OICC Press Majlesi Journal of Electrical Engineering 2345-3796 2026 11 06 Integrated Sensing and Communication-Assisted Orthogonal Time Frequency Space in a Non-Guard Band-Orthogonal Multiple Access Downlink Architecture for Vehicle-to-Infrastructure Networks 10.57647/j.mjee.2025.17385 EN Ghasem Saeidi Department of Electrical Engineering, Yazd University, Yazd, Iran https://orcid.org/0000-0002-0653-6426 Hamid Saeedi-Sourck Department of Electrical Engineering, Yazd University, Yazd, Iran https://orcid.org/0000-0002-8363-5030 Journal Article 2026 11 06 Orthogonal time frequency space (OTFS) modulation has emerged as a robust solution for high-mobility wireless communication and radar sensing by leveraging the delay-Doppler (DD) domain. This paper tackles challenges in resource allocation and multi-user interference (MUI) suppression in integrated sensing and communication (ISAC)-enabled vehicle-to-infrastructure (V2I) networks. We leverage a non-guard band-orthogonal multiple access (non-GB-OMA) scheme using interleaved DD-domain resource allocation with zero padding (ZP), thereby eliminating guard bands and reducing MUI. A two-dimensional (2D) correlation-based radar sensing method with an adaptive threshold detects user terminals (UTs), enabling UT-aware downlink resource allocation, channel estimation, and data detection. Channel estimation is treated as a sparse signal recovery problem, solved via the subspace pursuit (SP) algorithm using structured pilot patterns, a dedicated frame structure, and a specific external phase matrix. Furthermore, to combat high peak-to-average power ratio (PAPR) in OTFS systems, we employ low-power Zadoff-chu (Zch) and quadrature amplitude modulation (QAM) pilot sequences that maintain orthogonality and accuracy. Eventually, a two-stage feedback mechanism adapts the block linear-minimum mean square error (BL-MMSE) detector for data recovery. The proposed framework effectively manages PAPR, inter-symbol interference (ISI), and MUI, enhancing V2I communication reliability and efficiency under high mobility. Simulation results demonstrate improved SNR and BER performance.