electronics Article Gyre Precoding and T-Transformation-Based GFDM System for UAV-Aided mMTC Network Joarder Jafor Sadique 1, * , Shaikh Enayet Ullah 2 , Raad Raad 3 , Md. Rabiul Islam 3 , Md. Mahbubar Rahman 4 , Abbas Z. Kouzani 5 and M. A. Parvez Mahmud 5   Citation: Sadique, J.J.; Ullah, S.E.; Raad, R.; Islam, M.R.; Rahman, M.M.; Kouzani, A.Z.; Mahmud, M.A.P. Gyre Precoding and T-Transformation-Based GFDM System for UAV-Aided mMTC Network. Electronics 2021, 10, 2915. https://doi.org/10.3390/ electronics10232915 Academic Editors: Jiankang Zhang, Shuai Wang and Jinming Wen Received: 26 August 2021 Accepted: 12 October 2021 Published: 25 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Electrical and Electronic Engineering, Begum Rokeya University, Rangpur 5404, Bangladesh 2 Department of Electrical and Electronic Engineering, University of Rajshahi, Rajshahi 6205, Bangladesh; enayet_apee@ru.ac.bd 3 Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW 2522, Australia; raad@uow.edu.au (R.R.); mrislam@uow.edu.au (M.R.I.) 4 Department of Electrical and Electronic Engineering, Islamic University, Kushtia 7003, Bangladesh; mahbublv@eee.iu.ac.bd 5 School of Engineering, Deakin University, Geelong, VIC 3216, Australia; abbas.kouzani@deakin.edu.au (A.Z.K.); m.a.mahmud@deakin.edu.au (M.A.P.M.) * Correspondence: joarder@brur.ac.bd Abstract: In this paper, an unmanned aerial vehicle (UAV)-aided multi-antenna configured downlink mmWave cooperative generalized frequency division multiplexing (GFDM) system is proposed. To provide physical layer security (PLS), a 3D controlled Lorenz mapping system is introduced. Further- more, the combination of T-transformation spreading codes, walsh Hadamard transform, and discrete Fourier transform (DFT) techniques are integrated with a novel linear multi-user multiple-input multiple-output (MU-MIMO) gyre precoding (GP) for multi-user interference reduction. Furthermore, concatenated channel-coding with multi-user beamforming weighting-aided maximum-likelihood and zero forcing (ZF) signal detection schemes for an improved bit error rate (BER) are also used. The system is then simulated with a single base station (BS), eight massive machine-type communications (mMTC) users, and two UAV relay stations (RSs). Numerical results reveal the robustness of the proposed system in terms of PLS and an achievable ergodic rate with signal-to-interference-plus-noise ratio (SINR) under the implementation of T-transformation scheme. By incorporating the 3D mobility model, brownian perturbations of the UAVs are also analyzed. An out-of-band (OOB) reduction of 320 dB with an improved BER of 1 × 10 −4 in 16-QAM for a signal-to-noise ratio, E b /N 0 , of 20 dB is achieved. Keywords: generalized frequency division multiplexing; cooperative unmanned aerial vehicle; massive machine type communication; physical layer security; T-transformation spreading codes; out-of-band; signal-to-interference-plus-noise ratio; gyre precoding 1. Introduction An uncrewed aircraft handled by remote control or embedded computer programs is commonly known as an unmanned aerial vehicle (UAV) or drone. Recently, there has been tremendous amount of interest growing to develop UAV-ground communications using low-cost massive UAVs under existing 5G as well as future-generation (B5G/6G) cellular networks. To maintain secure and reliable flight operation, UAVs can exchange safety- critical information with remote pilots, closest aerial vehicles, and air traffic controllers with an assistance of control and non-payload communication (CNPC). UAVs are also delivering goods and improving the throughput of 5G networks [1–3]. Additionally, mission-oriented data, such as high-resolution video, data packets, and aerial images, are possible to seamlessly transfer with UAVs in payload communication. Even in an emergency situation when terrestrial mobile stations go through unexpected discontinuity due to disasters, UAVs can be utilized as a base station (BS) or as a relay Electronics 2021, 10, 2915. https://doi.org/10.3390/electronics10232915 https://www.mdpi.com/journal/electronics