Abstract
Ambient backscatter communication is an emerging and promising low-energy technology for the Internet of Things. In such a system, a tag sends a binary message to a reader by backscattering a radio frequency signal generated by an ambient source. The tag can operate without battery and without generating additional radio waves. However, the tag-to-reader link suffers from the source-to-reader interference. In this paper, we propose a polarization-based reconfigurable antenna in order to improve the robustness of the tag-to-reader link against the source-to-reader direct interference. More precisely, we compare different types of tags' antennas, different tags' encoding schemes, and different detectors at the reader. By using analysis, numerical simulations, and experiments, we show that a polarization-based reconfigurable tag with four polarization directions significantly outperforms a non-reconfigurable tag, and provides almost the same performance as an ideal reconfigurable tag with a large number of reconfigurable polarization patterns.
Highlights
T HE RECENT development of the Internet of Things (IoT) has massively increased the number of connected devices
Numerical simulations, and experiments, we show that a polarization-based reconfigurable tag with four polarization directions significantly outperforms a nonreconfigurable tag, and provides almost the same performance as an ideal reconfigurable tag with a large number of reconfigurable polarization patterns
OUTAGE PROBABILITY ANALYSIS In the previous section, we have shown that a polarization-based reconfigurable (PR) tag can improve the performance of an ambient backscatter (AmB) system in terms of Bit Error Rate (BER)
Summary
T HE RECENT development of the Internet of Things (IoT) has massively increased the number of connected devices. We propose to use these PR antennas to backscatter the ambient signal and to improve the robustness of AmB communications as well This PR tag attains log2(4) = 2 bits per switching period instead of 1 bit per switching period (that would be obtained with a 2-state tag). In the first considered coding scheme, the tag, as any standard two-state tag, sends its message by switching its operation between a backscattering state and a transparent state This is realized by switching the antenna between two different load impedances. We model the tag as a device that can switch between Npol radiation and corresponding polarization patterns This is obtained by mechanically rotating a dipole antenna across Npol different orientations. We introduce a second coding scheme, according to which the tag backscatters ambient signals with different polarization patterns. The outage probability is defined, for given values of SNRTx or SNRcaptured, as the probability of the event BER < BERtarget
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