Research On The Reliability Of The LTE-M System And Its Test And Analysis Of The Integrated Service Carrying Capacity

WLAN technology works in the open frequency band which makes it susceptible to external interference,it can not meet the growing service requirements of urban rail transit in China.LTE-M has become a development direction of urban rail transit train-ground communication technology due to its significant anti-interference ability and high transmission rate.Firstly,the LTE operation modes,wireless frame structures,key technologies and LTE-M system network architecture are described,and different coverage modes of LTE-M system access network are studied.On this basis,the availability of different coverage systems is calculated by using fault tree analysis method,which shows the system have high reliability.The fault tree models of systems are transformed into Petri net models,and the minimum cut sets are solved by using the incidence matrix method.Then the causes of system failure are analyzed,and measures to improve system reliability are formulated.Then,various services and their transmission rate requirements and performance indicators are described,and LTE-M system networking scheme is given.The coverage of the cell is analyzed,the theoretical peak rate of the uplink and downlink of the TD-LTE physical layer is calculated,interference factors of this system are analyzed,and the corresponding anti-interference measures are given.Finally,relying on the Qingdao Metro Line 2 project,the LTE-M system test platform is built to study this system's the integrated service carrying capacity.The system performance test is used to obtain the uplink and downlink throughput of each bandwidth,and combined with the service transmission rate requirement,the service carrying capacity of each bandwidth can be estimated.On this basis,LTE-M system's single-service and integrated service carrying test schemes are given,and this system test is carried out.The system wireless network coverage performance test shows that the minimum value of RSRP is-94 dBm,which meets the requirements of RSRP not less than-95 dBm of System requirement specification for LTE-M.Through the single service test of this system,the capacity of this system to carry CBTC,PIS and CCTV services under various bandwidth is obtained.On this basis,the integrated service carrying capacity of the 5MHz/10MHz/15MHz/20 MHz bandwidth of this system is tested and analyzed.The research results of this paper can provide theoretical support for the design and planning of urban rail transit communication system,and have good application value.