HAPS- and UAV-Based 6G NTN Architecture for Rural Vehicular Connectivity

High-altitude platform stations (HAPS) and unmanned aerial vehicles (UAVs) are key elements of non-terrestrial networks (NTNs) for rural vehicular connectivity and emergency response in sixth-generation (6G) systems. In regions where terrestrial infrastructure is sparse or slow to restore, HAPS provide long-endurance, wide-area coverage from the stratosphere, while UAVs enable rapid, localized access. This article presents a layered NTN baseline that integrates satellites (GEO/MEO/LEO), HAPS, UAVs, and selective terrestrial infrastructure with mobile edge computing (MEC). In the proposed design, HAPS operate as control and backhaul anchors, whereas UAVs function as relay and access nodes, maintaining session continuity along road corridors through make-before-break (MBB) handovers. We evaluate three standards-aligned key performance indicators (KPIs): (i) end-to-end latency for safety messaging, map updates, and incident video; (ii) distance-based service availability over a 100-km route using joint SINR and deadline constraints; and (iii) backhaul goodput under clear, moderate, and heavy weather conditions for GEO, MEO, LEO, HAPS–FSO, HAPS–mmWave, and micro-wave links. The reported results, derived under stated assumptions, provide practical guidance on design trade-offs, including tier selection, MEC placement, handover strategy, and weather-aware backhaul. This article also highlights key challenges and outlines future research directions.