Coexistence of OFDM and FBMC for Underlay D2D Communication in 5G Networks

Device-to-device (D2D) communication is being heralded as an important part of the solution to the capacity problem in future networks, and is expected to be natively supported in 5G. Given the high network complexity and required signalling overhead associated with achieving synchronization in D2D networks, it is necessary to study asynchronous D2D communications. In this paper, we consider a scenario whereby asynchronous D2D communication underlays an OFDMA macro-cell in the uplink. Motivated by the superior performance of new waveforms with increased spectral localization in the presence of frequency and time misalignments, we compare the system-level performance of a set-up for when D2D pairs use either OFDM or FBMC/OQAM. We first demonstrate that inter-D2D interference, resulting from misaligned communications, plays a significant role in clustered D2D topologies. We then demonstrate that the resource allocation procedure can be simplified when D2D pairs use FBMC/OQAM, since the high spectral localization of FBMC/OQAM results in negligible inter-D2D interference. Specifically, we identify that FBMC/OQAM is best suited to scenarios consisting of small, densely populated D2D clusters located near the encompassing cell's edge.Comment: 7 pages, 9 figures, Accepted at IEEE Globecom 2016 Workshop

Dynamic characterisation of a honeycomb sandwich structure in a wide frequency range

This presentation deals with the experimental characterisation of a thick sandwich plate with a honeycomb core. Measurements were conducted by means of a 3D laser Doppler Vibrometer, allowing the assessment of the out-of-plane and in-plane displacements of the sandwich structure due to piezo excitation. In addition, similar laser Doppler measurements were performed using a pump laser to excite the plate up to 300 kHz. Trough this experimental study, the complex dynamic behaviour of the structure (shearing of the core, coupling of the dispersion curves, dynamic evolution of the mechanical properties) is identified and analysed. Dispersion measurement results, obtained by using wave fitting methods (Hankel and IWC : Inhomogeneous Wave Correlation) as well as the CFAT (Corrected Force Analysis Technique) method, are shown. These results are compared to the Lamb wave theory and an equivalent model based on the work of Guyader (JSV 1978)

Modèle monocouche équivalent de plaque multicouche orthotrope

La caractérisation de matériaux complexes comme les multicouches a déjà fait preuve de nombreux travaux. Différentes approches existent, et en particulier, celles basées sur la recherche d'une plaque équivalente homogène (Equivalent Single Layer Model). Ces dernières comparent le multicouche à une plaque mince dont les paramètres simulent le comportement dynamique du multicouche à une fréquence donnée. La caractérisation du multicouche se fait donc par l'obtention de ces paramètres « équivalents ». En particulier, le modèle développé par J.L. Guyader [Internoise 2007] est de type plaque mince, se limitant à la caractérisation d'un multicouche isotrope, indépendant du nombre de couche et permettant d'obtenir comme paramètres équivalents, un module d'Young et un amortissement dynamique. A une fréquence donnée, la plaque équivalente présente le même nombre d'onde naturel que le multicouche. En reprenant une méthodologie similaire, nous proposons d'étendre le modèle de Guyader au cas des multicouches orthotropes, par le calcul des différentes rigidités de flexion D1, D2, D3 et D4 solutions de l'équation de dispersion de la plaque mince équivalente orthotrope. Cette méthode permet d'obtenir une représentation des caractéristiques du multicouche sur le plan d'onde kx ? ky. Des comparaisons expérimentales (vibrométrie laser) / analytiques seront présentées entre 2 et 8 kHz pour différents cas d'orthotropie sur des plaques en fibre de carbone afin d'illustrer les performances de la méthode

Lattices of quantized vortices in polariton superfluids

In this review, we will focus on the description of the recent studies conducted in the quest for the observation of lattices of quantized vortices in resonantly injected polariton superfluids. In particular, we will show how the implementation of optical traps for polaritons allows for the realization of vortex–antivortex lattices in confined geometries and how the development of a flexible method to inject a controlled orbital angular momentum (OAM) in such systems results in the observation of patterns of same-sign vortices

On the structural dynamics of laminated composite plates and sandwich structures; a new perspective on damping identification

This paper presents the modelling and the dynamic characterisation of laminated composite plates and sandwich structures in terms of stiffness and damping. The developments used in this paper are based on the analytical multilayer model of Guyader and Lesueur (JSV, 1978). The model considers linear shear, membrane and bending effects in each layer. The characteristics of the structure are determined by means of an equivalent thin plate methodology. The first main novelty of this paper consists in adapting this methodology for laminated plates (orthotropic multilayers with arbitrary orthotropic angle per layer). An experimental validation of this adaptation is presented for a laminated composite plate. Concerning the modelling of the structural loss factor, a space domain definition based on the spatial attenuation of a plane wave is compared to an energetic method and an equivalent definition based on the thin plate theory. The results show that the equivalent definition overestimates the loss factor in high frequencies since the thin plate theory only considers the flexural behaviour of the structure. On the contrary, the space domain definition (which give similar results as compared to the energetic one for lightly damped structures) considers the frequency dependent variation of the dynamic behaviour of the structure by means of the ratio between the group and phase velocities. The latter approach is considered to be more correct. The second main novelty of this article is on the experimental validation of this space domain definition. The structural loss factors of two sandwich structures are identified from measurements using modal, energetic and spatial methods. The results using the space domain definition are in very good agreement with the analytical predictions and the estimations of the modal and energetic methods for both plates for a large frequency band (up to 20 kHz), demonstrating the validity of the approach developed in this paper.status: publishe

Enabling Asynchronous Machine-Type D2D Communication Using Multiple Waveforms in 5G

In this paper, we explore the idea that 5G will permit the use of multiple waveforms, with each service employing a waveform that is best suited for it. We look at a 5G machinetype communication (MTC) scenario consisting of clustered user equipment employing device-to-device (D2D) communication, such as a smart factory with intercommunicating machinery. The overhead associated with synchronizing a large number of machine-type D2D user equipment (DUE) comes at a cost that may render synchronous communication infeasible or undesirable. Based on this motivation, we consider multiple possible combinations of prominent 5G waveform candidates for cellular users and DUEs, examining the asynchronous performance of all waveforms under consideration and using the performance of synchronous orthogonal frequency division multiplexing (OFDM) as a baseline for comparison. Specifically, we focus on the coexistence of waveforms in which the ordinary cellular users employ OFDM for synchronous communication, as in LTE, and the machine-type DUEs, operating asynchronously, employ a different waveform. When DUEs employ filter bank multicarrier with offset-QAM, the average achieved rate is marginally greater than the synchronous OFDM baseline case, and approximately 43% greater than the asynchronous OFDM case. This result is encouraging, as the benefits of asynchronous D2D communication could be enjoyed in MTC scenarios without suffering any performance reduction compared to the synchronous OFDM scenario. We then investigate how the relative performance of different waveform choices depends on the scenario by varying key parameters. Notably, for asynchronous communication, increasing the transmit power of DUEs results in diminishing benefits unless the DUEs employ a waveform that mitigates interdevice leakage interference