Satellite routing device that considers unbalanced traffic distribution, and distributed routing method therefor

Abstract

The satellite routing device of the present invention comprises: a satellite transceiver for transmitting and receiving data packets; and a satellite router that determines the next satellite to which the data packets are transmitted, thereby transmitting the data packets, wherein the satellite router generates a routing table of the satellite by assigning a weight to a link between satellites according to predicted traffic flow, and uses a routing table to determine whether to reroute the data packets by checking a buffer queue status in the next-hop direction.

Description

Satellite routing device considering unbalanced traffic distribution and its distributed routing method

[0001] Embodiments disclosed herein relate to a satellite routing device and a distributed routing method thereof for distributing overload acting on a satellite due to unbalanced traffic distribution.

[0002] A low-earth orbit (LEO) satellite network is a network system that deploys multiple low-earth orbit satellites at an altitude of 700 to 2,000 km, lower than the standard geostationary satellite orbit of 36,000 km, and communicates with user equipment (UE) on the ground, thereby enabling mobile communication services anywhere in the world. LEO satellite networks are an alternative to conventional terrestrial network technologies that support wide coverage and high-speed communication speeds. At the same time, they are a next-generation network technology that various countries and companies are competing to research and develop. These LEO satellite networks can provide communication services through multi-hop routing to remote areas, mountainous regions, and oceans where terrestrial network infrastructure is lacking.

[0003] However, low-orbit satellite networks can experience traffic imbalances among satellites due to geographic characteristics, such as densely populated areas. Satellites located in densely populated areas can overuse the inter-satellite link (ISL)—the link used to communicate with other satellites—which can lead to overloading satellite resources and data packet loss.

[0004] Additionally, low-orbit satellite networks periodically transmit and receive data packets containing relevant information with neighboring satellites to distribute the load on the satellites. This resulted in the network wasting network resources that could otherwise be used for actual data transmission, as the network transmitted and received network management information for overload distribution rather than actual data.

[0005] Meanwhile, the background technology described above is technical information that the inventor possessed for the purpose of deriving the present invention or acquired during the process of deriving the present invention, and cannot necessarily be said to be publicly known technology disclosed to the general public prior to the application for the present invention.

[0006] Embodiments disclosed in this specification provide a satellite routing device and a distributed routing method thereof capable of distributing overload of a satellite located in an area with dense traffic distribution.

[0007] Embodiments disclosed herein provide a satellite routing device and a distributed routing method thereof that minimize the transmission of related information for overload distribution of a satellite.

[0008] As a technical means for achieving the above-described technical task, according to one embodiment, a satellite routing device includes a satellite transceiver for transmitting and receiving a data packet, and a satellite router for determining a next satellite to transmit the data packet and transmitting the data packet, wherein the satellite router generates a routing table of the satellite by assigning weights to links between satellites according to a predicted traffic flow, and determines whether to bypass the data packet by checking a buffer queue status in a next hop direction to transmit the data packet using the routing table.

[0009] According to another embodiment, a distributed routing method of a satellite routing device includes the steps of: generating a topology graph of a satellite network; predicting a traffic flow to be transmitted through the satellite network; updating a weight for each inter-satellite link in the topology graph with a queue delay time of the inter-satellite link calculated from the traffic flow; generating a routing table for each satellite; when receiving a data packet, checking a best next hop satellite (BH) and a second-best next hop satellite (SBH) for a destination satellite; and checking an occupancy rate of a buffer queue to determine a next satellite to transmit the data packet, thereby transmitting the data packet.

[0010] Any of the aforementioned problem solving methods can distribute the overload of satellites located in areas with dense traffic distribution.

[0011] Any of the aforementioned problem solving methods can minimize the transmission of relevant information for satellite overload distribution.

[0012] Any one of the aforementioned problem solving means can reduce the end-to-end delay of data packets and minimize the loss rate of data packets.

[0013] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0014] FIG. 1 is a block diagram illustrating a satellite system according to one embodiment.

[0015] FIG. 2 is a diagram illustrating the creation of a network topology according to a satellite constellation diagram according to one embodiment.

[0016] FIG. 3 is a diagram illustrating a network topology in which a satellite constellation is connected by an inter-satellite link according to one embodiment.

[0017] FIG. 4 is a diagram illustrating traffic distribution density values ​​of a ground surface area according to one embodiment.

[0018] FIG. 5 is a diagram illustrating selection of a best next-hop satellite and a second-best next-hop satellite according to one embodiment.

[0019] FIG. 6 is a flowchart illustrating distributed routing operations in a routing device according to one embodiment.

[0020] FIG. 7 is a graph showing the average packet loss rate of packets arriving at a destination while changing the packet generation rate according to one embodiment.

[0021] FIG. 8 is a graph showing the processing amount of packet data while changing the packet generation rate according to one embodiment.

[0022] FIG. 9 is a graph showing the average end-to-end delay of packets as the packet generation rate changes according to one embodiment.

[0023] FIG. 10 is a graph showing the average queue delay at the destination as the packet generation rate changes according to one embodiment.

[0024] FIG. 11 is a graph showing the average end-to-end delay of all packets as the packet generation rate changes according to one embodiment.

[0025] FIG. 12 is a graph showing a distribution index while changing a packet generation rate according to one embodiment.

[0026] FIG. 13 is a graph illustrating the average end-to-end delay of packet flows between major cities around the world according to one embodiment.

[0027] Below, various embodiments are described in detail with reference to the attached drawings. The embodiments described below may be modified and implemented in various different forms. To more clearly explain the features of the embodiments, detailed descriptions of matters widely known to those skilled in the art to which the embodiments pertain below have been omitted. In addition, parts of the drawings that are not related to the description of the embodiments have been omitted, and similar parts have been designated with similar drawing reference numerals throughout the specification.

[0028] Throughout the specification, when a component is said to be "connected" to another component, this includes not only the "direct connection" but also the "connection with other components in between." Furthermore, when a component is said to "include" another component, this does not exclude other components, but rather implies that other components may be included, unless otherwise specifically stated.

[0029] Before describing the embodiments with reference to the attached drawings below, the terms to be explained below will be briefly explained.

[0030] The satellites described below are based on low-earth orbit (LEO) satellites, but may include satellites in orbits other than LEO satellites, and may also include various other satellites or aircraft located in planetary orbits. Furthermore, satellites may be described using the terms node, hop, or point along a routing path to describe routing operations.

[0031] Meanwhile, the present invention is explained based on a low-orbit satellite network of the Walker-star constellation model. Satellites in the Walker-star constellation model move along orbits based on a given inclination, and the geometric plane contained in such orbits is called an orbital plane. All satellites in the low-orbit satellite network have the same orbital altitude in each of a plurality of orbital planes, and satellites within the same orbital plane can be arranged at equal intervals from each other. In addition, a phase difference exists between satellites in adjacent orbits to avoid collisions or interference at the intersection of orbital planes.

[0032] The low-orbit satellite network of the Walker-Star constellation model described above is described for convenience of explanation, and the proposed distributed routing method can be used for various types of satellite networks other than the low-orbit satellite network described above to distribute overload of inter-satellite links in high-density areas.

[0033] The embodiments will be described in detail with reference to the attached drawings below.

[0034] FIG. 1 is a block diagram illustrating a satellite system according to one embodiment.

[0035] Referring to FIG. 1, a satellite system may include a plurality of satellites (110, 120, 130). Here, each of the satellites (110, 120, 130) may be connected to a link for information exchange with other adjacent satellites and may communicate with base stations or terminals on the ground.

[0036] The first satellite (110) may include a memory (111), a control unit (112), and a transceiver (113). The second satellite (120) may include a memory (121), a control unit (122), and a transceiver (123). In addition, the n-th satellite may include a memory (131), a control unit (132), and a transceiver (133).

[0037] In this way, the first satellite (110) to the nth satellite (130) are positioned at different altitudes within a certain orbital section on the Earth, but have similar structures and functions overall, so they will be briefly described based on the first satellite (110).

[0038] The memory (111) may store programs for operating the satellite, such as a driving program for moving the first satellite (110) along an orbit, and data transmitted and received by transmitting and receiving data packets may be temporarily stored.

[0039] The control unit (112) can control the overall operation of the satellite, and can also control the operation of the satellite or store data packets transmitted and received using data stored in the memory (111).

[0040] A transceiver (113) is connected to an antenna and can transmit and receive data packets. The transceiver (113) can communicate with other satellites, ground base stations, or ground terminals using the antenna.

[0041] In addition to the above-described memory (111), control unit (112), and transmitter / receiver (113), the first satellite (110) may additionally include other components such as a power supply unit (not shown).

[0042] Meanwhile, the satellite routing device (100) proposed in the present invention may include a satellite router (101) and a satellite transceiver (102).

[0043] A satellite router (101) can perform routing of data packets transmitted and received between satellites. At this time, since the satellite router (101) routes through each of the satellites located in the transmission path of the data packet, it can be implemented through each of a plurality of satellites (110, 120, 130), and in particular, it can be implemented using memories (111, 121, 131) and / or control units (112, 122, 132) included in each of the satellites.

[0044] The satellite router (101) can generate a satellite routing table by assigning weights to the inter-satellite links (ISLs) connecting satellites according to traffic flow. Furthermore, the satellite router (101) can use the generated routing table to check the buffer queue status toward the next hop, i.e., the next satellite, to which data packets will be transmitted, to determine whether to bypass the data packet, and then transmit the data packet.

[0045] The detailed operation of the satellite router (101) is described in detail with reference to FIGS. 2 to 11 below.

[0046] The satellite transceiver (102) can transmit and receive data packets transmitted from each of the satellites (110, 120, 130) under the control of the satellite router (101).

[0047] Below, the operation of the satellite router (101) will be described in detail with reference to FIGS. 2 to 5.

[0048] A satellite router (101) can generate a data packet. The data packet data can include information on a source satellite (SRC: Source) and a destination (or arrival) satellite (DST: Destination), and includes information, i.e., data, to be transmitted to another satellite.

[0049] The satellite router (101) can represent the satellite's constellation in a graph. In addition, the satellite router (101) can generate a network topology according to the satellite's constellation.

[0050] FIG. 2 is a diagram illustrating the creation of a network topology according to a satellite constellation according to one embodiment. Referring to FIG. 2, a network topology (200) depicts a satellite constellation in which 11 satellites are arranged on each of six planes. Each area indicated by a coordinate (X, Y) represents a satellite, and in the coordinates, X represents a plane number and Y represents a satellite number. On each plane, each satellite is arranged with the latitude positioned at the far right of the network topology as the center.

[0051] If a part of this network topology (200) is connected using an inter-satellite link (ISL), it can be diagrammed as in Fig. 3.

[0052] FIG. 3 is a diagram illustrating a network topology in which satellite constellations are connected by inter-satellite links according to one embodiment. Referring to FIG. 4, the network topology (300) is a diagrammatic representation of a portion of the network topology (200) of FIG. 3. Within the network topology (300), each satellite may correspond to a node, and the inter-satellite links (ISLs) connecting each satellite may correspond to edges. Here, the inter-satellite links (ISLs) may have directionality. In the network topology (300), satellites are represented by circles, and edges are represented by solid and dotted lines.

[0053] In the network topology (300), satellites located in polar regions have difficulty connecting satellite-to-satellite links (ISLs) with satellites located in adjacent orbits because the antenna angle must be large in order to connect the satellite-to-satellite links (ISLs) with satellites located in adjacent orbits. In addition, satellites moving toward the North or South Poles have a very large relative speed difference compared to other satellites, so there exists a seam region where satellite-to-satellite links (ISLs) with satellites located in adjacent orbits are not connected. In other words, satellites moving toward the North or South Poles have difficulty connecting satellite-to-satellite links with satellites located in adjacent orbits due to the seam region.

[0054] In the network topology (300), satellites in the uppermost row, indicated by a dark color, represent satellites located in polar regions. Looking at the first satellite (310) among the satellites located in polar regions, the first satellite (310) can have two in-orbit inter-satellite links (ISLs), indicated by solid lines. Meanwhile, satellites located in the deep region can have two in-orbit inter-satellite links (ISLs) and one adjacent-orbit inter-satellite link (ISL).

[0055] In the network topology (300), most of the satellites, excluding those located in polar regions or deep regions, have two inter-satellite links (ISLs) and two inter-satellite links (ISLs) in adjacent orbits, forming a total of four inter-satellite links (ISLs).

[0056] For example, looking at the second satellite (320) in the network topology (300), the second satellite (320) may have two inter-satellite links (ISLs) (a1, a2) in the same orbit indicated by solid lines, and two inter-satellite links (ISLs) (b1, b2) in adjacent orbit indicated by dotted lines, forming four inter-satellite links (ISLs).

[0057] Therefore, satellites communicate directly with neighboring satellites using inter-satellite links (ISL). Because satellites orbit at a constant altitude, the distance between neighboring satellites is determined by latitude. The distance between satellites creates a propagation delay during the communication process.

[0058] Meanwhile, the satellite router (101) determines the optimal neighboring satellite for transmitting data packets to the destination satellite (DST) according to the routing method of each satellite. The satellite router (101) may have a predetermined number of buffer queues, for example, four, in which data packets to be transmitted to each neighboring satellite wait. The satellite router (101) may wait packets inserted into the buffer queues in the buffer queues according to the processing speed of the inter-satellite link (ISL), and this waiting time may cause queuing delay. If the size of data stored in the buffer queue reaches the maximum size of the buffer queue, data packets inserted into the buffer queue thereafter may be lost. Therefore, the sum of the propagation delay and the queuing delay from the time when transmission from the source satellite (SRC) begins until the time when the data packet arrives at the destination satellite (DST) may be defined as the end-to-end delay (E2E delay).

[0059] Accordingly, the satellite router (101) utilizes the global traffic distribution density to minimize the end-to-end delay (E2E delay) loss of data packets in the low-orbit satellite network. Furthermore, the satellite router (101) predicts traffic flow based on the traffic distribution density, generates a routing table, and then uses the generated routing table to select a detour route that can transmit data packets while reducing the load on the routing path.

[0060] The decision code based on the routing table design operation based on traffic distribution in the satellite router (101) can be expressed as shown in Table 1 below.

[0061]

[0062] A satellite router (101) can generate a topology graph (G(V, E, W)) of a satellite network, which includes each satellite as a node (V), an inter-satellite link (ISL) as an edge (E), and a weight (W) applied to each edge (E). Here, the initial weight applies a propagation delay value according to the length of the inter-satellite link (ISL).

[0063] The satellite router (101) can search for a data packet transmission path using Dijkstra's algorithm. This Dijkstra's algorithm is an algorithm that searches for a path with the minimum edge weight value between nodes. Therefore, the satellite router (101) can minimize the transmission delay of data packets by applying Dijkstra's algorithm to a topology graph.

[0064] The satellite router (101) uses the propagation delay as the initial value of the weight (W) in the topology graph. For example, the satellite router (101) can calculate the propagation delay between the first satellite (v) and the second satellite (v') using the following mathematical expression 1.

[0065]

[0066] Here, is the distance between satellites in the same orbit, is the distance between adjacent orbit satellites. At this time, the satellite router (101) can calculate the distance between satellites in the same orbit using the following mathematical formula 2, and can calculate the distance between satellites in adjacent orbits using the following mathematical formula 3.

[0067]

[0068]

[0069] Here, is the number of satellites included in one orbital plane, is the phase difference between adjacent satellites, is the latitude difference between the two satellites, is a satellite Indicates the current latitude.

[0070] is always a constant value when satellites are uniformly distributed within a given satellite model. On the other hand, The value changes depending on the current latitude of the satellite. For satellites located at high latitudes, has a smaller value than satellites located at low latitudes. Therefore, in routing technology based on the shortest path, the propagation delay between high-latitude satellites is shorter, so high-latitude regions are preferred for traffic transmission between adjacent orbits.

[0071] Afterwards, the satellite router (101) can predict the traffic flow to reflect the weight for the queue delay.

[0072] FIG. 4 is a diagram illustrating traffic distribution density values ​​of a ground surface area according to one embodiment.

[0073] Referring to Figure 4, the earth's surface is divided into 8 X 16 unit areas, and a traffic distribution density value is recorded within each unit area. This traffic distribution density value can be calculated based on, for example, the number of Internet users and the population.

[0074] Looking at the traffic distribution density, the unit areas (411, 413, 415) have relatively high traffic distribution density values ​​compared to other areas, which may result in a large amount of traffic being distributed. Conversely, the unit area (417) has relatively low traffic distribution density values ​​compared to other areas, which may result in a small amount of traffic being distributed. In other words, a higher traffic distribution density value indicates a more congested traffic distribution.

[0075] The satellite router (101) can predict traffic flow based on the traffic distribution density and calculate a weight for the queue delay of each inter-satellite link (ISL). The satellite router (101) can calculate the weight of the predicted queue delay for the data packet transmitted from the source satellite (SRC) where the traffic is generated to the destination satellite (DST). ) can be calculated using the following mathematical formula 4.

[0076]

[0077] Here, is in the traffic distribution density is the density value of the area. Next, the satellite router (101) finds the minimum weighted sum path from the source satellite (SRC) to the destination satellite (DST) using the Dijkstra shortest path algorithm in the topology graph to reflect the weight. The satellite router (101) calculates the minimum weighted sum path from all inter-satellite links (ISLs) of the found path, i.e., the existing weight (W) of the edge in the topology graph. The weights can be updated by adding them up.

[0078] The satellite router (101) weights the topology graph based on the pairs of the source satellite (SRC) and destination satellite (DST) of each satellite. This allows the weights of frequently used inter-satellite links (ISLs) with high traffic flow to be higher than those of less frequently used inter-satellite links (ISLs) with low traffic flow. This allows the satellite router (101) to distribute routing paths by reflecting traffic flow in the weights of the topology graph. However, routing paths in areas with dense traffic distribution continue to use the same paths.

[0079] Therefore, the satellite router (101) reflects the iterative prediction queue delay weight to distribute the routing path in the dense area. For example, the satellite router (101) finds the minimum weight sum path again in the topology graph with changed weights and adjusts the weight of the predicted queue delay ( ) is added. The satellite router (101) can repeat this weight reflection operation to increase the weight of the inter-satellite link (ISL) in a high-density traffic distribution area, thereby avoiding overlapping of routing paths. That is, the satellite router (101) can reduce the situation in which routing paths overlap, thereby preventing overload of the data queue provided for transmitting data packets to each inter-satellite link (ISL).

[0080] The satellite router (101) can update weights in a topology graph to prevent overload on a routing path, and can generate a routing table for each satellite using the topology graph with updated weights. Here, the routing table can store information about the best next hop satellite (BH) and the second-best next hop satellite (SBH) for the destination satellite (DST).

[0081] The decision code based on the load distribution routing operation in the satellite router (101) can be expressed as shown in Table 2 below.

[0082]

[0083] The satellite router (101) can check information about the next hop satellite (BH: Best next Hop satellite) and the next best next hop satellite (SBH: Second-Best next Hop satellite) in the routing table and check whether to use it as a detour route for load distribution.

[0084] FIG. 5 is a diagram illustrating selection of a best next-hop satellite and a second-best next-hop satellite according to one embodiment.

[0085] Referring to FIG. 5, based on the satellite constellation, a satellite (N1) can select either a best next hop satellite (BH) or a second-best next hop satellite (SBH) to transmit data packets. The best next hop satellite (BH) may be the satellite with the best inter-satellite link (ISL) status for transmitting data packets around the satellite (N1), and the second-best next hop satellite (SBH) may be the satellite (SBH) with the best status among the inter-satellite links (ISLs) with the remaining hop satellites excluding the best next hop satellite (BH). Therefore, if an overload occurs in transmitting data packets to the best next hop satellite (BH), the routing path can be bypassed using the second-best next hop satellite (SBH).

[0086] In conventional satellite networks, the buffer queue status of neighboring satellites or all satellites is periodically collected to select the next-hop satellite. However, this requires periodic exchange of information between satellites. If a link becomes overloaded due to data packet transmission, routing tables are modified instead of data packets, or the increased use of signals to distribute the load consumes network resources (e.g., inter-satellite links (ISLs), buffer queues, etc.) for actual data packet transmission.

[0087] Meanwhile, even if the routing path is distributed, the satellite router (101) may experience an overload on the inter-satellite link (ISL) if traffic volume increases. Therefore, the satellite router (101) performs load-balancing routing to divert packets based on the buffer queue status.

[0088] In this way, the satellite router (101) can check the current size of the buffer queue in each direction of the satellite for transmission of data packets without exchanging information between satellites, and determine the next hop satellite based on the buffer queue occupancy rate.

[0089] The satellite router (101) can calculate the size of the buffer queue in the v' direction of satellite v at time t using the following mathematical expression 5.

[0090]

[0091] Here, represents the amount of packets whose next hop is v' among the packets received by satellite v at time t.

[0092] Additionally, the satellite router (101) can calculate the occupancy rate of the buffer queue using the following mathematical expression 6.

[0093]

[0094] Here, is the maximum size of the buffer queue.

[0095] The satellite router (101) is the occupancy rate of the buffer queue of the best next hop satellite (BH). If the threshold is greater than or equal to a predetermined threshold, the data packet can be transmitted by detouring to the next best hop satellite (SBH). The satellite router (101) may cause a routing loop due to the detour path. To prevent this, the satellite router (101) applies a detour prevention condition according to the transmission of three data packets. For example, the satellite router (101) may not detour the data packet and transmit it to the best next hop satellite (BH) if at least one of the following conditions exists: if the next hop satellite (BH) is the destination; if the occupancy rate of the buffer queue in the SBH direction is greater than or equal to a predetermined threshold; and if the SBH is the satellite of the previous path on which the data packet was transmitted.

[0096] FIG. 6 is a flowchart illustrating distributed routing operations in a routing device according to one embodiment.

[0097] Referring to FIG. 6, the satellite routing device (100) assigns a weight to each inter-satellite link (ISL) to generate a topology graph of a satellite network (step 611). The satellite routing device (100) can generate a topology graph (G(V,E,W)) including a node (V) which is a satellite, an edge (E) which is an inter-satellite link (ISL), and a weight (W) for the inter-satellite link (ISL). The satellite routing device (100) can set the propagation delay between satellites as an initial value of the weight in the topology graph.

[0098] The satellite routing device (100) can predict the traffic flow to be transmitted through the satellite network (step 613). Here, the traffic flow can be calculated using the traffic distribution density for each unit area dividing the Earth's surface, and the traffic distribution density can be calculated based on the number of Internet users and the population within the unit area.

[0099] The satellite routing device (100) can reflect the predicted traffic flow as a weight within the topology graph (step 615). The satellite routing device (100) can use a gravity model to reflect the weight in the inter-satellite link (ISL). Here, the gravity model is a model used to predict the flow between two points, and predicts the traffic flow between the two points using a traffic distribution density index.

[0100] Additionally, the satellite routing device (100) can update the weight for each inter-satellite link (ISL) in the topology graph with the queuing delay time (predicted queuing delay time) of the inter-satellite link calculated as a traffic flow.

[0101] The satellite routing device (100) determines whether to repeatedly reflect the weight (step 617). If the satellite routing device determines that it wishes to repeatedly reflect the weight based on the determination result of step 617, it proceeds to step S615, and repeatedly searches for the shortest path with the minimum weight a predetermined number of times to calculate the calculated queue delay, thereby repeatedly updating the weight.

[0102] If the satellite routing device (100) terminates the repeated reflection of the weights as a result of the judgment in step 617, it proceeds to step S619.

[0103] The satellite routing device (100) can create a routing table for each satellite (step 619).

[0104] The satellite routing device (100) checks whether a data packet has been received (step 621).

[0105] As a result of the verification in step 621, if the satellite routing device (100) does not receive a data packet, it waits until it receives a data packet.

[0106] As a result of the verification in step 621, if the satellite routing device (100) receives a data packet, it proceeds to step S623. The satellite routing device (100) uses the routing table to check the best next hop satellite (BH) and the next best next hop satellite (SBH) for the destination satellite of the received data packet (step 625).

[0107] The satellite routing device (100) can check the size of the buffer queue for each direction of the satellite (step 627). That is, the satellite routing device (100) can check the usage of the buffer queue for each direction of the satellite, i.e., the occupancy status of data packets.

[0108] The satellite routing device (100) determines the next hop satellite based on the current buffer queue occupancy rate (step 629).

[0109] At this time, the satellite routing device (100) can determine whether the conditions for selecting a detour route are met when transmitting a data packet (step 629).

[0110] If the satellite routing device (100) determines that the condition for selecting a detour path is met based on the judgment result of step 629, it proceeds to step 631. If the condition for selecting a detour path is met, the satellite routing device (100) transmits the data packet without detouring (step 631).

[0111] Here, the conditions for selecting a detour route are as follows. First, the destination is the Best Next Hop Satellite (BH). Second, the buffer queue occupancy rate toward the Second-Best Next Hop Satellite (SBH) exceeds a predetermined threshold. Third, the SBH is the satellite along the previous route along which the data packet was transmitted. Therefore, the satellite routing device (100) can forward the packet without detouring if at least one of the three conditions above is met.

[0112] As a result of the judgment in step 629, if the satellite routing device (100) does not correspond to the detour path selection condition, the satellite routing device (100) proceeds to step 635. For data packets that do not correspond to the detour path selection condition, the satellite routing device (100) transmits the data packets by detour according to the buffer queue occupancy rate of the best next hop satellite (BH).

[0113] In step 633, the satellite routing device (100) determines whether the packet has reached its destination. If the packet has reached its destination in step 633, the satellite routing device (100) can terminate the process. However, if the packet has not reached its destination in step 633, the satellite routing device (100) proceeds to step 621 to receive and process the data packet.

[0114] As described above, existing systems fail to distribute the load on inter-satellite links (ISLs) resulting from unbalanced traffic distribution. This unbalanced traffic distribution results in significant traffic flow between certain regions, and since these traffic flows transmit packets through the same routing path, they overload specific ISLs. This ISL overload increases the end-to-end delay (E2E) of packets that use the ISL as a routing path, and as traffic volume increases, packet loss occurs. High E2E delay results in a degraded user experience, such as service interruptions and delayed response times, and packet loss triggers packet retransmission, further exacerbating the ISL overload problem.

[0115] However, the distributed routing technology proposed in the present invention generates a routing table that reflects traffic distribution, enabling the distribution of routing paths to reflect traffic flow. Distributed routing paths minimize overlapping packet routing paths, thereby reducing the occurrence of inter-satellite link (ISL) overload. Furthermore, the load-balancing routing algorithm can bypass packet routing paths based on buffer queue load, thereby minimizing ISL overload and reducing end-to-end packet delay and packet loss.

[0116] This paper briefly describes the simulation environment for evaluating the performance of the technology proposed in this invention. The simulation environment consists of 128 LEO satellites, 16 of which are deployed in eight orbital planes. The orbital planes have an orbital inclination of approximately 89°, and the satellites within the orbital planes are evenly spaced at an altitude of approximately 800 km. The satellites have approximately four 2.5 MB buffer queues, each capable of storing packets to be forwarded to neighboring satellites. The inter-satellite link (ISL) processes packets in the buffer queues at a rate of 260 Mbps. The simulation environment evaluates routing performance over one minute (60,000 ms) by increasing the packet generation rate from 6.0 to 11.5 Gbps in 0.5 Gbps increments. Packets are 1 KB in size and generated every 1 ms. The packet generation and destination are determined based on a gravity model based on traffic distribution density.

[0117] To compare the performance of the present invention, we utilize two techniques. First, the technique proposed in the present invention is denoted as "Proposed." The first benchmark technique is an explicit load balancing technique, denoted as ELB in the simulation graph. This technique explicitly exchanges information about congestion status with neighboring satellites and routes packets based on the congestion level. The second benchmark technique is a traffic light-based load balancing technique, denoted as TLR in the simulation graph. This technique determines the color of the traffic lights based on the congestion status of the buffer queues in each direction and the congestion status of neighboring satellites, and routes packets based on the corresponding traffic light color. Both techniques for comparison periodically collect information about the congestion status of satellites across the network and update their routing tables.

[0118] FIG. 7 is a graph showing the average packet loss rate of packets arriving at a destination while changing the packet generation rate according to one embodiment.

[0119] Referring to Fig. 7, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents the packet loss rate. Here, packet loss only considers cases where packets are lost due to a drop-tail buffer queue. The packet loss rate is the ratio of the number of lost packets to the total number of generated packets. The proposed embodiment is compared with the comparative technologies, TLR technology and ELB technology, by increasing the packet generation rate. As a result, it can be confirmed that the number of lost packets is close to zero (0) until a certain number of packets are generated, and the packet loss rate is significantly lower than that of the comparative technologies.

[0120] FIG. 8 is a graph showing the processing amount of packet data while changing the packet generation rate according to one embodiment.

[0121] Referring to Figure 8, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents throughput. Here, packet throughput represents the number of data packets that reach the destination out of the total number of data packets generated. The proposed embodiment, when compared with the comparative technologies TLR and ELB, shows a relatively high data packet throughput when the packet generation rate is increased.

[0122] FIG. 9 is a graph showing the average end-to-end delay of packets as the packet generation rate changes according to one embodiment.

[0123] Referring to Figure 9, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents the average end-to-end delay. Here, the average end-to-end delay refers to the arrival time from the source satellite to the destination satellite. The proposed embodiment was compared with the comparative technologies, TLR and ELB, while increasing the packet generation rate. As a result, it was confirmed that the average end-to-end delay has a significantly shorter time until the data packet generation rate exceeds 10.5 Gbps.

[0124] FIG. 10 is a graph showing the average queue delay at the destination as the packet generation rate changes according to one embodiment.

[0125] Referring to Figure 10, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents the average queuing delay. Here, the average queuing delay refers to the sum of the delay times of the queues that occur along the packet routing path. The proposed embodiment was compared with the comparative technologies, TLR and ELB, while increasing the packet generation rate. As a result, it was confirmed that the average queuing delay has a significantly shorter end-to-end delay time until the data packet generation rate exceeds 10.5 Gbps.

[0126] FIG. 11 is a graph showing the average end-to-end delay of all packets as the packet generation rate changes according to one embodiment.

[0127] Referring to Figure 11, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents the average end-to-end delay of all packets. Here, to compare the end-to-end delay by reflecting packet loss, the end-to-end delay of the lost packet is considered to have the maximum queuing delay on the shortest routing path. The proposed embodiment was compared with the comparative technologies, TLR and ELB, by increasing the packet generation rate, and it can be confirmed that the average end-to-end delay is significantly shorter.

[0128] FIG. 12 is a graph showing a distribution index while changing a packet generation rate according to one embodiment.

[0129] Referring to Figure 12, the horizontal axis of the graph represents the packet generation rate, and the vertical axis represents the distribution index (DI). The utilization of the inter-satellite link (ISL) can be calculated using the distribution index (DI), as shown in the following mathematical equation (7).

[0130]

[0131] Here, the total number of packets is dog, The number of times the second inter-satellite link (ISL) was used , and the dispersion index (DI) can have a value between 0 and 1. When the number of uses of all inter-satellite links (ISLs) is the same, the dispersion index (DI) is 1, and when only a specific inter-satellite link (ISL) is primarily used, the dispersion index (DI) decreases.

[0132] The proposed embodiment is compared with the comparative technologies, TLR technology and ELB technology, by increasing the packet generation rate, and it can be confirmed that the distribution index (DI) is high.

[0133] Referring to Figure 13, the horizontal axis of the graph represents major cities on the continent where packets are transmitted end-to-end, and the vertical axis represents the average end-to-end delay. This graph compares the average end-to-end delay of packets transmitted between two regions using three routing methods, selecting major cities on each continent. The packets from representative major cities are New York (NYC) → Seoul (SEL), Tokyo (TYO) → London (LON), Paris (PAR) → Johannesburg (JNB), Cairo (CAI) → Perth (PER), Sydney (SYD) → Buenos Aires (BUE), and São Paulo (GRU) → Los Angeles (LAX).

[0134] The proposed embodiment compares the average end-to-end delay for transmission of major intercity data packets with the comparative technologies, TLR technology and ELB technology, and it can be confirmed that the performance is superior in some cases and does not deteriorate significantly compared to the comparative technologies in the remaining cases.

[0135] The term '~ unit' used in the above embodiments means a software or hardware component such as an FPGA (field programmable gate array) or an ASIC, and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium or may be configured to play one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables.

[0136] The functionality provided within the components and '~sub-components' may be combined into a smaller number of components and '~sub-components' or separated into additional components and '~sub-components'.

[0137] Additionally, components and '~parts' may be implemented to regenerate one or more CPUs within a device or secure multimedia card.

[0138] The embodiments described above are provided for illustrative purposes only, and those skilled in the art will readily appreciate that the embodiments described above can be readily modified into other specific forms without altering the technical concepts or essential characteristics of the embodiments described above. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, components described as being single may be implemented in a distributed manner, and similarly, components described as being distributed may be implemented in a combined manner.

[0139] The scope of protection sought through this specification is indicated by the claims described below rather than the detailed description above, and should be interpreted to include all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts.

Claims

1. A satellite transceiver for transmitting and receiving data packets; and Including a satellite router that determines the next satellite to transmit the data packet and transmits the data packet, The satellite router is a satellite routing device that creates a routing table of the satellite by assigning weights to links between satellites according to a predicted traffic flow, and determines whether to bypass the data packet by checking the status of a buffer queue in the direction of the next hop to which the data packet is to be transmitted using the routing table.

2. In paragraph 1, The above satellite router, Generate a topology graph of a satellite network where satellites are nodes and inter-satellite links (ISLs) are edges. A satellite routing device in which edges in the above topology graph have weights, and the weights are initially set to the inter-satellite propagation delay time.

3. In paragraph 2, The above satellite router, We use a gravity model to predict traffic flow between two points using an indicator of traffic distribution density divided into multiple unit areas. In the above topology graph, the weight for each inter-satellite link is the weight of the queue delay time of the inter-satellite link calculated by the traffic flow ( ) is updated by determining it with the following mathematical formula, Here, is in the traffic distribution density Satellite routing device that is the density value of the area.

4. In paragraph 3, The above satellite router, A routing table for each satellite is generated by using a topology graph in which the weight is updated by calculating the queue delay calculated by repeatedly searching for the shortest path with the minimum weight a predetermined number of times. The search for the above shortest path is a satellite routing device that uses the Dijkstra shortest distance algorithm to find the minimum weighted sum path from the source satellite (SRC) to the destination satellite (DST).

5. In paragraph 1, The above satellite router, A satellite routing device that checks the best next hop satellite (BH) and the second-best next hop satellite (SBH) in the routing table of the above satellite and determines the next satellite to transmit the next data packet based on the occupancy rate of the buffer queue.

6. In paragraph 5, The above satellite router, The size of the above buffer queue is calculated using the following mathematical formula: Here, represents the amount of packets received by satellite v at time t whose next hop is v'. The occupancy rate of the above buffer queue is calculated using the following mathematical formula: Here, A satellite routing device with a maximum size of a buffer queue.

7. In paragraph 6, The above satellite router, The occupancy rate of the buffer queue of the best next hop satellite (BH) above is A satellite routing device that bypasses transmission to the next best hop satellite (SBH) when the value exceeds a predetermined threshold.

8. In paragraph 5, The above satellite router, For data packets that correspond to the detour path selection conditions, the data packets are transmitted without detouring, and for data packets that do not correspond to the detour path selection conditions, the data packets are transmitted by detouring according to the buffer queue occupancy rate of the best next hop satellite (BH). A satellite routing device including at least one of the conditions for selecting the above-mentioned bypass path when the best next-hop satellite (BH) is the destination, when the occupancy rate of the buffer queue in the direction of the next-hop satellite (SBH) is greater than or equal to a predetermined threshold, and when the next-hop satellite (SBH) is a satellite of the previous path through which the data packet was transmitted.

9. In a distributed routing method of a satellite routing device, Step of generating a topology graph of a satellite network; A step of predicting traffic flow to be transmitted through the above satellite network; A step of updating the weight for each inter-satellite link in the above topology graph with the queue delay time of the inter-satellite link calculated by the traffic flow; Step 1: Generate a routing table for each satellite; Upon receiving a data packet, a step of determining the best next hop satellite (BH) and the second-best next hop satellite (SBH) for the destination satellite; and A distributed routing method comprising the step of determining the next satellite to transmit the data packet by checking the occupancy rate of a buffer queue and transmitting the data packet.

10. In paragraph 9, The steps of generating the above topology graph are; A distributed routing method further comprising the step of setting the initial value of the weight in the above topology graph to the propagation delay time between adjacent satellites.

11. In paragraph 9, The step of updating with the above queue delay time is: Weighting of the queuing delay time of the inter-satellite link calculated by the above traffic flow ( ) includes a step of updating by determining it using the following mathematical formula, Here, is in the traffic distribution density A distributed routing method that uses density values ​​in the area.

12. In paragraph 9, The step of updating with the above queue delay time is: Further comprising a step of updating the weight by calculating the queue delay calculated by repeatedly searching the shortest path with the minimum weight a predetermined number of times or more, The search for the above shortest path is a distributed routing method that uses the Dijkstra shortest distance algorithm.

13. In paragraph 9, The step of predicting the above traffic flow is; Further comprising a step of using a gravity model to predict traffic flow between two points using an indicator of traffic distribution density divided into multiple unit areas, The above traffic distribution density indicator is a distributed routing method that includes the number of Internet users and the population in a unit area.

14. In paragraph 9, The step of transmitting the above data packet is: A step of calculating the size of the above buffer queue using the following mathematical formula; and Here, represents the amount of packets received by satellite v at time t whose next hop is v'. Including a step of calculating the occupancy rate of the above buffer queue using the following mathematical formula: Here, A distributed routing method with a maximum size of the buffer queue.

15. In paragraph 9, The step of transmitting the above data packet is: A step of transmitting a data packet without detouring for a data packet corresponding to a detour path selection condition; and For data packets that do not correspond to the detour path selection conditions, a step of transmitting the data packets by detour according to the buffer queue occupancy rate of the best next hop satellite (BH) is included. A distributed routing method including at least one of the conditions for selecting the above-mentioned bypass path when the best next-hop satellite (BH) is the destination, when the occupancy rate of the buffer queue in the direction of the next-hop satellite (SBH) is greater than or equal to a predetermined threshold, and when the next-hop satellite (SBH) of the next-optimal is a satellite of the previous path through which the data packet was transmitted.

16. As a computer-readable recording medium, A computer-readable recording medium having recorded thereon a program for performing distributed routing according to any one of claims 9 to 15.

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