Dynamic system model for optimal configuration of mobile RFID systems ?
In many practical RFID applications tags are attached to items that pass through the readers field moving at a constant speed, following a fixed path. The time-constrained presence of the tags in the identification region introduce the possibility that tags exit the system without being identified (lost tags). Reliability is a practical requirement in most applications, which implies that the portion of lost tags should be kept below a very small threshold. Therefore, we take this fact as the starting point in the design process. We present a mathematical model for RFID systems implementing Frame Slotted Aloha as the collision resolution protocol. Upon this model it is possible to compute the tag loss ratio and therefore to obtain the optimal frame size in terms of reliability. While previous works generally use a Markovian approach, our model is based on dynamic systems theory, having a smaller computational cost which, in addition, is independent of the dimension of the system. Moreover, the proposed model allows us to identify the multiplicity of the equilibrium points in the system, an interesting and relevant property that has been overlooked in RFID systems so far. Finally, we present a design procedure based on our model that allows to configure the physical parameters of the system in order to adjust both the throughput and the reliability.
frame slotted aloha tag loss ratio radio frequency identification equilibrium point analysis stability discrete time system