSI-related bits. We propose a low-complexity cooperative channel estimation algorithm which exploits the local communications near-optimally and is robust to arbitrary feedback noise statistics. The proposed method has application in future decentralized CoMP scenarios, where we show clear advantages over the conventional channel state information exchange mechanisms.
    Full-text · Conference Paper · Jun 2015
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    ABSTRACT: In this paper, an analytical performance study for multi-antenna Cognitive Radio (CR) systems is presented. The two most popular CR approaches, namely, the interweave and underlay system designs, are considered and based on the derived analytical framework, a throughput-based comparison of these two system designs is presented. The system parameters are selected such that a quality of service (QoS) constraint on primary communication, is satisfied. Closed form expressions for the outage probability at the Primary User (PU), as well as expressions for the ergodic rate of the Secondary User (SU) are derived, for both system designs. The derived expressions are functions of key design parameters, such as the sensing time and the detection threshold in the case of interweave CR, and the maximum allowable interference power received by the PU, in the case of underlay CR. Based on the derived expressions, for interweave CR, the sensing parameters, i.e., sensing time and energy detection threshold, are optimized such as to maximize the secondary system rate. By comparing the throughput performance for both system designs, the existence of specific regimes (in terms of primary activity, number of transmit and receive antennas as well as the outage probability of the PU), where one CR approach outperforms the other, is highlighted.
    No preview · Article · May 2015 · IEEE Transactions on Wireless Communications
  • P. De Kerret · M.C. Filippou · D. Gesbert
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    ABSTRACT: In this work1, we study a cognitive radio setting consisting of a primary multiple-antenna transmitter (TX) serving a single-antenna primary user (PU) and a secondary multiple-antenna TX serving a secondary user (SU). The main specificity of this work is that we let the primary TX coordinate its transmit strategy with the secondary TX, while considering a realistic channel state information (CSI) scenario where each TX has solely access to the instantaneous knowledge of its direct channel and the statistics of the multi-user channel. This setting gives rise to a Team Decision problem where the TXs aim at cooperating on the basis of individual information. We develop a novel coordination scheme where the TXs coordinate without any exchange of information or any iteration to guarantee the fulfillment of the primary constraint while maximizing the rate of the SU. The coordination is done on the basis of statistical information such that the coordination can be optimized offline. The proposed scheme outperforms conventional schemes from the literature and has low complexity. It can thus be used in settings with low signal processing capabilities and a weak backhaul infrastructure.
    No preview · Article · Apr 2015
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    Mohammed Teeti · Jun Sun · David Gesbert · Yingzhuang Liu
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    ABSTRACT: A subspace method for channel estimation has been recently proposed [1] for tackling the pilot contamination effect, which is regarded by some researchers as a bottleneck in massive MIMO systems. It was shown in [1] that if the power ratio between the desired signal and interference is kept above a certain value, the received signal spectrum splits into signal and interference eigenvalues, namely, the "pilot contamination" effect can be completely eliminated. However, [1] assumes an independently distributed (i.d.) channel, which is actually not much the case in practice. Considering this, a more sensible finite-dimensional physical channel model (i.e., a finite scattering environment, where signals impinge on the base station (BS) from a finite number of angles of arrival (AoA)) is employed in this paper. Via asymptotic spectral analysis, it is demonstrated that, compared with the i.d. channel, the physical channel imposes a penalty in the form of an increased power ratio between the useful signal and the interference. Furthermore, we demonstrate an interesting "antenna saturation" effect, i.e., when the number of the BS antennas approaches infinity, the performance under the physical channel with P AoAs is limited by and nearly the same as the performance under the i.d. channel with P receive antennas.
    Preview · Article · Apr 2015 · IEEE Transactions on Wireless Communications
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    Paul de Kerret · David Gesbert · Umer Salim
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    ABSTRACT: Obtaining accurate Channel State Information (CSI) at the transmitters (TX) is critical to many cooperation schemes such as Network MIMO, Interference Alignment etc. Practical CSI feedback and limited backhaul-based sharing inevitably creates degradations of CSI which are specific to each TX, giving rise to a distributed form of CSI. In the Distributed CSI (D-CSI) broadcast channel setting, the various TXs design elements of the precoder based on their individual estimates of the global multiuser channel matrix, which intuitively degrades performance when compared with the commonly used centralized CSI assumption. This paper tackles this challenging scenario and presents a first analysis of the rate performance for the distributed CSI multi-TX broadcast channel setting, in the large number of antenna regime. Using Random Matrix Theory (RMT) tools, we derive deterministic equivalents of the Signal to Interference plus Noise Ratio (SINR) for the popular regularized Zero-Forcing (ZF) precoder, allowing to unveil the price of distributedness for such cooperation methods.
    Preview · Article · Feb 2015
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    Xinping Yi · Hua Sun · Syed A. Jafar · David Gesbert
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    ABSTRACT: The main result of this work is that fractional coloring (orthogonal access) achieves the all-unicast capacity (degrees of freedom (DoF)) region of the index coding (topological interference management (TIM)) problem if and only if the bipartite network topology graph (with sources on one side and destinations on the other, and edges identifying presence of nontrivial channels whose communication capacity is not zero or infinity) is chordal, i.e., every cycle that can contain a chord, does contain a chord. The all-unicast capacity (DoF) region includes the capacity (DoF) region for any arbitrary choice of a unicast message set, so e.g., the results of Maleki and Jafar on the optimality of orthogonal access for the sum-capacity (DoF) of one-dimensional convex networks are recovered as a special case.
    Preview · Article · Jan 2015
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    Rajeev Gangula · David Gesbert · Deniz Gündüz
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    ABSTRACT: Optimization of a point-to-point (p2p) multipleinput single-output (MISO) communication system is considered when both the transmitter (TX) and the receiver (RX) have energy harvesting (EH) capabilities. The RX is interested in feeding back the channel state information (CSI) to the TX to help improve the transmission rate. The objective is to maximize the throughput by a deadline, subject to the EH constraints at the TX and the RX. The throughput metric considered is an upper bound on the ergodic rate of the MISO channel with beamforming and limited feedback. Feedback bit allocation and transmission policies that maximize the upper bound on the ergodic rate are obtained. Tools from majorization theory are used to simplify the formulated optimization problems. Optimal policies obtained for the modified problem outperform the naive scheme in which no intelligent management of energy is performed.
    Full-text · Article · Jan 2015 · IEEE Journal on Selected Areas in Communications
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    Xinping Yi · David Gesbert
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    ABSTRACT: Interference networks with no channel state information at the transmitter (CSIT) except for the knowledge of the connectivity graph have been recently studied under the topological interference management (TIM) framework. In this paper, we consider a similar problem with topological knowledge but in a distributed broadcast channel setting, i.e. a network where transmitter cooperation is enabled. We show that the topological information can also be exploited in this case to strictly improve the degrees of freedom (DoF) as long as the network is not fully connected, which is a reasonable assumption in practice. Achievability schemes based on selective graph coloring, interference alignment, and hypergraph covering, are proposed. Together with outer bounds built upon generator sequence, the concept of compound channel settings, and the relation to index coding, we characterize the symmetric DoF for so-called regular networks with constant number of interfering links, and identify the sufficient and/or necessary conditions for the arbitrary network topologies to achieve a certain amount of symmetric DoF.
    Preview · Article · Dec 2014 · IEEE Transactions on Information Theory
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    Bruno Clerckx · David Gesbert
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    ABSTRACT: Studies of the MISO Broadcast Channel (BC) with delayed Channel State Information at the Transmitter (CSIT) have so far focused on the sum-rate and Degrees-of-Freedom (DoF) region analysis. In this paper, we investigate for the first time the error rate performance at finite SNR and the diversity-multiplexing tradeoff (DMT) at infinite SNR of a space-time encoded transmission over a two-user MISO BC with delayed CSIT. We consider the so-called MAT protocol obtained by Maddah-Ali and Tse, which was shown to provide 33% DoF enhancement over TDMA. While the asymptotic DMT analysis shows that MAT is always preferable to TDMA, the Pairwise Error Probability analysis at finite SNR shows that MAT is in fact not always a better alternative to TDMA. Benefits can be obtained over TDMA only at very high rate or once concatenated with a full-rate full-diversity space-time code. The analysis is also extended to spatially correlated channels and the influence of transmit correlation matrices and user pairing strategies on the performance are discussed. Relying on statistical CSIT, signal constellations are further optimized to improve the error rate performance of MAT and make it insensitive to user orthogonality. Finally, other transmission strategies relying on delayed CSIT are discussed.
    Preview · Article · Nov 2014 · IEEE Transactions on Communications

Publication Stats

11k Citations
234.32 Total Impact Points

Institutions

  • 2005-2013
    • Institut de France
      Lutetia Parisorum, Île-de-France, France
  • 2004-2013
    • University of Nice-Sophia Antipolis
      Nice, Provence-Alpes-Côte d'Azur, France
    • University Graduate Center at Kjeller (UNIK)
      Kristiania (historical), Oslo County, Norway
    • University of Minnesota Duluth
      • Department of Electrical Engineering
      Duluth, Minnesota, United States
  • 1995-2009
    • France Télécom
      Lutetia Parisorum, Île-de-France, France
  • 2008
    • University of Texas at Austin
      • Department of Electrical & Computer Engineering
      Austin, Texas, United States
  • 2007
    • Tai Sophia Institute
      Maryland City, Maryland, United States
  • 2002-2004
    • University of Oslo
      • Department of Informatics
      Kristiania (historical), Oslo, Norway
  • 1997-2001
    • Stanford University
      • Information Systems Laboratory
      Stanford, CA, United States
  • 1999
    • Mountain View Pharmaceuticals, Inc.
      Menlo Park, California, United States