# US 9,521,671 B2 · Method and device for performing channel access in WLAN system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,671 B2 - Document ID: US9521671B2 - Status: Granted - Kind: B2 - Application number: 14/411,833 - Filed: 2013-08-05 - Published: 2015-08-20 - Granted: 2016-12-13 - Earliest claimed: 2013-03-27 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Jinsoo Choi; Hangyu Cho; Jeongki Kim - Web page: https://patentgrep.com/patent/US9521671B2 ## CPC - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04B 7/0452: Multi-user MIMO systems - H04W 4/70: Services for machine-to-machine communication [M2M] or machine type communication [MTC] - H04W 52/0216: {using a pre-established activity schedule, e.g. traffic indication frame} - H04W 52/0219: {where the power saving management affects multiple terminals} - H04W 52/0235: {where the received signal is a power saving command} - H04W 52/0238: {where the received signal is an unwanted signal, e.g. interference or idle signal} - H04W 72/121: for groups of terminals or users - H04W 72/1215: {for collaboration of different radio technologies} - H04W 72/30: Resource management for broadcast services - H04W 74/06: using polling - H04L 61/5069: for group communication, multicast communication or broadcast communication - H04W 74/04: Scheduled access (hybrid access H04W74/02) - H04W 84/12: WLAN [Wireless Local Area Networks] - Y02D 30/70: in wireless communication networks - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract One embodiment of the present invention relates to a method whereby a station (STA) which is irrelevant to a multi user (MU) group performs channel access in a wireless communication system, the method for performing channel access comprising the steps of: receiving a resource allocation frame; and checking a group indicator field comprised in the resource allocation frame, wherein the STA determines a slot start offset through the first bit of a slot allocation field for the MU group in case the group indicator field indicates the presence of the slot allocation field for the MU group in the resource allocation frame. ## Claims ### Claim 1 A method for performing channel access at a station (STA) which does not belong to a multiuser (MU) group in a wireless communication system, the method comprising: receiving a resource assignment frame comprising one or more slot assignment fields; and checking a group indicator field included in the resource assignment frame, wherein, if the group indicator field indicates that a slot assignment field for the MU group is present in the one or more slot assignment fields, the STA determines, by using a first bit of the slot assignment field for the MU group, a slot assignment field, of the one or more slot assignment fields, containing a subfield which includes information to be used for a comparison with an association ID (AID) of the STA, wherein the first bit indicates whether the slot assignment field is a last slot assignment field for the MU group. ### Claim 2 (depends on 1) The method according to claim 1, wherein, if the first bit indicates that the slot assignment field is a last slot assignment field for the MU group, the STA performs a comparison of AIDs in a next slot assignment field of the one or more slot assignment fields. ### Claim 3 (depends on 2) The method according to claim 2, wherein the STA compares, in the next slot assignment field, information included in a second subfield, which is next to a first subfield corresponding to the first bit, with an AID of the STA, and if the information in the second subfield corresponds to the AID of the STA, the STA obtains a start time of medium access from a last subfield of the slot assignment field. ### Claim 4 (depends on 3) The method according to claim 3, wherein the STA transmits a power save-poll, PS-Poll, frame after contention at the start time of medium access. ### Claim 5 (depends on 1) The method according to claim 1, wherein, if the first bit indicates that a next slot assignment field for the MU group is present after the slot assignment field, the STA recognizes a first bit in the next slot assignment field, of the one or more slot assignment fields, as the same indicator as the first bit of the slot assignment field. ### Claim 6 (depends on 5) The method according to claim 5, wherein the STA disregards the other subfields of the slot assignment field except for a subfield corresponding to the first bit. ### Claim 7 (depends on 1) The method according to claim 1, further comprising, if the group indicator field indicates that a slot assignment field for the MU group is not present in the resource assignment frame, comparing information, included in a second subfield, which is next to a first subfield corresponding to the first bit of the slot assignment field, with an AID of the STA. ### Claim 8 (depends on 7) The method according to claim 7, further comprising, if the second subfield corresponds to the AID of the STA: obtaining a start time of medium access from a last subfield of the slot assignment; and transmitting a power save-poll (PS-Poll) frame after contention at the start time of medium access. ### Claim 9 (depends on 1) The method according to claim 1, wherein the slot assignment field for the MU group is located first at the beginning of one or more slot assignment fields included in the resource assignment frame. ### Claim 10 (depends on 1) The method according to claim 1, wherein, if the group indicator field indicates that a slot assignment field for the MU group is present in the resource assignment frame, the resource assignment frame includes at least one slot assignment field for an MU group and zero or more slot assignment fields for each STA. ### Claim 11 (depends on 1) The method according to claim 1, wherein, if the group indicator field indicates that a slot assignment field for the MU group is not present in the resource assignment frame, the resource assignment includes only a slot assignment field for each STA. ### Claim 12 A station (STA) which does not belong to a multiuser (MU) group in a wireless communication system, the STA comprising: a transceiver that receives a resource assignment frame comprising one or more slot assignment fields; and a processor that checks a group indicator field included in the resource assignment frame, wherein if the group indicator field indicates that a slot assignment field for the MU group is present in the one or more slot assignment fields, the STA determines, by using a first bit of the slot assignment field for the MU group, a slot assignment field, of the one or more slot assignment fields, containing a subfield which includes information to be used for a comparison with a an association ID (AID) of the STA, wherein the first bit indicates whether the slot assignment field is a last slot assignment field for the MU group. ### Claim 13 (depends on 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12) The STA according to claim 12, wherein the STA performs the method according to any one of claims 2 to 11.