  Resource-efficient and robust validation of systems designed to measure a
multi-dimensional parameter space is an unsolved problem as it would require
millions of test permutations for comprehensive validation coverage. In the
paper, an efficient and comprehensive validation approach based on a Gaussian
Process (GP) model of the test system has been developed that can operate
system-agnostically, avoids calibration to a fixed set of known validation
benchmarks, and supports large configuration spaces. The approach consists of
three steps that can be performed independently by different parties: 1) GP
model creation, 2) model confirmation, and 3) targeted search for critical
cases. It has been applied to two systems that measure specific absorption rate
(SAR) for compliance testing of wireless devices and apply different SAR
measurement methods: a probe-scanning system (per IEC/IEEE 62209-1528), and a
static sensor-array system (per IEC 62209-3). The results demonstrate that the
approach is practical, feasible, suitable for proving effective equivalence,
and can be applied to any measurement method and implementation. The presented
method is sufficiently general to be of value not only for SAR system
validation, but also in a wide variety of applications that require critical,
independent, and efficient validation.
