What is MU?
MU (Measurement Uncertainty) is a statistical parameter that quantifies the range of values within which the true value of a measurement is expected to lie, given a specified level of confidence. In 5G device and base station testing, MU is a critical consideration because test results must account for the inherent limitations of measurement equipment, environmental conditions, and test methodology. Understanding and managing MU ensures that pass/fail decisions on conformance tests are reliable and fair.
How Does MU Work?
MU is typically expressed as an expanded uncertainty at a 95% confidence level (coverage factor k=2). It is calculated by combining all individual uncertainty contributions — instrument accuracy, mismatch, cable loss variation, temperature drift, DUT positioning, and repeatability — using root-sum-of-squares (RSS) method per the GUM (Guide to the expression of Uncertainty in Measurement). In 5G OTA testing, MU is particularly challenging due to additional factors like chamber reflections, positioner accuracy, and probe coupling. 3GPP defines Test Tolerances (TT) and Test System Uncertainties (TSU) for each conformance test, and results must be compared against limits that account for these uncertainties.
Use Cases
5G NR device conformance testing, OTA measurement accuracy assessment, test laboratory accreditation, production test guardbanding, and regulatory compliance verification.
3GPP / Standards Reference
3GPP TS 38.521-1/2/3 (NR UE conformance testing — uncertainty budgets), 3GPP TR 38.903 (Derivation of test tolerances), GUM (JCGM 100:2008)
Related Terms
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
