Inter-Carrier Interference Reduction Technique for Backscattered OFDM

The objective of this letter is to improve the bit error performance of backscattering sensors that implement Orthogonal Frequency Division Multiplexing (OFDM). Many recent works in the literature have demonstrated the implementation of OFDM transmission from backscattering tags. A persistent shortcoming in such systems is the Bit Error Rate (BER) floor due to increased levels of Inter-Carrier Interference resulting from spectral spreading. In this letter, the authors employ unused subcarriers of the OFDM modulator to design an interference cancellation signal. The time domain signal is matched to the resolution of the impedance switching states of the tag. Significant suppression of the inter-carrier interference is possible with roughly equal numbers of used and unused subcarriers. Lower interference values result in lower BER floors. Furthermore, this technique allows the use of a larger number of data subcarriers than other existing techniques in the literature. The tag energy consumption per bit can therefore be reduced.