Interference-Free Backscatter Communications for OFDM-Based Symbiotic Radio

TL;DR

This paper introduces an OFDM-based interference-free backscatter communication scheme using frequency shift keying, enabling reliable data transmission in symbiotic radio systems by orthogonalizing backscatter and primary signals.

Contribution

It proposes three novel FSK-based backscatter modulation schemes that ensure orthogonality with primary OFDM signals, facilitating interference-free communication and non-coherent detection.

Findings

Achieves lower bit-error rate up to 10^-4 at 30 dB

Eliminates direct link interference in backscatter communication

Provides theoretical BER performance analysis

Abstract

This study proposes an orthogonal frequency division multiplexing (OFDM) based scheme to achieve interference-free backscatter communications (BC) in a symbiotic radio system. In specific, we propose three frequency shift keying (FSK) based backscatter modulation schemes to shift the primary signal, i.e., the OFDM symbols transmitted from a base station (BS), in the frequency domain to transmit its information. Symbiotically, the BS empties specific subcarriers within the band so that the received frequency-shifted signals from the backscatter device and the primary signal are always orthogonal. The first scheme relies on the combination of on-off keying (OOK) within the FSK modulation while the second and the third schemes are based on the conventional FSK modulation with different in-band null-subcarrier allocation. These schemes allow the use of non-coherent detection at the receiver which addresses the channel estimation challenge for the signals arriving from a backscatter device. We derive the bit-error rate performance of the detector theoretically. The comprehensive simulations show that the proposed approach achieves a lower bit-error rate up to 10-4 at 30 dB with BC by eliminating direct link interference.