# US 12,192,830 B2 · Method and apparatus for accessing a random access channel by selectively using dedicated or contention-based preambles > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,192,830 B2 - Document ID: US12192830B2 - Status: Granted - Kind: B2 - Application number: 18/224,213 - Filed: 2023-07-20 - Published: 2023-11-16 - Granted: 2025-01-07 - Earliest claimed: 2008-03-04 - Assignees: InterDigital Patent Holdings, Inc. - Applicants: InterDigital Patent Holdings, Inc. - Inventors: Guodong Zhang; Jin Wang - Web page: https://patentgrep.com/patent/US12192830B2 ## CPC - H04W 36/0005: {Control or signalling for completing the hand-off} - H04W 74/004: {in the uplink, i.e. towards network} - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04W 74/0838: using contention-free random access [CFRA] - H04W 74/0866: {using a dedicated channel for access} - H04W 36/08: Reselecting an access point - H04W 74/0836: with 2-step access - 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 A method and apparatus for accessing a random access channel (RACH) during handover are disclosed. A handover procedure is initiated and a maximum handover interruption timer is activated. A dedicated preamble is transmitted in an attempt to access the RACH on a condition that the dedicated preamble is reserved in a current random access opportunity and the maximum handover interruption timer has not expired. A contention-based preamble is transmitted in an attempt to access the RACH on a condition that a dedicated preamble is not reserved in a current random access opportunity. If the maximum handover interruption timer has expired, a contention-based preamble is transmitted in an attempt to access the RACH. ## Claims ### Claim 1 A wireless transmit/receive unit (WTRU) comprising: a processor configured to: receive configuration information comprising an indication of one or more non-contention-based random access channel (RACH) resources, the one or more non-contention-based RACH resources comprising a subset of available RACH resources; attempt a first RACH access using a RACH resource of the one or more non-contention-based RACH resources during a time period associated with the one or more non-contention-based RACH resources indicated in the configuration information; determine that the time period has ended; and attempt a second RACH access using a contention-based RACH resource after the time period has ended. ### Claim 2 (depends on 1) The WTRU of claim 1, wherein the processor is configured to transmit one or more dedicated non-contention-based RACH preambles in accordance with the configuration information. ### Claim 3 (depends on 2) The WTRU of claim 2, wherein the processor is configured to transmit the one or more dedicated non-contention-based RACH preambles in a subset of available RACH opportunities. ### Claim 4 (depends on 2) The WTRU of claim 2, wherein the configuration information comprises an indication of the one or more dedicated non-contention-based RACH preambles, and wherein the indication of the one or more non-contention-based RACH resources comprises the indication of the one of the one or more dedicated non-contention-based RACH preambles. ### Claim 5 (depends on 4) The WTRU of claim 4, wherein the configuration information comprises an indication of a subset of available RACH opportunities for attempting RACH access using the one or more dedicated non-contention-based RACH preambles. ### Claim 6 (depends on 1) The WTRU of claim 1, wherein the processor is configured to transmit a contention-based RACH preamble. ### Claim 7 (depends on 1) The WTRU of claim 1, wherein the processor is configured to receive the configuration information from a base station. ### Claim 8 (depends on 1) The WTRU of claim 1, wherein the processor is configured to transmit a dedicated non-contention-based RACH preamble in a subset N out of M available random access opportunities, wherein N and M are integers and N is not equal to M. ### Claim 9 (depends on 1) The WTRU of claim 1, wherein the processor is configured to attempt the first RACH access and the second RACH access during a handover procedure for handover to a target cell. ### Claim 10 (depends on 1) The WTRU of claim 1, wherein the RACH resource of the one or more non-contention-based RACH resources comprises a first RACH preamble; and wherein the contention-based RACH resource comprises a second RACH preamble. ### Claim 11 A method comprising: receiving configuration information comprising an indication of one or more non-contention-based random access channel (RACH) resources, the one or more non-contention-based RACH resources comprising a subset of available RACH resources; attempting a first RACH access using a RACH resource of the one or more non-contention-based RACH resources during a time period associated with the one or more non-contention-based RACH resources indicated in the configuration information; determining that the time period has ended; and attempting a second RACH access using a contention-based RACH resource after the time period has ended. ### Claim 12 (depends on 11) The method of claim 11, wherein attempting the first RACH access comprises: transmitting one or more dedicated non-contention-based RACH preambles in accordance with the configuration information. ### Claim 13 (depends on 12) The method of claim 12, wherein transmitting the one or more dedicated non-contention-based RACH preambles in accordance with the configuration information further comprises: transmitting the one or more dedicated non-contention-based RACH preambles in a subset of available RACH opportunities. ### Claim 14 (depends on 12) The method of claim 12, wherein the configuration information comprises an indication of the one or more dedicated non-contention-based RACH preambles, and wherein the indication of the one or more non-contention-based RACH resources comprises the indication of the one of the one or more dedicated non-contention-based RACH preambles. ### Claim 15 (depends on 14) The method of claim 14, wherein the configuration information comprises an indication of a subset of available RACH opportunities for attempting RACH access using the one or more dedicated non-contention-based RACH preambles. ### Claim 16 (depends on 11) The method of claim 11, wherein attempting the second RACH access comprises: transmitting a contention-based-RACH preamble. ### Claim 17 (depends on 11) The method of claim 11, wherein the configuration information is received from a base station. ### Claim 18 (depends on 11) The method of claim 11, wherein attempting the first RACH access comprises: transmitting a dedicated non-contention-based RACH preamble in a subset N out of M available random access opportunities, wherein N and M are integers and N is not equal to M. ### Claim 19 (depends on 11) The method of claim 11, wherein the first RACH access and the second RACH access are attempted during a handover procedure for handover to a target cell. ### Claim 20 (depends on 11) The method of claim 11, wherein the RACH resource of the one or more non-contention-based RACH resources comprises a first RACH preamble; and wherein the contention-based RACH resource comprises a second RACH preamble.