A slice load balancing method and device for space-ground integrated railway mobile communication

Abstract

This invention discloses a method and apparatus for slice load balancing in integrated space-ground railway mobile communication. The method includes the following steps: S1. Determining the network coverage scheme of the integrated space-ground railway mobile communication system; S2. Designing the overall network slicing scheme of the integrated space-ground railway mobile communication system; S3. Performing slice load balancing on terminals in different states. This invention achieves three-dimensional network coverage for railway mobile communication systems by integrating satellite and terrestrial railway mobile communication systems; and by flexibly managing network orchestration and slice load balancing of the integrated space-ground railway mobile communication system according to railway service characteristics, it effectively improves the performance of the railway mobile communication system by achieving slice load balancing.

Description

Technical Field

[0001] This invention relates to the field of mobile communications, and in particular to a method and apparatus for slicing load balancing in integrated terrestrial and satellite railway mobile communications. Background Technology

[0002] Railway mobile communication systems are critical information infrastructure for ensuring the safe and efficient operation of trains. Currently, the development is moving from the Global Mobile Communication System for Railways (GSM-R) based on second-generation (2G) mobile communication technology to the next-generation Railway Mobile Communication System (FRMCS), which is the new generation of railway mobile communication systems (5G-R) based on fifth-generation (5G) mobile communication technology. However, with the development of high-speed railways, train speeds are constantly increasing, from hundreds of kilometers per hour to thousands of kilometers per hour. 5G-R, based on Orthogonal Frequency Division Multiplexing (OFDM) technology, faces the significant challenge of the Doppler effect. To overcome the Doppler effect challenge, Orthogonal Time-Frequency-Space (OTFS) modulation waveform technology has been proposed in recent years, introducing a time-delay-Doppler domain to achieve excellent diversity gain in high-mobility scenarios, thus improving system performance. Furthermore, the construction of high-speed railways in complex and challenging mountainous areas faces frequent natural disasters, making traditional land-based railway mobile communication systems vulnerable and seriously threatening train operation safety. Therefore, building an integrated land-ground railway mobile communication system is a major future development trend.

[0003] With the development of intelligent high-speed rail, new high-speed rail services are constantly emerging. Efficiently meeting the diverse needs of these new services is a key challenge for integrated space-ground railway mobile communication systems. Network slicing technology, by orchestrating the network of an integrated space-ground railway mobile communication system and dividing the physical network into several logical slices, can efficiently and flexibly meet the needs of different high-speed rail services. However, due to the uneven distribution of high-speed rail services, integrated space-ground railway mobile communication systems face the problem of uneven slice load. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and device for slicing load balancing in integrated air-ground railway mobile communication.

[0005] The objective of this invention is achieved through the following technical solution: a slice load balancing method for integrated terrestrial and satellite railway mobile communication, comprising the following steps:

[0006] S1. Determine the network coverage scheme for the integrated land-air-ground railway mobile communication system;

[0007] S2. Design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system;

[0008] S3. Perform load balancing on terminals in different states:

[0009] For terminals in the connected state, slice load balancing is performed, and the load of the selected terminals is migrated to the target base station to make the load distribution of the slice balanced.

[0010] When an idle terminal needs to access the network, the terminal performs cell reselection based on the slice cell reselection priority and the available slice capacity to achieve slice load balancing.

[0011] When the base station releases the terminal's RRC connection, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of the dedicated slice. This controls the terminal, which has entered the idle state, to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

[0012] A slice load balancing device for integrated terrestrial and satellite railway mobile communication includes:

[0013] The coverage scheme determination module is used to determine the network coverage scheme of the integrated terrestrial and ground-based railway mobile communication system.

[0014] The network slicing scheme design module is used to design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system.

[0015] The load balancing module is used to perform load balancing on terminals in different states, including:

[0016] The connected load balancing unit is used to perform slice load balancing on terminals in the connected state, and migrate the load of the selected terminals to the target base station slice, so that the load distribution of the slice is balanced.

[0017] The idle-state load balancing unit is used to enable terminals in the idle state to reselect cells based on slice cell reselection priority and slice available capacity when they need to access the network, thereby achieving slice load balancing.

[0018] When the terminal releases the load balancing unit, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of dedicated slice when the base station releases the terminal's RRC connection. This controls the terminal entering the idle state to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

[0019] The beneficial effects of this invention are: by integrating satellite and land-based railway mobile communication systems into a network, the railway mobile communication system can achieve three-dimensional network coverage; by flexibly arranging the network and managing the slice load balancing of the integrated space-ground railway mobile communication system according to the characteristics of railway services, the load balancing of the slices is achieved, effectively improving the performance of the railway mobile communication system. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method of the present invention;

[0021] Figure 2 A schematic diagram of a network coverage scheme for a railway mobile communication system.

[0022] Figure 3 This is a schematic diagram of the second network coverage scheme for the railway mobile communication system.

[0023] Figure 4 A schematic diagram of the overall network slicing scheme for the integrated space-ground railway mobile communication system.

[0024] Figure 5 A schematic diagram of the second network slicing scheme for the integrated land-air-ground railway mobile communication system;

[0025] Figure 6 A schematic diagram of a connected slice load balancing scheme;

[0026] Figure 7 A schematic diagram of an idle-state slice load balancing scheme;

[0027] Figure 8 A schematic diagram of a slice cell selection method that uses slice resource status information for dedicated RRC signaling to assist in slice load balancing;

[0028] Figure 9 This is a schematic diagram of a slice load balancing scheme based on fast switching in the connected state. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0030] like Figure 1 As shown, a slice load balancing method for integrated air-ground railway mobile communication includes the following steps:

[0031] S1. Determine the network coverage scheme for the integrated land-air-ground railway mobile communication system;

[0032] For existing GSM-R railways being upgraded to FRMCS railways, and for the coexistence of GSM-R and FRMCS before the decommissioning of GSM-R, the railway mobile communication system network coverage scheme remains the same. Figure 2 As shown, the wireless network coverage layer consists of the GSM-R network layer and the FRMCS network layer. GSM-R employs dual-network backup coverage or single-network interleaved redundancy backup. The FRMCS network layer consists of a terrestrial network and a satellite network, with the FRMCS terrestrial network employing dual-network backup coverage or single-network interleaved redundancy backup.

[0033] For network coverage of newly built railways, or the railway network coverage after the decommissioning of GSM-R, the railway mobile communication system only has FRMCS network coverage, i.e., railway mobile communication system network coverage scheme two. Figure 3 As shown, the FRMCS network layer consists of a terrestrial network and a satellite network, with the FRMCS terrestrial network employing dual-network backup coverage or single-network interleaved redundancy backup.

[0034] S2. Design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system;

[0035] A schematic diagram of the overall scheme for network slicing in the integrated space-ground railway mobile communication system is shown below. Figure 4 As shown, the network mainly consists of the physical network plane, the logical network management and orchestration plane, and the service and application requirements plane. The network slicing orchestration and controller performs network slicing and orchestration on the physical network based on the service and application characteristics from the railway service and application requirements plane, dividing it into N network slices. Each network slice consists of allocated network slice resources, the cells supported by the slice, the services supported by the slice, and their service characteristic parameters.

[0036] Furthermore, this invention also provides a second network slicing scheme for an integrated terrestrial and satellite railway mobile communication system, such as... Figure 5 As shown, the logical network management and orchestration plane consists of two levels of network slice orchestration and controllers. The first-level network slice orchestration and controller manages the second-level network slice orchestration and controller, which comprises a space-based network slice orchestration and controller and a terrestrial network slice orchestration and controller. The second-level space-based network slice orchestration and controller performs network slice orchestration and control for railway services and applications supported by the space-based satellite network. The second-level terrestrial network slice orchestration and controller performs network slice orchestration and control for railway services and applications supported by the terrestrial network.

[0037] S3. Perform load balancing on terminals in different states:

[0038] For terminals in the connected state, slice load balancing is performed, and the load of the selected terminals is migrated to the target base station to make the load distribution of the slice balanced.

[0039] Due to the uneven distribution of terminals and services in the access network, the load on slices is uneven, resulting in some base stations having heavy slice loads while others have light slice loads, severely impacting slice performance. By performing slice load balancing on terminals in the connected state, the load of selected terminals is migrated to the target base station slice, resulting in a more balanced slice load distribution and effectively improving slice performance. The connected state slice load balancing scheme of this invention is as follows: Figure 6 As shown, the specific processing steps are as follows:

[0040] Step A1: Record the satellite or ground base station serving the current terminal as the current base station. The current base station determines the list of neighboring base stations for slice load balancing, which contains N neighboring base stations, denoted as {neighboring base station 1, ..., neighboring base station N}. The available slice capacity of the neighboring base stations is obtained through the resource status report process. Then, proceed to step A2.

[0041] Step A2: The current base station decides whether to perform slice load balancing based on the available capacity of the obtained slice. If slice load balancing is required, based on the slice load balancing strategy, terminals that meet the conditions are selected, and one or more candidate target base stations are selected from neighboring base stations. The slice load balancing strategy can employ handover or dual connectivity, etc. Proceed to step A3;

[0042] Step A3: If the slice load balancing strategy is handover, the current base station executes a slice-based cell handover procedure, handing the selected terminal to the candidate target base station. During the handover procedure, when the current base station receives a handover request acknowledgment message from the candidate target base station, if the handover request acknowledgment message carries a Packet Data Unit Session Resources Not Admitted List (PDU Session Resources Not Admitted List) and is not empty, the current base station does not hand over the terminal to the candidate target base station, and the current base station continues to select the next candidate target base station to initiate the handover procedure. If the handover request acknowledgment message does not carry a PDU Session Resources Not Admitted List, the current base station hands over the terminal to the candidate target base station. Optionally, the current base station sends a handover request message to one or more candidate target base stations. The current base station receives the handover request acknowledgment messages from the one or more candidate target base stations and selects the candidate target base station with the highest priority and whose handover request acknowledgment message does not carry a PDU Session Resources Not Admitted List to initiate the handover.

[0043] If the slice load balancing strategy is dual connectivity, the current base station offloads the slice services of the selected terminals to candidate target base stations through the dual connectivity process. In the dual connectivity process, the current base station acts as the primary base station and sends a Sub-Base Station Addition Request (S-NODE ADDITION REQUEST) to the candidate target base station, carrying the slice services to be load balanced. Upon receiving the S-NODE ADDITION REQUEST, the candidate target base station performs admission control on the carried slice services and replies to the primary base station with an S-NODE ADDITION REQUEST ACKNOWLEDGE. After receiving the S-NODE ADDITION REQUEST ACKNOWLEDGE message, if the primary base station carries a list of unadmitted Packet Data Unit (PaDR) session resources, it selects the next candidate target base station to initiate a S-NODE ADDITION REQUEST. If all candidate target base stations have slice services that failed to be admitted, the base station establishes a dual connectivity with the highest priority candidate target base station, offloading the successfully admitted slice services to that candidate target base station, while the primary base station retains the slice services that failed to be admitted by the secondary base station.

[0044] During handover, if the railway mobile communication system uses OTFS modulation waveform technology, the number of symbols N in the OTFS frame can be further optimized to reduce latency while ensuring the reliability of handover signaling transmission. If the size of an OTFS frame is denoted as M×N and the time of one symbol is denoted as T, then the transmission latency of one OTFS frame symbol is T. OTFS,Tx =NT, the reception delay of one OTFS symbol frame is T OTFS,Tx =NT. The time it takes for the OTFS transmitter to process a handover signaling message is T. HO,Proc,Tx The time T is the time for the OTFS receiver to process a handover signaling message. HO,Proc,Rx The delay in the transmission of a handover signaling message between a base station and a terminal over the air interface (Uu) is denoted as T. Uu Therefore, the transmission and reception delay of a handover signaling message is T. HO =T HO，,Proc,Tx +T OTFS,Tx +T Uu +T OTFS,Rx +T HO,Proc,Rx When an error occurs during the transmission of a switching signaling message, it needs to be retransmitted. In this case, the transmission and reception delay of a single HAQR request message is T. HARQ =T HARQ,Proc,Tx +T OTFS,Tx +T Uu +T OTFS,Rx +T HARQ,Proc,Rx T HARQ,Proc,Tx T is the time it takes for the transmitter to process a retransmission request message. HARQ,Proc,Rx This is the time it takes for the receiver to process a retransmission request message. Therefore, the transmit / receive delay for a single handover signaling message retransmission is T. HO-HARQ =THARQ +T HO Given the number of subcarriers M and the maximum allowable delay T for a single handover signaling message. HO,max First, we obtain the expression relating transmission reliability to the number of symbols N, and the number of Hybrid Automatic Repeat Message (HARQ) attempts N for handover signaling messages. HO,HARQ The functional relationship between N and the number of OTFS symbols is denoted as N. HO,HARQ =f(N); then calculate N. HO,HARQ The total delay T of the second retransmission HO,Total =T HO +N HO-HARQ T HO-HARQ =T HO +f(N)T HO-HARQ Finally, construct inequality T. HO,Total ≤T HO,max Thus, the minimum number of symbols N that meets the requirements is obtained.

[0045] When an idle terminal needs to access the network, the terminal performs cell reselection based on the slice cell reselection priority and the available slice capacity to achieve slice load balancing.

[0046] Traditional slice-based cell selection only considers the priority of cell reselection within the network slice, without taking into account the resource status information of the slice. When an idle terminal needs to access the network, the uneven distribution of terminals and their services leads to uneven load on the slice after the terminal accesses the network, severely affecting the performance of the slice.

[0047] For integrated terrestrial and satellite mobile communication systems for railways, an idle-state load balancing method assisted by slice resource status information is proposed. This method enables terminals to reselect cells based on slice cell reselection priorities and available slice capacity, thereby achieving slice load balancing and effectively improving slice performance. The idle-state slice load balancing scheme of this invention is as follows: Figure 7 As shown, the specific processing steps are as follows:

[0048] Step B1: The satellite or ground base station obtains slice cell reselection priority and slice available capacity information. The slice cell reselection priority can be obtained from the network management system's configuration information. Regarding slice available capacity information, the available resources for this base station are obtained through interaction between the Radio Resource Control (RRC) sublayer and the Media Access Control (MAC) sublayer, while the available slice capacity of neighboring base stations or cells is obtained through a resource status reporting process between base stations.

[0049] Step B2: The base station broadcasts network slice cell reselection priority and slice load information to the terminal via the System Information Block (SIB). Specifically, for the 5G-R system, the base station broadcasts slice-based cell reselection information to the terminal via System Information Block 16 (SIB16), where the relevant information cells for the newly added slice available capacity in SIB16 are shown in the table below:

[0050]

[0051]

[0052] In the embodiments of this application, the SIB16 signaling in 3GPP TS 38.331 is modified as follows:

[0053]

[0054] Step B3: The terminal performs slice-based cell reselection based on the received slice cell reselection priority and slice available capacity. Specifically, the terminal first obtains the priority order of slice cells according to the slice frequency priority list; then, the terminal sorts the slices that meet the conditions that the downlink slice available capacity is greater than or equal to the downlink data rate of the terminal slice service and the uplink slice available capacity is greater than or equal to the uplink data rate of the terminal slice service; finally, the terminal selects the highest priority slice from the slices that meet the service QoS requirements.

[0055] When the base station releases the terminal's RRC connection, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of the dedicated slice. This controls the terminal, which has entered the idle state, to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

[0056] When the base station releases the terminal's RRC connection, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of the dedicated slice. This controls the terminal, which has entered the idle state, to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

[0057] In the integrated terrestrial-ground railway mobile communication system, base stations

[0058] Traditional slice-based cell selection only considers the priority of cell reselection within the network slice, neglecting slice load information. This leads to selected slices that fail to meet the Quality of Service (QoS) requirements of railway services. The present invention proposes a slice cell selection method that uses slice resource status information from dedicated RRC signaling to assist in slice load balancing. Figure 8 As shown. The specific processing steps are as follows:

[0059] Step C1: The satellite or ground base station obtains slice cell reselection priority and slice available capacity information. The slice cell reselection priority can be obtained from the network management system's configuration information. Regarding slice available capacity information, the available resources for this base station's slices are obtained through interaction between the Radio Resource Control (RRC) sublayer and the Media Access Control (MAC) sublayer, while the available slice capacity of neighboring base stations or cells is obtained through a resource status reporting process between base stations.

[0060] Step C2: The base station sends dedicated slice cell reselection priority and dedicated slice available capacity information to the terminal via a dedicated signaling RRC release (RRCRelease) message. The newly added dedicated slice available capacity related information elements in the RRC release message are shown in the table below:

[0061]

[0062] In the embodiments of this application, the following new cell reselection information element is added to the RRRCRelease message in 3GPP TS 38.331:

[0063]

[0064]

[0065] Step C3: The terminal receives the RRC release message and performs slice-based cell reselection according to the received cell reselection priority and the available capacity of the dedicated slice. Specifically, the terminal first obtains the priority order of the slice cells according to the dedicated slice frequency priority list in the cell reselection priority; then, the terminal sorts the slices that meet the conditions that the available capacity of the downlink slice in the dedicated slice is greater than or equal to the downlink data rate of the terminal slice service and the available capacity of the uplink slice in the dedicated slice is greater than or equal to the uplink data rate of the terminal slice service; finally, the terminal selects the slice with the highest priority from the slices that meet the service QoS requirements.

[0066] In the embodiments of this application, step A3 uses the existing 3GPP handover procedure for handover. However, when used for slice load balancing in connected mode, it faces the problem of large handover latency and the risk of dropped calls during handover. Therefore, in the embodiments of this application, a slice load balancing scheme based on fast handover is further provided, such as... Figure 9 As shown. The specific processing steps are as follows:

[0067] Step D1: The satellite or ground base station (current base station) determines the list of neighboring base stations for slice load balancing, which contains N neighboring base stations, denoted as {neighboring base station 1, ..., neighboring base station N}, and obtains the slice available capacity of the neighboring base stations through the resource status report process, and then jumps to step D2;

[0068] Step D2: The current base station decides whether to perform slice load balancing based on the available capacity of the obtained slices. If slice load balancing is required, select terminals that meet the conditions and one or more handover candidate base stations, and proceed to step D3;

[0069] Step D3: The current base station organizes handover assistance information, including candidate base stations, available capacity of candidate base station slices, handover parameters, etc., and sends it to the terminal through Radio Resource Control Reconfiguration (RRCReconfiguration) messages, then proceeds to step D4;

[0070] Step D4: The terminal receives and saves the Radio Resource Control reconfiguration message, then proceeds to step D5;

[0071] Step D5: The current base station performs data backhaul to the selected handover candidate base station. If early data forwarding is available, the current base station sends an Early State Transition (EARLY STATUS TRANSFER) message to the selected handover candidate base station, then performs user data forwarding, and jumps to step D6;

[0072] Step D6: The terminal measures the stored candidate base stations for handover and selects the candidate base station that meets the conditions as the target base station for handover based on the measurement results. Further, the process of selecting the target base station for handover is as follows: The terminal selects a list 1 of candidate base stations that meet the handover signal conditions based on the measurement results. Then, the terminal selects a list 2 of candidate base stations from the list 1 that meets the condition that the available slice capacity is not less than the terminal slice service data rate. The terminal sorts the candidate base stations in list 2 and finally selects the candidate base station with the highest priority as the target base station for handover. Optionally, another process for selecting the target base station for handover is as follows: The terminal selects a list of candidate base stations 1 that meet the handover signal conditions based on the measurement results. Then, the terminal selects a list of candidate base stations 2 from the selected list of candidate base stations 1 that meet the requirement that the available slice capacity is not less than the terminal slice service data rate. The candidate base stations in the list of candidate base stations 2 are then weighted and sorted according to the measurement signal results and the available slice capacity. Finally, the candidate base station with the highest priority is selected as the target base station for handover. The source base station is disconnected, and synchronization is performed to the target base station for handover. The process then proceeds to step D7.

[0073] Step D7: The terminal sends a Radio Resource Control (RRC) reconfiguration message to the target base station to complete the handover. The target base station sends a Handover Success message to the source base station, notifying the terminal that the handover to the target base station was successful.

[0074] A slice load balancing device for integrated terrestrial and satellite railway mobile communication includes:

[0075] The coverage scheme determination module is used to determine the network coverage scheme of the integrated terrestrial and ground-based railway mobile communication system.

[0076] The network slicing scheme design module is used to design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system.

[0077] The load balancing module is used to perform load balancing on terminals in different states, including:

[0078] The connected load balancing unit is used to perform slice load balancing on terminals in the connected state, and migrate the load of the selected terminals to the target base station slice, so that the load distribution of the slice is balanced.

[0079] The idle-state load balancing unit is used to enable terminals in the idle state to reselect cells based on slice cell reselection priority and slice available capacity when they need to access the network, thereby achieving slice load balancing.

[0080] When the terminal releases the load balancing unit, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of dedicated slice when the base station releases the terminal's RRC connection. This controls the terminal entering the idle state to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

[0081] Finally, it should be noted that although the method in this invention uses a railway mobile communication system as an example, it is not limited thereto. Although the invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this invention without departing from the spirit and scope of the invention, and all such modifications and substitutions should be covered within the scope of the claims of this invention.

Claims

1. A method for load balancing in integrated space-ground railway mobile communication, characterized in that: Includes the following steps: S1. Determine the network coverage scheme for the integrated land-air-ground railway mobile communication system; For existing GSM-R railways being upgraded to FRMCS railways, and for the coexistence of GSM-R and FRMCS before the decommissioning of GSM-R, the network coverage scheme for the railway mobile communication system is as follows: the wireless network coverage layer consists of a GSM-R network layer and a FRMCS network layer; GSM-R adopts dual-network backup coverage or single-network interleaved redundancy backup; the FRMCS network layer consists of a terrestrial network and a satellite network, wherein the FRMCS terrestrial network adopts dual-network backup coverage or single-network interleaved redundancy backup; For the network coverage of newly built railways, or the railway network coverage after the decommissioning of GSM-R, the railway mobile communication system only has FRMCS network layer coverage; S2. Design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system; S3. Perform load balancing on terminals in different states: For terminals in the connected state, slice load balancing is performed, migrating the load of selected terminals to the target base station to achieve a balanced load distribution across slices; including: A1: The satellite or ground base station serving the current terminal is recorded as the current base station. The current base station determines the list of neighboring base stations for slice load balancing, which contains N neighboring base stations, denoted as {neighboring base station 1, ..., neighboring base station N}. The available slice capacity of the neighboring base stations is obtained through the resource status report process. Then, proceed to step A2. A2: The current base station decides whether to perform slice load balancing based on the available capacity of the slices obtained: If slice load balancing is required, based on the slice load balancing strategy, select terminals that meet the conditions and select one or more candidate target base stations from the neighboring base stations, and jump to step A3; A3: Assume the slice load balancing strategy adopts switching or dual connectivity; A31: If the slice load balancing strategy is handover, the current base station executes a slice-based cell handover procedure, switching the selected terminal to the candidate target base station. During the handover procedure, when the current base station receives the handover request confirmation message from the candidate target base station: If the handover request confirmation message carries a list of unaccepted Packet Data Unit session resources and is not empty, the current base station will not hand over the terminal to the candidate target base station, and the current base station will continue to select the next candidate target base station to initiate the handover preparation process. If the handover request confirmation message does not carry a list of unaccepted Packet Data Unit session resources, the current base station will hand over the terminal to the candidate target base station; A32: If the slice load balancing strategy is dual connectivity, the current base station will offload the slice services of the selected terminal to the candidate target base station through the dual connectivity process: The current base station, acting as the primary base station, sends a secondary base station addition request to the candidate target base station, carrying the slice services that need to be load balanced; upon receiving the secondary base station addition request, the candidate target base station performs admission control on the carried slice services and replies to the primary base station with a confirmation of the secondary base station addition request; after the primary base station receives the confirmation message of the secondary base station addition request; If a list of unaccepted Packet Data Unit session resources is carried, then the next candidate target base station is selected to initiate a secondary base station addition request; If all candidate target base stations fail to accept slice services, the base station establishes a dual connection with the candidate target base station with the highest priority, offloads the successfully accepted slice services to the candidate target base station, and the main base station retains the slice services that failed to accept the secondary base station. When an idle terminal needs to access the network, the terminal performs cell reselection based on the slice cell reselection priority and the available slice capacity to achieve slice load balancing. When the base station releases the terminal's RRC connection, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of the dedicated slice. This controls the terminal, which has entered the idle state, to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

2. The method for slice load balancing in integrated space-ground railway mobile communication according to claim 1, characterized in that: In step S2, the overall network slicing scheme of the integrated terrestrial and ground railway mobile communication system includes a physical network plane, a logical network management and orchestration plane, and a service and application requirement plane. The physical network plane includes space-based satellite networks and terrestrial networks; The business and application requirements plane is used to provide railway business and application requirements; The logical network management orchestration plane includes two cases: First, the logical network management and orchestration plane consists of a single network slice orchestration and controller. The network slice orchestration and controller performs network slice orchestration on the physical network according to the needs of railway business and applications, dividing it into N network slices: each network slice consists of allocated network slice resources, cells supported by the slice, services supported by the slice, and service characteristic parameters. Second, the logical network management orchestration plane consists of two levels of network slice orchestration and controllers, where the first level of network slice orchestration and controllers is responsible for managing the second level of network slice orchestration and controllers; The second-level network slicing orchestration and controller consists of a space-based network slicing orchestration and controller, and a ground-based network slicing orchestration and controller; the space-based network slicing orchestration and controller performs network slicing orchestration and control for the space-based satellite network to support railway services and applications; The terrestrial network slicing orchestration and controller performs network slicing orchestration and control on railway services and applications supported by the terrestrial network.

3. The method for slice load balancing in integrated space-ground railway mobile communication according to claim 1, characterized in that: During handover, if the railway mobile communication system uses OTFS modulation waveform technology, the number of symbols in the OTFS frame should be further optimized. Reduce latency while ensuring reliable handover signaling transmission: The size of an OTFS frame is denoted as A symbolic time is denoted as The transmission delay of one OTFS frame symbol is then... The reception delay of one OTFS symbol frame is ; The time it takes for the OTFS transmitter to process a handover signaling message is The time it takes for an OTFS receiver to process a handover signaling message is ; The delay in the transmission of a handover signaling message between a base station and a terminal over the air interface is denoted as . The latency for sending and receiving a handover signaling message is ; When an error occurs during the transmission of a switching signaling message, retransmission is required. In this case, the transmission and reception delay of a single HAQR request message is... ,in It is the time it takes for the transmitter to process a retransmission request message. It is the time it takes for the receiver to process a retransmission request message; Therefore, the transmission and reception delay for a single handover signaling message retransmission is ; Given number of subcarriers and the maximum allowed latency of a handover signaling message At that time, the transmission reliability and the number of symbols are first obtained. The relational expression between them, and the number of automatic retransmissions of mixed handover signaling messages. With the number of OTFS symbols The functional relationship between them is denoted as ; Then calculate Total delay of the second retransmission Finally, construct the inequality. Thus, the minimum number of symbols required to satisfy the requirement is obtained. .

4. The method for slice load balancing in integrated space-ground railway mobile communication according to claim 1, characterized in that: When a terminal in an idle state needs to access the network, the terminal performs cell reselection based on the slice cell reselection priority and the available slice capacity to achieve slice load balancing, including: B1: Satellite or ground base stations obtain slice cell reselection priority and slice available capacity information; among them, slice cell reselection priority comes from the configuration information of the network management system, and slice available capacity information is obtained by the interaction between the radio resource control sublayer and the media access control sublayer for the slice available resources of this base station, while the slice available capacity of neighboring base stations or neighboring cells is obtained through the resource status reporting process between base stations. B2: The base station broadcasts network slice cell reselection priority and slice load information to the terminal via System Information Block (SIB): For 5G-R systems, base stations broadcast cell reselection information based on slices to terminals through System Information Block (SIB16). The newly added slice available capacity related information elements in SIB16 include: slice available capacity list, network slice access layer packet identifier information, downlink slice available capacity value, and uplink slice available capacity value. B3: The terminal performs slice-based cell reselection based on the received slice cell reselection priority and available slice capacity. The terminal first obtains the priority order of the sliced ​​cells according to the slice frequency priority list; Then, the terminal sorts the slices that meet the conditions that the available capacity of the downlink slice is greater than or equal to the downlink data rate of the terminal slice service and the available capacity of the uplink slice is greater than or equal to the uplink data rate of the terminal slice service. Finally, the terminal selects the highest priority slice from the slices that meet the service QoS requirements.

5. The method for slice load balancing in integrated space-ground railway mobile communication according to claim 1, characterized in that: When the base station releases the terminal's RRC connection, the base station sends an RRC release message to the terminal carrying the dedicated slice cell reselection priority and the available capacity of the dedicated slice. This controls the terminal entering the idle state to select a suitable cell during slice-based cell reselection, thereby achieving slice load balancing. This includes: C1: Satellite or ground base station obtains slice cell reselection priority and slice available capacity information: Among them, the cell reselection priority of the slice comes from the configuration information of the network management system; as for the slice available capacity information, the slice available resource information of this base station is obtained by the interaction between the radio resource control sublayer and the media access control sublayer, while the slice available capacity of neighboring base stations or neighboring cells is obtained through the resource status reporting process between base stations. C2: The base station sends dedicated slice cell reselection priority and dedicated slice available capacity information to the terminal through dedicated signaling RRC release message; The newly added dedicated slice available capacity related information elements in the RRC release message include: a dedicated slice available capacity list, network slice access layer packet identification information, downlink slice available capacity value, and uplink slice available capacity value; C3: The terminal receives the RRC release message and performs slice-based cell reselection based on the received cell reselection priority and the available capacity of the dedicated slice. The terminal first obtains the priority order of the sliced ​​cells according to the dedicated slice frequency priority list in the cell reselection priority; Then, the terminal sorts the slices that meet the conditions that the available capacity of the downlink slice in the dedicated slice is greater than or equal to the downlink data rate of the terminal slice service and the available capacity of the uplink slice in the dedicated slice is greater than or equal to the uplink data rate of the terminal slice service. Finally, the terminal selects the highest priority slice from the slices that meet the service QoS requirements.

6. A slicing load balancing device for integrated terrestrial and satellite railway mobile communication, employing the method described in any one of claims 1 to 5, characterized in that: include: The coverage scheme determination module is used to determine the network coverage scheme of the integrated terrestrial and ground-based railway mobile communication system. The network slicing scheme design module is used to design the overall network slicing scheme for the integrated terrestrial and satellite railway mobile communication system. The load balancing module is used to perform load balancing on terminals in different states.

7. A slice load balancing device for integrated space-ground railway mobile communication according to claim 6, characterized in that: The load balancing module includes: The connected load balancing unit is used to perform slice load balancing on terminals in the connected state, and migrate the load of the selected terminals to the target base station slice, so that the load distribution of the slice is balanced. The idle-state load balancing unit is used to enable terminals in the idle state to reselect cells based on slice cell reselection priority and slice available capacity when they need to access the network, thereby achieving slice load balancing. When the terminal releases the load balancing unit, the base station sends an RRC release message to the terminal carrying the priority of dedicated slice cell reselection and the available capacity of dedicated slice when the base station releases the terminal's RRC connection. This controls the terminal entering the idle state to select a suitable cell when performing slice-based cell reselection, thereby achieving slice load balancing.

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