Image voice network data communication system of spacecraft and ground system

Abstract

An image voice network data communication system of a spacecraft and a ground system is characterized in that on the basis of a 1553B bus widely used by the spacecraft, space-ground image voice data transmission is carried out through an IP network, a space-ground gateway realizes cross-network segment connection of a space-ground subnetwork, and protocol conversion of a 1553B bus instruction, a telemetry data packet and an IP network packet is carried out in the space-ground gateway; according to the technical scheme, a gateway of a 1553B bus and an IP network is constructed, the working reliability of network equipment is improved, a method for controlling the IP packet length according to the frame length of a heaven and earth link is provided for fully utilizing heaven and earth link bandwidth resources, the heaven and earth link resources are effectively improved, and integrated, efficient and reliable communication of heaven and earth image voice network data is ensured.

Description

Technical Field

[0001] The invention relates to an image, voice and network data communication system between a spacecraft and a ground system, belonging to the field of aerospace measurement and control communication. Background Art

[0002] With the development of computer network technology, TCP / IP network has become the global information infrastructure. In order to achieve information sharing, various organizations have established their own TCP / IP networks. Now there are more and more computer systems used in spacecraft products, and it has become a trend to transmit image and voice data between the earth and the sky through TCP / IP network. The traditional image and voice transmission of spacecraft adopts bit stream insertion service, which can ensure the utilization rate of the ground-to-space channel and data smoothness. However, due to the special protocol used between the ground and the space, the spacecraft image and voice equipment needs to perform protocol conversion when the data reaches the spacecraft uplink communication equipment. After the data reaches the ground communication network, it needs to perform protocol conversion again. There are many protocol conversion links, which adds unnecessary links and cannot achieve end-to-end ground-to-space integrated network communication. At present, some spacecraft have adopted IP overCCSDS protocol for ground-to-space integrated network communication between the ground and the space. It has become possible for image and voice data to communicate between the ground and the space through IP packets. Due to the limited bandwidth and long delay of the ground-to-space link, the ground-to-space link adopts a special format. Since the IP packet length does not match the ground-to-space link frame length, directly applying the existing network data transmission protocol will bring about the problem of low utilization rate of the ground-to-space channel. If no measures are taken, the problem of frame loss will occur when the amount of data transmitted between the ground and the space is close to the link bandwidth. At the same time, if the spacecraft image and voice terminal only relies on the ground-to-space network to communicate with the ground, once the ground-to-space network equipment is abnormal, the ground will not be able to operate the image and voice terminal, which will delay the execution of flight events at the least and may cause equipment failure at the worst. How to efficiently utilize the bandwidth of the ground-to-space link to achieve smooth transmission of image and voice data and safe and reliable operation of equipment has become the current problem. Summary of the invention

[0003] The technical problem solved by the present invention is: in view of the problem that it is difficult to realize efficient transmission of image and voice data of ground-to-space link and efficient utilization of equipment in the current prior art, an image and voice network data communication system between a spacecraft and a ground system is proposed.

[0004] The present invention solves the above technical problems by the following technical solutions:

[0005] An image, voice and network data communication system between a spacecraft and a ground system, comprising a spacecraft IP network, a space-ground gateway, a ground measurement and control communication network, and a relay satellite;

[0006] The spacecraft IP network is connected to each terminal device in the spacecraft through an Ethernet switch, collects the space and earth image and voice data transmitted by each terminal device in the spacecraft, encapsulates it using the RTP protocol, transmits it through the UDP protocol, and transmits it to the space and earth gateway after being encapsulated in IP packets. The space and earth gateway also realizes the data protocol conversion between the spacecraft IP network and the 1553B data bus, and uses the relay satellite to establish a wireless link to send the converted data to the ground measurement and control communication network; the space and earth image and voice data collected by the spacecraft IP network undergo data protocol conversion between the IP network and the 1553B data bus.

[0007] The spacecraft IP network includes an application layer, a transport layer, a network layer, a link layer and a physical layer;

[0008] The application layer uses the real-time transport protocol RTP to encapsulate and encode to form an RTP encapsulation packet, and modifies the terminal device parameters through the bus instructions transmitted through the 1553B data bus, and checks the status of each terminal device through the 1553B data bus or configures or checks the terminal device parameters through the HTTP protocol; the application layer of the space network realizes data conversion between the space image and voice data of each terminal device in the spacecraft and the 1553B bus;

[0009] The transport layer uses the UDP protocol to implement data transmission, and the network layer uses the IP protocol to encapsulate data packets. Different transmission protocols are preset for the wired network and wireless network inside the spacecraft. After receiving the IP data packet, the space-ground gateway encapsulates and transmits the data packet through the protocol.

[0010] The link layer uses the Ethernet protocol for wired networks inside and between spacecraft compartments, and the preset network protocol for wireless networks; the wired network inside the spacecraft is connected by preset twisted pair or coaxial cables, and twisted pair cables are used between different compartments, and two-way communication is achieved with the ground measurement and control communication network through relay Ka links.

[0011] The spacecraft IP network presets an image and voice transmission control strategy according to the transmission task requirements of the earth-space image and voice data, and caches each earth-space image and voice data according to the frame length of the earth-space image and voice data, and sends the current data packet after the data packet length reaches the wireless link frame length if the delay is allowed.

[0012] The spacecraft IP network is connected to the image terminal and voice terminal in the spacecraft through an Ethernet switch, and communicates with the ground measurement and control communication network through the wireless link established by the space-ground gateway and the relay satellite. The communication of the internal equipment of the ground measurement and control communication network is completed through the ground switch, and the communication of the terminal equipment inside the spacecraft is exchanged through the link layer or the network layer; the spacecraft IP network and the 1553B data bus realize data conversion according to the data protocol at the application layer, interconnect at the link layer and exchange Ethernet data, and the space-ground gateway exchanges data between the ground and the ground through the network layer.

[0013] The earth and sky image and voice data are encapsulated by RTP protocol at the application layer, transmitted by UDP protocol at the transport layer, encapsulated by IP packet at the network layer, and encapsulated by IP packet for wireless link transmission; the earth and sky image and voice data are installed with RFC3550 at the application layer to execute the real-time transport protocol RTP, and the earth and sky image and voice data are configured by HTTP protocol. After configuration, the IP packet encapsulation method is as follows:

[0014] The ground-to-earth image data is split into IP packets, ensuring that the length of the header packet and the middle packet is consistent with the length of the link layer transmission frame data area, and allowing the packet length of the last IP packet of the image frame to be smaller than the ground-to-earth link transmission frame length; for voice data, if delay is allowed, a preset number of voice frames are combined into one IP packet for transmission, and the combined IP packet is sent after the IP packet length reaches the ground-to-earth link frame length, so as to maximize channel utilization while ensuring real-time communication.

[0015] In the spacecraft IP network, the image terminal and voice terminal in the spacecraft collect the assembled data packets and send them to the ground-to-space gateway. According to the data transmission requirements, protocol framing is performed at the application layer and the transport layer. The destination IP address of the network layer is set to the IP address of the ground image and voice terminal of the ground measurement and control communication network, and the destination MAC address of the link layer is set to the MAC address of the ground-to-space gateway. After receiving the data packets sent by the spacecraft IP network, the ground-to-space gateway encapsulates them according to the protocol format and transmits them to the ground measurement and control communication network through a wireless link, and forwards each IP message to the corresponding ground network terminal.

[0016] The control instructions received by the image terminal and voice terminal in the spacecraft are transmitted via the UDP protocol and transmitted by the transport layer; the payload area of ​​the UDP encapsulation packet uses the first byte as the type identifier to distinguish between instructions and telemetry data, and the remaining bytes are instructions or telemetry data of variable length.

[0017] When the UDP encapsulation packet is an instruction encapsulation packet, it is used to control the working status switching of the image terminal and the voice terminal through the transport layer. The spacecraft IP network changes the parameter configuration of the image terminal and the voice terminal through the UDP encapsulation packet, including the sending destination IP address, gateway address, and image encoding method; the spacecraft IP network is connected to the networked ground-to-earth wireless link through the transport layer through the UDP encapsulation packet, and the working status data of the image terminal and the voice terminal are transmitted in real time, or transmitted between the equipment terminals inside the spacecraft by the transport layer.

[0018] The sky-ground gateway converts the UDP telemetry and instruction packets transmitted by the transport layer into 1553B instructions and 1553B telemetry packets, and transmits them to the non-network sky-ground wireless link through the 1553B bus, and transmits them through the non-network wireless link.

[0019] When the networked wireless link channel is blocked, the ground command and control center sends control data to the central unit of the spacecraft through other non-network wireless uplinks. The central unit performs 1553B bus data protocol conversion through the space-ground gateway, converts the 1553B bus instructions into UDP instruction packets and sends them to the image and voice terminal. At the same time, the image and voice terminal encapsulates the telemetry parameters into UDP packets and sends them to the gateway. The gateway converts the UDP telemetry parameter packets into 1553B telemetry parameter packets, and transmits the converted 1553B bus data in the form of telemetry parameters through other non-network downlinks.

[0020] The advantages of the present invention compared with the prior art are:

[0021] (1) The present invention provides an image and voice network data communication system between a spacecraft and a ground system, which transmits image and voice data between the ground and the earth through an IP network. The ground-to-earth gateway realizes the cross-segment connection of the ground-to-earth subnets. At the same time, the ground-to-earth gateway performs protocol conversion between 1553B bus instructions, telemetry data packets and IP network packets, builds a gateway between the 1553B bus and the IP network, realizes dual-network backup, improves the reliability of the image and voice equipment, and ensures the integrated, efficient and reliable communication of image and voice network data between the ground and the earth.

[0022] (2) The present invention is based on the integration of IP network and 1553B bus. The image and voice data are encapsulated by RTP / UDP / IP packets. The control data can be transmitted through IP network or 1533B bus. Wireless hotspots and switches are used in the cabin. The IP packet transmission method between the ground and the sky improves the flexibility of ground-ground communication. At the same time, in order to ensure the smoothness of the transmission of image and voice data and make full use of the bandwidth resources of the ground-ground link, an image and voice IP packet encapsulation method is designed according to the characteristics of image and voice data. For image data, since the image frame is large, it needs to be split into multiple IP packets for transmission. The splitting method is as follows: the length of the header packet and the middle packet is consistent with the length of the link layer transmission frame data area, and the packet length of the last IP packet (tail packet) of the image frame is allowed to be less than the ground-ground link transmission frame length; for voice data, if the delay is allowed, it is necessary to combine the voice frames into one IP packet for transmission. Usually, multiple voice frames are buffered and the IP packet is sent after the length of the IP packet reaches the ground-ground link frame length. Under the premise of ensuring the real-time nature of the call, the channel utilization rate is maximized;

[0023] (3) The present invention is based on the integration of IP network and 1553B bus. The image and voice terminal in the spacecraft uses RTP / UDP / IP protocol to encapsulate the original data. The IP packets are forwarded between the ground and the earth. The instructions and telemetry data can be transmitted through the IP network or 1533B bus, realizing the network transmission method of image and voice data between the ground and the earth. At the same time, the UDP protocol can be selected to configure or inject data according to the capacity of the ground-ground channel. It can also be sent to the gateway to the device through the 1553B bus after uplinking through other ground-ground links. The gateway device realizes the conversion of 1553B bus instructions, telemetry packets and UDP protocol to realize cross-network data transmission. The spacecraft image and voice terminal should perform rate control when sending raw data, and the image data should be controlled at an average rate according to the I frame period. For voice data, in order to maintain lip synchronization, a cache with the same delay as the image data is set before playback. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The structure diagram of the ground-to-earth integrated network communication system that integrates the IP network and 1553B bus provided by the invention;

[0025] Figure 2 A flow chart of the integrated network communication between the earth and the sky by integrating the IP network and the 1553B bus provided by the invention;

[0026] Figure 3 A schematic diagram of the network instructions and telemetry data formats provided for the invention; DETAILED DESCRIPTION

[0027] The invention discloses an image and voice network data communication system between a spacecraft and a ground system. The system is based on the 1553B bus widely used in spacecraft. The space-ground image and voice data are transmitted through an IP network. The space-ground gateway realizes the cross-segment connection of the space-ground subnet. At the same time, the protocol conversion between the 1553B bus instructions, telemetry data packets and IP network packets is performed in the space-ground gateway. The gateway between the 1553B bus and the IP network is constructed to improve the reliability of network equipment. In order to make full use of the bandwidth resources of the space-ground link, a method of controlling the IP packet length according to the space-ground link frame length is proposed, which effectively improves the space-ground link resources and ensures the integrated, efficient and reliable communication of image and voice network data between the space and the ground.

[0028] The image, voice, network and data communication system between the spacecraft and the ground system, including the spacecraft IP network, the space-ground gateway, the ground measurement and control communication network, and the relay satellite;

[0029] The spacecraft IP network is connected to each terminal device in the spacecraft through an Ethernet switch, collects the ground-to-earth image and voice data transmitted by each terminal device in the spacecraft, realizes the data protocol conversion between the spacecraft IP network and the 1553B data bus through the ground-to-earth gateway, and then uses the relay satellite to establish a wireless link to access the ground measurement and control communication network; the ground-to-earth image and voice data collected by the spacecraft IP network are encapsulated using the RTP protocol, transmitted through the UDP protocol, and encapsulated in IP packets and transmitted to the ground-to-earth gateway for data protocol conversion between the IP network and the 1553B data bus.

[0030] The spacecraft IP network includes the application layer, transport layer, network layer, link layer and physical layer;

[0031] The application layer uses the real-time transport protocol RTP to encapsulate and encode to form an RTP encapsulation packet, and modifies the terminal device parameters through the bus instructions transmitted through the 1553B data bus, and checks the status of each terminal device through the 1553B data bus or configures or checks the terminal device parameters through the HTTP protocol; the application layer of the space network performs data conversion on the 1553B bus data and the space image and voice data of each terminal device in the spacecraft;

[0032] The transport layer uses the UDP protocol to implement data transmission, and the network layer uses the IP protocol to encapsulate data packets. Different transmission protocols are preset for the wired network and wireless network inside the spacecraft. After receiving the IP data packet, the space-ground gateway encapsulates and transmits the data packet through the protocol.

[0033] The link layer uses the Ethernet protocol for wired networks inside and between spacecraft compartments, and the preset network protocol for wireless networks; the wired network inside the spacecraft is connected by preset twisted pair or coaxial cables, and twisted pair cables are used between different compartments, and two-way communication is achieved with the ground measurement and control communication network through relay Ka links.

[0034] The spacecraft IP network presets the image and voice transmission control strategy according to the transmission mission requirements of the space and earth image and voice data. According to the frame length of the space and earth image and voice data, and when the delay is allowed, it caches each space and earth image and voice data until the data packet length reaches the wireless link frame length and then sends the current data packet.

[0035] The spacecraft IP network is connected to the image terminal and voice terminal in the spacecraft through Ethernet switches, and communicates with the ground measurement and control communication network through wireless links established by the space-ground gateway and relay satellites. The communication of internal equipment in the ground measurement and control communication network is completed through the ground switch, and the communication of terminal equipment inside the spacecraft is exchanged through the link layer or network layer. The spacecraft IP network and the 1553B data bus realize data protocol conversion at the application layer, interconnect at the link layer and exchange Ethernet data, and the space-ground gateway exchanges data between the ground and the ground through the network layer.

[0036] The earth-sky image and voice data are encapsulated by RTP protocol at the application layer, transmitted by UDP protocol at the transport layer, and encapsulated by IP packet at the network layer, and then transmitted by wireless link. The earth-sky image and voice data are installed with RFC3550 at the application layer to execute the real-time transport protocol RTP. When the earth-sky image and voice data are configured through HTTP protocol, the relationship between the IP packet length and the data frame length transmitted at the link layer after configuration satisfies:

[0037] For image data, since the image frames are large, they need to be split into multiple IP packets for transmission. The splitting method is as follows: the length of the header packet and the middle packet is consistent with the length of the link layer transmission frame data area, allowing the packet length of the last IP packet (tail packet) of the image frame to be smaller than the ground-to-earth link transmission frame length; for voice data, if delay is allowed, it is necessary to combine the voice frames into one IP packet for transmission. Usually, multiple voice frames are buffered and the IP packet is sent after the length of the IP packet reaches the ground-to-earth link frame length, so as to maximize the channel utilization while ensuring the real-time nature of the call.

[0038] In the spacecraft IP network, the image terminal and voice terminal in the spacecraft collect the assembled data packets and send them to the ground-to-space gateway. According to the data transmission requirements, the protocol frames are grouped at the application layer and the transport layer. The destination IP address of the network layer is set to the IP address of the ground image and voice terminal of the ground measurement and control communication network, and the destination MAC address of the link layer is set to the MAC address of the ground-to-space gateway. After receiving the data packets sent by the spacecraft IP network, the ground-to-space gateway encapsulates them according to the protocol format and transmits them to the ground measurement and control communication network through the wireless link, and forwards each IP message to the corresponding ground network terminal.

[0039] The control commands received by the image terminal and voice terminal in the spacecraft are transmitted through the UDP protocol and transmitted by the transport layer; the payload area of ​​the UDP encapsulation packet uses the first byte as the type identifier to distinguish between commands and telemetry data, and the remaining bytes are commands or telemetry data of variable length.

[0040] When the UDP encapsulated packet is a command encapsulated packet, it is used through the transport layer to control the working status switching of the image terminal and the voice terminal. The spacecraft IP network changes the parameter configuration of the image terminal and the voice terminal through the UDP encapsulated packet, including the sending destination IP address, gateway address, and image encoding method. The spacecraft IP network is connected to the wireless link through the transport layer through the UDP encapsulated packet, and the working status data of the image terminal and the voice terminal are transmitted in real time, or transmitted between the equipment terminals inside the spacecraft by the transport layer.

[0041] The sky-ground gateway converts the UDP telemetry and command packets transmitted at the transport layer into 1553B commands and 1553B telemetry packets and transmits them to the non-network sky-ground wireless link through the 1553B bus.

[0042] When the networked wireless link channel is blocked, the ground command and control center sends control data to the central unit of the spacecraft through other non-network wireless uplinks. The central unit performs 1553B bus data protocol conversion through the space-ground gateway, converts the 1553B bus instructions into UDP instruction packets and sends them to the image and voice terminal. At the same time, the image and voice terminal encapsulates the telemetry parameters into UDP packets and sends them to the gateway. The gateway converts the UDP telemetry parameter packets into 1553B telemetry parameter packets, and transmits the converted 1553B bus data in the form of telemetry parameters through other non-network downlinks.

[0043] Furthermore, the spacecraft image, voice and data ground-to-earth integrated network communication system based on the fusion of IP network and 1553B bus is based on a gateway and Ethernet switch as the core. The gateway realizes the cross-segment transmission of the ground-to-earth network and the protocol conversion between the 1553B bus and the IP network; the Ethernet switch connects the network camera, voice terminal, and other network terminals to the communication network, provides at least one wireless transceiver for the wireless devices in the cabin to access the network, establishes a wireless link connection with the ground measurement and control system through the relay terminal equipment, and accesses the ground measurement and control communication network. Figure 1 As shown;

[0044] Image and voice data are encapsulated using the RTP protocol at the application layer. Based on the characteristics of image and voice data, which have high real-time requirements but relatively low reliability requirements, the UDP protocol is used for transmission at the transport layer, and IP packets are encapsulated at the network layer. IP packets are transmitted between the sky and the earth to realize network communication of image and voice data between the sky and the earth.

[0045] The network protocol stack of the spacecraft IP network adopts a five-layer structure, including the application layer, transport layer, network layer, link layer and physical layer. Figure 2 As shown, the specific protocol system is designed as follows:

[0046] 1) Application layer design

[0047] For real-time transmission data such as images and voice, the bit error rate requirement is not high but the real-time requirement is high. The packet loss retransmission mechanism can be ignored. The Real-time Transport Protocol (RTP) is used at the application layer. The encoded image frames or voice frames are encapsulated in RTP packets. Multiple image or voice frames can be put into one RTP packet, or one image or voice frame can be split into multiple RTP packets for transmission.

[0048] The image terminal or voice terminal supports HTTP protocol to configure and view terminal parameters. The terminal parameters can also be modified through 1553B bus instructions or injected data, and the terminal status can be viewed through 1553B bus telemetry parameters.

[0049] The gateway realizes the conversion between 1553B bus data and network data packets at the application layer. The bus instructions and telemetry parameters transmitted by the 1553B bus are transmitted in the IP network through the UDP protocol. The encapsulation method is as follows: Figure 3 shown.

[0050] 2) Transport layer design

[0051] In order to adapt to the asymmetry of the ground-to-earth link, remove the dependence of image and voice data transmission on the uplink, and ensure smooth link transmission, the transport layer adopts the UDP protocol to ensure that the transmission delay is as small as possible and greatly improve the communication rate. The UDP protocol is recommended, and the TCP protocol is also supported (but not recommended).

[0052] 3) Network layer design

[0053] The network layer uses the IP protocol to exchange data at the network layer. The space-ground gateway completes the protocol conversion of IP packets in the space-ground-sky path. The spacecraft's internal wired network and communication with the space station use the IEEE 802.3 protocol, and the spacecraft's internal wireless network uses the IEEE 802.11g / n transmission protocol.

[0054] The cargo spacecraft and the ground control and communication network use IP over CCSDS protocol, CCSDS encapsulation protocol, and AOS protocol for transmission. After receiving the IP packet, the gateway encapsulates the IP packet data through the encapsulation protocol and puts it into the CCSDS AOS frame data area for transmission.

[0055] 4) Link layer design

[0056] The wired network inside and between cabins adopts Ethernet protocol (IEEE Std 802.3 TM The wireless network uses the IEEE 802.11g / n protocol for transmission. The IP over CCSDS protocol is used to transmit IP packets between the ground and the sky. The existing ground-to-sky link protocol is not changed. The IP packets are encapsulated into the ground-to-sky link protocols such as the Advanced On-Orbit System (AOS), Telemetry Protocol (TM), and Telecontrol Protocol (TC) through the encapsulation packet service (CCSDS133.1-B-2, ENCAPSULATIONSERVICE) for transmission.

[0057] 5) Physical layer design

[0058] The spacecraft's internal wired network uses 100BASE-TX twisted pair and 1000BASE-X coaxial cables. 100BASE-TX 100M twisted pair cables are used between different compartments of the spacecraft, and two-way high-speed communication is achieved with the ground through a relay Ka link.

[0059] The characteristics of the present invention are that it is based on the integration of IP network and 1553B bus, image and voice data are encapsulated by RTP / UDP / IP packets, control data can be transmitted through IP network or 1533B bus, wireless hotspots and switches are used in the cabin, and the IP packet transmission method between the ground and the sky improves the flexibility of ground-ground communication.

[0060] Due to the limited bandwidth between the ground and the sky, in order to ensure the real-time transmission of image and voice data, an image and voice rate control strategy is designed according to the characteristics of image and voice data. Since the dynamic image refresh rate is 25 to 30 frames per second, one I frame per second, the image device is required to send one frame of image data after completing the encoding of one frame of image, and the encoding end caches a maximum of one frame of image data (I frame or P frame), and the cycle does not exceed 40ms. Similarly, the voice data is sent immediately after each frame of encoding, but because the voice frame length is usually smaller than the channel frame length, if the delay is allowed, multiple voice frames are usually cached, and the IP packet is sent after the length of the IP packet reaches the ground-to-sky link frame length, so as to maximize the channel utilization while ensuring the real-time nature of the call.

[0061] The following is further described in conjunction with the accompanying drawings and preferred embodiments of the specification:

[0062] In the current embodiment, the specific configuration information of the image, voice, network and data communication system between the spacecraft and the ground system is:

[0063] 1. System Configuration

[0064] The cabin is equipped with a switch (or WiFi) to connect the image and voice terminals, which allows astronauts to communicate with the ground and take images through wireless terminals, improving the convenience of astronauts' work in the cabin. The matching Ethernet switch, the ground-to-space gateway, and the ground image and voice equipment are connected to the ground communication system network. The ground-to-space link consists of communication equipment between the spacecraft and the ground. The network communication of the network equipment inside the spacecraft and the network communication between the internal equipment of the ground system are completed through the switch, which can use link layer (layer 2) switching or network layer (layer 3) switching.

[0065] The gateway performs protocol conversion between the spacecraft's internal IP network and 1553B at the application layer, connecting the 1553B bus to Ethernet.

[0066] Spacecraft are interconnected through Ethernet switches, and Ethernet frames are exchanged at the link layer. The ground and the sky are connected through gateways for layer 3 switching and IP packet communication.

[0067] Network protocol stack and communication process such as Figure 2 shown.

[0068] 2. Image and voice terminal data encapsulation

[0069] 2.1. The image and voice network terminal equipment performs image and voice encoding and performs RTP encapsulation on the encoded data

[0070] Image and voice data are encapsulated using the RTP protocol at the application layer. Based on the characteristics of image and voice data, which have high real-time requirements but relatively low reliability requirements, the UDP protocol is used for transmission at the transport layer, and IP packet encapsulation is used at the network layer. IP packets are transmitted between the sky and the earth to realize network communication of image and voice data between the sky and the earth.

[0071] The Real-time Transport Protocol (RTP) is used at the application layer and the protocol is implemented in accordance with RFC3550.

[0072] For image terminals or voice terminals, terminal parameters can be configured by injecting data or supporting HTTP protocol. In particular, the IP packet length can be configured to be consistent with the link layer transmission frame length, requiring that the header packet or middle packet of the I frame or P frame should be consistent with the frame length, and allowing the last IP packet length of the last I frame or P frame to be less than the frame length.

[0073] 2.2. Image device performs transport layer encapsulation on network data

[0074] To ensure the real-time transmission, the transport layer uses the connectionless UDP protocol, which complies with the specifications in RFC768.

[0075] 2.3. The image device performs network layer encapsulation on the network data:

[0076] The IP protocol is used for data exchange at the network layer. The spacecraft and the ground complete the three-layer forwarding, and the specific IP protocol complies with the RFC791 specification.

[0077] 2.4: Image devices perform link layer encapsulation and physical layer transmission of network data

[0078] The data link layer and physical layer of the wired network 100M transmission conform to the 10BASE-T / 100BASE-TX standard of the IEEE 802.3 and 802.3u specifications, and the data link layer and physical layer of the wired network gigabit fiber transmission conform to the 1000BASE-LX standard in the IEEE802.3z specification.

[0079] The Ethernet data link layer adopts IEEE Std 802.3 TM Medium MAC frame format.

[0080] The wireless Wi-Fi transmission protocol complies with the IEEE 802.11g / n transmission specification.

[0081] A high-speed relay link is used between the sky and the ground to achieve bidirectional transmission of network data. The link frame format complies with CCSD701.0-B-3, as shown in Table 1:

[0082] Table 1 Frame format for transmission between ground and earth

[0083]

[0084]

[0085] IP packets are transmitted using IP over CCSDS space links (CCSDS 702.1-B-1), as shown in Table 2;

[0086] Version number: "01";

[0087] Spacecraft identifier SCID filling rules (8 bits in total): unique identifier of the spacecraft.

[0088] Virtual channel identifier VCID: It is used to identify different data types. It is recommended that the same virtual channel number be used for image and voice network data.

[0089] Virtual channel frame count: The transmission frames generated on each virtual channel are numbered in sequence;

[0090] Signaling domain: "00H" is real-time data, "80H" is playback;

[0091] The data area uses multi-channel protocol data unit (MPDU) to transmit IP packets, which complies with CCSD701.0-B-3. The MPDU format is: header: The MPDU header length is 16 bits, of which the first 5 bits are set as the spare field and filled with all 0s, and the last 11 bits are the first header pointer. The first header pointer directly points to the starting position of the first source packet. Each independent source packet can be distinguished according to the packet length mark in the source packet.

[0092] IPE header: 33 (21H) corresponds to IPv4 data packets, 87 (57H) corresponds to IPv6 data packets;

[0093] According to the link frame length, the present invention recommends setting the IP packet length of the image and voice preferably to N-9 bytes. If it is less than N-9 bytes, it is encapsulated according to the actual length.

[0094] 3. Image, voice and data communication process

[0095] The camera or voice terminal first sends the packaged data packets to the default spacecraft ground-to-earth gateway. The camera performs protocol framing on the application layer and the transport layer according to the data requirements. The destination IP address of the network layer is filled with the IP address of the ground image and voice terminal, and the destination MAC address of the data link layer is filled with the MAC address of the spacecraft ground-to-earth gateway (when the MAC address of the gateway is not stored when the camera is turned on, the ARP protocol is used to search for the MAC address of the network main control module). After receiving the data packet, the gateway removes the encapsulation of the physical layer and the data link layer, encapsulates the extracted IP packet in the IP over CCSDS format, and transmits it to the ground. After receiving the data, the ground front end restores the IP packet according to the protocol format and forwards each IP packet to the corresponding ground network terminal. Since the ground network transmission data requires the information of the destination IP address and the destination MAC address, the ground front end needs to perform ARP broadcast within the ground subnet. When the corresponding terminal feedbacks the information, the corresponding relationship between the MAC address information and the IP address information is stored in the internal memory of the ground front end, and then the image IP packet transmitted is sent to the corresponding terminal. The ground uplink data processing process is consistent with the downlink processing process.

[0096] Since the bandwidth between the ground and the sky is limited, in order to ensure the real-time transmission of image and voice data, a speed limit strategy based on data type is proposed according to the characteristics of image and voice data. The speed limit method is adopted according to different time periods to ensure that the channel occupancy is uniform and does not affect the transmission of other data between the ground and the sky. Since the dynamic image refresh rate is 25 to 30 frames per second, one I frame per second, the image device is required to send one frame of image data after completing the encoding of one frame of image, and the encoding end buffers a maximum of one frame of image data (I frame or P frame), and the cycle does not exceed 40ms. Similarly, the voice data is sent immediately after each frame of encoding is completed, but since the voice frame length is usually smaller than the channel frame length, if the delay is allowed, multiple voice frames are usually buffered, and the IP packet is sent after the IP packet length reaches the ground-ground link frame length, so as to maximize the channel utilization rate while ensuring the real-time nature of the call.

[0097] 4. Command and telemetry communication process

[0098] The commands and telemetry of the image and voice terminal can be transmitted via UDP / IP. The format is shown in Table 2. In the payload area of ​​the UDP packet, the first byte is the type identifier to distinguish between commands and telemetry, followed by commands or telemetry parameters of variable length. The command UDP packet can be used to control the switching of the working state of the image and voice terminal, and the parameter configuration of the image and voice terminal can also be changed, including the sending destination IP address, gateway address, image encoding method and other parameters; the telemetry UDP packet can be used to download the working state of the image and voice terminal in real time. The command and telemetry UDP packets can be transmitted between the ground and the sky, and can also be transmitted between the internal network terminals of the spacecraft.

[0099] The gateway device can convert the above UDP telemetry and instructions into 1553B instructions and telemetry packets for transmission via the 1553B bus, and transmit instructions or telemetry data through other non-network ground-to-ground telemetry and remote control channels.

[0100] When the ground-to-space network channel is blocked, control data can be sent to the central unit (CTU) through other non-network ground-to-space remote control channel uplinks. The CTU sends the command to the gateway through the 1553B bus, and the gateway converts the corresponding command into UDP / IP protocol and sends it to the network terminal. At the same time, the gateway also receives the telemetry parameters sent by the network terminal through the UDP protocol, converts them into 1553B bus data, and transmits them downlink through other channels in the form of spacecraft telemetry parameters. At the same time, the camera can be switched to low-rate mode. After receiving the low-speed image data, the gateway converts it into PCM code stream form and transmits the image data downlink through the non-network data transmission link.

[0101] In this embodiment, based on the integration of IP network and 1553B bus, the image and voice terminal in the spacecraft uses RTP / UDP / IP protocol to encapsulate the original data, and forwards the IP packets between the ground and the earth through the ground-to-earth communication. Commands and telemetry data can be transmitted through the IP network or the 1533B bus, thereby realizing a networked transmission method for image and voice data between the ground and the earth. The IP packets of image and voice network data between the ground and the earth are transmitted according to the IP over CCSDS protocol. The IP packet length can be configured through 1553B injection data, HTTP protocol or UDP protocol. The configured IP packet length matches the ground-to-earth link frame length.

[0102] The original data of the image and voice terminal device of this embodiment can only be transmitted using the UDP protocol. The configuration or injection data can use the UDP protocol according to the capacity of the ground-to-space channel, or it can be sent to the gateway to the device through the 1553B bus after being uplinked through other ground-to-space links. The gateway device implements the conversion of 1553B bus instructions and telemetry packets into UDP protocol to achieve cross-network data transmission. The spacecraft image and voice terminal should perform rate control when sending original data, and the image data should be controlled at an average rate according to the I frame period. For voice data, in order to maintain lip synchronization, a cache with the same delay as the image data is set before playback.

[0103] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0104] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An image, voice, network and data communication system between a spacecraft and a ground system, characterized by: Including spacecraft IP network, space-ground gateway, ground measurement and control communication network, and relay satellite; The spacecraft IP network is connected to each terminal device in the spacecraft through an Ethernet switch, collects the ground and earth image and voice data transmitted by each terminal device in the spacecraft, encapsulates them using the RTP protocol, transmits them through the UDP protocol, and transmits them to the ground and earth gateway after being encapsulated in IP packets. The data protocol conversion between the spacecraft IP network and the 1553B data bus is realized through the ground and earth gateway, and a wireless link is established using relay satellites to send the converted data to the ground measurement and control communication network.

2. The image, voice and network data communication system between a spacecraft and a ground system according to claim 1, characterized in that: The spacecraft IP network includes an application layer, a transport layer, a network layer, a link layer and a physical layer; The application layer uses the real-time transport protocol RTP to encapsulate and encode to form an RTP encapsulation packet, and modifies the terminal device parameters through the bus instructions transmitted through the 1553B data bus, and checks the status of each terminal device through the 1553B data bus or configures or checks the terminal device parameters through the HTTP protocol; the application layer of the space network realizes data conversion between the space image and voice data of each terminal device in the spacecraft and the 1553B bus; The transport layer uses the UDP protocol to implement data transmission, and the network layer uses the IP protocol to encapsulate data packets. Different transmission protocols are preset for the wired network and wireless network inside the spacecraft. After receiving the IP data packet, the space-ground gateway encapsulates and transmits the data packet through the protocol. The link layer uses the Ethernet protocol for wired networks inside and between spacecraft compartments, and the preset network protocol for wireless networks; the wired network inside the spacecraft is connected by preset twisted pair or coaxial cables, and twisted pair cables are used between different compartments, and two-way communication is achieved with the ground measurement and control communication network through relay Ka links.

3. The image, voice and network data communication system between a spacecraft and a ground system according to claim 2, characterized in that: The spacecraft IP network presets an image and voice transmission control strategy according to the transmission task requirements of the earth-space image and voice data, and caches each earth-space image and voice data according to the frame length of the earth-space image and voice data, and sends the current data packet after the data packet length reaches the wireless link frame length if the delay is allowed.

4. The image, voice and network data communication system between a spacecraft and a ground system according to claim 3, characterized in that: The spacecraft IP network is connected to the image terminal and voice terminal in the spacecraft through an Ethernet switch, and communicates with the ground measurement and control communication network through the wireless link established by the space-ground gateway and the relay satellite. The communication of the internal equipment of the ground measurement and control communication network is completed through the ground switch, and the communication of the terminal equipment inside the spacecraft is exchanged through the link layer or the network layer; the spacecraft IP network and the 1553B data bus realize data conversion according to the data protocol at the application layer, interconnect at the link layer and exchange Ethernet data, and the space-ground gateway exchanges data between the ground and the ground through the network layer.

5. The image, voice and network data communication system between a spacecraft and a ground system according to claim 2, characterized in that: The earth and sky image and voice data are encapsulated by RTP protocol at the application layer, transmitted by UDP protocol at the transport layer, encapsulated by IP packet at the network layer, and encapsulated by IP packet for wireless link transmission; the earth and sky image and voice data are installed with RFC3550 at the application layer to execute the real-time transport protocol RTP, and the earth and sky image and voice data are configured by HTTP protocol. After configuration, the IP packet encapsulation method is as follows: The ground-to-earth image data is split into IP packets, ensuring that the length of the header packet and the middle packet is consistent with the length of the link layer transmission frame data area, and allowing the packet length of the last IP packet of the image frame to be smaller than the ground-to-earth link transmission frame length; for voice data, if delay is allowed, a preset number of voice frames are combined into one IP packet for transmission, and the combined IP packet is sent after the IP packet length reaches the ground-to-earth link frame length, so as to maximize channel utilization while ensuring real-time communication.

6. The image, voice, network and data communication system between a spacecraft and a ground system according to claim 5, characterized in that: In the spacecraft IP network, the image terminal and voice terminal in the spacecraft collect the assembled data packets and send them to the ground-to-space gateway. According to the data transmission requirements, protocol framing is performed at the application layer and the transport layer. The destination IP address of the network layer is set to the IP address of the ground image and voice terminal of the ground measurement and control communication network, and the destination MAC address of the link layer is set to the MAC address of the ground-to-space gateway. After receiving the data packets sent by the spacecraft IP network, the ground-to-space gateway encapsulates them according to the protocol format and transmits them to the ground measurement and control communication network through a wireless link, and forwards each IP message to the corresponding ground network terminal.

7. The image, voice, network and data communication system between a spacecraft and a ground system according to claim 1, characterized in that: The control instructions received by the image terminal and voice terminal in the spacecraft are transmitted via the UDP protocol and transmitted by the transport layer; the payload area of ​​the UDP encapsulation packet uses the first byte as the type identifier to distinguish between instructions and telemetry data, and the remaining bytes are instructions or telemetry data of variable length.

8. The image, voice, network and data communication system between a spacecraft and a ground system according to claim 7, characterized in that: When the UDP encapsulation packet is an instruction encapsulation packet, it is used to control the working status switching of the image terminal and the voice terminal through the transport layer. The spacecraft IP network changes the parameter configuration of the image terminal and the voice terminal through the UDP encapsulation packet, including the sending destination IP address, gateway address, and image encoding method; the spacecraft IP network is connected to the networked ground-to-earth wireless link through the transport layer through the UDP encapsulation packet, and the working status data of the image terminal and the voice terminal are transmitted in real time, or transmitted between the equipment terminals inside the spacecraft by the transport layer.

9. The image, voice, network and data communication system between a spacecraft and a ground system according to claim 8, characterized in that: The sky-ground gateway converts the UDP telemetry and instruction packets transmitted by the transport layer into 1553B instructions and 1553B telemetry packets, and transmits them to the non-network sky-ground wireless link through the 1553B bus, and transmits them through the non-network wireless link.

10. The image, voice, network and data communication system between a spacecraft and a ground system according to claim 9, characterized in that: When the networked wireless link channel is blocked, the ground command and control center sends control data to the central unit of the spacecraft through other non-network wireless uplinks. The central unit performs 1553B bus data protocol conversion through the space-ground gateway, converts the 1553B bus instructions into UDP instruction packets and sends them to the image and voice terminal. At the same time, the image and voice terminal encapsulates the telemetry parameters into UDP packets and sends them to the gateway. The gateway converts the UDP telemetry parameter packets into 1553B telemetry parameter packets, and transmits the converted 1553B bus data in the form of telemetry parameters through other non-network downlinks.

Images