In this report, I expose the main researches I conducted, within the H2020 MSCA ADAM5 project, to tackle the aforementioned massive MU-MIMO issues. It is divided into four sections, as follows.
Section I: Low-Complexity Linear Precoding for PAPR reduction in Massive MU-MIMO-OFDM Downlink Systems
we developed a downlink transmission scheme to address the PAPR reduction problem for OFDM-based massive MIMO wireless systems, which leaves the processing required at each mobile terminal untouched while affecting only the signal processing at the BS. Our proposed method performs jointly MU precoding and PAPR reduction that are formulated as a convex optimization problem and solved online with instantaneous processed data via gradient descent (GD) approach.
This work has been published in: R. Zayani, H. Shaiek and D. Roviras, "PAPR-Aware Massive MIMO-OFDM Downlink," in IEEE Access, vol. 7, pp. 25474-25484, 2019, doi: 10.1109/ACCESS.2019.2900128.
Section II: Joint MU Precoding and Energy-Eciency enhancement Algorithm
We introduced a new downlink transmission approach to address the power amplifier (PA) nonlinearity issue in wireless massive MU-MIMO systems. We introduce a PA-aware precoding scheme that is formulated as a simple convex optimization problem that enables efficient and reliable algorithm implementations. The aim of the proposed approach is to optimize precoded signals that, when amplified and then passed through the channel, guarantee ideal transmission quality.
R. Zayani, H. Shaïek and D. Roviras, "Efficient Precoding for Massive MIMO Downlink Under PA Nonlinearities," in IEEE Communications Letters, vol. 23, no. 9, pp. 1611-1615, Sept. 2019, doi: 10.1109/LCOMM.2019.2924001.
Section III: Analysis and Cancellation of Inter-Numerology Interference in Massive MIMO-OFDM Systems
We investigated the use of spatial multiplexing of users, sharing the same bandwidth, whose associated numerologies are different. We first introduced a precoding/combiner design that aims to manage the mixed numerologies spectrum sharing (SS) transmission. Then, we analyzed the inter-numerology interference (INI) and derive the theoretical expressions of its radiation pattern in massive MIMO-OFDM downlink/uplink systems.
X. Cheng, R. Zayani, H. Shaiek and D. Roviras, "Analysis and Cancellation of Mixed-Numerologies Interference for Massive MIMO-OFDM UL," in IEEE Wireless Communications Letters, vol. 9, no. 4, pp. 470-474, April 2020, doi: 10.1109/LWC.2019.2959526.
X. Cheng, R. Zayani, H. Shaiek and D. Roviras, "Inter-Numerology Interference Analysis and Cancellation for Massive MIMO-OFDM Downlink Systems," in IEEE Access, vol. 7, pp. 177164-177176, 2019, doi: 10.1109/ACCESS.2019.2957194.
Section IV: Recent contributions
IV.1. Low-Complexity Linear Precoding for Low-PAPR Massive MU-MIMO-OFDM Downlink Systems
In order to optimize the tradeoff between performance and complexity, linear precoders based on matrix polynomials (M-POLY) and gradient-iterative approaches are studied for both data and PCSs precoding. Simulation results reveal that these latter provide satisfactory performance while they need much lower computational complexity compared to classical method in literature.
submitted to : International Journal on Communication Systems (IJCS) 2021
IV.2.Low Complexity Downlink Transmission scheme for massive MU-MIMO-OFDM under PA nonlinearities
The goal is to design a transmission scheme taking into consideration MU precoding, PAPR reduction and DPD, with a special focus the computational complexity. Then, a simple convex optimization problem is formulated to solve the massive MIMO precoding optimization problem considering PA nonlinearities and it is solved via GD approach. Our analysis and simulation results reveal that the proposed transmission scheme provides low computational complexity than the schemes studied in literature while closely approaching their performance, offering interesting insights for the design of energy-efficient massive MIMO-OFDM systems.
submitted to : IEEE transaction on Vehicular Technology
