A Directional TDMA Protocol for High Throughput URLLC in mmWave Vehicular Networks

Abstract

Future vehicular wireless applications, such as autonomous and remote driving, will demand High Throughput Ultra-Reliable Low Latency Communication (HT-URLLC) unsupported by current wireless standards. Hybrid network designs that combine Millimeter-Wave (mmWave) and Sub-6GHz communications were recently proposed to establish HTURLLC in Vehicle-To-Everything (V2X) networks. To enable such integration, new Medium Access Control (MAC) protocols must be developed. As such, we consider a linear vehicular network, in which vehicles driving closely in the same lane utilize both front and rear directional mmWave antennas to form a Lane Cluster (LC). Data packets, then, propagate forwards and backwards along the LC towards its terminals in a multihop fashion. In turn, the LC terminals utilize omnidirectional antennas at Sub-6GHz frequencies to disseminate the cluster's packets to nearby LCs, Road Side Units (RSUs), and cellular base stations. To resolve the channel contention between subsequent LC members, we devised a two-timeslot MAC scheme with a schedule alignment mechanism. Additionally, we developed centralized and distributed schedule coordination protocols aligning the schedules of adjacent LCs to mitigate cross-lane interference due to antenna beam misalignment. The proposed protocols were evaluated using VEINS (extension of OMNET++ network simulator) and compared against the CSMA-CA scheme of IEEE 802.11p under different parameters and scenarios. The results show that the proposed linear topology along with the scheduling protocols can potentially achieve HT-URLLC while addressing the mmWave practicality issues.