Low-power wake-up signal (LP-WUS) procedures

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

a first radio;

a second radio, an operation of which consumes more power than the first radio;

one or more memories, individually or in combination, having instructions; and

one or more processors, individually or in combination, configured to execute the instructions and cause the UE to:

receive, via the first radio, a low-power wake-up signal (LP-WUS) indicating a downlink communication; and

receive the downlink communication via the second radio after the LP-WUS is received,

wherein the second radio is in a low-power state prior to the LP-WUS being received, and wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

receive, via the first radio and prior to the LP-WUS being received, a periodic reference signal; and

synchronize, prior to the LP-WUS being received, a timing of the second radio with a timing of a network entity based on the periodic reference signal.

2 . The UE of claim 1 , wherein the LP-WUS is an on-off keying (OOK) modulated waveform.

3 . The UE of claim 1 , wherein the downlink communication is an OFDM modulated waveform.

4 . The UE of claim 1 , wherein the LP-WUS is received from the network entity, and wherein the LP-WUS is another reference signal characterized by an on-off keying (OOK) modulated waveform.

5 . The UE of claim 1 , wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

receive, from the network entity via the second radio, an indication of at least one of a time resource or a frequency resource for receiving the periodic reference signal.

6 . The UE of claim 1 , wherein the second radio is in the low-power state prior to the LP-WUS being received, and wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

power on the second radio or put the second radio into a wake state after receiving the LP-WUS; and

receive, via the second radio prior to the downlink communication being received, at least one of a dedicated reference signal or the periodic reference signal, wherein the dedicated reference signal and the periodic reference signal are configured to provide a basis for the UE to:

(i) synchronize a frequency of the second radio with a frequency of the downlink communication, prior to receiving the downlink communication, or

(ii) synchronize the timing and the frequency of the second radio with a timing and the frequency of the downlink communication, prior to receiving the downlink communication.

7 . The UE of claim 6 , wherein the dedicated reference signal is a tracking reference signal (TRS), and wherein the LP-WUS comprises at least one of:

(i) an indication of one or more communication parameters associated with the TRS, or

(ii) an indication of a duration of time between receiving the LP-WUS and receiving the TRS.

8 . The UE of claim 6 , wherein the periodic reference signal is a synchronization signal block (SSB) or a channel state information reference signal (CSI-RS), and wherein the LP-WUS comprises at least one of:

(i) an indication of one or more communication parameters associated with the periodic reference signal, or

(ii) an indication of a duration of time between receiving the LP-WUS and receiving the periodic reference signal.

9 . The UE of claim 6 , wherein the dedicated reference signal or the periodic reference signal is received via a first receive beam, and wherein the LP-WUS is received via the first receive beam.

10 . The UE of claim 6 , wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

monitor, via the second radio, a downlink channel for the downlink communication after at least one of the dedicated reference signal or the periodic reference signal is received.

11 . The UE of claim 1 , wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

cycle power to the second radio at one or more intervals consistent with a periodicity associated with reception of a reference signal.

12 . The UE of claim 11 , wherein the one or more processor, individually or in combination, are further configured to cause the UE to:

receive, from the network entity and via the second radio, the reference signal according to the periodicity, wherein the reference signal is configured to provide a basis for the UE to:

(i) synchronize a frequency of the second radio with a frequency of the downlink communication, prior to receiving the downlink communication, or

(ii) synchronize the timing and the frequency of the second radio with a timing and the frequency of the downlink communication, prior to receiving the downlink communication.

13 . The UE of claim 1 , wherein the second radio is in the low-power state prior to the LP-WUS being received, and wherein the one or more processors, individually or in combination, are further configured to cause the UE to:

receive, via the first radio and prior to the LP-WUS being received, a signal amplitude indicative of a synchronization signal block (SSB); and

synchronize, prior to the LP-WUS being received, a timing of the UE with the timing of the network entity based on a time the signal amplitude was received.

14 . The UE of claim 13 , wherein the SSB is received via the first radio using a first beam, and wherein the LP-WUS is received via the first radio using the first beam.

15 . An apparatus for wireless communication, comprising:

one or more memories, individually or in combination, having instructions; and

one or more processors, individually or in combination, configured to execute the instructions and cause the apparatus to:

output a low-power wake-up signal (LP-WUS) for transmission, the LP-WUS indicating a downlink communication; and

output the downlink communication for transmission after the LP-WUS is outputted,

wherein the one or more processors, individually or in combination, are further configured to cause the apparatus to:

output, prior to the LP-WUS being outputted, a periodic reference signal for transmission, wherein the periodic reference signal is configured to provide a basis for a user equipment (UE) to synchronize a timing of a radio of the UE with a timing of the apparatus.

16 . The apparatus of claim 15 , wherein at least one of:

the downlink communication is an OFDM modulated waveform;

the LP-WUS is an on-off keying (OOK) modulated waveform; or

the LP-WUS is transmitted as part of a periodic LP-WUS transmission.

17 . The apparatus of claim 16 , wherein the one or more processors, individually or in combination, are further configured to cause the apparatus to:

output for transmission an indication of at least one of a time resource or a frequency resource for receiving the LP-WUS.

18 . The apparatus of claim 15 , further comprising one or more transceivers, individually or in combination, configured to:

transmit the LP-WUS; and

transmit the downlink communication, wherein the apparatus is configured as a network entity.

19 . A method for wireless communications at a wireless node, comprising:

obtaining, via a first radio, a low-power wake-up signal (LP-WUS) indicating a downlink communication; and

obtaining the downlink communication via a second radio after the LP-WUS is received,

wherein the second radio is in a low-power state prior to the LP-WUS being obtained, and wherein the method further comprises:

obtaining, via the first radio and prior to the LP-WUS being obtained, a periodic reference signal; and

synchronizing, prior to the LP-WUS being obtained, a timing of the second radio with a timing of a network entity based on the periodic reference signal.