Beam-Pattern Assisted Low-Complexity Beam Alignment for Fixed Wireless mmWave xHaul

This paper presents the design of two-stage beam alignment methods employing a hybrid analog-digital antenna array and exploiting the beam pattern in a point-to-point millimeter-wave (mmWave) radio for mmWave massive multiple-input multiple-output systems. We investigate an antenna deactivating approach that generates wider beams at the coarse alignment stage and exploit the theoretical beam pattern at the fine alignment stage. Our numerical results show that the proposed two-stage methods can achieve a better beam alignment than existing exhaustive methods and avail measurements/complexity reductions by tuning key parameters governing the alignment performance

Beam Alignment in mmWave User-Centric Cell-Free Massive MIMO Systems

The problem of beam alignment (BA) in a cell-free massive multiple-input multiple-output (CF-mMIMO) system operating at millimeter wave (mmWaves) carrier frequencies is considered in this paper. Two estimation algorithms are proposed, in association with a protocol that permits simultaneous estimation, on a shared set of frequencies, for each user equipment (UE), of the direction of arrival and departure of the radio waves associated to the strongest propagation paths from each of the surrounding access points (APs), so that UE-AP association can take place. The proposed procedure relies on the existence of a reliable control channel at sub-6 GHz frequency, so as to enable exchange of estimated values between the UEs and the network, and assumes that APs can be identifies based on the prior knowledge of the orthogonal channels and transmit beamforming codebook. A strategy for assigning codebook entries to the several APs is also proposed, with the aim of minimizing the mutual interference between APs that are assigned the same entry. Numerical results show the effectiveness of the proposed detection strategy, thus enabling one shot fast BA for CF-mMIMO systems.Comment: 6 pages, 3 figures, submitted to the 2021 IEEE Global Communications Conference (GLOBECOM

Common Codebook Millimeter Wave Beam Design: Designing Beams for Both Sounding and Communication with Uniform Planar Arrays

Fifth generation (5G) wireless networks are expected to utilize wide bandwidths available at millimeter wave (mmWave) frequencies for enhancing system throughput. However, the unfavorable channel conditions of mmWave links, e.g., higher path loss and attenuation due to atmospheric gases or water vapor, hinder reliable communications. To compensate for these severe losses, it is essential to have a multitude of antennas to generate sharp and strong beams for directional transmission. In this paper, we consider mmWave systems using uniform planar array (UPA) antennas, which effectively place more antennas on a two-dimensional grid. A hybrid beamforming setup is also considered to generate beams by combining a multitude of antennas using only a few radio frequency chains. We focus on designing a set of transmit beamformers generating beams adapted to the directional characteristics of mmWave links assuming a UPA and hybrid beamforming. We first define ideal beam patterns for UPA structures. Each beamformer is constructed to minimize the mean squared error from the corresponding ideal beam pattern. Simulation results verify that the proposed codebooks enhance beamforming reliability and data rate in mmWave systems.Comment: 14 pages, 10 figure

Polarimetric Wireless Indoor Channel Modelling Based on Propagation Graph

This paper generalizes a propagation graph model to polarized indoor wireless channels. In the original contribution, the channel is modeled as a propagation graph in which vertices represent transmitters, receivers, and scatterers, while edges represent the propagation conditions between vertices. Each edge is characterized by an edge transfer function accounting for the attenuation, delay spread, and the phase shift on the edge. In this contribution, we extend this modeling formalism to polarized channels by incorporating depolarization effects into the edge transfer functions and hence, the channel transfer matrix. We derive closed form expressions for the polarimetric power delay spectrum and cross-polarization ratio of the indoor channel. The expressions are derived considering average signal propagation in a graph and relate these statistics to model parameters, thereby providing a useful approach to investigate the averaged effect of these parameters on the channel statistics. Furthermore, we present a procedure for calibrating the model based on method of moments. Simulations were performed to validate the proposed model and the derived approximate expressions using both synthetic data and channel measurements at 15 GHz and 60 GHz. We observe that the model and approximate expressions provide good fit to the measurement data

Dually-Polarized Microwave Components Based on Polarization-Selective Coupling for Green Wireless Systems

RÉSUMÉ Avec le développement rapide et continu de technologies et de réseaux sans fil de nouvelle génération tels que la 5G et avec les ressources limitées d'énergie et de spectre disponibles pour soutenir ces développements sans fil rapides, l'exploration des bandes millimétriques sous-utilisées devient incontournable. Il devient de plus en plus crucial de se concentrer sur la réduction de la consommation d'énergie dans les futurs systèmes sans fil. Le moyen le plus efficace de réception d'énergie d'onde électromagnétique est de capturer complètement les deux composantes orthogonales de son vecteur de champ de propagation en relation avec la diversité de polarisation. De plus, l'utilisation d'ondes bi-polarisées permet l'amélioration d'une capacité de transmission via la réception simultanée de deux canaux orthogonaux. Cette thèse montre comment proposer et exploiter le concept très original de la diversité de polarisation sur la bande de fréquences mmW qui a été assignée aux applications sans fil. Auparavant, la diversité de polarisation était mise en oeuvre dans des profils non planaires, ce qui compliquait son intégration avec l'application de carte de circuit imprimé (PCB). Par conséquent, la motivation principale de cette thèse est de mettre en oeuvre la diversité de polarisation dans les profils planaires aux bandes de fréquence récemment assignées autour de 28 GHz et 38 GHz pour être intégrée dans la cinquième génération (5G) de communication sans fil. Ceci est fait en développant la théorie du fonctionnement et de la procédure de conception des composants MMW à double polarisation. La nouveauté présentée dans ce travail de thèse réside dans le développement d'un principe de fonctionnement permettant de concevoir et de mettre en évidence une classe de composants mmW bi-polarisés, à savoir les coupleurs 3dB, les coupleurs 0dB et les déphaseurs. Cela permet le développement de réseaux de formation de faisceau bi-polarisés tels que la matrice de Butler et les systèmes de télédétection à polarisation, basés sur une jonction à six ports à double polarisation. Une procédure de conception analytique complète est présentée avec des vérifications à travers des simulations pleine onde et des mesures de prototypes. La diversité de polarisation a été un facteur essentiel dans la performance et l'amélioration de la capacité de divers systèmes sans fil, y compris les réseaux cellulaires. Par conséquent, la conception et le développement de structures d'alimentation d'antenne bi-polarisées dans la bande mmW sont indispensables.----------ABSTRACT With the rapid and continuous development of new generation wireless technologies and networks such as 5G and with the limited enabling energy and spectrum resources available in support of such fast-moving wireless developments, exploring the underutilized millimeter-wave (mmW) bands becomes inescapable. It becomes more and more crucial to focus on the reduction of energy use in future wireless systems. The most efficient way of electromagnetic wave energy reception is to fully capture the two orthogonal components of its propagating field vector in connection with polarization diversity. In addition, the use of dually-polarized waves allows the enhancement of a transmission capability via the simultaneous reception of two orthogonal channels. This thesis shows how to propose and exploit the highly original concept of polarization diversity over the mmW frequency band which has been assigned for wireless applications. Previously, the polarization diversity was implemented within non-planar profiles which complicates its integration with the printed circuit board (PCB) application. Therefore, the main motivation of this thesis is to implement the polarization diversity within planar profiles at the recently assigned frequency bands around 28 GHz and 38 GHz to be suitable for integration in the fifth generation (5G) of wireless communication. This is done by developing the theory of operation and design procedure of dually-polarized mmW components. The novelty presented in this thesis work lies in developing a principle of operation to come up with the design and demonstration of a class of dually-polarized mmW components, namely 3dB couplers, 0dB couplers and phase shifters. This allows the development of dually-polarized beamforming networks such as Butler matrix and polarization-inclusive remote sensing systems based on a dually-polarized six-port junction. A full analytical design procedure is presented with verifications through full-wave simulations and prototype measurements. Polarization diversity has been an essential factor in the performance and capacity enhancement of various wireless systems including cellular networks. Accordingly, the design and development of dually-polarized antenna feeding structures in the mmW band is a must. Firstly, as the basic dual-polarized device, a compact orthomode transducer (OMT) design in the Ka-band is proposed. The novelty of the proposed OMT stems from a distinct concept of handling dually-polarized signals based on a polarization selective coupler (PSC)