LODS-MTI: A Link-Adaptive, 0rthogonal, and De-slotted Protocol for Robust and Fast RFID Missing Tag Identification

Existing Missing Tag Identification (MTI) protocols face a trade-off between logic-layer scheduling reliability and physical-layer spectral efficiency. To bridge this gap, we propose LODS-MTI, a Link-adaptive Orthogonal De-slotted protocol. LODS-MTI restructures uplink transmission into a batch-synchronized continuous bitstream, eliminating inter-tag guard times by exploiting short-term channel coherence. The protocol enforces a hardware-minimalist design, replacing arithmetic division with bitwise logic via power-of-2 batching. To address the structural vulnerability of de-slotted streams to synchronization loss, we introduce a digital majority voting logic capable of neutralizing single-bit timing slips ("Soft Synchronization") and accommodating clock drifts up to 0.4%. This is coupled with a tolerance-driven adaptive mechanism (ϵ = 0.30) that autonomously selects redundancy levels based on link quality. Theoretical analysis and simulations confirm that this mechanism establishes a Safe Operating Area (SOA), maintaining 99.10% accuracy even under truncated payload windows (128 bits). LODS-MTI achieves a normalized time efficiency of η ≈ 3.52, surpassing state-of-the-art baselines by over 50%. The system sustains a goodput ranging from 5,200 tags/s (Pe ≈ 0.1) to 8,811 tags/s, while stabilizing energy consumption at 0.15 µJ/tag, an order-of-magnitude improvement over analog collision resolution schemes. The code and datasets are available at GitHub.