Dense RFID Reader Deployment in Europe using Synchronization Kin Seong Leong Auto-ID Laboratory, School of Electrical and Electronic Engineering, the University of Adelaide Email: kleong@eleceng.adelaide.edu.au Mun Leng Ng, Alfio R. Grasso, Peter H. Cole Auto-ID Laboratory, School of Electrical and Electronic Engineering, the University of Adelaide Email: {mng,alf,cole}@eleceng.adelaide.edu.au Abstract—For a dense RFID reader deployment, such as in a warehouse, where hundreds of readers will be positioned in a building, the interference between all these readers must be studied carefully to avoid disruption of operations. Strict RFID regulations and standards have been imposed, trying to address the problem of reader collision and also the problem of RFID devices interfering with other devices operating in the same and nearby frequency bands. However, these guidelines and regulations are not entirely friendly for dense RFID reader deployment; in some cases it is not possible to have a feasible RFID system while adhering to these regulations. Hence, this paper proposes the synchronization of RFID readers to enable successful dense RFID reader deployment. A case study targeted at European operations is presented in this paper to illustrate the actual synchronization of RFID readers in real applications. Some fine-tuning methods are also suggested to further improve the performance of readers in a high reader density population area. Index Terms—Radio frequency identification, RFID, synchronization, dense reader. I. INTRODUCTION Radio Frequency Identification (RFID) has received much attention recently as it is widely believed that RFID can revolutionize supply chain management, replacing barcodes as the main object tracking system. Several major supply chain operators and retailers, such as Wal- Mart in the USA, have deployed RFID systems in some of their supply chains [1]. Initial test runs of RFID deployment show encouraging results [2], and hence large scale RFID deployment is planned. However, before any successful deployment can be achieved, some RFID issues have to be resolved. One of them is the RFID reader collision problem, which is the focus of this paper. The term “reader collision(s)” is discussed extensively in [3] and [4]. In this paper, reader collision is simply defined as the phenomenon where an interrogation signal from a certain reader disrupts the communication between a tag and another reader, and this reader collision problem is potentially magnified in a dense reader environment, such as in a warehouse. Various regulatory and standardization bodies have tried to regulate the operations of RFID readers. In this paper, the ETSI 302 208 as introduced by the European regulatory body and the EPC Class 1 Generation 2 as recommended by EPCglobal are used as the basis of RFID reader operations. However, as will be discussed in more detail in the later part of this paper, the restrictions that are put on the operation of RFID readers are very strict, making it quite impossible to have an uncoordinated large scale deployment of RFID readers. Hence, this paper introduces the idea of RFID reader synchronization, to enable good RFID performance in a dense reader environment, while adhering to strict regulations. The next section introduces the ETSI 302 208 and EPC Class 1 Generation 2 Protocol and their impact on RFID reader deployment. Section III explains the concept of RFID reader synchronization and how it adheres to strict regulations. Section IV suggests possible ways in implementing a RFID synchronization system. A case study on RFID reader synchronization is presented in Section V. Ways of fine-tuning RFID reader positioning is discussed in Section VI. Variation of possible reader synchronization schemes is presented in Section VII, followed by conclusion in Section VIII. This paper is the extended version of [5]. It expands from the basics of RFID synchronization as introduced in [5] to the actual implementation methods and variations. II. BACKGROUND A. ETSI 302 208 ETSI 302 208 is a European regulation governing the operation of RFID readers [6]. It allocates the frequency band of 865 to 868 MHz for RFID deployment. This frequency band is then divided into fifteen sub-bands or Based on “Synchronization of RFID Readers for Dense RFID Reader Environments”, by Kin Seong Leong, Mun Leng Ng, Alfio R. Grasso, Peter H. Cole, which appeared in the Proceedings of the International Symposium on Applications and the Internet 2006, Phoenix, Arizona, USA, January 2006. © 2006 IEEE. JOURNAL OF COMMUNICATIONS, VOL. 1, NO. 7, NOVEMBER/DECEMBER 2006 9 © 2006 ACADEMY PUBLISHER