Research On Multiple Access Technology Of Low Power Wide Area Network

Low Power Wide Area Network(LPWAN),as a wireless communication technology,provides a broad application foundation for the Internet of Things.Based on the premise of low power consumption,low cost and low throughput,it can provides massive access to Internet of Things end devices.It can be seen that LPWAN is suitable for the scenarios that need massive connectivity to low-power end devices,such as smart grid,smart city,environmental monitoring and other applications.This type of applications occupy a large proportion in the Internet of Things market.As LoRa is one of the LPWAN technologies that attract the most attention from researchers,this thesis considers to conduct a research on it.Firstly,this thesis discusses the related concepts and properties of the LoRa physical layer and MAC layer.In the physical layer,the LoRa symbol and its properties are mainly studied,and the modulation and demodulation process of LoRa is discussed.In the MAC layer,the structure of the LoRa network and the functions of each component are studied.In addition,the frame structure of LoRa is analyzed in detail.Secondly,this thesis studies the BER performance of LoRa signal in AWGN channel,and studies the influence of other LoRa interference signals on LoRa modulation performance.This thesis derives the expression of the symbol error rate of LoRa modulation through appropriate approximation depending on whether the spreading factor(SF)of the transmission signal is the same as the SF of the interference signal.And how different parameters,such as SIR,SF,etc,influence the SER performance of LoRa modulation are analyzed.Finally,this thesis studies the overall performance of the LoRa network.Based on the MAC layer,the throughput expression and the packet transmission success rate of the LoRa network are derived.After that,the system model and channel model of the LoRa network are established,and the overall performance of the LoRa network was simulated at the system level.Although the signals with different LoRa SFs are approximately orthogonal,the simulation results show that the interference signals with different SFs have a significant impact on the performance of the LoRa network.In addition,this thesisa also studies how the parameters configuration in the LoRa network,such as power control and SF allocation strategies,affects the performance of the LoRa system.