Method for disassembling frames, assembling frames and transmitting data frames of space-ground link for low-earth orbit satellite hopping beam

Abstract

The present invention discloses a method for disassembling frames, assembling frames and transmitting data frames of the space-ground link for low-orbit satellite hopping beams, which relates to the adaptation technology between the link layer and the physical layer in the field of satellite communication. Aiming at the adaptation problem between the fixed-length carrier blocks in the downlink burst and the variable-length high-layer link frames in the application of low-orbit satellite hopping beams, the present invention proposes to form a high-layer data stream queue based on the location area and the station type. This data stream is disassembled into frames at the on-board base station modulator based on the virtual location area number and the virtual channel number of the physical layer, and assembled into frames after filtering out the burst fixed-length carriers of non-this location area and virtual channel at the ground terminal. This method can achieve a high transmission efficiency and reduce the processing difficulty at the modulation end of the on-board baseband platform. The present invention can be used in the design of disassembling and assembling frames of the downlink TDM carrier in the satellite communication system based on on-board processing.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a method for disassembling frames, assembling frames, and transmitting data frames of a space-ground link for a low-earth orbit satellite hopping beam in the field of low-earth orbit satellite communication technologies. Background Art

[0002] In a low-earth orbit satellite communication system, within the visible range of the satellite, the beam irradiates the earth's surface to form a projection area, forming several wave positions in the satellite Internet network. Hopping beam communication is an important issue in a low-earth orbit satellite communication system, and modulation and demodulation processing is required to avoid crosstalk between signals in different location areas. In the field of satellite communication, there is an adaptation problem between fixed-length carrier blocks and variable-length high-layer link frames. At the modulation end, the high-layer link frame needs to be split into multiple fixed-length carrier blocks, and at the demodulation end, the fixed-length carrier blocks need to be restored to the link frame. This process should minimize the loss of frame transmission efficiency as much as possible.

[0003] Traditional methods disassemble and recombine link frames based on the link layer. At the modulation end, the long link frame needs to be split according to the length of the carrier block and the frame header needs to be refilled to obtain multiple short link frames each corresponding to a single carrier block. The short frame header marks which long frame this frame belongs to. When the demodulation end recombines the link frame, the extra filled frame header is removed, and the original link frame is recombined according to the marked information. This method greatly reduces the link frame efficiency because it needs to fill the link layer frame header additionally, occupying a longer data area length. In addition, since traditional methods need to disassemble the link frame at the modulation end link layer, a frame search function needs to be added to locate link frames of different lengths to ensure the integrity of each short frame, thus increasing the processing difficulty and resource occupancy of the modulation end of the on-board baseband platform, which is not conducive to cost control of the on-board baseband platform. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and propose a method for disassembling frames, assembling frames, and transmitting data frames of a space-ground link for a low-earth orbit satellite hopping beam, which can achieve a relatively high data frame transmission efficiency.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for disassembling frames of a space-ground link for a low-earth orbit satellite hopping beam, applied to an on-board base station, includes the following steps:

[0007] Step 101, through the CPU of the on-board baseband platform, divide the high-layer data stream into different queues according to the flow location area and station type. Each queue corresponds to a virtual location area number and a virtual channel number, and output the queue to the FPGA of the on-board baseband platform; the virtual location area number is used to make each frame of burst service frame correspond to a unique location area separately, and the virtual channel number is used to uniquely number different station types within the same location area;

[0008] Step 102: For a certain queue of data, the on-board baseband platform FPGA splits the link frames longer than the length of the pre-encoded data block and distributes them to multiple data blocks. The first 32-bit data of each data block is filled with the virtual channel number corresponding to this queue.

[0009] Step 103: Convert the data blocks into coded blocks according to the set code rate to complete the coding.

[0010] Step 104: For the coded blocks of each queue, first map the coded blocks into symbols, and then fill the virtual location area number in the frame header according to the burst service frame structure to obtain the burst fixed-length service frames of each queue, thus completing the framing of all queues' burst fixed-length service frames.

[0011] A method for satellite-ground link framing of a low-earth orbit satellite hopping beam, which is applied to the ground terminal of satellite communication, includes the following steps:

[0012] Step 201: The ground terminal demodulates the downlink service frame according to the current carrier rate and modulation method, and then completes the first-level location area layer filtering according to the virtual location area number filled in the service frame to obtain the burst service frame under the location area of this terminal; the virtual location area number is used to make each burst service frame uniquely correspond to a single location area.

[0013] Step 202: Decode the coded blocks in the burst service frame to obtain data blocks.

[0014] Step 203: Through the virtual channel number filled in the decoded data block, complete the second-level station type layer filtering to obtain the link frame segments split into each data block. The virtual channel number is used to uniquely number different station types within the same location area; reassemble the link frame segments into a complete link frame and output it.

[0015] A method for satellite-ground link data frame transmission of a low-earth orbit satellite hopping beam includes the following steps:

[0016] Step S1: Set the virtual location area number to number the multiple location areas covered by the hopping beam, so that each burst service frame uniquely corresponds to a single location area.

[0017] Step S2: Set the virtual channel number to number multiple station types within the same location area to distinguish the link frames of different station type terminals.

[0018] Step S3: On the on-board base station, through the on-board baseband platform CPU, divide the high-layer data stream into different queues according to the flow direction location area and station type. Each queue corresponds to a virtual location area number and a virtual channel number, and output the queue to the on-board baseband platform FPGA.

[0019] Step S4: For the data of a certain queue, the FPGA of the on-board baseband platform splits the link frames longer than the length of the data block before encoding, disperses them into multiple data blocks, and fills the first 32-bit data of each data block with the virtual channel number corresponding to this queue.

[0020] Step S5: Convert the data blocks into encoded blocks according to the set code rate to complete the encoding.

[0021] Step S6: For the encoded blocks of each queue, first map the encoded blocks into symbols, and then fill the virtual position area number in the frame header according to the burst service frame structure to obtain the burst fixed-length service frames of each queue, completing the framing of all queues' burst fixed-length service frames.

[0022] Step S7: The on-board base station sequentially covers each ground terminal by means of beam hopping. The ground terminal demodulates the downlink service frame according to the current carrier rate and modulation method, and then completes the first-level filtering at the location area level according to the virtual position area number filled in the service frame to obtain the burst service frame under the location area of this terminal.

[0023] Step S8: The ground terminal decodes the encoded blocks in the burst service frame to obtain the data blocks.

[0024] Step S9: The ground terminal completes the second-level filtering at the station type level through the virtual channel number filled in the data block after decoding, obtains the link frame segments split into each data block, and recombines the link frame segments into a complete link frame and outputs it.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The prior art splits and recombines link frames based on the link layer, splits link frames of different lengths into short frames, and fills in additional link layer frame headers, so that each carrier block contains several complete link frames. However, since the filled frame headers occupy a relatively long data area length, the link frame efficiency is greatly reduced. The present invention splits and recombines link frames based on the virtual position area number and virtual channel number at the physical layer, and the filled virtual position area number and virtual channel number are of short length, so it has higher transmission efficiency.

[0027] 2. The prior art needs to add a frame search function to split link frames at the modulation end of the link layer, which increases the processing difficulty and resource occupancy of the modulation end of the on-board baseband platform and is not conducive to cost control of the on-board baseband platform. The present invention can treat the link layer data as a continuous data stream, reducing the processing difficulty and cost of the on-board baseband platform. Description of the Drawings

[0028] Figure 1 It is a block diagram of the satellite-ground link system with beam hopping according to the embodiment of the present invention;

[0029] Figure 2Schematic diagram of the burst service frame structure in an embodiment of the present invention;

[0030] Figure 3 Schematic diagram of the process of disassembling frames by the on - board base station modulator in an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the process of assembling frames by the ground terminal demodulator in an embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the process of assembling frames by the ground terminal demodulator in an embodiment of the present invention. Detailed implementation manners

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] A method for disassembling frames of a space - to - ground link with a low - earth - orbit satellite hopping beam, as Figure 3 shown, includes the following steps:

[0035] Implement the assembly of the high - layer data stream queue 1 through the CPU of the on - board baseband platform. Divide the high - layer data stream into different queues according to the flow location area and station type. Each queue corresponds to a virtual location area number and a virtual channel number, and output to the FPGA to form a downlink burst service frame.

[0036] Implement the disassembly of the link frame 2 through the FPGA of the on - board baseband platform. For the data of a certain queue, disassemble the link frame with a length greater than the length of the data block before encoding, and disperse it into multiple data blocks. The first 32 - bit data of each data block is filled with the virtual channel number corresponding to this queue.

[0037] The encoder completes the encoding 3 through the agreed code rate and converts the data block into an encoded block.

[0038] Assemble the burst fixed - length service frame 4. For the encoded block of this queue, first map it into symbols, and then fill the virtual location area number in the frame header according to the burst service frame structure to obtain the burst fixed - length service frame of this queue. Complete the frame assembly of the burst fixed - length service frames of all queues in sequence.

[0039] A method for assembling frames of a space - to - ground link with a low - earth - orbit satellite hopping beam, as Figure 4 shown, includes the following steps:

[0040] Disassemble the burst fixed - length service frame 5. The ground terminal realizes the demodulation of the downlink service frame according to the current carrier rate and modulation method, and then completes the first - level filtering at the location area level according to the virtual location area number filled in the service frame to obtain the burst service frame under the location area of this terminal.

[0041] Send the encoded block in the service frame to the decoder and obtain the data block through decoding 6.

[0042] Recombine link frame 7. Through the virtual channel numbers filled in the decoded data blocks, perform the second-level station type filtering to obtain the link frame segments split into each data block, recombine them into a complete link frame and output it to the CPU of the ground terminal.

[0043] In the application scenario of low-earth orbit satellite hopping beam, the satellite covers ground terminals in multiple location areas and multiple station types through beam hopping. The on-board base station modulator of this method splits frames according to the virtual location area numbers and virtual channel numbers, splits the link frames flowing to terminals in different location areas and station types, and fills them into the burst frames of fixed-length carriers. The on-board base station covers ground terminals in turn through beam hopping. After the ground terminal filters out the burst fixed-length carriers of its own location area and station type, it recombines the link frames at the physical layer. By using this method to complete frame splitting and recombination at the physical layer without reducing the link frame efficiency, a relatively high transmission efficiency can be achieved.

[0044] Refer to Figure 1 , this method can support the space-ground link system with i location areas and j station types. The on-board base station modulator splits frames according to the virtual location area numbers and virtual channel numbers, splits the link frames flowing to terminals in different location areas and station types, and fills them into the burst frames of fixed-length carriers. The on-board base station covers ground terminals in turn through beam hopping. After the ground terminal filters out the burst fixed-length carriers of its own location area and station type, it recombines the link frames at the physical layer. By using this method to complete frame splitting and recombination at the physical layer without reducing the link frame efficiency, a relatively high transmission efficiency can be achieved.

[0045] Figure 2 This is the burst service frame structure of this method. Among them, each burst service frame includes a frame synchronization header, virtual location area numbers, coding blocks, and a frame tail. Among them, virtual location area numbers 1 to i correspond to i location areas, and one burst service frame only corresponds to one of them, and the i location areas are arranged in a cycle. Before coding, a fixed-length data block is composed of 32-bit virtual channel numbers and service data, and the corresponding coding block is obtained through coding. The 32-bit virtual channel numbers correspond to a total of j station types. In one burst service frame, the coding blocks of the j station types are arranged in a cycle to fill the burst service frame. By dividing the link frame into service data code blocks, the link frame of the on-board baseband platform modulator can be transmitted to the corresponding ground terminal demodulator according to different location areas and station types.

[0046] Figure 5 The following shows the frame recombination process of the ground terminal demodulator. Among them, the satellite communication channel sequentially sends the downlink burst service frames generated by the on-board baseband platform to each ground terminal through beam hopping. Terminals in different locations and different station types are affected by the location area gain and can only correctly demodulate the downlink service frames sent to their own location area and extract the link frames corresponding to their own station types. Through the physical layer filtering method, frame recombination errors caused by factors such as channel bit errors and unmatched modulation methods can be avoided. The specific implementation is as follows:

[0047] First, the ground terminal access control issues the virtual location area code vn_1 and the virtual channel number vch_1 corresponding to this terminal. After the demodulator captures the synchronization header, it locates the virtual location area code vn_x filled in the current burst service frame, and the physical layer filters out the burst service frames with vn_x equal to vn_1 and sends them to the decoder to complete the location area level filtering before decoding.

[0048] Then, after decoding, the first 32-bit data vch_x of the data block is compared with the virtual channel number vch_1, and the decoded data of the terminal station type with vch_x equal to vch_1 is filtered out.

[0049] Finally, through link frame search, the data split into each data block is restored to a complete link frame and output to the CPU.

[0050] A method for transmitting satellite-ground link data frames of a low-earth orbit satellite hopping beam includes the following steps:

[0051] Step S1, set the virtual location area code, number the multiple location areas covered by the hopping beam so that each frame of burst service frame corresponds to a unique location area;

[0052] Step S2, set the virtual channel number, number the multiple station types within the same location area to distinguish the link frames of different station type terminals;

[0053] Step S3, on the on-board base station, through the on-board baseband platform CPU, divide the high-layer data stream into different queues according to the flow direction location area and station type, each queue corresponding to the virtual location area code and the virtual channel number, and output the queue to the on-board baseband platform FPGA;

[0054] Step S4, for the data of a certain queue, the on-board baseband platform FPGA splits the link frame with a length greater than the length of the data block before coding, disperses it into multiple data blocks, and fills the first 32-bit data of each data block with the virtual channel number corresponding to this queue;

[0055] Step S5, convert the data block into a coded block according to the set code rate to complete coding;

[0056] Step S6, for each queue's coded block, first map the coded block into symbols, and then fill the virtual location area code in the frame header according to the burst service frame structure to obtain the burst fixed-length service frames of each queue, and complete the framing of all queues' burst fixed-length service frames;

[0057] Step S7, the on-board base station sequentially covers each ground terminal by means of beam hopping, the ground terminal demodulates the downlink service frame according to the current carrier rate and modulation method, and then completes the first-level location area level filtering according to the virtual location area code filled in the service frame to obtain the burst service frames under the terminal location area;

[0058] Step S8, the ground terminal decodes the coded blocks in the burst service frame to obtain data blocks;

[0059] Step S9, the ground terminal completes the second-level station type layer filtering through the virtual channel numbers filled in the decoded data blocks, obtains the link frame segments split into each data block, recombines the link frame segments into a complete link frame and outputs it.

[0060] This method is applicable to the hopping beam downlink channel. The spaceborne baseband platform covers the ground terminals located in multiple location areas by means of beam hopping, and the ground terminals perform filtering to obtain the service frames corresponding to the location areas of this terminal.

[0061] Since adjacent location areas may capture and demodulate each other to generate error codes, the modulator of the spaceborne baseband platform needs to fill the virtual location area number in the burst service frame header so that each burst service frame corresponds to a unique location area. After the ground terminal demodulator captures synchronization, it can extract the virtual location area number of the current service frame through frame positioning, compare it with the requirements of this terminal, and perform symbol-level filtering on the service frame to ensure the correctness of the data output to the subsequent decoding stage.

[0062] This method is applicable to the service transmission of multiple station type terminals in the same location area. When multiple station type terminals are located in the same location area, the virtual location area numbers corresponding to the burst service frames of each station type are the same. Therefore, virtual channel numbers are set to number the station types to distinguish the link frames of different station type terminals.

[0063] The modulator of the spaceborne baseband platform classifies the pre-coded data blocks according to the flow direction station type information, splices the virtual channel numbers in front of each coded data block, and a burst service frame contains multiple virtual channel number blocks. After the ground terminal decodes, by extracting the virtual channel number information located at the head of the data block, it filters out the data blocks corresponding to the station type of this terminal and recombines the data blocks into link frames.

[0064] This method performs frame splitting and recombination based on the virtual location area number (corresponding to the location area) and virtual channel number (corresponding to the station type) at the physical layer, has higher transmission efficiency, and reduces the processing difficulty at the modulation end of the spaceborne baseband platform.

[0065] To complete the adaptation between the fixed-length carrier blocks and the variable-length high-layer link frames, when the length of the high-layer link frame is greater than the length of the fixed-length carrier block, it is necessary to split the high-layer link frame at the modulation end and add markers for distinction, and then distribute it to multiple carrier blocks. The demodulation end extracts the link frame segments from the carrier blocks, removes the markers and completes the recombination.

[0066] This method is based on splitting and recombining link frames at the physical layer. At the modulation end, the link frame is divided into different data blocks by filling virtual location area numbers and virtual channel numbers at the physical layer. Each data block can correspond to the flow position area according to the virtual location area number and the flow station type according to the virtual channel number. At the demodulation end, the data blocks corresponding to the local location area and the local station type are filtered out through the physical layer, and the link frame is recombined.

[0067] This method has two advantages. One is that the link frame is split at the physical layer, and the lengths of the filled virtual location area numbers and virtual channel numbers are short, so it has higher transmission efficiency. The other is that the on-board baseband platform does not need to locate the link frame by searching for frames. The link layer data can be treated as a continuous data stream and distributed to different data blocks, which reduces the processing difficulty of the on-board baseband platform and is convenient for cost control.

[0068] In summary, the present invention aims at the adaptation problem between the fixed-length carrier blocks and the variable-length high-layer link frames in the downlink burst in the low-earth-orbit satellite hopping beam application. It proposes to form a high-layer data stream queue based on the location area and the station type. The data stream is frame-split at the on-board base station modulator based on the virtual location area number (corresponding to the location area) and the virtual channel number (corresponding to the station type) at the physical layer, and framed after filtering out the burst fixed-length carriers of non-local location areas and virtual channels at the ground terminal. This method can achieve high transmission efficiency and reduce the processing difficulty of the modulation end of the on-board baseband platform, and can be used in the downlink TDM carrier frame-splitting and framing design of satellite communication systems based on on-board processing.

Claims

1. A method for disassembling frames of a satellite-ground link with hopping beams for low-earth orbit satellites, characterized in that, Applied to the spaceborne base station, it includes the following steps: Step 101: Through the CPU of the spaceborne baseband platform, divide the high-layer data stream into different queues according to the flow direction location area and station type. Each queue corresponds to a virtual location area number and a virtual channel number, and output the queue to the FPGA of the spaceborne baseband platform; the virtual location area number is used to make each burst service frame correspond to a unique location area separately, and the virtual channel number is used to uniquely number different station types within the same location area; Step 102: The FPGA of the spaceborne baseband platform splits the link frame larger than the length of the data block before encoding for a certain queue of data, disperses it into multiple data blocks, and fills the first 32-bit data of each data block with the virtual channel number corresponding to this queue; Step 103: Convert the data block into an encoded block according to the set code rate to complete the encoding; Step 104: For the encoded blocks of each queue, first map the encoded blocks into symbols, and then fill the virtual location area number in the frame header according to the burst service frame structure to obtain the burst fixed-length service frames of each queue, and complete the framing of the burst fixed-length service frames of all queues.

2. A method for framing satellite-ground links of low-earth orbit satellite hopping beams, characterized in that, Applied to the ground terminal of satellite communication, it includes the following steps: Step 201: The ground terminal demodulates the downlink service frame according to the current carrier rate and modulation method, and then completes the first-level location area layer filtering according to the virtual location area number filled in the service frame to obtain the burst service frame under the location area of this terminal; the virtual location area number is used to make each burst service frame correspond to a unique location area separately; Step 202: Decode the encoded blocks in the burst service frame to obtain data blocks; Step 203: Through the virtual channel number filled in the data block after decoding, complete the second-level station type layer filtering to obtain the link frame segments split into each data block. The virtual channel number is used to uniquely number different station types within the same location area; recombine the link frame segments into a complete link frame and output it.

3. A method for transmitting satellite-ground link data frames with hopping beams for low-earth orbit satellites, characterized in that, It includes the following steps: Step S1: Set the virtual location area number, number the multiple location areas covered by the hopping beam, so that each burst service frame corresponds to a unique location area separately; Step S2: Set the virtual channel number, number the multiple station types within the same location area, and distinguish the link frames of different station type terminals; Step S3: On the spaceborne base station, through the CPU of the spaceborne baseband platform, divide the high-layer data stream into different queues according to the flow direction location area and station type. Each queue corresponds to a virtual location area number and a virtual channel number, and output the queue to the FPGA of the spaceborne baseband platform; Step S4: The FPGA of the spaceborne baseband platform splits the link frame larger than the length of the data block before encoding for a certain queue of data, disperses it into multiple data blocks, and fills the first 32-bit data of each data block with the virtual channel number corresponding to this queue; Step S5: Convert the data block into an encoded block according to the set code rate to complete the encoding; Step S6: For the encoded blocks of each queue, first map the encoded blocks into symbols, and then fill the virtual location area number in the frame header according to the burst service frame structure to obtain the burst fixed-length service frames of each queue, and complete the framing of the burst fixed-length service frames of all queues. Step S7: The spaceborne base station sequentially covers each ground terminal by means of beam hopping. The ground terminal demodulates the downlink service frame according to the current carrier rate and modulation mode, and then completes the first-level location area layer filtering based on the virtual location area code filled in the service frame to obtain the burst service frame under the location area of this terminal; Step S8: The ground terminal decodes the coding block in the burst service frame to obtain a data block; Step S9: The ground terminal completes the second-level station type layer filtering through the virtual channel number filled in the decoded data block, obtains the link frame segments split into each data block, recombines the link frame segments into a complete link frame and outputs it.

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