Method and apparatus for reference signal configuration of a wireless communication system

1. A method for reference signal configuration of a wireless communication system, comprising:

receiving, by a base station, an uplink channel from a user equipment (UE);

estimating, by the base station, a frequency offset, and a coherence time effected by a phase noise and a Doppler shift in response to the uplink channel; and

configuring, by the base station, a reference signal format in response to the frequency offset, and the coherence time effected by the phase noise and the Doppler shift, wherein the step of configuring the reference signal format in response to the frequency offset, and the coherence time effected by the phase noise and the Doppler shift comprises:

configuring a demodulation reference signal when a correlation level corresponding to the coherence time is greater than or equal to a threshold; and

configuring the demodulation reference signal and a phase-tracking reference signal when the correlation level corresponding to the coherence time is less than the threshold.

2. The method of claim 1 , further comprising:

transmitting, by the base station, a reference signal configuration to the UE in response to the reference signal format;

receiving, by the base station, a physical uplink shared channel from the UE; and

performing, by the base station, a channel estimation in response to an uplink impulse response of the received physical uplink shared channel.

3. The method of claim 1 , wherein the uplink channel is a physical random access channel.

4. The method of claim 1 , wherein the uplink channel is a physical uplink control channel.

5. The method of claim 4 , wherein the step of estimating the frequency offset in response to the uplink channel further comprises:

estimating a channel impulse response in a first band edge and generating a first frequency offset;

estimating the channel impulse response in a second band edge and generating a second frequency offset, wherein a frequency of the first band edge is higher than the frequency of the second band edge; and

performing a maximum ratio combining and averaging on the first frequency offset and the second frequency offset and estimating the frequency offset.

6. The method of claim 1 , wherein the reference signal format includes a demodulation reference signal.

7. The method of claim 1 , wherein the reference signal format includes a phase-tracking reference signal.

8. The method of claim 1 , wherein the step of configuring the reference signal format in response to the frequency offset and the coherence time effected by the phase noise and the Doppler shift comprises:

configuring a time density of a reference signal.

9. The method of claim 1 , wherein the step of configuring the reference signal format in response to the frequency offset and the coherence time effected by the phase noise and the Doppler shift comprises:

configuring a frequency density of a reference signal.

10. A base station, comprising:

a processor configured to perform instruction for:

receiving an uplink channel from a user equipment (UE):

estimating, by the base station, a frequency offset, and a coherence time effected by a phase noise and a Doppler shift in response to the uplink channel; and

configuring, by the base station, a reference signal format in response to the frequency offset and the coherence time effected by the phase noise and the Doppler shift, wherein when the reference signal format is configured, the processor is further configured to perform instruction for:

configuring a demodulation reference signal when a correlation level corresponding to the coherence time is greater than or equal to a threshold; and

configuring the demodulation reference signal and a phase-tracking reference signal when the correlation level corresponding to the coherence time is less than the threshold.

11. The base station of claim 10 , wherein the processor is further configured to perform instruction for:

transmitting a reference signal configuration to the UE in response to the reference signal format:

receiving a physical uplink shared channel from the UE; and

performing a channel estimation in response to an uplink impulse response of the received physical uplink shared channel.

12. The base station of claim 10 , wherein the uplink channel is a physical random access channel.

13. The base station of claim 10 , wherein the uplink channel is a physical uplink control channel.

14. The base station of claim 13 , wherein when the frequency offset is estimated, the processor is further configured to perform instruction for:

estimating a channel impulse response in a first band edge and generating a first frequency offset; and

estimating the channel impulse response in a second band edge and generating a second frequency offset, wherein a frequency of the first band edge is higher than the frequency of the second band edge, and

performing a maximum ratio combining and averaging on the first frequency offset and the second frequency offset and estimating the frequency offset.

15. The base station of claim 10 , wherein the reference signal format includes a demodulation reference signal.

16. The base station of claim 10 , wherein the reference signal format includes a phase-tracking reference signal.

17. The base station of claim 10 , wherein when the reference signal format is configured, the processor is further configured to perform instruction for:

configuring a time density of a reference signal.

18. The base station of claim 10 , wherein when the reference signal format is configured, the processor is further configured to perform instruction for:

configuring a frequency density of a reference signal.