Research On The Architecture Of Distributed Multi-GNSS Signal Acquisition And Analysis Platform

With the development and maturity of satellite navigation industry,the technology of inversion of ionospheric plasma temperature and density by using navigation signals received from the ground is becoming more and more mature,and the multi-mode and multi-frequency receiver has become a research hotspot.The data transmission processing of muti-mode and muti-frequency navigation needs to solve the problems of wide frequency band,high sampling rate and high transmission rate.This thesis studies the architecture of distributed multi-GNSS signal acquisition and analysis platform to complete its architecture design.The object is to invert the ionospheric TEC based on the distributed network composed of multi-mode and multi-frequency receivers,and to use the distributed detection technology and information fusion technology to detect space flying objects,obtain space meteorological information and abnormal astronomical phenomenon information.Compared with the IGS platform,the platform can receive satellite signals of the Global Navigation System,complete the platform objectives through the information of the visible satellites,improve the accuracy of the ionospheric model on the premise of big data,and realize the detection of space flying objects and other information.In this thesis,the top-level design technology commonly used in engineering is selected to realize the design of the platform architecture.The research content of this thesis is roughly divided into the following questions:(1)This thesis performs demand analysis for the distributed multi-GNSS signal acquisition and analysis platform.This thesis analyzes the problems to be solved in the multi-mode multi-frequency data processing module.That is the conversion of multi-system time benchmarks,the conversion of multi-system coordinate reference and the rapid selection of multi-system stars.And sum up the algorithms to solve these problems.The datum station of the platform adopts distributed network to collect data,and the distributed network is timed and unified by BDS.Analyze the platform's environment,context and metrics.In this thesis,the general flow of multi-mode multi-frequency receiver and ground double frequency ionospheric inversion are analysed.In this thesis,the specific implementation module of the platform is obtained by using the requirement analysis method based on objectives in the requirement analysis stage.IDEF requirement description method is proposed in requirement analysis description and verification stage.The task triggering process of GNSS data signal acquisition platform is described by IDEF0.The static characteristic model of GNSS data signal acquisition platform is described by IDEF1.IDEF3 describes the process flow and object state transition process of the whole platform.(2)This thesis designs the architecture of the distributed multi-GNSS signal acquisition and analysis platform.A data-centric activity-based architecture design approach are adopted.This article,details the steps in turn,including analyzing the scope and purpose of the platform architecture,identifying the data required for architectural development,determining the association of data,and documenting the results using the various views provided by Do DAF 2.0 that are consistent with the data metadata specification.This thesis analyzes the data transmission network of the platform and clarifies the key points of base station site selection.At the same time,the data flow graph and the uniform format of the data flow are analyzed.In this thesis,the frequency points of four systems received by the platform are analyzed,and the frequency points that the multi-mode multi-frequency receiver needs to receive and process are defined through the functions of each frequency point.The data transmission rate of each frequency point are calculated.In the phase of data association,the data transmission rate of each frequency point is analyzed to determine the transmission mode and protocol of the reference station and data center.Specific indicators of cloud storage storage mode are clarified.In this thesis,views are used to express platform nodes,information exchange matrix,organizational relationship and activity model.(3)This thesis carries out information resource planning for the distributed multi-GNSS signal acquisition and analysis platform.EA planning is adopted as the resource planning method of the platform.The requirements analysis stage is divided into two parts: functional requirements analysis and data requirements analysis.In the functional requirements analysis part,the functional domain model,business process model and the three-layer decomposition structure of "functional domain-business process-business activity" are established.In the data demand analysis part,the data flow diagram based on specific functional domain is established.In the system modeling stage,functional modeling,data modeling and overall modeling are realized.In the functional modeling part,the model and scheme design of data and control center are realized through public cloud and self-built data centers.(4)By comparing the three structures of SDR,direct sampling and low IF sampling are set up by Simulink for simulation.Direct sampling has higher requirements on AD sampling device,and the signal is easy to distort,while low IF sampling is easy to generate mirror signal.At the same time,the dynamic range and sensitivity parameters of the RF front end of the zero IF structure are calculated as reference values.