Phase continuity tracking

1 . A User Equipment (UE) comprising:

at least one processor; and

at least one memory including computer program instructions;

the at least one memory and the computer program instructions being configured to, with the at least one processor, cause the UE to perform:

transmit, to a network node, a UE phase continuity capability message comprising information defining an ability of the UE to perform selection between different Reference Signal arrangements to indicate a phase continuity status;

receive, from the network node, a Downlink Control Information (DCI) field including a first RS arrangement and a second RS arrangement, wherein the DCI field defines a shift parameter for generating the second RS arrangement from the first RS arrangement;

determine whether a coherence criterion has been met, wherein:

the coherence criterion comprises a phase continuity criterion for maintaining the same phase for a previous Physical Uplink Shared Channel (PUSCH) transmission and a subsequent PUSCH transmission,

the previous PUSCH transmission and the subsequent PUSCH transmission occur in different slots, the different slots are non-consecutive slots,

the determination is based, at least in part, on

(i) a change in transmit power of the UE between the previous PUSCH transmission and the subsequent PUSCH transmission, and

(ii) at least one of: monitoring a Downlink (DL) occasion, UE-dependent time adjustments, or impairments at a Radio Frequency (RF) stage of the UE;

based at least in part on the determination, select, one of the first RS arrangement and the second RS arrangement, wherein:

the first RS arrangement is different from the second RS arrangement,

one of the first and second RS arrangements comprises a cyclic shift of the other of the first and second RS arrangements,

the first RS arrangement is associated with the coherence criterion being met and the second RS arrangement is associated with the coherence criterion not being met,

the cyclic shift comprises mapping a last sample of a reference signal sequence to a first sub-carrier,

the cyclic shift is applied to a sequence mapping of the reference signal sequence before mapping samples of the reference signal sequence to sub-carriers, and

the reference signal sequence is a Type 1, 1-port De-Modulation Reference Signal (DMRS) sequence; and

transmit an RS having the selected RS arrangement as part of a DMRS within the subsequent PUSCH transmission.

2 . The UE of claim 1 , wherein the second RS arrangement is selected by the network node from a plurality of candidate second RS arrangements and indicated to the UE in the DCI field, and wherein the plurality of candidate second RS arrangements is pre-configured at the UE via higher-layer signaling.

3 . The UE of claim 2 , wherein the first RS arrangement is a default De-Modulation Reference Signal (DMRS) arrangement defined in a 3GPP specification, and wherein the second RS arrangement is associated with per-slot channel estimation for the subsequent PUSCH transmission at the network node instead of joint channel estimation.

4 . The UE of claim 3 , wherein the determination further comprises determining that the coherence criterion has not been met responsive to a downlink transmission occurring in a slot between the previous PUSCH transmission and the subsequent PUSCH transmission.

5 . The UE of claim 3 , wherein the determination further comprises determining that the coherence criterion has not been met responsive to at least one of:

the change in transmit power of the UE exceeding a pre-defined threshold between the previous PUSCH transmission and the subsequent PUSCH transmission; or

a change in a transmit waveform from Cyclic-Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) to Direct Fourier Transform spread Orthogonal Frequency Division Multiplexing (DFT-s-OFDM), or vice-versa, between the previous PUSCH transmission and the subsequent PUSCH transmission.

6 . The UE of claim 5 , wherein the previous PUSCH transmission and the subsequent PUSCH transmission occur in non-consecutive slots, and wherein the second RS arrangement indicated in the DCI field is selected by the network node to optimize DMRS detectability for a low number of allocated Physical Resource Blocks (PRBs) for the subsequent PUSCH transmission.

7 . The UE of claim 6 , wherein the coherence criterion is determined based on a configuration or load condition of a power amplifier of the UE indicating whether phase continuity between the previous PUSCH transmission and the subsequent PUSCH transmission can be maintained.

8 . The UE of claim 7 , wherein the first RS arrangement corresponds to a default DMRS arrangement and the second RS arrangement corresponds to a non-default DMRS arrangement indicating that phase continuity has not been maintained.

9 . The UE of claim 8 , wherein the cyclic shift applied to the reference signal sequence comprises a sequence rotation prior to mapping the DMRS samples to the sub-carriers.

10 . The UE of claim 9 , wherein the RS having the selected RS arrangement is transmitted over a plurality of slots comprising consecutive or non-consecutive slots.

11 . The UE of claim 10 , wherein the DCI field dynamically configures the shift parameter to enable the network node to optimize detection of the RS arrangement based on at least one of Physical Resource Block allocation or Modulation and Coding Scheme.

12 . The UE of claim 11 , wherein selecting the first RS arrangement indicates to the network node that the subsequent PUSCH transmission is suitable for Joint Channel Estimation bundling with the previous PUSCH transmission.

13 . A method performed by a User Equipment (UE), the method comprising:

transmitting, to a network node, a UE phase continuity capability message,

wherein the UE phase continuity capability message comprises information defining the UE's ability to perform selection between different Reference Signal arrangements to indicate a phase continuity status;

receiving, from the network node, a Downlink Control Information (DCI) field,

wherein the DCI field indicates a first Reference Signal (RS) arrangement and a second RS arrangement, and

wherein the DCI field defines a shift parameter for generating the second RS arrangement from the first RS arrangement;

determining whether a coherence criterion has been met,

wherein the coherence criterion comprises a phase continuity criterion for maintaining the same phase for a previous Physical Uplink Shared Channel (PUSCH) transmission and a subsequent PUSCH transmission,

wherein the previous PUSCH transmission and the subsequent PUSCH transmission occur in different slots, the different slots are non-consecutive slots,

wherein the determination is based, at least in part, on a change in transmit power of the UE between the previous PUSCH transmission and the subsequent PUSCH transmission, and

wherein the determination is further based, at least in part, on at least one of: monitoring a Downlink (DL) occasion, UE-dependent time adjustments or impairments at a Radio Frequency (RF) stage of the UE;

selecting, based at least in part on the determination, one of the first RS arrangement and the second RS arrangement,

wherein the first RS arrangement is different from the second RS arrangement,

wherein one of the first and second RS arrangements comprises a cyclic shift of the other of the first and second RS arrangements,

wherein the first RS arrangement is associated with the coherence criterion being met and the second RS arrangement is associated with the coherence criterion not being met,

wherein the cyclic shift comprises mapping a last sample of a reference signal sequence to a first sub-carrier,

wherein the cyclic shift is applied to a sequence mapping of the reference signal sequence before mapping samples of the reference signal sequence to sub-carriers, and

wherein the reference signal sequence is a Type 1, 1-port De-Modulation Reference Signal (DMRS) sequence; and

transmitting the selected RS arrangement as part of a DMRS within the subsequent PUSCH transmission.

14 . A non-transitory computer readable medium encoded with instructions that, when performed by at least one processor of a User Equipment (UE), causes the UE to perform:

transmit, to a network node, a UE phase continuity capability message,

wherein the UE phase continuity capability message comprises information defining the UE's ability to perform selection between different Reference Signal arrangements to indicate a phase continuity status;

receive, from the network node, a Downlink Control Information (DCI) field,

wherein the DCI field indicates a first Reference Signal (RS) arrangement and a second RS arrangement; and

wherein the DCI field defines a shift parameter for generating the second RS arrangement from the first RS arrangement;

determining whether a coherence criterion has been met,

wherein the coherence criterion comprises a phase continuity criterion for maintaining the same phase for a previous Physical Uplink Shared Channel (PUSCH) transmission and a subsequent PUSCH transmission,

wherein the previous PUSCH transmission and the subsequent PUSCH transmission occur in different slots, the different slots are non-consecutive slots,

wherein the determination is based, at least in part, on a change in transmit power of the UE between the previous PUSCH transmission and the subsequent PUSCH transmission, and

wherein the determination is further based, at least in part, on at least one of: monitoring a Downlink (DL) occasion, UE-dependent time adjustments or impairments at a Radio Frequency (RF) stage of the UE;

selecting, based at least in part on the determination, one of the first RS arrangement and the second RS arrangement,

wherein the first RS arrangement is different from the second RS arrangement,

wherein one of the first and second RS arrangements comprises a cyclic shift of the other of the first and second RS arrangements,

wherein the first RS arrangement is associated with the coherence criterion being met and the second RS arrangement is associated with the coherence criterion not being met,

wherein the cyclic shift comprises mapping a last sample of a reference signal sequence to a first sub-carrier,

wherein the cyclic shift is applied to a sequence mapping of the reference signal sequence before mapping samples of the reference signal sequence to sub-carriers, and

wherein the reference signal sequence is a Type 1, 1-port De-Modulation Reference Signal (DMRS) sequence; and

transmitting the selected RS arrangement as part of a DMRS within the subsequent PUSCH transmission.