WO2021212396A1

WO2021212396A1 - Phase tracking reference signal density selection in a multiuser superposition transmission configuration

Info

Publication number: WO2021212396A1
Application number: PCT/CN2020/086316
Authority: WO
Inventors: Hui Guo; Sony Akkarakaran; Kapil Gulati; Tien Viet NGUYEN; Min Huang
Original assignee: Qualcomm Incorporated
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-10-28

Abstract

Certain aspects of the present disclosure provide techniques for determining time domain density and/or frequency domain density for resources for communicating phase tracking reference signal (PT-RS) when operating in a multiuser superposition transmission (MUST) configuration.

Description

PHASE TRACKING REFERENCE SIGNAL DENSITY SELECTION IN A MULTIUSER SUPERPOSITION TRANSMISSION CONFIGURATION

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for phase tracking reference signal (PT-RS) density selection in a multiuser superposition transmission (MUST) configuration.

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc. ) . Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (e.g., 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) . To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

As the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include more accurate and reliable PT-RS density selection while operating in a MUST configuration.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE) . The method, while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device, generally includes, receiving, from the device, assistance information for multiple superposed signals for a multiple of UEs on a same one or more time-frequency resources, the multiple superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. The method also includes storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. The method further includes communicating, with the device, a PT-RS based on at least one of:a fixed time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and a fixed frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE) . The method, while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device, generally includes, receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. The method also includes storing, by the UE, one or more of a first time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a first frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. The method further includes storing, by the UE, one or more of one or more second time density tables that map scheduled MCS values to time densities for PT-RSs and one or more second frequency density tables that map scheduled bandwidth values to frequency densities for PT-RSs for when the UE is operating in the MUST configuration. The method also includes communicating, with the device, a PT-RS based on at least one of: a time density based on the one or more second time density tables and the scheduled MCS based on operating in the MUST configuration; and a frequency density based on the one or more second frequency density tables and the scheduled bandwidth based on operating in the MUST configuration.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE) . The method, while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device, generally includes, receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. The method also includes determining at least one of an MCS offset and a frequency offset. The method further includes storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs. The method also includes communicating, with the device, a PT-RS based on at least one of: a time density based on the time density table and a sum of the scheduled MCS and the frequency offset based on operating in the MUST configuration; and a frequency density based on the frequency density table and a sum of the scheduled bandwidth and the MCS offset based on operating in the MUST configuration.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE) . The method, while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device, generally includes, receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. The method also includes storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. The method further includes receiving, from the device, one or more of a configured time density and a configured frequency density. The method also includes communicating, with the device, a PT-RS based on at least one of: the configured time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and the configured frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.

Certain aspects of the subject matter described in this disclosure can be implemented in a method for wireless communication by a device. The method, while operating in a multiuser superposition transmission (MUST) configuration for communication between the device and a plurality of user equipments (UEs) , generally includes, transmitting, to the plurality of UEs, a plurality of superposed signals for the plurality of UEs on a same plurality of time-frequency resources, wherein the plurality of time-frequency resources is divided into a plurality of subbands, wherein at least a first time-frequency resource of the plurality of time-frequency resources include signals for a first number of UEs, and wherein at least a second time-frequency resource of the plurality of time-frequency resources include signals for a second number of UEs different than the first number of UEs. The method also includes at least one of: for each of the plurality of subbands, determining a corresponding time density for transmitting phase-tracking reference signal (PT-RS) to the plurality of UEs; and for each of the plurality of subbands, determining a corresponding frequency density for transmitting PT-RS to the plurality of UEs. The method further includes for each of the plurality of subbands, transmitting PT-RS to the plurality of UEs using at least one of: one of: a maximum of time density of the determined time densities, a minimum time density of the determined time densities, or the corresponding time density; and one of: a maximum of frequency density of the determined frequency densities, a minimum frequency density of the determined frequency densities, or the corresponding frequency density.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing the methods described herein.

Aspects of the present disclosure provide means for, apparatus, processors, and computer-readable mediums for performing techniques and methods that may be complementary to the operations by the UE described herein, for example, by a BS.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example wireless communication network, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram conceptually illustrating a design of an example a base station (BS) and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 3 is an example frame format for certain wireless communication systems (e.g., new radio (NR) ) , in accordance with certain aspects of the present disclosure.

FIGs. 4A and 4B illustrate vehicle to everything (V2X) systems, in accordance with certain aspects of the present disclosure.

FIG. 5A illustrate an example V2V communication network that supports MUST operations, in accordance with certain aspects of the present disclosure.

FIG. 5B illustrate an example process of modulating the superposed signals in a MUST configuration, in accordance with certain aspects of the present disclosure.

FIGs. 6A and 6B illustrate an example mapping between a coding scheme used by a transmitting device time density and frequency density values, in accordance with certain aspects of the present disclosure.

FIG. 7 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 8 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 9 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 10 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

FIG. 11 is a flow diagram illustrating example operations for wireless communication by a BS or a UE, in accordance with certain aspects of the present disclosure.

FIG. 12 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatuses, methods, processing systems, and computer readable mediums for PT-RS density selection in a MUST configuration.

In certain aspects, MUST enables the simultaneous transmission of multiple superposed data layers/signals from a single transmitting device (e.g., a base station (BS) , user equipment (UE) , etc. ) to co-scheduled (e.g., in the same resources) receiving devices (e.g., UE, BS, etc. ) . For example, multiple superposed data layers may be transmitted in the same resources (e.g., time, frequency, and spatial resources) , each layer intended for a different receiving device. In certain aspects, MUST improves intra-cell interference cancellation.

In certain aspects, in a MUST configuration, the transmitting device may modulate the superposed data layersbased on a scheduled modulation coding scheme (MCS) and transmit the modulated superposed signals to the receiving devices based on a scheduled bandwidth. The transmitting device may further provide control signaling (e.g., radio resource control (RRC) signaling, downlink control information (DCI) , media access control –control element (MAC-CE) , etc. ) to the receiving devices that indicates the scheduled MCS and the scheduled bandwidth, as such information may be utilized by the receiving devices to demodulate the modulated superposed signals. In certain aspects, the receiving devices may utilize different MCS and or bandwidth assumptions for demodulating the different layers of the superposed signals (e.g., as indicated in assistance information for each receiving device, such as transmitted via RRC signaling, DCI, MAC-CE, etc. ) .

In certain aspects, a transmitting device may be configured to transmit a PT-RS, which a receiving device utilizes to perform time/frequency tracking of signals transmitted by the transmitting device. For example, the PT-RS enables suppression of phase noise and common phase error (CPE) such as at higher mmW frequencies, such as FR2.

The transmitting device may transmit the PT-RS with a particular density in the time domain and a particular density in the frequency domain. The receiving device may need to have information regarding the density in the time domain and the density in the frequency domain with which the transmitting device transmits the PT-RS in order to determine which resources (e.g., resource blocks, time-frequency resources, etc. ) are carrying the PT-RS to properly receive the PT-RS and use it for time/frequency tracking.

In certain aspects, each receiving device is configured with a table that maps MCS (used by the transmitting device for modulating data transmitted to the receiving device) to a time domain density for the PT-RS. Further, in certain aspects, each receiving device is configured with a table that maps bandwidth (used by the transmitting device for transmitting to the receiving device) to a frequency domain density for the PT-RS. Such tables, however, in certain aspects, may only be useful for when the transmitting device is operating in a non-MUST configuration, as the PT-RS time domain density and/or frequency domain density that the tables map to may not be suitable for PT-RS when using superposition coding as in MUST.

Accordingly, certain aspects of the present disclosure provide various techniques for determining/selecting a PT-RS time domain density and/or frequency domain density for MUST communications. In certain aspects, the techniques for determining/selecting a PT-RS as described herein are based on factors other than or in addition to the MCS used to modulate data transmissions and/or bandwidth used to transmit the data transmissions by the transmitting device. Accordingly, the transmitting device and receiving devices can use a PT-RS time domain density and/or frequency domain density that are better suited for MUST communications and not just those used for non-MUST communications.

The following description provides examples of determining/selecting a PT-RS time domain density and/or frequency domain density in a MUST enabled communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.

The techniques described herein may be used for various wireless networks and radio technologies. While aspects may be described herein using terminology commonly associated with 3G, 4G, and/or new radio (e.g., 5G NR) wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems.

NR access may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond) , millimeter wave (mmW) targeting high carrier frequency (e.g., e.g., 24 GHz to 53 GHz or beyond) , massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC) . These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe. NR supports beamforming and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells.

FIG. 1 illustrates an example wireless communication network 100 in which aspects of the present disclosure may be performed. For example, the wireless communication network 100 may be an NR system (e.g., a 5G NR network) . As shown in FIG. 1, the wireless communication network 100 may be in communication with a core network 132. The core network 132 may in communication with one or more base station (BSs) 110 and/or user equipment (UE) 120 in the wireless communication network 100 via one or more interfaces.

According to certain aspects, a UE 120a/BS 110a may be configured to transmit data to a plurality of

UEs

120b and 120c in a MUST enabled configuration. For example, the UE 120a/BS 110a may be configured to modulate superposed data layers/signals based on a scheduled MCS and transmit the modulated signals according to a scheduled bandwidth to UEs 120b and 120c, in accordance with aspects of the present disclosure. In certain aspects, the UE 120a/BS 110a may be configured to transmit assistance information to the

UEs

120b and 120c to which they transmit the superposed data layers. As shown in FIG. 1, the UE 120a may include a MUST manager 122a that is configured to determine time domain density and/or frequency domain density values for PT-RS, in accordance with aspects of the present disclosure. Further, the BS 110a may include a MUST manager 112 that is configured to determine time domain density and/or frequency domain density values for a PT-RS, in accordance with aspects of the present disclosure. The UE 120a/BS 110a may be further configured to transmit/receive PT-RS based on the determined time domain density and/or frequency domain density values to/from

UEs

120b and 120c, in accordance with aspects of the present disclosure.

The UE 120b/120c may include a MUST manager 122b/122c that is configured to determine time domain density and/or frequency domain density values for PT-RS, in accordance with aspects of the present disclosure. The UE 122b/122c may be further configured to receive/transmit PT-RS based on the determined time domain density and/or frequency domain density values from/to UE 120a/BS 110a, in accordance with aspects of the present disclosure.

As described herein, a UE 120 is referred to as a “transmitter UE 120, ” when the UE 120 transmits superposed data layers to other devices. As described herein, a UE 120 is referred to as a “receiver UE, ” when the UE 120 receives one or more superposed datalayers from a computing device.

As illustrated in FIG. 1, the wireless communication network 100 may include a number of BSs 110a-z (each also individually referred to herein as BS 110 or collectively as BSs 110) and other network entities. A BS 110 may provide communication coverage for a particular geographic area, sometimes referred to as a “cell” , which may be stationary or may move according to the location of a mobile BS 110. In some examples, the BSs 110 may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in FIG. 1, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BSs for the

femto cells

102y and 102z, respectively. A BS may support one or multiple cells.

The BSs 110 communicate with UEs 120a-y (each also individually referred to herein as UE 120 or collectively as UEs 120) in the wireless communication network 100. The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless communication network 100, and each UE 120 may be stationary or mobile. Wireless communication network 100 may also include relay stations (e.g., relay station 110r) , also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE 120 or a BS 110) , or that relays transmissions between UEs 120, to facilitate communication between devices.

A network controller 130 may be in communication with a set of BSs 110 and provide coordination and control for these BSs 110 (e.g., via a backhaul) . In certain aspects, the network controller 130 may be in communication with a core network 132 (e.g., a 5G Core Network (5GC) ) , which provides various network functions such as Access and Mobility Management, Session Management, User Plane Function, Policy Control Function, Authentication Server Function, Unified Data Management, Application Function, Network Exposure Function, Network Repository Function, Network Slice Selection Function, etc.

FIG. 2 illustrates example components of BS 110a and UE 120a (e.g., the wireless communication network 100 of FIG. 1) , which may be used to implement aspects of the present disclosure.

At the BS 110a, a transmit processor 220 may receive data from a data source 212 and control information from a controller/processor 240. The control information may be for the physical broadcast channel (PBCH) , physical control format indicator channel (PCFICH) , physical hybrid ARQ indicator channel (PHICH) , physical downlink control channel (PDCCH) , group common PDCCH (GC PDCCH) , etc. The data may be for the physical downlink shared channel (PDSCH) , etc. A medium access control (MAC) -control element (MAC-CE) is a MAC layer communication structure that may be used for control command exchange between wireless nodes. The MAC-CE may be carried in a shared channel such as a physical downlink shared channel (PDSCH) , a physical uplink shared channel (PUSCH) , or a physical sidelink shared channel (PSSCH) .

The processor 220 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 may also generate reference symbols, such as for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , PBCH demodulation reference signal (DMRS) , and channel state information reference signal (CSI-RS) . A transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 232a-232t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120a, the antennas 252a-252r may receive the downlink signals from the BS 110a and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 256 may obtain received symbols from all the demodulators 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120a to a data sink 260, and provide decoded control information to a controller/processor 280.

On the uplink, at UE 120a, a transmit processor 264 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 262 and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor 280. The transmit processor 264 may also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS) ) . The symbols from the transmit processor 264 may be precoded by a TX MIMO processor 266 if applicable, further processed by the modulators in transceivers 254a-254r (e.g., for SC-FDM, etc. ) , and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a may be received by the antennas 234, processed by the modulators 232, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120a. The receive processor 238 may provide the decoded data to a data sink 239 and the decoded control information to the controller/processor 240.

The

memories

242 and 282 may store data and program codes for BS 110a and UE 120a, respectively. A scheduler 244 may schedule UEs for data transmission on the downlink and/or uplink.

Antennas 252,

processors

266, 258, 264, and/or controller/processor 280 of the UE 120a and/or antennas 234,

processors

220, 230, 238, and/or controller/processor 240 of the BS 110a may be used to perform the various techniques and methods described herein. For example, as shown in FIG. 2, the controller/processor 240 of the BS 110a has a MUST manager 241 that is configured to determine time domain density and/or frequency domain density values for PT-RS, according to aspects described herein. As shown in FIG. 2, the controller/processor 280 of the UE 120a has a MUST manager 281 that is configured to determine time domain density and/or frequency density values, according to aspects described herein. Although shown at the controller/processor, other components of the UE 120a and BS 110a may be used to perform the operations described herein.

NR may utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. NR may support half-duplex operation using time division duplexing (TDD) . OFDM and single-carrier frequency division multiplexing (SC-FDM) partition the system bandwidth into multiple orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. Modulation symbols may be sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers may be dependent on the system bandwidth. The minimum resource allocation, called a resource block (RB) , may be 12 consecutive subcarriers. The system bandwidth may also be partitioned into subbands. For example, a subband may cover multiple RBs. NR may support a base subcarrier spacing (SCS) of 15 KHz and other SCS may be defined with respect to the base SCS (e.g., 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. ) .

FIG. 3 is a diagram showing an example of a frame format 300 for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots (e.g., 1, 2, 4, 8, 16, …slots) depending on the SCS. Each slot may include a variable number of symbol periods (e.g., 7, 12, or 14 symbols) depending on the SCS. The symbol periods in each slot may be assigned indices. A mini-slot, which may be referred to as a sub-slot structure, refers to a transmit time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols) . Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched. The link directions may be based on the slot format. Each slot may include DL/UL data as well as DL/UL control information.

In NR, a synchronization signal block (SSB) is transmitted. In certain aspects, SSBs may be transmitted in a burst where each SSB in the burst corresponds to a different beam direction for UE-side beam management (e.g., including beam selection and/or beam refinement) . The SSB includes a PSS, a SSS, and a two symbol PBCH. The SSB can be transmitted in a fixed slot location, such as the symbols 0-3 as shown in FIG. 3. The PSS and SSS may be used by UEs for cell search and acquisition. The PSS may provide half-frame timing, the SS may provide the CP length and frame timing. The PSS and SSS may provide the cell identity. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SSBs may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI) , system information blocks (SIBs) , other system information (OSI) can be transmitted on a physical downlink shared channel (PDSCH) in certain subframes. The SSB can be transmitted up to sixty-four times, for example, with up to sixty-four different beam directions for mmWave. The multiple transmissions of the SSB are referred to as a SS burst set. SSBs in an SS burst set may be transmitted in the same frequency region, while SSBs in different SS bursts sets can be transmitted at different frequency regions.

FIGs. 4A and 4B illustrate vehicle to everything (V2X) systems, in accordance with certain aspects of the present disclosure. The V2X systems, provided in FIGS. 4A and 4B provides two complementary transmission modes. A first transmission mode involves direct communications (e.g., also referred to herein as sidelink communications between UEs) between participants in the local area. Such communications are illustrated in FIG. 4A. A second transmission mode involves network communications through a network as illustrated in FIG. 4B, which may be implemented over a Uu interface (e.g., a wireless communication interface between a radio access network (RAN) and a UE) .

Referring to FIG. 4A, a V2X system is illustrated with two vehicles. The first transmission mode allows for direct communication between different participants in a given geographic location. As illustrated, a vehicle can have a wireless communication link with an individual (V2P) (e.g., via a UE) through a PC5 interface. Communications between a vehicle and another vehicle (V2V) may also occur through a PC5 interface. In a like manner, communication may occur from a vehicle to other highway components or roadside units (RSUs) , such as a traffic signal or sign (V2I) through a PC5 interface. In each example illustrated, two-way communication may take place between elements, therefore each element may be a transmitter and a receiver of information. In the configuration provided, the first transmission mode may be a self-managed system without assistance from a network such as a RAN. Such transmission modes may enable improved spectral efficiency, reduced cost, and increased reliability as network service interruptions do not occur during handover operations for moving vehicles. Resource assignments do not need coordination between operators and subscription to a network is not necessary, therefore there is reduced complexity for such self-managed systems. The V2X system may be configured to operate in a licensed or unlicensed spectrum, thus any vehicle with an equipped system may access a common frequency and share information. Such harmonized/common spectrum operations allows for safe operation. The V2X system. While FIG. 4A illustrates a V2X system with two vehicles, those skilled in the art should realize that the V2X system is not limited to two vehicles.

Referring to FIG. 4B, a second of two complementary transmission modes is illustrated. In the illustrated embodiment, a vehicle may communicate to another vehicle through network communications. These network communications may occur through discrete nodes, such as a base station (e.g., an eNB or gNB) , that send and receive information between vehicles. The network communications may be used, for example, for long range communications between vehicles, such as noting the presence of an accident in the distance. Other types of communication may be sent by the node to vehicles, such as traffic flow conditions, road hazard warnings, environmental/weather reports, service station availability and other like data. Such data can be obtained from cloud-based sharing services.

Referring to FIG. 5A, a V2V communication network that supports MUST operations is illustrated. FIG. 5A illustrates a sidelink communication between the

UEs

501, 502, 503, which are operating in MUST configuration. In certain aspects, the

UEs

501, 502, 503 are similarly configured as UEs 120, described above with reference to FIGs. 1, 2, and 3. As illustrated in FIG. 5A, UE 503 is the transmitter UE, and

UEs

501 and 502 are the receiver UEs. UE 501 is at a distance farther away from UE 503 than UE 502. The UE 502 is at a distance closer to the UE 503 than UE 501. The UE 501 may be referred to herein as MUST-far UE, and the UE 502 may be referred to herein as a MUST-near UE. Due to the different distances of the UE 501 and UE 502, different power factors are applied by the transmitting UE 503 to modulate the corresponding data layers/signals superposed on the same time-frequency resources. For example, a data layer for the UE 502 may have a different power factor applied as compared to a data layer for the UE 501 by the UE 503. The plurality of superposed data layers, however, may be modulated using a scheduled MCS common to the plurality of superposed data layers and transmitted using a scheduled bandwidth for transmitting the plurality of superposed data layers.

An example process of modulating the superposed signals is illustrated in FIG. 5B. As shown in FIG. 5B, a transmitting device (e.g., UE 503) may modulate transport blocks superposed on a same time-frequency resources based on a scheduled modulation coding scheme (MCS) and allocate different power factors, and transmit the superposed signals to receiving devices (e.g., UE 501, and UE 502) based on a scheduled bandwidth.

Due to the different distances of the UE 501 and UE 502 from the transmitting UE 503, the UE 502 may be communicating with UE 503 via a stronger transport channel than the UE 501, and the signal-to-noise ratio (SNR) of the transport channel between

UE

503 and 502 may be greater than the SNR of the transport channel between

UE

501 and 503. Due to the differences in SNR, UE 501 and UE 502, while operating in a MUST configuration, may be configured to demodulate signals based on different demodulation schemes (e.g., QPSK, 16QAM, and the like) than a coding scheme used to modulate the signals (e.g., scheduled MCS) . The UE 501 and UE 502 may be configured to decode their respective data layers from the superposed signals using assistance information transmitted from UE 503. The assistance information may include the schedule MCS and/or the scheduled bandwidth used by UE 503. In certain aspects, the assistance information may include other information, as discussed herein. In certain aspects, the assistance information may be derived and/or determined by the UE by blind detection, higher layer signaling, and/or dynamic signaling based on the UE’s scheduling information.

In certain aspects, a discussed, resources for communicating PT-RS are selected/determined based on the a determined time domain density and/or frequency domain density for PT-RS. In certain aspects, time domain density and frequency domain density are determined based on high layer parameter values timeDensity and frequencyDensity, respectively, which may be signaled from the transmitting device to the receiving device, such as using RRC signaling, DCI, MAC-CE, etc. For example, the higher layer parameters timeDensity and frequencyDensity in a PTRS-UplinkConfig message indicate the threshold values ptrs-MCSi, i=1, 2, 3 and N _RBi, i=0, 1.

In certain aspects, while operating in a non-MUST configuration, the receiving devices (e.g., UEs 501 and 502) may receive information regarding a scheduled MCS (e.g., I _MCS value) and/or scheduled bandwidth (e.g., N _RB number of resource blocks) used by a transmitting device (e.g., UE 503) , such as in assistance information. In certain aspects, based on the determined threshold values for ptrs-MCSi, and the scheduled MCS, the receiving and/or transmitting devices can determine, based on the table in FIG. 6A, the time domain density (L _PT-RS) for PT-RS. For example, one of the conditions listed under Scheduled MCS in the table of FIG. 6A will be true for the determined threshold values for ptrs-MCSi and the scheduled MCS, which then maps to a value for L _PT-RS. The value of L _PT-RS either indicates that there is no PT-RS, or indicates how many symbols of every L _PT-RS symbols are allocated for PT-RS.

Similarly, in certain aspects, based on the determined threshold values for N _RBi, and the scheduled bandwidth, the receiving and/or transmitting devices can determine, based on the table in FIG. 6B, the frequency domain density (K _PT-RS) for PT-RS. For example, one of the conditions listed under Scheduled bandwidth in the table of FIG. 6B will be true for the determined threshold values for N _RBi and the scheduled bandwidth, which then maps to a value for K _PT-RS. The value of K _PT-RS either indicates that there is no PT-RS, or indicates how many resource blocks of every K _PT-RS resource blocks are allocated for PT-RS.

However, while operating in a MUST configuration, since the receiving devices may not demodulate received signals based on the same coding scheme (e.g., scheduled MCS) and/or the same bandwidth (e.g., scheduled bandwidth) as used by the transmitting device, then determining time density and/or frequency density values for PT-RS based on the scheduled MCS and/or scheduled bandwidth used by the transmitting device and the same tables as used for non-MUST configuration may result in selecting PT-RS resources that do not allow to accurately estimate CPE and may not minimize the effects of CPE on the performance of the communication network.

Accordingly, what is needed are techniques and apparatus for determining time domain density and/or frequency domain density values to select PT-RS resources such that PT-RS can be used to accurately estimate CPE and minimize the effects of CPE on the performance of the communication network.

Example phase tracking reference signal density selection in a multiuser superposition transmission configuration

Aspects of the present disclosure provide techniques for determining time domain density and/or frequency domain density values for PT-RS for devices operating in a MUST configuration (e.g., engaging in MUST communications) .

FIG. 7 is a flow diagram illustrating example operations 700 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 700 may be performed, for example, by a UE (e.g., the UE 120a/b/c in the wireless communication network 100) . The operations 700 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 700 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 700 may occur while the UE/device is operating in a MUST configuration for communication between the UE and a device. Operations 700 may begin, at 702, where the UE receives, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. At 704, the UE stores one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. For example, the time density table may be the table shown in FIG. 6A and the frequency density table may be the table shown in FIG. 6B. At 706, the UE communicates, with the device, a PT-RS based on at least one of: a fixed time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and a fixed frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.

In certain aspects, communicating comprises transmitting the PT-RS to the device. In certain aspects, communicating comprises receiving the PT-RS from the device. In certain aspects, the device comprises one of a second UE or a base station (BS) . In certain aspects, operations 700 further include receiving, from the device, the plurality of superposed signals and decoding, by the UE, the first signal of the plurality of superposed signals based on the assistance information.

In certain aspects, the fixed time density may be a default time density value with which the UE is configured with (e.g., via RRC signaling, DCI, MAC-CE, etc. ) for a MUST configuration. For example, in certain aspects, the default time density value is L _PT-RS = 1. For example, in certain aspects, the higher layer parameter timeDensity is ignored for MUST configuration

In certain aspects, the fixed frequency density may be a default frequency density value with which the UE is configured with (e.g., via RRC signaling, DCI, MAC-CE, etc. ) for a MUST configuration. For example, in certain aspects, the default frequency density value is K _PT-RS = 2. For example, in certain aspects, the higher layer parameter frequencyDensity is ignored for MUST configuration

In certain aspects, a default time density value and/or default frequency density value means no additional control overhead is needed, thereby advantageously decreasing resources needed for communicating control overhead.

FIG. 8 is a flow diagram illustrating example operations 800 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 800 may be performed, for example, by a UE (e.g., the UE 120a/b/c in the wireless communication network 100) . The operations 800 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 800 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 800 may occur while the UE/device is operating in a MUST configuration for communication between the UE and a device. Operations 800 may begin, at 802, where the UE receives, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. At 804, the UE stores one or more of a first time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a first frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. For example, the first time density table may be the table shown in FIG. 6A and the first frequency density table may be the table shown in FIG. 6B.

At 806, the UE stores one or more of one or more second time density tables that map scheduled MCS values to time densities for PT-RSs and one or more second frequency density tables that map scheduled bandwidth values to frequency densities for PT-RSs for when the UE is operating in the MUST configuration. At 808, the UE communicates, with the device, a PT-RS based on at least one of: a time density based on the one or more second time density tables and the scheduled MCS based on operating in the MUST configuration; and a frequency density based on the one or more second frequency density tables and the scheduled bandwidth based on operating in the MUST configuration.

For example, in certain aspects, in addition (or alternative) to a time density table used for non-MUST configuration, such as shown in FIG. 6A, the UE is configured with one or more time density tables that map scheduled MCS values to time densities for PT-RSs when the UE is operating in MUST configuration. In certain aspects, each of the one or more time density tables has a similar structure to the table of FIG. 6A, but may include different values in the table. In certain aspects, different time density tables are associated with different threshold values (e.g., for ptrs-MCSi) . In certain aspects, different time density tables are associated with different numbers of superposed data layers, and/or power factor ratio, and/or MUST categories, and/or other information such as included in assistance information. For example, the UE may receive information in assistance information that maps to one of the different time density tables and use such a time density table for determining the time density value for a corresponding PT-RS.

For example, in certain aspects, in addition (or alternative) to a frequency density table used for non-MUST configuration, such as shown in FIG. 6B, the UE is configured with one or more frequency density tables that map scheduled bandwidth values to frequency densities for PT-RSs when the UE is operating in MUST configuration. In certain aspects, each of the one or more frequency density tables has a similar structure to the table of FIG. 6B, but may include different values in the table. In certain aspects, different frequency density tables are associated with different threshold values (e.g., for N _RBi) . In certain aspects, different frequency density tables are associated with different numbers of superposed data layers, and/or power factor ratio, and/or MUST categories, and/or other information such as included in assistance information. For example, the UE may receive information in assistance information that maps to one of the different frequency density tables and use such a frequency density table for determining the frequency density value for a corresponding PT-RS.

In certain aspects, one or more of: the one or more second time density tables at 806 consist of a single time density table; and the one or more second frequency density tables at 806 consist of a single frequency density table.

In certain aspects, one or more of: the one or more second time density tables at 806 comprise a plurality of time density tables, each of the plurality of time density tables associated with a different set of values for one or more parameters indicated in the assistance information, wherein the time density is based on one of the plurality of time density tables associated with a set of values equal to values in the assistance information; and the one or more second frequency density tables at 806 comprise a plurality of frequency density tables, each of the plurality of frequency density tables associated with a different set of values for one or more parameters indicated in the assistance information, wherein the frequency density is based on one of the plurality of frequency density tables associated with a set of values equal to values in the assistance information. In certain aspects, the one or more parameters comprise one or more of a number of superposed data layers, a power factor ratio, and a MUST category.

In certain aspects, communicating comprises transmitting the PT-RS to the device. In certain aspects, communicating comprises receiving the PT-RS from the device. In certain aspects, the device comprises one of a second UE or a base station (BS) . In certain aspects, operations 800 further include receiving, from the device, the plurality of superposed signals and decoding, by the UE, the first signal of the plurality of superposed signals based on the assistance information.

FIG. 9 is a flow diagram illustrating example operations 900 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 900 may be performed, for example, by UE (e.g., the UE 120a/b/c in the wireless communication network 100) . The operations 900 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 900 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 900 may occur while the UE/device is operating in a MUST configuration for communication between the UE and a device. Operations 900 may begin, at 902, where the UE receives, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. At 904, the UE determines at least one of a MCS offset and a frequency offset. At 906, the UE stores one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs. For example, the time density table may be the table shown in FIG. 6A and the frequency density table may be the table shown in FIG. 6B.

At 908, the UE communicates, with the device, a PT-RS based on at least one of: a time density based on the time density table and a sum of the scheduled MCS and the MCS offset based on operating in the MUST configuration; and a frequency density based on the frequency density table and a sum of the scheduled bandwidth and the frequency offset based on operating in the MUST configuration.

For example, in certain aspects, the MCS offset is defined in higher layer signaling (e.g., RRC signaling, DCI, MAC-CE, etc. ) in addition to the time density table. In certain aspects, if superposition coding is enabled, scheduled MCS plus the MCS offset and the table is used for PT-RS time domain density determination, similar to as discussed with respect to FIG. 6A, but with the MCS offset applied to I _MCS. In certain aspects, different MCS offsets are associated with different numbers of superposed data layers, and/or power factor ratio, and/or MUST categories, and/or other information such as included in assistance information. For example, the UE may receive information in assistance information that maps to a MCS offset and use such a MCS offset for determining the time density value for a corresponding PT-RS. In certain other aspects, the MCS offset is explicitly signaled to the receiver UE (s) in control information (e.g., RRC signaling, DCI, MAC-CE, etc. ) .

For example, in certain aspects, the frequency offset is defined in higher layer signaling (e.g., RRC signaling, DCI, MAC-CE, etc. ) in addition to the frequency density table. In certain aspects, if superposition coding is enabled, scheduled bandwidth plus the frequency offset and the table is used for PT-RS frequency domain density determination, similar to as discussed with respect to FIG. 6B, but with the frequency offset applied to N _RB. In certain aspects, different frequency offsets are associated with different numbers of superposed data layers, and/or power factor ratio, and/or MUST categories, and/or other information such as included in assistance information. For example, the UE may receive information in assistance information that maps to a frequency offset and use such a frequency offset for determining the frequency density value for a corresponding PT-RS. In certain other aspects, the frequency offset is explicitly signaled to the receiver UE (s) in control information (e.g., RRC signaling, DCI, MAC-CE, etc. ) .

In certain aspects, determining the at least one of the MCS offset and the frequency offset at 904 comprises receiving the at least one of the MCS offset and the frequency offset from the device.

In certain aspects, the assistance information at 902 comprises the at least one of the MCS offset and the frequency offset.

In certain aspects, determining the at least one of the MCS offset and the frequency offset at 904 is based on a function or table that maps one or more parameters of the assistance information to the at least one of the MCS offset and the frequency offset. In certain aspects, the one or more parameters comprise one or more of a number of superposed data layers, a power factor ratio, and a MUST category.

In certain aspects, communicating comprises transmitting the PT-RS to the device. In certain aspects, communicating comprises receiving the PT-RS from the device. In certain aspects, the device comprises one of a second UE or a base station (BS) . In certain aspects, operations 900 further include receiving, from the device, the plurality of superposed signals and decoding, by the UE, the first signal of the plurality of superposed signals based on the assistance information.

FIG. 10 is a flow diagram illustrating example operations 1000 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 1000 may be performed, for example, by UE (e.g., the UE 120a/b/c in the wireless communication network 100) . The operations 1000 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280 of FIG. 2) . Further, the transmission and reception of signals by the UE in operations 1000 may be enabled, for example, by one or more antennas (e.g., antennas 252 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor 280) obtaining and/or outputting signals.

The operations 1000 may occur while the UE/device is operating in a MUST configuration for communication between the UE and a device. Operations 1000 may begin, at 1002, where the UE receives, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals. At the 1004, the UE stores one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration. For example, the time density table may be the table shown in FIG. 6A and the frequency density table may be the table shown in FIG. 6B.

At 1006, the UE receives, from the device, one or more of a configured time density and a configured frequency density. At 1008, the UE communicates, with the device, a PT-RS based on at least one of: the configured time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and the configured frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.

In certain aspects, the one or more of the configured time density and the configured frequency density is conveyed to the receiver UE by a higher layer parameter. In certain aspects, the one or more of the configured time density and the configured frequency density at 1006 is received via a radio resource control (RRC) signal. In certain aspects, timeDensity and/or frequencyDensity is not valid if configured time density and/or the configured frequency density is configured at the receiver UE and MUST is enabled.

In certain aspects, the one or more of the configured time density and the configured frequency density at 1006 is received in the assistance information.

In certain aspects, one or more of the configured time density and the configured frequency density is conveyed to the receiver UE in control information, such as in extra control information so that L _PT-RS and/or K _PT-RS is updated according to a current transmission configuration.

In certain aspects, communicating comprises transmitting the PT-RS to the device. In certain aspects, communicating comprises receiving the PT-RS from the device. In certain aspects, the device comprises one of a second UE or a base station (BS) . In certain aspects, operations 1000 further include receiving, from the device, the plurality of superposed signals and decoding, by the UE, the first signal of the plurality of superposed signals based on the assistance information.

FIG. 11 is a flow diagram illustrating example operations 1100 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 1100 may be performed, for example, by a device such as a UE or a BS (e.g., the UE 120a or BS 110 in the wireless communication network 100) . The operations 1100 may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor 280/240 of FIG. 2) . Further, the transmission and reception of signals by the UE/BS in operations 1000 may be enabled, for example, by one or more antennas (e.g., antennas 252/234 of FIG. 2) . In certain aspects, the transmission and/or reception of signals by the UE/BS may be implemented via a bus interface of one or more processors (e.g., controller/processor 280/240) obtaining and/or outputting signals.

The operations 1100 may occur while operating in a MUST configuration for communication between the device and a plurality of UEs. Operations 1100 may begin, at 1102, where the device transmits, to the plurality of UEs, a plurality of superposed signals for the plurality of UEs on a same plurality of time-frequency resources, wherein the plurality of time-frequency resources is divided into a plurality of subbands, wherein at least a first time-frequency resource of the plurality of time-frequency resources include signals for a first number of UEs, and wherein at least a second time-frequency resource of the plurality of time-frequency resources include signals for a second number of UEs different than the first number of UEs. At 1104, the device at least one of: for each of the plurality of subbands, determines a corresponding time density for transmitting phase-tracking reference signal (PT-RS) to the plurality of UEs; and for each of the plurality of subbands, determines a corresponding frequency density for transmitting PT-RS to the plurality of UEs. At 1106, the device, for each of the plurality of subbands, transmits PT-RS to the plurality of UEs using at least one of: one of: a maximum of time density of the determined time densities, a minimum time density of the determined time densities, or the corresponding time density; and one of: a maximum of frequency density of the determined frequency densities, a minimum frequency density of the determined frequency densities, or the corresponding frequency density.

In certain aspects, each of the plurality of subbands at 1102 is used for transmission of a different type of data (e.g., one subband is used for CSI reporting) . In certain aspects, each of the plurality of subbands is used for transmission to a different number of UEs. In certain aspects, each of the plurality of subbands is used for transmission to a different set of UEs.

For example, the overall scheduled bandwidth (e.g., RB allocation) used by the device to transmit superposed data layers may be divided into a number of different subbands, such as if the number of superposed data layers within the overall scheduled bandwidth is not constant. For example, some RBs may be overlapped with different numbers of superposed UEs, meaning different RBs are assigned to different numbers of UEs, or different sets (e.g., one or more) of UEs. For example, a first RB may be for 2 UEs, while a second RB may be for 3 UEs, etc. Further, in an example, a first RB may be for UEs A and B, while a second RB may be for UEs B and C.

In certain aspects, the same K _PT-RS is determined for all the subbands and is the maximum among the K _PT-RS determined for each subband, such as according to any of the techniques discussed herein. In certain aspects, the same K _PT-RS is determined for all the subbands and is the minimum among the K _PT-RS determined for each subband, such as according to any of the techniques discussed herein.

In certain aspects, the same L _PT-RS is determined for all the subbands and is the maximum among the L _PT-RS determined for each subband, such as according to any of the techniques discussed herein. In certain aspects, the same L _PT-RS is determined for all the subbands and is the minimum among the L _PT-RS determined for each subband, such as according to any of the techniques discussed herein.

In certain aspects, separate K _PT-RS are determined for each of the subbands, such as according to any of the techniques discussed herein. In certain aspects, separate L _PT-RS are determined for each of the subbands, such as according to any of the techniques discussed herein.

FIG. 12 illustrates a communications device 1200 that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in FIGs. 7, 8, 9, 10, and/or 11. The communications device 1200 includes a processing system 1202 coupled to a transceiver 1208 (e.g., a transmitter and/or a receiver) . The transceiver 1208 is configured to transmit and receive signals for the communications device 1200 via an antenna 1210, such as the various signals as described herein. The processing system 1202 may be configured to perform processing functions for the communications device 1200, including processing signals received and/or to be transmitted by the communications device 1200.

The processing system 1202 includes a processor 1204 coupled to a computer-readable medium/memory 1212 via a bus 1206. In certain aspects, the computer-readable medium/memory 1212 is configured to store instructions (e.g., computer-executable code) that when executed by the processor 1204, cause the processor 1204 to perform the operations illustrated in FIGs. 7, 8, 9, 10, and/or 11, or other operations for performing the various techniques discussed herein for determining time domain density and/or frequency domain density for resources for communicating phase tracking reference signal (PT-RS) when operating in a multiuser superposition transmission (MUST) configuration. . In certain aspects, computer-readable medium/memory 1212 stores code for operations of FIGs. 7, 8, 9, 10, and/or 11, such as one or more of code for receiving 1214, code for storing 1216, code for determining 1218, and code for communicating 1220. In certain aspects, the processor 1204 has circuitry configured to implement the code stored in the computer-readable medium/memory 1212. The processor 1204 includes circuitry for operations illustrated in FIGs. 7, 8, 9, 10, and/or 11, such as one or more of circuitry for receiving 1224, circuitry for storing 1226, circuitry for determining 1228, and circuitry for communicating 1230.

The techniques described herein may be used for various wireless communication technologies, such as NR (e.g., 5G NR) , 3GPP Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single-carrier frequency division multiple access (SC-FDMA) , time division synchronous code division multiple access (TD-SCDMA) , and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . LTE and LTE-Aare releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-Aand GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . NR is an emerging wireless communications technology under development.

In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) and/or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB) , access point (AP) , distributed unit (DU) , carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having an association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) , UEs for users in the home, etc. ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS.

A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, a smart phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices.

In some examples, access to the air interface may be scheduled. A scheduling entity (e.g., a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) , and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity.

The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112 (f) unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine- readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in FIGs. 7, 8, 9, 10, and/or 11.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

A method of wireless communication by a user equipment (UE) , comprising:

while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device:

receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals;

storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration; and

communicating, with the device, a PT-RS based on at least one of:

a fixed time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and

a fixed frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.
A method of wireless communication by a user equipment (UE) , comprising:

while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device:

receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals;

storing, by the UE, one or more of a first time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a first frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration;

storing, by the UE, one or more of one or more second time density tables that map scheduled MCS values to time densities for PT-RSs and one or more second frequency density tables that map scheduled bandwidth values to frequency densities for PT-RSs for when the UE is operating in the MUST configuration; and

communicating, with the device, a PT-RS based on at least one of:

a time density based on the one or more second time density tables and the scheduled MCS based on operating in the MUST configuration; and

a frequency density based on the one or more second frequency density tables and the scheduled bandwidth based on operating in the MUST configuration.
The method of claim 2, wherein one or more of:

the one or more second time density tables consist of a single time density table; and

the one or more second frequency density tables consist of a single frequency density table.
The method of claim 2, wherein one or more of:

the one or more second time density tables comprise a plurality of time density tables, each of the plurality of time density tables associated with a different set of values for one or more parameters indicated in the assistance information, wherein the time density is based on one of the plurality of time density tables associated with a set of values equal to values in the assistance information; and

the one or more second frequency density tables comprise a plurality of frequency density tables, each of the plurality of frequency density tables associated with a different set of values for one or more parameters indicated in the assistance information, wherein the frequency density is based on one of the plurality of frequency density tables associated with a set of values equal to values in the assistance information.
The method of claim 4, wherein the one or more parameters comprise one or more of a number of superposed data layers, a power factor ratio, and a MUST category.
A method of wireless communication by a user equipment (UE) , comprising:

while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device:

receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals;

determining at least one of a MCS offset and a frequency offset;

storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs; and

communicating, with the device, a PT-RS based on at least one of:

a time density based on the time density table and a sum of the scheduled MCS and the MCS offset based on operating in the MUST configuration; and

a frequency density based on the frequency density table and a sum of the scheduled bandwidth and the frequency offset based on operating in the MUST configuration.
The method of claim 6, wherein determining the at least one of the MCS offset and the frequency offset comprises receiving the at least one of the MCS offset and the frequency offset from the device.
The method of claim 6, wherein the assistance information comprises the at least one of the MCS offset and the frequency offset.
The method of claim 6, wherein determining the at least one of the MCS offset and the frequency offset is based on a function or table that maps one or more parameters of the assistance information to the at least one of the MCS offset and the frequency offset.
The method of claim 9, wherein the one or more parameters comprise one or more of a number of superposed data layers, a power factor ratio, and a MUST category.
A method of wireless communication by a user equipment (UE) , comprising:

while operating in a multiuser superposition transmission (MUST) configuration for communication between the UE and a device:

receiving, from the device, assistance information for a plurality of superposed signals for a plurality of UEs on a same one or more time-frequency resources, the plurality of superposed signals comprising a first signal for the UE, the assistance information comprising a scheduled modulation coding scheme (MCS) used by the device to modulate the plurality of superposed signals and a scheduled bandwidth for transmitting the plurality of superposed signals;

storing, by the UE, one or more of a time density table that maps scheduled MCS values to time densities for phase-tracking reference signals (PT-RSs) and a frequency density table that maps scheduled bandwidth values to frequency densities for PT-RSs for when the UE is not operating in the MUST configuration;

receiving, from the device, one or more of a configured time density and a configured frequency density; and

communicating, with the device, a PT-RS based on at least one of:

the configured time density, instead of a time density based on the time density table and the scheduled MCS, based on operating in the MUST configuration; and

the configured frequency density, instead of a frequency density based on the frequency density table and the scheduled bandwidth, based on operating in the MUST configuration.
The method of claim 11, wherein the one or more of the configured time density and the configured frequency density is received via a radio resource control (RRC) signal.
The method of claim 11, wherein the one or more of the configured time density and the configured frequency density is received in the assistance information.
The method of any of claims 1-13, wherein communicating comprises transmitting the PT-RS to the device.
The method of any of claims 1-13, wherein communicating comprises receiving the PT-RS from the device.
The method of any of claims 1-13, wherein the device comprises one of a second UE or a base station (BS) .
The method of any of claims 1-13, further comprising, while operating in the MUST configuration:

receiving, from the device, the plurality of superposed signals; and

decoding, by the UE, the first signal of the plurality of superposed signals based on the assistance information.
A method of wireless communication by a device, comprising:

while operating in a multiuser superposition transmission (MUST) configuration for communication between the device and a plurality of user equipments (UEs) :

transmitting, to the plurality of UEs, a plurality of superposed signals for the plurality of UEs on a same plurality of time-frequency resources, wherein the plurality of time-frequency resources is divided into a plurality of subbands, wherein at least a first time-frequency resource of the plurality of time-frequency resources include signals for a first number of UEs, and wherein at least a second time-frequency resource of the plurality of time-frequency resources include signals for a second number of UEs different than the first number of UEs;

at least one of:

for each of the plurality of subbands, determining a corresponding time density for transmitting phase-tracking reference signal (PT-RS) to the plurality of UEs; and

for each of the plurality of subbands, determining a corresponding frequency density for transmitting PT-RS to the plurality of UEs; and

for each of the plurality of subbands, transmitting PT-RS to the plurality of UEs using at least one of:

one of: a maximum of time density of the determined time densities, a minimum time density of the determined time densities, or the corresponding time density; and

one of: a maximum of frequency density of the determined frequency densities, a minimum frequency density of the determined frequency densities, or the corresponding frequency density.
The method of claim 18, wherein each of the plurality of subbands is used for transmission of a different type of data.
The method of claim 18, wherein each of the plurality of subbands is used for transmission to a different number of UEs.
The method of claim 18, wherein each of the plurality of subbands is used for transmission to a different set of UEs.
A user equipment (UE) comprising:

a memory; and

a processor coupled to the memory, wherein the memory and the processor are configured to perform the method of one or more of claims 1-17.
A user equipment (UE) comprising:

various means for performing the method of one or more of claims 1-17.
A non-transitory computer-readable medium including instructions that when executed by a user equipment (UE) , cause the UE to perform the method of one or more of claims 1-17.
A device comprising:

a memory; and

a processor coupled to the memory, wherein the memory and the processor are configured to perform the method of one or more of claims 18-21.
A device comprising:

various means for performing the method of one or more of claims 18-21.
A non-transitory computer-readable medium including instructions that when executed by a device, cause the device to perform the method of one or more of claims 18-21.