Research On LoRa System Based On LEO Satellite Internet Of Things

LoRa(Long Range)is widely used in the ground Internet of Things because of its low power consumption and long transmission distance.The LEO satellite Internet of Things is the extension and development of the ground Internet of Things.So,it has far-reaching significance for the development of communication mechanism under the LEO satellite Internet of Things to explore whether LoRa technology can be applied in the LEO satellite Internet of Things scenario,and study how to combine the LoRa technology with the LEO satellite Internet of Things scenario.This paper mainly studies the LoRa system based on LEO satellite Internet of Things.After confirming that LoRa meets the throughput performance requirements of LEO satellite Internet of Things,combining with the characteristics of LEO satellite Internet of Things,the paper analyses the inadaptability of LoRa protocol and provides the corresponding solutions,and modifies the frame format according to the transmission process of LoRa-based LEO satellite Internet of ThingsFirstly,the existing LoRa protocols are deeply studied,including LoRa network architecture,frame format,working mode,terminal secure communication,available frequency band and so on,which provides basis and material for LoRa adaptability analysis and modification.Secondly,this paper analyses whether LoRa modulation technology can be applied to LEO satellite Internet of Things scenarios.First,the paper studies whether LoRa can meet the throughput requirements of LEO satellite Internet of Things scenario.Then the effects of different carrier frequencies,power and modulation factors on the system performance are analyzed.Finally,the performance of LoRa modulation is compared with BPSK and QPSK modulation.The results show that LoRa modulation can be applied to LEO satellite Internet of Things scenario.Furthermore,the adaptability of LoRa protocol is analyzed according to the characteristics of LEO satellite Internet of Things system including LoRa network architecture,working mode,access mechanism and frequency band,and the mode of work.Among three kinds of working modes of LoRa,Class B mode is more suitable for the current scenario.The synchronous addressing,ping random monitoring,unicast and multicast of Class B mode are deeply analyzed,and the suggestions of adaptability improvement are given.What's more,LoRa's ALOHA access mechanism is simulated.It is pointed out that under the influence of adaptive rate,duty cycle,number of receiving paths and demodulation threshold,packet collision will be significantly improved.At last,some adaptable modifications of LoRa system are made based on the LEO satellite Internet of Things.The network architecture of LoRa in the scenario of LEO satellite Internet of Things is designed.And the adaptability of LoRa's Class B working mode,retransmitting mechanism and access mechanism is improved.What's more,the transmission process of LEO satellite Internet of Things based on LoRa is designed according to synchronization,resource allocation and power consumption.and the frame format is modified.