Estimation of UHF RFID read-regions in real environments

The reading range is one of the most critical performance indicators of radio-frequency identification (RFID) systems. It depends on many physical and geometrical parameters. Typically, in the ultra-high-frequency band (UHF: 860 MHz to 960 MHz), the maximum size of the reading region is estimated by the free-space propagation model. This is based on the Friis formula, even if much more accurate predictions may be accomplished nowadays by time-consuming electromagnetic simulations, accounting for the antennas and the interaction with the nearby environment. This paper proposes a general parameterization of the three-dimensional reading region. This done having introduced all of the accessible system data, such as the emitted power, the reader and tag-over-object radiation patterns, and also the interrogation duty cycle, the scenario features, and the safety regulation constraints. Within this framework, the opportunity and some improvements of the free-space model are analyzed. They are compared with measurements and with more-accurate three-dimensional simulations of realistic environments. The discussion demonstrates the validity range of the free-space approximations, and evaluates-the improvement achieve-d by including the main interactions with the environment. The derivedformulas are ready to use and to be applied for the planning and optimization of reader-tag networks.