  Citation: Sabeeh, S.; Wesolowski, K.; Sroka, P. C-V2X Centralized Resource Allocation with Spectrum Re-Partitioning in Highway Scenario. Electronics 2022, 11, 279. https:// doi.org/10.3390/electronics11020279 Academic Editor: Athanasios Kanatas Received: 1 December 2021 Accepted: 13 January 2022 Published: 16 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 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/). electronics Article C-V2X Centralized Resource Allocation with Spectrum Re-Partitioning in Highway Scenario Saif Sabeeh * , Krzysztof Wesolowski and Pawel Sroka Institute of Radiocommunications, Poznan University of Technology, 60-965 Poznan, Poland; krzysztof.wesolowski@put.poznan.pl (K.W.); pawel.sroka@put.poznan.pl (P.S.) * Correspondence: saifsadeq1982@gmail.com Abstract: Cellular Vehicle-to-Everything communication is an important scenario of 5G technologies. Modes 3 and 4 of the wireless systems introduced in Release 14 of 3GPP standards are intended to support vehicular communication with and without cellular infrastructure. In the case of Mode 3, dynamic resource selection and semi-persistent resource scheduling algorithms result in a signalling cost problem between vehicles and infrastructure, therefore, we propose a means to decrease it. This paper employs Re-selection Counter in centralized resource allocation as a decremental counter of new resource requests. Furthermore, two new spectrum re-partitioning and frequency reuse techniques in Roadside Units (RSUs) are considered to avoid resource collisions and diminish high interference impact via increasing the frequency reuse distance. The two techniques, full and partial frequency reuse, partition the bandwidth into two sub-bands. Two adjacent RSUs apply these sub-bands with the Full Frequency Reuse (FFR) technique. In the Partial Frequency Reuse (PFR) technique, the sub-bands are further re-partitioned among vehicles located in the central and edge parts of the RSU coverage. The sub-bands assignment in the nearest RSUs using the same sub-bands is inverted concerning the current RSU to increase the frequency reuse distance. The PFR technique shows promising results compared with the FFR technique. Both techniques are compared with the single band system for different vehicle densities. Keywords: C-V2X; connected vehicles; full frequency reuse distance; partial frequency reuse distance; resource allocation; vehicular communication 1. Introduction Cellular Vehicle-to-Everything (C-V2X) communication is a new technology that has been added to the LTE cellular system to support intelligent transportation systems [1]. 3GPP has introduced two modes of communication in Release 14 to exchange information between vehicles on the road, to increase self-driving car safety, to improve situational awareness and travel comfort, and to decrease traffic congestion [2]. Each vehicle should broadcast a Cooperative Awareness Message (CAM) periodically to inform the surrounding vehicles about its status [3]. C-V2X Mode 3 is a kind of communication in which the cellular infrastructure supports centralized resource allocation for vehicles located inside the cellular coverage area. The cel- lular infrastructure is responsible for selecting, re-selecting, scheduling, and managing the radio resources used for distribution of awareness messages transmitted by vehicles [4–6]. The C-V2X communication of vehicles operating in Mode 4 applies decentralized resource allocation and is mainly used outside the cellular coverage. The vehicles operating in Mode 4 are responsible for autonomous selection, re-selection, scheduling, and managing the resource allocation for broadcasting CAM messages [7]. Single-Carrier Frequency Division Multiple Access (SC-FDMA) has been selected as the C-V2X communication technique [8]. The resource blocks in SC-FDMA have been divided into groups to form sub-channels in the frequency domain, while two consecutive Electronics 2022, 11, 279. https://doi.org/10.3390/electronics11020279 https://www.mdpi.com/journal/electronics