Industry 6.0 Smart-Grid Communications Resilience: Requirements, Existing Pathways, and Limits of ION/Plasma Mechanisms

Industry 6.0 still needs the grid to preserve observation and control when conventional communications degrade. Communications failure is treated as a resilience problem that can be independent of, or correlated with, power-system failure. A minimum survivable information layer is defined as a requirement envelope, not a broadband specification. Existing private fiber, microwave, private broadband, land-mobile radio, power-line carrier, satellite, and mesh systems already cover substantial residual demand when ownership and supporting power are genuinely diverse. The remaining gap is deployment and end-to-end common-mode diversity, not the absence of a physical medium. Debye length is not communications range; plasma frequency is not a usable carrier; a sheath is not a channel; whistlers and field-aligned ducts are not addressed utility links; gaseous plasma antennas remain local electromagnetic devices. No new ion- or plasma-mediated grid communications medium is opened. Conventional HF skywave remains ordinary radio. Industry 6.0 does not require a plasma network. Addendum A (6 September 2026). Equal-energy MSIL endpoint test (device layer only). Plasma as a communications medium is not reopened. Plasma as a local antenna/device class is not withdrawn. The parent claim that plasma antennas improve grid resilience relative to metallic antennas is not established and is held for the five-line equal-energy test in Addendum A.