A space-air-ground-sea integrated network system for 6G

Abstract

The embodiment of the application provides a space-air-ground-sea integrated network system for 6G, which comprises a space-based layer, an air-based layer, a ground-based layer and a sea-based layer which are cooperatively connected from top to bottom. The space-based layer comprises low-orbit satellites, which are equipped with inter-satellite laser communication terminals and multi-frequency band space-ground radio frequency terminals, and are used for establishing inter-satellite laser links and communicating with the next three layers. The air-based layer comprises aerostats, aircrafts and helicopters, which are equipped with terahertz communication modules, and are used for establishing terahertz links with the space-based layer, the ground-based layer and the sea-based layer. The ground-based layer comprises heterogeneous cellular base stations, satellite gateway stations and 6G core network nodes, which are equipped with millimeter wave modules, and are used for user terminal broadband access; the core network adopts an SDN / NFV architecture and is internally provided with resource scheduling, slice management and cross-layer handover cooperation units, and is used for unified scheduling of four-layer resources. The sea-based layer comprises surface ships, underwater submersibles and underwater sensing nodes, which are equipped with underwater acoustic and blue light modules, and are used for underwater long-distance low-speed and short-distance high-speed transmission, respectively.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to an integrated air-space-ground-sea network system for 6G. Background Technology

[0002] In existing technologies, fifth-generation mobile communication technology (5G) focuses on terrestrial networking and cannot cover space, high-altitude areas, underwater environments, and remote uninhabited areas. It suffers from limitations such as single coverage dimension, fragmented spatial scenarios, and poor cross-domain collaboration capabilities, failing to meet future global connectivity needs. The core development goal of sixth-generation mobile communication technology (6G) is to achieve integrated coverage across air, space, and sea, constructing a next-generation mobile communication system that deeply integrates multi-dimensional heterogeneous networks. However, existing air, space, and sea-related networking solutions still have significant technical shortcomings in their system architecture and mechanisms.

[0003] For example, at the network architecture level, traditional solutions are mostly independent and loosely coupled designs of space-based, air-based, ground-based, and sea-based networks. They have not formed a 6G characteristic technology system that is precisely adapted to the physical scenarios at each level. As a result, key 6G candidate technologies such as inter-satellite lasers, terahertz, millimeter waves, and underwater communication cannot play their maximum role in their most suitable scenarios. The end-to-end transmission performance is far from the peak rate, latency, and other performance requirements of 6G.

[0004] For example, in terms of mobility management and cross-domain collaboration, existing solutions lack standardized cross-domain mobile handover mechanisms. When terminals move continuously between different spatial scenarios such as land, air, space, and underwater, link interruptions, service delays, or even disconnections are easily caused by delayed handover decisions and inconsistent processes. The handover latency is too high, failing to guarantee service continuity in all-domain mobile scenarios. For instance, in the special scenario of the underwater ocean, due to its extremely complex channel environment and severe signal attenuation, existing solutions have not designed a dedicated network access signaling protocol adapted to this environment. This results in cumbersome processes, high handshake interaction latency, and difficulty in establishing cross-domain routing when underwater nodes access the network, leading to a severe lack of interconnectivity between underwater networks and air, land, and space networks. Furthermore, the entire heterogeneous air-space-ground network lacks a unified control and scheduling plane. Cross-level spectrum, computing power, routing, and other resources cannot be allocated collaboratively, and there is a lack of effective redundancy and backup mechanisms between heterogeneous links. In high-reliability and extremely demanding application scenarios such as national defense emergency response, oceanographic research, and emergency disaster relief, the network's robustness is poor, making it difficult to meet actual usage requirements.

[0005] Therefore, there is an urgent need to design an integrated air-space-ground-sea network system with a clear layered architecture, smooth cross-domain switching, standardized underwater access, and full-link deep adaptation to 6G core technologies. Summary of the Invention

[0006] This application provides a 6G-oriented integrated air-space-ground-sea network system to solve the problems of traditional heterogeneous network hierarchical fragmentation, cross-domain service interruption, underwater access difficulties, and high transmission latency and low reliability, so as to achieve seamless coverage, low latency and high reliability communication, and full-domain service continuity.

[0007] This application provides an integrated air-space-ground-sea network system for 6G, the system comprising: a top-down interconnected air-based layer, air-based layer, ground-based layer, and sea-based layer; The space-based layer includes low-orbit satellites, which are equipped with inter-satellite laser communication terminals and multi-band space-ground radio frequency terminals. The inter-satellite laser communication terminals are used to establish laser communication links between low-orbit satellites, and the multi-band space-ground radio frequency terminals are used to conduct radio frequency communication with the air-based layer, the ground-based layer, and the sea-based layer. The airborne base includes at least one of near-space airships, aircraft and helicopters, and is equipped with a terahertz communication module for establishing terahertz communication links with the space base, ground base and sea base. The ground layer includes heterogeneous cellular base stations, ground satellite gateway stations, and 6G core network nodes. The heterogeneous cellular base stations are equipped with millimeter-wave communication modules, which are used for broadband access communication with user terminals in the millimeter-wave band. The ground satellite gateway stations are used for link communication with low-orbit satellites in the space layer. The 6G core network nodes adopt an SDN / NFV service architecture and have built-in cross-domain resource scheduling units, network slicing management units, and cross-layer handover coordination and control units, which are used to uniformly schedule the resources of the four-layer network and coordinate cross-layer handover. The seabed includes surface ships, underwater vehicles, and underwater sensor nodes. The seabed is equipped with an underwater acoustic communication module and a blue-light visible light communication module. The underwater acoustic communication module is used for the transmission of long-distance, low-speed data underwater, while the blue-light visible light communication module is used for the transmission of short-distance, high-bandwidth data underwater.

[0008] The integrated air-space-ground-sea network system for 6G provided in this application embodiment constructs a four-layer network architecture—space-based, ground-based, and sea-based—that is interconnected from top to bottom. Differentiated 6G communication modules are configured for each layer, ensuring precise matching of communication methods to the propagation characteristics of corresponding physical scenarios. This fully leverages the performance advantages of 6G candidate technologies such as inter-satellite laser, terahertz, millimeter wave, and underwater acoustic / blue light, significantly improving end-to-end bandwidth and reducing end-to-end transmission latency. Specifically, the space-based layer uses inter-satellite laser communication terminals to establish laser links between satellites to provide high-bandwidth backbone transmission. The ground-based layer uses terahertz communication modules to establish terahertz links with the space, ground, and sea-based layers, acting as high-speed relay bridges. The ground-based layer uses millimeter wave communication modules to enable broadband access for user terminals and leverages the cross-domain resource scheduling unit, network slicing management unit, and cross-layer handover collaborative control unit built into the SDN / NFV service-oriented core network to uniformly schedule the spectrum, computing power, and routing resources of the four-layer network. The sea-based layer uses underwater acoustic communication modules and blue / visible light communication modules to adapt to long-distance, low-rate underwater monitoring and short-distance, high-bandwidth data transmission, respectively. Furthermore, by centrally deploying cross-domain resource scheduling, network slicing management, and cross-layer handover collaborative control functions at the 6G core network nodes at the ground level, unified scheduling of four-layer network resources and centralized decision-making for cross-layer mobile handover can be achieved. Pre-handover configuration and context migration can be completed in advance based on the user terminal's mobile trajectory, channel quality, and service quality of service (QoS) level, effectively ensuring the service continuity of the terminal in cross-domain mobile scenarios. Moreover, by providing physically isolated dedicated resources for different services through network slicing, the system's reliability, security, and scenario adaptability are greatly improved. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A schematic diagram of an integrated air-space-ground-sea network system for 6G provided in an embodiment of this application; Figure 2 A schematic diagram of an integrated air-space-ground-sea network handover process is provided for an embodiment of this application; Figure 3 A schematic diagram of the signaling flow for the first stage provided in an embodiment of this application; Figure 4 A schematic diagram of the signaling flow for the second stage provided in this application embodiment; Figure 5A schematic diagram of the signaling flow for the third stage provided in this application embodiment; Figure 6 A schematic diagram of the signaling flow for the fourth stage provided in this application embodiment; Figure 7 This is a schematic diagram of the signaling flow for the fifth stage provided in an embodiment of this application. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0012] It should be noted that, in the cases involving user information in the embodiments of this application, the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in the embodiments of this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions, and corresponding operation entry points are provided for users to choose to authorize or refuse. In addition, the various models involved in this application (including but not limited to language models or large models) comply with relevant laws and standards.

[0013] Furthermore, the timing of the steps in the following method embodiments is merely an example and not a strict limitation.

[0014] Figure 1 This is a schematic diagram of an integrated air-space-ground-sea network system for 6G, provided as an embodiment of this application. Figure 1 As shown in the embodiments of this application, the integrated air-space-ground-sea network system for 6G includes a top-down interconnected air-based layer, air-based layer, ground-based layer, and sea-based layer.

[0015] 1. Heavenly base The space-based layer includes low-Earth orbit (LEO) satellites, which are equipped with inter-satellite laser communication terminals and multi-band space-ground radio frequency (RF) terminals. The inter-satellite laser communication terminals are used to establish laser communication links between LEO satellites, while the multi-band space-ground RF terminals are used for radio frequency communication with the air-based layer, the ground-based layer, and the sea-based layer.

[0016] In practice, the space-based layer can be composed of a low-Earth orbit (LEO) Walker satellite constellation to form the space-based layer backbone network. For example, a constellation with an orbital altitude of 1000km-1500km, an orbital inclination of approximately 55°, and multiple orbital planes with multiple satellites distributed on each orbital plane, can achieve uniform global coverage. Each LEO satellite is equipped with an inter-satellite laser communication terminal and a multi-band space-to-ground radio frequency terminal.

[0017] Optionally, the inter-satellite laser communication terminal uses a 1550nm wavelength and is configured with a single inter-satellite link transmission rate of ≥100Gbps, supporting full-duplex or half-duplex communication modes. In actual deployment, laser links can be established between adjacent satellites in the same orbital plane and between satellites in different orbital planes, forming a space-based all-optical backbone network. Inter-satellite data can be directly routed and forwarded between satellites without passing through ground gateway stations, thereby significantly reducing transmission latency in long-distance communication scenarios such as transoceanic and polar regions.

[0018] Optionally, the multi-band terrestrial radio frequency terminal is compatible with both terahertz and millimeter-wave bands. This means the terminal can dynamically select the terahertz band for communication with the airborne ground layer or the millimeter-wave band for communication with the ground layer, based on communication link requirements, further covering seaborne ground-based scenarios. For example, when a low-Earth orbit satellite needs to transmit high-speed data back to a ground gateway station, a millimeter-wave band can be used to establish a feed link; when relay communication with aerial drones or airships is required, it can switch to the terahertz band to utilize its large bandwidth advantage.

[0019] In one optional embodiment, the low-Earth orbit satellite of the astronomical layer is also equipped with an onboard intelligent processing unit. This onboard intelligent processing unit is used for on-orbit processing of inter-satellite routing and forwarding.

[0020] Specifically, a low-Earth orbit satellite receives laser link data from a neighboring satellite. The onboard intelligent processing unit on the low-Earth orbit satellite queries the onboard routing table based on the destination information in the data packet, decides the next-hop satellite node, and forwards the data to the target satellite through a laser communication terminal.

[0021] Optionally, the onboard intelligent processing unit can also perform some edge computing tasks, such as on-orbit preprocessing of remote sensing data (e.g., image compression, feature extraction), and only sending key data to the ground, thereby saving space-to-ground link bandwidth resources. In addition, the onboard intelligent processing unit can monitor the working status of each module on the satellite in real time, perform fault self-checks and recovery operations, and ensure the reliability of the space-to-ground network.

[0022] 2. Empty base layer The airborne layer includes at least one of near-space airships, aircraft, and helicopters. Near-space airships, such as long-endurance stratospheric airships or high-altitude balloons, can remain stationary for extended periods in near-space at altitudes of approximately 20 km to 100 km, serving as airborne backbone relay nodes. Aircraft include fixed-wing UAVs and manned aircraft, used for mobile access and relay in low-altitude areas; helicopters are suitable for emergency communication scenarios requiring hovering or vertical takeoff and landing. Each node in the airborne layer (i.e., near-space airships, aircraft, and helicopters) is equipped with a terahertz communication module to establish terahertz communication links with the spaceborne, ground-based, and sea-based layers.

[0023] Optionally, the terahertz communication module of the air layer adopts a fully electronic or optoelectronic terahertz transceiver, with an operating frequency band of 0.1THz to 10THz. This frequency band has both large bandwidth (supporting transmission rates of Gbps and above) and good directivity, making it suitable as a high-speed wireless bridge between air nodes and upper and lower layers.

[0024] In one alternative embodiment, the terahertz communication module can be configured to establish the following four types of terahertz links: The air-to-space link, namely the terahertz link between the air-based layer and the space-based layer, can be further specifically established as a terahertz link between the air-based layer node and the low-orbit satellite. This link is used to relay data gathered on the ground or sea surface to the satellite via air relay, or to fill in the gaps in satellite signal transmission when the satellite signal is affected by rain attenuation.

[0025] Air-to-ground links, or terahertz links between air-based and ground-based infrastructure, can be further defined as terahertz links established between air-based nodes and ground-based cellular base stations or gateways to provide temporary or supplementary backhaul channels for areas with blind spots in ground network coverage (such as mountainous areas, deserts, and disaster areas).

[0026] The air-sea link, or terahertz link between the air-based layer and the sea-based layer, can be further defined as establishing a terahertz link between the air-based layer node and the surface ship or buoy of the sea-based layer for high-speed data backhaul in the open ocean area, avoiding reliance on low-speed maritime satellites.

[0027] Air-to-air links are terahertz links between different air nodes within the airborne layer. For example, near-space aerostats can be used as high-altitude backbones to form an aerial mesh relay network with multiple drones or helicopters below, thereby expanding coverage and improving link redundancy.

[0028] With the above link configuration, the peak rate of a single link of the terahertz communication module can reach ≥10Gbps, which can meet the real-time transmission requirements of services such as high-definition video and large-scale sensor data.

[0029] In an optional embodiment, the terahertz communication module is also configured with a beam tracking unit for real-time tracking of the communication beam in high-speed moving scenarios.

[0030] In practice, since both airborne base nodes (such as drones and helicopters) and space-based satellites are in high-speed motion, the beam tracking unit maintains link quality in real time through the following methods: First, the position, velocity, and attitude information of both the local node and the peer node are acquired through GNSS positioning, inertial measurement units, or ephemeris data. Next, a phased array antenna or mechanical servo turntable is used to dynamically adjust the direction of the terahertz beam, ensuring it remains aligned with the peer node. Then, closed-loop fine-tuning is performed using channel quality feedback (such as received signal strength and signal-to-noise ratio) to compensate for beam offset caused by atmospheric turbulence or platform vibration. Through this beam tracking unit, the space-based terahertz link can maintain a stable connection in scenarios with relative velocities reaching hundreds of meters per second (such as between a UAV and a low-Earth orbit satellite).

[0031] Optionally, the airborne base can also deploy edge computing servers, such as lightweight computing units mounted on airships or large drones, to process locally collected data (such as disaster area videos and marine monitoring data) in real time, and only upload small-volume feature information after processing to space-based or ground-based networks, thereby saving terahertz link bandwidth and reducing end-to-end latency.

[0032] 3. Subgrade The ground-level infrastructure includes heterogeneous terrestrial cellular base stations, terrestrial satellite gateway stations, and 6G core network nodes. The heterogeneous terrestrial cellular base stations are equipped with millimeter-wave communication modules, used for broadband access communication with user terminals in the millimeter-wave band. The terrestrial satellite gateway stations are used for link communication with low-Earth orbit satellites in the space-level infrastructure. The 6G core network nodes adopt a Software Defined Network (SDN) / Network Functions Virtualization (NFV) service architecture, and have built-in cross-domain resource scheduling units, network slicing management units, and cross-layer handover coordination and control units, used to uniformly schedule resources of the four-layer network and coordinate cross-layer handovers.

[0033] In practical implementation, the terrestrial base station, serving as the control center of the entire 6G-oriented integrated air-space-ground-sea network system, is deployed in the terrestrial environment. Ground-based heterogeneous cellular base stations are categorized into macro base stations, micro base stations, and pico base stations based on their coverage capabilities, forming a multi-layered heterogeneous cellular network. Macro base stations are deployed in wide-area coverage scenarios such as suburbs and highways, providing basic continuous coverage; micro base stations and pico base stations are densely deployed in high-traffic areas such as urban hotspots, transportation hubs, and sports venues to improve system capacity and user experience.

[0034] Optionally, the millimeter-wave communication module at the ground level operates in the 24GHz to 100GHz frequency band. This band has abundant spectrum resources and can support peak rates of over 10Gbps per carrier, meeting the ultra-high speed requirements of 6G. Due to the significant path loss and weak penetration of the millimeter-wave band, terrestrial heterogeneous cellular base stations need to employ dense deployment and beamforming technology to ensure coverage quality.

[0035] In one optional embodiment, the terrestrial heterogeneous cellular base station is configured with a massive MIMO metasurface antenna array. This MIMO metasurface antenna array is used to form a multi-layered heterogeneous terrestrial cellular network comprising macro base stations, micro base stations, and pico base stations. Massive MIMO technology, by configuring dozens or even hundreds of antenna elements, can form multiple parallel beams in space, simultaneously serving multiple user terminals, significantly improving spectral efficiency and network capacity. The metasurface antenna array further enhances the flexibility and accuracy of beamforming, dynamically adjusting the beam direction according to the real-time location of the user terminal, thereby reducing interference and improving link quality.

[0036] Ground-based satellite gateway stations, built in areas far from urban electromagnetic interference, are equipped with large-aperture parabolic antennas or phased array antennas to establish feeder links with low-Earth orbit satellites on the ground level. On one hand, the satellite gateway station receives downlink data from the satellite and connects it to the ground core network; on the other hand, it transmits uplink data from user terminals to the satellite via millimeter-wave or terahertz links, and the satellite then relays it to other areas via inter-satellite laser links. The gateway station can also perform management functions such as satellite orbit monitoring, ephemeris updates, and telemetry and remote control.

[0037] The 6G core network nodes adopt an SDN / NFV service architecture, which, compared with the traditional core network, features the separation of control plane and user plane, on-demand deployment of network functions, and elastic scaling of resources.

[0038] The 6G core network node can be configured to: coordinate the spectrum resources, computing resources and routing resources of the four-layer network through the cross-domain resource scheduling unit; manage network slice instances across the four-layer network through the network slice management unit; and coordinate the cross-layer handover process through the cross-layer handover coordination and management unit.

[0039] Specifically, the cross-domain resource scheduling unit is responsible for coordinating the inter-satellite laser link bandwidth at the space level, the terahertz link resources at the air level, the millimeter-wave spectrum and computing resources at the ground level, and the underwater acoustic and blue light communication resources at the sea level, so as to achieve unified allocation and dynamic adjustment of resources across levels.

[0040] The network slice management unit is used to create, modify, and delete network slice instances across Layer 4 networks, providing end-to-end quality of service (QoS) guarantees for different services (such as emergency communications, IoT data acquisition, and high-definition video backhaul). Each slice can be logically isolated, sharing the same physical infrastructure but without interfering with each other.

[0041] The cross-layer handover collaborative management unit is configured to detect scene changes when user terminals move between different network layers, and trigger cross-domain boundary handover rules according to scene changes to determine the target communication link, perform link handover and service context migration.

[0042] The cross-domain handover types supported by the cross-layer handover collaborative management unit include: handover between ground-level networks and air-level networks, handover between air-level networks and space-level networks, handover between sea-level networks and ground-level networks, handover between sea-level networks and space-level networks, and handover between ground-level networks and sea-level networks.

[0043] To achieve seamless handover at the millisecond level, the cross-layer handover collaborative management and control unit is configured to be uniformly scheduled by the SDN / NFV service architecture. It combines the user terminal's mobile trajectory information, channel quality information, and service quality level information to complete the pre-handover link configuration and context migration in advance, so that the service interruption latency during the handover process is lower than the set time threshold (e.g., 5ms).

[0044] For ease of understanding, combined with Figure 2 A detailed explanation of the integrated air-space-ground-sea switching process is provided. Figure 2 This is a schematic diagram of an integrated air-space-ground-sea network handover process provided in an embodiment of this application.

[0045] like Figure 2 As shown, the user terminal first accesses the network. The core network (specifically, the 6G core network nodes at the ground level) determines the initial communication mode based on the user terminal's current spatial environment: if the terminal is on the ground or in an urban environment, it accesses the 6G millimeter-wave coverage network (ground level); if the terminal is underwater, it accesses the 6G underwater communication network (sea level); if the terminal is in the air, it accesses the 6G terahertz transmission network (space level); and if the terminal is in space, it accesses the inter-satellite laser communication network (space level).

[0046] After access, the network monitors the user terminal's movement trajectory in real time throughout the entire process. When the terminal crosses the boundaries of different scenarios, the corresponding cross-domain handover rules are automatically triggered. Specifically, this includes, but is not limited to, the following handover types: 1) Ground to low-altitude movement: When the user terminal moves from the ground to the air, it triggers the ground-low-altitude boundary switch, switching the communication link from the ground-level millimeter-wave network to the air-level terahertz transmission network.

[0047] 2) Low-altitude to space movement: The user terminal continues to ascend from low altitude to high altitude or near-Earth space, triggering a low-altitude-space boundary switch, switching the communication link from the space-based terahertz network to the space-based inter-satellite laser communication network.

[0048] 3) Re-entry from space to low altitude: The user terminal re-enters the atmosphere from space and descends to low altitude, triggering the space-low altitude boundary switch, and the communication link switches from the space layer back to the air layer.

[0049] 4) Landing from the air to the ground: The user terminal lands from the air to the ground, triggering an air-to-ground boundary switch, and the communication link switches from the air-to-ground layer back to the ground-to-ground layer.

[0050] 5) Surfacing from underwater: The underwater terminal (a type of user terminal) surfaces, triggering a water-to-land boundary switch or an underwater-to-ground boundary switch, and the communication link switches from the seabed-based underwater acoustic / blue light network to the ground-based millimeter-wave network.

[0051] 6) Land to Ocean: When the terminal moves from land to sea, it triggers a land-sea boundary switch, and the communication link switches from the land layer to the sea layer.

[0052] 7) Direct connection from underwater to space: In deep-sea long-distance scenarios, underwater terminals can establish a direct connection with space-based satellites via surface relays, triggering a special underwater-space cross-domain handover. The communication link is switched to an inter-satellite laser link via an underwater relay node, a space-based terahertz node (optional).

[0053] After the handover is triggered, the system automatically matches the target communication mode and completes the link switch, service context migration, and routing path update. For the above-mentioned special cross-domain scenarios, the system can directly execute the cross-domain handover decision, skipping intermediate layers and matching the optimal cross-layer transmission link.

[0054] In this embodiment of the application, the above-mentioned cross-layer handover actions are uniformly scheduled by the SDN / NFV unified control plane (i.e., executed by the cross-layer handover collaborative management and control unit in the ground-level 6G core network), and QoS guarantee and seamless handover of redundant links are performed synchronously.

[0055] Optionally, the 6G-oriented integrated air-space-ground-sea network system is also equipped with a multi-link redundancy backup mechanism, which is used to automatically switch between multiple heterogeneous links. When multiple heterogeneous links exist (such as maintaining millimeter wave and terahertz links simultaneously), the system supports redundancy backup and automatic fault switching to ensure uninterrupted service and continuous stable connection throughout the entire process, ultimately achieving smooth roaming handover across all scenarios.

[0056] It should be noted that, Figure 2The “6G terahertz transmission node”, “6G inter-satellite laser communication satellite constellation”, “6G underwater communication node” and various boundary handover triggering conditions shown are only examples. In actual deployment, they can be flexibly configured according to network topology and terminal capabilities, but all follow the above-mentioned unified handover decision and execution process.

[0057] 4. Seabed The seabed includes surface ships, underwater vehicles, and underwater sensor nodes. The seabed is equipped with underwater acoustic communication modules and blue-light and visible-light communication modules. The underwater acoustic communication modules are used for long-distance, low-speed data transmission underwater, while the blue-light and visible-light communication modules are used for short-distance, high-bandwidth data transmission underwater.

[0058] In practice, the seabed layer covers the entire marine environment, both surface and underwater. Surface ships can serve as backbone nodes of the sea-based network, carrying communication relay equipment, edge computing units, and satellite communication terminals to bridge the underwater network with air, space, and ground networks. Underwater vehicles (such as autonomous underwater vehicles (AUVs) and remotely operated underwater vehicles (ROVs)) and underwater sensing nodes (such as nodes of seabed observation networks and hydrological monitoring buoys) constitute the underwater sensing and data acquisition layer.

[0059] In one optional embodiment, the seabed-based underwater acoustic communication module employs a low-frequency underwater acoustic communication system for transmitting long-distance, low-rate monitoring data underwater. For example, between underwater sensor nodes deployed in deep-sea areas, or between underwater sensor nodes and surface ships, marine environmental monitoring data such as temperature, salinity, depth, and ocean currents can be transmitted at rates of several kbps to tens of kbps per second via an underwater acoustic link with a frequency of 1kHz to 30kHz. The communication distance can reach several kilometers to tens of kilometers. Although low-frequency underwater acoustic communication has a low data rate, it can maintain a stable link connection in complex underwater multipath and high-attenuation channels.

[0060] In one optional embodiment, the blue-visible light communication module employs an underwater blue-light communication system for short-range, high-bandwidth data transmission underwater. For example, when an underwater vehicle approaches a surface ship or underwater base station (typically within tens to two hundred meters), blue-green laser or LED visible light communication in the 450nm–550nm band can be used to achieve high-speed data transmission at Mbps to Gbps levels, enabling the transmission of high-capacity services such as high-definition video, underwater target images, and sonar data. Blue-light communication offers advantages such as high bandwidth, low latency, and resistance to electromagnetic interference; however, its transmission distance is limited due to absorption and scattering in the water medium, making it suitable for short-range, high-speed unloading scenarios.

[0061] In an optional embodiment, the seabed layer is further configured with a protocol compatibility unit, which enables the communication module of the seabed layer to achieve protocol layer interconnection with the satellite communication link of the skybed layer, the terahertz communication link of the airbed layer, and the millimeter-wave communication link of the ground layer.

[0062] Specifically, the protocol compatibility unit is used to convert and adapt underwater communication protocols (such as underwater acoustic MAC layer protocols and blue light physical layer protocols) to terrestrial standard protocols (such as the 5G / 6G NR Uu interface protocol). For example, when data reported by an underwater terminal needs to be relayed via a space-based satellite, the protocol compatibility unit encapsulates the data packets carried by underwater acoustic or blue light into Protocol Data Units (PDUs) conforming to the satellite link transmission format, and performs necessary address mapping, routing encapsulation, and QoS mapping to ensure end-to-end data interoperability. This unit can be deployed on surface ships or underwater relay nodes, or it can exist as an independent gateway device.

[0063] In one optional embodiment, the 6G-oriented integrated air-space-ground-sea network system further includes a standardized underwater node access controller. This standardized underwater node access controller is located in the 6G core network node at the ground level, is compatible with 5G and 6G protocol stacks, and has communication interfaces including RACH, RRC, NAS, N2, and N3 interfaces. It interacts with the AMF (Access and Mobility Management), SMF (Session Management), and UPF (User Plane Functions) network elements of the 6G core network node via signaling, and is configured to execute the five-stage signaling process for underwater terminal network access. Phase 1: Perform Random Access (RACH), Radio Resource Control (RRC) connection establishment, Non-Access Stratum (NAS) attach request, and two-way authentication for the underwater terminal (User Equipment, UE).

[0064] Phase 2: Receive depth, location, and movement trajectory information reported by the underwater terminal, perform location registration, and predict cross-domain movement trends.

[0065] Phase 3: Establish a data tunnel between the underwater terminal and the underwater relay node in the seabed layer, thus opening up the path from the underwater to the seabed network.

[0066] Phase 4: Establish full-domain routing sequentially from underwater to ground level, from ground level to air level, and from air level to sky level.

[0067] Phase 5: Periodically receive location information reported by the underwater terminal, update link parameters, and dynamically adjust the modulation and coding scheme and hybrid automatic repeat request parameters according to the underwater channel conditions.

[0068] For ease of understanding, combined with Figures 3 to 7 The signaling process for the above five stages will be explained.

[0069] Figure 3 A schematic diagram of the signaling flow for the first stage provided in this application embodiment, as shown below. Figure 3As shown, this stage includes steps 1 to 13: Step 1: The UE sends a dedicated underwater RACH random access preamble to the 6G underwater communication node. Random access is the first step in establishing an initial connection between the terminal and the base station, used to request uplink synchronization and resource allocation. The random access preamble is a special sequence used by the base station to identify the presence of the terminal and estimate its transmission delay. In this embodiment, a preamble format adapted to the long latency and low signal-to-noise ratio characteristics of underwater acoustic channels can be used to cope with the harsh propagation conditions of underwater acoustic channels.

[0070] Step 2: After receiving the preamble, the 6G underwater communication node returns a Random Access Response (RAR). Optionally, the RAR includes a Timing Advance (TA), which is used to compensate for the long delay in underwater signal propagation and ensure that the data sent by the terminal is aligned with the base station's receiving time slot.

[0071] Step 3: The UE sends a Radio Resource Control (RRC) connection request to the 6G underwater communication node, carrying the establishment reason as "mo-data" (mobile-initiated data). RRC is a signaling protocol between the terminal and the base station, responsible for connection management, measurement configuration, and other functions.

[0072] Step 4: The 6G underwater communication node sends an RRC connection establishment message to the underwater UE.

[0073] Step 5: After the UE completes the RRC connection establishment, it carries a Non-Access Stratum (NAS) attach request in the RRC connection establishment completion message. NAS is a signaling protocol between the terminal and the core network, used for mobility management and session management.

[0074] Step 6: The 6G underwater communication node encapsulates the NAS attach request into an initial UE message and forwards it to the AMF network element of the core network through the N2 interface (signaling interface between the base station and the core network).

[0075] Step 7: The AMF network element triggers the Authentication and Key Agreement (AKA) process to complete the two-way authentication and key configuration between the UE and the network. AKA is a standard security mechanism in mobile communication systems that ensures the legitimacy of the terminal and the network.

[0076] Step 8: After successful authentication, the AMF sends an Initial Context Establishment Request to the underwater communication node, which includes an Attach Accept message. The initial context includes the UE's security context, QoS configuration, bearer information, etc.

[0077] Step 9: The 6G underwater communication node sends an RRC reconfiguration message to the UE to enable the UE to activate the security mode (integrity protection and encryption) and establish a Data Radio Bearer (DRB). The DRB is the logical channel for transmitting user data between the terminal and the network.

[0078] Step 10: The UE replies that the 6G underwater communication node RRC reconfiguration is complete.

[0079] Step 11: The 6G underwater communication node returns the initial context establishment completed to the AMF.

[0080] Step 12: AMF returns an attachment completion message to the 6G underwater communication node.

[0081] Step 13: The 6G underwater communication node decides to send a release RRC connection or maintain connection message to the UE based on the service requirements of the core network.

[0082] Through steps 1 to 13 above, the underwater terminal has completed basic network registration, obtained an IP address or data network identifier assigned by the network, and has the basic ability to send and receive data.

[0083] Figure 4 A schematic diagram of the signaling flow for the second stage provided in this application embodiment is shown below. Figure 4 As shown, this stage includes steps 14 to 16: Step 14: The UE reports its depth information, current location coordinates, and movement trajectory (such as speed and heading) to the 6G underwater communication node via a measurement report message. The measurement report is a mechanism in the RRC protocol for terminals to report wireless environment measurement results. In this embodiment, the content of the measurement report is expanded to include underwater-specific sensor data such as depth and position.

[0084] Step 15: The 6G underwater communication node sends this information to the AMF of the 6G core network via the N2 interface as a UE location reporting message. The N2 interface is the signaling interface between the base station and the core network, used to transmit NAS messages and terminal location information, etc.

[0085] Step 16: The 6G core network performs location registration based on the reported information, that is, updates the UE's location record in Unified Data Management (UDM) or context, and predicts whether the UE may subsequently surface, submerge, or move across domains. Based on the prediction results, the core network reserves link resources in advance for cross-layer handover. For example, if the depth gradually decreases and the heading is towards the coast, it is determined that the terminal is about to surface, and the core network can reserve millimeter wave or terahertz link resources in advance at the target surface base station or airborne base station node.

[0086] Figure 5 A schematic diagram of the signaling flow for the third stage provided in this application embodiment is shown below. Figure 5 As shown, this stage is mainly triggered when the UE needs to float up or pass through a relay, including steps 17 to 21: Step 17: The 6G underwater communication node initiates a data forwarding request to the 6G millimeter-wave base station on the water surface or shore, requesting the establishment of an N3 tunnel. The N3 tunnel, or GTP-U (GPRS Tunneling Protocol – User Plane) tunnel, is used to carry encapsulated user data packets.

[0087] Step 18: The 6G millimeter-wave base station confirms and returns a tunnel establishment confirmation, completing the establishment of the user plane tunnel from underwater to the ground. At this point, the UE has the capability for bidirectional data transmission between itself and the ground.

[0088] Step 19: If there is downlink data that needs to be sent to the UE on the core network side, then send the downlink data notification to the 6G millimeter wave base station.

[0089] Step 20: The 6G millimeter-wave base station forwards downlink data to the 6G underwater communication node through the established N3 tunnel.

[0090] Step 21: The 6G underwater communication node transmits downlink data to the UE.

[0091] The transmission path of uplink data is symmetrical to the above process. The data sent by the UE reaches the 6G millimeter wave base station through the underwater communication node and the N3 tunnel, and is then forwarded by the 6G millimeter wave base station to the target application server in the 6G core network.

[0092] The third phase successfully established the basic pathway for underwater-surface-terrestrial millimeter-wave networks. Subsequently, underwater terminals can conduct basic data communication via terrestrial networks.

[0093] Figure 6 This is a schematic diagram of the signaling flow for the fourth stage provided in the embodiments of this application. This stage is mainly triggered when the underwater node is located at a long distance in the deep sea, without terrestrial network coverage, and requires satellite relay. Figure 6 As shown, steps 22 to 29 are included: Step 22: The 6G underwater communication node sends a relay path request to the 6G millimeter-wave base station, which explicitly requires satellite backhaul (i.e., requests the establishment of a global route via the space-based terahertz node and the space-based laser satellite).

[0094] Step 23: The 6G millimeter-wave base station sends a path establishment request to the 6G terahertz transmission node in the air. This request contains the necessary routing information.

[0095] Step 24: The 6G terahertz transmission node requests the establishment of an inter-satellite laser link from the 6G inter-satellite laser communication WeChat. The space-based satellites then establish inter-satellite laser links based on the request. The inter-satellite laser links use the 1550nm band, with a single link rate ≥100Gbps, and are used to directly forward data between satellites without requiring ground relay.

[0096] Step 25: The space-based satellite simultaneously connects to the ground-based 6G core network via a feed link. The feed link is the communication link between the satellite and the ground gateway station, typically using millimeter wave or laser frequency bands to transmit user data and signaling.

[0097] Steps 26 to 28: Each level of node (space-based satellite, airborne terahertz node, and ground-based millimeter-wave base station) returns a path confirmation message, confirming that the route has been established. Before confirming, each node checks whether its own resources are sufficient and allocates the corresponding link resources.

[0098] Step 29: After receiving the relay path confirmation, the final 6G underwater communication node notifies the underwater UE: the global routing has been established, and the underwater node has now achieved global connectivity through the integrated air-space-ground-sea network.

[0099] Through the fourth phase, the underwater node established an end-to-end global route from "underwater → ground → airborne terahertz → space-based laser satellite".

[0100] Figure 7 A schematic diagram of the signaling flow for the fifth stage provided in the embodiments of this application is shown below. Figure 7 As shown, this stage includes steps 30 to 34: Step 30: The UE periodically initiates a periodic Tracking Area Update (TAU) request. The tracking area is a mobility area managed by the core network, used to track the UE's location in idle mode. The TAU request is used to notify the core network of the UE's current location area and update the mobility management context.

[0101] Step 31: After receiving the TAU request, the 6G underwater communication node sends a Location Update Request to the 6G core network.

[0102] Step 32: The 6G core network replies to the 6G underwater communication node with a Location Update Accept.

[0103] Step 33: The 6G underwater communication node sends a TAU acceptance message to the UE to confirm that the location update is complete and may allocate a new tracking area identifier list.

[0104] Step 34: The 6G underwater communication node dynamically adjusts QoS parameters based on the current underwater acoustic channel conditions (such as signal-to-noise ratio (SNR), multipath delay, and bit error rate). For example, it changes the modulation and coding scheme (MCS) and Hybrid Automatic Repeat Request (HARQ) parameters. When channel quality deteriorates, the network can instruct the UE to use more robust lower-order modulation and a lower code rate, and increase the number of HARQ retransmissions; when channel quality improves, it can switch to higher-order modulation to improve transmission efficiency.

[0105] Through the fifth-stage process, the system can ensure the long-term stability and reliability of underwater terminal communication and dynamically adapt to the time-varying characteristics of underwater channels.

[0106] In one optional embodiment, edge computing nodes are distributed and deployed in the 6G core network nodes of the air-based, space-based, and ground-based layers, as well as in the sea-based layer. The 6G core network nodes of the ground-based layer constitute the central cloud node. The edge computing nodes have data communication links with the central cloud node, forming a three-level collaborative computing architecture of cloud, edge, and terminal with the user terminal.

[0107] Specifically, edge computing nodes refer to computing devices deployed at the edge of the network (close to the data source or user terminal) that have the ability to store, process, and analyze data.

[0108] In this embodiment, the edge computing nodes of the Tianji layer can be deployed in the on-board intelligent processing unit of the low-orbit satellite for on-orbit processing of remote sensing data, performing lightweight computing tasks such as image compression and feature extraction, and only sending key results to the ground, thereby significantly saving satellite-to-ground link bandwidth.

[0109] The edge computing nodes of the airborne base layer can be deployed on near-space airships or drone platforms to perform real-time relay processing of data from space-based or ground-based systems, such as merging, caching, or format conversion of multiple video streams to reduce backhaul latency.

[0110] Ground-based edge computing nodes can be deployed on the access network side of heterogeneous terrestrial cellular base stations (such as MEC platforms) to process low-latency services (such as autonomous driving and industrial control), and can also be used for preliminary parsing and forwarding of data uploaded by underwater terminals.

[0111] Edge computing nodes at the seabed level can be deployed on surface ships or underwater relay nodes to perform local aggregation, filtering, and anomaly detection on data collected by underwater sensors, transmitting only valuable data to the upper-level network.

[0112] The central cloud node is supported by 6G core network nodes at the ground level (such as central cloud servers or cloud data centers), possessing powerful computing, storage, and network resources. The central cloud node is responsible for global computing resource scheduling, complex model training (such as AI models), network-wide status monitoring, and long-term data storage and analysis.

[0113] The workflow of the cloud-edge-device three-tier collaborative computing architecture is as follows: On the edge: User terminals (such as underwater vehicles, drones, and mobile phones) collect raw data, perform preliminary processing (such as data cleaning and compression), and send the processed data to the nearest edge computing node.

[0114] Edge computing nodes receive data from the end-user side and perform real-time analysis, local decision-making, or data caching based on business needs. For services requiring low-latency responses (such as emergency obstacle avoidance for underwater equipment), edge nodes can directly issue decision commands to the end-user side without uploading them to the central cloud.

[0115] Cloud side: For tasks requiring a global perspective or large-scale computing (such as cross-regional marine environment modeling and full-network AI model training), edge nodes upload the aggregated data to the central cloud node, where the central cloud performs in-depth analysis and model optimization, and then distributes the updated model parameters to the edge and end-side.

[0116] Through the aforementioned three-tiered collaborative architecture, the system can achieve a layered computing power layout that enables data to be processed locally and critical data to be uploaded to the cloud, significantly reducing the latency of long-distance transmission across layers and meeting the stringent requirements of 6G for ubiquitous low-latency computing services (such as augmented reality, real-time control, and immersive communication).

[0117] In an optional embodiment, the 6G-oriented integrated air-space-ground-sea network system further includes an end-to-end security protection system, which includes: The terminal access authentication unit is used to authenticate user terminals accessing the Layer 4 network of the access system. Specifically, when a user terminal (whether it is a ground-based mobile phone, drone, underwater vehicle, or satellite terminal) accesses the network for the first time or switches across layers, this unit invokes the core network's Authentication Service Function (AUSF) and Unified Data Management (UDM) to execute the 5G / 6G standard Authentication and Key Agreement (AKA) process, including two-way authentication, key generation, and distribution. For underwater terminals, the authentication process is adapted to the long latency characteristics of the underwater acoustic channel, allowing for a more flexible timing window and retransmission mechanism. Only terminals that pass authentication are authorized to access the corresponding network resources.

[0118] The link encryption unit is used to encrypt and protect inter-satellite laser communication links, space-based terahertz links, ground-based millimeter-wave links, and sea-based underwater acoustic and blue light links. The cross-domain data isolation unit is used to achieve logical or physical isolation of data between different network layers. Specifically, based on network slicing technology, this unit creates independent virtual networks for services with different security levels (such as secure communication, civilian internet access, and marine scientific research data acquisition). For high-security services, physical isolation can be used, i.e., allocating dedicated hardware resources (such as independent core network elements, dedicated base stations, and dedicated satellite transponders); for services with general security levels, logical isolation can be used, achieving data flow separation through VLAN (Virtual Local Area Network), VxLAN, or GTP-U tunnel encapsulation to ensure that unauthorized access or data leakage does not occur during cross-domain data exchange.

[0119] The intrusion detection unit (IDU) is used to detect intrusion activities across the entire Layer 4 network. Deployed in the network management system (NMS) or security operations center (SOC) of the core network, this unit collects traffic logs, signaling records, and device alarms from each layer of the network. Combining rule-based feature matching and machine learning-based anomaly detection algorithms, it identifies security threats such as denial-of-service (DDoS) attacks, man-in-the-middle attacks, and unauthorized access in real time. Once an intrusion is detected, the system automatically triggers an alarm and can coordinate with other security units (such as isolation units) to block or restore access.

[0120] In practice, the end-to-end security protection system works in conjunction with the network slicing management unit to provide dedicated slices with physical or logical isolation for different service types based on network slicing technology. For example, a civilian broadband slice is created using logical isolation to provide ordinary users with high-bandwidth, low-latency internet access; a marine scientific research slice is created using intermediate isolation levels to ensure the integrity and authenticity of marine monitoring data and prevent data tampering. Through the aforementioned security mechanisms, this system can build an end-to-end multi-layered defense-in-depth system from access authentication, link encryption, data isolation to intrusion detection, meeting the high security requirements of 6G full-domain communication scenarios.

[0121] In summary, the integrated air-space-ground-sea network system for 6G provided in this application firstly achieves seamless coverage across all dimensions—space, air, ground, and sea—by constructing a top-down, collaboratively interconnected four-layer architecture. Each layer is adapted with inter-satellite laser, terahertz, millimeter-wave, and underwater acoustic / blue light dual-mode communication technologies, enabling true global ubiquitous 6G communication capabilities. Simultaneously, this layered and precise adaptation fully leverages the technical advantages of each frequency band, resulting in end-to-end bandwidth, latency, and reliability far exceeding traditional heterogeneous networking. Secondly, by utilizing the cross-layer handover collaborative management unit and the unified SDN / NFV control plane built into the terrestrial 6G core network, the system can monitor terminal movement trajectories in real time and complete pre-handover configuration in advance, achieving millisecond-level smooth cross-layer handover (service interruption latency less than 5ms). Combined with multi-heterogeneous link redundancy backup and automatic fault switching mechanisms, it solves the pain point of service interruption in cross-domain mobile scenarios. Furthermore, the standardized five-stage access signaling process for underwater nodes is fully compatible with 5G / 6G protocol stacks, treating underwater terminals as standard UEs and incorporating them into the core network management. This significantly reduces the network access latency and interaction complexity of underwater nodes, enabling seamless communication across the entire link from underwater to surface to air to space. Finally, a cloud-edge-device three-level collaborative computing architecture enables data processing locally. Combined with network slicing technology, it provides dedicated resources with physical or logical isolation for different services and deploys an end-to-end security protection system. This results in excellent performance in resource scheduling, security protection, scenario scalability, and network robustness, making it widely adaptable to various complex application scenarios such as emergency response, oceanographic research, disaster relief, and civilian broadband.

[0122] Finally, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0123] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A 6G-oriented integrated air-space-ground-sea network system, characterized in that, The system comprises a top-down interconnected air-based layer, space-based layer, ground-based layer, and sea-based layer; The space-based layer includes low-orbit satellites, which are equipped with inter-satellite laser communication terminals and multi-band space-ground radio frequency terminals. The inter-satellite laser communication terminals are used to establish laser communication links between low-orbit satellites, and the multi-band space-ground radio frequency terminals are used to conduct radio frequency communication with the air-based layer, the ground-based layer, and the sea-based layer. The airborne base includes at least one of near-space airships, aircraft and helicopters, and is equipped with a terahertz communication module for establishing terahertz communication links with the space base, ground base and sea base. The ground layer includes heterogeneous cellular base stations, ground satellite gateway stations, and 6G core network nodes. The heterogeneous cellular base stations are equipped with millimeter-wave communication modules, which are used for broadband access communication with user terminals in the millimeter-wave band. The ground satellite gateway stations are used for link communication with low-orbit satellites in the space layer. The 6G core network nodes adopt an SDN / NFV service architecture and have built-in cross-domain resource scheduling units, network slicing management units, and cross-layer handover coordination and control units, which are used to uniformly schedule the resources of the four-layer network and coordinate cross-layer handover. The seabed includes surface ships, underwater vehicles, and underwater sensor nodes. The seabed is equipped with an underwater acoustic communication module and a blue-light visible light communication module. The underwater acoustic communication module is used for the transmission of long-distance, low-speed data underwater, while the blue-light visible light communication module is used for the transmission of short-distance, high-bandwidth data underwater.

2. The system according to claim 1, characterized in that, The low-orbit satellite of the aforementioned ground plane is also equipped with an on-board intelligent processing unit, which is used for on-orbit processing of inter-satellite routing and forwarding; the inter-satellite laser communication terminal is a laser communication terminal using the 1550nm band, and the single inter-satellite link transmission rate of the inter-satellite laser communication terminal is configured to be ≥100Gbps; the multi-band ground-to-ground radio frequency terminal is compatible with terahertz band and millimeter wave band.

3. The system according to claim 1, characterized in that, The terahertz communication module of the air-based substrate operates in the frequency band of 0.1THz to 10THz. The terahertz communication module is configured to establish terahertz links between the air-based substrate and the space-based substrate, between the air-based substrate and the ground-based substrate, between the air-based substrate and the sea-based substrate, and between different air nodes within the air-based substrate, with a single link peak rate ≥10Gbps. The terahertz communication module is also equipped with a beam tracking unit for real-time tracking of the communication beam in high-speed mobile scenarios.

4. The system according to claim 1, characterized in that, The millimeter-wave communication module of the ground layer operates in the frequency band of 24GHz to 100GHz. The ground heterogeneous cellular base station is equipped with a massive MIMO metasurface antenna array. The MIMO metasurface antenna array is used to form a multi-layer heterogeneous ground cellular network including macro base stations, micro base stations and pico base stations. The 6G core network node at the ground level is configured to: coordinate the spectrum resources, computing resources and routing resources of the four-layer network through the cross-domain resource scheduling unit; manage network slice instances across the four-layer network through the network slice management unit; and coordinate the cross-layer handover process through the cross-layer handover coordination and control unit.

5. The system according to claim 1, characterized in that, The underwater acoustic communication module of the seabed layer adopts a low-frequency underwater acoustic communication system for the transmission of long-distance, low-rate underwater monitoring data; the blue light visible light communication module adopts an underwater blue light communication system for the transmission of short-distance, high-bandwidth underwater data; the seabed layer is also equipped with a protocol compatibility unit, which enables the communication module of the seabed layer to achieve protocol-layer interconnection with the satellite communication link of the sky layer, the terahertz communication link of the air layer, and the millimeter-wave communication link of the ground layer.

6. The system according to claim 1, characterized in that, The cross-layer handover collaborative management and control unit is configured to detect scene changes when the user terminal moves between different network layers, and trigger cross-domain boundary handover rules according to the scene changes to determine the target communication link and perform link handover and service context migration. The cross-domain handover types supported by the cross-layer handover collaborative management and control unit include: handover between ground-level network and air-level network, handover between air-level network and space-level network, handover between sea-level network and ground-level network, handover between sea-level network and space-level network, and handover between ground-level network and sea-level network. The system is also configured with a multi-link redundancy backup mechanism, which is used to automatically switch between multiple heterogeneous links in case of failure.

7. The system according to claim 6, characterized in that, The cross-layer handover collaborative management and control unit is configured to be uniformly scheduled by the SDN / NFV service architecture. It combines the user terminal's mobile trajectory information, channel quality information, and service quality level information to complete the pre-handover link configuration and context migration in advance, so that the service interruption latency during the handover process is lower than the set time threshold.

8. The system according to claim 1, characterized in that, The system also includes a standardized underwater node access controller, which is located in the 6G core network node of the ground layer and is configured to execute the signaling process for underwater terminals to access the network. Perform random access, radio resource control connection establishment, non-access stratum attach request, and two-way authentication of the underwater terminal; Receive depth information, location information, and movement trajectory information reported by the underwater terminal, perform location registration, and predict cross-domain movement trends; Establish a data tunnel between the underwater terminal and the underwater relay node in the seabed layer, thus opening up the path from the underwater to the ground layer network; Establish full-domain routes sequentially from underwater to ground level, from ground level to air level, and from air level to sky level; The system periodically receives location information reported by the underwater terminal, updates link parameters, and dynamically adjusts modulation and coding schemes and hybrid automatic repeat request parameters according to underwater channel conditions. The standardized underwater node access controller is compatible with 5G and 6G protocol stacks, and its communication interfaces include RACH, RRC, NAS, N2, and N3 interfaces. It has signaling interaction with the AMF, SMF, and UPF network elements of the 6G core network node.

9. The system according to claim 1, characterized in that, Edge computing nodes are distributed and deployed in the 6G core network nodes of the air-based, space-based, and ground-based layers, as well as in the sea-based layer. The 6G core network nodes of the ground-based layer constitute a central cloud node. The edge computing nodes have data communication links with the central cloud node, forming a three-level collaborative computing architecture of cloud, edge, and terminal with the user terminal.

10. The system according to claim 1, characterized in that, The system also includes an end-to-end security protection system, which includes: The terminal access authentication unit is used to perform access authentication on user terminals accessing the Layer 4 network of the system. The link encryption unit is used to encrypt and protect inter-satellite laser communication links, space-based terahertz links, ground-based millimeter-wave links, and sea-based underwater acoustic and blue light links. Cross-domain data isolation units are used to perform logical or physical isolation of data between different network layers; An intrusion detection unit is used to detect intrusion behavior across the entire four-layer network. The end-to-end security protection system works in conjunction with the network slice management unit to provide dedicated slices with physical or logical isolation for different service types based on network slicing technology.

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