# US 2025/0168898 A1 · Cross-carrier random access channel transmission triggering > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0168898 A1 - Document ID: US20250168898A1 - Status: Published application - Kind: A1 - Application number: 19/029,238 - Filed: 2025-01-17 - Published: 2025-05-22 - Earliest claimed: 2022-08-11 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Fang YUAN; Yan ZHOU; Tao LUO - Web page: https://patentgrep.com/patent/US20250168898A1 ## CPC - H04W 74/006: {in the downlink, i.e. towards the terminal} - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04L 5/0094: {Indication of how sub-channels of the path are allocated} - H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA - H04W 76/38: triggered by timers - H04L 5/001: {the frequencies being arranged in component carriers} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Certain aspects of the present disclosure provide a method of wireless communication by a user equipment (UE), generally including receiving signaling configuring the UE with a set of candidate cells, receiving, from a serving cell, downlink control information (DCI) indicating one candidate cell of the set of candidate cells as a target cell for transmitting a physical random access channel (PRACH), and transmitting the PRACH in the target cell. ## Claims ### Claim 1 A method of wireless communication at a user equipment (UE), comprising: receiving signaling configuring the UE with a set of candidate cells; receiving, from a serving cell, downlink control information (DCI) indicating one candidate cell of the set of candidate cells as a target cell for transmitting a physical random access channel (PRACH); and transmitting the PRACH in the target cell. ### Claim 2 (depends on 1) The method of claim 1, wherein the set of candidate cells support mobility signaling via physical (PHY) layer or medium access control (MAC) layer signaling. ### Claim 3 (depends on 1) The method of claim 1, further comprising receiving, from the serving cell, a timing adjustment (TA) command to apply in the target cell. ### Claim 4 (depends on 1) The method of claim 1, wherein the DCI indicates the target cell by including an ID of the candidate cell. ### Claim 5 (depends on 4) The method of claim 4, wherein the ID is included in a candidate primary cell (Pcell) index field of the DCI. ### Claim 6 (depends on 1) The method of claim 1, wherein the DCI indicates the target cell via a carrier indicator field (CIF). ### Claim 7 (depends on 6) The method of claim 6, wherein a value of the CIF is associated with the target cell. ### Claim 8 (depends on 7) The method of claim 7, wherein the DCI indicates the value of the CIF is associated with the target cell if: a cyclic redundancy check (CRC) of the DCI is scrambled with a certain radio network temporary identifier (RNTI); and bits of a frequency domain resource assignment (FDRA) field of the DCI are set to certain values. ### Claim 9 A method of wireless communication at a network entity, comprising: transmitting signaling configuring a user equipment (UE) with a set of candidate cells; and transmitting downlink control information (DCI) indicating one candidate cell of the set of candidate cells as a target cell for the UE to transmit a physical random access channel (PRACH). ### Claim 10 (depends on 9) The method of claim 9, wherein the set of candidate cells support mobility signaling via physical (PHY) layer or medium access control (MAC) layer signaling. ### Claim 11 (depends on 9) The method of claim 9, further comprising: receiving, from the target cell, an indication of timing based on the PRACH; and transmitting a timing adjustment (TA) command, based on the indication of timing, for the UE to apply in the target cell. ### Claim 12 (depends on 9) The method of claim 9, wherein the DCI indicates the target cell by including an ID of the candidate cell. ### Claim 13 (depends on 12) The method of claim 12, wherein the ID is included in a candidate primary cell (Pcell) index field of the DCI. ### Claim 14 (depends on 9) The method of claim 9, wherein the DCI indicates the target cell via a carrier indicator field (CIF). ### Claim 15 (depends on 14) The method of claim 14, wherein a value of the CIF is associated with the target cell. ### Claim 16 (depends on 15) The method of claim 15, wherein the DCI indicates the value of the CIF is associated with the target cell if: a cyclic redundancy check (CRC) of the DCI is scrambled with a certain radio network temporary identifier (RNTI); and bits of a frequency domain resource assignment (FDRA) field of the DCI are set to certain values. ### Claim 17 An apparatus for wireless communication at a user equipment (UE), comprising: at least one memory comprising instructions; and at least one processor configured to execute the instructions to cause the apparatus to: receive signaling configuring the UE with a set of candidate cells; receive, from a serving cell, downlink control information (DCI) indicating one candidate cell of the set of candidate cells as a target cell for transmitting a physical random access channel (PRACH); and transmit the PRACH in the target cell. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein the set of candidate cells support mobility signaling via physical (PHY) layer or medium access control (MAC) layer signaling. ### Claim 19 (depends on 17) The apparatus of claim 17, wherein the at least one processor is configured to execute the instructions to further cause the apparatus to receive, from the serving cell, a timing adjustment (TA) command to apply in the target cell. ### Claim 20 (depends on 17) The apparatus of claim 17, wherein the DCI indicates the target cell by including an ID of the candidate cell. ### Claim 21 (depends on 20) The apparatus of claim 20, wherein the ID is included in a candidate primary cell (Pcell) index field of the DCI. ### Claim 22 (depends on 17) The apparatus of claim 17, wherein the DCI indicates the target cell via a carrier indicator field (CIF). ### Claim 23 (depends on 22) The apparatus of claim 22, wherein a value of the CIF is associated with the target cell. ### Claim 24 (depends on 23) The apparatus of claim 23, wherein the DCI indicates the value of the CIF is associated with the target cell if: a cyclic redundancy check (CRC) of the DCI is scrambled with a certain radio network temporary identifier (RNTI); and bits of a frequency domain resource assignment (FDRA) field of the DCI are set to certain values. ### Claim 25 An apparatus for wireless communication at a network entity, comprising: at least one memory comprising instructions; and at least one processor configured to execute the instructions to cause the apparatus to: transmit signaling configuring a user equipment (UE) with a set of candidate cells; and transmit downlink control information (DCI) indicating one candidate cell of the set of candidate cells as a target cell for the UE to transmit a physical random access channel (PRACH). ### Claim 26 (depends on 25) The apparatus of claim 25, wherein the set of candidate cells support mobility signaling via physical (PHY) layer or medium access control (MAC) layer signaling. ### Claim 27 (depends on 25) The apparatus of claim 25, wherein the at least one processor is configured to execute the instructions to further cause the apparatus to: receive, from the target cell, an indication of timing based on the PRACH; and transmit a timing adjustment (TA) command, based on the indication of timing, for the UE to apply in the target cell. ### Claim 28 (depends on 25) The apparatus of claim 25, wherein the DCI indicates the target cell by including an ID of the candidate cell. ### Claim 29 (depends on 28) The apparatus of claim 28, wherein the ID is included in a candidate primary cell (Pcell) index field of the DCI. ### Claim 30 (depends on 25) The apparatus of claim 25, wherein the DCI indicates the target cell via a carrier indicator field (CIF).