Spaceflight TT&C downlink random access multiple access signal power control method

Abstract

The present application relates to the field of spaceflight measurement and control, and discloses a kind of spaceflight measurement and control downlink random access multiple access signal power control method, and ground station is estimated according to the acquisition road different method and estimates the ratio of signal to interference, in the preset protection interval of carrier-to-noise ratio, in the preset maximum threshold of ratio of signal to interference, the transmission power of satellite access signal is controlled, and the purpose that random access downlink signal is normally captured and received by ground station is achieved.The present application is favorable to improve the accuracy of ratio of signal to interference estimation;Strong signal level is controlled preferentially, and frequent control to other medium-strong signal level can be avoided;It is favorable to prevent satellite transmission power from being adjusted too large or too small, ensure the effectiveness of power control, and can be applied in spaceflight measurement and control random access system.

Description

Technical Field

[0001] This invention relates to the field of aerospace telemetry and control, and in particular to a method for controlling the downlink random access multiple access signal power in aerospace telemetry and control. Background Technology

[0002] Satellite-enabled downlink signals utilize spread spectrum multiple access, resulting in contention among multiple downlink signals and multiple access interference. Furthermore, due to the long distance between the satellite and ground station, a near-far effect occurs, causing strong signals to interfere with the ground station's acquisition and demodulation of weak signals. Therefore, under necessary conditions, power control of the satellite-enabled downlink signals is required to prevent multiple access interference from strong signals to weak signals, ensuring that weak signals can also be properly connected to the telemetry and control station.

[0003] Downlink signal power control methods typically include open-loop power control and closed-loop power control. Open-loop power control is a method where the satellite autonomously adjusts its power, for example, based on its position or uplink signal measurements. This method relies on other information to predict the downlink signal level, and the reliability and effectiveness of this prediction cannot be fully guaranteed. Closed-loop power control, on the other hand, involves real-time measurement of the satellite's downlink signal, with the ground station controlling the downlink signal power according to certain criteria.

[0004] In mobile communication systems, some scholars have proposed determining the maximum transmission power of a user based on the established uplink multiple access scheme and the power level of the user equipment. Others have proposed using the failure probability of power control commands to determine whether power control is enabled or disabled. Still others have proposed employing different transmit power control schemes for users in different areas (urban, suburban), while also considering the average throughput of the cell.

[0005] Unlike mobile communication systems, the information transmission rate of multiple access signals in aerospace telemetry and control systems is fixed. Increasing the transmission power not only fails to increase the transmission rate but also increases multiple access interference. Conversely, excessively reducing the transmission power may result in an access signal that is too weak to be detected by ground stations. Power control of multiple access links in aerospace telemetry and control involves factors such as the number of multiple access interference paths, the accuracy of interference measurement, and antenna gain fluctuations. Its power control methods are relatively complex, and no relevant literature has been reported to date. Summary of the Invention

[0006] In view of this, the present invention discloses a method for controlling the power of downlink random access multiple access signals in aerospace telemetry and control. The method estimates the interference-to-signal ratio (ISR) using different methods based on the number of channels acquired by the ground station, and controls the transmission power of the satellite access signal within a preset protection range of the carrier-to-noise ratio and a preset maximum threshold of the ISR.

[0007] The technical solution adopted in this invention is as follows:

[0008] A method for controlling the downlink random access multiple access signal power in aerospace telemetry and control includes the following steps:

[0009] (1) Measure the carrier-to-noise ratio of the captured multiple downlink signals;

[0010] (2) Determine whether the number of captured signal channels has reached the maximum number of baseband channels, and determine whether the carrier-to-noise ratio is within the preset range;

[0011] (3) If the number of captured signal channels reaches the maximum number of baseband processing channels, calculate the interference-to-signal ratio of other signals relative to the weakest signal; if the number of captured signal channels is less than the maximum number of baseband processing channels, calculate the interference-to-signal ratio of the captured signal relative to the capture threshold.

[0012] (4) If the carrier-to-noise ratio of a single signal is within the preset range, the satellite transmission power remains unchanged; if the carrier-to-noise ratio of a single signal is greater than the preset range, the satellite transmission power is reduced under the principle that the received signal-to-interference ratio does not exceed the preset threshold; if the carrier-to-noise ratio of a single signal is less than the preset range, it is determined whether the satellite signal has been attenuated. If it has been attenuated, the satellite transmission power is increased; if it has not been attenuated, the satellite transmission power remains unchanged.

[0013] Furthermore, the calculation method for step (3) is as follows:

[0014] If the number of captured signal channels reaches the maximum number of baseband processing channels, the interference-to-signal ratio is calculated as follows:

[0015]

[0016] In the formula, L represents the number of signals captured simultaneously. max L represents the maximum number of baseband processing channels, L = L max , This represents the carrier power of the measured k-th signal;

[0017] If the number of captured signal channels is less than the maximum number of baseband processing channels, the interference-to-signal ratio is calculated as follows:

[0018]

[0019] In the formula, L <L max Γ0 represents the capture threshold. Indicates noise power.

[0020] Furthermore, the preset range of the carrier-to-noise ratio in step (4) is: [Γ1,Γ2];

[0021] Where Γ1=Γ0+Δ1 represents the lower limit of the preset interval, Γ2=Γ0+Δ2 represents the upper limit of the preset interval, and Δ2>Δ1>0.

[0022] Furthermore, in step (4), if the carrier-to-noise ratio of a single signal is greater than a preset range, then, under the principle that the received signal-to-interference ratio does not exceed a preset threshold, the satellite is controlled to reduce the transmission power of the downlink signal, specifically as follows:

[0023] If the carrier-to-noise ratio of the k-th signal If the interference-to-signal ratio J / R > Γ3, then control the corresponding satellite number to reduce the transmission power and recalculate the interference-to-signal ratio J / R until J / R ≤ Γ3;

[0024] In the formula, Γ3 represents the maximum value that J / R can tolerate, and its expression is:

[0025] Γ3=Δ2+10log 10 (L max ).

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (i) Based on the number of channels captured by the ground station, the interference-to-signal ratio is estimated using different methods to improve the accuracy of the interference-to-signal ratio estimation, thereby improving the effectiveness of power control;

[0028] (ii) Based on the total signal-to-weight ratio, priority is given to controlling the strong signal level, which can avoid frequent control of other medium and strong signal levels;

[0029] (iii) The preset power control protection range can effectively prevent the satellite transmission power from being adjusted too high or too low, and avoid problems such as signal reduction and difficulty in being captured by ground stations caused by power control. Attached Figure Description

[0030] Figure 1 This is a flowchart of the process of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific implementation steps:

[0032] This invention discloses a method for controlling the downlink power of aerospace telemetry and control systems under random access multiple access (MIMO) signals, referring to... Figure 1 The specific steps include:

[0033] ① Measure the carrier-to-noise ratio of each captured downlink signal, where the carrier power of the measured k-th signal is: and noise power The expression for the carrier-to-noise ratio is:

[0034] 2. Determine whether the number of captured signal channels has reached the maximum number of baseband channels, and determine whether the carrier-to-noise ratio is within the preset range;

[0035] ③ Calculate the interference-to-signal ratio (ISR) in different ways depending on whether the number of simultaneously acquired signals reaches the maximum baseband processing capacity. If the number of simultaneously acquired signals reaches the maximum baseband processing capacity, calculate the ISR of the other signals relative to the weakest signal. The expression for this is:

[0036]

[0037] In the formula, L represents the number of signals captured simultaneously, and its maximum value is represented by the symbol L. max This means that L = L max Example L max =8 indicates that the baseband can capture a maximum of 8 signals simultaneously;

[0038] If the number of signals captured simultaneously is less than the maximum number of baseband processing channels, then the interference-to-signal ratio (ISR) of the captured signal relative to the capture threshold is calculated, and its expression is:

[0039]

[0040] In the formula, L <L max Γ0 represents the capture threshold.

[0041] ④ Adjust the transmission power in different ways according to the preset range. If the carrier-to-noise ratio of a single signal is within the preset range, keep the satellite transmission power unchanged.

[0042] The carrier-to-noise ratio preset range is [Γ1,Γ2], where Γ1=Γ0+Δ1 represents the lower limit of the preset range, Γ2=Γ0+Δ2 represents the upper limit of the preset range, and Δ2>Δ1>0. For example, Γ1=Γ0+3dB and Γ2=Γ0+7dB.

[0043] If the carrier-to-noise ratio of the k-th signal If the interference-to-signal ratio J / R > Γ3, then control the corresponding satellite number to reduce the transmission power and recalculate the interference-to-signal ratio J / R until J / R ≤ Γ3;

[0044] In the formula, Γ3 represents the maximum value that J / R can tolerate, and its expression is:

[0045] Γ3=Δ2+10log 10 (L max )

[0046] Example Γ3=Δ2+10log 10 (L max =16dB.

[0047] If the carrier-to-noise ratio of a single signal is less than a preset range, that is... Furthermore, if it is determined that the transmit power of the satellite corresponding to the k-th signal has been adjusted downwards, then its transmit power needs to be increased; if it is determined that the transmit power of the satellite corresponding to the k-th signal has not been adjusted, then the satellite transmit power remains unchanged. For example, the satellite output power adjustment range is 0–6 dB, with a step size of 2 dB.

[0048] 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 controlling the power of aerospace telemetry and control downlink random access multiple access signals, characterized in that, Includes the following steps: (1) Measure the carrier-to-noise ratio of the captured multiple downlink signals; (2) Determine whether the number of captured signal channels has reached the maximum number of baseband channels, and determine whether the carrier-to-noise ratio is within the preset range; (3) If the number of captured signal channels reaches the maximum number of baseband processing channels, calculate the interference-to-signal ratio of other signals relative to the weakest signal; if the number of captured signal channels is less than the maximum number of baseband processing channels, calculate the interference-to-signal ratio of the captured signal relative to the capture threshold. (4) If the carrier-to-noise ratio of a single signal is within the preset range, the satellite transmission power remains unchanged; if the carrier-to-noise ratio of a single signal is greater than the preset range, the satellite transmission power of the downlink signal is reduced, provided that the received signal-to-interference ratio does not exceed the preset threshold. If the carrier-to-noise ratio of a single signal is less than the preset range, it is determined whether the satellite signal has been attenuated. If it has been attenuated, the satellite transmission power is increased; if it has not been attenuated, the satellite transmission power is kept unchanged. The calculation method for step (3) is as follows: If the number of captured signal channels reaches the maximum number of baseband processing channels, the interference-to-signal ratio is calculated as follows: In the formula, Indicates the number of signals captured simultaneously. Indicates the maximum number of baseband processing channels. = , The measurement of the first The carrier power of the signal; If the number of captured signal channels is less than the maximum number of baseband processing channels, the interference-to-signal ratio is calculated as follows: In the formula, < , Indicates the capture threshold. Indicates noise power; In step (4), if the carrier-to-noise ratio of a single signal is greater than a preset range, then, under the principle that the received signal-to-interference ratio does not exceed a preset threshold, the satellite is controlled to reduce the transmission power of the downlink signal, specifically as follows: If the Carrier-to-noise ratio of the signal And dry credit ratio > Then, the corresponding satellite with the specified number will reduce its transmission power and the interference-to-signal ratio will be recalculated. until ; In the formula, express The maximum tolerable value is expressed as: ； The preset range for the carrier-to-noise ratio is: ; This indicates the lower limit of the preset interval. This indicates the upper limit of the preset range. > >0.

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