Covert backscatter communication with directional MIMO
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We study a backscatter communication protocol over a AWGN channel, where a transmitter illuminates a tag with a directional multi-antenna. The tag performs load modulation on the signal while hiding its physical presence from a warden. We show that, if the transmitter-to-tag channel is inaccessible to the warden, then Θ(n) reliable and covert bits can be transmitted over n channel usages. This overcomes the square-root law for covert communication. This paper provides the first evidence for practical implementation of covert backscatter communication, with potential applications in IoT security.
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