Method and device for auxiliary selection of NTN cell based on ephemeris information

Abstract

The invention discloses a method for auxiliary selection of an NTN cell based on ephemeris information. And the terminal calculates and obtains all available NTN cell frequency point lists C1 or current effective NTN cell frequency point lists C2 according to the ephemeris information, and adds the available NTN cell frequency point lists C1 or the current effective NTN cell frequency point lists C2 into a historical frequency point list. And the terminal executes network scanning according to the network searching parameters to obtain a candidate frequency point list. And the terminal sequentially selects each candidate frequency point from the candidate frequency point list, tries to detect and synchronize the cell corresponding to the candidate frequency point, and obtains the MIB of the cell. And the terminal obtains the SIB1 of the cell. And the terminal selects to reside in the cell. And the terminal acquires residual system information of the cell and judges whether the cell is an NTN cell. And if the cell is the NTN cell, the terminal acquires the SIB19 of the NTN cell. And the terminal successfully resides in the cell. According to the invention, the ephemeris information assists the terminal in accelerating the network search and selection process of the NTN cell, and the capability of the terminal in quickly residing and accessing the NTN cell is enhanced.

Description

Technical Field

[0001] This application relates to a mobile communication technology, and particularly to a method for NTN (Non-Terrestrial Networks) cell selection in a 5G mobile communication system. Background Art

[0002] Cell selection refers to the process in which a UE (user equipment, i.e., a terminal) searches for available cells and selects a suitable cell to camp on when it powers on or enters the RRC idle state (RRC_IDLE).

[0003] Please refer to Figure 1 , the existing cell selection process includes the following steps.

[0004] Step S11: The terminal performs network scanning according to the network search parameters to obtain a list of candidate frequency points. Usually, the list of candidate frequency points is sorted in descending order of the received signal strength of each candidate frequency point.

[0005] Step S12: The terminal sequentially selects each candidate frequency point from the list of candidate frequency points, attempts to detect and synchronize with the cell corresponding to the candidate frequency point, and obtains the MIB (master indication block) of the cell. If successful, go to step S13. If failed, the terminal selects the next candidate frequency point from the list of candidate frequency points and repeats step S12.

[0006] Step S13: The terminal obtains the SIB1 (system information block type 1) of the cell.

[0007] Step S14: The terminal selects to camp on this cell.

[0008] Step S15: The terminal obtains the remaining system information of this cell.

[0009] Step S16: The terminal successfully camps on this cell. The cell selection process ends, and the terminal can perform normal access and services.

[0010] The 5G mobile communication network introduces NTN, mainly referring to satellite communication networks. NTN can be used to provide network services in areas where TN (Terrestrial Networks) cannot cover or has weak coverage.

[0011] In the scenario where NTN and TN coexist, it is necessary to consider the time and complexity of network search to improve the user experience. Different from TN cells, due to the high-speed satellite movement, the coverage area of NTN cells will change rapidly, increasing the complexity of cell selection. Correspondingly, the 5G NR mobile communication system includes ephemeris information, a parameter unique to NTN, in SIB19 (System Information Block Type 19), indicating the short-term law of satellite movement. Ephemeris is a table describing the precise position or trajectory of celestial bodies over time. The prior art mainly focuses on how to use ephemeris information to divide the priority of cell reselection and does not involve using ephemeris information to assist cell selection. Summary of the Invention

[0012] The technical problem to be solved by this application is: how to use the ephemeris information previously saved by the terminal to assist the terminal to detect and access NTN cells faster.

[0013] To solve the above technical problem, this application proposes a method for assisting in selecting NTN cells based on ephemeris information, including the following steps. Step S21: The terminal calculates and obtains a list C1 of all available NTN cell frequencies or a list C2 of currently valid NTN cell frequencies according to the ephemeris information and adds them to the historical frequency list as part of the network search parameters. Step S22: The terminal performs a network scan according to the network search parameters to obtain a list of candidate frequencies. Step S23: The terminal sequentially selects each candidate frequency from the list of candidate frequencies, attempts to detect and synchronize with the cell corresponding to the candidate frequency, and obtains the MIB of the cell; if successful, go to step S24; if failed, the terminal selects the next candidate frequency from the list of candidate frequencies and repeats step S23. Step S24: The terminal obtains the SIB1 of the cell. Step S25: The terminal selects to camp on the cell. Step S26: The terminal obtains the remaining system information of the cell and determines whether the cell is an NTN cell. If the cell is not an NTN cell, go to step S27. If the cell is an NTN cell, the terminal obtains the SIB19 of the NTN cell; if the SIB19 of the NTN cell indicates that the service time of the NTN cell has not ended, go to step S27; if the SIB19 of the NTN cell indicates that the service time of the NTN cell has ended, the terminal selects the next candidate frequency from the list of candidate frequencies and repeats step S23. Step S27: The terminal successfully camps on the cell.

[0014] Further, in the step S21, the terminal calculates and obtains a list C1 of all available NTN cell frequencies according to the ephemeris information, and adds the list C1 to the historical frequency list as part of the network search parameters. Alternatively, in the step S21, the terminal calculates and obtains a list C1 of all available NTN cell frequencies according to the ephemeris information, then further calculates and obtains a currently valid NTN frequency list C2, and adds the list C2 to the historical frequency list as part of the network search parameters.

[0015] Further, in the step S21, the terminal places all available NTN cell frequencies recorded in the list C1 at the front of the historical frequency list, or sets a high priority for all available NTN cell frequencies recorded in the list C1. Alternatively, in the step S21, the terminal places the currently valid NTN cell frequencies recorded in the list C2 at the front of the historical frequency list B, or sets a high priority for the currently valid NTN cell frequencies recorded in the list C2.

[0016] Further, in the step S21, the terminal inserts the currently valid NTN cell frequencies recorded in the list C2 into the historical frequency list multiple times.

[0017] Further, in the step S21, the terminal also obtains the list C1 according to one or more of the public land mobile network PLMN of the terminal's home operator, the tracking area code TAC of the historical tracking area, and the terminal location information.

[0018] Further, in the step S22, the terminal places the NTN frequency band at the front of the list of frequency bands supported by the terminal, or sets a high priority for the NTN frequency band.

[0019] Further, in the step S22, the terminal performs network scanning hierarchically. First, it scans the currently valid NTN cell frequencies recorded in the list C2, then scans all available NTN cell frequencies recorded in the list C1, then scans the remaining frequencies in the historical frequency list, and finally performs full-band scanning according to the list of frequency bands supported by the terminal.

[0020] Further, in the steps S23 and S24, the terminal calculates the frequency offset compensation information, time compensation information, azimuth, and distance information of the current candidate frequency according to the ephemeris information.

[0021] Further, in step S26, if the cell is an NTN cell, the terminal obtains SIB19 of the NTN cell during the cell selection and reselection phase when initiating access to the NTN cell. Alternatively, the terminal actively initiates or periodically attempts to receive SIB19 of the NTN cell in the RRC idle state or RRC inactive state. Alternatively, the terminal obtains the updated SIB19 according to the system information update indication of the NTN cell. Alternatively, if SIB19 is configured by the network side as a non-broadcast mode, the terminal actively initiates a system message request to the NTN cell, so that the NTN cell schedules the broadcast of SIB19 for the terminal to obtain on time as needed. Alternatively, when the terminal in the RRC connected state receives the RRC reconfiguration message of the NTN cell, if the content of SIB19 of the NTN cell is indicated in the RRC reconfiguration message, the terminal obtains SIB19 of the NTN cell therefrom. Alternatively, the terminal receives other signaling messages of the NTN network that directly or indirectly contain the content of SIB19.

[0022] Further, before step S21, step S20 is further included. Step S20: Set the network search mode of the terminal to be the NTN-only mode, or the TN-only mode, or the TN+NTN mode.

[0023] Further, in step S26, after the terminal obtains SIB19 of the NTN cell, the following steps are executed to enable the terminal to locally maintain ephemeris information. Step S31: The terminal parses the ephemeris information of the NTN cell from the NTN configuration field in SIB19 of the NTN cell. Step S32: The terminal obtains the orbital period of the satellite corresponding to the NTN cell from the ephemeris information of the NTN cell and determines the type of the NTN cell. Step S33: The terminal saves the NTN cell information in the list C1 of all available NTN cell frequencies, and at the same time saves the data recording time; the NTN cell information includes one or more of the following: NTN configuration field, ephemeris information, orbital period, cell type, cell frequency, physical cell identifier, epoch time, current time stamp, location information, timing advance information, service time for the next entry into the current geographical location. Step S34: The terminal sets priorities for the NTN cells in the list C1 of all available NTN cell frequencies and sorts them.

[0024] Further, in step S32, if the network supports it, the NTN cell adds information on the orbital period T of the corresponding satellite for this cell and its neighboring cells in SIB19. At this time, the terminal directly obtains the orbital period T of the satellite corresponding to this NTN cell from SIB19 of this NTN cell. If the network does not support it, the terminal estimates the orbital period T of the satellite corresponding to this NTN cell from the ephemeris information of this NTN cell. If the orbital period T of the satellite corresponding to this NTN cell is equal to or approximately equal to 24 hours, the type of this NTN cell is an earth-fixed cell. If there is a referenceLocation field in SIB19 of this NTN cell, the type of this NTN cell is a quasi-earth-fixed cell. If there is a movingReferenceLocation field in SIB19 of this NTN cell, the type of this NTN cell is an earth-mobile cell.

[0025] Further, in step S33, if the type of this NTN cell is an earth-fixed cell, the cell frequency point, physical cell identifier, epoch time, NTN configuration field, timing advance information, and ephemeris information of this NTN cell directly record the corresponding information in SIB19 of this NTN cell; the location information of the earth-fixed cell is recorded as the location information obtained by the terminal from the GNSS module when obtaining SIB19 of this NTN cell. If the type of this NTN cell is a quasi-earth-fixed cell or an earth-mobile cell, the location information records the values of the distanceThresh, movingReferenceLocation, and referenceLocation fields in SIB19 of this NTN cell, and the processing method for other information is the same as that for the information of the earth-fixed cell.

[0026] Further, in step S33, if there is a satSwitchWithReSync field in SIB19 of this NTN cell, the terminal saves the information in the satSwitchWithReSync field to the list C1 of all available NTN cell frequency points, and the cell type is recorded as satellite handover; after re-residing in an NTN cell, the NTN cell information of the type of satellite handover is deleted from the list C1 of all available NTN cell frequency points.

[0027] Further, in step S34, first, the terminal sets the NTN cell with the cell type of satellite handover as the highest priority and arranges it at the front; sets the NTN cell with the cell type of geostationary cell as the second highest priority and arranges it after the highest priority; sets the remaining NTN cells as low priority and arranges them at the end. Then, within the same priority level, the terminal calculates the current geographical location of each satellite according to the six orbital elements in the ephemeris information in the list C1 of available NTN cell frequencies of all NTN cells, and then calculates the distance between the current geographical location of each satellite and the terminal, and sorts the NTN cells corresponding to each satellite in ascending order of distance.

[0028] Further, in step S21, the terminal sets priorities for the NTN cells in the list C1 of available NTN cell frequencies of all NTN cells and sorts them. First, the terminal adds all the NTN cells with the type of satellite handover in the list C1 of available NTN cell frequencies of all NTN cells to the current effective NTN frequency list C2. Secondly, except for the NTN cells with the type of satellite handover, the terminal performs the following four-stage judgment process; assuming that the current timestamp is Time0 and the data record time of the i-th NTN cell saved in the list C1 of available NTN cell frequencies of all NTN cells is time i . When 0 < Time0 - time i < time thresh , the terminal sets the frequency of the i-th NTN cell as the highest priority; where time thresh is twice the service time of the i-th NTN cell. When time thresh ≤ Time0 - time i < T i + time thresh , the terminal considers that the ephemeris information of the i-th NTN cell is credible; where T i is the orbital period of the satellite corresponding to the i-th NTN cell; the terminal calculates the geographical location (x s , y s , z s ) of the satellite corresponding to the i-th NTN cell at the current moment according to the six orbital elements of the ephemeris information of the NTN cell, and obtains the geographical location (x0, y0, z0) of the terminal at the current moment through the positioning module; if the terminal recognizes and sets the frequency of the i-th NTN cell as the highest priority; where d xy is the length of the distance vector when the satellite and the terminal are simultaneously mapped on the XOY plane, and d thresh is the distance threshold when the satellite and the terminal are simultaneously mapped on the XOY plane; if not satisfied the terminal does not change the priority of the NTN cell. When T i + time thresh≤Time0-time i When ≤ Time0-time i , the terminal considers the ephemeris information of the i-th NTN cell to be untrusted; the terminal sets the frequency point of the i-th NTN cell to a low priority and places it at the end of the frequency point list C1 of all available NTN cells, or deletes the information of the i-th NTN cell from the frequency point list C1 of all available NTN cells. When the terminal determines that the satellite corresponding to the i-th NTN cell passes overhead based on information other than location and time information, that is, the satellite is above the terminal, the terminal sets the frequency point of the i-th NTN cell to the highest priority.

[0029] Further, in the step S21, after the terminal updates the priorities of the NTN cells in the frequency point list C1 of all available NTN cells, it adds the frequency points of all NTN cells with the highest priority to the current valid NTN frequency point list C2; if the number of frequency points of the NTN cells in the current valid NTN frequency point list C2 is less than 3, it adds the frequency points of all NTN cells with the highest priority and the second highest priority in the frequency point list C1 of all available NTN cells to the current valid NTN frequency point list C2.

[0030] The present application also proposes a device for assisting in selecting NTN cells based on ephemeris information, including a network search parameter extension unit, a network scanning unit, a cell detection and synchronization unit, a cell SIB1 acquisition unit, a cell residence initiation unit, a cell remaining system message acquisition unit, and a cell residence completion unit. The network search parameter extension unit is used to calculate and obtain a list C1 of all available NTN cell frequencies or a list C2 of currently valid NTN cell frequencies according to ephemeris information, and add them to the historical frequency list as part of the network search parameters of the terminal. The network scanning unit is used to perform network scanning by the terminal according to the network search parameters to obtain a candidate frequency list. The cell detection and synchronization unit is used to sequentially select each candidate frequency from the candidate frequency list, and the terminal attempts to detect and synchronize with the cell corresponding to the candidate frequency to obtain the MIB of the cell. The cell SIB1 acquisition unit is used to obtain the SIB1 of the cell by the terminal when the cell detection and synchronization unit successfully obtains the MIB of the cell. The cell residence initiation unit is used to select and reside in the cell by the terminal when the cell SIB1 acquisition unit successfully obtains the SIB1 of the cell. The cell remaining system message acquisition unit is used to obtain the remaining system information of the cell by the terminal when the cell residence unit selects to reside in the cell, and determine whether the cell is an NTN cell; if the cell is an NTN cell, the terminal obtains the SIB19 of the NTN cell and determines whether the service time of the NTN cell has ended. The cell residence completion unit is used to successfully reside in the cell by the terminal when the cell remaining system message acquisition unit determines that the cell is not an NTN cell, or when the cell remaining system message acquisition unit determines that the cell is an NTN cell and the service time of the NTN cell has not ended.

[0031] The technical effect achieved by the present application is that the ephemeris information is used to assist the terminal in accelerating the network search and selection process of NTN cells, and enhancing the ability of the terminal to quickly reside in and access NTN cells. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the existing cell selection process.

[0033] Figure 2 It is a schematic diagram of the process of the method for assisting in selecting NTN cells based on ephemeris information proposed by the present application.

[0034] Figure 3 It is a schematic diagram of the process of the method for the terminal to locally maintain ephemeris information provided by the present application.

[0035] Figure 4 It is a schematic diagram of the structure of the device for assisting in selecting NTN cells based on ephemeris information proposed by the present application.

[0036] Description of the reference numerals in the figure: Network search parameter expansion unit 21, network scanning unit 22, cell detection and synchronization unit 23, cell SIB1 acquisition unit 24, cell residence initiation unit 25, cell remaining system message acquisition unit 26, cell residence completion unit 27. Detailed implementation manners

[0037] Please refer to Figure 2 , the method for assisting in selecting NTN cells based on ephemeris information proposed in this application includes the following steps.

[0038] Step S21: The terminal calculates and obtains all available NTN cell frequency lists C1 or the current valid NTN cell frequency list C2 according to the ephemeris information, and adds them to the historical frequency list as part of the network search parameters. The network search parameters usually include the frequency band list A supported by the terminal, the historical frequency list B, the information of the cells where the terminal has resided or registered, and other contents.

[0039] In this step, the ephemeris information obtained by the terminal is preferably the ephemeris information maintained locally by the terminal. Alternatively, the ephemeris information is pre-configured by the terminal at the time of factory. Alternatively, the ephemeris information is obtained by the terminal from a third-party service provider.

[0040] This step can be specifically processed in the following two cases, and either one can be selected.

[0041] The first case: The terminal calculates and obtains all available NTN cell frequency lists C1 according to the ephemeris information, and adds the list C1 to the historical frequency list B as part of the network search parameters. Preferably, the terminal sets all the available NTN cell frequencies recorded in the list C1 at the front of the historical frequency list B, or sets a higher priority for all the available NTN cell frequencies recorded in the list C1, so as to give all the available NTN cell frequencies recorded in the list C1 the opportunity to perform network scanning attempts first.

[0042] The second case: The terminal calculates and obtains all available NTN cell frequency lists C1 according to the ephemeris information, and then further calculates and obtains the current valid NTN frequency list C2, and adds the list C2 to the historical frequency list B as part of the network search parameters. The list C2 is a subset of the list C1. Preferably, the terminal places the current valid NTN cell frequencies recorded in the list C2 at the front of the historical frequency list B, or sets a higher priority for the current valid NTN cell frequencies recorded in the list C2, so as to give the current valid NTN cell frequencies recorded in the list C2 the opportunity to perform network scanning attempts first. Further preferably, the terminal inserts the current valid NTN cell frequencies recorded in the list C2 into the historical frequency list B multiple times to give the list

[0043] More repeated search opportunities for the currently valid NTN cell frequencies recorded in C2. For example, if the number of currently valid

[0044] NTN cell frequencies recorded in list C2 is greater than a preset threshold, the terminal places the currently valid NTN cell frequencies recorded in list C2 at the front of the historical frequency list B. If the number of currently valid NTN cell frequencies recorded in list C2 is less than or equal to the preset threshold, the terminal repeatedly inserts the currently valid NTN cell frequencies recorded in list C2 into the historical frequency list B multiple times. The preset threshold can be adjusted according to the time consumed by the terminal to search for a currently valid NTN cell frequency, and the time consumed to search for all currently valid NTN cell frequencies should be within the time limit of one round of NTN network search.

[0045] In this step, in addition to obtaining list C1 according to ephemeris information, the terminal can also obtain list C1 according to one or more of the PLMN (Public Land Mobile Network) information of the terminal's home operator, the TAC (Tracking Area Code) of the historical tracking area, and the terminal location information.

[0046] Step S22: The terminal performs a network scan according to the network search parameters to obtain a candidate frequency list. Usually, the candidate frequency list is sorted in descending order of the received signal strength of each candidate frequency.

[0047] Preferably, in this step, the NTN frequency band is set at the front of the frequency band list A supported by the terminal, or a higher priority is set for the NTN frequency band to give the NTN frequency band the opportunity to perform a network scan first. Preferably, the terminal performs the network scan hierarchically, first scanning the currently valid NTN cell frequencies recorded in list C2 (if list C2 exists), then scanning all available NTN cell frequencies recorded in list C1, then scanning the remaining frequencies in the historical frequency list B, and finally performing a full-band network scan according to the frequency band list A supported by the terminal.

[0048] Step S23: The terminal sequentially selects each candidate frequency from the candidate frequency list, attempts to detect and synchronize with the cell corresponding to the candidate frequency, and obtains the MIB of the cell. If successful, it enters step S24. If failed, the terminal selects the next candidate frequency from the candidate frequency list and repeats step S23.

[0049] Step S24: The terminal obtains the SIB1 of the cell.

[0050] Preferably, in the steps S23 and S24, the terminal calculates frequency offset compensation information, time compensation information, azimuth, distance information, etc. of the current candidate frequency point according to the ephemeris information, so as to obtain the synchronization signal block (SSB), MIB, and SIB1 better, faster, and more accurately on the current candidate frequency point.

[0051] Step S25: The terminal selects to camp on this cell.

[0052] Step S26: The terminal obtains the remaining system information of this cell.

[0053] If this cell is not an NTN cell, go to step S27.

[0054] If this cell is an NTN cell, first the terminal must obtain the SIB19 of this NTN cell. For example, the terminal obtains the SIB19 of this cell during the cell selection and camping phase when initiating to this NTN cell. Another example is that the terminal actively initiates or periodically attempts to receive the SIB19 of this NTN cell in the RRC idle state (RRC_IDLE) or RRC inactive state (RRC_INACTIVE). Another example is that the terminal obtains the updated SIB19 according to the system information update indication of this NTN cell. Another example is that if the SIB19 is configured by the network side as a non-broadcast mode, the terminal actively initiates a system message request to this NTN cell, so that this NTN cell schedules the broadcast of the SIB19 for the terminal to obtain it on time as needed. Another example is that when the terminal receives the rrcReconfiguration message of this NTN cell in the RRC connected state, if the dedicatedSystemInformationDelivery field included in the rrcReconfiguration message indicates the content of the SIB19 of this NTN cell, the terminal can also obtain the SIB19 of the NTN cell therefrom. Another example is that the terminal receives the content directly or indirectly including the SIB19 indicated by other signaling messages of this NTN network. Subsequently, if the SIB19 of this NTN cell indicates that the service time of this NTN cell has not ended, go to step S27. If the SIB19 of this NTN cell indicates that the service time of this NTN cell has ended, the terminal selects the next candidate frequency point from the candidate frequency point list and repeats step S23.

[0055] Step S27: The terminal successfully camps on this cell. The cell selection process ends, and the terminal can perform normal cell access, signaling registration and update, data services, voice services, video services, positioning services, etc.

[0056] Optionally, before step S21, step S20 is further included. Step S20: Set the network search mode of the terminal to be the NTN-only mode, or the TN-only mode, or the TN+NTN mode. For example, the user manually selects, selects according to the terminal coordinates and prior location information, or selects the network search mode according to whether the terminal radio frequency and GNSS (Global Navigation Satellite System) module support the NTN network. Usually, the network search mode of the terminal is the TN+NTN mode, first searching for TN frequency points and then searching for NTN frequency points. In high-altitude areas and uninhabited areas where there are no ground base stations, the terminal intelligently switches to the NTN-only mode, which helps to quickly search for the network. In urban areas and buildings where ground base stations are dense, the terminal selects the TN-only mode to achieve energy saving and quick network registration.

[0057] Please refer to Figure 3 , this application provides a method for a terminal to locally maintain ephemeris information, which is performed after the terminal obtains the SIB19 of the NTN cell in step S26, and specifically includes the following steps.

[0058] Step S31: The terminal parses the ephemeris information (EphemerisInfo) of the NTN cell from the NTN configuration (ntn-Config) field in the SIB19 of the NTN cell. For example, the NTN configuration field may exist in the ntn-NeighCellConfigList structure or the ntn-NeighCellConfigListExt structure in the SIB19.

[0059] Step S32: The terminal obtains the orbital period of the satellite corresponding to the NTN cell from the ephemeris information of the NTN cell, and determines the type of the NTN cell.

[0060] If the network supports it, the NTN cell can add information about the orbital period T of the corresponding satellite for this cell and neighboring cells in the SIB19. At this time, the terminal directly obtains the orbital period T of the satellite corresponding to the NTN cell from the SIB19 of the NTN cell. If the network does not support it, the terminal estimates the orbital period T of the satellite corresponding to the NTN cell by itself from the ephemeris information of the NTN cell. At this time, the terminal estimates the orbital period T according to the semi-major axis in the ephemeris information. Among them, π is the pi, a is the semi-major axis of the satellite orbit, G is the gravitational constant, and M is the mass of the Earth. Ephemeris information is used to describe the parameters of the satellite orbit change in a future period. As time goes by, the satellite's motion trajectory may gradually deviate from the originally given ephemeris information, that is, the longer the time, the less reliable the ephemeris information. The orbital period is used to judge the validity of the ephemeris information. If the time interval since the terminal last received the SIB19 of the same NTN cell is within the orbital period of the satellite corresponding to this NTN cell, it is considered that the ephemeris information of this NTN cell is valid; otherwise, it is considered that the ephemeris information of this NTN cell is unreliable.

[0061] First, if the orbital period T of the satellite corresponding to this NTN cell is equal to or approximately equal to 24 hours, then the type of this NTN cell is an earth-fixed cell; otherwise, proceed to the subsequent judgment. Second, if there is a referenceLocation field in the SIB19 of this NTN cell, then the type of this NTN cell is a quasi-earth-fixed cell. If there is a movingReferenceLocation field in the SIB19 of this NTN cell, then the type of this NTN cell is an earth-moving cell. Otherwise, the type of this NTN cell is uncertain. Judging the type of the NTN cell helps to judge the over-the-top conditions of the satellite corresponding to this NTN cell. Except for the earth-fixed cell, the orbital period of the satellite is approximately equal to the time interval when the NTN cell corresponding to the satellite passes above the terminal. Since the earth-fixed cell is synchronous with the Earth, as long as the terminal does not move across regions, it can be considered that it is always above the terminal. However, the earth-fixed cell is at a high altitude from the ground, and communication may be more difficult than other cells, so it is set to the second highest priority later.

[0062] Step S33: The terminal saves the NTN cell information in the list C1 of all available NTN cell frequencies, and at the same time saves the data recording time. The NTN cell information includes one or more of the following: NTN configuration field, ephemeris information, orbital period, cell type, cell frequency, physical cell identifier, epoch time, current timestamp, location information, timing advance information, service time for the next entry into the current geographical location.

[0063] If the type of the NTN cell is a geostationary cell, the cell frequency, physical cell identifier, epoch time, NTN configuration field, timing advance information, and ephemeris information of the NTN cell can directly record the corresponding information in the SIB19 of the NTN cell. The location information of the geostationary cell can be recorded as the location information obtained by the terminal from the GNSS module when obtaining the SIB19 of the NTN cell. The cell type and orbital period are obtained either by network broadcast or calculated and judged by the terminal itself.

[0064] If the type of the NTN cell is a quasi-geostationary cell or a geostationary mobile cell, the location information needs to record the values of the distanceThresh, movingReferenceLocation, and referenceLocation fields in the SIB19 of the NTN cell. This location information helps to assist the terminal in accessing and enhancing mobility. The processing method of other information is the same as that of the information of the geostationary cell.

[0065] The satSwitchWithReSync field in the SIB19 of the NTN cell records potential available NTN serving cells, which is specially provided by the network to the terminal to maintain the continuity of network services, especially important in the scenario of satellite handover. If the satSwitchWithReSync field exists in the SIB19 of the NTN cell, the terminal saves the information of the satSwitchWithReSync field to all available NTN cell frequency lists C1. The cell type is recorded as satSwitch (satellite handover), and the cell frequency and physical cell identifier are the same as those of the current serving cell; other information is obtained according to the protocol or calculated, and the non-existent information fields are null values. After re-residing in an NTN cell, the NTN cell information of the satellite handover type is deleted from all available NTN cell frequency lists C1.

[0066] Step S34: The terminal sets priorities for the NTN cells in all available NTN cell frequency lists C1 and sorts them. First, the NTN cells with the cell type of satellite handover are set to the highest priority and ranked at the front; the NTN cells with the cell type of geostationary cell are set to the second highest priority and ranked behind the highest priority; the remaining NTN cells are set to the lowest priority and ranked at the end. Then, within the same priority level, the terminal calculates the current geographical location of each satellite according to the six orbital elements (semi-major axis a, eccentricity e, orbital inclination i, argument of perigee ω, right ascension of the ascending node Ω, and true anomaly φ) in the ephemeris information of all available NTN cell frequency lists C1, and then calculates the distance between the current geographical location of each satellite and the terminal. The NTN cells corresponding to each satellite are sorted in ascending order of distance.

[0067] It should be noted that in step S34, when the terminal camps on a certain NTN cell, it saves data such as the ephemeris information of the NTN cell to the list C1 of all available NTN cell frequencies. At this time, priorities are set for the NTN cells in the list C1 and sorted to dynamically update the list C1.

[0068] In step S21, when the terminal searches for a network, it has been some time since the last acquisition of the ephemeris information of the NTN cell. The original priorities in the list C1 of all available NTN cell frequencies may not conform to the current situation. Therefore, when the terminal searches for a network, it needs to update the priorities of the list C1 again, and then optionally calculate and obtain the current valid NTN frequency list C2 based on the list C1 of all available NTN cell frequencies. The following gives an example of a method for setting priorities and sorting the NTN cells in the list C1 of all available NTN cell frequencies when the terminal searches for a network.

[0069] First, the terminal adds all NTN cells of the satellite handover type in the list C1 of all available NTN cell frequencies to the current valid NTN frequency list C2.

[0070] Secondly, except for the NTN cells of the satellite handover type, the terminal performs the following four-stage judgment process. Assume that the current timestamp is Time0, and the data recording time of the i-th NTN cell saved in the list C1 of all available NTN cell frequencies is time i 。

[0071] When 0 < Time0 - time i < time thresh , the terminal sets the frequency of the i-th NTN cell to the highest priority. Among them, time thresh is twice the service time of the i-th NTN cell. For example, for an NTN cell of a LEO (low earth orbit) satellite, the service time is within 5 minutes, and time thresh can be taken as 10 minutes.

[0072] When time thresh ≤ Time0 - time i < T i + time thresh , the terminal considers that the ephemeris information of the i-th NTN cell is credible. Among them, T i is the orbital period of the satellite corresponding to the i-th NTN cell. The terminal calculates the geographical location (x s , y s , z s), and obtain the geographical location (x0, y0, z0) of the terminal at the current moment through the positioning module. If it satisfies The terminal believes that the satellite corresponding to the NTN cell is above the terminal and is a potential serving cell, and the terminal sets the frequency point of the i-th NTN cell to the highest priority. Among them, d xy is the length of the distance vector when the satellite and the terminal are simultaneously mapped onto the XOY plane, and d thresh is the distance threshold when the satellite and the terminal are simultaneously mapped onto the XOY plane. If it does not satisfy The terminal does not change the priority of this NTN cell.

[0073] When T i + time thresh ≤ Time0 - time i The terminal believes that the ephemeris information of the i-th NTN cell is not credible. This may be caused by the ephemeris information not being updated for more than one orbital period. The terminal sets the frequency point of the i-th NTN cell to a low priority, places it at the end of the list C1 of frequency points of all available NTN cells, or deletes the information of the i-th NTN cell from the list C1 of frequency points of all available NTN cells.

[0074] When the terminal determines, based on information other than location and time information, that the satellite corresponding to the i-th NTN cell passes overhead, that is, the satellite is above the terminal, the terminal sets the frequency point of the i-th NTN cell to the highest priority.

[0075] After the terminal updates the priorities of the NTN cells in the list C1 of frequency points of all available NTN cells according to the above rules, optionally, it adds the frequency points of all NTN cells with the highest priority to the current valid NTN frequency point list C2. If the number of frequency points of the NTN cells in the current valid NTN frequency point list C2 is less than 3, then it adds the frequency points of all NTN cells with the highest priority and the second-highest priority in the list C1 of frequency points of all available NTN cells to the current valid NTN frequency point list C2.

[0076] Please refer to Figure 4 , the apparatus for assisting in selecting NTN cells based on ephemeris information proposed in this application includes a network search parameter extension unit 21, a network scanning unit 22, a cell detection and synchronization unit 23, a cell SIB1 acquisition unit 24, a cell residence initiation unit 25, a cell remaining system message acquisition unit 26, and a cell residence completion unit 27. Figure 4 The apparatus shown corresponds to Figure 2 the method shown.

[0077] The network search parameter expansion unit 21 is used to calculate and obtain all available NTN cell frequency point lists C1 or the current valid NTN cell frequency point list C2 according to ephemeris information, and add them to the historical frequency point list as part of the network search parameters of the terminal.

[0078] The network scanning unit 22 is used to perform network scanning by the terminal according to the network search parameters to obtain a candidate frequency point list.

[0079] The cell detection and synchronization unit 23 is used to sequentially select each candidate frequency point from the candidate frequency point list, and the terminal attempts to perform cell detection and synchronization for the cell corresponding to the candidate frequency point to obtain the MIB of the cell. If it fails, the cell detection and synchronization unit 32 selects the next candidate frequency point from the candidate frequency point list to attempt cell detection and synchronization.

[0080] The cell SIB1 acquisition unit 24 is used to have the terminal acquire the SIB1 of the cell when the cell detection and synchronization unit 23 successfully acquires the MIB of the cell.

[0081] The cell residence initiation unit 25 is used to have the terminal select to reside in the cell when the cell SIB1 acquisition unit 24 successfully acquires the SIB1 of the cell.

[0082] The cell remaining system message acquisition unit 26 is used to have the terminal acquire the remaining system information of the cell and determine whether the cell is an NTN cell when the cell residence unit 25 selects to reside in the cell. If the cell is an NTN cell, the terminal acquires the SIB19 of the NTN cell and determines whether the service time of the NTN cell has ended. If the service time of the NTN cell has ended, it jumps to the cell detection and synchronization unit 32 and selects the next candidate frequency point from the candidate frequency point list to attempt cell detection and synchronization.

[0083] The cell residence completion unit 27 is used to have the terminal successfully reside in the cell when the cell remaining system message acquisition unit 26 determines that the cell is not an NTN cell, or when the cell remaining system message acquisition unit 26 determines that the cell is an NTN cell and the service time of the NTN cell has not ended.

[0084] This application proposes a method for assisting in selecting NTN cells based on ephemeris information. When the terminal performs cell search and selection for the entire TN+NTN frequency band or only for the entire NTN frequency band, the ephemeris information is used to locally search the frequency points where NTN cells are most likely to exist in a targeted manner, which helps the terminal find a suitable NTN cell to camp on in advance, thereby shortening the time for NTN cell search and enhancing the accuracy of NTN cell search. The frequency points where NTN cells are most likely to exist are obtained by dynamically updating list C1 each time the ephemeris information of NTN cells is acquired and each time the network is searched. If the terminal can find an NTN cell at the frequency points where NTN cells are most likely to exist, the cell search time can be shortened and a global search with high time complexity can be avoided.

[0085] Compared with the prior art, the main technical innovations of this application are summarized as follows. This application mainly focuses on the cell search and selection process rather than the cell reselection process. On the one hand, this application is predefined by the device or selected by the user for the network search mode, which acts on the network search process rather than the cell reselection process. On the other hand, with the assistance of ephemeris information, this application dynamically updates the priority of the frequency points of NTN cells in list C1 each time the ephemeris information of NTN cells is acquired and each time the network is searched, optimizing and shortening the network search time for NTN cells.

[0086] The above are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, various changes and modifications can be made to this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A method for assisting in selecting NTN cells based on ephemeris information, characterized in that It includes the following steps; Step S21: The terminal calculates and obtains all available NTN cell frequency point lists C1 or the current valid NTN cell frequency point list C2 according to the ephemeris information, and adds them to the historical frequency point list as part of the network search parameters; Step S22: The terminal performs a network scan according to the network search parameters to obtain a candidate frequency point list; Step S23: The terminal sequentially selects each candidate frequency point from the candidate frequency point list, attempts to detect and synchronize with the cell corresponding to the candidate frequency point, and obtains the MIB of the cell; If successful, go to step S24; If failed, the terminal selects the next candidate frequency point from the candidate frequency point list and repeats step S23; Step S24: The terminal obtains the SIB1 of the cell; Step S25: The terminal selects to camp on this cell; Step S26: The terminal obtains the remaining system information of the cell and determines whether the cell is an NTN cell; If the cell is not an NTN cell, go to step S27; If the cell is an NTN cell, the terminal obtains the SIB19 of the NTN cell; if the SIB19 of the NTN cell indicates that the service time of the NTN cell has not ended, go to step S27; if the SIB19 of the NTN cell indicates that the service time of the NTN cell has ended, the terminal selects the next candidate frequency point from the candidate frequency point list and repeats step S23; Step S27: The terminal successfully camps on this cell.

2. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, wherein In the step S21, the terminal calculates and obtains all available NTN cell frequency point lists C1 according to the ephemeris information, and adds the list C1 to the historical frequency point list as part of the network search parameters; Alternatively, in the step S21, the terminal calculates and obtains all available NTN cell frequency point lists C1 according to the ephemeris information, and then further calculates and obtains the current valid NTN frequency point list C2, and adds the list C2 to the historical frequency point list as part of the network search parameters.

3. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 2, wherein In the step S21, the terminal places all the available NTN cell frequency points recorded in the list C1 at the front of the historical frequency point list, or sets a high priority for all the available NTN cell frequency points recorded in the list C1; Alternatively, in the step S21, the terminal places the current valid NTN cell frequency points recorded in the list C2 at the front of the historical frequency point list B, or sets a high priority for the current valid NTN cell frequency points recorded in the list C2.

4. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 2, characterized in that, In the step S21, the terminal repeatedly inserts the current valid NTN cell frequency points recorded in the list C2 into the historical frequency point list multiple times.

5. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, characterized in that, In the step S21, the terminal also obtains the list C1 according to one or more of the public land mobile network PLMN of the terminal's home operator, the tracking area code TAC of the historical tracking area, and the terminal location information.

6. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, wherein In the step S22, the terminal places the NTN frequency band at the front of the frequency band list supported by the terminal, or sets a high priority for the NTN frequency band.

7. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 6, wherein In step S22, the terminal performs network scanning in a hierarchical manner. First, it scans the frequencies of the currently valid NTN cells recorded in list C2, then scans the frequencies of all available NTN cells recorded in list C1, then scans the remaining frequencies in the historical frequency list, and finally performs full-band scanning according to the frequency band list supported by the terminal.

8. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, characterized in that, In steps S23 and S24, the terminal calculates frequency offset compensation information, time compensation information, azimuth, and distance information of the current candidate frequency based on ephemeris information.

9. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, wherein In step S26, if the cell is an NTN cell, the terminal obtains SIB19 of the NTN cell during the cell selection and reselection stage for the NTN cell. Alternatively, the terminal actively initiates or periodically attempts to receive SIB19 of the NTN cell in the RRC idle state or RRC inactive state. Alternatively, the terminal obtains the updated SIB19 according to the system information update indication of the NTN cell. Alternatively, if SIB19 is configured by the network side in a non-broadcast manner, the terminal actively initiates a system message request to the NTN cell, so that the NTN cell schedules the broadcast of SIB19 for the terminal to obtain on time and on demand. Alternatively, when the terminal is in the RRC connected state and receives the RRC reconfiguration message of the NTN cell, if the RRC reconfiguration message indicates the content of SIB19 of the NTN cell, the terminal obtains SIB19 of the NTN cell therefrom. Alternatively, the terminal receives the content of SIB19 directly or indirectly indicated by other signaling messages of the NTN network.

10. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, characterized in that, in Before step S21, there is also step S20. Step S20: Set the network scanning mode of the terminal to be the NTN-only mode, or the TN-only mode, or the TN+NTN mode.

11. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, wherein In step S26, after the terminal obtains SIB19 of the NTN cell, the following steps are performed to enable the terminal to maintain ephemeris information locally. Step S31: The terminal parses the ephemeris information of the NTN cell from the NTN configuration field in SIB19 of the NTN cell. Step S32: The terminal obtains the orbital period of the satellite corresponding to the NTN cell from the ephemeris information of the NTN cell and determines the type of the NTN cell. Step S33: The terminal saves the NTN cell information in the list C1 of all available NTN cell frequencies, and also saves the data recording time; the NTN cell information includes one or more of the following: NTN configuration field, ephemeris information, orbital period, cell type, cell frequency, physical cell identifier, epoch time, current timestamp, location information, timing advance information, service time for the next entry into the current geographical location. Step S34: The terminal sets priorities for the NTN cells in the list C1 of all available NTN cell frequencies and sorts them.

12. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 11, wherein In step S32, if the network supports it, the NTN cell adds information on the orbital period T of the corresponding satellite for this cell and its neighboring cells in SIB19. At this time, the terminal directly obtains the orbital period T of the satellite corresponding to the NTN cell from SIB19 of the NTN cell. If the network does not support it, the terminal estimates the orbital period T of the satellite corresponding to the NTN cell by itself from the ephemeris information of the NTN cell; If the orbital period T of the satellite corresponding to the NTN cell is equal to or approximately equal to 24 hours, the type of the NTN cell is an earth-fixed cell; If there is a referenceLocation field in the SIB19 of the NTN cell, the type of the NTN cell is a quasi-earth-fixed cell; If there is a movingReferenceLocation field in the SIB19 of the NTN cell, the type of the NTN cell is an earth-mobile cell.

13. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 12, wherein In step S33, if the type of the NTN cell is an earth-fixed cell, the cell frequency point, physical cell identifier, epoch time, NTN configuration field, timing advance information, and ephemeris information of the NTN cell directly record the corresponding information in the SIB19 of the NTN cell; the location information of the earth-fixed cell is recorded as the location information obtained by the terminal from the GNSS module when obtaining the SIB19 of the NTN cell; If the type of the NTN cell is a quasi-earth-fixed cell or an earth-mobile cell, the location information records the values of the distanceThresh, movingReferenceLocation, and referenceLocation fields in the SIB19 of the NTN cell, and the processing method of other information is the same as that of the information of the earth-fixed cell.

14. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 12, wherein In step S33, if there is a satSwitchWithReSync field in the SIB19 of the NTN cell, the terminal saves the information of the satSwitchWithReSync field to the list C1 of all available NTN cell frequency points, and the cell type is recorded as satellite handover; After re-residing in an NTN cell, the NTN cell information of the type of satellite handover is deleted from the list C1 of all available NTN cell frequency points.

15. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 14, wherein In step S34, first, the terminal sets the NTN cell with the cell type of satellite handover to the highest priority and arranges it at the front; the NTN cell with the cell type of earth-fixed cell is set to the second highest priority and arranged behind the highest priority; The remaining NTN cells are set to low priority and arranged at the end; Then within the same priority, the terminal calculates the current geographical location of each satellite according to the six orbital elements in the ephemeris information in the list C1 of all available NTN cell frequency points, and then calculates the distance between the current geographical location of each satellite and the terminal, and sorts the NTN cells corresponding to each satellite in ascending order of distance.

16. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 1, wherein In step S21, the terminal sets priorities and sorts the NTN cells in the list C1 of all available NTN cell frequency points; First, the terminal adds all the NTN cells of the type of satellite handover in the list C1 of all available NTN cell frequency points to the current effective NTN frequency point list C2; Secondly, except for NTN cells of the satellite handover type, the terminal performs the following four-stage judgment process; assuming that the current timestamp is Time0, the data recording time of the i-th NTN cell stored in the list C1 of all available NTN cell frequencies is time i ; When 0 < Time0 - time i < time thresh the terminal sets the frequency point of the i-th NTN cell to the highest priority; where time thresh is twice the service time of the i-th NTN cell; When time thresh ≤ Time0 - time i <T i + time thresh the terminal considers the ephemeris information of the i-th NTN cell to be reliable; where T i is the orbital period of the satellite corresponding to the i-th NTN cell; the terminal calculates the geographical location (x s , y s , z s ) of the satellite corresponding to the NTN cell at the current moment according to the six orbital elements of the ephemeris information of the NTN cell, and obtains the geographical location (x0, y0, z0) of the terminal at the current moment through the positioning module; if is satisfied, the terminal sets the frequency point of the i-th NTN cell to the highest priority; where d xy is the length of the distance vector when the satellite and the terminal are simultaneously projected onto the XOY plane, and d thresh is the distance threshold when the satellite and the terminal are simultaneously projected onto the XOY plane; if is not satisfied, the terminal does not change the priority of the NTN cell; When T i + time thresh ≤ Time0 - time i The terminal considers the ephemeris information of the i-th NTN cell to be untrusted; the terminal sets the frequency point of the i-th NTN cell to a low priority and places it at the end of the frequency point list C1 of all available NTN cells, or deletes the information of the i-th NTN cell from the frequency point list C1 of all available NTN cells; When the terminal determines that the i-th NTN cell corresponds to an over-the-top satellite based on information other than location and time information, that is, the satellite is above the terminal, the terminal sets the frequency point of the i-th NTN cell to the highest priority.

17. The method for assisting in selecting an NTN cell based on ephemeris information according to claim 16, wherein In step S21, after the terminal updates the priorities of the NTN cells in the list C1 of all available NTN cell frequency points, it adds the frequency points of all NTN cells with the highest priority to the current valid NTN frequency point list C2. If the number of frequency points of the NTN cells in the current valid NTN frequency point list C2 is less than 3, then the frequency points of all NTN cells with the highest priority and the second highest priority in the list C1 of all available NTN cell frequency points are added to the current valid NTN frequency point list C2.

18. An apparatus for assisting in selecting an NTN cell based on ephemeris information, characterized in that, It includes a network search parameter expansion unit, a network scan unit, a cell detection and synchronization unit, a cell SIB1 acquisition unit, a cell residence initiation unit, a cell remaining system message acquisition unit, and a cell residence completion unit. The network search parameter expansion unit is used to calculate and obtain the list C1 of all available NTN cell frequency points or the current valid NTN cell frequency point list C2 according to the ephemeris information, and add them to the historical frequency point list as part of the network search parameters of the terminal. The network scan unit is used to perform a network scan by the terminal according to the network search parameters to obtain a candidate frequency point list. The cell detection and synchronization unit is used to sequentially select each candidate frequency point from the candidate frequency point list, and the terminal attempts to detect and synchronize with the cell corresponding to the candidate frequency point to obtain the MIB of the cell. The cell SIB1 acquisition unit is used to obtain the SIB1 of the cell by the terminal when the cell detection and synchronization unit successfully obtains the MIB of the cell. The cell residence initiation unit is used to select to reside in the cell by the terminal when the cell SIB1 acquisition unit successfully obtains the SIB1 of the cell. The cell remaining system message acquisition unit is used to obtain the remaining system information of the cell by the terminal when the cell residence unit selects to reside in the cell, and determine whether the cell is an NTN cell; if the cell is an NTN cell, the terminal obtains the SIB19 of the NTN cell and determines whether the service time of the NTN cell has ended. The cell residence completion unit is used to successfully reside in the cell by the terminal when the cell remaining system message acquisition unit determines that the cell is not an NTN cell, or when the cell remaining system message acquisition unit determines that the cell is an NTN cell and the service time of the NTN cell has not ended.

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