A satellite-ground IP integrated communication system and method for low-Earth orbit satellite constellations

Abstract

This invention relates to an integrated space-ground IP communication system and method for low-Earth orbit satellite constellations, belonging to the field of spacecraft space-ground communication technology. It addresses the problem of low communication efficiency and high latency caused by the need for multi-layer protocol conversion when using a dedicated bus protocol on board and an IP protocol on the ground. The system includes a space segment and a ground segment. The space segment includes: onboard payloads equipped with standard Ethernet interfaces, interconnected via onboard Ethernet switches to form an intra-satellite local area network (LAN), with each onboard payload having a unique intra-satellite IP address; an IPoC gateway module connecting the onboard Ethernet switch and the space-ground radio frequency front-end, performing bidirectional protocol conversion between IP packets and CCSDS frames; the ground segment includes: a ground router equipped with a static routing table, directing IP packets destined for the intra-satellite LAN to a ground IPoC modem, which performs bidirectional protocol conversion between IP packets and CCSDS frames to adapt to space-ground radio frequency link transmission. This system is applicable to the field of communication satellites.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft-to-ground communication technology, and in particular relates to an integrated space-to-ground IP communication system for low-Earth orbit satellite constellations. Background Technology

[0002] Low Earth Orbit (LEO) satellite constellations have become a hot topic in satellite internet and global remote sensing monitoring in recent years due to their significant advantages such as strong global coverage, low transmission latency, and low launch and maintenance costs. Commercial constellations such as Starlink and OneWeb, as well as various high-resolution remote sensing satellite constellations, are all in a phase of rapid deployment. These systems place extremely high demands on the real-time performance, flexibility, and scalability of satellite-to-ground communication. However, the existing LEO satellite communication architecture still mainly follows the design paradigm of traditional aerospace engineering, revealing serious technical bottlenecks when dealing with new business needs.

[0003] Within satellite platforms, device interconnection generally relies on traditional aerospace-specific buses such as 1553B, CAN, and SpaceWire. These buses have different protocol standards, leading to incompatibility between interfaces of different payloads. This necessitates extensive customized adaptation development during the satellite integration phase. For example, when adding new imaging equipment or scientific instruments to an already launched remote sensing satellite, interface protocol incompatibility often requires redesigning hardware adapter boards and modifying underlying driver software. This results in the integration and debugging of new payloads taking weeks, significantly limiting the satellite's on-orbit functional expansion capabilities.

[0004] More importantly, the dedicated onboard bus protocol is inherently disconnected from the IP protocol system of the terrestrial internet. In the traditional architecture, data generated by onboard devices must undergo multiple complex protocol conversions before it can be understood by ground users. This cross-protocol stack processing not only consumes a large amount of onboard computing resources but also introduces significant communication latency. Ground user terminals cannot directly access the onboard payload; data must be received by ground stations, preprocessed by data centers, and forwarded through multiple levels of networks before reaching users. End-to-end latency typically reaches minutes or even longer, which is completely unacceptable for interactive application scenarios with stringent real-time requirements, such as emergency command, disaster monitoring, and remote control.

[0005] Furthermore, existing solutions lack support for plug-and-play payload capabilities. When new devices connect to the satellite network, the entire satellite's software configuration and routing table must be manually modified, failing to achieve the automated management that allows for device recognition upon connection, as is the case in terrestrial LANs. Although there have been attempts to introduce the TCP / IP protocol stack into satellite networks, most are limited to simply replacing the intra-satellite bus or only encapsulating and transmitting IP packets at the satellite-to-ground link layer, failing to build an end-to-end IP transparent channel from the ground terminal to the satellite payload. Some solutions attempt to run the standard TCP / IP protocol directly on the satellite-to-ground link, but due to the typical long-thickness and high error rate characteristics of low-Earth orbit satellite links, the congestion control mechanism of the TCP protocol will severely fail, leading to a sharp drop in transmission efficiency and failing to fully utilize the bandwidth potential of the satellite-to-ground link. Therefore, there is an urgent need for a new system architecture that can break down the barriers between intra-satellite and satellite-to-ground protocols and enable direct communication between the ground terminal and the satellite payload. Summary of the Invention

[0006] In view of this, the present invention aims to propose a space-ground IP integrated communication system and method for low-Earth orbit satellite constellations, in order to solve the problem of low communication efficiency and large latency caused by the use of a dedicated bus protocol on the satellite and an IP protocol on the ground, which requires multiple layers of protocol conversion between the two.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a space-ground IP integrated communication system for low-Earth orbit satellite constellations, the system comprising a space segment and a ground segment; The space segment is deployed on a low-Earth orbit satellite platform and includes an onboard Ethernet switch, an IPoC gateway module, and at least one onboard payload. The on-board payloads are equipped with standard Ethernet interfaces and interconnected through the on-board Ethernet switches to form an intra-satellite local area network. Each on-board payload is assigned a unique intra-satellite IP address in the intra-satellite local area network. The IPoC gateway module is connected to the onboard Ethernet switch and the satellite-to-ground radio front-end respectively, and is used to perform bidirectional protocol conversion between IP packets and CCSDS frames. The ground segment includes a ground IPoC modem and a ground router; the ground router is configured with a static routing table to direct IP packets destined for the satellite local area network to the ground IPoC modem; the ground IPoC modem is configured to perform bidirectional protocol conversion between IP packets and CCSDS frames to adapt to satellite-to-ground radio frequency link transmission.

[0008] Furthermore, a preferred embodiment is proposed, wherein the IPoC gateway module includes an uplink processing unit and a downlink processing unit: The uplink processing unit is used to receive Ethernet frames from the onboard Ethernet switch, extract IP packets, segment and encapsulate the IP packets according to the CCSDS specification, add virtual channel identifiers, and output them to the data transmitter of the satellite-to-ground radio frequency front-end. The downlink processing unit is used to receive CCSDS frames from the satellite-to-ground radio frequency front-end, perform frame synchronization, demapping and fragmentation reassembly operations, restore the IP packets, and send the IP packets to the satellite Ethernet switch.

[0009] Furthermore, a preferred embodiment is proposed, wherein the IPoC gateway module is also used for: Read the Quality of Service (QoS) identifier field from the IP packet header; Based on the priority corresponding to the quality of service identifier field, high-priority packets are prioritized for encapsulation and scheduled for transmission. When the satellite-to-ground link rate is lower than the satellite-internal Ethernet rate, uplink IP packets are cached through the built-in FIFO buffer queue, and idle frames are inserted into the CCSDS frame stream for rate matching.

[0010] Furthermore, a preferred embodiment is proposed, wherein the on-board payload includes an imaging device, a satellite computer, and a high-capacity storage unit; The satellite computer runs a lightweight IP protocol stack and acts as a DHCP server for the satellite's local area network, dynamically allocating IP addresses to onboard payloads connected to the satellite's Ethernet switch. The high-capacity storage unit is used to receive and store IP packets from the IPoC gateway module when the low-orbit satellite leaves the line-of-sight range of the ground station.

[0011] Furthermore, a preferred embodiment is proposed, wherein the large-capacity storage unit is also used for: Stored IP packets are indexed and organized according to timestamps and priorities; In response to the signal that the low-orbit satellite enters the line-of-sight range of the ground station, the IPoC gateway module is activated by a hardware wake-up signal and automatically transmits the stored IP packets back in priority order.

[0012] Furthermore, a preferred method is proposed, wherein the user terminal of the ground segment runs a standard TCP / IP protocol stack, and the destination IP address of the IP packet generated by the user terminal directly points to the intra-satellite IP address of the on-board payload of the space segment; The onboard Ethernet switch is configured to perform Layer 3 forwarding based solely on the header information of the IP packets, without parsing application layer data, in order to achieve end-to-end transparent IP transmission between the ground terminal and the onboard payload.

[0013] Based on the same inventive concept, this invention also proposes a space-ground IP integrated communication method for low-Earth orbit satellite constellations, implemented based on any of the above-described systems, the method including an uplink communication step: The ground terminal generates an IP packet with the destination IP address of the satellite payload; The ground router forwards the IP packets to the ground IPoC modem according to the static routing rules; The terrestrial IPoC modem encapsulates the IP packets into CCSDS frames and transmits them via radio frequency through the terrestrial antenna. The satellite receives the CCSDS frames, which are then decapsulated and restored into IP packets by the onboard IPoC gateway module. The onboard Ethernet switch forwards the IP packet to the corresponding onboard payload based on the destination IP address of the IP packet.

[0014] Furthermore, a preferred embodiment is proposed, wherein the method further includes a downlink communication step: The onboard payload generates return IP packets with the source IP address of this payload. The onboard Ethernet switch aggregates the backhaul IP packets to the IPoC gateway module; The IPoC gateway module encapsulates the return IP packets into CCSDS frames and transmits them to the ground station via a data transmitter. The ground station receives the CCSDS frame, decapsulates it to restore it to an IP packet, and then forwards it to the ground terminal through a ground router.

[0015] Furthermore, a preferred embodiment is proposed, wherein the method further includes a store-and-forward step: In response to situations where there is no line-of-sight connection between the satellite and the ground station, the IPoC gateway module redirects the backhaul IP packets to be transmitted to a large-capacity storage unit for persistent storage. In response to a satellite entering its transit window, the large-capacity storage unit reads the stored IP packets and triggers the IPoC gateway module to execute downlink communication steps.

[0016] Furthermore, a preferred method is proposed in which the IP packet is a UDP packet in the uplink communication step; The on-board IPoC gateway module uses a lightweight IP protocol stack to process the UDP packets. The lightweight IP protocol stack supports IP, UDP and ICMP protocols, but removes the full TCP protocol processing function.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a unified IP semantic layer that spans both the space and ground segments, breaking down the protocol barriers between the dedicated intra-satellite bus and the terrestrial internet in traditional space-to-ground communication. Its implementation is not a simple stacking of protocols, but rather achieved through layered decoupling and edge adaptation.

[0018] In the space segment, the system abandons the traditional point-to-point dedicated bus architecture and instead establishes an intra-satellite local area network based on standard Ethernet. By using the onboard Ethernet switch as the hub for information exchange across the entire satellite and assigning a unique IP address to each onboard payload, network interconnection of onboard devices is achieved at the hardware level. This architecture allows onboard data exchange to no longer rely on specific physical interfaces or proprietary protocols, but rather on routing based on universal IP packets.

[0019] At the satellite-to-ground boundary, this invention introduces an IP over CCSDS (IPoC) gateway module as the core of the protocol conversion. This module resides on the satellite and performs translation functions. In the uplink, it encapsulates standard IP packets from the ground into frame structures conforming to the Space Data Systems Advisory Committee (CCSDS) specifications to adapt to the unique telemetry and remote control frame formats and radio frequency transmission characteristics of satellite communication; in the downlink, it performs reverse decapsulation. This approach cleverly avoids the performance degradation problem of a bloated network caused by running the standard TCP protocol directly on the satellite-to-ground link, because the ground end retains the complete TCP / IP protocol stack to handle the complex network environment, while the satellite only needs to run a simplified, lightweight IP / UDP protocol stack, significantly reducing the onboard computing load and memory consumption.

[0020] Furthermore, addressing the unique challenges of intermittent connections and bandwidth asymmetry inherent in low-Earth orbit satellites, the system employs a store-and-forward mechanism with adaptive rate control. The IPoC gateway module incorporates FIFO caching and flow control logic, enabling it to temporarily store IP packets in a large-capacity storage device when the satellite-to-ground link bandwidth fluctuates or is interrupted. Once the link is restored, packets are automatically transmitted back according to priority. This not only overcomes the limitations of the physical transit window but also enables dynamic scheduling of satellite-to-ground link resources by recognizing the Type of Service (ToS) field in the IP packet header, ensuring the real-time transmission of high-priority data such as remote control commands.

[0021] Compared to existing technologies, this invention achieves true end-to-end transparent IP transmission. Ground users do not need to install dedicated clients or go through multiple data relays; they can directly use standard network tools such as Ping, Telnet, and HTTP to access the onboard payload located hundreds of kilometers away in space. This experience, similar to accessing a local area network device, completely eliminates the minute-level transmission latency of traditional methods, compressing the command response time within line of sight to the millisecond level, thus meeting the needs of high-end applications such as emergency remote sensing and real-time control.

[0022] Meanwhile, compared to existing systems, this significantly improves the on-orbit scalability and agility of the satellite platform. Thanks to the adoption of a standard Ethernet interface, adding or replacing onboard payloads only requires connecting them to the onboard switch and assigning an IP address to complete network integration. No modifications to the satellite's underlying drivers or hardware adaptations are needed, reducing the payload adaptation cycle from weeks to hours, truly achieving plug-and-play functionality.

[0023] Furthermore, this invention significantly reduces system complexity and hardware costs. Replacing expensive and closed aerospace-specific bus equipment with mature commercial off-the-shelf Ethernet switching chips not only reduces power consumption of individual units and the entire satellite but also simplifies the complexity of satellite integration. Simultaneously, by decoupling the complex onboard TCP protocol processing and adopting a lightweight IP protocol stack, protocol performance fluctuations under high latency and high error rate environments are effectively avoided, ensuring the stability and efficiency of data transmission. Through the rate matching and store-and-forward strategy of the IPoC gateway, the system can adapt to the short transit time and discontinuous coverage characteristics of low-Earth orbit satellites. Even when the satellite leaves the line-of-sight range from the ground station, data is not lost but automatically resumes transmission after returning to line-of-sight, fully utilizing the limited transit window bandwidth and improving system robustness. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a diagram illustrating the overall architecture of a space-ground IP integrated communication system for low-Earth orbit satellite constellations as described in this invention. Figure 2 This is a flowchart illustrating the internal logic of the IPoC gateway module described in this invention. Figure 3 This is a comparison diagram of the satellite-to-ground protocol stack described in this invention; Figure 4 This is the uplink communication timing diagram described in this invention; Figure 5 This is the downlink communication timing diagram described in this invention; Figure 6 This is a schematic diagram of ground routing and terminal access as described in this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0026] Implementation Method 1: This implementation method addresses the problem of low communication efficiency and high latency caused by the use of a dedicated bus protocol on the satellite and an IP protocol on the ground, which requires multiple protocol conversions between the two. It proposes an integrated space-ground IP communication system for low-Earth orbit satellite constellations, which includes a space segment and a ground segment. The space segment is deployed on a low-Earth orbit satellite platform and includes an onboard Ethernet switch, an IPoC gateway module, and at least one onboard payload. The on-board payloads are equipped with standard Ethernet interfaces and interconnected through the on-board Ethernet switches to form an intra-satellite local area network. Each on-board payload is assigned a unique intra-satellite IP address in the intra-satellite local area network. The IPoC gateway module is connected to the onboard Ethernet switch and the satellite-to-ground radio front-end respectively, and is used to perform bidirectional protocol conversion between IP packets and CCSDS frames. The ground segment includes a ground IPoC modem and a ground router; the ground router is configured with a static routing table to direct IP packets destined for the satellite local area network to the ground IPoC modem; the ground IPoC modem is configured to perform bidirectional protocol conversion between IP packets and CCSDS frames to adapt to satellite-to-ground radio frequency link transmission.

[0027] In this embodiment, the IPoC gateway module includes an uplink processing unit and a downlink processing unit: The uplink processing unit is used to receive Ethernet frames from the onboard Ethernet switch, extract IP packets, segment and encapsulate the IP packets according to the CCSDS specification, add virtual channel identifiers, and output them to the data transmitter of the satellite-to-ground radio frequency front-end. The downlink processing unit is used to receive CCSDS frames from the satellite-to-ground radio frequency front-end, perform frame synchronization, demapping and fragmentation reassembly operations, restore the IP packets, and send the IP packets to the satellite Ethernet switch.

[0028] In this embodiment, the IPoC gateway module is further used for: Read the Quality of Service (QoS) identifier field from the IP packet header; Based on the priority corresponding to the quality of service identifier field, high-priority packets are prioritized for encapsulation and scheduled for transmission. When the satellite-to-ground link rate is lower than the satellite-internal Ethernet rate, uplink IP packets are cached through the built-in FIFO buffer queue, and idle frames are inserted into the CCSDS frame stream for rate matching.

[0029] In this embodiment, the onboard payload includes an imaging device, a satellite computer, and a high-capacity storage unit; The satellite computer runs a lightweight IP protocol stack and acts as a DHCP server for the satellite's local area network, dynamically allocating IP addresses to onboard payloads connected to the satellite's Ethernet switch. The high-capacity storage unit is used to receive and store IP packets from the IPoC gateway module when the low-orbit satellite leaves the line-of-sight range of the ground station.

[0030] In this embodiment, the large-capacity storage unit is also used for: Stored IP packets are indexed and organized according to timestamps and priorities; In response to the signal that the low-orbit satellite enters the line-of-sight range of the ground station, the IPoC gateway module is activated by a hardware wake-up signal and automatically transmits the stored IP packets back in priority order.

[0031] In this embodiment, the user terminal on the ground segment runs a standard TCP / IP protocol stack, and the destination IP address of the IP packet generated by the user terminal directly points to the on-board IP address of the satellite payload in the space segment. The onboard Ethernet switch is configured to perform Layer 3 forwarding based solely on the header information of the IP packets, without parsing application layer data, in order to achieve end-to-end transparent IP transmission between the ground terminal and the onboard payload.

[0032] Implementation Method Two: This implementation method proposes a space-ground IP integrated communication method for low-Earth orbit satellite constellations, based on the system described in Implementation Method One. The method includes an uplink communication step: The ground terminal generates an IP packet with the destination IP address of the satellite payload; The ground router forwards the IP packets to the ground IPoC modem according to the static routing rules; The terrestrial IPoC modem encapsulates the IP packets into CCSDS frames and transmits them via radio frequency through the terrestrial antenna. The satellite receives the CCSDS frames, which are then decapsulated and restored into IP packets by the onboard IPoC gateway module. The onboard Ethernet switch forwards the IP packet to the corresponding onboard payload based on the destination IP address of the IP packet.

[0033] In this embodiment, the method further includes a downlink communication step: The onboard payload generates return IP packets with the source IP address of this payload. The onboard Ethernet switch aggregates the backhaul IP packets to the IPoC gateway module; The IPoC gateway module encapsulates the return IP packets into CCSDS frames and transmits them to the ground station via a data transmitter. The ground station receives the CCSDS frame, decapsulates it to restore it to an IP packet, and then forwards it to the ground terminal through a ground router.

[0034] In this embodiment, the method further includes a store-and-forward step: In response to situations where there is no line-of-sight connection between the satellite and the ground station, the IPoC gateway module redirects the backhaul IP packets to be transmitted to a large-capacity storage unit for persistent storage. In response to a satellite entering its transit window, the large-capacity storage unit reads the stored IP packets and triggers the IPoC gateway module to execute downlink communication steps.

[0035] In the uplink communication step, the IP packet is a UDP packet; The on-board IPoC gateway module uses a lightweight IP protocol stack to process the UDP packets. The lightweight IP protocol stack supports IP, UDP and ICMP protocols, but removes the full TCP protocol processing function.

[0036] Implementation Method 3, see below Figures 1 to 5 Description of the implementation method. This implementation method provides a complete embodiment of the integrated space-ground IP communication system for low-Earth orbit satellite constellations described in Implementation Method 1, including: This embodiment provides a space-ground IP integrated communication system for low-Earth orbit satellite constellations, which solves the technical problems in the prior art such as heterogeneous intra-satellite bus protocols, inconsistent space-ground protocols, inability of ground terminals to directly connect to onboard payloads, and long adaptation cycles for new payloads.

[0037] like Figure 1 As shown, the integrated space-ground IP communication system provided in this embodiment includes two parts: a space segment and a ground segment.

[0038] The space segment is deployed on a low-Earth orbit satellite platform, which is equipped with an onboard Ethernet switch, an IPoC gateway module, and onboard payloads. All payloads (cameras, storage, data transmission, etc.) are equipped with standard Ethernet interfaces and connected to the switch in a star topology to form an intra-satellite LAN. Each payload is assigned a unique intra-satellite IP address; The ground station system includes a ground antenna, a ground IPoC modem, and a ground router / gateway. The ground router has static routing capabilities, directing IP packets destined for the satellite subnet to the ground IPoC modem, enabling ground terminals to communicate directly with the satellite using the standard IP protocol stack. The IP over CCSDS (IPoC) protocol is used between satellite and ground, which encapsulates IP packets into CCSDS frames for radio frequency transmission, thereby achieving protocol unification of satellite-ground links.

[0039] The IPoC gateway module includes an uplink processing unit and a downlink processing unit, and its internal logic flow is as follows: Figure 2 As shown.

[0040] The IPoC gateway module is the core protocol conversion device on the satellite, comprising two processing units: Uplink processing unit: receives Ethernet frames, extracts IP packets, segments and encapsulates them according to the CCSDS specification, adds virtual channel identifiers, and outputs them to the data transmitter. Downlink processing unit: receives CCSDS frames, performs frame synchronization, demapping, fragmentation and reassembly, restores the IP packets, and sends them to the onboard Ethernet switch.

[0041] The satellite employs a lightweight IP protocol stack (such as uIP), implementing only IP, UDP, and ICMP protocols, thus conserving satellite resources. Ground terminals run a standard TCP / IP protocol stack, requiring no application modifications.

[0042] The satellite uses a private IP address range (e.g., 10.10.1.x / 24), which is dynamically assigned or statically bound by the satellite's computer acting as a DHCP server. Ground stations are configured with static routes to enable interconnection between the ground subnet and the satellite subnet.

[0043] like Figure 3 As shown, this invention differs fundamentally from existing conventional solutions at the protocol stack level. Figure 4 and Figure 5 As shown, when a ground terminal needs to communicate with an on-board payload, the ground terminal first generates an IP packet with a destination IP address pointing to a specific on-board payload. This packet is transmitted to a ground router via the local network. The ground router makes an addressing decision based on a pre-configured static routing table and forwards the packet to a ground IPoC modem. After receiving the IP packet, the ground IPoC modem performs protocol encapsulation, mapping and encapsulating it into a CCSDS frame structure conforming to the space communication protocol. Subsequently, the radio frequency signal carrying the data is transmitted to the satellite via a ground antenna.

[0044] After receiving the aforementioned radio frequency signals, the satellite within the transit window decapsulates the CCSDS frames using its onboard IPoC gateway module, recovering the original IP packets. These IP packets are then sent to the onboard Ethernet switch. The switch parses the destination IP address in the packet header and, based on the onboard LAN's routing table, accurately forwards the packet to the target satellite's payload, thus completing the uplink communication process.

[0045] During downlink backhaul, the onboard payload generates backhaul IP packets containing service data, which are sent to the onboard Ethernet switch for aggregation. The switch routes the packet to the IPoC gateway module based on its destination IP address. The IPoC gateway module encapsulates the backhaul IP packet into a CCSDS frame and delivers it to the data transmitter for radio frequency downhaul. After the ground station antenna captures this downlink radio frequency signal, the ground IPoC modem performs decapsulation to restore the standard IP packet. Finally, the ground router forwards the IP packet to the requesting ground terminal based on its address information.

[0046] Throughout the communication process, the satellite platform only performs three-layer forwarding based on the IP packet header, without parsing the application layer data, thus achieving end-to-end transparent IP transmission between the ground terminal and the on-board payload, just like accessing a local area network device.

[0047] When the satellite-to-ground link rate is lower than the satellite-internal Ethernet rate, the IPoC gateway module has a built-in FIFO buffer for uplink IP packets and inserts idle frames into CCSDS frames to adapt to the radio frequency link rate and prevent data overflow.

[0048] The IPoC gateway module reads the ToS field or DiffServ tag in the IP packet header, encapsulates and sends high-priority packets (such as remote control commands) first, and ensures the real-time performance of critical services.

[0049] When the satellite is not within line-of-sight of the ground station, IP packets are automatically temporarily stored in the onboard storage unit and organized according to priority. Once the satellite enters the line-of-sight of the ground station, the storage unit wakes up the IPoC gateway and automatically transmits historical data, resolving the issue of discontinuous transit windows for low-Earth orbit satellites.

[0050] Implementation Method Four, see below Figure 6 Description of the implementation method. This implementation method is a specific embodiment of the integrated space-ground IP communication system for low-Earth orbit satellite constellations described in Implementation Method 3, including: This embodiment uses a 6U CubeSat operating in a 550km sun-synchronous orbit as an example to illustrate the specific implementation of the present invention. The satellite platform parameters in this example are shown in Table 1. The onboard equipment and IP address allocation are shown in Table 2.

[0051] Table 1 Satellite Platform Parameters

[0052] Table 2 On-board equipment and IP address allocation

[0053] Hardware selection and connection: The onboard Ethernet switch is a Microchip KSZ9897 (7-port Gigabit switch), which has undergone radiation-resistant screening and hardened packaging. The switch connects to the onboard computer via a PC104 interface. The IPoC gateway module is implemented using a Xilinx Artix-7 FPGA, integrating MAC layer processing, CCSDS framing / deframing, and FIFO buffering (4MB). One side of the module connects to the onboard switch via an RMII interface, and the other side connects to the data transmitter via an LVDS interface. The connection method is that each payload is connected to the switch via shielded twisted-pair cable in a star topology, with the cable length not exceeding 30cm.

[0054] Protocol stack configuration: Onboard IP Protocol Stack: A lightweight uIP protocol stack (open source) is used, implementing only IP, UDP, and ICMP protocols, omitting full TCP (to save resources). The satellite computer acts as a DHCP server, dynamically assigning IP addresses to each payload. Ground Routing Configuration: The ground station computer (Ubuntu system) executes the following command to add a static route: "sudo route add -net10.10.1.0 netmask 255.255.255.0 gw 192.168.0.10", where 192.168.0.10 is the IP address of the ground IPoC modem.

[0055] Example of communication process, emergency imaging command (Scenario: The ground command center detects abnormal activity in a certain sea area and needs to immediately instruct the onboard camera to take pictures and transmit the images back in real time): Uplink instruction flow: The operator opens the control software on the ground terminal (IP: 192.168.1.100) and clicks the "Shoot" button; The control software generates a UDP packet with a destination IP of 10.10.1.10 (camera) and a destination port of 8080. The packet content is {"cmd":"capture","area":"lon:121.5,lat:31.2","priority":1}. The ground router forwards the UDP packets to the ground IPoC modem (192.168.0.10) according to the static routing table. The terrestrial IPoC modem encapsulates UDP packets into CCSDS frames and transmits them via the antenna; When a satellite passes overhead (elevation angle > 10°), the onboard antenna receives radio frequency signals. The onboard IPoC gateway module is decapsulated and the UDP packets are restored. The onboard Ethernet switch forwards packets to the hyperspectral camera based on the destination IP (10.10.1.10); The camera interprets the command, executes the shooting, and generates a JPEG image (approximately 5MB).

[0056] Downlink image processing flow: The camera segments the JPEG image into multiple UDP packets (1400 bytes each), with source IP=10.10.1.10 and destination IP=192.168.1.100; The switch aggregates packets to the IPoC gateway module; The IPoC gateway module encapsulates each UDP packet into a CCSDS frame (2048 bytes per frame) and adds a virtual channel identifier; The data transmitter downloads at a rate of 10 Mbps; After receiving the data, the ground station decapsulates it using a ground IPoC modem to restore the UDP packet. The ground router forwards the message to the operator terminal (192.168.1.100). The control software reconstructs and displays the image.

[0057] Transmission performance: The end-to-end delay from the sending of the command to the completion of the reception of a single 5MB image is about 8 seconds (including camera exposure and compression processing time), of which the satellite-to-ground transmission part is about 4 seconds.

[0058] Store-and-forward mode (without transit): When the satellite is not within line-of-sight of any ground station: Image data captured by the camera cannot be downloaded in real time; When the IPoC gateway module detects no carrier signal, it automatically stores the IP packets in a large-capacity storage unit (10.10.1.20). The storage unit organizes file directories by timestamp and priority; 30 seconds before the satellite enters line-of-sight range from the ground station, the storage unit wakes up the IPoC gateway module via a GPIO signal. During transit, storage units transmit historical data back according to the principle of "highest priority first".

[0059] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A space-ground IP integrated communication system for low-Earth orbit satellite constellations, characterized in that, The system includes a space segment and a ground segment; The space segment is deployed on a low-Earth orbit satellite platform and includes an onboard Ethernet switch, an IPoC gateway module, and at least one onboard payload. The on-board payloads are equipped with standard Ethernet interfaces and interconnected through the on-board Ethernet switches to form an intra-satellite local area network. Each on-board payload is assigned a unique intra-satellite IP address in the intra-satellite local area network. The IPoC gateway module is connected to the onboard Ethernet switch and the satellite-to-ground radio front-end respectively, and is used to perform bidirectional protocol conversion between IP packets and CCSDS frames. The ground segment includes a ground IPoC modem and a ground router; the ground router is configured with a static routing table to direct IP packets destined for the satellite local area network to the ground IPoC modem; the ground IPoC modem is configured to perform bidirectional protocol conversion between IP packets and CCSDS frames to adapt to satellite-to-ground radio frequency link transmission.

2. The integrated space-ground IP communication system for low-Earth orbit satellite constellations according to claim 1, characterized in that, The IPoC gateway module includes an uplink processing unit and a downlink processing unit: The uplink processing unit is used to receive Ethernet frames from the onboard Ethernet switch, extract IP packets, segment and encapsulate the IP packets according to the CCSDS specification, add virtual channel identifiers, and output them to the data transmitter of the satellite-to-ground radio frequency front-end. The downlink processing unit is used to receive CCSDS frames from the satellite-to-ground radio frequency front-end, perform frame synchronization, demapping and fragmentation reassembly operations, restore the IP packets, and send the IP packets to the satellite Ethernet switch.

3. The integrated space-ground IP communication system for low-Earth orbit satellite constellations according to claim 2, characterized in that, The IPoC gateway module is also used for: Read the Quality of Service (QoS) identifier field from the IP packet header; Based on the priority corresponding to the quality of service identifier field, high-priority packets are prioritized for encapsulation and scheduled for transmission. When the satellite-to-ground link rate is lower than the satellite-internal Ethernet rate, uplink IP packets are cached through the built-in FIFO buffer queue, and idle frames are inserted into the CCSDS frame stream for rate matching.

4. The integrated space-ground IP communication system for low-Earth orbit satellite constellations according to claim 1, characterized in that, The on-board payload includes imaging equipment, a satellite computer, and a high-capacity storage unit. The satellite computer runs a lightweight IP protocol stack and acts as a DHCP server for the satellite's local area network, dynamically allocating IP addresses to onboard payloads connected to the satellite's Ethernet switch. The high-capacity storage unit is used to receive and store IP packets from the IPoC gateway module when the low-orbit satellite leaves the line-of-sight range of the ground station.

5. A space-ground IP integrated communication system for low-Earth orbit satellite constellations according to claim 4, characterized in that, The high-capacity storage unit is also used for: Stored IP packets are indexed and organized according to timestamps and priorities; In response to the signal that the low-orbit satellite enters the line-of-sight range of the ground station, the IPoC gateway module is activated by a hardware wake-up signal and automatically transmits the stored IP packets back in priority order.

6. A space-ground IP integrated communication system for low-Earth orbit satellite constellations according to claim 1, characterized in that, The user terminal on the ground segment runs a standard TCP / IP protocol stack, and the destination IP address of the IP packet generated by the user terminal directly points to the on-board IP address of the satellite payload in the space segment. The onboard Ethernet switch is configured to perform Layer 3 forwarding based solely on the header information of the IP packets, without parsing application layer data, in order to achieve end-to-end transparent IP transmission between the ground terminal and the onboard payload.

7. A satellite-ground IP integrated communication method for low-Earth orbit satellite constellations, implemented based on the system described in any one of claims 1 to 6, characterized in that, The method includes an uplink communication step: The ground terminal generates an IP packet with the destination IP address of the satellite payload; The ground router forwards the IP packets to the ground IPoC modem according to the static routing rules; The terrestrial IPoC modem encapsulates the IP packets into CCSDS frames and transmits them via radio frequency through the terrestrial antenna. The satellite receives the CCSDS frames, which are then decapsulated and restored into IP packets by the onboard IPoC gateway module. The onboard Ethernet switch forwards the IP packet to the corresponding onboard payload based on the destination IP address of the IP packet.

8. A satellite-ground IP integrated communication method for low-Earth orbit satellite constellations according to claim 7, characterized in that, The method also includes a downlink communication step: The onboard payload generates return IP packets with the source IP address of this payload. The onboard Ethernet switch aggregates the backhaul IP packets to the IPoC gateway module; The IPoC gateway module encapsulates the return IP packets into CCSDS frames and transmits them to the ground station via a data transmitter. The ground station receives the CCSDS frame, decapsulates it to restore it to an IP packet, and then forwards it to the ground terminal through a ground router.

9. A satellite-ground IP integrated communication method for low-Earth orbit satellite constellations according to claim 8, characterized in that, The method further includes a store-and-forward step: In response to situations where there is no line-of-sight connection between the satellite and the ground station, the IPoC gateway module redirects the backhaul IP packets to be transmitted to a large-capacity storage unit for persistent storage. In response to a satellite entering its transit window, the large-capacity storage unit reads the stored IP packets and triggers the IPoC gateway module to execute downlink communication steps.

10. A satellite-ground IP integrated communication method for low-Earth orbit satellite constellations according to claim 7, characterized in that, In the uplink communication step, the IP packet is a UDP packet; The on-board IPoC gateway module uses a lightweight IP protocol stack to process the UDP packets. The lightweight IP protocol stack supports IP, UDP and ICMP protocols, but removes the full TCP protocol processing function.

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