# US 2017/0288748 A1 · Preamble selection for simultaneous transmissions in wireless local area network (wlan) systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0288748 A1 - Document ID: US20170288748A1 - Status: Published application - Kind: A1 - Application number: 15/510,383 - Filed: 2015-09-11 - Published: 2017-10-05 - Earliest claimed: 2014-09-12 - Assignees: InterDigital Patent Holdings, Inc. - Applicants: InterDigital Patent Holdings, Inc. - Inventors: Hanqing Lou; Oghenekome Oteri; Pengfei Xia; Robert L. Olesen - Web page: https://patentgrep.com/patent/US20170288748A1 ## CPC - H04B 7/0452: Multi-user MIMO systems - H04B 7/0617: {for beam forming} - H04L 1/0612: {Space-time modulation} - H04L 1/0681: {adapting space time parameters, i.e. modifying the space time matrix} - H04L 5/0094: {Indication of how sub-channels of the path are allocated} - H04L 27/26025: {Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking (allocating sub-channels of the transmission path H04L5/003)} - H04L 27/2666: {Acquisition of further OFDM parameters, e.g. bandwidth, subcarrier spacing, or guard interval length} - H04B 7/024: Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems - H04L 1/06: using space diversity - H04L 1/0618: {Space-time coding} - 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)} - H04W 84/12: WLAN [Wireless Local Area Networks] - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Systems, methods, and instrumentalities are provided to determine a physical layer (PHY) protocol data unit (PPDU) format. A determination may be made if a basic service set (BSS) includes a first-type legacy station, wherein the first-type legacy station is a pre-802.1 In device. A determination may be made if stations in the BSS support a short format preamble. A determination may be made if beamforming or precoding is to be used in association with an upcoming multi-user transmission. An indication of a selected PPDU preamble format may be sent to a station in the BSS via a multi-user transmission, wherein a long format preamble is selected when the BSS includes the first-type legacy station, beamforming is to be used in association with the upcoming multi-user transmission, or precoding is to be used in association with the upcoming multi-user transmission, and the short format preamble is selected when the BSS does not include the first-type legacy station, beamforming is to not be used in association with the upcoming multi-user transmission, and precoding is not to be used in association with the upcoming multi-user transmission. ## Claims ### Claim at position 1 1-20. (canceled) ### Claim 21 A device comprising: a processor configured to: determine a number of data streams associated with a high efficiency transmission, wherein the determined number of data streams is between 2 and 8; select a number of symbols to be one of 2, 4, 6, or 8, wherein the selected number of symbols is equal to the determined number of data streams or a next higher number than the determined number of data streams; and send a high efficiency long training field (LTF) using the selected number of symbols, wherein being configured to send the high efficiency LTF is based on a function of a subcarrier index comprising a relationship where a subcarrier is an element of subchannels. ### Claim 22 (depends on 21) The device of claim 21, wherein the determined number of data streams is a total number of data streams for multi-user multiple input multiple-output (MU MIMO) users in the high efficiency transmission. ### Claim 23 (depends on 21) The device of claim 21, wherein the processor is further configured to determine a group identifier and identify a position of the device in a group associated with the group identifier. ### Claim 24 (depends on 21) The device of claim 21, wherein the high efficiency transmission is a transmission associated with multi-user multi-user multiple input multiple-output (MU MIMO). ### Claim 25 (depends on 21) The device of claim 21, wherein the LTF is part of a high efficiency PPDU. ### Claim 26 (depends on 25) The device of claim 25, wherein the processor is further configured to receive an indication that the device is assigned to transmit legacy one or more legacy fields. ### Claim 27 (depends on 26) The device of claim 26, wherein the indication is indicated in a received control frame. ### Claim 28 A method for transmission associated with multi-user multiple input multiple-output (MU MIMO) comprising: determining a number of data streams associated with a high efficiency transmission, wherein the determined number of data streams is between 2 and 8; selecting a number of symbols to be one of 2, 4, 6, or 8, wherein the selected number of symbols is equal to the determined number of data streams or a next higher number than the determined number of data streams; and sending a high efficiency long training field (LTF) using the selected number of symbols, wherein sending the high efficiency LTF is based on a function of a subcarrier index comprising a relationship where a subcarrier is an element of subchannels. ### Claim 29 (depends on 28) The method of claim 28, wherein the determined number of data streams is a total number of data streams for multi-user multiple input multiple-output (MU MIMO) users in the high efficiency transmission. ### Claim 30 (depends on 28) The method of claim 28, further comprising determining a group identifier and identifying a position of a device in a group associated with the group identifier. ### Claim 31 (depends on 28) The method of claim 28, wherein the high efficiency transmission is a transmission associated with multi-user multi-user multiple input multiple-output (MU MIMO). ### Claim 32 (depends on 28) The method of claim 28, wherein the LTF is part of a high efficiency PPDU. ### Claim 33 (depends on 32) The method of claim 32, further comprising receiving an indication that a device is assigned to transmit legacy one or more legacy fields. ### Claim 34 (depends on 33) The method of claim 33, wherein the indication is indicated in a received control frame.