Satellite joint channel estimation method, system and device based on CRDSA and medium

Abstract

The invention provides a satellite joint channel estimation method, system and device based on CRDSA and a medium, and belongs to the technical field of aerospace communication, and the method comprises the steps: obtaining an access waveform corresponding to a current time frame; the access node uses at least two time slots to send the same service copy packet in the current time frame; performing time slot-by-time signal detection on the access waveform to obtain a signal of each time slot; detecting a current active node under each time slot according to the signal of each time slot; and if the current active node is a plurality of nodes, performing joint channel estimation according to front and back time slots in the at least two time slots of each node, and obtaining a decoding waveform of each node from the superposed waveform. According to the method, a time diversity mechanism is used, an access node sends the same data at different times, so that a receiving end combines signals of a plurality of time slots to perform channel estimation, and even if the signals are subjected to fading or serious interference at some moments, reliable signals at other moments can supplement information, so that the channel estimation accuracy is improved.

Description

TECHNICAL FIELD

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

[0002] With the rise of low-altitude economy, emerging application scenarios such as unmanned aerial vehicle logistics and urban air mobility (UAM, Urban Air Mobility) have higher requirements for the real-time performance and stability of satellite communication. Low Earth orbit satellite communication system (LEO, Low Earth Orbit satellite communication) has become an important technical support in the above-mentioned emerging application scenarios due to its global coverage and low delay characteristics. In the process of low-altitude aircraft (such as unmanned aerial vehicles) accessing the low-orbit satellite communication channel, the common random access method is CRDSA (Contention Resolution Diversity Slotted Aloha, Conflict Resolution Diversity Slotted Aloha) technology.

[0003] However, in the high-speed relative motion scenario of low-orbit satellite communication, the low-orbit satellite motion speed reaches 7-8km / s, resulting in rapid changes in channel parameters, Doppler shift, and fading coefficients, and the time delay expansion of interference multipath signals and the Doppler expansion caused by satellite motion are coupled with each other, resulting in large channel estimation errors. In addition, the existing CRDSA technology only uses duplicate packets for communication conflict resolution, and the utilization rate of duplicate packets is insufficient, which makes it difficult to improve the throughput of the low-orbit satellite communication channel, resulting in a limited number of low-altitude aircraft accessing the low-orbit satellite, and the channel communication quality is not enough.

[0004] It can be seen that in the high-speed relative motion scenario of low-orbit satellite communication, the multipath fading and Doppler shift problems caused by time-varying multipath channels seriously affect the communication quality and transmission efficiency, and become a key bottleneck restricting the large-scale application of low-altitude economy and the performance improvement of satellite Internet services. SUMMARY

[0005] The present application provides a satellite joint channel estimation method, system, device and medium based on CRDSA, to solve the defect that the channel estimation is not accurate enough caused by time-varying multipath channels and round-trip delay, Doppler shift in the prior art, reduce the error probability of channel detection, and improve the accuracy of channel estimation.

[0006] The present application provides a satellite joint channel estimation method based on CRDSA, comprising the following steps.

[0007] acquire an access waveform corresponding to a current time frame, wherein the access waveform is a superposition waveform superimposed with multipath interference and / or time delay after the access node sends; the access node sends the same service copy package using at least two time slots in the current time frame; perform time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; detect a current active node under each time slot according to the signals of each time slot; if the current active node is a multi-node, perform joint channel estimation according to the front and rear time slots of the at least two time slots of each node in the multi-node to obtain a decoding waveform of each node in the multi-node from the superposition waveform.

[0008] According to the satellite joint channel estimation method based on CRDSA provided by the application, the joint channel estimation according to the front and rear time slots of the at least two time slots of each node in the multi-node to obtain a decoding waveform of each node in the multi-node from the superposition waveform if the current active node is a multi-node, comprises: if the current active node is a multi-node, perform joint channel estimation according to the front and rear time slots of the at least two time slots of each node in the multi-node to obtain a maximum likelihood parameter estimation and a multipath channel estimation of each node; perform physical layer waveform reconstruction on each node according to the maximum likelihood parameter estimation and the multipath channel estimation to obtain a reconstructed waveform; perform serial interference cancellation on the reconstructed waveform to obtain a decoding waveform of each node in the multi-node.

[0009] According to the satellite joint channel estimation method based on CRDSA provided by the application, the detection of a current active node under each time slot according to the signals of each time slot further comprises: if the current active node is a single node, perform net time slot signal detection and channel estimation to obtain a service data decoding result of the single node.

[0010] According to the satellite joint channel estimation method based on CRDSA provided by the application, the detection of a current active node under each time slot according to the signals of each time slot further comprises: if there is no current active node in the current time slot, end the current time slot detection and enter the next time slot.

[0011] According to the satellite joint channel estimation method based on CRDSA provided by the application, if the current active node is a multi-node, joint channel estimation is performed according to the front and rear time slots in the at least two time slots of each node in the multi-node, to obtain the maximum likelihood parameter estimation and the multipath channel estimation of each node, comprising: If the current active node is a multi-node, whether there is a known node in the multi-node is judged according to a preset node time slot index. Joint channel estimation is performed according to the front and rear time slots in the at least two time slots of each known node, to obtain the maximum likelihood parameter estimation and the multipath channel estimation of each known node.

[0012] The application further provides a satellite joint channel estimation system based on CRDSA, comprising a low-orbit satellite and a user node, wherein the low-orbit satellite is loaded with a satellite-borne receiver. The user node is used for transmitting 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 superposition waveform transmitted by an access node, superimposed with multipath interference and / or time delay. The satellite-borne receiver is used for performing each step in the satellite joint channel estimation method based on CRDSA.

[0013] The application further provides a satellite joint channel estimation device based on CRDSA, comprising the following modules: An access model acquisition module is used for acquiring an access waveform corresponding to a current time frame; wherein the access waveform is a superposition waveform transmitted by an access node, superimposed with multipath interference and / or time delay; the access node transmits the same service copy package in at least two time slots in the current time frame; A time slot-by-time slot detection module is used for performing time slot-by-time slot signal detection on the access waveform, to obtain signals of each time slot; A current active node detection module is used for detecting a current active node under each time slot according to the signals of each time slot; A joint channel estimation module is used for, if the current active node is a multi-node, performing joint channel estimation according to the front and rear time slots in the at least two time slots of each node in the multi-node, to obtain a decoding waveform of each node in the multi-node from the superposition waveform.

[0014] The application further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor; when the processor executes the computer program, the satellite joint channel estimation method based on CRDSA is realized.

[0015] The application further provides a non-transitory computer-readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the CRDSA-based satellite joint channel estimation method.

[0016] The application further provides a computer program product, which comprises a computer program, and the computer program is executed by a processor to implement the CRDSA-based satellite joint channel estimation method.

[0017] The application provides a CRDSA-based satellite joint channel estimation method, system, device and medium, which comprises the following steps: acquiring an access waveform corresponding to a current time frame; wherein the access waveform is a superposition waveform superimposed with multipath interference and / or time delay and sent by an access node; the access node sends the same service copy package in at least two time slots in the current time frame; performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; detecting a current active node in each time slot according to the signals of each time slot; if the current active node is a plurality of nodes, performing joint channel estimation according to the front and rear time slots in the at least two time slots of each node in the plurality of nodes to obtain a decoding waveform of each node in the plurality of nodes from the superposition waveform. The method uses a time diversity mechanism, sends the same data at different times by the access node, and makes the receiving end perform channel estimation in combination with signals of a plurality of time slots, so that reliable signals at other time slots can make up information and reduce error probability to improve channel estimation accuracy even if signals at some time are seriously affected by fading or interference, and the time delay, Doppler shift and fading coefficient of at least two copy packages are jointly attacked on the multipath channel, so that the joint estimation accuracy reaches CRLB (Cramér-Rao Lower Bound), thereby improving system throughput. BRIEF DESCRIPTION OF DRAWINGS

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

[0019] Figure 1 is a flowchart of the CRDSA-based satellite joint channel estimation method provided by the present application.

[0020] Figure 2 is a schematic diagram of a satellite-ground CRDSA multi-user access scenario provided by the present application.

[0021] Figure 3 is a schematic diagram of a time-varying multipath channel model provided by the present application.

[0022] Figure 4 is the JCE-CRDSA access algorithm processing flowchart provided by the present application.

[0023] Figure 5 is the JCE-CRDSA access system principle block diagram provided by the present application.

[0024] Figure 6 is the structural schematic diagram of the satellite joint channel estimation device based on CRDSA provided by the present application.

[0025] Figure 7 is the structural schematic diagram of the electronic device provided by the present application. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0027] The specific embodiments of the present application will be described below in combination with Figures 1-7 .

[0028] Figure 1 is the flowchart of the satellite joint channel estimation method based on CRDSA provided by the present application, and the execution subject of the method is the satellite side, specifically, the on-board receiver. As shown in Figure 1 , the method comprises the following steps: Step 101, acquiring an access waveform corresponding to a current time frame ; wherein the access waveform is a superposition waveform superimposed with multipath interference and / or time delay after being sent by an access node; the access node uses at least two time slots in the current time frame to send the same service copy package.

[0029] Wherein, one time frame contains a fixed number of time slots. In a time division multiplexing communication system, multiple different signal sources (such as multiple unmanned aerial vehicles) are allowed to share the same physical transmission channel. Each signal source (sending end) is allocated a specific time slot to transmit its own data, and the receiving end (i.e. the satellite) can extract the corresponding signal data from the specific time slot of each time frame.

[0030] Specifically, in the present embodiment, the signal sending end (hereinafter also referred to as “node” or “user”) sends a radio frequency signal to the satellite, as shown in Figure 2 , Figure 2The schematic diagram of satellite-to-ground CRDSA multi-user access scenario is shown. nodes To access low-orbit communication satellites, in the CRDSA access study, 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, . 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) are the same and can point out each other's positions. After MAC 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 time domain RF signal generated has a transmission power of . Symbol vector and the modulation mapping mode specified by the sender and receiver determine the .

[0031] This application still 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) Among them, R represents the real part of the complex number. 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; is the pulse shape of the output of the transmission shaping filter, Indicates that the pulse output by the sending shaping filter is shifted in time , used to limit signal bandwidth and reduce inter-symbol interference; denotes the duration of a symbol, denotes the center angular frequency of the carrier of the radio frequency signal transmitted; denotes the jth symbol; j is the imaginary unit.

[0032] Further, the transmission pattern of the user in the time slot is defined as follows: ; (2) Suppose that the node generates two service copy packets in the time slot and the time slot respectively. Figure 3 A schematic diagram of the time-varying multipath channel model of the node when accessing the low-orbit satellite in different time slots is given. As shown in the diagram, the main path distance of the node Figure 3 in the time slot is , and the distance of the secondary path in the time slot 1 after considering the scatterer is . Assuming that the node and the scatterer are invariable before , the main path distance of the node in the time slot is , and the distance of the secondary path in the time slot n after considering the scatterer is . In summary, the superimposed signal received by the satellite-borne receiver when only considering the main path is as follows: ; (3) wherein denotes the amplitude true value of the signal received by the node in the time slot , the time delay true value of the signal received by the node in the time slot , the carrier frequency offset true value of the signal received by the node in the time slot , the carrier initial phase true value of the signal received by the node in the time slot , and the additive white Gaussian noise generated by the satellite-borne receiver in the time slot ; K denotes the total number of user nodes accessing the channel in the time slot n.

[0033] ​​​​​​​​If further considering the path and time dynamic model, it can be expressed as: ; (4) ; (5) wherein formula (4) is a superposition signal model received by the spaceborne receiver at time slot n (considering multipath effect), is a signal received from the main path at time slot n, is a signal received from the secondary path at time slot n, is additive white Gaussian noise generated by the spaceborne receiver at time slot n; formula (5) is a superposition signal further considering the time dynamic model (considering time delay effect) on the basis of formula (4), wherein, is the time delay.

[0034] Since the low-orbit satellite orbit is known, and the time slot interval of different copy packets is known, the channel parameters of the main and secondary paths can be solved among different time slots, which is the basic principle of joint channel parameter estimation in the front and rear time slots of joint CRDSA.

[0035] The following takes any one node to illustrate the signal access process as follows: First, the node generates an exclusive time slot index , which is used to identify which time slot or time slots in the current time frame the node transmits the service copy packet, for example, when , it indicates that the node transmits the service copy packet in time slot 3 and time slot 5. The exclusive time slot index is used to provide an identification basis for subsequent signal processing.

[0036] Radio frequency signal generation: the node generates radio frequency signals (i.e. service copy packets) according to the generated time slot index , for transmission in the time slot corresponding to the time slot index.

[0037] Channel superposition: the radio frequency signal transmitted by the node in time slot n is superimposed in the wireless channel after multipath, other user effects, etc. to generate , and further considering the influence of the secondary path, the superposition is .

[0038] At this time, the satellite-borne receiver on the satellite collects the access waveform in the current time frame, and the access waveform in the current time frame contains superimposed signals of each time slot.

[0039] Step 102, performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; Specifically, the satellite-borne receiver extracts signals of each time slot from the access waveform corresponding to the current time frame, wherein the signal corresponding to time slot n is expressed as The signal is a superimposed signal superimposed with multipath interference and / or Round Trip Time (RTT), and also includes signals of other nodes concurrently accessing the channel (i.e., sending a service copy packet) in the time slot.

[0040] Step 103, calculating the current active node in each time slot according to the signals of each time slot.

[0041] The current active node refers to a user node that sends a service copy packet in the current time slot.

[0042] Specifically, each time slot of a data transmission frame (i.e., a time frame) can have three states: no service copy packet is sent, a single service copy packet is sent, and multiple service copy packets are sent. 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 identifier in the data packet.

[0043] Step 104, if the current active node is multiple nodes, performing joint channel estimation according to the previous and subsequent time slots of each node in the multiple nodes to obtain a decoding waveform of each node in the multiple nodes from the superimposed waveform.

[0044] For a time slot in which multiple service copy packets are sent, it can be considered that a data collision has occurred. The present application uses the CRDSA protocol to implement signal access, i.e., for a time slot in which multiple service copy packets collide, the receiver stores the superimposed signal received in the time slot, rather than directly discarding it. Since each service copy packet contains a dedicated time slot index created by the sending node, the dedicated time slot index can be used to indicate the service copy packet sent by the sending node in other time slots.

[0045] Specifically, as shown in Figure 2 , if the receiver receives multiple user node collision data packets in time slot 2 and time slot 3, it stores them. In time slot n, the receiver receives a service copy packet of user , successfully receives it and obtains the time slot index of user , and knows that user The service copy packet is sent in time slot 2. By reconstructing and subtracting it, the user The packet is successfully received, and the service duplicate packets of other users are finally obtained using the same method. At the end of the time frame, if there are still some service duplicate packets that have not been successfully received, the stored conflicting data packets are discarded. The user who failed to transmit the service duplicate packet will resend the service duplicate packet in the next time frame.

[0046] The above embodiment obtains the access waveform corresponding to the current time frame; wherein the access waveform is a superimposed waveform sent by the access node with multipath interference and / or time delay superimposed; the access node uses at least two time slots in the current time frame to send the same service copy packet; the access waveform is subjected to time slot-by-time slot signal detection to obtain the signal of each time slot; based on the signal of each time slot, the current active node in each time slot is detected; if the current active node is a multiple node, a joint channel estimation is performed based on the previous and next time slots in the at least two time slots of each node in the multiple nodes, and a decoding waveform of each node in the multiple nodes is obtained from the superimposed waveform. This method uses a time diversity mechanism, in which access nodes send the same data at different times, allowing the receiver to combine signals from multiple time slots for channel estimation. Even if the signal is severely faded or interfered with at certain moments, reliable signals at other times can provide additional information, reducing the error probability and improving the accuracy of channel estimation. At least two replica packets are used to jointly assess the delay, Doppler shift, and fading coefficient of the multipath channel, so that the joint estimation accuracy reaches CRLB (Cramér-Rao Lower Bound), thereby improving system throughput.

[0047] In one embodiment, the above-mentioned step 104 includes: if the currently active node is a multi-node, performing joint channel estimation based on the previous and next time slots of the at least two time slots of each node in the multi-nodes to obtain the maximum likelihood parameter estimate and multipath channel estimate of each node; reconstructing the physical layer waveform of each node based on the maximum likelihood parameter estimate and the multipath channel estimate to obtain a reconstructed waveform; and performing serial interference cancellation on the reconstructed waveform to obtain a decoding waveform of each node in the multi-nodes.

[0048] In another embodiment, if the currently active node is a plurality of nodes, it is determined whether there are known nodes among the plurality of nodes according to a 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.

[0049] Specifically, if Figure 4 As shown, Figure 4The JCE-CRDSA (Joint Channel Estimation-basedCRDSA) access algorithm processing flow chart is shown in Figure 4 In 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.

[0050] 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", and solve the coupling problem of multipath and multi-user interference in traditional methods.

[0051] In one embodiment, after step 103, the method 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.

[0052] 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.

[0053] 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.

[0054] In one embodiment, after step 103, the following further steps are included: if there is no currently active node in the current time slot, then the current time slot detection is ended and the next time slot is entered.

[0055] Specifically, if Figure 4 As shown, if the current active node , it means that there is no active node, the current time slot is an empty time slot, and it directly enters the next time slot.

[0056] The above embodiment provides a method for processing empty time slots, improving the processing flow of the entire technical solution.

[0057] The following describes the JCE-CRDSA access algorithm processing flow proposed in the present application in an overall manner: Figure 4 The JCE-CRDSA access algorithm processing flow proposed in the present application is described in an overall manner as follows: (1) Start stage.

[0058] a) Start: the access algorithm flow is started; b) Exclusive time slot index generation: the node generates an exclusive time slot index to provide an identification basis for subsequent signal processing.

[0059] c) Radio frequency signal generation: the node generates a radio frequency signal according to the generated time slot index , for transmission in the corresponding time slot.

[0060] (2) Channel superposition and collection stage.

[0061] a) Channel superposition: the radio frequency signal is superimposed in the wireless channel to generate after superimposition of Doppler and other user influences. Further consideration is given to the influence of the path, and the superposition is .

[0062] b) Access waveform collection: the satellite collects the access waveform to obtain the signal information sent by the node, as a data basis for subsequent processing.

[0063] (3) Iterative initialization and control.

[0064] a) Iterative initialization: the number of iterations is initialized to set the initial state for subsequent iterative processing.

[0065] b) Iteration number update: each time the iteration flow is entered, the iteration number is increased by 1, i.e. .

[0066] c) Maximum iteration judgment: whether the maximum iteration number set in advance is reached is judged. If it is reached, the next time frame is entered; if it is not reached, subsequent processing is continued.

[0067] (4) Signal detection and channel estimation.

[0068] a) Time slot-by-time slot signal detection and channel estimation: time slot-by-time slot signal detection is performed on the collected access waveform, and channel estimation is simultaneously performed to obtain signal characteristics and channel-related parameters of each time slot.

[0069] b) Maximum time slot judgment: whether the maximum time slot If reached, complete one iteration and corresponding processing; if not reached, continue the following steps.

[0070] (5) Active node number calculation and branch processing.

[0071] a) Active node number calculation: calculate the number of active nodes in the current time slot .

[0072] b) Branch processing: ① : clean time slot, first perform clean time slot signal detection and channel estimation, then successively perform demodulation, frame demodulation, decoding operation to obtain service data decoding result, solve time slot index and update, and enter the next time slot.

[0073] 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 before and after time slot joint maximum likelihood parameter estimation, known user before and after time slot joint multipath channel estimation, known user physical layer waveform reconstruction, and finally serial interference deletion known user waveform; if there is no known user, directly enter the next time slot.

[0074] ③ : no active node case, empty time slot, directly enter the next time slot.

[0075] (6) Loop and end: when completing a round of iteration (reaching the maximum time slot or processing all cases), according to whether the maximum iteration number is reached, it is determined whether to enter the next time frame, continue the next round of iteration processing, until the end condition is met.

[0076] The application also provides a satellite joint channel estimation system based on CRDSA, 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 used for transmitting 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 superposition waveform transmitted by an access node after superposition of multipath interference and / or time delay; The satellite-borne receiver is used for performing each step in the satellite joint channel estimation method based on CRDSA.

[0077] As Figure 5 shown, Figure 5 a JCE-CRDSA access system principle block diagram is shown, which comprises at least one node CRDSA sending unit and spaceborne multi-user multipath CRDSA access processing unit, the composition structure and function principle of each unit are described as follows: I. At least one node CRDSA sending unit (i.e. node JCE-CRDSA sending unit), it is worth mentioning that the node CRDSA sending unit completely multiplexes the traditional CRDSA algorithm. The node CRDSA sending unit specifically includes the following modules: (1) Service data input module (not shown in the figure): service data symbol vector into the node CRDSA sending unit, is sent into the "service queue" for temporary storage.

[0078] (2) MAC layer framing module: service data in the "service queue" enters the MAC layer for framing operation, and organizes the data into CRDSA frame structure.

[0079] (3) Encoding and modulation module: the framed service data is processed by encoding and modulation.

[0080] (4) Access timing control and pattern generation module: the access timing control module generates the access pattern and determines the time slot ID through timing control. The access pattern generation module cooperates with the radio frequency gate to control the sending time and mode of the radio frequency signal.

[0081] (5) Radio frequency signal output module: generates the radio frequency signal and outputs to the multi-user access channel.

[0082] II. Spaceborne multi-user multipath CRDSA access processing unit, with multi-user multipath CRDSA access processing capability. Including the following modules: (1) Time slot by time slot signal detection module: time slot by time slot signal detection is performed on the multi-user time slot access waveform.

[0083] (2) Clean time slot judgment and processing module: judge whether the detected time slot is a clean time slot. If it is a clean time slot, perform clean time slot multipath channel parameter estimation, then perform demodulation, framing, decoding operation in turn to obtain service data decoding result; if it is not a clean time slot, enter the interference deletion and related processing flow.

[0084] ​(3) Multi-user iterative serial interference cancellation & known user optimal channel estimation module: including modules such as known user MAC layer frame reconstruction, known user front and back time slot joint maximum likelihood parameter estimation, known user front and back time slot joint channel estimation, known user physical layer waveform reconstruction, and serial iterative interference cancellation (SIC), which realizes effective processing of multi-user signals and known user optimal channel estimation.

[0085] The satellite joint channel estimation device based on CRDSA provided by the present invention is described below. The satellite joint channel estimation device based on CRDSA described below and the satellite joint channel estimation method based on CRDSA described above can refer to each other.

[0086] like Figure 6 As shown, Figure 6 The module structure diagram of the satellite joint channel estimation device based on CRDSA is shown, including the following modules: Access model acquisition module 601 is configured to acquire an access waveform corresponding to a current time frame; wherein the access waveform is a superimposed waveform transmitted by an access node with multipath interference and / or time delay superimposed thereon; and the access node transmits the same service copy packet using at least two time slots in the current time frame. A time slot detection module 602 is configured to perform time slot-by-time slot signal detection on the access waveform to obtain a signal of each time slot; The current active node detection module 603 is used to detect the current active node in each time slot based on the signal of each time slot; The joint channel estimation module 604 is used to perform joint channel estimation based on the previous and next time slots of the at least two time slots of each node in the multiple nodes if the currently active node is multiple nodes, and obtain the decoding waveform of each node in the multiple nodes from the superimposed waveform.

[0087] In one embodiment, the joint channel estimation module 604 is further configured to: If the currently active node is multiple nodes, performing joint channel estimation based on the previous and next time slots of the at least two time slots of each node in the multiple nodes to obtain a maximum likelihood parameter estimate and a multipath channel estimate for each node; Reconstructing a physical layer waveform for each node according to the maximum likelihood parameter estimate and the multipath channel estimate to obtain a reconstructed waveform; Serial interference cancellation is performed on the reconstructed waveform to obtain a decoding waveform of each node in the multiple nodes.

[0088] In one embodiment, the joint channel estimation module 604 is further configured to: If the current active node is a single node, then net slot signal detection and channel estimation are performed to obtain service data decoding results of the single node.

[0089] In an embodiment, the joint channel estimation module 604 is further configured to: If there is no current active node in the current time slot, then the current time slot detection is ended and the next time slot is entered.

[0090] In an embodiment, the joint channel estimation module 604 is further configured to: If the current active node is a multi-node, then it is determined whether there is a known node in the multi-node according to a preset node time slot index. Joint channel estimation is performed 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.

[0091] Figure 7 An example of an entity structure diagram of an electronic device is shown in FIG. 7. Figure 7 As shown in FIG. 7, the electronic device can include a processor 710, a communications interface 720, a memory 730, and a communications bus 740, wherein the processor 710, the communications interface 720, and the memory 730 can communicate with each other through the communications bus 740. The processor 710 can invoke a logic instruction in the memory 730 to execute a satellite joint channel estimation method based on CRDSA, which includes: obtaining an access waveform corresponding to a current time frame; wherein the access waveform is a superimposed waveform superimposed with multipath interference and / or time delay after being sent by an access node; the access node uses at least two time slots to send the same service copy package in the current time frame; performing time slot-by-time slot signal detection on the access waveform to obtain signals of each time slot; detecting a current active node under each time slot according to the signals of each time slot; if the current active node is a multi-node, then performing joint channel estimation according to the front and rear time slots in the at least two time slots of each node in the multi-node to obtain a decoding waveform of each node in the multi-node from the superimposed waveform.

[0092] In addition, the logic instructions in the memory 730 described above can be implemented in the form of software functional units and sold or used as independent products, and can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the parts that contribute to the prior art or parts 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 a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The foregoing 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 media that can store program codes.

[0093] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program can be stored on a non-transitory computer readable storage medium, and the computer program can be executed by a processor to enable a computer to perform the CRDSA-based satellite joint channel estimation method provided by the above-mentioned methods. The method comprises: obtaining an access waveform corresponding to a current time frame; wherein the access waveform is a superposition waveform superimposed with multipath interference and / or time delay and sent by an access node; the access node sends the same service copy package using at least two time slots in the current time frame; performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; detecting a current active node under each time slot according to the signals of each time slot; and if the current active node is a plurality of nodes, performing joint channel estimation according to the front and rear time slots of each node in the at least two time slots of each node in the plurality of nodes to obtain a decoding waveform of each node in the plurality of nodes from the superposition waveform.

[0094] 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 executed by a processor to implement the CRDSA-based satellite joint channel estimation method provided by the above-mentioned methods. The method comprises: obtaining an access waveform corresponding to a current time frame; wherein the access waveform is a superposition waveform superimposed with multipath interference and / or time delay and sent by an access node; the access node sends the same service copy package using at least two time slots in the current time frame; performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; detecting a current active node under each time slot according to the signals of each time slot; and if the current active node is a plurality of nodes, performing joint channel estimation according to the front and rear time slots of each node in the at least two time slots of each node in the plurality of nodes to obtain a decoding waveform of each node in the plurality of nodes from the superposition waveform.

[0095] The apparatus embodiments described above are merely illustrative, wherein the units described as separated components can or can not be physically separated, 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 to multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0096] Through the description of the above embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software and the necessary universal hardware platform, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of software products, and the computer software products can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and include a plurality of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments.

[0097] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to 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 part of the technical features; 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 satellite joint channel estimation method based on CRDSA, characterized in that: include: Acquire an access waveform corresponding to the current time frame; wherein the access waveform is a superimposed waveform sent by the access node with multipath interference and / or time delay superimposed; the access node uses at least two time slots in the current time frame to send the same service copy packet; Performing time slot signal detection on the access waveform to obtain a signal of each time slot; According to the signal of each time slot, detect the current active node in each time slot; If the currently active node is multiple nodes, joint channel estimation is performed based on the preceding and following time slots of the at least two time slots of each node in the multiple nodes, and a decoding waveform of each node in the multiple nodes is obtained from the superimposed waveform.

2. The satellite joint channel estimation method based on CRDSA according to claim 1, characterized in that: If the currently active node is multiple nodes, performing joint channel estimation based on the preceding and following time slots of the at least two time slots of each node in the multiple nodes, and obtaining a decoding waveform of each node in the multiple nodes from the superimposed waveform, including: If the currently active node is multiple nodes, performing joint channel estimation based on the previous and next time slots of the at least two time slots of each node in the multiple nodes to obtain a maximum likelihood parameter estimate and a multipath channel estimate for each node; Reconstructing a physical layer waveform for each node according to the maximum likelihood parameter estimate and the multipath channel estimate to obtain a reconstructed waveform; Serial interference cancellation is performed on the reconstructed waveform to obtain a decoding waveform of each node in the multiple nodes.

3. The satellite joint channel estimation method based on CRDSA according to claim 1, characterized in that: After detecting the current active node in each time slot according to the signal of each time slot, the method further includes: If the currently active node is a single node, clear time slot signal detection and channel estimation are performed to obtain a service data decoding result of the single node.

4. The satellite joint channel estimation method based on CRDSA according to claim 1, characterized in that: After detecting the current active node in each time slot according to the signal of each time slot, the method further includes: If there is no currently active node in the current time slot, the current time slot detection ends and enters the next time slot.

5. The satellite joint channel estimation method based on CRDSA according to claim 2, characterized in that: If the currently active node is a plurality of nodes, performing joint channel estimation according to the preceding and following time slots of the at least two time slots of each node in the plurality of nodes to obtain a maximum likelihood parameter estimate and a multipath channel estimate for each node, including: If the currently active node is multiple nodes, determine whether there is a known node among the multiple nodes according to a 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 a maximum likelihood parameter estimate and a multipath channel estimate for each known node.

6. A satellite joint channel estimation system based on CRDSA, characterized in that: The system comprises a low-orbit satellite and a user node, wherein the low-orbit satellite carries a satellite-borne receiver; The user node is configured to use at least two time slots in each time frame to send the same service copy packet to form an access waveform corresponding to each time frame; the access waveform is a superimposed waveform sent by the access node with multipath interference and / or time delay superimposed; The satellite-borne receiver is used to execute the CRDSA-based satellite joint channel estimation method according to any one of claims 1 to 5.

7. A satellite joint channel estimation device based on CRDSA, characterized in that: include: An access model acquisition module, configured to acquire an access waveform corresponding to a current time frame; wherein the access waveform is a superimposed waveform transmitted by an access node with multipath interference and / or time delay superimposed thereon; and wherein the access node transmits the same service copy packet using at least two time slots in the current time frame; A time slot detection module, configured to perform time slot signal detection on the access waveform to obtain a signal of each time slot; The current active node detection module is used to detect the current active node in each time slot based on the signal of each time slot; A joint channel estimation module is used to perform joint channel estimation based on the preceding and following time slots of the at least two time slots of each node in the multiple nodes if the currently active node is multiple nodes, and obtain a decoding waveform of each node in the multiple nodes from the superimposed waveform.

8. 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, the CRDSA-based satellite joint channel estimation method according to any one of claims 1 to 5 is implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the CRDSA-based satellite joint channel estimation method according to any one of claims 1 to 5 is implemented.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the CRDSA-based satellite joint channel estimation method according to any one of claims 1 to 5 is implemented.

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