DoA estimation in EM lens assisted massive antenna system using subsets based antenna selection and high resolution algorithms

In recent times, massive antenna array technology has captured significant attention among wireless communication researchers. This is a field with strong potential to increase rates of data transfer; mitigate interference and serve a large number of users simultaneously. To contribute further to this emerging technology, this paper presents an approach for the line-of-sight (LoS) based direction of arrival (DoA) estimation using the electromagnetic (EM) lens-focusing antenna concept. The EM lens focuses the received signal energy as a function of the angle of arrival (AoA) to a small subset/area of the antenna array. This is advantageous, as it helps to reduce both hardware implementation (RF chains) and the complexity of signal processing in the large number of antennas system. Furthermore, this focusing capability of the EM lens provides additional interference rejection gain which leads to estimate the DoA of user terminals precisely. Hence, in this work, subsets based antenna selection approach and subspace-based high resolution DoA estimation algorithms have been considered in combination with the EM lens assisted massive antenna system. In simulations where the DoA is estimated with the EM lens, the results are comparable with conventional methods of DoA estimation without an EM lens, despite the significantly reduced overall system complexity

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

Terahertz Communications and Sensing for 6G and Beyond: A Comprehensive View

The next-generation wireless technologies, commonly referred to as the sixth generation (6G), are envisioned to support extreme communications capacity and in particular disruption in the network sensing capabilities. The terahertz (THz) band is one potential enabler for those due to the enormous unused frequency bands and the high spatial resolution enabled by both short wavelengths and bandwidths. Different from earlier surveys, this paper presents a comprehensive treatment and technology survey on THz communications and sensing in terms of the advantages, applications, propagation characterization, channel modeling, measurement campaigns, antennas, transceiver devices, beamforming, networking, the integration of communications and sensing, and experimental testbeds. Starting from the motivation and use cases, we survey the development and historical perspective of THz communications and sensing with the anticipated 6G requirements. We explore the radio propagation, channel modeling, and measurements for THz band. The transceiver requirements, architectures, technological challenges, and approaches together with means to compensate for the high propagation losses by appropriate antenna and beamforming solutions. We survey also several system technologies required by or beneficial for THz systems. The synergistic design of sensing and communications is explored with depth. Practical trials, demonstrations, and experiments are also summarized. The paper gives a holistic view of the current state of the art and highlights the issues and challenges that are open for further research towards 6G.Comment: 55 pages, 10 figures, 8 tables, submitted to IEEE Communications Surveys & Tutorial

Extremely Large-Scale MIMO: Fundamentals, Challenges, Solutions, and Future Directions

Extremely large-scale multiple-input-multiple-output (XL-MIMO) is a promising technology to empower the next-generation communications. However, XL-MIMO, which is still in its early stage of research, has been designed with a variety of hardware and performance analysis schemes. To illustrate the differences and similarities among these schemes, we comprehensively review existing XL-MIMO hardware designs and characteristics in this article. Then, we thoroughly discuss the research status of XL-MIMO from "channel modeling", "performance analysis", and "signal processing". Several existing challenges are introduced and respective solutions are provided. We then propose two case studies for the hybrid propagation channel modeling and the effective degrees of freedom (EDoF) computations for practical scenarios. Using our proposed solutions, we perform numerical results to investigate the EDoF performance for the scenarios with unparallel XL-MIMO surfaces and multiple user equipment, respectively. Finally, we discuss several future research directions.Comment: 8 pages, 6 figures, to appear in IEEE Wireless Communication