Credit-based random access method in satellite network

Abstract

The invention discloses a credit-based random access method in a satellite network, solves the problem of contradiction between time-sensitive service guarantee and system efficiency, and belongs to the technical field of data communication transmission. The random access method comprises the following steps: S1, determining a signaling structure which comprises a BCH broadcast message and a preemption request signal; s2, a satellite initializes system parameters, and broadcasts the parameters and the current frame structure to all terminals; s3, the satellite periodically and dynamically adjusts the size proportion of the CR area and the GR area through the real-time network load and the time-sensitive service volume, and notifies the terminal through broadcast signaling; s4, each terminal maintains a credit counter in a local memory, and credit value updating is driven by a terminal local clock and the received satellite broadcast parameters; before a terminal sends, a physical layer continuously monitors and preempts a channel; and S5, when the terminal has data to be sent, a corresponding service process is adopted according to the service type.

Description

Technical Field

[0001] This invention relates to a credit-based random access method in satellite networks, belonging to the field of data communication transmission technology. Background Technology

[0002] Currently, random access mechanisms in satellite networks and broadband access systems are mainly based on slotted ALOHA (S-ALOHA) and its derivative protocols (such as CRDSA and IRSA). Traditional methods face the following challenges: First, services lack differentiated capabilities, with all terminals competing for resources under the same rules, failing to provide low-latency, high-reliability transmission guarantees for time-sensitive services (such as emergency commands and command and control information); second, resource allocation strategies are rigid, with some schemes using static priority differentiation to guarantee high-priority services by reserving fixed time slots, which inevitably leads to low resource utilization or insufficient guarantee capabilities when traffic fluctuates; third, congestion control mechanisms are lagging and costly, with mainstream solutions relying on terminals adjusting their transmission behavior based on feedback information from satellite broadcasts (such as collision probability) after detecting a collision. This is a passive, reactive control method with frequent signaling interactions and a sharp drop in efficiency when congestion worsens. Summary of the Invention

[0003] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and resolve the contradiction between time-sensitive business assurance and system efficiency.

[0004] The objective of this invention is achieved through the following technical solutions: A credit-based random access method in a satellite network includes: S1. Determine the signaling structure, including BCH broadcast messages and preemption request signals; S2. The satellite initializes system parameters and broadcasts the parameters along with the current frame structure to all terminals. S3. The satellite periodically and dynamically adjusts the size ratio of the CR and GR areas based on real-time network load and time-sensitive service volume, and notifies the terminal via broadcast signaling. S4. Each terminal maintains a credit counter in its local memory. The credit value is updated by the terminal's local clock and the received satellite broadcast parameters. Before transmission, the physical layer continuously listens for and preempts the channel. S5. When the terminal has data to send, the corresponding business process is adopted according to the business type.

[0005] Compared with the prior art, the present invention has the following advantages: (1) In terms of time-sensitive service protection: a dual protection path (dedicated GR + preemptive CR) is provided for time-sensitive services, which significantly reduces access latency and improves access success rate.

[0006] (2) In terms of high resource utilization: the size of the GR area is dynamically adjustable, avoiding the waste of static reservation; the preemption mechanism ensures that any time slot can be used for time-sensitive services when necessary, resulting in high resource utilization.

[0007] (3) In terms of low signaling overhead: the credit mechanism is a local open-loop control of the terminal. The satellite only needs to broadcast parameters and does not need to perform frequent interactive signaling for congestion control; the preemption signaling is short and efficient.

[0008] (4) In terms of good compatibility and feasibility: Based on the S-ALOHA improvement, there is no need to change the physical layer waveform and frame structure, making it easy to deploy and implement in existing systems.

[0009] (5) By introducing credit shaping and dynamic preemption mechanisms, this invention effectively coordinates the contradiction between time-sensitive service protection and system efficiency while being compatible with the S-ALOHA protocol, and provides a low-overhead, highly reliable and easy-to-implement satellite random access solution. Attached Figure Description

[0010] Figure 1 This is a block diagram illustrating the principle of the method of the present invention.

[0011] Figure 2 This is a schematic diagram of the composition of each frame.

[0012] Figure 3 This is a schematic diagram of the BCH broadcast message format.

[0013] Figure 4 A schematic diagram of the preemption request signal format. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0015] A credit-based random access method for satellite networks is proposed. This method constructs a traffic shaping mechanism based on credit values, maintains a credit counter for each terminal, and adaptively manages its data transmission behavior to contention zones through incrementing and decrementing rules. This suppresses ordinary service traffic at the source, greatly reducing the probability of network congestion. Simultaneously, a dynamic partitioning and credit-state-based preemption method is proposed. The satellite dynamically divides contention zones (CR) and guaranteed zones (GR) according to network status. Time-sensitive services not only prioritize GR, but also, when GR resources are insufficient, preempt time slots reserved by ordinary terminals with "overdrawn credit" in CR, achieving on-demand allocation and efficient utilization of resources.

[0016] like Figure 1 As shown, a credit-based random access method in a satellite network includes the following steps: S1. Determine the signaling structure. This invention mainly involves two types of signaling: BCH broadcast messages and preemption signal, and specifies their signaling structures as follows: BCH Broadcast Message Format: Messages broadcast by the satellite within the BCH time slot should employ an efficient and reliable encoding method (such as BPSK + strong error correction code), e.g. Figure 3 As shown.

[0017] Preemption request signal format: This signal is sent during the guard time before the start of the time slot and must have high detection probability and low bit error rate, such as... Figure 4 As shown.

[0018] The preemption request signal consists of a predefined, unique preamble sequence. This sequence should have good autocorrelation and cross-correlation to distinguish it from the preamble of a normal data packet and to allow for rapid detection. For example, a segment of the Gold sequence could be used.

[0019] The length of the preemption request signal should be extremely short, and its transmission time should fall entirely within the protection interval, never encroaching on the main part of the subsequent data time slot.

[0020] Power of the preemption request signal: The transmission power should be 3-6 dB higher than that of a normal data packet to ensure reliable listening by all terminals within the target time slot.

[0021] S2. The satellite initializes system parameters (such as credit growth rate r, credit consumption value c, negative credit limit -L) and broadcasts these parameters along with the current frame structure (including the division of CR and GR regions) to all terminals.

[0022] S21. Table 1 shows the default configuration under typical satellite scenarios. Any parameter can be dynamically adjusted within the listed range through network management commands at the satellite network management center and broadcast to each terminal via broadcast messages.

[0023] Table 1

[0024] S22. This system adopts a layered frame structure design, including frames and slots. Each frame consists of three parts: the Broadcast Channel (BCH) slot, located at the beginning of the frame, used by the satellite to broadcast system control information to all terminals, including credit parameters (r, c, L, Credit_Max) and frame structure information (G, N_slot); the Contention Zone (CR) slot, used for random contention access for ordinary services when the credit value allows; and the Guaranteed Zone (GR) slot, dedicated to time-sensitive service terminal access, the size of which is dynamically variable, such as... Figure 2 As shown.

[0025] Frame length L: can be fixed according to link budget and latency requirements, for example, 100ms.

[0026] CR time slot number M and GR time slot number G: These are dynamic values ​​that satisfy M + G = L - 1. The satellite adjusts M and G according to the network status and broadcasts the value of G via BCH, allowing the terminal to calculate the area boundary.

[0027] Time slot length: It must include the data portion and the guard time. The design of the guard time must take into account the timing error of the terminal and the processing delay.

[0028] S3. Satellite-side dynamic adjustment logic. The satellite periodically and dynamically adjusts the size ratio of the CR and GR regions based on real-time network load and time-sensitive service volume, and notifies the terminal via broadcast signaling. The specific adjustment process involves the satellite monitoring network. Statistics on time-sensitive business volume Calculate the new G at the end of the superframe The new parameters (r,c,L,G) are broadcast via BCH in the first frame of the next superframe.

[0029] S31. The network management module on the satellite dynamically calculates and updates the optimal size ratio of CR / GR for the next cycle based on the historical statistics of recent time-sensitive service access requests (such as average queue length).

[0030] S32. The satellite maintains a time-sensitive service request counter C_t, which is counted during each superframe time.

[0031] S33. Dynamic adjustment algorithm: At the beginning of each superframe, G (GR slot number) is set to the exponentially weighted moving average of C_t in the previous superframe, and a fixed margin (such as +2) is added to cope with burst traffic.

[0032] G_{new}=α G_{old}+(1-α) C_t+2 Where α is a smoothing factor, for example, 0.7. At the same time, upper and lower limits of G are set (e.g., G_min=2, G_max=10) to prevent excessive compression of the CR region or waste of GR resources, and G_{old} is the initial region length.

[0033] S34. Broadcast the updated parameters (r,c,L,G) through the broadcast channel (BCH) time slot in the first frame of the next superframe.

[0034] S4, Terminal-side processing logic S41. Terminal Credit Mechanism. Each terminal maintains a credit counter in its local memory. Credit value updates are driven by the terminal's local clock and received satellite broadcast parameters, without the need for satellite control intervention. The specific process is as follows: Initialization: When a terminal first joins the network, its credit value is initialized to 0.

[0035] Credit update rules (executed at the end of each frame): Sending behavior: If the terminal successfully sends a data packet in the CR area of ​​this frame, then Credit = Credit - c. The value of c comes from the BCH broadcast.

[0036] Recovery behavior: Credit value is recovered for each frame, regardless of whether it is sent: Credit = min(Credit + r, Credit_Max). The value of r comes from the BCH broadcast. Credit_Max is set to a large value (e.g., 10). c).

[0037] Sending license rules: The terminal only sends licenses to Credit. Only when the value is 0 is it allowed to compete for transmission in the CR region of the next frame.

[0038] S42, Terminal preemption signal monitoring mechanism.

[0039] Before transmission, the terminal's physical layer continuously listens for and preempts the channel. After decoding the preemption signal and determining that the target time slot matches the time slot it intends to transmit in, it immediately queries its local credit value. If Credit < 0, a transmission interruption is triggered, and the transmission is abandoned.

[0040] S5. Terminal Service Process. When a terminal has data to send, it first determines the service type (time-sensitive service or ordinary service).

[0041] S51. For regular transactions, first check the local credit value. If the credit value is... If Credit is 0, then a time slot will be randomly selected in the CR area of ​​the next frame to send data. Upon successful transmission, Credit = Credit - c will be executed. If Credit < 0, then transmission will be prohibited in this frame. Regardless of whether transmission occurs, the credit value is recovered at a rate r: Credit = min(Credit + r, Max_Credit). S52. For time-sensitive services, first check if there is an available time slot in the GR region of the next frame. If so, select one and send directly. If the GR region is full or has no dedicated resources, switch to the preemption process. S53. Time-Sensitive Service Preemption Procedure: A target time slot S is randomly selected within the CR area. Within a very short period before the start of time slot S, a preemption request signal (containing the target time slot ID and preemption preamble) is sent to the satellite. Any ordinary terminal planning to transmit in time slot S and whose current credit value is <0 must forcibly abandon transmission in that time slot upon detecting this preemption request signal. The time-sensitive service terminal then transmits its own data packets within time slot S.

[0042] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0043] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A credit-based random access method in a satellite network, characterized in that, include: S1. Determine the signaling structure, including BCH broadcast messages and preemption request signals; S2. The satellite initializes system parameters and broadcasts the parameters along with the current frame structure to all terminals. S3. The satellite periodically and dynamically adjusts the size ratio of the CR and GR areas based on real-time network load and time-sensitive service volume, and notifies the terminal via broadcast signaling. S4. Each terminal maintains a credit counter in its local memory. The credit value is updated by the terminal's local clock and the received satellite broadcast parameters. Before transmission, the physical layer continuously listens for and preempts the channel. S5. When the terminal has data to send, the corresponding business process is adopted according to the business type.

2. The random access method according to claim 1, characterized in that, In S1, the content of the preemption request signal is a predefined preamble sequence; the transmission power of the preemption request signal should be 3-6 dB higher than that of a normal data packet.

3. The random access method according to claim 1, characterized in that, S2 specifically includes: S21. Determine the default configuration. The parameters in the default configuration can be dynamically adjusted within the listed range by network management commands at the satellite network management center and broadcast to each terminal via broadcast messages. S22. A layered frame structure is adopted, including frames and time slots; each frame consists of three parts: a broadcast channel time slot, located at the beginning of the frame, used by the satellite to broadcast system control information to all terminals; a contention area time slot, used by ordinary services to randomly compete for access when the credit value allows; and a guarantee area time slot, used by time-sensitive service terminals for access, the size of which is dynamically variable.

4. The random access method according to claim 1, characterized in that, S3 specifically includes: S31. The network management module on the satellite dynamically calculates and updates the optimal size ratio of CR / GR for the next cycle based on the historical statistics of recent time-sensitive service access requests (such as average queue length). S32. The satellite maintains a time-sensitive service request counter C_t, which is counted during each superframe time. S33. At the beginning of each superframe, set the number of GR time slots to the exponentially weighted moving average of C_t in the previous superframe, and add a fixed margin to cope with burst traffic. S34. Broadcast the updated parameters through the broadcast channel time slot in the first frame of the next superframe.

5. The random access method according to claim 1, characterized in that, S4 specifically includes: S41. Each terminal maintains a credit counter in its local memory. The credit value is updated by the terminal's local clock and the received satellite broadcast parameters. S42. Before transmission, the physical layer continuously listens for and preempts the channel; after decoding the preemption signal and determining that the target time slot is consistent with the time slot to be transmitted, it immediately queries the local credit value; if it is less than 0, it triggers a transmission interruption and abandons this transmission.

6. The random access method according to claim 1, characterized in that, In S5, business types include time-sensitive business or ordinary business.

7. The random access method according to claim 6, characterized in that, For regular services, first check the local credit value. If the credit value is not less than 0, then randomly select a time slot in the CR area of ​​the next frame to send data. After successful transmission, update the local credit value. If the credit value is less than 0, then transmission is prohibited in this frame.

8. The random access method according to claim 7, characterized in that, For regular business, the credit value is recovered at a rate r, regardless of whether it is sent or not.

9. The random access method according to claim 6, characterized in that, For time-sensitive services, the system first checks if there are any free time slots in the protection area of ​​the next frame; if so, it selects one and sends it directly; if the protection area is full or there are no dedicated resources, it switches to the preemption process. The time-sensitive service preemption process is as follows: a target time slot S is randomly selected in the competition area. During a period of time before the start of time slot S, a preemption request signal is sent to the satellite. Any ordinary terminal that plans to send in time slot S and whose current credit value is <0 must forcibly give up sending in that time slot after hearing this preemption request signal. The time-sensitive service terminal sends data packets in time slot S.

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