LS Channel Estimation and Signal Separation for UHF RFID Tag Collision Recovery on the Physical Layer

• Published in: Sensors (Basel, Switzerland) Vol. 16; no. 4; p. 442
• Main Authors: Duan, Hanjun, Wu, Haifeng, Zeng, Yu, Chen, Yuebin
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.03.2016; MDPI
• Subjects: Access control; Algorithms; Antennas; channel estimation; Channels; Communication; Errors; Estimates; Information systems; least-square; Radio frequency; Radio frequency identification; Recovery; RFID; Sensors; Separation; signal separation; tag collision; Tags; UHF; RFID; least-square; channel estimation; signal separation; tag collision
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s16040442

In a passive ultra-high frequency (UHF) radio-frequency identification (RFID) system, tag collision is generally resolved on a medium access control (MAC) layer. However, some of collided tag signals could be recovered on a physical (PHY) layer and, thus, enhance the identification efficiency of the RFID system. For the recovery on the PHY layer, channel estimation is a critical issue. Good channel estimation will help to recover the collided signals. Existing channel estimates work well for two collided tags. When the number of collided tags is beyond two, however, the existing estimates have more estimation errors. In this paper, we propose a novel channel estimate for the UHF RFID system. It adopts an orthogonal matrix based on the information of preambles which is known for a reader and applies a minimum-mean-square-error (MMSE) criterion to estimate channels. From the estimated channel, we could accurately separate the collided signals and recover them. By means of numerical results, we show that the proposed estimate has lower estimation errors and higher separation efficiency than the existing estimates.