Techniques for pre-opening notch filter in wireless communications system

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

receiving one or more downlink grants;

activating a notch filter at a first time, wherein the first time is at least a threshold period of time prior to a beginning of a first downlink transmission associated with the one or more downlink grants;

filtering interference from a signal at the UE using the activated notch filter; and

communicating with a base station in accordance with the one or more downlink grants and based at least in part on filtering the interference.

2. The method of claim 1 , further comprising:

waking up from a state of sleep at the first time, wherein activating the notch filter is based at least in part on waking up from the state of sleep.

3. The method of claim 2 , further comprising:

measuring the interference after waking up from the state of sleep and activating the notch filter; and

identifying, based at least in part on measuring the interference, at least one of an amplitude of the interference, a frequency of the interference, or a phase of the interference, wherein filtering the interference at the UE is based at least in part on the amplitude of the interference, the frequency of the interference, or the phase of the interference.

4. The method of claim 3 , further comprising:

activating one or more analog phase locked loops based at least in part on waking up from the state of sleep; and

identifying the phase associated with the interference based at least in part on activating the one or more analog phase locked loops, wherein the one or more analog phase locked loops of the UE remain deactivated while the UE is in the state of sleep.

5. The method of claim 1 , further comprising:

determining a second time associated with the beginning of the first downlink transmission, wherein the second time is later than the first time and a difference between the first time and the second time is greater than or equal to the threshold period of time.

6. The method of claim 5 , wherein filtering the interference further comprises:

filtering the interference after the second time associated with the beginning of the first downlink transmission associated with the one or more downlink grants.

7. The method of claim 5 , further comprising:

configuring the notch filter with a plurality of filtering coefficients at the first time, wherein filtering the interference further comprises filtering the interference using the configured notch filter.

8. The method of claim 7 , further comprising:

performing one or more measurements of the interference based at least in part on configuring the notch filter; and

determining that the configured notch filter satisfies an accuracy threshold based at least in part on the one or more measurements.

9. The method of claim 8 , wherein the notch filter satisfies the accuracy threshold prior to the second time associated with the beginning of the first downlink transmission associated with the one or more downlink grants.

10. The method of claim 1 , further comprising:

performing a set of channel measurements, wherein activating the notch filter comprises activating the notch filter at the first time based at least in part on determining that the set of channel measurements satisfies a threshold.

11. The method of claim 1 , wherein a convergence of the notch filter to the interference occurs prior to the beginning of the one or more downlink grants.

12. The method of claim 1 , wherein the interference includes a spur generated at the UE.

13. The method of claim 1 , wherein activating the notch filter at the first time is based at least in part on a low noise amplifier state change, an analog front end state change, an analog digital converter state change, a phase locked loop reconfiguration, or a combination thereof.

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 one or more downlink grants;

activate a notch filter at a first time, wherein the first time is at least a threshold period of time prior to a beginning of a first downlink transmission associated with the one or more downlink grants;

filter interference from a signal at the UE using the activated notch filter; and

communicate with a base station in accordance with the one or more downlink grants and based at least in part on filtering the interference.

15. The apparatus of claim 14 , wherein the instructions are further executable by the processor to cause the apparatus to:

wake up from a state of sleep at the first time, wherein activating the notch filter is based at least in part on waking up from the state of sleep.

16. The apparatus of claim 15 , wherein the instructions are further executable by the processor to cause the apparatus to:

measure the interference after waking up from the state of sleep and activating the notch filter; and

identify, based at least in part on measuring the interference, at least one of an amplitude of the interference, a frequency of the interference, or a phase of the interference, wherein filtering the interference at the UE is based at least in part on the amplitude of the interference, the frequency of the interference or the phase of the interference.

17. The apparatus of claim 16 , wherein the instructions are further executable by the processor to cause the apparatus to:

activate one or more analog phase locked loops based at least in part on waking up from the state of sleep; and

identify the phase associated with the interference based at least in part on activating the one or more analog phase locked loops, wherein the one or more analog phase locked loops of the UE remain deactivated while the UE is in the state of sleep.

18. The apparatus of claim 14 , wherein the instructions are further executable by the processor to cause the apparatus to:

determine a second time associated with the beginning of the first downlink transmission, wherein the second time is later than the first time and a difference between the first time and the second time is greater than or equal to the threshold period of time.

19. The apparatus of claim 18 , wherein the instructions to filter the interference are further executable by the processor to cause the apparatus to:

filter the interference after the second time associated with the beginning of the first downlink transmission associated with the one or more downlink grants.

20. The apparatus of claim 18 , wherein the instructions are further executable by the processor to cause the apparatus to:

configure the notch filter with a plurality of filtering coefficients at the first time, wherein filtering the interference further comprises filtering the interference using the configured notch filter.

21. The apparatus of claim 20 , wherein the instructions are further executable by the processor to cause the apparatus to:

perform one or more measurements of the interference based at least in part on configuring the notch filter; and

determine that the configured notch filter satisfies an accuracy threshold based at least in part on the one or more measurements.

22. The apparatus of claim 21 , wherein the notch filter satisfies the accuracy threshold prior to the second time associated with the beginning of the first downlink transmission associated with the one or more downlink grants.

23. The apparatus of claim 14 , wherein the instructions are further executable by the processor to cause the apparatus to:

perform a set of channel measurements, wherein activating the notch filter comprises activating the notch filter at the first time based at least in part on determining that the set of channel measurements satisfies a threshold.

24. The apparatus of claim 14 , wherein a convergence of the notch filter to the interference occurs prior to the beginning of the one or more downlink grants.

25. The apparatus of claim 14 , wherein the interference includes a spur generated at the UE.

26. The apparatus of claim 14 , wherein activating the notch filter at the first time is based at least in part on a low noise amplifier state change, an analog front end state change, an analog digital converter state change, a phase locked loop reconfiguration, or a combination thereof.

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

means for receiving one or more downlink grants;

means for activating a notch filter at a first time, wherein the first time is at least a threshold period of time prior to a beginning of a first downlink transmission associated with the one or more downlink grants;

means for filtering interference from a signal at the UE using the activated notch filter; and

means for communicating with a base station in accordance with the one or more downlink grants and based at least in part on filtering the interference.

28. The apparatus of claim 27 , further comprising:

means for waking up from a state of sleep at the first time, wherein activating the notch filter is based at least in part on waking up from the state of sleep.

29. A non-transitory computer-readable medium storing code for wireless communication at a user equipment (UE), the code comprising instructions executable by a processor to:

receive one or more downlink grants;

activate a notch filter at a first time, wherein the first time is at least a threshold period of time prior to a beginning of a first downlink transmission associated with the one or more downlink grants;

filter interference from a signal at the UE using the activated notch filter; and

communicate with a base station in accordance with the one or more downlink grants and based at least in part on filtering the interference.

30. The non-transitory computer-readable medium of claim 29 , wherein the instructions are further executable by the processor to:

wake up from a state of sleep at the first time, wherein activating the notch filter is based at least in part on waking up from the state of sleep.