A terminal login access method based on satellite communication contention window dynamic management

Abstract

The application discloses a terminal login access method based on satellite communication competition window dynamic management, and aims at the large-scale terminal centralized network access problem of a low-orbit satellite LoRa system under the scenarios of satellite maintenance, fault recovery or network restart, etc., constructs an access structure of superframes / multiframes / time slots, introduces a competition window dynamic adjustment mechanism based on collision rate feedback, and combines a priority backoff access strategy to realize adaptive configuration of the competition window length. Compared with the existing random access or fixed superframe multiframe access scheme, the application is shorter in time required for completing access of all terminals under the condition of the same terminal login scale.

Description

Technical Field

[0001] This invention belongs to the field of satellite communication technology, specifically relating to a terminal login access method based on dynamic management of satellite communication contention windows, which is applied to the MAC access layer of a low-orbit satellite LoRa system composed of satellite base stations and a large number of ground terminals. Background Technology

[0002] With the continuous development and application of Low Power Wide Area Network (LPWAN) technology, more and more devices and sensors are being deployed in various environments, including smart cities, environmental monitoring, agricultural automation, and the Industrial Internet of Things (IIoT). However, in remote or complex scenarios such as deserts, uninhabited areas, marine environmental monitoring, and disaster emergency alarms, the construction and maintenance costs of ground base stations are extremely high, making it difficult for traditional terrestrial LPWAN systems to achieve continuous and reliable network coverage. Therefore, low Earth orbit (LEO) satellites can be used for data transmission, effectively solving the problem of insufficient terrestrial network coverage.

[0003] Leveraging the wide coverage and flexible deployment of low-Earth orbit (LEO) satellites, the LoRa ground gateway function can be "moved up" to LEO satellites, effectively solving the LoRa access problem in situations where ground base stations are lacking. Compared to traditional terrestrial LoRa networks, which are limited by gateway deployment density, using LEO satellites as airborne access nodes significantly improves the system's coverage and environmental adaptability. This effectively supports applications in remote or complex scenarios such as oceans, mountains, and deserts, demonstrating significant engineering application value and promising prospects for widespread adoption.

[0004] However, unlike the limited coverage of a single LoRa gateway on the ground, when LoRa systems are introduced into low-Earth orbit satellite communication scenarios, the coverage area of ​​a single satellite is wide, and the number of terminals that can access the network at any given time is far greater than in ground gateway scenarios, leading to a significant increase in the number of terminals competing for access simultaneously. Especially in specific scenarios such as satellite-side maintenance, fault recovery, or network restart, a large number of terminals are in a waiting state for network access due to the inability to access the network in the early stages. Once satellite service is restored, these terminals will launch network access requests in a concentrated manner, forming an "access flood." At this time, the channel collision rate will rise sharply, resulting in a large number of failed network access requests, a significant increase in access latency, and even channel congestion, which seriously reduces channel utilization and data transmission reliability.

[0005] The P-ALOHA access protocol is a commonly used basic random access scheme in low-Earth orbit (LEO) satellite LoRa systems. Due to its simplicity and lack of additional signaling overhead, it can maintain basic communication efficiency in scenarios with a small number of dispersed terminals. However, in LEO satellite LoRa systems, especially during "access surges" caused by satellite maintenance, fault recovery, or network restarts, the P-ALOHA protocol lacks any channel resource scheduling mechanism. All terminals randomly preempt channels, leading to a sharp increase in the probability of multiple terminals simultaneously occupying the same channel. The vast majority of network access requests fail due to collisions, requiring terminals to repeatedly retransmit, creating a vicious cycle of "collision-retransmission-collision," resulting in a near-zero access success rate and making it completely impossible to process batches of terminal network access requests.

[0006] Meanwhile, existing solutions attempt to alleviate access surge issues by using terminal multiframe access. This type of solution divides a superframe into multiple multiframes, allowing terminal nodes to randomly select a multiframe within the superframe to initiate a network access request, reducing the number of terminals competing for access within the same multiframe and thus lowering the probability of collisions. However, it suffers from excessively long access times; terminals often require a considerable amount of time to complete all access procedures, impacting service response efficiency.

[0007] In summary, existing access solutions for low-Earth orbit (LEO) satellite LoRa systems generally suffer from high collision rates, low access success rates, and excessively long access latency when dealing with "access surge" scenarios, making them unsuitable for the needs of large-scale centralized terminal network access. Therefore, there is an urgent need to design a terminal access solution that balances low collision rates and controllable latency to address the shortcomings of existing technologies. Summary of the Invention

[0008] To address the aforementioned issues, this invention discloses a terminal login access method based on dynamic management of satellite communication contention windows. Based on a superframe / multiframe / timeslot structure, it clarifies the access methods for different service types, dynamically adjusts the sliding contention window length with collision rate as a reference, and employs a priority backoff algorithm for contention time slots. This allows a large number of terminals to complete login within a short time.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A terminal login access method based on dynamic management of satellite communication contention windows is proposed. The method constructs an access structure of superframe / multiframe / timeslot, introduces a dynamic adjustment mechanism of contention windows based on collision rate feedback, and combines it with a priority backoff access strategy to achieve adaptive configuration of access resources.

[0011] Furthermore, the design method for the superframe / multiframe / timeslot structure is as follows:

[0012] The system services include two types: contention-based services (bursting services) and non-contention-based services (periodic services). A superframe consists of several multiframes, and the length of each multiframe in a superframe is configurable. Each multiframe includes a Beacon frame, a contention zone (CP period), and a non-contention zone (CFP period). Both the CP period and the CFP period consist of several numbered time slots. The contention zone is accessed in S-Aloha mode and is used for contention by bursting services. The non-contention zone is accessed in TDM mode and is used for allocation by periodic services. Regardless of whether it is a contention zone or a non-contention zone, there is a protection time interval between time slots to avoid collisions between nodes caused by clock skew or minor errors, thus providing a buffer for data transmission.

[0013] For the contention zone, each contention time slot is further divided into an uplink data transmission part and a downlink ACK confirmation part. A protection time interval is also set between the two. Whether it is the protection time interval between time slots or the protection time interval between uplink and downlink data within the contention time slot, the same value is taken.

[0014] In contention-ridden time slots, uplink data transmission employs priority backoff, with four priority levels. The first priority level transmits directly, while the second, third, and fourth priorities are transmitted after a delay of 1, 2, and 3 units, respectively. When a terminal selects to transmit a burst service in a contention-ridden time slot, the terminal determines the transmission priority based on an algorithm and listens to the transmission status of the time slot before transmission. If a signal is detected based on RSSI before the transmission time, it indicates that a higher priority terminal has already occupied the time slot, and the terminal abandons the transmission opportunity and continues to try in the next multiframe.

[0015] Based on the contention window length information contained in the Beacon frame, the terminal selects which time slot in which multiframe to attempt access contention. When the corresponding time slot arrives, the terminal is woken up to perform priority backoff access. If a higher priority terminal occupies the time slot, the multiframe number is incremented by 1, and access attempts are made in the same time slot number of the next multiframe.

[0016] Furthermore, based on the aforementioned superframe / multiframe / timeslot structure, a terminal login access method with contention-based window dynamic sliding management is designed, the specific process of which is as follows:

[0017] Step 1: Before each round of superframe distribution, the base station calculates the collision rate of the previous round of superframe contention window;

[0018] Step 2: Calculate the number of remaining users based on the collision rate. For different numbers of accessing users, use the "offline calibration" model to select the corresponding optimal contention length.

[0019] Step 3: Write the optimal contention window length into the Num field of the Beacon frame and broadcast it on the downlink;

[0020] Step 4: The terminal selects which contention slot in which multiframe to access the network based on the contention window division in the Beacon frame.

[0021] Step 5: The terminal calculates the transmission priority based on three status indicators: service type, transmission stage, and data backlog. The priority is divided into four levels, with values ​​of 0, 1, 2, and 3 from highest to lowest.

[0022] Step 6: The terminal wakes up before the time slot arrives and performs backoff access according to priority. If other terminals have already sent in this time slot before the access time arrives, it backs off and re-initiates access in the next superframe.

[0023] As a preferred method, step 1 involves calculating the collision rate of the previous round of super-frame competition regions, specifically as follows:

[0024] Collision rate definition:

[0025] ;

[0026] In the formula, This represents the number of time slots where collisions occur within the contention zone of a superframe. This represents the total number of contention slots in a superframe.

[0027] As a preferred option, step 2 involves deducing the remaining number of users from the collision rate and selecting the optimal competition length based on the "offline calibration" model, as follows:

[0028] Assuming that the competition for time slots by terminals follows a Poisson distribution, the collision rate and load intensity have the following relationship:

[0029] ;

[0030] in, This represents the average load intensity per unit time slot. , This indicates the number of users who have not yet completed the login process. This represents the total number of time slots in the contention zone of a superframe. Based on the above formula, the number of remaining users who have not yet completed login can be deduced from the collision rate.

[0031] For offline calculation of the optimal contention window length for different numbers of users, the specific details are as follows:

[0032] Competition window length Definition: The contention window length represents the number of multiframes contained within a superframe, and each multiframe has... In the optimization process, each multiframe contains a contention time slot. Fix, directly As an optimized output;

[0033] Determine the objective function for offline optimization, for a fixed number of users. Given a competition window length Perform a complete login process until the number of unlogged-in users becomes 0, and obtain the total number of multiframes required to complete the process. Selecting an appropriate competition window length through simulation. To minimize the total time required for the system to complete all user logins, the access event can be represented by the total number of multiframes required for access. Reflection, i.e., optimization goal:

[0034] ;

[0035] For each candidate In the simulation, implement a loop: Initial number of unlogged-in users Each superframe contains a contention window of length of 1. In each multiframe, currently unlogged users select time slots according to random access rules, and the number of terminals that successfully complete access in a superframe is counted. ,renew: ,when Record window length ;

[0036] For each This allows us to obtain the corresponding optimal competition window length. This minimizes the total number of multiframes required for all terminals to complete login access within this competitive window.

[0037] As a preferred method, step 5 calculates its own transmission priority, specifically as follows:

[0038] Priority calculation reference indicator 1: Burden type (alarm-related bursts, mode switching bursts, regular bursts, periodic services) Sudden mode switching routine emergencies Cyclical business For alarm-type emergencies, there's no need to calculate priority parameters; they are always of the highest priority. .

[0039] Priority calculation reference indicator 2: Transmission phase (remaining time: rising phase, early decline phase, mid decline phase, late decline phase) Extrapolate based on RSSI trends. Extrapolation is only activated when the signal deteriorates. The terminal relies on continuously listening to the Beacon's RSSI. This means that for each Beacon received, one sample is recorded. In order to reduce shaking, Perform an exponential moving average:

[0040] ;

[0041] Smoothing factor Set the value to 0.3. Take the five most recent smoothed samples, perform linear fitting, and obtain the slope. : ,in, This represents a tiny change in the smoothed RSSI value, indicating the magnitude of increase or decrease in signal strength over a very short period of time. This represents the small time difference between two signal samples. (The question is incomplete and requires further context.) If positive, it indicates that the sending phase is in an upward phase, and trend extrapolation does not need to be enabled; if If the value is negative, it is considered to have entered a downward phase, and trend extrapolation is initiated. The minimum RSSI threshold is set as follows: Therefore, extrapolate the remaining time :

[0042] ;

[0043] in, Indicates that the terminal is in The time-smoothed RSSI value is the signal strength data after exponential smoothing. Right now This indicates the preset minimum RSSI threshold. The absolute value of the slope represents the rate at which the signal strength decreases.

[0044] Assuming typical available window duration For the signal decline phase, based on the remaining time It is divided into three levels, corresponding to different sending stage indicators. Value: When the remaining time satisfy At that time, the terminal was in the initial stage of decline. The value is 0.2; when the remaining time satisfy At that time, the terminal was in the middle stage of decline. The value is 0.5; when the remaining time satisfy At that time, the terminal was in the late stage of decline. The value is 0.8.

[0045] Priority calculation reference indicator 3: Data backlog: (describes the pressure on the terminal's local cache) : ,in, Indicates that the terminal is in The amount of locally cached data backlog at any given time reflects the real-time cache pressure. This indicates the maximum capacity of the terminal's local cache. It is the upper limit of the cache set by the terminal hardware or system, and is a fixed threshold. express The data backlog rate at any given time, with a value range of [value missing]. The closer the value is to 1, the closer the cache is to full load, and the greater the backlog pressure.

[0046] Therefore, priority It can be represented as:

[0047] ;

[0048] in, This represents the weighting coefficient for the type of outbreak. , This represents the weighting coefficient during the transmission phase. , This represents the data backlog weighting coefficient. .

[0049] According to priority The value categorizes priorities into four levels. First priority It is the second priority. It is the third priority. It is the fourth priority.

[0050] The beneficial effects of this invention are as follows:

[0051] This invention solves the problem of soaring collision rates in concentrated login scenarios such as satellite maintenance and fault recovery in the traditional P-ALOHA protocol by dynamically adjusting the contention window size based on the number of remaining unconnected users and combining it with a priority backoff mechanism. It also alleviates the problem of excessively long access time under the existing superframe and multiframe design. In the shortest possible time, it designs an access solution that balances low collision rate and controllable latency for the problem of a large number of users logging in at the same time. Attached Figure Description

[0052] Figure 1 This is a flowchart of the present invention;

[0053] Figure 2 This is a diagram of the superframe / multiframe / timeslot structure of the present invention;

[0054] Figure 3 This is a time slot partitioning structure diagram of the present invention;

[0055] Figure 4 This is the contention slot priority backoff diagram of the present invention;

[0056] Figure 5 This is a simulation result diagram when the initial number of users is 300 in an embodiment of the present invention;

[0057] Figure 6 This is a simulation result diagram when the initial number of users is 800 in an embodiment of the present invention. Detailed Implementation

[0058] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0059] Example:

[0060] This invention provides a terminal login access method based on dynamic management of satellite communication contention windows, as detailed below:

[0061] A superframe / multiframe / timeslot access structure is constructed, and a dynamic contention window adjustment mechanism based on collision rate feedback is introduced. The satellite side calculates the remaining number of users based on the collision rate statistics of the previous superframe, and then selects the optimal contention window length for the current superframe according to different user counts. The terminal side combines a priority backoff access strategy to process login requests. See details... Figure 1 .

[0062] The design requirements for the application scenarios are clearly defined. In this embodiment, the main focus is on the LoRa system for low-Earth orbit satellites. In specific scenarios such as satellite-side maintenance, fault recovery, or network restart, a large number of terminals are in a waiting-to-join-network state because they could not access the network in the early stages. Once the satellite service is restored, these terminals will launch login access requests in a concentrated manner, forming an "access flood". At this time, the channel collision rate will rise sharply, and the time required to complete the access of all users is very long. Therefore, this invention designs a terminal access scheme that takes into account both low collision rate and controllable latency. Under the condition that all users complete the access, the time spent is minimized. The time overhead can be represented by the number of multiframes. Furthermore, Matlab simulation is used to analyze and compare this method with the traditional P-ALOHA protocol and conventional superframe / multiframe schemes.

[0063] In the embodiments, the simultaneous login requests of 300 and 800 terminals were studied. Once a terminal successfully logged in, the number of terminals making login requests would decrease in the next superframe until all terminals completed the login. The total time consumed was analyzed, which is the number of multiframes.

[0064] Scenario parameters in the embodiment: The study investigates simultaneous login requests from 300 and 800 terminals, both scenarios are conducted on a channel with a spreading factor of 8, a channel bandwidth of 125 kHz, and a coding rate of 4 / 5. The time slot length is calculated using the following formula: ;

[0065] In the formula, It is the length of bytes that a time slot can transmit, and SF is the spreading factor. It is the channel bandwidth. This refers to the channel coding rate. A superframe consists of several multiframes. The login service data frame is 39 bytes long, including an 8-symbol preamble and an implicit mode header, a 15-byte data payload, and 7 bytes of other necessary overhead. The ACK frame is 9 bytes long. The login service is a contention-based service and is located in the contention zone (CP period). The periodic service data frame is 23 bytes long, including an 8-symbol preamble and an implicit mode header, an 8-byte data payload, and 7 bytes of other necessary overhead. The periodic service is a non-contention-based service and is located in the non-contention zone (CFP period). The beacon frame is 27 bytes long. See details. Figure 2 .

[0066] Contention-bound time slots are divided into uplink data portions (login service data frames) and downlink acknowledgment portions (ACK frames), with a 2ms time protection interval between them. Non-contention-bound time slots contain only uplink data (periodic service data frames). See details. Figure 3 Based on the above formula, the contention slot length is 104ms, the non-contention slot length is 60ms, and the Beacon frame occupies a length of 56ms.

[0067] The number of time slots N can be calculated using the following formula:

[0068] ;

[0069] In the formula, The length of the multiframe is in milliseconds (ms). The Beacon slot length (ms) Let be the slot length (ms). From the above formula, we can see that under the conditions of a spreading factor of 8, a channel bandwidth of 125 kHz, a coding rate of 4 / 5, a guard interval of 2 ms, and a 1:1 ratio of contention to non-contention time slot lengths, if the multiframe length is 32 s, then there are 150 contention slots and 246 non-contention slots.

[0070] The terminal login access method, in detail, is as follows:

[0071] Step 1: Calculate the collision rate of the previous round of super-frame competition zone. definition:

[0072] ;

[0073] In the formula, This represents the number of time slots where collisions occur within the contention zone of a superframe. This represents the total number of contention slots in a superframe.

[0074] Step 2: Calculate the number of remaining users based on the collision rate. For different numbers of accessing users, use the "offline calibration" model to select the corresponding optimal contention length.

[0075] Assuming that the competition for time slots by terminals follows a Poisson distribution, the collision rate and load intensity have the following relationship:

[0076] ;

[0077] in, This represents the average load intensity per unit time slot. , This indicates the number of users who have not yet completed the login process. This represents the total number of time slots in the contention zone of a superframe. Based on the above formula, the number of remaining users who have not yet completed login can be deduced from the collision rate.

[0078] Competition window length This represents the number of multiframes contained within a superframe, for a fixed number of users. Given a competition window length Perform a complete login process until the number of unlogged-in users becomes 0, and obtain the total number of multiframes required to complete the process. Selecting an appropriate competition window length through simulation. To minimize the total time required for the system to complete all user logins, the access event can be represented by the total number of multiframes required for access. Reflection, i.e., optimization goal:

[0079] ;

[0080] For each candidate In the simulation, implement a loop: Initial number of unlogged-in users Each superframe contains a contention window of length of 1. In each multiframe, currently unlogged users select time slots according to random access rules, and the number of terminals that successfully complete access in a superframe is counted. ,renew: ,when Record window length For each This allows us to obtain the corresponding optimal competition window length. .

[0081] Using users from 0 to 1000 as parameters, and incrementing by 50 each time, calculate the corresponding optimal contention window length. The following table is obtained:

[0082]

[0083] Step 3: Write the optimal competition window length into the Num field of the Beacon frame.

[0084] Step 4: The terminal selects which contention slot in which multiframe to access the network based on the contention window division in the Beacon frame.

[0085] Step 5: The terminal calculates its own transmission priority based on three status indicators: burst type, transmission stage, and data backlog. The priority is divided into four levels, with values ​​of 0, 1, 2, and 3 from highest to lowest.

[0086] For reference indicator 1: Sudden event type (alarm-related sudden events, mode switching sudden events, regular sudden events, periodic business events) There is a mode switching type of sudden event. routine emergencies Cyclical business For alarm-related emergencies, which are always of the highest priority, there's no need to calculate the three parameter indicators; simply set... This gives it the highest transmission priority. For reference metric 2: Transmission Phase According to the remaining time Divided into three levels, Reference Indicator 3: Data Backlog value range The closer the value is to 1, the closer the cache is to full load, and the greater the backlog pressure.

[0087] Priority It can be expressed by the following formula:

[0088] ;

[0089] ;

[0090] according to The priority of value pairs is shown in Table 2 below:

[0091] ;

[0092] Step 6: The terminal wakes up before the corresponding contention time slot arrives and performs backoff access according to its own priority. If another terminal has already sent in this time slot before the access time arrives, it backs off and re-initiates access in the next superframe. When two terminals choose to send in the same time slot at the same time, it indicates that a collision has occurred in that time slot.

[0093] The first priority signal is sent immediately, while the second, third, and fourth priority signals are sent with delays of 1, 2, and 3 units respectively, because the speed of light is approximately [missing information]. The delay unit is taken as 0.5ms, according to the propagation distance formula: , Indicates the speed of light propagation. Indicates the delay time. Therefore, the distance at which priority backoff can be performed between terminals is This fully conforms to real-world application scenarios. For details on the priority backoff structure within the same contention time slot, please refer to [link / reference]. Figure 4 .

[0094] The following is a simulation example of the present invention:

[0095] Assuming 300 or 800 terminals simultaneously request login, once a terminal successfully logs in, the number of terminals requesting login decreases in the next superframe until all terminals have completed login. The total time consumed, i.e., the number of multiframes, is analyzed. The study is conducted on a channel with a spreading factor of 8, a channel bandwidth of 125 kHz, and a coding rate of 4 / 5. Each multiframe is 32 seconds long, containing 150 contention slots and 246 non-contention slots.

[0096] For two different user numbers (300 and 800), Matlab simulations were performed on the traditional P-ALOHA, the conventional superframe multiframe access scheme, and the access scheme of this invention, respectively. The time (number of multiframes) used was analyzed to ensure that all users are connected, so as to determine whether the scheme has the advantages of balancing low collision rate and controllable latency.

[0097] The results obtained are as follows Figure 5 , Figure 6 As shown, the access performance of the P-ALOHA protocol, the conventional superframe multiframe scheme, and the contention window dynamic management scheme proposed in this invention were compared under scenarios where 300 and 800 terminals simultaneously initiated login requests, respectively. It can be seen that the traditional P-ALOHA protocol has a high probability of conflict under high load conditions and poor access capability; the conventional superframe multiframe scheme, due to fixed contention resources, results in a slow decrease in the number of users waiting to log in, and a longer time required to complete access. In contrast, this invention can dynamically adjust the contention window according to the access status, matching the contention resources with the number of unlogged-in terminals. When the initial number of login users is 300, this invention only requires 10 multiframes to complete the access of all users, while the traditional superframe multiframe scheme requires 16 multiframes, reducing the time by 37.5%. When the initial number of login users is 800, this invention only requires 20 multiframes to complete the access of all users, while the traditional superframe multiframe scheme requires 30 frames, reducing the time by 33.3%.

[0098] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A terminal login access method based on dynamic management of satellite communication contention windows, characterized in that: A superframe / multiframe / timeslot access structure was constructed, a contention window dynamic adjustment mechanism based on collision rate feedback was introduced, and combined with a priority backoff access strategy, the adaptive configuration of access resources was realized. The superframe / multiframe / timeslot structure design method is as follows: The system services include both contention-based and non-contention-based services. A superframe consists of several multiframes, each with a configurable length. Each multiframe includes a Beacon frame, a contention-based zone, and a non-contention-based zone. Both the contention-based and non-contention-based zones consist of several numbered time slots. The contention-based zone is accessed using S-Aloha mode and is used by contention-based services, while the non-contention-based zone is accessed using TDM mode and is allocated for non-contention-based services. Regardless of whether it is a contention-based or non-contention-based zone, there is a protection interval between time slots. For contention zones, each contention time slot is further divided into an uplink data transmission portion and a downlink ACK confirmation portion, with a protection time interval set between the two. The same value is used for both the protection time interval between time slots and the protection time interval between uplink and downlink data within a contention time slot. During contention-ridden time slots, uplink data transmission employs priority backoff, with four priority levels. The first priority level transmits directly, while the second, third, and fourth priority levels are transmitted after a delay of 1, 2, and 3 units, respectively. Based on the contention window length information contained in the Beacon frame, the terminal selects which multiframe and which time slot to attempt to compete for access. When the corresponding time slot arrives, the terminal is woken up to perform priority backoff access. The specific process of the contention window dynamic adjustment mechanism based on collision rate feedback is as follows: Step 1: Before each round of superframe distribution, the base station calculates the collision rate of the competition zone in the previous round of superframes; Step 2: Calculate the remaining number of users based on the collision rate. For different numbers of accessing users, use the "offline calibration" model to select the corresponding optimal contention window length. ; Specifically: Competition window length Definition: The contention window length represents the number of multiframes contained within a superframe, and each multiframe has... In the optimization process, each multiframe contains a contention time slot. The length of the competition window is fixed. It can be output directly in multiple frames; For each user There is a corresponding optimal competitive window length. This ensures that, within this contention window length, the total number of multiframes required for all terminals to complete login access is [number missing]. Minimum; Step 3: Determine the optimal competition window length Write the Num field into the Beacon frame and broadcast it on the downlink; Step 4: The terminal selects which contention slot in which multiframe to access the network based on the contention window division in the Beacon frame. Step 5: The terminal calculates its own transmission priority based on three status indicators: burst type, transmission stage, and data backlog. The priority is divided into 4 levels, with values ​​of 0, 1, 2, and 3 from highest to lowest. Step 6: The terminal wakes up before the time slot arrives and performs backoff access according to priority. If other terminals have already sent in this time slot before the access time arrives, it backs off and re-initiates access in the next superframe.

2. The terminal login access method based on dynamic management of satellite communication contention window according to claim 1, characterized in that: Step 1: Calculate the collision rate of the previous round of super-frame contention zones, specifically: Collision rate definition: ； In the formula, This represents the number of time slots where collisions occur within the contention zone of a superframe. This represents the total number of contention slots in a superframe.

3. The terminal login access method based on dynamic management of satellite communication contention window according to claim 1, characterized in that: Based on the collision rate, the number of remaining users is calculated. For different numbers of access users, the optimal contention window length is selected using the "offline calibration" model. Specifically: Assuming that the competition for time slots by terminals follows a Poisson distribution, the collision rate and load intensity have the following relationship: ； in, This represents the average load intensity per unit time slot. , This indicates the number of users who have not yet completed the login process. The total number of time slots in the contention zone of a superframe; based on the above formula, the number of remaining users who have not yet completed login can be deduced from the collision rate; For offline calculation of the optimal competition window length for different numbers of users Specifically: Competition window length Definition: The contention window length represents the number of multiframes contained within a superframe, and each multiframe has... In the optimization process, each multiframe contains a contention time slot. The length of the competition window is fixed. It can be output directly in multiple frames; Determine the objective function for offline optimization, for a fixed number of users. Given a competition window length Perform a complete login process until the number of unlogged-in users becomes 0, and obtain the total number of multiframes required to complete the process. The optimal competition window length is selected through simulation, denoted as . To minimize the total time required for the system to complete all user logins, the access event uses the total number of multiframes required for access. Reflection, i.e., optimization goal: ； For each candidate In the simulation, implement a loop: Initial number of unlogged-in users Each superframe contains a contention window of length of 1. In each multiframe, currently unlogged users select time slots according to random access rules, and the number of terminals that successfully complete access in a superframe is counted. ,renew: ,when At that time, record the total number of multiframes required for the process. ; For each There is a corresponding optimal competitive window length. This ensures that, within this contention window length, the total number of multiframes required for all terminals to complete login access is [number missing]. Minimum.

4. The terminal login access method based on dynamic management of satellite communication contention window according to claim 1, characterized in that: Step 5, which involves calculating one's own transmission priority, specifically involves: Priority calculation reference indicator 1: Emergency type : Divided into alarm-related emergencies and mode-switching emergencies Routine emergencies Cyclical business For alarm-related emergencies, priority parameters do not need to be calculated; they are always of the highest priority. ; Priority calculation reference index 2: Sending phase Extrapolate based on RSSI trends. Extrapolation is only activated when the signal deteriorates. The terminal relies on continuously listening to the Beacon's RSSI. This means that for each Beacon received, one sample is recorded. In order to reduce shaking, Perform an exponential moving average: ； Smoothing factor Set the value to 0.3; take the five most recent smoothed samples, perform linear fitting, and obtain the slope. : ,in, This represents a tiny change in the smoothed RSSI value, indicating the magnitude of increase or decrease in signal strength over a very short period of time. This represents the small time difference between two signal samples; determine if... If positive, it indicates that the sending phase is in an upward phase, and trend extrapolation does not need to be enabled; if If the value is negative, it is considered to have entered a downward phase, and trend extrapolation is initiated. The minimum RSSI threshold is set as follows: Therefore, extrapolate the remaining time : ； in, Indicates that the terminal is in The time-smoothed RSSI value is the signal strength data after exponential smoothing. Right now This indicates the preset minimum RSSI threshold. The absolute value of the slope represents the rate at which the signal strength decreases. Typical available window duration For the signal decline phase, based on the remaining time It is divided into three levels, corresponding to different sending stage indicators. Value: When the remaining time satisfy At that time, the terminal was in the initial stage of decline. The value is 0.2; when the remaining time satisfy At that time, the terminal was in the middle stage of decline. The value is 0.5; when the remaining time satisfy At that time, the terminal was in the late stage of decline. The value is 0.8; Priority calculation reference indicator 3: Data backlog : ,in, Indicates that the terminal is in The amount of locally cached data backlog at any given time reflects the real-time cache pressure. This indicates the maximum capacity of the terminal's local cache, which is the upper limit of the cache set by the terminal hardware or system, and is a fixed threshold. Therefore, priority Represented as: ； in, This represents the weighting coefficient for the type of outbreak. , This represents the weighting coefficient during the transmission phase. , This represents the data backlog weighting coefficient. ; According to priority The value categorizes priorities into four levels. First priority It is the second priority. It is the third priority. It is the fourth priority.

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