Research And Implementation Of Large Capacity Internet Of Things Gateway Technology

Recently,with the fast evolution of IoT technology and the increment of peoples demand for large-area interconnection,LPWAN technology has been broadly concerned.Among LPWAN technologies,LoRa technology is widely adopted because of its outstanding anti-interference ability,sensitivity and flexibility.LoRa is essentially a physical layer technology.The LoRa WAN,which is a pure Aloha-based access mechanism,is a widely used MAC layer standard based on LoRa.There is a high conflict rate,low channel utilization when terminals transmit a large amount of data,resulting in limited IoT capacity.In view of these problems,this article researches how to relieve the conflict and enlarge network capacity based on LoRa technology and aims to propose a MAC protocol and design a gateway that supports 10 parallel receiving channels.The efforts and outcomes of this article are shown primarily as follows:1.This thesis discusses the postulate of LoRa technology in depth,and investigates the rules of LoRa modeming from the formula,analyzes and simulates the modem performance of LoRa with different parameters,studies the demodulation characteristics of LoRa in the case of conflict,and discusses the data format and configuration mode on LoRa chip.2.This thesis analyzes the principle of the classic MAC layer anti-collision protocol,aiming at the conflict problem in the scene of large-scale Internet of things terminal access,combined with the characteristics of Lora technology and the requirements of application scenarios,designed an improved DFSA protocol.The gateway can reduce the conflict probability of the terminal by reasonably scheduling the slot resources to achieve efficient access and ensure the reliable transmission of terminal information by reply and retransmission mechanism.The system efficiency,access rate,access delay of the proposed method are emulated.The consequences show that the mentioned qualifications are reached.Rivaled with other algorithms,the method this article invented has advantages in system efficiency,access probability and so on.3.The new generation of LoRa gateway chip SX1302 and terminal chip SX1262 are used to design the hardware platform of the gateway.The SX1302 provides nine uplink channels,and SX1262 supplements the uplink channels and realizes the channel monitoring function.In terms of software,the functions of the gateway are divided into two basic tasks: AT command parsing and protocol state machine.The Free RTOS is used to manage each task,which has the characteristics of strong real-time performance.4.A full experiment of the gateway reveals that the strongest RF power of the gateway can reach 30 d Bm.In the case of distance transmission,the gateway and terminal can communicate reliably at a distance of 3km.According to the test results,the gateway and terminal can communicate at the maximum distance of 90 km.In the case of 30 IoT terminals for networking testing,the consequences denote that the gateway can run firmly and durably without losing packets.The gateway designed in this thesis has the characteristics of strong anti-conflict ability,the capability of accommodating a large number of terminals,simple configuration and so on.It can meet the needs of large capacity scenarios and has great practical value in the wide-area coverage and the need to deploy a large number of sensor terminals.