Method and apparatus for supporting RACH-less mobility with pre-allocated beams in wireless communication system
地域：
Seoul
摘要
A method and apparatus for supporting a random access channel (RACH)-less mobility with pre-allocated beams in a wireless communication system is provided. A user equipment (UE) receives a mobility command message which includes information on a pre-allocated UL resource for UL transmission with pre-allocated beams, synchronizes to a target cell, and performs the UL transmission to the target cell via the pre-allocated beams based on the pre-allocated UL resource for UL transmission to transmit a mobility complete message via a UL grant. If the UL transmission fails, the UE may perform RACH procedure.
說明書
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This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2019/001791, filed on Feb. 14, 2019, which claims the benefit of U.S. Provisional Application No. 62/630,272 filed on Feb. 14, 2018, the contents of which are all hereby incorporated by reference herein in their entirety.
The present invention relates to wireless communications, and more particularly, to a method and apparatus for supporting a random access channel (RACH)-less mobility with pre-allocated beams in a wireless communication system.
3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.
權(quán)利要求
What is claimed is:1. A method performed by a user equipment (UE) operating in a wireless communication system, the method comprising:receiving, from a source base station, a measurement configuration; reporting, to the source base station, measurement results according to the measurement configuration; receiving, from the source base station, a mobility control information message generated by a target base station, wherein the mobility control information message includes a rach-Skip field informing the UE that a random access procedure is to be skipped, wherein the mobility control information message includes a pre-allocated uplink (UL) grant configuration including i) information on one or more pre-allocated beams and ii) information on a quality threshold, and wherein the one or more pre-allocated beams are associated with one or more synchronization signal (SS) blocks or one or more channel state information (CSI) reference signals (RSs) transmitted by the target base station; synchronizing to a target cell served by the target base station based on the mobility control information message; based on a quality of at least one of the one or more pre-allocated beams meeting the quality threshold, performing an UL transmission to the target base station via the at least one pre-allocated beam based on the pre-allocated UL grant configuration, without performing the random access procedure with the target base station based on the rach-Skip field informing the UE that the random access procedure is to be skipped; and based on none of the one or more pre-allocated beams meeting the quality threshold, performing the random access procedure with the target base station. 2. The method of claim 1 , wherein the UL transmission includes a mobility complete message in response to the reception of the mobility control information message. 3. The method of claim 1 , wherein the method further comprises:retransmitting the UL transmission to the target base station based on the pre-allocated UL grant configuration until an acknowledgement is received from the target base station or a maximum number of retransmissions is reached. 4. The method of claim 3 , wherein the retransmission is performed via beams other than the at least one beam meeting the threshold. 5. The method of claim 1 , wherein the method further comprises:considering mobility to the target cell successfully completed based on a reception of an acknowledgement from the target base station. 6. The method of claim 5 , wherein a successful reception of a physical downlink control channel (PDCCH) transmission addressed to a UE-specific radio network temporary identity (RNTI) is considered as the reception of the acknowledgement. 7. The method of claim 1 , wherein the method further comprises:considering mobility to the target cell unsuccessfully completed based on an acknowledgement not being received from the target base station before a timer expires or a maximum number of retransmissions is reached. 8. The method of claim 7 , wherein the method further comprises:releasing the pre-allocated UL grant configuration; and triggering a radio resource control (RRC) connection reestablishment procedure. 9. The method of claim 1 , wherein the mobility control information message includes a pre-allocated sounding reference signal (SRS) configuration including information on the one or more pre-allocated beams, andwherein the UL transmission includes an SRS transmission. 10. The method of claim 9 , wherein the SRS transmission is performed until a PDCCH addressed to a UE-specific RNTI is successfully received. 11. The method of claim 10 , wherein the method further comprises:transmitting a mobility complete message to the target base station based on successful reception of the PDCCH addressed to the UE-specific RNTI. 12. The method of claim 10 , wherein the method further comprises:performing the random access procedure with the target base station based on the PDCCH addressed to the UE-specific RNTI not being successfully received before a timer expires or a maximum number of SRS transmissions is reached. 13. The method of claim 1 , wherein the UE is in communication with at least one of a mobile device, a network, and/or autonomous vehicles other than the UE. 14. A user equipment (UE) configured for operating in a wireless communication system, the UE comprising:at least one transceiver; at least one processor; and at least one memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform operations comprising: receiving, from a source base station using the at least one transceiver, a measurement configuration; reporting, to the source base station using the at least one transceiver, measurement results according to the measurement configuration; receiving, from the source base station using the at least one transceiver, a mobility control information message generated by a target base station, wherein the mobility control information message includes a rach-Skip field informing the processor that a random access procedure is to be skipped, wherein the mobility control information message includes a pre-allocated uplink (UL) grant configuration including i) information on one or more pre-allocated beams and ii) information on a quality threshold, and wherein the one or more pre-allocated beams are associated with one or more synchronization signal (SS) blocks or one or more channel state information (CSI) reference signals (RSs) transmitted by the target base station; synchronizing to a target cell served by the target base station based on the mobility control information message; based on a quality of at least one of the one or more pre-allocated beams meeting the quality threshold, performing, using the at least one transceiver, an UL transmission to the target base station via the at least one pre-allocated beams based on the pre-allocated UL grant configuration, without performing the random access procedure with the target base station based on the rach-Skip field informing the processor that the random access procedure is to be skipped; and based on none of the one or more pre-allocated beams meeting the quality threshold, performing, using the at least one transceiver, the random access procedure with the target base station. 15. A processing apparatus configured to operate a wireless device in a wireless communication system, the processing apparatus comprising:at least one processor; and at least one memory operably connectable to the at least one processor, wherein the at least one processor is configured to perform operations comprising: obtaining a measurement configuration; generating measurement results according to the measurement configuration; obtaining a mobility control information message generated by a target base station, wherein the mobility control information message includes a rach-Skip field informing the processor that a random access procedure is to be skipped, wherein the mobility control information message includes a pre-allocated uplink (UL) grant configuration including i) information on one or more pre-allocated beams and ii) information on a quality threshold, and wherein the one or more pre-allocated beams are associated with one or more synchronization signal (SS) blocks or one or more channel state information (CSI) reference signals (RSs) transmitted by the target base station; synchronizing to a target cell served by the target base station based on the mobility control information message; based on a quality of at least one of the one or more pre-allocated beams meeting the quality threshold, controlling the wireless device to perform an UL transmission to the target base station via the at least one pre-allocated beam based on the pre-allocated UL grant configuration, without performing the random access procedure with the target base station based on the rach-Skip field informing the processor that the random access procedure is to be skipped; and based on none of the one or more pre-allocated beams meeting the quality threshold, controlling the wireless device to perform the random access procedure with the target base station.
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