Distributed coherent terminal cluster communication method and system based on satellite transparent forwarding mode

Abstract

The present invention relates to a distributed coherent terminal cluster communication method and system based on a satellite transparent forwarding mode, wherein the method includes: 100, transmitting group network nodes complete carrier synchronization in a master-slave architecture; 200, the transmitting group network nodes complete beamforming using a beamforming protocol; 300, the transmitting group network nodes complete satellite-to-ground distributed network planning using a network forming protocol; 400, the transmitting group network sends data to a transparent satellite in a distributed coherent communication mode; 500, the transparent satellite transparently forwards and frequency-converts the received data and transmits it to a receiving group network; 600, the receiving group network receives, distributes, and demodulates and recovers the forwarded data in a distributed coherent communication mode. The present invention adopts a transparent satellite forwarding mode to effectively implement satellite communication between distributed coherent terminal clusters.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite communication and distributed coherent communication, and in particular to a distributed coherent terminal cluster communication method and system based on a satellite transparent forwarding mode. Background Art

[0002] Distributed coherent communication enables radio networks to extend their communication range by coordinating the transmission of common messages. In this way, after propagation, the signals arrive at the intended receiving node simultaneously and in phase. The received power is the product of the total transmitted power and the total antenna array gain, both of which increase linearly with the number of transmitting nodes, resulting in a quadratic increase in the power reaching the communication destination node. However, in order to perform "distributed transmit beamforming", all transmitting source nodes must agree on the common message, need to transmit "simultaneously", synchronize their carrier frequencies, and control their carrier phases. Therefore, the main challenges in realizing distributed coherent communication include time synchronization, cooperative information sharing, and the most critical distributed carrier synchronization.

[0003] On the other hand, transparent forwarding satellite communications is currently the mainstream satellite communication method. However, in the field of satellite communications, there is little research on combining distributed coherent communication with transparent forwarding satellite mode. Therefore, it is necessary to study the architecture and method of a distributed coherent communication system in a satellite communication scenario based on transparent forwarding mode, in which each terminal adopts the system. The communication process, synchronization strategy, and beamforming protocol in this scenario should be determined to reduce signaling overhead and ensure the feasibility of such a communication system. Summary of the Invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a distributed coherent terminal cluster communication method and system based on satellite transparent forwarding mode to realize satellite communication between distributed coherent terminal clusters.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a distributed coherent terminal cluster communication method based on a satellite transparent forwarding mode, comprising:

[0007] 100, the nodes of the transmitting group network complete carrier synchronization in a master-slave architecture;

[0008] 200, the nodes of the transmitting group network complete beamforming using a beamforming protocol;

[0009] 300, the nodes of the transmitting group network complete the satellite-ground distributed network planning using the network shaping protocol;

[0010] 400, the transmitting group network sends data to the transparent satellite in a distributed coherent communication manner;

[0011] 500, the transparent satellite transparently forwards and frequency-converts the received data, and transmits the data to a receiving group network;

[0012] 600. The receiving group network receives, distributes, and demodulates and recovers the forwarded data in a distributed coherent communication manner.

[0013] According to one aspect of the present invention, the transmitting group network is a transmitting terminal cluster consisting of initializing any small satellite communication terminal that needs to perform distributed coherent communication and serves as a master node, and its surrounding small satellite communication terminals that are close to each other and serve as slave nodes;

[0014] The receiving group network is a receiving terminal cluster composed of small satellite communication terminals that are located at different distances from the transmitting group network.

[0015] According to one aspect of the present invention, in step 100, the nodes of the transmitting group network use an open-loop synchronization method in a master-slave architecture to complete carrier synchronization, and the carrier synchronization includes frequency synchronization and phase synchronization of the carrier.

[0016] According to one aspect of the present invention, step 100 includes:

[0017] 101, each slave node randomly adjusts its carrier phase;

[0018] 102, the master node acts as a distributed beamformer and simultaneously broadcasts a sinusoidal signal to each slave node;

[0019] 103, each slave node estimates the signal-to-noise ratio of the received signal and estimates and corrects the frequency offset of the signal;

[0020] 104. Each slave node broadcasts a bit of feedback to the master node, indicating whether its signal-to-noise ratio is better or worse than before the master node adjusted its phase. If it is better, all slave nodes maintain the latest phase adjustment. Otherwise, all slave nodes cancel the latest phase adjustment and continue to iterate steps 101 to 104 to achieve the desired phase convergence level.

[0021] According to one aspect of the present invention, a time division duplex communication protocol is adopted between the master node and the slave nodes.

[0022] According to one aspect of the present invention, in order to successfully perform step 200, before step 200, the method further includes: each node of the transmission group network estimates its own channel response to the transparent satellite.

[0023] According to one aspect of the present invention, each node of the transmit group network estimates its own channel response to the transparent satellite, comprising:

[0024] The master node broadcasts data within the transmission group network to implement data exchange within the transmission group network;

[0025] Since all transmitting nodes are synchronized, each transmitting source node can independently estimate the complex channel gain from itself to the destination using its frequency and phase synchronized local oscillator. Each node in the transmitting group network sends a pilot signal to estimate all channels of the transparent satellite at the receiving node in the receiving group network.

[0026] Channel state information is fed back to the nodes of the transmission group network.

[0027] In a second aspect, the present invention further provides a distributed coherent terminal cluster communication system implemented by the above-mentioned distributed coherent terminal cluster communication method based on the satellite transparent forwarding mode, comprising:

[0028] A transmitting group network, configured to perform carrier synchronization, beamforming, and network planning for nodes within the transmitting group network, and to send data to transparent satellites in a distributed coherent communication manner;

[0029] The transparent satellite is used to transparently forward and frequency-convert the received data and transmit it to the receiving group network;

[0030] The receiving group network is used to receive, distribute and demodulate and recover the forwarded data in a distributed coherent communication manner.

[0031] According to another aspect of the present invention, the transmitting group network is a transmitting terminal cluster consisting of any small satellite communication terminal that initializes any distributed coherent communication and serves as a master node, and its surrounding small satellite communication terminals that are close to the master node and serve as slave nodes.

[0032] According to another aspect of the present invention, the receiving group network is a receiving terminal cluster composed of small satellite communication terminals that are located at different distances from the transmitting group network.

[0033] Beneficial effects:

[0034] According to the present invention, multiple closely spaced small satellite communication terminals can form a transmitting terminal cluster, forming a transmitting group network. This cluster can then communicate using a transparent satellite forwarding mode with multiple closely spaced small satellite communication terminals located at another location within the coverage of a satellite beam, forming a receiving terminal cluster, forming a receiving group network. This invention effectively provides an application model for distributed coherent communication in satellite communication scenarios.

[0035] According to one solution of the present invention, an open-loop synchronization method using a master-slave architecture is used to achieve carrier synchronization between transmitting terminal clusters, thereby avoiding to the greatest extent the huge overhead problem of a closed-loop carrier synchronization system requiring multiple round trips between the satellite and the ground to achieve synchronization, and meeting the basic requirements of the communication system for synchronization overhead in the satellite transparent forwarding mode.

[0036] According to one solution of the present invention, based on the business needs of satellite communication terminals, when transmitting multiple data streams and multiple receiving nodes, beamforming protocols and network forming protocols can be used to perform beamforming, network planning and distributed coherent communication on the transmitting terminal cluster after carrier synchronization, thereby realizing satellite communication between distributed coherent terminal clusters. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0038] Figure 1 A schematic diagram schematically illustrates a "mosaic" communication application mode in a satellite transparent forwarding communication mode disclosed in an embodiment of the present invention;

[0039] Figure 2 A diagram schematically illustrates a network architecture of a distributed coherent terminal cluster communication system based on a satellite transparent forwarding mode disclosed in an embodiment of the present invention;

[0040] Figure 3 A flowchart schematically illustrates a distributed coherent terminal cluster communication method based on a satellite transparent forwarding mode disclosed in an embodiment of the present invention;

[0041] Figure 4 A schematic diagram schematically illustrates a method for implementing carrier synchronization of network nodes in a transmitting group using a master-slave architecture disclosed in an embodiment of the present invention;

[0042] Figure 5 The figure schematically shows the process of distributed coherent terminal cluster communication disclosed in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The description of the embodiments in this specification should be combined with the corresponding drawings, which should be considered a complete part of this specification. In the drawings, the shapes and thicknesses of the embodiments may be exaggerated and indicated for simplicity or convenience. Furthermore, the various structural components in the drawings will be described separately. It is worth noting that components not shown in the drawings or not described in words are known to those of ordinary skill in the art.

[0044] The description of the embodiments herein and any references to directions and orientations are for ease of description only and are not to be construed as limiting the scope of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination. The present invention is not specifically limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0045] According to the concept of the present invention, the embodiment of the present invention discloses a communication network architecture / communication system of a distributed coherent terminal cluster based on a satellite transparent forwarding mode and a method for implementing key technologies of distributed coherent communication, wherein the key technologies here include synchronization of the transmitting terminal cluster, beamforming protocol and network forming protocol, such as Figure 1-5 shown.

[0046] Transparent forwarding satellite communication is the current mainstream satellite communication method, but in portable and mobile communication scenarios, there are problems such as large terminal size and difficulty in improving communication speed. Figure 1 As shown, the "mosaic" communication application mode under the satellite transparent forwarding communication mode refers to the dispersed installation of mobile, self-forming, and self-repairing small satellite communication transceiver groups (small satellite communication transceiver terminal clusters) on ships, vehicles, unmanned / manned aircraft, satellites or soldiers to form a "mosaic" satellite communication array, which can improve communication speed, anti-interference and safety performance.

[0047] Figure 2 The network architecture diagram of the distributed coherent terminal cluster communication system in satellite transparent forwarding mode is given. Figure 2 As shown, an embodiment of the present invention discloses a distributed coherent terminal cluster communication system based on a satellite transparent forwarding mode, which mainly includes: a transmitting group network (source - squad unit), a transparent satellite, and a receiving group network (destination - squad unit). The transmitting group network is used to perform carrier synchronization, beamforming, and network planning for nodes within the transmitting group network, and to send data to the transparent satellite using a distributed coherent communication method. The transparent satellite is used to transparently forward and frequency-convert the received data and transmit it to the receiving group network. The receiving group network is used to receive, distribute, and demodulate and recover the forwarded data using a distributed coherent communication method.

[0048] Furthermore, the transmitting group network is a cluster of transmitting terminals consisting of any small satellite communication terminal that initializes distributed coherent communication and serves as a master node, along with its surrounding small satellite communication terminals that are located in a similar position and serve as slave nodes. The receiving group network is a cluster of receiving terminals consisting of small satellite communication terminals located in different locations but in a similar position. The transmitting group network utilizes an open-loop synchronization method based on a master-slave architecture to achieve open-loop transmitting node carrier synchronization with minimal signaling overhead. It then employs appropriate physical layer beamforming protocols and network layer network forming protocols for distributed coherent communication to the transparent satellite. After the beamformed signal is forwarded and frequency-converted at the transparent satellite, it is then transmitted by the transparent satellite to a receiving group network located elsewhere for distributed coherent communication. At the destination receiving group, the data stream transmitted by the transmitting group network is received and demodulated and recovered, completing data reception.

[0049] The metrics for achieving distributed coherent communication can be the coherence gain, information transmission rate improvement, and transmission power saving compared to single-node incoherent communication. The embodiments of the present invention also need to comprehensively consider the reasonable cross-layer protocol design and the key technologies and algorithms for the specific implementation of each layer protocol. To this end, Figure 3 As shown, an embodiment of the present invention discloses a distributed coherent terminal cluster communication method based on a satellite transparent forwarding mode, which specifically includes the following steps:

[0050] Step 100: Nodes of the transmitting group network complete carrier synchronization in a master-slave architecture.

[0051] Furthermore, in some embodiments, based on the requirements of each terminal for distributed coherent communication, a transmitting group network is a transmitting terminal cluster consisting of any small satellite communication terminal that initiates distributed coherent communication and serves as a master node, and its surrounding small satellite communication terminals that are located in a similar position and serve as slave nodes. A receiving group network is a receiving terminal cluster consisting of small satellite communication terminals that are located in a different position from the transmitting group network but are located in a similar position.

[0052] In some embodiments, the nodes of the transmitting group network in step 100 use an open-loop synchronization method in a master-slave architecture to complete carrier synchronization. Figure 4 This is a schematic diagram describing a method for implementing carrier synchronization of transmitting nodes using a master-slave architecture. Figure 4 As shown, the specific implementation process of step 100 includes:

[0053] Step 101: Each slave node randomly adjusts its carrier phase.

[0054] In step 102 , the master node acts as a distributed beamformer and simultaneously broadcasts a sinusoidal signal to each slave node.

[0055] Step 103: Each slave node estimates the signal-to-noise ratio of the received signal and estimates and corrects the frequency offset of the signal.

[0056] In step 104, each slave node broadcasts a bit of feedback to the master node, indicating whether its signal-to-noise ratio is better or worse than before the master node adjusted its phase. If it is better, all slave nodes maintain the latest phase adjustment. Otherwise, all slave nodes cancel the latest phase adjustment and continue to iterate steps 101 to 104 to achieve the desired phase convergence level.

[0057] In this embodiment, carrier synchronization includes carrier frequency and phase synchronization. Frequency synchronization utilizes a master-slave architecture, where a slave node uses a phase-locked loop (PLL) to lock onto a reference carrier signal broadcast by a master node. A source node that estimates the frequency offset of the reference carrier signal to be , can multiply its complex baseband transmit signal by . This operation can be implemented in a digital signal processor before digital-to-analog conversion and carrier multiplication. Depending on the stability of the oscillator, the frequency synchronization process may need to be repeated.

[0058] Phase synchronization utilizes an open-loop phase synchronization method. It should be noted that the embodiments of the present invention consider distributing small, self-forming, and self-repairing satellite communication transceiver terminals on ships, vehicles, unmanned / manned aircraft, satellites, or soldiers to form a "mosaic" satellite communication array, enabling distributed coherent communication between these arrays (transmitting nodes) and satellites (receiving nodes). If closed-loop synchronization is used for carrier synchronization, the signaling transmission time overhead between the satellite-to-ground link is significant, which would affect the coherent gain achieved by the receiving node and increase system complexity. Therefore, the embodiments of the present invention utilize an open-loop synchronization method for carrier synchronization.

[0059] In an open-loop system, sources interact with each other with minimal signaling from the destination. Instead of providing feedback to adjust the source phase, the destination node can simply broadcast an unmodulated sinusoidal beacon to the source node. The transmitting source node uses this beacon, along with signals from other source-source interactions, to achieve appropriate phase compensation for beamforming to the destination. The focus of an open-loop system is to use local interactions between sources to minimize interactions with the distant destination (the transparent satellite).

[0060] Furthermore, in this embodiment, a time division duplex (TDD) communication protocol is used between the master and slave nodes. Its main feature is that the feedback process is from the master to the slave nodes, without involving extensive signaling interactions between the destination node (transparent satellite) and the distributed terminal cluster.

[0061] In step 200, the nodes of the transmitting group network perform beamforming using a beamforming protocol.

[0062] In some embodiments, before the nodes of the transmitting group network use the beamforming protocol to complete beamforming in step 200, the method further includes: each node of the transmitting group network estimates its own channel response to the transparent satellite.

[0063] It's important to note that in order for sensors to beamform toward a destination node, each terminal must estimate its channel response to the transparent satellite. This is accomplished by having the transparent satellite broadcast a beacon (e.g., a sinusoidal signal at a carrier frequency) to the nodes in the transmitting terminal cluster. Because the transmitting terminal cluster nodes are synchronized, each node can independently estimate its own complex channel gain to the satellite using its frequency- and phase-synchronized local oscillator. Nodes can then act as distributed beamformers to transmit toward the transparent satellite by taking the complex conjugate of these gains (typically at baseband) and applying them to their transmitted signals.

[0064] For example, consider a coherent communication scenario where N transmitting nodes coherently transmit data to M receiving nodes, M ≥ 1, such as Figure 5 As shown in Figure 2, the specific implementation process of each node in the transmitting group network estimating its own channel response to the transparent satellite includes: the master node broadcasts data within the transmitting group network to enable data exchange within the transmitting group network; each node in the transmitting group network sends a pilot signal, and each node estimates all channels of the transparent satellite at the receiving node in the receiving group network; the channel state information is fed back to the nodes in the transmitting group network. Afterwards, all nodes in the transmitting group network transmit signals to the receiving group network with appropriate amplitude and phase.

[0065] Implementing beamforming requires that the inter-group channel remain static during coherent transmission. Nodes in the transmitting node group (i.e., the transmitting group network) exchange data before the coherent transmission duration. Nodes in the receiving node group (i.e., the receiving group network) exchange their signals for coherent combining after the coherent transmission from the transmitting node group. Therefore, the intra-group channel does not need to be static during intra-group data exchange. For coherent communication, channel sensing is necessary to gather channel information, such as channel gain and phase shift, between each pair of transmitting and receiving nodes.

[0066] After obtaining the channel gain and phase shift between any transmitting and receiving nodes and achieving synchronization between the transmitting nodes, a coherent beamforming protocol is proposed to maximize the power gain of the receiving node.

[0067] Step 300: The nodes of the transmitting group network complete the satellite-ground distributed network planning using the network shaping protocol.

[0068] Step 400: Use the transmission group network to send data to the transparent satellite in a distributed coherent communication manner.

[0069] Step 500: transparently forward and frequency-convert the received data using a transparent satellite, and transmit the data to a receiving group network.

[0070] Step 600: Utilize the receiving group network to receive, distribute, demodulate and recover the forwarded data in a distributed coherent communication manner.

[0071] In some embodiments, when there are multiple data flows, each data flow has its own source-destination node pair, so each sending node and each receiving node is assigned a source and a destination. Therefore, the sending nodes and receiving nodes are dynamically grouped into different sending node groups and receiving node groups, respectively, based on the requirements of the data flows.

[0072] The distributed coherent terminal cluster communication method and system based on a satellite transparent forwarding mode provided by the embodiments of the present invention first organizes multiple satellite terminals to communicate into a transmitting terminal cluster based on their location information. Then, a master-slave open-loop synchronization method is used to synchronize the carriers of the transmitting terminal cluster. Next, distributed coherent communication is performed using beamforming and network forming protocols based on the service requirements and characteristics of the transmitting terminals. After the transmitted data stream reaches the transparent satellite, it undergoes transparent forwarding and frequency conversion by the satellite. Distributed coherent reception is then performed by a terminal cluster to receive the signal at another location within the satellite's coverage beam, ultimately completing the communication process for the distributed coherent terminal cluster.

[0073] The serial numbers of the above-mentioned steps involved in the method of the present invention do not mean the order of execution of the method. The execution order of each step should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A distributed coherent terminal cluster communication method based on a satellite transparent forwarding mode, comprising:

100. The nodes of the transmitting group network complete carrier synchronization in a master-slave architecture. The nodes of the transmitting group network complete carrier synchronization in a master-slave architecture using an open-loop synchronization method. The carrier synchronization includes frequency synchronization and phase synchronization of the carrier, including: 101, each slave node randomly adjusts its carrier phase; 102, the master node acts as a distributed beamformer and simultaneously broadcasts a sinusoidal signal to each slave node; 103, each slave node estimates the signal-to-noise ratio of the received signal and estimates and corrects the frequency offset of the signal; 104. Each slave node broadcasts a bit of feedback to the master node, indicating whether its signal-to-noise ratio is better or worse than before the master node adjusted its phase. If it is better, all slave nodes maintain the latest phase adjustment. Otherwise, all slave nodes cancel the latest phase adjustment and continue to iterate steps 101 to 104 to achieve the desired phase convergence level. 200, the nodes of the transmitting group network complete beamforming using a beamforming protocol; 300, the nodes of the transmitting group network complete the satellite-ground distributed network planning using the network shaping protocol; 400, using the transmission group network to send data to the transparent satellite in a distributed coherent communication manner; 500, transparently forwarding and frequency-converting the received data using the transparent satellite, and transmitting the data to a receiving group network; 600. Utilize the receiving group network to receive, distribute, and demodulate and recover the forwarded data in a distributed coherent communication manner.

2. The method according to claim 1, characterized in that The transmitting group network is a transmitting terminal cluster composed of initializing any small satellite communication terminal that needs to perform distributed coherent communication and serves as a master node, and its surrounding small satellite communication terminals that are close to each other and serve as slave nodes; The receiving group network is a receiving terminal cluster composed of small satellite communication terminals that are located at different distances from the transmitting group network.

3. The method according to claim 1, characterized in that A time division duplex communication protocol is used between the master node and the slave nodes.

4. The method according to claim 1, wherein Before step 200, the method further includes: each node of the transmission group network estimates its own channel response to the transparent satellite.

5. The method according to claim 4, characterized in that Each node of the transmit group network estimates its own channel response to the transparent satellite, including: The master node broadcasts data within the transmission group network to implement data exchange within the transmission group network; Each node of the transmitting group network sends a pilot signal to estimate all channels of the transparent satellite at the receiving node of the receiving group network; Channel state information is fed back to the nodes of the transmission group network.

6. A distributed coherent terminal cluster communication system, used to implement the distributed coherent terminal cluster communication method based on satellite transparent forwarding mode according to any one of claims 1 to 5, characterized in that: include: A transmitting group network, configured to perform carrier synchronization, beamforming, and network planning for nodes within the transmitting group network, and to send data to transparent satellites in a distributed coherent communication manner; The transparent satellite is used to transparently forward and frequency-convert the received data and transmit it to the receiving group network; The receiving group network is used to receive, distribute and demodulate and recover the forwarded data in a distributed coherent communication manner.

7. The system according to claim 6, characterized in that The transmitting group network is a transmitting terminal cluster composed of any small satellite communication terminal that initializes any distributed coherent communication and acts as a master node, and its surrounding small satellite communication terminals that are close to it and act as slave nodes.

8. The system according to claim 6, wherein: The receiving group network is a receiving terminal cluster composed of small satellite communication terminals that are located at different distances from the transmitting group network.

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