Channel estimation in tag collision scenarios

Multiple tags in Radio Frequency Identification (RFID) systems are scheduled by a medium access control layer using the Framed Slotted Aloha (FSA) or binary tree protocol. The focus of our research is on FSA and passive Ultra High Frequency (UHF) RFID. In current standards, only one tag can be acknowledged per slot. In this work we propose the increase of the theoretical throughput of FSA RFID systems with multiple antennas for physical layer collision recovery by acknowledging two tags per slot. The expected throughput increase is approximately 5.03 times the throughput of a conventional reader. In order to profit of such increase we propose a method for channel estimation with a modified tag response, a so-called "postpreamble". The influence of the channel estimation on the performance is investigated through simulations.