INVESTIGATION OF THE INFLUENCE OF DOPPLER EFFECT ON THE OPERATION OF THE LORAWAN SATELLITE SYSTEM

Анотація

The application of low-Earth-orbit satellite systems for the provision of Internet of Things services in sensor networks is considered. The prospects of using LoRaWAN technology in satellite low-Earth-orbit Internet systems are shown. The model developed by the authors for the analysis of the influence of the Doppler effect on the functioning of the LoRaWAN protocol is described. The consequences of the negative effect of the Doppler effect on the transmission of information in the LoRaWAN system by LoRa modulation are shown. The dependence of the error in determining the information symbol on the magnitude of the frequency shift due to the influence of the Doppler effect is determined. A method of compensating for the effect of the Doppler effect in a satellite low- orbit system using the LoRaWAN protocol is proposed. It is shown that the structure of the physical layer frame of the LoRaWAN protocol transmitted in the uplink makes it possible to measure the frequency shift caused by the Doppler effect and adjust the receiving path of the LoRaWAN network gateway on board the satellite to this shift to avoid distortion. processing in the receiver-demodulator LoRa. It is proposed to use a predictive frequency offset of the signal transmitted on the downlink to compensate for the current value of the frequency offset. The proposed method allows not to complicate the receiving equipment of the Internet of Things terminal - the final node of the LoRaWAN network.