information Article Analysis of Power Allocation for NOMA-Based D2D Communications Using GADIA Husam Rajab 1,* , Fatma Benkhelifa 2 and Tibor Cinkler 1   Citation: Rajab, H.; Benkhelifa, F.; Cinkler, T. Analysis of Power Allocation for NOMA-Based D2D Communications Using GADIA. Information 2021, 12, 510. https:// doi.org/10.3390/info12120510 Academic Editor: Willy Susilo Received: 18 November 2021 Accepted: 3 December 2021 Published: 8 December 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 Telecommunications and Media Informatics, Budapest University of Technology and Economics, 1111 Budapest, Hungary; Cinkler@tmit.bme.hu 2 Department of Computing, Faculty of Engineering, Imperial College London, London SW7 2BX, UK; f.benkhelifa@imperial.ac.uk * Correspondence: Husamrajab@tmit.bme.hu Abstract: The new era of IoT brings the necessity of smart synergy for diverse communication and computation entities. The two extremes are, on the one hand, the 5G Ultra-Reliable Low-Latency Communications (URLLC) required for Industrial IoT (IIoT) and Vehicle Communications (V2V, V2I, V2X). While on the other hand, the Ultra-Low Power, Wide-Range, Low Bit-rate Communications, such as Sigfox, LoRa/LoRaWAN, NB-IoT, Cat-M1, etc.; used for smart metering, smart logistics, monitoring, alarms, tracking applications. This extreme variety and diversity must work in synergy, all inter-operating/inter-working with the Internet. The communication solutions must mutually cooperate, but there must be a synergy in a broader sense that includes the various communication solutions and all the processing and storage capabilities from the edge cloud to the deep-cloud. In this paper, we consider a non-orthogonal multiple access (NOMA)-based device to device (D2D) communication system coexisting with a cellular network and utilize Greedy Asynchronous Dis- tributed Interference Avoidance Algorithm (GADIA) for dynamic frequency allocation strategy. We analyze a max–min fairness optimization problem with energy budget constraints to provide a reasonable boundary rate for the downlink to all devices and cellular users in the network for a given total transmit power. A comprehensive simulation and numerical evaluation is performed. Further, we compare the performance of maximum achievable rate and energy efficiency (EE) at a given spectral efficiency (SE) while employing NOMA and orthogonal frequency-division multiple access (OFDMA). Keywords: IoT; 5G; eMBB; mMTC; URLLC; GADIA; NOMA; OFDMA 1. Introduction Recently, a rising consensus in the fifth generation (5G) of wireless network technology has been developed to sustain the massive number of users. It will support a broad range of vertical industries demands by linking everyone and everything, particularly smart devices, machines, and sensors. The 5G network will drive innovation and has the prospect to change the way we live, work and play. According to the International Telecommunication Union (ITU), 5G wireless systems are classified to support three generic services as enhanced Mobile Broadband (eMBB), massive Machine-Type Communications (mMTC), and Ultra-Reliable and Low-Latency Communications (URLLC) [1,2]. These use cases empower various services provided by the 5G network: (a) the eMBB provides a stable connections service of mobile broadband with significantly high peak data rates that assist in providing consistent user experience; (b) the mMTC furnishes a massive number of Internet of Things (IoT) devices, which are transmitting small data payloads periodically; (c) the URLLC services will open up additional diverse capabilities of the network by expanding its limits for high reliability and low-latency from a restricted set of terminals. The miscellaneous deployment of the 5G network is due to the increase in various new characteristics, i.e., scalable numerology, along with compatibility, elastic Information 2021, 12, 510. https://doi.org/10.3390/info12120510 https://www.mdpi.com/journal/information