Research On Sub-GHz Unlicensed Band Multiple Access Technology

With the development of the communication technology,Sub-GHz which only has narrow band is unsuited to high-speed mobile communication.But in Internet of Things(Io T)field,Sub-GHz gains attentions.The requirements of Io T are wide coverage,massive connection,low power consumption,low cost,etc.The transmission rate requirement is not strict.Sub-GHz has low pathloss and results in long spread distance.Thus it is an ideal band for many Io T technologies.LoRa as a promising technology working in this spectrum is studied.First,the physical layer of LoRa is studied.the symbol of LoRa is made of chirp signal.The characteristics of the Chirp signal are analyzed.With mathematical representation of the LoRa modulation,the performance of LoRa in AWGN and Multipath is analyzed.Then,the MAC layer of LoRa is studied.Conventional performance analysis,which isolates interference from noise,underestimates the performance of the system.We obtain the performance curves under interference.Basing on joint impact of inference and noise,system performance is analyzed.Performance of terminals at different locations is analyzed.Simulation result shows that the joint analysis of interference and noise is more accurate than the literature where noise and interference are calculated independently.Finally,the SF configuration of LoRa and the multi-gateway situation are studied.By comparing the configuration schemes of different SFs,a relatively superior configuration scheme is obtained.From single gateway to multiple gateways,we model multi-gateway scenario.Multiple gateways diversity can improve transmission performance.The established model can help determine the deployment location and quantity.