Echo time acquisition for non-terrestrial network (NTN) handover

Abstract

Aspects describe a user equipment (UE) comprising: a transceiver configured to enable wireless communication with a serving cell and a target cell; and a processor communicatively coupled to the transceiver. The processor is configured to receive a handover command from the serving cell. The handover command includes an epoch index and ephemeris information of the target cell. The processor is further configured to determine an epoch time of the target cell based on the epoch index, and perform time synchronization with the target cell using the epoch time and the ephemeris information.

Description

[0001] Cross-reference

[0002] This application claims priority to U.S. Non - Provisional Application No. 18 / 507,243, filed on November 13, 2023, entitled "EPOCH TIME ACQUISITION FOR NON - TERRESTRIAL NETWORKS (NTN) HANDOVER", which claims the benefit of U.S. Provisional Application No. 63 / 430,089, filed on December 5, 2022, entitled "EPOCH TIME ACQUISITION FOR NON - TERRESTRIAL NETWORKS (NTN) HANDOVER". The entire contents of these two applications are incorporated herein by reference. Background Art Technical Field

[0003] The described aspects generally relate to an epoch time acquisition process in wireless communication of a wireless network including one or more satellites. Summary of the Invention

[0004] Some aspects of the present disclosure relate to systems, apparatuses, and methods for implementing epoch time acquisition during a non - terrestrial network (NTN) handover process. For example, systems, apparatuses, and methods are provided for determining an epoch time based on an epoch index of a target cell.

[0005] Some aspects of the present disclosure relate to a user equipment (UE) including: a transceiver configured to enable wireless communication with a serving cell and a target cell; and a processor communicatively coupled to the transceiver. The processor is configured to: receive a handover command from the serving cell. The handover command includes an epoch index of the target cell and ephemeris information. The processor is further configured to: determine the epoch time of the target cell based on the epoch index, and perform time synchronization with the target cell using the epoch time and the ephemeris information.

[0006] Some aspects of the present disclosure relate to a method of operating a UE. The method includes receiving a handover command from a serving cell. The handover command includes an epoch index of the target cell and ephemeris information. The method further includes: determining the epoch time of the target cell based on the epoch index, and performing time synchronization with the target cell using the epoch time and the ephemeris information.

[0007] Some aspects of the present disclosure relate to a base station, which includes: a transceiver configured to enable wireless communication with a UE and a second base station; and a processor communicatively coupled to the transceiver. The processor is configured to: generate a handover command including an epoch index and ephemeris information of the second base station; and send the handover command to the UE. The epoch index is referenced to the timing of a reference base station. The epoch index is associated with an epoch time for the UE to perform time synchronization with the second base station.

[0008] The present invention content is provided only for the purpose of exemplifying some aspects to provide an understanding of the subject matter described herein. Therefore, the above features are only examples and should not be construed as narrowing the scope or essence of the subject matter in the present disclosure. Other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings incorporated herein and forming a part of the specification illustrate the present disclosure and, together with the specification, further serve to explain the principles of the present disclosure and enable those skilled in the relevant art to make and use the present disclosure.

[0010] Figure 1 An example system implementing a non-terrestrial network (NTN) handover process according to some aspects of the present disclosure is illustrated.

[0011] Figure 2 A block diagram of an example system of an electronic device for an NTN handover process according to some aspects of the present disclosure is illustrated.

[0012] Figure 3 An example method of an NTN handover process according to aspects of the present disclosure is illustrated.

[0013] Figure 4 An example method of an epoch time acquisition process according to aspects of the present disclosure is illustrated.

[0014] Figure 5 An example method of generating and sending a handover command according to aspects of the present disclosure is illustrated.

[0015] Figure 6 An example of a time index period according to aspects of the present disclosure is illustrated.

[0016] Figure 7 An exemplary computer system for implementing some aspects of the present disclosure or portions thereof is shown.

[0017] The present disclosure is described with reference to the drawings. In the drawings, generally, the same reference numerals indicate the same or functionally similar elements. Additionally, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. Detailed implementation manners

[0018] Some aspects of the present disclosure relate to systems, apparatuses, and methods for implementing an epoch time acquisition process in wireless communication. For example, systems, apparatuses, and methods are provided for determining epoch time based on an epoch index of a target cell.

[0019] In some aspects, a UE communicates with a serving cell via a wireless connection to send and receive data. When the UE moves towards the edge of the serving cell, the UE may be configured to switch to another cell. For example, the UE may establish a wireless connection with a target cell that provides a stronger signal compared to the serving cell. In some aspects, when establishing a wireless connection with the target cell, the UE performs synchronization with the target cell (such as downlink synchronization).

[0020] In some aspects, the serving cell and the target cell may be supported by an NTN base station (such as a satellite). For example, the UE may be connected to the serving cell and the target cell via a first satellite and a second satellite respectively. In this case, the UE may need ephemeris information (such as the speed and position of the satellite) to connect to the satellite. For example, the UE may need the speed and position information of the second satellite to perform downlink synchronization with the target cell. In some aspects, the serving cell may send a handover command to the UE, where the handover command includes the ephemeris information of the second satellite of the target cell. Additionally, since the second satellite may change its speed and position over time, the ephemeris information of the target cell changes over time. Therefore, the UE also needs to know when the ephemeris information is valid, which is the epoch time. In this case, the UE needs to perform synchronization with the target cell (such as downlink synchronization) to determine the epoch time based on the epoch index. In other words, the UE needs to perform synchronization to determine when the ephemeris information is valid. Therefore, the UE faces a deadlock situation where synchronization requires the epoch time, which is obtained via synchronization.

[0021] In some aspects, the serving cell may include an epoch index in the handover command sent to the UE. However, the serving cell may receive the epoch index from the target cell, and thus the epoch index may refer to the timing of the second satellite. For example, the epoch index may be the system frame number (SFN) of the second satellite. To solve the deadlock situation, the serving cell may request the epoch index from the target cell and convert the epoch index to refer to the timing of the serving cell. Since the UE has previously completed synchronization with the serving cell when connected to the serving cell, the UE may use the converted epoch index to determine the epoch time of the target cell. In this case, the UE may determine when the ephemeris information is valid and perform synchronization with the target cell based on the ephemeris information.

[0022] In some aspects, a second satellite supporting a target cell may be in a geosynchronous orbit (GSO), such as a geostationary orbit (GEO). In this case, the ephemeris information may remain the same over time. For example, the position and velocity of the second satellite relative to the target cell may remain the same. In this case, the ephemeris information may be valid regardless of the epoch time. Thus, the UE may use the ephemeris information to perform synchronization without obtaining the epoch time. On the other hand, the second satellite may be in a non-GSO, such as a low Earth orbit (LEO). In this case, the UE needs to obtain the epoch time to perform the synchronization as described above.

[0023] Figure 1 Example system 100 illustrates an example process for obtaining an epoch time in accordance with some aspects of the present disclosure. Example system 100 is provided for illustrative purposes only and does not limit the disclosed aspects. Example system 100 may include, but is not limited to, UE 102, a base station 104 supporting a first communication cell, and a base station 106 supporting a second communication cell. At least a portion of each of base stations 102 and 104 is implemented as a satellite, as Figure 1 shown. Additionally, in an implementation, base stations 104 and 106 may also include corresponding ground stations (not shown) to enable communication of the corresponding cells. UE 102 may be implemented as an electronic device configured to operate based on a variety of wireless communication technologies. These technologies may include, but are not limited to, technologies based on the 3rd Generation Partnership Project (3GPP) standards. For example, UE 102 may be configured to operate using one or more 3GPP releases (such as Release 15 (Rel-15), Release 16 (Rel-16), Release 17 (Rel-17), or other 3GPP releases). UE 102 may include, but is not limited to, a wireless communication device, a smart phone, a laptop computer, a desktop computer, a tablet computer, a personal assistant, a monitor, a television, a wearable device, an Internet of Things (IoT) device, a vehicle communication device, etc. Base stations 104 and 106 may include one or more nodes configured to operate based on a wide variety of wireless communication technologies (such as, but not limited to, technologies based on 3GPP standards). For example, base stations 104 and 106 may include nodes configured to operate using Rel-15, Rel-16, Rel-17, or other 3GPP releases. Base stations 104 and 106 may include, but are not limited to, satellites, high altitude platforms (HAPs) (such as hot air balloons), aerial base stations, unmanned aerial vehicles (UAVs), NodeB, eNodeB, gNB, new radio base stations (NR BS), access points (APs), remote radio heads, relay stations, etc.

[0024] In some aspects, the UE 102 is connected to the base station 104 via the communication link 108. The communication link 108 may include an uplink (UL) connection and a downlink (DL) connection. In some aspects, the UE 102 may move away from the base station 104 and towards the base station 106. The base station 104 may determine that the UE 102 needs a handover operation to connect to the base station 106. For example, the base station 104 may monitor the movement and location of the UE 102. When the UE 102 moves to the cell edge close to the base station 104, the base station 104 determines that a handover operation is needed. The base station 104 may also know the topology of the network (such as NTN) including the base stations 104 and 106. Therefore, the base station 104 may determine that the UE 102 is moving towards the base station 106 based on the movement and location of the UE 102. In this case, the base station 104 may send a handover command to the UE 102 to configure the UE to hand over to the base station 106. The handover command may include the ephemeris information and epoch index of the base station 106. The UE 102 may perform synchronization with the base station 106 to establish the communication link 110 using the ephemeris information and epoch index.

[0025] In some aspects, the UE 102 may also determine the need for a handover operation by monitoring the received signal strength. For example, when the UE 102 moves away from the base station 104, the UE 102 may determine that the strength of the signal received from the base station 104 is lower than a threshold, and the UE 102 needs to connect to another base station to maintain the quality of service (QoS), such as data throughput and communication latency. In addition, the UE 102 may use at least one of two methods to determine the target base station to which to hand over. First, the UE 102 may determine the target base station based on the handover command. For example, the UE may send a handover request to the base station 104, which indicates the need for a handover operation but the target base station is to be determined. In response to receiving the handover request, the base station 104 may determine that the UE 102 needs to hand over to the base station 106 and send a handover command to the UE 102 as described above. The handover command may explicitly indicate that the base station 106 is the target base station. Second, the UE 102 may determine the base station without a handover command. For example, the UE 102 may determine to hand over to the base station 106 by monitoring the signal received from the base station 106. For example, the UE 102 may determine that the strength of the signal received from the base station 106 is higher than a second threshold. Also, for example, the UE 102 may further determine that the strength of the signal received from the base station 106 is higher than the strength of the signals received from other base stations. In either case, the UE 102 may also send a handover request to the base station 104 indicating that the target base station is the base station 106.

[0026] In some aspects, base station 104 may obtain ephemeris information and epoch index from base station 106. For example, base station 104 is connected to base station 106 via communication link 112. Communication link 112 may be a direct wireless connection. Communication link 112 may also be an indirect connection via one or more ground stations. In some aspects, base station 104 may send a request for information to base station 106, which may send a response back to base station 104. The response may include the ephemeris information and epoch index of base station 106. Base station 104 may repeatedly send requests for information to base station 106. For example, base station 104 may send requests for information periodically. In this case, when base station 104 determines that base station 106 is the target base station for a handover operation, base station 104 already has the ephemeris information and epoch index of base station 106 and may send a handover command to UE 102 without waiting to receive the ephemeris information and epoch index from base station 106. In some aspects, base station 104 may send a request for information to base station 106 after determining that base station 106 is the target base station. In this case, base station 104 waits for a response from base station 106 and then sends a handover command to the UE. In other words, the transmission of the handover command is delayed, but the ephemeris information and epoch index included in the handover command are up-to-date.

[0027] In some aspects, base station 106 may be in GSO or non-GSO. In either case, base station 104 may obtain such orbital information of base station 106. For example, the base station may obtain orbital information from base station 106. Base station 104 may also obtain orbital information from the backhaul network via one or more ground stations. Base station 104 may send the orbital information to UE 102 by including the orbital information in the handover command.

[0028] Figure 2 A block diagram of an electronic device 200 implementing an epoch time acquisition process according to some aspects of the present disclosure is illustrated. Electronic device 200 may be any of the electronic devices in system 100 (e.g., UE 102 and base stations 104 and 106). Electronic device 200 includes a processor 210, a transceiver 220, a communication infrastructure 240, a memory 250, an operating system 252, an application 254, device capabilities 256, and an antenna 260. The illustrated system is provided as an exemplary part of electronic device 200, and electronic device 200 may include other circuits and subsystems. Moreover, although the system of electronic device 200 is illustrated as separate components, aspects of the present disclosure may include any combination of these components (e.g., fewer components or more components).

[0029] Memory 250 may include random access memory (RAM) and / or cache, and may include control logic (e.g., computer software) and / or data. Memory 250 may include other storage devices or memories. According to some examples, operating system 252 may be stored in memory 250. Operating system 252 may manage the transfer of data from memory 250 and / or one or more applications 254 to processor 210 and / or transceiver 220. In some examples, operating system 252 maintains one or more network protocol stacks (e.g., Internet protocol stack, cellular protocol stack, etc.) that may include multiple logical layers. At the corresponding layers of the protocol stack, operating system 252 includes control mechanisms and data structures to perform functions associated with that layer.

[0030] According to some examples, applications 254 may be stored in memory 250. Applications 254 may include applications used by electronic device 200 and / or the user of electronic device 200 (e.g., user applications). The applications in applications 254 may include, but are not limited to, applications such as radio current, video streaming, remote control, and / or other user applications. In some aspects, device capabilities 256 may be stored in memory 250.

[0031] Electronic device 200 may also include communication infrastructure 240. Communication infrastructure 240 provides communication, for example, between processor 210, transceiver 220, and memory 250. In some embodiments, communication infrastructure 240 may be a bus.

[0032] Transceiver 220 transmits and receives communication signals including conventional reference signals and other data communication signals. Additionally, transceiver 220 transmits and receives communication signals that support mechanisms for measuring communication links, generating and transmitting system information, and receiving system information. According to some aspects, transceiver 220 may be coupled to antenna 260 to wirelessly transmit and receive these communication signals. Antenna 260 may include one or more antennas, which may be of the same or different types and may form one or more antenna ports. Transceiver 220 allows electronic device 200 to communicate with other devices that may be wired and / or wireless. In some examples, transceiver 220 may include a processor, controller, radio components, sockets, plugs, buffers, and similar circuits / devices for connecting to a network and communicating on the network. According to some examples, transceiver 220 includes one or more circuits for connecting to a wired network and / or a wireless network and communicating on the wired network and / or the wireless network.

[0033] In addition, the transceiver 220 may include one or more circuits (including a cellular transceiver) for connecting to and communicating over a cellular network. The cellular network may include, but is not limited to, 3G / 4G / 5G networks, such as Universal Mobile Telecommunications System (UMTS), Long-Term Evolution (LTE), etc. For example, the transceiver 220 may be configured to operate according to one or more of Rel-15, Rel-16, Rel-17, or other versions of the 3GPP standard.

[0034] In addition, one or more transceivers may include one or more circuits for connecting to and communicating with a satellite network. Such satellite networks may include, but are not limited to, wireless communication networks, such as 3G / 4G / 5G networks, such as Universal Mobile Telecommunications System (UMTS), Long-Term Evolution (LTE), and specific satellite communication network protocols for gateway functionality and control functionality from satellite ground stations. For example, one or more transceivers 220 may be configured to operate according to one or more of Rel-15, Rel-16, Rel-17, or other versions of the 3GPP standard. Additionally, for LEO geostationary type satellites (see below), an additional capability is provided to direct a beam to a fixed point on the Earth's surface either through beamforming or through a mechanically steerable beam method.

[0035] As discussed in more detail below Figures 3 to 7 with respect to Figure 1 the system 100, the processor 210 may implement different mechanisms for the epoch time acquisition process, as discussed with respect to Figures 3 to 6 For example, in some embodiments, the memory 250 may store instructions that, when executed by the processor 210, cause the processor 210 to perform or cause the electronic device 200 to perform the operations described herein, such as operations supporting epoch time acquisition in NTN. Alternatively, the processor 210 may be "hard-wired" to perform the operations described herein. In some embodiments, the processor 210 may be configured to perform Figures 3 to 6 the operations described in

[0036] Figure 3 An example method 300 of the NTN handover process is shown. The example method 300 is provided for illustrative purposes only and does not limit the disclosed aspects. For convenience and not by way of limitation, Figure 3 reference may be made to Figure 1 , Figure 2 and Figure 7 elements to describe. The example method 300 may represent the operations of an electronic device (e.g., Figure 1 the UE 102 of Figure 2 as well as base stations 104 and 106) implementing the NTN handover process. The example method 300 may also be performed by Figure 7 the electronic device 200 (controlled or implemented by the processor 210) of Figure 7is executed by computer system 700. However, example method 300 is not limited to the specific aspects depicted in those figures and may be executed using other systems, as will be understood by those skilled in the art. It should be understood that not all operations may be required and that these operations may not be performed in the Figure 3 same order as shown.

[0037] At 302, a first base station (such as base station 104) that supports a serving cell sends a request for information to a second base station (such as base station 106) that supports a target cell. In some aspects, the request indicates the ephemeris information and epoch index of the target cell. As described above, the first base station may repeatedly send requests to the second base station to obtain updated ephemeris information and epoch index of the target cell. The first base station may also send a request to the second base station in response to determining that a UE (such as UE 102) needs to handover to the target cell. In some aspects, the first base station may send the request via a communication link (such as communication link 112) between the first base station and the second base station.

[0038] At 304, the second base station sends a response with the information to the second base station. In some aspects, the response may include the ephemeris information and epoch index of the target cell. The epoch index may refer to the timing of the target cell or the timing of the serving cell.

[0039] At 306, the first base station generates a handover (HO) command. The HO command may include the ephemeris information and epoch index of the target cell. In some aspects, the epoch index received from the second base station refers to the timing of the target cell. In this case, the first base station may update the epoch index to refer to the timing of the serving cell. Thus, regardless of whether the epoch index received from the second base station refers to the timing of the serving cell, the HO command includes an epoch index that refers to the timing of the serving cell.

[0040] At 308, the first base station may send the HO command to the UE. For example, the first base station may send the HO command to the UE via communication link 108.

[0041] At 310, the UE may determine the epoch time of the target cell. For example, the UE may determine the epoch time based on the epoch index received from the first base station. As described above, the epoch index refers to the timing of the serving cell. In this case, as discussed in more detail below, the UE may determine the epoch time of the target cell.

[0042] In some aspects, the UE may also determine the status of the second base station. For example, the HO command may indicate whether the second base station supporting the target cell is in GSO or non-GSO. The UE may determine that the second base station is in GSO based on the HO command and proceed to step 312 without determining the epoch time. The UE may also determine whether to use the HO command to determine the epoch time. For example, as discussed in more detail below, the UE may determine the epoch time based on the neighboring cell system information previously received from the first base station.

[0043] At 312, the UE performs synchronization and / or measurements based on the ephemeris information and the epoch time. As described above, the ephemeris information includes the position and velocity information of the second base station and is required for the UE to perform synchronization of the target cell (such as downlink synchronization) and other measurements (such as signal strength and correlation value measurements). Additionally, the epoch time indicates when the ephemeris information becomes valid as the second base station may change its position and / or velocity from time to time. Therefore, the UE may apply the ephemeris information based on the epoch time to perform synchronization and measurements.

[0044] Figure 4 An example method 400 of the epoch time acquisition process is shown. The provision of example method 400 is for illustrative purposes only and does not limit the various aspects disclosed. For convenience and not limitation, Figure 4 reference may be made to Figure 1 、 Figure 2 and Figure 7 elements to describe. Example method 400 may represent the operations of an electronic device (e.g., Figure 1 the UE 102) implementing the epoch time acquisition process. Example method 400 may also be executed by Figure 2 the electronic device 200 (controlled or implemented by the processor 210) and / or Figure 7 the computer system 700. However, example method 400 is not limited to the specific aspects depicted in those figures and may be executed using other systems as will be understood by those skilled in the art. It should be understood that not all operations may be required and these operations may not be performed in the Figure 4 same order as shown.

[0045] At 402, the UE receives an HO command from the first base station supporting the serving cell, as described in Figure 3 308. The HO command includes the epoch index and ephemeris information of the target cell supported by the second base station.

[0046] At 404, the UE determines the epoch time of the target cell based on the epoch index. In some aspects, the epoch index refers to the timing of the serving cell. In this case, the UE can directly determine the epoch time based on the epoch index because the UE is synchronized with the serving cell. In some aspects, the epoch index refers to the timing of the serving cell but has a time offset. In this case, the UE can determine the epoch time based on the epoch index and the time offset. The UE can determine the time offset based on the HO command received from the first base station. The first base station can also notify the UE of the time offset via a configuration message before sending the HO command.

[0047] In some aspects, the epoch index can be a subframe number, a system frame number (SFN), a hyperframe number (HFN) / super SFN, and / or a combination thereof. In this case, the UE further determines whether the epoch time is before or after the time when the epoch index is received. For example, the SFN is a sequence from 0 to 1023 that repeats over multiple cycles, as shown below Figure 6 shown. If the epoch index is the SFN, the epoch index corresponds to the SFN in each SFN cycle, and thus the UE does not determine which SFN the epoch time corresponds to. To resolve this ambiguity, the UE can determine or the first base station can configure the UE to determine that the epoch time corresponds to the matching SFN in the SFN cycle of the received HO command or the matching SFN in the SFN cycle closest to the time when the HO command is received. However, the UE may still need to select between the two matching SFNs. In this case, the first base station can notify the UE which of the two matching SFNs to select. For example, the first base station can indicate in the HO command or the configuration message whether the epoch time corresponds to the SFN before or after the time when the HO command is received. Step 404 can be further described by Figure 6 and the corresponding discussion provided herein.

[0048] In some aspects, the UE can determine the epoch time based on the neighboring cell system information. For example, the first base station can repeatedly collect information about neighboring cells (such as the target cell) before the handover operation of the UE. Thus, the first base station can obtain the epoch index and ephemeris information before the UE moves towards the second base station and requires a handover operation to the target cell. The first base station can also periodically send the neighboring cell system information, such as the epoch index and ephemeris information of the target cell, to the UE. For example, the first base station can periodically send the neighboring cell system information to the UE via a system information block (such as NTN-neighcellconfig-r17). The epoch index can refer to the timing of the serving cell, and thus the UE can determine the epoch time based on the epoch index. In some aspects, the UE can determine whether to calculate the epoch time of the target cell based on the HO command or based on the neighboring cell system information based on the configuration message received from the first base station.

[0049] At 406, the UE performs synchronization with a target cell (such as Figure 3 the target cell) based on the ephemeris information received in step 402 and the epoch time determined in step 404.

[0050] Figure 5 Illustrates an example method 500 for generating and sending a handover command. The provision of example method 500 is for illustrative purposes only and does not limit the disclosed aspects. For convenience and not limitation, Figure 5 reference may be made to Figure 1 、 Figure 2 and Figure 7 elements to describe. Example method 500 may represent the operation of an electronic device (e.g., Figure 1 base stations 104 and 106) that implements generating and sending a handover command. Example method 500 may also be performed by Figure 2 electronic device 200 (controlled or implemented by processor 210) and / or Figure 7 computer system 700. However, example method 500 is not limited to the specific aspects depicted in those figures, and the method may be performed using other systems, as will be understood by those skilled in the art. It should be understood that not all operations may be required and these operations may not be performed in the Figure 5 same order as shown.

[0051] At 502, a first base station supporting a serving cell receives an epoch index of a target cell. As described above, the first base station may send a request for information to a second base station supporting the target cell to obtain the ephemeris information and epoch index of the target cell. The first base station sends the request repeatedly or after determining that a UE served by the serving cell needs to hand over to the target cell.

[0052] At 504, the first base station generates a HO command, where the HO command includes the epoch index and ephemeris information of the target cell supported by the second base station. In some aspects, the epoch index received from the second base station may refer to the timing of the target cell. In this case, the first base station may convert the epoch index to an updated epoch index that references the timing of the serving cell. The conversion of the epoch index by the first base station is further described by the Figure 6 discussion.

[0053] At 506, the first base station may send the HO command to the UE. For example, the first base station may send the HO command to the UE via Figure 1 communication link 108.

[0054] Figure 6 Illustrates an example 600 of a time index period to further illustrate the above Figures 3 to 5One or more operations. Example 600 is provided for illustrative purposes only and is not intended to limit the disclosed aspects. For convenience and not limitation, Figure 6 You can refer to Figure 1 , Figure 2 and Figure 7 Example 600 may represent an electronic device (e.g., Figure 1 Example 600 may also be implemented by Figure 2 The electronic device 200 (controlled or implemented by the processor 210) and / or Figure 7 The example 600 is not limited to the specific aspects depicted in those figures, and other systems may be used to perform the method, as will be appreciated by those skilled in the art. It should be understood that not all operations may be required, and these operations may not be performed in order. Figure 6 The same order as shown is followed.

[0055] Figure 6 1 and 2. The time index period includes time index period N and time index period N+1. The time index period may correspond to a time index period N+1. Figure 1 Base station 104) supports Figure 3 In some aspects, the time index period may be a SFN period, and the epoch index may be a SFN. As described above, the SFN repeats from 0 to 1023. When the SFN runs from 0 to 1023, the SFN completes the SFN period and enters the next SFN period. In some aspects, the SFN increases by 1 every 10 ms. Therefore, the SFN goes through one SFN period in 10.24 seconds. Since the UE is synchronized with the serving cell when it is connected to the serving cell, the UE knows the current value of the SFN running at the serving cell. Therefore, the first base station can use the SFN to indicate a point in time to the UE. For example, a HO command (such as a HO command) generated and sent by the first base station Figure 3 Steps 306 and 308, Figure 4 Step 402 and Figure 6 The HO command of steps 504 and 506 of the HO command) may indicate to the UE via the epoch index that the time point is the time when the SFN changes to 700. When receiving the HO command, the UE may determine that the current value of the SFN at the serving cell is 200. Therefore, the UE determines that the time point indicated by the first base station arrives after the SFN is incremented 500 times, that is, 500*10ms=5000ms=5 seconds after the current time. In other words, if the first base station indicates that a message will be sent when the SFN changes to 700, the UE understands that the message will be sent after 5 seconds. In some aspects, the UE Figure 3 Step 310 and Figure 4Determine the epoch time in step 404 as described herein. In summary, the SFN at the serving cell and the SFN interpretation at the UE are similar to two synchronized clocks that the first base station and the UE possess. Therefore, the time point indicated by the first base station can be understood by the UE.

[0056] In some aspects, the UE may receive a HO command from the first base station at a time point 606 within the time index period 602. The time point 606 corresponds to a first value of the SFN at the serving cell, e.g., 900. Additionally, the HO command may include an epoch index 512. As described above, the epoch time indicated by the epoch index is within the same SFN cycle or in the next closest SFN cycle. In this case, the epoch time can be time point 608 or time point 610, where time point 608 corresponds to the SFN value 512 in the time index period 602, and time point 610 corresponds to the SFN value 512 in the time index period 604. The first base station may configure the UE to select the time point before or after receiving the HO command. If the first base station configures the UE to select the epoch time before receiving the HO command, the epoch time is time point 608. Since the index difference between time points 608 and 606 is 900 - 512 = 388, the UE can determine that the epoch time is 3880 ms before receiving the HO command. On the other hand, if the first base station configures the UE to select the epoch time after receiving the HO command, the epoch time is time point 610. Since the index difference between time points 606 and 610 is 1024 - 900 + 512 = 636, the UE can determine that the epoch time is 6360 ms after receiving the HO command. In some aspects, the UE determines the epoch time in Figure 3 step 310 and Figure 4 step 404 as described above and herein.

[0057] In some aspects, the HO command further includes a time offset or an index offset. For example, the HO command may include a time offset of 300 ms or an index offset of 30. In this case, after the UE calculates the epoch time of the target cell, such as 3880 ms before receiving the HO command or 6360 ms after receiving the HO command, the UE uses the time offset or the index offset to update the epoch time of the target cell. Specifically, if the epoch time is 3880 ms before receiving the HO command, the UE may increase it by 300 ms, and thus update the epoch time to 3580 ms before receiving the HO command. Similarly, if the epoch time is 6360 ms after receiving the HO command, the UE may increase it by 300 ms, and thus update the epoch time to 6660 ms after receiving the HO command. In some aspects, the time offset or the index offset corresponds to the time difference or the index difference between the serving cell and the target cell. For example, a time offset of 300 ms may indicate that the serving cell is 300 ms ahead of the target cell. Similarly, an index offset of 30 may indicate that the SFN of the serving cell is 30 less than the SFN of the target cell. In some aspects, the serving cell may determine the time offset or the index offset because the serving cell is synchronized with the target cell. This method may also be understood as the epoch index referring to the timing of the target cell, but the serving cell enables the UE to use the epoch index without being synchronized with the target cell by providing the UE with the time offset or the index offset, where the offset is relative to the SFN of the serving cell.

[0058] In some aspects, the serving cell may convert the epoch index based on the time offset or the index offset. For example, the serving cell receives an epoch index of 512 from the target cell. The serving cell may determine that the index difference between the serving cell and the target cell is 30. In this case, the serving cell may convert the epoch index to 542 and include the converted epoch index in the HO command. Therefore, the serving cell does not need to include the time offset or the index offset in the HO command. Similarly, the UE does not need to use the time offset or the index offset to adjust the epoch time.

[0059] In some aspects, the time offset or the index offset may also be negative. For example, the time offset may be -300 ms and the index offset may be -30. In this case, the epoch time of 3880 ms before receiving the HO command is adjusted to 4180 ms before receiving the HO command, and the epoch time of 6360 ms after receiving the HO command is adjusted to 6060 ms after receiving the HO command. In some aspects, the HO command may include a parameter for indicating whether the time offset or the index offset is positive or negative.

[0060] In some aspects, the epoch index may also indicate a subframe number. In some aspects, the subframe number repeats from 0 to 9 and increments every 1 ms. Thus, in addition to the SFN, the subframe number may indicate a more accurate time than the SFN alone. For example, the epoch index may indicate SFN 512 and subframe number 4. In this case, based on the example discussed above, the epoch time may be 3876 ms before receiving the HO command or 6364 ms after receiving the HO command. In some aspects, the epoch index may also indicate a hyperframe number (HFN) or super SFN. The HFN repeats from 0 to 1023 and increments by 1 every 10.24 seconds. In some aspects, the epoch index may be associated with a time slot index. For example, the time slot index may indicate in which time slot the ephemeris information becomes valid. Additionally, as described above, the first base station may configure the UE to select a time point before or after receiving the HO command. Thus, the first base station may configure the UE to select the most recent past SFN, the most recent past subframe number, or the most recent past time slot index or the most recent future SFN index, the most recent future subframe number, or the most recent future time slot index.

[0061] The computer system 700 may also include one or more auxiliary storage devices or memories 710. The auxiliary memory 710 may include, for example, a hard disk drive 712 and / or a removable storage device or drive 714. The removable storage drive 714 may be a floppy disk drive, a tape drive, an optical disk drive, an optical storage device, a tape backup device, and / or any other storage device / drive.

[0062] The removable storage drive 714 may interact with a removable storage unit 718. The removable storage unit 718 includes a computer-usable or readable storage device on which computer software (control logic) and / or data is stored. The removable storage unit 718 may be a floppy disk, a tape, an optical disk, a DVD, an optical storage disk, and / or any other computer data storage device. The removable storage drive 714 reads from and / or writes to the removable storage unit 718 in a well-known manner.

[0063] According to some aspects, the auxiliary memory 710 may include other components, tools, or other methods for allowing the computer system 700 to access computer programs and / or other instructions and / or data. Such components, tools, or other methods may include, for example, a removable storage unit 722 and an interface 720. Examples of the removable storage unit 722 and the interface 720 may include a program cartridge and a cartridge interface (such as the interface found in video game devices), a removable memory chip (such as an EPROM or PROM) and an associated socket, a storage stick and a USB port, a memory card and an associated memory card slot, and / or any other removable storage unit and associated interface.

[0064] The computer system 700 may also include a communication or network interface 724. The communication interface 724 enables the computer system 700 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (collectively and individually referred to by reference numeral 728). For example, the communication interface 724 may allow the computer system 700 to communicate with the remote device 728 via a communication path 726, which may be wired and / or wireless and may include any combination of LAN, WAN, the Internet, etc. Control logic and / or data may be sent to and from the computer system 700 via the communication path 726.

[0065] The operations in the foregoing aspects can be implemented in various configurations and architectures. Thus, some or all of the operations in the foregoing aspects may be performed in hardware, in software, or in both hardware and software. In some aspects, a tangible, non-transitory device or article includes a tangible, non-transitory computer-usable or readable medium having control logic (software) stored thereon, also referred to herein as a computer program product or a program storage device. This includes, but is not limited to, the computer system 700, the main memory 608, the secondary memory 710, and the removable storage units 718 and 722, as well as tangible articles embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices such as the computer system 700, causes such data processing devices to operate as described herein.

[0066] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the relevant arts how to make and use aspects of this disclosure using data processing devices, computer systems, and / or computer architectures other than Figure 7 those shown. In particular, the aspects may operate in conjunction with software, hardware, and / or operating system implementations other than those described herein.

[0067] It should be understood that the detailed description section, rather than the summary and abstract sections, is intended to be used to interpret the claims. The summary and abstract sections may set forth one or more, but not all, exemplary aspects of the disclosure as contemplated by the inventors, and are therefore not intended to limit the disclosure or the appended claims in any way.

[0068] Although this disclosure has been described with reference to exemplary aspects of exemplary fields and applications, it should be understood that this disclosure is not limited thereto. Other aspects and modifications are possible and are within the scope and spirit of this disclosure. For example, and without limiting the generality of this paragraph, the aspects are not limited to the software, hardware, firmware, and / or entities illustrated in the figures and / or described herein. Additionally, the aspects, whether or not explicitly described herein, have significant utility for fields and applications other than those exemplified herein.

[0069] Aspects have been described herein with reference to functional building blocks of specific implementations that illustrate particular functions and relationships. For the sake of convenience in description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternate boundaries may be defined so long as the specified functions and relationships (or their equivalents) are appropriately performed. Additionally, alternative aspects may perform functional blocks, steps, operations, methods, etc. in an order different from that described herein.

[0070] References herein to "one implementation", "an implementation", "an example implementation", or similar phrases indicate that the implementation described may include a particular feature, structure, or characteristic, but every implementation may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same implementation. Further, when a particular feature, structure, or characteristic is described in connection with an implementation, such feature, structure, or characteristic is within the knowledge of those skilled in the relevant art to combine into other aspects whether or not explicitly recited or described herein.

[0071] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

[0072] It is well known that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of inadvertent or unauthorized access or use, and the nature of authorized use should be clearly explained to users.

[0073] The present disclosure anticipates that entities responsible for the collection, analysis, disclosure, transmission, storage, or other use of such personal information data will comply with sound privacy policies and / or privacy measures. Specifically, such entities should implement and adhere to the use of privacy policies and measures that are recognized as meeting or exceeding industry or government requirements for maintaining the privacy and security of personal information data. Such policies should be accessible to users and should be updated as the collection and / or use of data changes. Personal information from users should be collected for legitimate and reasonable entity purposes and should not be shared or sold outside of those legitimate purposes. Additionally, such collection / sharing should only occur upon receipt of user informed consent. Further, such entities should consider taking any necessary steps for protecting and safeguarding access to such personal information data and ensuring that other entities with access to personal information data comply with their privacy policies and procedures. Additionally, such entities may subject themselves to third-party assessments to demonstrate their compliance with widely accepted privacy policies and practices. Moreover, policies and practices should be adapted to the specific types of personal information data being collected and / or accessed and to the applicable laws and standards, including consideration of special jurisdictional scopes. For example, in the United States, the collection or acquisition of certain health data may be governed by federal and / or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); while health data in other countries may be subject to other regulations and policies and should be handled accordingly. Thus, different privacy measures should be asserted for different types of personal data in each country.

Claims

1. A user equipment (UE), comprising: a transceiver configured to enable wireless communication with a serving cell and a target cell; and a processor communicatively coupled to the transceiver and configured to: receive a handover command from the serving cell using the transceiver, wherein the handover command includes an epoch index and ephemeris information of the target cell; determine an epoch time of the target cell based on the epoch index; and perform time synchronization with the target cell using the epoch time and the ephemeris information.

2. The UE according to claim 1, wherein, in order to determine the epoch time, the processor is further configured to: determine that the epoch index corresponds to the serving cell; determine a current time index of the serving cell; and determine the epoch time based on the epoch index and the current time index.

3. The UE according to claim 1, wherein the epoch index includes one of a system frame number (SFN), a subframe number, or a time slot index.

4. The UE according to claim 1, wherein the handover command indicates whether the epoch index refers to the timing of the serving cell.

5. The UE according to claim 1, wherein the processor is further configured to: determine the epoch time based on the epoch index and an offset value, wherein the handover command includes the offset value.

6. The UE according to claim 1, wherein, in order to perform time synchronization with the target cell using the epoch time and the ephemeris information of the target cell, the processor is further configured to: determine that the target cell is associated with a geostationary orbit of a satellite.

7. The UE according to claim 1, wherein the processor is further configured to: receive adjacent cell system information from the serving cell using the transceiver, wherein the adjacent cell system information includes a second epoch index of the target cell; and determine the epoch time based on the second epoch index.

8. The UE according to claim 7, wherein the processor is further configured to: receive a configuration message using the transceiver, the configuration message indicating whether to determine the epoch time based on the epoch index or the second epoch index.

9. A method of operating a user equipment (UE), comprising: receiving a handover command from a serving cell, wherein the handover command includes an epoch index and ephemeris information of a target cell; determining an epoch time of the target cell based on the epoch index; and performing time synchronization with the target cell using the epoch time and the ephemeris information.

10. The method according to claim 9, wherein determining the epoch time further comprises: determining that the epoch index corresponds to the serving cell; determining a current time index of the serving cell; and determining the epoch time based on the epoch index and the current time index.

11. The method according to claim 9, wherein the handover command indicates whether the epoch index refers to the timing of the serving cell.

12. The method according to claim 9, further comprising: Determining the epoch time based on the epoch index and the offset value, wherein the handover command includes the offset value.

13. The method according to claim 9, wherein performing the time synchronization with the target cell using the epoch time and the ephemeris information further comprises: Determining that the target cell is associated with the geostationary orbit of the satellite.

14. The method according to claim 9, further comprising: Receiving adjacent cell system information from the serving cell, wherein the adjacent cell system information includes a second epoch index of the target cell; and Determining the epoch time based on the second epoch index.

15. A base station, comprising: A transceiver configured to enable wireless communication with a user equipment (UE) and a second base station; and A processor communicatively coupled to the transceiver and configured to: Generate a handover command including an epoch index and ephemeris information of the second base station; and Transmit the handover command to the UE using the transceiver, wherein the epoch index refers to the timing of the base station, and wherein the epoch index is associated with an epoch time for the UE to perform time synchronization with the second base station.

16. The base station according to claim 15, wherein, in order to generate the handover command, the processor is further configured to: Transmit a request for information to the second base station; Receive a response from the second base station, wherein the response includes a second epoch index and the ephemeris information; and Convert the second epoch index to the epoch index.

17. The base station according to claim 15, wherein, in order to generate the handover command, the processor is further configured to: Determine a time offset between the base station and the second base station, wherein the handover command includes the time offset.

18. The base station according to claim 17, wherein the handover command further indicates whether the time offset is positive or negative.

19. The base station according to claim 15, wherein the processor is further configured to: Generate a configuration message that configures the UE to determine the epoch time based on the epoch index or a second epoch index of adjacent cell system information; and Transmit the configuration message to the UE using the transceiver.

20. The base station according to claim 15, wherein the processor is further configured to: Generate a configuration message indicating whether the epoch index is associated with: One of the most recent past system frame number (SFN), the most recent past subframe number, or the most recent past time slot index, or One of the most recent future SFN index, the most recent future subframe number, or the most recent future time slot index; and Transmit the configuration message to the UE using the transceiver.

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