Inter-satellite reliable routing method based on fault domain model

Abstract

The application claims a kind of inter-satellite reliable routing method based on fault domain model, belong to satellite communication technical field.Aiming at the problems that inter-satellite link is influenced by space environment and human interference, leading to transmission failure and routing interruption, a centralized inter-satellite reliable routing method based on inter-satellite link attribute is proposed.According to the real-time state and failure reason of inter-satellite link, the inter-satellite link is classified, the initial topology model containing global network information is constructed, the boundary diffusion method is designed combined with the state of boundary node of fault link, the fault link is aggregated into block to form fault domain topology model to limit the influence range of fault.Analysis of the influence of buffer queue capacity, link signal-to-noise ratio and path length on routing, construct comprehensive link utility function to quantify link quality, propose multi-attribute bypass path selection method to solve the problem of load imbalance caused by single path selection criterion, reduce system packet loss rate and end-to-end delay, improve the fault response capability of satellite network.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology. Specifically, it relates to an inter-satellite reliable routing method based on a fault domain model. Background Technology

[0002] In recent years, with the rapid growth of users and the explosion of data traffic, users have increasingly stringent requirements for communication reliability, stability, and real-time performance. Compared with traditional communication methods, satellite communication, with its excellent global coverage and high reliability and low latency, and especially with the development of reusable rocket technology and multi-satellite launch technology, is expected to become an important part of the next-generation network. Inter-satellite routing technology can ensure reliable and efficient data transmission between satellites, enabling ground users to achieve global communication coverage via satellite. However, the high-speed movement and spatial characteristics of satellites also bring a series of new problems to inter-satellite routing, such as dynamic topology, susceptibility to failure, and limited resources. Moreover, unlike on the ground, satellite failures are more difficult to maintain and repair. Therefore, it is necessary to focus on the reliability of routing and conduct more in-depth research on reliable inter-satellite routing strategies by analyzing network fault information and designing routing algorithms.

[0003] Software Defined Network (SDN) technology decouples the forwarding plane from the control plane. Its main advantages are flexibility, programmability, and logical centralization. SDN technology facilitates centralized management of satellite nodes to address the management challenges posed by current mega-constellations. Simultaneously, SDN technology can also be applied to inter-satellite routing. Due to the unique management methods of SDN, traditional distributed routing schemes are no longer suitable for the SDN architecture. Therefore, SDN-based routing schemes can achieve centralized node management and reduce the probability of satellite node failures to some extent.

[0004] Based on existing research on inter-satellite routing methods, they can be divided into two categories according to their handling of dynamic topology: dynamic routing algorithms and static routing algorithms. The former floods routing information, including fault information, to the global network and then designs routing methods based on real-time dynamic monitoring information within the network. However, in the context of current large constellations, simply flooding information globally leads to a significant increase in transmission latency. To address this issue, static routing algorithms divide routing into multiple time-slot "snapshots" of topology information. Since the network topology remains largely unchanged within each time slot, path calculation can be performed using static routing algorithms. This method perfectly captures the network topology changes caused by satellite movement, eliminating the need for flooding. However, it is not sensitive enough to sudden topology changes in the network and can also lead to excessive routing overhead.

[0005] This invention proposes an inter-satellite reliable routing method based on a fault domain model. Considering the excessive flooding delay of dynamic routing, this invention employs a static routing method to address dynamic topology issues. A multi-layered SDN architecture is designed to manage satellite nodes and facilitates the computation of the static routing algorithm. To address the insensitivity of static routing to sudden topology changes, this method first establishes a virtual topology based on logical addresses. Then, based on the fault block model, a routing fault model is designed to reduce the waste of available nodes and manage topology information. Based on this model, a path selection method is proposed. This method segments the routing process according to routing requirements. In path selection, a link utility function is obtained by weighting path length, signal-to-noise ratio, and queue buffer capacity to select the routing path. This effectively avoids potential load imbalance problems and reduces packet loss rate and average end-to-end latency. Summary of the Invention

[0006] This invention aims to solve the problems of the prior art. It proposes a distributed user-gateway method that guarantees user mobility and latency requirements. This method considers the characteristics and needs of users, as well as the characteristics of heterogeneous networks, and uses a distributed algorithm to obtain user association results. The technical solution of this invention is as follows:

[0007] An inter-satellite reliable routing method based on a fault domain model includes the following steps;

[0008] S1: Establish a virtual topology based on logical addresses according to the initial topology information of the satellite network;

[0009] S2: Based on the node state, reclassify the nodes into faulty nodes, boundary nodes, unreachable nodes, unreliable nodes, and available nodes. Then, traverse the faulty nodes to obtain the boundary node states. Finally, merge the faulty nodes in the boundary node set with the original faulty nodes, unreliable nodes, and unreachable nodes surrounded by faulty nodes to obtain the faulty node set F{N}.i,j} and the set of boundary nodes B{N i,j}, the available node set S{N i,j} through the total set and the set of faulty nodes F{N i,j} and the set of boundary nodes B{N i,j The difference between the source and destination nodes is calculated to obtain the positions of the source and destination nodes, and the detour priority (Round) and the initial boundary node (B) are calculated. s and the boundary destination node B d Location;

[0010] S3: Determine whether the shortest path between the source node and the destination node is blocked by the fault area. If it is blocked, execute the fault domain-based routing algorithm; otherwise, execute the regular routing algorithm.

[0011] S4: Execute the fault domain routing algorithm, calculate the signal-to-noise ratio utility function U(s), link length utility function U(l), buffer queue utility function U(b), and comprehensive utility function U(x) based on network information, and obtain the optimal routing path.

[0012] Furthermore, the specific process of establishing a virtual topology based on logical addresses in step S1 is as follows:

[0013] First, the topology of the satellite network is represented by a diagram. express, Denotes the set of satellites, ε = {l 11 l 12 ... l ij} represents the set of interconnections between these satellites. The connection relationships are represented by an incidence matrix, where elements in the matrix are 0 to indicate a link and 1 to indicate no link.

[0014] Secondly, a virtual topology model will be established based on the constellation topology, assigning each satellite a fixed logical address. The logical topology of the satellites will change as they move. The logical address of satellite S is (i,j), and N... i,j Let j represent the j-th satellite node on the i-th orbital plane, i = 0, ..., M-1; j = 0, ..., N-1; then determine the instantaneous topology of the satellite network by using the actual position of a satellite and the relative position obtained from the hello data packet.

[0015] Furthermore, step S2 specifically includes:

[0016] The set of faulty nodes F{N i,j} represents the set of locations of all faulty and unreachable nodes;

[0017] B{N} set of boundary nodes i,jThe boundary of the faulty node is represented by the available nodes adjacent to it; the initial node during the boundary traversal process is called the boundary initial node B. s The node where the detour ends is named the boundary destination node B. d ;

[0018] Define the detour priority Round(0,1) as a judgment condition. Round is calculated directly by which direction has a smaller number of hops. A value of 0 represents clockwise and a value of 1 represents counterclockwise.

[0019] Furthermore, step S3, the fault domain-based routing algorithm step, specifically includes:

[0020] Based on the relative positions of the source and destination nodes, and combined with the comprehensive link utility function, the routing paths from source to initial boundary, initial boundary to destination, and destination to destination are calculated in segments. The three paths are then integrated to obtain the most reliable routing path that is blocked by the fault domain.

[0021] Furthermore, the signal-to-noise ratio utility function U(s) in step S4 specifically includes:

[0022] During laser link transmission, the signal-to-noise ratio is mainly affected by free-space propagation loss, which can be quantified by the following formula:

[0023]

[0024] Among them, y ij For the final signal, h ij n is the link loss factor. ij Gaussian white noise; G is the source node transmit power, L ij Where γ is the distance and γ is the path loss exponent; in formula (1), SNR ij (t) is the signal-to-noise ratio of the link, and N0 is Gaussian white noise;

[0025] When the signal-to-noise ratio (SNR) during transmission falls below the receiving threshold α, data transmission will be impossible. Therefore, the probability of an interruption event is derived as follows:

[0026]

[0027] The probability of data packet interruption between satellites i and j is derived as follows:

[0028]

[0029] To ensure efficient data packet transmission, the signal-to-noise ratio utility function U(s) is defined as the probability of successful data packet transmission, expressed as:

[0030] U(s) = 1 - P r{SNR ij (t)<α} (4).

[0031] Furthermore, the path length utility function U(l) in step S4 specifically includes:

[0032] The shortest path can be calculated using the following formula:

[0033] MinL = MinL v +MinL h (5)

[0034] Where L v L represents the in-plane ISL length. h The interplane ISL length is represented by the following formulas (6)-(8):

[0035]

[0036] L h =δ×cos(lat) (7)

[0037]

[0038] Where lat represents the latitude of the interplane ISL, the satellite network has M polar orbit planes, and each polar orbit plane has N satellites; the angular distance between two adjacent planes is 360° / (2×M), and the angular distance between two adjacent satellites in the same orbit plane is 360° / N;

[0039] The path length utility formula can be used to calculate path length:

[0040] U(l)=MinL (9).

[0041] Furthermore, in step S4, the buffer queue utility function U(b) is specifically as follows:

[0042] According to queuing theory, the arrival rate of data packets follows a Poisson distribution with an average rate of λ. A(t) represents the number of data packets arriving within period t, and the probability function of A(t) = k is:

[0043]

[0044] The service time of each message follows an independent and identical distribution function, denoted as B(t), where v is defined. n The processing time for the nth data packet is [time].

[0045]

[0046] V nD(t) represents the independent processing time of a data packet, and D(t) represents the number of data packets processed by the satellite within time t.

[0047] D(t) = max{n:V n ≤t} (12)

[0048] P(D(t)=n)=B n (t)-B n+1 (t)=C n (t) (13)

[0049] In the formula B n (t) is an n-fold convolution of B(t), C n (t) represents the probability function that the satellite processes an equal number of data packets within time t, which can be calculated by (13). Then, at time t, the data packet length X(t) is expressed as:

[0050] X(t)=m+A(t)-D(t) (14)

[0051] Where m is the number of remaining packets at time t, the processing probability p of the current data queue X(t) is obtained. m,k (t), where j represents the number of data packets processed by the satellite in the current data queue;

[0052]

[0053] A buffer queue can characterize the congestion handling capacity of a link; therefore, the ISL utility function of a buffer queue is:

[0054] U(b)=p m,k (t) (16).

[0055] Furthermore, the comprehensive link utility function U(x) in step S4 is specifically as follows:

[0056]

[0057] Where ω represents the weight of each utility function, and formula (15) satisfies the following two constraints:

[0058]

[0059] The advantages and beneficial effects of this invention are as follows:

[0060] This invention addresses the specific problems of dynamic topology and frequent communication failures in inter-satellite routing by proposing a reliable inter-satellite routing method based on a fault domain model. The main innovation of this invention lies in proposing a topology model that more effectively describes fault information in static routing, and based on this model, proposing a routing method that can still achieve high reliability at a low cost when nodes in the satellite network fail, ensuring communication continuity. Existing research focuses on how to design and implement highly reliable routing algorithms and select routing paths based on simple factors such as shortest path or minimum hop count. Therefore, the reliable routing method based on the fault model proposed in this invention is not easily conceived by those skilled in the art. Furthermore, this invention invents a routing fault model and a highly reliable inter-satellite routing algorithm based on the characteristics of current low-Earth orbit satellite constellations, thereby generating reliable routing designs with low-Earth orbit constellation characteristics. Therefore, this invention possesses uniqueness and inventiveness. Because the space environment in which satellites operate is susceptible to influences from solar activity, malicious attacks, and other satellites, failures frequently occur during satellite communication. This invention fully considers the factors causing failures and integrates them with the topology model to complete the design of a routing failure model based on the concept of fault blocks. It also thoroughly analyzes the state and parameters of each satellite node and inter-satellite links, developing a highly reliable routing algorithm. In existing research, the research models set by researchers are too idealistic and do not consider the changing constraints under extreme scenarios. Therefore, this invention is creative and difficult to implement in its solution. By building a simulation platform for constellation operation and inputting the orbital and link parameters of the constellation, reliable transmission of routes is achieved. Furthermore, based on actual conditions, inter-satellite routing is specially processed. Attached Figure Description

[0061] Figure 1 This invention provides a preferred embodiment of a routing fault model based on a virtual network.

[0062] Figure 2 This is a network scenario diagram based on software-defined networking constructed according to the present invention;

[0063] Figure 3 This is a flowchart of the inter-satellite reliable routing algorithm based on fault domains described in this invention. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. The described embodiments are merely some embodiments of the present invention.

[0065] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0066] A reliable inter-satellite routing method based on SDN is proposed. The method flow is as follows: Figure 2 First, based on the existing static routing virtual topology model, the satellite nodes are divided into three subsets—available nodes, faulty nodes, and fault boundary nodes—according to the state and reachability of the nodes in the satellite network, thus constructing a network topology model. Then, based on the segmented routing concept, a detour routing method is designed and implemented. Simultaneously, this method introduces a comprehensive utility function combining multiple elements such as link signal-to-noise ratio, path length, and buffer queues to assist in route path selection, ultimately achieving reliable inter-satellite routing. This method reduces the waste of available nodes in the satellite network and lowers the packet loss rate and average end-to-end latency of inter-satellite links. The specific steps are as follows:

[0067] Step 101: Establish a virtual topology based on logical addresses according to the satellite network;

[0068] Step 102: Establish an inter-satellite routing fault model based on node status and reachability. The faulty node is traversed to obtain the status of its boundary nodes, and then this state is combined with the original faulty node and the unreachable nodes surrounded by the faulty node to obtain the faulty node set F{N}. i,j B{N} is the set of boundary nodes. i,j}, the available node set S{N i,j The position of the source node and the destination node can be obtained by calculating the difference between the total set and the two nodes mentioned above, and the detour priority (Round) and the initial boundary node (B) can be calculated. s and the boundary destination node B d Location;

[0069] Step 103: Determine whether the shortest path between the source node and the destination node is blocked by the fault region. If so, execute the routing algorithm based on the fault region; otherwise, return the shortest path directly.

[0070] Step 104: Execute the fault domain routing algorithm to calculate the signal-to-noise ratio utility function U(s), link length utility function U(l), buffer queue utility function U(b), and comprehensive utility function U(x) based on network information, and calculate the optimal routing path;

[0071] The model involved in this invention is as follows:

[0072] (1) Network Model:

[0073] The primary scenario of this invention is a multi-layered space-ground converged network based on SDN, as shown in the figure, which can be divided into two parts: a space segment and a ground segment. The space segment includes three parts: LEO satellites, MEO satellites, and GEO satellites. The ground segment includes an SDN control center, users, and base stations. At the logical level, the ground, MEO satellites, and GEO satellites form the control layer, on which an SDN controller is deployed. Low-Earth orbit (LEO) satellites serve as the data plane, possessing only simple forwarding functions. MEO satellites, as a secondary control layer, can collect and store LEO satellite topology data (including historical data) within their coverage area, which is ultimately managed uniformly by high-Earth orbit (HEO) satellites. Simultaneously, GEO satellites transmit the collected constellation information back to the ground; therefore, the computing and management modules of GEO satellites need to be software-defined to facilitate interaction with the ground.

[0074] (2) Routing Failure Model:

[0075] The fault model designed in this invention is as follows: Figure 1 As shown in the figure, satellite nodes are represented by points, and edges represent connections. This method classifies nodes into five types based on their status and connections: available nodes, faulty nodes, unreachable nodes, unreliable nodes, and boundary nodes.

[0076] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions.

[0077] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0078] The above embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. An inter-satellite reliable routing method based on a fault domain model, characterized in that, Includes the following steps; S1: Establish a virtual topology based on logical addresses according to the initial topology information of the satellite network; S2: Based on the node state, reclassify the nodes into faulty nodes, boundary nodes, unreachable nodes, unreliable nodes, and available nodes. Then, traverse the faulty nodes to obtain the boundary node states. Finally, merge the faulty nodes in the boundary node set with the original faulty nodes, unreliable nodes, and unreachable nodes surrounded by faulty nodes to obtain the faulty node set F{N}. i,j } and the set of boundary nodes B{N i,j }, the available node set S{N i,j } through the total set and the set of faulty nodes F{N i,j } and the set of boundary nodes B{N i,j The difference between the source and destination nodes is calculated to obtain the positions of the source and destination nodes, and the detour priority (Round) and the initial boundary node (B) are calculated. s and the boundary destination node B d Location; S3: Determine whether the shortest path between the source node and the destination node is blocked by the fault area. If it is blocked, execute the fault domain-based routing algorithm; otherwise, execute the regular routing algorithm. S4: Execute the fault domain routing algorithm, calculate the signal-to-noise ratio utility function U(s), link length utility function U(l), buffer queue utility function U(b), and comprehensive link utility function U(x) based on network information, and calculate the optimal routing path criterion; The path length utility function U(l) in step S4 specifically includes: The shortest path can be calculated using the following formula: MinL<MinL v +MinL h . (1) Where L v L represents the in-plane ISL length. h The interplane ISL length is represented by the following formulas (2)-(4): L h =δ×cos(lat) (3) Where lat represents the latitude of the interplane ISL, the satellite network has M polar orbit planes, and each polar orbit plane has N satellites; the angular distance between two adjacent planes is 360° / (2×M), and the angular distance between two adjacent satellites in the same orbit plane is 360° / N; The path length utility formula can be used to calculate path length: U(l)=MinL (5); In step S4, the buffer queue utility function U(b) is specifically as follows: According to queuing theory, the arrival rate of data packets follows a Poisson distribution with an average rate of λ. A(t) represents the number of data packets arriving within period t, and the probability function of A(t) = k is: The service time of each message follows an independent and identical distribution function, denoted as B(t), where v is defined. n The processing time for the nth data packet is [time]. V n D(t) represents the independent processing time of a data packet, and D(t) represents the number of data packets processed by the satellite within time t. D(t)=max{n:V n ≤t} (8) P(D(t)=n)=B n (t)-B n+1 (t)=C n (t) (9) In the formula B n (t) is an n-fold convolution of B(t), C n (t) represents the probability function that the satellite processes an equal number of data packets within time t, which can be calculated by (13). Then, at time t, the data packet length X(t) is expressed as: X(t)=m+A(t)-D(t) (10) Where m is the number of remaining packets at time t, the processing probability p of the current data queue X(t) is obtained. m,k (t), where j represents the number of data packets processed by the satellite in the current data queue; A buffer queue can characterize the congestion handling capacity of a link; therefore, the ISL utility function of a buffer queue is: U(b)=p m,k (t) (12); The comprehensive link utility function U(x) in step S4 is specifically as follows: Where ω represents the weight of each utility function, and formula (15) satisfies the following two constraints:

2. The inter-satellite reliable routing method based on a fault domain model according to claim 1, characterized in that, The specific process of establishing a virtual topology based on logical addresses in step S1 of the satellite network is as follows: First, the topology of the satellite network is represented by a diagram. express, Denotes the set of satellites, ε = {l 11 l 12 ... l ij } represents the set of interconnections between these satellites. The connection relationships are represented by an incidence matrix, where elements in the matrix are 0 to indicate a link and 1 to indicate no link. Secondly, a virtual topology model will be established based on the constellation topology, assigning each satellite a fixed logical address. The logical topology of the satellites will change as they move. The logical address of satellite S is (i,j), and N... i,j Let j represent the j-th satellite node on the i-th orbital plane, i = 0, ..., M-1; j = 0, ..., N-1; then determine the instantaneous topology of the satellite network by using the actual position of a satellite and the relative position obtained from the hello data packet.

3. The inter-satellite reliable routing method based on a fault domain model according to claim 1, characterized in that, Step S2 specifically includes: The set of faulty nodes F{N i,j } represents the set of locations of all faulty and unreachable nodes; B{N} set of boundary nodes i,j The boundary of the faulty node is represented by the available nodes adjacent to it; the initial node during the boundary traversal process is called the boundary initial node B. s The node where the detour ends is named the boundary destination node B. d ; Define the detour priority Round(0,1) as a judgment condition. Round is calculated directly by which direction has a smaller number of hops. A value of 0 represents clockwise and a value of 1 represents counterclockwise.

4. The inter-satellite reliable routing method based on a fault domain model according to claim 1, characterized in that, The specific steps of the fault domain-based routing algorithm in step S3 include: First, based on the relative positions of the source and destination nodes, the routing paths from source to boundary initial, boundary initial to boundary destination, and boundary destination to destination are calculated in segments using the comprehensive link utility function U(x). The routing path from boundary initial to boundary destination is calculated based on detour priority. Finally, the three paths are integrated to obtain the most reliable routing path that is blocked by the fault domain.

5. The inter-satellite reliable routing method based on a fault domain model according to claim 1, characterized in that, The signal-to-noise ratio utility function U(s) in step S4 specifically includes: During laser link transmission, the signal-to-noise ratio is mainly affected by free-space propagation loss, which can be quantified by the following formula: Among them, y ij For the final signal, h ij n is the link loss factor. ij Gaussian white noise; G is the source node transmit power, L ij Where γ is the distance and γ is the path loss exponent; in formula (1), SNR ij (t) is the signal-to-noise ratio of the link, and N0 is Gaussian white noise; When the signal-to-noise ratio (SNR) during transmission falls below the receiving threshold α, data transmission will be impossible. Therefore, the probability of an interruption event is derived as follows: The probability of data packet interruption between satellites i and j is derived as follows: To ensure efficient data packet transmission, the signal-to-noise ratio utility function U(s) is defined as the probability of successful data packet transmission, expressed as: U(s)=1-P r {SNR ij (t)<α} (18)。

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