A large constellation multiple access measurement and control spread spectrum signal despread bit width quantization method

Abstract

The application relates to the field of spaceflight measurement and control, and discloses a large constellation multiple access measurement and control spread spectrum signal despread bit width quantization method. Signal samples are counted, a noise deterioration factor and a bit width quantization model are respectively established, the despread bit width is accurately extended, and the optimal balance between resources and performance is realized. The application solves the problem that the detection range of strong and weak signals is limited when a single receiver simultaneously detects multiple satellite same-frequency signals, significantly improves the system capacity, and has the characteristics of quantizability, large dynamic range and multi-constellation adaptation.

Description

Technical Field

[0001] This invention relates to the field of aerospace telemetry and control technology, and is particularly applicable to the despreading and quantization design of telemetry and control spread spectrum signals in low-Earth orbit constellation multiple access systems. It solves the problem of limited detection range of strong and weak signals when a single receiver simultaneously detects signals from multiple satellites at the same frequency, and significantly improves system capacity. Background Technology

[0002] With the deployment of thousands or even tens of thousands of low-Earth orbit satellite constellations, some scholars have proposed large-scale constellation multiple access telemetry, tracking, and command (TT&C) communication technologies. Ground stations need to process hundreds of signals of the same frequency in parallel. Due to factors such as differences in satellite orbital altitude and satellite platform, the received signal levels may vary significantly. Therefore, it is necessary to address the problem of limited detection range of strong and weak signals by a single receiver.

[0003] Literature review revealed that typical methods for addressing limited dynamic range include Automatic Gain Control (AGC) and fixed high bit width. ① AGC automatically adjusts the receiver gain through a feedback loop; however, in multi-satellite co-frequency scenarios, AGC still indiscriminately adjusts the gain of the received signal, causing weak signals to be overwhelmed. For example, the measured weak signal loss rate in the Starlink system reached 35%. ② Fixed high bit width extends the dynamic range by simply increasing the analog-to-digital converter (ADC) or processing bit width. For instance, the European Space Agency's EDRS system uses a 16-bit high bit width across all channels, consuming over 70% of FPGA resources and resulting in wasted computing power. Summary of the Invention

[0004] To address the problems in the background technology, a method for despreading bit width quantization of telemetry and control spread spectrum signals in large constellations is proposed. By statistically analyzing signal samples, noise degradation factor and bit width quantization model are established respectively to accurately expand the despreading bit width and achieve the optimal balance between resources and performance.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for despreading and quantizing the spread spectrum signal of a large constellation multiple access telemetry and control system includes the following steps:

[0007] (1) Collect multi-target signal samples from the constellation, normalize the signal amplitude distribution, and statistically analyze the weak signal amplitude quantiles A. min Among them, the percentage of samples with a value of α that are greater than a certain threshold is called the weak signal amplitude quantile A. min where 0 < α < 1;

[0008] (2) Calculate the noise degradation factor based on the weak signal amplitude quantile, the analog-to-digital converter bit width, and the spreading factor;

[0009] (3) Calculate the post-despreading bit width based on the noise degradation factor.

[0010] Furthermore, in step (2), the noise degradation factor k noise The calculation method is as follows:

[0011]

[0012] In the formula, B ADC SF is the bit width of the analog-to-digital converter.

[0013] Furthermore, the calculation method for the post-despreading bit width N in step (3) is as follows:

[0014]

[0015] In the formula, Indicates rounding up. This indicates rounding down to the nearest integer.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (i) Quantifiability: This invention establishes a noise degradation factor model and a bit width calculation model to replace empirical design, guide engineers to accurately calculate the bit width after despreading, and achieve the optimal balance between resources and performance;

[0018] (ii) Large dynamic range: This invention increases the dynamic range of a single receiver for simultaneous detection of multiple target signals by increasing the bit width slightly after despreading;

[0019] (iii) Multi-constellation adaptation: This invention develops a parameter mapping table mechanism to adapt to all scenarios such as near-Earth / hybrid / deep-space constellations. Attached Figure Description

[0020] Figure 1 This is a flowchart of the processing steps of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to specific implementation steps:

[0022] A method for despreading and quantizing the spread spectrum signal of a large constellation multiple access telemetry and control system includes the following steps:

[0023] (1) Collect multi-target signal samples from the constellation, normalize the signal amplitude distribution, and statistically analyze the weak signal amplitude quantiles A. min Among them, the percentage of samples with a value of α that are greater than a certain threshold is called the weak signal amplitude quantile A. min where 0 < α < 1;

[0024] In this example, 1000 samples were collected, and after signal amplitude normalization, they were distributed in the [0,1] interval. Among them, 99% of the samples were greater than the weak signal quantile A.min A was obtained through testing. min =0.02.

[0025] (2) Calculate the noise degradation factor k based on the weak signal amplitude quantile, the analog-to-digital converter bit width, and the spreading factor. noise :

[0026]

[0027] In the formula, B ADC is the ADC bit width, and SF is the spreading factor.

[0028] Example: ADC bit width B ADC =8, spreading factor SF = 1023, k is calculated noise =163.16.

[0029] (3) Calculate the post-despreading processing bit width N based on the noise degradation factor:

[0030]

[0031] In the formula, Indicates rounding up. This indicates rounding down to the nearest integer.

[0032] In the example, for a dense constellation near the Earth, N=10 was calculated.

[0033] (4) Project adaptation and deployment verification.

[0034] The table below is a parameter mapping table for the near-Earth / hybrid / deep-space constellations of this invention, and provides recommended values ​​for the despreading bit width of typical constellations.

[0035] Near-Earth dense constellations 50～150 10 people High and low orbit mixed constellations 150～300 14-digit Deep Space Exploration Constellation 300～1000 16-bit

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for despreading and bit-width quantization of telemetry and control spread spectrum signals for large constellation multiple access, characterized in that, Includes the following steps: (1) Collect multi-target signal samples from the constellation, normalize the signal amplitude distribution, and statistically analyze the weak signal amplitude quantiles A. min Among them, the percentage of samples with a value of α that are greater than a certain threshold is called the weak signal amplitude quantile A. min where 0 < α < 1; (2) Calculate the noise degradation factor based on the weak signal amplitude quantile, the analog-to-digital converter bit width, and the spreading factor; (3) Calculate the post-despreading bit width based on the noise degradation factor; Among them, the noise degradation factor in step (2) The calculation method is as follows: In the formula, Where SF is the bit width of the analog-to-digital converter, and SF is the spreading factor. In step (3), the despreading post-processing bit width The calculation method is as follows: In the formula, Indicates rounding up. This indicates rounding down to the nearest integer.

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