Signaling of a channel state information reference signal (CSI-RS) mapping configuration for a new radio (NR) system

1. A base station operable to communicate a channel state information reference signal (CSI-RS) resource element (RE) mapping configuration to a user equipment (UE), the apparatus comprising:

one or more processors configured to:

determine, at the base station, a CSI-RS RE mapping configuration that identifies resource elements for a CSI-RS resource at a frequency domain location (k) and at a time domain location (l);

identify the resource elements for the CSI-RS resource, wherein a CSI-RS code division multiplexing (CDM)-8 (CDM-8) is applied using two frequency domain resource elements (FD2) and four time domain resource elements (TD4) when a number of antenna ports is equal to 32;

encode, at the base station, the CSI-RS RE mapping configuration for transmission to the UE via higher layer signaling; and

a memory interface configured to retrieve from a memory the CSI-RS RE mapping configuration.

2. The base station of claim 1 , wherein the one or more processors are further configured to encode a CSI-RS for transmission to the UE using the CSI-RS resource defined by the CSI-RS RE mapping configuration.

3. The base station of claim 1 , wherein the one or more processors are further configured to select a location for the CSI-RS resource based on the CSI-RS RE mapping configuration that indicates that the CSI-RS resource occupies identical frequency domain resources in occupied orthogonal frequency division multiplexing (OFDM) symbols.

4. The base station of claim 1 , wherein the one or more processors are further configured to encode the CSI-RS RE mapping configuration for transmission to the UE, wherein the CSI-RS RE mapping configuration includes a bitmap that indicates the frequency domain location of the CSI-RS resource, wherein the bitmap is provided by a CSI-RS resource mapping (CSI-RS-ResourceMapping) higher-layer parameter in the CSI-RS RE mapping configuration.

5. The base station of claim 4 , wherein the one or more processors are further configured to form the bitmap using a number of bits that is reduced based on an actual number of symbols used for the transmission of the CSI-RS to the UE.

6. The base station of claim 1 , wherein the one or more processors are further configured to encode the CSI-RS for transmission to the UE in accordance with a CDM group with a size selected from a set of {1, 2, 4, 8}.

7. The base station of claim 6 , wherein the one or more processors are further configured to limit the CDM group to co-located REs in the frequency domain and the time domain.

8. The base station of claim 1 , wherein the FD2 are adjacent and the TD4 are adjacent.

9. The base station of claim 1 , wherein the resource elements are within resource blocks occupied by the CSI-RS resource which is configured for the UE.

10. The base station of claim 1 , wherein the one or more processors are further configured to encode the CSI-RS RE mapping configuration for transmission to the UE, wherein the CSI-RS RE mapping configuration includes an indication of sub-bands which are configured for the transmission of the CSI-RS to the UE.

11. The base station of claim 1 , wherein the one or more processors are further configured to encode the CSI-RS RE mapping configuration for transmission to the UE, wherein the CSI-RS RE mapping configuration includes a second bitmap that indicates a time-domain location of the CSI-RS resource, wherein the second bitmap is provided by a CSI-RS resource mapping (CSI-RS-ResourceMapping) higher-layer parameter in the CSI-RS RE mapping configuration.

12. The base station of claim 1 , wherein the one or more processors are further configured to encode an indication of a CDM type for transmission to the UE, wherein the CDM type includes two bits for a frequency domain CDM value from a set of {1, 2, 4, 8} and two bits for a time domain CDM value from the set of {1, 2, 4, 8}.

13. A user equipment (UE) operable to decode a channel state information reference signal (CSI-RS) resource element (RE) mapping configuration received from a base station, the apparatus comprising:

one or more processors configured to:

decode, at the UE, a CSI-RS RE mapping configuration received from the base station via radio resource control (RRC) signaling, wherein the CSI-RS RE mapping configuration identifies resource elements for a CSI-RS resource at a frequency domain location (k) and at a time domain location (l), and wherein a CSI-RS code division multiplexing (CDM)-8 (CDM-8) is applied using two frequency domain resource elements (FD2) and four time domain resource elements (TD4) when a number of antenna ports is equal to 32; and

decode, at the UE, a CSI-RS received from the base station using the CSI-RS RE mapping configuration that defines the CSI-RS resource for the CSI-RS; and

a memory interface configured to send to a memory the CSI-RS RE mapping configuration.

14. The UE of claim 13 , wherein the one or more processors are further configured to:

decode the CSI-RS RE mapping configuration received from the base station, wherein the CSI-RS RE mapping configuration includes a bitmap that indicates the frequency domain location of the CSI-RS resource, wherein the bitmap is provided by a CSI-RS resource mapping (CSI-RS-ResourceMapping) higher-layer parameter in the CSI-RS RE mapping configuration; or

decode the CSI-RS received from the base station in accordance with a code division multiplexing (CDM) group with a size selected from a set of {1, 2, 4, 8}.

15. The UE of claim 13 , wherein the CSI-RS resource constitutes of one or more CSI-RS resource components with (k, l), where a starting sub-carrier index of a (k, l) CSI-RS component is an integral multiple of k, wherein aggregated CSI-RS resource components occupy identical frequency domain resources in occupied orthogonal frequency division multiplexing (OFDM) symbols.

16. The UE of claim 13 , wherein the one or more processors are further configured to decode the CSI-RS RE mapping configuration received from the base station, wherein the CSI-RS RE mapping configuration includes a second bitmap that indicates a time-domain location of the CSI-RS resource, wherein the second bitmap is provided by a CSI-RS resource mapping (CSI-RS-ResourceMapping) higher-layer parameter in the CSI-RS RE mapping configuration.

17. At least one non-transitory machine readable storage medium having instructions embodied thereon for communicating a channel state information reference signal (CSI-RS) resource element (RE) mapping configuration from a base station to a user equipment (UE), the instructions when executed by one or more processors at the base station perform the following:

determining, at the base station, a CSI-RS RE mapping configuration that identifies resource elements for a CSI-RS resource at a frequency domain location (k) and at a time domain location (l);

identifying the resource elements for the CSI-RS resource, wherein a CSI-RS code division multiplexing (CDM)-8 (CDM-8) is applied using two frequency domain resource elements (FD2) and four time domain resource elements (TD4) when a number of antenna ports is equal to 32;

encoding, at the base station, the CSI-RS RE mapping configuration for transmission to the UE via higher layer signaling; and

encoding, at the base station, a CSI-RS for transmission to the UE using the CSI-RS resource defined by the CSI-RS RE mapping configuration.

18. The at least one non-transitory machine readable storage medium of claim 17 , further comprising instructions when executed perform the following: selecting a location for the CSI-RS resource based on the CSI-RS RE mapping configuration that indicates that the CSI-RS resource occupies identical frequency domain resources in occupied orthogonal frequency division multiplexing (OFDM) symbols.

19. The at least one non-transitory machine readable storage medium of claim 17 , further comprising instructions when executed perform the following:

encoding the CSI-RS RE mapping configuration for transmission to the UE, wherein the CSI-RS RE mapping configuration includes a bitmap that indicates the frequency domain location of the CSI-RS resource, wherein the bitmap is provided by a CSI-RS resource mapping (CSI-RS-ResourceMapping) higher-layer parameter in the CSI-RS RE mapping configuration; and

forming the bitmap using a number of bits that is reduced based on an actual number of symbols used for the transmission of the CSI-RS to the UE, wherein the CSI-RS resource constitutes of one or more CSI-RS resource components with (k, l), with k adjacent REs in a frequency domain and k adjacent REs in a time domain, and a bit set to ‘l’ indicates a start of the CSI-RS resource component (k, l).

20. The at least one non-transitory machine readable storage medium of claim 17 , further comprising instructions when executed perform the following:

encoding the CSI-RS for transmission to the UE in accordance with a CDM group with a size selected from a set of {1, 2, 4, 8}; and

limiting the CDM group to co-located REs in the frequency domain and the time domain.

21. The at least one non-transitory machine readable storage medium of claim 17 , further comprising instructions when executed perform the following: encoding the CSI-RS RE mapping configuration for transmission to the UE, wherein the CSI-RS RE mapping configuration includes an indication of sub-bands which are configured for the transmission of the CSI-RS to the UE.

22. The at least one non-transitory machine readable storage medium of claim 17 , further comprising instructions when executed perform the following: encoding an indication of a CDM type for transmission to the UE, wherein the CDM type includes two bits for a frequency domain CDM value from a set of {1, 2, 4, 8} and two bits for a time domain CDM value from the set of {1, 2, 4, 8}.