Air-space-ground integrated network architecture based on cellular-free network and network switching method

Abstract

The invention provides an air-space-ground integrated network architecture based on a cellular-free network and a network switching method. The network architecture comprises a space layer, an air layer and a ground layer, the space layer is used for providing communication service for the first communication area; the air layer is provided with a low-altitude communication system based on a cellular-free network architecture and is used for providing communication service for the second communication area; wherein the low-altitude communication system comprises a low-altitude communication core network, a cellular-free wireless access network and a terminal; the low-altitude communication core network is used for performing communication management on the terminal; the cellular-free wireless access network is used for providing a connection channel for the low-altitude communication core network and the terminal; the terminal is used for initiating an access request and receiving control data; the ground layer is used for providing communication service for the third communication area. The vertical coverage blind area of a traditional network is eliminated through the network architecture, and the problems that an existing air-space-ground integrated network is complex in switching process, unstable in communication link and the like are solved through the corresponding network switching method.

Description

Technical Field

[0001] The present invention relates to the technical field of communication network architectures, and particularly to a non-terrestrial integrated network architecture based on a cell-free network and a network handover method. Background Art

[0002] Low-altitude airspace generally refers to the airspace with a vertical distance from the ground plane within 1000 meters, which can be extended to within 3000 meters according to the characteristics of different regions and actual needs. Stable air-ground communication links must be established for low-altitude flight to send control instructions to the aircraft in real time and disposal commands in case of emergencies, so as to ensure flight safety. The low-altitude communication system is the key foundation for constructing a low-altitude airspace management system and has a direct impact on the success or failure of low-altitude flight management.

[0003] Traditional cellular networks rely on a large number of fixed base stations for coverage. In the low-altitude airspace range of 120 meters to 3000 meters above the city, traditional cellular networks lack effective communication capabilities and are difficult to meet the requirements of non-terrestrial full coverage. In addition, they have problems such as high handover latency, poor service quality for edge users, and high construction costs. Existing non-terrestrial integrated networks mostly adopt a hierarchical heterogeneous architecture, but there are large protocol differences between satellite networks, air layer networks, and ground networks, the handover process is complex, and centralized resource management is difficult to adapt to dynamic changes. Cell-free network technology can improve network capacity and coverage uniformity through distributed antennas and cooperative transmission, but its application in non-terrestrial scenarios is not yet mature.

[0004] The following problems currently exist for non-terrestrial integrated networks and their network handover methods:

[0005] 1. In the low-altitude airspace range of 120 meters to 3000 meters above the city, there is a lack of effective communication methods. Traditional terrestrial 4G / 5G public networks are limited by cellular communication systems and are difficult to cover low-altitude airspace. In addition, the site density required for continuous coverage of the sky is large. When traditional cellular base stations cover the sky, cell overlap is serious, cell boundary management is difficult, and the neighboring cell relationship of the base stations is extremely complex, making it difficult to achieve smooth handover across cells. Especially, the communication link quality above 120 meters degrades severely, unable to meet the requirements of low-altitude services. At the same time, large-scale construction of base stations will also lead to high construction and operation and maintenance costs.

[0006] 2. The existing terrestrial public network communication technology has poor communication coverage continuity in remote areas and has many communication coverage blind spots, seriously affecting the stable and reliable transmission of communication data between the low-altitude airspace management system and low-altitude aircraft.

[0007] 3. Existing non-terrestrial integrated networks mostly adopt a hierarchical heterogeneous architecture, but there are large protocol differences between satellite networks, air layer networks, and ground networks, the handover process is complex, resulting in unstable communication links and centralized resource management being difficult to adapt to dynamic changes. Summary of the Invention

[0008] The object of the present invention is to provide a space-air-ground integrated network architecture based on a cell-free network and a network handover method, aiming to solve the above problems in the prior art.

[0009] An embodiment of the present invention provides a space-air-ground integrated network architecture based on a cell-free network, including a space layer, an air layer, and a ground layer that communicate with each other;

[0010] The space layer is used to provide communication services for a first communication area;

[0011] The air layer is provided with a low-altitude communication system based on a cell-free network architecture, which is used to provide communication services for a second communication area; wherein, the low-altitude communication system includes a low-altitude communication core network, a cell-free radio access network, and a terminal connected in sequence; the low-altitude communication core network is used to manage the communication of the terminal; the cell-free radio access network is used to provide a connection channel for the low-altitude communication core network and the terminal; the terminal is used to initiate an access request and receive control data;

[0012] The ground layer is used to provide communication services for a third communication area.

[0013] An embodiment of the present invention provides a space-air-ground integrated network handover method based on a cell-free network, including:

[0014] Continuously monitoring the communication networks of the space layer, the air layer, and the ground layer through the terminal;

[0015] Performing dual-connection handover on the network connections between the terminal and the space layer, the air layer, and the ground layer based on the signal strength and load rate of the communication networks.

[0016] Adopting the embodiment of the present invention may include the following beneficial effects: Through the cell-free network architecture, the embodiment of the present invention can solve problems such as the inability of public network communication to cover the airspace more than 120 meters above low altitude, and the frequent handover between cells due to the large number of public network communication station sites, resulting in packet loss; and through the space-air-ground integrated network architecture based on cell-free network technology, the vertical coverage blind area of the traditional network is eliminated, and by proposing a network handover method for the space-air-ground integrated network architecture based on cell-free network technology, problems such as the complex process of handover in the existing space-air-ground integrated network and unstable communication links are solved. Description of the Drawings

[0017] To more clearly illustrate the technical solutions in one or more embodiments of this specification or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in this specification. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 is a schematic diagram of a space-air-ground integrated network architecture based on a cell-free network according to an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of a cell-free network system according to an embodiment of the present invention;

[0020] Figure 3 is an architecture diagram of a cell-free network system according to an embodiment of the present invention;

[0021] Figure 4 is an architecture diagram of a space-air-ground integrated network according to an embodiment of the present invention;

[0022] Figure 5 is a flowchart of the handover from the ground layer 4G / 5G public network to the cell-free network in the air layer according to an embodiment of the present invention;

[0023] Figure 6 is a flowchart of the handover from the cell-free network in the air layer to the ground layer 4G / 5G public network according to an embodiment of the present invention;

[0024] Figure 7 is a flowchart of the handover from the space layer star network to the cell-free network in the air layer according to an embodiment of the present invention;

[0025] Figure 8 is a flowchart of the method for switching a space-air-ground integrated network based on a cell-free network according to an embodiment of the present invention. Specific Embodiments

[0026] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will clearly and completely describe the technical solutions in one or more embodiments of this specification in conjunction with the accompanying drawings in one or more embodiments of this specification. Obviously, the described embodiments are only some of the embodiments of this specification, rather than all the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this document.

[0027] System Embodiment

[0028] According to an embodiment of the present invention, a space-air-ground integrated network architecture based on a cell-free network is provided. Figure 1It is a schematic diagram of the space-air-ground integrated network architecture based on the cell-free network in the embodiment of the present invention. As Figure 1 shown, the space-air-ground integrated network architecture based on the cell-free network in the embodiment of the present invention specifically includes a space layer, an air layer, and a ground layer that are communicatively connected to each other;

[0029] The space layer 10 is used to provide communication services for the first communication area;

[0030] The air layer 12 is provided with a low-altitude communication system based on the cell-free network architecture and is used to provide communication services for the second communication area; wherein, the low-altitude communication system includes a low-altitude communication core network, a cell-free radio access network, and a terminal that are connected in sequence; the low-altitude communication core network is used to perform communication management on the terminal; the cell-free radio access network is used to provide a connection channel for the low-altitude communication core network and the terminal; the terminal is used to initiate an access request and receive control data;

[0031] Among them, the cell-free radio access network specifically includes:

[0032] A radio remote unit (RRU) and an antenna, which are connected to the terminal and an edge distributed processing unit (EDU), are used to receive the terminal signals allowed to access the low-altitude communication network, and distribute the control data from the EDU to the corresponding terminal;

[0033] The edge distributed processing unit (EDU), which is connected to the RRU and the antenna and a central processing unit (CU) and a user-centric distributed unit (UCDU), is used to aggregate several RRU signals and send the aggregated signals to the CU and UCDU, and send the control data from the CU and UCDU to the RRU and the antenna;

[0034] The EDU is deployed in the vicinity of the RRU and is redundantly hot standby in terms of hardware devices;

[0035] Among them, the vicinity is the network edge area of the RRU; one EDU is networked with at least 4 RRUs;

[0036] The central processing unit (CU) and the user-centric distributed unit (UCDU), which are connected to the EDU and the low-altitude communication core network, are used to merge and precode the data streams of the same user in the aggregated signals and send the processed data to the low-altitude communication core network, and distribute the control data from the low-altitude communication core network to the corresponding EDU;

[0037] Among them, the CU and the UCDU are deployed on the same hardware device and are redundantly deployed at the same site or deployed for disaster tolerance in different locations;

[0038] The ground layer 14 is used to provide communication services for the third communication area;

[0039] Among them, the first communication area is a wide-area high-altitude area above 3000 meters; the second communication area is a medium-low altitude area within 120 meters to 3000 meters; the third communication area is a dense urban area below 120 meters.

[0040] The following will combine the specific situation of the cell-free network-based air-space-ground integrated network architecture of the embodiments of the present invention to elaborate in detail on the above technical solutions of the embodiments of the present invention.

[0041] The embodiments of the present invention propose a novel air-space-ground integrated network architecture and network handover method based on cell-free network technology. Among them, the architecture consists of a space layer (satellite), an air layer (cell-free communication network), and a ground layer (4G / 5G public network), supports full-domain coverage and efficient resource management, and is applicable to satellite communication, low-altitude communication networks, and various low-altitude economic application scenarios. The embodiments of the present invention make full use of the advantages of cell-free network technology, deploy base stations on TV transmission towers or high points in cities and regions to solve the airspace coverage problem in the airspace from 120 meters to 3000 meters above the city. Combining the 4G / 5G public network to cover the airspace below 120 meters in the city, and the satellite network as a communication supplement, the cell-free network, the ground 4G / 5G public network, and the satellite communication network jointly form an air-space-ground integrated network, so as to meet the full-domain coverage requirements of the air-space-ground; in addition, in order to solve problems such as large protocol differences, complex handover processes, and unstable communication links between satellite networks, air-layer networks (cell-free networks), and ground networks, an air-space-ground integrated network handover method is also proposed.

[0042] The cell-free network system consists of a cell-free core network, base stations, and terminals. In order to further improve network flexibility, a three-level architecture is adopted, that is, radio remote unit (RRU) and antenna + edge distributed processing unit (EDU) - central processing unit (CU) + user-centric distributed unit (UCDU) - core network, as specifically Figure 2 shown.

[0043] UCDU and CU are logical divisions: UCDU mainly includes a physical layer with strong real-time performance, a media access control layer (MAC), and a radio link control layer (RLC). The user-centric distributed unit (User centric DU, UCDU) can merge / precode the data streams of the same user sent / received by different EDUs. CU includes processing with lower real-time requirements, such as packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), and radio resource control (RRC). In actual deployment, UCDU and CU are deployed on the same hardware device, and redundant hot standby is performed on the hardware, and subsequent cloudification deployment of UCDU, CU, and the core network can be gradually realized.

[0044] Edge Distributed Processing Unit (EDU), which aims to converge multiple RRU signals and complete distributed baseband signal processing. Taking the uplink reception as an example, for instance, the aircraft airborne terminal transmits flight status information, video stream backhaul data, etc. After the RRU receives the user data stream of the aircraft airborne terminal, the EDU sends it to the User Centric Distributed Unit (UCDU). In actual deployment, different numbers of EDUs can be deployed according to the communication scenario. One terminal user can be associated with multiple EDUs and connected to the UCDU. In the UCDU, the data streams of the same user sent by different EDUs can be merged. For the downlink transmission, for example, the aircraft control data is distributed from the UCDU to the associated EDU, and then distributed to the aircraft airborne terminal through the connected RRU. When the EDU device is actually deployed, it should be close to the RRU device, and redundant hot standby should be carried out on the hardware.

[0045] The EDU and the CU+UCDU distributed architecture. The EDU edge distributed processing unit is deployed in the network edge area close to the RRU, which is convenient for centralized management and control of the RRU. One EDU can be networked with at least 4 sets of RRUs. The CU+UCDU can be set up in the same computer room through the core network in the city or deployed for disaster tolerance in different locations in a primary and standby redundant manner. The system networking schematic diagram in the low-altitude communication solution based on the cell-free network architecture is as Figure 3 shown.

[0046] The air-ground-space integrated network based on the cell-free network technology consists of the following levels, as Figure 4 shown:

[0047] 1. Space layer: Carried by the satellite network, interconnected with the ground gateway station through the inter-satellite laser link, providing wide-area backhaul and communication supplementary coverage;

[0048] 2. Air layer: Carried by the cell-free network, mainly supporting the low-altitude airspace communication coverage from above 120 meters to below 3000 meters;

[0049] 3. Ground layer: Carried by the 4G / 5G public network, mainly supporting the airspace communication coverage below 120 meters.

[0050] For the above air-ground-space integrated network, the embodiment of the present invention proposes a corresponding network switching method. To maintain the stability of the communication state, this switching method adopts dual-channel switching: that is, except in special cases, two communication links, namely the 4G / 5G public network and the satellite network, or the cell-free network and the satellite network, remain working, and the 4G / 5G public network and the cell-free private network should be able to automatically switch.

[0051] 1. The following is the switching method from the ground layer's 4G / 5G public network to the air layer's cell-free network, as Figure 5 shown:

[0052] (1) When the user equipment (UE) powers on, it accesses the 4G / 5G public network and the satellite network, and at the same time accesses the cell-free network, but does not perform data transmission.

[0053] (2) The UE continuously monitors the RSRP / SINR of the ground-layer base station, the RSRP / SINR of the cell-free network base station in the air layer, and its own altitude. When the signal of the air-layer base station minus the signal of the ground layer is higher than a certain value (e.g., 5 dB) or the altitude of the UE is close to 120 meters, proceed to the next step.

[0054] (3) Check whether the signal strength of the cell-free base station in the air layer meets the basic threshold: RSRP_air > RSRP_basic_threshold; and check the base station load rate: if the load rate ≤ 80% (not overloaded), it is confirmed to be available and proceed to step 4; if overloaded (> 80%), postpone the handover and return to step 2 to continue monitoring.

[0055] (4) Maintain the existing ground-layer connection (ensure that the service is not interrupted) and establish a new connection with the target cell-free network base station in the air layer.

[0056] (5) Monitor the stability of the air-layer signal (for 100 ms, RSRP fluctuation < 3 dB, SINR ≥ target threshold); after confirming the signal is stable, release the ground-layer connection. At this time, the UE accesses the cell-free network in the air layer and the satellite network. Thus, the handover from the 4G / 5G public network to the cell-free network is completed.

[0057] 2. The following is the handover method from the cell-free network in the air layer to the ground-layer 4G / 5G public network, as Figure 6 shown:

[0058] (1) The UE accesses the cell-free network and the satellite network, and the UE continuously monitors the RSRP, SINR, and delay parameters of the cell-free base station and the ground-layer base station.

[0059] (2) When the UE detects that the ground-layer signal is higher than the air-layer signal by a certain value (e.g., 5 dB) or the user altitude is lower than 120 meters, according to the signal strength threshold RSRP_ground > RSRP_basic_threshold, start screening the ground base stations, and exclude the overloaded base stations with a load rate > 80% to generate a list of candidate base stations that meet the conditions.

[0060] (3) According to the scoring algorithm Sc = 0.6 × ground base station signal strength + 0.3 × (1 / load rate) - 0.1 × distance, find the base station with the highest score from the list of candidate base stations.

[0061] (4) Maintain the existing connection with the cell-free network and establish a connection with the target base station (the base station with the highest score above).

[0062] (5) Check the signal stability of the ground base station (for 100 ms, RSRP fluctuation ≤ 3 dB). After confirmation of stability, release the connection to the non-cellular network, and the handover is completed. At this time, the UE is connected to the ground-layer 4G / 5G public network and the satellite network.

[0063] 3. When the UE is only connected to the satellite network in the space layer due to special circumstances, but to meet the communication link stability, ensure communication quality, and other special reasons (such as in a state of war, the satellite network may not be continuously available in the future), the UE needs to switch to the non-cellular network in the air layer. The following is the handover method from the satellite network in the space layer to the non-cellular network in the air layer, as Figure 7 shown:

[0064] (1) The UE continuously monitors the satellite signal strength and the non-cellular network signal strength.

[0065] (2) Satellite signal attenuation prediction: When it is predicted that the satellite signal strength Ssat1 at a certain future moment is lower than the threshold Sth or the time delay Tdl is greater than the threshold Tth, the UE sends a handover request to the non-cellular base station, carrying the current channel state and location information.

[0066] The predicted satellite signal strength is:

[0067]

[0068] where Ssat1(t + Δt) is the predicted satellite signal strength at a future moment, Ssat1(t) is the current satellite signal strength, λ is the environmental attenuation coefficient, V ue is the user's moving speed (m / s), θ is the angle between the user's moving direction and the center of the satellite beam, and L t is the dynamic environmental loss (including rain fade, building blockage, etc.).

[0069] (3) The non-cellular base station selects the optimal 3 beams from multiple beams according to the UE's location to form a cooperation cluster.

[0070] (4) The non-cellular base station sends an RRC (Radio Resource Control) reconfiguration message to notify the UE to prepare for dual connection.

[0071] (5) The UE simultaneously receives the satellite and non-cellular base station signals. After the data stream is stable, context migration is started.

[0072] (6) The satellite encrypts the UE context (IP, QoS key), and the base station obtains and decrypts the context.

[0073] (7) Check the ground signal stability (for 100 ms, RSRP fluctuation ≤ 3 dB). If it is stable, the base station sends an RRCRelease to release the satellite link; otherwise, go back to step 4.

[0074] (8) The UE disconnects from the satellite connection, and the handover from the satellite network to the non-cellular network is completed.

[0075] Method embodiment

[0076] According to an embodiment of the present invention, a method for switching an air-space-ground integrated network based on a non-cellular network is provided. Figure 8 It is a flowchart of the method for switching an air-space-ground integrated network based on a non-cellular network according to an embodiment of the present invention. As Figure 8 shown, the method for switching an air-space-ground integrated network based on a non-cellular network according to an embodiment of the present invention specifically includes:

[0077] Step S801, continuously monitor the communication networks of the space layer, air layer, and ground layer through the terminal;

[0078] Step S802, perform dual-connection handover on the network connections of the terminal with the space layer, air layer, and ground layer based on the signal strength and load rate of the communication networks, specifically including:

[0079] When the terminal is enabled, it accesses the ground layer communication network and continuously monitors the signal strength of the ground layer communication network, the non-cellular communication network of the air layer, and the height of the terminal itself. If the difference between the signal strength of the air layer minus the signal strength of the ground layer exceeds a preset threshold, or the height of the terminal itself is approaching the second communication area, then judge the signal strength and load rate of the non-cellular communication network of the air layer. If the signal strength of the non-cellular communication network of the air layer meets the basic threshold and the load rate is below the preset threshold, then establish a connection between the terminal and the non-cellular communication network of the air layer while maintaining the connection between the terminal and the ground layer communication network. When the non-cellular communication network state of the air layer becomes stable after the connection, release the connection between the terminal and the ground layer communication network;

[0080] If the signal strength of the non-cellular communication network of the air layer does not meet the basic threshold, or the load rate is higher than the preset threshold, then delay the network handover operation and continuously monitor the signal strength of the ground layer communication network, the non-cellular communication network of the air layer, and the height of the terminal itself;

[0081] When the terminal is connected to the air-layer non-cellular communication network, continuously monitor the signal strength of the ground-layer communication network, the air-layer non-cellular communication network, and the terminal's own height. If the difference between the ground-layer signal strength and the air-layer signal strength exceeds a preset threshold, or the terminal's own height is already lower than the second communication area, and the signal strength of the ground-layer communication network is greater than the basic threshold, then screen the ground base stations according to the load rate to generate a list of candidate base stations, and use a scoring algorithm to score each ground base station in the candidate base station list to obtain the ground base station with the highest score as the target base station. Establish a connection between the terminal and the target base station while maintaining the connection between the terminal and the air-layer non-cellular communication network. When the status of the target base station tends to be stable after the connection, release the connection between the terminal and the air-layer non-cellular communication network;

[0082] When the terminal is connected to the space-layer communication network, continuously monitor the signal strength of the space-layer communication network and the air-layer non-cellular communication network. When the predicted signal strength of the space layer is lower than the preset threshold or the signal delay of the space layer is greater than the preset threshold, the terminal sends a network handover request to the non-cellular communication base station in the air layer. The non-cellular communication base station selects the optimal 3 beams from multiple beams as a cooperation cluster according to the terminal's position and sends an RRC reconfiguration message to the terminal. After receiving the indication, the terminal simultaneously receives the signals of the space-layer communication network and the non-cellular communication base station and starts context migration. When the status of the non-cellular communication base station tends to be stable, release the connection between the terminal and the space-layer communication network;

[0083] Among them, the mathematical expression of the predicted signal strength of the space layer is:

[0084]

[0085] Among them, Ssat1(t+Δt) represents the predicted signal strength of the satellite at a future time, Ssat1(t) is the current satellite signal strength, λ is the environmental attenuation coefficient, V ue is the user's moving speed, θ is the angle between the user's moving direction and the center of the satellite beam, L t is the dynamic environmental loss.

[0086] The embodiments of the present invention are method embodiments corresponding to the above system embodiments. The specific operations of each step can be understood with reference to the description of the system embodiments and will not be elaborated here.

[0087] In summary, compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0088] 1. Break the static limitation of the wireless resource management of the traditional cellular network: Utilize the ultra-large aperture sparse antenna array to significantly improve the signal gain, extend the communication distance of airborne ordinary commercial terminals, and effectively improve the transmission distance.

[0089] 2. The coverage distance of a single physical site is improved, and the number of physical sites for communication network construction is reduced. In terms of user experience (service carrying), inter-cell switching is reduced, packet loss is reduced, network reliability is improved, and stable and reliable data transmission is guaranteed.

[0090] 3. Strong network design customization capabilities: During the engineering design phase, the coverage capabilities of a single physical site can be customized for expansion and lightweighting based on coverage requirements, further enhancing the customization capabilities of wireless network solutions.

[0091] 4. Reduce the difficulty of network optimization: During the construction phase, the difficulty and cycle of network optimization can be reduced due to the significant reduction of handovers between cells.

[0092] 5. Greater flexibility: Once the single-point coverage capacity of a traditional physical site is determined during the design phase, the upper limit of coverage cannot be changed. Therefore, if a weak coverage area occurs due to insufficient coverage distance, the only way to strengthen coverage in this area is to add new physical sites. However, using cell-free technology, single-point coverage distance can be increased by increasing the capacity and optimizing existing sites during network optimization or operation and maintenance, providing greater network flexibility.

[0093] 6. Reduce project investment: The number of physical sites is reduced, which can reduce the engineering workload of other communication subsystems (such as transmission, power supply, dynamic environment, etc.), shorten the construction period, and reduce investment in infrastructure (optical cables, power supply, interval equipment houses, etc.).

[0094] 7. Eliminate vertical coverage blind spots of traditional networks: Eliminate vertical coverage blind spots of traditional networks through an integrated air-ground-space network architecture based on cellular network technology.

[0095] 8. Full-area three-dimensional coverage: The spatial layer covers a wide area at high altitudes, the air layer has no cellular network to adapt to the dynamic needs of medium and low altitudes, and the ground layer DAS ensures ultra-dense access in the city, eliminating the vertical coverage blind spots of traditional networks.

[0096] 9. Optimize the air-space-ground integrated network switching process: The air-space-ground integrated network switching method proposed in the embodiment of the present invention solves the problems of complex air-space-ground integrated network switching process, large delay, unstable communication link, etc.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cell-free based integrated air, space and ground network architecture, characterized in that, It includes a space layer, an air layer, and a ground layer that are communicatively connected to each other; The space layer is used to provide communication services for a first communication area; The air layer is provided with a low-altitude communication system based on a cell-free network architecture, which is used to provide communication services for a second communication area; wherein, the low-altitude communication system includes a low-altitude communication core network, a cell-free radio access network, and a terminal connected in sequence; the low-altitude communication core network is used to manage the communication of the terminal; the cell-free radio access network is used to provide a connection channel for the low-altitude communication core network and the terminal; the terminal is used to initiate an access request and receive control data; The ground layer is used to provide communication services for a third communication area.

2. The integrated space-air-ground network architecture according to claim 1, wherein The first communication area is a wide-area high-altitude area higher than 3000 meters; the second communication area is a medium-low altitude area within 120 meters to 3000 meters; the third communication area is a dense urban area below 120 meters.

3. The integrated space-air-ground network architecture according to claim 1, characterized in that The cell-free radio access network specifically includes: A radio remote unit (RRU) and an antenna, which are connected to the terminal and an edge distributed processing unit (EDU), and are used to receive the terminal signals allowed to access the low-altitude communication network, and distribute the control data from the EDU to the corresponding terminal; The edge distributed processing unit (EDU), which is connected to the RRU and antenna, and a central processing unit (CU) and a user-centric distributed unit (UCDU), is used to aggregate several RRU signals and send the aggregated signals to the CU and UCDU, and send the control data from the CU and UCDU to the RRU and antenna; The central processing unit (CU) and the user-centric distributed unit (UCDU), which are connected to the EDU and the low-altitude communication core network, are used to merge and precode the data streams of the same user in the aggregated signals, and send the processed data to the low-altitude communication core network, and distribute the control data from the low-altitude communication core network to the corresponding EDU.

4. The integrated space-air-ground network architecture according to claim 3, wherein The EDU is deployed in the vicinity of the RRU and has redundant hot standby in terms of hardware devices; Among them, the vicinity is the network edge area of the RRU; one EDU is networked with at least 4 RRUs.

5. The integrated space-air-ground network architecture according to claim 3, wherein The CU and UCDU are deployed on the same hardware device and have redundant deployment at the same site or disaster recovery deployment at different sites.

6. A method for switching an air-space-ground integrated network based on a cell-free network, which is used for the air-space-ground integrated network architecture described in any one of claims 1 to 5, and the method specifically includes: Continuously monitor the communication networks of the space layer, the air layer, and the ground layer through the terminal; Perform dual-connection switching on the network connections between the terminal and the space layer, the air layer, and the ground layer based on the signal strength and load rate of the communication networks.

7. The method according to claim 6, wherein Performing dual-connection switching on the network connections between the terminal and the space layer, the air layer, and the ground layer based on the signal strength and load rate of the communication networks specifically includes: When the terminal is enabled, it accesses the ground-layer communication network and continuously monitors the signal strengths of the ground-layer communication network and the air-layer non-cellular communication network, as well as the terminal's own height. If the difference between the signal strength of the air layer and the signal strength of the ground layer exceeds a preset threshold, or the terminal's own height is approaching the second communication area, then the signal strength and load rate of the air-layer non-cellular communication network are judged. If the signal strength of the air-layer non-cellular communication network meets the basic threshold and the load rate is below the preset threshold, then a connection between the terminal and the air-layer non-cellular communication network is established while maintaining the connection between the terminal and the ground-layer communication network. When the state of the air-layer non-cellular communication network stabilizes after the connection, the connection between the terminal and the ground-layer communication network is released; If the signal strength of the air-layer non-cellular communication network does not meet the basic threshold, or the load rate is higher than the preset threshold, then the network switching operation is delayed and the signal strengths of the ground-layer communication network and the air-layer non-cellular communication network, as well as the terminal's own height, are continuously monitored.

8. The method according to claim 6, characterized in that, The dual-mode switching of the network connections between the terminal and the space layer, air layer, and ground layer based on the signal strength and load rate of the communication network specifically includes: When the terminal accesses the air-layer non-cellular communication network, the signal strengths of the ground-layer communication network and the air-layer non-cellular communication network, as well as the terminal's own height, are continuously monitored. If the difference between the signal strength of the ground layer and the signal strength of the air layer exceeds a preset threshold, or the terminal's own height is lower than the second communication area, and the signal strength of the ground-layer communication network is greater than the basic threshold, then the ground base stations are screened according to the load rate to generate a list of candidate base stations, and a scoring algorithm is used to score each ground base station in the list of candidate base stations to obtain the ground base station with the highest score as the target base station. A connection between the terminal and the target base station is established while maintaining the connection between the terminal and the air-layer non-cellular communication network. When the state of the target base station stabilizes after the connection, the connection between the terminal and the air-layer non-cellular communication network is released.

9. The method according to claim 6, characterized in that, The dual-mode switching of the network connections between the terminal and the space layer, air layer, and ground layer based on the signal strength and load rate of the communication network specifically includes: When the terminal accesses the space-layer communication network, the signal strengths of the space-layer communication network and the air-layer non-cellular communication network are continuously monitored. When the predicted signal strength of the space layer is lower than the preset threshold or the signal delay of the space layer is greater than the preset threshold, the terminal sends a network switching request to the non-cellular communication base station in the air layer. The non-cellular communication base station selects the optimal 3 beams from multiple beams as a cooperation cluster according to the terminal's location and sends an RRC reconfiguration message to the terminal. After receiving the indication, the terminal simultaneously receives the signals of the space-layer communication network and the non-cellular communication base station and starts context migration. When the state of the non-cellular communication base station stabilizes, the connection between the terminal and the space-layer communication network is released.

10. The method according to claim 9, wherein The mathematical expression of the predicted signal strength of the space layer is: Among them, Ssat1(t + Δt) represents the predicted satellite signal strength at a future time, Ssat1(t) is the current satellite signal strength, λ is the environmental attenuation coefficient, V ue is the user's moving speed, θ is the angle between the user's moving direction and the center of the satellite beam, L t is the dynamic environmental loss.

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