Electromagnetic Compatibility Analysis Of Low Power Wide Area Internet Of Things Access Technologies In Key Frequency Bands

With the advent of the inter-connection of all things,the devices of Internet of things have growth explosively,and various Internet of things access technologies have continuously emerged.To meet the need of the long-range transmission of the Internet of things,LPWAN(Low-Power Wide Area Network)access technologies which are characterized by high coverage,low power consumption,wide-area connectivity were generated.LPWAN include LoRa(Long-Range),Sigfox and other spectrum-free access technologies and cellular access technologies based on authorized spectrum,such as NB-IoT(Narrow Band Internet of Things),e MTC(enhanced Machine-Type Communication)and so on.Among them,LoRa and NB-IoT systems were first implementation for commercial usage in China.The main candidate bands of the LoRa system are the 470-510 MHz and the 920-925 MHz.When deploying the LoRa system in the above frequency bands,it is necessary to avoid interference with other systems in the same and adjacent frequency bands.Therefore,we should carry out the electromagnetic compatibility research between the LoRa system and the related business systems in the above frequency bands.Operators can directly deploy NB-IoT systems on their assigned FDD(frequency division duplex)mode in IMT system bands,which may interfere with other business systems in adjacent bands.With the largescale commercialization of NB-IoT systems,it is urgent to carry out research on the interference coexistence between NB-IoT systems and related business systems.The electromagnetic compatibility between LoRa system,NB-IoT system and related business systems were carried out in this paper.Firstly,the equivalent interference model between LoRa system and terrestrial television broadcasting system is proposed to solve the interference problem in the 470-510 MHz frequency bands.the interference degrees under different isolation distances were analyzed,and whether the two systems can be deployed at the same frequency was evaluated,and the feasibility analysis of deploying LoRa system in the frequency band was given.Then,aiming at the electromagnetic compatibility problem between LoRa system and RFID(radio frequency identification)system in the 920-925 MHz frequency bands,the mutual interference between LoRa system and RFID system was analyzed by deterministic calculation method,and the feasibility and interference avoidance measures of deploying LoRa system in this frequency band were given.Finally,for the coexistence problem between NB-IoT system in 1800 MHz and TDLTE(long term evolution)system in 1900 MHz,an interference equivalent model was proposed to analyze the degree of interference of the emission index of the jamming system to the disturbed system.we evaluated the frequency interval of the two systems which can coexist with the adjacent frequency by using the experimental method and provides a theoretical basis for the deployment of NB-IoT systems in this paper.