Redcap terminal inter-network roaming network selection method and device

Abstract

The application discloses a method for network selection of RedCap terminal roaming in a different network. A 5G RedCap terminal records a different network roaming information table of a cell of a home network. When the 5G RedCap terminal is ready to initiate 5G roaming in a different network from a current location, it is determined whether the current location is within the coverage range of a "5G roaming in a different network failure location" superimposed with an "offset" in the different network roaming information table of the current service cell of the home network. If the value of the "support roaming in a different network flag" indicates that the current service cell of the home network does not support the 5G RedCap terminal to perform 5G roaming in a different network, the 5G RedCap terminal starts a timer. Before the expiration of the timer, the 5G RedCap terminal does not initiate 5G roaming in a different network at the current location. The application is beneficial to guarantee the continuity of the 5G RedCap terminal in a service state in a 5G roaming in a different network scenario.

Description

Technical Field

[0001] This application relates to a mobile communication technology, and more particularly to a RedCap terminal inter-network roaming selection method. Background Technology

[0002] 5G inter-network roaming refers to the ability of a user (UE, or user equipment, terminal) to access the 5G networks of other mobile operators and continue using 5G services when the UE's mobile operator does not have 5G network coverage. For simplicity, the UE's mobile operator is referred to as the home operator, and the home operator's mobile network is called the home network. Other mobile operators besides the UE's home operator are called visited operators, and the visited operator's mobile network is called the visited network.

[0003] Typical scenarios for 5G inter-network roaming are as follows: (1) In a location with a 5G cell without a home network and a 5G cell with a visited network, the UE accesses the 5G cell with the visited network. (2) In a location with both a 4G cell with a home network and a 5G cell with a visited network, the UE prioritizes accessing the 5G cell with the visited network. (3) In a location with any cell without a home network and a 5G cell with a visited network, the UE accesses the 5G cell with the visited network. In 5G inter-network roaming scenarios, the visiting operator only provides 5G network roaming and does not provide 4G network roaming.

[0004] At the boundary between the home network and the visited network, the UE mobility scenarios supported by 5G inter-network roaming are as follows: (1) The UE roams from the 4G cell of the home network to the 5G cell of the visited network. (2) The UE roams from the 5G cell of the visited network back to the 4G cell of the home network. (3) The UE roams from the 5G cell of the home network to the 5G cell of the visited network. (4) The UE roams from the 5G cell of the visited network back to the 5G cell of the home network.

[0005] With the advancement of RedCap (reduces performance) technology, more and more wearable devices are being registered as 5G RedCap terminals. When used domestically, 5G RedCap terminals can easily enter areas near the boundary between their home and visited networks. 5G cells are divided into "5G RedCap cells" that allow 5G RedCap terminals to access and "ordinary 5G cells" that deny access. If the visited network's 5G cell does not support 5G RedCap terminal access, and an idle 5G RedCap terminal attempts to access a visited ordinary 5G cell using EPLMN (Equivalent Public Land Mobile Network) cell selection or reselection, or a connected 5G RedCap terminal attempts to access a visited ordinary 5G cell using redirection or handover, access will be denied. This results in the 5G RedCap terminal performing multiple network searches, leading to multiple prolonged periods of no service and consuming significant battery power. Summary of the Invention

[0006] The technical problem this application aims to solve is: how to keep 5G RedCap terminals in service for as long as possible in 5G inter-network roaming scenarios to improve user experience; and how to reduce power consumption caused by frequent network searches of 5G RedCap terminals.

[0007] To address the aforementioned technical issues, this application proposes a method for RedCap terminal inter-network roaming selection, comprising the following steps: Step S1: Each time a 5G RedCap terminal initiates 5G inter-network roaming from a cell in its home network to a 5G cell in the visited network, it records the inter-network roaming information table of that cell in its home network. The inter-network roaming information table of each cell in the home network records: inter-network roaming support flag, 5G inter-network roaming failure location, and offset. Step S2: When the 5G RedCap terminal is about to initiate 5G inter-network roaming from its current location, the 5G RedCap terminal determines whether the currently serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table. If yes, proceed to step S3. If no, the 5G RedCap terminal initiates 5G inter-network roaming normally and returns to step S1. Step S3: The 5G RedCap terminal determines whether the current location is within the coverage area of ​​a "5G inter-network roaming failure location" plus an "offset" in the inter-network roaming information table of the currently serving cell of the home network. If yes, proceed to step S4. If no, the 5G RedCap terminal initiates 5G inter-network roaming normally and returns to step S1. Step S4: The 5G RedCap terminal reads the "Support Inter-network Roaming Flag" from the inter-network roaming information table of the current serving cell of its home network. If the value of the "Support Inter-network Roaming Flag" indicates that the current serving cell of the home network supports the 5G RedCap terminal in performing 5G inter-network roaming, the 5G RedCap terminal initiates 5G inter-network roaming normally and returns to step S1. If the value of the "Support Inter-network Roaming Flag" indicates that the current serving cell of the home network does not support the 5G RedCap terminal in performing 5G inter-network roaming, proceed to step S5. Step S5: The 5G RedCap terminal starts a timer. Before the timer expires, the 5G RedCap terminal does not initiate 5G inter-network roaming at its current location. After the timer expires, the 5G RedCap terminal re-initiates 5G inter-network roaming at its current location.

[0008] Further, in step S1, when a 5G RedCap terminal attempts to perform 5G inter-network roaming at one or more locations within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal discovers at least one 5G cell in the visited network that allows the 5G RedCap terminal to access at at least one of the attempted locations, it indicates that the cell in the home network supports 5G RedCap terminal 5G inter-network roaming, and the "Support Inter-network Roaming Flag" is set to 1; if the 5G RedCap terminal discovers that all 5G cells in the visited network reject the 5G RedCap terminal's access at all the attempted locations, it indicates that the cell in the home network does not support 5G RedCap terminal 5G inter-network roaming, and the "Support Inter-network Roaming Flag" is set to 0.

[0009] Furthermore, in step S1, when a 5G RedCap terminal attempts to perform 5G inter-network roaming within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal finds that all 5G cells in the visited network refuse access at a certain location, it indicates that the 5G RedCap terminal's 5G inter-network roaming at that location has failed, and this location is recorded as the 5G inter-network roaming failure location; there are one or more 5G inter-network roaming failure locations in the inter-network roaming information table of a cell in the home network.

[0010] Furthermore, in step S1, the offset is the coverage radius of each "5G inter-network roaming failure location"; when there are multiple "5G inter-network roaming failure locations", there are also multiple offsets of the same kind, or the offset is the same one.

[0011] Furthermore, in step S1, the inter-network roaming information table is recorded on a per-cell basis within the home network; if the 5G RedCap terminal initiates 5G inter-network roaming in multiple cells of the home network, the inter-network roaming information table for the multiple cells of the home network is recorded.

[0012] Furthermore, in step S1, if the cell of the home network of the 5G RedCap terminal already has an inter-network roaming information table, then the inter-network roaming information table of the cell of the home network is updated.

[0013] Furthermore, in step S1, when the 5G RedCap terminal attempts to access a 5G cell in the visited network, it obtains an indication from the System Information Block (SIB) message sent by the 5G cell in the visited network whether the 5G cell supports access by the 5G RedCap terminal.

[0014] Furthermore, in step S5, before the timer expires, the 5G RedCap terminal removes the EPLMN (Equivalent Public Land Mobile Network) corresponding to the visited network from its local EPLMN list. After the timer expires, the 5G RedCap terminal adds the EPLMN corresponding to the visited network back to its local EPLMN list.

[0015] Furthermore, the method also includes: the 5G RedCap terminal periodically deleting "5G inter-network roaming failure locations" from the inter-network roaming information table of all cells in the home network.

[0016] This application also proposes a device for RedCap terminal inter-network roaming selection, including an information table recording unit, an information table query unit, a location determination unit, a flag reading unit, and a timing and processing unit. The information table recording unit records the inter-network roaming information table of the home network's cell each time a 5G RedCap terminal initiates 5G inter-network roaming from a cell in its home network to a 5G cell in the visited network. Each cell in the home network's inter-network roaming information table records: an inter-network roaming support flag, a 5G inter-network roaming failure location, and an offset. The information table query unit determines whether the current serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table when the 5G RedCap terminal is about to initiate 5G inter-network roaming from its current location. If so, the subsequent processing is handled by the location determination unit. The location determination unit determines whether the 5G RedCap terminal's current location is within the coverage area of ​​a "5G inter-network roaming failure location" plus an "offset" in the inter-network roaming information table of the current serving cell of its home network. If so, the subsequent processing is handled by the flag reading unit. The flag reading unit is used to read the "Support Inter-Network Roaming Flag" from the inter-network roaming information table of the current serving cell of the home network. If the value of the "Support Inter-Network Roaming Flag" indicates that the current serving cell of the home network does not support 5G RedCap terminals to perform 5G inter-network roaming, the subsequent processing is handled by the timing unit. The timing and processing unit is used to start a timer; before the timer expires, 5G RedCap terminals are prohibited from initiating 5G inter-network roaming at the current location; after the timer expires, 5G RedCap terminals are allowed to initiate 5G inter-network roaming at the current location again.

[0017] The technical effect achieved by this application is that it helps to ensure the continuity of service status of 5G RedCap terminals in 5G inter-network roaming scenarios. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the RedCap terminal inter-network roaming selection method proposed in this application.

[0019] Figure 2 This is a schematic diagram of an exemplary use case of this application.

[0020] Figure 3 This is a schematic diagram of the RedCap terminal inter-network roaming network selection device proposed in this application.

[0021] The attached diagram is labeled as follows: Information table recording unit 1, Information table query unit 2, Location judgment unit 3, Flag reading unit 4, Timing and processing unit 5. Detailed Implementation

[0022] Please see Figure 1The method for selecting a network for RedCap terminal roaming across different networks proposed in this application includes the following steps.

[0023] Step S1: Each time a 5G RedCap terminal initiates a 5G inter-network roaming from a cell in its home network to a 5G cell in the visited network, it records the inter-network roaming information table of that cell in its home network.

[0024] The inter-network roaming information table is recorded on a per-cell basis within the home network. If a 5G RedCap terminal initiates 5G inter-network roaming in multiple cells of its home network, the inter-network roaming information table for those multiple cells is recorded.

[0025] The inter-network roaming information table for each cell in the home network records, for example, the following information.

[0026] First, support for inter-network roaming flags. When a 5G RedCap terminal attempts to roam across multiple locations within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal finds at least one 5G cell in the visited network that allows it to access at at least one of the attempted locations, it indicates that the home network cell supports 5G RedCap roaming, and the "Support for inter-network roaming flag" is set to 1. If the 5G RedCap terminal finds that all 5G cells in the visited network reject its access at all the attempted locations, it indicates that the home network cell does not support 5G RedCap roaming, and the "Support for inter-network roaming flag" is set to 0.

[0027] Second, the location of 5G inter-network roaming failure. When a 5G RedCap terminal attempts to roam across different 5G networks within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal finds that all 5G cells in the visited network refuse access at a certain location, it indicates that the 5G inter-network roaming at that location has failed, and this location is recorded as the 5G inter-network roaming failure location. Within the coverage area of ​​a cell in the home network, a 5G RedCap terminal may attempt to roam across different 5G networks at one or more locations; therefore, there may be one or more "5G inter-network roaming failure locations".

[0028] Third, offset. This is the coverage radius of each "5G inter-network roaming failure location", which can be set to 200 meters, 500 meters, 1000 meters, etc. When there are multiple "5G inter-network roaming failure locations", there will also be a corresponding number of offsets, or the offset can be the same.

[0029] In this step, if the cell of the home network of the 5G RedCap terminal already has an inter-network roaming information table, then the inter-network roaming information table of the cell of the home network is updated. For example, when the corresponding conditions are met, the "support inter-network roaming flag" is updated, and the "5G inter-network roaming failure location" is updated.

[0030] In this step, when a 5G RedCap terminal attempts to access a visited 5G cell in a certain location, it obtains an indication of whether the 5G cell supports 5G RedCap terminal access from the SIB (System Information Block) message sent by the visited 5G cell. For example, if the value of intraFreqReselectionRedCap in the SIB message sent by the visited 5G cell is notAllowed, it indicates that the 5G cell does not support 5G RedCap terminal access. Similarly, if the value of cellBarredRedCap1Rx-r17 or cellBarredRedCap2Rx-r17 in the SIB message sent by the visited 5G cell is barred, it indicates that the 5G cell does not support 5G RedCap terminal access.

[0031] Step S2: When the 5G RedCap terminal is about to initiate 5G inter-network roaming from its current location, the 5G RedCap terminal determines whether the current serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table.

[0032] If so, proceed to step S3.

[0033] If not, the 5G RedCap terminal initiates 5G inter-network roaming normally and returns to step S1. During the process of initiating 5G inter-network roaming, the 5G RedCap terminal adds and records the inter-network roaming information table of the current serving cell of the home network to which the current location belongs.

[0034] Step S3: The 5G RedCap terminal determines whether its current location is within the coverage area of ​​a "5G inter-network roaming failure location" plus "offset" in the inter-network roaming information table of the current serving cell of its home network.

[0035] If so, proceed to step S4.

[0036] If not, the 5G RedCap terminal initiates 5G inter-network roaming normally and returns to step S1. During the process of initiating 5G inter-network roaming, the 5G RedCap terminal updates the inter-network roaming information table of the current serving cell of the home network, such as updating the "inter-network roaming support flag" and updating the "5G inter-network roaming failure location" when the corresponding conditions are met.

[0037] Step S4: The 5G RedCap terminal reads the "Support Inter-Network Roaming Flag" from the inter-network roaming information table of the current serving cell of the home network.

[0038] If the value of "Support Inter-Network Roaming Flag" is 1, it means that the current serving cell of the home network supports 5G RedCap terminals for 5G inter-network roaming. The 5G RedCap terminal then initiates 5G inter-network roaming normally and returns to step S1. During the process of initiating 5G inter-network roaming, the 5G RedCap terminal updates the inter-network roaming information table of the current serving cell of the home network, such as updating the "Support Inter-Network Roaming Flag" and updating the "5G Inter-Network Roaming Failure Location" when the corresponding conditions are met.

[0039] If the value of "Support inter-network roaming flag" is 0, it means that the current serving cell of the home network does not support 5G RedCap terminals to roam 5G across networks, and proceed to step S5.

[0040] Step S5: The 5G RedCap terminal starts a timer, for example, for 1800 seconds.

[0041] Before the timer expires, the 5G RedCap terminal will not initiate 5G inter-network roaming at its current location, meaning it will not attempt to access any 5G cells of the visited network. For example, the 5G RedCap terminal will remove the EPLMN corresponding to the visited network from its local EPLMN list. This allows the 5G RedCap terminal to select other available cells to camp on, ensuring it remains in a service state as much as possible. This improves user experience and reduces power consumption caused by frequent network searches.

[0042] After the timer expires, the 5G RedCap terminal re-initiates 5G inter-network roaming at its current location, that is, it re-attempts to access the 5G cell of the visited network. For example, the 5G RedCap terminal adds the EPLMN corresponding to the visited network back to its local EPLMN list, and then searches for the network according to the 3GPP procedure.

[0043] The method also includes: the 5G RedCap terminal periodically (e.g., every 24 hours, 48 ​​hours, 72 hours, etc.) deleting the "5G inter-network roaming failure position" from the inter-network roaming information table of all cells in the home network. This takes into account that the configuration information of the visited network may change. For example, a 5G cell in the visited network may be updated from a regular 5G cell that "rejects 5G RedCap terminal access" to a 5G RedCap cell that "supports 5G RedCap terminal access", or a new 5G RedCap cell may be opened in the visited network.

[0044] Please see Figure 2This is an example of a use case for this application. The largest ellipse represents the home network's 4G cell, the smaller ellipses filled with left diagonal lines represent the visited network's ordinary 5G cells, and the smaller ellipses filled with squares represent the visited network's 5G RedCap cells. Point A is located in the overlapping area of ​​the home network's 4G cell and the visited network's ordinary 5G cell. Point B is located in the overlapping area of ​​the home network's 4G cell and the visited network's 5G RedCap cell.

[0045] If the existing 5G RedCap terminal's 5G inter-network roaming selection method is used, when the 5G RedCap terminal is located at point A, the idle 5G RedCap terminal uses EPLMN cell selection or reselection to try to access the ordinary 5G cell of the visited network, or the connected 5G RedCap terminal uses redirection or handover to try to access the ordinary 5G cell of the visited network. Because the ordinary 5G cell rejects the 5G RedCap terminal's access, this access attempt will be rejected, causing the 5G RedCap terminal to search for networks multiple times, resulting in multiple long periods of no service and consuming the 5G RedCap terminal's power.

[0046] If the 5G inter-network roaming selection method of the 5G RedCap terminal in this application is adopted, when the 5G RedCap terminal first attempts to initiate 5G inter-network roaming at point A, because all 5G cells of the visited network at point A reject the 5G RedCap terminal's access, the "Support Inter-network Roaming Flag" value is set to 0 in the inter-network roaming information table of the cells of the home network at point A. When the 5G RedCap terminal is at point A again, based on the previously recorded inter-network roaming information table of the cells of the home network at point A, the 5G RedCap terminal knows that the "Support Inter-network Roaming Flag" value is 0, and sets a timer. Before the timer expires, the 5G RedCap terminal does not initiate 5G inter-network roaming at point A. After the timer expires, the 5G RedCap terminal re-initiates 5G inter-network roaming at point A. This reduces the number of network searches performed by the 5G RedCap terminal, increases the duration of service, and reduces the power consumption of the 5G RedCap terminal. When a 5G RedCap terminal moves from point A to point B, it is no longer bound by the timer due to the change in location. The 5G RedCap terminal discovers a 5G RedCap cell with a visitable network through network search, initiates 5G inter-network roaming, and records or updates the inter-network roaming information table of the cell in the home network of point B for use in subsequent 5G inter-network roaming network selection.

[0047] Please see Figure 3The device for RedCap terminal roaming network selection proposed in this application includes an information table recording unit 1, an information table query unit 2, a location judgment unit 3, a flag reading unit 4, and a timing and processing unit 5. Figure 3 The device shown corresponds to Figure 1 The method shown.

[0048] The information table recording unit 1 is used to record the inter-network roaming information table of the home network cell each time a 5G RedCap terminal initiates 5G inter-network roaming from a cell in the home network to a 5G cell in the visited network. The inter-network roaming information table of each cell in the home network records: inter-network roaming support flag, 5G inter-network roaming failure location, and offset.

[0049] The information table query unit 2 is used to determine whether the current serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table when the 5G RedCap terminal is preparing to initiate 5G inter-network roaming from the current location. If so, the subsequent processing is handled by the location determination unit 3.

[0050] The location determination unit 3 is used to determine whether the current location of the 5G RedCap terminal is within the coverage area of ​​a certain "5G inter-network roaming failure location" superimposed with "offset" in the inter-network roaming information table of the current serving cell of its home network. If so, it is then handed over to the flag reading unit 4 for further processing.

[0051] The flag reading unit 4 is used to read the "Support Inter-network Roaming Flag" in the inter-network roaming information table of the current serving cell of the home network. If the value of the "Support Inter-network Roaming Flag" is 0, it means that the current serving cell of the home network does not support 5G RedCap terminals to roam in 5G inter-networks, and the subsequent processing is handled by the timing unit 5.

[0052] The timing and processing unit 5 is used to start a timer. Before the timer expires, the 5G RedCap terminal is prohibited from initiating 5G inter-network roaming at its current location. After the timer expires, the 5G RedCap terminal is allowed to initiate 5G inter-network roaming at its current location again.

[0053] 5G RedCap terminals, using existing 5G inter-network roaming methods, may frequently and repeatedly attempt to access ordinary 5G cells in the visited network. Because ordinary 5G cells do not allow 5G RedCap terminals to access, each access attempt will be rejected. This will cause the 5G RedCap terminal to perform multiple network searches, resulting in multiple prolonged periods of no service and consuming the 5G RedCap terminal's battery power.

[0054] The 5G RedCap terminal employs the 5G inter-network roaming selection method of this application. By recording inter-network roaming information in a table for each cell of the home network, the number of times the 5G RedCap terminal attempts to access ordinary 5G cells of the visited network is reduced from a first aspect (steps S2-S4). Furthermore, by using a timer constraint, the number of times the 5G RedCap terminal attempts to access ordinary 5G cells of the visited network is reduced from a second aspect (step S5). Therefore, this application reduces the overall number of network searches by the 5G RedCap terminal, allowing it to remain in a service-available state for a longer period and reducing its power consumption.

[0055] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for selecting a network when a RedCap terminal roams across different networks, characterized in that, Includes the following steps; Step S1: Each time a 5G RedCap terminal initiates a 5G inter-network roaming from a cell in its home network to a 5G cell in the visited network, it records the inter-network roaming information table of that cell in its home network; the inter-network roaming information table of each cell in the home network records: inter-network roaming support flag, 5G inter-network roaming failure location, and offset. When a 5G RedCap terminal attempts to perform 5G inter-network roaming at one or more locations within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal finds at least one 5G cell in the visited network that allows the 5G RedCap terminal to access at at least one of the attempted locations, it indicates that the home network cell supports 5G RedCap terminal 5G inter-network roaming, and the "Support Inter-network Roaming Flag" is set to 1; if the 5G RedCap terminal finds that all 5G cells in the visited network reject the 5G RedCap terminal's access at all the attempted locations, it indicates that the home network cell does not support 5G RedCap terminal 5G inter-network roaming, and the "Support Inter-network Roaming Flag" is set to 0. When a 5G RedCap terminal attempts to access a 5G cell in a visited network, it obtains an indication from the System Information Block (SIB) message sent by the 5G cell in the visited network as to whether the 5G cell supports access for the 5G RedCap terminal. Step S2: When the 5G RedCap terminal is about to initiate 5G inter-network roaming from its current location, the 5G RedCap terminal determines whether the current serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table. If so, proceed to step S3; If not, the 5G RedCap terminal normally initiates 5G inter-network roaming and returns to step S1; Step S3: The 5G RedCap terminal determines whether its current location is within the coverage area of ​​a "5G inter-network roaming failure location" plus "offset" in the inter-network roaming information table of the current serving cell of its home network; If so, proceed to step S4; If not, the 5G RedCap terminal normally initiates 5G inter-network roaming and returns to step S1; Step S4: The 5G RedCap terminal reads the "Support Inter-Network Roaming Flag" from the inter-network roaming information table of the current serving cell of its home network; If the value of "Support inter-network roaming flag" indicates that the current serving cell of the home network supports 5G RedCap terminal to perform 5G inter-network roaming, then the 5G RedCap terminal can normally initiate 5G inter-network roaming and return to step S1. If the value of "Support inter-network roaming flag" indicates that the current serving cell of the home network does not support 5G RedCap terminals to roam in 5G inter-networks, proceed to step S5; Step S5: The 5G RedCap terminal starts a timer; Before the timer expires, the 5G RedCap terminal will not initiate 5G inter-network roaming at its current location; After the timer expired, the 5G RedCap terminal re-initiated 5G inter-network roaming at its current location.

2. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, In step S1, when a 5G RedCap terminal attempts to perform 5G inter-network roaming within the coverage area of ​​a cell in its home network, if the 5G RedCap terminal finds that all 5G cells in the visited network refuse access at a certain location, it indicates that the 5G RedCap terminal's 5G inter-network roaming at that location has failed, and this location is recorded as the 5G inter-network roaming failure location. In the inter-network roaming information table of a cell in the home network, there are one or more 5G inter-network roaming failure locations.

3. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, In step S1, the offset is the coverage radius of each "5G inter-network roaming failure location"; when there are multiple "5G inter-network roaming failure locations", there are also multiple offsets of the same kind, or the offset is the same one.

4. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, In step S1, the inter-network roaming information table is recorded on a per-cell basis within the home network; if the 5G RedCap terminal initiates 5G inter-network roaming in multiple cells of the home network, the inter-network roaming information table for the multiple cells of the home network is recorded.

5. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, In step S1, if the cell of the home network of the 5G RedCap terminal already has an inter-network roaming information table, then the inter-network roaming information table of the cell of the home network is updated.

6. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, In step S5, before the timer expires, the 5G RedCap terminal removes the EPLMN (Equivalent Public Land Mobile Network) corresponding to the visited network from its local EPLMN list. After the timer expires, the 5G RedCap terminal will re-add the EPLMN corresponding to the visited network to its local EPLMN list.

7. The method for selecting a network for RedCap terminal roaming across different networks according to claim 1, characterized in that, The method also includes: the 5G RedCap terminal periodically deleting the "5G inter-network roaming failure location" from the inter-network roaming information table of all cells in the home network.

8. A device for RedCap terminal roaming and network selection, characterized in that, It includes an information table recording unit, an information table query unit, a location determination unit, a flag reading unit, and a timing and processing unit; The information table recording unit is used to record the inter-network roaming information table of the home network cell each time a 5G RedCap terminal initiates 5G inter-network roaming from a cell in the home network to a 5G cell in the visited network. The inter-network roaming information table of each cell in the home network records: inter-network roaming support flag, 5G inter-network roaming failure location, and offset. When a 5G RedCap terminal attempts 5G inter-network roaming at one or more locations within the coverage area of ​​a cell in the home network, if the 5G RedCap terminal finds at least one 5G cell in the visited network that allows the 5G RedCap terminal to access at at least one of the attempted locations, it indicates that the home network cell supports 5G RedCap terminal 5G inter-network roaming, and the "inter-network roaming support flag" is set to 1. If the 5G RedCap terminal finds that all 5G cells in the visited network refuse access at all the attempted locations, it indicates that the home network cell does not support 5G RedCap terminal 5G inter-network roaming, and the "inter-network roaming support flag" is set to 0. When a RedCap terminal attempts to access a 5G cell in a visited network, it obtains an indication from the System Information Block (SIB) message sent by the 5G cell in the visited network as to whether the 5G cell supports access by the RedCap terminal. The information table query unit is used to determine whether the current serving cell of the home network to which the current location belongs has a recorded inter-network roaming information table when the 5G RedCap terminal is preparing to initiate 5G inter-network roaming from the current location; if so, the subsequent processing is handled by the location determination unit. The location determination unit is used to determine whether the current location of the 5G RedCap terminal is within the coverage area of ​​a certain "5G inter-network roaming failure location" superimposed with "offset" in the inter-network roaming information table of the current serving cell of its home network; if so, it is subsequently handed over to the flag reading unit for processing. The flag reading unit is used to read the "Support Inter-network Roaming Flag" in the inter-network roaming information table of the current serving cell of the home network; if the value of the "Support Inter-network Roaming Flag" indicates that the current serving cell of the home network does not support 5G RedCap terminals to roam in 5G, it will be handed over to the timing unit for processing. The timing and processing unit is used to start a timer; before the timer expires, the 5G RedCap terminal is prohibited from initiating 5G inter-network roaming at the current location; after the timer expires, the 5G RedCap terminal is allowed to initiate 5G inter-network roaming at the current location again.

Images