Long-range (LoRa) communication has attracted much attention recently
due to its application for many Internet of Things applications.
However, one of the key problems of the LoRa technology is it is
vulnerable to noise/interference due to the use of only up-chirp signals
during modulation. In this paper, to solve this problem, unlike the
conventional LoRa modulation scheme, we propose a modulation scheme for
LoRa communication based on joint up- and down-chirps. A fast Fourier
transform (FFT) based demodulation scheme is devised to detect modulated
symbols. To further improve demodulation performance, a hybrid
demodulation scheme, comprised of FFT and correlation-based demodulation
is also proposed. The performance of the proposed scheme is evaluated
through extensive simulation results. Compared to the conventional LoRa
modulation scheme, we show that the proposed scheme exhibits over 3 dB
performance gain at bit error rate of 10^-4.