BACKGROUND OF DISCLOSURE

1. Field of the Disclosure

[0001] The present disclosure relates to the field of communication systems, and more particularly, to an apparatus and a method of wireless communication, which can provide a good communication performance and/or high reliability.

2. Description of the Related Art

[0002] Non-terrestrial networks (NTNs) refer to networks, or segments of networks, using a spacebome vehicle or an airborne vehicle for transmission. Spacebome vehicles include satellites including low earth orbiting (LEO) satellites, medium earth orbiting (MEO) satellites, geostationary earth orbiting (GEO) satellites, and highly elliptical orbiting (HEO) satellites. Airborne vehicles include high altitude platforms (HAPs) encompassing unmanned aircraft systems (UAS) including lighter than air (LTA) unmanned aerial systems (UAS) and heavier than air (HTA) UAS, all operating in altitudes typically between 8 and 50 km, quasi-stationary.

[0003] Communication via a satellite is an interesting means thanks to its well-known coverage, which can bring the coverage to locations that normally cellular operators are not willing to deploy either due to non-stable crowd potential client, e.g., extremely rural, or due to high deployment cost, e.g., middle of ocean or mountain peak. Nowadays, the satellite communication is a separate technology to a 3rd generation partnership project (3GPP) cellular technology. Coming to 5G era, these two technologies can merge together, i.e., we can imagine having a 5G terminal that can access to a cellular network and a satellite network. The NTN can be good candidate technology for this purpose. It is to be designed based on 3GPP new radio (NR) with necessary enhancement. [0004] In new radio (NR) and/or NTN systems, a handover procedure for a user equipment (UE) switching from a serving cell to a target cell requires the UE to perform a random access channel (RACK) procedure. This may increase a handover latency.

SUMMARY

[0005] An object of the present disclosure is to propose an apparatus (such as a user equipment (UE), a serving cell, and/or a target cell) and a method of wireless communication, which can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability. [0006] In a first aspect of the present disclosure, a method of wireless communication by a user equipment (UE) comprises receiving, from a serving cell, a handover command for a handover procedure for the UE switching from the serving cell to a target cell, transmitting, to the target cell, an uplink transmission according to the handover command, and receiving, from the target cell, a message.

[0007] In some embodiments of the above method according to the first aspect of the present disclosure, the handover command comprises a command for a random access channel-less (RACH-less) handover for the UE switching from the serving cell to the target cell.

[0008] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the handover command comprises at least one of following information: an ephemeris data of the target cell; common timing advance (TA) relevant parameters of the target cell; an offset value; a new cell-radio network temporary identifier (C-RNTI); a configuration for one or more physical uplink shared channel (PUSCH) resources of the target cell, or a configuration of a search space.

[0009] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the one or more PUSCH resources comprises one or more configured uplink grants (CUL grants).

[0010] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, when the ephemeris data of the target cell is not provided by the serving cell, the UE assumes that the ephemeris data of the target cell is same as an ephemeris data of the serving cell.

[0011] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, when the common TA relevant parameters of the target cell are not provided by the serving cell, the UE assumes that the common TA relevant parameters of the target cell are same as common TA relevant parameters of the serving cell, or the UE assumes that a common TA of the target cell is zero.

[0012] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the method further comprises performing synchronization with the target cell. [0013] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the synchronization uses the ephemeris data of the target cell and/or the common TA relevant parameters of the target cell.

[0014] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, after the synchronization is performed by the UE, the UE selects a first available PUSCH resource from the one or more PUSCH resources for uplink transmission. [0015] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the one or more CUL grants are dynamically scheduled by the target cell.

[0016] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the method further comprises starting to monitor a physical downlink control channel (PDCCH) in the search space.

[0017] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the search space is configured for RACH-less handover.

[0018] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the uplink transmission comprises the new C-RNTI or a TA relevant information of the UE.

[0019] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the message from the target cell comprises the new C-RNTI, a contention resolution identifier (ID), or an acknowledgement.

[0020] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, if the UE verifies that the contention resolution ID is matched with an ID of the UE, the handover procedure is complete.

[0021] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, if the UE receives the acknowledgement, the handover procedure is complete. [0022] In some embodiments of any one of the above methods according to the first aspect of the present disclosure, the acknowledgement is carried by a downlink control information (DCI) and/or the acknowledgement comprises a hybrid automatic repeat request acknowledgment (HARQ-ACK) information.

[0023] In a second aspect of the present disclosure, a method of wireless communication by a serving cell comprises transmitting, to a target cell, a handover request for a handover procedure for a user equipment (UE) switching from the serving cell to the target cell, receiving, from the target cell, a response, and transmitting, to the UE, a handover command for the handover procedure for the UE switching from the serving cell to the target cell.

[0024] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the handover request comprises an ID of the UE.

[0025] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the response comprises a new C-RNTI.

[0026] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the handover command comprises a command for a random access channelless (RACH-less) handover for the UE switching from the serving cell to the target cell. [0027] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the handover command comprises at least one of following information: an ephemeris data of the target cell; common timing advance (TA) relevant parameters of the target cell; an offset value; a new cell-radio network temporary identifier (C-RNTI); a configuration for one or more physical uplink shared channel (PUSCH) resources of the target cell, or a configuration of a search space.

[0028] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the one or more PUSCH resources comprises one or more configured uplink grants (CUL grants).

[0029] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, when the ephemeris data of the target cell is not provided by the serving cell, the UE assumes that the ephemeris data of the target cell is same as an ephemeris data of the serving cell.

[0030] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, when the common TA relevant parameters of the target cell are not provided by the serving cell, the UE assumes that the common TA relevant parameters of the target cell are same as common TA relevant parameters of the serving cell, or the UE assumes that a common TA of the target cell is zero.

[0031] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the method further comprises controlling the UE to perform synchronization with the target cell.

[0032] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the synchronization uses the ephemeris data of the target cell and/or the common TA relevant parameters of the target cell.

[0033] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, after the synchronization is performed by the UE, the serving cell controls the UE to select a first available PUSCH resource from the one or more PUSCH resources for uplink transmission.

[0034] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the one or more CUL grants are dynamically scheduled by the target cell.

[0035] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the method further comprises controlling the UE to monitor a physical downlink control channel (PDCCH) in the search space. [0036] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the search space is configured for RACH-less handover.

[0037] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the uplink transmission comprises the new C-RNTI or a TA relevant information of the UE.

[0038] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the message from the target cell comprises the new C-RNTI, a contention resolution identifier (ID), or an acknowledgement.

[0039] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, if the UE verifies that the contention resolution ID is matched with an ID of the UE, the handover procedure is complete.

[0040] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, if the UE receives the acknowledgement, the handover procedure is complete.

[0041] In some embodiments of any one of the above methods according to the second aspect of the present disclosure, the acknowledgement is carried by a downlink control information (DCI) and/or the acknowledgement comprises a hybrid automatic repeat request acknowledgment (HARQ-ACK) information.

[0042] In a third aspect of the present disclosure, a method of wireless communication by a target cell comprises receiving, from a serving cell, a handover request for a handover procedure for a user equipment (UE) switching from the serving cell to the target cell, transmitting, to the serving cell, a response, receiving, from the UE, an uplink transmission relevant to a handover command, and transmitting, to the UE, a message.

[0043] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the handover request comprises an ID of the UE.

[0044] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the response comprises a new C-RNTI.

[0045] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the handover command comprises a command for a random access channelless (RACH-less) handover for the UE switching from the serving cell to the target cell.

[0046] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the handover command comprises at least one of following information: an ephemeris data of the target cell; common timing advance (TA) relevant parameters of the target cell; an offset value; a new cell-radio network temporary identifier (C-RNTI); a configuration for one or more physical uplink shared channel (PUSCH) resources of the target cell, or a configuration of a search space.

[0047] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the one or more PUSCH resources comprises one or more configured uplink grants (CUL grants).

[0048] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, when the ephemeris data of the target cell is not provided by the serving cell, the UE assumes that the ephemeris data of the target cell is same as an ephemeris data of the serving cell.

[0049] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, when the common TA relevant parameters of the target cell are not provided by the serving cell, the UE assumes that the common TA relevant parameters of the target cell are same as common TA relevant parameters of the serving cell, or the UE assumes that a common TA of the target cell is zero.

[0050] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the method further comprises controlling the UE to perform synchronization with the target cell.

[0051] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the synchronization uses the ephemeris data of the target cell and/or the common TA relevant parameters of the target cell.

[0052] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, after the synchronization is performed by the UE, the serving cell controls the UE to select a first available PUSCH resource from the one or more PUSCH resources for uplink transmission.

[0053] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the one or more CUL grants are dynamically scheduled by the target cell.

[0054] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the method further comprises controlling the UE to monitor a physical downlink control channel (PDCCH) in the search space.

[0055] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the search space is configured for RACH-less handover.

[0056] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the uplink transmission comprises the new C-RNTI or a TA relevant information of the UE. [0057] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the message from the target cell comprises the new C-RNTI, a contention resolution identifier (ID), or an acknowledgement.

[0058] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, if the UE verifies that the contention resolution ID is matched with an ID of the UE, the handover procedure is complete.

[0059] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, if the UE receives the acknowledgement, the handover procedure is complete.

[0060] In some embodiments of any one of the above methods according to the third aspect of the present disclosure, the acknowledgement is carried by a downlink control information (DCI) and/or the acknowledgement comprises a hybrid automatic repeat request acknowledgment (HARQ-ACK) information.

[0061] In a fourth aspect of the present disclosure, a user equipment comprises a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to perform the above method.

[0062] In a fifth aspect of the present disclosure, a serving cell comprises a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to perform the above method.

[0063] In a sixth aspect of the present disclosure, a serving cell comprises a memory, a transceiver, and a processor coupled to the memory and the transceiver. The processor is configured to perform the above method.

[0064] In a seventh aspect of the present disclosure, a non-transitory machine-readable storage medium has stored thereon instructions that, when executed by a computer, cause the computer to perform the above method.

[0065] In an eighth aspect of the present disclosure, a chip includes a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the above method.

[0066] In a ninth aspect of the present disclosure, a computer readable storage medium, in which a computer program is stored, causes a computer to execute the above method.

[0067] In a tenth aspect of the present disclosure, a computer program product includes a computer program, and the computer program causes a computer to execute the above method.

[0068] In an eleventh aspect of the present disclosure, a computer program causes a computer to execute the above method. BRIEF DESCRIPTION OF DRAWINGS

[0069] In order to illustrate the embodiments of the present disclosure or related art more clearly, the following figures will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present disclosure, a person having ordinary skill in this field can obtain other figures according to these figures without paying the premise.

[0070] FIG. 1 A is a block diagram of one or more user equipments (UEs), a serving cell, and/or a target cell of communication in a communication network system according to an embodiment of the present disclosure.

[0071] FIG. IB is a block diagram of one or more user equipments (UEs) and a base station (e.g., gNB or eNB) of communication in a non-terrestrial network (NTN) system according to an embodiment of the present disclosure.

[0072] FIG. 2 is a flowchart illustrating a method of wireless communication performed by a user equipment (UE) according to an embodiment of the present disclosure.

[0073] FIG. 3 is a flowchart illustrating a method of wireless communication performed by a serving cell according to an embodiment of the present disclosure.

[0074] FIG. 4 is a flowchart illustrating a method of wireless communication performed by a target cell according to an embodiment of the present disclosure.

[0075] FIG. 5 is a schematic diagram illustrating a communication system including a base station (BS) and a UE according to an embodiment of the present disclosure.

[0076] FIG. 6 is a schematic diagram illustrating that a BS transmits 3 beams to the ground forming 3 footprints according to an embodiment of the present disclosure.

[0077] FIG. 7 is a schematic diagram illustrating an uplink-downlink timing relation according to an embodiment of the present disclosure.

[0078] FIG. 8 is a schematic diagram illustrating a handover procedure for a UE switching from a serving cell to a target cell according to an embodiment of the present disclosure.

[0079] FIG. 9 is a block diagram of a system for wireless communication according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0080] Embodiments of the present disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the disclosure.

[0081] FIG. 1A illustrates that, in some embodiments, one or more user equipments (UEs) 10, a serving cell 20 (or called a source cell) (e.g., gNB or eNB), and a target cell 30 (e.g., gNB or eNB) in a communication network system 40 (e.g., non-terrestrial network (NTN) or terrestrial network) according to an embodiment of the present disclosure are provided. The communication network system 40 includes the one or more UEs 10, the serving cell 20, and the target cell 30. The one or more UEs 10 may include a memory 12, a transceiver 13, and a processor 11 coupled to the memory 12 and the transceiver 13. The serving cell 20 may include a memory 22, a transceiver 23, and a processor 21 coupled to the memory 22 and the transceiver 23. The target cell 30 may include a memory 32, a transceiver 33, and a processor 31 coupled to the memory 32 and the transceiver 33. The processor 11, 21, or 31 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of radio interface protocol may be implemented in the processor 11, 21, or 31. The memory 12, 22, or 32 is operatively coupled with the processor 11 , 21 , or 31 and stores a variety of information to operate the processor 11, 21, or 31. The transceiver 13, 23, or 33 is operatively coupled with the processor 11, 21, or 31, and the transceiver 13, 23, or 33 transmits and/or receives a radio signal.

[0082] The processor 11, 21, or 31 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The memory 12, 22, or 32 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The transceiver 13, 23, or 33 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in the memory 12, 22, or 32 and executed by the processor 11, 21, or 31. The memory 12, 22, or 32 can be implemented within the processor 11, 21, or 31 or external to the processor 11, 21, or 31 in which case those can be communicatively coupled to the processor 11, 21, or 31 via various means as is known in the art.

[0083] In some embodiments, the communication between the UE 10 and a base station (BS) 50 comprises non-terrestrial network (NTN) communication. In some embodiments, the base station 50 comprises spacebome platform or airborne platform or high altitude platform station. The base station 50 can communicate with the UE 10 via a spacebome platform or airborne platform, e.g., NTN satellite 60, as illustrated in FIG. IB. The BS 50 can be a serving cell or a target cell.

[0084] FIG. IB illustrates a system which includes a base station 50 and one or more UEs 10. Optionally, the system may include more than one base station 50, and each of the base stations 50 may connect to one or more UEs 10. In this disclosure, there is no limit. As an example, the base station 50 as illustrated in FIG. IB may be a moving base station, e.g., spacebome vehicle (satellite) or airborne vehicle (drone). The UE 10 can transmit transmissions to the base station 50 and the UE 10 can also receive the transmission from the base station 50. Optionally, not shown in FIG. IB, the moving base station can also serve as a relay which relays the received transmission from the UE 10 to a ground base station or vice versa. Optionally, a satellite 60 may be seen as a relay point which relays the communications between a UE 10 and a base station 50, e.g., gNB/eNB. Spacebome platform includes satellite 60 and the satellite 40 includes LEO satellite, MEO satellite, and GEO satellite. While the satellite 60 is moving, the LEO satellite and MEO satellite are moving with regard to a given location on earth. However, for GEO satellite, the GEO satellite is relatively static with regard to a given location on earth.

[0085] Spacebome platform includes a satellite and the satellite includes low earth orbiting (LEO) satellite, medium earth orbiting (MEO) satellite and geostationary earth orbiting (GEO) satellite. While the satellite is moving, the LEO and MEO satellite is moving with regard to a given location on earth. However, for GEO satellite, the GEO satellite is relatively static with regard to a given location on earth.

[0086] In some embodiments, the transceiver 13 is configured to receive, from the serving cell 20, a handover command for a handover procedure for the UE 10 switching from the serving cell 20 to the target cell 30, the transceiver 13 is configured to transmit, to the target cell 30, an uplink transmission according to the handover command, and the transceiver 13 is configured to receive, from the target cell 30, a message. This can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability.

[0087] In some embodiments, the transceiver 23 is configured to transmit, to the target cell 30, a handover request for a handover procedure for the UE 10 switching from the serving cell 20 to the target cell 30, the transceiver 23 is configured to receive, from the target cell 30, a response, and the transceiver 23 is configured to transmit, to the UE 10, a handover command for the handover procedure for the UE 10 switching from the serving cell 20 to the target cell 30. This can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability.

[0088] In some embodiments, the transceiver 33 is configured to receive, from the serving cell 20, a handover request for a handover procedure for the UE 10 switching from the serving cell 20 to the target cell 30, the transceiver 33 is configured to transmit, to the serving cell 20, a response, the transceiver 33 is configured to receive, from the UE 10, an uplink transmission relevant to a handover command, and the transceiver 33 is configured to transmit, to the UE 10, a message. This can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability. [0089] FIG. 2 illustrates a method 200 of wireless communication by a user equipment (UE) according to an embodiment of the present disclosure. In some embodiments, the method 200 includes: a block 210, receiving, from a serving cell, a handover command for a handover procedure for the UE switching from the serving cell to a target cell, a block 220, transmitting, to the target cell, an uplink transmission according to the handover command, and a block 230, receiving, from the target cell, a message. This can provide a quick handover latency for nonterrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability.

[0090] FIG. 3 illustrates a method 300 of wireless communication by a serving cell according to an embodiment of the present disclosure. In some embodiments, the method 300 includes: a block 310, transmitting, to a target cell, a handover request for a handover procedure for a user equipment (UE) switching from the serving cell to the target cell, a block 320, receiving, from the target cell, a response, and a block 330, transmitting, to the UE, a handover command for the handover procedure for the UE switching from the serving cell to the target cell. This can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability.

[0091] FIG. 4 illustrates a method 400 of wireless communication by a target cell according to an embodiment of the present disclosure. In some embodiments, the method 400 includes: a block 410, receiving, from a serving cell, a handover request for a handover procedure for a user equipment (UE) switching from the serving cell to the target cell, a block 420, transmitting, to the serving cell, a response, a block 430, receiving, from the UE, an uplink transmission relevant to a handover command, and a block 440, transmitting, to the UE, a message. This can provide a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system, provide a good communication performance, and/or provide high reliability.

[0092] In some embodiments, the handover command comprises a command for a random access channel-less (RACH-less) handover for the UE switching from the serving cell to the target cell. In some embodiments, the handover command comprises at least one of following information: an ephemeris data of the target cell; common timing advance (TA) relevant parameters of the target cell; an offset value; a new cell-radio network temporary identifier (C-RNTI); a configuration for one or more physical uplink shared channel (PUSCH) resources of the target cell, or a configuration of a search space. In some embodiments, the one or more PUSCH resources comprises one or more configured uplink grants (CUL grants).

[0093] In some embodiments, when the ephemeris data of the target cell is not provided by the serving cell, the UE assumes that the ephemeris data of the target cell is same as an ephemeris data of the serving cell. In some embodiments, when the common TA relevant parameters of the target cell are not provided by the serving cell, the UE assumes that the common TA relevant parameters of the target cell are same as common TA relevant parameters of the serving cell, or the UE assumes that a common TA of the target cell is zero. In some embodiments, the method further comprises performing synchronization by the UE with the target cell. In some embodiments, the synchronization uses the ephemeris data of the target cell and/or the common TA relevant parameters of the target cell. In some embodiments, after the synchronization is performed by the UE, the UE selects a first available PUSCH resource from the one or more PUSCH resources for uplink transmission.

[0094] In some embodiments, the one or more CUL grants are dynamically scheduled by the target cell. In some embodiments, the method further comprises starting to monitor a physical downlink control channel (PDCCH) in the search space by the UE. In some embodiments, the search space is configured for RACH-less handover. In some embodiments, the uplink transmission comprises the new C-RNTI or a TA relevant information of the UE. In some embodiments, the message from the target cell comprises the new C-RNTI, a contention resolution identifier (ID), or an acknowledgement. In some embodiments, if the UE verifies that the contention resolution ID is matched with an ID of the UE, the handover procedure is complete. In some embodiments, if the UE receives the acknowledgement, the handover procedure is complete. In some embodiments, the acknowledgement is carried by a downlink control information (DCI) and/or the acknowledgement comprises a hybrid automatic repeat request acknowledgment (HARQ-ACK) information.

[0095] FIG. 5 illustrates a communication system including a base station (BS) and a UE according to another embodiment of the present disclosure. Optionally, the communication system may include more than one base station, and each of the base stations may connect to one or more UEs. In this disclosure, there is no limit. As an example, the base station illustrated in FIG. 1A may be a moving base station, e.g., spacebome vehicle (satellite) or airborne vehicle (drone). The UE can transmit transmissions to the base station and the UE can also receive the transmission from the base station. Optionally, not shown in FIG. 5, the moving base station can also serve as a relay which relays the received transmission from the UE to a ground base station or vice versa. [0096] Spacebome platform includes satellite and the satellite includes LEO satellite, MEO satellite and GEO satellite. While the satellite is moving, the LEO and MEO satellite is moving with regards to a given location on earth. However, for GEO satellite, the GEO satellite is relatively static with regards to a given location on earth. A moving base station or satellite, e.g., in particular for LEO satellite or drone, communicates with a user equipment (UE) on the ground. Due to long distance between the UE and the base station on satellite, the beamformed transmission is needed to extend the coverage.

[0097] Optionally, as illustrated in FIG. 6, where a base station is integrated in a satellite or a drone, and the base station transmits one or more beams to the ground forming one or more coverage areas called footprint. In FIG. 6, an example illustrates that the BS transmits three beams (beam 1 , beam 2 and beam3) to form three footprints (footprint 1, 2 and 3), respectively. Optionally, 3 beams are transmitted at 3 different frequencies. In this example, the bit position is associated with a beam. FIG. 6 illustrates that, in some embodiments, a moving base station, e.g., in particular for LEO satellite or drone, communicates with a user equipment (UE) on the ground. Due to long distance between the UE and the base station on satellite, the beamformed transmission is needed to extend the coverage. As illustrated in FIG. 6, where a base station is transmitting three beams to the earth forming three coverage areas called footpoints. Moreover, each beam may be transmitted at dedicated frequencies so that the beams for footprint 1 , 2 and 3 are non-overlapped in a frequency domain. The advantage of having different frequencies corresponding to different beams is that the inter-beam interference can be minimized.

[0098] In some embodiments, a moving base station (BS), e.g., in particular for LEO satellite or drone, communicates with a user equipment (UE) on the ground. A round trip time (RTT) between the BS and the UE is time varying. The RTT variation is related to a distance variation between the BS and the UE. The RTT variation rate is proportional to a BS motion velocity. To ensure a good uplink synchronization, the BS will adjust an uplink transmission timing and/or frequency for the UE. In some embodiments of this disclosure, a method for uplink synchronization adjustment is provided, and the uplink synchronization adjustment comprises at least one of the followings: a transmission timing adjustment or a transmission frequency adjustment. Optionally, the transmission timing adjustment further comprises a timing advance (TA) adjustment.

[0099] FIG. 7 illustrates an uplink-downlink timing relation according to an embodiment of the present disclosure. FIG. 7 illustrates that, in some embodiments, downlink, uplink, and sidelink transmissions are organized into frames with 7 = (A _max /v _f /100) r _c = 10 ms duration, each consisting of ten subframes of T _rf = (A _max /V _f /1000) -7’ _c = lms duration. T _f refers to a radio frame duration. A/ refers to subcarrier spacing. n _f refers to a system frame number (SFN). T _c refers to a basic time unit for NR. refers to a subframe duration. The number of consecutive orthogonal frequency division multiplexed (OFDM) symbols per subframe is = ^re f ^ers to number of OFDM symbols per subframe for subcarrier spacing configuration . refers to number of symbols per slot. ^ ^s ^ ^frame ’^ refers to number of slots per subframe for subcarrier spacing configuration Each frame is divided into two equally-sized half-frames of five subframes each with half- frame 0 consisting of subframes 0 to 4 and half-frame 1 consisting of subframes 5 to 9. There is one set of frames in the uplink and one set of frames in the downlink on a carrier. Uplink frame number i for transmission from the UE starts TTA=(NTA+NTA,offsct)T _c , before the start of the corresponding downlink frame at the UE where N _{TA offset} is given by TS 38.213, except for a message A (msgA) transmission on physical uplink shared channel (PUSCH) where T _TA = 0 is used. TJA refers to timing advance between downlink and uplink. A _TA refers to timing advance between downlink and uplink. N _TA ^ _offset refers to a fixed offset used to calculate the timing advance. T _c refers to a basic time unit for NR. [0100] The examples given in this disclosure can be applied for loT device or NB-IoT UE in NTN systems, but the method is not exclusively restricted to NTN system nor for loT devices or NB-IoT UE. The examples given in this disclosure can be applied for NR systems, LTE systems, orNB-IoT systems.

[0101] FIG. 8 illustrates a handover procedure for a UE switching from a serving cell to a target cell according to an embodiment of the present disclosure. FIG. 8 illustrates that, in some examples, a handover procedure for a UE to handover from a source cell (or called a serving cell) to a target cell without going through an RACK procedure, that is also called an RACH-less procedure, for NR system is depicted as follows.

[0102] In some examples, when a UE receives a handover command from the serving cell, the handover command may trigger a handover procedure. If the UE is also configured with an RACH- less configuration, the UE may go through an RACH-less procedure.

[0103] In some examples, in the RACH-less procedure, the handover message from the source cell contains at least one of the following information: an ephemeris data of the target cell; common TA relevant parameters of the target cell; an offset value; a new C-RNTI. Optionally, the UE is provided with a configuration for one or more PUSCH resources of the target cell, where each of the configured PUSCH resource is called a configured uplink grant (CUL grant). In some examples, when the ephemeris data of the target cell is not provided by the serving cell (source cell), the UE assumes that the ephemeris data of the target cell is the same as the source cell. In some examples, when the common TA relevant parameters of the target cell are not provided by the serving cell, the UE assumes that the common TA relevant parameters of the target cell are the same as the source cell or optionally the UE assumes that the common TA of the target cell is zero. [0104] Then, the UE may perform synchronization with the target cell. Optionally, the synchronization may use the ephemeris data and/or the common TA parameters. When the synchronization is performed, the UE may determine an uplink grant for uplink transmission. In some examples, when the UE is provided one or more CUL grants, the UE may select a first available PUSCH resource after synchronization is complete. In some examples, the uplink grant is dynamically scheduled by the target cell. The UE may start to monitor the PDCCH in a search space. In some examples, the search space is configured for RACK less handover. In some examples, the search space configuration is provided to the UE in handover command message.

[0105] Next, the UE performs uplink transmission in the selected uplink resource. In some examples, the UE includes the new C-RNTI in the uplink transmission. Optionally, UE reports its TA relevant information in the uplink transmission.

[0106] In some examples, when the target cell receives the uplink transmission, the target cell verifies the C-RNTI. If the C-RNTI is verified, the target cell sends a contention resolution message to the UE. The contention resolution message includes the C-RNTI or a contention resolution ID. Optionally, the target cell sends an acknowledgement to the UE, where the acknowledgement may be a DCI containing HARQ-ACK information. Optionally, the acknowledgement may be a DCI scheduling an uplink transmission.

[0107] In some examples, in one step, when the UE receives the contention resolution message from the cell, the UE verifies the contention resolution ID, if the ID is matched with the UE ID, the handover procedure is complete. Optionally, when the UE receives an ACK information for the uplink transmission from the cell, the handover procedure is complete, where the ACK information may be carried by a DCI and the ACK information is a HARQ-ACK information.

[0108] Commercial interests for some embodiments are as follows. 1. Providing a quick handover latency for non-terrestrial network (NTN) and/or new radio (NR) system. 2. Providing a good communication performance. 3. Providing a high reliability. 4. Some embodiments of the present disclosure are used by 5G-NR chipset vendors, V2X communication system development vendors, automakers including cars, trains, trucks, buses, bicycles, moto-bikes, helmets, and etc., drones (unmanned aerial vehicles), smartphone makers, communication devices for public safety use, AR/VR device maker for example gaming, conference/seminar, education purposes. Some embodiments of the present disclosure are a combination of “techniques/processes” that can be adopted in 3 GPP specification to create an end product. Some embodiments of the present disclosure could be adopted in the 5G NR unlicensed band communications. Some embodiments of the present disclosure propose technical mechanisms.

[0109] FIG. 7 is a block diagram of an example system 700 for wireless communication according to an embodiment of the present disclosure. Embodiments described herein may be implemented into the system using any suitably configured hardware and/or software. FIG. 7 illustrates the system 700 including a radio frequency (RF) circuitry 710, a baseband circuitry 720, an application circuitry 730, a memory/storage 740, a display 750, a camera 760, a sensor 770, and an input/output (I/O) interface 780, coupled with each other at least as illustrated. The application circuitry 730 may include a circuitry such as, but not limited to, one or more single- core or multi-core processors. The processors may include any combination of general-purpose processors and dedicated processors, such as graphics processors, application processors. The processors may be coupled with the memory/storage and configured to execute instructions stored in the memory/storage to enable various applications and/or operating systems running on the system.

[0110] The baseband circuitry 720 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processors may include a baseband processor. The baseband circuitry may handle various radio control functions that enables communication with one or more radio networks via the RF circuitry. The radio control functions may include, but are not limited to, signal modulation, encoding, decoding, radio frequency shifting, etc. In some embodiments, the baseband circuitry may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry may support communication with an evolved universal terrestrial radio access network (EUTRAN) and/or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry is configured to support radio communications of more than one wireless protocol may be referred to as multimode baseband circuitry.

[oni] In various embodiments, the baseband circuitry 720 may include circuitry to operate with signals that are not strictly considered as being in a baseband frequency. For example, in some embodiments, baseband circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency. The RF circuitry 710 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. In various embodiments, the RF circuitry 710 may include circuitry to operate with signals that are not strictly considered as being in a radio frequency. For example, in some embodiments, RF circuitry may include circuitry to operate with signals having an intermediate frequency, which is between a baseband frequency and a radio frequency.

[0112] In various embodiments, the transmitter circuitry, control circuitry, or receiver circuitry discussed above with respect to the user equipment, eNB, or gNB may be embodied in whole or in part in one or more of the RF circuitry, the baseband circuitry, and/or the application circuitry. As used herein, “circuitry” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and/or a memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. In some embodiments, the electronic device circuitry may be implemented in, or functions associated with the circuitry may be implemented by, one or more software or firmware modules. In some embodiments, some or all of the constituent components of the baseband circuitry, the application circuitry, and/or the memory/storage may be implemented together on a system on a chip (SOC). The memory/storage 740 may be used to load and store data and/or instructions, for example, for system. The memory/storage for one embodiment may include any combination of suitable volatile memory, such as dynamic random access memory (DRAM)), and/or non-volatile memory, such as flash memory.

[0113] In various embodiments, the I/O interface 780 may include one or more user interfaces designed to enable user interaction with the system and/or peripheral component interfaces designed to enable peripheral component interaction with the system. User interfaces may include, but are not limited to a physical keyboard or keypad, a touchpad, a speaker, a microphone, etc. Peripheral component interfaces may include, but are not limited to, a non-volatile memory port, a universal serial bus (USB) port, an audio jack, and a power supply interface. In various embodiments, the sensor 770 may include one or more sensing devices to determine environmental conditions and/or location information related to the system. In some embodiments, the sensors may include, but are not limited to, a gyro sensor, an accelerometer, a proximity sensor, an ambient light sensor, and a positioning unit. The positioning unit may also be part of, or interact with, the baseband circuitry and/or RF circuitry to communicate with components of a positioning network, e.g., a global positioning system (GPS) satellite.

[0114] In various embodiments, the display 750 may include a display, such as a liquid crystal display and a touch screen display. In various embodiments, the system 700 may be a mobile computing device such as, but not limited to, a laptop computing device, a tablet computing device, a netbook, an ultrabook, a smartphone, an AR/VR glasses, etc. In various embodiments, system may have more or less components, and/or different architectures. Where appropriate, methods described herein may be implemented as a computer program. The computer program may be stored on a storage medium, such as a non-transitory storage medium.

[0115] A person having ordinary skill in the art understands that each of the units, algorithm, and steps described and disclosed in the embodiments of the present disclosure are realized using electronic hardware or combinations of software for computers and electronic hardware. Whether the functions run in hardware or software depends on the condition of application and design requirement for a technical plan. A person having ordinary skill in the art can use different ways to realize the function for each specific application while such realizations should not go beyond the scope of the present disclosure. It is understood by a person having ordinary skill in the art that he/she can refer to the working processes of the system, device, and unit in the above-mentioned embodiment since the working processes of the above-mentioned system, device, and unit are basically the same. For easy description and simplicity, these working processes will not be detailed.

[0116] It is understood that the disclosed system, device, and method in the embodiments of the present disclosure can be realized with other ways. The above-mentioned embodiments are exemplary only. The division of the units is merely based on logical functions while other divisions exist in realization. It is possible that a plurality of units or components are combined or integrated in another system. It is also possible that some characteristics are omitted or skipped. On the other hand, the displayed or discussed mutual coupling, direct coupling, or communicative coupling operate through some ports, devices, or units whether indirectly or communicatively by ways of electrical, mechanical, or other kinds of forms.

[0117] The units as separating components for explanation are or are not physically separated. The units for display are or are not physical units, that is, located in one place or distributed on a plurality of network units. Some or all of the units are used according to the purposes of the embodiments. Moreover, each of the functional units in each of the embodiments can be integrated in one processing unit, physically independent, or integrated in one processing unit with two or more than two units.

[0118] If the software function unit is realized and used and sold as a product, it can be stored in a readable storage medium in a computer. Based on this understanding, the technical plan proposed by the present disclosure can be essentially or partially realized as the form of a software product. Or, one part of the technical plan beneficial to the conventional technology can be realized as the form of a software product. The software product in the computer is stored in a storage medium, including a plurality of commands for a computational device (such as a personal computer, a server, or a network device) to run all or some of the steps disclosed by the embodiments of the present disclosure. The storage medium includes a USB disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a floppy disk, or other kinds of media capable of storing program codes.

[0119] While the present disclosure has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.