Satellite telemetry compression parameter negotiation method

Abstract

The application relates to a satellite telemetry compression parameter negotiation method, which comprises the following steps: a ground station sends a compression initialization request command to a satellite through a remote control uplink, the compression initialization request command contains a compression parameter proposal; the satellite receives and extracts the compression initialization request command, evaluates the on-satellite compression capability based on the compression parameter proposal, and sends a compression initialization response command to the ground station through a telemetry downlink; the ground station receives the compression initialization response command, confirms whether the satellite accepts the negotiation, and sends a compression confirmation command to the satellite when the satellite accepts the negotiation; and the satellite receives the compression confirmation command, enters a compression running state when the random number verification is correct, and sends a compression telemetry frame to the ground station. The method creatively utilizes a remote control / telemetry cross channel to construct a bidirectional negotiation channel, fills the blank of the dynamic compression parameter negotiation mechanism in the CCSDS standard system, and enables the telemetry compression to truly have an engineering on-orbit deployment capability.

Description

Technical Field

[0001] This invention relates to the field of telemetry compression technology, and in particular to a method for negotiating satellite telemetry compression parameters. Background Technology

[0002] Satellite telemetry, tracking, and command (TT&C) systems mainly consist of a telemetry (TC) uplink and a telemetry (TM) downlink. The two-way communication channel between satellite and ground typically employs an asymmetric frequency band design. The uplink can operate in the S, X, and Ka bands, while the downlink also adapts to the S, X, and Ka bands. Currently, the communication protocols and frame formats of the satellite-to-ground TT&C links follow dedicated standardized protocols. Specifically, the CCSDS232.0-B space data link protocol specification defines the frame structure and transmission protocol of the telemetry uplink, and the CCSDS132.0-B space data link protocol specification defines the frame structure and transmission protocol of the telemetry downlink.

[0003] However, the existing CCSDS telemetry and control protocol system has significant unidirectional design flaws. The uplink remote control protocol and the downlink telemetry protocol are independent of each other and perform their own functions. There is no defined application-layer interaction and negotiation mechanism across uplink and downlink channels, resulting in a lack of two-way collaborative control between satellite and ground, dynamic parameter configuration, and fault linkage repair capabilities. This makes it impossible to meet the engineering requirements for dynamically optimized telemetry compressed transmission in orbit. The specific limitations of existing satellite telemetry compressed transmission technology are as follows: First, there is a lack of a standardized on-orbit telemetry compression parameter negotiation mechanism. Currently, the core parameters for satellite telemetry compression, including compression algorithm type, quantization accuracy, and compression dictionary version, are fixed in the onboard software at the satellite's manufacturing stage and do not support dynamic adjustment and updates in orbit. The CCSDS 121.0-B data compression standard only addresses the various telemetry compression algorithms themselves and does not establish a negotiation mechanism for compression parameters between the satellite and the ground. This fixed configuration mode poses significant engineering risks. When the resolution capabilities and adaptation parameters of the ground decompression equipment do not match the onboard compression parameters, it will directly cause large-scale telemetry data decompression failures. Furthermore, this parameter adaptation failure cannot be repaired through on-orbit operations, severely impacting the reliability of telemetry data transmission.

[0004] Second, the unidirectional maintenance of the compression context results in insufficient synchronization stability and fault tolerance. Context-based incremental telemetry compression technology relies on maintaining completely consistent compression context data between the satellite and ground ends, including historical parameter caches and hierarchical mapping table versions. Context synchronization consistency is a core prerequisite for ensuring the normal decompression of continuous telemetry frames. However, satellite telemetry downlink is affected by complex space environments such as satellite-to-ground transmission distance, spatial obstruction, and space electromagnetic interference, posing a risk of frame loss. When downlink frames are lost, the compression context at the ground receiver may fail to synchronize with the onboard compression context, leading to decompression errors in subsequent telemetry frames. Furthermore, the existing technology lacks a ground-based active intervention mechanism; the ground end cannot actively trigger onboard data retransmission, context reset, or synchronization updates, resulting in a lack of self-healing capabilities.

[0005] Third, the terrestrial mobile communication compression feedback mechanism is not suitable for satellite telemetry and control scenarios. The existing 3GPP ROHC protocol (RFC 5795) has designed a compression context feedback mechanism for terrestrial mobile communication scenarios. The decompression end can send ACK, NACK, STATIC-NACK, and other feedback commands through the reverse channel to achieve dynamic updating and fault repair of the compression context. However, this protocol mechanism has limitations in scenario adaptation: First, the ROHC feedback mechanism is based on the IP protocol stack, with feedback latency in the millisecond range, while the propagation latency of satellite telemetry and control links varies greatly, ranging from several milliseconds for low-Earth orbit satellites to up to 270 milliseconds for geostationary orbit satellites. This mismatch in latency characteristics means that the ROHC feedback mechanism cannot be directly ported to satellite telemetry and control scenarios. Second, the ROHC protocol lacks a dynamic parameter negotiation process; the compression configuration file is pre-defined by both communication ends, which does not support on-orbit dynamic negotiation adaptation and cannot meet the telemetry compression optimization requirements under varying satellite operating conditions.

[0006] Fourth, the traditional remote control command system lacks a two-way confirmation mechanism. The existing CCSDS remote control standard only specifies the uplink transmission format and sending procedure for remote control commands. After the satellite executes the remote control command, there is no dedicated, standardized telemetry response feedback mechanism. The ground station can only determine the execution status of the remote control command by indirectly monitoring changes in the satellite's downlink telemetry operating parameters. For critical operations requiring high precision and high reliability, such as on-orbit changes to compressed parameters, the indirect status verification method cannot provide accurate and reliable execution confirmation, posing a risk of operational failures and abnormal parameter configurations going undetected in a timely manner. This fails to guarantee the effectiveness and security of operations such as dynamic configuration of telemetry compressed parameters.

[0007] In summary, the existing satellite CCSDS telemetry and control protocol system and telemetry compression technology have not formed a satellite-ground collaborative mechanism based on TC / TM cross-channels. They lack standardized technical solutions for on-orbit dynamic negotiation of telemetry compression parameters, real-time synchronization of compression context, and rapid recovery from transmission failures. As a result, they cannot achieve on-orbit dynamic optimization and high-reliability operation of telemetry compression transmission, which is the core technical bottleneck restricting the large-scale engineering application of high-precision and high-efficiency satellite telemetry compression transmission technology. Summary of the Invention

[0008] To address at least some of the problems mentioned above in the prior art, the present invention provides a satellite telemetry compression parameter negotiation method, comprising: The ground station sends a compression initialization request command to the satellite via remote uplink. The compression initialization request command contains a compression parameter proposal. The satellite receives and extracts the compression initialization request command, proposes to evaluate the on-board compression capability based on the compression parameters, and sends the compression initialization response command to the ground station through the telemetry downlink. The ground station receives the compression initialization response command, confirms whether the satellite accepts the negotiation, and sends a compression confirmation command to the satellite if the satellite accepts the negotiation; and The satellite receives the compression confirmation command. If the random number is verified to be correct, it enters the compression operation state and sends compressed telemetry frames to the ground station.

[0009] Furthermore, the compression parameter proposal includes multiple fields such as: protocol version number, algorithm bitmap, parameter dictionary version, context window size, B-type parameter quantization precision, minimum compression ratio; and / or The compression initialization response command includes multiple of the following fields: result code, selected compression algorithm, parameter dictionary version used, valid frame sequence number EFFECTIVE_SEQ, memory usage, CPU overhead, actual compression ratio, and random number; and / or The compression confirmation command shall include at least the following fields: random number echo and ground time.

[0010] Furthermore, based on compression parameters, an evaluation of on-board compression capabilities is proposed, including: Does the bitmap of ground-supported compression algorithm capabilities correspond to the compression algorithms on the satellite? Does the parameter dictionary version used on the ground correspond to the parameter dictionary version currently used on the satellite? Assess whether the satellite's current CPU utilization meets the requirements of the selected compression algorithm.

[0011] Furthermore, when the on-board compression capability meets the requirements, the result code = 0x00, indicating acceptance; When the result code is 0x01, it means that the algorithm is not supported; When the result code is 0x02, it indicates that the algorithm dictionary version does not match; When the result code is 0x03, it indicates insufficient computing power; When the result code is 0x04, it indicates rejection.

[0012] Furthermore, after receiving the compression confirmation command and verifying the random number, the satellite switches to compression encoding mode starting from the EFFECTIVE_SEQ frame, and the compressed telemetry frame is transmitted through the application process identifier APID=0x200.

[0013] Furthermore, it also includes: during compressed operation, the ground station continuously monitors whether the context is out of sync, and when the context is out of sync, it executes the context out-of-sync recovery process.

[0014] Furthermore, the continuity of frame sequence numbers and the consistency of Class A parameter hashes in compressed telemetry frames are detected to determine whether the context has lost synchronization; The context synchronization recovery process includes: the ground station sending a compressed resynchronization request command containing a resynchronization mode field to the satellite via remote uplink; the satellite receiving the compressed resynchronization request command and selecting a context repair response strategy based on the resynchronization mode field; the satellite sending a recovery frame to the ground station, which is transmitted with the application process identifier APID=0x202. After identification by the ground station, it is used to reconstruct the compressed context PCC. After recovery is completed, the application process identifier APID is switched back to 0x200.

[0015] Furthermore, in a multi-ground-station scenario, each ground station independently maintains its own compression context but shares the same parameter dictionary; when a ground station triggers a compression resynchronization request command, the full recovery frame sent by the satellite simultaneously updates the compression context of all authorized ground stations via telemetry multiplexing; and / or During compressed operation, the ground station sends a compression parameter update command; after receiving the compression parameter update command, the satellite updates the corresponding entries in the parameter dictionary and informs the ground station in the parameter dictionary change notification field of the next compressed telemetry frame to ensure parameter dictionary synchronization.

[0016] Furthermore, when the satellite detects an improvement in downlink channel quality, it proactively sends a capability notification packet via telemetry frames to inform the ground station of the current onboard compression capability, allowing the ground station to decide whether to initiate negotiation; and / or During the initial negotiation, the compression algorithm with the lowest compression ratio is selected. After the satellite enters a stable compression operation state and runs for several frames, the ground station automatically initiates a second negotiation, appending parameter values ​​to the compression initialization request command for compression, ultimately achieving full-function compression; and / or Negotiation is triggered immediately at the start of each overhead arc segment, and the compressed mode completes negotiation and takes effect within 30 seconds of the arc segment's arrival; and / or When the negotiation times out or the satellite returns a rejection response, if the problem is due to a mismatch in the algorithm bitmap, the ground station will automatically reduce to the minimum algorithm set supported by both parties and retry. If the problem is due to a mismatch in the parameter dictionary version, the ground station will initiate the parameter dictionary uplink injection process and then retry the negotiation.

[0017] Furthermore, a 32-bit random number is used; or Bind the random number NONCE to the ground timestamp: Use the lower 32 bits of the 48-bit timestamp as the seed for the random number NONCE, and generate the required random number through CRC-32 transformation.

[0018] The present invention has at least the following beneficial effects: The method of this invention achieves dynamic on-orbit negotiation of telemetry compression for the first time: it creatively utilizes the TC / TM cross channel to construct a two-way negotiation channel, and uses remote control frames to carry compression requests and telemetry frames to carry on-board responses to complete the negotiation, filling the gap in the dynamic negotiation mechanism of compression parameters in the CCSDS standard system, and enabling telemetry compression to truly have the capability for engineering on-orbit deployment.

[0019] The three-phase handshake of this invention ensures negotiation reliability: The negotiation process of this invention is analogous to the TCP three-way handshake. In the first phase, the ground station sends a compression initialization request command to the satellite. In the second phase, the satellite sends a compression initialization response command to the ground station. In the third phase, the ground station sends a compression confirmation command to the satellite. The three-phase handshake mechanism effectively solves the latency uncertainty problem in TC / TM asynchronous interaction, and ensures the uniqueness and correctness of the negotiation process through a random number anti-replay mechanism, avoiding confusion in the negotiation state due to command retransmission and ensuring negotiation reliability.

[0020] Rapid recovery from context synchronization failure: This invention shortens the recovery time from "waiting for the next satellite restart" to "within 2 remote / telemetry round-trip delays" based on the COMPRESS_RESYNC_REQ command and recovery frame mechanism, greatly improving the system robustness, which is especially important for low-Earth orbit satellites (single arc segment is only 8-15 minutes).

[0021] This invention supports concurrent management of multiple ground stations: the broadcast recovery mechanism solves the context consistency problem in multi-station joint telemetry and control scenarios, and provides technical support for the operation of complex telemetry and control networks.

[0022] This invention enables fine-tuning of parameters online: the COMPRESS_PARAM_UPDATE command allows operators to adjust compression strategies in real time for specific parameters, meeting the differentiated requirements for monitoring accuracy of specific parameters at different task stages (such as automatically improving the accuracy of relevant parameters when the load is started).

[0023] Low-overhead bidirectional protocol: Each negotiation command packet sent by the satellite and the ground station does not exceed 16 bytes, and has a very low overhead ratio in the standard CCSDS TC frame (maximum 248 bytes of user data), which does not affect the transmission efficiency of normal remote control commands. Attached Figure Description

[0024] To further illustrate the above and other advantages and features of the various embodiments of the present invention, a more specific description of the embodiments of the invention will be presented with reference to the accompanying drawings. It is to be understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by identical or similar reference numerals for clarity.

[0025] Figure 1 The flowchart of a satellite telemetry compressed parameter negotiation method according to the present invention is shown.

[0026] Figure 2 A schematic diagram of the compressed negotiation state machine of the present invention is shown. Detailed Implementation

[0027] It should be noted that the components in the accompanying drawings may be shown exaggerated for illustrative purposes and may not be to scale.

[0028] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0029] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0030] It should also be noted that, in the embodiments of the present invention, only a portion of the parts or components may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, the required parts or components can be added as needed for specific scenarios.

[0031] It should also be noted that within the scope of this invention, the terms "same", "equal", and "equal to" do not mean that the two values ​​are absolutely equal, but allow for a certain reasonable error. In other words, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0032] It should also be noted that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not explicitly or implicitly suggest that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] Furthermore, the embodiments of the present invention describe the process steps in a specific order. However, this is only for the convenience of distinguishing each step, and is not a limitation on the order of each step. In different embodiments of the present invention, the order of each step can be adjusted according to the process.

[0034] The technical problem this invention aims to solve is: in an asymmetric asynchronous satellite-to-ground interaction channel composed of a satellite remote control uplink and a telemetry downlink, how to achieve reliable bidirectional negotiation of telemetry compression algorithm parameters, continuous synchronous monitoring of the compression context, and rapid recovery after context synchronization loss. Specifically, it includes the following sub-problems: (1) How to design a compression negotiation command format based on remote uplink so that the ground can propose compression algorithm parameters to the satellite; (2) How to design a compressed response telemetry format based on telemetry downlink so that the satellite can send back the negotiation results to the ground (including on-board processing capacity constraints). (3) How to handle the time delay uncertainty (from several milliseconds to hundreds of milliseconds) between remote control commands and telemetry responses to ensure the correctness of the negotiation; (4) How to quickly restore a consistent compressed context using the remote control TC / telemetry TM cross channel when context synchronization loss is detected; (5) How to support context consistency management in scenarios with concurrent access from multiple ground stations.

[0035] This invention proposes a cross-channel telemetry compression parameter negotiation method (CTCNM) for satellite telemetry (TC / TM). This method achieves bidirectional interactive negotiation and continuous synchronous monitoring between satellite and ground by defining a dedicated compression control command (CCC) in the remote control frame and a dedicated compression status telemetry packet (CSTP) in the telemetry frame.

[0036] Figure 1 The flowchart of a satellite telemetry compressed parameter negotiation method according to the present invention is shown. Figure 2 A schematic diagram of the compressed negotiation state machine of the present invention is shown.

[0037] like Figure 1 As shown, a satellite telemetry compressed parameter negotiation method includes the following steps: Step 1: The ground station sends a compression initialization request command to the satellite via remote uplink. The compression initialization request command contains a compression parameter proposal.

[0038] The ground control software checks the current telemetry reception quality with the satellite, confirms that the current bit error rate (BER) is less than 10^-6 (the channel quality is good), and decides to initiate compression negotiation. It constructs a compression initialization request command (COMPRESS_INIT_REQ), encapsulates it into a CCSDS remote control space data link frame (CCSDS TC frame), and sends it to the satellite via the remote control uplink (e.g., S-band).

[0039] The fields included in the compression initialization request command are shown in the table below.

[0040] The compressed initialization request command is 12 bytes in total.

[0041] In one embodiment, the compression parameter proposal includes the following fields: protocol version number, algorithm bitmap, parameter dictionary version, context window size, B-type parameter quantization precision, and minimum compression ratio.

[0042] B_PRECISION (Class B parameter quantization precision level) is a field in the COMPRESS_INIT_REQ command, used to specify the quantization precision level (0 to 3, a total of 4 levels, corresponding to the quantization bit width of the differential residual of 4 / 8 / 16 / 32 bits) for Class B (gradually varying) telemetry parameters. The satellite uses this to assess its onboard capabilities and configure the quantizer.

[0043] This method employs "Physical Parametric Compression (PVLC)," classifying telemetry parameters into three levels based on their fluctuation characteristics (this classification aligns with the static / dynamic field concept of ROHC robust header compression in terrestrial mobile communications). Level A static parameters do not transmit values, only periodically transmitting set hash verification; Level C event parameters transmit complete values ​​only when their values ​​change; neither involves quantization. Only Level B slowly varying parameters use "differential residual + adaptive quantization bit width" encoding. Quantization accuracy is only meaningful for Level B parameters; therefore, the negotiation command includes a dedicated B_PRECISION field to limit the quantization accuracy of Level B parameters.

[0044] The following table shows the relevant information for parameters of types A, B, and C.

[0045] The quantization accuracy level (0-3) is the quantization bit width level of the differential residual of Class B parameters, as shown in the table below. The higher the level, the higher the restoration accuracy and the lower the compression rate. There are 4 levels from coarse to fine.

[0046] In one embodiment, the protocol version number PROTOCOL_VER=1, the algorithm bitmap ALG_BITMAP=0x0001 (PVLC only), the parameter dictionary version DICT_VERSION=0x0013, the context window size CTX_WIN_SIZE=10 (10-frame context window), the Class B parameter quantization precision B_PRECISION=1 (medium precision), the maximum compression ratio MIN_RATIO=70% (expected at least 70% compression ratio), and the timeout seconds TIMEOUT_SECS=30 (30-second timeout).

[0047] The ground station encapsulates the COMPRESS_INIT_REQ command into a CCSDS TC frame (Virtual Channel Identifier VCID=0, Spacecraft Identifier SCID=Satellite ID, Multiplexed Access Point Identifier MAPID=Dedicated MAP) and transmits it via the S-band uplink.

[0048] The SCID (Spacecraft Identifier) ​​is a field in the CCSDS TC frame header used to identify the target spacecraft. The on-board link layer uses the SCID to determine whether the remote control frame belongs to the satellite.

[0049] Virtual channel identifiers (VCIDs) are used to divide the same spacecraft's main channel into multiple logical virtual channels, achieving isolation between different service remote control streams. Each VCID has an independent frame counter for frame loss detection. In this scheme, VCID = 0, and virtual channel 0 is used to carry CCSDS TC frames.

[0050] The CCSDS TC frame configures the SCID spacecraft identifier to the target satellite ID, the VCID virtual channel identifier to a value of 0, and configures a dedicated MAPID multiplexed access point identifier for carrying compressed negotiation services.

[0051] Step 2: The satellite receives and extracts the compression initialization request command, proposes to evaluate the on-board compression capability based on the compression parameters, and sends a compression initialization response command to the ground station.

[0052] The satellite sends a compressed initialization response command to the ground station via the telemetry downlink.

[0053] The fields included in the compression initialization response command are shown in the table below.

[0054] The compressed initialization response command is 15 bytes in total (encapsulated in the CCSDS space packet, APID=0x201).

[0055] In one embodiment, proposing to evaluate on-board compression capabilities based on compression parameters includes: Does the bitmap of ground-supported compression algorithm capabilities correspond to the compression algorithms on the satellite? Does the parameter dictionary version used on the ground correspond to the parameter dictionary version currently used on the satellite? Assess whether the satellite's current CPU utilization meets the requirements of the selected compression algorithm.

[0056] When all of the above conditions are met, it indicates that the on-board compression capability is matched.

[0057] In one embodiment, the satellite telemetry processing unit receives and parses the CCSDS TC frame, extracting the content of the compression initialization request command COMPRESS_INIT_REQ: The algorithm bitmap ALG_BITMAP=0x0001 was detected, and the satellite supports PVLC (bit0=1), so the pass was granted. The parameter dictionary version DICT_VERSION=0x0013 was found to be consistent with the onboard parameter dictionary version, so the check was successful. Assess the current CPU utilization on the satellite: Parameter-level compression PVLC encoding is expected to occupy 3.2% (<10% threshold), pass.

[0058] Generate NONCE=0xA3F2C891 (pseudo-random number), and calculate the telemetry TM frame sequence number EFFECTIVE_SEQ for compression: current frame sequence number + 100; Construct a compression initialization response command COMPRESS_INIT_ACK (result code RESULT_CODE=0x00), encapsulate it as a CCSDS space packet (APID=0x201), and immediately send it to the ground station.

[0059] Step 3: The ground station receives the compression initialization response command, confirms whether the satellite accepts the negotiation, and sends a compression confirmation command to the satellite when the satellite accepts the negotiation.

[0060] The fields included in the compression confirmation command are shown in the table below.

[0061] The compression confirmation command is 16 bytes in total.

[0062] In one embodiment, after the ground receives the compression confirmation command COMPRESS_INIT_ACK: Verification result code: When RESULT_CODE=0x00, it indicates that the satellite has accepted the negotiation. Record the TM frame sequence number EFFECTIVE_SEQ and the random number NONCE that indicate the compression is effective; Construct a compression confirmation command COMPRESS_CONFIRM(NONCE_ECHO=0xA3F2C891), encapsulate it into a TC frame, and send it to the satellite; at the same time, initialize the local compression context PCC to the current telemetry parameter buffer value, and prepare to receive compressed frames.

[0063] In one embodiment, such as Figure 2 As shown, a compressed negotiation state machine is defined in the satellite service management software, which includes the following six states: UNCOMPRESSED: Initial state, telemetry is transmitted in full, uncompressed form; NEGOTIATING: The satellite has received the COMPRESS_INIT_REQ command and is processing it. CONFIRMING: The satellite has sent the COMPRESS_INIT_ACK command and is waiting for confirmation from the ground. COMPRESSED (Compression running state): Compression mode is running normally; DEGRADED (Degraded Operation Mode): Channel quality deteriorates, automatically reducing the compression level; RECOVERING: Context synchronization failure detected, recovery process is underway.

[0064] Step 4: The satellite receives the compression confirmation command. When the random number verification is correct, it enters the compression operation state and sends compressed telemetry frames to the ground station through the telemetry downlink.

[0065] In one embodiment, after the satellite receives the compression confirmation command COMPRESS_CONFIRM and verifies the random number, the telemetry processing unit switches to PVLC compression coding mode starting from the EFFECTIVE_SEQ frame, and the compressed telemetry frame is transmitted via APID=0x200.

[0066] In one embodiment, the negotiation can be abandoned if the negotiation times out or a rejection response is returned in step 2.

[0067] Step 5: In compressed operation mode, the ground station continuously monitors whether the context is out of step, and executes the context out of step recovery process when the context is out of step.

[0068] In one embodiment, the continuity of the frame sequence number of the compressed telemetry frame and the consistency of the Class A parameter hash are detected to determine whether the context is out of sync.

[0069] In COMPRESSED state, the ground station continuously monitors the following two indicators: (a) Frame sequence number continuity: For each compressed telemetry frame received, check if the frame sequence number is equal to the previous frame sequence number + 1. If a jump occurs (indicating frame loss), record the number of lost frames; (b) Level A parameter hash consistency: When the compressed telemetry frame carries a Level A hash, it is compared with the local cache; The ground station determines that the context has lost synchronization when any of the following conditions are met: Continuous frame loss ≥ Nmax (configurable, default Nmax=3); The hashes at level A are inconsistent; Physically unreasonable values ​​appear in the decompression output (such as temperature values ​​exceeding the sensor's range).

[0070] The context synchronization recovery process includes: the ground station sending a compressed resynchronization request command COMPRESS_RESYNC_REQ containing a resynchronization mode field to the satellite via remote uplink; the satellite receiving the compressed resynchronization request command and selecting a context repair response strategy based on the resynchronization mode field; the satellite sending a recovery frame to the ground station, which is transmitted with the application process identifier APID=0x202. After identification by the ground station, it is used to reconstruct the compressed context PCC. After recovery is completed, the application process identifier APID switches back to 0x200, which corresponds to normal compressed telemetry.

[0071] The fields included in the Compressed Resynchronization Request command are shown in the table below.

[0072] The satellite receives a compressed resynchronization request command and selects a context repair response strategy based on the resynchronization mode field: When RESYNC_MODE = 0x00: continuously send N_snapshot frames (default N_snapshot = 5) full telemetry frames (uncompressed, all parameters carry complete values) to reconstruct the ground compression context; When RESYNC_MODE = 0x01: Retransmit in compressed mode starting from LAST_GOOD_SEQ+1 frame (requires a history buffer on the satellite). When RESYNC_MODE = 0x02: Send 1 full telemetry frame (fastest recovery, suitable for emergency situations).

[0073] In one embodiment, after 3 hours, the satellite enters the Earth's shadow, its signal is blocked, and 7 compressed telemetry frames are lost consecutively. The ground detects a frame sequence number jump (current frame sequence number = N+7, while expected = N+1), determining that the context is out of synchronization. The ground sends a Compressed Resynchronization Request command COMPRESS_RESYNC_REQ (LAST_GOOD_SEQ=N,RESYNC_MODE=0x00). The satellite switches to RECOVERING state and continuously transmits 5 full telemetry TM frames (APID=0x202). The ground receives 5 full telemetry TM frames, reconstructs the compressed context PCC, and restores all 256 parameters to their confirmed values. The satellite sends a Compressed Context (PCC) reconstruction completion notification (embedded in the auxiliary field of a normal TM frame). After confirmation from the ground, the satellite returns to COMPRESSED state, and APID switches back to 0x200. The entire recovery process takes approximately 2 × T_prop (LEO approximately 0.02 seconds) from the remote control TC (compressed resynchronization request command) to the TM response (satellite sends recovery frames to ground station), and approximately 0.5 seconds for the full recovery of 5 frames, totaling less than 1 second to complete the recovery.

[0074] Optionally, in step 6, the ground station sends a compression parameter update command to the satellite to adjust the compression parameters.

[0075] In the compression operation state (COMPRESSED), the ground can send a compression parameter update command (COMPRESS_PARAM_UPDATE) at any time to dynamically adjust the compression level or quantization accuracy of specified parameters without the need for a complete renegotiation.

[0076] After receiving the compressed parameter update command, the satellite immediately updates the corresponding entries in the parameter dictionary (PLT) and informs the ground in the parameter dictionary change notification field of the next compressed telemetry frame to ensure parameter dictionary synchronization.

[0077] The fields and corresponding contents of the compression parameter update command are shown in the table below.

[0078] The COMPRESS_PARAM_UPDATE lightweight command fine-tunes the compression level or quantization precision of a single parameter. PARAM_ID specifies the parameter to be updated; NEW_LEVEL is the new fluctuation level (0=A, 1=B, 2=C), and NEW_LEVEL defines which category (A, B, or C) the parameter belongs to; NEW_PRECISION is the new quantization precision level for B-class parameters.

[0079] This parameter update does not require re-execution of the three-phase complete negotiation. After the onboard update, the ground is notified through the parameter dictionary change notification field of the next compressed frame, ensuring the synchronization of the satellite and ground dictionaries.

[0080] Multi-ground station context consistency management: In multi-ground station scenarios (such as multi-station joint telemetry and control), each ground station independently maintains its own compressed context (PCC) but shares the same parameter dictionary (PLT). When a ground station triggers the COMPRESS_RESYNC_REQ command, the full recovery frame sent by the satellite simultaneously updates the compressed context of all authorized ground stations via telemetry multicast. Specific mechanism: Each authorized ground station is assigned a unique ground station ID (GS_ID, 8 bits) after successfully completing the three-phase handshake steps 1 to 4 with the satellite. The satellite maintains the list of authorized ground stations. When any ground station triggers resynchronization, the satellite appends GS_ID=0xFF (broadcast identifier) ​​to the auxiliary field of the frame header of the recovery frame, instructing all ground stations to update the compression context. Differences in the algorithm bitmap field (ALG_BITMAP) and dictionary version between different ground stations are resolved through independent negotiation of the Compressed Initialization Request command (COMPRESS_INIT_REQ) (independent negotiation per station).

[0081] Compression parameters are updated dynamically online: In COMPRESSED state, the ground can send the COMPRESS_PARAM_UPDATE command at any time to dynamically adjust the compression level or quantization precision of specific parameters without having to re-execute the full negotiation.

[0082] The fields included in the compression parameter update command are shown in the table below.

[0083] The compression parameter update command is 8 bytes in total.

[0084] After receiving the compressed parameter update command, the satellite immediately updates the corresponding entries in the parameter dictionary and informs the ground station in the parameter dictionary change notification field of the next compressed telemetry frame to ensure parameter dictionary synchronization.

[0085] The above-mentioned satellite telemetry compressed parameter negotiation method is the basic scheme. The following section introduces the improvements and modifications compared to the basic scheme.

[0086] (1) Adaptive negotiation triggering mechanism (no ground command required): The basic scheme requires ground-based negotiation. In the improved scheme, the satellite adds autonomous negotiation triggering logic: when the satellite detects an improvement in downlink channel quality (such as the signal-to-noise ratio recovering from below the threshold to normal), the satellite actively sends a COMPRESS_CAPABILITY_ADV (Capability Advertisement) packet through a telemetry TM frame to inform the ground station of the current satellite compression capability, and the ground decides whether to initiate negotiation.

[0087] (2) Enhanced security of random number NONCE: The basic scheme uses a 32-bit random number (NONCE) to prevent replay attacks. The improved scheme binds the NONCE to a ground timestamp (using the lower 32 bits of a 48-bit timestamp as the NONCE seed, which is then transformed using CRC-32 to generate the required random number). Even if an attacker intercepts the NONCE, they cannot construct a valid replay attack without knowing the exact timestamp, thus improving negotiation security.

[0088] (3) Gradual compression negotiation: The improved solution supports phased increases in compression level: During the initial negotiation, the most conservative (lowest compression ratio) compression algorithm (e.g., only header compression) is selected. After running stably for N frames, a second negotiation is automatically initiated, adding parameter values ​​to the compression based on the first stage (step 1), ultimately achieving full-featured compression. This solution reduces the risk of negotiation failure and is suitable for the initial deployment of new compression algorithms.

[0089] (4) Optimization of negotiation timing based on the measurement and control arc segment: Considering the limited duration of each satellite overpass arc (typically 8-15 minutes for LEO satellites), negotiation can be triggered immediately at the start of the arc (after channel establishment). The compression mode should be negotiated and take effect within the first 30 seconds of the arc, maximizing the utilization of compression gain within the arc. The improved scheme adds an automated negotiation process triggered by the arc start event. In other words, negotiation occurs at the start of the overpass arc.

[0090] (5) Downgrade strategy in case of negotiation failure: When negotiation times out or the satellite returns a rejection response, the basic solution simply abandons the negotiation. The improved solution adds a degradation negotiation strategy: if the algorithm bitmap ALG_BITMAP does not match, the ground station automatically reduces to the minimum algorithm set supported by both parties and retryes; if the parameter dictionary version does not match, the ground station initiates the parameter dictionary uplink injection process and then retryes the negotiation.

[0091] The method of this invention achieves dynamic on-orbit negotiation of telemetry compression for the first time: This invention creatively utilizes the TC / TM cross channel to construct a bidirectional negotiation channel, filling the gap in the dynamic negotiation mechanism of compression parameters in the CCSDS standard system, and enabling telemetry compression to truly have the capability for engineering on-orbit deployment.

[0092] The three-phase handshake of this invention ensures the reliability of negotiation: analogous to the TCP three-way handshake, the three-phase handshake mechanism effectively solves the latency uncertainty problem in TC / TM asynchronous interaction, and ensures the uniqueness and correctness of the negotiation process through a random number anti-replay mechanism, avoiding confusion in the negotiation state due to command retransmission.

[0093] Rapid recovery from context synchronization failure: This invention shortens the recovery time from "waiting for the next satellite restart" to "within 2 remote / telemetry round-trip delays" based on the COMPRESS_RESYNC_REQ command and recovery frame mechanism, greatly improving the system robustness, which is especially important for low-Earth orbit satellites (single arc segment is only 8-15 minutes).

[0094] This invention supports concurrent management of multiple ground stations: the broadcast recovery mechanism solves the context consistency problem in multi-station joint telemetry and control scenarios, and provides technical support for the operation of complex telemetry and control networks.

[0095] This invention enables fine-tuning of parameters online: the COMPRESS_PARAM_UPDATE command allows operators to adjust compression strategies in real time for specific parameters, meeting the differentiated requirements for monitoring accuracy of specific parameters at different task stages (such as automatically improving the accuracy of relevant parameters when the load is started).

[0096] Low-overhead bidirectional protocol: Each negotiation command packet sent by the satellite and the ground station does not exceed 16 bytes, and has a very low overhead ratio in the standard CCSDS TC frame (maximum 248 bytes of user data), which does not affect the transmission efficiency of normal remote control commands.

[0097] While some embodiments of the present invention have been described in this application, those skilled in the art will understand that these embodiments are merely illustrative. Numerous variations, alternatives, and improvements will arise in those skilled in the art under the teachings of this invention without departing from its scope. The appended claims are intended to define the scope of the invention and thereby cover methods and structures within the scope of the claims themselves and their equivalents.

Claims

1. A method for negotiating compressed parameters for satellite telemetry, characterized in that, include: The ground station sends a compression initialization request command to the satellite via remote uplink. The compression initialization request command contains a compression parameter proposal. The satellite receives and extracts the compression initialization request command, proposes to evaluate the on-board compression capability based on the compression parameters, and sends the compression initialization response command to the ground station through the telemetry downlink. The ground station receives the compression initialization response command, confirms whether the satellite accepts the negotiation, and sends a compression confirmation command to the satellite when the satellite accepts the negotiation; as well as The satellite receives the compression confirmation command. If the random number is verified to be correct, it enters the compression operation state and sends compressed telemetry frames to the ground station.

2. The satellite telemetry compression parameter negotiation method according to claim 1, characterized in that, The compression parameter proposal includes multiple fields such as: protocol version number, algorithm bitmap, parameter dictionary version, context window size, B-type parameter quantization precision, minimum compression ratio; and / or The compression initialization response command includes multiple of the following fields: result code, selected compression algorithm, parameter dictionary version used, valid frame sequence number EFFECTIVE_SEQ, memory usage, CPU overhead, actual compression ratio, and random number; and / or The compression confirmation command shall include at least the following fields: random number echo and ground time.

3. The satellite telemetry compression parameter negotiation method according to claim 2, characterized in that, Based on compression parameter proposals, the on-board compression capability is evaluated, including: Does the bitmap of ground-supported compression algorithm capabilities correspond to the compression algorithms on the satellite? Does the parameter dictionary version used on the ground correspond to the parameter dictionary version currently used on the satellite? Assess whether the satellite's current CPU utilization meets the requirements of the selected compression algorithm.

4. The satellite telemetry compression parameter negotiation method according to claim 2, characterized in that, When the on-board compression capability meets the requirements, the result code is 0x00, indicating acceptance. When the result code is 0x01, it means that the algorithm is not supported; When the result code is 0x02, it indicates that the algorithm dictionary version does not match; When the result code is 0x03, it indicates insufficient computing power; When the result code is 0x04, it indicates rejection.

5. The satellite telemetry compression parameter negotiation method according to claim 2, characterized in that, After receiving the compression confirmation command and verifying the random number, the satellite telemetry processing unit switches to compression coding mode starting from the EFFECTIVE_SEQ frame. The compressed telemetry frame is transmitted through the application process identifier APID=0x200.

6. The satellite telemetry compression parameter negotiation method according to claim 1, characterized in that, Also includes: During compressed operation, the ground station continuously monitors whether the context is out of step, and executes the context out-of-step recovery process when the context is out of step.

7. The satellite telemetry compression parameter negotiation method according to claim 6, characterized in that, The continuity of frame sequence numbers and consistency of Class A parameter hashes in compressed telemetry frames are checked to determine whether the context has lost synchronization. The context synchronization recovery process includes: the ground station sending a compressed resynchronization request command containing a resynchronization mode field to the satellite via remote uplink; the satellite receiving the compressed resynchronization request command and selecting a context repair response strategy based on the resynchronization mode field; the satellite sending a recovery frame to the ground station, which is transmitted with the application process identifier APID=0x202. After identification by the ground station, it is used to reconstruct the compressed context PCC. After recovery is completed, the application process identifier APID is switched back to 0x200.

8. The satellite telemetry compression parameter negotiation method according to claim 1, characterized in that, In a multi-ground-station scenario, each ground station maintains its own compression context independently, but shares the same parameter dictionary; when a ground station triggers a compression resynchronization request command, the full recovery frame sent by the satellite updates the compression context of all authorized ground stations simultaneously through telemetry multiplex broadcast. and / or During compressed operation, the ground station sends a compression parameter update command; after receiving the compression parameter update command, the satellite updates the corresponding entries in the parameter dictionary and informs the ground station in the parameter dictionary change notification field of the next compressed telemetry frame to ensure parameter dictionary synchronization.

9. The satellite telemetry compression parameter negotiation method according to claim 1, characterized in that, When the satellite detects an improvement in downlink channel quality, it proactively sends a capability notification packet through a telemetry frame to inform the ground station of the current on-board compression capability, and the ground station decides whether to initiate negotiation. and / or During the initial negotiation, the compression algorithm with the lowest compression ratio is selected. After the satellite enters a stable compression operation state and runs for several frames, the ground station automatically initiates a second negotiation, appending parameter values ​​to the compression initialization request command for compression, ultimately achieving full-function compression; and / or Negotiation is triggered immediately at the start of each overhead arc segment, and the compressed mode completes negotiation and takes effect within 30 seconds of the arc segment's arrival; and / or When the negotiation times out or the satellite returns a rejection response, if the problem is due to a mismatch in the algorithm bitmap, the ground station will automatically reduce to the minimum algorithm set supported by both parties and retry. If the problem is due to a mismatch in the parameter dictionary version, the ground station will initiate the parameter dictionary uplink injection process and then retry the negotiation.

10. The satellite telemetry compression parameter negotiation method according to claim 1, characterized in that, Use 32-bit random numbers; or Bind the random number NONCE to the ground timestamp: Use the lower 32 bits of the 48-bit timestamp as the seed for the random number NONCE, and generate the required random number through CRC-32 transformation.

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