PHY1: Antenna Phased Arrays and Beamforming

Wednesday, 9 June 2021, 11:30-13:00, Zoom Room

Session Chair: Luis Pessoa (INESC TEC, Portugal)

Performance Comparison of Near-Field Focused and Conventional Phased Antenna Arrays at 140 GHz

Dinesh Acharya, Joonas Kokkoniemi and Aarno Pärssinen (University of Oulu, Finland); Markus Berg (University of Oulu & Excellant LTd., Finland)
The future high frequency systems require very high antenna gains to cope with the large channel losses. In order to obtain large gain and flexible beamforming, large antenna arrays are often considered. With hundreds or thousands of antenna elements, the transmit energy can be highly concentrated on the target. However, large numbers of antenna elements make the antennas very large compared to the wavelength. Therefore, it is likely for the user to be in the near field of the array. In this region, the maximum antenna gain is obtained by focusing the energy on the wanted locations. The downside is a need for exact locations of the radios. This paper focuses on analysis of the traditional linear phase beam steering and near field focusing beam steering and the impact of the user location uncertainty on the achievable antenna gain. The uncertainty in the user location can arise, for instance, from the user movement. The results show that the near field focusing gives superior gain in the near field of the antenna array, but is more sensitive to the user location information than the linear phase beam steering.

A Systematic Beam Broadening Method for Large Phased Arrays

Corentin Fonteneau (Orange Labs, France); Matthieu Crussière (Univ Rennes, INSA Rennes, CNRS, IETR, France); Bruno Jahan (France Telecom, France)
Hybrid beamforming architecture is a key enabler for implementing Massive Multiple-Input Multiple-Output (mMIMO) solutions in next generation wireless communication systems. With such an approach, precoder and combiner designs not only depend on digital weights but also on modulus constraint analog weights controlled by phase shifters. This becomes a critical issue since the calculation of weights becomes a non-convex problem that needs extensive search or complex iterative methods. In particular, beam broadening capability is of key interest for mMIMO systems to find a trade-off between the array gain and the beamwidth. Indeed, a high gain narrow beam is not always beneficial as far as mobility scenarios or control channel transmissions are concerned. In this paper, a non-iterative phase-only beam broadening method is proposed, relying on a quadratic phase excitation pattern applied to linear and planar arrays. We establish the key laws driving the beamwidth and steering angle adaption. We show that our technique can be applied systematically and is especially well-suited for large antenna arrays.

Analysis and Optimization of Reconfigurable Intelligent Surfaces Assisted MIMO Systems

Le Hao (Technische Universität Wien, Austria); Stefan Schwarz (TU Wien & CD-Lab Society in Motion, Austria); Markus Rupp (TU Wien, Austria)
Reconfigurable intelligent surface (RIS) technology has recently gained a lot of attention since it promises to enhance the spectral and energy efficiency of future wireless communication systems. In this paper, we propose several approaches to optimize the beamformers at the base station (BS) and the phase shifts at the RIS for an RIS-assisted multiple-input multiple-output (MIMO) system. By comparing the minimum signal power, minimum signal to interference plus noise ratio (SINR) and rate achieved by the proposed maximum ratio transmission (MRT), zero-forcing (ZF) and max min SINR based optimizations, we conclude that the MRT based optimization can achieve the highest minimum signal power among other approaches, whereas the max min SINR optimization can achieve the highest minimum SINR and minimum rate. In addition, the effect of quantized RIS-phase shifts is analyzed, showing that almost optimal performance can be achieved with relatively high phase resolution.

Hybrid Beamforming with Fixed Phase Shifters for Uplink Cell-Free Millimetre-Wave Massive MIMO System

Abdulrahman Saeed Al Ayidh (University of Glasgow, United Kingdom (Great Britain)); Yusuf A. Sambo (University of Glasgow & School of Engineering, United Kingdom (Great Britain)); Shuja Ansari and Muhammad Ali Imran (University of Glasgow, United Kingdom (Great Britain))
Several innovative ideas are being proposed by researchers to lay a foundation for future generations of wireless communications due to anticipated explosive demand for throughput, ultra-low latency, ultra-high reliability and ubiquitous coverage. However, these demands will consume huge amount of resources, especially for cell-free (CF) millimetre-wave (mm-Wave) massive multiple input multiple output systems (MIMO), which is the promising direction for the coming wireless generations. In this paper, we present hybrid beamforming scheme based on alternating minimization and a few number of fixed phase shifters to maximize energy efficiency in the uplink CF mm-Wave massive MIMO systems. Simulation results illustrate that our proposed scheme with much fewer fixed phase shifters, e.g., 10 phase shifters, achieves up to approximately 20 % and 50 % energy efficiency improvement compared to adaptive radio frequency (RF) chains activation/deactivation and antenna selection schemes.

Towards Power Efficient 6G Sub-THz Transmission

Hardy Halbauer and Thorsten Wild (Nokia Bell Labs, Germany)
Extreme high rate demands for 6G can be addressed by communication technologies in the millimeter wave and Terahertz bands. In these high carrier frequencies, power consumption can become a key limiting factor and thus has to be assessed thoroughly. This paper considers the power consumption of the RF frontend of a transceiver for the use in a hot spot scenario. A power consumption model for the main functional blocks has been derived for different frequencies and array architectures, both at transmit and receive side. The impact of the EIRP reduction over the frequency range from 90 GHz up to 230 GHz due to increased path loss and reduced output power of the power amplifiers has been assessed and the related power consumption has been evaluated. Further, the impact of analog-to-digital converters on the overall power consumption of the receive part have been carved out. Key dominating components have been identified indicating the number of antenna elements needed for different architectures and the related power consumption.

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