Transmitting channel state information reference signals in new radio

1. A method for wireless communications by a base station, comprising:

determining a configuration of channel state information reference signals (CSI-RSs), wherein the configuration indicates a set of resource elements (REs) to be used for CSI-RSs and a first mapping of CSI-RS ports to the set of REs, wherein the configuration further indicates orthogonal cover codes (OCCs) used for transmitting the CSI-RSs,

wherein the set of REs comprises one or more RE groups, wherein a RE group of the one or more RE groups comprises two or more localized REs within one orthogonal frequency division multiplexing (OFDM) symbol, wherein the two or more localized REs are adjacent to each other in the frequency domain, and

wherein the mapped CSI-RS ports are separated by the orthogonal cover codes (OCCs) applied to the one or more RE groups in frequency domain only;

sending an indication of the configuration of the CSI-RSs; and

transmitting the CSI-RSs according to the determined configuration, wherein the configuration indicates a combination of one OFDM symbol CSI-RSs with a first numerology having a first subcarrier spacing and two OFDM symbols CSI-RSs with a second numerology having a second subcarrier spacing.

2. The method of claim 1 , wherein:

the configuration indicates that the one OFDM symbol CSI-RSs comprises a cyclic prefix (CP) overhead, and

transmitting the CSI-RSs comprises:

applying the OCCs in the time domain, and

transmitting the CSI-RSs using at least two OFDM symbols with the second numerology having the second subcarrier spacing, wherein the second subcarrier spacing is at least double the first subcarrier spacing and the same CP overhead.

3. The method of claim 1 , wherein determining the configuration comprises:

determining a plurality of REs to be used for a downlink transmission to a receiver; and

selecting a group of REs, which are latest in time REs of the plurality of REs, for the set of REs to be used for the CSI-RSs.

4. The method of claim 3 , wherein data signals are not allowed to be multiplexed on the group of the latest REs.

5. The method of claim 3 , further comprising:

receiving an acknowledgment (ACK) or a negative acknowledgment (NAK), of the data transmitted in the downlink transmission in a slot, mini-slot, or set of aggregated slots, in an uplink portion located in the end of the same slot, mini-slot, or set of aggregated slots.

6. The method according to claim 1 , wherein transmitting the CSI-RSs comprises transmitting the CSI-RSs on uniformly distributed REs in one orthogonal frequency domain multiplexing (OFDM) symbol.

7. The method of claim 1 , wherein transmitting the CSI-RSs comprises transmitting the CSI-RSs on REs having one frequency and uniformly distributed over time.

8. The method of claim 1 , further comprising:

signaling the configuration using at least one of radio resource control (RRC) signaling, layer 2 (L2) signaling, or layer 1 (L1) signaling.

9. A method for wireless communications by a user equipment, comprising:

receiving an indication of a configuration of channel state information reference signals (CSI-RSs) from a transmission reception point (TRP), wherein the configuration indicates a set of resource elements (REs) to be used for CSI-RSs and a first mapping of CSI-RS ports to the set of REs, wherein the configuration further indicates orthogonal cover codes (OCCs) used for transmitting the CSI-RSs,

wherein the set of REs comprises one or more RE groups, wherein a RE group of the one or more RE groups comprises two or more localized REs within one orthogonal frequency division multiplexing (OFDM) symbol, wherein the two or more localized REs are adjacent to each other in the frequency domain, and

wherein the mapped CSI-RS ports are separated by orthogonal cover codes (OCCs) applied to the one or more RE groups in frequency domain only;

processing CSI-RSs based on the indicated configuration to determine channel state information, wherein the configuration indicates a combination of one OFDM symbol CSI-RSs with a first numerology having a first subcarrier spacing and two OFDM symbols CSI-RSs with a second numerology having a second subcarrier spacing; and

reporting the channel state information to the TRP.

10. The method of claim 9 , wherein the configuration further indicates the orthogonal cover codes (OCCs) used for transmitting the CSI-RSs.

11. The method of claim 10 , wherein:

the configuration indicates the one OFDM symbol CSI-RSs comprises a cyclic prefix (CP) overhead, and

processing the CSI-RSs comprises:

applying the OCCs in the time domain, and

receiving the CSI-RSs using at least two OFDM symbols with the second numerology having the second subcarrier spacing, wherein the second subcarrier spacing that is at least double the first subcarrier spacing and the same CP overhead.

12. The method of claim 9 , wherein the configuration:

specifies a group of REs that are latest REs of a set of REs used for a downlink transmission to the receiver.

13. The method of claim 12 , wherein data signals are not allowed to be multiplexed on the group of the latest REs.

14. The method of claim 12 , further comprising:

reporting an acknowledgment (ACK) or a negative acknowledgment (NAK), of the data transmitted on the downlink transmission in a slot, mini-slot, or set of aggregated slots, in an uplink portion located in the end of the same slot, mini-slot, or set of aggregated slots.

15. The method according to claim 9 , wherein processing the CSI-RSs comprises receiving the CSI-RSs on uniformly distributed REs in one orthogonal frequency domain multiplexing (OFDM) symbol.

16. The method of claim 9 , wherein processing the CSI-RSs comprises receiving the CSI-RSs on REs having one frequency and uniformly distributed over time.

17. The method of claim 9 , further comprising:

receiving the configuration using at least one of radio resource control (RRC) signaling, layer 2 (L2) signaling, or layer 1 (L1) signaling.

18. An apparatus for wireless communications in a base station, comprising:

a processor configured to:

determine a configuration of channel state information reference signals (CSI-RSs), wherein the configuration indicates a set of resource elements (REs) to be used for CSI-RSs and a first mapping of CSI-RS ports to the set of REs, wherein the configuration further indicates the orthogonal cover codes (OCCs) used for transmitting the CSI-RSs,

wherein the set of REs comprises one or more RE groups, wherein a RE group of the one or more RE groups comprises two or more localized REs within one orthogonal frequency division multiplexing (OFDM) symbol, wherein the two or more localized REs are adjacent to each other in the frequency domain, and

wherein the mapped CSI-RS ports are separated by orthogonal cover codes (OCCs) applied to the one or more RE groups in frequency domain only;

send an indication of the configuration of the CSI-RSs; and

transmit the CSI-RSs according to the determined configuration, wherein the configuration indicates a combination of one OFDM symbol CSI-RSs with a first numerology having a first subcarrier spacing and two OFDM symbols CSI-RSs with a second numerology having a second subcarrier spacing; and

a memory coupled with the processor.

19. The apparatus of claim 18 , wherein the processor is configured to transmit the CSI-RSs by transmitting the CSI-RSs on uniformly distributed REs in one orthogonal frequency domain multiplexing (OFDM) symbol.

20. The apparatus of claim 18 , wherein the processor is configured to transmit the CSI-RSs by transmitting the CSI-RSs on REs having one frequency and uniformly distributed over time.

21. An apparatus for wireless communications in a user equipment, comprising:

a processor configured to:

receive an indication of a configuration of channel state information reference signals (CSI-RSs) from a transmission reception point (TRP), wherein the configuration indicates a set of resource elements (REs) to be used for CSI-RSs and a first mapping of CSI-RS ports to the set of REs, wherein the configuration further indicates the orthogonal cover codes (OCCs) used for transmitting the CSI-RSs,

wherein the set of REs comprises one or more RE groups, wherein a RE group of the one or more RE groups comprises two or more localized REs within one orthogonal frequency division multiplexing (OFDM) symbol, wherein the two or more localized REs are adjacent to each other in the frequency domain, and

wherein the mapped CSI-RS ports are separated by orthogonal cover codes (OCCs) applied to the one or more RE groups in frequency domain only;

process CSI-RSs based on the indicated configuration to determine channel state information, wherein the configuration indicates a combination of one OFDM symbol CSI-RSs with a first numerology having a first subcarrier spacing and two OFDM symbols CSI-RSs with a second numerology having a second subcarrier spacing; and

report the channel state information to the TRP; and

a memory coupled with the processor.

22. The apparatus of claim 21 , wherein:

the configuration further indicates the orthogonal cover codes (OCCs) used for transmitting the CSI-RSs; and

the processor is configured to process the CSI-RSs based on the OCCs.

23. The apparatus of claim 22 , wherein:

the configuration indicates the one OFDM symbol CSI-RSs comprises a cyclic prefix (CP) overhead, and

the processor is configured to process the CSI-RSs by:

applying the OCCs in the time domain, and

receiving the CSI-RSs using at least two OFDM symbols with the second numerology, wherein the second subcarrier spacing that is at least double the first subcarrier spacing and the same CP overhead.

24. The apparatus of claim 23 , wherein:

the configuration specifies a group of REs that are latest REs of a set of REs used for a downlink transmission to the apparatus; and

the processor is configured to process the CSI-RSs by processing the CSI-RSs in the group of the latest REs.

25. The apparatus of claim 24 , wherein data signals are not allowed to be multiplexed on the group of the latest REs.

26. The apparatus of claim 24 , wherein the processor is configured to:

report an acknowledgment (ACK) or a negative acknowledgment (NAK), of the data transmitted on the downlink transmission in a slot, mini-slot, or set of aggregated slots, in an uplink portion located in the end of the same slot, mini-slot, or set of aggregated slots.

27. The apparatus of claim 21 , wherein the processor is configured to process the CSI-RSs by receiving the CSI-RSs on uniformly distributed REs in one orthogonal frequency domain multiplexing (OFDM) symbol.

28. The apparatus of claim 21 , wherein the processor is configured to process the CSI-RSs by receiving the CSI-RSs on REs having one frequency and uniformly distributed over time.

29. The apparatus of claim 21 , wherein the processor is configured to:

receive the configuration using at least one of radio resource control (RRC) signaling, layer 2 (L2) signaling, or layer 1 (L1) signaling.