Multi-service Coexistence Analysis And Interference Avoidance Study In The 1.8 GHz Band Of The Radio Spectrum

In the context of the lack of global radio spectrum resources,China's Ministry of Industry and Information Technology re-released the regulations for the use of the 1785 to1805 MHz band in 2015,and officially launched the pilot work on November 27,2017.It is determined that the use of Time Division Long Term Evolution(TD-LTE)system construction in this frequency band can provide special safe and reliable security services for emergency communications,command and dispatch,etc.for government and public security departments.Dedicated wireless communication network.However,in the same area,there are still some other wireless systems adjacent to the frequency band or even in the same frequency band.The simultaneous existence and development of these systems will inevitably cause mutual interference between systems and reduce the performance of the system.How to reduce the interference between the TD-LTE system and other systems in this frequency band and improve the use efficiency of the wireless private network is particularly important.This paper mainly focuses on the TD-LTE system in the 1.8 GHz band and the International Mobile Telecommunications(IMT)and Multi-Carrier Wireless Information Local Loop(McWiLL),which are based on the same or adjacent frequency.The communication between the Communication Based Train Control System(CBTC)and the Frequency Division Duplexing(LTE FDD)is analyzed and researched,and the corresponding interference avoidance suggestions are proposed.Engineering practice provides a reference.First of all,the paper introduces the background knowledge of LTE,from the global LTE spectrum allocation to the outdoor macro base station frequency usage scheme.Then,the LTE system will be introduced from the main technical characteristics of the LTE system,the LTE network architecture,the LTE physical layer overview,and the key technologies of LTE.Secondly,the LTE inter-system interference is theoretically analyzed,and the causes and types of interference,key indicators of inter-system interference,interference scenarios,inter-system interference avoidance criteria and isolation measures are clarified,and three types of system interference are introduced.The analysis methods of deterministic calculation,simulation and live network test are introduced respectively.The first two methods are used to analyze the inter-system interference analysis.Then,the deterministic calculation method is used to analyze the interference coexistence between the 1.8GHz band TD-LTE system and the IMT system,the McWiLL system and the CBTC system,and the corresponding measures to avoid interference are given.Introduce the use of the 1.8 GHz band,analyze the various types of systems that may have interference,and query the 3rd Generation Partnership Project(3GPP)to isolate the spurious interference analysis and blocking interference analysis.The degree calculation formula calculates the corresponding isolation requirement that satisfies the coexistence,and then converts it into a specific isolation distance by the formula.Focus on analyzing the data,and propose interference isolation measures such as adding filters,performing spatial isolationand frequency isolation for different system requirements,so as to meet the requirements of coexistence between systems.Finally,for the two-duplex mode of TDD and FDD supported by LTE system,the Monte Carlo simulation method is used to analyze the interference coexistence between the two systems,and the corresponding simulations are proposed for the interference avoidance measures.The interference scenarios of the two systems of TD-LTE and LTE FDD are analyzed,and the interference between the base stations is obtained as the main interference.The static Monte Carlo model is established and related parameters are set,and the simulation is performed to obtain the corresponding simulation map.Focusing on the simulation results,it is concluded that the interference of the TD-LTE system to the LTE FDD system is mainly downlink interference,and the interference in the urban environment is more serious than in the rural environment;the isolation required by the two systems co-location is less than that of the interfered base station.The cell edge of the system;the TD-LTE system with 10 MHz bandwidth has stronger interference to the 5MHz bandwidth LTE FDD system,and the beamforming technology and the inter-cell interference coordination mechanism significantly reduce the inter-system interference.