Unlicensed access method for dynamic time slot optimization under low earth orbit satellite

Abstract

The invention relates to an authorization-free access method for dynamic time slot optimization under a low earth orbit satellite, and belongs to the field of satellite communication and the Internet of Things. The method comprises the following steps: S1, dynamically adjusting the number of access time slots, and increasing or decreasing the number of time slots according to a comparison result of the proportion of active equipment in a system and a preset threshold; s2, a load-aware intelligent pilot frequency selection mechanism is adopted, and equipment selects pilot frequencies with few conflicts by referring to real-time load information of a system; s3, satellite signal processing and feedback; s4, the satellite carries out pilot frequency estimation and cache processing in a subsequent time slot, and conflicting user data is recovered through continuous interference elimination; and S5, data decoding, state updating and performance optimization. According to the method, the problems of information timeliness lag, low resource allocation efficiency, frequent pilot conflict and the like of a random access protocol in the satellite Internet of Things are effectively solved, the access failure probability in a high-load scene is reduced, the channel resource utilization rate is improved, and effective updating and reliable transmission of information are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the fields of satellite communication and the Internet of Things, and relates to an unlicensed access method for dynamic time slot optimization under low-earth orbit satellites. Background Art

[0002] Under the wave of the industrial revolution in the era of the Internet of Everything, the global digital transformation is giving rise to ubiquitous and high-concurrency communication demands. Many application fields urgently need the ability to perform broadband multiple access anytime and anywhere. For example, emerging scenarios such as soil moisture monitoring arrays in smart agriculture, industrial robotic arm collaborative networks in smart manufacturing, millisecond-level fault location systems in smart power grids, and ultra-low latency in-flight entertainment systems on civil airliners have put forward revolutionary requirements for wireless communication systems: the ability to support non-orthogonal multiple access for more than ten thousand terminals per square kilometer at any geographical coordinate and any time node.

[0003] The current terrestrial communication network architecture is facing three fundamental challenges: First, the coverage of cellular networks shows a significant urban agglomeration effect, and in special scenarios such as deserts, oceans, and polar regions, the single base station coverage cost is high; second, in the traditional scheduling-based licensed access mechanism (such as the LTE RACH process), when the terminal density is high, the pilot collision probability increases exponentially, and the access success rate is greatly reduced; third, the resource allocation mode with a fixed frame structure is difficult to adapt to the bursty characteristics of mMTC services, resulting in insufficient spectrum utilization, causing a serious coexistence phenomenon of resource vacancy and competition congestion.

[0004] In this context, the low-earth orbit satellite Internet of Things (LEO-SIoT) system has become the key to breaking the situation due to its physical layer advantages: The near-earth satellite network composed of SpaceX's second-generation Starlink satellites (orbital altitude of 340 km) and Telesat Lightspeed constellations (1015 km) can provide ubiquitous service capabilities with an end-to-end propagation delay of 7 - 15 ms and an instantaneous coverage diameter of up to 1900 km for a single satellite. It is particularly worth noting that the International Telecommunication Union (ITU) clearly pointed out in the "Technical White Paper on Space-Ground Integrated Networks" released in 2024 that the per-bit transmission cost of the LEO satellite system has been reduced to 1 / 8 of that of ground base stations, and the service continuity in areas with sparse user distribution has been improved by 4 orders of magnitude. Since the satellite and the user are hundreds or thousands of kilometers apart, unlicensed random access can reduce the propagation delay in the total access delay and the signaling overhead generated in the traditional licensed scheme. For an unlicensed random access system, each active user randomly selects a pilot sequence from a predefined set of pilot sequences and then updates it to the low-earth orbit satellite together with the data payload, which can alleviate system overload and pilot conflicts. Therefore, for S-IoT, it is an option to tend to decentralized pilot allocation and adopt unlicensed random access. Therefore, it is of great significance to reduce the overhead according to dynamic time slot allocation in combination with the characteristics of low-earth orbit satellites. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide an unlicensed access method with dynamic time slot optimization under low-earth orbit satellites, so as to solve the problems faced by the random access protocol in satellite Internet of Things, such as lagging information timeliness, low resource allocation efficiency, and frequent pilot conflicts, reduce the access failure probability in high-load scenarios, improve the utilization rate of channel resources, and ensure the effective update and reliable transmission of information.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An unlicensed access method with dynamic time slot optimization under low-earth orbit satellites specifically includes the following steps:

[0008] S1: Dynamically adjust the number of access time slots;

[0009] S2: Intelligent pilot selection;

[0010] S3: Satellite signal processing and feedback;

[0011] S4: Time slot pilot estimation and cache processing;

[0012] S5: Data decoding, status update and performance optimization.

[0013] Further, in step S1, the dynamic adjustment of the number of access time slots specifically includes the following steps:

[0014] S11: Real-time monitor the device activity in the system, and calculate the proportion of active devices ρ = K a / K total , where K a is the number of active devices at a certain moment, and K total is the total number of devices in the system. This process can ensure that the obtained device activity information is accurate and timely, providing a reliable basis for subsequent time slot adjustment;

[0015] S12: Compare the proportion of active devices ρ with the preset lower threshold ρ min and upper threshold ρ max . These thresholds are not fixed, but are dynamically determined according to the long-term operation data of the system and the requirements of different service scenarios through big data analysis and intelligent algorithms to adapt to the complex and changeable network environment;

[0016] S13: Increase or decrease the access time slots according to the comparison result, and ensure that the number of access time slots N meets the relevant constraints of the satellite link.

[0017] Further, step S13 specifically includes the following steps:

[0018] S131: Determine the current number of time slots N;

[0019] S132: Determine the influence of the active device ratio ρ, and change the number of time slots according to the following situations;

[0020]

[0021] Among them, α1 and α2 are resource recovery efficiency coefficients;

[0022] S133: Complete the change of the number of time slots and confirm that the satellite link constraint conditions are met.

[0023] Furthermore, in step S133, after adjusting the number of time slots, through a series of link quality detection means, including signal strength monitoring or bit error rate analysis, etc., ensure that the new number of time slots will not have a negative impact on the stability and reliability of the satellite link, and guarantee the smooth progress of communication.

[0024] The signal strength monitoring is specifically as follows: Collect the received signal strength indication (RSSI). Dynamically set a reasonable threshold range of RSSI according to the service type of the satellite communication system and the current environmental conditions.

[0025] The bit error rate analysis is specifically as follows: Conduct bit error statistics on the transmitted data respectively after the demodulation module of the satellite receiving device and at the ground receiving station. Compare the original data sent by the sending end and the data received by the receiving end, accurately calculate the number of error code elements, and then obtain the bit error rate (BER). For example, for every 10,000 bits of data transmitted, count the number of error bits and calculate the bit error rate.

[0026] Furthermore, in step S2, the intelligent pilot selection specifically includes the following steps:

[0027] S21: The device obtains the current number of active devices in the system, its own priority and data generation rate, as well as the historical usage records and conflict times of all pilots;

[0028] S22: Calculate the access frequency, load index, and historical conflict rate of each pilot;

[0029] S23: Calculate the evaluation index S according to the indicators in S22 j , and select the pilot with the minimum S j value as the access pilot for this time, and regularly update the historical usage records and conflict times of the pilot.

[0030] Furthermore, in step S22, the formula for calculating the historical conflict rate is:

[0031]

[0032] Among them, T represents the time period, C j,t and Hj,t respectively represent the number of collisions and the number of uses of pilot P within the t-th time unit j , and w t is the time weight coefficient, satisfying and generally, for time units closer to the current time, the value of w t is larger to highlight the importance of recent collision situations.

[0033] The formula for calculating the load indicator is as follows:

[0034]

[0035] where f ij represents the access frequency of the i-th active device to pilot P j , and K a represents the number of active devices. To accurately obtain P j , the system counts the number of access attempts of each active device to each pilot within each time unit. The determination method of the weight coefficient w i is as follows: The priority of the device is p i , and the data generation rate is r i , then w i =α1p i +α2r i , where α1 and α2 are weight adjustment parameters.

[0036] Furthermore, in step S23, the formula for calculating the evaluation indicator S j is as follows:

[0037] S j =αL j +(1 - α)R j

[0038] where α is the weight coefficient, L j is the load indicator, and R j is the historical collision rate.

[0039] Furthermore, in step S3, the satellite signal processing and feedback specifically include the following steps:

[0040] S31: Before the start of each transmission frame, the satellite broadcasts initialization information to all user devices, including the available pilot set, the number of initial access time slots, and the synchronization signal;

[0041] S32: In the first access time slot, the active users select a pilot according to the intelligent pilot selection mechanism and send it to the satellite;

[0042] S33: The satellite identifies the pilot sequence status based on the received signal power and statistical channel information, which is divided into idle pilots, individual pilots, and conflicting pilots. It immediately decodes the data payload for individual pilots, records the information of idle pilots and conflicting pilots, and feeds back the conflict situation to the involved users, and re-feeds the remaining pilot set.

[0043] Further, in step S4, the slot pilot estimation and caching process specifically includes the following steps:

[0044] S41: In the subsequent N - 1 access slots, the satellite estimates the received pilot sequence, identifies the single pilot sequence, and caches the devices that have collided.

[0045] S42: When the Nth slot ends, the satellite first recovers the status data packet through the individual pilot sequence. If there is still potentially conflicting user data in the buffer, it performs successive interference cancellation through the recovered individual users to recover the collided user data.

[0046] Further, step S5 specifically includes the following steps:

[0047] S51: After the satellite successfully decodes all the data, it sends an acknowledgment (ACK) signal to the corresponding user.

[0048] S52: After the user receives the acknowledgment (ACK) signal, it updates its internal state.

[0049] S52: Perform Markov analysis, specifically including average age of information optimization, system throughput maximization, and optimal access slots, so as to optimize the system performance.

[0050] The beneficial effects of the present invention are as follows: Aiming at the problems in the satellite IoT scenario, due to the lack of real-time intelligent decision-making in the pilot selection mechanism during the satellite access process, long propagation delays, and sudden user equipment transmissions leading to information congestion in the satellite Internet of Things, especially seriously affecting the protocol and system performance during the RA (random access) process, the present invention proposes an unlicensed access method for dynamic slot optimization under low-earth orbit satellites. By improving the satellite access part, that is, by constructing a dynamic slot optimization framework and an intelligent pilot decision-making system, the access failure probability in high-load scenarios of low-earth orbit satellite Internet of Things (LEO - SIoT) is reduced, the channel resource utilization rate is improved, and the effective update and reliable transmission of information are ensured.

[0051] The method of the present invention specifically adopts: (1) Dynamically adjusting the number of access time slots, increasing or decreasing the number of time slots according to the comparison result between the proportion of active devices in the system and a preset threshold; (2) Adopting a load-aware intelligent pilot selection mechanism, where devices select pilots with fewer conflicts with reference to the real-time load information of the system; (3) After the satellite receives the signal, it identifies the pilot status and feeds it back to the user, and simultaneously records relevant information; (4) The satellite performs pilot estimation and caching processing in subsequent time slots, and uses successive interference cancellation to recover the data of conflicting users; (5) After completing data decoding, the satellite sends an acknowledgment signal to the user; after retransmission, the random access part is completed. The present invention effectively solves the problems faced by the random access protocol in satellite Internet of Things, such as the lag of information timeliness, low resource allocation efficiency, and frequent pilot conflicts, reduces the access failure probability in high-load scenarios, improves the utilization rate of channel resources, and ensures the effective update and reliable transmission of information.

[0052] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0053] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0054] Figure 1 It is the overall flowchart of the license-free access method for dynamic time slot optimization under low-earth orbit satellites provided by the present invention;

[0055] Figure 2 It is the detailed flowchart of the license-free access method for dynamic time slot optimization under low-earth orbit satellites provided by the present invention;

[0056] Figure 3 It is a schematic diagram of the node access process in the satellite IoT scenario. Detailed Embodiments

[0057] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0058] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams rather than physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0059] In the attached drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0060] Please refer to Figures 1 to 3 , the present invention provides an unauthorized access method for low-orbit satellite dynamic time slot optimization, which specifically includes the following steps:

[0061] Step 1: Dynamic adjustment of time slots, specifically including:

[0062] 11) Real-time monitor the device activity in the system, and calculate the proportion of active devices ρ = K a / K total , where K a is the number of active devices at a certain moment, and K total is the total number of devices in the system. This process can ensure that the obtained device activity information is accurate and timely, providing a reliable basis for subsequent time slot adjustment;

[0063] 12) Compare the proportion of active devices ρ with the preset lower threshold ρ min and upper threshold ρ max . These thresholds are not fixed, but are dynamically determined through big data analysis and intelligent algorithms according to the long-term operation data of the system and the requirements of different service scenarios to adapt to the complex and changeable network environment;

[0064] 13) Increase or decrease the access time slots according to the comparison result, and ensure that the number of access time slots N meets the satellite link related constraint conditions, specifically including:

[0065] 131) Determine the current number of time slots N;

[0066] 132) Judge the influence of the proportion of active devices ρ, and transform the number of time slots according to the situation to

[0067]

[0068] Among them, α1 and α2 are resource recovery efficiency coefficients.

[0069] 133) Complete the change in the number of time slots and confirm that the satellite link constraint conditions are met. After adjusting the number of time slots, through a series of link quality detection means, such as signal strength monitoring, bit error rate analysis, etc., ensure that the new number of time slots will not have a negative impact on the stability and reliability of the satellite link, and guarantee the smooth progress of communication.

[0070] Step 2: Intelligent pilot selection, specifically including:

[0071] 21) The device obtains the current number of active devices in the system, its own priority and data generation rate, as well as the historical usage records and conflict times of all pilots;

[0072] 22) Calculate the access frequency and load index L of each pilot j and historical conflict rate R j ;

[0073] 23) Calculate the evaluation index S according to the calculated indexes j =αL j +(1 - α)R j , where α is the weight coefficient, and select the pilot with the minimum S j value as the pilot for this access, and regularly update the historical usage records and conflict times of the pilot.

[0074] Step 3: Satellite signal processing and feedback, including:

[0075] 31) Before the start of each transmission frame, the satellite broadcasts initialization information to all user devices, including the available pilot set, the initial access time slot number, and the synchronization signal;

[0076] 32) In the first access time slot, the active user selects a pilot according to the intelligent pilot selection mechanism and sends it to the satellite;

[0077] 33) The satellite identifies the pilot sequence status based on the received signal power and statistical channel information, divides it into idle pilots, individual pilots, and conflicting pilots, immediately decodes the data payload for individual pilots, records the information of idle pilots and conflicting pilots, and feeds back the conflict situation to the involved users and re - feeds back the remaining pilot set.

[0078] Step 4: Time - slot pilot estimation and caching processing, including:

[0079] 41) In the subsequent N - 1 access time slots, the satellite estimates the received pilot sequence, identifies the single pilot sequence, and caches the devices that have collided;

[0080] 42) When the Nth time slot ends, the satellite first restores the status data packet through the dedicated pilot sequence. If there is still potentially conflicting user data in the buffer, successive interference cancellation is performed through the restored dedicated users to restore the collided user data.

[0081] Step 5: Data decoding, status update, and performance optimization, including:

[0082] 51) After the satellite successfully decodes all data, it sends an acknowledgment (ACK) signal to the corresponding user;

[0083] 52) After receiving the ACK, the user updates its internal status to prepare for the next data transmission;

[0084] 53) Perform Markov analysis to improve the overall system performance, including increasing the throughput and reducing the age of information.

[0085] 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 them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for unlicensed access with dynamic time slot optimization in low-orbit satellite, characterized in that: The method specifically comprises the following steps: S1: Dynamically adjust the number of access time slots; S2: intelligent pilot selection; S3: Satellite signal processing and feedback; S4: time slot pilot estimation and buffer processing; S5: Data decoding, status update and performance optimization.

2. The authorization-free access method according to claim 1, characterized in that: In step S1, the dynamically adjusting the number of access time slots specifically includes the following steps: S11: Real-time monitoring of device activity in the system, calculation of the active device ratio ρ = K a / K total , where K a is the number of active devices at a certain moment, K total is the total number of devices in the system; S12: Compare the active device ratio ρ with the preset lower limit threshold ρ min and the upper threshold ρ max Make comparisons; S13: Increase or decrease the access time slot according to the comparison result, and ensure that the number of access time slots N meets the satellite link related constraints.

3. The authorization-free access method according to claim 2, characterized in that: Step S13 specifically includes the following steps: S131: Determine the current number of time slots N; S132: Determine the influence of the active device ratio ρ and change the number of time slots according to the following conditions; Among them, α1 and α2 are resource recovery efficiency coefficients; S133: Complete the change in the number of time slots and confirm that the satellite link constraint conditions are met.

4. The authorization-free access method according to claim 3, characterized in that: In step S133, after adjusting the number of time slots, link quality detection means, including signal strength monitoring or bit error rate analysis, are used to ensure that the new number of time slots will not have a negative impact on the stability and reliability of the satellite link, thereby ensuring smooth communication.

5. The authorization-free access method according to claim 1, characterized in that: In step S2, the smart pilot selection specifically includes the following steps: S21: The device obtains the number of currently active devices in the system, its own priority and data generation rate, as well as the historical usage records and conflict times of all pilots; S22: Calculate the access frequency, load index and historical conflict rate of each pilot; S23: Calculate the evaluation index S based on the index of S22 j , and select S j The pilot with the smallest value is used as the pilot for this access, and the historical usage record and number of conflicts of the pilot are updated regularly.

6. The authorization-free access method according to claim 5, characterized in that: In step S23, the evaluation index S is calculated. j The formula is: S j =αL j +(1-α)R j Among them, α is the weight coefficient, L j is the load index, R j is the historical conflict rate.

7. The authorization-free access method according to claim 1, characterized in that: In step S3, the satellite signal processing and feedback specifically includes the following steps: S31: Before the start of each transmission frame, the satellite broadcasts initialization information to all user devices, including the available pilot set, the number of initial access time slots, and the synchronization signal; S32: In the first access time slot, the activated user selects a pilot signal and sends it to the satellite according to the intelligent pilot signal selection mechanism; S33: The satellite identifies the pilot sequence status based on the received signal power and statistical channel information, and divides it into idle pilots, single pilots and conflicting pilots. It immediately decodes the data payload of the single pilot, records the idle pilot and conflicting pilot information, and feeds back the conflict situation to the users involved, and re-feeds back the remaining pilot set.

8. The authorization-free access method according to claim 1, characterized in that: In step S4, the time slot pilot estimation and cache processing specifically includes the following steps: S41: In the subsequent N-1 access time slots, the satellite estimates the received pilot sequence, identifies a single pilot sequence, and caches the device that has collided; S42: When the Nth time slot ends, the satellite first recovers the status data packet through a separate pilot sequence. If there is still potential conflicting user data in the buffer, continuous interference cancellation is performed through the recovered separate user to recover the colliding user data.

9. The authorization-free access method according to claim 1, characterized in that: Step S5 specifically includes the following steps: S51: After successfully decoding all data, the satellite sends a confirmation signal to the corresponding user; S52: After receiving the confirmation signal, the user updates its internal state; S52: Perform Markov analysis to optimize system performance.

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