Trade-off between maximum cardinality of collision sets and accuracy of RFID reader-to-reader collision detection

Abstract

As the adoption of the radio-frequency identification (RFID) technology is increasing, many applications require a dense reader deployment. In such environments, reader-to-reader interference becomes a critical problem, so the proposal of effective anti-collision algorithms and their analysis are particularly important. Existing reader-to-reader anti-collision algorithms are typically analyzed using single interference models that consider only direct collisions. The additive interference models, which consider the sum of interferences, are more accurate but require more computational effort. The goal of this paper is to find the difference in accuracy between single and additive interference models and how many interference components should be considered in additive models. An in-depth analysis evaluates to which extent the number of the additive components in a possible collision affects the accuracy of collision detection. The results of the investigation shows that an analysis limited to direct collisions cannot reach a satisfactory accuracy, but the collisions generated by the addition of the interferences from a large number of readers do not affect significantly the detection of RFID reader-to-reader collisions.

Simulation and Evaluation of the Interference Models for RFID Reader-to-Reader Collisions

“…Since the greatest amount of interference is generated by close readers, a good approximation of the total interference can be achieved by summing the contributions of the k closest readers. This is confirmed by the analysis in [21]. The interference graph that derives from this assumption is called random proximity graph.…”

“…Besides, the evaluation considers a homogeneous RFID network where each reader is identical with the same antenna gains. The values of the parameters adopted in the system are shown in Table 1 [21]. The threshold distance D th of the unit disk graph model is given by equation (1): substituting the values in Table 1 into equation (1), it results D th = 288.675 m. This distance is used to determine whether two readers are neighbors in the unit disk graph model.…”

“…In [19] it was analyzed how the collisions that are detected according to the two groups of models are influenced by some system parameters, like the path loss exponent, the background noise power, and the SIR (Signal to Interference Ratio) required for correct tag identification. A trade-off between the computation effort and the accuracy of the interference models was investigated in [21]. However, so far the analysis and evaluation of the interference models have been performed only from a theoretical point of view.…”