Navigation and communication signal integration method

Abstract

According to the navigation and communication signal integration method provided by the invention, aiming at a conduction integration signal system application scene, the positioning precision and the anti-multipath capability are selected as evaluation indexes, and the navigation and communication integration signal precision and performance are analyzed and evaluated based on the performance theoretical limit. By combining the characteristics of a communication signal and a navigation signal, taking compatibility of the communication signal and the navigation signal as a starting point and adopting a burst multicarrier modulation mode, a navigation signal, namely a burst multicarrier signal (BCC signal) which can be broadcasted in a time slot of a communication channel and is compatible with multiple communication systems is constructed. Mi subcarriers are modulated on a single frequency point of a signal source i, the frequency interval between the subcarriers is fixed, the signal duration is adjustable, the subcarriers have burst characteristics, each subcarrier is modulated with the same pseudo code, meanwhile, the signal power of each subcarrier can be adjusted according to needs, and finally, the signals of the Mi subcarriers are combined together and transmitted out. Different pseudo codes are used for representing different signal sources.

Description

Technical Field

[0001] The present invention belongs to the field of navigation and communication technology, and in particular relates to a navigation and communication signal integration method. Background Art

[0002] At present, for satellite navigation and positioning systems that use the Radio Navigation Satellite System (RNSS) system, navigation messages are broadcast in a passive reception mode. For general positioning needs, this passive reception mode is sufficient, but in related operations such as sea, land, and air, the requirement for two-way communication is natural. For example, in applications in the management of ships, vehicles, and aircraft, the managed ships, vehicles, and aircraft need to transmit their location information to the management center at any time. The actual application needs make the integration of navigation and communication an inevitable trend.

[0003] As a cutting-edge cross-integration technology, integrated communication has been widely valued by academia and industry. Considering the process elements of information system development, the current research on integrated communication includes integrated communication signal design, integrated communication channel model, integrated communication signal processing, integrated communication network architecture, integrated communication network management and other aspects. With the development and iteration of communication and navigation and positioning technology, the coupling relationship between the two must not only meet the system level, but also realize the flexible integration of navigation and communication. The efficient and compatible design of signals is the foundation of the foundation. The integrated design of communication and positioning in the signal system has gradually become a hot topic in current research.

[0004] Due to the scarcity of frequency band resources, using limited resources to implement integrated navigation and communication signal design is a feasible solution to this problem. However, since the integrated navigation and communication signal crosses the two fields of navigation and communication, it is necessary to ensure the high rate of the integrated navigation and communication signal to meet the relevant index requirements in the current communication field; it is also necessary to ensure the positioning accuracy of the integrated navigation and communication signal to meet the relevant index requirements in the current navigation field. In addition, the different usage scenarios of navigation and communication signals will also cause difficulties to varying degrees, making the use of integrated navigation and communication signals face many difficulties. Summary of the invention

[0005] This application document utilizes limited resources to realize the integrated navigation and communication signal design, which effectively solves the problem of scarce frequency band resources to a certain extent. It also uses positioning accuracy and anti-multipath capability as evaluation indicators for the application scenarios of the integrated signal system, and solves the problem of the integrated signal's ability to be used in the two fields of navigation and communication.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a navigation and communication signal integration method, selects positioning accuracy and anti-multipath capability as evaluation indicators for the application scenario of the integrated signal system, and analyzes and evaluates the accuracy and performance of the navigation and communication integrated signal based on the theoretical limit of performance. Combining the characteristics of communication signals and navigation signals, taking the compatibility of communication signals and navigation signals as the starting point, a burst multi-carrier modulation method is adopted to construct a navigation signal that can be broadcast in the time slot of the communication channel and is compatible with a variety of communication systems - a burst multi-carrier signal (BCC signal).

[0007] Mi subcarriers are modulated at a single frequency point of the signal source i. The frequency interval between each subcarrier is fixed and the signal duration is adjustable, which has a burst characteristic. Each subcarrier modulates the same pseudo code. At the same time, the signal power of each subcarrier can be adjusted as needed. Finally, the signals of Mi subcarriers are combined and transmitted, and different pseudo codes are used to represent different signal sources.

[0008] Furthermore, the positioning accuracy of the integrated navigation and communication signal is described in detail as follows:

[0009] Under Gaussian white noise conditions, the code tracking error of the coherent (CELP, Coherent Early-Late Processing) delay locked loop is:

[0010]

[0011] In the formula, B L is the single-side bandwidth of the tracking loop, d is the correlator interval, T c is the symbol period, is the receiver signal-to-noise ratio, G s (f) is the normalized power spectral density, H(f) is the bandwidth [B r / 2,-B r / 2] is an ideal bandpass filter. Assuming the correlator interval d→0, the code tracking accuracy limit of the coherent EML loop is:

[0012]

[0013] According to parameter estimation theory, in a Gaussian white noise environment, the Cramer-Rao lower bound of the code tracking accuracy error is:

[0014]

[0015] in, is the Gabor bandwidth (rad / s).

[0016] Therefore, Gabor bandwidth is usually used to measure positioning accuracy, that is:

[0017]

[0018] That is, the signal root mean square (RMS) bandwidth.

[0019] Furthermore, for the narrowband interference between navigation and communication integrated signals, the interference power spectrum density is modeled as:

[0020] G J (f) = δ(ff J )

[0021] where f J The frequency corresponding to the narrowband interference of the integrated navigation and communication signal.

[0022] The effect of narrowband interference depends on the normalized power spectrum density of the signal. The interference effect on demodulation performance is most obvious when the frequency of the narrowband interference corresponds to the maximum value of the signal power spectrum.

[0023] Among them, the demodulation quality factor against narrowband interference is:

[0024]

[0025] Among them, R d is the information rate.

[0026] Code tracking anti-narrowband interference quality factor:

[0027]

[0028] Furthermore, for the matching spectrum interference between navigation and communication integrated signals, specifically,

[0029] Demodulation quality factor against matching spectrum interference:

[0030]

[0031] Code tracking quality factor against matching spectrum interference:

[0032]

[0033] From the above four equations, we can see that the performance of the navigation signal in resisting narrowband interference mainly considers the concentration of the signal spectrum. Demodulation anti-narrowband focuses on the influence of the normalized signal power spectrum, and tracking anti-narrowband focuses on the influence of the spectrum power after the signal frequency square weighting. The more concentrated the power is, the worse the anti-narrowband interference performance is. The performance of the navigation signal in resisting matching spectrum interference mainly considers the signal power overlap. Demodulation anti-matching spectrum interference focuses on the overlap of the normalized power of the signal, and tracking anti-matching spectrum interference focuses on the overlap of the power spectrum after frequency weighting. The greater the power spectrum overlap, the more serious the matching spectrum interference.

[0034] After adopting the above technical solution, the beneficial effects of the present invention are:

[0035] 1. The integrated navigation and communication signal adopts a burst multi-carrier signal format (BCC signal), which is compatible with the characteristics of both communication and navigation signals. Compared with traditional communication signals, the BCC signal outputs a low navigation message rate, effectively reducing bit errors; compared with traditional navigation signals, the BCC signal has both multi-subcarrier and time division characteristics, and has the ability to resist near-far effects, higher positioning accuracy performance, and anti-multipath capabilities.

[0036] 2. Signals based on the BCC signal system are different from other navigation signals and communication signals. Compared with the data transmission requirements of communication signals, their symbol output rate is high. The navigation message rate output by the BCC signal is much lower than the rate of the communication signal, which can effectively reduce the bit error rate. Compared with other navigation signals, the BCC signal has the characteristics of multiple subcarriers and time division, and has many characteristics that other navigation signals do not have. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0038] Figure 1 It is a time domain and frequency domain diagram of a BCC signal in an embodiment of the present invention;

[0039] Figure 2 is an autocorrelation diagram of a BBC signal in an embodiment of the present invention;

[0040] Figure 3 This is a diagram showing the variation of Gabor bandwidth with receiver pre-filtering bandwidth under medium power conditions in an embodiment of the present invention;

[0041] Figure 4 Graph showing the variation of Gabor bandwidth of a BCC signal with pre-filtering bandwidth in an embodiment of the present invention;

[0042] Figure 5 This is a comparison diagram of signal anti-interference quality factors at 20MHz bandwidth in an embodiment of the present invention;

[0043] Figure 6 This is a comparison chart of the anti-interference performance of BCC signals under 20 MHz bandwidth in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] Example:

[0046] like Figures 1 to 6 As shown, the present invention provides a navigation and communication signal integration method. For the application scenario of the integrated signal system, positioning accuracy and anti-multipath capability are selected as evaluation indicators. Based on the theoretical limit of performance, the accuracy and performance of the navigation and communication integrated signal are analyzed and evaluated. Combining the characteristics of communication signals and navigation signals, and taking compatibility of communication signals and navigation signals as the starting point, a burst multi-carrier modulation method is adopted to construct a navigation signal that can be broadcast in the time slot of the communication channel and is compatible with a variety of communication systems - a burst multi-carrier signal (BCC signal). Mi subcarriers are modulated on a single frequency point of the signal source i. The frequency interval between each subcarrier is fixed and the signal duration is adjustable. It has a burst characteristic. Each subcarrier modulates the same pseudo code. At the same time, the signal power of each subcarrier can also be adjusted as needed. Finally, the signals of Mi subcarriers are combined and transmitted, and different pseudo codes are used to represent different signal sources.

[0047] In the embodiment of the present application, the design concept is as follows: in the frequency domain, the frequency bandwidth occupied by a single transmitting frequency point of a ranging channel is divided into Mi sub-bands. In the time domain, the signal duration on each subcarrier is transmitted according to a pre-set transmission time slot. The number of time slots is determined by the duty cycle. At the same time, the frequency intervals between each subcarrier are equal, and their widths are multiples of the pseudo code rate. The signal distribution in time and frequency is as follows: Figure 1 Show.

[0048] In the present application embodiment, Figure 2 It can be seen that under the same bandwidth, the peak of the BCC signal autocorrelation function is the sharpest, even better than the P code, reflecting the smallest pseudo code tracking error. Theoretically, it can be reflected that multi-carrier navigation signals can enable the receiver to get rid of the ultra-long pseudo code phase search operation (P code) and use short codes plus multiple frequencies to improve code accuracy.

[0049] In the embodiment of the present application, the positioning accuracy of the integrated navigation and communication signal is specifically described as follows:

[0050] Under Gaussian white noise conditions, the code tracking error of the coherent (CELP, Coherent Early-Late Processing) delay locked loop is:

[0051]

[0052] In the formula, B L is the single-side bandwidth of the tracking loop, d is the correlator interval, T c is the symbol period, is the receiver signal-to-noise ratio, G s (f) is the normalized power spectral density, H(f) is the bandwidth [B r / 2,-B r / 2] is an ideal bandpass filter. Assuming the correlator interval d→0, the code tracking accuracy limit of the coherent EML loop is:

[0053]

[0054] According to parameter estimation theory, in a Gaussian white noise environment, the Cramer-Rao lower bound of the code tracking accuracy error is:

[0055]

[0056] in,

[0057]

[0058] is the Gabor bandwidth (rad / s). Therefore, the Gabor bandwidth is usually used to measure the positioning accuracy, that is:

[0059]

[0060] That is, the signal root mean square (RMS) bandwidth.

[0061] In the present application embodiment, Figure 3 The figure shows the variation of Gabor bandwidth with receiver pre-filter bandwidth under equal power conditions. Specifically, it should meet the following conditions:

[0062] Assume that the number of BCC signal subcarriers M=10, the subcarrier code rate is 1.023 MHz, and the subcarrier spacing is 2.046 MHz.

[0063] Assume that the number of BCC signal subcarriers M=10, the subcarrier code rate is 1.023 MHz, and the subcarrier spacing is 2.046 MHz.

[0064] Assume that the number of BCC signal subcarriers M=10, 5, 2, the subcarrier pseudo code rates are 1.023 MHz, 2.046 MHz, 5.115 MHz, respectively, and the subcarrier frequency intervals are 2.046 MHz, 4.092 MHz, 10.23 MHz, respectively.

[0065] In the present application embodiment, Figure 4 The figure shows the change of Gabor bandwidth of BCC signal with pre-filter bandwidth. Under the condition of the same main lobe width, when the pre-filter bandwidth is lower (4MHz), the number of BCC signal subcarriers M=10, 5, the corresponding Gabor bandwidth performance is better than M=2; when the pre-filter bandwidth is between 4MHz and 18MHz, the number of BCC signal M=2 corresponds to the best Gabor bandwidth performance, and the number of subcarriers M=10, 5 corresponds to alternating Gabor bandwidth performance; when the pre-filter bandwidth is greater than 18MHz, the number of BCC signal subcarriers M=10, 5 has the best performance. With the change of front-end bandwidth, the larger the high-frequency component at the edge of the restricted bandwidth, the larger the Gabor bandwidth, and the smaller the code tracking error.

[0066] In the embodiment of the present application, for the narrowband interference between the integrated navigation and communication signals, the interference power spectrum density is modeled as:

[0067] G J (f) = δ(ff J )

[0068] where f J The frequency corresponding to the narrowband interference of the integrated navigation and communication signal.

[0069] The effect of narrowband interference depends on the normalized power spectrum density of the signal. The interference effect on demodulation performance is most obvious when the frequency of the narrowband interference corresponds to the maximum value of the signal power spectrum.

[0070] Among them, the demodulation quality factor against narrowband interference is:

[0071]

[0072] Among them, R d is the information rate.

[0073] Code tracking anti-narrowband interference quality factor:

[0074]

[0075] In the embodiment of the present application, for the matching spectrum interference between navigation and communication integrated signals, specifically,

[0076] Demodulation quality factor against matching spectrum interference:

[0077]

[0078] Code tracking quality factor against matching spectrum interference:

[0079]

[0080] From the above four equations, we can see that the performance of the navigation signal in resisting narrowband interference mainly considers the concentration of the signal spectrum. Demodulation anti-narrowband focuses on the influence of the normalized signal power spectrum, and tracking anti-narrowband focuses on the influence of the spectrum power after the signal frequency square weighting. The more concentrated the power is, the worse the anti-narrowband interference performance is. The performance of the navigation signal in resisting matching spectrum interference mainly considers the signal power overlap. Demodulation anti-matching spectrum interference focuses on the overlap of the normalized power of the signal, and tracking anti-matching spectrum interference focuses on the overlap of the power spectrum after frequency weighting. The greater the power spectrum overlap, the more serious the matching spectrum interference.

[0081] In the present application embodiment, Figure 5 Assume that the number of BCC signal subcarriers M = 10, the subcarrier code rate is 1.023MHz, and the subcarrier spacing is 2.046MHz. The performance of BCC signal demodulation in terms of anti-narrowband and demodulation matching spectrum is better than C / A code, BOC (1,1) code, MBOC (6,1,1 / 11) and MSK code, and second only to P code; in terms of tracking anti-narrowband and tracking anti-matching spectrum interference, the anti-interference performance of BCC signal is not outstanding, but this is because the BCC signal involved in the simulation is full of main lobe signals within the 20MHz bandwidth, and the power distribution is equal. The narrowband interference target range is too large and the matching spectrum interference overlaps significantly. The proportion of high-frequency signal power spectrum is also small, resulting in low performance. In actual scene applications, the flexible subcarrier frequency configuration of the BCC signal can avoid narrowband interference frequency points as much as possible, reduce the overlapping part of matching spectrum interference, and increase the high-frequency signal energy by adjusting the subcarrier signal amplitude, highlighting the performance advantage of anti-matching spectrum interference.

[0082] In the present application embodiment, Figure 6 Assume that the number of BCC signal subcarriers M = 10, 5, 2, the subcarrier pseudo code rate is 1.023MHz, 2.046MHz, 5.115MHz, and the subcarrier frequency interval is 2.046MHz, 4.092MHz, 10.23MHz. When the BCC signal has the same main lobe width but different subcarrier numbers, the performance in terms of anti-narrowband interference is not much different. But in general, when the number of BCC signals is less extended, the interference is less affected.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A navigation and communication signal integration method, characterized in that: The method comprises the following steps: S1: For the application scenario of integrated signal system, positioning accuracy and anti-multipath capability are selected as evaluation indicators; S2: Burst multi-carrier modulation is adopted. Through burst multi-carrier signals, Mi sub-carriers are modulated at a single frequency point of signal source i. The frequency interval between each sub-carrier is fixed and the signal duration is adjustable. S3: Each subcarrier modulates the same pseudo code, and the signal power of each subcarrier is adjusted as needed. Finally, the signals of Mi subcarriers are combined and the combined signal is transmitted, and different pseudo codes are used to represent different signal sources.

2. A navigation and communication signal integration method as claimed in claim 1, characterized in that: When selecting the positioning accuracy in step S1, under the condition of Gaussian white noise, the coherent delay locked loop code tracking error is: Among them, in the formula, B L is the single-side bandwidth of the tracking loop, d is the correlator interval, T c is the symbol period, is the receiver signal-to-noise ratio, G s (f) is the normalized power spectral density, H(f) is the bandwidth [B r / 2,-B r / 2] within an ideal bandpass filter.

3. A navigation and communication signal integration method as claimed in claim 2, characterized in that: When the correlator interval d→0, the code tracking accuracy limit of the coherent EML loop is: According to parameter estimation theory, the Cramer-Rao lower bound of code tracking accuracy error in Gaussian white noise environment is: in is the Gabor bandwidth (rad / s).

4. A navigation and communication signal integration method as claimed in claim 3, characterized in that: The positioning accuracy is measured by Gabor bandwidth, that is, by the signal root mean square bandwidth: where f J The frequency corresponding to the narrowband interference of the integrated navigation and communication signal.

5. A navigation and communication signal integration method as claimed in claim 1, characterized in that: In the application scenario of step S1, there is narrowband interference, narrowband interference between navigation and communication integrated signals, and the interference power spectrum density is modeled as: GJ(f)=δ(f-fJ) where f J The frequency corresponding to the narrowband interference of the integrated navigation and communication signal.

6. A navigation and communication signal integration method as claimed in claim 5, characterized in that: The effect of the narrowband interference depends on the normalized power spectrum density of the signal. When the frequency of the narrowband interference corresponds to the maximum value of the signal power spectrum, the interference effect on the demodulation performance is the greatest.

7. A navigation and communication signal integration method as claimed in claim 6, characterized in that: The demodulation quality factor against narrowband interference is: Among them, R d is the information rate.

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