Low-orbit satellite communication timing method and device based on angle synthesis

Abstract

The present invention discloses a low-orbit satellite communication bit timing method and device based on angle synthesis. The method includes: extracting the offset information of the current code element of the input signal based on the power of the input signal to obtain the offset angle representation value of the current code element; correcting the offset angle representation value of the current code element by using the offset angle representation value of the previous code element to expand the sampling space to obtain the corrected offset angle representation value of the current code element; fitting the sampling center of the current code element by using the corrected offset angle representation value; sampling in the fitting interval based on the sampling center of the current code element to obtain the sampling data of the current code element. The method provided by the present invention can expand the sampling interval and sampling points toward the optimal sampling point; thereby, it can avoid code element duplication and code element omission caused by sampling offset at a low cost, thereby enhancing the satellite positioning effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal processing, and in particular relates to a low-orbit satellite communication timing method and device based on angle synthesis. Background Art

[0002] Satellites provide efficient global coverage, particularly for communication over remote areas and oceans. With the rapid deployment of low-Earth orbit satellites and technological advancements, their applications in providing high-speed internet, IoT connectivity, and disaster relief are promising. Satellite communication systems face numerous technical challenges in operation. First, because signals must travel extremely long distances, they experience severe free-space loss, resulting in weak received signals. Second, as signals pass through the atmosphere, they are susceptible to distortion due to multipath effects, ionospheric delays, and tropospheric delays. Finally, the high-speed motion of low-Earth orbit satellites introduces high-dynamics issues in signal transmission, requiring communication systems to possess extremely high signal tracking sensitivity.

[0003] However, current bit timing technology performs poorly when faced with the sampling point drift caused by the high dynamic characteristics of satellite communications, and is prone to missing or repeating code elements. Summary of the Invention

[0004] The embodiment of the present invention provides a low-orbit satellite communication bit timing method based on angle synthesis, which can solve the problem that the current bit timing technology is prone to missing or repeated code elements in the satellite communication scenario.

[0005] In a first aspect, an embodiment of the present invention provides a low-orbit satellite communication timing method based on angle synthesis, the method comprising:

[0006] Extracting the offset information of the current symbol of the input signal according to the power of the input signal to obtain an offset angle representation value of the current symbol;

[0007] Correcting the offset angle representation value of the current symbol by using the offset angle representation value of the previous symbol to expand the sampling space to obtain the corrected offset angle representation value of the current symbol, wherein the sampling space is a selectable space for sampling points;

[0008] Fitting the sampling center of the current symbol by the corrected offset angle characterization value;

[0009] Sampling is performed on a fitting interval based on the sampling center of the current symbol to obtain sampling data of the current symbol.

[0010] In a second aspect, an embodiment of the present invention provides a low-orbit satellite communication bit timing device based on angle synthesis, comprising:

[0011] An offset quantization unit, configured to extract offset information of a current symbol of the input signal according to the power of the input signal to obtain an offset complex representation value of the current symbol;

[0012] an offset correction unit, the offset correction unit being configured to determine an offset angle representation value of the current symbol based on the offset complex representation value of the current symbol, and correct the offset angle representation value of the current symbol using the offset angle representation value of the previous symbol to expand a sampling space to obtain the corrected offset angle representation value of the current symbol, wherein the sampling space is a selectable space for sampling points;

[0013] A sampling unit is used to fit the sampling center of the current code element through the corrected offset angle characterization value; and to obtain sampling data of the current code element by sampling in a fitting interval based on the sampling center of the current code element.

[0014] Compared with the prior art, the embodiments of the present invention have the following advantages: according to the method provided by the present invention, the position of the sampling point is dynamically adjusted by the difference between two adjacent code element offset values, so that the sampling interval and the sampling point are extended toward the optimal sampling point; thereby, code element duplication and code element omission caused by sampling offset can be avoided at a low cost, thereby enhancing the satellite positioning effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart of an implementation method for low-orbit satellite communication timing based on angle synthesis provided by an embodiment of the present invention;

[0016] Figure 2 A schematic diagram of the effect of adjusting the sampling interval provided by an embodiment of the present invention;

[0017] Figure 3 A schematic structural diagram of a low-orbit satellite communication timing device based on angle synthesis provided by an embodiment of the present invention;

[0018] Figure 4 A comparative constellation diagram before and after bit timing provided by an embodiment of the present invention;

[0019] Figure 5 A schematic diagram of a comparison of bit error curves provided in an embodiment of the present invention;

[0020] Figure 6 A schematic diagram of the relationship between bias variance and signal-to-noise ratio provided by an embodiment of the present invention;

[0021] Figure 7 A schematic diagram of the relationship between the number of converged code elements and the signal-to-noise ratio provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0023] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0024] It will also be understood that the term "and / or" used in the present description and appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0025] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0026] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0027] References to "one embodiment" or "some embodiments" in the present specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present invention. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0028] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0029] Figure 1 The flowchart shown is a method for implementing a low-orbit satellite communication timing method based on angle synthesis according to an embodiment of the present invention. As an example and not a limitation, the method may include steps S101-S104, each of which is described below.

[0030] S101 , extracting offset information of a current symbol of an input signal according to the power of the input signal to obtain an offset angle representation value of the current symbol.

[0031] In one possible implementation, the offset complex representation value of the current codeword can be determined based on the power of the input signal and the quantization vector of the current codeword, and then the offset complex representation value of the current codeword is smoothed integrated and angle synthesized to obtain the offset angle representation value of the current codeword.

[0032] Exemplarily, the offset complex representation value of the current symbol may satisfy the following formula:

[0033] θ=angle(α)(1.1)

[0034] θ is the offset angle representation value of the current code element, and α is the smoothing result of the current code element;

[0035] The smoothing result of the m+1th symbol satisfies the following formula:

[0036] α(m+1)=(temp(m+1)-α(m)) / δ+α(m)(1.2)

[0037] δ is the smoothing coefficient, which is generally a power of 2 for ease of hardware implementation; α(m+1) is the smoothing result of the m+1th code element, temp(m+1) is the offset complex representation value of the m+1th code element, and angle is the complex angle function.

[0038] Specifically, the angle function may be directly called in the software code, or a coordinate rotation digital computer (cordic) algorithm may be selected in the hardware for implementation.

[0039] In an example, the input signals may be two complex signals I(m) and Q(m), and the instantaneous power of the input signals may be obtained by summing the squares of the amplitudes to remove the information carried by the signals.

[0040] Exemplarily, the power of the mth symbol of the input signal may satisfy the following formula:

[0041] P(m)=I(m) 2 +Q(m) 2 (1.3)

[0042] Wherein, P(m) is the mth code element of the input signal.

[0043] In one example, a quantization interval can be first generated based on the number of samples n per codeword; then, a quantization vector is combined based on the quantization interval, and the unit complex value of the quantization vector is solved using the Euler formula; finally, the unit complex value of the quantization vector is taken as the inner product with the instantaneous power of the previous codeword to obtain the offset complex representation value of the current codeword.

[0044] For example, the quantization interval, the quantization vector, and the unit complex value of the quantization vector, i.e., the offset complex representation value, may satisfy the following formulas:

[0045] gap=2π / n(1.4)

[0046]

[0047] Among them, gap, are the quantization interval, quantization vector, and unit complex value of the quantization vector, respectively. temp(m) is the offset complex representation value of the m-th codeword, and P(m-1) is the instantaneous power of the m-1-th codeword.

[0048] S102, correcting the offset angle representation value of the current symbol by using the offset angle representation value of the previous symbol to expand the sampling space to obtain the corrected offset angle representation value of the current symbol.

[0049] Exemplarily, the sampling space is a selectable space of sampling points.

[0050] In one possible implementation, the offset angle characterization value of the current code element may be processed secondary using the difference between the offset angle characterization values ​​of two adjacent code elements (i.e., the adjacent angle difference) as a judgment condition to ensure the stability and accuracy of the offset.

[0051] In one example, multiple preset correction ranges can be pre-set, and a corresponding preset correction value can be configured for each preset correction range. Subsequently, when correcting the offset angle representation value, the difference between the offset angle representation value of the previous code element and the offset angle representation value of the current code element can be first determined to obtain an adjacent angle difference; then, a first preset range within which the adjacent angle difference falls can be determined; and finally, based on the positive or negative sign of the adjacent angle difference, the preset correction value corresponding to the first preset range is added or subtracted from the offset angle representation value of the current code element or the offset angle representation value of the previous code element to obtain the corrected offset angle representation value of the current code element.

[0052] For example, if four preset correction ranges are set, they can be recorded in order of range size: #1, #2, #3, and #4. Range #1 is the normal range. If the adjacent angle difference is within range #1, the offset angle representation value of the current code element is not processed and is directly output as the corrected offset angle representation value of the current code element.

[0053] If the adjacent angle difference is within #2 or #4, the offset angle representation value θ(m) of the mth codeword can be added or subtracted from the preset correction value corresponding to #2 or #4 according to the adjacent angle difference to obtain the corrected offset angle representation value of the m+1th codeword.

[0054] If the adjacent angle difference is within #3, the preset correction value corresponding to #3 can be added or subtracted on θ(m) according to the adjacent angle difference to obtain the corrected offset angle representation value of the m+1th code element.

[0055] S103, fitting the sampling center of the current symbol by using the corrected offset angle representation value.

[0056] In a possible implementation, before determining the sampling center, the sampled fitting interval may be determined first.

[0057] In one example, the fitting interval may include a plurality of consecutive symbol data, and the current symbol is not the first or last symbol of the fitting interval.

[0058] In a possible implementation, after determining the fitting interval, the sampling center of the current symbol may be determined, and then the following step S104 is performed to select a sampling space according to the value of the sampling center.

[0059] In one example, the difference between the first preset angle and the corrected offset angle characterization value can be determined to obtain the first preset angle difference; and the quotient of the first preset angle difference and the angle ratio is determined as the sampling center of the current code element.

[0060] Exemplarily, the first preset angle may be used to determine the position of the sampling space.

[0061] Exemplarily, the angle ratio is the quotient of the angle period and the ratio parameter.

[0062] In one example, to implement proportional quantization of the subsequent sinc fitting function in hardware, since negative values ​​and decimals do not exist in hardware implementation, the proportional parameter ω needs to be controlled as a factor of the angular period. Furthermore, when quantizing the sinc function, the position number of the maximum value of the final result needs to be included in the calculation of the sampling center. Therefore, the difference between the second preset angle and the corrected offset angle representation value can be first determined to obtain the second preset angle difference. The quotient of the second preset angle difference and the angle ratio is then used to determine the sampling center of the current symbol.

[0063] Exemplarily, the second preset angle is the sum of the first preset angle and the maximum position number of the fitting interval.

[0064] Generally, the sampling space is 1 symbol in size, and the offset angle representation value is between 0 and 360 degrees. Figure 2 In (a), when the two receiving ends are far apart, the optimal sampling point exceeds the sampling interval. Traditional methods will fix the sampling interval size and reset the offset value to zero and readjust the offset value so that the offset value is always within interval #1. For example, adjusting it from 370 degrees to 10 degrees prevents the sampling point from approaching the optimal sampling point. In the present invention, through the correction in step S102, when the difference between two adjacent offset values ​​is large, the sampling space is expanded so that the sampling point can approach the optimal sampling point. Figure 2 (b) in the figure, thereby enhancing the satellite positioning effect.

[0065] S104 , performing sampling on the fitting interval based on the sampling center of the current symbol to obtain sampling data of the current symbol.

[0066] In a possible implementation, the sampling data of the current symbol may be obtained by performing interpolation sampling on the current symbol data based on the sampling center of the current symbol.

[0067] In one example, when performing fitting interpolation sampling, a sinc function proportional quantization may be performed first, and after obtaining a fitting function value through the fitting function, the fitting function value is multiplied by the fitting interval to obtain sampling data of the current symbol.

[0068] Exemplarily, the fitting function value may satisfy: SINC=sinc(-4:1 / ω:4).

[0069] Exemplarily, the sampling data of the current symbol may satisfy the following formula:

[0070] out=SINC(i-2n:i+2n-1)×X(1.8)

[0071] Where out is the sampling data of the current symbol, i is the sampling center, and X is the fitting interval.

[0072] According to the method provided by the present invention, the position of the sampling point is dynamically adjusted by the difference between the offset values ​​of two adjacent code elements, so that the sampling interval and the sampling points are expanded toward the optimal sampling point. This can avoid code element duplication and code element omission caused by sampling offset at a low cost, thereby enhancing the satellite positioning effect.

[0073] Furthermore, using complex vector angles (i.e., offset angle representation values) to estimate the offset of complex signals can fully utilize the codeword waveform characteristics; using two simple measures, conditional restrictions and simple integration, to determine the offset and sampling interval can achieve faster convergence speed and lower resource overhead and debugging costs.

[0074] Figure 3 The figure shows a schematic diagram of the structure of a low-orbit satellite communication bit timing device based on angle synthesis according to an embodiment of the present invention. By way of example and not limitation, device 300 can be used to implement the above method. Device 300 may include an offset quantization unit 310, an offset correction unit 320, and a sampling unit 330.

[0075] Exemplarily, the offset quantization unit 310 is used to extract the offset information of the current codeword of the input signal according to the power of the input signal to obtain the offset complex representation value of the current codeword; the offset correction unit 320 is used to determine the offset angle representation value of the current codeword according to the offset complex representation value of the current codeword, and correct the offset angle representation value of the current codeword by the offset angle representation value of the previous codeword to expand the sampling space to obtain the corrected offset angle representation value of the current codeword, wherein the sampling space is the selectable space of the sampling points; the sampling unit 330 is used to fit the sampling center of the current codeword by the corrected offset angle representation value, and perform sampling on the fitting interval based on the sampling center of the current codeword to obtain the sampling data of the current codeword.

[0076] Specifically, the offset correction unit 320 may use a counter to record the amount of data and reset the extended sampling frame back to its original position within the protection interval of the communication protocol to ensure continuous operation.

[0077] In one possible implementation, as described in the above method, the fitting interval may include multiple consecutive symbol data, and the current symbol is not the first symbol or the last symbol in the fitting interval. Therefore, the apparatus 300 may further include a data combining unit 340. The data combining unit may be configured to combine the serial data stream by intervals to obtain symbol data within the fitting interval for use by the sampling unit 330.

[0078] In one example, based on the above formula (1.8), the apparatus 300 may further include a sinc storage module 350 .

[0079] For example, the sinc storage module 350 can be used to store the sinc values ​​for different i values, which is convenient for subsequent sampling unit 330 to call and can simplify the structure of the device 300.

[0080] In order to better illustrate the beneficial effects of the present invention, the following simulation experiments were conducted:

[0081] For example, in a simulation experiment, device 300 was used as a bit timing module in a low-orbit satellite frequency-hopping communication system. The modulation scheme was DQPSK, and the module operated at a 122.88 MHz clock. The number of samples per symbol, n, was 12, the symbol rate was 10.24 MHz, and the sampling rate was 122.88 MHz. ω was set to 30, β to 0, and δ to 128. The module was fully pipelined, with no communication or data storage involved, thus preventing congestion. Its input consisted of two complex signals, quantized to 16 bits.

[0082] Figure 4 Shown is a comparative constellation diagram before and after bit timing provided by an embodiment of the present invention.

[0083] See also Figure 4 ,in Figure 4 (a) is the DQPSK signal constellation diagram before bit timing. Figure 4 (b) in the figure is the constellation diagram of the DQPSK signal after bit timing.

[0084] See also Figure 4 and Figure 5 As can be seen from the bit error curve graph in the figure, under QPSK modulation, 12 samples per symbol, and a hard decision method, when the signal-to-noise ratio is high, the bit error curve of the present invention basically overlaps with the bit error curve that always maintains the optimal sampling point. When the signal-to-noise ratio drops below 0 dB, the result of the present invention begins to fluctuate and deviate from the optimal sampling point.

[0085] Figure 6 FIG2 shows a schematic diagram of the relationship between the deviation variance and the signal-to-noise ratio provided by an embodiment of the present invention.

[0086] See also Figure 6 It can be seen that the deviation variance of the sampling point deviation estimation result of the present invention is under control before -4dB, and the deviation increases significantly after -4dB.

[0087] Figure 7 The figure shows the relationship between the number of converged symbols and the signal-to-noise ratio according to an embodiment of the present invention, wherein each signal-to-noise ratio point is tested 50 times and the average value is obtained.

[0088] See also Figure 7 As can be seen, the convergence speed of the present invention is slightly better than that of the general-purpose Gardner timing recovery loop. The significant increase in the number of converged symbols after -4dB at low signal-to-noise ratios is due to both a longer initial oscillation time and the increased oscillation amplitude due to noise, making it difficult to meet the variance criterion for convergence.

[0089] Therefore, according to the method provided by the present invention, the position of the sampling point is dynamically adjusted by the difference between two adjacent code element offset values, so that the sampling interval and sampling points are expanded toward the optimal sampling point; thereby, code element duplication and code element omission caused by sampling offset can be avoided at a low cost, thereby enhancing the satellite positioning effect.

[0090] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

Claims

1. A low-orbit satellite communication timing method based on angle synthesis, characterized in that: include: Extracting the offset information of the current symbol of the input signal according to the power of the input signal to obtain an offset angle representation value of the current symbol; Correcting the offset angle representation value of the current symbol by using the offset angle representation value of the previous symbol to expand the sampling space to obtain the corrected offset angle representation value of the current symbol, wherein the sampling space is a selectable space for sampling points; Fitting the sampling center of the current symbol by the corrected offset angle characterization value; Sampling is performed on a fitting interval based on the sampling center of the current symbol to obtain sampling data of the current symbol.

2. The method according to claim 1, characterized in that The extracting the offset information of the current symbol of the input signal according to the power of the input signal to obtain the offset angle representation value of the current symbol includes: Determining an offset complex representation value of the current symbol according to the power of the input signal and a quantization vector of the current symbol; The offset complex representation value of the current codeword is smoothed integrated and angle synthesized to obtain the offset angle representation value of the current codeword.

3. The method according to claim 2, characterized in that The offset angle representation value of the current symbol satisfies the following formula: θ=angle(α) Wherein, θ is the offset angle representation value of the current code element, and α is the smoothing result of the current code element; The smoothing result of the m+1th symbol satisfies the following formula: α(m+1)=(temp(m+1)-α(m)) / δ+α(m) Wherein, δ is the smoothing coefficient, α(m+1) is the smoothing result of the m+1th codeword, temp(m+1) is the offset complex representation value of the m+1th codeword, and angle is the complex angle function.

4. The method according to claim 1, wherein The step of correcting the offset angle representation value of the current symbol by using the offset angle representation value of the previous symbol to expand the sampling space to obtain the corrected offset angle representation value of the current symbol includes: Determine the difference between the offset angle representation value of the previous codeword and the offset angle representation value of the current codeword to obtain an adjacent angle difference; Determine a first preset range in which the absolute values ​​of the adjacent angular differences are located, wherein the first preset range is one of the correction preset ranges, and each of the correction preset ranges corresponds to a preset correction value; According to the positive or negative sign of the adjacent angle difference, the preset correction value corresponding to the first preset range is added or subtracted from the offset angle characterization value of the current code element or the offset angle characterization value of the previous code element to obtain the corrected offset angle characterization value of the current code element.

5. The method according to claim 1, wherein The step of fitting the sampling center of the current symbol using the corrected offset angle representation value includes: Determine a difference between a first preset angle and the corrected offset angle representation value to obtain a first preset angle difference, wherein the first preset angle is used to determine the position of the sampling space; The quotient of the first preset angle difference and the angle ratio is determined as the sampling center of the current code element, wherein the angle ratio is the quotient of the angle period and the ratio parameter.

6. The method according to claim 1, characterized in that The step of fitting the sampling center of the current symbol using the corrected offset angle representation value includes: Determine a difference between a second preset angle and the corrected offset angle representation value to obtain a second preset angle difference, wherein the second preset angle is the sum of the first preset angle and the maximum position sequence number of the fitting interval; The quotient of the second preset angle difference and the angle ratio is determined as the sampling center of the current code element, wherein the angle ratio is the quotient of the angle period and the ratio parameter.

7. The method according to claim 1, characterized in that The sampling data of the current symbol satisfies the following formula: out=SINC(i-2n:i+2n-1)×X Wherein, out is the sampling data of the current symbol, i is the sampling center of the current symbol, n is the number of sample points per symbol, X is the fitting interval; SINC=sinc(-4:1 / ω:4), ω is the proportional parameter.

8. The method according to claim 7, characterized in that The fitting interval includes a plurality of continuous symbol data, and the current symbol is not the first symbol or the last symbol in the fitting interval.

9. A low-orbit satellite communication timing device based on angle synthesis, characterized in that: include: An offset quantization unit, configured to extract offset information of a current symbol of the input signal according to the power of the input signal to obtain an offset complex representation value of the current symbol; an offset correction unit, the offset correction unit being configured to determine an offset angle representation value of the current symbol based on the offset complex representation value of the current symbol, and correct the offset angle representation value of the current symbol using the offset angle representation value of the previous symbol to expand a sampling space to obtain the corrected offset angle representation value of the current symbol, wherein the sampling space is a selectable space for sampling points; A sampling unit is used to fit the sampling center of the current code element through the corrected offset angle characterization value; and to obtain sampling data of the current code element by sampling in a fitting interval based on the sampling center of the current code element.

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