Aircraft direction of arrival estimation method, system and equipment based on CRDSA and medium

Abstract

The invention provides an aircraft arrival direction estimation method, system and device based on CRDSA and a medium, and belongs to the technical field of aerospace communication. The method comprises the following steps: acquiring an access waveform sent by an access node; in each time frame of the access waveform, detecting a signal of each time slot in each time frame in sequence; judging whether the signal of each time slot is a signal sent by a plurality of active nodes or not; if it is detected that the signal of any time slot is the signal sent by a plurality of active nodes, extracting a target signal received by each vibration element in the time slot; calculating a relative time delay between the target signal and a reference signal received by the reference element by using maximum likelihood function estimation; and according to the relative time delay, obtaining an element spacing and an incident angle corresponding to the target signal. According to the method, the direction finding function and communication access are completely fused, additional frequency point / time slot resources are not needed, and the system capacity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space-air communication, and in particular to a CRDSA-based aircraft direction of arrival estimation method, system, device and medium. BACKGROUND

[0002] In the modern aerospace field, unmanned aerial vehicles, low-altitude aircraft and the like have extremely high requirements for the immediacy and reliability of communication. With the rise of low-altitude economy, the types and numbers of low-altitude aircraft are increasing, and their communication requirements are more complex and diverse. Satellite communication has the unique advantages of global coverage and stable communication quality, and can enable these aircraft to maintain stable connections with command centers and other aircraft, thus becoming an ideal choice for communication of various aircraft.

[0003] Under the above background, random access technology (Random Access, RA) allows multiple users to randomly send information to the same channel without fixed time slot allocation, has great flexibility and high access efficiency, and is particularly suitable for small data volume transmission and burst multi-user access scenarios. Common random access methods include ALOHA (Additive LinkOn-line Hawaii Area), slotted-ALOHA (S-ALOHA) and contention resolution diversity slotted ALOHA (CRDSA). Among them, the CRDSA random access method significantly improves the system throughput and access success rate by increasing data packet copies and successive interference cancellation (SIC), and is widely used.

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

[0005] The present application provides a CRDSA-based aircraft direction of arrival estimation method, system, device and medium, which solves the defect that the existing CRDSA technology cannot measure the direction of incoming waves, and realizes the technical effect of simultaneously realizing multi-user access and incoming wave direction measurement using CRDSA technology.

[0006] The present application provides a CRDSA-based aircraft direction of arrival estimation method, comprising the following steps.

[0007] Collecting an access waveform sent by an access node; In each time frame of the access waveform, the signals of each time slot in each time frame are detected in turn. determining whether the signal of each time slot is a signal transmitted by multiple active nodes; extracting a target signal received by each element in the time slot if it is detected that the signal of any time slot is a signal transmitted by multiple active nodes; calculating a relative time delay between the target signal and a reference signal received by a reference element using maximum likelihood function estimation; obtaining an element spacing and an incident angle corresponding to the target signal according to the relative time delay.

[0008] According to the aircraft direction of arrival estimation method based on CRDSA provided by the application, the access node transmits the same service copy package in at least two time slots in each time frame; if it is detected that the signal of any time slot is a signal transmitted by multiple active nodes, the target signal received by each element in the time slot is extracted, which comprises: if it is detected that the signal of any time slot is a signal transmitted by multiple active nodes, joint channel estimation is performed according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes, and the target signal of each active node in the multiple active nodes in the time slot is obtained from the access waveform; wherein the target signal is the signal received by each element in the time slot.

[0009] According to the aircraft direction of arrival estimation method based on CRDSA provided by the application, if it is detected that the signal of any time slot is a signal transmitted by multiple active nodes, joint channel estimation is performed according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes, and the target signal of each active node in the multiple active nodes in the time slot is obtained from the access waveform, which comprises: if it is detected that the signal of any time slot is a signal transmitted by multiple active nodes, joint channel estimation is performed according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes, and the maximum likelihood parameter estimate of each active node is obtained; physical layer waveform reconstruction is performed on each active node according to the maximum likelihood parameter estimate, and the reconstructed waveform of each active node received by each element is obtained; the reconstructed waveform is taken as the target signal; after the target signal corresponding to the element spacing and the incident angle are obtained according to the relative time delay, the method further comprises: serial interference cancellation is performed on the target signal, and a decoding waveform of each active node in the multiple active nodes is obtained.

[0010] According to the aircraft direction of arrival estimation method based on CRDSA provided by the application, the method further comprises: If the active node is detected as a single node, net time slot signal detection and channel estimation are performed to obtain service data decoding results of the single node.

[0011] According to the aircraft direction of arrival estimation method based on CRDSA provided by the application, the method further comprises: If the target signal is a narrowband signal, the carrier phase difference is used as the relative time delay.

[0012] According to the aircraft direction of arrival estimation method based on CRDSA provided by the application, the method further comprises: If there is no current active node in the current time slot, the current time slot detection is ended, and the next time slot is entered.

[0013] The application further provides an aircraft direction of arrival estimation system based on CRDSA, comprising a low-orbit satellite and an access node, wherein the low-orbit satellite is loaded with a satellite-borne receiver. The access node is configured to send the same service copy package in at least two time slots in each time frame to form an access waveform corresponding to each time frame. The satellite-borne receiver is configured to perform each step in the aircraft direction of arrival estimation method based on CRDSA.

[0014] The application further provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the aircraft direction of arrival estimation method based on CRDSA when executing the computer program.

[0015] The application further provides a non-transitory computer readable storage medium, which stores a computer program executable by a processor to implement the aircraft direction of arrival estimation method based on CRDSA.

[0016] The application further provides a computer program product comprising a computer program executable by a processor to implement the aircraft direction of arrival estimation method based on CRDSA.

[0017] The application provides a CRDSA-based aircraft direction of arrival estimation method, system, device and medium, access waveforms transmitted by access nodes are collected; in each time frame of the access waveforms, signals in each time slot in each time frame are detected in sequence; whether the signals in each time slot are signals transmitted by multiple active nodes is judged; if it is detected that the signals in any time slot are signals transmitted by multiple active nodes, target signals received by each element in the time slot are extracted; a maximum likelihood function estimation is used to calculate a relative time delay between the target signals and reference signals received by a reference element; and an element spacing and an incident angle corresponding to the target signals are obtained according to the relative time delay. The method completely fuses the direction finding function and the communication access, does not need additional frequency / time slot resources, and improves the system capacity. Further, the method does not need special sequence training, the direction finding information is implicitly in the access waveforms, and the system anti-interception performance is improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0019] Figure 1 It is a flowchart of the CRDSA-based aircraft direction of arrival estimation method provided by the application.

[0020] Figure 2 It is a scene diagram of multiple aircraft users of different directions accessing a communication satellite.

[0021] Figure 3 It is a model diagram of collecting signals using a multiple antenna array.

[0022] Figure 4 It is a processing flowchart of the EDOA-CRDSA access algorithm.

[0023] Figure 5 It is a system implementation block diagram of the CRDSA-based aircraft direction of arrival estimation system provided by the application.

[0024] Figure 6 It is a system block diagram of a missile-borne processing unit provided by the application.

[0025] Figure 7 It is a structure diagram of the CRDSA-based aircraft direction of arrival estimation device provided by the application.

[0026] Figure 8 It is a structure diagram of an electronic device provided by the application. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] The following combination Figures 1-8 Specific embodiments of the present invention are described.

[0029] Figure 1 FIG. 1 is a flow chart of a method for estimating the direction of arrival of an aircraft based on CRDSA provided by the present invention. The execution subject of the method is the satellite side, specifically, the satellite-borne receiver. Figure 1 As shown, the method includes the following steps.

[0030] Step 101: Collect the access waveform sent by the access node .

[0031] The access node refers to a user node, such as an aircraft.

[0032] It should be noted that the satellite receiver in this embodiment uses a multi-antenna array. In this embodiment, a signal transmitter (ie, an access node, hereinafter also referred to as a "node" or "user") sends a radio frequency signal to a satellite.

[0033] Specifically, the access waveform sent by the access node is received by the multi-antenna array , which can be an access waveform sent by one or more access nodes .

[0034] like Figure 2 As shown, Figure 2 A schematic diagram of the scenario where multiple aircraft users from different directions randomly access the communication satellite is given. All of them need to access the communication satellite. Random access technology mainly solves the multi-user collision problem in the uplink communication link of "multiple aircraft sending - single communication satellite receiving". In the CRDSA access research, it is assumed that the satellite and all aircraft nodes have a unified time base. The satellite divides each uplink communication time frame into The length is The access time slot of the time frame is indexed by express, .

[0035] With nodes To access low-orbit communication satellites, in CRDSA access research, it is assumed that the satellite and all aircraft nodes have a unified time base. A time frame contains a fixed number of time slots. In other words, the satellite divides each uplink communication time frame into The length is The access time slot of the time frame is indexed by express, In a time-division multiplexing (TDM) communication system, multiple signal sources (e.g., drones) can share the same physical transmission channel. Each signal source (transmitter) is assigned a specific time slot to transmit its data, and the receiver (i.e., the satellite) can extract the corresponding signal data from the specific time slot in each time frame.

[0036] like Figure 2 As shown, the user node According to the CRDSA (Contradiction Resolution Diversity Slotted Random Access) mechanism, at least two time slots are selected in each time frame to send service copy packets, that is, the number of service copy packets .node Sent in an uplink time frame Business copy pack symbol vector (That is, the time slot index created by the node, which will be explained in detail later) is the same, and can point out the time slot positions of the multiple service copy packets in the same time frame. Symbol vector After MAC (Medium Access Control Layer) framing, modulation coding and RF module processing, the output is the uplink signal To facilitate subsequent derivation, define As: Take the starting point of any time slot n as time zero, In a time slot, the node The generated time domain RF signal has a transmission power of . Symbol vector and the modulation mapping mode specified by the sender and receiver determine the .

[0037] This application uses single-carrier BPSK (Binary Phase Shift Keying) as the modulation mapping, which is one of the most commonly used modulations in space-to-air cross-domain communication scenarios. The RF signal sent in time slot n is a function of time t and is expressed as follows, where the subscript k identifies the kth user and the superscript n identifies the nth time slot: ; (1) in, is the number of symbols to be sent, that is, the node The total number of symbols transmitted in time slot n; For nodes The symbol vector in the current time frame; To send the pulse shape of the shaping filter, shift it in time , used to limit signal bandwidth and reduce inter-symbol interference; is the duration of the transmitted symbol, The center angular frequency of the carrier of the transmitted radio frequency signal; Indicates the symbols. R represents the real part of the complex number, and j represents the imaginary unit.

[0038] Further Represents a user In the time slot Send pattern, definition as follows: ; (2) The satellite receiver uses the signal received by the "single antenna", that is, the access waveform The expression is as follows.

[0039] ; (3) in, Representation node In the time slot The amplitude true value of the received signal when the main path is Representation node In the time slot The true value of the delay of the received signal when the main path is Representation node In the time slot The carrier frequency deviation true value of the received signal when the main path is Representation node In the time slot The true value of the initial phase of the carrier of the received signal when the main path is Indicates that the satellite receiver is in time slot The generated additive white Gaussian noise; K represents the total number of user nodes accessing the channel in time slot n.

[0040] like Figure 3 As shown, Figure 3 The schematic diagram of the model using a multi-antenna array to collect signals is shown. When a multi-antenna array is used on a satellite, the user In the time slot When it reaches the satellite receiving array, it will also carry wireless signals to the information When the signal wavelength is Frequency is , the number of satellite array elements is , the array element spacing is , the reference array element is the first received signal , then Array elements ( ) received signal It can be expressed as: ; (4) in, Represents a user In the time slot Arriving at the satellite array antenna The relative delay of the reference array element is determined by the array element spacing. and the angle of incidence Decide, satisfy: ; (5) in, is the speed of light. For narrowband signals, the delay can also be approximated as the carrier phase difference: ; (6) It is not difficult to see that the essence of the satellite-borne phased array angle and direction measurement method is to In the time slot Arriving at the satellite receiving array Array element time Parameter estimation is performed. The CRDSA mechanism requires that multiple service replica packets be uploaded for each communication access. Decoding any one of these packets yields the time slot ID and complete demodulated data of the other service replica packet. This information enables accurate angle and direction measurement of incoming signals within the array processing unit, while also enabling precise SIC (Iterative Serial Interference) cancellation at the element level. This is a joint processing method that leverages both the spatial diversity of the phased array and the temporal diversity of the CRDSA mechanism.

[0041] Furthermore, since the LEO satellite orbit is known and the time slot intervals of different replica packets are known, the channel parameters of the master-slave path can be solved for each other in different time slots. This is the basic principle of performing joint channel parameter estimation in the previous and next time slots of joint CRDSA.

[0042] Next, take any of the nodes The signal access process is as follows: First, the node Generate a dedicated time slot index , the exclusive time slot index is used to identify the node In which time slot or timeslots in the current time frame is the service copy packet sent? For example, when =00101, indicating a node The service replica packet is transmitted in time slot 3 and time slot 5. The exclusive time slot index For providing an identification basis for subsequent signal processing.

[0043] Radio frequency signal generation: node According to the generated time slot index , a radio frequency signal (i.e. service replica packet) is generated for transmission in the time slot corresponding to the time slot index.

[0044] Channel superposition: node The radio frequency signal transmitted in time slot n is superimposed in the wireless channel to generate .

[0045] At this time, the satellite-borne receiver on the satellite collects the access waveform of the current time frame, and the access waveform of the current time frame contains the superimposed signals of each time slot.

[0046] Step 102, in each time frame of the access waveform, the signal of each time slot in each time frame is detected in turn.

[0047] Specifically, the satellite-borne receiver extracts the signal of each time slot from the access waveform corresponding to the above-mentioned current time frame, wherein the signal corresponding to time slot n is expressed as , which can be a superimposed signal superimposed with multipath interference and / or Round Trip Time (RTT, Round Trip Time), and also includes the signals of other nodes concurrently accessing the channel (i.e. transmitting service replica packets) in the time slot.

[0048] Step 103, determine whether the signal of each time slot is the signal sent by multiple active nodes.

[0049] Wherein, the active node refers to a user node that has transmitted a service replica packet in the current time slot.

[0050] Specifically, each time slot of a data transmission frame (i.e. a time frame) can have three states: no service replica packet is transmitted, a single service replica packet is transmitted, and multiple service replica packets are transmitted. The satellite-borne receiver can identify the three states of each time slot, and detect the current active node in each time slot according to the user node identification in the data packet.

[0051] Step 104, if it is detected that the signal of any time slot is the signal sent by multiple active nodes, the target signal received by each element in the time slot is extracted.

[0052] ​If there are multiple service replica packets sent in a time slot, it is considered that a data collision occurs, i.e., multiple active nodes send service replica packets in the time slot. The present application uses the CRDSA protocol to realize signal access, i.e., for a time slot with multiple service replica packet collisions, the receiving opportunity stores the superimposed signal received in the time slot instead of directly discarding it. Since each service replica packet contains a dedicated time slot index created by the sending node, the dedicated time slot index can be used to indicate the service replica packet sent by the sending node in other time slots.

[0053] Specifically, when it is detected that there are multiple active nodes sending signals in any time slot in the current time frame, the target signal received by each element in the time slot is extracted, as shown in the above formula (4).

[0054] Step 105, using maximum likelihood function estimation, calculating the relative time delay between the target signal and the reference signal received by the reference element.

[0055] Among them, the maximum likelihood estimation (Maximum Likelihood Estimation, MLE) is a core method for estimating the parameters of a probability model in statistics. The core idea is: under the premise of known observation data, find a set of parameter values, so that the probability (likelihood) of the observation data under the parameter is the maximum.

[0056] Specifically, for the above formula (4) and the positional relationship between the elements, using maximum likelihood function estimation, calculating the relative time delay between the target signal and the reference signal received by the reference element .

[0057] Step 106, according to the relative time delay, obtaining the element spacing and the incident angle corresponding to the target signal.

[0058] Specifically, according to the above formula (6), the element spacing and the incident angle corresponding to the target signal are calculated.

[0059] The above embodiment acquires an access waveform sent by an access node; detects signals in each time slot in each time frame of the access waveform; determines whether the signals in each time slot are signals sent by multiple active nodes; extracts target signals received by each element in the time slot if it is determined that the signals in any time slot are signals sent by multiple active nodes; calculates a relative time delay between the target signals and reference signals received by a reference element by using maximum likelihood function estimation; and obtains an element spacing and an incident angle corresponding to the target signals according to the relative time delay. The method completely integrates the direction finding function and the communication access, does not require additional frequency / time slot resources, and improves the system capacity. Further, the method does not require special sequence training, and the direction finding information is implicitly included in the access waveform, thereby improving the system anti-interception performance.

[0060] In an embodiment, the access waveform is a superposition waveform to which multipath interference, Doppler shift and time delay are superposed and sent by the access node; the access node sends the same service copy packet in at least two time slots in each time frame; and the step 104 includes: if it is determined that the signals in any time slot are signals sent by multiple active nodes, jointly performing channel estimation according to the front and rear time slots in the at least two time slots of each active node in the multiple active nodes to obtain target signals of each active node in the multiple active nodes in the time slot from the access waveform; and the target signals are signals received by each element in the time slot.

[0061] In another embodiment, if the current active node is a multiple node, determining whether there is a known node in the multiple node according to a preset node time slot index; and jointly performing channel estimation according to the front and rear time slots in the at least two time slots of each known node to obtain a maximum likelihood parameter estimate and a multipath channel estimate of each known node.

[0062] Specifically, as shown in Figure 4 , Figure 4 An EDOA-CRDSA (Endogenous Direction-Of-Arrival based CRDSA, random access and direction finding integrated) access algorithm processing flowchart is shown in Figure 4In the case of multiple active nodes in the same timeslot, this indicates a data packet collision in that timeslot, necessitating dirty slot detection (indicates a timeslot subject to data interference and containing erroneous data). The system first queries the known user timeslot index to determine whether a known user exists in this dirty timeslot. If so, the system sequentially performs MAC layer frame reconstruction, joint maximum likelihood parameter estimation for the preceding and following timeslots, joint multipath channel estimation for the preceding and following timeslots, and physical layer waveform reconstruction. Finally, the known user waveform is removed by serial interference. If no known user exists, the system proceeds directly to the next timeslot.

[0063] The above embodiment, through joint multi-channel estimation, physical layer waveform reconstruction and serial interference cancellation, can realize the closed-loop processing of "multipath decoupling-joint estimation-interference cancellation", solving the coupling problem of multipath and multi-user interference in traditional methods.

[0064] In one embodiment, after step 103, the following further includes: if the currently active node is a single node, performing clear time slot signal detection and channel estimation to obtain a service data decoding result of the single node.

[0065] Specifically, if the current active node For a single node, such as Figure 4 As shown, in When , it means that the current time slot is a clean time slot (no data conflict). Clean time slot signal detection and channel estimation are performed first, and then demodulation, deframing, and decoding operations are performed in sequence to obtain the service data decoding result, calculate the time slot index and update it, and enter the next time slot.

[0066] In the above embodiment, by detecting whether the current time slot is a clear time slot, the service data decoding result of the single node corresponding to the current time slot can be directly obtained, which is conducive to providing an effective data basis for joint channel estimation of other time slots.

[0067] In one embodiment, after step 103, the following further comprises: if there is no currently active node in the current time slot, ending the current time slot detection and entering the next time slot.

[0068] Specifically, if Figure 4 As shown, if the current active node =0, it means there is no active node, the current time slot is an empty time slot, and it goes directly to the next time slot.

[0069] The above embodiment provides a method for processing empty time slots, improving the processing flow of the entire technical solution.

[0070] The following combination Figure 4 The following is an overall description of the EDOA-CRDSA access algorithm processing flow proposed in this application: (1) Initial stage

[0071] a) Start: Access algorithm process starts; b) Exclusive time slot index generation: Node Generates exclusive time slot index Provides identification basis for subsequent signal processing.

[0072] c) Radio frequency signal generation: Node According to the generated time slot index , generates a radio frequency signal for transmission in the corresponding time slot.

[0073] (2) Channel superposition and acquisition phase.

[0074] a) Channel superposition: Radio frequency signals are superimposed in the wireless channel to generate after Doppler, other user influences, etc. Further consider the influence from the path, superimposed as .

[0075] b) Access waveform acquisition: Satellite collects access waveform , obtains signal information sent by the node, as the data basis for subsequent processing.

[0076] (3) Iterative initialization and control.

[0077] a) Iterative initialization: Initializes the number of iterations , sets the initial state for subsequent iterative processing.

[0078] b) Iteration number update: Each time the iteration process is entered, the iteration number is increased by 1, i.e. .

[0079] c) Maximum iteration judgment: Judge whether the maximum iteration number set in advance is reached. If reached, enter the next time frame; if not reached, continue subsequent processing.

[0080] (4) Signal detection and channel estimation.

[0081] a) Time slot by time slot signal detection and channel estimation: Perform time slot by time slot signal detection on the collected access waveform, and simultaneously perform channel estimation to obtain signal characteristics and channel related parameters of each time slot.

[0082] b) Maximum time slot judgment: Judge whether the maximum time slot is reached. If reached, complete an iteration and perform corresponding processing; if not reached, continue subsequent steps.

[0083] (5) Active node number calculation and branch processing.

[0084] a) Active node number calculation: Calculate the number of active nodes in the current time slot .

[0085] b) Branch processing: ① : Clean time slot, first perform clean time slot signal detection and channel estimation, then successively perform demodulation, frame decoding, and decoding operation to obtain service data decoding results, solve the time slot index and update, and enter the next time slot.

[0086] ② : Multiple active nodes, dirty time slot. First query the known user time slot index to determine whether the dirty time slot exists known user. If it exists, successively perform known user MAC layer frame reconstruction, known user based MAC layer reconstructed frame and front and rear time slot joint direction finding, known user per-vibration element waveform reconstruction, and known user arrival direction solving, and finally independently perform serial interference cancellation (SIC) in the vibration element; if there is no known user, directly enter the next time slot.

[0087] ③ : No active node case, empty time slot, directly enter the next time slot.

[0088] (6) Loop and end: When a round of iteration is completed (the maximum time slot is reached or all cases are processed), it is decided whether to enter the next time frame according to whether the maximum iteration number is reached, and the next round of iteration processing is continued until the end condition is met.

[0089] The application also provides a CRDSA-based aircraft arrival direction estimation system, which comprises a low-orbit satellite and a user node, wherein the low-orbit satellite is loaded with a satellite-borne receiver; The user node is configured to send the same service copy package in at least two time slots in each time frame to form an access waveform corresponding to each time frame; the access waveform is a superimposed waveform sent by an access node after superimposing multipath interference and / or time delay; The satellite-borne receiver is configured to perform each step in the CRDSA-based aircraft arrival direction estimation method embodiment.

[0090] As Figure 5 shown, Figure 5 a system implementation block diagram of the CRDSA-based aircraft arrival direction estimation system is shown, and the system components are as follows: Node EDOA-CRDSA sending unit, it is worth mentioning that the sending unit fully multiplexes the traditional CRDSA algorithm. The EDOA-CRDSA sending unit specifically includes the following modules: I. Spaceborne antenna array: The spaceborne antenna array is composed of antenna units, each antenna unit includes a low noise amplifier (LNA), a mixer (LO), a bandpass filter (BPF), and the like.

[0091] II. Spaceborne CRDSA access & direction finding integrated processing unit, which is a core processing unit, including: (1) Array beamforming network: The multiple signals input from the spaceborne antenna array enter the array beamforming network, and through weighted summation and other processing of the signals of each array element, a beam with a specific directionality is formed, the signal in the desired direction is enhanced, the interference in other directions is suppressed, and the reception quality and directivity of the signal are improved.

[0092] (2) Time slot by time slot signal detection: The signals processed by the beamforming are detected time slot by time slot, to determine whether there is a signal in each time slot and the characteristics of the signal, and to detect whether the time slot is a clean time slot.

[0093] (3) Clean time slot judgment and processing: If a clean time slot is detected, clean time slot parameter estimation is performed, and then demodulation, frame decoding, and decoding operations are performed in turn, and finally the service data decoding result is obtained. If it is not a clean time slot, it enters the DOA estimation and SIC module.

[0094] (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 subsequent time slots, known user multi-array waveform reconstruction based on direction, and array element by array element iterative interference cancellation.

[0095] As shown in Figure 6 , the missile-borne processing unit system block diagram is shown in the following figure: Figure 6 The system components are as follows: (1) Service data input module: The service data symbol vector enters the sending unit and is temporarily stored in the service queue.

[0096] (2) MAC layer framing module: The service data in the service queue enters the MAC layer for framing operation, and the data is organized into a CRDSA frame structure.

[0097] (3) Encoding and modulation module: The framed service data is encoded and modulated.

[0098] (4) Access timing control and pattern generation module: the access timing control module generates access pattern through timing control and determines a time slot ID. The access pattern generation module cooperates with the radio frequency gate to control the sending time and mode of the radio frequency signal.

[0099] (5) Radio frequency signal output module: generates radio frequency signal and outputs to the multi-user access channel.

[0100] The CRDSA-based aircraft direction of arrival estimation device provided by the application is described below, and the CRDSA-based aircraft direction of arrival estimation device described below can be mutually corresponding to the CRDSA-based aircraft direction of arrival estimation method described above.

[0101] As Figure 7 shown, Figure 7 a module structure schematic diagram of the CRDSA-based aircraft direction of arrival estimation device is shown, which includes the following modules: The access waveform acquisition module 701 is used to acquire the access waveform sent by the access node; The time slot signal detection module 702 is used to detect the signal of each time slot in each time frame of the access waveform in turn; The active node judgment module 703 is used to judge whether the signal of each time slot is the signal sent by multiple active nodes; The target signal extraction module 704 is used to extract the target signal received by each element in the time slot if it is detected that the signal of any time slot is the signal sent by multiple active nodes; 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 by using maximum likelihood function estimation; The signal direction finding module 706 is used to obtain the element spacing and the incident angle corresponding to the target signal according to the relative time delay.

[0102] In an embodiment, the access node uses at least two time slots to send the same service copy package in each time frame; the target signal extraction module 704 is further used to: If it is detected that the signal of any time slot is the signal sent by multiple active nodes, joint channel estimation is performed according to the front and rear time slots in the at least two time slots of each active node in the multiple active nodes, and the target signal of each active node in the multiple active nodes in the time slot is obtained from the access waveform; wherein the target signal is the signal received by each element in the time slot.

[0103] In an embodiment, the target signal extraction module 704 is further configured to: If it is detected that the signal of any time slot is sent by multiple active nodes, jointly channel estimation is performed according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes, to obtain a maximum likelihood parameter estimate of each active node; Physical layer waveform reconstruction is performed on each active node according to the maximum likelihood parameter estimate, to obtain a reconstructed waveform of each active node received by each element; and the reconstructed waveform is taken as the target signal; After the relative time delay is obtained, the target signal corresponding to the element spacing and the incident angle are further obtained. Serial interference cancellation is performed on the target signal, to obtain a decoding waveform of each active node in the multiple active nodes.

[0104] In an embodiment, the target signal extraction module 704 is further configured to: If it is detected that the active node is a single node, net time slot signal detection and channel estimation are performed, to obtain a service data decoding result of the single node.

[0105] In an embodiment, the relative time delay calculation module 705 is further configured to: If the target signal is a narrowband signal, a carrier phase difference is taken as the relative time delay.

[0106] In an embodiment, the active node judgment module 703 is further configured to: If there is no current active node in the current time slot, the current time slot detection is ended, and the next time slot is entered.

[0107] Figure 8 An example of an entity structure diagram of an electronic device is shown in FIG. 1. Figure 8As shown, the electronic device can include a processor 810, a communications interface 820, a memory 830, and a communications bus 840, wherein the processor 810, the communications interface 820, and the memory 830 complete communications with each other through the communications bus 840. The processor 810 can invoke a logic instruction in the memory 830 to execute a CRDSA-based aircraft arrival direction estimation method, which includes: collecting an access waveform sent by an access node; in each time frame of the access waveform, sequentially detecting a signal of each time slot in each time frame; determining whether the signal of each time slot is a signal sent by multiple active nodes; if it is detected that the signal of any time slot is a signal sent by multiple active nodes, extracting a target signal received by each element in the time slot; using maximum likelihood function estimation to calculate a relative time delay between the target signal and a reference signal received by a reference element; and obtaining an element spacing and an incident angle corresponding to the target signal according to the relative time delay.

[0108] In addition, the logic instruction in the memory 830 described above can be implemented in the form of a software functional unit and sold or used as an independent product, and can be stored in a computer-readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0109] In another aspect, the present application also provides a computer program product comprising a computer program, which can be stored on a non-transitory computer readable storage medium, and the computer program is executable by a processor to enable a computer to perform the CRDSA-based aircraft direction of arrival estimation method provided by the above-mentioned methods, which comprises: collecting an access waveform sent by an access node; in each time frame of the access waveform, detecting signals in each time slot of the time frame in sequence; determining whether the signals in each time slot are signals sent by multiple active nodes; if it is detected that the signals in any time slot are signals sent by multiple active nodes, extracting target signals received by each element in the time slot; using maximum likelihood function estimation, calculating a relative time delay between the target signals and reference signals received by a reference element; and obtaining an element spacing and an incident angle corresponding to the target signals according to the relative time delay.

[0110] In yet another aspect, the present application also provides a non-transitory computer readable storage medium having a computer program stored thereon, and the computer program is executable by a processor to implement the CRDSA-based aircraft direction of arrival estimation method provided by the above-mentioned methods, which comprises: collecting an access waveform sent by an access node; in each time frame of the access waveform, detecting signals in each time slot of the time frame in sequence; determining whether the signals in each time slot are signals sent by multiple active nodes; if it is detected that the signals in any time slot are signals sent by multiple active nodes, extracting target signals received by each element in the time slot; using maximum likelihood function estimation, calculating a relative time delay between the target signals and reference signals received by a reference element; and obtaining an element spacing and an incident angle corresponding to the target signals according to the relative time delay.

[0111] The apparatus embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the present embodiment scheme according to actual needs. Those skilled in the art can understand and implement it without creative labor.

[0112] Those skilled in the art can clearly understand the technical solutions of the various embodiments from the above description of the embodiments, and the various embodiments can be implemented by means of software with the necessary general hardware platforms, and of course, can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in other words, the part of the prior art that makes a contribution, can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, and the like, and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0113] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for some technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A CRDSA-based aircraft direction of arrival estimation method, characterized in that, The method comprises: collecting an access waveform sent by an access node; in each time frame of the access waveform, sequentially detecting a signal of each time slot in each time frame; judging whether the signal of each time slot is a signal sent by multiple active nodes; if it is detected that the signal of any time slot is a signal sent by multiple active nodes, extracting a target signal received by each element in the time slot; using maximum likelihood function estimation, calculating a relative time delay between the target signal and a reference signal received by a reference element; according to the relative time delay, obtaining an element spacing and an incident angle corresponding to the target signal.

2. The CRDSA-based aircraft direction of arrival estimation method of claim 1, wherein, The access node uses at least two time slots in each time frame to send the same service copy package; and if it is detected that the signal of any time slot is a signal sent by multiple active nodes, the target signal received by each element in the time slot is extracted, which comprises: if it is detected that the signal of any time slot is a signal sent by multiple active nodes, jointly performing channel estimation according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes to obtain, from the access waveform, a target signal of each active node in the multiple active nodes in the time slot; wherein the target signal is the signal received by each element in the time slot.

3. The CRDSA-based aircraft direction of arrival estimation method of claim 2, wherein, The jointly performing channel estimation according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes to obtain, from the access waveform, a target signal of each active node in the multiple active nodes in the time slot, comprises: if it is detected that the signal of any time slot is a signal sent by multiple active nodes, jointly performing channel estimation according to the front and back time slots of the at least two time slots of each active node in the multiple active nodes to obtain a maximum likelihood parameter estimate of each active node; performing physical layer waveform reconstruction on each active node according to the maximum likelihood parameter estimate to obtain a reconstructed waveform of each active node received by each element; and taking the reconstructed waveform as the target signal; after the obtaining of the element spacing and the incident angle corresponding to the target signal according to the relative time delay, the method further comprises: performing serial interference cancellation on the target signal to obtain a decoding waveform of each active node in the multiple active nodes.

4. The CRDSA-based aircraft direction of arrival estimation method of claim 1, wherein, The method further comprises: if it is detected that the active node is a single node, performing net time slot signal detection and channel estimation to obtain a service data decoding result of the single node.

5. The CRDSA-based aircraft direction of arrival estimation method of claim 1, wherein, The method further comprises: if the target signal is a narrowband signal, taking a carrier phase difference as the relative time delay.

6. The CRDSA-based aircraft direction of arrival estimation method of claim 1, wherein, The method further comprises: if there is no current active node in the current time slot, ending the current time slot detection and entering the next time slot.

7. A CRDSA-based aircraft direction of arrival estimation system, characterized in that, The system comprises a low-orbit satellite and an access node, wherein the low-orbit satellite is loaded with a satellite-borne receiver; the access node is configured to use at least two time slots in each time frame to send the same service copy package, thereby forming an access waveform corresponding to each time frame; The satellite-borne receiver is configured to perform the CRDSA-based aircraft direction of arrival estimation method according to any one of claims 1 to 6.

8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and running on the processor, characterized in that, The processor realizes the CRDSA-based aircraft direction of arrival estimation method according to any one of claims 1 to 6 when executing the computer program. 9.A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program realizes the CRDSA-based aircraft direction of arrival estimation method according to any one of claims 1 to 6 when executed by the processor.

10. A computer program product comprising a computer program, characterized in that, The computer program realizes the CRDSA-based aircraft direction of arrival estimation method according to any one of claims 1 to 6 when executed by the processor.

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