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.

[1]  Robert Langwieser,et al.  RFID Reader Receivers for Physical Layer Collision Recovery , 2010, IEEE Trans. Commun..

[2]  Christoph Angerer,et al.  Early Frame Restart in RFID Systems , 2008 .

[3]  Daniel W. Engels,et al.  Extracting information from tag collisions , 2009, 2009 IEEE International Conference on RFID.

[4]  Rohit U. Nabar,et al.  Introduction to Space-Time Wireless Communications , 2003 .

[5]  Harish Viswanathan,et al.  Optimal channel training for multiple antenna systems , 2000 .

[6]  Markus Rupp,et al.  Inter-Carrier Interference Estimation in MIMO OFDM Systems with Arbitrary Pilot Structure , 2011, 2011 IEEE 73rd Vehicular Technology Conference (VTC Spring).

[7]  F.J. Gonzalez-Castao,et al.  Analysis of DFSA anti-collision protocols in passive RFID environments , 2009, 2009 35th Annual Conference of IEEE Industrial Electronics.

[8]  Markus Rupp,et al.  Slot-wise maximum likelihood estimation of the tag population size in FSA protocols , 2010, IEEE Transactions on Communications.

[9]  Alle-Jan van der Veen,et al.  Separation of overlapping RFID signals by antenna arrays , 2008, 2008 IEEE International Conference on Acoustics, Speech and Signal Processing.

[10]  Robert Langwieser,et al.  RFID reader with multi antenna physical layer collision recovery receivers , 2011, 2011 IEEE International Conference on RFID-Technologies and Applications.

[11]  Junyu Wang,et al.  Separation of multiple passive RFID signals using Software Defined Radio , 2009, 2009 IEEE International Conference on RFID.

[12]  Xiangdong Huang,et al.  An anti-collision algorithm based on smart antenna in RFID system , 2008, 2008 International Conference on Microwave and Millimeter Wave Technology.