A multi-structure GNSS receiver switching method based on signal quality monitoring

Abstract

The application discloses a multi-structure GNSS receiver switching method based on signal quality monitoring. The method comprises the following steps: constructing a satellite signal quality index set, matching different working modes of the multi-structure GNSS receiver under different external environments according to the satellite signal quality index set; calculating a real-time satellite signal quality index value; when the external environment changes, switching the multi-structure GNSS receiver to a working mode suitable for the environment, and continuously monitoring the satellite signal quality under the current working mode, so that the multi-structure GNSS receiver can output stable and reliable navigation solutions under various complex external environments. The application can effectively save the total power consumption of the system, improve the real-time performance of the receiver, and significantly improve the navigation performance under various complex environments by monitoring the satellite signal quality in real time and switching the working mode of the receiver adaptively.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation multi-structure receiver technology, and specifically relates to a switching method for multi-structure GNSS receivers based on signal quality monitoring. Background Technology

[0002] As the application environment of Global Navigation Satellite System (GNSS) becomes increasingly complex, user GNSS receivers are gradually being deployed to complex environments such as dense urban areas, dense forests and canyons, or indoor spaces. In these environments, multipath interference and signal blockage are the main factors affecting the positioning performance of GNSS receivers. In complex environments, the navigation performance of traditional scalar tracking loops (STLs) deteriorates significantly or even fails to function properly. Although vector tracking loops (VTLs) can couple all tracking channels together to achieve mutual assistance between channels, improving the receiver's tracking performance to some extent, the computational complexity of VTLs is significantly increased compared to STLs. Furthermore, channel coupling also leads to error propagation problems. When the number of lost tracking channels increases further in complex environments, the navigation performance of VTLs cannot be guaranteed.

[0003] Direct Position Estimation (DPE) receivers improve signal gain by combining the summation of signals from all visible satellites. In complex environments, especially in weak signal conditions such as indoors and dense forests, they offer significant advantages over STL and VTL in navigation performance. However, DPE requires calculating the correlation values ​​between each satellite signal and its local reference signal at all preset grid points in the navigation domain to obtain the combined summation output. Since correlation calculation itself involves a large computational load, existing DPEs suffer from high computational complexity, high system resource consumption, and are not conducive to engineering applications. In summary, when satellite signal quality changes in complex environments, the above three receiver types struggle to balance navigation performance and operational efficiency. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for switching multi-structure GNSS receivers based on signal quality monitoring.

[0005] To achieve the above objectives, the multi-structure GNSS receiver switching method based on signal quality monitoring provided by the present invention includes the following steps performed in sequence:

[0006] 1) A multi-structure GNSS receiver is constructed by embedding a signal quality monitoring module in a scalar receiver, a vector receiver, and a direct position estimation receiver. Based on the signal requirements for the scalar receiver, vector receiver, and direct position estimation receiver to maintain stable operation, the multi-structure GNSS receiver constructs a set of satellite signal quality indicators and matches the corresponding operating modes under different external environments according to the set of satellite signal quality indicators. Moreover, these operating modes can be switched.

[0007] 2) The multi-structure GNSS receiver calculates the satellite signal quality index value in real time based on the satellite ephemeris parameters and tracking parameters of each tracking channel output by the real-time received signal tracking output, so as to monitor the signal quality in the actual external environment;

[0008] 3) Based on the satellite signal quality index value calculated in real time in step 2) and the working mode obtained in step 1), when the external environment changes, control the multi-structure GNSS receiver to switch to a working mode suitable for the environment, and continuously monitor the satellite signal quality in the current working mode, so that the multi-structure GNSS receiver can output a stable and reliable navigation solution in a variety of complex external environments.

[0009] In step 1), the method for constructing a satellite signal quality index set based on the signal requirements for stable operation of the multi-structure GNSS receiver, including scalar receivers, vector receivers, and direct position estimation receivers, and matching the multi-structure GNSS receiver with corresponding operating modes under different external environments based on the satellite signal quality index set is as follows:

[0010] First, based on the signal requirements for stable operation of scalar receivers, vector receivers, and direct position estimation receivers, the multi-structure GNSS receiver constructs a set of satellite signal quality indicators. This set includes the number of visible satellites (L), spatial position accuracy factor (PDOP), carrier-to-noise ratio (C / N0), phase-locked indication (PLI), and DoubleDelta index (M). DD Satellite signal quality indicators, including those included.

[0011] Then, based on the above set of satellite signal quality indicators, the multi-structure GNSS receiver is matched with the corresponding operating modes under different external environments: when the receiver is in an open environment, the satellite signal quality indicators are: L≥4, PDOP<T. PDOP , PLI i >T PLI And T u >M DD >T l The multi-structure GNSS receiver operates in scalar receiver mode; where T PDOPThis represents the threshold value for the spatial location precision factor; Indicates the number of satellites with high carrier-to-noise ratio; T PLI This indicates the preset threshold value for the phase lock indicator; T u T l These represent the upper and lower thresholds of the Double Delta indicator value;

[0012] When there is signal obstruction in the external environment of the receiver, the satellite signal quality indicators are: L≥4, PDOP<T. PDOP , or PLI i <T PLI The multi-structure GNSS receiver operates in vector receiver mode;

[0013] When the receiver is in a weak signal environment, the satellite signal quality index is as follows: or Num{PLI i >T PLI}<L / 2, the multi-structure GNSS receiver operates in direct position estimation receiver mode; where, Num{PLI i >T PLI} indicates the number of satellites whose phase lock indicator value (PLI) is greater than the preset threshold for the phase lock indicator value;

[0014] When multipath interference is present, the satellite signal quality index is: M DD >T u Or M DD <T l If, after excluding multipath interference channels, L≥4 and PDOP<T PDOP In this case, observations from multipath channels are excluded during navigation solution calculation to eliminate the influence of multipath interference on the navigation solution; if L < 4 or PDOP ≥ T after excluding multipath interference channels. PDOP Narrow correlation techniques are then used to reduce positioning errors caused by multipath interference.

[0015] In step 2), the multi-structure GNSS receiver calculates the satellite signal quality index value in real time based on the satellite ephemeris parameters output from the real-time received signal tracking and the tracking parameters of each tracking channel. This method, used to monitor signal quality in the actual external environment, is as follows:

[0016] First, the multi-structure GNSS receiver calculates the number of visible satellites and the spatial position accuracy factor in the current environment based on the satellite ephemeris parameters output by the real-time received signal tracking, and calculates the carrier-to-noise ratio, phase-locked indication value, and Double Delta index value in real time based on the tracking parameters of each tracking channel.

[0017] In step 3), the method of switching the multi-structure GNSS receiver to a suitable operating mode for a changing external environment using a signal quality monitoring module based on the satellite signal quality index value calculated in real time in step 2) and the different operating modes obtained in step 1), and continuously monitoring the satellite signal quality in the current operating mode, so that the multi-structure GNSS receiver can output a stable and reliable navigation solution in various complex external environments, is as follows:

[0018] Using the different operating modes obtained in step 1), and based on the satellite signal quality index values ​​calculated in real time in step 2), when the external environment changes, the multi-structure GNSS receiver is controlled to adaptively switch between scalar receiver mode, vector receiver mode, and direct position estimation receiver mode. In the current operating mode, the receiver continuously outputs satellite ephemeris parameters and tracking parameters to monitor the satellite signal quality in real time, so that it can output stable and reliable navigation solutions in various complex environments.

[0019] The multi-structure GNSS receiver switching method based on signal quality monitoring provided by this invention has the following advantages compared with the prior art:

[0020] (1) The present invention embeds a signal quality monitoring module in a multi-structure GNSS receiver to determine the changes in satellite signal quality under actual external environment, which is beneficial for the multi-structure GNSS receiver to switch to a working mode suitable for the environment. Therefore, it can effectively save the total power consumption of the system and improve the real-time performance of the receiver.

[0021] (2) This invention fully leverages the advantages of STL, VTL and DPE, and combines the signal characteristics of the receiver in the actual working environment to control the multi-structure GNSS receiver to adaptively switch when the application environment changes, thus providing an important foundation for reliable navigation of GNSS receivers in complex environments. Attached Figure Description

[0022] Figure 1 The flowchart of the multi-structure GNSS receiver switching method based on signal quality monitoring provided by the present invention is shown.

[0023] Figure 2 The positioning error results are for a multi-structure GNSS receiver.

[0024] Figure 3 Tracking results of PRN1 satellites by a multi-structure GNSS receiver between 10 and 50 seconds: Figure 3 (a) shows the results related to the instantaneous code of the I branch. Figure 3 (b) is the binary decision result of the Double Delta index value.

[0025] Figure 4The estimated results of the phase lock indication of the PRN2 tracking channel for a multi-structure GNSS receiver during the 45-75s period are given.

[0026] Figure 5 The following are the STL and VTL tracking results for a multi-structure GNSS receiver during the 45-75s interval: Figure 5 (a) shows the results of the STL I-branch instantaneous code. Figure 5 (b) shows the results of the instantaneous code of the I branch of VTL.

[0027] Figure 6 The results show the carrier-to-noise ratio (CNR) estimates for each tracking channel of a multi-structure GNSS receiver during the 65-100s period.

[0028] Figure 7 This is the joint accumulation output result of DPE under weak signal conditions. Detailed Implementation

[0029] The following detailed description of the multi-structure GNSS receiver switching method based on signal quality monitoring provided by the present invention, with reference to the accompanying drawings and specific embodiments, is provided in detail.

[0030] like Figure 1 As shown, the multi-structure GNSS receiver switching method based on signal quality monitoring provided by this invention is applicable to GNSS receivers operating in scalar receiver (STL) mode in open environments and having entered a stable operating state. It is used to solve the positioning problem when the receiver enters a complex environment, and includes the following steps performed sequentially:

[0031] 1) A multi-structure GNSS receiver is constructed by embedding a signal quality monitoring module in a scalar receiver, a vector receiver, and a direct position estimation receiver. Based on the signal requirements for the scalar receiver, vector receiver, and direct position estimation receiver to maintain stable operation, the multi-structure GNSS receiver constructs a set of satellite signal quality indicators and matches the corresponding operating modes under different external environments according to the set of satellite signal quality indicators. Moreover, these operating modes can be switched.

[0032] First, based on the signal requirements for stable operation of scalar receivers, vector receivers, and direct position estimation receivers, the multi-structure GNSS receiver constructs a set of satellite signal quality indicators. This set includes the number of visible satellites (L), spatial position accuracy factor (PDOP), carrier-to-noise ratio (C / N0), phase-locked indication (PLI), and DoubleDelta index (M). DDThe satellite signal quality indicators include the number of visible satellites and the spatial position accuracy factor, which can be calculated from the satellite ephemeris parameters. The carrier-to-noise ratio, phase lock indicator value, and Double Delta index value can be calculated from the tracking parameters of each tracking channel output by the receiver in real time.

[0033] Then, based on the above set of satellite signal quality indicators, the multi-structure GNSS receiver is matched with the corresponding operating modes under different external environments, as shown in Table 1:

[0034] When the receiver is in an open environment, L≥4 and PDOP<T PDOP , PLI i >T PLI And T u >M DD >T l The multi-structure GNSS receiver operates in scalar receiver mode; where T PDOP This represents the threshold value for the spatial location precision factor; Indicates the number of satellites with high carrier-to-noise ratio; T PLI This indicates the preset threshold value for the phase lock indicator; T u T l These represent the upper and lower thresholds of the Double Delta index value, respectively. The external environment of the multi-structure GNSS receiver is characterized by good satellite geometry, high carrier-to-noise ratio of each satellite signal, low or no multipath interference. Therefore, the multi-structure GNSS receiver operates in the default STL mode and continuously outputs navigation solutions, maintaining a relatively fast operating efficiency.

[0035] When M DD >T u o or M DD <T l , PLI i >T PLI This indicates severe multipath interference in the external environment of the multi-structure GNSS receiver. If, after excluding the multipath interference channels, L≥4 and PDOP<T, this indicates the presence of such interference. PDOP The multi-structure GNSS receiver operates in STL mode, and multipath channel observations are excluded during navigation calculation to eliminate the impact of multipath interference on the navigation solution; if L < 4 or PDOP ≥ T after excluding multipath interference channels. PDOP The multi-structure GNSS receiver then adopts the STL mode and uses narrow correlation technology to reduce positioning errors caused by multipath interference.

[0036] When there is signal obstruction in the external environment of a multi-structure GNSS receiver, the satellite signal quality indicators are: L≥4, PDOP<T.PDOP , or PLI i <T PLI 、Τ u >M DD >T l This indicates that the external environment of the multi-structure GNSS receiver has low or no multipath interference, but the quality of some satellite signals deteriorates or is lost, causing the tracking loop to lose lock, resulting in fewer than 4 high-quality satellite signals. In this case, the multi-structure GNSS receiver's operating mode can be quickly switched to the VTL mode, which has higher tracking sensitivity, to ensure the positioning performance of the multi-structure GNSS receiver in environments with signal obstruction.

[0037] When M DD >T u Or M DD <T l , or PLI i <T PLI This indicates severe multipath interference in the external environment of the multi-structure GNSS receiver and an insufficient number of high-quality satellite signals. In this case, if the multipath interference channels are excluded, L≥4 and PDOP<T PDOP In this case, the multi-structure GNSS receiver will switch to VTL mode and exclude observations from multipath channels during navigation calculations to eliminate the impact of multipath interference on the navigation solution. If L < 4 or PDOP ≥ T after excluding multipath interference channels... PDOP Then the working mode is switched to VTL mode and narrow correlation technology is used to reduce the positioning error caused by multipath interference.

[0038] When a multi-structure GNSS receiver is in a weak signal environment, the satellite signal quality index is as follows: or Num{PLI i >T PLI}<L / 2,Τ u >M DD >T l , where Num{PLI i >T PLI The number of satellites whose Phase Lock Indicator (PLI) value is greater than the preset threshold indicates that the external environment of the multi-structure GNSS receiver is characterized by extremely low carrier-to-noise ratios (CNR) for most or all satellite signals, with low or no multipath interference. In this case, the multi-structure GNSS receiver will switch to the DPE mode, which offers superior navigation performance, to ensure navigation accuracy in weak signal environments.

[0039] when M DD >T u o or M DD <Tl This indicates that the external environment of the multi-structure GNSS receiver is characterized by extremely low carrier-to-noise ratios for most or all satellite signals, and severe multipath interference. Therefore, the operating mode of the multi-structure GNSS receiver is DPE mode, and the observations of multipath channels are excluded during navigation calculation to eliminate the impact of multipath interference on the navigation solution.

[0040] Table 1. Operating modes of multi-structure GNSS receivers

[0041]

[0042] 2) The multi-structure GNSS receiver calculates the satellite signal quality index value in real time based on the satellite ephemeris parameters and tracking parameters of each tracking channel output by the real-time received signal tracking output, so as to monitor the signal quality in the actual external environment;

[0043] First, the multi-structure GNSS receiver calculates the real-time visible satellite count L and spatial position accuracy factor PDOP based on the satellite ephemeris parameters tracked from the real-time received signal tracking output. Then, based on the tracking parameters of each tracking channel, it calculates the real-time carrier-to-noise ratio C / N0, phase-locked indication value PLI, and Double Delta index value M. DD This is to monitor signal quality in actual external environments.

[0044] The number of visible satellites (L) is a crucial factor affecting the positioning accuracy of multi-structure GNSS receivers. The reliability of positioning and measurement observations using multi-structure GNSS receivers primarily depends on the number of visible satellites involved in the GNSS positioning calculation and their redundancy. Compared to open environments, in special environments such as urban canyons and remote mountainous areas, GNSS satellite signals are blocked, resulting in a significant reduction in the number of visible satellites. In some cases, the GNSS receiver may even malfunction due to receiving fewer than four satellites.

[0045] Furthermore, the Spatial Position Precision Factor (PDOP) is an important indicator for measuring the impact of satellite geometry on positioning accuracy. It represents the geometric strength of the relative positions of the satellites participating in the navigation calculation at the current moment. Generally, when the GNSS receiver's observation accuracy is the same, the better the satellite geometry, the higher the positioning accuracy. The Spatial Position Precision Factor (PDOP) can be calculated by the following formula:

[0046]

[0047] Where, σ URE For pseudorange error, σ x ,σ y and σ z These are the root mean square error components for the receiver's three-dimensional position estimation. Generally, when T... PDOPA value greater than 6 indicates that the satellite's geometric distribution is not ideal and the positioning accuracy is low.

[0048] The carrier-to-noise ratio (CNR) is the ratio of signal carrier power to noise power spectral density, and it directly reflects the strength of the tracking satellite signal. Generally, a CNR greater than 40 dB·Hz is considered a strong signal, while a CNR less than 28 dB·Hz is considered a weak signal. The narrow bandwidth power ratio method is a typical CNR estimation method, and the narrow bandwidth power ratio can be calculated using the following formula:

[0049]

[0050] Next, calculate the mean of the narrowband and wideband power ratios over M time epochs:

[0051]

[0052] Therefore, the carrier-to-noise ratio C / N0 can be obtained as follows:

[0053]

[0054] The phase-locking status between the local signal and the received signal can be obtained by measuring the power difference of the correlation values ​​of the in-phase / quadrature branches. The phase-locking indication value (PLI) can be calculated by the following formula:

[0055]

[0056] For a Costas PLL employing a two-quadrant arctangent function phase detector, when the phase lock indication value PLI is close to 1, it indicates that the loop remains locked; when the carrier phase error δφ exceeds 15°, i.e. This indicates that the loop is out of lock.

[0057] Multipath interference monitoring typically involves determining whether the correlation values ​​of the instantaneous code, lead code, and lag code in the receiver tracking loop are abnormal. In the absence of multipath interference, the satellite signal correlation function is a symmetrical triangle; however, with multipath interference, the correlation function will be distorted. The Double Delta index given in the following formula is usually used to monitor correlation function distortion:

[0058]

[0059] Among them Λ I,E1 ,Λ I,L1 and Λ I,E2 ,Λ I,L2 These represent the correlation values ​​of the leading and lagging codes corresponding to different code delays, respectively. The Double Delta index uses two sets of early-late correlators with different intervals, and monitors the symmetry of the correlation peak by comparing whether the output values ​​of the in-phase branches are equal. In the absence of multipath interference, the Double Delta index can be approximately considered to follow M...Double Delta ~N(μ,σ 2 The normal distribution of ), where μ = 0 and T represents the mean and variance of the Double Delta index. coh Let P be the coherent integration time. Assume the false alarm probability is P. f The preset threshold can then be expressed as:

[0060]

[0061] In the formula, erfc -1 This is the inverse complementary error function. The receiver monitors multipath interference by comparing the Double Delta index value with a preset threshold. Once the preset threshold is exceeded, multipath interference is determined to exist, and multipath mitigation techniques should be employed.

[0062] 3) Based on the satellite signal quality index value calculated in real time in step 2) and the working mode obtained in step 1), when the external environment changes, the signal quality monitoring module is used to switch the multi-structure GNSS receiver to a working mode suitable for the environment, and continuously monitors the satellite signal quality in the current working mode, so that the multi-structure GNSS receiver can output a stable and reliable navigation solution in a variety of complex external environments.

[0063] Using the different operating modes of the multi-structure GNSS receiver obtained in step 1), the satellite signal quality index value calculated in real time in step 2) is used to control the adaptive switching of the multi-structure GNSS receiver between STL, VTL and DPE operating modes when the external environment changes. In the current operating mode, satellite ephemeris parameters and tracking parameters are continuously output to monitor the satellite signal quality in real time, so that it can output a stable and reliable navigation solution in a variety of complex environments.

[0064] Experiment Description: GPS L1 band signals were generated using a GNSS satellite signal simulator. The simulation data included signals from five satellites and lasted for 100 seconds. The simulated signal parameters are shown in Table 2. The experiment simulated open environments, environments with signal obstruction, environments with multipath interference, and weak signal environments. The operating modes, tracking loop performance, and navigation and positioning performance of the multi-structure GNSS receiver based on signal quality monitoring were presented under different conditions.

[0065] Table 2 Simulation signal parameters

[0066]

[0067]

[0068] Figure 2 Positioning error results for multi-structure GNSS receivers are presented.

[0069] from Figure 2 As can be seen, the multi-structure GNSS receiver can maintain good positioning performance in STL mode under high signal-to-noise ratio environment in the first 30 seconds.

[0070] Figure 3 Tracking results of PRN1 satellites with a multi-structure GNSS receiver between 10 and 50 seconds are presented:

[0071] in Figure 3 (a) shows the results related to the instantaneous code of the I branch.

[0072] Figure 3 (b) gives the binary decision result of the Double Delta index value.

[0073] from Figure 3 As can be seen, when multipath interference occurs in the satellite signal within 30-45 seconds, the presence of interference can be detected immediately using the Double Delta index value, and the information is then fed back to the navigation solution module. After detecting multipath interference on the PRN1 satellite, the navigation solution module employs multipath mitigation techniques, excluding observations from multipath channels during navigation solution calculation to eliminate the impact of multipath interference on the navigation solution.

[0074] The positioning error results show that after multipath interference was introduced into the PRN1 satellite within 30-45 seconds, the STL positioning error increased sharply. However, the positioning result of the multi-structure GNSS receiver remained within normal range after multipath interference detection and suppression. This indicates that the multi-structure GNSS receiver based on signal quality monitoring has better anti-interference performance after incorporating multipath mitigation technology.

[0075] Figure 4 The phase-lock indication results of the PRN2 tracking channel of the multi-structure GNSS receiver during the 45-75s period are presented.

[0076] from Figure 4 It can be seen that when the PRN2 satellite signal is blocked at 55s, the PLI value of this channel is lower than the empirical value of 0.5, indicating that the tracking loop of this channel is lost. At this time, the multi-structure GNSS receiver switches from STL mode to VTL mode.

[0077] Figure 5 The STL and VTL tracking results of the receiver during the 45-75s period are given:

[0078] in Figure 5 (a) shows the results of the STL I-branch instantaneous code.

[0079] Figure 5 (b) shows the results of the instantaneous code of the I branch of VTL.

[0080] from Figure 5 As can be seen, when the PRN2 satellite is blocked at 55s, the tracking loop of the STL's PRN2 channel immediately loses lock. Even after the signal recovers at 65s, it cannot relock and remains in a locked state, requiring reacquisition of the satellite. In contrast, the tracking loop of the VTL's PRN2 channel, after a brief loss of lock during the 55-65s signal blockage, can still maintain tracking with the assistance of other satellites with good signal quality. Furthermore, after the lost tracking channel's satellite signal recovers, it can estimate parameters such as the channel's code phase and carrier frequency based on the navigation filter, thus quickly re-entering tracking without needing reacquisition. The positioning error results show that VTL can immediately relock when the signal reappears at 65s, restoring the positioning result to normal values, while STL remains locked after the signal is blocked at 55s. The receiver's positioning performance deteriorates sharply, indicating that VTL has superior tracking performance and signal re-tracking capability in environments with signal blockage.

[0081] Figure 6 The carrier-to-noise ratio estimation results for each tracking channel from 65 to 100 seconds are given.

[0082] from Figure 6 It can be seen that after 80s, the carrier-to-noise ratio of all tracking channels is very low. At this time, the receiver is in a weak signal environment, and the multi-structure receiver switches from VTL mode to DPE mode.

[0083] Figure 7 The joint accumulation output results of the DPE receiver under weak signal conditions are presented.

[0084] from Figure 7 It can be seen that although the signal quality of each satellite is severely affected by noise in weak signal environments, the DPE receiver can still effectively accumulate satellite signals by combining the signals from all visible satellites. The positioning error results show that when all satellite signals are weak, the positioning performance of VTL also deteriorates. However, the DPE improves signal gain by accumulating signal energy in the navigation domain by combining the signals from all visible satellites, thus maintaining superior navigation performance even in weak signal environments.

[0085] In summary, the multi-structure GNSS receiver switching method based on signal quality monitoring provided by this invention monitors satellite signal quality in real time and then adaptively controls the multi-structure GNSS receiver to work in different modes according to the monitoring results, thereby enabling the multi-structure GNSS receiver to meet the requirements of low power consumption and real-time operation while ensuring navigation performance.

Claims

1. A method for multi-architecture GNSS receiver handover based on signal quality monitoring, characterized in that: The multi-structure GNSS receiver switching method based on signal quality monitoring comprises the following steps in sequence: 1) embedding a signal quality monitoring module in a scalar receiver, a vector receiver and a direct position estimation receiver to form a multi-structure GNSS receiver; The multi-structure GNSS receiver constructs a satellite signal quality index set according to the signal requirements for stable operation of the scalar receiver, the vector receiver and the direct position estimation receiver, and matches corresponding working modes of the multi-structure GNSS receiver in different external environments according to the satellite signal quality index set, and the working modes can be switched; 2) the multi-structure GNSS receiver calculates satellite signal quality index values in real time according to satellite ephemeris parameters output by real-time signal tracking and tracking parameters of each tracking channel to monitor signal quality in actual external environments; 3) according to the satellite signal quality index values calculated in real time in step 2) and the working modes obtained in step 1), when the external environment changes, the multi-structure GNSS receiver is switched to a working mode suitable for the environment, and the satellite signal quality is continuously monitored in the current working mode, so that the multi-structure GNSS receiver can output stable and reliable navigation solutions in various complex external environments; In step 1), the method for the multi-structure GNSS receiver to construct a satellite signal quality index set according to the signal requirements for stable operation of the scalar receiver, the vector receiver and the direct position estimation receiver, and to match corresponding working modes of the multi-structure GNSS receiver in different external environments according to the satellite signal quality index set is: Firstly, according to the signal requirements that the scalar receiver, the vector receiver and the direct position estimation receiver can keep stable work, the multi-structure GNSS receiver constructs a satellite signal quality index set, which includes the number of visible satellites L, the spatial position dilution of precision PDOP, the carrier-to-noise ratio C / N0, the phase lock indication value PLI and the Double Delta index value M DD the satellite signal quality index within the satellite signal quality index set Then, according to the above satellite signal quality index set, the multi-structure GNSS receiver is matched with corresponding working modes under different external environments: when the receiver is in an open environment, at this time, the satellite signal quality index is: L≥4, PDOP PDOP , or PLI i >T PLI , T u >M DD >T l , the working mode of the multi-structure GNSS receiver is a scalar receiver mode; wherein, T PDOP represents a spatial position accuracy factor threshold value; represents the number of satellites with high carrier-to-noise ratio; T PLI represents a phase lock indication value preset threshold; T u , T l respectively represent upper and lower thresholds of Double Delta index value; When the receiver external environment exists signal shielding, at this time satellite signal quality index is: or PLI i <T PLI The working mode of the multi-structure GNSS receiver is a vector receiver mode. When the receiver is in a weak signal environment, at this time the satellite signal quality index is: or Num{PLI i > T PLI} < L / 2, the working mode of the multi-structure GNSS receiver is a direct position estimation receiver mode; wherein, Num{PLI i > T PLI} represents the number of satellites whose phase lock indication value PLI is greater than the phase lock indication value preset threshold. When there is multipath interference, the satellite signal quality index is M DD > T u or M DD < T l If L≥4 and PDOP < T PDOP after excluding the multipath interference channel, the observation quantity of the multipath channel is excluded in the navigation solution to eliminate the influence of the multipath interference on the navigation solution; if L < 4 or PDOP≥T PDOP after excluding the multipath interference channel, the narrow correlation technology is used to reduce the positioning error caused by the multipath interference.

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