# US 2019/0174372 A1 · Timing advance determination by target base station for rach-less handover > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0174372 A1 - Document ID: US20190174372A1 - Status: Published application - Kind: A1 - Application number: 16/322,224 - Filed: 2017-08-10 - Published: 2019-06-06 - Earliest claimed: 2016-08-12 - Assignees: KYOCERA Corporation - Applicants: Kyocera Corporation - Inventors: David COMSTOCK - Web page: https://patentgrep.com/patent/US20190174372A1 ## CPC - H04W 36/08: Reselecting an access point - H04W 36/00: Hand-off or reselection arrangements - H04W 36/0077: {of access information of target access point} - H04W 36/00837: {Determination of triggering parameters for hand-off} - H04W 56/005: {compensating for timing error by adjustment in the receiver} - H04W 88/08: Access point devices - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract RACH-less handovers can be used to reduce the additional time required to complete the RACH procedure when the Timing Advance (TA) must be determined as part of the handover procedure. In order to facilitate a RACH-less handover, the source base station informs the target base station of a radio transmission configuration that will be used by the UE device to transmit uplink signals to the source base station, and the source base station configures the UE device in accordance with the radio transmission configuration. The UE device transmits uplink signals to the source base station using the specified radio transmission configuration, and the target base station receives the uplink signals. The UE device transmits these uplink signals to the source base station before the handover procedure is initiated. The target base station calculates the TA, based on the uplink signals, which can be signaled to the UE device in a handover command. ## Claims ### Claim 1 A method comprising: transmitting, to a target base station, user equipment (UE) device radio transmission configuration information associated with a UE device, the UE device being served by a source base station; transmitting, by the UE device, a first transmission using a UE device radio transmission configuration associated with the UE device radio transmission configuration information; receiving, by the target base station, the first transmission; determining, by the target base station, a timing difference between the target base station and the UE device, based at least partially on the received first transmission; and after determining the timing difference, initiating a handover of the UE device from the source base station to the target base station. ### Claim 2 (depends on 1) The method of claim 1, wherein the UE device radio transmission configuration information comprises: a preamble assigned to the UE device; and a subframe identifier identifying a subframe to be used by the UE device for transmitting the assigned preamble as part of the first transmission. ### Claim 3 (depends on 2) The method of claim 2, wherein transmitting the first transmission comprises: transmitting, by the UE device, a Random-Access Channel (RACH) transmission using the assigned preamble and the subframe identified by the subframe identifier. ### Claim 4 (depends on 1) The method of claim 1, further comprising: transmitting a Timing Advance to the UE device, the Timing Advance based at least partially on the timing difference. ### Claim 5 (depends on 4) The method of claim 4, wherein the Timing Advance is transmitted as part of a Handover Command. ### Claim 6 (depends on 4) The method of claim 4, wherein the Timing Advance is transmitted during the handover procedure. ### Claim 7 (depends on 1) The method of claim 1, wherein transmitting, to the target base station, UE device radio transmission configuration information comprises transmitting a Resource Status Request message. ### Claim 8 A base station comprising: a receiver configured to: receive user equipment (UE) device radio transmission configuration information associated with a UE device, the UE device being served by another base station, and receive, from the UE device, a first transmission using a UE device radio transmission configuration associated with the UE device radio transmission configuration information; and a controller coupled to the receiver, the controller configured to: determine a timing difference between the base station and the UE device, based at least partially on the received first transmission, and cooperate with a handover of the UE device from the another base station to the base station, the handover initiated by the another base station after the timing difference has been determined. ### Claim 9 (depends on 8) The base station of claim 8, wherein the UE device radio transmission configuration information comprises: a preamble assigned to the UE device; and a subframe identifier identifying a subframe to be used by the UE device for transmitting the assigned preamble as part of the first transmission. ### Claim 10 (depends on 9) The base station of claim 9, wherein the first transmission comprises: a Random-Access Channel (RACH) transmission that is transmitted using the assigned preamble and the subframe identified by the subframe identifier. ### Claim 11 (depends on 8) The base station of claim 8, further comprising: a transmitter coupled to the controller, the transmitter configured to transmit a Timing Advance to the UE device, the Timing Advance based at least partially on the timing difference. ### Claim 12 (depends on 11) The base station of claim 11, wherein the transmitter is further configured to transmit the Timing Advance as part of a Handover Command. ### Claim 13 (depends on 11) The base station of claim 11, wherein the transmitter is further configured to transmit the Timing Advance during the handover procedure. ### Claim 14 A system comprising: a user equipment (UE) device; a source base station serving the UE device, the source base station comprising: a transmitter configured to transmit UE device radio transmission configuration information associated with the UE device, and a controller configured to initiate a handover of the UE device from the source base station to the target base station; and a target base station comprising: a receiver configured to: receive the UE device radio transmission configuration information, and receive, from the UE device, a first transmission using a UE device radio transmission configuration associated with the UE device radio transmission configuration information, and a controller coupled to the receiver, the controller configured to: determine a timing difference between the target base station and the UE device, based at least partially on the received first transmission, and cooperate with the handover of the UE device from the source base station to the target base station, the handover initiated by the source base station after the timing difference has been determined. ### Claim 15 (depends on 14) The system of claim 14, wherein the transmitter of the source base station is further configured to transmit the UE device radio transmission configuration information as a Resource Status Request message. ### Claim 16 (depends on 14) The system of claim 14, wherein the UE device radio transmission configuration information comprises: a preamble assigned to the UE device; and a subframe identifier identifying a subframe to be used by the UE device for transmitting the assigned preamble as part of the first transmission. ### Claim 17 (depends on 16) The system of claim 16, wherein the first transmission comprises: a Random-Access Channel (RACH) transmission that is transmitted using the assigned preamble and the subframe identified by the subframe identifier. ### Claim 18 (depends on 14) The system of claim 14, wherein the target base station further comprises: a transmitter coupled to the controller, the transmitter configured to transmit a Timing Advance to the UE device, the Timing Advance based at least partially on the timing difference. ### Claim 19 (depends on 18) The system of claim 18, wherein the transmitter of the target base station is further configured to transmit the Timing Advance as part of a Handover Command. ### Claim 20 (depends on 18) The system of claim 18, wherein the transmitter of the target base station is further configured to transmit the Timing Advance during the handover procedure.