DFT-spread-OFDM Based Chirp Transmission
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In this study, we propose a low-complexity transceiver for chirp-based communications by exploiting discrete Fourier transform-spread orthogonal frequency division multiplexing (DFT-s-OFDM). We show that a well-designed frequency-domain spectral shaping (FDSS) function for DFT-s-OFDM can convert its single-carrier nature to a linear combination of chirp signals circularly translated in the time domain. By utilizing Bessel functions and Fresnel integrals for FDSS coefficients, we synthesize modulated sinusoidal and linear chirps. We show that the chirp signals with low ripples in the frequency domain result in a lower bit-error ratio (BER) due to the less noise enhancement during the single-tap frequency-domain equalization (FDE). Numerical results indicate that the signal-to-noise ratio (SNR) degradation can be as high as 4 dB for sinusoidal chirps while it is approximately 0.5 dB for linear chirps as compared to DFT-s-OFDM without FDSS. The proposed scheme offers a way to efficiently generate chirp signals that can be used in Internet-of-Things (IoT) or radar applications with existing DFT-s-OFDM transceivers.
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