Sidelink control channel successive parameter estimation

1. A method for wireless communication at a user equipment (UE), comprising:

receiving, within a subframe, a plurality of sidelink control channel signals providing scheduling information for a plurality of sidelink shared channel signals that are also received within the subframe;

determining, based at least in part on a previous attempt to decode at least one of the plurality of sidelink shared channel signals being unsuccessful, to use one or more of the plurality of sidelink control channel signals as pilot signals for decoding the at least one of the plurality of sidelink shared channel signals; and

decoding the at least one of the plurality of sidelink shared channel signals based at least in part on the plurality of sidelink control channel signals as pilot signals.

2. The method of claim 1 , wherein the plurality of sidelink control channel signals are encoded sidelink control channel signals, the method further comprising:

decoding one or more of the encoded sidelink control channel signals as one or more decoded sidelink control channel signals;

re-encoding, based on the determining, the one or more decoded sidelink control channel signals as one or more re-encoded sidelink control channel signals; and

determining a first set of parameters associated with the one or more of sidelink control channels on which the encoded sidelink control channel signals are received, the first set of parameters determined based at least in part on a comparison of the one or more encoded sidelink control channel signals and the one or more re-encoded sidelink control channel signals, wherein the first set of parameters are used in the decoding of the at least one of the plurality of sidelink shared channel signals.

3. The method of claim 2 , wherein decoding the at least one of the plurality of sidelink shared channel signals comprises:

refraining from determining a second set of parameters based on sidelink shared channel pilot signals for a plurality of sidelink shared channels on which the at least one of the plurality of sidelink shared channel signals are received; and

using the first set of parameters as estimated channel parameters in decoding the at least one of the plurality of sidelink shared channel signals.

4. The method of claim 2 , wherein decoding the at least one of the plurality of sidelink shared channel signals comprises:

determining a second set of parameters based on sidelink shared channel pilot signals for a plurality of sidelink shared channels on which the at least one of the plurality of sidelink shared channel signals are received;

using the first set of parameters as coarse channel parameters in a first step of decoding the at least one of the plurality of sidelink shared channel signals; and

using the second set of parameters in a second step of decoding the at least one of the plurality of sidelink shared channel signals.

5. The method of claim 2 , wherein decoding the at least one of the plurality of sidelink shared channel signals comprises:

determining a second set of parameters based on sidelink shared channel pilot signals for a plurality of sidelink shared channels on which the at least one of the plurality of sidelink shared channel signals are received;

determining jointly estimated channel parameters based at least in part on the first set of parameters and the second set of parameters; and

using the determined jointly estimated channel parameters in decoding the at least one of the plurality of sidelink shared channel signals.

6. The method of claim 2 , further comprising:

selecting a channel parameter estimation option from a plurality of channel parameter estimation options using the first set of parameters, a second set of parameters based on sidelink shared channel pilot signals, or a combination thereof, for decoding of the at least one of the plurality of sidelink shared channels.

7. The method of claim 2 , wherein the first set of parameters comprises at least one of a frequency offset, or a timing offset, or a Doppler spread, or a delay spread, or a noise covariance estimation, or a channel response estimation, or a combination thereof.

8. The method of claim 2 , wherein decoding one or more of the plurality of encoded sidelink control channel signals as one or more decoded sidelink control channel signals further comprises:

verifying that each of the one or more decoded sidelink control channel signals passes a cyclic redundancy check.

9. The method of claim 1 , further comprising:

determining a first set of parameters based on the one or more of the plurality of sidelink control channel signals as pilot signals;

determining a second set of parameters based on sidelink shared channel pilot signals for a plurality of sidelink shared channels on which the at least one of the plurality of sidelink shared channel signals are received; and

using the first set of parameters and the second set of parameters in decoding the at least one of the plurality of sidelink shared channel signals.

10. The method of claim 1 , wherein determining to use one or more of the sidelink control channel signals as pilot signals comprises:

identifying that at least one of the plurality of sidelink control channel signals and at least one of the plurality of sidelink shared channel signals are transmitted using a same antenna port.

11. The method of claim 1 , wherein determining to use one or more of the sidelink control channel signals as pilot signals comprises:

identifying that at least one of the plurality of sidelink control channel signals and at least one of the plurality of sidelink shared channel signals are transmitted on adjacent frequencies.

12. The method of claim 1 , wherein the plurality of sidelink control channel signals and the plurality of sidelink shared channel signals are cellular vehicle-to-everything (CV2X) signals.

13. The method of claim 1 , wherein the plurality of sidelink control channel signals are physical sidelink control channel (PSCCH) signals and the plurality of sidelink shared channel signals are physical sidelink shared channel (PSSCH) signals.

14. An apparatus for wireless communication at a user equipment (UE), comprising:

a processor,

memory coupled with the processor; and

instructions stored in the memory and executable by the processor to cause the apparatus to:

receive, within a subframe, a plurality of sidelink control channel signals providing scheduling information for a plurality of sidelink shared channel signals that are also received within the subframe;

determine, based at least in part on a previous attempt to decode at least one of the plurality of sidelink shared channel signals being unsuccessful, to use one or more of the plurality of sidelink control channel signals as pilot signals for decoding the at least one of the plurality of sidelink shared channel signals; and

decode the at least one of the plurality of sidelink shared channel signals based at least in part on the plurality of sidelink control channel signals as pilot signals.

15. An apparatus for wireless communication at a user equipment (UE), comprising:

means for receiving, within a subframe, a plurality of sidelink control channel signals providing scheduling information for a plurality of sidelink shared channel signals that are also received within the subframe;

means for determining, based at least in part on a previous attempt to decode at least one of the plurality of sidelink shared channel signals being unsuccessful, to use one or more of the plurality of sidelink control channel signals as pilot signals for decoding the plurality of sidelink shared channel signals; and

means for decoding the at least one of the plurality of sidelink shared channel signals based at least in part on the plurality of sidelink control channel signals as pilot signals.