I. INTRODUCTION
Radio Frequency Identification (RFID) system is a new wireless data transmission and reception technique for automatic identification, asset tracking, security surveillance etc. A typical RFID system is shown in Fig. 1.
A RFID system consists of three major components: a reader or integrator, which sends the interrogation signals to a RFID transponder or tag, which is to be identified; a RFID tag, which contains the identification code; and a middleware, which maintains the interface and the software protocol to encode and decode the identification data from the reader into a mainframe or a personal computer. Realising the fact that the barcode and other means for identifications and asset tracking are inadequate for recent demands, RFID technology has been taking the world of logistics, supply chain managements, asset tracking, security access control, and many other applications areas by storm. RFID was first proposed by H. Stockman [1]. He has introduced RFID systems in his landmark paper "Communication by Means of Reflected Power" [2]. Stockman advocates that considerable research and development works need to be done to solve the basic problems of wireless identification by means of reflected power [1].