Performance Analysis of RFID Protocols: CDMA Versus the Standard EPC Gen-2

Radio frequency identification (RFID) is a ubiquitous wireless technology which allows objects to be identified automatically. An RFID tag is a small electronic device with an antenna and has a unique identification (ID) number. RFID tags can be categorized into passive and active tags. For passive tags, a standard communication protocol known as EPC-global Generation-2, or briefly EPC Gen-2, is currently in use. RFID systems are prone to transmission collisions due to the shared nature of the wireless channel used by tags. The EPC Gen-2 standard recommends using dynamic framed slotted ALOHA technique to solve the collision issue and to read the tag IDs successfully. Recently, some researchers have suggested to replace the dynamic framed slotted ALOHA technique used in the standard EPC Gen-2 protocol with the code division multiple access (CDMA) technique to reduce the number of collisions and to improve the tag identification procedure. In this paper, the standard EPC Gen-2 protocol and the CDMA-based tag identification schemes are modeled as absorbing Markov chain systems. Using the proposed Markov chain systems, the analytical formulae for the average number of queries and the total number of transmitted bits needed to identify all tags in an RFID system are derived for both the EPC Gen-2 protocol and the CDMA-based tag identification schemes. In the next step, the performance of the EPC Gen-2 protocol is compared with the CDMA-based tag identification schemes and it is shown that the standard EPC Gen-2 protocol outperforms the CDMA-based tag identification schemes in terms of the number of transmitted bits and the average time required to identify all tags in the system.