Optimal Non-Coherent Detector for Ambient Backscatter Communication System

TL;DR

This paper derives the probability density function of signals in ambient backscatter communication systems and designs optimal non-coherent detectors, demonstrating their performance and computational advantages through numerical analysis.

Contribution

It introduces two novel non-coherent detectors based on the derived pdf, including a channel-estimation-based detector, and compares their performance with existing methods.

Findings

Both detectors achieve similar BER performance.

The second detector is computationally simpler.

Energy detector approximates the second detector.

Abstract

The probability density function (pdf) of the received signal of an ambient backscatter communication system is derived, assuming that on-off keying (OOK) is performed at the tag, and that the ambient radio frequency (RF) signal is white Gaussian. The pdf of the received signal is then utilized to design two different types of non-coherent detectors. The first detector directly uses the received signal to perform a hypothesis test. The second detector first estimates the channel based on the observed signal and then performs the hypothesis test. Test statistics and optimal decision threshold of the detectors are derived. The energy detector is shown to be an approximation of the second detector. For cases where the reader is able to avoid or cancel the direct interference from the RF source (e.g., through successive interference cancellation), a third detector is given as a special case of the first detector. Numerical results show that both the first and the second detectors have the same bit error rate (BER) performance, making the second detector preferable over the first detector due to its computational simplicity.