CN114095072B - Pseudo satellite positioning signal processing analysis simulation platform and simulation method - Google Patents
Pseudo satellite positioning signal processing analysis simulation platform and simulation method Download PDFInfo
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Abstract
The invention provides a pseudolite positioning signal processing analysis simulation platform and a simulation method, wherein the platform comprises a pseudolite signal generation unit, a wireless channel simulation unit, a receiver baseband signal processing unit, a positioning resolving unit, a pseudolite signal comprehensive analysis unit, and an external software transmitter, a spatial environment model, a software receiver and a receiver; the positioning accuracy of the method is determined according to the density of the acquisition points of the observed quantity characteristic fingerprint library, and the method can realize quick and efficient positioning in an indoor environment. The invention provides a complete signal processing flow frame for the research of a pseudo satellite positioning system, realizes the functions of optimizing multipath algorithm parameters and verifying multipath resistance effects in the baseband signal processing process, and provides a platform foundation for the research of debugging the baseband signal processing process of a pseudo satellite receiver, testing and analyzing a multipath signal suppression method, verifying simulation of a software radio algorithm and the like.
Description
Technical Field
The invention relates to a pseudo satellite positioning signal processing analysis simulation platform and a simulation method, and belongs to the technical field of radio navigation positioning.
Background
The global satellite navigation system is a network covering the world, provides navigation, positioning and time service without intermittence and regional difference for users, and provides an additional signal emission source for pseudolites, so that the coverage area of satellites can be increased, the constellation matching of the navigation satellite system is improved, the fault of the navigation satellites can be dealt with or the geometric structure defect of the system can be made up, and better navigation service can be provided for users. However, for pseudolite signal test analysis, a more convenient and comprehensive analysis method does not exist at present. The actual pseudo satellite positioning environment is expensive to build, and the signal processing process of the transmitter and the receiver is inconvenient to change, so that the method is not beneficial to test and analysis; the simulation of pseudolite signals by using the conventional GNSS signal simulator has certain limitations, the signal system of the pseudolite cannot be changed at will, and the effect of the indoor complex environment on the signals cannot be effectively reflected. Therefore, a need exists for a test analysis platform and method specific to pseudolite signal transceiver systems for improving pseudolite signal processing flow and positioning algorithms.
Disclosure of Invention
Technical problems: the invention provides a simulation platform and a simulation method for pseudolite positioning signal processing analysis, aiming at solving the problem of inconvenient pseudolite signal processing analysis and test. The simulation platform provided by the invention can simulate the signal processing flow of the whole pseudolite receiving and transmitting system, analyze the processes of pseudolite signal generation, wireless signal modeling, intermediate frequency signal analysis, capturing process analysis, tracking process analysis, PVT resolving effect analysis and the like, evaluate the influence of multipath signals in space environment modeling on the signal processing flow of a pseudolite receiver, and test the effects of multipath suppression algorithms of different baseband signals.
The technical scheme is as follows: the method for solving the technical problems is realized by the following technical scheme:
the invention relates to a pseudolite positioning signal processing analysis simulation platform, which comprises a pseudolite signal generating unit, a wireless channel simulation unit, a receiver baseband signal processing unit, a positioning resolving unit, a pseudolite signal comprehensive analysis unit, and an external software transmitter, a spatial environment model, a software receiver and a receiver;
the pseudo satellite signal generating unit is used for simulating and generating pseudo satellite signals, simulating and simulating the pseudo satellite signals according to set pseudo satellite signal parameters, generating a sampling data stream of standard pseudo satellite signals, and storing the sampling data stream as a standard signal data file;
the wireless channel simulation unit is used for simulating a pseudolite signal space propagation model and multipath effect, setting simulation parameters by a space environment model, inputting a standard signal data file generated by the pseudolite signal generation unit, outputting a simulation signal data stream and storing the simulation signal data stream as a simulation signal data file;
the receiver baseband signal processing unit is used for processing intermediate frequency signals of pseudolites and realizing the capturing and tracking processes of the pseudolites, and the intermediate frequency signals processed by the unit are simulation signal data files output by the wireless channel simulation unit or intermediate frequency signal sampling data files acquired by a software receiver;
the positioning resolving unit is used for realizing PVT resolving function of the receiver, and is used for performing positioning resolving performance on pseudo satellite simulation data or actual measurement data, inputting original observed quantity data actually measured by the receiver baseband signal processing unit or the receiver, and outputting a receiver positioning result and an error analysis result;
the pseudolite signal comprehensive analysis unit is used for analyzing intermediate data generated by pseudolite signal processing and simulation;
the space environment model is a model established according to the environment needing to be simulated, parameters of pseudolite signals propagating in space are given through the model, including noise, distortion, experiments and fading added by the given pseudolite signals propagating in space, the parameters are input into the wireless signal simulation unit, and standard signals are processed to generate simulation signals;
the pseudolite software transmitter up-converts the pseudolite standard signal sampling data stream generated by the pseudolite signal generating unit and then transmits the data stream through the TX transmitting antenna;
the software receiver is a pseudolite signal intermediate frequency signal collector formed by software radio equipment and is used for carrying out down-conversion on a pseudolite radio frequency signal received by an RX receiving antenna, sampling the pseudolite radio frequency signal into pseudolite intermediate frequency sampling data, and then inputting the pseudolite intermediate frequency sampling data into the receiver baseband signal processing unit for processing;
the receiver is a common hardware receiver, and is used for receiving pseudolite signals and outputting original observed quantity data in RINEX format.
Further, the pseudo satellite signal generating unit comprises a pseudo random code generating module, a navigation message generating module, an intermediate frequency carrier generating module, a spread spectrum module and a modulating module.
Further, the wireless channel simulation unit comprises a channel model module, a radio frequency signal propagation attenuation module, a signal delay module and a signal superposition module.
Further, the receiver baseband signal processing unit comprises an intermediate frequency signal preprocessing module, a capturing module, a tracking module and an observed quantity measuring module.
Further, the pseudolite signal comprehensive analysis unit consists of a signal system performance analysis module, a space signal propagation analysis module, a baseband signal processing analysis module and a positioning algorithm effect analysis software; the signal system performance analysis module is used for processing and inputting standard signal data generated by the pseudolite signal generation unit, carrying out pseudolite signal system performance analysis and improving pseudolite signals; the space signal propagation analysis module inputs simulation signals and space environment model parameters generated by the wireless channel simulation unit, performs space signal propagation effect analysis and is used for researching a propagation mechanism and an error generation model of the wireless positioning signals; the baseband signal processing analysis module inputs the process data and the generated observed quantity data of the receiver baseband signal processing unit to carry out baseband signal processing analysis and is used for improving the capturing and tracking algorithm of the pseudolite receiver; and the positioning algorithm effect analysis software inputs the positioning result data of the positioning resolving unit, calculates positioning errors, performs positioning algorithm effect analysis, and is used for improving a pseudolite positioning algorithm.
The invention also provides a method for simulating the pseudo satellite positioning signals by using the pseudo satellite positioning signal processing analysis simulation platform, which comprises the following steps:
s1: pseudolite signal simulation generation process
Pseudolite signals are formed by modulating ranging codes and navigation messages on carriers, and standard signals of pseudolites p are expressed as s (p) (t) the signal expression is as follows:
s (p) (t)＝A p D p (t)C p (t)cos(2πf c t) (1)
the pseudo satellite signal simulation generating process is realized by a pseudo satellite signal generating unit, in order to reduceThe sampling rate, the pseudolite signal generation unit actually generates it at f IF Intermediate frequency signal of central frequencyThe expression is as follows:
wherein p represents the PRN number of the pseudolite, A represents the amplitude of the pseudolite signal, D (t) is navigation message data, C (t) is ranging code data, and f c For pseudolite signal frequency, f IF The up-conversion frequency relation is as follows:
f c ＝f IF +f Lo (3)
wherein f Lo For the local oscillation frequency of the transmitter, f c For pseudolite signal frequency, f IF Is the frequency of the intermediate frequency signal;
in the actual simulation process, the simulation data of the pseudolite standard signal generated by the pseudolite signal generating unit is the discrete sampling signal x (p) [k]The relation is as follows:
wherein p represents the pseudolite PRN number, the simulated discrete sampled signal x [ k ]]The intermediate frequency signal is s IF (t)，f IF Is the frequency of the intermediate frequency signal, T s Representing sampling time, k being a sampling point;
s2: wireless channel simulation process
In the process of wireless signal transmission, a wireless channel model is established according to a transmission mechanism from a transmitting antenna TXP to a receiving antenna RXr; the wireless channel model is expressed by h (t), and the factors affecting h (t) are set parameters W, and mainly comprise signal delay tau, amplitude attenuation coefficient alpha and path power loss value L p The phase delay θ and other parameters are expressed as W= { τ, α, L p ,θ,…}；
Simulating the pseudo satellite standard signal S obtained in the step S1 (p) (t) obtaining an output simulation signal through a wireless channel system model h (t)
Wherein h (t) represents a wireless channel model, and for the simulation of a time-invariant system, the parameters are set to be constant values, which are called constant parameter channels; for time-varying system simulation, the time-varying relation of each parameter in the system needs to be found out, which is called a parameter-dependent channel;
the signal received by the receiver at a certain point should be the superposition of the signals simulated above, i.e
Wherein s is R (t) represents the simulation signal of the receiving antenna at the R point, S represents the number of pseudolites,representing the simulation signal;
s3: receiver baseband signal processing
By pseudolite receiving antenna RX r The received pseudolite p signal is expressed as
The simulated discrete data are:
in the formulas (7) and (8), r is the number of the receiver, p is the number of the pseudolite PRN, j is the imaginary unit, A (t) is the function of the amplitude of the pseudolite signal with time,represents the filtered receiver signal, τ (t) represents the time delay function, f D (t) denotes a Doppler shift function, phi (t) denotes a phase shift function, and n (t) denotes a noise function; x is x R [k]Representing receiver discrete data, T s Representing sampling time, k being a sampling point;
the capturing and tracking process of the pseudolite signals is mainly completed in the receiver, and the original observed quantity OBS data of the pseudolite are output;
s4: positioning calculation simulation process
Performing pseudolite positioning algorithm calculation by using the pseudolite original observed quantity OBS data obtained in the step S3 to obtain PVT information, wherein the PVT information comprises position, speed and time, and the reliability of an analysis algorithm is evaluated according to positioning errors;
s5: pseudolite signal processing comprehensive analysis process
According to the simulation results of the four steps S1-S4, the quality of a pseudolite communication link is analyzed, the algorithm execution effect of each link in the pseudolite signal processing is evaluated, and the pseudolite signal simulation effect is comprehensively evaluated from four aspects of pseudolite signal system, pseudolite wireless channel propagation, baseband signal processing and PVT positioning calculation.
Further, the wireless channel simulation process in the step S2 performs signal simulation according to different scenes, and specifically includes a free space ideal channel and a multipath channel;
the free space ideal channel simulation process comprises the following steps: establishing a space model, setting the positions of a pseudolite transmitting antenna TX and a receiving antenna RX, and calculating a direct signal propagation parameter set W of each path of pseudolite signals from TX to RX according to the geometric relation 0 Including the amplitude alpha of the direct signal received by the RX 0 Time delay τ 0 Phase delay theta 0 . Obtaining simulation signals according to the simulation parameter setting
Wherein,representing the received signal by RX obtained after passing through the wireless channel W, wherein the direct signal has an amplitude of alpha 0 The direct signal time delay is τ 0 The Doppler frequency shift of the direct signal is f D0 Direct signal phase delay θ 0 J is an imaginary unit.
The multipath channel simulation process comprises the following steps: first, a propagation characteristic parameter set W of a pseudolite wireless signal in a space environment is calculated by a space environment model, wherein the wireless signal characteristic parameters comprise: the number of multipath pieces M, the time delay τ, the attenuation coefficient α, the phase delay θ, and the like of each path of multipath signal, w= { τ, α, θ, M }.
Wherein the number of multipath is M, i represents multipath number, and the time delay of the ith multipath signal is tau i Attenuation coefficient alpha i Doppler shift of f Di Phase delay of theta i 。
Further, in the pseudolite signal simulation generation process, multiple pseudolite standard signals are generated through simulation, then a space environment model is utilized to simulate wireless channels of each standard signal, and finally superimposed pseudolite simulation signals are output and are connected to a receiver for processing.
Further, in the process of processing the baseband signals of the receiver, the multipath pseudolite signal receiver is adopted to simulate the processing flow of the receiver at different receiving points or simulate the data processing process of the array pseudolite signal receiver.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
the invention provides a set of complete signal processing flow frame for the research of a pseudo satellite positioning system, integrates various simulation functions of pseudo satellite signal simulation, receiving and transmitting system simulation, wireless channel simulation, baseband signal processing simulation, positioning algorithm calculation and the like, realizes the functions of multipath algorithm parameter optimization and multipath-resisting effect verification in the baseband signal processing process, and provides a platform foundation for the research of the debugging of the pseudo satellite receiver baseband signal processing process, multipath signal suppression method test analysis, software radio algorithm verification simulation and the like. The simulation platform can simulate the signal processing flow of the whole pseudo satellite receiving and transmitting system through the pseudo satellite positioning signal processing, analyzes the processes of pseudo satellite signal generation, wireless signal modeling, intermediate frequency signal analysis, capturing process analysis, tracking process analysis, PVT resolving effect analysis and the like, evaluates the influence of multipath signals in space environment modeling on the signal processing flow of a pseudo satellite receiver, and tests the effects of multipath suppression algorithms of different baseband signals.
Drawings
FIG. 1 is a block diagram of a pseudolite signal processing analysis simulation platform of the present invention;
FIG. 2 is a schematic diagram of a simulation of a multi-channel pseudolite signal;
fig. 3 is a schematic diagram of an array pseudolite signal receiver.
Detailed Description
The following describes the implementation of the present invention in detail with reference to examples and drawings.
Example 1:
as shown in fig. 1, the simulation platform for processing and analyzing the positioning signals of the pseudolite in this embodiment is composed of five parts, namely a pseudolite signal simulation unit, a wireless channel simulation unit, a receiver baseband signal processing unit, a positioning resolving unit and a pseudolite signal comprehensive analysis unit, and is mainly used for simulating the signal processing process in the whole pseudolite receiving and transmitting system. And an external software transmitter, a space environment model, a software receiver and a receiver are needed.
In a pseudolite signal transceiver system, the pseudolite PRN number p signal may be denoted as s (p) (t) the pseudolite signals transmitted via the transmitting antenna TX areIs received by a receiving antenna after being propagated by a space wireless channel, and the received signal is that
The simulation platform for pseudolite positioning signal processing analysis can be constructed into a software transmitter and a software receiver by utilizing a software radio, can be used for constructing a real pseudolite receiving and transmitting system to verify the pseudolite space signal propagation process, and can also simulate the signal processing flow for simulating and analyzing the pseudolite signal processing effect. The specific implementation mode is as follows:
(1) The pseudolite signal generating unit is mainly used for generating the pseudolite standard signal s in a simulation manner (p) (t), wherein p represents a pseudolite PRN number. The unit mainly comprises a pseudo-random code generation module, a navigation message generation module, an intermediate frequency carrier generation module, a spread spectrum module, a modulation module and other modules, and performs simulation of pseudolite signals according to set pseudolite signal parameters to generate intermediate frequency data of standard pseudolite signalsAnd saved as a standard signal data file. Said pseudolite standard signal data +_>Can be input into a wireless channel simulation unit or can be transmitted to a transmitting antenna TX numbered m through a software transmitter m The actual transmission is performed on the signal, the signal of the actual transmission is expressed as +.>
(2) The wireless channel simulation unit is mainly used for simulating a pseudolite signal space propagation model and multipath effects. According to the space environment model, simulating the generation mechanism of the multipath signals, adding delay and attenuation to the signals, and forming multipath signals formed by superposition of multipath signals. The system mainly comprises a channel model module, a radio frequency signal propagation attenuation module, a signal delay module, a signal superposition module and the like; the unit sets simulation parameters W by a space environment model, and inputs standard signals s generated by the pseudolite signal generating unit (p) (t) outputting a simulation signalAnd saved as a simulated signal data file.
(3) The main function of the receiver baseband signal processing unit is to process the actual received signalOr a simulated pseudolite signal->Data. The unit module realizes the capturing and tracking process of the pseudolite signals, can be used for analyzing the baseband signal processing process of the receiver and is used for verifying an improved multipath resistant algorithm. The system mainly comprises an intermediate frequency signal preprocessing module, a capturing module, a tracking module, an observed quantity measuring module and the like; the intermediate frequency signal processed by the unit can be the simulation signal output by the wireless channel simulation unit>Or the intermediate frequency signal sampling data acquired by the software receiver>The signal received by the receiver antenna is +.>Intermediate frequency signal table acquired via receiverShown as +.>r represents the receiver number;
(4) The positioning resolving unit mainly realizes PVT resolving function of the receiver and is used for performing positioning resolving performance on pseudo satellite simulation data or actual measurement data. The module inputs the observed quantity OBS data stream output by the receiver baseband signal processing unit or the original observed quantity RINEX data measured by the actual receiver, the content of which comprises the pseudo rangeCarrier phase->Doppler shift->A plurality of observables are calculated; and outputting a receiver positioning result and an error analysis result.
(5) The pseudolite signal comprehensive analysis unit is mainly used for analyzing intermediate data generated by pseudolite signal processing and simulation. The unit consists of a signal system performance analysis module, a spatial signal propagation analysis module, a baseband signal processing analysis module and a positioning algorithm effect analysis software. The signal system performance analysis module is mainly used for processing and inputting standard signal data s generated by the pseudolite signal generation unit (p) (t) performing a pseudolite signal regime performance analysis for modifying the pseudolite signal; the spatial signal propagation effect analysis module inputs the simulation signal generated by the wireless channel simulation unitAnd a space environment model parameter W, which is used for carrying out space signal propagation effect analysis and researching a propagation mechanism and an error generation model of the wireless positioning signal; the baseband signal processing and analyzing module inputs the process data of the receiver baseband signal processing unit and the generated OBS observed quantity data to carry out basebandThe signal processing analysis is used for improving a pseudolite receiver capturing and tracking algorithm; and the positioning algorithm effect analysis is used for inputting the positioning result data of the positioning resolving unit, calculating a positioning error, and carrying out positioning algorithm effect analysis for improving a pseudolite positioning algorithm.
The space environment model is a model established according to the environment needing simulation, a parameter set W of noise, distortion, experiment, fading and the like added by the pseudolite signal in space propagation is given through the model, the parameter set W is input into the wireless signal simulation unit, and standard signals are processed to generate simulation signals
The pseudolite software transmitter and the software receiver are both software radio devices. The software transmitter can sample the pseudolite standard signal data stream generated by the pseudolite signal generation unitUp-converting and then transmitting through the TX transmitting antenna; the software receiver refers to a pseudolite signal intermediate frequency signal collector composed of software radio equipment, which mainly receives a pseudolite radio frequency signal +.>Down-converting, sampling to obtain intermediate frequency sampling data of pseudolite, and inputting to the baseband signal processing unit of the receiver for processing.
The receiver is a common hardware receiver, which can receive pseudolite signals and output original observed data in the RINEX format.
The following is a pseudolite signal simulation processing procedure:
s1: pseudolite signal simulation generation process
Pseudolite signals are formed by modulating ranging codes and navigation messages on carriers, and standard signals of pseudolites p are expressed as s (p) (t) its signalThe expression is as follows:
s (p) (t)＝A p D p (t)C p (t)cos(2πf c t) (1)
the pseudolite signal simulation generation process is realized by a pseudolite signal generation unit which actually generates the pseudolite signal in order to reduce the sampling rate IF Intermediate frequency signal of central frequencyThe expression is as follows:
wherein p represents the PRN number of the pseudolite, A represents the amplitude of the pseudolite signal, D (t) is navigation message data, C (t) is ranging code data, and f c For pseudolite signal frequency, f IF The up-conversion frequency relation is as follows:
f c ＝f IF +f Lo (3)
wherein f Lo For the local oscillation frequency of the transmitter, f c For pseudolite signal frequency, f IF Is the frequency of the intermediate frequency signal;
in the actual simulation process, the simulation data of the pseudolite standard signal generated by the pseudolite signal generating unit is the discrete sampling signal x (p) [k]The relation is as follows:
wherein p represents the pseudolite PRN number, the simulated discrete sampled signal x [ k ]]The intermediate frequency signal is s IF (t)，f IF Is the frequency of the intermediate frequency signal, T s Representing sampling time, k being a sampling point;
s2: wireless channel simulation process
In the course of wireless signal transmission, according to the transmission from the transmitting antenna TXP to the receiving antenna RXrThe mechanism is that a wireless channel model is established; the wireless channel model is expressed by h (t), and the factors affecting h (t) are set parameters W, and mainly comprise signal delay tau, amplitude attenuation coefficient alpha and path power loss value L p The phase delay θ and other parameters are expressed as W= { τ, α, L p ,θ,…}；
Simulating the pseudo satellite standard signal S obtained in the step S1 (p) (t) obtaining an output simulation signal through a wireless channel system model h (t)
Wherein h (t) represents a wireless channel model, and for the simulation of a time-invariant system, the parameters are set to be constant values, which are called constant parameter channels; for time-varying system simulation, the time-varying relation of each parameter in the system needs to be found out, which is called a parameter-dependent channel;
the signal received by the receiver at a certain point should be the superposition of the signals simulated above, i.e
Wherein s is R (t) represents the simulation signal of the receiving antenna at the R point, S represents the number of pseudolites,representing the simulation signal;
s3: receiver baseband signal processing
By pseudolite receiving antenna RX r The received pseudolite p signal is expressed as
The simulated discrete data are:
in the formulas (7) and (8), r is the number of the receiver, p is the number of the pseudolite PRN, j is the imaginary unit, A (t) is the function of the amplitude of the pseudolite signal with time,represents the filtered receiver signal, τ (t) represents the time delay function, f D (t) denotes a Doppler shift function, phi (t) denotes a phase shift function, and n (t) denotes a noise function; x is x R [k]Representing receiver discrete data, T s Representing sampling time, k being a sampling point;
the capturing and tracking process of the pseudolite signals is mainly completed in the receiver, and the original observed quantity OBS data of the pseudolite are output;
s4: positioning calculation simulation process
Performing pseudolite positioning algorithm calculation by using the pseudolite original observed quantity OBS data obtained in the step S3 to obtain PVT information, wherein the PVT information comprises position, speed and time, and the reliability of an analysis algorithm is evaluated according to positioning errors;
s5: pseudolite signal processing comprehensive analysis process
According to the simulation results of the four steps S1-S4, the quality of a pseudolite communication link is analyzed, the algorithm execution effect of each link in the pseudolite signal processing is evaluated, and the pseudolite signal simulation effect is comprehensively evaluated from four aspects of pseudolite signal system, pseudolite wireless channel propagation, baseband signal processing and PVT positioning calculation.
An ideal channel, a multipath channel, etc.
Space ideal channel simulation: establishing a space model, setting the positions of a pseudolite transmitting antenna TX and a pseudolite receiving antenna RX, and calculating each path of pseudolite according to the geometric relationshipDirect signal propagation parameter set W for signal from TX to RX 0 Including the amplitude alpha of the direct signal received by the RX 0 Time delay τ 0 Phase delay theta 0 . Obtaining simulation signals according to the simulation parameter setting
Multipath channel simulation: first, a propagation characteristic parameter set W of a pseudolite wireless signal in a space environment is calculated by a space environment model, wherein the wireless signal characteristic parameters comprise: the number of multipath pieces M, the time delay τ, the attenuation coefficient α, the phase delay θ, and the like of each path of multipath signal, w= { τ, α, θ, M }.
Wherein p represents the PRN number of the pseudolite, and the simulation signal output after multipath channel simulation iss (p) (t) is an input standard pseudo satellite signal, j is an imaginary unit, the multipath number is M, i represents the multipath number, and the time delay of the ith multipath signal is tau i Attenuation coefficient alpha i Doppler shift of f Di Phase delay of theta i 。
Example 2: construction of indoor Wireless channel system model by utilizing Wireless Insite software
The Wireless suite is a set of simulation software which uses a Ray tracking model (Ray tracking) algorithm and can be applied to analyze the working characteristics of radio wave transmission and Wireless communication systems on individual sites, and can perform electromagnetic wave transmission paths and communication systems in complex large geographic areas, urban areas, or relatively small indoor environments, or environments with mixed conditionsSimulation and prediction of the operating characteristics of each channel. The invention can carry out indoor Wireless channel simulation modeling of pseudo-satellite signals by means of the Wireless institute software, and establishes an indoor Wireless channel h (t) by utilizing parameters such as time delay, phase shift, doppler, power loss and the like of each path of signals in an indoor space environment model output by the Wireless institute software and combining with a construction function of an indoor Wireless channel system model in the step S2 of a pseudo-satellite positioning signal processing analysis simulation method. Then pseudo satellite signal simulation is carried out to obtain a simulation signal generated after the established indoor wireless channel model
Example 3: multipath pseudolite signal simulation
This embodiment differs from embodiment 1 in that in a positioning system, typically a plurality of pseudolite transmitters transmit different pseudolite signals, and the positioning resolution function is only implemented after more than 4 pseudolite signals are received by the receiver. As shown in FIG. 2, the pseudolite signal processing analysis simulation platform is composed of a pseudolite signal Transmitter (PL-Transmitter, T 1 ～T m ) Generating m paths of pseudo satellite standard signals s (p) (t), p= {1,2, …, m }; the generated pseudolite standard signal can be transmitted through a pseudolite transmitter (SDT, transmitting antenna: TX 1 ,TX 2 ,…,TX m ) The actual signal transmission can be performed by setting the antenna gain coefficient GT m Then, carrying out wireless channel simulation; radio channel simulation (PL-Wireless, W 1 ,W 2 ,…,W m ) Carrying out wireless channel simulation on each path of standard signal by using a space environment model, and obtaining simulation signals by simulationAnd respectively inputting the superimposed signals into a receiver antenna for processing.
Example 4: multipath pseudolite receiver signal processing simulation
The present embodiment is different from embodiment 1 in that the multipath pseudolite signal receiver can be simulated at different location pointsThe receiver processing flow can also simulate the data processing process of the array pseudo satellite signal receiver. As shown in fig. 3, the n-way receiver baseband signal processing units (PL-SDR, R1, R2, …, rn) are received by the software receiver (SDR, receiving antenna: RX 1 ,RX 2 ,…,RX n ) The acquired intermediate frequency signal is either transmitted via the receiving antenna coefficient (GR 1 ,GT 2 ,…,GT n ) Processed receiver simulation signalAnd obtaining observed quantity data corresponding to the n paths of signals after baseband signal processing, and obtaining coordinates of n receiver antennas after processing by PVT units. And finally, performing comparison analysis or array signal comprehensive processing on n paths of pseudolite received signals.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the specific embodiments described above, and that the above specific embodiments and descriptions are provided for further illustration of the principles of the present invention, and that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention is defined by the claims and their equivalents.
Claims (8)
1. The simulation platform is characterized by comprising a pseudolite signal generation unit, a wireless channel simulation unit, a receiver baseband signal processing unit, a positioning resolving unit, a pseudolite signal comprehensive analysis unit, and an external software transmitter, a spatial environment model, a software receiver and a receiver;
the pseudo satellite signal generating unit is used for simulating and generating pseudo satellite signals, simulating and simulating the pseudo satellite signals according to set pseudo satellite signal parameters, generating a sampling data stream of standard pseudo satellite signals, and storing the sampling data stream as a standard signal data file;
the wireless channel simulation unit is used for simulating a pseudolite signal space propagation model and multipath effect, setting simulation parameters by a space environment model, inputting a standard signal data file generated by the pseudolite signal generation unit, outputting a simulation signal data stream and storing the simulation signal data stream as a simulation signal data file;
the receiver baseband signal processing unit is used for processing intermediate frequency signals of pseudolites and realizing the capturing and tracking processes of the pseudolites, and the intermediate frequency signals processed by the unit are simulation signal data files output by the wireless channel simulation unit or intermediate frequency signal sampling data files acquired by a software receiver;
the positioning resolving unit is used for realizing PVT resolving function of the receiver, and is used for performing positioning resolving performance on pseudo satellite simulation data or actual measurement data, inputting original observed quantity data actually measured by the receiver baseband signal processing unit or the receiver, and outputting a receiver positioning result and an error analysis result;
the pseudolite signal comprehensive analysis unit is used for analyzing intermediate data generated by pseudolite signal processing and simulation;
the space environment model is a model established according to the environment needing to be simulated, parameters of pseudolite signals propagating in space are given through the model, including noise, distortion, experiments and fading added by the given pseudolite signals propagating in space, the parameters are input into the wireless channel simulation unit, and standard signals are processed to generate simulation signals;
the pseudolite software transmitter up-converts the pseudolite standard signal sampling data stream generated by the pseudolite signal generating unit and then transmits the pseudolite standard signal sampling data stream through a TX transmitting antenna;
the software receiver is a pseudolite signal intermediate frequency signal collector formed by software radio equipment and is used for carrying out down-conversion on a pseudolite radio frequency signal received by an RX receiving antenna, sampling the pseudolite radio frequency signal into pseudolite intermediate frequency sampling data, and then inputting the pseudolite intermediate frequency sampling data into the receiver baseband signal processing unit for processing;
the receiver is a common hardware receiver and is used for receiving pseudolite signals and outputting original observed quantity data in RINEX format;
the pseudolite signal comprehensive analysis unit consists of a signal system performance analysis module, a space signal propagation analysis module, a baseband signal processing analysis module and positioning algorithm effect analysis software; the signal system performance analysis module is used for processing and inputting standard signal data generated by the pseudolite signal generation unit, carrying out pseudolite signal system performance analysis and improving pseudolite signals; the space signal propagation analysis module inputs simulation signals and space environment model parameters generated by the wireless channel simulation unit, performs space signal propagation effect analysis and is used for researching a propagation mechanism and an error generation model of the wireless positioning signals; the baseband signal processing analysis module inputs the process data and the generated observed quantity data of the receiver baseband signal processing unit to carry out baseband signal processing analysis and is used for improving the capturing and tracking algorithm of the pseudolite receiver; and the positioning algorithm effect analysis software inputs the positioning result data of the positioning resolving unit, calculates positioning errors, performs positioning algorithm effect analysis, and is used for improving a pseudolite positioning algorithm.
2. The simulation platform for processing and analyzing the pseudo satellite positioning signals according to claim 1, wherein the pseudo satellite signal generating unit comprises a pseudo random code generating module, a navigation message generating module, an intermediate frequency carrier generating module, a spread spectrum module and a modulating module; the pseudo-random code generation module is used for generating PRN codes comprising C/A codes and P codes; the navigation message generation module generates a navigation message data stream according to the pseudo satellite ephemeris file; the pseudo-random code and the navigation message data stream are subjected to modulo double addition operation to generate spread spectrum code data; the spread spectrum code data and the intermediate frequency carrier signal generated by the intermediate frequency carrier generating module are modulated, and common modulation modes comprise BPSK, QPSK, BOC; the signals modulated by the modulation module are pseudo satellite standard simulation signals.
3. The simulation platform of claim 1, wherein the wireless channel simulation unit comprises a channel model module, a radio frequency signal propagation attenuation module, a signal delay module, and a signal superposition module.
4. The simulation platform of claim 1, wherein the receiver baseband signal processing unit comprises an intermediate frequency signal preprocessing module, a capturing module, a tracking module, and an observed quantity measuring module.
5. A method of pseudolite positioning signal simulation using a pseudolite positioning signal processing analysis simulation platform according to any one of claims 1-4, the method comprising the steps of:
s1: pseudolite signal simulation generation process
Pseudolite signals are formed by modulating ranging codes and navigation messages on carriers, and standard signals of pseudolites p are expressed as s (p) (t) the signal expression is as follows:
s (p) (t)＝A p D p (t)C p (t)cos(2πf c t) (1)
the pseudolite signal simulation generation process is realized by a pseudolite signal generation unit which actually generates the pseudolite signal in order to reduce the sampling rate IF Intermediate frequency signal of intermediate frequency signal frequencyThe expression is as follows:
wherein p represents the PRN number of the pseudolite, A represents the amplitude of the pseudolite signal, D (t) is navigation message data, C (t) is ranging code data, and f c For pseudolite signal frequency, f IF The up-conversion frequency relation is as follows:
f c ＝f IF +f Lo (3)
wherein f Lo For the local oscillation frequency of the transmitter, f c For pseudolite signal frequency, f IF Is the frequency of the intermediate frequency signal;
in the actual simulation process, the simulation data of the pseudolite standard signal generated by the pseudolite signal generating unit is the discrete sampling signal x (p) [k]The relation is as follows:
wherein p represents the pseudolite PRN number, the simulated discrete sampled signal x [ k ]]The intermediate frequency signal is s IF (t)，f IF Is the frequency of the intermediate frequency signal, T s Representing sampling time, k being a sampling point;
s2: wireless channel simulation process
In the process of wireless signal transmission, a wireless channel model is established according to a transmission mechanism from a transmitting antenna TXP to a receiving antenna RXr; the wireless channel model is expressed by h (t), and the factors affecting h (t) are set parameters W, and mainly comprise signal delay tau, amplitude attenuation coefficient alpha and path power loss value L p The phase delay θ and other parameters are expressed as W= { τ, α, L p ,θ,…}；
Simulating the pseudo satellite standard signal S obtained in the step S1 (p) (t) obtaining an output simulation signal through a wireless channel system model h (t)
Wherein h (t) represents a wireless channel model, and for the simulation of a time-invariant system, the parameters are set to be constant values, which are called constant parameter channels; for time-varying system simulation, the time-varying relation of each parameter in the system needs to be found out, which is called a parameter-dependent channel;
the signal received by the receiver at a certain point should be the superposition of the signals simulated above, i.e
Wherein s is R (t) represents the simulation signal of the receiving antenna at the R point, S represents the number of pseudolites,representing the simulation signal;
s3: receiver baseband signal processing
By pseudolite receiving antenna RX r The received pseudolite p signal is expressed as
The simulated discrete data are:
in the formulas (7) and (8), r is the number of the receiver, p is the number of the pseudolite PRN, j is the imaginary unit, A (t) is the function of the amplitude of the pseudolite signal with time,represents the filtered receiver signal, τ (t) represents the time delay function, f D (t) denotes a Doppler shift function, phi (t) denotes a phase shift function, and n (t) denotes a noise function; x is x R [k]Representing receiver discrete data, T s Representing sampling time, k being a sampling point;
the capturing and tracking process of the pseudolite signals is mainly completed in the receiver, and the original observed quantity OBS data of the pseudolite are output;
s4: positioning calculation simulation process
Performing pseudolite positioning algorithm calculation by using the pseudolite original observed quantity OBS data obtained in the step S3 to obtain PVT information, wherein the PVT information comprises position, speed and time, and the reliability of an analysis algorithm is evaluated according to positioning errors;
s5: pseudolite signal processing comprehensive analysis process
According to the simulation results of the four steps S1-S4, the quality of a pseudolite communication link is analyzed, the algorithm execution effect of each link in the pseudolite signal processing is evaluated, and the pseudolite signal simulation effect is comprehensively evaluated from four aspects of pseudolite signal system, pseudolite wireless channel propagation, baseband signal processing and PVT positioning calculation.
6. The method for simulating pseudo-satellite positioning signals according to claim 5, wherein the wireless channel simulation in step S2 performs signal simulation in different scenarios, and specifically includes free space ideal channels and multipath channels;
the free space ideal channel simulation process comprises the following steps: establishing a space model, setting the positions of a pseudolite transmitting antenna TX and a receiving antenna RX, and calculating a direct signal propagation parameter set W of each path of pseudolite signals from TX to RX according to the geometric relation 0 Including the amplitude alpha of the direct signal received by the RX 0 Time delay τ 0 Phase delay theta 0 The method comprises the steps of carrying out a first treatment on the surface of the Obtaining simulation signals according to the simulation parameter setting
Wherein the amplitude of the direct signal received by RX is alpha 0 The direct signal time delay is τ 0 Direct signal phase delay θ 0 ；
The multipath channel simulation process comprises the following steps: first, a propagation characteristic parameter set W of a pseudolite wireless signal in a space environment is calculated by a space environment model, wherein the wireless signal characteristic parameters comprise: multipath number M, time delay τ, attenuation coefficient α, phase delay θ, W= { τ, α, θ, M } of each multipath signal
Wherein the number of multipath is M, i represents multipath number, and the time delay of the ith multipath signal is tau i Attenuation coefficient alpha i Doppler shift of f Di Phase delay of theta i 。
7. The method for simulating pseudolite positioning signals according to claim 5, wherein the pseudolite signals are simulated to generate multiple paths of pseudolite standard signals in the simulation generating process, then each path of standard signals is subjected to wireless channel simulation by using a space environment model, and finally superimposed pseudolite simulation signals are output and are accessed into a receiver for processing.
8. A method of pseudolite positioning signal simulation according to claim 5, wherein the receiver baseband signal processing is performed using a plurality of pseudolite signal receivers to simulate receiver processing at different reception points or to simulate data processing at an array of pseudolite signal receivers.
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