WO2025153167A1

WO2025153167A1 - Reference signal design for doppler/micro-doppler estimation

Info

Publication number: WO2025153167A1
Application number: PCT/EP2024/050820
Authority: WO
Inventors: Xitao Gong; Qi Wang; Shibin GE; Mario Hernán Castañeda Garcia; Richard Stirling-Gallacher
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2024-01-15
Filing date: 2024-01-15
Publication date: 2025-07-24
Anticipated expiration: 2026-07-15

Abstract

The present disclosure provides a configuration entity for reference signal configuration, configured to: determine one or more resource sets for one or more reference signals, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and provide reference signal configuration information to a transmitting entity and/or a receiving entity, wherein the reference signal configuration information indicates the one or more reference signals and/or the one or more resource sets for transmitting or receiving the one or more reference signals.

Description

REFERENCE SIGNAL DESIGN FOR DOPPLER/MICRO-DOPPLER ESTIMATION

TECHNICAL FIELD

The present disclosure relates to the field of wireless communication technologies, more specifically to sensing and positioning within wireless networks. It focuses on advancements in sensing and positioning technologies, essential for next-generation wireless networks, including but not limited to 5G-NR (New Radio), 5.5G, and future 6G systems. The disclosure provides devices and methods relevant to the design and implementation of reference signals for high-resolution Doppler or microDoppler estimation in these systems.

BACKGROUND

The evolution of wireless networks is increasingly integrating sensing and positioning capabilities, recognized as crucial enablers for the next generation of wireless communication systems. Existing systems such as the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) and New Radio (NR), as well as prospective 6G networks, provide the foundational framework for positioning active devices. Sensing, in this context, refers to the acquisition of information about passive objects through the analysis of emitted or reflected signals, which may include data about an object's presence, position, distance, direction, motion, shape, and velocity.

An Integrated Sensing and Communication (ISAC) system leverages radio frequency signals reflected from targets or objects, estimating sensing parameters like velocity or speed, which are pivotal for understanding target movement, motions, and micromotions. This process often involves time-frequency analysis, such as examining Doppler or micro-Doppler components within the reflected signals.

However, in current LTE or 5G-NR systems, the existing reference signals within a single slot or sub-frame are inadequate for the requirements of ISAC, particularly concerning velocity resolution and accuracy. For instance, in the 5G-NR system, a slot's length ranges from 125 microseconds to 1 millisecond, which falls short of the 5.5G/6G ISAC requirements for velocity measurements. Table 1 shows examples of velocity estimation based on 5.5G/6G ISAC requirements.

Table 1

As seen in Table 1, e.g., for the 4.9GHz band, to achieve the desired velocity resolution, it is estimated that reference signals’ observation duration should exceed 20 milliseconds, encompassing at least 20 slots.

Therefore, the technical challenge addressed by this application is the development of reference signals that can fulfill the high resolution Doppler or micro-Doppler estimation needs, especially in the context of future ISAC systems. This advancement is crucial for enhancing the performance and capabilities of next-generation wireless communication networks. SUMMARY

In view of the above-mentioned deficiencies, embodiments of the present disclosure aim to provide a reference signal design, specifically for enhancing Doppler and micro-Doppler estimation. One objective is, in particular, to tailor reference signal design for improved sensing efficiency and resource utilization. Another objective is to introduce greater flexibility and adaptability in reference signal resource allocation and multiplexing. Another objective is to develop advanced reference signal sequence designs for more accurate Doppler-based estimations. Yet another objective is to achieve high resolution and high accuracy in Doppler/Micro-Doppler measurements.

This and other objectives are achieved by the embodiment provided in the enclosed independent claims. Advantageous implementations of the embodiments of the present disclosure are further defined in the dependent claims.

A first aspect of the disclosure provides a configuration entity for reference signal configuration, configured to: determine one or more resource sets for one or more reference signals, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and provide reference signal configuration information to a transmitting entity and/or a receiving entity, wherein the reference signal configuration information indicates the one or more reference signals and/or the one or more resource sets for transmitting or receiving the one or more reference signals.

This disclosure proposes a reference signal design for Doppler or micro-Doppler estimation, in particular, a reference signal design mechanism across time units, including reference signal pattern and sequence span over multiple time units. Consequently, said reference signal is named as Doppler reference signal (DRS) in this application. DRS configuration is provided by the configuration entity to the DRS transmitting unit and/or receiving unit.

In an implementation form of the first aspect, the multiple time units in one resource are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the configuration entity is further configured to: configure for each resource one or more of the following parameters: an indication of the associated time unit set; an indication of one or more bundled time unit sets in the associated time unit set; a first symbol in a time unit inside the associated or bundled time unit set; a quantity of symbols in a time unit inside the associated or bundled time unit set; and a time unit offset with respect to a first time unit of a resource set.

DRS resource is spanning in the time units given in the associated time unit set. One DRS sequence is spanning in the time units given in the bundled time unit set.

In an implementation form of the first aspect, the reference signal configuration information comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource; indices of the associated time units in one resource; a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

DRS configuration may include resource mapping design and indication, such as how to indicate the allocated physical resources specifically in time domain and frequency domain for reference signals. In particular, new parameters are introduced in the mapping function. For instance, the quantity of associated time units in one resource represents how many time units in the DRS resource are associated with making sensing (e.g., Doppler-based) measurements or sensing parameter estimation. The quantity of bundled time units in each bundled time unit set represents how many time units are bundled to span one RS sequence to make sensing (e.g., Doppler-based) measurement or sensing parameter estimation.

In an implementation form of the first aspect, one time unit is one of the following: one slot, one sub-frame, or one frame.

That is, DRS sequence and pattern may be cross-slot, cross-subframe, or cross-frame.

In an implementation form of the first aspect, the multiple time units in one resource comprise consecutive or non-consecutive time units.

In an implementation form of the first aspect, each resource is associated with a particular spatial filter.

Optionally, multiple DRSs or DRS resources may be multiplexed, e.g., associated with different spatial filters.

In an implementation form of the first aspect, the one or more resources comprise a first resource and a second resource, wherein the first resource is associated with a first sequence, and the second resource is associated with a second sequence.

Optionally, different DRS resources may be associated/scrambled with different orthogonal code sequences.

In an implementation form of the first aspect, the first resource and the second resource are multiplexed in at least one of the following domains: time domain; frequency domain; time and frequency domain; code domain; spatial filter domain.

Optionally, this disclosure allows different DRSs or DRS resources multiplexing options. That is, DRS resources may be multiplexed in frequency domain and/or time domain, or code domain, or multiplexed by associating different spatial filters.

In an implementation form of the first aspect, the reference signal configuration information further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence. Optionally, for DRS sequence generation, the sequence generator function may need to be parameterized by settings of the bundled time unit set. For instance, the length of the sequence (which is related to the number of DRS resource elements in bundled time units, and the symbol index among all DRS symbols in the bundled time units), the power of the sequence, and the spatial filters of the sequence.

In an implementation form of the first aspect, the associated time unit set comprises a first bundled time unit set spanning a first sequence and a second bundled time unit set spanning a second sequence, wherein the first bundled time unit set is associated with a first spatial filter, and the second bundled time unit set is associated with a second spatial filter.

Possibly, the DRS symbols in each bundled time unit set formulate one DRS sequence.

In an implementation form of the first aspect, the one or more reference signals comprise one or more of the following: a dedicated reference signal for Doppler/micro-Doppler estimation, a phase tracking reference signal (PTRS), a positioning reference signal (PRS), a demodulation reference signal (DMRS), a channel state information reference signal (CSI-RS), a synchronization signal (SS), a broadcast signal.

It may be worth mentioning that the proposed reference signals do not have to be dedicated reference signals for Doppler/micro- Doppler estimation, it may be based on or extended from any current reference signals in the wireless systems.

In an implementation form of the first aspect, the configuration entity is implemented in a core network node, or an access network node, or a user.

In an implementation form of the first aspect, when the configuration entity is implemented in the access network node, the configuration entity is further configured to receive an indication from the transmitting entity or the receiving entity, wherein the indication indicates that the transmitting entity or the receiving entity is able to support the one or more reference signals, and the transmitting entity or the receiving entity is a user.

Optionally, for UE to receive downlink DRS or transmit uplink DRS, the UE may first indicate that receiving or transmitting DRS cross multiple time units is being supported at the UE (e.g., in Radio Resource Control (RRC) signaling), or UE indicates that it can only support a certain number of cross-slots to receive or transmit DRS.

In an implementation form of the first aspect, the configuration entity is configured to obtain measurements using the one or more reference signals based on the reference signal configuration information.

In a particular example, the configuration entity may also be the receiving entity of the DRS. In this case, the configuration entity performs the measurements based on the received DRS.

A second aspect of the present disclosure provides a transmitting entity for transmitting one or more reference signals, configured to: obtain reference signal configuration information from a configuration entity, wherein the reference signal configuration information indicates the one or more reference signals and/or one or more resource sets for transmitting the one or more reference signals, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and transmit the one or more reference signals to a receiving entity based on the reference signal configuration information.

Embodiments of the disclosure further propose a transmitting entity that is used for transmitting DRS. It may be worth mentioning that the transmitting entity and the configuration entity may be implemented in the same entity. In this case, the transmitting entity obtains DRS configuration internally. If the transmitting entity and the configuration entity are separate entities, the transmitting entity may receive DRS configuration from the configuration entity.

In an implementation form of the second aspect, the multiple time units in one resource are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the reference signal configuration information comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource; indices of the associated time units in one resource; a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

In an implementation form of the second aspect, the reference signal configuration information further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence.

In an implementation form of the second aspect, the transmitting entity is further configured to generate the reference signal sequence based on the reference signal generation information.

In an implementation form of the second aspect, the transmitting entity is implemented in an access network node, or a user.

In an implementation form of the second aspect, when the transmitting entity is implemented in the user, the transmitting entity is further configured to: before transmitting the one or more reference signals, send a request for a resource grant to an access network node, and receive the resource grant from the access network node.

In an implementation form of the second aspect, the access network node is the receiving entity, or the configuration entity.

In an implementation form of the second aspect, the transmitting entity is configured to send an indication to the configuration entity, wherein the indication indicates that the transmitting entity is able to support the one or more reference signals. Optionally, for UE to transmit uplink DRS, the UE may first indicate that transmitting DRS across multiple time units is being supported at the UE (e.g., in Radio Resource Control (RRC) signaling), or UE indicates that it can only support a certain number of cross-slots to transmit DRS.

A third aspect of the present disclosure provides a receiving entity for receiving one or more reference signals, configured to receive one or more reference signals from a transmitting entity based on one or more resource sets, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and obtain measurements using the one or more reference signals.

Embodiments of the disclosure further propose a receiving entity that is used for receiving DRS. It may be worth mentioning that the receiving entity and the configuration entity may be implemented in the same entity.

In an implementation form of the third aspect, before receiving the one or more reference signals, the receiving entity is configured to obtain reference signal configuration information from a configuration entity, wherein the reference signal configuration information indicates the one or more reference signals and/or one or more resource sets for receiving the one or more reference signals.

In an implementation form of the third aspect, the multiple time units in one resource are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the reference signal configuration information comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource; indices of the associated time units in one resource; a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

In an implementation form of the third aspect, the receiving entity is implemented in an access network node, or a user.

In an implementation form of the third aspect, when the receiving entity is implemented in the user, the receiving entity is further configured to send an indication to the configuration entity, wherein the indication indicates that the receiving entity is able to support the one or more reference signals.

Optionally, for UE to receive downlink DRS, the UE may first indicate that receiving DRS cross multiple time units is being supported at the UE (e.g., in Radio Resource Control (RRC) signaling), or UE indicates that it can only support a certain number of cross-slots to receive DRS.

A fourth aspect of the present disclosure provides a method for reference signal configuration, wherein the method comprises: determining one or more resource sets for one or more reference signals, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and providing reference signal configuration information to a transmitting entity and/or a receiving entity, wherein the reference signal configuration information indicates the one or more reference signals and/or the one or more resource sets for transmitting or receiving the one or more reference signals.

The method of the fourth aspect may have implementation forms that correspond to the implementation forms of the configuration entity of the first aspect. The method of the fourth aspect and its implementation forms provide the same advantages and effects as described above for the configuration entity of the first aspect and its respective implementation forms.

A fifth aspect of the present disclosure provides a method for transmitting one or more reference signals, the method comprising: obtaining reference signal configuration information from a configuration entity, wherein the reference signal configuration information indicates the one or more reference signals and/or one or more resource sets for transmitting the one or more reference signals, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and transmitting the one or more reference signals to a receiving entity based on the reference signal configuration information.

The method of the fifth aspect may have implementation forms that correspond to the implementation forms of the transmitting entity of the second aspect. The method of the fifth aspect and its implementation forms provide the same advantages and effects as described above for the transmitting entity of the second aspect and its respective implementation forms.

A sixth aspect of the present disclosure provides a method for receiving one or more reference signals, the method comprising: receiving one or more reference signals from a transmitting entity based on one or more resource sets, wherein the one or more reference signals are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets comprises one or more resources each comprising multiple resource elements spanning over multiple time units; and obtaining measurements using the one or more reference signals.

The method of the sixth aspect may have implementation forms that correspond to the implementation forms of the receiving entity of the third aspect. The method of the sixth aspect and its implementation forms provide the same advantages and effects as described above for the receiving entity of the third aspect and its respective implementation forms.

A seventh aspect of the disclosure provides computer readable code instructions which, when run in a computer will cause the computer to perform the method according to the fourth aspect and any implementation forms of the fourth aspect, the fifth aspect and any implementation forms of the fifth aspect, or the sixth aspect and any implementation forms of the sixth aspect.

An eighth aspect of the present disclosure provides computer program code instructions, being executable by a computer, for performing the method according to the fourth aspect and any implementation forms of the fourth aspect, the fifth aspect and any implementation forms of the fifth aspect, or the sixth aspect and any implementation forms of the sixth aspect.

It has to be noted that all entities, elements, units, and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps that are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity that performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements or any kind of combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

The above-described aspects and implementation forms of the present disclosure will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which:

FIG. 1 shows a configuration entity according to an embodiment of the disclosure.

FIG. 2 shows an ISAC system with downlink sensing signals.

FIG. 3 shows a general signaling procedure for DRS configuration and transmission according to an embodiment of the disclosure.

FIG. 4 shows a resource mapping indication of DRS according to an embodiment of the disclosure.

FIG. 5 shows a DRS resource set and resources according to an embodiment of the present disclosure.

FIG. 6 shows an example of the time-frequency allocation of a DRS resource according to an embodiment of the present disclosure.

FIG. 7 shows examples of associated and bundled slots according to an embodiment of the present disclosure.

FIG. 8 shows DRS multiplexing according to an embodiment of the present disclosure.

FIG. 9 shows a signaling procedure for DL DRS configuration and transmission according to an embodiment of the present disclosure.

FIG. 10 shows a signaling procedure for UL DRS configuration and transmission according to an embodiment of the present disclosure.

FIG. 11 shows a signaling procedure for SL DRS configuration and transmission according to an embodiment of the present disclosure.

FIG. 12 shows a transmitting entity according to an embodiment of the present disclosure.

FIG. 13 shows a receiving entity according to an embodiment of the present disclosure.

FIG. 14 shows a method according to an embodiment of the present disclosure.

FIG. 15 shows a method according to an embodiment of the present disclosure.

FIG. 16 shows a method according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF EMBODIMENTS

Illustrative embodiments of entities, methods, and program products relevant to the design and implementation of reference signals for Doppler or micro-Doppler estimation are described with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

Moreover, an embodiment/example may refer to other embodiments/examples. For example, any description including but not limited to terminology, element, process, explanation, and/or technical advantage mentioned in one embodiment/example is applicative to the other embodiments/examples.

FIG. 1 shows a configuration entity 100 for reference signal configuration according to an embodiment of the disclosure. The configuration entity 100 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the configuration entity 100 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors.

In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the configuration entity 100 to perform, conduct, or initiate the operations or methods described herein.

In particular, the configuration entity 100 is configured to determine one or more resource sets 101 for one or more reference signals 102, wherein the one or more reference signals 102 are for Doppler or micro-Doppler estimation. Each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. The configuration entity 100 is further configured to provide reference signal configuration information 103 to a transmitting entity 200 and/or a receiving entity 300. Notably, the reference signal configuration information 103 indicates the one or more reference signals 102 and/or the one or more resource sets 101 for transmitting or receiving the one or more reference signals 102.

For instance, the configuration entity 100 may comprise a processor, a memory and a transceiver. The memory may be configured to store executable program codes executed by the processor. The transceiver may be configured to communicate with other devices in the same network. For instance, the transceiver may be configured to transmit reference signal configuration information 103 to a transmitting entity 200 and/or a receiving entity 300. The processor may be configured to execute the operations or method steps described in the following.

Notably, typical wireless communication systems may include radio access networks (RANs), core networks (CNs), and user equipment (UE). RAN is a major component of a wireless telecommunications system that connects individual UE to other parts of a network through a radio link. Sensing transmission and reception may be conducted by RAN or UE, while the receiving entity may perform the measurements based on received signals. The measurements may be analyzed and the velocity /Doppler of the dedicated target may be estimated/computed. The transmission, reception, measurement, and sensing parameter estimation may be performed by different network entities located in RAN or CN, or at the UE. The exemplary information of interest for sensing (or in other words: localization, positioning, or ranging) are object presence, position, distance/range, direction, motion, shape, velocity/speed, etc. In this application, the terms localization, positioning, and sensing may be used interchangeably. One exemplary scenario is depicted in FIG. 2, in which RAN 1 node transmits a downlink sensing reference signal to the target (e.g., car), and the sensing signal is received by another RAN node (RAN 2). Based on received radio frequency signals at RAN 2, target parameters (position, velocity, etc) could be estimated, either at RAN nodes, CN, or some UE. In this application, the terms target and object may be used interchangeably.

The configuration entity 100 proposed in this disclosure may be implemented in the CN node, or RAN node, or a user.

Embodiments of the disclosure propose the reference signal design mechanism for cross-multiple time units, including reference signal pattern and sequence span over multiple slots, subframes, or frames. In this disclosure, one time unit may be one of the following: one slot, one sub-frame, or one frame. It should be noted that in the following description, the idea of this disclosure may be addressed in terms of multiple slots for simplicity. However, this disclosure also applies to multiple subframes or frames. The main target of this disclosure is to design the reference signals for Doppler or micro-Doppler estimation, thus the consequent reference signal is named as Doppler reference signal (DRS) in this application.

Notably, the Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. In telecommunications, this is often observed with radio waves or sound waves. For instance, if a source emitting a signal moves towards an observer, the frequency appears higher; if it moves away, the frequency appears lower. Typically, Doppler estimation involves measuring the change in frequency of a wave (like radio or sound) to understand the relative motion between a transmitter and a receiver (which affects signal quality and strength). The frequency shift between the wave sent out and the one received back indicates how fast the object is moving towards or away from the source of the wave. This frequency shift is directly proportional to the velocity of the object, enabling accurate velocity estimation.

Micro-Doppler refers to modulations in the Doppler frequency shift caused by the more intricate or smaller-scale movements of a target or elements of a target. For example, in addition to the primary motion of a vehicle, the rotating wheels can introduce additional variations in the Doppler shift, which are termed as micro-Doppler effects. These micro-Doppler signatures allow for the estimation of velocities of these smaller movements, providing a more detailed understanding of the object's overall motion.

In both cases, the underlying principle is the Doppler effect, where the relative motion between the wave source (like a radar) and the target object causes a shift in the frequency of the waves, which is then used to estimate the velocity of the object or its components. It may be understood that the Doppler or micro-Doppler estimation are fundamentally about analyzing velocity.

It may be worth mentioning that DRS does not have to be a dedicated reference signal for Doppler/micro-Doppler estimation, it may be based on or extended from any current reference signals in the wireless systems, such as PRS, PTRS, DMRS, CSI- RS, synchronization signal/PBCH block (SSB). Consequently, reference signals for Doppler/Micro-Doppler estimation could have a standalone name such as DRS or have no specific name, e.g., under the extension of PRS, PTRS, or other sensing/communication reference signal. In this application, the term DRS may be used for simplicity, but also covers the second case.

DRS configuration is provided by the DRS configuration unit, e.g., the configuration entity 100 as shown in FIG. 1, to the DRS transmitting unit and receiving unit. Sometimes the DRS configuration unit is the same entity as the transmitting unit, thus this part of the DRS configuration signaling falls back to the internal decision of the transmitting unit. Based on the DRS configuration, DRS is transmitted from the transmitting unit to the receiving unit. FIG. 3 shows general signaling procedures for DRS configuration and transmission according to an embodiment of this disclosure. The three units that are shown in FIG. 3 may be any radio nodes inside wireless radio networks. It should be noted that some necessary signaling in between, e.g., requesting DRS resource grants and acknowledgments, are omitted here.

Embodiments of this disclosure mainly contain three parts:

1. DRS configuration which contains resource mapping design and indication: how to indicate the allocated physical resources specifically in the time domain and frequency domain for reference signals. In particular, introduce new parameters in the mapping function:

• Associated number of slots: represents how many slots in the DRS resource are associated with making sensing (e.g., Doppler-based) measurement or sensing parameter estimation.

• Associated index of slots: the indices of slots that are associated in the DRS resource to make sensing (e.g., Doppler-based) measurement or sensing parameter estimation.

• Bundled number of slots: represents how many slots are bundled to span one reference signal sequence to make sensing (e.g., Doppler-based) measurement or sensing parameter estimation.

• Bundled slot number/index: the indices of the slots that are bundled to span one reference signal sequence to make sensing (e.g., Doppler-based) measurement or sensing parameter estimation, which formulated a bundled slot set.

• For the bundled DRS slots, power may be scaled to match the transmit power constraint over multiple slots or multiple DRS symbols inside bundled DRS slots by scaling factor Beta_scale_DRS.

• Indicator of spatial filters/beamforming vector or indicator of using the same spatial filters (or beamforming vectors) for the bundled or associated slots.

2. DRS configuration which contains sequence generation mechanism for DRS. In particular, the sequence generation formula needs to be revised to enable the sequence spanning over bundling slot/sub-frames/frames defined in the first part.

3. Configuration of reference signal resource pattern and sequence (probably for Doppler/Micro-Doppler estimation) to the UE, which contains:

• UE procedure for receiving DL-DRS, including UE capability indication and configuration parameters (e.g., in RRC protocol).

• UE procedure to transmit UL-DRS, including resource request and grant.

• UE procedure to transmit SL-DRS, including resource request and grant.

It may be understood that the multiple time units in one resource 1011 as shown in FIG. 1 are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence. According to an embodiment of this disclosure, the configuration entity 100 is further configured to configure for each resource 1011 one or more of the following parameters: an indication of the associated time unit set; an indication of one or more bundled time unit sets in the associated time unit set; a first symbol in a time unit inside the associated or bundled time unit set; a quantity of symbols in a time unit inside the associated or bundled time unit set; and a time unit offset with respect to a first time unit of a resource set. According to an embodiment of this disclosure, the reference signal configuration information 103 may comprise resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource 1011; indices of the associated time units in one resource 1011 a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

FIG. 4 shows an example of resource mapping indication of DRS according to an embodiment of this disclosure. In this example, DRSs are allocated between the 1st slot and M slots. Associated slots indicate which slots contain DRSs for Doppler-based sensing measurement. For example, if all M slots contain DRS apart from the 2nd slot, then the number of associating slots is M-l. Suppose one DRS sequence spans several slots, these slots formulate the bundling slots. For example, if slots 1,3,4 out of M slots in FIG. 4 have been bundled for one DRS sequence, the bundled number of slots is 3, and the index of the bundled slot is [1 , 3, 4], which forms a bundled slot set. In such a case, the power of the DRS resource element (resource element is the smallest resource unit, which occupies a single sub-carrier and symbol) needs to be scaled based on the number of bundled slots and the number of DRS symbols inside bundled slot sets. Furthermore, spatial filters of the DRSs may need to be indicated, or whether the same spatial filters of DRSs are used needs to be indicated.

FIG. 5 shows an exemplary illustration of the DRS resource set and resources according to an embodiment of the disclosure. A single network node or a single UE may have one or more DRS resource sets, i.e., the one or more resource sets 101 shown in FIG. 1, while one DRS resource set 101 may contain one or more DRS resources 1011 (e.g., for different spatial filters, or different targets), in which different DRS resources may use orthogonal resource either in frequency or time or space or code domain.

Resource allocation properties of DRS include:

• Time domain property: a single DRS resource contains multiple resource elements spanning more than one time unit (e.g., slots/sub-frames/frames, the time units can be consecutive or non-consecutive, as shown in FIG. 6.)

• Spatial domain property: a single DRS resource is associated with the same spatial filter (beam).

• Code domain property: different DRS resources are associated/scrambled with orthogonal code sequences.

• Frequency property: If one DRS resource contains more than one resource element, then these resource elements are preferably allocated in the same set of subcarrier(s) (can be consecutive or non-consecutive subcarriers, as shown in FIG. 6.)

Optionally, the one or more resources 1011 comprise a first resource and a second resource, wherein the first resource is associated with a first sequence, and the second resource is associated with a second sequence.

FIG. 6 shows an example of the time-frequency allocation of a DRS resource according to an embodiment of the disclosure. In this example, the DRS is allocated in several consecutive slots from the 1 st slot to the Mth slot, and occupies subcarriers scl and sc 3.

FIG. 7 shows an example of associated and bundled slots according to an embodiment of the disclosure. In this example, solid and dashed boxes represent the symbols with different sequences, respectively. As discussed in the previous embodiments, one or more of the following parameters are configured for DRS resources:

• Associated slot set indication: o DRS resource is spanning in the slots given in the associated slot set. F or example, slot set = [1, 2, . . . M] for the example shown in FIG. 6. o First slot and last slot, or first slot and slot number. In the second case, it is assumed that DRS is allocated in several consecutive slots. Given the example in FIG. 6, first slot: 1, last slot: M, or slot number M (may be any number smaller than M if it satisfies Doppler estimation requirements).

• Bundling slot set indication: o One sequence is spanning in the slot given in the bundled slot set. For example, the bundling slot sets may be [1,2], ....[M-l, M] as shown in FIG. 7, since the DRS symbols in each bundled slot set formulate one DRS sequence. o First slot, last slot, or slot index in the bundled slot set.

• The first symbol in a slot inside an associated/bundled slot set.

• Number of symbols in a slot inside an associated/bundled slot set.

• Slot offset to the first slot of a DL PRS resource set (if the resource is separated in slot domain).

It may be worth mentioning that in the above example, the bundled slot sets have the same size. However, in other embodiments of this disclosure, the bundled time unit set can have different sizes, depending on the lengths of the DRS sequences. Optionally, the bundled time unit set is the associated time unit set. In this example, one DRS sequence is spanning in the whole associated time unit set.

FIG. 8 shows a DRS multiplexing example according to an embodiment of this disclosure. According to this embodiment, multiple DRSs or DRS resources can be multiplexed, e.g., associated with different spatial filters or sensing to different sensing receivers, illuminating different sensing targets, or illuminating the same sensing target from different spatial/time/frequency resources. In the following, DRS and DRS resources are used interchangeably. Different multiplexing options are illustrated in FIG. 8.

• Optl : DRS resources are multiplexed in the frequency domain.

• Opt2: DRS resources are multiplexed in frequency and time domain (e.g., staggered as shown in the figure).

• Opt3.1: DRS resources are multiplexed in the code domain, e.g., with different code sequences which sequence offsets or parameters like a cyclic shift.

• Opt3.2: DRS resources are multiplexed by associating different spatial filters, e.g., multiple sensing receivers are assigned the same time-frequency locations but different code sequences, e.g., sequence offsets or parameters like cyclic shift.

• Opt4: DRS resources are multiplexed in time domain mapping to different slots/sub-frame/frames.

According to another embodiment of this disclosure, the base sequence format of DRS may reuse any base sequence with good time-frequency localization, e.g., pseudo-random sequence in 5G-NR, such as M-sequence, Golay sequences in 802. Had, Polyphase sequence, Walsh-Hadamard sequence, Zadoff-Chu sequence, low-PAPR (Peak-to-A verage Power Ratio) sequence type 1 and type 2.

According to an embodiment of this disclosure, the reference signal configuration information 103 further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence.

For DRS sequence generation, the sequence generator function may need to be parameterized by settings of bundled slot sets. In particular, one or more of the following parameters need to be considered: the length of the sequence (which is related to the number of DRS resource elements in the bundling slots, and the symbol index among all DRS symbols in bundled slots), the power of the sequence, the spatial filters of the sequence.

One example of a sequence generator of DRS is illustrated as follows:

Stepl: the sequence is generated according to the following equation: where m =0: 1 : DRS symbol numbers in bundling slot sets, c(.) is the base sequence, e.g., pseudo-random sequence generator. c(.) may be the function of one of the following parameters: random sequence ID, number of DRS symbols in bundling slots, symbol index among all DRS symbols in bundling slots, slot number inside the radio frame, symbol number index within the slot, etc.

Step 2: When mapping the sequence to the allocated resource elements for DRS, the sequence needs to be multiplied with the amplitude/power scaling factor Beta_scale_DRS.

Step 3: If the spatial filters (beams) are applicable to DRS, all DRS symbols spanning over multiple slots embedding a single DRS sequence may be associated with the same spatial filters. For example, the solid-filled resource elements (symbol and subcarrier allocation unit) are applied with the same spatial filter A, while the grid-filled resource elements are applied with another same spatial filter B. Spatial filters of different sets of resource elements in bundling slots (e.g., A and B) may be different but may also be the same. If the same, the indicator of using the same spatial filters (or beamforming vectors) for the bundled or associated slots (introduced in the previous embodiments) is used.

Optionally, the associated time unit set may comprise a first bundled time unit set spanning a first DRS sequence and a second bundled time unit set spanning a second DRS sequence, wherein the first bundled time unit set is associated with a first spatial filter, and the second bundled time unit set is associated with a second spatial filter.

As previously discussed, the current existing reference signals in communication systems are mainly limited to one slot since channel parameter estimation is assumed to be the same within the current slot length. In order to extend the existing reference signals for DRS usage, several modifications may need to be performed:

• If the current existing reference signal needs to be transmitted with data, then it may need to decouple the transmission of reference signal and data, since now the function of reference signals is not limited to estimating the channel for data transmission, but based on sensing or positioning requirements.

• For sequence generation, 1 ) the sequence lengths need to be enlengthened to be the number of all RS symbols in bundling slots (not in the current slot); 2) apart from current parameters considered in the base sequence, the base sequence needs to be parameterized with the symbol index among all DRS symbols in bundling slots, number of DRS symbols in bundling slots. In addition, the random sequence ID may be different from that of current reference signal settings. • Mapping to physical resource: current amplitude/power scaling of existing reference signals is performed to the symbols inside the slot. When extending for DRS usage, amplitude/power scaling of existing reference signals may be performed over the symbols inside the bundling slots.

• Application of spatial filters (beams): currently, the same spatial filter of existing reference signals is performed in the symbols inside the slot. When extending for DRS usage, the same spatial filter of existing reference signals may be performed over the symbols inside the bundling slots.

According to another embodiment of this disclosure, different from the current wireless system in which the same spatial filters are applied within the slot, DRS resource elements spreading over different slots (within the bundled slot set) need to be associated with the same spatial filter. Such spatial filters may be indicated. As mentioned in previous embodiments, spatial filters of different sets of resource elements in bundling slots may be different but may also be the same. If the same, the indicator of using the same spatial filters (or beamforming vectors) for the bundled or associated slot sets is used.

The current amplitude or power scaling of existing reference signals is applied to the symbols inside the slot. When extending for DRS usage, amplitude/power scaling of existing reference signals may be performed over the symbols inside the bundling slots inside one bundled slot set.

FIG. 9 shows a signaling procedure for downlink DRS configuration and transmission according to an embodiment of this disclosure. In this embodiment, the RAN node is the configuration entity 100, and it is also the transmitting entity 200. The UE is the receiving entity 300. In particular, this downlink DRS configuration and transmission procedure is for UE to receive downlink DRS.

In the first step: UE has been configured to receive cross-slots DRS as configured by parameters such as DRS resource sets, DRS resource, associated slot set, bundling slot set, and other DRS configuration parameters.

In the second step (optional): UE indicates that receiving DRS cross-slots is being supported at the UE (e.g., in RRC signaling), or UE indicates that it can only support a certain number of cross-slots to receive DRS.

In the third step, the RAN node transmits DRS for UE measurements which is performed in Step 4.

Notably, in this example, the configuration entity 100 is implemented in the RAN node. The configuration entity 100 is further configured to receive an indication from the transmitting entity 200 or the receiving entity 300, wherein the indication indicates that the transmitting entity 200 or the receiving entity 300 is able to support the one or more reference signals 102, and the transmitting entity 200 or the receiving entity 300 is a user.

FIG. 10(a) and FIG. 10(b) illustrates two options of the uplink DRS configuration and transmission procedures for UE to transmit downlink DRS.

Specifically, in the embodiment shown in FIG. 10(a), the RAN node is the configuration entity 100, and it is also the receiving entity 300. The UE is the transmitting entity 200.

In the first step: UE has been configured to transmit cross-slots DRS as configured by parameters such as DRS resource sets, DRS resource, associated slot set, bundled slot set, and other DRS configuration parameters, as well as resource allocation grant. In the second step (optional): UE indicates that transmitting DRS cross-slots is being supported at the UE (e.g., in RRC signaling), or UE indicates that it can only support a certain number of cross-slots for transmitting DRS.

In the third step, UE transmits DRS to the RAN node for RAN’s measurements in Step 4.

In the embodiment shown in FIG. 10(b), the DRS configuration unit is the configuration entity 100, the UE is the transmitting entity 200, and the RAN node is the receiving entity 300.

In the first step: UE receives DRS configuration from the DRS configuration unit which resides not inside the RAN node (e.g., core network), in which cross-slots DRS are configured by parameters such as DRS resource sets, DRS resource, associated slot set, bundling slot set, and other DRS configuration parameters.

In the second step, UE transmits to the RAN node requesting a DRS resource grant.

In the third step, UE has been assigned from the RAN node with a resource allocation grant for the DRS transmission ion grant.

In the fourth step, UE transmits DRS to the RAN node for RAN’s measurements in Step 5.

In this example, the configuration entity 100 is further configured to obtain measurements using the one or more reference signals 102 based on the reference signal configuration information 103.

FIG. 11(a) and FIG. 11(b) illustrates two options of the uplink DRS configuration and transmission procedures for UE to transmit sidelink DRS.

Specifically, in the embodiment shown in FIG. 11(a), the RAN node is the configuration entity 100, UE A is the transmitting entity 200, and UE B is the receiving entity 300.

In the first step: UE A has been configured to transmit cross-slots DRS as configured by parameters such as DRS resource sets, DRS resource, associated slot set, bundling slot set, and other DRS configuration parameters, as well as resource allocation grant.

In the second step (optional): UE A indicates that transmitting DRS cross-slots is being supported at the UE A (e.g., in RRC signaling), or UE A indicates that it can only support a certain number of cross-slots for transmitting DRS.

In the third step, UE A is transmitting DRS to UE B for UE B’s measurements in Step 4.

In the embodiment shown in FIG. 11(b), the DRS configuration unit is the configuration entity 100, UE A is the transmitting entity 200, and UE B is the receiving entity 300.

In the first step: UE A receives DRS configuration from the DRS configuration unit which resides not inside the RAN node (e.g., core network), in which cross-slots DRS are configured by parameters such as DRS resource sets, DRS resource, associated slot set, bundling slot set, and other DRS configuration parameters.

In the second step, UE A transmits to the RAN node requesting a DRS resource grant. In the third step, UE A has been assigned from the RAN node with a resource allocation grant for the DRS transmission ion grant.

In the fourth step, UE A is transmitting DRS to UE B for another UE B’s measurements in Step 5.

It should be noted that for embodiments shown in FIG. 9 to FIG. 11 , phase continuality needs to be guaranteed over the spanned slots containing the same DRS bundled slot set (maybe up to RAN node/UE’s implementation).

FIG. 12 shows a transmitting entity 200 for transmitting one or more reference signals according to an embodiment of the disclosure. The transmitting entity 200 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the transmitting entity 200 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors.

In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the transmitting entity 200 to perform, conduct, or initiate the operations or methods described herein.

In particular, the transmitting entity 200 is configured to obtain reference signal configuration information 103 from a configuration entity 100. The configuration entity 100 may be the configuration entity shown in FIG. 1. The reference signal configuration information 103 indicates the one or more reference signals 102 and/or one or more resource sets 101 for transmitting the one or more reference signals 102. Notably, the one or more reference signals 102 are for Doppler or microDoppler estimation. Each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. The transmitting entity 200 is further configured to transmit the one or more reference signals 102 to a receiving entity 300 based on the reference signal configuration information 103.

For instance, the transmitting entity 200 may comprise a processor, a memory, and a transceiver. The memory may be configured to store executable program codes executed by the processor. The transceiver may be configured to communicate with other devices in the same network. For instance, the transceiver may be configured to transmit the one or more reference signals 102 to a receiving entity 300. The processor may be configured to execute the operations or method steps described in the following.

Similar to the previous embodiments, the multiple time units in one resource 1011 are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the reference signal configuration information 103 comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource 1011; indices of the associated time units in one resource 1011 a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units. According to an embodiment of this disclosure, the reference signal configuration information 103 further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence.

Accordingly, the transmitting entity 200 is further configured to generate the reference signal sequence based on the reference signal generation information.

Optionally, the transmitting entity 200 is implemented in an RAN node, or a user.

When the transmitting entity 200 is implemented in the user, the transmitting entity 200 is further configured to, before transmitting the one or more reference signals 102, send a request for a resource grant to an RAN node (in a particular example, the RAN node is the receiving entity 300, or the configuration entity 100), and receive the resource grant from the access network node. Further details of this embodiment align with those previously elaborated in relation to FIG. 10 and FIG. 11.

According to an embodiment of this disclosure, the transmitting entity 200 is further configured to send an indication to the configuration entity 100, wherein the indication indicates that the transmitting entity 200 is able to support the one or more reference signals 102.

FIG. 13 shows a receiving entity 300 for receiving one or more reference signals according to an embodiment of the disclosure. The receiving entity 300 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the receiving entity 300 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors.

In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the receiving entity 300 to perform, conduct, or initiate the operations or methods described herein.

In particular, the receiving entity 300 is configured to receive one or more reference signals 102 from a transmitting entity 200 based on one or more resource sets 101. The transmitting entity 200 may be the transmitting entity shown in FIG. 12. Notably, the one or more reference signals 102 are for Doppler or micro-Doppler estimation. Each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. The receiving entity 300 is further configured to obtain measurements using the one or more reference signals 102.

For instance, the receiving entity 300 may comprise a processor, a memory and a transceiver. The memory may be configured to store executable program codes executed by the processor. The transceiver may be configured to communicate with other devices in the same network. For instance, the transceiver may be configured to receive the one or more reference signals 102 from the transmitting entity 200. The processor may be configured to execute the operations or method steps described in the following. According to an embodiment of this disclosure, before receiving the one or more reference signals 102, the receiving entity 300 may be configured to obtain reference signal configuration information 103 from a configuration entity 100, wherein the reference signal configuration information 103 indicates the one or more reference signals 102 and/or one or more resource sets 101 for receiving the one or more reference signals 102. The configuration entity 100 may be the configuration entity shown in FIG. 1.

Optionally, the receiving entity 300 may be implemented in an RAN node, or a user.

When the receiving entity 300 is implemented in the user, the receiving entity 300 is further configured to send an indication to the configuration entity 100, wherein the indication indicates that the receiving entity 300 is able to support the one or more reference signals 102. Further details of this embodiment align with those previously elaborated in relation to FIG. 9.

FIG. 14 shows a method 1400 according to an embodiment of the present disclosure. In particular, the method 1400 is performed by a configuration entity 100 as shown in FIG. 1. The method 1400 comprises a step 1401 of determining one or more resource sets 101 for one or more reference signals 102, wherein the one or more reference signals 102 are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. The method 1400 also comprises a step 1402 of providing reference signal configuration information 103 to a transmitting entity 200 and/or a receiving entity 300, wherein the reference signal configuration information 103 indicates the one or more reference signals 102 and/or the one or more resource sets 101 for transmitting or receiving the one or more reference signals 102.

FIG. 15 shows a method 1500 according to an embodiment of the present disclosure. In particular, the method 1500 is performed by a transmitting entity 200 as shown in FIG. 12. The method 1500 comprises a step 1501 of obtaining reference signal configuration information 103 from a configuration entity 100, wherein the reference signal configuration information 103 indicates the one or more reference signals 102 and/or one or more resource sets 101 for transmitting the one or more reference signals 102, wherein the one or more reference signals 102 are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. Possibly, the configuration entity 100 is the configuration entity 100 shown in FIG. 1.

The method 1500 further comprises a step 1502 of transmitting the one or more reference signals 102 to a receiving entity 300 based on the reference signal configuration information 103. Possibly, the receiving entity 300 is the receiving entity 300 shown in FIG. 13.

FIG. 16 shows a method 1600 according to an embodiment of the present disclosure. In particular, the method 1600 is performed by a receiving entity 300 as shown in FIG. 13. The method 1600 comprises a step 1601 of receiving one or more reference signals 102 from a transmitting entity 200 based on one or more resource sets 101, wherein the one or more reference signals 102 are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets 101 comprises one or more resources 1011 each comprising multiple resource elements spanning over multiple time units. Possibly, the transmitting entity 200 is the transmitting entity 200 shown in FIG. 12.

The method 1600 further comprises a step 1602 of obtaining measurements using the one or more reference signals 102.

To summarize, this disclosure proposes a cross-slot/subframe/frame reference signal design for Doppler-relevant estimation. It allows to design of reference signals according to sensing needs and leads to more efficient resource usage than reusing state- of-the-art RS. Embodiments of this disclosure provide an indication of cross-slot reference signal resource allocation, including reference signal multiplexing, thereby allowing more flexible reference signal resource allocation and multiplexing. Embodiments of this disclosure also provide an indication of DRS sequence generation, which allows for more flexible RS resource allocation and more effective sequence design for RS, enabling more accurate Doppler-based estimation. This disclosure also enables configurations for reference signal patterns and sequences for Doppler/Micro-Doppler estimation to the UE. The enhanced design allows the gNB/UE to achieve high resolution and high accuracy in Doppler and Micro-Doppler estimations. This is made possible by permitting the use of longer sequences compared to the current state-of-the-art reference signals. This advancement in sequence length significantly improves the precision of velocity and movement measurements, essential in modem communication systems. The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

Claims

1. A configuration entity (100) for reference signal configuration, configured to: determine one or more resource sets (101) for one or more reference signals (102), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets (101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and provide reference signal configuration information (103) to a transmitting entity (200) and/or a receiving entity (300), wherein the reference signal configuration information (103) indicates the one or more reference signals (102) and/or the one or more resource sets (101) for transmitting or receiving the one or more reference signals (102).

2. The configuration entity (100) according to claim 2, wherein the multiple time units in one resource (1011) are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the configuration entity (100) is further configured to: configure for each resource (1011) one or more of the following parameters: an indication of the associated time unit set; an indication of one or more bundled time unit sets in the associated time unit set; a first symbol in a time unit inside the associated or bundled time unit set; a quantity of symbols in a time unit inside the associated or bundled time unit set; and a time unit offset with respect to a first time unit of a resource set.

3. The configuration entity (100) according to claim 2, wherein the reference signal configuration information (103) comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource (1011); indices of the associated time units in one resource (1011); a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

4. The configuration entity (100) according to one of the claims 1 to 3, wherein one time unit is one of the following: one slot, one sub-frame, or one frame.

5. The configuration entity (100) according to one of the claims 1 to 4, wherein the multiple time units in one resource (1011) comprise consecutive or non-consecutive time units.

6. The configuration entity (100) according to one of the claims 1 to 5, wherein each resource is associated with a particular spatial filter.

7. The configuration entity (100) according to one of the claims 1 to 6, wherein the one or more resources (1011) comprise a first resource and a second resource, wherein the first resource is associated with a first sequence, and the second resource is associated with a second sequence.

8. The configuration entity (100) according to claim 7, wherein the first resource and the second resource are multiplexed in at least one of the following domains: time domain; frequency domain; time and frequency domain; code domain; spatial filter domain.

9. The configuration entity (100) according to claim 2 or 3, or one of the claims 4 to 8 when depending on claim 2, wherein the reference signal configuration information (103) further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence.

10. The configuration entity (100) according to claim 9, wherein the associated time unit set comprises a first bundled time unit set spanning a first sequence and a second bundled time unit set spanning a second sequence, wherein the first bundled time unit set is associated with a first spatial filter, and the second bundled time unit set is associated with a second spatial filter.

11. The configuration entity (100) according to one of the claims 1 to 10, wherein the one or more reference signals (102) comprise one or more of the following: a dedicated reference signal for Doppler/micro-Doppler estimation, a phase tracking reference signal, a positioning reference signal, a demodulation reference signal, a channel state information reference signal, a synchronization signal, a broadcast signal.

12. The configuration entity (100) according to one of the claims 1 to 11, wherein the configuration entity (100) is implemented in a core network node, or an access network node, or a user.

13. The configuration entity (100) according to claim 12, when the configuration entity (100) is implemented in the access network node, the configuration entity (100) is further configured to: receive an indication from the transmitting entity (200) or the receiving entity (300), wherein the indication indicates that the transmitting entity (200) or the receiving entity (300) is able to support the one or more reference signals (102), and the transmitting entity (200) or the receiving entity (300) is a user.

14. The configuration entity (100) according to claim 12 or 13, configured to: obtain measurements using the one or more reference signals (102) based on the reference signal configuration information (103).

15. A transmitting entity (200) for transmitting one or more reference signals (102), configured to: obtain reference signal configuration information (103) from a configuration entity (100), wherein the reference signal configuration information (103) indicates the one or more reference signals (102) and/or one or more resource sets (101) for transmitting the one or more reference signals (102), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets (101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and transmit the one or more reference signals (102) to a receiving entity (300) based on the reference signal configuration information (103).

16. The transmitting entity (200) according to claim 15, wherein the multiple time units in one resource (1011) are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the reference signal configuration information (103) comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource (1011); indices of the associated time units in one resource (1011); a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

17. The transmitting entity (200) according to claim 15 or 16, wherein the reference signal configuration information (103) further comprises reference signal generation information, wherein the reference signal generation information indicates a sequence generation mechanism of a reference signal sequence, wherein the sequence generation mechanism is based on one or more of the following parameters: a quantity of resource elements of each bundled time unit set; symbol indices of all symbols in the bundled time unit set; a power scaling indicator of the reference signal sequence; a spatial filter associated with the reference signal sequence.

18. The transmitting entity (200) according to claim 17, configured to: generate the reference signal sequence based on the reference signal generation information.

19. The transmitting entity (200) according to one of the claims 15 to 18, wherein the transmitting entity (200) is implemented in an access network node, or a user.

20. The transmitting entity (200) according to claim 19, when the transmitting entity (200) is implemented in the user, the transmitting entity (200) is further configured to: before transmitting the one or more reference signals (102), send a request for a resource grant to an access network node, and receive the resource grant from the access network node.

21. The transmitting entity (200) according to claim 20, wherein the access network node is the receiving entity (300), or the configuration entity (100).

22. The transmitting entity (200) according to claim 20 or 21, configured to: send an indication to the configuration entity (100), wherein the indication indicates that the transmitting entity (200) is able to support the one or more reference signals (102).

23. A receiving entity (300) for receiving one or more reference signals (102), configured to: receive one or more reference signals (102) from a transmitting entity (200) based on one or more resource sets (101), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets (101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and obtain measurements using the one or more reference signals (102).

24. The receiving entity (300) according to claim 23, before receiving the one or more reference signals (102), configured to: obtain reference signal configuration information (103) from a configuration entity (100), wherein the reference signal configuration information (103) indicates the one or more reference signals (102) and/or one or more resource sets (101) for receiving the one or more reference signals (102).

25. The receiving entity (300) according to claim 24, wherein the multiple time units in one resource (1011) are associated as an associated time unit set to be used for sensing measurement or sensing parameter estimation, and one or more time units of the multiple time units are bundled as a bundled time unit set for spanning one reference signal sequence, wherein the reference signal configuration information (103) comprises resource mapping information, wherein the resource mapping information indicates one or more of the following parameters: a quantity of associated time units in one resource (1011); indices of the associated time units in one resource (1011); a quantity of bundled time units in each bundled time unit set; indices of the bundled time units; a power scaling factor for the one or more bundled time unit sets; a spatial filter indicator for indicating a common spatial filter to be used by the associated or bundled time units.

26. The receiving entity (300) according to one of the claims 23 to 25, wherein the receiving entity (300) is implemented in an access network node, or a user.

27. The receiving entity (300) according to claim 26, when the receiving entity (300) is implemented in the user, the receiving entity (300) is further configured to: send an indication to the configuration entity (100), wherein the indication indicates that the receiving entity (300) is able to support the one or more reference signals (102).

28. A method (1400) for reference signal configuration, comprises: determining (1401) one or more resource sets (101) for one or more reference signals (102), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets

(101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and providing (1402) reference signal configuration information (103) to a transmitting entity (200) and/or a receiving entity (300), wherein the reference signal configuration information (103) indicates the one or more reference signals

(102) and/or the one or more resource sets (101) for transmitting or receiving the one or more reference signals (102).

29. A method (1500) for transmitting one or more reference signals (102), comprises: obtaining (1501) reference signal configuration information (103) from a configuration entity (100), wherein the reference signal configuration information (103) indicates the one or more reference signals (102) and/or one or more resource sets ( 101 ) for transmitting the one or more reference signals (102), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets (101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and transmitting (1502) the one or more reference signals (102) to a receiving entity (300) based on the reference signal configuration information (103). 30. A method (1600) for receiving one or more reference signals (102), comprises: receiving (1601) one or more reference signals (102) from a transmitting entity (200) based on one or more resource sets (101), wherein the one or more reference signals (102) are for Doppler or micro-Doppler estimation, wherein each of the one or more resource sets (101) comprises one or more resources (1011) each comprising multiple resource elements spanning over multiple time units; and obtaining (1602) measurements using the one or more reference signals (102).

31. A computer program product comprising a program code for carrying out, when implemented on a processor, the method (1400, 1500, 1600) according to one of the claims 28 to 30.