A Robust IRS-Assisted URLLC Architecture for B5G/6G-Enabled Intelligent Transportation: Retransmission-Based Reliability With Reserved Bandwidth Allocation

Abstract

Intelligent reflecting surfaces (IRS) have emerged as a transformative technology for B5G/6G networks, offering the ability to actively reshape the wireless propagation environment and support reliable line-of-sight communication. In the context of intelligent transportation systems, however, meeting the stringent reliability and latency demands of ultra-reliable low latency communication (URLLC) remains a significant challenge, particularly under packet collision scenarios. To address this, we propose a retransmission-based protocol called retransmission mechanism with reserved bandwidth in IRS (RMRI), tailored to satisfy URLLC requirements in IRS-assisted vehicular networks. RMRI leverages a finite set of reserved bandwidth channels to instantly retransmit collided packets, combined with a packet diversity principle using 3-, 5-, and 7-packet duplication and a slotted Aloha mechanism operating within 0.2 ms time slots. We evaluate the protocol in terms of the minimum subcarriers needed to achieve 99.9999% reliability within a 0.2 ms latency threshold, maximum supported users, end-to-end latency, and path loss using the 3GPP UMi model. Results show that RMRI consistently outperforms conventional schemes, offering reduced subcarrier usage, enhanced reliability, and low latency, effectively meeting the demands of next-generation intelligent transportation systems.