Method and apparatus for enabling flexible numerology in multi-user MIMO system

1. A user equipment (UE) in a wireless communication system, the UE comprising:

a transceiver configured to receive, from a base station (BS), downlink signals comprising at least one available set of transmission parameters using a multi-user multi-input multi-output (MU-MIMO), the MU-MIMO based on a re-sampled CSI of at least one co-scheduled UE in a UE set and a selected UE in the UE set;

wherein the re-sampled CSI are based upon:

selection of the selected UE to be scheduled from the UEs included in the UE set:

comparison of subcarrier spacing of the selected UE with subcarrier spacing of at least one co-scheduled UE included in the UE set;

interpolation of at least one subcarrier included in the set of transmission parameters that is allocated to the at least one co-scheduled UE using an interpolation factor when the subcarrier spacing of the at least one co-scheduled UE is wider than subcarrier spacing of the selected UE; and

decimation of at least one subcarrier included in the set of transmission parameters that is allocated to the at least one co-scheduled UE using a decimation factor when the subcarrier spacing of the at least one co-scheduled UE is narrower than the subcarrier spacing of the selected UE; and

at least one processor configured to determine at least one preferred set of transmission parameters including a subcarriers spacing based on the received downlink signals, wherein the transceiver is further configured to transmit a report message including the at least one preferred set of transmission parameters.

2. The UE of claim 1 , wherein the at least one processor is further configured to:

remove a cyclic prefix (i) of the received downlink signals in a time domain; and

convert the CP removed downlink signals to frequency domain signals using a plurality of fast Fourier transforms (FFTs).

3. The UE of claim 1 , wherein the transceiver is further configured to:

receive the downlink signals comprising a set of transmission parameters using the MU-MIMO; and

transmit the report message including channel state information (CSI) based on the received downlink signals.

4. The UE of claim 1 , wherein the transceiver is further configured to:

receive the downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (i) mode, or a space division multiplexing (SDM) mode in a same frequency band, the downlink signals comprising reference symbols located in different positions in the downlink signals; and

transmit the report message using uplink signals based on the received downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (FDM) mode, or a space division multiplexing (SDM) mode in the same frequency band.

5. A base station (BS) in a wireless communication system, the BS comprising:

at least one processor configured to:

identify a set of transmission parameters comprising a numerology, wherein the numerology includes a subcarrier spacing;

determine a plurality of baseband signal generation chains each of which includes the set of transmission parameters comprising different numerology;

select a UE to be scheduled from UEs included in a plurality of groups;

compare the subcarrier spacing of the selected UE with subcarrier spacing of at least one UE included in the plurality of groups;

interpolate at least one subcarrier included in the set of transmission parameters that is allocated to the at least one UE using an interpolation factor when the subcarrier spacing of the at least one UE is wider than subcarrier spacing of the selected UE; and

decimate at least one subcarrier included in the set of transmission parameters that is allocated to the at least one UE using a decimation factor when the subcarrier spacing of the at least one UE is narrower than the subcarrier spacing of the selected UE; and

a transceiver configured to transmit, to at least one user equipment (UE), downlink signals comprising the set of transmission parameters using a multi-user multi-input multi-output (MU-MIMO).

6. The BS of claim 5 , wherein:

the at least one processor is further configured to multiplex output signals from the plurality of baseband signal generation chains each of which includes the set of transmission parameters comprising the different numerology; and

the transceiver is further configured to transmit the downlink signals comprising the multiplexed output signals through a plurality of antenna ports using the MU-MIMO.

7. The BS of claim 5 , wherein the at least one processor is further configured to:

determine a plurality of precoders each of which includes the set of transmission parameters comprising the different numerology, the plurality of precoders being included the plurality baseband signal generation chains;

convert output signals from each of the plurality of precoders to time domain signals using a plurality of inverse fast Fourier transforms (IFFTs); and

add a cyclic prefix (CP) to each of the time domain signals that is outputted from each of the plurality of precoders, wherein the time domain signals outputted from different precoders include different CP lengths.

8. The BS of claim 5 , wherein:

the at least one processor is further configured to determine a plurality of groups comprising the at least one UE; and

the transceiver is further configured to receive a report message from the at least one UE included in the plurality of groups.

9. The BS of claim 5 , wherein the at least one processor is further configured to

maintain the set of transmission parameters that is allocated to the at least one UE when the subcarrier spacing of the at least one UE is equal to the subcarrier spacing of the selected UE.

10. The BS of claim 5 , wherein:

the at least one processor is further configured to determine at least one available set of transmission parameters including the subcarriers spacing; and

the transceiver is further configured to:

broadcast, to the at least one UE, the downlink signals comprising the at least one available set of transmission parameters using the MU-MIMO; and

receive a response message including at least one preferred set of transmission parameters from the at least one UE.

11. The BS of claim 5 , wherein the transceiver is further configured to:

transmit the downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (FDM) mode, or a space division multiplexing (SDM) mode in a same frequency band, the downlink signal comprising reference symbols located in different positions in the downlink signals; and

receive a report message using uplink signals based on the transmitted downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (FDM) mode, or a space division multiplexing (SDM) mode in the same frequency band.

12. A method of operating a base station (BS) in a wireless communication system, the method comprising:

identifying a set of transmission parameters comprising a numerology, wherein the numerology includes a subcarrier spacing;

determining a plurality of baseband signal generation chains each of which includes the set of transmission parameters comprising different numerology;

selecting a UE to be scheduled from UEs included in a plurality of groups;

comparing the subcarrier spacing of the selected UE with subcarrier spacing of at least one UE included in the plurality of groups;

interpolating at least one subcarrier included in the set of transmission parameters that is allocated to the at least one UE using an interpolation factor when the subcarrier spacing of the at least one UE is wider than subcarrier spacing of the selected UE;

decimating at least one subcarrier included in the set of transmission parameters that is allocated to the at least one UE using a decimation factor when the subcarrier spacing of the at least one UE is narrower than the subcarrier spacing of the selected UE; and

transmitting, at least one user equipment (UE), downlink signals comprising the set of transmission parameters using a multi-user multi-input multi-output (MU-MIMO).

13. The method of claim 12 , further comprising:

multiplexing output signals from the plurality of baseband signal generation chains each of which includes the set of transmission parameters comprising the different numerology; and

transmitting the downlink signals comprising the multiplexed output signals through a plurality of antenna ports using the MU-MIMO.

14. The method of claim 12 , further comprising:

determining a plurality of precoders each of which includes the set of transmission parameters comprising the different numerology, the plurality of precoders being included the plurality of baseband signal generation chains;

converting output signals from each of the plurality of precoders to time domain signals using a plurality of inverse fast Fourier transforms (IFFTs); and

adding a cyclic prefix (CP) to each of the time domain signals that is outputted from each of the plurality of precoders, wherein the time domain signals outputted from different precoders include different CP lengths.

15. The method of claim 12 , further comprising:

determining a plurality of groups comprising the at least one UE; and

receiving a report message from the at least one UE included in the plurality of groups.

16. The method of claim 12 , further comprising:

maintaining the set of transmission parameters that is allocated to the at least one UE when the subcarrier spacing of the at least one UE is equal to subcarrier spacing of the selected UE.

17. The method of claim 12 , further comprising:

determining at least one available set of transmission parameters including the subcarriers spacing;

broadcasting the downlink signals comprising the at least one available set of transmission parameters using the MU-MIMO; and

receiving a response message including at least one preferred set of transmission parameters from the at least one UE.

18. The method of claim 12 , further comprising:

transmitting the downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (FDM) mode, or a space division multiplexing (SDM) mode in a same frequency band, the downlink signal comprising reference symbols located in different positions in the downlink signals; and

receiving a report message using uplink signals based on the transmitted downlink signals in at least one of multiplexing modes including a time division multiplexing (TDM) mode, a frequency division multiplexing (FDM) mode, or a space division multiplexing (SDM) mode in the same frequency band.