SSB search during satellite transitions using cell transition assistance information

Abstract

A UE connected to a BS using a current cell served by a first satellite receives information from the BS, the information including assistance information for a cell transition from the current cell to a cell served by a second satellite. The information is received prior to a stop time indicating when the current cell will stop serving the UE. The UE performs a cell transition from the current cell to a cell served by the second satellite using at least the assistance information to find cell synchronization block (s) for the cell served by the second satellite. The BS transmits information from the BS, the information including assistance information for a cell transition from the current cell to a cell served by the second satellite. And the BS closes the current cell at the stop time.

Description

Technical Field

[0001] Examples of embodiments herein relate generally to wireless communications, and more particularly to transitions of user equipment (UE) between satellites. Background Art

[0002] User Equipment (UE) is a wireless (usually mobile) device that connects to a cellular network. Modern cellular networks can use satellites to communicate with UEs. Some satellites move relative to the Earth and can create cells in a certain geographic area on the Earth through which UEs can connect to the cellular network. As the satellite moves away from the geographic area, at some point the satellite will not be able to form a cell in that geographic area. For example, another satellite moving in the same direction as the first satellite can also form the same cell in the same geographic area.

[0003] As the first satellite leaves and the second satellite takes over to form the cell, the UE switches between the cell served by the first satellite and the cell served by the second satellite. This switching between cells can be problematic. Summary of the invention

[0004] This section is intended to include examples, not limitations.

[0005] In an exemplary embodiment, a method is disclosed, the method comprising: receiving, by a user equipment connected to the base station using a current cell served by a first satellite, information from the base station, the information comprising assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, a cell switch from the current cell to the cell served by the second satellite using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0006] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0007] An exemplary apparatus includes one or more processors and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus to at least perform: receiving, by a user equipment connected to the base station using a current cell served by a first satellite, information from a base station, the information including assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, a cell switch from the current cell to the cell served by the second satellite using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0008] An exemplary computer program product includes a computer-readable storage medium carrying instructions that, when executed by an apparatus, cause the apparatus to at least perform: receiving, by a user equipment connected to the base station using a current cell served by a first satellite, information from a base station, the information including assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, a cell switch from the current cell to the cell served by the second satellite using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0009] In another exemplary embodiment, an apparatus includes components for performing the following: receiving, by a user equipment connected to the base station using a current cell served by a first satellite, information from the base station, the information including assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, the cell switch from the current cell to the cell served by the second satellite using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0010] In an exemplary embodiment, a method is disclosed, the method comprising: sending, by a base station, information from the base station to a user equipment connected to the base station using a current cell served by a first satellite, the information comprising assistance information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a stop time.

[0011] Another exemplary embodiment includes a computer program including instructions for performing the method of the previous paragraph when the computer program is run on a device. A computer program according to this paragraph, wherein the computer program is a computer program product including a computer readable medium carrying instructions embodied therein for use with the device. Another example is a computer program according to this paragraph, wherein the program is directly loadable into an internal memory of the device.

[0012] An exemplary apparatus includes one or more processors and one or more memories storing instructions, which instructions, when executed by the one or more processors, cause the apparatus to at least perform: sending, by a base station, information from a base station to a user equipment connected to the base station using a current cell served by a first satellite, the information including auxiliary information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a stop time.

[0013] An exemplary computer program product includes a computer-readable storage medium carrying instructions that, when executed by an apparatus, cause the apparatus to at least perform: sending, by a base station, information from a base station to a user equipment connected to the base station using a current cell served by a first satellite, the information including assistance information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a stop time.

[0014] In another exemplary embodiment, an apparatus includes components for performing the following: sending, by a base station, information from a base station to a user equipment connected to the base station using a current cell served by a first satellite, the information including assistance information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a stop time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the attached picture:

[0016] Figure 1A Illustration of the quasi-geofixed cell change of a single gNB on Earth during satellite switching;

[0017] Figure 1B illustrates a quasi-geo-fixed cell change during satellite handover for a gNB with a CU on Earth and individual DUs on satellite;

[0018] Figure 1C The diagram shows the change of quasi-geo-fixed cells of individual gNBs on a satellite during satellite switching;

[0019] Figure 2 is a flow chart of a method for a UE to perform SSB search using cell offset information during satellite switching;

[0020] Figure 2A An example of using frequency offset as resource space for soft cell switching assistance information is illustrated;

[0021] Figure 3 is a flow chart of a method for a gNB to perform SSB search using cell offset information during satellite switching; and

[0022] Figure 4 is a block diagram of one possible non-limiting exemplary system in which exemplary embodiments may be practiced. DETAILED DESCRIPTION

[0023] Abbreviations that may appear in the specification and / or drawings are defined below at the end of the Detailed Description section.

[0024] The word "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred over other embodiments. All embodiments described in this detailed description are exemplary embodiments, which are intended to enable those skilled in the art to make or use the invention, rather than to limit the scope of the invention, which is defined by the claims.

[0025] Generally in this specification, when more than one figure reference numeral, word or abbreviation with “ / ” is used in this specification, “ / ” may be interpreted as “or”, “and” or “both”. As used herein, “at least one of the following: ” and “at least one of ” and similar expressions (wherein a list of two or more elements is connected by “and” or “or”) refer to at least any one of these elements, or at least any two or more of these elements, or at least all of these elements.

[0026] As used herein, the singular forms "a", "an" and "the" also include the plural forms, unless the context clearly indicates otherwise. It is further understood that the terms "comprises", "comprising", "has", "having", "includes" and / or "including" when used herein specify the presence of stated features, elements and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0027] Any flowchart in this article (see Figure 2 or Figure 3) or signaling diagrams are considered to be logical flow diagrams and illustrate the operation of the exemplary method according to the exemplary embodiments, the result of execution of computer program instructions embodied on a computer readable memory, the functions performed by hardware implemented logic, and / or the interconnected components for performing the functions. Figure 1A , Figure 1B , Figure 1C , Figure 4 ) also illustrates the operation of an exemplary method according to an exemplary embodiment, the results of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and / or interconnected components for performing functions.

[0028] Non-terrestrial communications can complement terrestrial deployments, where satellite connections can provide coverage beyond terrestrial deployments. 3GPP has defined and completed Rel-17 work items on non-terrestrial networks (NTN) in RP-201256 (see RP-201256, Thales, "Solutions for NR to support non-terrestrial networks (NTN)", 3GPP TSG RAN meeting #88e, e-meeting, June 29-July 3, 2020), and Rel-18 work items on NTN performance enhancement.

[0029] One of the goals of Rel-18 NR NTN is to continue to enhance mobility and service continuity for both NTN-NTN and NTN-TN. This work will consider the existing approaches of NR TN and Rel-17 NR NTN as a baseline for further enhancements, including the following:

[0030] "Specify NTN-NTN handover enhancements for RRC_CONNECTED UEs in Quasi-Earth Fixed Cells and Earth Mobile Cells to reduce signalling overhead. [RAN2, RAN3]."

[0031] At the previous RAN2 meeting, there was some discussion on handover enhancements and some agreement was reached related to the unchanged PCI solution as follows (as shown between the opening and closing quotes):

[0032] "protocol:

[0033] 2. New Proposal 2: RAN2 continues to discuss (e.g., at RAN2#120) a solution to keep the same PCI after satellite switching. At least clarify the following:

[0034] RAN1 impact

[0035] The need to perform UL beam switching and / or RA

[0036] Suitable for hard or soft satellite conversion

[0037] Working Assumptions:

[0038] 1. In the case of quasi-geo fixed cells, for hard satellite transition in the same SSB frequency and same gNB (no key change), satellite transition without PCI change (no L3 mobility required) is supported.

[0039] protocol:

[0040] 1. In the case of quasi-geo fixed cells, for hard satellite transition within the same SSB frequency and same gNB (no key change), satellite transition without PCI change (no L3 mobility required) is supported unless RAN1 identifies significant technical issues (typically RAN2 will aim to minimize the regulatory impact to keep it compliant with Rel-18).”

[0041] In Rel-17 NTN, cells originating from different satellites are associated with different PCIs. Therefore, when the serving satellite moves out of coverage and a new satellite takes over the coverage of a geographical area, the stationary UE will experience continuous L3 mobility. The unchanged PCI technique was introduced to avoid the need for L3 mobility, which can reduce the signaling overhead considering the large number of UEs served within an NTN cell. It should be noted that the examples in this article can work with either the unchanged PCI technique or the changed PCI technique.

[0042] Go to Figure 1A , which illustrates the change of a quasi-geo-fixed cell 120 for a single gNB on Earth during a satellite handoff. Satellites 1 110-1 and 2 110-2 are moving in corresponding directions 111-1 and 111-2, which means that satellite 1 110-1 is moving out of range of cell 120, so satellite 2 110-2 will take over cell 120. That is, UE 10 will handoff from satellite 1 110-1 to satellite 2 110-2.

[0043] Satellite 1 110-1 communicates with GW 90-1 and gNB 70-1 via satellite dish 160 and link 140, where gNB 70-1 uses antenna 150. Link 140 can be wired or wireless. In this example, satellite 1 110-1 acts as a repeater, and there is a path 130-1 from GW 90-1 to UE 10. That is, satellite 1 110-1 repeats communications to or from UE 10 on link 130-1a via link 130-1b, and path 130-1 includes both links 130-1a and 130-1b. Similarly, satellite 2 110-2 communicates with GW 90-1 and gNB 70-1 via satellite dish 160 and link 140. In this example, satellite 2 110-2 acts as a repeater, and there is a path 130-2 from GW 90-1 to UE 10. That is, satellite 2 110-2 repeats communications to or from UE 10 on link 130-2a via link 130-2b, and path 130-2 includes both links 130-2a and 130-2b.

[0044] Cell 120 corresponds to geographic area 121. Although one "cell" 120 is illustrated, slight differences in the cell locations are shown: cell 120-1 is the "old" (or current) cell formed by satellite 1 110-1; and cell 120-2 is the "new" cell formed by satellite 2 110-2.

[0045] like Figure 1A As shown, for the quasi-geo-fixed cell scenario, if the unchanged PCI concept is used, this depends on the geographic area 121 associated with the PCI 170 and the gNB 70-1. There, the gNB 70-1 can provide services to the same coverage area while connected to different satellites 110-1, 110-2, and the PCI 170 remains unchanged after the satellite switch. Since the PCI 170 and the serving gNB 70-1 configuration remain unchanged, the satellite switch can be substantially transparent to (multiple) UEs 10.

[0046] The following steps will be performed during the satellite transition (see Figure 1A ):

[0047] 1. A stationary or mobile UE 10 is being served by Satellite 1 110-1.

[0048] 2. As satellite 1 110-1 moves away from UE 10 and satellite 2 110-2 gets closer, gNB 70-1 (routing serving cell 120-1 through satellite 1 110-1) can indicate when satellite 1 110-1 will be shut down, when satellite 2 110-2 will be available, and how to perform resynchronization with the new cell.

[0049] 3. Once satellite 2 110-2 takes over (cell 120-2, which takes over from cell 120-1), the UE performs DL / UL synchronization operations to resume TX / RX.

[0050] As previously described, even though the UE 10 is being served by a new satellite, the UE does not change the serving gNB so that the UE can maintain the cell configuration. Satellite 1 110-1 and Satellite 2 110-2 are configured with the same PCI 170 (in this example), the same UE context, and the same protocol stack (including, for example, SSB generation, encoding / decoding, modulation / demodulation, same CORESET configuration, and transition routing). However, Satellite 1 110-1 and Satellite 2 110-2 introduce different frequency (i.e., Doppler) and timing drifts, based on the UE's reference. Note that no specific agreement has yet been reached as part of the 3GPP discussions on the behavior of the UE and NW in the case of a satellite transition.

[0051] The conditions under which the PCI mechanism remains unchanged include the following:

[0052] a) NTN cells must be deployed as quasi-Earth Fixed Cells (EFC) because the cell coverage area should not change;

[0053] b) The network (NW) should indicate to the UE how / when to perform DL and UL synchronization after satellite switching; and

[0054] c) The network will accept the interruption gap so that the UE detects the new timing and adapts to it. The network needs to have a way to avoid Radio Link Failure (RLF) during this interruption gap (i.e. after the "old" / "current" cell disappears and before the "new" cell takes over).

[0055] In Rel-18 the focus is on transparent architecture and the most obvious case is when cells are provided by the same gNB, i.e. the same cell with fixed PCI is provided by the same gNB, so only the satellite node changes. However, in theory this could also apply to different gNBs and potentially even to regeneration scenarios.

[0056] That is to say, except Figure 1A In addition to the configuration in which the gNB 70 is located on the earth, other configurations are possible. Figure 1B , which illustrates the quasi-geo-fixed cell change during satellite transition for a gNB with a CU on Earth and individual DUs on satellite. Figure 1BIn the example of FIG. 1 , the gNB 70-2 is split into a central unit (CU) 150-1 on Earth and individual distributed units (DUs) on satellite 1 110-1: DU 150-2a; and DU 150-2b on satellite 2 110-2. This example requires additional coordination between the gNB-CU 150-1 and the gNB-DUs 150-2a and 150-2b (relative to Figure 1A structure in), because there is communication between CU and DU to establish coordination.

[0057] Figure 1C Another possibility of quasi-geo-fixed cell change of individual gNBs on satellite during satellite switching is illustrated. This example has gNBs 70 implemented on satellites: gNB#1 70-1 is implemented on satellite 1 110-2; gNB#2 70-2 is implemented on satellite 2 110-2. In this scenario, Figure 1B Compared with the coordination required in LTE, a relatively high degree of coordination is required between gNBs. Figure 1C The diagram shows a regeneration situation in which the satellite 110 regenerates the information sent by the GW 90-1.

[0058] In addition, a similar concept of changed PCI vs. unchanged PCI is discussed in R2-2306517 (see R2-2306517, Sequans Communications, "'Unchanged PCI' solution vs'PCI change only' solution", 3GPP TSG-RAN WG2 Meeting #122, Incheon, South Korea, 22nd–26th May 2023), which can solve the problem that unchanged PCI is not supported by Rel.17 terminals. Therefore, for changed PCI, some of these problems may exist in unchanged PCI. That is, the changed PCI technology is a compromise technology used to avoid affecting Rel-17 UEs. The working principle is the same (no L3 mobility), but the new cell should use a different PCI.

[0059] As mentioned above, the examples in this article are applicable to both cases of changed PCI or unchanged PCI. That is, whether the PCI changes or not, the UE still needs some auxiliary information to know when / how to perform cell switching, and the examples in this article can provide this auxiliary information.

[0060] At the RAN2#121-bis-e meeting and the RAN2#122 meeting, the following agreements were reached on the unchanged PCI topics.

[0061] At the RAN2#121-bis-e and RAN2#122 meetings, the following agreements were reached on this topic (both between the introduction and conclusion):

[0062] "Protocol in RAN2#121-bis-e

[0063] 1. In case of quasi-geo-fixed cells, for hard satellite transition in the same SSB frequency and same gNB (no key change), satellite transition without PCI change (no L3 mobility required) is supported unless RAN1 identifies significant technical issues (typically RAN2 will aim to minimize the regulatory impact to keep it compliant with Rel-18)

[0064] 2. In the LS to RAN1, remove the part in brackets “Generally RAN2 will aim to minimise the regulatory impact so that it complies with Rel-18. The action to RAN1 will also require feedback on hard satellite transitions (not just soft satellite transition cases), for example, the action to RAN1 is to see if there are any major technical issues (as described in the agreement).”

[0065] "Protocol in RAN2#122

[0066] The t-Service in SIB19 can also be interpreted by Rel-18 UE in connected mode to know that a satellite change or feeder link change has occurred.

[0067] In a hard transition unchanged PCI scenario (i.e. no handover), the UE needs to know when the UE will attempt to resynchronize. (FFS - whether a new "t-Start" / t-gap is needed, or if the gap is very short / zero, whether t-Service can be reused (i.e. no other IE)).”

[0068] This means that at least it is agreed to support hard satellite transition with unchanged PCI and without L3 mobility. However, so far, there are no clear details. In addition, in RAN1#113, the following LS is resolved (R1-2304323, "LS on unchanged PCI", 3GPP TSG RAN WG1#113, Incheon, Korea, May 22nd–May 26th, 2023) (this is between the opening and closing quotes):

[0069] “For mobility enhancement in Rel-18 NR NTN, in the case of quasi-Earth fixed cells, RAN2 discussed unchanged PCI scenarios, including hard satellite handoff (non-overlapping satellite coverage at handoff) and soft satellite handoff (overlapping satellite coverage at handoff).

[0070] RAN2 has agreed that in the case of quasi-geo-fixed cells, for hard satellite handover in the same SSB frequency and same gNB (no key change), satellite handover without PCI change (no L3 mobility required) is supported unless RAN1 finds significant technical issues. RAN2 understands that the standard impact includes that the UE may be notified to reacquire DL / UL synchronization with the serving cell after satellite handover.

[0071] RAN2 understands that the feasibility of soft satellite transition without PCI change (no L3 mobility required) is more relevant to RAN1 side and wants to check its feasibility with RAN1.

[0072] Action: RAN2 kindly requests RAN1 to consider the above agreement on hard satellite transition without PCI change and provide feedback if RAN1 identifies any significant technical issues and provide feedback on the feasibility of supporting soft satellite transition without PCI change.”

[0073] During RAN1 #113, this topic was briefly discussed and RAN1 provided a LS response to RAN2 in R1-2306210 with the following information (mostly concerning hard transitions) (this section is between the opening and closing quotes):

[0074] “Question 1: Has RAN1 identified any significant technical issues for the hard satellite switchover without PCI changes?

[0075] reply:

[0076] RAN1 discusses the resynchronization of the UE in case of hard handover, since a new common TA, K_mac, ephemeris and cell-specific K offset are applied during the resynchronization to the new satellite.

[0077] From a RAN1 perspective, there is no feasibility issue with a hard satellite switchover without PCI changes.”

[0078] During the RAN1 discussion for LS response, no consensus was reached on the response for soft satellite transition. Such discussions are expected to continue in RAN1#114 in August 2023.

[0079] In case of unchanged PCI, the satellite handoff is transparent to the UE. This means that the UE switches from the source satellite access node to the target satellite access node without performing L3 mobility and without changing the serving gNB.

[0080] In a soft satellite handover scenario, the intention is that the same geographic area will be served by two satellites at the same time, possibly with the same physical cell ID (PCI 170). Another possibility is that the cell of the incoming satellite will become available before the cell of the outgoing satellite is turned off. Therefore, it can be understood that the two cells (e.g., created using the same PCI) need to be simultaneously indistinguishable by the UE (to create the illusion of "same cell served by the same gNB") while allowing the UE to perform the "handover" in a controlled manner.

[0081] There was nothing specific in the RAN1#113 meeting about how soft satellite handovers work, for example, telling the UE to resynchronize to its current PCI (i.e., current serving cell) does not guarantee that the UE will find a different set of SSBs than it currently does. When performing a soft handover from an "old cell" to a "new cell", as part of the "resynchronization", the UE has the same probability of finding the old cell as it does of finding the new cell (with the same PCI). When trying to access a new cell, the UE faces the following risks:

[0082] a) Finding an "old cell" (i.e., same SSB position), which means that the UE will attempt to resynchronize with the outbound satellite. This may cause the UE to enter RLF and legacy RRC reestablishment, which will increase UE power consumption, reduce system capacity, and degrade user experience.

[0083] b) Long search for a “new cell” (i.e., an SSB from the same serving gNB but located in a different location).

[0084] c) Even when discovering a new cell, the UE needs to know which SSB belongs to the old cell and which SSB belongs to the new cell, for example, the satellite assistance information is different.

[0085] Examples herein address these and other issues. In one example herein, it is proposed to provide "cell switch assistance" information that allows the UE to perform a "guided search" for the same cell PCI (unchanged PCI scenario) when the UE 10 is requested to resynchronize with the cell 120 as part of NTN operation. The cell switch should occur without L3 mobility (i.e., without handover), and the UE should only resynchronize to the cell routed via the incoming satellite. The same "guided search" can also be applied to the changed PCI scenario, where the PCI of the new and old cells are different.

[0086] More specifically, the soft cell switching auxiliary information (also referred to as auxiliary information for soft cell switching) may include a set of one or more of the following elements:

[0087] 1) A time offset relative to the existing cell timing (i.e., instructing the UE to search for new SSBs after "X" slot offsets). Such an offset may use the first OFDM symbol from the last SSB read as a reference. Alternatively, the indication may include an absolute time at which the UE should start measuring.

[0088] 2) The frequency offset of the SSB used for synchronization (indicated as an absolute offset or a relative offset to the existing point A (also referred to as "Point A"), as described below, for the "old cell").

[0089] 3) A different set of SSB locations corresponding to the new cell may be provided. This may be achieved by reusing the same or similar IE as already present in 3GPP TS 38.331 (SSB-ToMeasure - potentially with an indication that the SS / PBCH block is an SSB with the same PCI as the current serving cell). For example, see 3GPP TS 38.331 V17.5.0 (2023-06). The bitmap in this IE will indicate the specific SSB indices provided by the outbound and inbound satellites.

[0090] 4) A time interval (eg, window) for the UE to perform a search for a resynchronization attempt.

[0091] 5) Ephemeris information to be applied when attempting to resynchronize, which the UE can use to at least subtract the time offset if the timing at the gNB (or reference point) is the same.

[0092] All information can be timestamped, since the offset may change (at least in time) due to the movement of the satellite. For timestamping, no matter which of (1)-(5) above is used, there can be a single timestamp, but each element can provide corresponding timestamps for individual elements.

[0093] Since most of the cell characteristics (i.e., cell configuration parameters) will remain unchanged during the soft switch of the serving satellite's configuration, it can be assumed that the general cell configuration (and UE-specific configuration) will remain constant. That is, the system bandwidth, CSI-RS configuration, CORESET configuration, UL BW and PUCCH configuration will remain unchanged. From a system operation point of view, it is mainly the time-frequency location of the SSB that will change (and of course the associated transmission timing relationship caused by feeder link and serving link delay variations, and Doppler shift changes caused by serving link changes - all of which will be associated with the ephemeris information, which is also assumed to be available to the UE before the resynchronization attempt).

[0094] It should be noted that while these examples describe operation under the NTN (where the examples will exploit the fact that one gNB 70 can serve UEs via multiple "remote radio heads" (satellites), these examples can also be extended to cover the case where the UE is able to autonomously determine its location in the network and the location of the gNB(s). For this case, it is also possible in principle to perform a "PCI translation" without involving L3 handover mechanisms. However, such an extension to terrestrial network operation can be complex.

[0095] As part of the operation, the UE shall recognize the frame structure described in 3GPP TS 38.211, see for example 3GPP TS 38.331 V17.5.0 (2023-06), where the central part of point A is quoted as follows (between the beginning and end references):

[0096] “Point A serves as a common reference point for the resource block grid and can be obtained from the following sources:

[0097] - offsetToPointA for PCell downlink, where offsetToPointA represents the frequency offset between point A and the lowest subcarrier of the lowest resource block, which overlaps the SS / PBCH block used by the UE for initial cell selection, expressed in resource blocks, assuming a subcarrier spacing of 15 kHz for FR1 and 60 kHz for FR2;

[0098] - For operation without shared spectrum channel access in FR1 and FR2-1, the lowest resource block has the subcarrier spacing provided by the higher layer parameter subCarrierSpacingCommon;

[0099] - For operation in FR1 or FR2 with shared spectrum channel access, and for operation in FR2-2 without shared spectrum channel access, the subcarrier spacing of the lowest resource block is the same as the SS / PBCH block used by the UE for initial cell selection;

[0100] - absoluteFrequencyPointA for all other cases, where absoluteFrequencyPointA represents the frequency position of point A represented in the ARFCN. ”

[0101] As shown, PointA is depicted as an offset from the SSB to a lower PRB in the system bandwidth. For the above case, the timing offset relative to the existing SSB structure will be relatively insignificant, while modifications to the PointA offset may require some additional considerations.

[0102] As shown in the example, the UE 10 may be configured with an additional value (e.g., delta-offsetToPointA) to be applied during resynchronization to ensure that a UE performing such an operation does not find the "current SSB" because the "new SSB" is located on another set of subcarriers. The purpose of delta-offsetToPointA is to cause the new SSB to be located at a different frequency (compared to the location of the current SSB) across the bandwidth system. The time offset may be optional, but some orthogonality via the frequency domain is useful.

[0103] Now let's describe the above details through an example. This example uses Figure 1A part of Figure 2 , Figure 2 1 is a flow chart of a method for a UE to perform SSB search using cell offset information during satellite switching. Figure 1A , UE 10 is currently connected to satellite 1 110, which is its "old" (e.g., current) satellite. Satellite 1 110-1 is also an outbound satellite because it is moving away from cell 120 (in direction 111-1). Meanwhile, satellite 2 110-2 is an inbound satellite (via direction 111-2) that will take over formation of cell 120. Thus, satellites 110-1 and 110-2 both form cell 120 to which UE 10 is or will be connected.

[0104] The outbound and incoming satellites will route the same cell 120 (from the same gNB 70-1). This means that for soft satellite handover, during the overlap period (when both satellites 110 form the same cell 120), the UE 10 is connected to the serving cell 120-1 (formed by the outbound satellite 110-1) and needs to resynchronize to the incoming satellite 110-2 and its corresponding cell 120-2. Since the cell configurations of both satellites are the same, the time and frequency positions of the SSBs of both satellites will also be the same. The UE needs assistance information so that it knows where to search / measure the new cell. Otherwise, the risk is that the UE again measures the SSBs from the current (e.g., old) cell 120-1 and resynchronizes to the outbound satellite 110-1.

[0105] In preparation for a soft cell (e.g., satellite) switch, and before the switch, the gNB 70-1 sends soft cell switch assistance information 230, and the UE 10 sends the soft cell switch assistance information 230 to the UE 10. Figure 1AReceive the information in box 205 of . The soft cell transition assistance information 230 is shown as 230-1 to 230-5 and is described below. In addition, in box 203, the UE 10 can determine a stop time, which indicates when the current (e.g., serving) cell will stop serving the UE. Therefore, box 205 is performed before the stop time. The stop time can be determined by corresponding reception of explicit signaling and an indication of the stop time, or using t-Service, t-Start, or t-Gap, for example, as described below. In other words, the UE 10 can determine the time when the current cell will stop serving the UE, and the determined time is the stop time.

[0106] In block 210, the UE 10 uses the "old" (current, e.g., serving) cell 120-1 (from the outbound satellite 110-1). In block 215, the UE 10 determines whether to perform a soft satellite handoff to the "new" cell 120-3 (formed by the second inbound satellite). The UE may determine when to perform a handoff in a variety of ways. In RAN2#122, it was agreed that the UE may interpret t-Service to know that a satellite handoff will occur (but no more specific agreement was reached). However, there is currently discussion of gNBs indicating when the new cell is available (t-Start) or how long the overlap period (also known as an interruption gap) is (t-gap). That is, the stop time determined in block 203 may be determined using these or via other techniques. Regardless of what is actually used, the UE 10 may determine in block 215 whether to perform a soft satellite handoff to the "new" cell 120-3. If not (block 215=No), the UE uses the old cell. If so (block 215=yes), the UE performs (reference numeral 218) a cell switch, which includes blocks 220 and 225. Note that the cell 120 may be formed by a satellite 110 or a BS (e.g., gNB 70), in which case the satellite 110 merely relays signals. Therefore, the term "served" is used here to indicate whether the cell 120 is formed by the satellite 110 itself or by the satellite 110 relaying signals from the gNB 70.

[0107] Specifically, the UE searches (block 220) for the "new" cell 120-2 synchronization block(s) from the incoming satellite 110-2. Block 220 has a plurality of sections 1-5, each corresponding to soft cell handover assistance information 230-1 to 230-5. Note that the soft cell handover assistance information 230-1 to 230-5 corresponds to the soft cell handover assistance information (1) to (5) described previously, and this information may be described as assistance information for soft cell handover.

[0108] In block 220-1, the UE performs a search using soft cell switching assistance information 230-1 of time offset(s) relative to the cell timing. The SSB may be shifted in frequency and time. (1) One idea of ​​(230-1) is to indicate the time offset or time offsets so that the UE knows at what instant the UE should measure the SSB from the incoming satellite.

[0109] In block 220-2, the UE performs a search using the soft cell transition assistance information 230-2 of the frequency offset. This can be considered a similar concept to (1)(230-2), but the offset is in the frequency domain. The UE is indicated a certain offset so that the UE knows the frequency at which the new SSB is located. Note that this assumes a certain orthogonality between the old and new SSBs. The frequency offset of the (multiple) SSBs is used for detection, measurement, and evaluation of the (multiple) SSBs of the cell served by the incoming (e.g., second) satellite.

[0110] As previously described, the UE 10 may be configured with an additional value (e.g., delta-offsetToPointA) to be applied during resynchronization to ensure that a UE performing such an operation does not find the "current SSB" because the "new SSB" is located on another set of subcarriers. An example of block 220-2 is block 220-2i, where the UE searches for the additional value (e.g., delta-offsetToPointA) using the soft cell transition assistance information 230-2i.

[0111] Go to Figure 2A, which illustrates an example of a resource space 270 using frequency offset as soft cell switching assistance information. The resource space 270 is a time (in symbols, such as OFDM symbols) and frequency (in subcarriers) space. The symbol offset 255 in time is located between the cell synchronization (e.g., SS / PBCH) blocks 280-1 and 280-2, and also between the cell synchronization (e.g., SS / PBCH) blocks 280-3 and 280-4. As an example of a cell synchronization block 280, each SS / PBCH block has a sync (synchronization) signal (SS, such as PSS, SSS) and a PBCH, which is a set of time-frequency resources around an internal synchronization signal. offsetToPointA 250 shows the frequency offset from the lowest frequency of the resource space 270 (e.g., the lowest subcarrier of the lowest resource block) to the first subcarrier of the SS / PBCH blocks 280-1 and 280-2. The frequency offset 260 (e.g., as delta-offsetToPointA) illustrates an offset from offsetToPointA where the first subcarrier of SS / PBCH blocks 280-3 and 280-4 is located. SS / PBCH blocks 280 in region 290 are for the old cell 120-1, while SS / PBCH blocks (as cell synchronization blocks) 280 in region 295 are for the new cell 120-2. Therefore, delta-offsetToPointA (as well as offsetToPointA) or another indicator of the starting subcarrier can be used to indicate the location of SS / PBCH blocks 280 in region 295.

[0112] In one example, the cell synchronization block 280 is a SS / PBCH block. The cell synchronization block 280 may also be referred to as an SSB, because an SSB contains a SS / PBCH block and is generally inseparable.

[0113] Note that time offsets (see block 220-1) may also be similarly applied. For example, reference numeral 286 indicates a possible time offset from time 285 (the start of SS / PBCH block 280-1), where the start symbol of SS / PBCL block 280-3 may be at reference numeral 287 and indicated by SS / PBCF block 280-3a. Note that both SS / PBCH blocks 280-3 and 280-4 will be offset to the right by the time offset shown by reference numeral 286 and offset from SS / PBCH blocks 280-3a and 280-4a.

[0114] exist Figure 2In block 220-3, the UE performs a search using soft cell transition assistance information 230-3 (e.g., in time / frequency) of different SSB location information sets. In more detail, as part of the SSB configuration, the UE may receive an IE SSB-ToMeasure indicating the time / frequency pattern of the SSB (e.g., possibly including indices of consecutive SSBs, which is more relevant to beam-based mobility management). In this case, the UE may receive a new SSB-ToMeasure IE so that the UE may know where / when to measure the new SSB.

[0115] In block 220-4, the UE performs a search using the soft cell handoff assistance information 230-4 for the time interval used for the search. This may involve similar principles as the above option, but the UE is only instructed to search from, for example, -T to T. In this case, the gNB 70-1 should ensure that within this time window, the UE will only find SSBs that are routed from the incoming satellite 110-2. Figure 2A , which have time periods different from and do not overlap with SS / PBCH blocks 280-1 and 280-2, and would be good candidates for blocks 220-4 / 230-4.

[0116] In block 220-5, the UE performs a search using the soft cell switch assistance information 230-5 of the ephemeris information. An example of a problem with such satellite switching without L3 mobility is that frequency and timing drift can change from one satellite to another. In an NTN, the UE knows the satellite ephemeris and the common TA (i.e., the RTT from the gNB to the satellite) so that the UE can pre-compensate for Doppler shift and timing drift due to satellite velocity. When switching from one satellite to another, the UE may need such assistance information (provided by the ephemeris information) to estimate the new Doppler and new RTT so that the UE can better discern when and where the new SSB is than without this information.

[0117] In block 225, the UE uses the "new" cell. Note (see block 228) that the cell switch can be performed using a PCI change between cells (ie, the current and new cells use different PCIs) or using the same PCI for both cells.

[0118] It should also be noted that multiple options in options 220-1 to 220-5 can be used. For example, both blocks 220-1 and 220-2 (and 220-2i) can be used together because the cell synchronization block 280 can move in both time (220-2) and frequency (220-2 and 220-2i). Another example is to use the time interval information in 220-4 while applying the frequency offset information in 220-2 or 220-2i. Another example is that block 220-5 can be combined with any one of blocks 220-1 to 220-4.

[0119] refer to Figure 3 , which is a flow chart of a method for gNB to use cell offset information for SSB search during satellite switching. In block 305, gNB 70 sends soft cell switching assistance information 230 to UE 10. If necessary, gNB 70 in block 310 communicates with another gNB so that the other gNB has information for sending (multiple) cell synchronization blocks 280 at (multiple) correct locations based on the soft cell switching assistance information. For example, Figure 1A In the transparent architecture case shown, there is usually no communication between the two satellites 110. Figure 1C In the case of the regenerative architecture shown, coordination can be performed between the gNB functions on the satellite 110. That is, the gNB 70-1 in satellite 1 110-1 transmits information to the gNB 70-2 in satellite 2 110-1 so that the gNB 70-2 sends out the cell synchronization block(s) 280 at the correct location(s) based on the soft cell switching assistance information.

[0120] In block 315, gNB 70 determines whether to perform a soft handoff to the new satellite. If not (block 315 = No), gNB 70 waits. If a soft handoff is to be performed (block 315 = Yes), block 320 is executed, where gNB 70 determines whether the new cell is under exclusive control of the gNB. If so (block 320 = Yes), in block 325, gNB 70 sends out cell sync block(s) at the correct position(s) based on the soft cell handoff assistance information. If not (block 320 = No), in block 330, gNB 70 communicates with other gNBs (e.g., Figure 1C70-2) so that the other gNB can determine to issue (multiple) cell synchronization blocks in the new cell. Note that box 330 is an option (option 1) and another option (box 331, option 2) is that the core network element can inform the other gNB when and how to issue the cell synchronization block in the new cell. In this process, the source gNB, the target gNB and the core network (CN) are involved because some mobility and high-level management are in the CN, and some content and context are transferred from the source gNB to the target gNB (which can be performed through the CN or directly). In addition, note that the two gNBs 70 can be prepared in advance (e.g., using gNB to gNB communication or communication from the core network element to the two gNBs 70), where one or more times indicate when, for example, a soft cell transition will occur. In box 335, the gNB 70 shuts down the original cell in the current location (e.g., at a stop time) (e.g., because the cell may reappear in a different location).

[0121] Go to Figure 4 , which shows a block diagram of one possible non-limiting example of a cellular network 1 connected to a user equipment (UE) 10. Figure 4 A plurality of network elements are shown in the cellular network of FIG: a base station 70; and a core network 90. ​​In this example, the base station 70 is a gNB (e.g., or other access node providing access of the UE 10 to the core network 90). The GW is part of the core network 90 and therefore also uses the reference numeral 90 (e.g., 90-1).

[0122] like Figure 1A As shown, satellite 110 may act as a "repeater" and form part of a cellular network 1 including gNB 70, in particular part of RAN 420. Satellite 110 includes circuitry 410, including, for example, processor(s), memory and other circuitry in UE 10, gNB 70 and core network 90. Figure 1B In FIG. 1 , gNB 70 is converted into two parts: CU 150-1 (on the earth) and DU 150-2 (in satellite 110), each of which has a corresponding circuit system shown in a dashed box. Figure 1C , gNB 70 is moved to the corresponding satellite 110.

[0123] exist Figure 4, a user equipment (UE) 10 wirelessly communicates with a base station 70 of a cellular network 1 via a radio link 11. The UE 10 is a wireless communication device, such as a mobile device, configured to access a cellular network. The UE 10 is illustrated as having one or more antennas 28. The ellipse 2 indicates that there may be multiple UEs 10 wirelessly communicating with the base station 70 via a radio link. The UE 10 includes one or more processors 13, one or more memories 15, and other circuit systems 16. The other circuit systems 16 include one or more receivers (Rx) 17 and one or more transmitters (Tx) 18. The program 12 is used to cause the UE 10 to perform the operations described herein. For the UE 10, the other circuit systems 16 may include circuit systems such as user interface elements (not shown) for a display.

[0124] The base station 70, as a network element of the cellular network 1, provides the UE 10 with access to the cellular network 1 and the data network 91 via the core network 90 (e.g., via the user plane function (UPF) of the core network 90). The base station 70 is shown as having one or more antennas 58. Generally, the base station 70 can be referred to as a RAN node 70, although many people will refer to it as a gNB (gNode B, base station for NR, new radio). However, there are many other examples of RAN nodes including eNB (evolved Node B) or TRP (transmission reception point). The base station 70 includes one or more processors 73, one or more memories 75 and other circuit systems 76. The other circuit systems 76 include one or more receivers (Rx) 77 and one or more transmitters (Tx) 78. The program 72 is used to cause the base station 70 to perform the operations described herein.

[0125] Note that base station 70 may instead be implemented via other wireless technologies, such as Wi-Fi (a wireless network protocol used by devices to communicate without a direct cable connection). In the case of Wi-Fi, link 11 may be characterized as a wireless link.

[0126] Two or more base stations 70 communicate using, for example, link(s) 79. Link(s) 79 may be wired or wireless or both, and may implement, for example, an Xn interface for 5G (fifth generation), an X2 interface for LTE (long term evolution), or other suitable interfaces for other standards.

[0127] The cellular network 1 may include a core network 90, as one or more third elements shown, which may include core network functions and provide a connection to a data network 91, such as a telephone network and / or a data communication network (e.g., the Internet), via one or more links 81. The core network 90 includes one or more processors 93, one or more memories 95, and other circuit systems 96. The other circuit systems 96 include one or more receivers (Rx) 97 and one or more transmitters (Tx) 98. The program 92 is used to cause the core network 90 to perform the operations described herein.

[0128] The core network 90 may be a 5GC (5G core network). The core network 90 may implement or include a plurality of network functions (NFs) 99, and the program 92 may include one or more NFs 99. The 5G core network may use hardware such as memory, processors, and virtualization layers. It may be a single independent computing system, a distributed computing system, or a cloud computing system. The NF 99 as a network element of the core network may be a container or a virtual machine running on the hardware of the (multiple) computing systems constituting the core network 90.

[0129] The core network functions of 5G may include access and mobility management functions provided by network functions 99, such as access and mobility management functions (AMF), and session management functions provided by network functions, such as session management functions (SMF). The core network functions for access and mobility management in LTE (Long Term Evolution) networks may be provided by MME (Mobility Management Entity) and / or SGW (Serving Gateway) functions, which route data to the data network. Many other functions are also possible, such as Figure 4 As shown in the example in: AMF; SMF; MME; SGW; GMLC (Gateway Mobile Location Center); LMF (Location Management Function); UDM (Unified Data Management) / UDR (Unified Data Repository); NRF (Network Repository Function); and / or E-SMLC (Evolved Serving Mobile Location Center). These are merely exemplary core network functions that may be provided by the core network 90, and note that both 5G and LTE core network functions may be provided by the core network 90. ​​The RAN node 70 is coupled to the core network 90 via a backhaul link 31. The RAN node 70 and the core network 90 may include an NG (Next Generation) interface for 5G, or an S1 interface for LTE, or other suitable interfaces for other radio access technologies, for communicating via the backhaul link 31.

[0130] In the data network 91, there is a computer-readable medium 94. The computer-readable medium 94 includes instructions that, when downloaded and installed into the memory 15, 75 or 95 of the corresponding UE 10, base station 70 and / or (multiple) core network element 90 and executed by (multiple) processors 13, 73 or 93, cause the corresponding device to perform the corresponding actions described herein. The computer-readable medium 94 may be implemented in other forms, such as via an optical disk or a memory stick.

[0131] Programs 12, 72 and 92 contain instructions stored by corresponding one or more memories 15, 75 or 95. These instructions, when executed by corresponding one or more processors 13, 73 or 93, cause corresponding devices 10, 70 or 90 to perform the operations described herein. Computer-readable memory 15, 75 or 95 can be any type suitable for the local technical environment, and can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, firmware, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. Computer-readable memory 15, 75 and 95 can be a component for performing storage functions. Processors 13, 73 and 93 can be any type suitable for the local technical environment, and can include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture, as non-limiting examples. Processors 13, 73 and 93 can be components for causing their corresponding devices to perform functions such as those described herein.

[0132] Receivers 17, 77 and 97 and transmitters 18, 78 and 98 may implement a wired or wireless interface. Receivers and transmitters may be grouped together as a transceiver.

[0133] The cellular network 1 can implement network virtualization, which is a process of combining hardware and software network resources and network functions into a software-based management entity (virtual network). Network virtualization involves platform virtualization (which is usually combined with resource virtualization). Network virtualization is divided into two categories: one is external, which combines many networks or network parts into virtual units; the other is internal, which provides network-like functions for software containers on a single system. Note that the virtualized entities (such as network functions 99) generated by network virtualization are still implemented using hardware such as processors 73 and / or 93 and memories 75 and / or 95 to some extent, and such virtualized entities will also produce technical effects.

[0134] In general, various embodiments of the user equipment 10 may include, but are not limited to, a cellular phone (such as a smartphone, a mobile phone, a cell phone, a voice over Internet Protocol (VoIP) phone, and / or a wireless local loop phone), a tablet, a portable computer, a vehicle or an onboard device for, for example, wireless V2X (vehicle-to-everything) communication, an image capture device (such as a digital camera), a gaming device, a music storage and playback device, an Internet appliance (including an IoT device), an IoT device with sensors and / or actuators for, for example, automation applications, and a portable unit or terminal incorporating such functions, a notebook embedded device (LEE), a laptop device (LME), a universal serial bus (USB) dongle, a smart device, a wireless client device (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automation process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. That is, the UE 10 may be any terminal device capable of wireless communication. By way of example and not limitation, a UE may also be referred to as a communication device, terminal equipment (MT), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT).

[0135] Without limiting the scope, interpretation or application of the following claims in any way, the technical effect and / or advantage of one or more of the exemplary embodiments disclosed herein is that L3 switching and associated signaling and delays are avoided. Another technical effect and / or advantage of one or more of the exemplary embodiments disclosed herein is that RACH (random access channel) resources are saved without using RACH.

[0136] The following are additional examples.

[0137] Example 1. A method, comprising: receiving, by a user equipment connected to a base station using a current cell served by a first satellite, information from the base station, the information comprising auxiliary information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received before a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, the cell switch from the current cell to the cell served by the second satellite using at least the auxiliary information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0138] Example 2. A method according to Example 1, wherein: the auxiliary information includes one or more time offsets relative to the existing cell timing for the current cell; and performing the cell switching uses at least the one or more time offsets to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0139] Example 3. A method according to any one of Examples 1 or 2, wherein: the auxiliary information includes a frequency offset of one or more cell synchronization blocks, the frequency offset being used for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite; and performing the cell switching uses at least the frequency offset to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0140] Example 4. A method according to Example 3, wherein: the auxiliary information includes an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is an offset from the first frequency to a first subcarrier of the one or more cell synchronization blocks to be used for synchronization for the cell served by the second satellite; and the cell switching is performed using at least the first frequency offset and the additional value to find the one or more cell synchronization blocks used for the synchronization for the cell served by the second satellite.

[0141] Example 5. A method according to Example 1, wherein: the auxiliary information includes a different set of positions in time and frequency for the one or more cell synchronization blocks, the different set of positions being provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from a set of positions in time and frequency for one or more cell synchronization blocks corresponding to the current cell; and performing the cell switching uses at least the different set of positions to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0142] Example 6. A method according to any one of Examples 1 to 5, wherein: the auxiliary information includes a time interval, the time interval is used for the user equipment to perform a search, the search is for a resynchronization attempt to the cell served by the second satellite; and the cell switching is performed using at least the time interval to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0143] Example 7. A method according to any one of Examples 1 to 6, wherein: the assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize to the cell served by the second satellite; and performing the cell switch uses at least the ephemeris information to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0144] Example 8. A method according to any one of Examples 1 to 7, wherein the cell switch uses one of: a change in a physical cell identifier between the current cell and the cell served by the second satellite, or the same physical cell identifier for both the current cell and the cell served by the second satellite.

[0145] Example 9. A method according to any one of Examples 1 to 8, wherein the one or more cell synchronization blocks include corresponding one or more synchronization signal blocks, and the corresponding one or more synchronization signal blocks include both a search signal and a physical broadcast channel.

[0146] Example 10. A method according to any one of Examples 1 to 9, wherein the current cell and the cell served by the second satellite both cover the same geographical area.

[0147] Example 11. A method according to any one of Examples 1 to 10, wherein the cell switch includes a soft cell switch in which there is overlapping satellite coverage at least at the switch time.

[0148] Example 12. A method comprising: sending, by a base station, information from the base station to a user equipment connected to the base station using a current cell served by a first satellite, the information comprising auxiliary information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a stop time.

[0149] Example 13. The method of Example 12, further comprising: before the shutting down, sending one or more cell synchronization blocks in the cell served by the second satellite based on the assistance information for the cell switching.

[0150] Example 14. The method according to Example 12 further includes: before the shutting down, communicating with other base stations so that the other base stations send one or more cell synchronization blocks according to the auxiliary information used for the cell switching.

[0151] Example 15. A method according to any one of Examples 12 to 14, wherein: the auxiliary information includes one or more time offsets relative to the existing cell timing for the current cell.

[0152] Example 16. A method according to any one of Examples 12 to 15, wherein: the auxiliary information includes a frequency offset of one or more cell synchronization blocks, and the frequency offset is used for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite.

[0153] Example 17. A method according to Example 16, wherein: the auxiliary information includes an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is an offset from the first frequency to a first subcarrier of the one or more cell synchronization blocks to be used for synchronization for the cell served by the second satellite.

[0154] Example 18. A method according to any one of Examples 12 to 14, wherein: the auxiliary information includes a different set of positions in time and frequency for the one or more cell synchronization blocks, and the different set of positions is provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from the set of positions in time and frequency for the one or more cell synchronization blocks corresponding to the current cell.

[0155] Example 19. A method according to any one of Examples 12 to 18, wherein: the assistance information includes a time interval, the time interval is used for the user equipment to perform a search, the search is for a resynchronization attempt to the cell served by the second satellite.

[0156] Example 20. A method according to any one of Examples 12 to 19, wherein: the assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize the cell served by the second satellite.

[0157] Example 21. A method according to any one of Examples 12 to 20, wherein the cell switch uses one of: a change in a physical cell identifier between the current cell and the cell served by the second satellite, or the same physical cell identifier for both the current cell and the cell served by the second satellite.

[0158] Example 22. A method according to any one of Examples 12 to 21, wherein the one or more cell synchronization blocks include corresponding one or more synchronization signal blocks, and the corresponding one or more synchronization signal blocks include both a search signal and a physical broadcast channel.

[0159] Example 23. A method according to any one of Examples 12 to 22, wherein the current cell and the cell served by the second satellite both cover the same geographic area.

[0160] Example 24. A method according to any one of Examples 12 to 23, wherein the cell switch includes a soft cell switch in which overlapping satellite coverage exists at least at the switch time.

[0161] Example 25. A computer program comprising instructions for performing a method according to any one of Examples 1 to 11 when the computer program is run on a device.

[0162] Example 26. A computer program according to Example 25, wherein the computer program is a computer program product comprising a computer readable medium carrying instructions embodied therein for use with the apparatus.

[0163] Example 27. The computer program of example 25, wherein the computer program is directly loadable into an internal memory of the apparatus.

[0164] Example 28. An apparatus comprising components for performing the following: receiving information from a base station by a user equipment connected to a base station using a current cell served by a first satellite, the information comprising auxiliary information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, the cell switch from the current cell to the cell served by the second satellite using at least the auxiliary information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0165] Example 29. An apparatus according to Example 28, wherein: the auxiliary information includes one or more time offsets relative to the existing cell timing for the current cell; and performing the cell switch uses at least the one or more time offsets to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0166] Example 30. An apparatus according to any one of Examples 28 or 29, wherein: the auxiliary information includes a frequency offset of one or more cell synchronization blocks, the frequency offset being used for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite; and performing the cell switching uses at least the frequency offset to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0167] Example 31. An apparatus according to Example 30, wherein: the auxiliary information includes an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is an offset from the first frequency to a first subcarrier of the one or more cell synchronization blocks to be used for synchronization for the cell served by the second satellite; and the cell switching is performed using at least the first frequency offset and the additional value to find the one or more cell synchronization blocks used for the synchronization for the cell served by the second satellite.

[0168] Example 32. An apparatus according to Example 28, wherein: the auxiliary information includes a different set of positions in time and frequency for the one or more cell synchronization blocks, the different set of positions being provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from the set of positions in time and frequency for one or more cell synchronization blocks corresponding to the current cell; and performing the cell switching uses at least the different set of positions to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0169] Example 33. An apparatus according to any one of Examples 28 to 32, wherein: the auxiliary information includes a time interval, the time interval is used by the user equipment to perform a search, the search is for a resynchronization attempt to the cell served by the second satellite; and the cell switching is performed using at least the time interval to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0170] Example 34. An apparatus according to any one of Examples 28 to 33, wherein: the assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize to the cell served by the second satellite; and performing the cell switch uses at least the ephemeris information to find the one or more cell synchronization blocks for the cell served by the second satellite.

[0171] Example 35. An apparatus according to any one of Examples 28 to 34, wherein the cell switch uses one of: a change in a physical cell identifier between the current cell and the cell served by the second satellite, or the same physical cell identifier for both the current cell and the cell served by the second satellite.

[0172] Example 36. An apparatus according to any one of Examples 28 to 35, wherein the one or more cell synchronization blocks include corresponding one or more synchronization signal blocks, and the corresponding one or more synchronization signal blocks include both a search signal and a physical broadcast channel.

[0173] Example 37. An apparatus according to any one of Examples 28 to 36, wherein the current cell and the cell served by the second satellite both cover the same geographic area.

[0174] Example 38. An apparatus according to any of Examples 28 to 37, wherein the cell switch comprises a soft cell switch in which there is overlapping satellite coverage at least at the switch time.

[0175] Example 39. An apparatus comprising components for performing the following: sending, by a base station, information from a base station to a user equipment connected to the base station using a current cell served by a first satellite, the information comprising auxiliary information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a current location at a stop time.

[0176] Example 40. The apparatus of Example 39, wherein the component is further configured to perform: before the shutting down, based on the assistance information for the cell switching, sending one or more cell synchronization blocks in the cell served by the second satellite.

[0177] Example 41. An apparatus according to Example 39, wherein the component is further configured to enable execution of: before the shutting down, communicating with other base stations so that the other base stations send one or more cell synchronization blocks according to the auxiliary information used for the cell switching.

[0178] Example 42. An apparatus according to any one of Examples 39 to 41, wherein: the auxiliary information includes one or more time offsets relative to the existing cell timing for the current cell.

[0179] Example 43. An apparatus according to any one of Examples 39 to 42, wherein: the auxiliary information includes a frequency offset of one or more cell synchronization blocks, and the frequency offset is used for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite.

[0180] Example 44. An apparatus according to Example 43, wherein: the auxiliary information includes an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is an offset from the first frequency offset to a first subcarrier of the one or more cell synchronization blocks to be used for synchronization for the cell served by the second satellite.

[0181] Example 45. An apparatus according to any one of Examples 39 to 41, wherein: the auxiliary information includes a different set of positions in time and frequency for the one or more cell synchronization blocks, and the different set of positions is provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from the set of positions in time and frequency for the one or more cell synchronization blocks corresponding to the current cell.

[0182] Example 46. An apparatus according to any one of Examples 39 to 45, wherein: the auxiliary information includes a time interval, and the time interval is used for the user equipment to perform a search, and the search is for a resynchronization attempt to the cell served by the second satellite.

[0183] Example 47. An apparatus according to any one of Examples 39 to 46, wherein: the assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize the cell served by the second satellite.

[0184] Example 48. An apparatus according to any one of Examples 39 to 47, wherein the cell switch uses one of: a change in a physical cell identifier between the current cell and the cell served by the second satellite, or the same physical cell identifier for both the current cell and the cell served by the second satellite.

[0185] Example 49. An apparatus according to any one of Examples 39 to 48, wherein the one or more cell synchronization blocks include corresponding one or more synchronization signal blocks, and the corresponding one or more synchronization signal blocks include both a search signal and a physical broadcast channel.

[0186] Example 50. An apparatus according to any one of Examples 39 to 49, wherein the current cell and the cell served by the second satellite both cover the same geographic area.

[0187] Example 51. An apparatus according to any of Examples 39 to 50, wherein the cell switch comprises a soft cell switch in which overlapping satellite coverage exists at least at the switch time.

[0188] Example 52. An apparatus according to any of the preceding apparatus examples, wherein the components include: at least one processor; and at least one memory storing instructions that, when executed by at least one processor, cause the apparatus to perform the operations.

[0189] Example 53. An apparatus comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus to at least perform: receiving information from a base station by a user equipment connected to a base station using a current cell served by a first satellite, the information comprising auxiliary information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received before a stop time indicating when the current cell will stop serving the user equipment; and performing, by the user equipment, the cell switch from the current cell to the cell served by the second satellite using at least the auxiliary information to find one or more cell synchronization blocks for the cell served by the second satellite.

[0190] Example 54. A device comprising: one or more processors; and one or more memories storing instructions, which, when executed by the one or more processors, cause the device to at least perform: sending, by a base station, information from a base station to a user equipment connected to the base station using a current cell served by a first satellite, the information comprising auxiliary information for cell switching from the current cell to a cell served by a second satellite; and shutting down, by the base station, the current cell at a current location at a stop time.

[0191] As used in this application, the term "circuitry" may refer to one, more, or all of the following:

[0192] (a) pure hardware circuit implementation (such as implementation in analog and / or digital circuitry only) and

[0193] (b) a combination of hardware circuitry and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of hardware processor(s) (including digital signal processor(s)), software and memory(s) with software, which work together to cause a device such as a mobile phone or server to perform various functions), and

[0194] (c) Hardware circuit(s) and / or processor(s), such as microprocessor(s) or portion(s) of microprocessor(s), that require software (e.g., firmware) to operate, but in which the software may not be present when not required for operation.

[0195] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also includes a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0196] The embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., application specific integrated circuits), or a combination of software and hardware. In example embodiments, the software (e.g., application logic, instruction sets) is maintained on any of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" may be any medium or component that can contain, store, communicate, propagate, or transport instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, where an example of a computer is, for example, a computer program product. Figure 4 Described and depicted in. Computer-readable media may include computer-readable storage media (e.g., memories 15, 75, and 95 or other devices), which may be any medium or component that can contain, store, and / or transmit instructions for use by or in conjunction with an instruction execution system, apparatus, or device (such as a computer). Computer-readable storage media do not include propagating signals and can therefore be considered non-transient. The term "non-transient" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), not a limitation on the persistence of data storage (e.g., random access memory RAM vs. read-only memory ROM).

[0197] If desired, the different functions discussed herein may be performed in different orders and / or simultaneously with each other. In addition, if desired, one or more of the above functions may be optional or may be combined.

[0198] Although various aspects of the invention are set out in the independent claim, further aspects of the invention include other combinations of features in the described embodiments and / or dependent claims with features of the independent claim, not just the combinations explicitly set out in the claim.

[0199] It should also be noted herein that although the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. On the contrary, several variations and modifications may be made without departing from the scope of the invention as defined in the appended claims.

[0200] The following abbreviations that may appear in the specification and / or drawings are defined as follows:

[0201] 3GPP: Third Generation Partnership Project

[0202] 5G: Fifth Generation

[0203] 6G: Sixth Generation

[0204] AMF: Access and Mobility Management Function

[0205] ARFCN: Absolute Radio Frequency Channel Number

[0206] BS: Base Station

[0207] BW: Bandwidth

[0208] CORESET: Control resource set

[0209] CN: Core Network

[0210] CSI-RS: Channel State Information Reference Signal

[0211] CU: Central Unit

[0212] DL: Downlink (from network to UE)

[0213] DU: Distributed Unit

[0214] EFC: Earth Fixed Cell

[0215] E-SMLC: Evolved Serving Mobile Location Center

[0216] GMLC: Gateway Mobile Location Center

[0217] GW: Gateway

[0218] eNB (or eNodeB): evolved Node B (e.g., LTE base station) gNB (or gNodeB): 5G / NR base station

[0219] ID: Identification

[0220] IE: Information Element

[0221] I / F: Interface

[0222] FR1: Frequency Range 1

[0223] FR2: Frequency Range 2

[0224] L3: Layer 3

[0225] LMF: Location Management Function

[0226] LS: Liaison Statement

[0227] LTE: Long Term Evolution

[0228] MME: Mobility Management Entity

[0229] NF: Network Function

[0230] ng or NG: Next Generation

[0231] NR: New Radio

[0232] NRF: Network Repository Function

[0233] NTN: Non-Terrestrial Network

[0234] N / W or NW: Network

[0235] OFDM: Orthogonal Frequency Division Multiplexing

[0236] Opt: Option

[0237] PBCH: Physical Broadcast Channel

[0238] PCI: Physical Cell ID

[0239] PSS: Primary Synchronization Signal

[0240] PRB: Physical Resource Block

[0241] PUCCH: Physical Uplink Control Channel

[0242] RAN: Radio Access Network

[0243] RAN2 and RAN3: Different TSGs before 3GpP

[0244] Rel: version

[0245] RLF: Radio Link Failure

[0246] Rx: Receiver

[0247] SGW: Serving Gateway

[0248] SMF: Session Management Function

[0249] SSB: Synchronization Signal Block

[0250] SS / PBCH: Synchronization Signal / Physical Broadcast Channel

[0251] SSS: Secondary synchronization signal

[0252] synch: synchronization

[0253] TN: Terrestrial Network

[0254] TRP: Transmission Reception Point

[0255] TSG: Technical Specification Group

[0256] Tx: Transmitter

[0257] UDM: Unified Data Management

[0258] UDR: Unified Data Repository

[0259] UE: User Equipment (e.g., wireless, usually mobile)

[0260] UL: Uplink (from UE to network)

[0261] UPF: User Plane Function

Claims

1. A method for communication, comprising: receiving, by a user equipment connected to a base station using a current cell served by a first satellite, information from the base station, the information comprising assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; as well as The cell switch from the current cell to the cell served by the second satellite is performed by the user equipment using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

2. The method according to claim 1, wherein: The assistance information comprises one or more time offsets relative to existing cell timing for the current cell; and The cell switch is performed using at least the one or more time offsets to find the one or more cell synchronization blocks for the cell served by the second satellite.

3. The method according to any one of claims 1 or 2, wherein: The assistance information includes frequency offsets of one or more cell synchronization blocks for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite; and The cell switch is performed using at least the frequency offset to find the one or more cell synchronization blocks for the cell served by the second satellite.

4. The method according to claim 3, wherein: the assistance information comprises an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is: from the first frequency offset to a first subcarrier of the one or more cell synchronization blocks used for synchronization for the cell served by the second satellite; and The cell switch is performed using at least the first frequency offset and the additional value to find the one or more cell synchronization blocks for the synchronization for the cell served by the second satellite.

5. The method according to claim 1, wherein: the assistance information comprising a different set of positions in time and frequency for the one or more cell synchronization blocks, the different set of positions being provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from a set of positions in time and frequency for the one or more cell synchronization blocks corresponding to the current cell; and The cell switch is performed using at least the different set of locations to find the one or more cell synchronization blocks for the cell served by the second satellite.

6. The method according to any one of claims 1 to 5, wherein: The assistance information includes a time interval for the user equipment to perform a search for a resynchronization attempt to the cell served by the second satellite; and The cell switch is performed using at least the time interval to find the one or more cell synchronization blocks for the cell served by the second satellite.

7. The method according to any one of claims 1 to 6, wherein: The assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize the cell served by the second satellite; and The cell switch is performed using at least the ephemeris information to find the one or more cell synchronization blocks for the cell served by the second satellite.

8. An apparatus for communication, comprising: one or more processors; as well as One or more memories storing instructions that, when executed by the one or more processors, cause the apparatus to: receiving, by a user equipment connected to a base station using a current cell served by a first satellite, information from the base station, the information comprising assistance information for a cell switch from the current cell to a cell served by a second satellite, wherein the information is received prior to a stop time indicating when the current cell will stop serving the user equipment; as well as The cell switch from the current cell to the cell served by the second satellite is performed by the user equipment using at least the assistance information to find one or more cell synchronization blocks for the cell served by the second satellite.

9. The device according to claim 8, wherein: The assistance information comprises one or more time offsets relative to existing cell timing for the current cell; and The cell switch is performed using at least the one or more time offsets to find the one or more cell synchronization blocks for the cell served by the second satellite.

10. The device according to any one of claims 8 or 9, wherein: The assistance information includes frequency offsets of one or more cell synchronization blocks for detection, measurement and evaluation of the one or more cell synchronization blocks of the cell served by the second satellite; and The cell switch is performed using at least the frequency offset to find the one or more cell synchronization blocks for the cell served by the second satellite.

11. The device according to claim 10, wherein: the assistance information comprises an additional value of a frequency offset, wherein a first frequency offset is an offset to a first subcarrier of one or more cell synchronization blocks used by the current cell, and the additional value of the frequency offset is: from the first frequency offset to a first subcarrier of the one or more cell synchronization blocks used for synchronization for the cell served by the second satellite; and The cell switch is performed using at least the first frequency offset and the additional value to find the one or more cell synchronization blocks for the synchronization for the cell served by the second satellite.

12. The device according to claim 8, wherein: the assistance information comprising a different set of positions in time and frequency for the one or more cell synchronization blocks, the different set of positions being provided corresponding to the cell served by the second satellite, wherein the different set of positions is different from a set of positions in time and frequency for the one or more cell synchronization blocks corresponding to the current cell; and The cell switch is performed using at least the different set of locations to find the one or more cell synchronization blocks for the cell served by the second satellite.

13. The device according to any one of claims 8 to 12, wherein: The assistance information includes a time interval for the user equipment to perform a search for a resynchronization attempt to the cell served by the second satellite; and The cell switch is performed using at least the time interval to find the one or more cell synchronization blocks for the cell served by the second satellite.

14. The device according to any one of claims 8 to 13, wherein: The assistance information includes ephemeris information corresponding to the second satellite to be applied when attempting to resynchronize the cell served by the second satellite; and The cell switch is performed using at least the ephemeris information to find the one or more cell synchronization blocks for the cell served by the second satellite.

15. An apparatus for communication, comprising: one or more processors; as well as One or more memories storing instructions that, when executed by the one or more processors, cause the apparatus to: transmitting, by a base station, to a user equipment connected to the base station using a current cell served by a first satellite, information from the base station, the information including assistance information for cell switching from the current cell to a cell served by a second satellite; as well as The current cell at the current location is shut down by the base station at a stop time.

16. The apparatus of claim 15, wherein the apparatus is further caused to perform: prior to the switching off, transmitting one or more cell synchronization blocks in the cell served by the second satellite according to the assistance information for the cell switching.

17. The apparatus according to claim 15, wherein the apparatus is further configured to perform: before the shutting down, communicating with other base stations so that the other base stations transmit one or more cell synchronization blocks according to the auxiliary information for the cell switching.

18. The apparatus of any one of claims 15 to 17, wherein the cell switch uses one of: a change in physical cell identifier between the current cell and the cell served by the second satellite, or the same physical cell identifier for both the current cell and the cell served by the second satellite.

19. The apparatus according to any one of claims 15 to 18, wherein the one or more cell synchronization blocks include corresponding one or more synchronization signal blocks, and the corresponding one or more synchronization signal blocks include both a search signal and a physical broadcast channel.

20. The apparatus of any one of claims 15 to 19, wherein the current cell and the cell served by the second satellite both cover the same geographical area.

21. The apparatus of any one of claims 15 to 20, wherein the cell switch comprises a soft cell switch in which there is overlapping satellite coverage at least at the switch time.

Images