A code doppler verification device and method

Abstract

This invention belongs to the field of communication technology, and particularly relates to a code Doppler verification device and method. An initial pseudo-random sequence C(t) is periodically sent from a signal source to a wireless channel simulator. The wireless channel simulator adds a code Doppler effect to the acquired initial pseudo-random sequence C(t) to obtain a pseudo-random sequence C′(t), and sends the pseudo-random sequence C′(t) and the initial pseudo-random sequence C(t) to a spectrum and signal analyzer. The spectrum and signal analyzer performs orthogonal demodulation and low-pass filtering on the initial pseudo-random sequence C(t) and the pseudo-random sequence C′(t) to obtain a pseudo-random sequence C0. n (t) and pseudo-random sequence C′ m (t), and the initial pseudo-random sequence C(t) and the pseudo-random sequence C n (t) and pseudo-random sequence C′ m (t) is sent to the host computer; the host computer, based on the initial pseudo-random sequence C(t) and the pseudo-random sequence C... n (t) and pseudo-random sequence C′ m (t) Verify whether the added code Doppler is consistent with the effect of symbol compression or expansion caused by the actual speed.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and in particular relates to a code Doppler verification device and verification method. Background Technology

[0002] Code Doppler and carrier Doppler are phenomena that occur when there is relative motion between the transmitting and receiving ends. Due to the limited speed of the communicating parties on the ground, carrier Doppler is more common. However, when communicating on high-speed aircraft (such as missiles), the communication between the transmitting and receiving parties is in a highly dynamic environment, and the effect of code Doppler must be considered. The effect of code Doppler can be added to wireless channel simulators. Current methods for verifying code Doppler generally involve observing the compression and broadening of the signal bandwidth affected by code Doppler using a spectrum analyzer. However, these observations are subjective and lack quantitative analysis. Therefore, it is necessary to propose a method that can quantitatively analyze and verify whether adding code Doppler conforms to the actual speed-induced symbol compression or broadening effect, in order to guide users in evaluating and developing dedicated algorithms for communication systems to eliminate the effect of code Doppler. Summary of the Invention

[0003] In order to solve the technical problems existing in the prior art, the present invention provides a code Doppler verification device and verification method, which aims to verify whether the added code Doppler conforms to the effect of symbol compression or expansion caused by the actual speed.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A code-Doppler verification device, comprising:

[0006] Signal source: used to periodically generate an initial pseudo-random sequence Send to the wireless channel emulator;

[0007] Wireless channel simulator: for the acquired initial pseudo-random sequence Adding the code Doppler effect yields a pseudo-random sequence. and pseudo-random sequence and initial pseudo-random sequence Send to the spectrum and signal analyzer;

[0008] Spectrum and Signal Analyzer: For initial pseudo-random sequences and pseudo-random sequences Orthogonal demodulation and low-pass filtering are performed to obtain a pseudo-random sequence. and pseudo-random sequences and the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences Send to the host computer;

[0009] Host computer: Based on the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences Verify whether the added code Doppler is consistent with the effect of symbol compression or expansion caused by the actual speed.

[0010] Furthermore, the wireless channel simulator incorporates the code Doppler effect using the following formula:

[0011] ;

[0012] In the formula: v represents the relative speed and c represents the speed of light.

[0013] Furthermore, the signal output by the wireless channel simulator to the configuration spectrum and signal simulator is represented as follows:

[0014] ;

[0015] ;

[0016] In the formula: This indicates a signal without added code for the Doppler effect; This indicates a signal with added code Doppler effect; Indicates the carrier frequency.

[0017] Furthermore, the specific steps for code Doppler verification performed by the host computer are as follows:

[0018] A. Using an initial pseudo-random sequence respectively with pseudo-random sequences and pseudo-random sequences Perform sliding correlation analysis and count the number of correlation peaks. and And the corresponding position index of the relevant peak;

[0019] in, The position index of each related peak is ; The position index of each related peak is , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0020] B. Find the minimum number of relevant peaks. ;

[0021] C. Calculate the sample point difference under the condition of having the same number of correlated peaks. , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0022] D. Calculate the time difference caused by code-Doppler. ,in This indicates the baseband sampling rate of the spectrum and signal analyzer.

[0023] E. Order ,in ,in v represents the relative speed, and c represents the speed of light;

[0024] F. If If the result is positive, it means the verification result meets the requirements; otherwise, it means the verification result does not meet the requirements.

[0025] A code Doppler verification method includes the following steps:

[0026] Step 1: Obtain the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences The initial pseudo-random sequence This refers to a pseudo-random sequence generated periodically by a signal source; pseudo-random sequence This represents a pseudo-random sequence that has undergone orthogonal demodulation and low-pass filtering; pseudo-random sequence This indicates a pseudo-random sequence that has undergone code Doppler effect addition and has been subjected to orthogonal demodulation and low-pass filtering;

[0027] Step 2: Using the initial pseudo-random sequence respectively with pseudo-random sequences and pseudo-random sequences Perform sliding correlation analysis and count the number of correlation peaks. and And the corresponding position index of the relevant peak;

[0028] in, The position index of each related peak is ; The position index of each related peak is , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0029] Step 3. Find the minimum number of relevant peaks. ;

[0030] Step 4. Calculate the sample difference under the condition of the same number of correlation peaks. , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0031] Step 5. Calculate the time difference caused by code Doppler. ,in This indicates the baseband sampling rate of the spectrum and signal analyzer.

[0032] Step 6. Let ,in ,in v represents the relative speed, and c represents the speed of light;

[0033] Step 7. If If the result is positive, it means the verification result meets the requirements; otherwise, it means the verification result does not meet the requirements.

[0034] The beneficial effects of this invention include:

[0035] Based on the verification device and method described in this invention, it is possible to verify whether the added code Doppler conforms to the effect of symbol compression or expansion caused by the actual speed. Simultaneously, it not only verifies the correctness of the code Doppler addition module in the wireless simulator, but also helps users evaluate and develop dedicated algorithms for communication systems to eliminate the effects of code Doppler. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the code Doppler verification device of the present invention.

[0037] Figure 2 This is the baseband periodic sequence emitted by the signal source of the present invention.

[0038] Figure 3 This is the unweighted Doppler sliding correlation peak periodic sequence of the present invention.

[0039] Figure 4 This invention provides a code Doppler sliding correlation peak periodic sequence with an addition speed of 32 km / s.

[0040] Figure 5 This is an approximate diagram illustrating the relevant calculations of the present invention.

[0041] Figure 6 This is a diagram illustrating the approximate calculations related to the presence of code Doppler in this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0043] The following is combined with Figures 1 to 6 The present invention will be further described in detail below:

[0044] The impact of code Doppler on communication is mainly reflected in the compression or expansion of symbols. Assuming the pseudo-random code received by the user is... The local random sequence is Then the correlation function between the two for:

[0045] (1)

[0046] In the formula: One chip width; The number of chips within the relevant time period; For code phase estimation error, To receive the pseudo-random code phase, Estimate the phase of the pseudo-random code locally.

[0047] See Figure 5 As shown, It is a local pseudo-random code. The received signal contains a pseudo-random code. It is the product of the two; in formula (1) This can be understood as being in Figure 1 The figure shows the average of the integral within the shaded region and the integral outside the shaded region for each chip; the shaded region represents the part where the local pseudo-random code and the received pseudo-random code are aligned, and the integral result is positive and accumulates over time; for the other part outside the shaded region, it is further assumed that... In the case of pseudo-random codes, If the value is random, its contribution to the integration result is approximately zero.

[0048] If a code Doppler exists and its value remains constant, causing the period of the received symbol to be compressed, then Figure 5 The sliding correlation integral result will becomeFigure 6 As shown;

[0049] from Figure 6 As can be seen from this, if the actual synchronous reception time of the integral is less than Figure 6 The critical integration time is shown. The integral can still produce correlation peaks, but the peak value will be smaller compared to the case without code Doppler. If the actual synchronous reception integration time is greater than the critical integration time, it is equivalent to the integration of multiple chip periods leading to... The accumulation exceeds one chip cycle. Due to the randomness of consecutive symbols in communication, further increasing the pseudo-random sequence length (symbol integration time) will not significantly change the relevant peak values.

[0050] The reciprocal of the critical integration time is the code Doppler frequency. Code Doppler is defined as follows:

[0051] (2)

[0052] In the formula: Indicates code rate, Indicates the carrier frequency. Indicates carrier Doppler frequency shift;

[0053] (3)

[0054] In the formula: v represents the relative speed, and c represents the speed of light. Substituting formula (3) into formula (2) yields:

[0055] (4)

[0056] because Equal to the system's signal bandwidth ,but

[0057] (5)

[0058] Formula (5) indicates that code Doppler is related to the bandwidth of the signal, the relative motion speed, and the speed of light. Due to the presence of speed, the bandwidth of the signal will change; the signal bandwidth corresponds to the symbol time. Due to the presence of code Doppler, the symbol length will change. High-speed motion scenarios (high-speed aircraft, satellites, etc.) will affect the synchronization performance of pseudo-random code sliding correlation technology; Formula (4) is transformed to obtain:

[0059] (6)

[0060] In the formula: Indicates the symbol period, This represents the pre-detection integration time, its physical meaning being the time elapsed after... Due to the influence of code Doppler, the received sequence is misaligned by one symbol period. Let:

[0061] (7)

[0062] Equation (7) represents the normalized (per second) absolute time difference caused by code Doppler (this value has positive and negative values, synchronized with the positive and negative values ​​of velocity). Combining equations (6) and (7), we can obtain:

[0063] (8)

[0064] Formula (8) represents the absolute time difference caused by code Doppler within one second; when the code Doppler in the wireless channel simulator is implemented in the digital domain, the time difference per second in Formula (8) is converted to the clock time difference in the digital domain, thereby realizing the code Doppler module at the digital domain sample level.

[0065] Based on the above derivation and analysis, this invention establishes as follows: Figure 1 The code Doppler verification device shown uses a signal source to periodically send a pseudo-random sequence to a wireless channel simulator (the pseudo-random sequence can be modulated before being sent to the wireless channel simulator). The code Doppler module is added using formula (8) at a user-specified speed. Then, the signal that has passed through the wireless channel simulator and is affected by code Doppler is output to the spectrum and signal analyzer for sampling. After sampling, the signal is transmitted to the host computer for analysis.

[0066] Assume the symbol transmitted by the signal source is After modulation, the output signal of the signal source can be expressed as:

[0067] (9)

[0068] In the formula: Indicates the carrier frequency.

[0069] This assumes the wireless channel simulator does not add channel fading to the signal; initially, the wireless channel simulator is configured not to add code Doppler effect, and the signal output to the spectrum and signal analyzer remains... The data, after orthogonal demodulation and low-frequency filtering by a spectrum and signal analyzer, is then collected and output to the host computer. ,in This indicates the number of collection cycles.

[0070] The spectrum and the data length (or sampling time) acquired by the signal analyzer are: Point; that is, the data collection length can be set according to the actual situation.

[0071] The wireless channel simulator is reconfigured, with the relative motion speed set to vkm / h. The signal transmitted by the signal source is still based on formula (9). The simulator adds code Doppler effect to the input signal according to formula (8) (without adding frequency offset Doppler). At this time, the output signal of the simulator can be expressed as:

[0072] (10)

[0073] The signal output to the spectrum and signal analyzer is After orthogonal demodulation and low-pass filtering by the spectrum and signal analyzer, the data is output to the host computer. The data output to the host computer is represented as follows: , where m represents the number of collection cycles;

[0074] Assume the baseband sampling frequency of the spectrum and signal analyzer is... The code Doppler verification method performed on the host computer is as follows:

[0075] A. Using an initial pseudo-random sequence respectively with pseudo-random sequences and pseudo-random sequences Perform sliding correlation analysis and count the number of correlation peaks. and And the corresponding position index of the relevant peak;

[0076] in, The position index of each related peak is ; The position index of each related peak is , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0077] B. Find the minimum number of relevant peaks. ;

[0078] C. Calculate the sample point difference under the condition of having the same number of correlated peaks. , Indicates the first The position of each relevant peak, where the value is a positive integer;

[0079] D. Calculate the time difference caused by code-Doppler. ,in This indicates the baseband sampling rate of the spectrum and signal analyzer.

[0080] E. Order ,in ,in v represents the relative speed, and c represents the speed of light;

[0081] F. If If the result is positive, it means the verification result meets the requirements; otherwise, it means the verification result does not meet the requirements.

[0082] use The verification result is because the time resolution of the spectrum and signal analyzer is... Error verified by sliding correlation This indicates that the error is likely due to the sliding correlation synchronization error, rather than an error inherent in the verification algorithm itself; since the sliding correlation error will not exceed a certain point in the spectrum and signal analyzer sampling, if If this is not the case, it indicates that the verification algorithm contains an error. Assume the emitted signal is a periodically modulated pseudo-random sequence, see [link to relevant documentation]. Figure 2 As shown, the spectrum and signal analyzer are set to a sampling rate. The data collection time is 10ms.

[0083] Based on Figure 3 and Figure 4 It can be seen that adding code Doppler reduces the correlation peak. In normal communication, due to limitations in symbol length and the movement speed of both communicating parties, synchronization may fail. By analyzing the data using the code Doppler verification method proposed in this paper, the relevant parameters can be obtained as shown in Table 1 below:

[0084] Table 1

[0085] ; Through calculation satisfy The conditions provided demonstrate the practicality and correctness of the code Doppler verification device and method proposed in this paper.

[0086] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A code Doppler verification device, characterized in that, include: Signal source: used to periodically generate an initial pseudo-random sequence Send to the wireless channel emulator; Wireless channel simulator: for the acquired initial pseudo-random sequence Adding the code Doppler effect yields a pseudo-random sequence. and pseudo-random sequence and initial pseudo-random sequence Send to the spectrum and signal analyzer; Spectrum and Signal Analyzer: For initial pseudo-random sequences and pseudo-random sequences Orthogonal demodulation and low-pass filtering are performed to obtain a pseudo-random sequence. and pseudo-random sequences and the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences Send to the host computer; Host computer: Based on the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences Verify whether the added code Doppler is consistent with the impact of symbol compression or expansion caused by the actual speed; The specific steps for code Doppler verification performed by the host computer are as follows: A. Using an initial pseudo-random sequence respectively with pseudo-random sequences and pseudo-random sequences Perform sliding correlation analysis and count the number of correlation peaks. and And the corresponding position index of the relevant peak; in, The position index of each related peak is ; The position index of each related peak is Indicates the first The position of each relevant peak, where the value is a positive integer; B. Find the minimum number of relevant peaks. ; C. Calculate the sample point difference under the condition of having the same number of correlated peaks. Indicates the first The position of each relevant peak, where the value is a positive integer; D. Calculate the time difference caused by code-Doppler. ,in This indicates the baseband sampling rate of the spectrum and signal analyzer. E. Order ,in in , Indicates relative running speed. Represents the speed of light; F. If If the result is positive, it means the verification result meets the requirements; otherwise, it means the verification result does not meet the requirements.

2. The verification device for code Doppler according to claim 1, characterized in that, The wireless channel simulator uses the following formula to add the code Doppler effect: ； In the formula: v Indicates relative running speed. c It represents the speed of light.

3. The code Doppler verification device according to claim 1, characterized in that, The signal output by the wireless channel simulator to the configuration spectrum and signal simulator is represented as follows: ； ； In the formula: This indicates a signal without added code for the Doppler effect; This indicates a signal with added code Doppler effect; Indicates the carrier frequency; Indicates carrier modulation; This indicates taking the real part of the complex signal.

4. A code Doppler verification method, characterized in that, Includes the following steps: Step 1: Obtain the initial pseudo-random sequence Pseudo-random sequences and pseudo-random sequences The initial pseudo-random sequence This represents a pseudo-random sequence generated periodically by the signal source; Pseudo-random sequences This represents a pseudo-random sequence that has undergone orthogonal demodulation and low-pass filtering; pseudo-random sequence This indicates a pseudo-random sequence that has undergone code Doppler effect addition and has been subjected to orthogonal demodulation and low-pass filtering; Step 2: Using the initial pseudo-random sequence respectively with pseudo-random sequences and pseudo-random sequences Perform sliding correlation analysis and count the number of correlation peaks. and And the corresponding position index of the relevant peak; in, The position index of each related peak is ; The position index of each related peak is , Indicates the first The position of each relevant peak, where the value is a positive integer; Step 3. Find the minimum number of relevant peaks. ; Step 4. Calculate the sample difference under the condition of the same number of correlation peaks. , Indicates the first The position of each relevant peak, where the value is a positive integer; Step 5. Calculate the time difference caused by code Doppler. ,in This indicates the baseband sampling rate of the spectrum and signal analyzer. Step 6. Let ,in ,in , Indicates relative running speed. Represents the speed of light; Step 7. If If the result is positive, it means the verification result meets the requirements; otherwise, it means the verification result does not meet the requirements.

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