Sounding reference signal (SRS) enhancements
This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for transmitting sounding reference signal (SRS) resources with frequency hopping. In some implementations, a user equipment (UE) may use different SRS ports, different antenna ports, different numbers and sizes of SRS resources, different periodicities, different offsets, different transmission comb values, different number of symbols, different power control parameters, and/or different transmission comb offset values for SRS transmissions on different frequency subbands of the frequency hopping pattern to ensure that sounding operations cover all antennas of the UE, cover the entire frequency range of interest, and provide sufficiently dense SRS transmissions from which a base station can determine the best channel for DL transmissions while also using a minimum amount of SRS resources and consuming minimal power in the UE.
1. A method of wireless communication performed by a user equipment, the method comprising:
receiving sounding reference signal (SRS) configuration information indicating a frequency hopping pattern;
receiving a message indicating a first number of symbols corresponding to a first frequency subband of the frequency hopping pattern;
transmitting one or more SRS resources on the first frequency subband of the frequency hopping pattern using the first number of symbols; and
transmitting the one or more SRS resources on a second frequency subband of the frequency hopping pattern using a second number of symbols different than the first number of symbols.
2. The method of claim 1 , wherein the first number of symbols is one symbol and the second number of symbols is two symbols.
3. The method of claim 1 , wherein the one or more SRS resources are configured as periodic SRS resources, semi-persistent SRS resources, or aperiodic SRS resources based on a radio resource control (RRC) configuration message.
4. The method of claim 3 , wherein the configured semi-persistent SRS resources are activated by a medium access control (MAC) control element (CE) (MAC-CE) command, and the aperiodic SRS resources are triggered by a downlink control information (DCI) message.
5. The method of claim 1 , wherein the SRS configuration information indicates the second number of symbols.
6. The method of claim 1 , wherein the message further indicates the second number of symbols.
7. The method of claim 1 , wherein the message comprises one of a medium access control (MAC) control element (CE) (MAC-CE) command or a downlink control information (DCI) message.
8. The method of claim 1 , wherein the one or more SRS resources are transmitted using a plurality of offset values.
9. A method of wireless communication performed by a base station, the method comprising:
transmitting sounding reference signal (SRS) configuration information indicating a frequency hopping pattern;
transmitting a message indicating a first number of symbols corresponding to a first frequency subband of the frequency hopping pattern;
receiving one or more SRS resources on the first frequency subband of the frequency hopping pattern using the first number of symbols; and
receiving the one or more SRS resources on a second frequency subband of the frequency hopping pattern from a second number of symbols different than the first number of symbols.
10. The method of claim 9 , wherein the first number of symbols is one symbol and the second number of symbols is two symbols.
11. The method of claim 9 , wherein the SRS configuration information indicates further indicates the second number of symbols.
12. The method of claim 9 , wherein the message further indicates the second number of symbols.
13. A user equipment (UE) for wireless communication, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to cause the UE to:
receive sounding reference signal (SRS) configuration information indicating a frequency hopping pattern;
transmit one or more SRS resources on the first frequency subband of the frequency hopping pattern using the first number of symbols; and
transmit the one or more SRS resources on a second frequency subband of the frequency hopping pattern using a second number of symbols different than the first number of symbols.
14. The UE of claim 13 , wherein the one or more SRS resources are transmitted using a plurality of offset values.
15. The UE of claim 13 , wherein the first number of symbols is one symbol and the second number of symbols is two symbols.
16. The UE of claim 13 , wherein the one or more SRS resources are configured as periodic SRS resources, semi-persistent SRS resources, or aperiodic SRS resources based on a radio resource control (RRC) configuration message.
17. The UE of claim 16 , wherein the configured semi-persistent SRS resources are activated by a medium access control (MAC) control element (CE) (MAC-CE) command, and the aperiodic SRS resources are triggered by a downlink control information (DCI) message.
18. The UE of claim 13 , wherein the SRS configuration information indicates the second number of symbols.
19. The UE of claim 13 , wherein the message further indicates the second number of symbols.
20. The UE of claim 13 , wherein the message comprises one of a medium access control (MAC) control element (CE)(MAC-CE) command or a downlink control information (DCI) message.
21. A base station for wireless communication, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to cause the base station to:
transmit sounding reference signal (SRS) configuration information indicating a frequency hopping pattern;
transmit a message indicating a first number of symbols corresponding to a first frequency subband of the frequency hopping pattern;
receive one or more SRS resources on the first frequency subband of the frequency hopping pattern using the first number of symbols; and
receive the one or more SRS resources on a second frequency subband of the frequency hopping pattern from a second number of symbols different than the first number of symbols.
22. The base station of claim 21 , wherein the one or more processors are further configured to cause the base station to:
estimate, based at least in part on the one or more SRS resources, channel conditions on the first frequency subband and the second frequency subband.
23. The base station of claim 21 , wherein the one or more processors are further configured to cause the base station to:
configure, based at least in part on the one or more SRS resources, a number of SRS resource sets for channel sounding.
24. The base station of claim 21 , wherein the one or more processors are further configured to cause the base station to:
identify, based at least in part on the one or more SRS resources, a channel quality indicator, a rank indicator, or a precoding matrix indicator.
25. The base station of claim 21 , wherein the first number of symbols is one symbol and the second number of symbols is two symbols.
26. The base station of claim 21 , wherein the SRS configuration information indicates the second number of symbols.
27. The base station of claim 21 , wherein the message further indicates the second number of symbols.