# US 2018/0323837 A1 · Method and device for transmitting feedback frame in wireless lan system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0323837 A1 - Document ID: US20180323837A1 - Status: Published application - Kind: A1 - Application number: 15/773,144 - Filed: 2016-11-25 - Published: 2018-11-08 - Earliest claimed: 2015-11-25 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Eunsung PARK; Jinyoung CHUN; Jinsoo CHOI; Dongguk LIM; Hangyu CHO - Web page: https://patentgrep.com/patent/US20180323837A1 ## CPC - H04L 27/2613: {Structure of the reference signals} - H04B 7/0452: Multi-user MIMO systems - 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 25/02: Details {; arrangements for supplying electrical power along data transmission lines (systems for transmitting signals via power distribution lines H04B3/54)} - H04L 27/26: Systems using multi-frequency codes (H04L27/32 takes precedence) - H04L 27/2695: {with channel estimation, e.g. determination of delay spread, derivative or peak tracking (channel estimation H04L25/0202)} - H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA - H04W 84/12: WLAN [Wireless Local Area Networks] - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Provided are a method and a device for transmitting a feedback frame in a wireless LAN system. Particularly, a first wireless station receives, from a second wireless station, a feedback request field including an LTF. The first wireless station configures feedback information on a wireless channel corresponding to a preset frequency band by using the feedback request field. The first wireless station transmits the feedback information to the second wireless station. ## Claims ### Claim 1 A method performed by a first wireless station of a wireless local area network, WLAN, system supporting a plurality of frequency resource units corresponding to different frequencies, the method comprising the steps of: receiving a feedback request field comprising a long training field, LTF, from a second wireless station; configuring feedback information regarding a radio channel corresponding to a predetermined frequency band based on the feedback request field, wherein the feedback information comprises channel status information about a predetermined subcarrier index, wherein the predetermined subcarrier index is determined based on a predetermined subcarrier grouping number, wherein, if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 4, the predetermined subcarrier indices are set to [−122, −120:4:−4, −2, 2, 4:4:120, 122], wherein, if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 16, the predetermined subcarrier indices are set to [−122, −116:16:−4, −2, 2, 4:16:116, 122], wherein, if the predetermined frequency band is 40 MHz and the predetermined subcarrier grouping number is set as Ng, the predetermined subcarrier indices are set to [−244:Ng:−4, 4:Ng:244], wherein, if the predetermined frequency band is 80 MHz and the predetermined subcarrier grouping number is set as Ng, the predetermined subcarrier indices are set to [−500:Ng:−4, 4:Ng:500]; and transmitting the feedback information to the second wireless station. ### Claim 2 (depends on 1) The method of claim 1, wherein, if the predetermined subcarrier index overlaps a pilot subcarrier index, the overlapped subcarrier index is set as a neighbor subcarrier index in which an LTF coefficient is located. ### Claim 3 (depends on 1) The method of claim 1, wherein, if the predetermined subcarrier index overlaps a null subcarrier index, the overlapped subcarrier index is set as a neighbor subcarrier index in which an LTF coefficient is located. ### Claim 4 (depends on 1) The method of claim 1, wherein, if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 4 or 16, indices [−122, −2, 2, 122] of the predetermined subcarrier indices are used to perform interpolation for channel estimation. ### Claim 5 (depends on 1) The method of claim 1, wherein: the feedback request field further comprises a legacy-long training field, L-LTF, and a size of inverse fast Fourier transform, IFFT, applied to the LTF is one times or two times a size of IFFT applied to the L-LTF. ### Claim 6 A first wireless station performing communication in a wireless local area network, WLAN, system supporting a plurality of frequency resource units corresponding to different frequencies, the first wireless station comprising: a radio frequency RF, unit transmitting and receiving radio signals; and a processor operatively coupled to the RF unit, wherein the processor is configured to: receive a feedback request field comprising a long training field, LTF, from a second wireless station, configure feedback information regarding a radio channel corresponding to a predetermined frequency band based on the feedback request field, wherein the feedback information comprises channel status information about a predetermined subcarrier index, wherein the predetermined subcarrier index is determined based on a predetermined subcarrier grouping number, wherein, if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 4, the predetermined subcarrier indices are set to [−122, −120:4:−4, −2, 2, 4:4:120, 122], wherein, if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 16, the predetermined subcarrier indices are set to [−122, −116:16:−4, −2, 2, 4:16:116, 122], wherein, if the predetermined frequency band is 40 MHz and the predetermined subcarrier grouping number is set as Ng, the predetermined subcarrier indices are set to [−244:Ng:−4, 4:Ng:244], wherein, if the predetermined frequency band is 80 MHz and the predetermined subcarrier grouping number is set as Ng, the predetermined subcarrier indices are set to [−500:Ng:−4, 4:Ng:500], and transmit transmits the feedback information to the second wireless station. ### Claim 7 (depends on 6) The first wireless station of claim 6, wherein if the predetermined subcarrier index overlaps a pilot subcarrier index, the overlapped subcarrier index is set as a neighbor subcarrier index in which an LTF coefficient is located. ### Claim 8 (depends on 6) The first wireless station of claim 6, wherein if the predetermined subcarrier index overlaps a null subcarrier index, the overlapped subcarrier index is set as a neighbor subcarrier index in which an LTF coefficient is located. ### Claim 9 (depends on 6) The first wireless station of claim 6, wherein if the predetermined frequency band is 20 MHz and the predetermined subcarrier grouping number is set to 4 or 16, indices [−122, −2, 2, 122] of the predetermined subcarrier indices are used to perform interpolation for channel estimation. ### Claim 10 (depends on 6) The first wireless station of claim 6, wherein: the feedback request field further comprises a legacy-long training field L-LTF, and a size of inverse fast Fourier transform, IFFT, applied to the LTF is one times or two times a size of IFFT applied to the L-LTF.