A non-orthogonal semi-license-free adaptive transmission method for low-orbit satellite communication

Abstract

A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit (LEO) satellite communication includes: simultaneously selecting scheduled licensed users and selected unlicensed users according to preset scheduling rules; comparing the channel gain of the licensed users with a preset transmission strategy decision threshold value, and selecting transmission strategy A or transmission strategy B; if transmission strategy A is executed: adjusting the transmission power of each user according to the power allocation method specified in transmission strategy A, and simultaneously uploading their respective signals to the LEO satellite using an uplink non-orthogonal access method; the LEO satellite decoding order is to decode the licensed user signal first, and then decode the unlicensed user signal; if transmission strategy B is executed: adjusting the transmission power of each user according to the power allocation method specified in transmission strategy B, and simultaneously uploading their respective signals to the LEO satellite using an uplink non-orthogonal access method; the LEO satellite decoding order is to decode the unlicensed user signal first, and then decode the licensed user signal.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a non-orthogonal semi-licensed adaptive transmission method for low-Earth orbit satellite communication. Background Technology

[0002] With the development of 6G communication, low-Earth orbit satellite networks have become an important component of the future global communication system, providing seamless coverage for remote areas, oceans, and battlefields. In the multi-user access design of satellite uplinks, user terminals can be broadly classified into two categories based on their service requirements and quality of service (QoS) assurance levels. One category is Grant-Based (GB) users, who typically undertake mission-critical communication or transmit high-value data, and have strict requirements for transmission reliability, latency, and speed. The other category is Grant-Free (GF) users, who are mostly massive, low-complexity IoT sensing devices, whose service models are characterized by sporadic, opportunistic transmissions.

[0003] Currently, in satellite communication systems, the traditional method for coordinating the coexistence of GB and GF users is to employ orthogonal multiple access (OMA) technology, which allocates mutually orthogonal radio channel resources to the two types of users in terms of time, frequency, or code domain. While this orthogonal separation strategy avoids inter-user interference and ensures the quality of service for GB users, it suffers from low spectral efficiency and limited system connection capacity, making it difficult to meet the access demands of the massive Internet of Things (IoT) in the future. To improve spectral efficiency and system connection capacity, non-orthogonal multiple access (NOMA) technology has been introduced as an innovative technique for coordinating the coexistence of GB and GF users. Specifically, NOMA allows GB and GF users to transmit non-orthogonally on the same time-frequency resource blocks, and performs multi-user detection at the receiver using continuous interference cancellation technology. For existing technologies in satellite hybrid access scenarios, a dynamic power control scheme for GF users based on interference thresholds is proposed. By constraining the transmit power of GF users, the uplink interference introduced by GF users is ensured to remain within the tolerable range for GB users, thereby guaranteeing the quality of service for GB users. However, this scheme consistently employs a single, fixed decoding method at the receiver, treating GF users as interference sources for GB users throughout the entire transmission process. This approach limits GF users' access to the network only when the GB user channel is sufficiently strong, resulting in low access opportunities and constrained communication performance. To address this, existing technologies have proposed a hybrid channel state information decoding strategy. This strategy switches the decoding order based on whether the interference from GF users to GB users exceeds an interference threshold, thus improving the performance limitations of GF users under static decoding. However, this scheme does not consider the impact of user scheduling on system performance and fails to provide a power allocation optimization mechanism for GB and GF users in satellite hybrid access scenarios. It lacks a joint design for user scheduling, power control, and dynamic decoding, leaving significant room for improvement in system performance.

[0004] In summary, existing technologies have the following shortcomings: Firstly, existing NOMA-based satellite GB and GF hybrid transmission methods fail to fully consider the coupling between GF and GB transmissions, ignoring the objective fact that GB user scheduling simultaneously affects the performance of both GB and GF transmissions, and lacking a user scheduling method design that simultaneously addresses the improvement of communication performance for both transmission modes. Secondly, existing NOMA-based satellite GB and GF hybrid transmission methods lack joint design and coordinated optimization of user scheduling, power control, and dynamic decoding, leaving significant room for improvement in system communication performance. Summary of the Invention

[0005] In view of the aforementioned shortcomings of existing technologies, this invention provides a non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit (LEO) satellite communication. By selecting a dynamic satellite transmission strategy and implementing adaptive transmission for unlicensed users, the method significantly improves the transmission success probability for unlicensed users while ensuring the quality of service for licensed users. The approximate optimal solution of the decision threshold is independent of the statistical characteristics of the communication channel, thus making it well-suited for the complex and rapidly changing LEO satellite communication environment and possessing significant practical application value.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A non-orthogonal semi-licensed adaptive transmission method for low-Earth orbit satellite communication includes the following steps:

[0008] S1. Within a transmission cycle, according to the preset scheduling rules, one authorized user and one unauthorized user are selected to participate in the uplink transmission, serving as the scheduled authorized user and the selected unauthorized user.

[0009] S2. The low-orbit satellite compares the channel gain of the licensed users participating in uplink transmission with the preset transmission strategy decision threshold value, and selects the transmission strategy for the current transmission period as transmission strategy A or transmission strategy B based on the comparison result.

[0010] S3. If the transmission strategy A is executed: the scheduled authorized user and the selected unauthorized user adjust their respective signal transmission power according to the power allocation method specified in the transmission strategy A, and simultaneously upload their respective signals to the low-orbit satellite in the uplink non-orthogonal access mode; the low-orbit satellite decodes the received signal, and the decoding order is to first decode the authorized user signal and then decode the unauthorized user signal;

[0011] S4. If the transmission strategy B is executed: the scheduled authorized user and the selected unauthorized user adjust their respective signal transmission power according to the power allocation method specified in the transmission strategy B, and simultaneously upload their respective signals to the low-Earth orbit satellite in the uplink non-orthogonal access mode; the low-Earth orbit satellite decodes the received signals, and the decoding order is to decode the unauthorized user signal first, and then decode the authorized user signal.

[0012] Preferably, S1 includes:

[0013] All licensed users send pilot sequences, and the low-Earth orbit satellite receives uplink pilot signals from each licensed user and estimates the channel gain of each licensed user in the current transmission cycle based on the uplink pilot signals; at the same time, the low-Earth orbit satellite updates the average channel gain of all licensed users.

[0014] The low-Earth orbit satellite calculates the scheduling weight for each licensed user; the scheduling weight is defined as the ratio of the channel gain of the licensed user in the current transmission cycle to the average channel gain.

[0015] The low-orbit satellite selects the authorized user with the highest scheduling weight as the scheduled authorized user to participate in uplink transmission in the current transmission cycle.

[0016] Preferably, S1 includes:

[0017] Unlicensed users estimate their channel gain for the current transmission period from the periodic broadcast pilot sequence of the satellite, and update their mean channel gain. Each unlicensed user calculates its own contention weight, which is defined as the ratio of the unlicensed user's channel gain for the current transmission period to its mean channel gain. The unlicensed user with the largest contention weight is selected as the unlicensed user to participate in uplink transmission for the current transmission period.

[0018] Preferably, S2 includes:

[0019] If the channel gain of the scheduled authorized user is not lower than the value of the transmission policy decision threshold, then transmission policy A is executed in the current transmission cycle; otherwise, transmission policy B is executed in the current transmission cycle.

[0020] Calculate the asymptotic expression for the transmission interruption probability of the scheduled authorized user; solve the partial derivative of the asymptotic expression with respect to the transmission policy decision threshold value; by setting the partial derivative to zero, obtain the approximate optimal solution that minimizes the transmission interruption probability of the authorized user as the transmission policy decision threshold value.

[0021] As a preferred embodiment, S2 also includes:

[0022] The authorized user scheduling results, transmission strategy, and control parameters are communicated to the ground user via signaling; the control parameters... The calculation method is as follows:

[0023] If the transmission strategy A is executed in the current transmission cycle, the control parameter in the signaling sent by the low-orbit satellite is the maximum interference value that the scheduled authorized user can tolerate. The maximum interference value is calculated as follows: the channel gain of the scheduled authorized user in the current transmission cycle is multiplied by the maximum transmit power allowed by the authorized user, then divided by the signal-to-noise ratio threshold required for demodulation by the authorized user, and then the noise power of the satellite receiver is subtracted and the negative result is set to zero.

[0024] If the above transmission strategy B is executed in the current transmission cycle, the control parameters in the signaling sent by the low-Earth orbit satellite are as follows: if the channel gain of the scheduled authorized user is not lower than the channel quality judgment threshold, the control parameter value is the product of the minimum signal-to-noise ratio required for the low-Earth orbit satellite to demodulate the authorized user signal and the noise power of the satellite receiver; otherwise, the control parameter value is zero. The channel quality judgment threshold is the product of the minimum signal-to-noise ratio required for demodulating the authorized user signal and the noise power of the satellite receiver, divided by the maximum transmit power allowed for the authorized user.

[0025] Preferably, S3 includes:

[0026] S31. The scheduled authorized user adjusts its transmit power to the maximum transmit power allowed by the authorized user; the selected unauthorized user compares its maximum power gain with the control parameter, whereby the maximum power gain is defined as the product of the channel gain of the selected unauthorized user in the current transmission cycle and the maximum available transmit power of the unauthorized user; if the maximum power gain of the selected unauthorized user is less than the control parameter, then the selected unauthorized user adjusts its transmit power to its maximum available power; otherwise, the transmit power is the ratio of the control parameter to the channel gain of the selected unauthorized user in the current transmission cycle.

[0027] As a preferred option, S3 also includes:

[0028] S32. The low-Earth orbit satellite first treats the authorized user signal as an interference signal, and decodes the signal of the scheduled authorized user under this interference; after the low-Earth orbit satellite successfully decodes the authorized user signal, it uses the obtained authorized user signal to perform serial interference cancellation, and then decodes the signal of the selected exempted user.

[0029] Preferably, S4 includes:

[0030] S41. The scheduled authorized user estimates its own channel gain and sets its own transmit power as the ratio of the control parameter to its own channel gain;

[0031] If the selected unlicensed user detects that its own channel gain is greater than or equal to the preset decision threshold, its transmit power is adjusted to the maximum available power; otherwise, its transmit power is adjusted to 0, indicating that the unlicensed user does not upload signals in the current transmission cycle, and the transmission cycle is only used to transmit signals from licensed users.

[0032] Preferably, S4 includes:

[0033] S42. If the selected unlicensed user's transmit power is not 0, then the user transmits its own signal to the low-orbit satellite.

[0034] The low-Earth orbit satellite performs decoding in the following two ways according to the transmission strategy B:

[0035] In scenario one, if the unlicensed user's transmit power is not zero, the low-Earth orbit satellite will receive aliased signals from both the unlicensed and licensed users. The low-Earth orbit satellite will first treat the licensed user's signal as interference and decode the selected unlicensed user's signal under interference. After successful decoding, serial interference cancellation will be performed, and the low-Earth orbit satellite will then decode the scheduled licensed user's signal.

[0036] Scenario 2: If the unlicensed user's transmit power is 0, the low-Earth orbit satellite will only receive and decode the signals sent by the scheduled authorized user.

[0037] :

[0038]

[0039] in, The control parameters are... This represents the signal-to-noise ratio threshold required for a low-Earth orbit satellite to correctly receive signals from unlicensed users. This indicates the noise power received by a low-Earth orbit satellite. The maximum available transmit power for unlicensed users.

[0040] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0041] This invention, based on GB user scheduling and channel strength awareness, proposes two adaptive transmission strategies for different channel conditions. The satellite dynamically selects the appropriate mode based on the current GB user channel status, thereby fully utilizing network degrees of freedom, including multi-user diversity, power allocation, and dynamic decoding order. This improves network resource utilization efficiency, suppresses interference between users, and enhances system transmission reliability and access fairness. Specifically, the proposed adaptive transmission method, on the one hand, optimizes user power allocation and satellite decoding order based on the user scheduling criterion of channel strength, ensuring that scheduling results, power configuration, and decoding order are mutually matched, effectively controlling interference between users and improving the decoding success rate at the receiver. On the other hand, the dynamic decoding strategy of this invention is determined by a transmission strategy decision threshold. Driven by theoretical analysis, the near-optimal threshold value is shown. It is only related to the transmit power of GB users and the target rate of GF / GB users, and is independent of the statistical characteristics of fast time-varying channels. Therefore, this near-optimal threshold value can be pre-calculated based on the quality of service target and power budget during the network planning stage and remains stable during operation. It does not require continuous estimation of the statistical distribution characteristics of the network channel, which allows this invention to overcome the implementation complexity caused by the reliance on accurate channel models in traditional methods while ensuring communication performance, and is easier to deploy in real satellite communication systems. Attached Figure Description

[0042] To more clearly illustrate the technical solution of the present invention, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the drawings described below are merely some exemplary embodiments of the present invention and are not intended to limit the entirety of the invention. For those skilled in the art, other drawings can be derived from these drawings without creative effort, and these drawings also fall within the protection scope of the present invention.

[0043] Figure 1 This is a flowchart of the method in Embodiment 1 of the present invention;

[0044] Figure 2 This is a scheduling flowchart of Embodiment 1 of the present invention;

[0045] Figure 3 This is a performance curve of GB user interruption probability under different transmission strategies in Embodiment 1 of the present invention;

[0046] Figure 4 This is a performance curve of the GF user interruption probability under different transmission strategies in Embodiment 1 of the present invention;

[0047] Figure 5 This is the transmission interruption probability of GB users and GF users under different transmission powers according to the transmission strategy decision threshold in Embodiment 1 of the present invention. Relationship diagram. Detailed Implementation

[0048] To make the technical means, inventive features, objectives, and effects of the invention readily understandable, the invention is further described below with reference to specific illustrations. However, the invention is not limited to the embodiments described below.

[0049] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0050] Example 1:

[0051] The low Earth Orbit (LEO) satellite communication network involved in this invention includes at least one LEO satellite and at least two grant-based (GB) ground users and two grant-free (GF) ground users within the satellite's coverage area. The LEO satellite acts as a communication access node, providing communication support to ground users within the coverage area. Grant-based users are ground nodes with fixed access permissions, which complete uplink signal transmission under satellite scheduling through signaling interaction with the satellite. The satellite dynamically selects between two network transmission strategies based on the channel status of the granted users and the user scheduling results. GF ​​users adopt an opportunistic access mechanism, do not need to interact with the satellite through signaling, and autonomously determine whether to access based on their own channel status and the dynamic transmission strategy selection results broadcast by the satellite. They share uplink channel resources with the scheduled granted users in a non-orthogonal manner to complete adaptive uplink signal transmission.

[0052] like Figure 1 , Figure 2 The non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication, as shown, includes the following steps:

[0053] S1. Within a transmission cycle, one authorized user (GB user) and one unauthorized user (GF user) are selected simultaneously to participate in uplink transmission according to the preset scheduling rules;

[0054] The low-orbit satellite estimates the channel state based on the user's uplink pilot signal and selects a GB user as the uplink transmission GB user scheduled for the current transmission cycle according to the scheduling rules; at the same time, the GF user self-organizes the scheduling of the GF user, that is, all GF users select a GF user that will participate in uplink transmission opportunistically in the current transmission cycle through inter-user competition.

[0055] The specific steps in S1 are as follows:

[0056] S11. All GB users transmit pilot sequences. The satellite receives uplink pilot signals from each GB user and estimates the channel gain of all GB users in the current transmission cycle based on the pilot signals. ,in This represents the total number of GB users in the network, and the average channel gain of GB users is updated using the following formula. :

[0057] ;

[0058] in, As an adjustment factor for mean updates, This represents the average channel gain over the previous transmission cycle; the satellite calculates the scheduling weight for each GB user, which is defined as the channel gain for the GB user. With the mean channel gain The ratio; from the entire set of GB users, select the GB user with the highest scheduling weight as the GB user to be scheduled for the current transmission period, that is...

[0059] ;

[0060] S12. At the beginning of each transmission cycle, the GF user estimates its own channel gain from the periodic broadcast pilot sequence of the satellite. ,in This represents the total number of GF users in the network, and the average channel gain of GF users is updated using the following formula. :

[0061] ;

[0062] in, As an adjustment factor for mean updates, This represents the average channel gain in the previous transmission cycle; each GF user calculates its own contention weight according to the following formula:

[0063] ,

[0064] And schedule weights According to the formula Mapped to countdown intervals, where For a function that is monotonically decreasing, such that The larger, The shorter; all GF users A countdown begins for the initial time. The first GF user to finish its countdown broadcasts a signal indicating that it has won the competition and will be the GF user executing opportunistic transmission in the current transmission cycle. Upon receiving this signal, other GF users still counting down stop their countdowns and relinquish their access opportunity for the current transmission cycle. The selected GF user (the selected unlicensed user) can be represented as...

[0065] .

[0066] S2. The low-orbit satellite compares the channel gain of the licensed users participating in uplink transmission with the preset transmission strategy decision threshold value, and selects the transmission strategy for the current transmission period as transmission strategy A or transmission strategy B based on the comparison result.

[0067] The satellite compares the channel gain of the scheduled GB users with the decision threshold values ​​for selecting two transmission strategies to determine whether the transmission strategy to be used in the current transmission cycle is transmission strategy A or transmission strategy B. The satellite then informs the ground users of the GB user scheduling results, transmission strategy selection results, and control parameters by issuing signaling. If the satellite selects transmission strategy A, it proceeds to step three; if the satellite selects transmission strategy B, it proceeds to step four.

[0068] The specific steps in S2 are as follows:

[0069] S21. The satellite will schedule the channel gain of GB users in the current transmission cycle. With transmission strategy decision threshold Compare and determine the transmission strategy for the current transmission cycle: If If so, then it is determined that transmission strategy A will be executed in the current transmission cycle; if If the current transmission cycle is determined to execute transmission strategy B, then the decision threshold for selecting the two different transmission strategies is as follows. The specific value is It is determined by the following method: calculating the asymptotic solution of the GF user transmission interruption probability, and solving the asymptotic solution with respect to... The partial derivatives are used to solve for the approximate optimal value that minimizes the probability of GF user transmission interruption by setting the partial derivatives to zero. for

[0070] ;

[0071] in, This indicates the maximum transmit power allowed for GB users; The signal-to-noise ratio threshold required for a satellite to correctly receive GB user signals is defined as follows: , This indicates the target rate required for a GB user signal to be successfully decoded by the satellite; The signal-to-noise ratio threshold required for a satellite to correctly receive GF user signals is defined as follows: , This indicates the target rate required for a GF user to be successfully decoded by the satellite; This indicates the noise power received by the satellite.

[0072] S22, Control Parameters The calculation method for the value is as follows: If transmission strategy A is executed in the current transmission cycle, the control parameters in the satellite signaling are calculated as follows: If transmission strategy B is executed during the current transmission cycle, the control parameters in the satellite signaling are calculated as follows:

[0073]

[0074] S3. The network executes transmission strategy A, in which GB users scheduled by the satellite and GF users self-organized by the network adjust their respective signal transmission power according to the power allocation method specified in transmission strategy A, and simultaneously upload their signals to the satellite using uplink non-orthogonal access. After receiving the user-uploaded signals, the satellite decodes the received signals according to the decoding order specified in transmission strategy A, i.e., "decode the GB user signals first, then decode the GF user signals".

[0075] The specific steps in step 3 are as follows:

[0076] S31. All users receive GB user scheduling results via satellite signaling. The current transmission cycle executes transmission strategy A, and the control parameters are... ; Scheduled GB users According to transmission strategy A, its own transmission power is adjusted to... GB users Actual transmit power its maximum transmission power GF users with self-organized scheduling Its maximum power gain With control parameters Comparison, among which Maximum available transmit power for GF users: If Then GF users Adjust the transmit power to its maximum usable power. ;like To avoid excessive interference to GB users, GF reduced the transmission power to [missing value]. That is, the actual transmit power of GF users. It can be summarized as

[0077]

[0078] S32, the scheduled GB user and GF users Simultaneously, each transmits its own signal to the satellite. The satellite determines the decoding order according to the currently executing transmission strategy A. That is, the satellite first treats the GF user signal as an interference signal and decodes the GB user signal under this interference. In this case, the signal-to-interference-plus-noise ratio (SIR) of the GB user signal can be expressed as: Its achievable rate is

[0079] ;

[0080] After the satellite successfully decoded the GB user signal The obtained GB user signal is used to perform serial interference cancellation, and then the GF user signal is decoded. In this case, the signal-to-noise ratio of the decoded GF user signal can be expressed as: Its corresponding achievable rate is

[0081] .

[0082] S4. The network executes transmission strategy B, in which GB users scheduled by the satellite and GF users self-organized by the network adjust their respective signal transmission power according to the power allocation method specified in transmission strategy B, and simultaneously upload their signals to the satellite using uplink non-orthogonal access. After receiving the user-uploaded signals, the satellite decodes the received signals according to the decoding order specified in transmission strategy B, i.e., "decode the GF user signals first, then decode the GB user signals".

[0083] The specific steps in S4 are as follows:

[0084] S41. All users receive GB user scheduling results via satellite signaling. The current transmission cycle executes transmission strategy B, and the control parameters are as follows: ; Scheduled GB users Estimating its own channel gain using satellite broadcast signaling And adjust its own transmission power according to transmission strategy B. Meanwhile, GF users Adjust its own transmission power according to transmission strategy B, as follows: If Then GF users Adjust its transmission power to its maximum usable power. ;like Then GF users The transmit power is adjusted to 0, indicating that the GF user will not upload signals during the current transmission cycle;

[0085] S42, the scheduled GB user It sends its own signal to the satellite. At this time, if the GF user... If the transmit power is not zero, the user simultaneously transmits its own signal to the satellite. The satellite performs decoding according to transmission strategy B in the following two scenarios: Scenario 1: If the GF user's transmit power is not zero, the satellite will receive aliased signals from both the GF and GB users. In this case, the satellite first treats the GB user signal as interference and decodes the GF user signal under this interference. The signal, the decoded signal-to-interference-plus-noise ratio can be expressed as: The corresponding achievable rate is

[0086] ;

[0087] Satellite successfully decodes GF user After the signal is received, serial interference cancellation is performed, and then the satellite decodes the GB user signal. In this process, the signal-to-noise ratio of the GB user signal can be expressed as: The corresponding achievable rate is

[0088] .

[0089] Scenario 2: If the GF user's transmit power is 0, the satellite will only receive data from the GB user. The transmitted signal is directly decoded, and the signal-to-noise ratio can be expressed as: The corresponding achievable rate is

[0090] .

[0091] The application effects of this invention will be described in detail below with reference to simulation experiments.

[0092] Figure 3 A performance comparison of the present invention, the transmission method based on dynamic power allocation, and the transmission method based on dynamic decoding in terms of GB user outage probability is presented. As shown in the figure, across the entire transmit power range, the outage probability curves of the present invention and the transmission method based on dynamic power allocation largely overlap, with the present invention being significantly lower than that of the transmission method based on dynamic decoding. With further increases in transmit power, the outage curves of the present invention and the transmission method based on dynamic power allocation exhibit an exponential decay, with the slope of the outage curve decreasing relative to the number of GB users within a large signal-to-noise ratio range, thus achieving full diversity performance. In contrast, the GB outage probability achieved by the transmission method based on dynamic decoding decreases slowly with increasing transmit power, reaching a plateau after the transmit power increases to 10 dBm, where it cannot decrease further. These results demonstrate that the present invention can consistently guarantee the quality of service for GB users while GF users are accessing the network.

[0093] Figure 4A performance comparison of this invention with transmission methods based on dynamic power allocation and dynamic decoding in terms of GF user outage probability is presented. As shown in the figure, within a relatively low transmit power range (approximately -5dBm to 5dBm), the GF users of the two comparative methods are always in a transmission outage state, i.e., the outage probability is 1. In contrast, this invention employs an adaptive transmission mechanism, achieving a lower outage probability. Within a relatively high transmit power range (approximately 10dBm to 15dBm), the GF user outage probability curves of all three methods decrease with increasing transmit power, but the rate of decrease in the outage probability under this invention is significantly faster than that of the two comparative methods. Therefore, it achieves a lower transmission outage probability at the same transmit power. Furthermore, as shown in the figure, within a large signal-to-noise ratio range, the slope of the outage curve of this invention is equal to the number of GF users, thus achieving full diversity performance. The above results demonstrate that this invention can significantly improve the transmission success probability of GF users.

[0094] Figure 5 This shows the interruption probability of GB users and GF users under different user transmit powers as a function of the decoding decision threshold. The changing curve is used to verify the optimal threshold derived in this invention. The accuracy of the threshold and the change in system performance when the threshold value deviates from the optimal point are observed in the figure. Despite variations in the value, the interruption probability of GB users remains relatively stable, indicating that the transmission reliability of GB users is consistently guaranteed under this invention. The changes are not sensitive. In contrast, the interruption probability of GF users is less sensitive to changes. The changes showed a clear sensitivity, as The increase in [value] shows an overall trend of first decreasing and then increasing. Furthermore, the dashed vertical line in the figure is used to indicate the optimal threshold calculated based on user service quality requirements and power budget. As shown in the figure, the dashed vertical line accurately matches the interruption probability of the GF user. The minimum value during the change process verifies The validity of the selection.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication, characterized in that, Includes the following steps: S1. Within a transmission cycle, according to the preset scheduling rules, one authorized user and one unauthorized user are selected to participate in the uplink transmission, serving as the scheduled authorized user and the selected unauthorized user. S2. The low-Earth orbit satellite compares the channel gain of the licensed users participating in uplink transmission with a preset transmission strategy decision threshold value, and selects either transmission strategy A or transmission strategy B for the current transmission period based on the comparison result; including: If the channel gain of the scheduled authorized user is not lower than the value of the transmission policy decision threshold, then transmission policy A is executed in the current transmission cycle; otherwise, transmission policy B is executed in the current transmission cycle. Calculate the asymptotic expression for the transmission interruption probability of the scheduled authorized user; solve the partial derivative of the asymptotic expression with respect to the transmission policy decision threshold value; by setting the partial derivative to zero, obtain the approximate optimal solution that minimizes the transmission interruption probability of the authorized user as the transmission policy decision threshold value; S3. If the transmission strategy A is executed: the scheduled authorized user and the selected unauthorized user adjust their respective signal transmission power according to the power allocation method specified in the transmission strategy A, and simultaneously upload their respective signals to the low-orbit satellite in the uplink non-orthogonal access mode; the low-orbit satellite decodes the received signal, and the decoding order is to first decode the authorized user signal and then decode the unauthorized user signal; S4. If the transmission strategy B is executed: the scheduled authorized user and the selected unauthorized user adjust their respective signal transmission power according to the power allocation method specified in the transmission strategy B, and simultaneously upload their respective signals to the low-Earth orbit satellite in the uplink non-orthogonal access mode; the low-Earth orbit satellite decodes the received signals, and the decoding order is to decode the unauthorized user signal first, and then decode the authorized user signal.

2. The non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 1, characterized in that, S1 includes: All licensed users send pilot sequences, and the low-Earth orbit satellite receives uplink pilot signals from each licensed user and estimates the channel gain of each licensed user in the current transmission cycle based on the uplink pilot signals; at the same time, the low-Earth orbit satellite updates the average channel gain of all licensed users. The low-Earth orbit satellite calculates the scheduling weight for each licensed user; the scheduling weight is defined as the ratio of the channel gain of the licensed user in the current transmission cycle to the average channel gain. The low-orbit satellite selects the authorized user with the highest scheduling weight as the scheduled authorized user to participate in uplink transmission in the current transmission cycle.

3. The non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 1, characterized in that, S1 includes: Unlicensed users estimate their channel gain for the current transmission period from the periodic broadcast pilot sequence of the satellite, and update their mean channel gain. Each unlicensed user calculates its own contention weight, which is defined as the ratio of the unlicensed user's channel gain for the current transmission period to its mean channel gain. The unlicensed user with the largest contention weight is selected as the unlicensed user to participate in uplink transmission for the current transmission period.

4. The non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 1, characterized in that, S2 include: The authorized user scheduling results, transmission strategy, and control parameters are communicated to the ground user via signaling; the control parameters... The calculation method is as follows: If the transmission strategy A is executed in the current transmission cycle, the control parameter in the signaling sent by the low-orbit satellite is the maximum interference value that the scheduled authorized user can tolerate. The maximum interference value is calculated as follows: the channel gain of the scheduled authorized user in the current transmission cycle is multiplied by the maximum transmit power allowed by the authorized user, then divided by the signal-to-noise ratio threshold required for demodulation by the authorized user, and then the noise power of the satellite receiver is subtracted and the negative result is set to zero. If the above transmission strategy B is executed in the current transmission cycle, the control parameters in the signaling sent by the low-Earth orbit satellite are as follows: if the channel gain of the scheduled authorized user is not lower than the channel quality judgment threshold, the control parameter value is the product of the minimum signal-to-noise ratio required for the low-Earth orbit satellite to demodulate the authorized user signal and the noise power of the satellite receiver; otherwise, the control parameter value is zero. The channel quality judgment threshold is the product of the minimum signal-to-noise ratio required for demodulating the authorized user signal and the noise power of the satellite receiver, divided by the maximum transmit power allowed for the authorized user.

5. A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 4, characterized in that, S3 include: S31. The scheduled authorized user adjusts its own transmit power to the maximum transmit power allowed by the authorized user; the selected unauthorized user compares its maximum power gain with the control parameter, the maximum power gain being defined as the product of the channel gain of the selected unauthorized user in the current transmission cycle and the maximum available transmit power of the unauthorized user; if the maximum power gain of the selected unauthorized user is less than the control parameter, the selected unauthorized user adjusts its transmit power to its maximum available power; otherwise, the transmit power is the ratio of the control parameter to the channel gain of the selected unauthorized user in the current transmission cycle.

6. The non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 5, characterized in that, S3 also includes: S32. The low-Earth orbit satellite first treats the authorized user signal as an interference signal, and decodes the signal of the scheduled authorized user under this interference; after the low-Earth orbit satellite successfully decodes the authorized user signal, it uses the obtained authorized user signal to perform serial interference cancellation, and then decodes the signal of the selected exempted user.

7. A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 4, characterized in that, S4 include: S41. The scheduled authorized user estimates its own channel gain and sets its own transmit power as the ratio of the control parameter to its own channel gain; If the selected unlicensed user detects that its own channel gain is greater than or equal to the preset decision threshold, its transmit power is adjusted to the maximum available power; otherwise, its transmit power is adjusted to 0, indicating that the unlicensed user does not upload signals in the current transmission cycle, and the transmission cycle is only used to transmit signals from licensed users.

8. A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 4, characterized in that, S4 include: S42. If the selected unlicensed user's transmit power is not 0, then the user transmits its own signal to the low-orbit satellite. The low-Earth orbit satellite performs decoding in the following two ways according to the transmission strategy B: Scenario 1: If the unlicensed user's transmit power is not zero, the low-Earth orbit satellite will receive aliased signals from both the unlicensed and licensed users. The low-Earth orbit satellite will first treat the licensed user's signal as interference and decode the selected unlicensed user's signal under interference. After successful decoding, serial interference cancellation will be performed, and the low-Earth orbit satellite will then decode the scheduled licensed user's signal. Scenario 2: If the unlicensed user's transmit power is 0, the low-Earth orbit satellite will only receive and decode the signals sent by the scheduled authorized user.

9. A non-orthogonal semi-unlicensed adaptive transmission method for low-Earth orbit satellite communication according to claim 7, characterized in that, The decision threshold is: in, The control parameters are... This represents the signal-to-noise ratio threshold required for a low-Earth orbit satellite to correctly receive signals from unlicensed users. This indicates the noise power received by a low-Earth orbit satellite. The maximum available transmit power for unlicensed users.

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