User terminal paging method of satellite-ground fusion network facing large-scale constellation

Abstract

The invention discloses a user terminal paging method for a satellite-ground convergence network of a large-scale constellation, and mainly solves the problems of low paging success rate and large time delay overhead in an independent ground network or a satellite network in the prior art. According to the implementation scheme, in a satellite-ground fusion network scene, when a calling party is a 5G network user and a called party is a satellite network user, the calling party queries a called management and control center in a ground core network, the core network forwards a paging request to the management and control center, the management and control center queries a called satellite location area, and a low-orbit satellite performs paging in the satellite location area; and when the calling party is a satellite network user and the called party is a 5G network user, the paging request is forwarded to a management and control center of a satellite network through a low-orbit satellite, the management and control center inquires a satellite location area identifier of the called party and forwards the paging request to a ground core network, and the base station performs paging in the satellite location area. According to the invention, the problem of paging failure caused by network switching is reduced, the paging success rate is improved, the paging delay and overhead are reduced, and the method can be used for satellite-ground convergence network communication.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, and in particular relates to a user terminal paging method, which can be used in a satellite-ground fusion network. Background Art

[0002] With the rapid development of science and technology, ground communication systems have achieved remarkable achievements and are now steadily moving towards the super 5G / 6G era, constantly expanding the boundaries and possibilities of communication. However, in the real world, there are still many geographical areas that pose huge challenges to ground communications, such as the deep sea, polar regions, deserts and other sparsely populated areas with harsh environments. In these places, the deployment of cellular networks faces problems such as high costs and great implementation difficulties, making it difficult to achieve basic communication coverage requirements. In addition, the communication objects of 5G are concentrated in a limited space within 10km of the land surface, and the communication vision of seamless coverage of air, land, and sea cannot be realized. In this context, the satellite-ground fusion network composed of satellite networks and ground networks has gradually become a key research direction in the field of future communication networks.

[0003] In view of the huge potential of the integration of satellite networks and terrestrial networks, many internationally renowned organizations have devoted themselves to related research and experimental work. For example, 3GPP began to carry out research on satellite-ground integrated networks as early as R14. In its TS22.261 standard document, it deeply discussed the role of satellites in 5G systems and their significant advantages over 5G systems; in the TR22.822 document, it focused on the research on satellite access in 5G networks and clearly defined twelve user scenarios under satellite-ground integrated networks; TR38.811 focused on the 5G new air interface for NTN networks, and determined the deployment plan and various parameters of satellite networks in detail; TR38.821 further discussed the new radio protocol NR in NTN networks, and innovatively proposed five network architecture models for satellite-ground integrated networks.

[0004] By combining the advantages of satellite's wide coverage with ground mobile communication network, service continuity and call quality can be efficiently guaranteed. How users can access the optimal network in real time according to network quality and how to design the paging process between users of different networks in the satellite-ground integrated network have become urgent issues to be solved.

[0005] The patent application document with application number CN202410568173.7 discloses a technical solution for location paging, and its implementation steps are as follows: (1) The access satellite queries the satellite where the destination user is located in the local location relationship database. If there is a valid entry, a new IP message header is encapsulated outside the service message payload and forwarded according to the routing protocol; (2) If there is no valid entry, the access satellite floods the query message within a limited range. Among them, the limited range follows the fixed TTL scheme, each satellite maintains the mapping relationship within the TTL range, and the mapping relationship of the satellite within the 2*TTL range can be obtained by query; (3) The satellite that receives the query message queries the local location relationship database, and if there is no mapping relationship, it continues to forward; if there is a mapping relationship, the encapsulated registration message is sent to the access satellite by unicast according to the routing protocol; (4) The access satellite maintains the local location relationship database based on the registration message information, encapsulates a new IP message header outside the service message payload, and forwards it according to the routing protocol. Since this solution relies on the satellite to query the local location relationship database for the satellite where the destination user is located, if there is no valid entry in the database, it is necessary to query within a limited range by means of flooding query messages, which can lead to inefficiency, especially when there are a large number of satellites or users are widely distributed. This flooding query will occupy a large amount of network resources and may cause network congestion.

[0006] The patent application document with application number CN202180099412.3 discloses a blockchain-based paging technology method, the implementation steps of which are: AMF queries the blockchain network for UE's paging information; the blockchain node exports the current active registration area RA when receiving a query request from AMF, and calculates one or more suitable paging routes from AMF to UE through a smart contract (SC); AMF pages the UE for downlink data based on the UE paging information. Although this method improves the security of paging data through the immutability of blockchain, since blockchain networks usually require a large number of nodes to participate in verifying and recording transactions, they require higher computing and storage resources as well as professional technical support and maintenance, which leads to reduced efficiency and increased costs. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose a user terminal paging method for a satellite-ground integrated network for a large-scale constellation, so as to reduce paging delay and overhead and improve network efficiency and service quality.

[0008] The technical idea to achieve the above purpose is: first, part of the core network functions are transplanted to the medium-orbit satellite, and it and the ground station are used as the control center of the satellite network, responsible for managing low-orbit satellites and managing the information of users accessing low-orbit satellites. After the user registers the information in the ground core network and the space-based core network, the 5G network user can find the information of the called satellite network user in the ground core network when initiating a call, and the satellite network user can find the information of the called 5G network user in the satellite network when initiating a call. The paging between users of different networks avoids cross-network information interaction, thereby reducing paging delay and overhead.

[0009] According to the above ideas, the present invention includes technical solutions in different scenarios:

[0010] Technical Solution 1: A user terminal paging method for a large-scale constellation satellite-ground integrated network in a scenario where the caller is a 5G network user and the called party is a satellite network user, characterized by comprising:

[0011] Transplant some functions of the core network to medium-orbit satellites, use medium-orbit satellites and ground stations together as the control center of the satellite network, and deploy access and mobility management function module AMF in the core network, access and mobility management function module AMF-M in medium-orbit satellites, and access and mobility management function module AMF-G in ground stations;

[0012] A registered 5G network user initiates a call, and the call request is accessed through the base station to the ground network and forwarded to the first access and mobility management function module A1;

[0013] After receiving the call request, the first access and mobility management function module A1 queries the second access and mobility management function module A2 storing the called user information, and sends the call request to A2;

[0014] The second access and mobility management function module A2 forwards the call request to the low-orbit satellite associated with the called party satellite network user, and the low-orbit satellite pages the satellite network user;

[0015] The called satellite network user answers the call request and returns the paging response to the calling 5G network user through the network.

[0016] Technical Solution 2: A user terminal paging method for a satellite-ground integrated network for a large-scale constellation in a scenario where the caller is a satellite network user and the called party is a 5G network user, characterized by comprising:

[0017] Porting some functions of the core network to the medium-orbit satellite, using the medium-orbit satellite and the ground station together as the control center of the satellite network, and deploying the first access and mobility management function module A1 in the core network and the second access and mobility management function module A2 in the control center;

[0018] A registered satellite network user initiates a call, and the call request is accessed through a low-orbit satellite. The low-orbit satellite selects its own control center based on the principle of minimum hops and shortest distance, and forwards the call request to the second access and mobility management function module A2 of the control center;

[0019] After receiving the call request, the second access and mobility management function module A2 queries the called user's information in the control center of the satellite network and sends the call request to the ground core network;

[0020] The ground core network forwards the call request to the base station associated with the called 5G network user, and the base station pages the 5G network user;

[0021] The called 5G network user answers the call request and returns the paging response to the calling satellite network user through the network.

[0022] Furthermore, the access and mobility management function module is used to manage the information of low-orbit satellites and their access users, including:

[0023] Registration management: allows user devices to register with the satellite network;

[0024] Connection management: ensuring the establishment and maintenance of satellite network connections by initializing communication links, continuously monitoring their status, and managing handoffs as users move;

[0025] Business request processing: responding to service requests initiated by users;

[0026] Paging: Finding user equipment in the satellite network;

[0027] User mobility management: Tracking user location by enforcing mobility restrictions, managing time subscriptions and notifications, handling intra-system mobility updates and handovers between base stations;

[0028] Location reporting: Allows user devices to report their location information to the satellite network;

[0029] Session management: establish, maintain and release user sessions;

[0030] NAS short message service: Through the transmission of short messages between the access and mobility management function module A2 and the user equipment, the user can send and receive information through the SMS service system.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] First, the satellite-ground fusion network architecture proposed in the present invention breaks the geographical restrictions of ground station construction by distributing access and mobility management functions in medium-orbit satellites, ground stations and ground core networks, and solves the problems of high paging delay and high transmission overhead caused by the difficulty of ground station construction. At the same time, the architecture avoids the ultra-high cost of centrally deploying functional modules on giant low-orbit satellite constellations, reduces the burden on the ground core network, effectively reduces paging delay and overhead, and significantly improves service quality and communication efficiency.

[0033] Second, based on the user dual registration mechanism, the present invention designs a paging solution between ground network users and satellite network users, which can realize a complete user paging process in the satellite-ground integrated network. Since this method allows users to directly query the called user information in the local database without the need for cross-network information exchange, it can quickly complete the delivery and return of signaling, significantly reducing paging delay and overhead. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a satellite-ground fusion network scene diagram of the present invention;

[0035] Figure 2 This is a satellite-ground fusion network protocol system diagram of the present invention;

[0036] Figure 3 This is a flowchart of the implementation of a 5G network user calling a satellite network user in the present invention;

[0037] Figure 4 This is a flowchart of the implementation of a satellite network user calling a 5G network user in the present invention;

[0038] Figure 5 This is a satellite-ground fusion network architecture diagram of the present invention;

[0039] Figure 6 A flowchart of a 5G network user initiating a call and accessing a terrestrial network according to the present invention;

[0040] Figure 7 A flow chart of the control center of the present invention querying and paging the called user through a low-orbit satellite;

[0041] Figure 8 A flow chart of a called satellite network user responding to a call request of the present invention;

[0042] Fig. 9 A flow chart of a satellite network user initiating a call and accessing a satellite network according to the present invention;

[0043] Fig.10 This is a flow chart of the present invention for querying called user information and initiating paging in a satellite network control center;

[0044] Fig.11This is a flow chart of the called 5G network user responding to a call request in the present invention. DETAILED DESCRIPTION

[0045] The embodiments and effects of the present invention are further described in detail below with reference to the accompanying drawings.

[0046] Reference Figure 1 , the implementation scenarios of the present invention include: user segment, ground segment and space segment, wherein:

[0047] The user segment includes various types of users on land, in the air, etc. The user terminals are pure 5G network user terminals, pure satellite network user terminals, and dual-mode user terminals, which can be directly connected to the satellite network or the 5G network.

[0048] The ground segment includes a network management center, a satellite management center, a 5G core network, a ground station, etc. Among them, the ground station can communicate directly with the satellite through a feeder link, and can serve as a control center to manage low-orbit satellites and manage user information accessing the satellite. It is equipped with a base station center module, an access and mobility management function module, and a session management function module.

[0049] The space segment adopts a network of multiple medium-orbit satellites and multiple low-orbit satellites to form a multi-layer constellation structure combining medium-orbit and low-orbit. Among them, the low-orbit constellation adopts a mixed layout of polar orbit and inclined orbit, while multiple medium-orbit satellites achieve full coverage of low-orbit satellites. Each low-orbit satellite is responsible for user access and also supports data forwarding. In order to reduce the dependence of the satellite communication system on the ground core network, the access and mobility management functions are extended to the space base. Each medium-orbit satellite is equipped with a SAMF unit, which is similar to the ground core network access and mobility management function AMF, which is responsible for the registration, update, storage of user and low-orbit satellite location information, as well as the authentication and security management of satellites, and maintains the relationship between users and satellites.

[0050] These medium-orbit satellites and ground stations together serve as the control center of the satellite network, responsible for managing low-orbit satellites and managing the information of users accessing low-orbit satellites.

[0051] Reference Figure 2 In this example, the user UE, low-orbit satellite LEO, low-orbit satellite relay station, medium-orbit satellite MEO, medium-orbit satellite relay station, ground station GS and 5G / 6G core network all have their own protocol modules, among which:

[0052] The protocol module of the user UE includes: non-access layer session management protocol NAS-SM, non-access layer mobility management protocol NAS-MM, radio resource control protocol RRC, packet data convergence protocol PDCP, radio link layer control protocol RLC, medium access control protocol MAC, new wireless physical layer protocol NR-PHY;

[0053] The protocol module of the low-orbit satellite LEO and the protocol module of the low-orbit satellite relay station both include: a satellite base station centralized unit gNB-CU, a packet data convergence protocol PDCP, a radio link layer control protocol RLC, a medium access control protocol MAC, a new wireless physical layer protocol NR-PHY, an inter-satellite link next generation application protocol ISL-NGAP, a stream control transmission protocol ISL-SCTP, an inter-satellite link physical layer ISL-L1, an inter-satellite link physical layer ISL-L2, an inter-satellite link physical layer ISL-L3, a location management stream control transmission protocol LM-SCTP, a location management physical layer LM-L3 and a location management wireless interface LM SRI;

[0054] The protocol module of the medium-orbit satellite MEO and the protocol module of the medium-orbit satellite MEO relay station both include: a satellite base station centralized unit gNB-CU-CP, an access and mobility management submodule AMF, a non-access layer mobility management protocol NAS-MM, a radio resource control protocol RRC, an inter-satellite link next generation application protocol ISL-NGAP, a location management stream control transmission protocol LM-SCTP, a location management physical layer LM-L1, a location management physical layer LM-L2, a location management physical layer LM-L3, a stream control transmission protocol SCTP, an internet interconnection IP protocol and a satellite ground wireless interface 5G SRI;

[0055] The protocol module of the ground station includes: a base station centralized unit gNB-CU-CP, an access and mobility management submodule AMF, a non-access layer mobility management protocol NAS-MM, a radio resource control protocol RRC, an internet interconnection IP protocol, a satellite ground wireless interface 5G SRI, a physical layer L1, and a physical layer L2;

[0056] The protocol module of the core network includes: non-access layer session management protocol NAS-SM, stream control transmission protocol SCTP, internetwork IP protocol, physical layer L1, and physical layer L2.

[0057] Based on the above scenario and protocol system module, the present invention provides the following two embodiments:

[0058] Embodiment 1, the calling party is a 5G network user, and the called party is a satellite network user in a satellite-ground integrated network scenario for a large-scale constellation.

[0059] refer to Figure 3 , the implementation steps of this example are as follows:

[0060] Step 1: Build a satellite-ground integrated network architecture.

[0061] refer to Figure 5The satellite-ground integrated network architecture includes two parts: space-based, ground-based and user UE.

[0062] The space-based part includes a low-orbit satellite, a medium-orbit satellite and a ground station, wherein the low-orbit satellite is equipped with a satellite-borne base station module RAN-L and a user plane function module UPF-L; the medium-orbit satellite is equipped with an access and mobility management module AMF-M and a session management function module SMF-M, and the ground station is equipped with an access and mobility management module AMF-G and a session management function module SMF-G, and the modules AMF-M and AMF-G together constitute a space-based access and mobility management module AMF-C, and the modules SMF-M and SMF-G together constitute a space-based session management function module SMF-C. Among them, the space-based access and mobility management module AMF-C has the functions of registration management, connection management, service request processing, paging, user mobility management, location reporting, session management, NAS short message service, etc. The medium-orbit satellite and the ground station jointly act as the space-based control center to control the low-orbit satellite. The onboard base station module RAN-L of the low-orbit satellite is connected to the access and mobility management function module and the session management function module of the space-based control center through the low-orbit satellite user plane function module UPF-L.

[0063] The ground-based part includes the access and mobility management function module AMF, the authentication server function module AUSF, the unified data management function module UDM, the policy control function module PCF, the network service presentation function module NEF, the network function registration function module NRF, the user plane function module UPF, the session management function module SMF, as well as the ground base station RAN-gNB and the operator data network. The ground base station RAN-gNB is connected to the AMF, AUSF, SMF, AF and other modules in the ground-based core network through the user plane function module UPF of the core network.

[0064] The user UE can access the space-based or ground-based network through the onboard base station module RAN-L of the low-orbit satellite or the ground base station RAN-gNB.

[0065] Step 2: A registered 5G network user initiates a call and accesses the terrestrial network through a base station.

[0066] Reference Figure 6 , the implementation of this step includes:

[0067] 2.1) A registered 5G network user initiates a call, and the NAS-MM protocol module creates a paging request message, which contains the user ID and satellite location area ID;

[0068] 2.2) The user selects the base station RAN with the strongest signal to access and establish a radio resource control RRC connection:

[0069] When the user is in idle state, after receiving the system information broadcast by the base station through the NR-PHY protocol module, the user initiates a call to trigger the radio resource control RRC connection establishment request. The RRC protocol layer encrypts and integrity protects the request through the PDCP protocol layer, and then processes it in segments through the RLC protocol layer. Finally, the MAC layer schedules resources and sends the request to the base station gNB through the public control channel.

[0070] After receiving the request, the base station gNB performs an access control check: if the cell allows user access, it starts the radio resource control RRC connection establishment process and sends configuration parameters to the user; otherwise, it denies user access;

[0071] After receiving the configuration parameters, the user sets the corresponding parameters and establishes a radio resource control RRC connection, and sets the current cell as the primary serving cell; after completing these settings, the user sends an RRC connection establishment completion message to the base station, and the communication link between the user and the base station is successfully established;

[0072] 2.3) The base station RAN forwards the call request to the user plane function module UPF of the ground core network, and the module UPF of the ground core network forwards the call request to the session management function module SMF to inform the arrival of the protocol data unit PDU;

[0073] 2.4) The session management function module SMF of the ground core network returns the response signaling to the user plane function module UPF, and sends a session message to the local access and mobility management function module AMF;

[0074] 2.5) The access and mobility management function module AMF of the ground core network responds to the session management function module SMF.

[0075] Step 3: The ground core network queries the control center of the called user and forwards the call request.

[0076] 3.1) The access and mobility management function module AMF of the core network receives the call request, accesses the database storing the mapping relationship between the user identity and the control center identity, searches the database according to the called user identity, thereby determining the control center of the called user, and then determining the space-based access and mobility management function module AMF-C where the called user information is located;

[0077] 3.2) The core network forwards the call request to the control center of the called user.

[0078] Step 4: The called user control center queries the low-orbit satellite associated with the called user, and the low-orbit satellite pages the called user.

[0079] Reference Figure 7 , the implementation of this step includes:

[0080] 4.1) The called user control center queries the called user's associated low-orbit satellite identification and satellite location area information;

[0081] 4.2) The control center sends a paging signal to the low-orbit satellite, which then pages the satellite network users in the satellite location area:

[0082] Calculating the distance and azimuth between the user terminal and the paging satellite;

[0083] Based on the geometric relationship between the user and the satellite and the signal propagation characteristics, the probability beam of possible paging success is calculated;

[0084] The calculated probability beams are grouped and paging signals are sent to users within the grouped beams.

[0085] Step 5: The called satellite network user answers the call request and returns the paging response to the calling 5G network user through the network.

[0086] Reference Figure 8 , the implementation of this step includes:

[0087] 5.1) The called user responds to the paging request of the low-orbit satellite LEO and sends a service request to the low-orbit satellite LEO;

[0088] 5.2) The low-orbit satellite LEO sends a session request to the ground core network access and mobility management function module AMF;

[0089] 5.3) The ground core network access and mobility management function module AMF sends a session request to the ground core network session management function module SMF;

[0090] 5.4) The terrestrial core network session management function module SMF sends a session update request to the user plane function module UPF;

[0091] 5.5) The user plane function module UPF responds to the session update request and forwards the paging response to the base station associated with the calling user;

[0092] 5.6) The base station forwards the paging response to the calling 5G network user;

[0093] 5.7) The calling 5G network user receives the paging response, confirms the call establishment, sends the data packet, and the paging is completed.

[0094] Embodiment 2, a user terminal paging method in a satellite-ground integrated network scenario for a large-scale constellation, in which the caller is a satellite network user and the called party is a 5G network user.

[0095] refer to Figure 4 The implementation steps of this example include the following:

[0096] Step A: Build a satellite-ground fusion network architecture.

[0097] The specific implementation of this step is the same as step 1 of Example 1.

[0098] Step B: A registered satellite network user initiates a call and accesses the satellite network via a low-orbit satellite.

[0099] Reference Fig. 9 , the implementation of this step includes:

[0100] B1) A registered satellite network user generates a paging request and sends it to an associated low-orbit satellite. The request message includes a user ID and a satellite location area ID.

[0101] B2) The NR-PHY protocol layer of the low-orbit satellite first receives the paging request signal from the user equipment (UE) and performs demodulation and decoding to extract the paging request message; then, the MAC protocol layer further decodes these signals and passes the paging request message to the RLC protocol layer, which is responsible for reassembling the message to ensure the integrity and accuracy of the message; then, the PDCP protocol layer decrypts and verifies the integrity of the reassembled message to restore the original paging request message; finally, the gNB-CU, the satellite base station centralized unit, receives the paging request message transmitted by the PDCP protocol layer and forwards it to the user plane function module UPF-L;

[0102] B3) The user plane function module UPF-L forwards the paging request to the session management function module SMF-L to inform the arrival of the PDU;

[0103] B4) The session management function module SMF-L returns the paging response signaling to the user plane function UPF-L module;

[0104] B5) Low-orbit satellites select a control center based on the principle of minimum hop count and shortest distance through the NGAP protocol module:

[0105] B51) Initialize the hop value from the low-orbit satellite to each medium-orbit satellite and ground station to 0, start from the low-orbit satellite, query the routing table, and count the hop counts from the low-orbit satellite to all medium-orbit satellites and ground stations;

[0106] B52) Select the control center based on the minimum number of hops from the ground station or medium-orbit satellite:

[0107] If there is only one ground station or medium-orbit satellite with the minimum number of hops, then the ground station or medium-orbit satellite is directly selected as the control center of the low-orbit satellite;

[0108] If there are multiple ground stations or medium-orbit satellites with the same minimum hop count, the low-orbit satellite further calculates its distance to these medium-orbit satellites and ground stations to determine the optimal control center;

[0109] B53) Initialize the distance value from the low-orbit satellite to each medium-orbit satellite and ground station to 0, calculate the distance from the low-orbit satellite to all medium-orbit satellites and ground stations according to the latitude and longitude information of the low-orbit satellite, the medium-orbit satellite and the ground station, and select the medium-orbit satellite or ground station with the shortest distance as the control center of the low-orbit satellite;

[0110] B6) The session management function module SMF-L sends a session message to the space-based access and mobility management function module AMF-C;

[0111] B7) The space-based access and mobility management function AMF-C responds to the low-orbit satellite session management function SMF-L.

[0112] Step C: The low-orbit satellite control center queries the called user information and forwards the call request to the ground core network.

[0113] Reference Fig.10 , the implementation of this step includes:

[0114] C1) The space-based access and mobility management function AMF-C receives the paging request and queries the called user information in the control center in the satellite network:

[0115] C11) Check whether the called user information exists in the space-based access and mobility management function module AMF-C of the current control center:

[0116] If it exists, directly obtain the satellite location area identifier of the called user;

[0117] Otherwise, execute step C12);

[0118] C12) Polling query in the control center in the satellite network:

[0119] If the current control center is a medium-orbit satellite, then query other medium-orbit satellites one by one in the order of numbers. If the called user information is still not found, continue to query the ground station;

[0120] If the current control center is a ground station, it will query other ground stations one by one in the order of numbers. If the called user information is still not found, it will continue to query the medium-orbit satellite;

[0121] C2) The space-based access and mobility management function module AMF-C sends a paging request to the ground core network.

[0122] Step D: The ground core network queries the base station associated with the called user, and the base station pages the called user.

[0123] D1) Counting the number of times the user resides in each paging cell and calculating the probability of the user residing in each paging cell;

[0124] D2) Group cells according to the residence probability and paging delay limit:

[0125] Arrange the paging cells in descending order of user residence probability, and divide the paging cells into multiple groups according to the preset paging delay limit:

[0126] The implementation of this step includes:

[0127] Assume that each location area contains N paging cells, and the paging delay is limited to D, that is, a maximum of D searches are allowed, and the time of each search is normalized to 1;

[0128] Based on the delay limit D, the N paging cells in the location area are divided into D paging groups, and the cells are arranged from high to low according to the size of the resident probability in each paging group.

[0129] D3) The base station performs paging in the order of the groups, giving priority to paging in the groups with higher resident probabilities. If no user response is received, the base station continues to paging in the groups with lower resident probabilities until all groups are paging or a user response is received.

[0130] Step E: The called 5G network user answers the call request and returns the paging response to the calling satellite network user through the network.

[0131] Reference Fig.11 , the implementation of this step includes:

[0132] E1) The called 5G network user responds to the paging request and sends a service request to the base station;

[0133] E2) The base station sends a session request to the space-based access and mobility management function module AMF-C;

[0134] E3) The space-based access and mobility management function module AMF-C sends a session request to the session management function module SMF-L of the low-orbit satellite;

[0135] E4) The session management function module SMF-L of the low-orbit satellite sends a session update request to the user plane function module UPF-L of the low-orbit satellite;

[0136] E5) The user plane function module UPF-L of the low-orbit satellite responds to the session update request and sends a paging response to the satellite network calling user;

[0137] E6) The calling user receives the paging response, confirms the call establishment, and sends a data packet to complete the paging.

[0138] The above descriptions are only two examples of the paging process between different network users designed for the satellite-ground integrated network scenario of the present invention, so as to solve the problems of excessive paging delay and high overhead caused by cross-network interaction information, and ensure that different network users in the satellite-ground integrated network can be quickly and efficiently paged, thereby improving network efficiency and service quality. However, it does not constitute any limitation to the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. For example, in addition to the usage scenarios of the above-mentioned embodiments, the present invention can also be applied to scenarios where 5G network users call 5G network users and satellite network users call satellite network users. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0139] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. A user terminal paging method for a large-scale constellation satellite-ground fusion network in a scenario where the calling party is a 5G network user and the called party is a satellite network user, characterized in that: include: Transplant some functions of the core network to medium-orbit satellites, use medium-orbit satellites and ground stations together as the control center of the satellite network, and deploy access and mobility management function module AMF in the core network, and deploy space-based access and mobility management function module AMF-C in the control center; A registered 5G network user initiates a call, and the call request is accessed through the base station to the ground network and forwarded to the access and mobility management function module AMF of the core network; After receiving the call request, the access and mobility management function module AMF of the core network queries the space-based access and mobility management function module AMF-C that stores the called user information, and sends the call request to AMF-C; The space-based access and mobility management function module AMF-C forwards the call request to the low-orbit satellite associated with the called party's satellite network user, and the low-orbit satellite pages the satellite network user; The called satellite network user answers the call request and returns the paging response to the calling 5G network user through the network.

2. The method according to claim 1, characterized in that The said part of the core network functions are transplanted to the medium-orbit satellite, including: 2a) Migrate the user data plane function module UPF, session management function module SMF, and access and mobility management function module AMF of the traditional terrestrial 5G core network to the satellite network; 2b) Deploy these modules in different locations: A user data plane function module UPF-L is deployed on the low-orbit satellite for routing lookup and data forwarding; The control center is equipped with a space-based session management function module SMF-C, which is used to establish, modify and release user terminal sessions. The control center is equipped with a space-based access and mobility management function module AMF-C, which is used to manage the information of low-orbit satellites and their access users.

3. The method according to claim 2, characterized in that The space-based access and mobility management function module AMF-C in step 2b) manages information of low-orbit satellites and their access users, including: Registration management: allows user devices to register with the satellite network; Connection management: ensuring the establishment and maintenance of satellite network connections by initializing communication links, continuously monitoring their status, and managing handoffs as users move; Business request processing: responding to service requests initiated by users; Paging: Finding user equipment in the satellite network; User mobility management: Tracking user location by enforcing mobility restrictions, managing time subscriptions and notifications, handling intra-system mobility updates and handovers between base stations; Location reporting: Allows user devices to report their location information to the satellite network; Session management: establish, maintain and release user sessions; NAS short message service: Short messages are transmitted between the space-based access and mobility management function module AMF-C and user equipment, enabling users to send and receive information through the SMS service system.

4. The method according to claim 1, characterized in that: The registered 5G network user initiates a call, including: (4a) After the user is in idle state and updates the system information, it initiates a call to trigger a radio resource control RRC connection establishment request, and sends the request to the base station gNB through the common control channel; (4b) After receiving the request, the base station gNB performs an access control check: if the cell allows the user to access, it starts the radio resource control RRC connection establishment process and sends the configuration parameters to the user; otherwise, it denies the user access; (4c) After receiving the configuration parameters, the user sets the corresponding parameters and establishes a radio resource control (RRC) connection, and sets the current cell as the primary serving cell. After completing these settings, the user sends an RRC connection establishment completion message to the base station, and the communication link between the user and the base station is successfully established.

5. The method according to claim 1, characterized in that After receiving the call request, the access and mobility management function module AMF of the core network queries the control center storing the called user information, including: The core network's access and mobility management function module AMF accesses a database that stores the mapping relationship between user identifiers and control center identifiers, and searches the database according to the called user identifier to determine the control center of the called user, and then determines the space-based access and mobility management function module AMF-C where the called user information is located.

6. The method according to claim 1, characterized in that The low-orbit satellite performs paging on the satellite network user, including: (6a) calculating the distance and azimuth between the user terminal and the paging satellite; (6b) Based on the geometric relationship between the user and the satellite and the signal propagation characteristics, the probability beam for successful paging is calculated; (6c) Group the calculated probability beams and send paging signals to users within the grouped beams.

7. A user terminal paging method for a large-scale constellation satellite-ground fusion network in a scenario where the calling party is a satellite network user and the called party is a 5G network user, characterized in that: include: Transplant some functions of the core network to medium-orbit satellites, use medium-orbit satellites and ground stations together as the control center of the satellite network, and deploy access and mobility management function module AMF in the core network, and deploy space-based access and mobility management function module AMF-C in the control center; A registered satellite network user initiates a call, which is accessed through a low-orbit satellite. The low-orbit satellite selects its own control center based on the principle of minimum hops and shortest distance, and forwards the call request to the space-based access and mobility management function module AMF-C of the control center. After receiving the call request, the space-based access and mobility management function module AMF-C queries the called user's information in the satellite network's control center and sends the call request to the ground core network; The ground core network forwards the call request to the base station associated with the called 5G network user, and the base station pages the 5G network user; The called 5G network user answers the call request and returns the paging response to the calling satellite network user through the network.

8. The method according to claim 7, characterized in that The low-orbit satellite selects its own control center based on the principle of minimum hop number and shortest distance, including: (8a) Initialize the hop count from the low-orbit satellite to each medium-orbit satellite and ground station to 0, query the routing table from the low-orbit satellite, and count the hop count from the low-orbit satellite to all medium-orbit satellites and ground stations; (8b) Select the control center based on the minimum number of hops from the ground station or medium-orbit satellite: If there is only one ground station or medium-orbit satellite with the minimum number of hops, then the ground station or medium-orbit satellite is directly selected as the control center of the low-orbit satellite; If there are multiple ground stations or medium-orbit satellites with the same minimum hop count, the low-orbit satellite further calculates its distance to these medium-orbit satellites and ground stations to determine the optimal control center; (8c) Initializing the distance value from the low-orbit satellite to each medium-orbit satellite and ground station to 0, and calculating the distance from the low-orbit satellite to all medium-orbit satellites and ground stations based on the latitude and longitude information of the low-orbit satellite, the medium-orbit satellite and the ground station; (8d) Select the medium-orbit satellite or ground station with the shortest distance as the control center of the low-orbit satellite.

9. The method according to claim 7, characterized in that: After receiving the call request, the space-based access and mobility management function module AMF-C queries the called user's information in the control center of the satellite network, including: (9a) Check whether the called user information exists in the space-based access and mobility management function module AMF-C of the current control center: If it exists, directly obtain the satellite location area identifier of the called user; Otherwise, execute step (9b); (9b) Polling query in the control center in the satellite network: If the current control center is a medium-orbit satellite, then query other medium-orbit satellites one by one in the order of numbers. If the called user information is still not found, continue to query the ground station; If the current control center is a ground station, it will query other ground stations one by one in the order of numbers. If the called user information is still not found, it will continue to query the medium-orbit satellite.

10. The method according to claim 7, characterized in that The base station performs paging on the 5G network user, including: (10a) Counting the number of times the user resides in each paging cell and calculating the probability of the user residing in each paging cell; (10b) grouping cells according to the residence probability and paging delay limit; (10c) The base station performs paging in the order of the groups, giving priority to paging the groups with higher retention probabilities. If no user response is received, the base station continues to paging the groups with lower retention probabilities until all groups are paging or a user response is received.

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