6 research outputs found
AOA estimation with EM lens-embedded massive arrays
Recently, EM lens-embedded massive array antennas have been proposed for next 5G mobile wireless communications, as the adoption of a lens allows to discriminate the AOA of signals in the analog domain, with the possibility to preserve the processing complexity lower with respect to traditional massive arrays. In fact, in such a way, complex ADC chains can be avoided and the number of required antennas can be decreased. By exploiting these advantages, in this paper we study the possibility to use a single EM lens massive array at mm-wave for the AOA estimation of the received signal. In this perspective, ML estimator and practical approaches, tailored for the considered scenario, are derived. Results, obtained for different number of antennas, confirm the possibility to achieve interesting AOA estimation performance with an extremely compact architecture
Direct position estimation from wavefront curvature with single antenna array
In this paper we investigate the possibility to perform direct positioning by retrieving information from the wavefront curvature. Despite such an approach has been considered in the past at microwave and acoustic frequencies using extremely large antennas, it is of interest to investigate its potential exploitation at mm-wave with practical size antennas in the context of next 5G systems. Thus, here we first consider a dedicated model to gather the source position information from the wavefront curvature for different array architectures, i.e., traditional and lens-based arrays, and successively we derive the maximum likelihood estimator to investigate the attainable performance. Results, obtained for different number of antennas, i.e., for different array apertures, confirm the possibility to achieve interesting positioning performance using a single antenna array with limited dimensions
Reconfigurable Intelligent Surfaces for Localization: Position and Orientation Error Bounds
Next-generation cellular networks will witness the creation of smart radio
environments (SREs), where walls and objects can be coated with reconfigurable
intelligent surfaces (RISs) to strengthen the communication and localization
coverage by controlling the reflected multipath. In fact, RISs have been
recently introduced not only to overcome communication blockages due to
obstacles but also for high-precision localization of mobile users in GPS
denied environments, e.g., indoors. Towards this vision, this paper presents
the localization performance limits for communication scenarios where a single
next-generation NodeB base station (gNB), equipped with multiple-antennas,
infers the position and the orientation of the user equipment(UE) in a
RIS-assisted SRE. We consider a signal model that is valid also for near-field
propagation conditions, as the usually adopted far-field assumption does not
always hold, especially for large RISs. For the considered scenario, we derive
the Cramer-Rao lower bound (CRLB) for assessing the ultimate localization and
orientation performance of synchronous and asynchronous signaling schemes. In
addition, we propose a closed-form RIS phase profile that well suits joint
communication and localization. We perform extensive numerical results to
assess the performance of our scheme for various localization scenarios and RIS
phase design. Numerical results show that the proposed scheme can achieve
remarkable performance, even in asynchronous signaling and that the proposed
phase design approaches the numerical optimal phase design that minimizes the
CRLB.Comment: 15 pages, 11 figure
Single-Anchor Localization and Orientation Performance Limits Using Massive Arrays: MIMO vs. Beamforming
In the next generation of cellular networks, it is
desirable to use single access points both for communication and
localization. This could be made possible thanks to the combination
of femtocells, mm-wave technology and massive antenna
arrays, and would overcome the problem of having an over-sized
infrastructure for positioning which is, nowadays, the bottleneck
for the widespread diffusion of indoor localization systems. In
this context, our paper aims at investigating the localization
and orientation performance limits employing massive arrays
both at the access point and mobile side. To this end, we first
asymptotically demonstrate the tightness of the Cram\ue9r-Rao
bound (CRB) in the massive array regime and that the effect
of multipath can be made negligible even for practical values
of SNR levels. Successively, we propose a comparison between
two different transmitter configurations, namely multiple-input
multiple-output (MIMO), where orthogonal waveforms are sent,
and beamforming, which takes advantage of highly correlated
waveforms and directive array patterns. We also consider random
weighting as a trade-off between the diversity gain of MIMO and
the high directivity guaranteed by the beamforming. CRB results
show the interplay between diversity and beamforming gain as
well as the benefits achievable by varying the number of antennas
in terms of localization accuracy and multipath mitigation
Joint Energy Detection and Massive Array Design for Localization and Mapping
The adoption of massive arrays for simultaneous localization and mapping or personal radar applications enables the possibility to detect and localize surrounding objects through an accurate beamforming procedure. Unfortunately, when a classical constant false alarm rate approach accounting for ideal-pencil beam pattern is adopted, ambiguities in signal detection could arise due to the presence of side-lobes which can cause non-negligible errors in target detection and ranging. To counteract such effect, in this paper we propose a joint threshold-array design approach, where the antenna characteristics are taken into account to best set the threshold and to guarantee the desired detection and ranging performance at the non-coherent receiver section. In order to consider realistic arrays impairments, we focus our attention on the number of antenna elements and of phase shifter bits used for beamforming as key players in defining a trade-off between structural complexity, well-defined radiation pattern, and localization performance. Simulation and measurement results show that the number of bits per phase shifter can be relaxed in favor of a simpler array design, if the number of antennas is sufficiently high and the side-lobes are kept within a suitable level allowing a desired robustness to interference signals