Measurement Chain Readiness for Instrument-Grade Energy Characterisation of Cellular IoT Devices

Before energy consumption can be measured defensibly, the measurement chain itself must be shown to produce trustworthy electrical measurements under controlled cellular network conditions.

ERS-2026-002 evaluates the readiness of a laboratory measurement chain for cellular IoT energy characterisation. The assessment covers the electrical current-measurement path, RF attenuation and combining, link-level repeatability, and the highest current-attribution level supported by the evaluated carrier board's access point.

The assessment does not report a device energy-consumption result. Instead, it establishes what the measurement chain can reliably measure, under which conditions, and where its attribution boundary lies.

1. 1Current measurement agreement. Independent reference measurements showed agreement between the evaluated current-measurement paths, with deviations of 0.55% in source-meter mode and 0.22% in ampere-meter mode against an independently derived reference.
2. 2RF chain characterisation. The evaluated 20 dB and 30 dB attenuators measured within 0.28 dB and 0.15 dB of nominal respectively, at the operating frequency. The Wilkinson divider used as a combiner showed a branch imbalance of 0.38 dB, with no measurable inter-port leakage above the measurement floor.
3. 3Link-level repeatability. Absolute RF level was not shown to be reproducible between sessions from configuration alone. In-session verification against a calibrated instrument is required before every measurement.
4. 4Attribution boundary. The evaluated carrier board does not provide a defensible module-only current measurement point under the applied no-modification constraint. Carrier-board (system) level attribution is the highest level supported by the evaluated access point.

• Electrical measurement: independent reference-load measurement and cross-checking of the evaluated current-measurement paths.
• RF network: characterisation of attenuation, combining and branch balance across the evaluated RF chain.
• Cellular conditions: controlled Band 25 FDD network emulation using the Amarisoft Callbox.
• Repeatability: cross-session RF level comparison, establishing the need for in-session verification.
• Attribution: assessment of the available current-access topology and its implications for module-level measurement.

Ready for system-level energy measurement. Following independent engineering evaluation, the measurement chain is considered fit to produce defensible energy measurements of cellular IoT devices at system level, subject to in-session verification of link level against a calibrated instrument and to measurements being reported at the attribution level they support.

Module-level energy attribution was not established under the no-modification constraint applied in this assessment. It requires a carrier board that exposes the module supply rail in series, or a modification to the evaluated board that this assessment's constraint excluded.