Deep space low signal-to-noise ratio pulse communication method and device

Abstract

The application provides a deep space low signal-to-noise ratio pulse communication method and device, and is applied to the technical field of deep space communication. The method comprises the following steps: performing low-density parity-check code (LDPC) encoding on an original information bit sequence to obtain an encoded bit sequence; performing load modulation on the encoded bit sequence by adopting a cyclic fixed interval double pulse modulation mode to obtain a plurality of cyclic fixed interval double pulse modulation symbols; taking the plurality of cyclic fixed interval double pulse modulation symbols as a load section of a sending frame signal; constructing the sending frame signal according to the load section, a preset frame header section and a preset pilot section; performing differential power configuration on the frame header section, the pilot section and the load section of the sending frame signal to generate a wireless radio frequency frame signal; and sending the wireless radio frequency frame signal to a ground tracking station. The method realizes high-reliability and low-power-consumption pulse communication from a deep space probe to the ground tracking station under the condition of extremely low signal-to-noise ratio.

Description

Technical Field

[0001] This application relates to the field of deep space communication technology, and in particular to a method and apparatus for low signal-to-noise ratio pulse communication in deep space. Background Technology

[0002] Extreme deep space communication is primarily used for lunar and beyond exploration missions, Mars and asteroid missions, exoplanet exploration, and deep space scientific data transmission. Compared to near-Earth links, deep space links are characterized by longer propagation distances, greater free-space path loss, lower received signal power, limited average transmit power, longer propagation delays, and significant dynamic changes in the link. As mission distance increases, the signal energy available to the receiver decreases significantly. Simultaneously, spacecraft platforms are constrained by payload size, pointing accuracy, thermal control conditions, and power budgets. Therefore, a physical layer transmission system with high energy efficiency, strong synchronization protection, and the ability to fully utilize soft decoding gain is required.

[0003] Pulse position modulation (PPM) technology is suitable for low signal-to-noise ratio (SNR) conditions because it concentrates energy within a limited time slot, and can be used to improve the energy efficiency of deep space communication. However, in ultra-low SNR environments, traditional PPM methods are prone to frame synchronization failures or severe data distortion at the receiver (such as ground control stations), resulting in an error rate and retransmission cost that cannot meet the reliability requirements of ultra-long-range deep space links.

[0004] Therefore, how to further reduce the whole-frame decoding error rate in ultra-low signal-to-noise ratio environments while maintaining extremely low transmission power, and ensure efficient and reliable data transmission, is a huge challenge facing the field of deep space pulse communication. Summary of the Invention

[0005] This application provides a method and apparatus for low signal-to-noise ratio (SNR) pulse communication in deep space. The method involves LDPC encoding of the original information bit sequence and load modulation of the encoded bit sequence using cyclic fixed-interval double-pulse modulation (CCP). Multiple CCP symbols are used as the payload segment of the transmitted frame signal. A complete frame signal is constructed by combining these with a preset frame header and pilot band. Differential power configurations are applied to the frame header, pilot, and payload segments to generate a wireless radio frequency frame signal for transmission to a ground control station. This method effectively combines the strong error correction capability of LDPC encoding with the advantages of high pulse position resolution and concentrated power utilization in low SNR environments using CCP. Furthermore, by prioritizing the allocation of limited transmission power to the frame header and pilot bands carrying critical synchronization information through differentiated power configuration, it maximizes the transmission efficiency and anti-interference capability of the payload segment in long-distance fading channels in deep space while ensuring frame synchronization and channel estimation reliability. This achieves highly reliable, low-power pulse communication between deep space probes and ground control stations under extremely low SNR conditions.

[0006] This application provides a method for low signal-to-noise ratio pulse communication in deep space, applied to deep space probes, including: The original information bit sequence is encoded using low-density parity-check code (LDPC) to obtain the encoded bit sequence. The encoded bit sequence is subjected to payload modulation using a cyclic fixed interval double pulse modulation method to obtain multiple cyclic fixed interval double pulse modulation symbols, and these multiple cyclic fixed interval double pulse modulation symbols are used as the payload segments of the transmitted frame signal. Based on the payload segment, the preset frame header segment, and the preset pilot segment, a transmission frame signal is constructed; the frame header segment, pilot segment, and payload segment of the transmission frame signal are configured with differentiated power to generate a wireless radio frequency frame signal; The wireless radio frequency frame signal is sent to the ground telemetry and control station.

[0007] Another embodiment of this application provides a method for low signal-to-noise ratio pulse communication in deep space, applied to a ground tracking and control station, including: The system receives radio frequency frame signals transmitted by a deep space probe. These radio frequency frame signals are generated by the deep space probe through differentiated power configuration of the frame header, pilot band, and payload segment of the transmitted frame signal. The payload segment includes multiple cyclic fixed-interval double-pulse modulation symbols, which are obtained by encoding the original information bit sequence using low-density parity-check (LDPC) coding to obtain an encoded bit sequence, and then modulating the encoded bit sequence using cyclic fixed-interval double-pulse modulation. The wireless radio frequency frame signal is demodulated to generate the full-frame payload soft information input vector corresponding to the plurality of cyclic fixed interval double pulse modulation symbols; The full-frame payload soft information input vector is input into a low-density parity-check code (LDPC) decoder to recover the original information bit sequence.

[0008] This application also provides a low signal-to-noise ratio pulse communication device for deep space, the device comprising a deep space probe and a ground control station, including: The deep space probe is used to implement the low signal-to-noise ratio pulse communication method for deep space provided in the above embodiments; The ground control station is used to implement the low signal-to-noise ratio pulse communication method for deep space provided in another embodiment above.

[0009] This application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the deep space low signal-to-noise ratio pulse communication method as described above.

[0010] This application also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the deep space low signal-to-noise ratio pulse communication method as described above.

[0011] This application also provides a computer program product, including a computer program that, when executed by a processor, implements any of the above-described methods for low signal-to-noise ratio pulse communication in deep space.

[0012] The method and apparatus for deep space low signal-to-noise ratio pulse communication provided in this application embodiment encodes the original information bit sequence using LDPC and modulates the encoded bit sequence using cyclic fixed-interval double-pulse modulation. Multiple cyclic fixed-interval double-pulse modulation symbols are used as the payload segment of the transmitted frame signal. A complete frame signal is constructed by combining a preset frame header segment and pilot segment. Differential power configurations are applied to the frame header segment, pilot segment, and payload segment to generate a wireless radio frequency frame signal for transmission to the ground control station. This method fully combines the strong error correction capability of LDPC encoding with the advantages of high pulse position resolution and concentrated power utilization of cyclic fixed-interval double-pulse modulation in low signal-to-noise ratio environments. Simultaneously, through differentiated power configuration, limited transmission power is preferentially allocated to the frame header segment and pilot segment carrying critical synchronization information. While ensuring frame synchronization and channel estimation reliability, this maximizes the transmission efficiency and anti-interference capability of the payload segment in the ultra-long-distance fading channel of deep space, thereby achieving highly reliable, low-power pulse communication from deep space probes to ground control stations under extremely low signal-to-noise ratio conditions. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a flowchart illustrating the low signal-to-noise ratio pulse communication method for deep space provided in an embodiment of this application; Figure 2 This is a schematic diagram of the frame structure of the transmitted frame signal provided in an embodiment of this application; Figure 3 This is a flowchart illustrating a low signal-to-noise ratio pulse communication method for deep space provided in another embodiment of this application; Figure 4 This is a schematic diagram illustrating an application scenario of the low signal-to-noise ratio pulse communication method for deep space provided in the embodiments of this application; Figure 5This is a comparison chart of the bit error rates of the three pulse position modulation methods provided in the embodiments of this application; Figure 6 This is a performance comparison chart of the low signal-to-noise ratio pulse communication method for deep space provided in the embodiments of this application at two low signal-to-noise ratios: 2dB and 4dB. Figure 7 This is a schematic diagram of the structure of a low signal-to-noise ratio pulse communication device for deep space provided in an embodiment of this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] To better understand the embodiments of this application, the prior art will first be described in detail: Existing technologies, including Pulse Position Modulation (PPM), Multi-Pulse Position Modulation (MPPM), Extended Pulse Position Modulation (XPPM), and PPM mechanisms combined with error correction coding, can all be used to improve the energy efficiency of deep space communication. However, in the extremely harsh deep space channel environment, the above mechanisms all suffer from insurmountable physical layer bottlenecks and also have the following drawbacks: Disadvantage 1: Under conditions of long-distance propagation and limited average power, the time slot correlation metric at the receiver is easily affected by noise interference, and the receiver makes a hard decision based solely on the energy of a single time slot. This crude energy comparison method leads to inaccurate state decisions, severe distortion of the soft information sent to the back-end decoder, and ultimately a sharp deterioration in the performance of the entire frame communication link.

[0017] Disadvantage 2: Although ordinary MPPM expands the symbol set through multiple active time slots, there may be overlap in active time slots between candidate states. If the receiver still uses the traditional simple energy summation or hard decision method, its processing logic essentially treats each time slot in isolation. In this case, the "physical confusion relationship" between states caused by time slot overlap cannot be extracted and quantized, let alone passed to the back-end low-density parity-check (LDPC) decoder. This causes the bit soft information input to the decoder to lose the prior knowledge of the physical layer modulation structure, further reducing the reliability of the bit soft information.

[0018] Disadvantage 3: To transmit more and faster data, traditional XPPM allows for many different pulse arrangements within a single frame, further expanding the state set to accommodate more flexible rate control. However, under conditions of extremely low signal-to-noise ratio and complex deep-space channel reception mismatch, the large state set actually introduces a higher dimensionality for search and decision-making. During demodulation, the receiver, lacking accurate channel state estimation and state penalty coordination, is prone to synchronization instability and header parameter recovery failure. Furthermore, the blurred boundaries between large state sets directly lead to a significant decrease in payload decoding performance.

[0019] Disadvantage 4: The PPM mechanism combining error correction coding, due to its equal protection of the synchronization header, parameter header, and payload in the physical layer frame structure, is prone to the phenomenon of "frame header being decoded incorrectly first" in ultra-low signal-to-noise ratio environments, resulting in the inability to unpack the entire frame payload. In addition, because the soft information construction of the payload is not improved, the quality of the soft information sent to the back-end error correction decoder is poor, which cannot fully release the iterative decoding gain of the LDPC long code and cannot fundamentally reverse the deadlock of high overall frame decoding error rate and low link reliability.

[0020] To address the aforementioned technical problems and shortcomings, this application provides a method for deep-space low signal-to-noise ratio pulse communication. This method is executed collaboratively by a deep-space probe and a ground-based tracking and control station across multiple layers. By introducing a cyclic fixed-interval dual-pulse modulation structure, optimizing the state bit mapping relationship, and using asymmetric power configuration with time-domain physical amplitude differences in the deep-space probe, the noise immunity gain of key control surfaces is forcibly increased. Furthermore, a global gain lower limit is protected by cascading large-sample convergence noise-avoidance pilot amplitude estimation at the ground-based tracking and control station. A symbol-level state-aware metric is constructed by fusing five-dimensional physical features such as normalized residuals and pulse balance. Simultaneously, a neighboring state correction penalty term based on symbol distance is introduced to construct a bit-level high-fidelity soft likelihood stream, thereby maximizing the release of the iterative decoding and error correction gain of the backend LDPC long code. This achieves highly reliable and low-power pulse communication data unpacking in harsh deep-space environments with ultra-low signal-to-noise ratios.

[0021] It should be noted that the execution entity involved in the embodiments of this application can be a deep space low signal-to-noise ratio pulse communication device, or an independently deployed deep space probe or a ground tracking and control station. The embodiments of this application will elaborate on the method flow using a deep space probe as the transmitting end and a ground tracking and control station as the receiving end.

[0022] Those skilled in the art should understand that the transmitting end involved in the embodiments of this application includes, but is not limited to, deep space probes, deep space spacecraft, orbiters, rovers (such as Mars rovers / lunar rovers), artificial satellites, space stations, space exploration airships, or ground tracking and control stations and ground launch centers that act as the main launch entity in the reverse control link. Correspondingly, the receiving end includes, but is not limited to, ground tracking and control stations, ground receiving antenna arrays, ocean-going tracking ships, airborne tracking and control aircraft, or relay satellites, orbiters, lunar / Mars surface base stations, space stations, and landers that act as relay receivers in deep space cross-node communication. Any equivalent transformation of the executing entity based on the inventive concept of this application, whether applied to the forward data transmission link or the reverse control command link, should be included within the scope of protection of this application.

[0023] The following section uses a deep space probe as an example to illustrate in detail the low signal-to-noise ratio pulse communication method for deep space provided in the embodiments of this application: Figure 1 This is a schematic flowchart of a low signal-to-noise ratio pulse communication method for deep space provided in an embodiment of this application. Figure 1 As shown, this method is applied to deep space probes and includes the following steps 101-104.

[0024] Step 101: Encode the original information bit sequence using low-density parity-check code (LDPC) to obtain the encoded bit sequence.

[0025] The raw information bit sequence refers to the uncoded binary source data sequence to be transmitted. This raw information bit sequence contains telemetry data, scientific images, control commands, or operational data such as voice and video from deep space exploration missions.

[0026] Optionally, the original information bit sequence is represented as a sequence of length . binary column vector ,in Indicates the length of the information block. It is an integer greater than 1.

[0027] Low-Density Parity-Check (LDPC) codes are linear block codes with sparse parity-check matrices.

[0028] In this embodiment, the deep space probe first acquires the raw, uncoded information bit sequence to be transmitted. Meanwhile, deep space probes pre-set key technical parameters for LDPC coding, such as setting the information block length. Original information bit sequence The range of values ​​of satisfies , ; Calculate and determine the code rate based on the information block length and codeword length. Next, the deep space probe uses LDPC encoding to process the original information bit sequence. Channel coding is performed, a step that utilizes linear block codes defined by the LDPC parity-check matrix H. The specific mapping process is as follows: the deep space probe runs a pre-defined LDPC coding algorithm. Through the verification matrix The relevant algorithms will allow the deep space probe to reach a length of The original information bit sequence Mapped to a length of Encoded bit sequence Among them, the encoded bit sequence The range of values ​​satisfies During the mapping process, the deep space probe adds sparse error correction redundancy to the encoded output to ensure the final generated encoded bit sequence. To ensure that the original information is fully contained and strictly conforms to the LDPC parity check requirements, the deep space probe verifies the following mathematical relationship to ensure that each line of the parity check equation is an even parity: .

[0029] The encoding process employed in this step enhances the noise tolerance of the iterative decoder and improves decoding reliability under low signal-to-noise ratio conditions. Simultaneously, the deep space probe adds sparse error correction redundancy to the encoded output, providing reliable input for subsequent cyclic fixed-interval dual-pulse modulation and soft-decision processing under low signal-to-noise ratio conditions, and creating conditions for fully releasing the gain of LDPC iterative decoding.

[0030] Step 102: The encoded bit sequence is modulated with payload using a cyclic fixed interval double pulse modulation method to obtain multiple cyclic fixed interval double pulse modulation symbols, which are then used as the payload segments of the transmitted frame signal.

[0031] Among them, the cyclic fixed interval double pulse modulation method is a variant of PPM. Within a modulation symbol period (or time slot window), information is carried by the position of two pulses, and the time slot interval between the two pulses is fixed. When the first pulse moves backward and causes the second pulse to go beyond the boundary, the second pulse will cycle back to the beginning position of the modulation symbol period.

[0032] In this embodiment, the deep space probe modulates the obtained coded bit sequence using a cyclic fixed-interval double-pulse modulation method, transforming the entire coded bit sequence into a signal stream composed of multiple cyclic fixed-interval double-pulse modulation symbols concatenated. The deep space probe then encapsulates these modulation symbol sequences into the payload segment of the transmitted frame signal. This step, through cyclic fixed-interval double-pulse modulation, simplifies pulse generation and synchronization complexity while utilizing a cyclic boundary mechanism to extend the legal symbol states within a finite time slot, thereby providing optimal payload signal input for subsequent high-reliability soft-decision and LDPC iterative decoding under low signal-to-noise ratio conditions.

[0033] Step 103: Construct a transmission frame signal based on the payload segment, the preset frame header segment, and the preset pilot segment; perform differentiated power configuration on the frame header segment, pilot segment, and payload segment of the transmission frame signal to generate a wireless radio frequency frame signal.

[0034] Among them, the preset frame header segment refers to a specific signal segment that is pre-set and fixed for frame synchronization and frame attribute indication.

[0035] Optionally, the preset frame header segment includes a preamble, a synchronization header, and a parameter header.

[0036] Preset pilot bands refer to known reference signal segments that are pre-defined and inserted into the frame structure.

[0037] Transmitting a frame signal refers to a complete baseband signal frame that is spliced ​​and assembled from a preset frame header segment, a preset pilot segment, and a payload segment according to a specific time-domain or spatial-domain structure.

[0038] For example, Figure 2 This is a schematic diagram of the frame structure of the transmitted frame signal provided in an embodiment of this application. From Figure 2 As can be seen, the transmitted frame signal also includes pre-protection, tail sequence, and post-protection. The complete transmitted frame signal includes a pre-protection interval, preamble, synchronization header, parameter header, pilot band, load segment, tail sequence, and post-protection interval. Each signal segment can be symbolically represented as follows: ;in, Indicates the transmission of a frame signal; and These represent the front protection interval and the rear protection interval, respectively. They employ zero signal or low-amplitude isolation signal to separate adjacent frames and provide time margin for synchronous searching by ground control stations. The durations of the front protection interval and the rear protection interval are respectively... and The lengths of the front protection interval and the rear protection interval are respectively and ; The preamble is used for coarse synchronization of ground telemetry and control stations. The preamble duration is... The length of the leader is ; This represents the synchronization header, used for fine synchronization and symbol boundary confirmation. The duration of the synchronization header is... The length of the synchronization head is ; The parameter header is used to transmit modulation, coding, and frame structure parameters. Ground control stations recover the data through repeated transmission, majority decision, and CRC check. The parameter header duration is [duration missing]. The length of the parameter header is ; This indicates the pilot band, used by ground control stations for amplitude reference estimation. The duration of the pilot band is... The length of the pilot band is ; This represents the load segment, used to carry the cyclic fixed-interval double-pulse modulation symbols generated in step 102. The duration of the load segment is... The length of the load section is ; The tail sequence is used to assist in frame end acknowledgment and receive buffering; the duration of the tail sequence is... The length of the tail sequence is After the above-mentioned transmission of frame signals This enables ground control stations to sequentially complete synchronization, parameter recovery, payload demodulation, and LDPC decoding according to predetermined boundaries. (Full frame duration) The duration of each signal segment can be symbolically represented as: .

[0039] Differential power configuration refers to allocating different transmit powers based on the different transmission reliability requirements of different signal segments within the transmitted frame signal.

[0040] In this embodiment, the frame construction module inside the deep space probe physically combines the three signal segments. The deep space probe reads a preset frame structure definition, first placing a preset frame header segment for synchronization with the ground control station, then inserting a preset pilot segment at a designated position, and finally splicing in the payload segment generated in step 102. Through the above pipelined assembly in the time or frequency domain, the deep space probe successfully constructs a structurally complete transmission frame signal at the digital baseband level. Subsequently, the deep space probe adjusts the gain of the transmission frame signal at different time periods according to a preset power allocation strategy. For the frame header segment and pilot segment, the deep space probe increases the input gain of the digital-to-analog converter or the gain of the RF amplifier to give the frame header segment and pilot segment higher transmit power, thereby enhancing noise immunity and anti-fading capability. For the payload segment, the deep space probe maintains the power of the payload segment at the expected standard level to meet the overall power consumption or peak-to-average power ratio requirements of the system. Finally, after completing the differentiated power configuration, the deep space probe sends the baseband frame signal, which has been assembled with the payload segment and frame header segment, to the radio frequency front end. Through the digital-to-analog converter, the deep space probe converts the digital signal into an analog baseband signal. Subsequently, the deep space probe modulates the low-frequency analog baseband signal onto a high-frequency wireless radio frequency carrier, converting it into a wireless radio frequency frame signal suitable for long-distance transmission in space.

[0041] This step, by assembling the transmitted frame signal and configuring its power differently, significantly enhances the reliability of noise-resistant transmission in low signal-to-noise ratio environments while ensuring efficient synchronization and channel estimation at ground telemetry and control stations, and also balances system power consumption.

[0042] Step 104: Send the wireless radio frequency frame signal to the ground telemetry and control station.

[0043] In this embodiment, the deep space probe amplifies the radio frequency frame signal using a solid-state power amplifier or a traveling wave tube amplifier to overcome free-space propagation loss. Subsequently, the deep space probe uses an attitude tracking system or a directional antenna drive mechanism to precisely align the main lobe of the transmitting antenna with the receiving antenna of the ground control station to maximize antenna gain. Finally, the deep space probe transmits the amplified radio frequency frame signal to the transmitting antenna via a feed line, converting it into electromagnetic waves that radiate to the ground control station. Because the radio frequency frame signal employs the aforementioned LDPC encoding and cyclic fixed-interval dual-pulse modulation, even under harsh conditions where long-distance transmission results in extremely low signal-to-noise ratios upon arrival at the ground control station, the iterative decoder and soft-decision system of the ground control station can still reliably recover the original information bit sequence.

[0044] In this embodiment, the technical solution described in steps 101-104 above involves LDPC encoding the original information bit sequence and using cyclic fixed-interval double-pulse modulation to modulate the encoded bit sequence as payload. Multiple cyclic fixed-interval double-pulse modulation symbols are used as payload segments of the transmitted frame signal. A complete frame signal is constructed by combining a preset frame header segment and pilot segment. Differential power configurations are applied to the frame header segment, pilot segment, and payload segment to generate a wireless radio frequency frame signal for transmission to the ground control station. This method fully combines the strong error correction capability of LDPC encoding with the advantages of high pulse position resolution and concentrated power utilization of cyclic fixed-interval double-pulse modulation in low signal-to-noise ratio environments. Simultaneously, through differentiated power configuration, limited transmission power is preferentially allocated to the frame header segment and pilot segment carrying critical synchronization information. While ensuring frame synchronization and channel estimation reliability, this maximizes the transmission efficiency and anti-interference capability of the payload segment in deep-space ultra-long-distance fading channels, thereby achieving highly reliable, low-power pulse communication between deep-space probes and ground control stations under extremely low signal-to-noise ratio conditions.

[0045] In some embodiments, the step of the deep space probe using cyclic fixed-interval double-pulse modulation to modulate the coded bit sequence to obtain multiple cyclic fixed-interval double-pulse modulation symbols may include: the deep space probe modulating the coded bit sequence according to a preset number of bits. Divide the bits into groups to obtain multiple bit groups. , , The total number of time slots within a cyclic fixed-interval double-pulse modulation symbol, and Powers of 2 It is a positive integer; the deep space probe is based on a preset state bit mapping relationship. , each bit group Mapped to a candidate load state ,in, , , For the set of candidate load states, , The deep space probe determines the state of each candidate payload based on a cyclic fixed-interval dual-pulse modulation structure. Dual-pulse activation time slot set ,in, , To fix the double-pulse time slot interval, This represents the modulo operation, and the set of dual-pulse activation time slots. Includes two time slot indices to indicate where the pulse is placed; based on the state of each candidate payload. The corresponding set of dual-pulse activation time slots This generates the corresponding cyclic fixed-interval double-pulse modulation symbol.

[0046] Among them, the preset number of bits This refers to the number of coded bits that can be carried by each cyclic fixed-interval double-pulse modulation symbol.

[0047] Candidate payload status This refers to the discrete modulation state index represented by the combination of double pulse positions within one modulation symbol period. All valid candidate payload states constitute a unified candidate payload state set. .

[0048] Preset state bit mapping relationship It refers to the mathematical labeling relationship used to map discrete binary bit combinations to the modulation state of symbols in a one-to-one correspondence.

[0049] For example, a preset state bit mapping relationship The definition of is: That is, through mapping relationships The first Candidate payload states corresponding to a fixed-interval double-pulse modulation symbol in a cycle With length bit group Mutual mapping is performed to achieve symbol-level modulation.

[0050] Cyclic fixed-interval dual-pulse modulation structure refers to a structure containing Within a symbol period of a time slot, the physical waveform structure of a state is indicated by the combined pulses of two active time slots. The first active time slot is located in the candidate load state. The index value corresponds to the time slot; the position of the second activation pulse is limited by the fixed double-pulse time slot interval. By analyzing the total number of time slots The state space is determined by performing a cyclic modulo operation, thereby limiting the unordered expansion of the state space.

[0051] For example, the deep space probe obtains the length generated in the aforementioned steps. Encoded bit sequence Encoded bit sequence It can be represented as Deep space probes are based on the formula Calculate the number of bits carried by each cyclic fixed-interval double-pulse modulation symbol. and with that number of bits The step size pairs the encoded bit sequence Perform equal-length cutting to obtain Individual bit groups ,in, Bit group It can be represented as: ,in, For each bit group For example, when hour, It can be represented as a set of binary data [0,1,1]. If the length N of the encoded bits is not divisible by q, then padding bits known from the ground control station are appended to the end of the encoded bit sequence so that the length after padding is divisible by q. The ground control station removes the padding bits when forming the input or output information bits for LDPC decoding.

[0052] Subsequently, the deep space probe invoked the preset state bit mapping relationship. The reverse mapping process involves matching the current bit group data with the standard bit labels to determine the optimal bit group. Corresponding candidate load state For example, when At that time, the total number of candidate load states (i.e., the total number of time slots) satisfies At this point, the candidate load state set It can be represented as Preset state bit mapping relationship Given a mapping table containing 8 sets of mapping relationships, the deep space probe obtains the current bit set. Then, by searching the preset mapping table, the bit group was found. The unique corresponding candidate payload state index is 3. The current candidate payload state determined by the deep space probe through inverse mapping satisfies... .

[0053] Understandable, Indicates by the first Bit groups The mapping obtained by the first The candidate load state, which is also the first The state corresponding to a fixed-interval double-pulse modulation symbol in a cycle.

[0054] Determining the state of candidate loads Subsequently, the deep space probe calculated the state of the candidate payload according to the standard time slot numbering method starting from zero. The set of double-pulse activation time slots corresponding to the symbol period This dual-pulse activation time slot set Represented as: This set of activation slots The specified number The two active time slots within a cyclic fixed-interval double-pulse modulation symbol are numbered. Assume the preset fixed double-pulse time slot interval satisfies... Then the deep space probe invokes the activation time slot calculation formula ,Will , and Substituting into the above formula, we obtain the first activation slot as follows: The second activation slot is At this point, the deep space probe calculates the set of double-pulse activation time slots corresponding to the candidate payload state within the current symbol period as follows: This dual-pulse activation time slot set It precisely specifies that within the current symbol period containing 8 time slots, the deep space probe should illuminate and place pulse signals at the two physical locations of time slot 3 and time slot 6.

[0055] To convert discrete activation time slots into radio frequency signals that can be transmitted through physical channels, the deep space probe further performs the following operations: The deep space probe, based on the set of dual-pulse activation time slots... Construct a length of Discrete binary state template Binary state template Represented as: ,in, Binary state template The time slot represents the activation pulse, a binary state template. The time slot represents the inactive pulse.

[0056] Finally, the deep space probe maps discrete activation time slots to actual transmitted pulses, synthesizing the first pulse in the continuous time domain. Continuous-time transmission waveform of a cyclic fixed-interval double-pulse modulation symbol Continuous time transmission waveform Represented as: ,in, For load power, For unit pulse template, For time slot width, For symbol width, In this physical synthesis process, the deep space probe introduces a preset payload power control waveform amplitude, extracts a preset unit pulse template, and combines the time slot width and symbol width for time delay superposition, finally outputting a continuous-time transmission waveform as a high-reliability payload segment for transmitting frame signals.

[0057] In some embodiments, the deep space probe follows a preset state-to-bit tag mapping relationship. The steps may include: the deep space detector calculates the cyclic distance between any two candidate payload states based on the proximity of their corresponding cyclic timing indices; the deep space detector calculates the activation slot difference between two candidate payload states based on the symmetric difference set of the activation slot sets corresponding to the candidate payload states of any two bit groups; the deep space detector constructs the state weights for each pair of candidate payload states by using an exponential and linear weighted combination of the cyclic distance and the activation slot difference; the deep space detector constructs an objective function for the state-bit mapping relationship based on the expected tag distance, Hamming distance, and state weights for each pair of candidate payload states; and the deep space detector performs an iterative minimization solution to the objective function to obtain the optimal state-bit mapping relationship.

[0058] The cyclic timing sequence number refers to the sequential number of each candidate load state within a modulation symbol period. Since the modulation structure has cyclic boundary characteristics, the cyclic timing sequence number is regarded as a cyclic sequence with the beginning and end connected (that is, the next timing sequence number of slot M-1 cycles back to slot 0).

[0059] Cycle distance refers to the shortest cycle step on the time axis between two candidate load states, taking into account the symbol period cycle boundary.

[0060] Activation slot difference refers to the physical measure of the degree to which the activation slot sets corresponding to two different candidate payload states do not overlap.

[0061] The expected tag distance is a target Hamming distance preset based on the physical proximity between candidate payload states, used to specify the expected distance that a pair of states should reach in the bit tag space.

[0062] Hamming distance refers to the number of different characters at corresponding positions between two equal-length binary bit sequences, and is used to measure the distinguishability of bit tags.

[0063] In this embodiment of the application, the deep space probe traverses the candidate payload state set. For all state pairs in the dataset, calculate the state of any two candidate loads. and candidate payload state The degree of proximity at the temporal and physical waveform levels, among which, The deep space probe calculates the candidate payload states based on the cyclic time slot sequence number of each candidate payload state within the modulation symbol period. and candidate payload state Shortest cycle distance , cycle distance The calculation formula is: This cyclic distance is used to evaluate the proximity of candidate states in the cyclic time slot arrangement. The smaller the value, the closer the two candidate load states are in the cyclic structure, and the easier it is for them to be physically confused at the ground control station due to noise, timing deviation or pulse leakage.

[0064] Next, the deep space probe extracts the state of candidate payloads. The corresponding first double-pulse activation time slot set and candidate payload state The corresponding second double-pulse activation time slot set The candidate load state is determined by calculating the number of elements in the symmetric difference between these two sets. and candidate payload state activation slot difference The difference in activation time slots The calculation formula is: ,in, Let |·| represent the symmetric difference of the sets, and |·| represent the number of elements in the sets. This activation slot difference is... The larger the value, the more obvious the difference in the position of the two pulses corresponding to the two candidate load states, and the easier it is for the ground telemetry and control station to distinguish them.

[0065] Subsequently, the deep space probe uses an exponential and linear weighted combination of the aforementioned cycle distance and activation time slot differences to construct state weights for each pair of candidate payload states, representing the overall similarity and confusion probability. The state weight The calculation formula is: The first exponential term gives higher weights to states that are close in cyclic distance, in order to focus on easily confused neighboring states; the second linear term is used to preserve the impact of activation slot differences on the mapping design.

[0066] To decouple and map the easily confused state features at the physical layer to a highly distinguishable binary bit label space, an objective function is constructed to optimize the state-bit mapping relationship. ,in, This represents the Hamming distance between state pairs. Indicates the candidate load state The corresponding bit group Indicates the candidate load state The corresponding bit set, Hamming distance The calculation formula is: ,in Indicates the candidate load state The first bit of the corresponding bit group Bits; Indicates the candidate load state and candidate payload state The expected label distance between them The calculation formula is: The desired target label distance is used to specify the Hamming distance that a particular state pair is expected to achieve in the bit label space, such that the more physically confused the state pairs (i.e., the closer their cyclic distances), the smaller their desired label Hamming distances.

[0067] Finally, the deep space probe obtains the optimal state bit mapping relationship by executing a preset iterative optimization algorithm (such as full permutation search, heuristic search, or genetic algorithm; in this embodiment, a full permutation search with fixed first labels can be used). The deep space probe performs a minimization iterative solution within the full permutation mapping space of states to bit tags. During the iterative optimization process, the deep space probe calculates the global weighted error value under the current mapping relationship in real time. When the weighted error value converges to a preset threshold range, or when the number of iterations reaches a preset termination condition, the deep space probe stops searching and obtains the state-bit mapping relationship that makes the overall weighted error value of the above objective function globally optimal. .

[0068] In subsequent step 102, the deep space probe directly invokes the optimally designed state bit mapping relationship. This allows physically confusing states to maintain a controlled distance in the bit tag space, thereby improving the soft decision quality of ground telemetry and control stations and comprehensively enhancing the reliability of LDPC decoding under low signal-to-noise ratio conditions.

[0069] It should be noted that the above optimal state bit mapping relationship The construction process not only optimizes the symbol mapping structure of the signal source in the deep space probe, but also forms a strongly coupled collaborative protection with the state perception and error correction decoding of the ground control station. Through this optimization process, physically easily confused states can maintain a controlled distance in the bit tag space, thereby improving the soft decision quality of the ground control station and enhancing the reliability of LDPC decoding under low signal-to-noise ratio conditions.

[0070] In some embodiments, the step of generating a radio frequency frame signal by performing differentiated power configuration on the frame header, pilot, and payload segments of the transmitted frame signal by the deep space probe may include: the deep space probe performing asymmetric linear scaling on the frame header, pilot, and payload segments of the transmitted frame signal respectively using a preset power configuration coefficient according to the average power upper limit constraint, so as to generate a radio frequency frame signal, and the average power of the entire frame of the radio frequency frame signal meets the average power upper limit constraint.

[0071] The average power upper limit constraint refers to the maximum allowable average transmit power per frame in a deep space communication link, expressed as: This average power upper limit constraint This is used to improve the ability to acquire weak signals while strictly controlling the overall power consumption, heat dissipation, and nonlinear distortion of the amplifier of the deep space probe, ensuring that the transmission power of the entire frame does not exceed the average power limit of the space link.

[0072] The preset power configuration factor refers to the normalized weighting factor used to amplify or scale the power of different functional segments in the transmitted frame signal. The preset power configuration factor includes the frame header power configuration factor. Pilot power configuration factor and load power configuration factor These three coefficients work together to affect the reference power. This enables asymmetric linear gain adjustment in the time domain for different signal segments.

[0073] In this embodiment of the application, the deep space probe reads the locally stored reference power. and the preset power configuration factor (i.e., the frame header power configuration factor) Pilot power configuration factor and load power configuration factor ), calculate the absolute value of the target transmit power for each signal segment, i.e., the transmit power of the frame header segment. Pilot band transmit power and payload section transmit power Frame header transmit power Used to enhance the detection reliability of preamble, sync head, and parameter head; pilot band transmit power. To improve the stability of amplitude estimation at ground control stations, the payload section transmit power... Used to meet the energy efficiency requirements of data transmission; among which, the frame header transmit power The calculation formula is: Pilot band transmit power The calculation formula is: payload section transmit power The calculation formula is: To improve the reliability of frame header detection and parameter recovery at ground control stations under low signal-to-noise ratio conditions, the following settings were implemented: > This is to give the frame header segment higher transmit power; at the same time, to ensure that the payload segment has the same pulse power level, the pilot segment and the payload segment adopt the same power configuration, that is, to satisfy... .

[0074] Before configuring the actual physical gain, the deep space probe extracts the time-domain duration parameters of each signal segment in the constructed transmission frame signal, i.e., the frame header duration. Pilot band duration Load duration and the duration of the entire frame The average power upper limit constraint equation is then substituted into the pre-defined average power upper limit constraint equation for compliance verification. The average power upper limit constraint equation is expressed as follows: By verifying the above relationships, deep space probes ensure that while enhancing the reliability of frame header and pilot transmission, the average transmission power of the entire frame remains strictly locked within the system's allowed average power limit. Within.

[0075] After passing the above verification, the deep space probe performs time-varying gain adjustment on the complete transmitted frame signal according to the timing pipeline. When the data stream flows through the frame header (preamble, synchronization header, and parameter header), the deep space probe increases the input gain of the digital-to-analog converter, implementing large-coefficient linear amplification to provide high-power protection for the frame header. When the data stream flows through the pilot and payload segments, the deep space probe reduces the gain and maintains it at the expected standard level to balance the energy of the entire frame. Finally, the deep space probe sends the asymmetrically linearly scaled baseband signal to the radio frequency front end for digital-to-analog conversion and high-frequency carrier modulation to generate the final wireless radio frequency frame signal, which is then sent to the antenna for long-distance space radiation transmission.

[0076] It is understandable that when the current protection interval and the subsequent protection interval are zero signals or low-energy isolation signals, their energy can be included in the total energy or ignored.

[0077] Optionally, the above parameter header Including parameter set This set of parameters can be represented as: in, This represents the number of physically active time slots corresponding to each fixed-interval double-pulse modulation symbol in a cycle; This represents the total number of known pilot symbols inserted into the transmitted frame signal; Represents the pilot state sequence, where Indicates the first The known pilot state index corresponding to each pilot symbol is used by ground control stations for channel estimation and amplitude reference extraction. ; This indicates the maximum number of iterations set when the ground telemetry and control station performs LDPC iterative decoding.

[0078] It should be noted that in the existing network engineering between deep space probes and ground tracking stations, the LDPC verification matrix... Optimal state mapping relationship and power configuration factor (i.e. The parameters have already been hardened as fixed preset parameters in the local memory at both ends, so the deep space probe constructs the parameter header. At this time, it is not necessary to carry the complete mapping table or dense matrix data in the frame header. Deep space probes only need to include the parameter set. The corresponding code index, mapping index, and power configuration index are written into the header, which significantly reduces the overhead of the parameter header and improves the anti-interference protection level of the frame header under low signal-to-noise ratio conditions. When the radio frequency frame signal arrives at the ground control station, the ground control station first demodulates and decodes it to recover the parameter set in the parameter header. The control module of the ground telemetry and control station retrieves a completely matching LDPC check matrix from the local preset table based on the recovered code index, mapping index, and power configuration index. Optimal state mapping relationship And differentiated power configuration parameters. Subsequently, the ground control station uses these extracted key technical parameters to collaboratively perform pilot amplitude reference estimation, state-aware candidate metric calculation, proximity state penalty, and LDPC iterative decoding. This mechanism significantly reduces channel overhead while ensuring perfect alignment of the communication systems at both ends.

[0079] The following section describes in detail another embodiment of the low signal-to-noise ratio pulse communication method for deep space, using a ground-based telemetry and control station as the implementing entity: Figure 3 This is a flowchart illustrating a low signal-to-noise ratio pulse communication method for deep space provided in another embodiment of this application. Figure 3 As shown, this method is applied to ground telemetry and control stations and includes the following steps 301-303.

[0080] Step 301: Receive the radio frequency frame signal sent by the deep space probe; wherein, the radio frequency frame signal is generated by the deep space probe through differentiated power configuration of the frame header segment, pilot segment and payload segment of the transmitted frame signal, and the payload segment includes multiple cyclic fixed interval double pulse modulation symbols, which are obtained by encoding the original information bit sequence with low density parity check code LDPC to obtain the encoded bit sequence, and then using cyclic fixed interval double pulse modulation to perform payload modulation on the encoded bit sequence.

[0081] In this embodiment of the application, the ground telemetry and control station receives the radio frequency frame signal transmitted through the deep space ultra-long distance fading channel via a large-aperture deep space telemetry and control antenna.

[0082] It is understandable that the radio frequency frame signal is constructed and radiated by the deep space probe through steps 101-104 above.

[0083] Step 302: Demodulate the wireless radio frequency frame signal to generate full-frame payload soft information input vectors corresponding to multiple cyclic fixed-interval double-pulse modulation symbols.

[0084] In this embodiment, the ground control station demodulates the acquired radio frequency frame signal, extracts the bit-level log-likelihood ratio information corresponding to all cyclic fixed interval double pulse modulation symbols in the payload segment of the radio frequency frame signal, and concatenates all bit-level log-likelihood ratio information to generate a full-frame payload soft information input vector covering the entire frame payload segment.

[0085] Step 303: Input the full-frame payload soft information input vector into the low-density parity-check code (LDPC) decoder to recover the original information bit sequence.

[0086] Among them, the low-density parity-check (LDPC) decoder refers to a decoder based on a sparse parity-check matrix. A soft-input soft-output or soft-input hard-output channel decoding module with parallel and iterative error correction computation capabilities was constructed.

[0087] In this embodiment, the ground control station calls its internal LDPC decoder, inputting the full-frame payload soft information input vector as prior probability information into the variable node of the LDPC decoder. The LDPC decoder then moves along the parity check matrix between the variable node and the parity check node. The indicated edges undergo round-by-round soft information transmission and iterative updates. Finally, the ground control station removes the redundant bits associated with channel error correction and verification, accurately extracts the original information blocks, and reassembles and outputs them, efficiently and completely recovering the original information bit sequence input by the deep space probe.

[0088] For example, the ground control station inputs the full-frame payload soft information into the vector. The input to the LDPC decoder can be represented as: ,in, To recover the information bit sequence, This is the LDPC parity check matrix. This represents the maximum number of iterations for LDPC decoding. The LDPC decoder iterates based on the input soft-decision information and the parity check matrix constraints, and outputs the final decoding result when the parity check conditions are met or the maximum number of iterations is reached.

[0089] In this embodiment, the technical solution described in steps 301-303 above receives a radio frequency frame signal transmitted by a deep space probe, which has a differentiated power configuration and uses cyclic fixed-interval dual-pulse modulation for the payload segment. The radio frequency frame signal is demodulated to generate a log-likelihood ratio soft information vector covering the entire payload segment. Then, an LDPC decoder is used for iterative decoding, enabling effective recovery of the original information bit sequence at the ground control station. This method fully combines the advantages of cyclic fixed-interval dual-pulse modulation in the low signal-to-noise ratio environment of deep space, such as high pulse position resolution and concentrated power utilization, with the error correction capability of LDPC codes approaching the Shannon limit and the anti-fading characteristics of iterative soft information decoding. This significantly improves the demodulation and decoding performance of weak signals in ultra-long-distance deep space transmission, achieving reliable and efficient communication under extremely low signal-to-noise ratio conditions.

[0090] In some embodiments, the step of a ground control station demodulating a radio frequency frame signal to generate a full-frame payload soft information input vector corresponding to multiple cyclic fixed-interval double-pulse modulation symbols includes: the ground control station performing frame synchronization processing on the frame header segment of the radio frequency frame signal to extract the corresponding payload segment from the radio frequency frame signal; the ground control station performing state awareness metric calculation on each cyclic fixed-interval double-pulse modulation symbol in the payload segment to obtain a state awareness metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol; the ground control station obtaining bit-level log-likelihood ratio information corresponding to each cyclic fixed-interval double-pulse modulation symbol according to the state awareness metric set and a preset state bit mapping relationship in the radio frequency frame signal, and concatenating the bit-level log-likelihood ratio information to generate a full-frame payload soft information input vector; the preset state bit mapping relationship is the preset state bit mapping relationship when the deep space probe transmits the radio frequency frame signal.

[0091] Among them, frame synchronization processing refers to the ground telemetry and control station using a locally preset known synchronization waveform template to perform sliding cross-correlation or sliding integral calculation with the frame header segment of the received radio frequency frame signal. By capturing the relevant energy peak, the starting physical boundary and symbol timing position of the whole frame signal in the time domain are accurately locked, thereby eliminating the influence of transmission delay and multipath jitter, and realizing physical time alignment of the whole frame at the symbol level and time slot level.

[0092] Bit-level log-likelihood ratio information refers to the relative log ratio of the conditional probability that a specific bit of the received payload data will take a binary "0" or a binary "1" after demodulation.

[0093] In the embodiments of this application, the ground control station intercepts the high-power configuration coefficient-protected frame header segment of the received radio frequency frame signal by calling its internal synchronization processing module. It then calculates the discrete time slot metric through matched filtering integration, and cascades preamble sliding cross-correlation coarse synchronization and synchronization header normalized correlation fine search. This allows for precise capture of symbol timing and frame start boundaries under extremely low signal-to-noise ratio conditions, and the complete payload segment to be demodulated is extracted based on these boundaries. Subsequently, the ground control station performs state-aware metric calculations on the extracted payload segment. For cyclic fixed-interval dual-pulse modulation symbols, it outputs a complete set of state-aware metrics that quantize the confidence of each discrete state. Finally, the ground control station extracts the preset state bit mapping relationship from the radio frequency frame signal, maps each cyclic fixed-interval dual-pulse modulation symbol to its corresponding bit-level log-likelihood ratio information, and cascades these bit-level log-likelihood ratio information to generate a full-frame payload soft information input vector.

[0094] It should be noted that by organically cascading the frame synchronization in the physical time domain with the bit mapping mechanism, the pulse waveform characteristics that are prone to overlap and confusion under harsh deep space channels can be smoothly transformed into a high-fidelity cross-layer bit confidence vector, thereby significantly improving the synchronization acquisition accuracy of ground telemetry and control stations and the noise immunity gain of soft decision decoding under extremely low signal-to-noise ratio conditions.

[0095] In some embodiments, the step of the ground control station performing frame synchronization processing on the frame header segment of the radio frequency frame signal and extracting the corresponding payload segment from the radio frequency frame signal includes: the ground control station performing time-domain integration of the continuously received radio frequency frame signal with a preset pulse matching template to convert it into a matched filter output sequence arranged in time slots; the ground control station performing correlation integration using the preamble in the frame header segment and the preset preamble template, and determining the coarse synchronization position by searching for the frame start point corresponding to the maximum correlation energy peak; the ground control station constructing a fine search window centered on the coarse synchronization position, calculating the normalized matching degree between the received time slot correlation output sequence and the preset synchronization header template within the fine search window, and correcting the frame start point by capturing the maximum matching degree peak to obtain the accurate fine synchronization position; the ground control station using the fine synchronization position as the physical time reference, skipping the frame header segment and pilot segment of known length in the time domain, and extracting and separating the payload segment containing multiple cyclic fixed-interval dual-pulse modulation symbols arranged in time sequence from the radio frequency frame signal.

[0096] In this embodiment, the ground control station first converts the continuously received radio frequency frame signals into discrete time slot metrics. The ground control station then calculates the number of time slots at the candidate synchronization position through integration. Matched filter output value of each time slot Matched filter output value It can be represented as: ,in, This indicates the received radio frequency frame signal. Indicates the candidate synchronization position. This indicates the pulse matching template preset by the ground control station. Indicates the time slot width. Indicates the time slot number.

[0097] Secondly, the ground control station performs coarse synchronization processing using a pre-set preamble template. The ground control station first uses the preamble portion in the frame header to perform matched filtering or correlation integration on the candidate frame start point to obtain the coarse synchronization position. coarse synchronization position The calculation formula is: ,in, For the preset preamble template in the first The ground control station determines the initial boundary by finding the frame starting point with the highest correlation (i.e., the highest energy peak) in each time slot, thereby achieving coarse step size positioning.

[0098] Next, the ground control station was at the coarse synchronization position. A fine search is conducted nearby. To eliminate the time delay and multipath jitter caused by long-distance deep space transmission, the ground control station further corrects the frame start point using the synchronization header correlation within a fine search window near the coarse synchronization position to obtain the precise fine synchronization position. fine synchronization position The calculation formula is: ,in, Indicates coarse synchronization position A fine search window pre-set at the center. The synchronization header correlation is used to characterize candidate synchronization positions. Next The degree of normalized matching between the time-slot-related output sequence and the preset synchronization header template, and the synchronization header correlation. The calculation formula is: ,in, This represents the set of time slot indices corresponding to the synchronization header. This indicates that the preset synchronization header template is in the [number]th [section]. Standard values ​​for each time slot.

[0099] Finally, the ground control station obtained a precise fine synchronization position. After that, the complete alignment of the physical time domain boundaries of the entire frame was achieved, and the ground telemetry and control station used this precise fine synchronization position. Using the time reference point, the frame header and pilot segments with known time domain lengths are directly skipped. The entire payload segment, which contains multiple parallel cyclic fixed-interval dual-pulse modulation symbols, is accurately extracted and separated from the received discrete digital baseband signal and used as the discrete time domain input for subsequent demodulation steps.

[0100] It should be noted that after obtaining the precise fine synchronization position through the aforementioned fine search process, the ground control station completes the full alignment of the physical time domain boundaries of the entire frame, laying the physical time reference for the accurate segmentation and extraction of subsequent data segments. Due to the time-varying fading and ultra-low signal-to-noise ratio characteristics of deep space communication channels, in order to ensure that the ground control station can perform adaptive demodulation and error correction decoding based on the current actual transmission status of the deep space probe, the radio frequency frame signal often contains dynamically adjusted transmission configuration parameters. Therefore, before using the aforementioned fine synchronization position to extract the payload segment to be demodulated, the ground control station must first recover and determine the validity of the control parameters in the parameter header immediately following the synchronization header.

[0101] For example, the parameter header is repeatedly transmitted, and the recovery result of the parameter bits is calculated using a majority decision function. Specifically, for the x-th parameter bit, the recovery result is... The recovery result is obtained by calculation using the majority decision function. It can be represented as: ,in, For the first The hard decision value is obtained by repeated reception. The number of times the parameter header is repeated. This represents the majority decision function, which outputs the bit value that appears most frequently in the repeated reception decision values. By synthesizing the decisions from multiple repeated receptions, the stability and reliability of parameter bit recovery are improved, thereby reducing the impact of a single bit misjudgment on subsequent frame processing.

[0102] After making a majority decision on all parameter bits, the ground control station concatenates the recovered bits sequentially according to the preset order of the parameter header field to form a complete parameter header bit vector. Parameter header bit vector It can be represented as: ,in, This represents the total number of parameter bits to be recovered in the parameter header.

[0103] Subsequently, the ground control station processed the parameter header bit vector according to the pre-agreed field format. The parameter set is obtained by parsing. , where superscript The parameters recovered from the ground control station.

[0104] After the parameter header is recovered and parsed, the ground control station can then use the recovered parameter set... This allows for proper demodulation of the subsequent pilot and payload segments, providing accurate configuration data for subsequent state-aware metric calculations and LDPC decoding.

[0105] It is understandable that the parameter set recovered by the aforementioned ground control stations... Configured with the actual deep space tracking and control station and embedded with the transmission frame signal parameter header Parameter set in Correspondingly, under ideal circumstances The ground control station achieves synchronous alignment of parameter configurations at both the transmitting and receiving ends through parameter header recovery and parsing, thereby ensuring that subsequent demodulation processing of the pilot and payload bands can be performed based on the correct configuration parameters.

[0106] Optionally, after completing the parameter header recovery and parsing, the ground control station also performs a validity check on the recovered parameters to confirm whether the currently transmitted frame signal meets the conditions for continued demodulation and decoding.

[0107] The logic for determining the validity of parameter headers can be defined as follows: ,in, This represents the logical AND operation. This indicates that the CRC check has passed. This indicates a match in the frame format identifier. Indicates a fixed header tag match. Indicates the relevance of the parameter header. Indicates the correlation of the synchronization header. This indicates the margin for decision in the parameter header. Indicates the parameter header relevance threshold. Indicates the judgment margin threshold. This represents the synchronization header correlation threshold. It only occurs when all the above conditions are met. Only after the parameter header is deemed valid can the ground telemetry and control station accept the recovered parameter set. And then proceed to the payload demodulation and LDPC decoding process; if If the current transmitted frame signal is marked as invalid, it will not enter the subsequent payload demodulation and LDPC decoding process, in order to avoid the whole frame being misdecoded due to incorrect modulation parameters, frame boundaries or decoding parameters.

[0108] It is understandable that the parameter header recovery result is not isolated header information, but rather a common priori basis for subsequent state template construction, state-aware metric calculation, bit-level log-likelihood ratio information construction, and LDPC decoding. Therefore, parameter header validity determination is a key decision node in the ground control station's entire frame processing flow, directly determining whether the currently transmitted frame signal is worth continuing demodulation and decoding. Through the aforementioned parameter header validity determination mechanism, the ground control station can effectively filter out invalid frames caused by the harsh transmission conditions of deep space channels, avoiding the cascading negative impacts of erroneous parameters on subsequent payload demodulation and LDPC decoding, and significantly improving the robustness and resource utilization efficiency of the ground control station in ultra-low signal-to-noise ratio environments.

[0109] In some embodiments, the step of the ground telemetry and control station performing state-aware metric calculations on each cyclic fixed-interval double-pulse modulation symbol in the payload segment to obtain the state-aware metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol includes: for the first... The ground control station acquires the first cyclic fixed-interval double-pulse modulation symbol. Each candidate state corresponding to a cyclic fixed-interval double-pulse modulation symbol For any candidate state The ground control station calculated the candidate states. State perception measurement State-aware measurement The calculation formula is as follows: ;in, , and These are the weighting coefficients. Indicates the degree of template matching. Indicates candidate state The average activation slot metric Indicates candidate state The average measure of inactive time slots, Indicates candidate state The balance term between the two activation pulses, Indicates the first Local amplitude estimates of a cyclic fixed-interval double-pulse modulation symbol Indicates candidate state Positive leakage term in inactive time slots; the ground control station traverses each candidate state. , obtained the A set of candidate state metrics corresponding to a cyclic fixed-interval double-pulse modulation symbol.

[0110] Among them, the Each candidate state corresponding to a cyclic fixed-interval double-pulse modulation symbol It refers to the first All possible candidate states of a cyclic fixed-interval double-pulse modulation symbol , , , The set of candidate states is a preset set, and the set of candidate payload states used by the deep space probe is a different set. Maintaining consistency (i.e.) ), This represents the total number of time slots within a fixed-interval double-pulse modulation symbol in each cycle.

[0111] In this embodiment of the application, the ground telemetry and control station obtains the currently processed first... For each candidate state corresponding to a fixed-interval double-pulse modulation symbol, a complete set of candidate states is constructed. For any candidate state in this set of candidate states... The ground control station extracts and calculates the candidate state from multiple physical feature dimensions. State perception measurement This state perception metric The calculation formula is: .

[0112] For example, the ground control station first... By performing correlation integration on each time slot of a cyclic fixed-interval double-pulse modulation symbol, the first symbol is generated. All time-slot matched filtering of a fixed double-pulse modulation symbol in a cycle Time slot matched filtering It can be represented as: ,in, For the first The cyclic fixed double-pulse modulation symbol of the th The matched filter value for each time slot. The ground control station selects the time slot with the largest matched filter value. Set of time slot locations The ground control station is currently monitoring the current... The average of the matched filter values ​​of the two time slots with the largest values ​​within each cyclic fixed double-pulse modulation symbol is used to calculate the first... Local amplitude estimates of a fixed-interval double-pulse modulation symbol in a cycle Local amplitude estimates The calculation formula is: .

[0113] It is understandable that in a cyclic fixed-interval double-pulse modulation structure, the number of physically activated time slots corresponding to each cyclic fixed-interval double-pulse modulation symbol of a deep space probe is... The number of physically activated time slots corresponding to each cyclic fixed-interval double-pulse modulation symbol reconstructed by the ground telemetry and control station based on the parameter header is also 2, that is... .

[0114] Secondly, the ground control station based on the candidate status Ideal set of activation slots Extract the candidate state The corresponding time slot matched filter value is calculated and the average metric of the active time slot is calculated. Activate slot average measurement The calculation formula is: .

[0115] Understandably, the ideal set of activation slots Includes candidate states In the physical waveform structure, the pulse should ideally have two time slot indices. Ideal activation time slot set. The ground control station determines the candidate status. The preset cyclic fixed interval double pulse modulation structure (i.e. The result is obtained by parsing and recovering the parameter header, i.e. .

[0116] The ground control station has this candidate state The candidate state is obtained by averaging the matched filter values ​​of the remaining inactive time slots outside the ideal active time slot set. Inactive slot average Non-inactive slot average measurement The calculation formula is: .

[0117] It should be noted that the average metric for inactive time slots... It reflects the level of background noise, pulse leakage, or interference outside the candidate state. and The larger the difference, the more likely it is to be a candidate state. The more obvious the advantage of the activation time slot, the more pronounced.

[0118] Subsequently, the ground control station recovers the candidate state template based on the parameter header parsing. Combined with the above local amplitude estimates The ideal reception characteristics under distortion-free conditions are calculated, and the Euclidean distance residual is calculated between the actual reception time slot metric distribution to obtain the normalized residual between the candidate state template and the time slot matched filter value. Used to characterize the degree of state template matching. The calculation formula is: If the distribution of time slot matched filter values ​​is consistent with the candidate state template, then the activation time slot is close to... The inactive time slots are close to 0, and the normalized residuals are... If the distribution of time slot matched filter values ​​is small and does not match the candidate state template, the residual will increase.

[0119] Considering the impact of time-varying fading in deep space channels on pulses at different positions within a single symbol, the ground control station calculates candidate states. Balance term between two activation pulses Candidate state Balance term between two activation pulses The calculation formula is: ,in, Candidate state The standard deviation of the activation slot metric. The amplitudes of the two activation pulses in a double-pulse symbol should be similar; as the difference increases, the candidate state... The balance term between the two activation pulses decreases, reducing the reliability of the candidate state.

[0120] To suppress candidate states with abnormally high correlation outputs in inactive time slots and reduce the impact of noise spikes or leakage from adjacent time slots on state decisions, the ground control station has taken measures to address this candidate state. For all inactive time slots, extract the maximum value between the time slot matched filter value and 0, sum them, and calculate the candidate state. Positive leakage terms in inactive time slots Positive leakage item The calculation formula is: .

[0121] Finally, the ground control station iterates through each possible candidate state using loop control logic, and calculates the state perception metric for each candidate state. Finally, the first one is gathered and output. The set of candidate state metrics corresponding to each cyclic fixed-interval double-pulse modulation symbol provides a highly reliable observation input for subsequent neighbor state correction and LDPC decoder.

[0122] It should be noted that by comprehensively integrating multi-dimensional physical features such as template matching, energy advantage, amplitude balance, and positive leakage to construct a state-aware metric, it effectively combats deep-space time-varying fading and noise interference, and significantly improves the robustness of state decision-making and the reliability of soft information demodulation of pulse modulation signals in low signal-to-noise ratio environments.

[0123] Understandably, to avoid ambiguous state decisions caused by waveform energy distortion in subsequent payload segments, the ground control station must prioritize calling the parameter set before formally entering the full-frame payload symbol-level state awareness metric calculation. The recovered frame structure time-domain indication is used to perform channel amplitude reference estimation on the known pilot bands in the radio frequency frame signal, in order to lock the global gain and amplitude reference.

[0124] For example, the ground control station uses the parameter set The frame structure parameters determine the start and end positions of the pilot band, based on... Determine the number of pilot symbols and based on the pilot state sequence. and modulation parameters and Construct the set of active time slots for each pilot state: , .

[0125] The ground control station performs matched filtering on the activation time slot of each pilot symbol to obtain the time slot matched filter value. The pilot symbol Matched filter value for each time slot It can be represented as: ,in, This indicates the received radio frequency frame signal. This indicates the pulse matching template preset by the ground control station. Indicates the time slot width. This represents the total time-domain length of the modulation symbol. This represents the time offset of the pilot band relative to the start point of the entire frame. .

[0126] The ground control station calculates the pilot amplitude reference estimate by extracting and jointly averaging the known activation slot correlation metrics for each pilot symbol. Pilot amplitude reference estimation The calculation formula is: ,in, This indicates the number of active time slots for each pilot symbol. By extracting only the relevant output from the ideal active time slot for averaging, the interference from background noise and leakage power in the inactive time slots can be completely eliminated, resulting in a more accurate amplitude reference. For the current dual-pulse structure, since each pilot symbol can provide two independent effective energy observation samples, a total of [number] samples are accumulated across the entire pilot band. The addition of amplitude observation samples significantly improves the convergence stability of amplitude estimation under low signal-to-noise ratio.

[0127] Next, the ground control station will obtain the pilot amplitude reference estimate. Scroll down the mapping to convert it into a global load amplitude reference value suitable for demodulation of subsequent load segments. When the pilot band transmit power is configured in the wireless radio frequency frame signal... With payload section transmit power The same input to the first power conversion branch directly makes When the pilot band transmit power With payload section transmit power When configuring differently, jump to the second power conversion branch and perform square root scaling based on the known power ratio. The calculation formula is as follows: .

[0128] To prevent excessive collapse of amplitude estimation due to transient fading at depths in extremely low signal-to-noise ratio channels, the ground control station further implements lower limit boundary protection constraints on the converted global payload amplitude reference value: ,in, The minimum amplitude reference value is preset. This lower limit protection can effectively prevent the normalized residual, positive leakage term and balance term from diverging or experiencing severe measurement fluctuations due to the low amplitude of the denominator during the subsequent load state demodulation process.

[0129] After completing the above global load amplitude reference value After extraction and boundary protection, the ground control station uses this as a physical prior to formally jump to execute the calculation of the complete set of state perception metrics for each cyclic fixed interval double pulse modulation symbol in the load segment.

[0130] In some embodiments, the method further includes the ground telemetry station performing neighboring state correction on the state-aware metric set to obtain the corrected state-aware metric. The steps include: selecting the candidate state with the largest metric value from the candidate state metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol, as the maximum metric state. According to the maximum metric state The neighboring states are used to correct other candidate states in the candidate state metric set to obtain the corrected state-aware metric. Corrected state-aware metric The calculation formula is as follows: ;in, Candidate state With the maximum metric state The cycle distance between them Candidate state With the maximum metric state Difference in activation slot sets between them This is represented as the cycle distance penalty coefficient. This represents the penalty coefficient for differences in activation time slots.

[0131] In this embodiment of the application, in order to reduce the severe interference to candidate state bit soft information caused by background noise spikes, multipath trails or non-active time slot leakage under the low signal-to-noise ratio conditions in deep space, the ground telemetry and control station introduces a neighboring state penalty mechanism to nonlinearly correct the original state-aware metric set based on the calculated state-aware metric set.

[0132] For example, the ground control station first starts from the first From the candidate state metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol, the candidate state with the largest metric value is selected as the maximum metric state through a maximization search. Maximum metric state The calculation formula is: .

[0133] Subsequently, the ground control station used this maximum measurement state. As a reference benchmark, measure other candidate states in the candidate state set. After applying a neighboring state penalty correction, the corrected state-aware metric is calculated. Corrected state-aware metric The calculation formula is: In the physical calculation process of the neighbor state penalty correction, Indicates the current candidate state With the maximum metric state The cycle distance between them Represented as the cycle distance penalty coefficient; Indicates the current candidate state With the maximum metric state Difference in activation slot sets between them This represents the penalty coefficient for differences in activation time slots.

[0134] Finally, the ground control station performs traversal calculations and uses the aforementioned double penalty term to correct each candidate state in the candidate state metric set. Through this neighboring state penalty correction, at the physical level, the metric values ​​of discrete candidate states that are far from the maximum metric state and have significant differences in activation slot structure are further reduced and stripped away; while for physical nearest neighbor states (or waveform highly correlated states) located near the maximum metric state, their metric values ​​retain a certain degree of uncertainty. This ensures that the output bit-level soft decision information can accurately and objectively reflect the real physical damage characteristics of the deep space channel, providing the LDPC decoder with a higher confidence likelihood observation input, significantly reducing the error propagation of soft decision information in low signal-to-noise ratio environments, and ensuring the error correction gain of LDPC decoding.

[0135] In some embodiments, the step of the ground telemetry and control station obtaining bit-level log-likelihood ratio information corresponding to each cyclic fixed-interval dual-pulse modulation symbol based on the state-aware metric set and a preset state bit mapping relationship in the radio frequency frame signal includes: the ground telemetry and control station determining the bit-level log-likelihood ratio information corresponding to each cyclic fixed-interval dual-pulse modulation symbol based on the preset state bit mapping relationship in the radio frequency frame signal. Number of bits corresponding to a cyclic fixed-interval double-pulse modulation symbol , , The total number of time slots within a fixed-interval double-pulse modulation symbol for each cycle, and Powers of 2 It is a positive integer; for any single bit. ,in, The ground control station calculated the first The first cyclic fixed-interval double-pulse modulation symbol Log-likelihood ratio information for each bit Log-likelihood ratio information The calculation formula is: ;in, Indicates the candidate state The corresponding bit group The value of each bit, This represents the corrected state awareness metric; the ground control station traverses each bit. , obtained the Bit-level log-likelihood ratio information for a cyclic fixed-interval double-pulse modulation symbol.

[0136] In this embodiment of the application, the ground telemetry and control station receives and invokes a preset state bit tag mapping relationship, maps and associates the discrete state space corresponding to each modulation symbol with the binary bit sequence, and calculates highly reliable bit-level log-likelihood ratio information.

[0137] For example, the ground control station first determines the first state bit mapping relationship in the radio frequency frame signal according to the preset mapping relationship. Number of bits carried by a cyclic fixed-interval double-pulse modulation symbol Subsequently, regarding the first Any bit within a cyclic fixed-interval double-pulse modulation symbol The ground control station comprehensively utilizes the corrected state awareness metrics corresponding to all candidate states calculated in the aforementioned steps. The first step is to calculate the solution according to the soft decision logic. The first cyclic fixed-interval double-pulse modulation symbol corresponds to the first Log-likelihood ratio information for each bit The log-likelihood is higher than the information. The calculation formula is: ;in, Indicates candidate state The corresponding bit group The value of each bit.

[0138] Finally, the ground control station uses loop control logic to traverse every bit within the fixed-interval double-pulse modulation symbol to obtain the... Complete bit-level log-likelihood ratio information for each cyclic fixed-interval double-pulse modulation symbol.

[0139] It should be noted that by performing nonlinear exponential conditional summation on the corrected metrics of all candidate states along the bit mapping axis, the overlapping ambiguity between candidate states is eliminated. This transforms the symbol-level waveform constraints into a soft-decision likelihood ratio that accurately characterizes the single-bit logic tendency, significantly enhancing the observation confidence input to the LDPC decoder. By introducing neighboring state penalties and bit-level log-likelihood ratio information, ground control stations can effectively distinguish candidate states under low signal-to-noise ratio conditions, improving the quality of bit soft information and thus enhancing the reliability of LDPC decoding.

[0140] In some embodiments, the step of the ground telemetry and control station concatenating the bit-level log-likelihood ratio information to generate a full-frame payload soft information input vector includes: the ground telemetry and control station concatenating the bit-level log-likelihood ratio information of all cyclic fixed-interval dual-pulse modulation symbols in series according to the transmission order to construct a full-frame payload soft information input vector. Full-frame payload soft information input vector It can be represented as: ,in, This indicates the total number of cyclic fixed-interval double-pulse modulation symbols contained in the transmitted frame signal.

[0141] For example, the ground control station sequentially acquires the first to the second data points within the entire frame payload segment by traversing the demodulation logic. A set of cyclic fixed-interval double-pulse modulation symbols, and extract the internal data from the first bit to the second bit of each cyclic fixed-interval double-pulse modulation symbol. All discrete bit-level log-likelihood ratio information To ensure that the soft-decision information is strictly aligned with the LDPC-encoded bitstream sequence originally transmitted by the deep space probe in the time domain topology, the ground control station uses matrix transposition or one-dimensional linear scalar concatenation to convert the total... Each independent log-likelihood ratio is cascaded end-to-end according to the physical emission time of the symbols. Finally, a single-dimensional output is generated. Full-frame payload soft information input vector This completes the lossless transformation from discrete symbol-level modulation observations to a unified frame-level bit soft metric vector, which serves as a high-confidence physical layer observation boundary condition and is directly fed into the LDPC decoder for global error correction iterative calculation.

[0142] It should be noted that by reorganizing the bit-level likelihood soft information of the discrete symbols of the whole frame into a one-dimensional global input vector according to the transmission time sequence, seamless physical alignment of the channel demodulation state constraints and the input architecture of the frame-level LDPC decoder is achieved, ensuring the complete and lossless transmission of soft decision confidence during the channel decoding stage.

[0143] To better understand the embodiments of this application, simulation experiments are conducted on the low signal-to-noise ratio pulse communication method for deep space provided in the embodiments of this application, and the simulation results are described in detail below: The simulation environment uses an LDPC engineering long code configuration with specific parameters of information bit length K=16384, code length N=32768, and code rate R=1 / 2. All comparison schemes were tested for bit error rate (BER) performance under the same energy-to-noise ratio per bit (Eb / N0) operating point and the same statistical caliber.

[0144] The comparison schemes in the simulation experiment include: baseline scheme one (i.e., single-pulse 8-PPM+LDPC scheme), baseline scheme two (i.e., ordinary double-pulse MPPM+LDPC scheme), and the fully cooperative master scheme (i.e., cyclic fixed-interval double-pulse MPPM+LDPC scheme). It should be noted that the cyclic fixed-interval double-pulse MPPM+LDPC scheme is the low signal-to-noise ratio pulse communication method for deep space provided in the embodiments of this application.

[0145] Figure 4 This is a schematic diagram illustrating an application scenario for the low signal-to-noise ratio pulse communication method for deep space provided in this application embodiment. From Figure 4 As can be seen from the embodiments of this application, the low signal-to-noise ratio pulse communication method for deep space proposed is mainly applied to ultra-long-distance wireless radio frequency link communication between deep space probes and ground control stations. The deep space probe, acting as the transmitter, performs optimized tag mapping and strong frame structure protection encapsulation on the collected data, and then transmits it outward through a radio frequency antenna with differentiated power configurations. The ground control station, acting as the receiver, receives the weak pulse signal eroded by the time-varying fading channel through a large mesh antenna, and sequentially calls pilot amplitude calibration, state-aware metric calculation, and proximity state correction logic, finally sending it to an LDPC decoder to output a high-confidence raw bit stream, thereby ensuring the closed-loop reliability of the deep space control link in an extremely low signal-to-noise ratio environment.

[0146] Figure 5 This is a comparison chart of the bit error rates of the three pulse position modulation methods provided in the embodiments of this application. From... Figure 5 It can be seen that in the extremely low signal-to-noise ratio (SNR) region, with strong background noise and power fading interference, all schemes exhibit high bit error rates (BER). However, as the SNR gradually increases, the BER curve of the cyclic fixed-interval dual-pulse MPPM+LDPC scheme shows a steeper downward trend, with a significantly better performance improvement than the other two baseline schemes. Especially under the 4dB condition, the BER of the single-pulse 8-PPM+LDPC scheme is approximately 4.98 × 10⁻⁶. -2 The BER of a typical dual-pulse MPPM+LDPC scheme is approximately 1.45 × 10⁻⁶.-1 The BER of the cyclic fixed-interval dual-pulse MPPM+LDPC scheme was reduced to approximately 1.32 × 10⁻⁶. -4 Under 6dB conditions, the BER of the cyclic fixed-interval dual-pulse MPPM+LDPC scheme was further reduced to approximately 5.09 × 10⁻⁶. -6 This is significantly lower than the 1.24 × 10⁻⁶ of the single-pulse 8-PPM+LDPC scheme. -2 Compared to the conventional dual-pulse MPPM+LDPC scheme, 5.02×10 -2 The simulation results above show that if the conventional dual-pulse modulation method only uses conventional stateless sensing reception processing, the overall link performance is not necessarily better than the traditional single-pulse modulation method due to state confusion caused by state space expansion. The cyclic fixed-interval dual-pulse MPPM+LDPC scheme can significantly reduce state confusion and soft information distortion by constraining the fixed cyclic dual-pulse interval at the transmitting end and integrating the design of state structure sensing metric calculation, neighbor state penalty and LDPC soft input decoding at the receiving end, thus achieving more reliable decoding performance under low signal-to-noise ratio deep space pulse communication conditions.

[0147] Figure 6 This is a performance comparison chart of the low signal-to-noise ratio (SNR) pulse communication method for deep space provided in the embodiments of this application at two low SNR levels: 2dB and 4dB. From... Figure 6 It can be seen that, Figure 6Further ablation comparison experiments were conducted on the multi-dimensional core technical features employed in the cyclic fixed-interval dual-pulse MPPM+LDPC scheme. The horizontal axis was set at two typical low signal-to-noise ratio operating points of 2dB and 4dB, and the vertical axis was the link bit error rate, also represented using a logarithmic coordinate axis. The bar chart schemes participating in the ablation comparison are defined as follows: Gray bars represent "discrete baselines," which are basic schemes without any specific optimizations, i.e., they do not include state bit optimization mapping, state-aware metrics, proximity state correction, frame header protection enhancement, and differentiated power configuration; Orange bars represent "mapping optimization only," which optimizes only the state bit mapping relationship; Blue bars represent "metric and LLR optimization only," which uses only state-aware metrics and bit-level log-likelihood ratio information; Green bars represent "frame header protection optimization only," which enhances the reliability of frame header segments such as synchronization headers and parameter headers; Purple bars represent "power allocation optimization only," which performs differentiated power configuration only between frame headers, pilots, and payloads; Red bars represent "fully collaborative master schemes," which simultaneously employ the collaborative design of state bit mapping optimization, strong protection frame structure, pilot amplitude reference estimation, state-aware metrics, proximity state correction, bit-level log-likelihood ratio information, and LDPC decoding. Under 2dB conditions, all schemes are still within a relatively noisy range. Only the optimized mapping and fully cooperative master schemes can reduce the bit error rate relative to the discrete baseline. Further observation of the results under 4dB conditions shows that the discrete baseline BER is approximately 8.39 × 10⁻⁶. -2 The optimized mapping is approximately 4.58 × 10⁻⁶. -2 With only the metric optimized, the LLR is approximately 6.90 × 10⁻⁶. -2 Optimizing only the frame header protection is approximately 8.55×10. -2 Optimized power distribution alone amounts to approximately 9.69 × 10⁻⁶. -2 The BER of the fully collaborative master solution is reduced to approximately 4.58 × 10⁻⁶. -5 The ablation comparison results show that introducing a single technical feature can only improve local links in the link, and the improvement effect is jointly constrained by synchronization, amplitude estimation, state confusion, and the quality of LDPC soft information. Only by jointly designing the optimization of state bit mapping, strong protection frame structure, pilot amplitude reference estimation, state-aware metric, neighboring state correction, bit-level log-likelihood ratio information, and LDPC decoding can a significant cascaded gain be achieved under low signal-to-noise ratio conditions. Therefore, the performance improvement of the cyclic fixed-interval dual-pulse MPPM+LDPC scheme is not caused by adjusting a single parameter, but by the synergistic effect of the transmitter's state structure design, frame structure design, and receiver's state-aware soft decision processing.

[0148] In summary, this application provides a method for low signal-to-noise ratio pulse communication in deep space. At the transmitting end, the deep space probe fully combines the strong error correction capability of LDPC coding with the advantages of high pulse position resolution and concentrated power utilization in low signal-to-noise ratio environments using cyclic fixed-interval dual-pulse modulation. At the same time, through differentiated power configuration, the limited transmission power is preferentially allocated to the frame header and pilot bands carrying key synchronization information. Under the premise of ensuring the reliability of frame synchronization and channel estimation, the transmission efficiency and anti-interference capability of the payload segment in the ultra-long distance fading channel in deep space are maximized. Thus, highly reliable and low-power pulse communication between the deep space probe and the ground control station is achieved under extremely low signal-to-noise ratio conditions. At the receiving end, the ground control station prioritizes extracting global payload amplitude reference values ​​with multi-sample cumulative convergence characteristics and constructs a highly robust boundary protection system by combining it with single-symbol local estimation. This allows for the comprehensive integration of multi-dimensional physical features, such as Euclidean distance template matching residuals, active time slot energy advantages, dual-pulse amplitude balance, and non-active time slot positive leakage suppression penalties, when calculating state-aware metrics. Furthermore, by cascading neighboring state correction logic, the system thoroughly corrects the state ambiguity caused by deep-space time-varying fading, continuously supplying high-fidelity bit-level soft likelihood stream information to subsequent error-correcting decoders. This method breaks through the gain bottleneck of the independent design of each processing module in traditional deep-space pulse communication systems, achieving optimal global pipeline coupling from the transmitter signal topology to the receiver's multi-dimensional feature-aware soft decision, demonstrating significant engineering application value. It also addresses the aforementioned drawbacks 1-4.

[0149] The following describes the deep space low signal-to-noise ratio pulse communication device provided in the embodiments of this application. The deep space low signal-to-noise ratio pulse communication device described below and the deep space low signal-to-noise ratio pulse communication method described above can be referred to in correspondence.

[0150] Figure 7 This is a schematic diagram of the structure of a low signal-to-noise ratio pulse communication device for deep space provided in an embodiment of this application. Figure 7 As shown, the device includes a deep space probe 701 and a ground control station 702.

[0151] The Deep Space Exploration Unit 701 is used to encode the original information bit sequence using Low-Density Parity-Check (LDPC) coding to obtain an encoded bit sequence. This encoded bit sequence is then modulated with a payload using a cyclic fixed-interval double-pulse modulation (CRP) method to obtain multiple CRP symbols. These multiple CRP symbols are used as the payload segment of the transmitted frame signal. Based on this payload segment, a preset frame header segment, and a preset pilot segment, a transmitted frame signal is constructed. Differentiated power configurations are applied to the frame header segment, pilot segment, and payload segment of the transmitted frame signal to generate a radio frequency (RF) frame signal. This RF frame signal is then transmitted to the ground control station.

[0152] Ground control station 702 is used to receive radio frequency frame signals transmitted by the deep space probe. These radio frequency frame signals are generated by the deep space probe through differentiated power configuration of the frame header, pilot band, and payload segment of the transmitted frame signal. The payload segment includes multiple cyclic fixed-interval double-pulse modulation symbols. These multiple cyclic fixed-interval double-pulse modulation symbols are obtained by encoding the original information bit sequence using low-density parity-check (LDPC) coding to obtain an encoded bit sequence, and then performing payload modulation on the encoded bit sequence using cyclic fixed-interval double-pulse modulation. The radio frequency frame signal is demodulated to generate a full-frame payload soft information input vector corresponding to the multiple cyclic fixed-interval double-pulse modulation symbols. This full-frame payload soft information input vector is then input into a low-density parity-check (LDPC) decoder to recover the original information bit sequence.

[0153] Optionally, the deep space probe 701 is also used to arrange the coded bit sequence according to a preset number of bits. Divide the bits into groups to obtain multiple bit groups. , , The total number of time slots within a cyclic fixed-interval double-pulse modulation symbol, and Powers of 2 It is a positive integer; based on the preset state bit mapping relationship , each of the bit groups Mapped to a candidate load state ,in, , , For the set of candidate load states, , Based on the cyclic fixed-interval double-pulse modulation structure, determine the state of each candidate load. Dual-pulse activation time slot set ,in, , To fix the double-pulse time slot interval, This represents the modulo operation, and the set of dual-pulse activation time slots. Includes two time slot indices to indicate where the pulse is placed; based on each candidate payload state The corresponding set of dual-pulse activation time slots This generates the corresponding cyclic fixed-interval double-pulse modulation symbol.

[0154] Optionally, the deep space probe 701 is further configured to: calculate the cyclic distance between any two candidate payload states based on the proximity of their corresponding cyclic timing indices; calculate the activation slot difference between two candidate payload states based on the symmetric difference set of the activation slot sets corresponding to any two candidate payload states of the bit group; construct the state weight for each pair of candidate payload states by performing an exponential and linear weighted combination of the cyclic distance and the activation slot difference; construct the objective function for the state bit mapping relationship based on the expected tag distance, Hamming distance, and the state weight for each pair of candidate payload states; and perform an iterative minimization solution to the objective function to obtain the optimal state bit mapping relationship.

[0155] Optionally, the deep space probe 701 is further configured to perform asymmetric linear scaling on the frame header, pilot band and payload segment of the transmitted frame signal according to the average power upper limit constraint using a preset power configuration coefficient, so as to generate a wireless radio frequency frame signal, and the average power of the entire frame of the wireless radio frequency frame signal meets the average power upper limit constraint.

[0156] Optionally, the ground control station 702 is also used to perform frame synchronization processing on the frame header segment of the radio frequency frame signal, extract the corresponding payload segment from the radio frequency frame signal; perform state awareness metric calculation on each cyclic fixed interval double pulse modulation symbol in the payload segment to obtain the state awareness metric set corresponding to each cyclic fixed interval double pulse modulation symbol; calculate the bit-level log-likelihood ratio information corresponding to each cyclic fixed interval double pulse modulation symbol according to the state awareness metric set and the preset state bit mapping relationship in the radio frequency frame signal, and concatenate the bit-level log-likelihood ratio information to generate the full frame payload soft information input vector; the preset state bit mapping relationship is the preset state bit mapping relationship when the deep space probe sends the radio frequency frame signal.

[0157] Optionally, ground control station 702 is also used for targeting the first... The cyclic fixed-interval double-pulse modulation symbols are obtained to acquire the ... Each candidate state corresponding to a cyclic fixed-interval double-pulse modulation symbol For any candidate state The candidate state is calculated. State perception measurement This state perception metric The calculation formula is as follows: ;in, , and These are the weighting coefficients. This represents the normalized residual between the candidate state template and the slot-matched filter value. This indicates the candidate state. The average activation slot metric This indicates the candidate state. The average measure of inactive time slots, This indicates the candidate state. The balance term between the two activation pulses, Indicates the first Local amplitude estimates of a cyclic fixed-interval double-pulse modulation symbol This indicates the candidate state. Positive leakage terms in inactive time slots; traversing each candidate state. , obtained the A set of candidate state metrics corresponding to a cyclic fixed-interval double-pulse modulation symbol.

[0158] Optionally, the ground control station 702 is also used to select the candidate state with the largest metric value from the candidate state metric set corresponding to each double-pulse modulation symbol of the fixed interval of the cycle, as the maximum metric state. According to the maximum metric state The neighboring states are used to correct the other candidate states in the candidate state metric set to obtain the corrected state-aware metric. The corrected state-aware metric The calculation formula is as follows: ;in, This is the candidate state. With the maximum metric state The cycle distance between them This is the candidate state. With the maximum metric state Difference in activation slot sets between them This is represented as the cycle distance penalty coefficient. This represents the penalty coefficient for differences in activation time slots.

[0159] Optionally, the ground control station 702 is also used to determine the first state bit mapping relationship in the radio frequency frame signal according to the preset state bit mapping relationship. Number of bits corresponding to a cyclic fixed-interval double-pulse modulation symbol , , The total number of time slots within a fixed-interval double-pulse modulation symbol for each cycle, and Powers of 2 It is a positive integer; for any single bit. ,in, Calculate the first The first cyclic fixed-interval double-pulse modulation symbol Log-likelihood ratio information for each bit The log-likelihood is higher than the information. The calculation formula is: ;in, This indicates the candidate state. The corresponding bit group The value of each bit, Represents the corrected state-aware metric; iterates through each bit. , to obtain the first Bit-level log-likelihood ratio information for a cyclic fixed-interval double-pulse modulation symbol.

[0160] On the other hand, embodiments of this application also provide a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the deep space low signal-to-noise ratio pulse communication method provided by the above methods.

[0161] In another aspect, embodiments of this application also provide a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, is implemented to perform the deep space low signal-to-noise ratio pulse communication method provided by the methods described above.

[0162] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0163] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the prior art, can be embodied in the form of software products. These computer software products can be stored in computer-readable storage media, such as ROM / RAM, magnetic disks, optical disks, etc., and include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or certain parts of embodiments.

[0164] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for low signal-to-noise ratio pulse communication in deep space, characterized in that, Applications in deep space probes include: The original information bit sequence is encoded using low-density parity-check code (LDPC) to obtain the encoded bit sequence. The encoded bit sequence is subjected to payload modulation using a cyclic fixed interval double pulse modulation method to obtain multiple cyclic fixed interval double pulse modulation symbols, and these multiple cyclic fixed interval double pulse modulation symbols are used as the payload segments of the transmitted frame signal. Based on the payload segment, the preset frame header segment, and the preset pilot segment, a transmission frame signal is constructed; the frame header segment, pilot segment, and payload segment of the transmission frame signal are configured with differentiated power to generate a wireless radio frequency frame signal; The wireless radio frequency frame signal is sent to the ground telemetry and control station.

2. The method for low signal-to-noise ratio pulse communication in deep space according to claim 1, characterized in that, The step of performing payload modulation on the coded bit sequence using a cyclic fixed-interval double-pulse modulation method to obtain multiple cyclic fixed-interval double-pulse modulation symbols includes: The encoded bit sequence is arranged according to a preset number of bits. Divide the bits into groups to obtain multiple bit groups. , , The total number of time slots within a cyclic fixed-interval double-pulse modulation symbol, and Powers of 2 It is a positive integer; According to the preset state bit mapping relationship Each of the bit groups Mapped to a candidate load state ,in, , , For the set of candidate load states, , ; The state of each candidate load is determined based on the cyclic fixed-interval double-pulse modulation structure. Dual-pulse activation time slot set ,in, , To fix the double-pulse time slot interval, The modulo operation is represented by the dual-pulse activation time slot set. Includes two time slot indices to indicate the location where the pulse is placed; According to each of the candidate load states The corresponding set of dual-pulse activation time slots This generates the corresponding cyclic fixed-interval double-pulse modulation symbol.

3. The method for low signal-to-noise ratio pulse communication in deep space according to claim 2, characterized in that, The pre-defined state-to-bit tag mapping relationship The steps include: Calculate the cyclic distance between any two candidate payload states based on the proximity of their corresponding cyclic timing numbers. Calculate the activation slot difference between two candidate payload states based on the symmetric difference set of the activation slot sets corresponding to the candidate payload states of any two bit groups; The state weights corresponding to each pair of candidate load states are constructed by using an exponential and linear weighted combination of the cyclic distance and the activation time slot difference. Based on the expected tag distance, Hamming distance, and state weights for each pair of candidate payload states, an objective function is constructed for the state bit mapping relationship. The objective function is minimized iteratively to obtain the optimal state bit mapping relationship.

4. The method for low signal-to-noise ratio pulse communication in deep space according to any one of claims 1-3, characterized in that, The step of generating a wireless radio frequency frame signal by performing differentiated power configuration on the frame header segment, pilot segment, and payload segment of the transmitted frame signal includes: Based on the average power upper limit constraint, the frame header segment, pilot segment, and payload segment of the transmitted frame signal are asymmetrically linearly scaled using a preset power configuration coefficient to generate a wireless radio frequency frame signal, so that the average power of the entire frame of the wireless radio frequency frame signal meets the average power upper limit constraint.

5. A method for low signal-to-noise ratio pulse communication in deep space, characterized in that, Applications to ground-based telemetry and control stations include: The system receives radio frequency frame signals transmitted by a deep space probe. The radio frequency frame signals are generated by the deep space probe through differentiated power configuration of the frame header, pilot, and payload segments of the transmitted frame signals. The payload segment includes multiple cyclic fixed-interval double-pulse modulation symbols. These multiple cyclic fixed-interval double-pulse modulation symbols are obtained by encoding the original information bit sequence with low-density parity-check code (LDPC) to obtain an encoded bit sequence, and then performing payload modulation on the encoded bit sequence using cyclic fixed-interval double-pulse modulation. The wireless radio frequency frame signal is demodulated to generate the full-frame payload soft information input vector corresponding to the plurality of cyclic fixed interval double pulse modulation symbols; The full-frame payload soft information input vector is input into a low-density parity-check code (LDPC) decoder to recover the original information bit sequence.

6. The method for low signal-to-noise ratio pulse communication in deep space according to claim 5, characterized in that, The step of demodulating the wireless radio frequency frame signal to generate the full-frame payload soft information input vector corresponding to the plurality of cyclic fixed-interval double-pulse modulation symbols includes: Frame synchronization processing is performed on the frame header segment of the wireless radio frequency frame signal, and the corresponding payload segment is extracted from the wireless radio frequency frame signal. A state-aware metric is calculated for each cyclic fixed-interval double-pulse modulation symbol in the load segment to obtain a state-aware metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol. Based on the state-aware metric set and the preset state bit mapping relationship in the radio frequency frame signal, the bit-level log-likelihood ratio information corresponding to each cyclic fixed interval dual-pulse modulation symbol is calculated, and the bit-level log-likelihood ratio information is concatenated to generate a full-frame payload soft information input vector; the preset state bit mapping relationship is the preset state bit mapping relationship when the deep space probe sends the radio frequency frame signal.

7. The method for low signal-to-noise ratio pulse communication in deep space according to claim 6, characterized in that, The step of performing state-aware metric calculations on each cyclic fixed-interval double-pulse modulation symbol in the load segment to obtain the state-aware metric set corresponding to each cyclic fixed-interval double-pulse modulation symbol includes: Regarding the first The cyclic fixed-interval double-pulse modulation symbols are obtained to acquire the ... Each candidate state corresponding to a cyclic fixed-interval double-pulse modulation symbol For any candidate state The candidate state is calculated. State perception measurement The state-aware metric The calculation formula is as follows: ； in, , and These are the weighting coefficients. This represents the normalized residual between the candidate state template and the slot-matched filter value. Indicates the candidate state The average activation slot metric, Indicates the candidate state The average measure of inactive time slots, Indicates the candidate state The balance term between the two activation pulses, Indicates the first Local amplitude estimates of a cyclic fixed-interval double-pulse modulation symbol Indicates the candidate state Positive leakage terms in inactive time slots; Traverse each candidate state , obtained the A set of candidate state metrics corresponding to a cyclic fixed-interval double-pulse modulation symbol.

8. The method for low signal-to-noise ratio pulse communication in deep space according to claim 7, characterized in that, The method further includes performing neighbor state correction on the state-aware metric set to obtain the corrected state-aware metric. The steps include: Select the candidate state with the largest metric value from the candidate state metric set corresponding to each of the cyclic fixed-interval double-pulse modulation symbols, as the maximum metric state. ; According to the maximum metric state The neighboring states of other candidate states in the candidate state metric set are corrected to obtain the corrected state-aware metric. The corrected state-aware metric The calculation formula is as follows: ； in, The candidate state With the maximum metric state The cycle distance between them The candidate state With the maximum metric state Difference in activation slot sets between them This is represented as the cycle distance penalty coefficient. This represents the penalty coefficient for differences in activation time slots.

9. The method for low signal-to-noise ratio pulse communication in deep space according to claim 8, characterized in that, The step of obtaining the bit-level log-likelihood ratio information corresponding to each cyclic fixed-interval dual-pulse modulation symbol based on the state-aware metric set and the preset state bit mapping relationship in the radio frequency frame signal includes: Based on the preset state bit mapping relationship in the wireless radio frequency frame signal, determine the first Number of bits corresponding to a cyclic fixed-interval double-pulse modulation symbol , , The total number of time slots within a fixed-interval double-pulse modulation symbol for each cycle, and Powers of 2 It is a positive integer; For any bit ,in, Calculate the first The first cyclic fixed-interval double-pulse modulation symbol Log-likelihood ratio information for each bit The log-likelihood ratio information The calculation formula is: ； in, Indicates the candidate state The corresponding bit group The value of each bit. This represents the corrected state-awareness metric. Traverse each bit , to obtain the first Bit-level log-likelihood ratio information for a cyclic fixed-interval double-pulse modulation symbol.

10. A low signal-to-noise ratio pulse communication device for deep space, characterized in that, The device includes a deep space probe and a ground control station, comprising: The deep space probe is used to implement the deep space low signal-to-noise ratio pulse communication method as described in any one of claims 1-4; The ground control station is used to implement the deep space low signal-to-noise ratio pulse communication method as described in any one of claims 5-9.

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