Measurement uncertainty limit analysis of biased estimators in RFID multiple tags system

Abstract

In the measurement of real radio frequency identification (RFID) system, due to the relative and absolute systematic errors, biased estimators do happen in the practical measurement, which are difficult to be analysed. In order to get effective biased estimators, the linear and nonlinear functions in the measurement of RFID tags are taken as a paradigm to study the equivalence between the bias-corrected estimators and biased estimators. The measurement curve of optimum distribution angles of multiple tags is analysed in particular based on Fisher information determinant (FID), which could be used to evaluate the optimum performance of multiple RFID tags system. The results demonstrate the bias-corrected estimators of the single tag’s reading distance and multiple tags’ measurement curve of optimum distribution angles in RFID system could be obtained by calculating the corresponding biased estimators. Particularly, the biased estimator of multiple tags’ measurement curve of optimum distribution angles reaches the CRB when and only when the bias-corrected estimator reaches its corresponding CRB. Finally, the general expression of the biased CRB case in UHF RFID measurement is obtained. This study could be used as an evaluation tool for the measurement uncertainty limit of biased estimators.