Abstract
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.
Highlights
Ultra-high frequency (UHF) radio frequency identification (RFID) is a non-contact electronic identification technology [1]
For the cross-layer approach in this numerical experiment, the media access control (MAC) algorithm is chosen as dynamic frame slot Aloha (DFSA), and the channel estimation on the PHY layer is s channel estimate (SCE), single-antenna zero-forcing (SAZF), least-squares channel estimate based on preambles (LCE), and Figure 9 gives STR for DFSA, SCE, SAZF, LCE, and orthogonal-matrix least-square channel estimate (OLCE) under the different number of tags when signal to noise ratio (SNR) is 20 dB
The reason is that the successful identified tags in the cross-layer approach may be both on the PHY layer and the MAC
Summary
Ultra-high frequency (UHF) radio frequency identification (RFID) is a non-contact electronic identification technology [1]. The approach combines random multiple access on an MAC layer with signal separation on a PHY layer to resolve the tag collisions. Good channel estimation will help to correctly recover the collided tag signal on the PHY layer. Constellation mapping (CM) [10] is an algorithm proposed to recover the collided tag signals on the PHY layer. Algorithm [11] can recover the collided signals on the PHY layer. Under a single-receiving-antenna environment, the algorithm can estimate the channel for only two collided tags. Successive-interference-cancel (SIC) algorithm [12] can recover more than two collided tag signals on the physical layer. The algorithm can accurately estimate the channel coefficients of more than two collided tags. From the estimated channel coefficients, we recover the UHF RFID tag collision on the PHY layer. The estimation errors of the algorithm are lower than the existing algorithms, and the separation efficiencies of the proposed algorithm are higher than the existing algorithms
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