Design Of DSP Software For Indoor GNSS Enhancement Positioning

With the continuous development of information technology and Internet of Things technology,the application scenarios of navigation and positioning technology are also expanding,not only limited to outdoor positioning.As people spend most of their time indoors,the demand for indoor positioning is getting higher and higher.Since users can't receive outdoor real satellite navigation signals indoors,this paper is based on GNSS indoor positioning enhancement technology,focusing on the software architecture of the DSP and the IF signal algorithm.The main work of this paper is as follows:1.The hardware platform of pseudo-satellite indoor positioning system is built,which is composed of host computer,DSP,FPGA,DAC,RF devices and antennas.Among them,the host computer is used to store DSP and FPGA binary code files and ephemeris,almanac data,DSP and FPGA are used to generate IF signals.DAC,RF devices and antennas constitute pseudo-satellite modules for signal broadcasting.The scheme of data interaction between the host computer and DSP is designed.Connect to DSP through the PCIe,the fast interaction between them is realized.SRIO is used to connect with FPGA,and DSP responds to FPGA to receive doorbell interrupt continuously,which realizes the real-time update of FPGA data.2.Adopt multi-core DSP architecture.The software is designed with SYS/BIOS.The software interrupt module is used to notify the host computer whether the data transmission is successful.The hardware interrupt module is configured to manage the interrupt system between the DSP and the FPGA to complete the trigger according to a certain priority.The task thread module is introduced to create multiple tasks,which are used to generate navigation messages,the calculation of initial parameters and update parameters of IF signal.Many tasks are scheduled orderly by the semaphore module.3.The constellation layout of the indoor positioning system and the signal algorithm of DSP are studied.The error between the pseudo range and the real pseudo range measured by receiving terminal is corrected with using the optimized satellite constellation.The signal data of pseudo-satellite is processed in the DSP.The configuration information of the pseudo-satellite is read from the user scene file.The navigation message is generated and stored through the RINEX file and the almanac data.The satellite position is calculated and the judgment of the satellite visibility is completed.An iterative algorithm is used to achieve accurate calculation of propagation delay.Finally,a mathematical model between the transmission delay and the Doppler frequency shift is established,and the calculation of initial parameters and control parameters is completed.4.The indoor positioning system of pseudo-satellite is tested and analyzed by using hardware receiver and PCIe driver testing software,including the test of each module,the performance of a single satellite,and the positioning effect of the whole system.The feasibility of the system is verified.