Method and terminal for transmitting feedback signal in wireless communication system
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.
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.
2. 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.
3. The method of claim 2 , wherein the compensation for the phase shift is defined by a k exp(j2π(k−x)Δfδ), where a k 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.
4. The method of claim 1 , wherein the compensation for the phase shift is defined by a k exp(j2π(k−x)Δf(δ−θ)), where a k 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.
5. 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)=a k exp(jB k ), a k denotes an amplitude of a multipath channel in a k-th frequency resource region, and B k denotes a phase of the multipath channel in the k-th frequency resource region.
6. 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.
7. 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.
8. 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.
9. 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)=a k exp(jB k ), where a k denotes an amplitude of the multipath channel in the k-th frequency resource region, and B k 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.
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.
11. 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.
12. 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.
13. 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.
14. 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.