Research On Demodulation And Channel Decoding Technology In Satellite Internet Of Things System

With the rapid development of computer technology and network technology,the Internet of things(IoT)has become an important technology,which has attracted the attention of researchers.However,the IoT technology is difficult to deploy in a wide range,across regions and under harsh environment.Because the current Wireless LAN communication technology is widely used in the IoT,and the commonly used wireless communication technology is difficult to communicate in a wide range and across regions.In addition,wireless communications are susceptible to strong interference.In order to solve these problems,IoT system is constructed based on satellite communication technology.This paper focuses on the research of Satellite IoT and achieves the following results.(1)To solve the problem that there is no universal design model of Satellite IoT,a satellite IoT model based on cloud computing system is designed.An intelligent frequency selection algorithm for Satellite IoT is designed.The source of communication interference in Satellite IoT is analyzed,and an anti-jamming plan is given,and the resource allocation algorithm in Satellite IoT is designed.(2)In view of the high bit error rate of Satellite IoT,differential modulation and dual differential modulation and demodulation in Satellite IoT are proposed.The simulation results show that the dual differential modulation data transmission method is used on satellite communication,which can effectively reduce the influence of Doppler frequency offset.(3)In order to further reduce the bit error rate,a coding and decoding method based on BCH and convolutional codes is proposed.The hardware circuit,convolutional code decoding circuit and two decoding cascade circuits are realized.Convolutional decoding algorithm guarantees the decoding rate and reduces the occupation of hardware resources by means of string combination and decoding.Simulation shows that the channel coding can effectively reduce the bit error rate.The ground terminal system is designed,and the modem and channel encoder are designed and implemented on the system.In order to test the performance of the ground terminal system,a hardware test platform is built.The test results show that the designed system can meet the expected functions.