A signal strength based tag estimation technique for RFID systems

Radio frequency identification (RFID) is a wireless communication technology that provides automatic identification and data collection. In RFID systems with a large number of tags, many tags respond to the reader at the same time. Thus, enhanced anti-collision algorithms are required to have a fast multiple tag identification process. Anti-collision algorithms can be classified as probabilistic (eg. ALOHA based) algorithms and deterministic (tree based) algorithms. Better performance is achieved in all algorithms when accurate estimation of the number of tags is achieved. This paper presents a new method of estimating number of tags using signal strength properties. The simulated results show that our algorithm (efficiency 35%) significantly improves on existing estimation algorithms. That is 1% away from the perfect estimator and the theoretical optimum efficiency of slotted Aloha (36%).