# US 12,004,226 B2 · Method and apparatus for switching between 2 step and 4 step random access (RA) procedures and contention resolutions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,004,226 B2 - Document ID: US12004226B2 - Status: Granted - Kind: B2 - Application number: 17/687,013 - Filed: 2022-03-04 - Published: 2022-08-25 - Granted: 2024-06-04 - Earliest claimed: 2019-04-24 - Assignees: Samsung Electronics Co., Ltd. - Applicants: Samsung Electronics Co., Ltd. - Inventors: Anil Agiwal; Jaehyuk Jang; Soenghun Kim - Web page: https://patentgrep.com/patent/US12004226B2 ## CPC - H04W 74/002: {Transmission of channel access control information} - H04W 74/0891: {for synchronized access} - H04L 1/1819: {with retransmission of additional or different redundancy} - H04L 1/1848: {Time-out mechanisms} - H04L 1/1854: {Scheduling and prioritising arrangements} - H04L 1/1896: {ARQ related signaling} - H04L 5/0055: {Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861)} - H04W 52/36: with a discrete range or set of values, e.g. step size, ramping or offsets - H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal - H04W 74/0836: with 2-step access - H04W 76/11: Allocation or use of connection identifiers - H04L 5/0044: {Allocation of payload; Allocation of data channels, e.g. PDSCH or PUSCH} - H04W 56/0005: {synchronizing of arrival of multiple uplinks} - H04W 74/0833: Random access procedures, e.g. with 4-step access - 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 A communication method and system for converging a 5th generation (5G) communication system for supporting higher data rates beyond a 4th generation (4G) system with a technology for Internet of things (IoT) are provided. A method performed by a terminal in a wireless communication system is provided that includes transmitting, to a base station, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including an RA preamble, receiving, from the base station, a message B (MsgB) as a response to the MsgA, identifying whether the 2 step RA procedure is successfully completed, and transmitting, to the base station, hybrid automatic repeat request (HARQ) acknowledge (ACK) information for a transport block (TB) associated with the MsgB, in case that the 2 step RA procedure is successfully completed. ## Claims ### Claim 1 A method performed by a terminal in a wireless communication system, the method comprising: transmitting, to a base station, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI); receiving, from the base station, a physical downlink control channel (PDCCH); and identifying whether the 2 step RA procedure is successfully completed, wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is received based on the downlink TB. ### Claim 2 (depends on 1) The method of claim 1, further comprising: switching from the 2 step RA procedure to a 4 step RA procedure, in case that the 2 step RA procedure is not successfully completed and a number of transmissions of the MsgA reaches to a specific value. ### Claim 3 (depends on 2) The method of claim 2, wherein a same RA preamble group as for the 2 step RA procedure is used for the 4 step RA procedure. ### Claim 4 (depends on 1) The method of claim 1, wherein the TA command included in a medium access control (MAC) protocol data unit (PDU) indicates an index value TA=0, 1, 2, . . . , 3846. ### Claim 5 A method performed by a base station in a wireless communication system, the method comprising: receiving, from a terminal, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI); and transmitting, to the terminal, a physical downlink control channel (PDCCH), wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is transmitted based on the downlink TB. ### Claim 6 (depends on 5) The method of claim 5, wherein the 2 step RA procedure is switched to a 4 step RA procedure, in case that the 2 step RA procedure is not successfully completed and a number of transmissions of the MsgA reaches to a specific value. ### Claim 7 (depends on 6) The method of claim 6, wherein a same RA preamble group as for the 2 step RA procedure is used for the 4 step RA procedure. ### Claim 8 (depends on 5) The method of claim 5, wherein the TA command included in a medium access control (MAC) protocol data unit (PDU) indicates an index value TA=0, 1, 2, . . . , 3846. ### Claim 9 A terminal in a wireless communication system, the terminal comprising: a transceiver; and at least one processor configured to: transmit, to a base station, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI), receive, from the base station, a physical downlink control channel (PDCCH), and identify whether the 2 step RA procedure is successfully completed, wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is received based on the downlink TB. ### Claim 10 (depends on 9) The terminal of claim 9, wherein the at least one processor is further configured to switch from the 2 step RA procedure to a 4 step RA procedure, in case that the 2 step RA procedure is not successfully completed and a number of transmissions of the MsgA reaches to a specific value. ### Claim 11 (depends on 10) The terminal of claim 10, wherein a same RA preamble group as for the 2 step RA procedure is used for the 4 step RA procedure. ### Claim 12 A base station in a wireless communication system, the base station comprising: a transceiver; and at least one processor configured to: receive, from a terminal, a message A (MsgA) associated with a 2 step random access (RA) procedure, the MsgA including a cell-radio network temporary identifier (C-RNTI), and transmit, to the terminal, a physical downlink control channel (PDCCH), wherein the 2 step RA procedure is successfully completed, in case that a time alignment timer (TAT) is running and the PDCCH scheduling an uplink transport block (TB) is addressed to the C-RNTI, and wherein the 2 step RA procedure is successfully completed, in case that the TAT is not running, the PDCCH scheduling a downlink TB is addressed to the C-RNTI and a timing advance (TA) command is transmitted based on the downlink TB. ### Claim 13 (depends on 12) The base station of claim 12, wherein the 2 step RA procedure is switched to a 4 step RA procedure, in case that the 2 step RA procedure is not successfully completed and a number of transmissions of the MsgA reaches to a specific value. ### Claim 14 (depends on 13) The base station of claim 13, wherein a same RA preamble group as for the 2 step RA procedure is used for the 4 step RA procedure.