# US 9,439,136 B2 · Method and apparatus for scanning in wireless LAN > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,136 B2 - Document ID: US9439136B2 - Status: Granted - Kind: B2 - Application number: 14/405,749 - Filed: 2013-07-11 - Published: 2015-06-25 - Granted: 2016-09-06 - Earliest claimed: 2012-07-11 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Giwon Park; Jinsam Kwak; Kiseon Ryu - Web page: https://patentgrep.com/patent/US9439136B2 ## CPC - H04W 48/16: Discovering, processing access restriction or access information - H04W 8/005: {Discovery of network devices, e.g. terminals} - H04W 52/0216: {using a pre-established activity schedule, e.g. traffic indication frame} - H04W 52/0229: {where the received signal is a wanted signal} - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04W 48/00: Access restriction (access security to prevent unauthorised access H04W12/08); Network selection; Access point selection - H04W 80/10: adapted for {application} session management, e.g. SIP [Session Initiation Protocol] {(connection management H04W76/00; arrangements for session management H04L67/14)} - H04W 80/12: Application layer protocols, e.g. WAP [Wireless Application Protocol] - H04W 84/12: WLAN [Wireless Local Area Networks] - H04W 88/00: Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices - H04W 88/06: adapted for operation in multiple networks {or having at least two operational modes}, e.g. multi-mode terminals - 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) - 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 A method and an apparatus for scanning in a wireless LAN are disclosed. The method for scanning in a wireless LAN comprises the steps of: enabling a station (STA) to receive, from a first access point (AP) operated in a first channel, a detection frame comprising identifier information of a second AP operated in a second channel and beacon frame transmission time information of the second AP, and enabling the STA to scan a beacon frame of the second AP on the basis of the beacon frame transmission time information of the second AP. Thus, the present invention can rapidly perform a scanning operation. ## Claims ### Claim 1 A method for scanning in a wireless local area network (LAN), the method comprising: receiving, by a station(STA), a discovery frame from a first access point(AP) operating on a first channel, the discovery frame including identifier information of a second AP operating on a second channel and beacon frame transmission time information of the second AP; and scanning, by the STA, a beacon frame of the second AP based on the beacon frame transmission time information of the second AP, wherein the beacon frame transmission time information of the second AP includes information on a difference between a transmission time of the discovery frame and a transmission time of a beacon frame of the second AP transmitted after the discovery frame is transmitted, and wherein a transmission period of the discovery frame is shorter than a transmission period of a beacon frame of the first AP. ### Claim 2 (depends on 1) The method of claim 1, wherein the discovery frame further includes information on a number of all of the STAs included in a basic service set (BSS) of the second AP. ### Claim 3 (depends on 1) The method of claim 1, wherein the first channel and the second channel do not overlap each other, and wherein the STA is included in a basic service set (BSS) of the first AP before the discovery frame is transmitted. ### Claim 4 (depends on 1) The method of claim 1, wherein the scanning, by the STA, the beacon frame of the second AP based on the beacon frame transmission time information of the second AP includes: when a remaining time of a transmission of the beacon frame from the second AP is larger than an operation mode switching threshold, switching, by the STA, an operation mode from an active mode to a sleep mode; and switching, by the STA, the operation mode from the sleep mode back to the active mode based on the beacon frame transmission time information of the second AP to monitor the beacon frame. ### Claim 5 (depends on 1) The method of claim 1, wherein the first AP transmits beacon frame transmission time information of the first AP, identifier information of the first AP, and load information of the first AP through a distribution system to the second AP, wherein the second AP transmits the beacon frame transmission time information of the second AP, identifier information of the second AP, and load information of the second AP through the distribution system to the first AP, wherein the load information of the first AP includes information on a number of all of the STAs included in a basic service set (BSS) of the first AP, and wherein the load information of the second AP includes information on a number of all of the STAs included in a BSS of the second AP. ### Claim 6 (depends on 1) The method of claim 1, wherein the scanning, by the STA, the beacon frame of the second AP based on the beacon frame transmission time information of the second AP includes: when a remaining time of a transmission of the beacon frame from the second AP is larger than a scanning mode switching threshold, switching, by the STA, a scanning mode from a passive mode to an active mode; transmitting, by the STA, a probe request frame including an identifier of the second AP; and receiving, by the STA, a probe response frame from the second AP in response to the probe request frame. ### Claim 7 (depends on 1) The scanning method of claim 1, wherein the second AP is an AP determined as a target to be scanned by the STA before the STA receives the discovery frame. ### Claim 8 An STA (station) of a wireless local area network (LAN) system, the STA comprising: a processor configured to: receive a discovery frame from a first access point(AP) operating on a first channel, the discovery frame including identifier information of a second AP operating on a second channel and beacon frame transmission time information of the second AP, and scan a beacon frame of the second AP based on the beacon frame transmission time information of the second AP, wherein the beacon frame transmission time information of the second AP includes information on a difference between a transmission time of the discovery frame and a transmission time of a beacon frame of the second AP transmitted after the discovery frame is transmitted, and wherein a transmission period of the discovery frame is shorter than a transmission period of a beacon frame of the first AP. ### Claim 9 (depends on 8) The STA of claim 8, wherein the discovery frame further includes information on a number of all of the STAs included in a basic service set (BSS) of the second AP. ### Claim 10 (depends on 8) The STA of claim 8, wherein the first channel and the second channel do not overlap each other, and wherein the STA is included in a basic service set (BSS) of the first AP before the discovery frame is transmitted. ### Claim 11 (depends on 8) The STA of claim 8, wherein the processor is configured to: when a remaining time of a transmission of the beacon frame from the second AP is larger than an operation mode switching threshold, switch an operation mode from active mode to sleep mode; and switch the operation mode from the sleep mode back to the active mode based on the beacon frame transmission time information of the second AP to monitor the beacon frame. ### Claim 12 (depends on 8) The STA of claim 8, wherein the first AP transmits beacon frame transmission time information of the first AP, identifier information of the first AP, and load information of the first AP through a distribution system to the second AP, wherein the second AP transmits the beacon frame transmission time information of the second AP, identifier information of the second AP, and load information of the second AP through the distribution system to the first AP, wherein the load information of the first AP includes information on a number of all of the STAs included in a basic service set (BSS) of the first AP, and wherein the load information of the second AP includes information on a number of all of the STAs included in a BSS of the second AP. ### Claim 13 (depends on 8) The STA of claim 8, wherein the processor is configured to: when a remaining time when the beacon frame is transmitted from the second AP is larger than a scanning mode switching threshold, switch a scanning mode from passive mode to active mode; transmit a probe request frame including an identifier of the second AP; and receive a probe response frame from the second AP in response to the probe request frame. ### Claim 14 (depends on 8) The STA of claim 8, wherein the second AP is an AP determined as a target to be scanned by the STA before the STA receives the discovery frame.