Coverage analysis of RFID indoor localization system for refrigerated warehouse based on 2-D Ray tracing

Abstract

Due to the ever increasing diffusion of Radio Frequency IDentification (RFID) in logistic processes, the localization of the tags in the environment is becoming an important feature for many RFID-based inventory management systems. RFID-based Location system will allow offering value-added services logistics operators, and RFID tags can be used for more than just labeling items. This paper proposes a Received Signal Strength (RSS) based positioning system for perishable products equipped with active UHF RFID tags inside a refrigerated warehouse (4C°). The major performance metrics of interest for indoor positioning systems are the accuracy and the precision in estimating signal strength within the coverage map. A fundamental problem in the design of RFID based localization system is the evaluation and mapping of the signals attenuation, which depends upon several parameters (fading from obstacles in the transmission path, reflections off surfaces and relative antenna orientation). Theoretical path loss models are therefore inadequate for a reliable prediction of the signal strength. In this paper, the design of the RFID localization system is tackled considering an initial experimental analysis of the ranging error with respect to the signal strength. The position of the antennas and the corresponding coverage map is finally obtained by means of a simulation tool based on 2D ray tracing algorithm, taking into account how the real environmental conditions in the warehouse, like temperature, humidity and the presence of the storage infrastructures, influence the attenuation of the signal.