Stochastical Model and Performance Analysis of Frequency Radio Identification

Abstract

RFID (Radio Frequency Identification) can assign a unique digital identifier to each physical item, and provide an efficient, cheap and contactless method for gathering the information of the physical items to enable their automatic tracking and tracing(Finkenzeller 2003). RFID technology serves as the back stone of the “Internet of Things”(Engels 2001), and is reviewed as a main enabler of the upcoming “Pervasive Computing”(Stanford 2003). RFID systems have been widely adopted in quite a lot applications, ranged from “smart box” to world-wide logistics management systems. A typical RFID system is consisted of some RFID tags, one or more RFID readers and the backend information system. Each RFID tag holds a unique identifier and is attached to a physical item. RFID reader is used to collect the identifiers stored in the RFID tags located in its vicinity and is often connected with the backend information system. During identification, The RFID reader asks the RFID tags to modulate their binary identifiers into signals and transmit these signals back to the reader through the air interface, which is a wireless communication channel for the RFID tag and reader to exchange information. Afterwards, The RFID reader sends the data gathered to the backend information system for further processing and dispatching to various applications. One of the main issues that affect the universal deployment and application of the RFID system is the collisions occurred during RFID tag identification(Wu 2006). The simultaneous modulated signals broadcasted by the RFID reader and transmitted from the RFID tags will interfere in the air interface, in which case, what the receivers can get is only a collision signal but no useful information. Collisions occurred in the RFID system can be categorized as the reader-reader, reader-tag and tag-tag collisions(Shih 2006). When two or more RFID readers try to broadcast messages through the air interface simultaneously, reader-reader collision occurs. Due to that they are often connected with the computer system and can be equipped with enough resource to monitor the air interface, RFID readers can detect the collision and coordinate with each other in advance. Reader-reader collision can be avoided and resolved completely with some deliberate designed protocols, such as the ColorWav(Waldrop 2003) and others(Leong 2006).