Over the air reliable digital pre-distortion
Methods, systems, and devices for wireless communications are described. Techniques provide for reliable signal processing and amplification of downlink signals. A network entity may apply a digital pre-distortion (DPD) process to a signal for transmission to a user equipment (UE) and may apply a crest factor reduction (CFR) process to the output of the DPD process. The output of the CFR process may be amplified by a power amplifier and transmitted via a downlink transmission to the UE. The CFR process limits the peak power of the signal provided to the power amplifier (e.g., to a configured level), thereby reducing the peak to average power ratio (PAPR) of the signal provided to the power amplifier. The DPD process may compensate for non-linearities of the power amplifier. A training procedure for the DPD process may account for the CFR process applied after the DPD process.
1. A method for wireless communications at a network entity, comprising:
performing a signal processing procedure on an input signal to generate an output signal, performing the signal processing procedure comprising:
performing a digital pre-distortion process on the input signal according to a set of digital pre-distortion coefficients to compensate for a distortion of a power amplifier; and
performing a crest factor reduction process on the input signal subsequent to performing the digital pre-distortion process, wherein the set of digital pre-distortion coefficients are based at least in part on performance of the crest factor reduction process;
amplifying the output signal via the power amplifier to generate an amplified signal; and
transmitting, to a user equipment (UE), the amplified signal via one or more antennas.
2. The method of claim 1 , further comprising:
identifying the set of digital pre-distortion coefficients based at least in part on performing a training process for the digital pre-distortion process.
3. The method of claim 2 , wherein performing the training process comprises:
transmitting, to the UE, control information indicative of a set of training values comprising a set of crest factor reduction parameters associated with performing the crest factor reduction process;
transmitting, to the UE, a reference signal; and
receiving, from the UE, the set of digital pre-distortion coefficients identified at the UE based at least in part on the set of training values and the reference signal.
4. The method of claim 3 , further comprising:
receiving, from the UE, second control information indicative of a capability of the UE to identify sets of digital pre-distortion coefficients accounting for the crest factor reduction process subsequent to the digital pre-distortion process, wherein performing the training process is based at least in part on the control information.
5. The method of claim 3 , further comprising:
transmitting, to the UE, an indication of a configured training signal, wherein the reference signal comprises the configured training signal.
6. The method of claim 3 , wherein the set of crest factor reduction parameters comprises at least one of a polar clipping parameter, a cartesian clipping parameter, a maximal peak power, an input root mean square to the power amplifier, or a target peak to average power ratio.
7. The method of claim 1 , wherein performing the signal processing procedure comprises:
clipping, via applying the crest factor reduction process, the output signal to a configured peak power level.
8. The method of claim 7 , wherein applying the crest factor reduction process is based at least in part on a set of crest factor reduction parameters comprising one or more clipping parameters.
9. The method of claim 1 , wherein performing the signal processing procedure further comprises:
performing a second crest factor reduction process prior to the digital pre-distortion process.
10. The method of claim 9 , wherein the second crest factor reduction process is configured match a complementary cumulative distribution function of the input signal and the output signal.
11. A method for wireless communications at a user equipment (UE), comprising:
receiving, from a network entity, control information indicative of a set of training values for a digital pre-distortion process associated with the network entity, the set of training values comprising a set of crest factor reduction parameters for a crest factor reduction process associated with the network entity;
receiving, from the network entity, a reference signal;
determining a set of digital pre-distortion coefficients associated with the digital pre-distortion process based at least in part on the set of training values and the reference signal; and
transmitting, to the network entity, an indication of the set of digital pre-distortion coefficients.
12. The method of claim 11 , further comprising:
transmitting, to the network entity, second control information indicative of a capability of the UE to identify sets of digital pre-distortion coefficients accounting for the crest factor reduction process subsequent to the digital pre-distortion process.
13. The method of claim 11 , further comprising:
receiving, from the network entity, an indication of a configured training signal, wherein the reference signal comprises the configured training signal.
14. The method of claim 11 , wherein the set of crest factor reduction parameters comprises at least one of a polar clipping parameter, a cartesian clipping parameter, a maximal peak power, an input root mean square to a power amplifier, or a target peak to average power ratio.
15. The method of claim 11 , further comprising:
receiving, from the network entity, a downlink transmission based at least in part on transmitting the indication of the set of digital pre-distortion coefficients.
16. An apparatus for wireless communications at a network entity, comprising:
a processor;
memory coupled with the processor; and
instructions stored in the memory and executable by the processor to cause the apparatus to:
perform a signal processing procedure on an input signal to generate an output signal, performing the signal processing procedure comprising:
perform a digital pre-distortion process on the input signal according to a set of digital pre-distortion coefficients to compensate for a distortion of a power amplifier; and
perform a crest factor reduction process on the input signal subsequent to performing the digital pre-distortion process, wherein the set of digital pre-distortion coefficients are based at least in part on performance of the crest factor reduction process;
amplify the output signal via the power amplifier to generate an amplified signal; and
transmit, to a user equipment (UE), the amplified signal via one or more antennas.
17. The apparatus of claim 16 , wherein the instructions are further executable by the processor to cause the apparatus to:
identify the set of digital pre-distortion coefficients based at least in part on performing a training process for the digital pre-distortion process.
18. The apparatus of claim 17 , wherein the instructions to perform the training process are executable by the processor to cause the apparatus to:
transmit, to the UE, control information indicative of a set of training values comprising a set of crest factor reduction parameters associated with performing the crest factor reduction process;
transmit, to the UE, a reference signal; and
receive, from the UE, the set of digital pre-distortion coefficients identified at the UE based at least in part on the set of training values and the reference signal.
19. The apparatus of claim 18 , wherein the instructions are further executable by the processor to cause the apparatus to:
receive, from the UE, second control information indicative of a capability of the UE to identify sets of digital pre-distortion coefficients accounting for the crest factor reduction process subsequent to the digital pre-distortion process, wherein performing the training process is based at least in part on the control information.
20. The apparatus of claim 18 , wherein the instructions are further executable by the processor to cause the apparatus to:
transmit, to the UE, an indication of a configured training signal, wherein the reference signal comprises the configured training signal.
21. The apparatus of claim 18 , wherein the set of crest factor reduction parameters comprises at least one of a polar clipping parameter, a cartesian clipping parameter, a maximal peak power, an input root mean square to the power amplifier, or a target peak to average power ratio.
22. The apparatus of claim 16 , wherein the instructions to perform the signal processing procedure are executable by the processor to cause the apparatus to:
clip, via applying the crest factor reduction process, the output signal to a configured peak power level.
23. The apparatus of claim 22 , wherein applying the crest factor reduction process is based at least in part on a set of crest factor reduction parameters comprising one or more clipping parameters.
24. The apparatus of claim 16 , wherein the instructions to perform the signal processing procedure are further executable by the processor to cause the apparatus to:
perform a second crest factor reduction process prior to the digital pre-distortion process.
25. The apparatus of claim 24 , wherein the second crest factor reduction process is configured match a complementary cumulative distribution function of the input signal and the output signal.
26. An apparatus for wireless communications 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, from a network entity, control information indicative of a set of training values for a digital pre-distortion process associated with the network entity, the set of training values comprising a set of crest factor reduction parameters for a crest factor reduction process associated with the network entity;
receive, from the network entity, a reference signal;
determine a set of digital pre-distortion coefficients associated with the digital pre-distortion process based at least in part on the set of training values and the reference signal; and
transmit, to the network entity, an indication of the set of digital pre-distortion coefficients.
27. The apparatus of claim 26 , wherein the instructions are further executable by the processor to cause the apparatus to:
transmit, to the network entity, second control information indicative of a capability of the UE to identify sets of digital pre-distortion coefficients accounting for the crest factor reduction process subsequent to the digital pre-distortion process.
28. The apparatus of claim 26 , wherein the instructions are further executable by the processor to cause the apparatus to:
receive, from the network entity, an indication of a configured training signal, wherein the reference signal comprises the configured training signal.
29. The apparatus of claim 26 , wherein the set of crest factor reduction parameters comprises at least one of a polar clipping parameter, a cartesian clipping parameter, a maximal peak power, an input root mean square to a power amplifier, or a target peak to average power ratio.
30. The apparatus of claim 26 , wherein the instructions are further executable by the processor to cause the apparatus to:
receive, from the network entity, a downlink transmission based at least in part on transmitting the indication of the set of digital pre-distortion coefficients.