# US 11,910,444 B2 · Random access channel (RACH) response (RAR) reception in an unlicensed radio frequency (RF) spectrum band > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,910,444 B2 - Document ID: US11910444B2 - Status: Granted - Kind: B2 - Application number: 17/410,757 - Filed: 2021-08-24 - Published: 2022-02-24 - Granted: 2024-02-20 - Earliest claimed: 2019-02-08 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Ozcan Ozturk; Xiaoxia Zhang; Tao Luo; Jing Sun - Web page: https://patentgrep.com/patent/US11910444B2 ## CPC - H04W 16/14: Spectrum sharing arrangements {between different networks} - H04L 12/413: with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD] - H04L 27/2692: {with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver} - H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal - H04W 74/00: Wireless channel access - H04W 74/006: {in the downlink, i.e. towards the terminal} - H04W 74/0833: Random access procedures, e.g. with 4-step access - H04W 74/0836: with 2-step access - H04W 74/0891: {for synchronized access} - H04W 76/11: Allocation or use of connection identifiers - 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 This disclosure provides systems, methods, and apparatuses to enable a user equipment (UE) and a base station to improve reception of a random access response (RAR) by the UE in an unlicensed spectrum. A network may define a procedure for calculating a random access radio network temporary identifier (RA-RNTI) specific to unlicensed spectrum based on an extended RAR window. The calculation procedure may allow UEs transmitting in the window to calculate a unique RA-RNTI and identify a RAR addressed to the UE using the unique RA-RNTI. Additionally, or alternatively, a base station may transmit a RAR including timing information associated with a corresponding random access request. Accordingly, a UE may receive the RAR and compare the timing information with its own random access request in order to determine whether the RAR is addressed to the UE. Additionally, a UE may monitor a secondary cell or a sub-band for the RAR. ## Claims ### Claim 1 An apparatus for wireless communications, comprising: a first interface configured to output a random access preamble for transmission in a first physical random access channel (PRACH) occasion; a second interface configured to obtain a first portion of a random access response (RAR) message within a RAR window, the first portion of the RAR message comprising a timing information indicator; and a processing system configured to determine if the first portion of the RAR message is in response to the random access preamble when the timing information indicator comprises a last portion of a system frame number (SFN) corresponding to the first PRACH occasion. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein at least one of the first interface or the second interface is configured to communicate with a base station using information in the first portion of the RAR message associated with a determination that the first portion of the RAR message is in response to the random access preamble. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein at least one of the first interface, the second interface, or the processing system operates according to a four-step random access procedure. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein at least one of the first interface, the second interface, or the processing system operates according to a two-step random access procedure. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein at least one of the first interface, the second interface, or the processing system is configured to switch to operate according to a four-step random access procedure associated with a second portion of the RAR message in response to the random access preamble not being received within the RAR window. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein at least one of the first interface, the second interface, or the processing system operates according to a random access procedure in an unlicensed radio frequency spectrum band. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the second interface is configured to: obtain monitoring information for the first portion of the RAR message within the RAR window, wherein obtaining the first portion of the RAR message is associated with the monitoring information. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the second interface is configured to: obtain monitoring information for the first portion of the RAR message on a primary cell and at least one of one or more secondary cells and one or more sub-bands. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises one or more least significant bits of the SFN. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the one or more least significant bits of the SFN comprises two least significant bits of the SFN. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises a last two bits of the SFN. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein: the processing system is configured to identify a plurality of PRACH occasions for transmitting the random access preamble; and the processing system is configured to select the first PRACH occasion from the plurality of PRACH occasions for transmitting the random access preamble, wherein the first PRACH occasion comprises an earliest available PRACH occasion of the plurality of PRACH occasions. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the processing system is configured to calculate a radio network temporary identifier (RNTI) associated with the first PRACH occasion. ### Claim 14 (depends on 1) The apparatus of claim 1, wherein: the first portion of the RAR message corresponds to downlink control information (DCI); and the timing information indicator corresponds to a field in the DCI. ### Claim 15 (depends on 1) The apparatus of claim 1, wherein: the random access preamble corresponds to a random access message 1 in a four-step random access procedure or a random access message A (msgA) in a two-step random access procedure; and the first portion of the RAR message corresponds to a random access message 2 in the four-step random access procedure or a random access message B (msgB) in the two-step random access procedure. ### Claim 16 (depends on 1) The apparatus of claim 1, wherein the first portion of the RAR message is identified by a radio network temporary identifier (RNTI). ### Claim 17 (depends on 1) The apparatus of claim 1, wherein at least a portion of the first portion of the RAR message is scrambled using a radio network temporary identifier (RNTI). ### Claim 18 (depends on 1) The apparatus of claim 1, wherein the apparatus is included in a user equipment (UE). ### Claim 19 An apparatus for wireless communications, comprising: a first interface configured to obtain a random access preamble in a first physical random access channel (PRACH) occasion; a processing system configured to determine a timing information indicator corresponding to obtaining the random access preamble, the timing information indicator comprising a last portion of a system frame number (SFN) corresponding to the first PRACH occasion; and a second interface configured to output, in response to the random access preamble, a first portion of a random access response (RAR) message for transmission within a RAR window, the first portion of the RAR message comprising the timing information indicator. ### Claim 20 (depends on 19) The apparatus of claim 19, wherein at least one of the first interface and the second interface is configured to communicate with a user equipment (UE) using information transmitted in the first portion of the RAR message associated with the RAR message being in response to the random access preamble. ### Claim 21 (depends on 19) The apparatus of claim 19, wherein at least one of the first interface, the second interface, or the processing system operates according to a four-step random access procedure. ### Claim 22 (depends on 19) The apparatus of claim 19, wherein at least one of the first interface, the second interface, or the processing system operates according to a two-step random access procedure. ### Claim 23 (depends on 19) The apparatus of claim 19, wherein at least one of the first interface, the second interface, or the processing system operates according to a random access procedure in an unlicensed radio frequency spectrum band. ### Claim 24 (depends on 19) The apparatus of claim 19, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises one or more least significant bits of the SFN. ### Claim 25 (depends on 24) The apparatus of claim 24, wherein the one or more least significant bits of the SFN comprises two least significant bits of the SFN. ### Claim 26 (depends on 19) The apparatus of claim 19, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises a last two bits of the SFN. ### Claim 27 (depends on 19) The apparatus of claim 19, wherein: the first portion of the RAR message corresponds to downlink control information (DCI); and the timing information indicator corresponds to a field in the DCI. ### Claim 28 (depends on 19) The apparatus of claim 19, wherein the processing system is configured to scramble at least a portion of the first portion of the RAR message using a radio network temporary identifier (RNTI). ### Claim 29 A method for wireless communications at a user equipment (UE), comprising: transmitting a random access preamble for transmission in a first physical random access channel (PRACH) occasion; receiving, from a base station, a first portion of a random access response (RAR) message within a RAR window, the first portion of the RAR message comprising a timing information indicator; and determining if the first portion of the RAR message is in response to the random access preamble when the timing information indicator comprises a last portion of a system frame number (SFN) corresponding to the first PRACH occasion. ### Claim 30 (depends on 29) The method of claim 29, wherein the UE is configured to communicate with the base station associated with a determination that the first portion or the RAR message is in response to the random access preamble. ### Claim 31 (depends on 29) The method of claim 29, wherein the UE operates according to a four-step random access procedure. ### Claim 32 (depends on 29) The method of claim 29, wherein the UE operates according to a two-step random access procedure. ### Claim 33 (depends on 32) The method of claim 32, wherein the UE is configured to switch to operate according to a four-step random access procedure associated with a second portion of the RAR message in response to the random access preamble not being received within the RAR window. ### Claim 34 (depends on 29) The method of claim 29, wherein the UE operates according to a random access procedure in an unlicensed radio frequency spectrum band. ### Claim 35 (depends on 29) The method of claim 29, further comprising: receiving monitoring information for the first portion of the RAR message within the RAR window, wherein receiving the first portion of the RAR message is associated with the monitoring information. ### Claim 36 (depends on 29) The method of claim 29, further comprising: receiving monitoring information for the first portion of the RAR message on a primary cell and at least one of one or more secondary cells and one or more sub-bands. ### Claim 37 (depends on 29) The method of claim 29, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises one or more least significant bits of the SFN. ### Claim 38 (depends on 37) The method of claim 37, wherein the one or more least significant bits of the SFN comprises two least significant bits of the SFN. ### Claim 39 (depends on 29) The method of claim 29, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises a last two bits of the SFN. ### Claim 40 (depends on 29) The method of claim 29, further comprising: identifying a plurality of PRACH occasions for transmitting the random access preamble; and selecting the first PRACH occasion from the plurality of PRACH occasions for transmitting the random access preamble, wherein the first PRACH occasion comprises an earliest available PRACH occasion of the plurality of PRACH occasions. ### Claim 41 (depends on 29) The method of claim 29, further comprising: calculating a radio network temporary identifier (RNTI) associated with the first PRACH occasion. ### Claim 42 (depends on 29) The method of claim 29, wherein: the first portion of the RAR message corresponds to downlink control information (DCI); and the timing information indicator corresponds to a field in the DCI. ### Claim 43 (depends on 29) The method of claim 29, wherein: the random access preamble corresponds to a random access message 1 in a four-step random access procedure or a random access message A (msgA) in a two-step random access procedure; and the first portion of the RAR message corresponds to a random access message 2 in the four-step random access procedure or a random access message B (msgB) in the two-step random access procedure. ### Claim 44 (depends on 29) The method of claim 29, wherein the first portion of the RAR message is identified by a radio network temporary identifier (RNTI). ### Claim 45 (depends on 29) The method of claim 29, wherein at least a portion of the first portion of the RAR message is scrambled using a radio network temporary identifier (RNTI). ### Claim 46 A method for wireless communications, comprising: receiving, from a user equipment (UE), a random access preamble in a first physical random access channel (PRACH) occasion; determining a timing information indicator corresponding to receiving the random access preamble, the timing information indicator comprising a last portion of a system frame number (SFN) corresponding to the first PRACH occasion; and transmitting, to the UE and in response to the random access preamble, a first portion of a random access response (RAR) message for transmission within a RAR window, the first portion of the RAR message comprising the timing information indicator. ### Claim 47 (depends on 46) The method of claim 46, further comprising: operating according to a two-step random access procedure or according to a four-step random access procedure. ### Claim 48 (depends on 46) The method of claim 46, further comprising: operating according to a random access procedure in an unlicensed radio frequency spectrum band. ### Claim 49 (depends on 46) The method of claim 46, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises one or more least significant bits of the SFN. ### Claim 50 (depends on 49) The method of claim 49, wherein the one or more least significant bits of the SFN comprises two least significant bits of the SFN. ### Claim 51 (depends on 46) The method of claim 46, wherein the last portion of the SFN corresponding to the first PRACH occasion comprises a last two bits of the SFN. ### Claim 52 (depends on 46) The method of claim 46, wherein: the first portion of the RAR message corresponds to downlink control information (DCI); and the timing information indicator corresponds to a field in the DCI. ### Claim 53 (depends on 46) The method of claim 46, further comprising: scrambling at least a portion of the first portion of the RAR message using a radio network temporary identifier (RNTI).