Short message communication long code spread spectrum signal parallel capturing method, system, medium, device and program product

Abstract

The invention provides a short message communication long code spread spectrum signal parallel capturing method, system, medium, device and program product, the method comprises the following steps: step 1, storage resource planning and time slice division are carried out, and N-beam ADC data parallel receiving processing is completed; step 2, calculating frequency compensation and local code FFT (Fast Fourier Transform), and storing an FFT conversion result of the local code added with Doppler; and step 3, completing capturing and threshold judgment on the N-beam ADC data by using the FFT conversion result of the local code added with the Doppler to obtain an effective short message signal and storing the effective short message signal. On the basis of the FFT + IFFT algorithm, parallel acquisition of multiple paths of signals is equivalently realized through storage resource planning and time slice division, parallel acquisition of burst spread spectrum signals is realized under the limitation of limited processing resources, and the receiving success rate meets the requirement.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a method, system, medium, device and program product for parallel capture of long code spread spectrum signals for short message communication. Background Art

[0002] The characteristics of short message long code spread spectrum signal are short signal duration, long code period, high capture sensitivity, etc. The parallel capture of multiple signals also has limitations on hardware resources. The existing capture algorithms are sorted out and analyzed in terms of capture time, sensitivity and resource constraints as follows:

[0003] (1) Time domain sliding correlation

[0004] Both the time domain and the frequency domain are serial searches. The digital intermediate frequency signal is mixed with the locally generated carrier to remove the carrier by IQ mixing, and then correlated with the locally generated pseudo-random code sequence. After coherent integration and incoherent integration, the obtained correlation peak is judged. If the correlation peak is greater than the threshold, it indicates that the signal is captured. Otherwise, the capturer changes the local carrier frequency and pseudo-random code phase and switches to the next search unit for search. Although this algorithm occupies less hardware resources, its efficiency is too low. It is mainly suitable for the capture of simple continuous navigation signals in the early system, and is not suitable for the reception of long-period code short message signals.

[0005] (2)XFAST

[0006] The XFAST capture algorithm is based on the FFT+IFFT concept. By overlapping the local reference signal in the time domain, the code phase search range can be expanded. It is mainly used to solve the long code capture problem with high time uncertainty and limited FFT resources. The XFAST algorithm expands the single code phase search range without increasing the number of FFT points, but at the cost of amplifying the noise floor and introducing multiple access interference. In addition, after the code phase is initially captured, the duplicate overlapping ambiguity needs to be further removed. Multi-channel parallel capture requires instantiation of multiple capture devices, which consumes a lot of resources. At the same time, short message signals have a short duration, the signal does not exist continuously, the sensitivity requirement is high, and long-term accumulation is not supported. Therefore, this algorithm is not suitable for parallel capture of burst short message signals.

[0007] (3)PMF-FFT

[0008] The algorithm is a parallel search in the frequency domain. If matched filtering is used in the time domain, it is also a parallel search in the time domain. If a correlator is used, it is a serial search in the time domain.

[0009] The time domain parallel PMF-FFT algorithm model is as follows Figure 1As shown, the input signal is a complex signal that has undergone IQ down-conversion and enters an M*X level matched filter. The matched filter can be divided into M groups of partially matched filters connected in series, and the number of partially matched filters is X. The output of the matched filter is not directly summed, but is used as the input of the M-point FFT operation. The maximum value of the M FFT output modulus values ​​is compared with the preset threshold to determine whether the capture is successful. When the signal sampling rate is constant, X is the length of the partial match, which determines the upper limit of the Doppler search range, and M is the number of FFT points, which together with X determines the Doppler search resolution.

[0010] The advantage of PMF-FFT algorithm is fast large dynamic Doppler search and long code phase search period. It is not suitable for receiving long period code short message signals.

[0011] (4) FFT+IFFT

[0012] The time domain is a parallel search. Considering that matched filtering is actually a convolution operation, the time domain convolution operation is equivalent to the frequency domain multiplication operation. Therefore, the received signal and the local reference signal can be multiplied after FFT operation (taking conjugate in the local frequency domain), and then IFFT is performed back to the time domain to obtain the correlation function.

[0013] This algorithm and matched filtering are both time-domain parallel algorithms. The difference is that this algorithm performs cyclic correlation operations on the same segment of received signals each time. It is usually necessary to convert cyclic correlation into linear correlation, which is achieved by padding the second half of the length of the local signal with zeros. For example, for short code signal capture, if the number of sampling points corresponding to one code period is N, the length of the received signal is 2*N, and the local reference signal is one code period (the number of sampling points is N) and then padded with N zeros, which can eliminate the influence of information bit modulation and complete signal capture. For long code signal capture, the local reference signal is N data followed by N zeros, and the length of the received signal is 2*N. It can be considered that N code phases are searched at one time. After each FFT+IFFT algorithm is run, the input signal continues to search with a length of N as a step. This algorithm has a fast capture speed and high capture sensitivity, and is suitable for short message spread spectrum signal reception. However, in terms of adapting to parallel capture, the algorithm needs to instantiate multiple capturers, which consumes a lot of resources.

[0014] By analyzing the characteristics of time domain sliding correlation, XFAST, PMF-FFT and FFT+IFFT algorithms, combined with the characteristics of short message long code spread spectrum signals, FFT+IFFT can be used for short message spread spectrum signal reception, but when multi-channel parallel capture is performed, the FPGA hardware resources are large. To solve this problem, the present invention proposes a short message communication long code spread spectrum signal parallel capture method, system, medium, device and program product based on the FFT+IFFT algorithm. Summary of the invention

[0015] Aiming at the problems faced by the IoT satellite's sudden inbound reception signals, such as short signal duration, large number of concurrent signals, random communication time, etc., the IoT satellite has a low orbit altitude and a small coverage range of a single antenna beam, and multiple beams are required to cover simultaneously to meet the access requirements of IoT terminal signals. Based on the FFT+IFFT algorithm, the present invention proposes a method, system, medium, device and program product for parallel capture of short message communication long code spread spectrum signals.

[0016] The present invention provides a method for parallel acquisition of a short message communication long code spread spectrum signal, comprising the following steps:

[0017] Step 1: storage resource planning and time slice division, and completing parallel reception and processing of N beam path ADC data;

[0018] Step 2, calculate frequency compensation and local code FFT, and store the FFT transformation result of the local code after adding Doppler;

[0019] Step 3: Use the FFT transformation result of the local code after adding Doppler to complete the capture and threshold judgment of the N-beam path ADC data, obtain the effective short message signal and store it.

[0020] Furthermore, step 1 includes the following sub-steps:

[0021] 1) N beam path ADC data, down-rate sampling, 2 sampling points per chip, code rate Rc, sampling rate Fs, store N ADC data in total, open N FIFOs in total, release reset synchronously, start storing data, storage depth of each signal is Ld+(2*Ld / Fs)*2*Rc, storage time is Tc, requirement (2*Ld / Fs)<(Tc / N);

[0022] 2) When the amount of data stored in the i-th FIFO is greater than Ld, use the sampling rate Fs clock to read the i-th FIFO data, stop FIFO reading after reading Ld points, fill Ld zero data, and send to FFT;

[0023] 3) After the Ldth 0 is sent to FFT, switch to the next FIFO to read, record the number of data sent to FFT calculation fifocont, repeat steps 2) to 3), i = 1 to N, and read FIFO data in sequence;

[0024] 4) When fifocont≥2*Ld*N, stop the ADC data FFT calculation, wait until the number of ADC data stored in FIFO is greater than Ld, restart the calculation process of steps 2) to 4), and equivalently complete the parallel reception processing of N beam path ADC data.

[0025] Furthermore, step 2 includes: pre-generating a local code, and pre-loading Doppler into the local code according to the capture Doppler requirement, and performing FFT transformation on the local code after adding Doppler, and storing the FFT transformation result into RAM.

[0026] Furthermore, the COE file generated by the FFT transformation result is loaded into the RAM.

[0027] Furthermore, step 3 includes the following sub-steps:

[0028] 1) The FFT IP core works in pipeline mode, continuously calculating 2*Ld point FFT operations, conjugating and multiplying the data stored in RAM, and then performing 2*Ld point IFFT, which is equivalent to performing correlation accumulation of Ld / 2 chips;

[0029] 2) The 2*Ld point FFT operation results are used to estimate the channel noise and generate the decision threshold TH for each beam;

[0030] 3) The IFFT operation result is compared with the respective beam decision threshold TH. The signal phase exceeding the decision threshold TH means that the ADC data has captured a valid short message signal.

[0031] 6. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 5, wherein step 3 further comprises:

[0032] 4) Store the phase information and beam information of the captured effective short message signal for the signal tracking system to complete signal tracking and demodulation.

[0033] The present invention also provides a short message communication long code spread spectrum signal parallel acquisition system, comprising:

[0034] The signal receiving and storage module is used to complete the parallel receiving and processing of N-beam ADC data through storage resource planning and time slice division;

[0035] A frequency compensation and local code FFT calculation module is used to calculate frequency compensation and local code FFT, and store the FFT transformation result of the local code after adding Doppler;

[0036] Capture and threshold judgment are used to complete capture and threshold judgment of N beam path ADC data using the FFT transformation result of the local code after adding Doppler, obtain valid short message signals and store them.

[0037] The present invention also provides a computer terminal storage medium storing computer terminal executable instructions, wherein the computer terminal executable instructions are used to execute the above-mentioned short message communication long code spread spectrum signal parallel capture method.

[0038] The present invention also provides a computing device, comprising:

[0039] At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the above-mentioned short message communication long code spread spectrum signal parallel acquisition method.

[0040] The present invention also provides a computer program product, which implements the above-mentioned short message communication long code spread spectrum signal parallel capture method when the computer program is executed by a processor.

[0041] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0042] The present invention is based on FFT+IFFT algorithm, and realizes the equivalent parallel capture of multi-path signals through storage resource planning and time slice division, and realizes the parallel capture of burst spread spectrum signals under the restriction of limited processing resources, and the reception success rate meets the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the time-domain parallel PMF-FFT algorithm model.

[0044] Figure 2 The schematic diagram of the parallel capture method of the long code spread spectrum signal for short message communication in an embodiment of the present invention is shown in FIG.

[0045] Figure 3 It is a capture simulation result diagram of the parallel capture method of the long code spread spectrum signal for short message communication in an embodiment of the present invention.

[0046] Figure 4 Graph showing the relationship between detection probability and signal-to-noise ratio of a parallel acquisition method for a long code spread spectrum signal for short message communication in an embodiment of the present invention.

[0047] Figure 5 The invention provides a method for parallel acquisition of a long code spread spectrum signal for short message communication. Figure 4 Capture probability curve at different Dopplers. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0050] Example

[0051] This embodiment proposes a method for parallel capture of long code spread spectrum signals for short message communication. The implementation principle of the method is: through storage resource planning and time slice division, the parallel capture of multiple signals is equivalently realized. At the same time, in order to reduce the consumption of logical resources, the functions of frequency compensation, local code FFT calculation, channel noise power estimation and generation of capture decision threshold are integrated to further reduce resource utilization.

[0052] like Figure 2 As shown, the short message communication long code spread spectrum signal parallel acquisition method comprises the following steps:

[0053] Step 1: Storage resource planning and time slice division:

[0054] 1) N beam path ADC data, down-rate sampling, 2 sampling points per chip, code rate Rc, sampling rate Fs, store N ADC data in total, open N FIFOs in total, release reset synchronously, start storing data, storage depth of each signal is Ld+(2*Ld / Fs)*2*Rc, storage time is Tc, requirement (2*Ld / Fs)<(Tc / N);

[0055] 2) When the amount of data stored in the i-th FIFO is greater than Ld, use the sampling rate Fs clock to read the i-th FIFO data, stop FIFO reading after reading Ld points, fill Ld zero data, and send to FFT;

[0056] 3) After the Ldth 0 is sent to FFT, switch to the next FIFO to read, record the number of data sent to FFT calculation fifocont, repeat steps 2) to 3), i = 1 to N, and read FIFO data in sequence;

[0057] 4) When fifocont≥2*Ld*N, stop the ADC data FFT calculation, wait until the number of ADC data stored in FIFO is greater than Ld, restart the calculation process of steps 2) to 4), and equivalently complete the parallel reception processing of N beam path ADC data.

[0058] Step 2, calculate frequency compensation and local code FFT:

[0059] Generate the local code in advance, and preload the Doppler into the local code according to the Doppler capture requirement, perform FFT transformation on the local code after adding the Doppler, generate a COE file and load it into RAM.

[0060] Step 3: Capture and threshold decision

[0061] 1) The FFT IP core works in pipeline mode, continuously calculating 2*Ld-point FFT operations, conjugating and multiplying the data stored in RAM (the FFT transform result of the local code after adding Doppler), and then performing 2*Ld-point IFFT, which is equivalent to performing the correlation accumulation of Ld / 2 code chips.

[0062] 2) The 2*Ld point FFT operation results are used to estimate the channel noise and generate the decision threshold TH for each beam;

[0063] 3) The IFFT operation result is compared with the respective beam decision threshold TH. The signal phase exceeding the decision threshold TH means that the ADC data has captured a valid short message signal;

[0064] 4) Store the phase information and beam information of the captured effective short message signal for the signal tracking system to complete signal tracking and demodulation.

[0065] Simulation and actual machine verification of the parallel acquisition method of the short message communication long code spread spectrum signal:

[0066] According to the invention content, Matlab captures the simulation results as follows Figure 3 shown.

[0067] When there is a user signal, after being detected by the capture module, the signal envelope Following the Rice distribution, the relationship between the detection probability, detection signal-to-noise ratio, and false alarm probability can be obtained:

[0068]

[0069] According to the above formula, if the false alarm probability Pf is specified as 10 -6 , we can get the detection probability Pd and signal-to-noise ratio SNR d The relationship is as Figure 4 As shown:

[0070] After testing, the capture probability results under different Dopplers are as follows: Figure 5 , which can meet 97% capture probability and satisfy the performance requirements.

[0071] Comparative analysis of the capture time of the parallel capture method of the short message communication long code spread spectrum signal: intercept the first 4096 code bits for correlation capture, and the sampling rate Fs is 122.88e6. The algorithm simulation comparison analysis is shown in Table 1.

[0072] Table 1, sampling rate Fs is 122.88e6 algorithm simulation comparison analysis:

[0073] Serial number algorithm Code rate Rc Code cycle Capture probability Capture time 1 Time domain sliding correlation - - - not applicable 2 XFAST algorithm 1.023Mchip / s 16777215 >97％ 8.6ms 3 PMF-FFT algorithm - - - not applicable 4 FFT+IFFT algorithm 1.023Mchip / s 16777215 >97％ 8.8ms 5 The present invention 1.023Mchip / s 16777215 >97％ 8.8ms

[0074] The comparative analysis of resource consumption of the parallel capture method of the short message communication long code spread spectrum signal is shown in Table 2.

[0075] Table 2, resource consumption comparison analysis:

[0076] Serial number algorithm Multiplier BRAM 18k DSP Slices Remark 1 Time domain sliding correlation - - - not applicable 2 XFAST algorithm 65 1404 702 - 3 PMF-FFT algorithm - - - not applicable 4 FFT+IFFT algorithm 65 2652 702 - 5 Algorithm of the present invention 5 376 36 -

[0077] The capture sensitivity comparison analysis of the parallel capture method for the short message communication long code spread spectrum signal is shown in Table 3.

[0078] Table 3, capture sensitivity comparison analysis:

[0079]

[0080]

[0081] Through comparative analysis and verification in several aspects such as capture time, resource consumption, capture sensitivity, etc., the algorithm of the present invention has lower resource consumption under similar performance conditions.

[0082] In addition, in order to verify the correctness of the present invention, the above-designed system was successfully used in a multi-user access payload of a low-orbit satellite. The system has passed the acceptance test, and the terminal message reception success rate meets the use requirements, verifying the correctness of the proposed method.

[0083] In addition, in some embodiments, a short message communication long code spread spectrum signal parallel acquisition system is proposed, comprising:

[0084] The signal receiving and storage module is used to complete the parallel receiving and processing of N-beam ADC data through storage resource planning and time slice division;

[0085] A frequency compensation and local code FFT calculation module is used to calculate frequency compensation and local code FFT, and store the FFT transformation result of the local code after adding Doppler;

[0086] Capture and threshold judgment are used to complete capture and threshold judgment of N beam path ADC data using the FFT transformation result of the local code after adding Doppler, obtain valid short message signals and store them.

[0087] The detailed working principle of the short message communication long code spread spectrum signal parallel acquisition system refers to the aforementioned short message communication long code spread spectrum signal parallel acquisition method, which will not be repeated here.

[0088] In addition, in some embodiments, a computer terminal storage medium is provided, which stores computer terminal executable instructions, and the computer terminal executable instructions are used to execute the short message communication long code spread spectrum signal parallel acquisition method as described in the above embodiments. Examples of computer storage media include magnetic storage media (e.g., floppy disks, hard disks, etc.), optical recording media (e.g., CD-ROMs, DVDs, etc.) or memories, such as memory cards, ROMs or RAMs, etc. Computer storage media can also be distributed on network-connected computer systems, such as application stores.

[0089] In addition, in some embodiments, a computing device is proposed, comprising: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the short message communication long code spread spectrum signal parallel acquisition method as described in the above embodiment. Examples of computing devices include PCs, tablet computers, smart phones, or PDAs.

[0090] In addition, in some embodiments, a computer program product is proposed, and when the computer program is executed by a processor, the above-mentioned short message communication long code spread spectrum signal parallel acquisition method is implemented.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for parallel acquisition of long code spread spectrum signals for short message communication, characterized in that: The steps include: Step 1: storage resource planning and time slice division, and completing parallel reception and processing of N beam path ADC data; Step 2, calculate frequency compensation and local code FFT, and store the FFT transformation result of the local code after adding Doppler; Step 3: Use the FFT transformation result of the local code after adding Doppler to complete the capture and threshold judgment of the N-beam path ADC data, obtain the effective short message signal and store it.

2. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 1, characterized in that: Step 1 includes the following sub-steps: 1) N beam path ADC data, down-rate sampling, 2 sampling points per chip, code rate Rc, sampling rate Fs, store N ADC data in total, open N FIFOs in total, release reset synchronously, start storing data, storage depth of each signal is Ld+(2*Ld / Fs)*2*Rc, storage time is Tc, requirement (2*Ld / Fs)<(Tc / N); 2) When the amount of data stored in the i-th FIFO is greater than Ld, use the sampling rate Fs clock to read the i-th FIFO data, stop FIFO reading after reading Ld points, fill Ld zero data, and send to FFT; 3) After the Ldth 0 is sent to FFT, switch to the next FIFO to read, record the number of data sent to FFT calculation fifocont, repeat steps 2) to 3), i = 1 to N, and read FIFO data in sequence; 4) When fifocont≥2*Ld*N, stop the ADC data FFT calculation, wait until the number of ADC data stored in FIFO is greater than Ld, restart the calculation process of steps 2) to 4), and equivalently complete the parallel reception processing of N beam path ADC data.

3. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 2, characterized in that: Step 2 includes: pre-generating a local code, and pre-loading Doppler into the local code according to the capture Doppler requirement, and performing FFT transformation on the local code after adding Doppler, and storing the FFT transformation result into RAM.

4. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 3, characterized in that: The COE file generated by the FFT transformation result is loaded into RAM.

5. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 2, characterized in that: Step 3 includes the following sub-steps: 1) The FFT IP core works in pipeline mode, continuously calculating 2*Ld point FFT operations, conjugating and multiplying the data stored in RAM, and then performing 2*Ld point IFFT, which is equivalent to performing correlation accumulation of Ld / 2 chips; 2) The 2*Ld point FFT operation results are used to estimate the channel noise and generate the decision threshold TH for each beam; 3) The IFFT operation result is compared with the respective beam decision threshold TH. The signal phase exceeding the decision threshold TH means that the ADC data has captured a valid short message signal.

6. The method for parallel acquisition of long code spread spectrum signals for short message communication according to claim 5, characterized in that: Step 3 also includes: 4) Store the phase information and beam information of the captured effective short message signal for the signal tracking system to complete signal tracking and demodulation.

7. A short message communication long code spread spectrum signal parallel acquisition system, characterized in that: include: The signal receiving and storage module is used to complete the parallel receiving and processing of N-beam ADC data through storage resource planning and time slice division; A frequency compensation and local code FFT calculation module is used to calculate frequency compensation and local code FFT, and store the FFT transformation result of the local code after adding Doppler; Capture and threshold judgment are used to complete capture and threshold judgment of N beam path ADC data using the FFT transformation result of the local code after adding Doppler, obtain valid short message signals and store them.

8. A computer terminal storage medium storing computer terminal executable instructions, characterized in that: The computer terminal executable instructions are used to execute the short message communication long code spread spectrum signal parallel acquisition method as described in any one of claims 1-7.

9. A computing device, characterized in that: include: at least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the short message communication long code spread spectrum signal parallel capture method as described in any one of claims 1-7.

10. A computer program product, characterized in that When the computer program is executed by a processor, the method for parallel acquisition of short message communication long code spread spectrum signals as described in any one of claims 1 to 7 is implemented.

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