Network Systems,
Constraints & Efficiency.

While computational overhead for NIST Post-Quantum Cryptography (PQC) standards like ML-KEM is manageable on embedded platforms, payload fragmentation over LPWAN protocols creates severe communication bottlenecks. Prior evaluations estimated transmission duration from payload size and nominal data rates alone, omitting mandatory duty cycles.

Using discrete-event network simulation in ns-3.48 with native EU868 sub-band duty-cycle enforcement, this work demonstrates that true uplink wall-clock completion time exceeds idealized estimates by three to five orders of magnitude—requiring 4.3 minutes at SF7 and up to 4.46 hours at SF12 for an ML-KEM-1024 handshake. An analytical decomposition confirms the simulation within 7%, showing that mandatory regulatory silence—not packet loss alone—is a primary barrier to practical IoT PQC adoption.

LRPT is a systems-level optimization doctrine asserting that, under realistic constraints of mass, cost, volume, complexity, and reliability, reclaiming and reusing unavoidable energy losses can yield greater net functional-efficiency gains than increasing primary energy input.

The framework establishes a formal inequality through classical energy balance, constraint-aware marginal analysis, and exergy reasoning. It is validated across electric vehicles, where the stated recovery gain is 15–30%; internal-combustion vehicles, 20–40%; aircraft; and data centers, with the CV recording 15–40%.

LRPT introduces no new physical laws. It is presented as a prescriptive optimization doctrine: original in formulation, falsifiable, and suitable for early-stage engineering design.