# US 11,451,426 B2 · Method and terminal for transmitting feedback signal in wireless communication system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,426 B2 - Document ID: US11451426B2 - Status: Granted - Kind: B2 - Application number: 17/255,327 - Filed: 2019-06-25 - Published: 2021-08-26 - Granted: 2022-09-20 - Earliest claimed: 2018-06-25 - Assignees: LG Electronics Inc. - Applicants: LG Electronics Inc. - Inventors: Hyukjin Chae; Seungmin Lee - Web page: https://patentgrep.com/patent/US11451426B2 ## CPC - H04L 27/2646: {using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length} - G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence) - 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 5/0053: {Allocation of signalling, i.e. of overhead other than pilot signals} - 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 27/261: {Details of reference signals} - H04L 27/3872: {Compensation for phase rotation in the demodulated signal} - H04W 4/40: for vehicles, e.g. vehicle-to-pedestrians [V2P] - H04W 56/0045: {compensating for timing error by altering transmission time} - H04W 64/00: Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management - H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract One embodiment of the present invention provides a method for transmitting, by a receiving terminal, a feedback signal to a transmitting terminal in a wireless communication system, the method comprising the steps of: receiving, by the receiving terminal, a reference signal from the transmitting terminal; and transmitting, by the receiving terminal, the feedback signal for the reference signal to the transmitting terminal, wherein the feedback signal is transmitted on the basis of compensation for a phase change that occurs when the reference signal is received. ## Claims ### Claim 1 A method of transmitting a feedback signal to a transmitting user equipment (UE) by a receiving UE in a wireless communication system, the method comprising: receiving information related to time-frequency resources for a reference signal; receiving, by the receiving UE from the transmitting UE, the reference signal through the time-frequency resources, wherein the reference signal is generated based on pseudo random sequence; and transmitting, by the receiving UE, the feedback signal for the reference signal to the transmitting UE, wherein the feedback signal is transmitted based on a phase rotation based on a time difference between a first fast Fourier transform (FFT) window for reference signal transmission at the transmitting UE and a second FFT window for reference signal reception at the receiving UE. ### Claim 2 (depends on 1) The method of claim 1, wherein transmitting the feedback signal to the transmitting UE comprises transmitting, by the receiving UE, the feedback single based on a timing of the second FFT window for the reference signal reception. ### Claim 3 (depends on 2) The method of claim 2, wherein the compensation for the phase shift is defined by ak exp(j2π(k−x)Δfδ), where ak denotes a complex value of a reference signal transmitted in a k-th frequency resource region, x denotes a reference frequency, Δf denotes a subcarrier spacing, and δ denotes a time difference between the first and second FFT windows. ### Claim 4 (depends on 1) The method of claim 1, wherein the compensation for the phase shift is defined by ak exp(j2π(k−x)Δf(δ−θ)), where ak denotes an amplitude of a multipath channel in a k-th frequency resource region, x denotes a reference frequency, Δf denotes a subcarrier spacing, δ denotes a time difference between the first FFT window for reference signal transmission at the transmitting UE and the second FFT window for reference signal reception at the receiving UE, and θ denotes a time difference between the second FFT window and a third FFT window for feedback signal transmission at the receiving UE. ### Claim 5 (depends on 1) The method of claim 1, wherein the compensation for the phase shift is based on a channel function for the reference signal, and wherein a sequence for the phase-shift compensation based on the channel function is defined by a k ⁢ λ H ⁡ ( k ) , where the channel function is defined by H(k)=ak exp(jBk), ak denotes an amplitude of a multipath channel in a k-th frequency resource region, and Bk denotes a phase of the multipath channel in the k-th frequency resource region. ### Claim 6 (depends on 1) The method of claim 1, wherein the feedback signal is transmitted by the receiving UE on a same frequency resource as a frequency resource on which the reference signal is received. ### Claim 7 (depends on 1) The method of claim 1, further comprising: based on presences of at least another UE transmitting another feedback signal to the transmitting UE, selecting a transmission resource for transmitting the feedback signal based on at least one of an identifier (ID) of the transmitting UE or an ID of the at least another UE according to sensing results of the receiving UE; and transmitting the feedback signal on the selected transmission resource. ### Claim 8 (depends on 1) The method of claim 1, wherein transmitting the feedback signal to the transmitting UE further comprises: configuring a sequence of the feedback signal based on at least one of an identifier (ID) of the transmitting UE or an ID of the receiving UE; and transmitting the feedback signal to the transmitting UE based on the configured sequence. ### Claim 9 (depends on 1) The method of claim 1, further comprising calculating a distance d between the transmitting and receiving UEs, wherein the distance d is calculated according to d = c · ( ∠ ⁢ ⁢ R _ ⁡ ( m ) - ∠ ⁢ ⁢ S ⁡ ( m ) ) 2 ⁢ ⁢ π ⁢ ⁢ m ⁢ ⁢ Δ ⁢ ⁢ f , where c denotes a speed of light, ∠R(m) denotes a phase based on an average of conjugate products of a first reference signal received at a first frequency and a second reference signal received at a second frequency, ∠S(m) denotes a phase based on the phase shift caused by multiple paths, m denotes a spacing between the first and second frequencies, Δf denotes a subcarrier spacing, and ∠ denotes a function for representing phases, wherein ∠R(m) is defined by R(m)=E(R(k,m))=exp(j2πmΔfδ)E(H(k)H′(k+m)), where H(k) denotes a multipath channel in a k-th frequency resource region and is defined by H(k)=ak exp(jBk), where ak denotes an amplitude of the multipath channel in the k-th frequency resource region, and Bk denotes a phase of the multipath channel in the k-th frequency resource region, and wherein S(m) is defined by S ⁡ ( m ) = ∑ l = 0 N - 1 ⁢ E ⁡ (  h ⁡ ( l )  2 ) ⁢ exp ⁡ ( j ⁢ 2 ⁢ ⁢ π N ⁢ l ⁢ ⁢ m ) , where N denotes a size of an FFT. ### Claim 10 A receiving user equipment (UE) for transmitting a feedback signal in a wireless communication system, the receiving UE comprising: a transceiver; and a processor configured to: receive information related to time-frequency resources for a reference signal; receive, from a transmitting UE, the reference signal through the time-frequency resources, wherein the reference signal is generated based on pseudo random sequence; and transmit the feedback signal for the reference signal to the transmitting UE, wherein the feedback signal is transmitted based on a phase rotation based on a time difference between a first fast Fourier transform (FFT) window for reference signal transmission at the transmitting UE and a second FFT window for reference signal reception at the receiving UE. ### Claim 11 (depends on 10) The receiving UE of claim 10, wherein the receiving UE is configured to communicate with at least one of a mobile terminal, a network, or an autonomous driving vehicle other than the receiving UE. ### Claim 12 (depends on 10) The receiving UE of claim 10, wherein the receiving UE is configured to implement at least one advanced driver assistance system (ADAS) function based on a signal for controlling movement of the receiving UE. ### Claim 13 (depends on 10) The receiving UE of claim 10, wherein the receiving UE is configured to switch a driving mode of the receiving UE from an autonomous driving mode to a manual driving mode or from the manual driving mode to the autonomous driving mode upon receipt of a user input. ### Claim 14 (depends on 10) The receiving UE of claim 10, wherein the receiving UE is configured to perform autonomous driving based on external object information, and wherein the external object information includes at least one of information about presence of an object, information about a location of the object, information about a distance between the receiving UE and the object, or information about a relative speed of the receiving UE with respect to the object.