Coverage analysis of RFID indoor localization system for refrigerated warehouses based on 2D-ray tracing

Localization systems are becoming an important feature for many RFID-based inventory and warehouse management support tools, due to the ever increasing diffusion of Radio Frequency IDentification (RFID) in logistic processes. RFID-based Location system will allow offering value-added services to logistics operators, where 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.). A fundamental problem in the design of RFID based localization system is the evaluation and mapping of the signal attenuation, which depends upon several parameters (fading from obstacles in the transmission path, reflections off surfaces and relative antenna orientation). Such information should be considered in the design phase, where instead simplified theoretical approaches are frequently employed. Theoretical path loss models are however inadequate for a reliable prediction of the signal strength, which significantly affects the accuracy of distance measurement and ultimately the precision of localization. An accurate prediction of the coverage level is hence required for obtaining a reliable design. In this paper, a case study on the design of an RFID localization system is presented, comparing a realistic signal distribution, obtained considering the influence of reflections and refractions, and the theoretical approach based on simple path loss models. Realistic coverage maps are obtained by means of a simulation tool based on 2D ray tracing algorithm