Method for terminal to select NTN or TN serving cell and corresponding terminal

Abstract

The invention discloses a method for a terminal to select an NTN or TN serving cell. And the terminal residing in the NTN cell judges whether the network resource of the current residing NTN cell can meet the rate requirement of the upper layer service. And if not, the terminal calculates the distance between the current GNSS position and the recorded GNSS position in each ternary data group, and takes the TN cell in the ternary data group of which each calculated distance is smaller than the distance threshold in the corresponding ternary data group as a target TN cell, and subsequently performs signal search on frequency point information of the target TN cell and tries to reside. According to the method and the device, the terminal can work in the TN cell which ensures the service quality as much as possible, and the use experience of the terminal in the overlapping area of the TN cell and the NTN cell is improved.

Description

Technical Field

[0001] The present application relates to a method for a 5G terminal (UE, user equipment) to select a service cell. Background Art

[0002] With the development of aerospace technology, 5G mobile communication systems have begun to support services provided by commercial or dedicated satellites. The 3GPP Rel-17 protocol supports 5G non-terrestrial networks (NTN) for the first time, which is a technology designed to connect 5G user terminals on or near the surface of the earth to non-terrestrial base stations on satellites.

[0003] At present, NTN communication has some insurmountable shortcomings. First, due to the high orbit of the satellite, the data transmission delay between the terminal and the satellite is large, and the probability of packet loss will increase significantly because the number of data retransmissions cannot be guaranteed. Second, the coverage of NTN cells is larger, and the capacity of each NTN cell is limited, so the resources that can be allocated to each terminal are likely to be limited, and the requirements of high-speed services cannot be met. These shortcomings will have an adverse impact on services with high speed requirements and strong real-time performance (such as video calls, video conferencing, etc.), affecting user experience.

[0004] See also Figure 1 , when the 5G terminal is in the overlapping coverage area of ​​the NTN cell and the TN (Terrestrial Network) cell. If the service cell can be selected according to the terminal's own business needs - for example, when the terminal has high-speed business needs, it can actively search and select the TN cell as the service cell, a better user experience can be achieved. At present, some documents have disclosed methods for 5G terminals to select NTN or TN service cells. These methods usually require modification of existing mobile communication protocols, or require network-side dominant configuration and terminal execution, which are not conducive to promotion and application in existing 5G mobile communication systems. Summary of the invention

[0005] The technical problem to be solved by this application is how to allow 5G terminals to select a service cell between NTN or TN cells according to their own business needs without modifying the mobile communication protocol and without the need for network participation.

[0006] In order to solve the above technical problems, the present application proposes a method for a terminal to select an NTN or TN service cell, comprising the following steps. Step S1: When the terminal leaves the TN cell and resides in an NTN cell, the terminal records the frequency information of the TN cell left, the global navigation satellite system GNSS position information of the terminal at this time, and a distance threshold as a triple data group of {frequency information of the TN cell, GNSS position information, distance threshold}. Step S2: When the terminal resides in the NTN cell, it determines whether the network resources of the currently residing NTN cell can meet the rate requirements of the upper-layer service. If yes, the terminal continues to work in the currently residing NTN cell. If not, proceed to step S3. Step S3: The terminal calculates the distance between the current GNSS position and the GNSS position in each recorded triple data group, and compares each calculated distance with the distance threshold in the corresponding triple data group. If the distance between the current GNSS position of the terminal and the GNSS position in a certain recorded ternary data group is less than the distance threshold in the ternary data group, the terminal selects the TN cell in the ternary data group as the target TN cell, and then proceeds to step S4. If the distance between the current GNSS position of the terminal and the GNSS positions in all the recorded ternary data groups is greater than the distance threshold in the corresponding ternary data group, the terminal continues to work in the currently residing NTN cell. Step S4: The terminal performs a signal search for the frequency information of the target TN cell and attempts to reside. If the terminal successfully resides in the target TN cell, proceed to step S5. If the terminal fails to reside in the target TN cell, the terminal returns to the currently residing NTN cell to work, and reduces the value of the distance threshold in the ternary data group recorded in the target TN cell, and returns to step S3. Step S5: The terminal performs a high-speed service in the target TN cell, starts a timer, and adds an offset to the received signal strength value of the target TN cell; the received signal strength offset is used to increase the received signal strength measurement value of the target TN cell. Step S6: The terminal determines whether the service required by the high rate has ended, and further determines whether the timer has timed out if the service required by the high rate has not ended. If the service required by the high rate has not ended and the timer has not timed out, the terminal keeps the received signal strength offset unchanged. If the service required by the high rate has not ended and the timer has timed out, the terminal sets the received signal strength offset to 0. If the service required by the high rate has ended, the terminal resets the timer to zero and sets the received signal strength offset to 0.

[0007] Furthermore, in step S1, the terminal leaves the TN cell and resides in an NTN cell, including any one of the following situations. The 5G terminal leaves the TN cell and resides in the NTN cell by cell switching. The 5G terminal leaves the TN cell and resides in the NTN cell by cell reselection. The 5G terminal residing in the TN cell manually searches for the NTN cell, leaves the TN cell, and resides in the NTN cell.

[0008] Furthermore, in step S1, each triple data group represents that the coverage range of the TN cell includes a range with the GNSS position therein as the center and the distance threshold therein as the radius.

[0009] Furthermore, in the step S1, the value of the distance threshold in each triple data group is positively correlated with the signal strength of the TN cell received by the terminal when the terminal leaves the TN cell in the triple data group.

[0010] Furthermore, in the step S1, the signal strength of each TN cell received by the terminal when leaving the TN cell is measured by the reference signal received power RSRP value. If the RSRP value of the TN cell is greater than -90dBm, the initialization value of the distance threshold corresponding to the TN cell is 200. If -100dBm<the RSRP value of the TN cell≤-90dBm, the initialization value of the distance threshold corresponding to the TN cell is 100. If the RSRP value of the TN cell is ≤-100dBm, the initialization value of the distance threshold corresponding to the TN cell is 50.

[0011] Furthermore, in step S3, if the distance between the current GNSS position of the terminal and the GNSS positions in the multiple recorded ternary data groups is less than the distance threshold in the corresponding ternary data group, the terminal selects the TN cell in these ternary data groups as the target TN cell. At this time, there are multiple target TN cells, and then enters step S4.

[0012] Furthermore, in step S4, if there are multiple target TN cells, the terminal searches for signals of the frequency information of the target TN cells and attempts to reside therein in ascending order of the distance between the current GNSS position and the GNSS position in the ternary data group corresponding to the target TN cells.

[0013] Furthermore, in step S4, if the terminal successfully camps on the target TN cell, the terminal records the frequency information of the target TN cell and the GNSS position information of the terminal at this time to update the ternary data group recorded in the target TN cell.

[0014] Furthermore, in step S4, if the distance between the current GNSS position of the terminal and the GNSS position in the ternary data group recorded by the target TN cell is within 50 meters, the operation of updating the ternary data group recorded by the target TN cell is omitted.

[0015] The present application also proposes a terminal for selecting an NTN or TN service cell, including a ternary data group recording unit, a service rate judgment unit, a distance calculation comparison unit, a TN cell resident unit, an offset setting unit, and an end optimization unit. The ternary data group recording unit is used to record the frequency information of the TN cell left by the terminal, the GNSS position information of the terminal at this time, and a distance threshold as a ternary data group of {frequency information of the TN cell, GNSS position information, and distance threshold} when the terminal leaves the TN cell and resides in an NTN cell. The service rate judgment unit is used to judge whether the network resources of the NTN cell where the terminal is currently residing can meet the rate requirements of the upper layer services of the terminal when the terminal resides in the NTN cell. The distance calculation and comparison unit is used to calculate the distance between the current GNSS position of the terminal and the GNSS position in each recorded ternary data group when the network resources of the NTN cell where the terminal currently resides cannot meet the rate requirements of the upper layer service of the terminal, and compare each calculated distance with the distance threshold in the corresponding ternary data group; if the distance between the current GNSS position of the terminal and the GNSS position in one or more recorded ternary data groups is less than the distance threshold in the corresponding ternary data group, the TN cell in the one or more ternary data groups is used as the target TN cell. The TN cell resident unit is used to perform signal search and attempt to reside on the frequency information of the target TN cell, and reduce the value of the distance threshold in the ternary data group recorded by the target TN cell when the terminal fails to reside in the target TN cell. The offset setting unit is used to perform the service with high rate requirements of the terminal in the target TN cell when the terminal successfully resides in the target TN cell, and start the timer to increase the offset for the received signal strength value of the target TN cell; the received signal strength offset is used to increase the received signal strength measurement value of the target TN cell. The termination optimization unit is used to determine whether the service required by the terminal at a high rate has ended, and to further determine whether the timer has timed out if the service required by the terminal at a high rate has not ended; if the service required by the terminal at a high rate has not ended and the timer has not timed out, the received signal strength offset is kept unchanged; if the service required by the terminal at a high rate has not ended and the timer has timed out, the received signal strength offset is set to 0; if the service required by the terminal at a high rate has ended, the timer is reset to zero and the received signal strength offset is set to 0.

[0016] The technical effect achieved by the present application is: without changing the mobile communication protocol, a method for intelligently selecting a TN cell or an NTN cell that is completely implemented by the terminal side is proposed. The terminal in the NTN cell autonomously searches for the TN cell according to the service requirements and the historical records of the TN cell, so that the terminal can work in the TN cell that better guarantees the service quality as much as possible. The present application can improve the user experience of the terminal in the overlapping area of ​​the TN cell and the NTN cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overlapping coverage area of ​​NTN cells and TN cells.

[0018] Figure 2 It is a flowchart of the method for a terminal to select an NTN or TN service cell proposed in this application.

[0019] Figure 3 It is a schematic diagram of the structure of a terminal for selecting an NTN or TN service cell proposed in this application.

[0020] Explanation of the reference numerals in the figure: triple data group recording unit 1, service rate determination unit 2, distance calculation and comparison unit 3, TN cell resident unit 4, offset setting unit 5, end optimization unit 6. DETAILED DESCRIPTION

[0021] See also Figure 2 The method for a terminal to select an NTN or TN service cell proposed in this application includes the following steps.

[0022] Step S1: When the terminal leaves the TN cell and resides in an NTN cell, including the cell switching mode, cell reselection mode, manual search for NTN cell mode, etc., the terminal records the frequency information of the TN cell left (i.e., the last TN cell resided before accessing the NTN cell), the GNSS (Global Navigation Satellite System) position information of the terminal at this time, and a distance threshold as a three-dimensional data group of {frequency information of the TN cell, GNSS position information, and distance threshold}. Each three-dimensional data group represents: the coverage range of the TN cell includes a range with the GNSS position as the center and the distance threshold as the radius.

[0023] The value of the distance threshold in each ternary data group is positively correlated with the signal strength of the TN cell received by the terminal when it leaves the TN cell. The greater the signal strength of the TN cell received by the terminal when it leaves the TN cell, the closer the terminal is to the TN cell, and the larger the value of the distance threshold. Vice versa, the smaller the signal strength of the TN cell received by the terminal when it leaves the TN cell, the farther the terminal is from the TN cell, and the smaller the value of the distance threshold. It should be noted that the values ​​of the distance threshold in each ternary data group may be the same or different.

[0024] As an example, the signal strength of each TN cell received by the terminal when leaving the TN cell is measured by the RSRP (Reference Signal Received Power) value. For example, if the RSRP value of the TN cell is greater than -90dBm, the initialization value of the distance threshold corresponding to the TN cell is 200. If -100dBm<the RSRP value of the TN cell≤-90dBm, the initialization value of the distance threshold corresponding to the TN cell is 100. If the RSRP value of the TN cell is ≤-100dBm, the initialization value of the distance threshold corresponding to the TN cell is 50.

[0025] Step S2: When the terminal is working (i.e., residing) in the NTN cell, it is determined whether the network resources (e.g., data upload and download rates, and the number of RBs allocated by the network) of the currently residing NTN cell can meet the data transmission rate requirements of upper layer services (e.g., voice calls, video calls, video conferences, games, etc.), where RB stands for resource block.

[0026] If the terminal determines that the network resources of the NTN cell where the terminal resides cannot meet the rate requirement of the upper layer service, the process proceeds to step S3.

[0027] If the terminal determines that the network resources of the NTN cell where it resides can meet the rate requirement of the upper layer service, the terminal continues to work in the currently residing NTN cell and returns to step S2.

[0028] Step S3: the terminal calculates the distance between the current GNSS position and the GNSS position in each recorded triplet data group, and compares each calculated distance with a distance threshold in the corresponding triplet data group.

[0029] If the distance between the current GNSS position of the terminal and the GNSS position in a recorded ternary data group is less than the distance threshold in the ternary data group, this indicates that the terminal is currently within the coverage of the recorded TN cell. The terminal selects the TN cell in the ternary data group as the target TN cell. At this time, there is only one target TN cell, and then proceeds to step S4.

[0030] If the distance between the current GNSS position of the terminal and the GNSS position in the multiple recorded ternary data groups is less than the distance threshold in the corresponding ternary data group, this indicates that the terminal is currently within the coverage of the multiple recorded TN cells. The terminal selects the TN cells in these ternary data groups as the target TN cells. At this time, there are multiple target TN cells, and then proceeds to step S4.

[0031] If the distances between the current GNSS position of the terminal and the GNSS positions in all the recorded ternary data groups are greater than the distance thresholds in the corresponding ternary data groups, this indicates that the terminal is not currently within the coverage of any recorded TN cell. The terminal continues to operate in the currently located NTN cell and returns to step S2.

[0032] If the distance between the current GNSS position of the terminal and the GNSS position in a certain recorded triplet data group is equal to the distance threshold in the triplet data group, any of the above judgment situations may be incorporated.

[0033] Step S4: The terminal performs a signal search for the frequency information of the target TN cell and attempts to reside in it. If there are multiple target TN cells, the terminal performs a signal search for the frequency information of the target TN cell and attempts to reside in the order of the distance between the current GNSS position and the GNSS position in the ternary data group corresponding to the target TN cell from small to large.

[0034] If the terminal successfully resides in the target TN cell, go to step S5. Preferably, at this time, the terminal records the frequency information of the target TN cell and the GNSS position information of the terminal at this time to update the ternary data group recorded in the target TN cell. The value of the distance threshold is positively correlated with the signal strength of the target TN cell received when the terminal accesses the target TN cell. If the distance between the GNSS position of the terminal at this time and the GNSS position in the ternary data group recorded in the target TN cell is very small, for example, within 50 meters, the operation of updating the ternary data group recorded in the target TN cell can be omitted.

[0035] If the terminal fails to reside in the target TN cell, the terminal returns to the currently residing NTN cell to work, and reduces the value of the distance threshold in the ternary data group recorded in the target TN cell, and returns to step S3.

[0036] Step S5: the terminal performs a service requiring a high rate in the target TN cell, starts a timer TN_Timer, and increases an offset TN_offset to the received signal strength value of the target TN cell.

[0037] The received signal strength offset TN_offset is used to increase the received signal strength measurement value of the target TN cell, which is generally a positive number, and is used to avoid ping-pong switching of the terminal between the NTN cell and the TN cell. QTNcellRSRP = Qrxlevelmeas + TN_offset, where QTNcellRSRP represents the RSRP value used by the terminal when judging the measurement event threshold, and Qrxlevelmeas represents the received level (RX level) value of the cell, that is, the received signal strength measurement value. For example, the received signal strength offset TN_offset is set to 8; the network sends an A2 measurement event, requiring the measurement report of the A2 event to be reported when the quality of the serving cell is less than the threshold of -80dBm. At this time, the RSRP value of the target TN cell measured by the terminal is -85dBm. If the received signal strength offset TN_offset is not used, -85dBm is less than the threshold of -80dBm, the terminal will report the measurement report of the A2 event, and may subsequently trigger a switch to the NTN cell. If the received signal strength offset TN_offset is used, QTNcellRSRP=-85+8=-78dBm, -78dBm is greater than the threshold -80dBm, the terminal does not report the measurement report of the A2 event, and subsequent possible handover to the NTN cell will not be triggered, thereby reducing the possibility of ping-pong handover.

[0038] Step S6: The terminal determines whether the service requiring a high rate has ended, and further determines whether the timer TN_Timer has timed out if the service requiring a high rate has not ended.

[0039] If the service requiring a high rate has not ended and the timer TN_Timer has not timed out, the terminal keeps the received signal strength offset TN_offset unchanged.

[0040] If the service requiring high rate is not finished and the timer TN_Timer times out, the terminal sets the received signal strength offset TN_offset to 0. At this point, the optimization algorithm represented by the entire method ends, and the terminal continues to work on subsequent services requiring high rate according to the conventional algorithm.

[0041] If the service requiring a high rate has ended, the terminal resets the timer TN_Timer to zero and sets the received signal strength offset TN_offset to 0. At this point, the optimization algorithm represented by the entire method ends.

[0042] See also Figure 3 The terminal for selecting NTN or TN service cell proposed in this application includes a three-dimensional data group recording unit 1, a service rate judgment unit 2, a distance calculation and comparison unit 3, a TN cell resident unit 4, an offset setting unit 5, and an end optimization unit 6. Figure 3 The terminals shown correspond to Figure 2 The method shown.

[0043] The triple data group recording unit 1 is used to record the frequency information of the TN cell left by the terminal, the GNSS position information of the terminal at this time, and a distance threshold as the triple data group of {frequency information of the TN cell, GNSS position information, and distance threshold} when the terminal leaves the TN cell and resides in an NTN cell.

[0044] The service rate determination unit 2 is used to determine whether the network resources of the NTN cell where the terminal currently resides can meet the rate requirement of the upper layer service of the terminal when the terminal resides in the NTN cell.

[0045] The distance calculation and comparison unit 3 is used to calculate the distance between the current GNSS position of the terminal and the GNSS position in each recorded triple data group when the network resources of the NTN cell where the terminal currently resides cannot meet the rate requirement of the upper layer service of the terminal, and compare each calculated distance with the distance threshold in the corresponding triple data group. If the distance between the current GNSS position of the terminal and the GNSS position in one or more recorded triple data groups is less than the distance threshold in the corresponding triple data group, the TN cell in the one or more triple data groups is used as the target TN cell.

[0046] The TN cell resident unit 4 is used to perform signal search on the frequency information of the target TN cell and attempt to reside in the target TN cell, and reduce the value of the distance threshold in the ternary data group recorded in the target TN cell when the terminal fails to reside in the target TN cell.

[0047] The offset setting unit 5 is used to perform a high-rate service of the terminal in the target TN cell when the terminal successfully resides in the target TN cell, and start a timer to increase an offset for the received signal strength value of the target TN cell. The received signal strength offset is used to increase the received signal strength measurement value of the target TN cell.

[0048] The end optimization unit 6 is used to determine whether the service required by the terminal at a high rate has ended, and further determine whether the timer has timed out if the service required by the terminal at a high rate has not ended. If the service required by the terminal at a high rate has not ended and the timer has not timed out, the received signal strength offset is kept unchanged. If the service required by the terminal at a high rate has not ended and the timer has timed out, the received signal strength offset is set to 0. If the service required by the terminal at a high rate has ended, the timer is reset to zero and the received signal strength offset is set to 0.

[0049] Compared with the prior art, the method proposed in this application for the terminal to select the NTN or TN service cell can better match the needs of services with high rate requirements and strong real-time performance. When services with high rate requirements and strong real-time performance appear, the terminal is allowed to preferentially access the TN cell with large capacity and a small number of resident terminals. This application triggers the reselection from the NTN cell to the TN cell according to the service needs (step S2), determines the location of the TN cell through the ternary data group of the terminal history record and the current GNSS information of the terminal (step S3), and completes the reselection from the NTN cell to the TN cell.

[0050] This application does not modify the existing mobile communication protocol, does not rely on any network-side configuration, and is completely implemented on the terminal side without the participation of the network side, so it is very suitable for promotion and application in the existing 5G mobile communication system. This application also does not add any interactive signaling between the terminal and the network, and will not affect the network and other terminals.

[0051] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should all be included in the protection scope of the present application.

Claims

1. A method for a terminal to select an NTN or TN service cell, characterized in that: The method comprises the following steps: Step S1: When the terminal leaves the TN cell and resides in an NTN cell, the terminal records the frequency information of the TN cell left, the GNSS position information of the terminal at this time, and a distance threshold as a triple data set of {frequency information of the TN cell, GNSS position information, and distance threshold}; Step S2: When the terminal resides in the NTN cell, it is determined whether the network resources of the currently residing NTN cell can meet the rate requirements of the upper layer service; If yes, the terminal continues to work in the currently residing NTN cell; If not, proceed to step S3; Step S3: the terminal calculates the distance between the current GNSS position and the GNSS position in each recorded triplet data group, and compares each calculated distance with the distance threshold in the corresponding triplet data group; If the distance between the current GNSS position of the terminal and the GNSS position in a recorded ternary data group is less than the distance threshold in the ternary data group, the terminal selects the TN cell in the ternary data group as the target TN cell, and then proceeds to step S4; If the distances between the current GNSS position of the terminal and the GNSS positions in all the recorded ternary data groups are greater than the distance thresholds in the corresponding ternary data groups, the terminal continues to work in the currently residing NTN cell; Step S4: the terminal performs a signal search on the frequency information of the target TN cell and attempts to reside there; If the terminal successfully camps on the target TN cell, proceed to step S5; If the terminal fails to reside in the target TN cell, the terminal returns to the currently residing NTN cell to work, and reduces the value of the distance threshold in the three-dimensional data group recorded in the target TN cell, and returns to step S3; Step S5: the terminal performs a service requiring a high rate in the target TN cell, starts a timer, and adds an offset to the received signal strength value of the target TN cell; the received signal strength offset is used to increase the received signal strength measurement value of the target TN cell; Step S6: The terminal determines whether the service requiring a high rate has ended, and further determines whether the timer has timed out if the service requiring a high rate has not ended. If the service requiring a high rate has not ended and the timer has not timed out, the terminal keeps the received signal strength offset unchanged; If the service requiring a high rate has not ended and the timer has timed out, the terminal sets the received signal strength offset to 0; If the service requiring a high rate has ended, the terminal resets the timer to zero and sets the received signal strength offset to zero.

2. The method for selecting an NTN or TN service cell by a terminal according to claim 1, wherein: In the step S1, the terminal leaves the TN cell and resides in an NTN cell, including any of the following situations: The 5G terminal leaves the TN cell and stays in the NTN cell by cell switching; The 5G terminal leaves the TN cell and resides in the NTN cell by cell reselection; The 5G terminal stationed in the TN cell manually searches for the NTN cell, leaves the TN cell, and stations in the NTN cell.

3. The method for selecting an NTN or TN service cell by a terminal according to claim 1, characterized in that: In step S1, each triple data group represents that the coverage range of the TN cell includes a range with the GNSS position therein as the center and the distance threshold therein as the radius.

4. The method for selecting an NTN or TN service cell by a terminal according to claim 1, characterized in that: In the step S1, the value of the distance threshold in each triple data group is positively correlated with the signal strength of the TN cell received by the terminal when the terminal leaves the TN cell in the triple data group.

5. The method for selecting an NTN or TN service cell by a terminal according to claim 1, characterized in that: In the step S1, the signal strength of each TN cell received by the terminal when leaving the TN cell is measured by a reference signal received power RSRP value; If the RSRP value of the TN cell is greater than -90dBm, the initialization value of the distance threshold corresponding to the TN cell is 200; If -100dBm<the RSRP value of the TN cell≤-90dBm, the initialization value of the distance threshold corresponding to the TN cell is 100; If the RSRP value of the TN cell is ≤-100dBm, the initialization value of the distance threshold corresponding to the TN cell is 50.

6. The method for selecting an NTN or TN service cell by a terminal according to claim 1, characterized in that: In step S3, if the distance between the current GNSS position of the terminal and the GNSS positions in the multiple recorded ternary data groups is less than the distance threshold in the corresponding ternary data group, the terminal selects the TN cell in these ternary data groups as the target TN cell. At this time, there are multiple target TN cells, and then enters step S4.

7. The method for selecting an NTN or TN service cell by a terminal according to claim 6, characterized in that: In step S4, if there are multiple target TN cells, the terminal searches for signals of the frequency information of the target TN cells in ascending order of the distance between the current GNSS position and the GNSS position in the ternary data group corresponding to the target TN cells and tries to reside there.

8. The method for selecting an NTN or TN service cell by a terminal according to claim 1, characterized in that: In the step S4, if the terminal successfully camps on the target TN cell, the terminal records the frequency information of the target TN cell and the GNSS position information of the terminal at this time to update the ternary data group recorded in the target TN cell.

9. The method for selecting an NTN or TN service cell by a terminal according to claim 8, characterized in that: In the step S4, if the distance between the GNSS position of the terminal at this time and the GNSS position in the ternary data group recorded in the target TN cell is within 50 meters, the operation of updating the ternary data group recorded in the target TN cell is omitted.

10. A terminal for selecting an NTN or TN service cell, characterized in that: It includes a three-dimensional data group recording unit, a service rate judgment unit, a distance calculation and comparison unit, a TN cell resident unit, an offset setting unit, and an end optimization unit; The triple data group recording unit is used to record the frequency information of the TN cell left by the terminal, the GNSS position information of the terminal at this time, and a distance threshold as a triple data group of {frequency information of the TN cell, GNSS position information, and distance threshold} when the terminal leaves the TN cell and resides in an NTN cell; The service rate determination unit is used to determine whether the network resources of the NTN cell where the terminal currently resides can meet the rate requirements of the upper layer service of the terminal when the terminal resides in the NTN cell; The distance calculation and comparison unit is used to calculate the distance between the current GNSS position of the terminal and the GNSS position in each recorded triple data group when the network resources of the NTN cell where the terminal currently resides cannot meet the rate requirement of the upper layer service of the terminal, and compare each calculated distance with the distance threshold in the corresponding triple data group; If the distance between the current GNSS position of the terminal and the GNSS position in the one or more recorded triplet data groups is less than the distance threshold in the corresponding triplet data group, taking the TN cell in the one or more triplet data groups as the target TN cell; The TN cell resident unit is used to perform signal search on the frequency information of the target TN cell and attempt to reside in the target TN cell, and reduce the value of the distance threshold in the ternary data group recorded by the target TN cell when the terminal fails to reside in the target TN cell; The offset setting unit is used to perform a high-rate service required by the terminal in the target TN cell when the terminal successfully camps on the target TN cell, and start a timer to increase an offset for a received signal strength value of the target TN cell; the received signal strength offset is used to increase a received signal strength measurement value of the target TN cell; The termination optimization unit is used to determine whether the service required by the terminal at a high rate has ended, and to further determine whether the timer has timed out if the service required by the terminal at a high rate has not ended; if the service required by the terminal at a high rate has not ended and the timer has not timed out, the received signal strength offset is kept unchanged; if the service required by the terminal at a high rate has not ended and the timer has timed out, the received signal strength offset is set to 0; if the service required by the terminal at a high rate has ended, the timer is reset to zero and the received signal strength offset is set to 0.

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