Method of and apparatus for transmitting data based on channel state in device-to-device communication

1. A method of performing device-to-device (D2D) communication by a first device, the method comprising:

in a first mode:

receiving at least one first reference signal from a second device;

estimating a channel state based on the at least one first reference signal; and

determining a plurality of transmission parameters based on the estimated channel state; or

in a second mode:

transmitting at least one second reference signal to the second device;

receiving channel state information from the second device corresponding to the at least one second reference signal; and

determining the plurality of transmission parameters based on the channel state information; and

in the first mode or the second mode:

obtaining at least one measurement value corresponding to a relative velocity between the first device and the second device;

adjusting at least one transmission parameter, among the plurality of transmission parameters, based on the at least one measurement value;

providing the adjusted at least one transmission parameter to the second device; and

transmitting data to the second device based on the adjusted at least one transmission parameter,

wherein the first mode is a channel reciprocity mode and the second mode is a channel state information feedback mode.

2. The method of claim 1 , wherein the obtaining the at least one measurement value comprises obtaining the at least one measurement value from the channel state information.

3. The method of claim 2 , wherein the at least one measurement value comprises a value corresponding to a Doppler shift that is measured based on the at least one second reference signal in the second device.

4. The method of claim 3 , wherein the at least one first reference signal or the at least one second reference signal comprises at least one of a synchronization signal, a tracking reference signal (TRS), a phase tracking reference signal (PT-RS), a demodulation reference signal (DMRS), and a channel state information reference signal (CSI-RS).

5. The method of claim 1 , wherein the obtaining the at least one measurement value comprises:

obtaining a velocity of the second device, measured in the second device, from the channel state information;

obtaining a velocity of the first device; and

obtaining the at least one measurement value based on the velocity of the first device and the velocity of the second device.

6. The method of claim 1 , wherein the obtaining the at least one measurement value comprises measuring a Doppler shift based on the at least one first reference signal.

7. The method of claim 6 , wherein the at least one first reference signal comprises at least one of a sounding reference signal (SRS), a phase tracking reference signal (PT-RS), and a demodulation reference signal (DMRS).

8. The method of claim 1 , further comprising measuring a variation of received power based on the at least one first reference signal in the first mode,

wherein the obtaining the at least one measurement value comprises determining the at least one measurement value based on the variation of the received power in the first mode.

9. The method of claim 1 , wherein the adjusting the at least one transmission parameter comprises:

adjusting the at least one transmission parameter to correspond to a first data rate based on the at least one measurement value corresponding to a negative relative velocity between the first device and the second device; and

adjusting the at least one transmission parameter to correspond to a second data rate based on the at least one measurement value corresponding to a positive relative velocity between the first device and the second device, and

wherein the first data rate is greater than the second data rate.

10. The method of claim 9 , wherein the adjusting the at least one transmission parameter to correspond to the first data rate comprises increasing a modulation and coding scheme (MCS) index, and

the adjusting the at least one transmission parameter to correspond to the second data rate comprises decreasing the MCS index.

11. The method of claim 1 , further comprising:

receiving an acknowledgement corresponding to the transmitting of the data, from the second device; and

measuring an error rate based on the acknowledgement,

wherein the adjusting the at least one transmission parameter is performed when the error rate is less than a first threshold value or is greater than a second threshold value.

12. A method of performing device-to-device (D2D) communication by a first device, the method comprising:

obtaining at least one measurement value corresponding to a relative velocity between the first device and a second device;

adjusting at least one transmission parameter based on the at least one measurement value;

providing the adjusted at least one transmission parameter to the second device;

transmitting data to the second device based on the adjusted at least one transmission parameter;

receiving an acknowledgement corresponding to the transmitting of the data, from the second device; and

measuring an error rate based on the acknowledgement,

wherein the adjusting the at least one transmission parameter comprises:

when the error rate is less than a first threshold value, adjusting the at least one transmission parameter to correspond to a first data rate;

when the error rate is greater than a second threshold value, adjusting the at least one transmission parameter to correspond to a second data rate; and

adjusting at least one of the first threshold value and the second threshold value based on the at least one measurement value,

wherein the first data rate is greater than the second data rate.

13. A method of performing device-to-device (D2D) communication by a second device, the method comprising:

transmitting at least one first reference signal to a first device in a first mode;

receiving, from the first device, at least one transmission parameter adjusted by the first device based on a relative velocity between the first device and the second device; and

receiving data from the first device based on the at least one transmission parameter received from the first device,

wherein the at least one transmission parameter is included in a plurality of transmission parameters determined by the first device based on an channel state in the first mode,

wherein the channel state is estimated by the first device based on the at least one first reference signal in the first mode,

wherein the method further comprises:

receiving at least one second reference signal from the first device in a second mode;

generating channel state information based on the at least one second reference signal in the second mode; and

providing the channel state information to the first device in the second mode,

wherein the plurality of transmission parameters is determined by the first device based on the channel state information in the second mode, and

wherein the first mode is a channel reciprocity mode and the second mode is a channel state information feedback mode.

14. The method of claim 13 , wherein the generating the channel state information comprises:

measuring a Doppler shift based on the at least one second reference signal; and

generating the channel state information including a value corresponding to the Doppler shift.

15. The method of claim 13 , wherein the generating the channel state information comprises:

obtaining a velocity of the second device; and

generating the channel state information including the velocity of the second device.

16. A first device configured to perform device-to-device (D2D) communication with a second device, the first device comprising:

at least one transceiver; and

at least one processor configured to process a first signal received from the second device through the at least one transceiver and to generate a second signal which is to be transmitted to the second device through the at least one transceiver,

wherein the at least one processor is further configured to:

in a first mode:

receive at least one first reference signal from the second device;

estimate a channel state based on the at least one first reference signal;

determine a plurality of transmission parameters based on the estimated channel state; or

in a second mode:

transmitting at least one second reference signal to the second device;

receiving channel state information from the second device corresponding to the at least one second reference signal; and

determining the plurality of transmission parameters based on the channel state information, and

in the first mode or the second mode:

obtain at least one measurement value corresponding to a relative velocity between the first device and the second device,

adjust at least one transmission parameter, among the plurality of transmission parameters, based on the at least one measurement value,

provide the adjusted at least one transmission parameter to the second device through the at least one transceiver, and

generate the second signal based on the adjusted at least one transmission parameter, and

wherein the first mode is a channel reciprocity mode and the second mode is a channel state information feedback mode.

17. The method of claim 1 , wherein the at least one measurement value is obtained prior to an establishment of a connection between the first device and the second device.

18. The method of claim 10 , wherein the adjusting the at least one transmission parameter comprises adjusting an MCS offset or an MCS hysteresis.