System and method for DMRS antenna port indication for URLLC

1. A method comprising:

receiving configuration information that indicates a bit-width value for an antenna port indication field of a downlink control information (DCI) format;

determining the bit-width value for the antenna port indication field of a DCI format based at least on the configuration information;

receiving a DCI message that is in accordance with the DCI format;

determining, based at least on the bit-width value, whether the bit-width value is equal to zero and to determine a default value for an antenna port configuration instead of determining a value for an antenna port configuration for one or more demodulation reference signals based on an antenna port indication field in the DCI message; and

communicating the one or more demodulation reference signals using the antenna port configuration based at least in part on a result of the determination whether the bit-width value is equal to zero and to determine the default value for the antenna port configuration instead of determining the value for the antenna port configuration for one or more demodulation reference signals based on the antenna port indication field in the DCI message.

2. The method of claim 1 , wherein determining whether the bit-width value is equal to zero comprises determining that the bit-width value is not equal to zero and the DCI message includes an antenna port indication value in the antenna port indication field,

the method comprising determining the antenna port configuration based on the antenna port indication value and a mapping between antenna port indication values and antenna port numbers that can be used for the communication of the one or more demodulation reference signals.

3. The method of claim 2 , wherein the configuration information specifies a subset of the mapping between potential antenna port indication values and antenna port numbers.

4. The method of claim 1 , wherein determining whether the bit-width value is equal to zero comprises determining that the DCI message does not include the antenna port indication field and to use the default value for the antenna port configuration based on a determination that the bit-width value is a zero value.

5. The method of claim 1 , wherein receiving the configuration information comprises receiving the configuration information via radio resource control (RRC) signaling.

6. The method of claim 1 , wherein communicating the one or more demodulation reference signals comprises receiving the one or more demodulation reference signals based on the determined antenna port configuration.

7. The method of claim 1 , wherein communicating the one or more demodulation reference signals comprises transmitting the one or more demodulation reference signals based on the determined antenna port configuration.

8. An apparatus comprising one or more processors configured to perform operations comprising:

receiving configuration information that indicates a bit-width value for an antenna port indication field of a downlink control information (DCI) format;

determining the bit-width value for the antenna port indication field of a DCI format based at least on the configuration information;

receiving a DCI message that is in accordance with the DCI format; and

determining, based at least on the bit-width value, whether the bit-width value is equal to zero and to determine a default value for an antenna port configuration instead of determining a value for an antenna port configuration for one or more demodulation reference signals based on an antenna port indication field in the DCI message; and

communicating the one or more demodulation reference signals using the antenna port configuration based at least in part on a result of the determination whether the bit-width value is equal to zero and to determine the default value for the antenna port configuration instead of determining the value for the antenna port configuration for one or more demodulation reference signals based on the antenna port indication field in the DCI message.

9. The apparatus of claim 8 , wherein determining whether the bit-width value is equal to zero comprises determining that the bit-width value is not equal to zero and the DCI message includes an antenna port indication value in the antenna port indication field,

the operations comprising determining the antenna port configuration based on the antenna port indication value and a mapping between antenna port indication values and antenna port numbers that can be used for the communication of the one or more demodulation reference signals.

10. The apparatus of claim 9 , wherein the configuration information specifies a subset of the mapping between potential antenna port indication values and antenna port numbers.

11. The apparatus of claim 8 , wherein determining whether the bit-width value is equal to zero comprises determining that the DCI message does not include the antenna port indication field and to use the default value for the antenna port configuration based on a determination that the bit-width value is a zero value.

12. The apparatus of claim 8 , wherein receiving the configuration information comprises receiving the configuration information via radio resource control (RRC) signaling.

13. The apparatus of claim 8 , comprising:

receiving the one or more demodulation reference signals based on the determined antenna port configuration.

14. The apparatus of claim 8 , comprising:

transmitting the one or more demodulation reference signals based on the determined antenna port configuration.

15. The apparatus of claim 8 , wherein the apparatus comprises a user equipment.

16. An apparatus comprising:

circuitry configured to receive configuration information that indicates a bit-width value for an antenna port indication field of a downlink control information (DCI) format;

circuitry configured to determine the bit-width value for the antenna port indication field of a DCI format based at least on the configuration information;

circuitry configured to receive a DCI message that is in accordance with the DCI format;

circuitry configured to determine, based at least on the bit-width value, whether the bit-width value is equal to zero and to determine a default value for an antenna port configuration instead of determining a value for an antenna port configuration for one or more demodulation reference signals based on an antenna port indication field in the DCI message; and

circuitry configured to communicate the one or more demodulation reference signals using the antenna port configuration based at least in part on a result of the determination whether the bit-width value is equal to zero and to determine the default value for the antenna port configuration instead of determining the value for the antenna port configuration for one or more demodulation reference signals based on the antenna port indication field in the DCI message.

17. The apparatus of claim 16 , wherein determining whether the bit-width value is equal to zero comprises determining that the bit-width value is not equal to zero and the DCI message includes an antenna port indication value in the antenna port indication field,

the apparatus comprising circuitry configured to determine the antenna port configuration based on the antenna port indication value and a mapping between antenna port indication values and antenna port numbers that can be used for the communication of the one or more demodulation reference signals.

18. The apparatus of claim 16 , wherein the circuitry configured to determine whether the bit-width value is equal to zero is configured to determine that the DCI message does not include the antenna port indication field and to use the default value for the antenna port configuration based on a determination that the bit-width value is a zero value.

19. The apparatus of claim 16 , comprising:

circuitry configured to transmit or receive the one or more demodulation reference signals based on the antenna port configuration.