Fine Frequency Offset Synchronization Scheme for Internet of Things Devices in 5G non-terrestrial network

In this paper, we propose a center frequency offset (CFO) estimation and correction algorithm for chirp-spread spectrum (CSS) modulated LoRa waveform in a non-terrestrial network (NTN). However, the frequency of the terrestrial LoRa compensates for signal bandwidth in reciprocal units of a symbol duration, which is coarse and therefore cannot effectively compensate for random frequency offset by the Doppler shift. Furthermore, to realize satellite IoT, a link budget must be achieved using large spreading factors, which are more problematic in satellite IoT because LoRa has the property of being sensitive to frequency offset as the spreading factor increases. To overcome this problem, we propose a fine frequency offset synchronization scheme using FFT. Computer simulation results show that our proposed algorithm works well in the Shadowed Rician fading channel.