# US 10,873,482 B2 · Transmitter schemes to facilitate side channel information estimation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,482 B2 - Document ID: US10873482B2 - Status: Granted - Kind: B2 - Application number: 16/136,572 - Filed: 2018-09-20 - Published: 2019-04-18 - Granted: 2020-12-22 - Earliest claimed: 2017-10-18 - Assignees: QUALCOMM Incorporated - Applicants: QUALCOMM Incorporated - Inventors: Lin Yang; Bin Tian; Jialing Li Chen; Louay Jalloul; Vincent Knowles Jones, IV; Ning Zhang; Chi-Lin Su; Ahmad Abdulrahman Mohammed - Web page: https://patentgrep.com/patent/US10873482B2 ## CPC - H04L 25/0242: {using matrix methods} - H04L 5/0023: {Time-frequency-space} - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04L 25/0204: {of multiple channels} - H04L 25/0224: {using sounding signals} - H04L 27/2605: {Symbol extensions, e.g. Zero Tail, Unique Word [UW]} - H04L 27/261: {Details of reference signals} - H04W 72/0473: {the resource being transmission power} - H04L 5/001: {the frequencies being arranged in component carriers} - 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 Methods, systems, and devices for wireless communication are described. In some systems (e.g., Wi-Fi systems), a transmitting device such as an access point (AP) or mobile station (STA), may identify a number of spatial streams for a data transmission that is less than a number of transmit antennas, and may transmit a packet over a channel. In a first implementation, the packet may be formatted in a multi-user frame format, with a number of long training field (LTF) symbols equal to the number of transmit antennas. In a second implementation, the packet may be a null data packet (NDP), and the device may transmit a separate data packet. In a third implementation, the packet may be formatted in single-user frame format with a modified LTF. A receiving device may receive the packet, and may perform channel estimation and power amplifier (PA) distortion cancellation based on the received packet. ## Claims ### Claim 1 A method for wireless communication at a mobile station (STA), comprising: receiving, from an access point (AP), a packet comprising a long training field (LTF), the LTF comprising a number of orthogonal frequency division multiplexing (OFDM) symbols that is equal to a number of transmit antennas for a data transmission, wherein the number of transmit antennas is equal to a first number of spatial streams used to receive the LTF, and the number of transmit antennas is greater than a second number of spatial streams used to receive the data transmission, and wherein the second number of spatial streams used to receive the data transmission is a subset of the first number of spatial streams used to receive the LTF; determining a channel estimation per spatial stream of the first number of spatial streams based at least in part on the received packet; and receiving the data transmission based at least in part on the determined channel estimation. ### Claim 2 (depends on 1) The method of claim 1, wherein the received packet is formatted in a multi-user frame format. ### Claim 3 (depends on 1) The method of claim 1, further comprising: demodulating the received packet using a pre-coding matrix, wherein the pre-coding matrix is common to the STA and the AP. ### Claim 4 (depends on 3) The method of claim 3, wherein the pre-coding matrix comprises an orthogonal matrix, wherein demodulating the received packet comprises: identifying a total signal power allocated to one or more transmit antennas associated with the transmission of the received packet, wherein the total signal power is spread over one or more transmit antennas in accordance with the orthogonal matrix. ### Claim 5 (depends on 2) The method of claim 2, wherein the spatial streams for the data transmission comprise the subset of spatial streams of a total set of spatial streams comprising the first number of spatial streams used to receive the LTF, a size of the total set of spatial streams equal to the number of transmit antennas, and wherein receiving the packet comprises: receiving the packet in the subset of the total set of spatial streams. ### Claim 6 (depends on 1) The method of claim 1, wherein the received packet is a null data packet (NDP), and receiving the packet comprises: receiving the packet in a packet transmission using a same number of spatial streams as transmit antennas for the packet transmission. ### Claim 7 (depends on 6) The method of claim 6, further comprising: determining a second channel estimation based at least in part on the received data transmission; and performing a calibration process on the channel estimation and the second channel estimation. ### Claim 8 (depends on 7) The method of claim 7, wherein performing the calibration process comprises: performing the calibration process based at least in part on a difference between the received packet and the received data transmission in automatic gain control (AGC), timing, frequency, phase, or a combination thereof. ### Claim 9 (depends on 1) The method of claim 1, wherein the packet further comprises a modified signaling (SIG) field, the method further comprising: determining the number of transmit antennas for the data transmission, the number of OFDM symbols for the LTF, or both based at least in part on an indication in the modified SIG field. ### Claim 10 An apparatus for wireless communication, comprising: a processor; memory in electronic communication with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: obtain a packet comprising a long training field (LTF), the LTF comprising a number of orthogonal frequency division multiplexing (OFDM) symbols that is equal to a number of transmit antennas for a data transmission, wherein the number of transmit antennas is equal to a first number of spatial streams used to receive the LTF, and the number of transmit antennas is greater than a second number of spatial streams used to receive the data transmission, and wherein the second number of spatial streams used to receive the data transmission is a subset of the first number of spatial streams used to receive the LTF; determine a channel estimation per spatial stream of the first number of spatial streams based at least in part on the obtained packet; and obtain the data transmission based at least in part on the determined channel estimation. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein the obtained packet is formatted in a multi-user frame format. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein the obtained packet is a null data packet (NDP), and the instructions to obtain the packet are executable by the processor to cause the apparatus to: obtain the packet in a packet transmission using a same number of spatial streams as transmit antennas for the packet transmission. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the instructions are further executable by the processor to cause the apparatus to: determine a second channel estimation based at least in part on the obtained data transmission; and perform a calibration process on the channel estimation and the second channel estimation. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the instructions to perform the calibration process are executable by the processor to cause the apparatus to: perform the calibration process based at least in part on a difference between the obtained packet and the obtained data transmission in automatic gain control (AGC), timing, frequency, phase, or a combination thereof. ### Claim 15 (depends on 10) The apparatus of claim 10, wherein the packet further comprises a modified signaling (SIG) field, the instructions further executable by the processor to cause the apparatus to: determine the number of transmit antennas for the data transmission, the number of OFDM symbols for the LTF, or both based at least in part on an indication in the modified SIG field. ### Claim 16 (depends on 10) The apparatus of claim 10, wherein the instructions are further executable by the processor to cause the apparatus to: demodulate the received packet using a pre-coding matrix, wherein the pre-coding matrix is common to a receiving device and a transmitting device. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the pre-coding matrix comprises an orthogonal matrix, wherein demodulating the received packet comprises: identifying a total signal power allocated to one or more transmit antennas associated with the transmission of the obtained packet, wherein the total signal power is spread over one or more transmit antennas in accordance with the orthogonal matrix. ### Claim 18 (depends on 11) The apparatus of claim 11, wherein the second number of spatial streams for the data transmission comprise the subset of spatial streams of a total set of spatial streams comprising the first number of spatial streams, a size of the total set of spatial streams equal to the number of transmit antennas, and comprises: receive the packet in the subset of the total set of spatial streams. ### Claim 19 (depends on 10) The apparatus of claim 10, wherein the packet further comprises a modified signaling (SIG) field, and the instructions are further executable by the processor to cause the apparatus to: determine the number of transmit antennas for the data transmission, the number of OFDM symbols for the LTF, or both based at least in part on an indication in the modified SIG field. ### Claim 20 (depends on 10) The apparatus of claim 10, further comprising: a receiver configured to receive the packet, wherein the apparatus is configured as one of a station (STA), an access point (AP), or a wireless node. ### Claim 21 An apparatus for wireless communication, comprising: means for receiving a packet comprising a long training field (LTF), the LTF comprising a number of orthogonal frequency division multiplexing (OFDM) symbols that is equal to a number of transmit antennas for a data transmission, wherein the number of transmit antennas is equal to a first number of spatial streams used to receive the LTF, and the number of transmit antennas is greater than a second number of spatial streams used to receive the data transmission, and wherein the second number of spatial streams used to receive the data transmission is a subset of the first number of spatial streams used to receive the LTF; means for determining a channel estimation per spatial stream of the first number of spatial streams based at least in part on the received packet; and means for receiving the data transmission based at least in part on the determined channel estimation. ### Claim 22 (depends on 21) The apparatus of claim 21, wherein the received packet is formatted in a multi-user frame format. ### Claim 23 (depends on 21) The apparatus of claim 21, further comprising: means for demodulating the received packet using a pre-coding matrix, wherein the pre-coding matrix is common to a transmitting device and a receiving device. ### Claim 24 (depends on 22) The apparatus of claim 22, wherein the second number of spatial streams for the data transmission comprise the subset of spatial streams of a total set of spatial streams comprising the first number of spatial streams, a size of the total set of spatial streams equal to the number of transmit antennas, and comprises: means for receiving the packet in the subset of the total set of spatial streams. ### Claim 25 (depends on 21) The apparatus of claim 21, wherein the received packet is a null data packet (NDP), and receiving the packet comprises: means for receiving the packet in a packet transmission using a same number of spatial streams as transmit antennas for the packet transmission. ### Claim 26 (depends on 25) The apparatus of claim 25, further comprising: means for determining a second channel estimation based at least in part on the received data transmission; and means for performing a calibration process on the channel estimation and the second channel estimation. ### Claim 27 A non-transitory computer-readable medium storing code for wireless communication, the code comprising instructions executable by a processor to: receive a packet comprising a long training field (LTF), the LTF comprising a number of orthogonal frequency division multiplexing (OFDM) symbols that is equal to a number of transmit antennas for a data transmission, wherein the number of transmit antennas is equal to a first number of spatial streams used to receive the LTF, and the number of transmit antennas is greater than a second number of spatial streams used to receive the data transmission, and wherein the second number of spatial streams used to receive the data transmission is a subset of the first number of spatial streams used to receive the LTF; determine a channel estimation per spatial stream of the first number of spatial streams based at least in part on the received packet; and receive the data transmission based at least in part on the determined channel estimation. ### Claim 28 (depends on 3) The method of claim 3, wherein the pre-coding matrix comprises a full rank square matrix based at least in part on the number of spatial streams used to transmit the LTF and the number of transmit antennas.