CRDSA-based methods, systems, equipment, and media for aircraft direction of arrival estimation.

Abstract

This invention provides a method, system, device, and medium for aircraft direction-of-arrival estimation based on CRDSA, belonging to the field of aerospace communication technology. The method includes: acquiring access waveforms transmitted by access nodes; sequentially detecting the signal in each time slot of each time frame within the access waveform; determining whether the signal in each time slot is transmitted by multiple active nodes; if the signal in any time slot is detected to be transmitted by multiple active nodes, extracting the target signal received by each element in that time slot; calculating the relative time delay between the target signal and the reference signal received by the reference element using maximum likelihood function estimation; and obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay. This method fully integrates direction-finding functionality with communication access, requiring no additional frequency / time slot resources and improving system capacity.

Description

Technical Field

[0001] This invention relates to the field of aerospace communication technology, and in particular to a method, system, device and medium for estimating the direction of arrival of an aircraft based on CRDSA. Background Technology

[0002] In the modern aerospace field, drones and low-altitude aircraft have extremely high requirements for the immediacy and reliability of communications. With the rise of the low-altitude economy, the types and numbers of low-altitude aircraft are increasing, and their communication needs are becoming more complex and diverse. Satellite communication, with its unique advantages of global coverage and stable communication quality, enables these aircraft to maintain stable connections with command centers and other aircraft, making it an ideal choice for communication across various aircraft.

[0003] Against this backdrop, Random Access (RA) technology allows multiple users to randomly send information to the same channel without fixed time slot allocation, offering great flexibility and extremely high access efficiency, making it particularly suitable for scenarios involving small data transmission volumes and bursty multi-user access. Common random access methods include ALOHA (Additive Link-On-line Hawaii Area), Slotted ALOHA (S-ALOHA), and Contention Resolution Diversity Slotted ALOHA (CRDSA). Among these, the CRDSA random access method is widely used because it significantly improves system throughput and access success rate by increasing packet replicas and using Successive Interference Cancellation (SIC).

[0004] However, existing CRDSA technology mainly focuses on multi-user access functions, and it is still difficult to guarantee high accuracy for direction and angle measurement of incoming waves. Summary of the Invention

[0005] This invention provides a method, system, device, and medium for estimating the direction of arrival of an aircraft based on CRDSA, in order to overcome the deficiency of existing CRDSA technology in being unable to measure the direction of arrival, and to achieve the technical effect of simultaneously enabling multi-user access and measuring the direction of arrival using CRDSA technology.

[0006] This invention provides a method for estimating the direction of arrival of an aircraft based on CRDSA, comprising the following steps.

[0007] Collect the access waveform sent by the access node;

[0008] In each time frame of the access waveform, the signal of each time slot in each time frame is detected sequentially;

[0009] Determine whether the signal in each time slot is sent by multiple active nodes;

[0010] If the signal in any time slot is detected to be sent by multiple active nodes, then the target signal received by each element in that time slot is extracted.

[0011] The relative time delay between the target signal and the reference signal received by the reference element is calculated using the maximum likelihood function estimation.

[0012] Based on the relative time delay, the interelement spacing and incident angle corresponding to the target signal are obtained.

[0013] According to a CRDSA-based aircraft direction of arrival estimation method provided by the present invention, the access node transmits the same service replica packet in at least two time slots in each time frame; if the signal in any time slot is detected to be transmitted by multiple active nodes, the target signal received by each element in that time slot is extracted, including:

[0014] If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots of each of the multiple active nodes, and the target signal of each of the multiple active nodes in that time slot is obtained from the access waveform; wherein, the target signal is the signal received by each element in that time slot.

[0015] According to the present invention, a CRDSA-based aircraft direction of arrival estimation method is provided. If the signal in any time slot is detected to be a signal transmitted by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots for each of the multiple active nodes, and the target signal of each of the multiple active nodes in that time slot is obtained from the access waveform. This includes:

[0016] If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots in the at least two time slots of each of the multiple active nodes to obtain the maximum likelihood parameter estimate of each active node.

[0017] Based on the maximum likelihood parameter estimate, physical layer waveform reconstruction is performed on each active node to obtain the reconstructed waveform of each active node received by each element; the reconstructed waveform is used as the target signal.

[0018] After obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay, the method further includes:

[0019] The target signal is subjected to serial interference removal to obtain the decoded waveform of each of the multiple active nodes.

[0020] According to the present invention, a CRDSA-based method for estimating the direction of arrival of an aircraft is provided, the method further includes:

[0021] If the active node is detected as a single node, then net time slot signal detection and channel estimation are performed to obtain the service data decoding result of the single node.

[0022] According to the present invention, a CRDSA-based method for estimating the direction of arrival of an aircraft is provided, the method further includes:

[0023] If the target signal is a narrowband signal, then the carrier phase difference is used as the relative time delay.

[0024] According to the present invention, a CRDSA-based method for estimating the direction of arrival of an aircraft is provided, the method further includes:

[0025] If there is no active node in the current time slot, the detection of the current time slot ends and the process moves to the next time slot.

[0026] The present invention also provides a CRDSA-based aircraft direction of arrival estimation system, including a low-Earth orbit satellite and an access node, wherein the low-Earth orbit satellite carries an onboard receiver;

[0027] The access node is used to send the same service replica packet in at least two time slots in each time frame to form the access waveform corresponding to each time frame;

[0028] The onboard receiver is used to perform each step in the CRDSA-based aircraft direction of arrival estimation method described above.

[0029] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the aircraft arrival direction estimation method based on CRDSA as described above.

[0030] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the aircraft arrival direction estimation method based on CRDSA as described above.

[0031] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the CRDSA-based aircraft direction of arrival estimation method as described above.

[0032] This invention provides a CRDSA-based method, system, device, and medium for estimating the direction of arrival (DOA) of an aircraft. The method involves acquiring access waveforms transmitted by access nodes; sequentially detecting the signal in each time slot of each time frame within the access waveform; determining whether the signal in each time slot is transmitted by multiple active nodes; if the signal in any time slot is detected to be transmitted by multiple active nodes, extracting the target signal received by each element in that time slot; calculating the relative time delay between the target signal and the reference signal received by the reference element using maximum likelihood estimation; and obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay. This method fully integrates direction finding functionality with communication access, requiring no additional frequency / time slot resources and improving system capacity. Furthermore, this method eliminates the need for dedicated sequence training, as the direction finding information is implicitly contained within the access waveform, enhancing the system's anti-interception performance. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this invention 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 invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a flowchart illustrating the CRDSA-based aircraft arrival direction estimation method provided by the present invention.

[0035] Figure 2 This is a schematic diagram of a scenario where multiple aircraft users from different directions randomly access a communication satellite, as provided by the present invention.

[0036] Figure 3 This is a schematic diagram of a model for acquiring signals using a multi-antenna array, provided by the present invention.

[0037] Figure 4 This is a flowchart of the EDOA-CRDSA access algorithm processing provided by the present invention.

[0038] Figure 5 This is a system implementation block diagram of the CRDSA-based aircraft arrival direction estimation system provided by the present invention.

[0039] Figure 6 This is a block diagram of the missile-borne processing unit system provided by the present invention.

[0040] Figure 7 This is a schematic diagram of the structure of the CRDSA-based aircraft arrival direction estimation device provided by the present invention.

[0041] Figure 8 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] The following is combined with Figures 1-8 Specific embodiments of the present invention are described below.

[0044] Figure 1 This is a flowchart illustrating the CRDSA-based aircraft direction-of-arrival estimation method provided by this invention. The execution entity of this method is on the satellite side, specifically, the onboard receiver. Figure 1 As shown, the method includes the following steps.

[0045] Step 101: Acquire the access waveform sent by the access node. .

[0046] In this context, the access node refers to the user node, such as an aircraft.

[0047] It should be noted that the satellite receiver in this embodiment uses a multi-antenna array. In this embodiment, the signal transmitting end (i.e., the access node, hereinafter also referred to as "node" or "user") transmits radio frequency signals to the satellite.

[0048] Specifically, the access waveform transmitted by the access node is received via a multi-antenna array. It can be an access waveform sent by one or more access nodes. .

[0049] like Figure 2 As shown, Figure 2 A schematic diagram is given of a scenario where multiple aircraft users from different directions randomly access a communication satellite, including high-speed aircraft. All require access to a communication satellite. Random access technology primarily addresses the multi-user collision problem in the uplink communication link of "multiple aircraft transmitting - single communication satellite receiving." In CRDSA access research, it is assumed that the satellite and all aircraft nodes have a unified time reference. The satellite divides each uplink communication time frame into... A length of The access time slot, the time slot index within the time frame is... express, .

[0050] It has Nodes To access low-Earth orbit communication satellites, the CRDSA access study assumes that the satellite and all spacecraft nodes share a unified time reference. A time frame contains a fixed number of time slots. That is, the satellite divides each uplink communication time frame into... A length of The access time slot, the time slot index within the time frame is... express, In a time-division multiplexing (TDM) communication system, multiple different signal sources (such as multiple drones) are allowed to share the same physical transmission channel. Each signal source (transmitter) is allocated a specific time slot to transmit its own data, and the receiver (i.e., the satellite) can extract the corresponding signal data from the specific time slot of each time frame.

[0051] like Figure 2 As shown, user node Based on the CRDSA (Conflict Resolution Diversity Slotted Random Access) mechanism, at least two slots are selected in each time frame to send service replica packets, i.e., the number of service replica packets. .node Transmitted in an uplink time frame Symbol vector of each business copy package (That is, the slot index created by this node, explained in detail later) is the same and can mutually indicate the slot positions of the multiple service replica packets within the same time frame. Symbol Vector After framing, modulation and coding, and radio frequency module processing at the MAC (Medium Access Control Layer), the output is an uplink signal. For ease of subsequent derivation, we define... For example: taking the starting point of any time slot n as the time zero point, in the nth time slot... In each time slot, the node The generated time-domain radio frequency signal has a transmit power of Symbolic vector The modulation mapping mode specified by both the sender and receiver determines the overall system. .

[0052] This application employs single-carrier BPSK (Binary Phase Shift Keying) as the modulation mapping, which is one of the most commonly used modulations in cross-domain space-air communication scenarios. Then the node... Radio frequency signal transmitted in time slot n The function of time t is expressed as follows, where the subscript k identifies the k-th user and the superscript n identifies the n-th time slot:

[0053] ; (1)

[0054] in, The number of symbols to be sent, i.e., the number of nodes. The total number of symbols transmitted in time slot n; For nodes The symbol vector in the current frame; is To transmit the pulse shape of the shaping filter, a time shift is performed. This is used to limit signal bandwidth and reduce inter-symbol interference; For the duration of the transmitted symbol, The center angular frequency of the carrier wave for transmitting radio frequency signals; Indicates the first The symbol R represents the real part of the complex number, and j represents the imaginary unit.

[0055] Further with Indicates user In the time slot The sending pattern is defined. as follows:

[0056] ; (2)

[0057] The satellite receiver uses the signal received by a "single antenna," i.e., the input waveform. The expression is as follows.

[0058] ; (3)

[0059] in, Represents a node In the time slot The true amplitude of the received signal is on the main path. Represents a node In the time slot The true value of the delay of the received signal on the main path. Represents a node In the time slot The true value of the carrier frequency offset of the received signal in the main path. Represents a node In the time slot The true value of the carrier initial phase of the received signal on the main path. Indicates the satellite receiver in the time slot The resulting additive white Gaussian noise; K represents the total number of user nodes accessing the channel in time slot n.

[0060] like Figure 3 As shown, Figure 3 This diagram illustrates a model for acquiring signals using a multi-antenna array. When a multi-antenna array is used on a satellite, the user... In the time slot It will also carry radio signals to the satellite receiving array upon arrival. When the signal wavelength is Frequency is The number of star-borne array elements is The spacing between array elements is The reference element is the first received signal. Then the first Each array element ( ) received signal It can be represented as:

[0061] ; (4)

[0062] in, Indicates user In the time slot Reaching the first satellite-borne array antenna The relative time delay of each array element to the reference array element is determined by the spacing between array elements. and angle of incidence Decision, satisfaction:

[0063] ; (5)

[0064] in, The speed of light. For narrowband signals, the time delay can also be approximated as the carrier phase difference:

[0065] ; (6)

[0066] It is not difficult to see that the essence of the spaceborne phased array angle and direction measurement method is to improve the user's... In the time slot Arrival at the satellite-borne receiving array Individual Array Element Parameter estimation is performed. The CRDSA mechanism requires multiple service replica packets to be uploaded with each access communication. Decoding any one of these packets yields the slot ID of another service replica packet and complete demodulated data. Based on this information, precise angle and direction measurement of the incoming signal can be performed at the array processing unit, and precise SIC (Iterative Serial Interference) removal can also be performed at the array element level. This is a joint processing method that simultaneously utilizes phased array spatial diversity and CRDSA time diversity.

[0067] Furthermore, since the low-Earth orbit satellite orbits are known and the time slot intervals of different replica packets are known, the channel parameters of the master and slave paths can be solved for each other in different time slots. This is the basic principle of joint channel parameter estimation in the time slots before and after joint CRDSA.

[0068] The following uses any one of these nodes. The signal access process is explained as follows:

[0069] First, nodes Generate a dedicated time slot index This dedicated time slot index is used to identify the node. In which time slots(s) of the current time frame was the service replica packet sent? For example, when... When =00101, it represents a node. Service replica packets were transmitted in time slots 3 and 5. (Dedicated time slot index) Used to provide an identifier basis for subsequent signal processing.

[0070] Radio frequency signal generation: node Based on the generated time slot index ,generate radio frequency signals (i.e., business copy packet), used for transmission within the time slot corresponding to the time slot index.

[0071] Channel overlay: Node Radio frequency signal transmitted in time slot n This is generated after superimposing Doppler frequency shift and other user influences onto the wireless channel. .

[0072] At this time, the satellite's onboard receiver collects the access waveform of the current time frame, which contains superimposed signals from each time slot.

[0073] Step 102: In each time frame of the access waveform, the signal of each time slot in each time frame is detected sequentially.

[0074] Specifically, the onboard receiver extracts the signals for each time slot from the access waveform corresponding to the current time frame, where the signal corresponding to time slot n is represented as follows: The signal can be a superimposed signal with multipath interference and / or time delay (Round Trip Time, RTT), and also includes the signals of other nodes that concurrently access the channel (i.e. send service copy packets) in this time slot.

[0075] Step 103: Determine whether the signal in each time slot is a signal sent by multiple active nodes.

[0076] Among them, an active node refers to a user node that has sent a service replica packet in the current time slot.

[0077] Specifically, each time slot of a data transmission frame (i.e., a time frame) may have three states: no service replica packets are sent, a single service replica packet is sent, and multiple service replica packets are sent. The onboard receiver can identify these three states for each time slot and detect the currently active node in each time slot based on the user node identifier in the data packet.

[0078] Step 104: If the signal in any time slot is detected to be a signal sent by multiple active nodes, then extract the target signal received by each element in that time slot.

[0079] In a time slot where multiple service replica packets are being sent, a data conflict can be considered to have occurred, meaning that multiple active nodes have sent service replica packets in that time slot. This application uses the CRDSA protocol to implement signal access. Specifically, for time slots with conflicting service replica packets, the receiver stores the superimposed signals received in that time slot instead of discarding them directly. Since each service replica packet contains a unique time slot index created by the sending node, this index can be used to identify service replica packets sent by the same sending node in other time slots.

[0080] Specifically, when it is detected that there are signals sent by multiple active nodes in any time slot of the current time frame, the target signal received by each element in that time slot is extracted, as shown in the above formula (4).

[0081] Step 105: Calculate the relative time delay between the target signal and the reference signal received by the reference element using the maximum likelihood function estimation.

[0082] Maximum Likelihood Estimation (MLE) is a core method in statistics used to estimate parameters of probabilistic models. Its core idea is to find a set of parameter values, given the observed data, that maximize the probability (likelihood) of the observed data occurring under those parameters.

[0083] Specifically, based on the above formula (4) and the positional relationship between each vibration element, the relative time delay between the target signal and the reference signal received by the reference vibration element is calculated using the maximum likelihood function estimation. .

[0084] Step 106: Based on the relative time delay, obtain the element spacing and incident angle corresponding to the target signal.

[0085] Specifically, the spacing between the elements and the incident angle corresponding to the target signal are calculated according to the above formula (6).

[0086] In the above embodiment, the access waveform sent by the access node is acquired; in each time frame of the access waveform, the signal of each time slot in each time frame is detected sequentially; it is determined whether the signal in each time slot is a signal sent by multiple active nodes; if the signal in any time slot is detected to be a signal sent by multiple active nodes, the target signal received by each element in that time slot is extracted; the relative time delay between the target signal and the reference signal received by the reference element is calculated using maximum likelihood function estimation; based on the relative time delay, the element spacing and incident angle corresponding to the target signal are obtained. This method fully integrates direction finding functionality with communication access, requiring no additional frequency / time slot resources and improving system capacity. Furthermore, this method does not require dedicated sequence training, and the direction finding information is implicit in the access waveform, improving the system's anti-interception performance.

[0087] In one embodiment, the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference, Doppler frequency shift, and time delay; the access node uses at least two time slots in each time frame to send the same service copy packet; the above step 104 includes: if the signal in any time slot is detected to be a signal sent by multiple active nodes, then performing joint channel estimation based on the preceding and following time slots of the at least two time slots of each of the multiple active nodes, and obtaining the target signal of each of the multiple active nodes in that time slot from the access waveform; wherein, the target signal is the signal received by each element in that time slot.

[0088] In another embodiment, if the currently active node is a multi-node, it is determined whether there is a known node among the multi-node based on the preset node time slot index; joint channel estimation is performed based on the preceding and following time slots of the at least two time slots of each known node to obtain the maximum likelihood parameter estimate and multipath channel estimate of each known node.

[0089] Specifically, such as Figure 4 As shown, Figure 4 The flowchart of the EDOA-CRDSA (Endogenous Direction-Of-Arrival based CRDSA, integrating random access and direction and angle measurement) access algorithm is shown. Figure 4In this process, when multiple active nodes exist in the same time slot, it means that data packets in that time slot have collided, requiring the initiation of dirty time slot (indicating a time slot affected by data interference and containing erroneous data) detection: First, query the known user time slot index to determine if a known user exists in this dirty time slot. If so, proceed sequentially as follows: MAC layer frame reconstruction for the known user, joint maximum likelihood parameter estimation of the time slots before and after the known user, joint multipath channel estimation of the time slots before and after the known user, physical layer waveform reconstruction for the known user, and finally, serial interference removal of the known user's waveform; if no known user exists, proceed directly to the next time slot.

[0090] The above embodiments, by combining multi-channel estimation, physical layer waveform reconstruction, and serial interference removal, can achieve a closed-loop processing of "multipath decoupling-joint estimation-interference removal", solving the coupling problem of multipath and multi-user interference in traditional methods.

[0091] In one embodiment, after step 103, the method further includes: if the currently active node is a single node, then performing net time slot signal detection and channel estimation to obtain the service data decoding result of the single node.

[0092] Specifically, if the currently active node For a single node, such as Figure 4 As shown, in When the current time slot is a net time slot (without data conflicts), the net time slot signal detection and channel estimation are performed first, followed by demodulation, deframing, and decoding operations in sequence to obtain the service data decoding result. The time slot index is calculated and updated, and then the next time slot is entered.

[0093] In the above embodiments, by detecting that the current time slot is a net time slot, the service data decoding result of the single node corresponding to the current time slot can be directly obtained, which is beneficial to provide an effective data foundation for joint channel estimation of other time slots.

[0094] In one embodiment, after step 103, the method further includes: if there is no currently active node in the current time slot, then the current time slot detection ends and the next time slot is entered.

[0095] Specifically, such as Figure 4 As shown, if the currently active node =0 means there are no active nodes, the current time slot is an empty time slot, and we will directly enter the next time slot.

[0096] The above embodiments provide a method for processing empty time slots, improving the processing flow of the entire technical solution.

[0097] The following is combined with Figure 4 The overall processing flow of the EDOA-CRDSA access algorithm proposed in this application is described as follows:

[0098] (1) Initial stage.

[0099] a) Start: The access algorithm process begins;

[0100] b) Generation of dedicated time slot indexes: Nodes Generate a dedicated time slot index This provides a basis for subsequent signal processing.

[0101] c) Radio frequency signal generation: node Based on the generated time slot index ,generate radio frequency signals It is used for transmission within the corresponding time slot.

[0102] (2) Channel superposition and acquisition stage.

[0103] a) Channel superposition: radio frequency signals The image is generated after superimposing Doppler and other user effects in the wireless channel. At the same time, the impact of the path should be further considered, and superimposed as... .

[0104] b) Access waveform acquisition: Satellite acquisition of access waveforms It acquires the signal information sent by the nodes, which serves as the data basis for subsequent processing.

[0105] (3) Iterative initialization and control.

[0106] a) Iterative initialization: Initialize the number of iterations. This sets the initial state for subsequent iterative processing.

[0107] b) Iteration count update: Each time the iteration process begins, the iteration count is incremented by 1, i.e. .

[0108] c) Maximum Iteration Detection: Determine if the preset maximum number of iterations has been reached. If reached, proceed to the next time frame; otherwise, continue with subsequent processing.

[0109] (4) Signal detection and channel estimation.

[0110] a) Time-slot-by-time signal detection and channel estimation: The acquired access waveform is subjected to time-slot-by-time signal detection, and channel estimation is performed simultaneously to obtain the signal characteristics and channel-related parameters of each time slot.

[0111] b) Maximum time slot determination: Determine whether the maximum time slot has been reached. If the condition is met, complete one iteration and perform the corresponding processing; if not, continue with the subsequent steps.

[0112] (5) Calculation of active node count and branch processing.

[0113] a) Calculation of active node count: Calculate the number of active nodes in the current time slot. .

[0114] b) Branch processing:

[0115] ① For the net time slot, first perform net time slot signal detection and channel estimation, then perform demodulation, deframing, and decoding operations in sequence to obtain the service data decoding result, calculate and update the time slot index, and then enter the next time slot.

[0116] ② Multiple active nodes, dirty timeslots. First, query the known user timeslot index to determine if a known user exists in this dirty timeslot. If so, sequentially perform known user MAC layer frame reconstruction, known user MAC layer reconstructed frame and joint direction finding of the preceding and following timeslots, known user element-by-element waveform reconstruction, known user arrival direction calculation, and finally... Successive Interference Cancellation (SIC) is performed independently within each oscillator; if no known user exists, the process proceeds directly to the next time slot.

[0117] ③ If there are no active nodes, the time slot is empty, and the process proceeds directly to the next time slot.

[0118] (6) Loop and End: After completing one round of iteration (reaching the maximum time slot or processing all cases), decide whether to enter the next time frame based on whether the maximum number of iterations has been reached, and continue the next round of iteration processing until the end condition is met.

[0119] This application also provides a CRDSA-based aircraft direction of arrival estimation system, which includes a low-Earth orbit satellite and a user node, wherein the low-Earth orbit satellite carries an onboard receiver.

[0120] The user node is used to send the same service replica packet in at least two time slots in each time frame to form the access waveform corresponding to each time frame; the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay.

[0121] The onboard receiver is used to perform the steps described in the above embodiment of the CRDSA-based aircraft direction of arrival estimation method.

[0122] like Figure 5 As shown, Figure 5 The system implementation block diagram of the CRDSA-based aircraft direction of arrival estimation system is shown, and its system composition is as follows:

[0123] node The EDOA-CRDSA transmitting unit is noteworthy for its complete reuse of the traditional CRDSA algorithm. Specifically, this EDOA-CRDSA transmitting unit includes the following modules:

[0124] I. Spaceborne Antenna Array: The spaceborne antenna array consists of... It consists of several antenna elements, each of which includes modules such as a low-noise amplifier (LNA), a local oscillator (LO), and a bandpass filter (BPF).

[0125] II. The spaceborne CRDSA access and direction finding integrated processing unit is the core processing unit, including:

[0126] (1) Array beamforming network: Multiple signals input from the spaceborne antenna array enter the array beamforming network. By performing weighted summation and other processing on the signals of each array element, a beam with specific directionality is formed, which enhances the signal in the desired direction, suppresses interference in other directions, and improves the signal reception quality and directionality.

[0127] (2) Time-slot-by-time signal detection: The signal after beamforming is detected in time slot by time slot to determine whether there is a signal and the characteristics of the signal in each time slot, and to determine whether the time slot is a net time slot.

[0128] (3) Net time slot determination and processing: If a time slot is detected as a net time slot, the net time slot parameter is estimated, and then demodulation, deframing, and decoding operations are performed in sequence to finally obtain the service data decoding result. If it is a non-net time slot, the DOA estimation and SIC modules are entered.

[0129] (4) DOA estimation and SIC module: including known user MAC layer frame reconstruction, known user joint direction finding based on reconstructed frame and previous and next time slots, known user multi-element waveform reconstruction based on direction of arrival, and element-by-element iterative interference removal.

[0130] like Figure 6 As shown, Figure 6 The following is a block diagram of the missile-borne processing unit system, whose system components are as follows:

[0131] (1) Business data input module: Business data symbol vector It enters the sending unit and is temporarily stored in the service queue.

[0132] (2) MAC layer framing module: The service data in the service queue enters the MAC layer for framing operation, and organizes the data into a CRDSA frame structure.

[0133] (3) Encoding and modulation module: The service data after framing is encoded and modulated.

[0134] (4) Access timing control and pattern generation module: The access timing control module generates access patterns through timing control. and determine Time slot ID. Access diagram. The generation module works in conjunction with the radio frequency gating to control the timing and method of transmitting radio frequency signals.

[0135] (5) Radio frequency signal output module: generates radio frequency signals And output to the multi-user access channel.

[0136] The following describes the CRDSA-based aircraft direction of arrival estimation device provided by the present invention. The CRDSA-based aircraft direction of arrival estimation device described below and the CRDSA-based aircraft direction of arrival estimation method described above can be referred to in correspondence.

[0137] like Figure 7 As shown, Figure 7 A schematic diagram of the module structure of a CRDSA-based aircraft direction of arrival estimation device is shown. This CRDSA-based aircraft direction of arrival estimation device includes the following modules:

[0138] The access waveform acquisition module 701 is used to acquire the access waveform sent by the access node;

[0139] The time slot signal detection module 702 is used to sequentially detect the signal of each time slot in each time frame of the access waveform.

[0140] The active node determination module 703 is used to determine whether the signal in each time slot is a signal sent by multiple active nodes;

[0141] The target signal extraction module 704 is used to extract the target signal received by each element in the time slot if the signal in any time slot is detected to be a signal sent by multiple active nodes.

[0142] The relative time delay calculation module 705 is used to calculate the relative time delay between the target signal and the reference signal received by the reference element using the maximum likelihood function estimation.

[0143] The signal direction finding module 706 is used to obtain the inter-element spacing and incident angle of the target signal based on the relative time delay.

[0144] In one embodiment, the access node transmits the same service replica packet using at least two time slots in each time frame; the target signal extraction module 704 is further configured to:

[0145] If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots of each of the multiple active nodes, and the target signal of each of the multiple active nodes in that time slot is obtained from the access waveform; wherein, the target signal is the signal received by each element in that time slot.

[0146] In one embodiment, the target signal extraction module 704 is further configured to:

[0147] If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots in the at least two time slots of each of the multiple active nodes to obtain the maximum likelihood parameter estimate of each active node.

[0148] Based on the maximum likelihood parameter estimate, physical layer waveform reconstruction is performed on each active node to obtain the reconstructed waveform of each active node received by each element; the reconstructed waveform is used as the target signal.

[0149] After obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay, the method further includes:

[0150] The target signal is subjected to serial interference removal to obtain the decoded waveform of each of the multiple active nodes.

[0151] In one embodiment, the target signal extraction module 704 is further configured to:

[0152] If the active node is detected as a single node, then net time slot signal detection and channel estimation are performed to obtain the service data decoding result of the single node.

[0153] In one embodiment, the relative delay calculation module 705 is further configured to:

[0154] If the target signal is a narrowband signal, then the carrier phase difference is used as the relative time delay.

[0155] In one embodiment, the active node determination module 703 is further configured to:

[0156] If there is no active node in the current time slot, the detection of the current time slot ends and the process moves to the next time slot.

[0157] Figure 8 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 8As shown, the electronic device may include a processor 810, a communications interface 820, a memory 830, and a communication bus 840. The processor 810, communications interface 820, and memory 830 communicate with each other via the communication bus 840. The processor 810 can call logical instructions in the memory 830 to execute a CRDSA-based aircraft direction-of-arrival estimation method. This method includes: acquiring access waveforms sent by access nodes; sequentially detecting the signal in each time slot of each time frame of the access waveform; determining whether the signal in each time slot is a signal sent by multiple active nodes; if the signal in any time slot is detected to be a signal sent by multiple active nodes, extracting the target signal received by each element in that time slot; calculating the relative time delay between the target signal and the reference signal received by the reference element using maximum likelihood estimation; and obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay.

[0158] Furthermore, the logical instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0159] On the other hand, the present invention also provides 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 can execute the CRDSA-based aircraft direction-of-arrival estimation method provided by the above methods. The method includes: acquiring access waveforms sent by access nodes; sequentially detecting the signal of each time slot in each time frame of the access waveform; determining whether the signal of each time slot is a signal sent by multiple active nodes; if the signal of any time slot is detected to be a signal sent by multiple active nodes, extracting the target signal received by each element in that time slot; calculating the relative time delay between the target signal and the reference signal received by the reference element using maximum likelihood function estimation; and obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay.

[0160] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the CRDSA-based aircraft direction-of-arrival estimation method provided by the methods described above. This method includes: acquiring an access waveform transmitted by an access node; sequentially detecting the signal in each time slot of each time frame of the access waveform; determining whether the signal in each time slot is a signal transmitted by multiple active nodes; if the signal in any time slot is detected to be a signal transmitted by multiple active nodes, extracting the target signal received by each element in that time slot; calculating the relative time delay between the target signal and the reference signal received by the reference element using maximum likelihood function estimation; and obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay.

[0161] 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.

[0162] 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 part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A method for estimating the direction of arrival of an aircraft based on CRDSA, characterized in that, include: Collect the access waveform sent by the access node; In each time frame of the access waveform, the signal of each time slot in each time frame is detected sequentially; Determine whether the signal in each time slot is sent by multiple active nodes; If the signal in any time slot is detected to be sent by multiple active nodes, then the target signal received by each array element in that time slot is extracted. The relative time delay between the target signal and the reference signal received by the reference array element is calculated using the maximum likelihood function estimation. Based on the relative time delay, the element spacing and incident angle corresponding to the target signal are obtained; The access node transmits the same service replica packet in at least two time slots in each time frame; if it is detected that the signal in any time slot is transmitted by multiple active nodes, the target signal received by each array element in that time slot is extracted, including: If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots of each of the multiple active nodes, and the target signal of each of the multiple active nodes in that time slot is obtained from the access waveform; wherein, the target signal is the signal received by each array element in that time slot; If the signal in any time slot is detected to be a signal transmitted by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots of each of the multiple active nodes, and the target signal of each of the multiple active nodes in that time slot is obtained from the access waveform, including: If the signal in any time slot is detected to be a signal sent by multiple active nodes, then joint channel estimation is performed based on the preceding and following time slots in the at least two time slots of each of the multiple active nodes to obtain the maximum likelihood parameter estimate of each active node. Based on the maximum likelihood parameter estimate, physical layer waveform reconstruction is performed on each active node to obtain the reconstructed waveform of each active node received by each array element; the reconstructed waveform is used as the target signal.

2. The aircraft arrival direction estimation method based on CRDSA according to claim 1, characterized in that, After obtaining the element spacing and incident angle corresponding to the target signal based on the relative time delay, the method further includes: The target signal is subjected to serial interference removal to obtain the decoded waveform of each of the multiple active nodes.

3. The aircraft arrival direction estimation method based on CRDSA according to claim 1, characterized in that, The method further includes: If the active node is detected as a single node, then net time slot signal detection and channel estimation are performed to obtain the service data decoding result of the single node.

4. The aircraft arrival direction estimation method based on CRDSA according to claim 1, characterized in that, The method further includes: If the target signal is a narrowband signal, then the carrier phase difference is used as the relative time delay.

5. The aircraft arrival direction estimation method based on CRDSA according to claim 1, characterized in that, The method further includes: If there is no active node in the current time slot, the detection of the current time slot ends and the process moves to the next time slot.

6. A CRDSA-based aircraft direction of arrival estimation system, characterized in that, It includes low-Earth orbit satellites and access nodes, wherein the low-Earth orbit satellites are equipped with onboard receivers; The access node is used to send the same service replica packet in at least two time slots in each time frame to form the access waveform corresponding to each time frame; The onboard receiver is used to perform the CRDSA-based vehicle direction of arrival estimation method as described in any one of claims 1 to 5.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the CRDSA-based aircraft direction of arrival estimation method as described in any one of claims 1 to 5.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the CRDSA-based aircraft direction of arrival estimation method as described in any one of claims 1 to 5.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the CRDSA-based aircraft direction of arrival estimation method as described in any one of claims 1 to 5.

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