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

Abstract

The application provides a satellite joint channel estimation method, system, device and medium based on CRDSA, and belongs to the technical field of space-air communication. The method comprises the following steps: acquiring an access waveform corresponding to a current time frame; using at least two time slots in the current time frame to send the same service copy package by an access node; performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot; detecting current active nodes under each time slot according to the signals of each time slot; if the current active nodes are multiple nodes, performing joint channel estimation according to the front and rear time slots in the at least two time slots of each node to obtain decoding waveforms of each node from a superposition waveform. The method uses a time diversity mechanism, sends the same data at different times by the access node, combines signals of multiple time slots for channel estimation at the receiving end, and even if the signals are seriously affected by fading or interference at some time, reliable signals at other times 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] 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 the access node transmits; the access node transmits the same service copy package using at least two time slots in the current time frame;

[0008] performing time-slot-by-time-slot signal detection on the access waveform to obtain signals of each time slot;

[0009] detecting a current active node in each time slot according to the signals of each time slot;

[0010] if the current active node is a multi-node, performing 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.

[0011] 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:

[0012] if the current active node is a multi-node, performing 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.

[0013] performing physical layer waveform reconstruction on each node according to the maximum likelihood parameter estimation and the multipath channel estimation to obtain a reconstructed waveform;

[0014] performing serial interference cancellation on the reconstructed waveform to obtain a decoding waveform of each node in the multi-node.

[0015] According to the satellite joint channel estimation method based on CRDSA provided by the application, the detection of a current active node in each time slot according to the signals of each time slot further comprises:

[0016] if the current 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.

[0017] According to the satellite joint channel estimation method based on CRDSA provided by the application, the detection of a current active node in each time slot according to the signals of each time slot further comprises:

[0018] if there is no current active node in the current time slot, ending the current time slot detection and entering the next time slot.

[0019] 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:

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 superposition waveform sent by an access node, superimposed with multipath interference and / or time delay.

[0024] The satellite-borne receiver is configured to perform each step in the satellite joint channel estimation method based on CRDSA.

[0025] The application further provides a satellite joint channel estimation device based on CRDSA, comprising the following modules:

[0026] An access model acquisition module is configured to acquire an access waveform corresponding to a current time frame; wherein the access waveform is a superposition waveform sent by an access node, superimposed with multipath interference and / or time delay; the access node sends the same service copy package in at least two time slots in the current time frame.

[0027] A time slot-by-time slot detection module is configured to perform time slot-by-time slot signal detection on the access waveform, to obtain signals of each time slot.

[0028] A current active node detection module is configured to detect a current active node in each time slot according to the signals of each time slot.

[0029] A joint channel estimation module is configured to, if the current active node is a multi-node, perform 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.

[0030] 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 CRDSA-based satellite joint channel estimation method according to any one of the above when executing the computer program.

[0031] The application further provides a non-transitory computer-readable storage medium, which stores a computer program, wherein the computer program is executed by a processor to implement the CRDSA-based satellite joint channel estimation method according to any one of the above.

[0032] The application further provides a computer program product, comprising a computer program, wherein the computer program is executed by a processor to implement the CRDSA-based satellite joint channel estimation method according to any one of the above.

[0033] 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 superimposed waveform superimposed with multipath interference and / or time delay and sent by an access node; the access node sends the same service copy packet 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 superimposed 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 multiple 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 packets are jointly attacked on a multipath channel, so that the joint estimation accuracy reaches CRLB (Cramér-Rao Lower Bound), thereby improving system throughput. BRIEF DESCRIPTION OF DRAWINGS

[0034] 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 those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0035] Figure 1 is a flowchart of the CRDSA-based satellite joint channel estimation method provided by the present application.

[0036] Figure 2 is a schematic diagram of a satellite-ground CRDSA multi-user access scenario provided by the present application.

[0037] Figure 3 is a schematic diagram of a time-varying multipath channel model provided by the present application.

[0038] Figure 4 is a flowchart of a JCE-CRDSA access algorithm processing provided by the present application.

[0039] Figure 5 is a principle block diagram of a JCE-CRDSA access system provided by the present application.

[0040] Figure 6 is a structural schematic diagram of a satellite joint channel estimation device based on CRDSA provided by the present application.

[0041] Figure 7 is a structural schematic diagram of an electronic device provided by the present application. DETAILED DESCRIPTION

[0042] 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 with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative work fall within the protection scope of the present application.

[0043] The specific embodiments of the present application will be described below with reference to the drawings. Figures 1-7 DETAILED DESCRIPTION

[0044] Figure 1 is a flowchart of a satellite joint channel estimation method based on CRDSA provided by the present application. The execution subject of the method is a satellite side, specifically, a satellite-borne receiver. As shown in Figure 1 , the method comprises the following steps:

[0045] 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.

[0046] A time frame contains a fixed number of time slots. In a time-division multiplexing communication system, multiple different signal sources (such as multiple drones) are allowed to share the same physical transmission channel. Each signal source (transmitter) is assigned a specific time slot to transmit its own data, and the receiver (i.e., the satellite) can extract the corresponding signal data from the specific time slot of each time frame.

[0047] Specifically, in this embodiment, the signal transmitting end (hereinafter also referred to as a "node" or "user") sends radio frequency signals to the satellite, such as... Figure 2 As shown, Figure 2 The diagram illustrates a multi-user access scenario using a satellite-to-ground CRDSA system, which includes... Nodes To access low-Earth orbit communication satellites, the CRDSA access study assumes that the satellite and all spacecraft nodes share a unified time reference. The satellite divides each uplink communication frame into... A length of The access time slot, the time slot index within the time frame is... express, User node Based on the CRDSA (Conflict Resolution Diversity Slotted Random Access) mechanism, at least two slots are selected in each time frame to send service replica packets, i.e., the number of service replica packets. .node Transmitted in an uplink time frame Symbol vector of each business copy package (That is, the time slot index created by this node, explained in detail later) are the same and can mutually indicate each other's positions. Symbol vector After framing, modulation and coding, and radio frequency module processing at the MAC layer, the output is an uplink signal. For ease of subsequent derivation, we define... For example: taking the starting point of any time slot n as the time zero point, in the nth time slot... In each time slot, the node The generated time-domain radio frequency signal has a transmit power of Symbolic vector The modulation mapping mode specified by both the sender and receiver determines the overall system. .

[0048] 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-air cross-domain communication scenarios. Then the node... Radio frequency signal transmitted in time slot n The function of time t is expressed as follows, where the subscript k identifies the k-th user and the superscript n identifies the n-th time slot:

[0049] ; (1)

[0050] where R represents the real part of a complex number, is the number of symbols to be transmitted, i.e., the node is the total number of symbols transmitted in time slot n; is the node is the symbol vector in the current time frame; is the pulse shape of the transmit shaping filter output, denotes the time shift of the transmit shaping filter output pulse for limiting the signal bandwidth and reducing inter-symbol interference; is the transmit symbol duration, is the center angular frequency of the transmit RF signal carrier; denotes the jth symbol; j is the imaginary unit.

[0051] Further, the transmit pattern of the user in time slot is denoted by and is defined as follows:

[0052] ; (2)

[0053] Let it be assumed that the node generates two service copy packets in time slot and time slot . Figure 3 A schematic diagram of the time-varying multipath channel model of the node when accessing the low earth orbit satellite at different time slots is given. As shown, the main path distance of the node Figure 3 in time slot is , and the distance of the secondary path after considering the scatterer in time slot 1 is . Assuming that the node and the scatterer are constant before , the main path distance of the node in time slot is , and the distance of the secondary path after considering the scatterer in time slot n is . In summary, the superimposed signal received by the satellite-borne receiver when only considering the main path is as follows:

[0054] ; (3)

[0055] where denotes the node in time slot​​ The true amplitude of the received signal is on the main path. Represents a node In the time slot The true value of the delay of the received signal on the main path. Represents a node In the time slot The true value of the carrier frequency offset of the received signal in the main path. Represents a node In the time slot The true value of the carrier initial phase of the received signal on the main path. Indicates the satellite receiver in the time slot The resulting additive white Gaussian noise; K represents the total number of user nodes accessing the channel in time slot n.

[0056] If we further consider the path and time dynamics model, it can be expressed as follows:

[0057] ; (4)

[0058] ; (5)

[0059] Formula (4) represents the superimposed signal model received by the satellite receiver in time slot n. (Multipath effects were taken into account) For the signal received from the main path in time slot n, For the signal received from the slave path in time slot n, For the spaceborne receiver in time slot The resulting additive white Gaussian noise;

[0060] Formula (5) is the superimposed signal based on Formula (4), further considering the time dynamic model (considering the time delay effect), where, For time delay.

[0061] Since the low-Earth orbit satellite orbits are known and the time slot intervals of different replica packets are known, the channel parameters of the master and slave paths can be solved for each other in different time slots. This is the basic principle of joint channel parameter estimation in the time slots before and after joint CRDSA.

[0062] The following uses any one of these nodes. The signal access process is explained as follows:

[0063] First, nodes Generate a dedicated time slot index This dedicated time slot index is used to identify the node. In which time slots(s) of the current time frame was the service replica packet sent? For example, when... When, it indicates a node Service replica packets were transmitted in time slots 3 and 5. (Dedicated time slot index) Used to provide an identifier basis for subsequent signal processing.

[0064] Radio frequency signal generation: node Based on the generated time slot index ,generate radio frequency signals (i.e., business copy packet), used for transmission within the time slot corresponding to the time slot index.

[0065] Channel overlay: Node Radio frequency signal transmitted in time slot n The image is generated after superimposing Doppler and other user effects in the wireless channel. Furthermore, considering the impact of the path, it is superimposed as .

[0066] At this time, the satellite's onboard receiver collects the access waveform of the current time frame, which contains superimposed signals from each time slot.

[0067] Step 102: Perform time-slot-by-time signal detection on the access waveform to obtain the signal of each time slot;

[0068] Specifically, the onboard receiver extracts the signals for each time slot from the access waveform corresponding to the current time frame, where the signal corresponding to time slot n is represented as follows: This signal is a superimposed signal with multipath interference and / or round trip time (RTT), and also includes the signals of other nodes that concurrently access the channel (i.e., send service copy packets) in this time slot.

[0069] Step 103: Calculate the current active node in each time slot based on the signals from each time slot.

[0070] Among them, the currently active node refers to the user node that sent the business replica packet in the current time slot.

[0071] Specifically, each time slot of a data transmission frame (i.e., a time frame) may have three states: no service replica packets are sent, a single service replica packet is sent, and multiple service replica packets are sent. The onboard receiver can identify these three states for each time slot and detect the currently active node in each time slot based on the user node identifier in the data packet.

[0072] Step 104: If the currently active node is a multi-node, then perform joint channel estimation based on the preceding and following time slots of each of the multi-nodes, and obtain the decoding waveform of each of the multi-nodes from the superimposed waveform.

[0073] In this context, a data conflict can be considered to have occurred in a time slot where multiple service replica packets are being sent. This application uses the CRDSA protocol to implement signal access. That is, for a time slot with multiple conflicting service replica packets, the receiver will store the superimposed signal received in that time slot instead of discarding it directly. Since each service replica packet contains a dedicated time slot index created by the sending node, the service replica packets sent by the sending node in other time slots can be identified based on this dedicated time slot index.

[0074] Specifically, such as Figure 2 As shown, if the receiver receives conflicting data packets from multiple user nodes in time slots 2 and 3, it stores them all. If a user node receives conflicting data packets in time slot n... The business copy package was successfully received and the user's information was obtained. Time slot index Knowing the user The service replica packet was sent in time slot 2. By reconstructing and subtracting it, the user can be obtained from the conflicting replica packet in time slot 2. The system successfully receives the packets and then uses the same method to obtain the service replica packets from other users. When the time frame ends, if there are still some service replica packets that have not been successfully received, the already stored conflicting packets are discarded. Users whose transmissions failed will resend the service replica packets in the next time frame.

[0075] In the above embodiment, the access waveform corresponding to the current time frame is obtained; wherein, the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay; 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 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 multiple nodes, joint channel estimation is performed based on the preceding and following time slots of the at least two time slots of each of the multiple nodes, and the decoding waveform of each of the multiple nodes is obtained from the superimposed waveform. This method uses a time diversity mechanism, where 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 fading or interfered with at some times, reliable signals from other times can supplement the information, reducing the error probability and improving the accuracy of channel estimation. It uses at least two replica packets to jointly attack the delay, Doppler shift, and fading coefficient of the multipath channel, achieving a joint estimation accuracy of CRLB (Cramér-Rao Lower Bound), thereby improving system throughput.

[0076] In an embodiment, the step 104 comprises: if the current active node is a multi-node, jointly estimating channels according to the front and back time slots of each node in the multi-node, to obtain maximum likelihood parameter estimates and multipath channel estimates of each node; performing physical layer waveform reconstruction on each node according to the maximum likelihood parameter estimates and multipath channel estimates, to obtain a reconstructed waveform; and performing serial interference cancellation on the reconstructed waveform, to obtain a decoded waveform of each node in the multi-node.

[0077] In another embodiment, if the current active node is a multi-node, determining whether there is a known node in the multi-node according to a preset node time slot index; and jointly estimating channels according to the front and back time slots of each known node, to obtain maximum likelihood parameter estimates and multipath channel estimates of each known node.

[0078] Specifically, as shown in Figure 4 , Figure 4 A JCE-CRDSA (Joint Channel Estimation-based CRDSA) access algorithm processing flowchart is shown in Figure 4 If there are multiple active nodes in the same time slot, it means that the data packets in the time slot have collided, and dirty time slot (a time slot with error data, indicating that the time slot is interfered by data) detection needs to be started: first, query the known user time slot index to determine whether there is a known user in the dirty time slot. If there is, sequentially perform 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 multipath channel estimation, known user physical layer waveform reconstruction, and finally serial interference cancellation of the known user waveform; if there is no known user, directly enter the next time slot.

[0079] The above embodiment can realize a closed-loop processing of "multipath decoupling-joint estimation-interference cancellation" through joint multi-channel estimation, physical layer waveform reconstruction, and serial interference cancellation, and solve the coupling problem of multipath and multi-user interference in the traditional method.

[0080] In an embodiment, the step 103 further comprises: if the current active node is a single node, performing clean time slot signal detection and channel estimation, to obtain a service data decoding result of the single node.

[0081] Specifically, if the current active node is a single node, as shown in Figure 4 , in When the current time slot is a clean time slot, the clean time slot signal detection and channel estimation are performed first, then the demodulation, frame demodulation and decoding operations are performed in sequence to obtain the service data decoding result, the time slot index is calculated and updated, and the next time slot is entered.

[0082] In the above embodiment, by detecting that the current time slot is a clean time slot, the service data decoding result of the single node corresponding to the current time slot can be directly obtained, which is beneficial to providing an effective data basis for joint channel estimation of other time slots.

[0083] In an embodiment, the step 103 further includes: if there is no current active node in the current time slot, ending the current time slot detection and entering the next time slot.

[0084] Specifically, as shown in Figure 4 , if the current active node , it means that there is no active node, the current time slot is an empty time slot, and the next time slot is directly entered.

[0085] The above embodiment provides a processing manner for the empty time slot, and perfects the processing flow of the whole technical solution.

[0086] The JCE-CRDSA access algorithm processing flow proposed in the present application will be described as a whole below: Figure 4

[0087] (1) Start stage.

[0088] a) Start: the access algorithm flow is started;

[0089] b) Exclusive time slot index generation: the node generates an exclusive time slot index , which provides an identification basis for subsequent signal processing.

[0090] c) Radio frequency signal generation: the node generates radio frequency signals according to the generated time slot index , which are used for transmission in the corresponding time slot.

[0091] (2) Channel superposition and collection stage.

[0092] a) Channel superposition: the radio frequency signals are superposed in the wireless channel to generate after the Doppler and other user influences. Further, the influence of the path is considered, and the superposition is .

[0093] b) Access waveform collection: the satellite collects the access waveform ​, the signal information sent by the node is acquired as the data basis for subsequent processing.

[0094] (3) Iterative initialization and control.

[0095] a) Iterative initialization: initialize the number of iterations , set the initial state for subsequent iterative processing.

[0096] b) Iterative number update: add 1 to the number of iterations each time the iterative process is entered, that is .

[0097] c) Maximum iteration judgment: judge whether the maximum number of iterations set in advance is reached. If reached, enter the next time frame; if not reached, continue subsequent processing.

[0098] (4) Signal detection and channel estimation.

[0099] 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.

[0100] b) Maximum time slot judgment: judge whether the maximum time slot is reached. If reached, complete one iteration and perform corresponding processing; if not reached, continue subsequent steps.

[0101] (5) Active node number calculation and branch processing.

[0102] a) Active node number calculation: calculate the number of active nodes in the current time slot.

[0103] b) Branch processing:

[0104] ① : clean time slot, first perform clean time slot signal detection and channel estimation, then perform demodulation, frame decoding, and decoding operations in turn to obtain service data decoding results, solve the time slot index and update, and enter the next time slot.

[0105] ② : multiple active nodes, dirty time slot. First query the known user time slot index to determine whether there is a known user in this dirty time slot. If there is, 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, and known user physical layer waveform reconstruction in turn, and finally serial interference delete known user waveform; if there is no known user, directly enter the next time slot.

[0106] ③ : no active node case, empty time slot, directly enter the next time slot.

[0107] (6) Cycle and end: when a round of iteration is completed (the maximum time slot is reached or all cases are processed), it is determined whether to enter the next time frame according to whether the maximum number of iterations is reached, and the next round of iteration processing is continued until the end condition is met.

[0108] The application also 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;

[0109] The user node is configured to send the same service copy packet in at least two time slots in each time frame to form an access waveform corresponding to each time frame; and the access waveform is a superposition waveform sent by the access node after superposition of multipath interference and / or time delay.

[0110] The satellite-borne receiver is configured to perform each step in the satellite joint channel estimation method based on CRDSA.

[0111] As shown in Figure 5 , a JCE-CRDSA access system principle diagram is shown, which comprises at least one node Figure 5 , a CRDSA sending unit, and a satellite-borne multi-user multipath CRDSA access processing unit. The composition structure and function principle of each unit are described as follows:

[0112] I. At least one node CRDSA sending unit (i.e., JCE-CRDSA sending unit of the node ), it is worth mentioning that the node CRDSA sending unit completely multiplexes the conventional CRDSA algorithm. The node CRDSA sending unit specifically comprises the following modules:

[0113] (1) Service data input module (not shown in the figure): a service data symbol vector enters the node CRDSA sending unit and is temporarily stored in the "service queue".

[0114] (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.

[0115] (3) Encoding and modulation module: the framed service data is subjected to encoding and modulation processing.

[0116] (4) Access timing control and pattern generation module: the access timing control module generates an access pattern by timing control and determines​ Time slot ID. Access diagram. The generation module works in conjunction with the radio frequency gating to control the timing and method of transmitting radio frequency signals.

[0117] (5) Radio frequency signal output module: generates radio frequency signals And output to the multi-user access channel.

[0118] II. Onboard Multi-User Multipath CRDSA Access Processing Unit, possessing multi-user multipath CRDSA access processing capabilities. Includes the following modules:

[0119] (1) Time-slot-by-time signal detection module: detects waveforms accessed by multiple users in a time-slot manner. Perform time-slot-by-time signal detection.

[0120] (2) Net time slot judgment and processing module: Determines whether the detected time slot is a net time slot. If it is a net time slot, performs net time slot multipath channel parameter estimation, and then performs demodulation, deframing and decoding operations in sequence to obtain the service data decoding result; if it is not a net time slot, it enters the interference deletion and related processing flow.

[0121] (3) Multi-user iterative serial interference removal & known user optimal channel estimation module: including known user MAC layer frame reconstruction, known user joint maximum likelihood parameter estimation of the preceding and following time slots, known user joint channel estimation of the preceding and following time slots, known user physical layer waveform reconstruction, serial iterative interference removal SIC and other modules, to realize effective processing of multi-user signals and optimal channel estimation of known users.

[0122] The CRDSA-based satellite joint channel estimation apparatus provided by the present invention will be described below. The CRDSA-based satellite joint channel estimation apparatus described below can be referred to in correspondence with the CRDSA-based satellite joint channel estimation method described above.

[0123] like Figure 6 As shown, Figure 6 A schematic diagram of the module structure of a CRDSA-based satellite joint channel estimation device is shown, including the following modules:

[0124] The access model acquisition module 601 is used to acquire the access waveform corresponding to the current time frame; wherein, the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay; the access node uses at least two time slots to send the same service replica packet in the current time frame;

[0125] The time-slot-by-time detection module 602 is used to perform time-slot-by-time signal detection on the access waveform to obtain the signal of each time slot;

[0126] The current active node detection module 603 is configured to detect a current active node in each time slot according to signals of the time slots.

[0127] The joint channel estimation module 604 is configured to, if the current active node is a multi-node, perform joint channel estimation according to front and back 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.

[0128] In an embodiment, the joint channel estimation module 604 is further configured to:

[0129] If the current active node is a multi-node, perform joint channel estimation according to front and back time slots of the at least two time slots of each node in the multi-node, to obtain maximum likelihood parameter estimates and multipath channel estimates of each node.

[0130] Perform physical layer waveform reconstruction on each node according to the maximum likelihood parameter estimates and the multipath channel estimates, to obtain a reconstructed waveform.

[0131] Perform serial interference cancellation on the reconstructed waveform, to obtain a decoding waveform of each node in the multi-node.

[0132] In an embodiment, the joint channel estimation module 604 is further configured to:

[0133] 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.

[0134] In an embodiment, the joint channel estimation module 604 is further configured to:

[0135] If there is no current active node in the current time slot, end the current time slot detection, and enter the next time slot.

[0136] In an embodiment, the joint channel estimation module 604 is further configured to:

[0137] If the current active node is a multi-node, determine whether there is a known node in the multi-node according to a preset node time slot index.

[0138] Perform joint channel estimation according to front and back time slots of the at least two time slots of each known node, to obtain maximum likelihood parameter estimates and multipath channel estimates of each known node.

[0139] Figure 7 An example of an entity structure diagram of an electronic device is shown in FIG. 1. Figure 7As shown, 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 complete communications with each other through the communications bus 740. The processor 710 can invoke a logic instruction in the memory 730 to execute a CRDSA-based satellite joint channel estimation method, which includes: 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 after being 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; if the current active node is a multi-node, performing joint channel estimation according to the front and rear time slots of each node in the multi-node in the at least two time slots to obtain a decoding waveform of each node in the multi-node from the superposition waveform.

[0140] In addition, the logic instruction in the memory 730 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, and the computer software product is stored in a storage medium, including a plurality of 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 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 program code storage media.

[0141] 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 can be executed by a processor to enable a computer to perform the CRDSA-based satellite joint channel estimation method provided by the above method, which comprises: obtaining an access waveform corresponding to a current time frame; wherein the access waveform is an access waveform sent by an access node after superposition of multipath interference and / or time delay; 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 in 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 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.

[0142] 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 can be executed by a processor to implement the CRDSA-based satellite joint channel estimation method provided by the above method, which comprises: obtaining an access waveform corresponding to a current time frame; wherein the access waveform is an access waveform sent by an access node after superposition of multipath interference and / or time delay; 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 in 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 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.

[0143] 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.

[0144] 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.

[0145] 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 satellite joint channel estimation method based on CRDSA, characterized in that, include: Obtain the access waveform corresponding to the current time frame; wherein, the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay; the access node uses at least two time slots in the current time frame to send the same service replica packet; The access waveform is subjected to time-slot-by-time signal detection to obtain the signal of each time slot; Based on the signals from each time slot, detect the currently active node in each time slot; wherein, the currently active node is the user node that sent the service replica packet in the current time slot; If the currently active node is a multi-node, then joint channel estimation is performed based on the preceding and following time slots of the at least two time slots of each of the multi-nodes to obtain the maximum likelihood parameter estimate and multipath channel estimate of each node. Based on the maximum likelihood parameter estimate and the multipath channel estimate, physical layer waveform reconstruction is performed on each node to obtain the reconstructed waveform; The reconstructed waveform is subjected to serial interference removal to obtain the decoded waveform of each node in the multi-node array.

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

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

4. The satellite joint channel estimation method based on CRDSA according to claim 1, characterized in that, If the currently active node is a multi-node, then joint channel estimation is performed based on the preceding and following time slots of at least two time slots for each of the multi-nodes to obtain the maximum likelihood parameter estimate and multipath channel estimate for each node, including: If the currently active node is a multi-node, determine whether there is a known node among the multi-node based on the preset node time slot index; Joint channel estimation is performed based on the preceding and following time slots of the at least two time slots for each known node to obtain the maximum likelihood parameter estimate and multipath channel estimate for each known node.

5. A satellite joint channel estimation system based on CRDSA, characterized in that, It includes low-Earth orbit satellites and user nodes, wherein the low-Earth orbit satellites are equipped with onboard receivers; The user node is used to send the same service replica packet in at least two time slots in each time frame to form the access waveform corresponding to each time frame; the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay; The onboard receiver is used to execute the CRDSA-based satellite joint channel estimation method as described in any one of claims 1 to 4.

6. A satellite joint channel estimation device based on CRDSA, characterized in that, include: The access model acquisition module is used to acquire the access waveform corresponding to the current time frame; wherein, the access waveform is a superimposed waveform sent by the access node after superimposing multipath interference and / or time delay; the access node uses at least two time slots to send the same service replica packet in the current time frame; The time-slot detection module is used to perform time-slot signal detection on the access waveform to obtain the 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 signals in each time slot; wherein, the current active node is the user node that sent the service replica packet in the current time slot; The joint channel estimation module is used to, if the currently active node is a multi-node, perform joint channel estimation based on the preceding and following time slots of at least two time slots of each of the multi-nodes to obtain the maximum likelihood parameter estimate and multipath channel estimate of each node; perform physical layer waveform reconstruction on each node based on the maximum likelihood parameter estimate and multipath channel estimate to obtain the reconstructed waveform; and perform serial interference removal on the reconstructed waveform to obtain the decoded waveform of each of the multi-nodes.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the CRDSA-based satellite joint channel estimation method as described in any one of claims 1 to 4.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the CRDSA-based satellite joint channel estimation method as described in any one of claims 1 to 4.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the CRDSA-based satellite joint channel estimation method as described in any one of claims 1 to 4.

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