Enhancement of reference signal

Abstract

Exemplary embodiments of the present disclosure relate to enhancement of reference signal. In an aspect, the terminal device receives, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input- multi-output (UL MU-MIMO) scheduling. The terminal device obtains information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration type. The terminal device further determines, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

Description

ENHANCEMENT OF REFERENCE SIGNALCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from, and the benefit of, EP Patent Application No. 25165586.6, filed March 24, 2025, the contents of which are hereby incorporated by reference in their entirety.FIELD

[0002] Exemplary embodiments of the present disclosure generally relate to the field of communications, and in particular, to devices, apparatuses, methods and a computer-readable storage medium for enhancing reference signal.BACKGROUND

[0003] A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network.

[0004] Such communication networks operate in according with standards such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute).SUMMARY

[0005] In general, exemplary embodiments of the present disclosure provide a solution for enhanced reference signal.

[0006] In a first aspect, there is provided a terminal device. The terminal device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to: receive, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and determine, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0007] In a second aspect, there is provided a network device. The network device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to: transmit, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and receive, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS)configuration type among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0008] In a third aspect, there is provided a method performed by a terminal device. The method comprises: receiving, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and determining, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0009] In a fourth aspect, there is provided a method performed by a network device. The method comprises: transmitting, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and receiving, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS) configuration type among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0010] In a fifth aspect, there is provided an apparatus. The apparatus comprises: means for receiving, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and means for determining, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) arenon-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0011] In a sixth aspect, there is provided an apparatus. The apparatus comprises: means for transmitting, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and means for receiving, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS) configuration type among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0012] In a seventh aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any of third to fourth aspects.

[0013] In an eighth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any of third to fourth aspects.

[0014] In a ninth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and determining circuitry configured to determine, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0015] In a tenth aspect, there is provided a network device. The network device comprises: transmitting circuitry configured to transmit, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and receiving circuitry configured to receive, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS) configuration type among at least two DMRS configuration types, and the at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a secondnumber of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0016] In an eleventh aspect, there is provided a terminal device. The terminal device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to: receive, from a network device, at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission; and determine, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0017] In a twelfth aspect, there is provided a network device. The network device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to: transmit, to a terminal device, an indication indicative of an initially indicated DMRS configuration type; transmit, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device; and receive, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0018] In a thirteenth aspect, there is provided a method performed by a terminal device. The method comprises: receiving, from a network device, at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission; and determining, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0019] In a fourteenth aspect, there is provided a method performed by a network device. The method comprises: transmitting, to a terminal device, an indication indicative of an initially indicated DMRS configuration type; transmitting, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device; and receiving, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0020] In a fifteenth aspect, there is provided an apparatus. The apparatus comprises: means for receiving, from a network device, at least one parameterthat is to be used to determine a DMRS configurationtype for uplink transmission; and means for determining, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0021] In a sixteenth aspect, there is provided an apparatus. The apparatus comprises: means for transmitting, to a terminal device, an indication indicative of an initially indicated DMRS configuration type; means for transmitting, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device; and means for receiving, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0022] In a seventeenth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any of thirteen to fourteen aspects.

[0023] In an eighteenth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any of thirteen to fourteen aspects.

[0024] In a nineteenth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission; and determining circuitry configured to determine, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0025] In a twentieth aspect, there is provided a network device. The network device comprises: first transmitting circuitry configured to transmit, to a terminal device, an indication indicative of an initially indicated DMRS configuration type; second transmitting circuitry configured to transit, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device; and receiving circuitry configured to receive, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0026] In a twenty-first aspect, there is provided a terminal device. The terminal device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least oneprocessor, cause the terminal device at least to: receive, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multiuser multi-input-multi-output (UL MU-MIMO) scheduling; obtain information about whether at least two coscheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and determine, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0027] In a twenty-second aspect, there is provided a network device. The network device comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to: transmit, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multiuser multi-input-multi-output (UL MU-MIMO) scheduling; transmit, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and receive, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0028] In a twenty-third aspect, there is provided a method performed by a terminal device. The method comprises: receiving, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; obtaining information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and determining, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0029] I n a twenty-fourth aspect, there is provided a method performed by a network device. The method comprises: transmitting, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; transmitting, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and receiving, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0030] In a twenty-fifth aspect, there is provided an apparatus. The apparatus comprises: means for receiving, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; means for obtaining information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and means for determining, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0031] In a twenty-sixth aspect, there is provided an apparatus. The apparatus comprises: means for transmitting, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; means for transmitting, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and means for receiving, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0032] In a twenty-seventh aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any of twenty-third to twenty-fourth aspects.

[0033] In an eighth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any of twenty-third to twenty-fourth aspects.

[0034] In a twenty-ninth aspect, there is provided a terminal device. The terminal device comprises: receiving circuitry configured to receive, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; obtaining circuitry configured to obtain information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and determining circuitry configured to determine, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0035] In a thirtieth aspect, there is provided a network device. The network device comprises: first transmitting circuitry configured to transmit, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; second transmitting circuitry configured to transmit, to the firstterminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and receiving circuitry configured to receive, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0036] It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Some exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0038] Fig. 1 illustrates an example of a network environment in which some exemplary embodiments of the present disclosure may be implemented;

[0039] Fig. 2A illustrates some examples of DMRS configuration type 1 and DMRS configuration type 2 in 5G NR;

[0040] Fig. 2B illustrates cubic metrics for configuration type 1 or 2, or Quadrature Phase Shift Keying (QPSK) data with and without shaping;

[0041] Fig. 3A illustrates an example signaling process in accordance with some embodiments of the present disclosure;

[0042] Fig. 3B illustrates an example of resource element allocation of a DMRS configuration type 3 in accordance with some embodiments of the present disclosure;

[0043] Fig. 3C illustrates cubic metrics for the configuration types 1, 2 and 3 in accordance with some embodiments of the present disclosure;

[0044] Fig. 3D illustrates cubic metrics for the configuration types 1, 2, 3 with FDSS (frequency domain spectral shaping) or filtering by a FIR filter and QPSK data with and without shaping in accordance with some embodiments of the present disclosure;

[0045] Fig. 4A illustrates an exemplary signaling process according to the embodiment of Fig. 3A;

[0046] Fig. 4B illustrates single symbol DMRS example with length 2 OCC in FD and configuration type 3 without TD OCC in accordance with some embodiments of the present disclosure;

[0047] Fig. 4C illustrates double symbol DMRS example with length 2 OCC in FD and in TD and configuration type 3 in accordance with some embodiments of the present disclosure;

[0048] Fig. 5A illustrates an exemplary signaling process according to some embodiments of the present disclosure;

[0049] Fig. 5B illustrates an exemplary signaling process according to the embodiment of Fig. 5A;

[0050] Fig. 6A illustrates an example signaling process in accordance with some embodiments of the present disclosure;

[0051] Fig. 6B illustrates an exemplary signaling process according to the embodiment of Fig. 6A;

[0052] Fig. 6C illustrates some examples for derivatives configuration type Y from configuration type X in accordance with some embodiments of the present disclosure, from the left to the right, first example of DMRS configuration subset type based DMRS configuration type 1, second example DMRS configuration subset type based DMRS configuration type 1, the DMRS configuration type 1, example of DMRS configuration subset types based DMRS configuration type 2, DMRS configuration type 2, example of DMRS configuration subset types based DMRS configuration type 3, and DMRS configuration type 3;

[0053] Fig. 6D illustrates application of FD OCC on the DMRS REs in accordance with the conventional method;

[0054] Fig. 6E illustrates application of FD OCC on the DMRS REs in accordance with some embodiments of the present disclosure;

[0055] Fig. 7A illustrates a flowchart of an example method implemented at a terminal device in accordance with some exemplary embodiments of the present disclosure;

[0056] Fig. 7B illustrates a flowchart of an example method implemented at a network device in accordance with some exemplary embodiments of the present disclosure;

[0057] Fig. 8A illustrates a flowchart of an example method implemented at a terminal device in accordance with some exemplary embodiments of the present disclosure;

[0058] Fig. 8B illustrates a flowchart of an example method implemented at a network device in accordance with some exemplary embodiments of the present disclosure;

[0059] Fig. 9A illustrates a flowchart of an example method implemented at a first terminal device in accordance with some exemplary embodiments of the present disclosure;

[0060] Fig. 9B illustrates a flowchart of an example method implemented at a network device in accordance with some exemplary embodiments of the present disclosure;

[0061] Fig. 10 illustrates a simplified block diagram of a device that is suitable for implementing some exemplary embodiments of the present disclosure; and

[0062] Fig. 11 illustrates a block diagram of an example of a computer-readable medium in accordance with some exemplary embodiments of the present disclosure.

[0063] Throughout the drawings, the same or similar reference numerals represent the same or similar elements.DETAILED DESCRIPTION

[0064] Principles of the present disclosure will now be described with reference to some exemplary embodiments. It is to be understood that these embodiments are described only for the purpose ofillustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein may be implemented in various manners other than the ones described below.

[0065] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0066] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0067] It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of exemplary embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0068] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0069] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0070] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0071] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as the future 6G standard, New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-loT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the fourth generation (4G), 4.5G, 5G, the future sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0072] As used herein, the term “network device” (also referred to as “network node”) refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

[0073] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminaldevice, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehiclemounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (for example, remote surgery), an industrial device and applications (for example, a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0074] 6G may support uplink discrete fourier transform-spread-orthogonal frequency division multiplexing (UL DFT-s-OFDM) for one or more layers (rank>= 1 ) similar to LTE to achieve higher UL transmit power (in some cases) and thus higher coverage for higher data rates.

[0075] LTE supported multi-input-multi-output (MIMO) DFT-s-OFDM, but LTE demodulation reference signal (DMRS) design was different than 5G, and thus DMRS design should be re-considered with DFT-s-OFDM in 6G, in order to maintain the support for important 5G NR MIMO features (single user (SU)-MIMO or multi-user (MU)-MIMO), 6G new features and very large number of ports.

[0076] 6G UE needs to be able to fully exploit its hardware (available antenna ports) regardless of the configured UL waveform (CP-OFDM or DFT-s-OFDM). DFT-s-OFDM supporting for multi-layer could be added in 6G, and UE needs to support larger number of ports & layers at least similar to 5G with CP-OFDM, but while maintaining DFT-s-OFDM peak to average power ratio (PAPR). The power level when transmitting with DFT-s-OFDM could be higher than that of CP-OFDM, since DFT-s-OFDM have lower PAPR and thus higher capability on UE maximum power. PAPR of CP-OFDM or DFT-s-OFDM is peak to average power ratio of the transmit signal generated with CP-OFDM or DFT-s-OFDM waveform. That is to say, DMRS sequence and configuration types should preserve the low PAPR property of DFT-s-OFDM in order to get its higher UL transmit power advantage.

[0077] However, straightforward extension of 5G doesn’t guarantee the low PAPR, e.g., DMRS configuration type 2 / enhanced type 2 (i.e. etype 2) specified in 5G NR to support more ports) leads to high PAPR. There is a need for a method or rule for implicit determination of DMRS configuration type without additional DCI overhead.

[0078] For illustrative purposes, principles and example embodiments of the present disclosure for enhancing reference signal will be described below with reference to Figs. 1-11. However, it is to be noted that these embodiments are given to enable the skilled in the art to understand concepts of the present disclosure and implement the solution as proposed herein, and not intended to limit scope of the present disclosure in any way.

[0079] Fig. 1 illustrates an example of a network environment 100 in which some exemplary embodiments of the present disclosure may be implemented. In the descriptions of the exemplary embodiments of the present disclosure, the network environment 100 may also be referred to as a communication system 100 (for example, a portion of a communication network). For illustrative purposes only, various aspects of exemplary embodiments will be described in the context of one or more terminal devices and network devices that communicate with one another. It should be appreciated, however, that the description herein may be applicable to other types of apparatus or other similar apparatuses that are referenced using other terminology.

[0080] The network device 102 may provide services to the terminal devices 101 and 103, and the network device 102 and the terminal devices 101 and 103 may communicate data and control information with each other. In some exemplary embodiments, the network device 102 and the terminal devices 101 and 103 may communicate with direct links / channels. In the communication system 100, a link from the network device 102 to the terminal devices 101 and 103 is referred to as a downlink (DL), while a link from the terminal device 101 or 103 to the network device 102 is referred to as an uplink (UL). In downlink, the network device 102 is a transmitting (TX) device (or a transmitter) and the terminal device 101 or 103 is a receiving (RX) device (or a receiver). In uplink, the terminal device 101 or 103 is a transmitting (TX) device (or a transmitter) and the network device 102 is a RX device (or a receiver). As shown in Fig. 1, the terminal device 101 and the terminal device 103 are co-scheduled terminal devices, and the terminal device 101 may be referred to as the first terminal device, and the terminal device 103 may be referred to as other terminal device of the co-scheduled terminal devices hereinafter.

[0081] Communications in the network environment 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0082] It is to be understood that the number of devices and their connection relationships and types shown in Fig. 1 are for illustrative purposes only without suggesting any limitation. The communication system 100 may comprise any suitable number of devices adapted for implementing embodiments of the present disclosure.

[0083] For 5G NR UL MIMO and DMRS, UE may support in UL DFT-s-OFDM and CP-OFDM. DFT-s-OFDM is only used for one layer (rank=1 ) UL transmission (per UE), while CP-OFDM can be used for one or more layer UL transmissions (rank>=1) (per UE). DMRS for PUSCH is specified with transform precoding enabled (DFT-s-OFDM) and disabled (CP-OFDM)

[0084] For the DMRS sequence, the gold sequence is used with CP-OFDM, and low PAPR (peak to average power ratio) type 1 and low PAPR type 2 (Zadoff-Chu sequence and pi / 2 BPSK (Binary Phase Shift Keying) based sequence respectively) are used with DFT-s-OFDM to preserve its low PAPR. Low PAPR type 2 is used for low order modulation / MCS (e.g., pi / 2 BPSK data modulation).

[0085] For precoding and mapping to physical resources, different DMRS configuration types (DMRS configuration type 1 or 2) and their enhancements (eTypel , eType2) are specified in 5G NR to support more antenna ports or layers, for example, Configuration type 1 (as known as DMRS type 1 allocation), 6 DMRS resource elements (Res) per resource block (RB) (Comb structure), and DMRS RE every other RE; Configuration type 2 (as known as DMRS type 2 allocation): 4 DMRS REs per RB, and each pair of DMRS REs are consecutive / contiguous.

[0086] In 5G NR, any DMRS example allocation in FD from Fig. 2A (one of the single column example) will be the same across all DMRS RBs / symbols (i.e., in FD and TD) for the same UE transmitted UL layer (PUSCH), as shown in Fig. 2A, which shows some examples of DMRS configuration type 1 and DMRS configuration type 2 in 5G NR.

[0087] Therefore, there are up to 2 orthogonal layers only without any orthogonal cover code (OCC) for type 1 & up to 3 orthogonal layers with type 2 without OCC due to FD orthogonality. Number of orthogonal layers can be increased with code domain (OCC) applied in FD and / or TD (x2 for OCC length 2 or x4 for OCC length 4 per domain).

[0088] For example, OCC can be applied in frequency / time domain (FD / TD), and OCC in TD is used with double DMRS symbol (Ien2 i.e., 2 consecutive time domain OFDM symbol are carrying DMRS).

[0089] OCC of length 2 in FD without or with OCC length 2 in TD (single / Double DMRS) is used initially for configuration type 1 or type 2 and leads to support the following maximum number of ports X shown in following table 1:Table 1 : maximum number of ports X for configuration type 1 or type 2 with OCC of length 2 in FD without or with OCC length 2 in TD (single / Double DMRS)

[0090] as shown in the table 1, minimum RS overhead of 1 / 14 and 2 / 14 is assuming full slot PUSCHallocation and posO (1 DMRS symbol), indeed more additional DMRS and / or smaller TDRA for PUSCH leads to larger DM-RS overhead.

[0091] The support of OCC length 4 in FD (DMRS-TypeEnh) is added in later 5G-A releases with length 2 in TD and CDM groups to support up to 16 ports with etype 1 and 24 ports with etype 2 as shown in following table 2.Table 2: maximum number of ports X for configuration etype 1 or etype 2 with OCC of length 4 in FD without or with OCC length 2 in TD (single / Double DMRS)

[0092] However, different from that in 5G NR in which DFT-s-OFDM is only used for one layer (rank=1 ) UL transmission (per UE), 6G may support UL DFT-s-OFDM for one or more layers (rank>=1) similar to LTE to achieve higher UL transmit power (in some cases) and thus higher coverage for higher data rates. LTE supported MIMO DFT-s-OFDM, but LTE DMRS design was different than 5G, and thus DMRS design should be re-considered with DFT-s-OFDM in 6G in order to maintain the support for important 5G NR MIMO features (SU / MU-MIMO), 6G new features and very large number of ports.

[0093] Thus, 6G UE needs to be able to fully exploit its hardware (available antenna ports) regardless of the configured UL waveform (CP-OFDM or DFT-s-OFDM). For example, DFT-s-OFDM support for multilayer rather than one layer could be added in 6G, and UE needs to support larger number of ports & layers at least similar to 5G with CP-OFDM, but while maintaining DFT-s-OFDM PAPR (i.e. low PAPR). DM-RS sequence and configuration types need to preserve the low PAPR property of DFT-s-OFDM in order to get its higher UL transmit power advantage.

[0094] However, straightforward extension of 5G does not guarantee the low PAPR, for example, since DMRS configuration type 2 / etype 2 leads to high PAPR and cubic metric as shown in Fig. 2B, which illustrates a cubic metric for configuration type 1 or 2, or Quadrature Phase Shift Keying (QPSK) data with and without shaping.

[0095] As shown in Fig. 2B, the CM of “DMRS Low PAPR 1 (ZC) type 2 configuration” is much larger than CM of QPSK data, while DMRS type 1 configuration supporting smaller number of ports for same RS overhead can have comparable CM with QPSK data.

[0096] Fig.2B also shows cubic metric for baseline QPSK, QPSK with frequency domain spectrum shaping (FDSS) (shown by curve QPSK FIR of Fig.2B) and QPSK with frequency domain spectrum shaping with spectrum extension (FDSS-SE) (shown by curve QPSK ext 0.25 of Fig.2B), since shaping methods such asFDSS / FDSS-SE could also be applied in DFT-s-OFDM case. If such methods are applied it is possible to utilize similar shaping for DMRS as data, which will further lower the CM of DMRS. Thus, as can be seen from Fig. 2B, CM of DMRS configuration type 2 is larger than data CM with DFT-s-OFDM for some modulation order(s) (or modulation and coding scheme, MCS) and / or potential shaping technique.

[0097] Hence, supporting the configuration type 2 as in 5G with DFT-s-OFDM won’t allow to achieve the full benefit of DFT-s-OFDM with higher power, since DMRS power level (for example, PAPR) is much larger than data power level (for example, data PAPR), that is to say, UE UL power gain with DFT-s-OFDM vs CP-OFDM can be partially or fully lost due to this DMRS PAPR issue.

[0098] However, it needs to note that DMRS configuration type2 or e-type2 provides the support of 50% more number of ports (i.e., 1.5x) for the same RS overhead compared to typel or e-type 1 , respectively, for DMRS symbols without data multiplexing, as show in above table 1 and table 2. In 6G, DFT-s-OFDM may need also to support MU-MIMO, and DMRS among co-scheduled paired UEs need to be carefully addressed. Therefore, the support of low PAPR 1 (ZC) with large number of ports as DMRS configuration (e)type 2 is also desired, since ZC of constant energy per resource element (EPRE) across DMRS REs may allow better channel estimation quality at Rx compared to low PAPR type 2 of non-constant EPRE across DMRS REs. The impact on channel estimation quality and Rx performance could be more pronounced with QPSK or higher and more layers, as compared to pi / 2 BPSK data MCSs and single layer where low PAPR type 2 is mainly used in 5G. It is also to be noted that conventional DMRS for CP-OFDM also has constant EPRE across DMRS REs, but they on the other hand have higher PAPR.

[0099] Therefore, there is a need of a scheme to support a larger number of DMRS ports compared to DMRS configuration type 1 with DFT-s-OFDM while providing low enough PAPR without increasing RS overhead compared to 5G. In other words, there a need of a solution to provide at least DMRS configuration (e)type 2 advantages but with lower PAPR DMRS configuration type suitable for DFT-s-OFDM and at least low modulation orders with or without shaping.

[0100] Further, there is also a need for a solution for determining or indicating DMRS configuration type mainly with minimum DCI overhead, and a solution for supporting efficient co-existence between UL MU-MIMO UEs using potentially different waveforms (for example, DFT-s-OFDM and CP-OFDM) and / or different DMRS configuration types from DMRS design perspectives.

[0101] In view of the foregoing, an example signaling process 300A in accordance with some embodiments of the present disclosure will be described with reference to Fig. 3A. For the purpose of discussion, the communication process 300A will be described with reference to Fig. 1. However, this communication process 300A may be likewise applied to other similar communication scenarios.

[0102] As shown in Fig. 3A, the network device 102 transmits (305) a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission. The terminal device 101 receives (310) the first parameter set. Then, the terminal device 101 determines (315) based on thefirst parameter set, a DMRS configuration type to be used for the uplink transmission among at least two DMRS configuration types. Then, the terminal device 101 transmits (320) the uplink transmission to the network device 102, and network device 102 receives (325) the uplink transmission. The uplink transmission is based on the determined DMRS configuration type.

[0103] The at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol. The terminal device 101 may be used in SU-MIMO scenario or MU-MIMO scenario, or combinations of those two scenarios.

[0104] In some embodiments, the terminal device 101 further obtain configuration information on a plurality of waveforms and modulation order with or without shaping or indication. The waveforms and modulation order may comprise: (i) CP-OFDM supporting any modulation order or shaping; (ii) a DFT-s-OFDM supporting a modulation order with or without a shaping above a modulation order threshold; or (iii) a DFT-s-OFDM supporting a modulation order with or without shaping below the modulation order threshold.

[0105] For example, the UE may be configured with at least two DMRS configs (for example, type 1, type 2, and proposed new type 3) supporting small and / or high number of antenna ports with small DMRS overhead. Optionally, the UE may be configured with two waveforms, for example, CP-OFDM and DFT-s-OFDM.

[0106] For example, the first configuration type of the at least two DMRS configs may be the DMRS configuration type 1 for smaller number of antenna ports and low PAPR / cubic metric (CM), and the DMRS configuration type 1 can be used with CP-OFDM and DFT-s-OFDM. Config type 1 may be used with DFT-s-OFDM or CP-OFDM regardless of modulation order (i.e., PAPR) for rank or number of ports or layers less than a threshold, since config type 1 may have low enough PAPR for all cases. One CP-OFDM or DFT-s-OFDM may be used for a single UE, and different WFs may be used among co-scheduled UL MIMO UEs. Therefore, in some embodiments, the terminal device 101 may transmit the uplink transmission to the network device 102 by using the first DMRS configuration type together with at least one of the CP-OFDM and the DFT-s-OFDM.

[0107] The second configuration type of the at least two DMRS configs may be DMRS configuration type X for higher number of antenna ports (above a threshold). The DMRS configuration type X may comprise for example, DMRS Configuration type 2, for example, DMRS configuration (e)Type 2, which is more optimized for CP OFDM, or DFT-s-OFDM using high modulation order or for non-power limited UE. Therefore, in some embodiments, the terminal device 101 may transmit the uplink transmission to the network device 102 by using by using the second configuration type together with the CP-OFDM, or by usingthe second configuration type together with the DFT-s-OFDM supporting the modulation order with or without shaping above the modulation order threshold.

[0108] The DMRS configuration type X may further comprise a new DMRS Configuration type 3 (e.g. proposed DMRS configuration (e)type 3), which is optimized for at least one UE scheduled with UL DFT-s-OFDM supporting low PAPR / CM modulation or shaping for SU-MIMO or MU-MIMO. Therefore, in some embodiments, the terminal device 101 may transmit the uplink transmission to the network device 102 by using the third configuration type together with the DFT-s-OFDM for SU-MIMO or MU-MIMO.

[0109] Furthermore, the new DMRS Configuration type 3 may be used with CP-OFDM as well, when at least one layer for other co-scheduled or paired UE in UL MU-MIMO is using DFT-s-OFDM with a modulation with or without shaping below a modulation threshold (i.e. , having low PAPR). UE may be scheduled with 1 layer (rank=1 ) transmission with UL MU-MIMO or with multi-layer (rank>1) UL transmission with SU-MIMO or MU-MIMO.

[0110] Therefore, in some embodiments, the terminal device 101 may transmit the uplink transmission to the network device 102 by using the third configuration type together with the CP-OFDM when at least one layer of a co-scheduled UE (rather than the terminal device 101) in UL MU-MIMO is using DFT-s-OFDM and a modulation with or without shaping below a modulation order threshold. A combination of a WF with a modulation with or without shaping could be indicative of data symbol PAPR, and DMRS configuration type at least for high rank / ports is accordingly determined, so that data symbol(s) PAPR for any layer of the at least one UE in UL SU-MIMO or MU-MIMO and DMRS symbol(s) PAPR with the selected configuration type are comparable (within a small marginal difference), or the latter PAPR is smaller than or equal to data symbol PAPR.

[0111] Hereinafter, an example of resource element allocation of a DMRS configuration type 3 will be described with reference to Fig. 3B.

[0112] As shown in Fig. 3B, in DMRS configuration type 3, the DMRS REs are non-contiguous in frequency domain and at least two non-DMRS REs (zero / empty or data) are separating consecutive DMRS REs in the same OFDM or DFT-s-OFDM symbol. For example, UE can determine the DMRS configuration type for the UL transmission and the DMRS sequence, then UE can transmit, for example, 4 equidistant DMRS RE in frequency domain per resource block and DMRS REs are non-contiguous in frequency domain and at least two non-DMRS REs (zero / empty or data) are separating consecutive DMRS REs in the same OFDM or DFT-s-OFDM symbol.

[0113] Configuration type (e.g. configuration type 3) may imply frequency domain granularity for a UE, or granularity may be separately indicated. Different configuration types or frequency domain granularities may be also used for different symbol groups or slots. The proposed example of configuration type 3 has 4 REs per RB like DMRS configuration type 2, but DMRS RE are not consecutives in FD.

[0114] In some embodiments, the first parameter set is further indicative of a rank for the uplinktransmission, and the first DMRS configuration type is further supporting a first rank below a rank threshold, and the second DMRS configuration type and the third DMRS configuration type are further supporting a second rank above a rank threshold.

[0115] For example, UE, that is allocated to transmit on certain resource block(s) / elements, utilizes Configuration type 1 or type 2 or type 3 for PUSCH regardless of the waveform selected based on explicit DMRS indication. For example, in some embodiments, the terminal device 101 may determine a waveform from the CP-OFDM and the DFT-s-OFDM; and transmit the uplink transmission by using the determined DMRS configuration type for the uplink transmission regardless of the determined waveform.

[0116] For example, DMRS Configuration type (e.g., configuration type 1) is selected if total rank or total number of antenna ports for UL SU-MIMO or MU-MIMO is below certain threshold. The total rank may be a total rank per cell (or a collaboration area covering multiple cells) for certain frequency / time resource for both SU-MIMO and MU-MIMO scenarios. Otherwise, for example, if total rank or total number of antenna ports is above the threshold, DMRS configuration type 2 or 3 is selected. For example, DMRS configuration type 3 is selected when at least one MIMO layer is using DFT-s-OFDM with low PAPR / CM modulation, whereas DMRS Configuration type 2 is selected otherwise.

[0117] Therefore, the DMRS configuration type 3 is a DMRS arrangement for DFT-s-OFDM supporting a high number of orthogonal ports, and reasonable DMRS overhead and low PAPR / CM is suitable for low PAPR modulation / shaping.

[0118] Hereinafter, cubic metrics for the configuration types 1, 2 and 3 will be described with reference to Fig. 3C, and cubic metrics for the configuration types 1, 2 and 3 with FDSS (frequency domain spectral shaping) or filtering by a FIR filter and Quadrature Phase Shift Keying (QPSK) data with and without shaping will be described with reference to Fig. 3D. In other words, Fig. 3D mainly considers different DMRS configuration types with FDSS (frequency domain spectral shaping) or filtering by a FIR filter vs data QPSK with / without same shaping.

[0119] Cubic Metric result example of Fig. 3C shows cubic metric for low PAPR 1 (ZC) and 2 (pi / 2 BPSK) DMRS with configuration types 1 and 2, and example configuration type 3 explained above. The CM of example (e)type 3 is significantly lower than configuration (e)type 2 that can support same number of ports with same RS overhead, and the CM of example (e)type 3 is on-par or better than data DFT-s-OFDM with shaping and low enough modulation order (need for pi / 2 BPSK is less probable with MIMO UL). As can be seen from Fig. 3C, config type 3 is always better than config type 2 using same DMRS sequence Low PAPR1 / 2, and even close to lower CM of config type 1 that supports less number of ports.

[0120] Cubic metric result example of Fig. 3D shows cubic metric for low PAPR 1 (ZC) and low PAPR 2 (pi / 2 BPSK) DMRS with FDSS and configuration types 1 and 2, and example configuration type 3 explained above. As can be seen from Fig. 3D, the CM of low PAPR 1 with example config type 3 is on par with QPSK data with the same FDSS filter (rel-18 scheme) while using low PAPR1 that can provide better channelestimation quality due to uniform DMRS EPRE especially in multi-layer transmission, and CM of low PAPR 2 type 3 is much better than CM of QPSK data with FDSS-SE.

[0121] Therefore, DMRS configuration type 3 can support the same number of ports like DMRS configuration (e)type2 while maintaining the low PAPR / CM needed for DFT-s-OFDM and same RS overhead, i.e., type 3 can support 50% more number of ports compared to (e)type 1 using same OCC configuration in FD / TD. That is to say, by DMRS configuration type 3, same RS overhead is maintained as (e)type2, and it allows to reach larger number of ports without the need to use double DMRS symbol of double RS overhead with (e)type 1 of low PAPR (e.g., 12 ports can be supported with single DMRS symbol of 7% minimum RS overhead, no need to use double DMRS etypel of 14% minimum RS overhead).

[0122] Thus, the proposed DMRS configuration type 3 provides lower PAPR for DMRS as required for DFT-s-OFDM low order modulations, large number of orthogonal ports, and similar overhead like DMRS configuration (e)type 2.

[0123] Hereinafter, the exemplary signaling process 400A according to the embodiment of Fig. 3A will be described with reference to Fig. 4A. It should be appreciated that the UE is an example of the terminal device 101, and the BS is an example of the network device 102.

[0124] As shown in Fig. 4A, UE, at 402, may indicate capability for proposed DMRS configuration implicitly or explicitly, or it’s indicated as mandatory feature for all UEs in the specs at 402. For example, the UE may transmit, to the BS, capability indication for (for example, DFT-s-OFDM) multi-layer support implicitly indicating low PAPR configuration type support (for example, the DMRS configuration type 3), and / or a separate dedicated capability for low PAPR Configuration type support. Therefore, in some embodiments, the terminal device may transmit, to the network device, capability indication for the at least two DMRS configuration types or at least for the third DMRS configuration type. The capability indication comprises support of waveforms for multi-layer uplink transmission; support of at least DFT-s-OFDM waveform for multilayer uplink transmission along with implicitly indicating of support of the third DMRS configuration type; support of the third DMRS configuration type; or combination thereof.

[0125] For example, UE indicates support of DFT-s-OFDM for multi-layer UL (rank>1) and / or support of low PAPR DMRS configuration type (optional capability). The former may indicate the latter implicitly. The latter could be indicating the capability with any waveform (CP-OFDM, DFT-s-OFDM) or could be split into multiple capabilities per waveform, etc. In some embodiments, support for the proposed DMRS would be a mandatory feature for all UEs. In some embodiments, another preference is that this would be mandatory for all UEs supporting UL rank >1.

[0126] At 404, the BS configures UE(s) (for example, at least two co-scheduled UEs) with at least two DMRS configuration set, and the first set may indicate DMRS configuration type 3 supporting large number of ports / layers and at least one layer with low PAPR DFT-s-OFDM or modulation, and the at least one second set may indicate Configuration typel and / or 2 supporting the other cases for DFT-s-OFDM and / or CP-OFDM.

[0127] Then, the BS, at 406, indicates to the UE, the configured DMRS configuration sets, and potentially at least one threshold related to total number of layer / ports with single and / or double DMRS symbol. Then, the BS, at 408, determines scheduling parameters and associated DMRS configuration set for at least one UE in SU-MIMO or MU-MIMO, based on the determination of whether low PAPR DFT-s-OFDM or modulation to use in at least one layer and the total number of ports / layers that is above or below a certain threshold.

[0128] Then, the BS, at 410, transmits to the UE, uplink scheduling grant, which includes explicit indication of DMRS configuration set, and / or indication of a first set of parameters comprising at least the total number of ports / layers in SU-MIMO or MU-MIMO and whether at least one layer is using low PAPR waveform (WF) DFT-s-OFDM or modulation, and potentially a second set of parameters. For example, UE is scheduled for UL with DFT-s-OFDM waveform (or CP-OFDM where at least one co-scheduled UE in UL MU-MIMO is using DFT-s-OFDM and not DMRS configuration type 1), including transmission rank (or TPMI) and MOS. In some embodiments, the second set of parameters may comprise an indication indicative of a DMRS sequence.

[0129] Then, the UE, at 412, determines which DMRS configuration set to use based on the received indication(s) and / or the first set of parameters.

[0130] For example, the DMRS configuration set to be used for UL may be determined based on the first set of parameters. For example, the first DMRS configuration set (for example, the configuration type 3), which has non-contiguous DMRS REs in frequency domain and at least two non-DMRS REs separating consecutive DMRS REs with at most 4 DMRS REs per each resource block, is selected, when the first set of parameter indicates that total number of layer / ports is above certain threshold with at least one layer using low PAPR DFT-s-OFDM or modulation. Otherwise, one of the at least one second DMRS configuration is selected. For example, when the first set of parameter indicates that total number of layer / ports is above certain threshold without at least one layer using low PAPR DFT-s-OFDM or modulation, the configuration type 2 will be selected, and when the first set of parameter indicates that the total number of layer / ports is below certain threshold, the configuration type 1 will be selected.

[0131] Furthermore, the DMRS configuration set to be used for UL may be determined based on the received indication(s), that is to say, the terminal device may receive an indication indicative of a DMRS configuration type for the uplink transmission. For example, the UE may determine DMRS new configuration type [and sequence / sequence length] [for UL] or DMRS related precoding and mapping to physical resources to be used for UL transmission at least partially based on explicit indication. Therefore, in some embodiments, the terminal device may determine the DMRS configuration type to be used in the uplink transmission based on the explicit indication indicative of the DMRS configuration type for the terminal device.

[0132] For example, explicit indication is based on higher layer configuration parameters for DMRS, and / or DCI, and the DMRS configuration type is explicitly indicated by NW at least in higher layer signaling as RRC(e.g., as configuration typel or 2 as conventional method, potentially also other type3).

[0133] At 414, the UE may determine the DMRS sequence base on the second set of parameters to be used in UL transmission. The second set of parameters may comprise: transform precoding indication, higher layer DMRS configuration indication, DMRS configuration type indication, or indicated or determined cyclic shift. Therefore, in some embodiments, the indication indicative of the DMRS sequence included in the second set of of parameters comprises: an indication of transform precoding; an indication of a DMRS configuration; an indication of a modulation order; an indication of a modulation and coding scheme (MCS); an indication of a configured DMRS Configuration type; an indication of cyclic shift for the DMRS sequence; an indication of time domain (TD) and / or FD (frequency domain) orthogonal cover code (OCC) for the DMRS sequence; or any combination thereof.

[0134] For example, the UE determines DMRS sequence and generates it at least based on transform precoding, for example, disabled transform precoding means gold sequence, and enabled transform precoding means ZC or pi / 2 BPSK.

[0135] For example, the UE may further generate the DMRS sequence based on higher layer DMRS configuration (lowPAPR-DMRS sequence enabled) and / or modulation order (e.g, pi / 2 BPSK or QPSK is configured) or MCS.

[0136] For example, the UE may further generate the DMRS sequence based on DMRS Configuration type, for example, UE may use lower PAPR sequence than conventional case (low PAPR type 1 or 2) when specific configuration type(s) is(are) configured / assumed.

[0137] For example, the UE may further generate the DMRS sequence based on indicated / determined cyclic shift(s) for DMRS sequence generation among layers or UEs, and when UE determines DMRS sequence, the UE may apply different cyclic shift for the sequence on different antenna ports, and UE may apply time domain and / or frequency OCC among different antenna ports. For example, any shifted DMRS sequence is not comprised or equal to any DMRS sequence after being applied the configured FD OCC in the same CDM group. For example, a subset of UEs or layers per UE may be using same cyclic shift and another subset of UEs or layers per UE in the same CDM group [and may be using same FDD OCC values] may be using another cyclic shift to minimize cross-correlation (quasi-orthogonal). UE subsets may be configured by NW such that inter-UE distance or spatial separation could provide further separation and better quasi-orthogonality among DMRS. Therefore, in some embodiments, the terminal device may apply the cyclic shift to the DMRS sequence; or apply the TD and / or FD OCC to the DMRS sequence, in a same CDM group, a first DMRS sequence which has been shifted by the cyclic shift is different from a second DMRS sequence which has been applied with the TD OCC and / or FD OCC. in some embodiments, in the same CDM group, a first subset of terminal devices or a first subset of layers per terminal device use a first cyclic shift, a second subset of terminal devices or a second subset of layers per terminal device use a second cyclic shift. Alternatively, in the same CDM group, the first subset of terminal devices or the firstsubset of layers per terminal device use a first TD OCC and / or FD OCC, the second subset of terminal devices or the second subset of layers per terminal device use a second TD OCC and / or FD OCC.

[0138] As shown in Fig. 4A, at 416, UE determines UL power level or EPRE of DMRS REs and data REs based on the determined DMRS configuration set. For example, the UE determines DMRS power or amplitude scaling factor or EPRE based on determined configuration type. For example, UE determines EPRE for DMRS or power boost factor for DMRS or amplitude scaling factor for any configuration type based on the number of DMRS REs per RB and / or additional EPRE DMRS power boost factor relative to data EPRE. Therefore, in some embodiments, the terminal device may determine, based on the determined DMRS configuration type for the uplink transmission, a DMRS power level for the uplink transmission, and the DMRS power level may comprise an EPRE for the DMRS, a power boost factor for the DMRS, an amplitude scaling factor for the DMRS, or the combination thereof.

[0139] For example, one example of configuration (e)type 3 uses 4 non-consecutive REs DMRS per RB, and configuration (e)type 2 may use the same DMRS EPRE boost relative to PUSCH EPRE (power boost by a factor of 3 linear or 4.77dB for number of CDM groups without data=3, 0 for number of CDM groups without data=1 and 3 dB for number of CDM groups without data=2), and their subsets configuration type (e.g., using 2 RE / RB in above figure) may use same or higher power boost (e.g., depending on number of CDM groups).

[0140] After determining DMRS configuration type and DMRS sequence, at 418, UE transmits UL transmission using the determined DMRS configuration type, and associated power level (DMRS and data EPRE).

[0141] In some embodiments, the UE may apply Frequency domain FD OCC only and may apply additionally TD OCC with configuration type 3 so as to increase the number of orthogonal layers or ports. For example, straightforward extension to larger OCC length in FD or TD is possible and it maintains low PAPR of the proposed configuration type3.

[0142] Hereinafter, single symbol DMRS example with length 2 OCC in FD and configuration type 3 without TD OCC will be described with reference to Fig. 4B.

[0143] As shown in Fig. 4B, length 2 OCC in FD is applied on the DMRS sequence, and there is no TD OCC. However, other OCC length can be used, e.g., length 4 OCC in FD as rel-18+. Cyclic shift may be applied on DMRS sequence among different ports to support more number of ports (e.g., 2 CS is used per each CDM group). More ports can be supported with sequence cyclic shift among ports, and the shifted sequence with [pre-defined / configured] cyclic shift is different than all possible sequences with pre-defined FD OCC configuration.

[0144] PUSCH allocation may contain one or more single / double symbol DMRS (e.g., posO, pos1, etc.) similar to the conventional scheme. Another similar example may be with 3 DMRS RE / RB supporting with single symbol: 4 ports or layers without FD OCC or 8 ports with FD OCC length 2 or 16 ports with FD OCClength 4.

[0145] Hereinafter, double symbol DMRS example with length 2 OCC in FD and in TD and configuration type 3 will be described with reference to Fig. 4C.

[0146] As shown in Fig. 4C, length 2 OCC in FD and length 2 OCC in TD are applied on the DMRS sequence. Other OCC length can be used in either domain (e.g., length 4 OCC or more). Another similar example may be with 3 DMRS RE / RB supporting with double symbol (TD OCC length 2): 8 ports or layers without FD OCC and more ports with sequence cyclic shift among ports and / or larger OCC.

[0147] Hereinafter, the exemplary signaling process 500A according to some embodiments of the present disclosure will be described with reference to Fig. 5A. For the purpose of discussion, the communication process 500A will be described with reference to Fig. 1. However, this communication process 500A may be likewise applied to other similar communication scenarios.

[0148] As shown in Fig. 5A, the network device 102 transmits (505) to the terminal device 101, an indication indicative of an initially indicated DMRS configuration type, and the terminal device 101 receives (510) the indication indicative of an initially indicated DMRS configuration type. Then, the network device 102 transmits (515) to the terminal device 101 at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission. The terminal device 101 receives (520) the at least one parameter. The at least one parameter may be configuration and / or scheduling parameter. Then, the terminal device 101 determines (525) based on the at least one parameter and a at least one predefined rule, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device. The predefined rule is used for determining the DMRS configuration type for the uplink transmission. Then, the terminal device 101 transmits (530) the uplink transmission to the network device 102, and the network device 102 (535) receives the uplink transmission, and the uplink transmission is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0149] Therefore, some specific rules are specified for implicit DMRS configuration determination (e.g., like the below, DCI type and CRC scrambling RNTI if any, PUSCH CG type 1 or type 2 or DG, etc.), and it may allow UE / NW to determine: which DMRS configuration type to use, valid DMRS configuration type and / or the use of same / another configuration type (e.g. configuration type3) compared to the initially indicated DMRS configuration type (e.g., type 1 or type2).

[0150] In some embodiments, the at least one parameter comprises: a transform precoding indication, a modulation order or MCS indication, a MCS table indication, a resource allocation type indication, a shaping or power boost feature indication, a configured grant indication, a radio network temporary identifier (RNTI) used for cyclic redundancy check (CRC) scrambling of a downlink control information (DCI), a codebooksubset indication, a transmit precoding matrix indicator (TPMI) transmitted precoding matrix indicator, a rank indication, a maximum MIMO layer indication, an uplink multi-user multi-input-multi-output (MU-MIMO) configuration indication, a frequency division resource allocation (FDRA) allocation indication, a DMRS sequence type indication, a number of DMRS symbol, or any combination thereof.

[0151] In some embodiments, the terminal device 101 determines the DMRS configuration type for the uplink transmission to be one of a second DMRS configuration type and a third DMRS configuration type. That is to say, if config type 1 is not selected, UE may further obtain at least configuration / scheduling parameters comprising at least one the above parameters and determines to use DMRS configuration type 3 based on at least one rule / condition is satisfied (i.e., obtained configuration is part of a pre-defined configuration subset) and otherwise determine to use DMRS configuration type 2.

[0152] For example, an example of pre-defined configuration subset and rules to select configuration type 3 may be that: resource allocation type is set to typel or dynamic switch and FDRA DCI field indicates type 1. An example of pre-defined configuration subset and rules to select configuration type 3 may be that MCS-table and MCS DCI field indication indicates a modulation order below a 1 st threshold. An example of pre-defined configuration subset and rules to select configuration type 3 may be Maximum MIMO layer indication above a 2nd threshold. An example of pre-defined configuration subset and rules to select configuration type 3 may be rank indication above a 3rd threshold. An example of pre-defined configuration subset and rules to select configuration type 3 may be that TPMI indicates a precoder matrix comprised in non-coherent codebooksubset or non-coherent codebooksubset is configured / indicated. An example of pre-defined configuration subset and rules to select configuration type 3 may be that transform precoding higher layer field, DWS related higher layer field(s) and DWS DCI bit field indicates DFT-s-OFDM. An example of pre-defined configuration subset and rules to select configuration type 3 may be that a power boost or shaping feature is enabled. An example of pre-defined configuration subset and rules to select configuration type 3 may be that RNTI used for CRC scrambling of scheduling or activating DCI indicates DG-PUSCH. An example of pre-defined configuration subset and rules to select configuration type 3 may be that UL MU-MIMO indication indicates at least one layer for a co-scheduled UE is using DFT-s-OFDM and potentially with modulation below a threshold or is using DMRS config type 3. An example of predefined configuration subset and rules to select configuration type 3 may be that more conditions based on the other parameters.

[0153] Hereinafter, rules for implicit DMRS configuration type determination may be described. CP-OFDM and DFT-s-OFDM can be dynamically switched (DWS), and several other parameters may also change dynamically in L1 DCI and thus the need for low PAPR DMRS type may dynamically change. Therefore, the following part covers some additional rules for determining DMRS configuration type allowing to dynamically adapt DMRS configuration type without additional DCI overhead.

[0154] For example, the UE may determine to use configuration type 1 for any WFs based on configurationand / or predefined rules [only] (e.g., higher layer RRC DMRS type parameter is absent as in 5G or set to type 1 or rules). Therefore, in some embodiments, the terminal device 101 may determine to use a first DMRS configuration type for the uplink transmission, based on determining that an RRC DMRS type parameter is absent or the initially indicated DMRS configuration type is indicating the first DMRS configuration type.

[0155] Other DMRS configuration type 2 or 3 is determined based on configuration / rules (e.g., based on RRC DMRS configuration type value set to type not equal to 1 or = 2 or 3) and / or additional condition(s), for example In one example, DMRS configuration type 2 is selected for CP-OFDM while configuration type 3 is selected with DFT-s-OFDM; and in another example, configuration type 3 is selected for DFT-s-OFDM if other condition(s) (subsequent conditions) are satisfied, otherwise configuration type 2 is selected. Therefore, in some embodiments, the terminal device 101 may determine, based on the at least one parameter and the at least one predefined rule, to use a second or third DMRS configuration type for the uplink transmission, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0156] In some embodiments, the at least one parameter may comprise the transform precoding indication, and the enable of the transform precoding indication may mean DFT-s-OFDM, and the disable of transform precoding indication may mean CP-OFDM. Configuration type 3 may be selected if transform precoding higher layer field, DWS related higher layer field(s) and DWS DCI bitfield indicates DFT-s-OFDM.

[0157] In some embodiments, the at least one parameter comprises the UL MU-MIMO indication, in one example, UE may determine to use DMRS configuration type 2 (when type 1 is not configured, or type2 or 3 initially configured) with CP-OFDM and / or DFT-s-OFDM, when UE receives any indication for UL MU-MIMO (i.e., preferring system gain of UL MU-MIMO over single UE gain of power boost with other low PAPR DMRS configuration type mainly with DFTs). In another example, UE determines to use DMRS configuration type 3, when UE receives any indication for UL MU-MIMO with at least one co-scheduled UE using DFT-s-OFDM (e.g., to achieve full power boost gain for that UE with DFT-s-OFDM). Indication for UL MU-MIMO may be part of scheduling DCI or DCI used for dynamic waveform switching, it may e.g. comprise MU-MIMO indication and waveform indication.

[0158] Therefore, in these embodiments, the terminal device may upon reception of the UL MU-MIMO configuration indication, determine to use the second DMRS configuration type with a waveform of CP-OFDM and / or DFT-s-OFDM, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type, or the second DMRS configuration type or the third DMRS configuration type is the initially indicated DMRS configuration type. Alternatively, the terminal device may upon reception of the UL MU-MIMO configuration indication, determine to use the third DMRS configuration type, based on determining that at least one co-scheduled terminal device of the terminal device uses the waveform of DFT-s-OFDM.

[0159] In some embodiments, the at least one parameter is the modulation order or MCS indication thatis more or less than a pre-defined or configured threshold. Modulation order or MCS may be larger / smaller than a pre-defined / configured threshold. For example, if configuration type 1 is not configured / indicated, an if MCS or modulation order is below a pre-defined subset, UE may determine to use configuration type 3 (e.g., low modulation order up to QPSK or 16QAM). Otherwise, configuration type 2 is selected e.g., for larger modulation order with DFT-s-OFDM and when RRC configured DMRS type is not indicating DMRS configuration type 1 (or indicating either type 2 or 3).

[0160] Therefore, in these embodiments, the terminal device may determine to use the third DMRS configuration type for the uplink transmission, based on determining that the modulation order or the MCS is below the pre-defined threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type. Alternatively, the terminal device may determine to use the second DMRS configuration type with the waveform of the DFT-s-OFDM supporting a modulation order with or without shaping above a modulation order threshold, based on determining that the modulation order or the MCS is more than the threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0161] In some embodiments, the at least one parameter is the TPMI transmitted precoding matrix indicator that is a configured, indicated or determined TPMI or precoding matrix or codebooksubset. For example, when configuration type 1 is not configured / indicated, UE may determine to use configuration type 3 [with DFT-s-OFDM] for TPMI comprised in specific codebooksubset (e.g., noncoherent only), and otherwise to use the configured DMRS configuration type. Alternatively, UE may determine to use configuration type 3 [with DFT-s-OFDM] when the determined precoding matrix W comprises at most 1 layer per antenna port (no layer is summed-up before transmission by any antenna port).

[0162] Therefore, for these embodiments, the terminal device determines to use the third DMRS configuration type with the waveform of DFT-s-OFDM for the TPMI comprised in a non-coherent codebook subset, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type. Alternatively, the terminal device may determine to use the third DMRS configuration type with the waveform of the DFT-s-OFDM, based on determining that a determined precoding metric comprises at most one layer per antenna port and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0163] In some embodiments, and the at least one parameter is the resource allocation type indication. For example, the RB allocation type may be RB length (for example, FDRA RB length larger than or less than a threshold) or RB position, or RB region outer edge and / or inner edge. For example, when configuration type 1 is not configured / indicated, UE may determine to use configuration type 3 only if contiguous RB allocation is configured, otherwise type 2 is selected.

[0164] Therefore, in these embodiments, the terminal device may determine to use the third DMRS configuration type, based on determining that contiguous RB allocation is configured and the initially indicatedDMRS configuration type is not indicating the first DMRS configuration type. Alternatively, the terminal device may determine to use the second DMRS configuration type, based on determining that contiguous RB allocation is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0165] In some embodiments, the at least one parameter is the DMRS sequence type indication. For example, the configured DMRS sequence type may be low PAPR type 112 ZC or pi / 2 BPSK or Gold sequence, for example, in RRC DMRS-Uplink-r16or DMRS-UplinkTransformPrecoding-r16). When configuration type 1 is not configured / indicated, UE may determine to use configuration type 2 if low PAPR type(s) is not configured, otherwise configuration type 3 is selected.

[0166] Therefore, in these embodiments, the terminal device may determine to use the second DMRS configuration type, based on determining that a DMRS sequence type with PAPR below a PAPR threshold is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type. Alternatively, the terminal device may determine to use the third DMRS configuration type, based on determining that a DMRS sequence type with PAPR below the PAPR threshold is configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type. The PAPR threshold could be not necessary indicated by UE or NW, but it could be obtained at both sides implicitly based on UL transmit signal configuration (i.e., WF & Mod / MCS and / or MCS table, contiguous RB or not, power boosting or shaping feature, etc.)

[0167] In some embodiments, the at least one parameter is the shaping or power boost feature indication. For example, UE power boosting indication / capability may be e.g., UE indicating capability for FDSS as a transparent scheme in rel-18 power boostQPSK-rel18 and / or additional or other similar configuration parameter, and it may be indication of feature enabling UL power boosting (e.g., shaping) or power boost above a threshold (strictly greater than 0 or other number).

[0168] When configuration type 1 is not configured / assumed by UE, UE may use configuration type 3 with lower PAPR with specific power boosting feature (e.g., transparent or non-transparent scheme reducing PAPR) and may use configuration type 2 without such feature. Additionally, or alternatively, the threshold(s) for other factor impacting the determination of DMRS configuration type could be different according to this capability (e.g., when configuration type 1 is not assumed / configured, if modulation <=2 (4), it may use configuration type 3 without (or with) UE specific power boosting feature, otherwise, it may use configuration type 2).

[0169] Therefore, for these embodiments, the terminal device may determine to use the third DMRS configuration type for the shaping or power boost feature indication indicating a power boost above a threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type. Alternatively, the terminal device may determine to use the second DMRS configuration type without the shaping or power boost feature indication indicating the power boost abovethe threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0170] In some embodiments, the at least one parameter is the configured grant configuration indication comprising configured grant (CG) type 1, or configured grant type 2, or dynamic grant (DG) PUSCH. For example, UE may use one pre-configuration type for at least one CG type and may follow pre-defined rules (as the example here) to determine DMRS configuration type for DG PUSCH or CG type 2.

[0171] Therefore, in these embodiments, the terminal device may determine to use the initially indicated DMRS configuration type for the CG type 1 or CG type 2. Alternatively, the terminal device may determine to use the determined DMRS configuration type for the DG PUSCH or CG type 2.

[0172] In some embodiments, the at least one parameter may be RNTI used for CRC scrambling for the scheduling or activation DCI (CG Type 2 or DG). For example, configuration type 3 may be selected if RNTI used for CRC scrambling of scheduling or activating DCI indicates DG-PUSCH.

[0173] In some embodiments, the at least one parameter may be number of DM-RS CDM groups without data if any (compared to a threshold).

[0174] In some embodiments, the at least one parameter may be absolute or relative number of allocated DMRS symbols per UL transmission vs a pre-defined threshold or PUSCH time domain allocation length vs a threshold. Number of DMRS symbol could be determined at UE based on several parameters (e.g., DMRS length as single / double DMRS symbol, additional DMRS configuration posO, pos1, etc.) and potentially other parameters (e.g., TDRA, etc.)

[0175] For example, UE may be able to use a configuration type of slightly higher PAPR vs data (e.g., configuration type 2 with 16QAM data) with small relative number of DMRS symbols per UL transmission (1 / 14) for example in UL MU-MIMO to maintain maximum number of DMRS REs for better channel estimation. Otherwise, UE could be forced to use another DMRS configuration type of lower PAPR (e.g., configuration type 3) to maintain the full advantage of higher UL power with DFT-s-OFDM.

[0176] Hereinafter, the exemplary signaling process 500B according to the embodiment of Fig. 5A will be described with reference to Fig. 5B. It should be appreciated that the UE is an example of the terminal device 101, and the BS is an example of the network device 102.

[0177] As shown in Fig. 5B, at 552, the UE may transmit, to the BS, capability indication for [DFT-s-OFDM] multi-layer support implicitly indicating low PAPR configuration type support, and / or a separate dedicated capability for low PAPR Configuration type support.

[0178] At 554, the BS configures UE with one initial DMRS configuration type, and the initial DMRS configuration type may be a first type, which indicates DMRS configuration type (e.g. type 1) supporting small number of layers / ports, and also may be a second [set of] DMRS configuration type, which indicates DMRS configuration type supporting large number of layers (e.g., type 2 [by default] and can indicate a new configuration type 3 based on some rules.

[0179] At 556, the BS indicates at least initial DMRS configuration type potentially in higher layer signaling (e.g., RRC), and potentially configured low PAPR modulation, low PAPR DMRS sequence, FDRA type, etc.

[0180] At 558, the BS determines UL scheduling parameters comprising or indicating at least one of: waveform (WF), modulation / MCS, TPMI, codebooksubset indication, FDRA, DMRS related indication, antenna ports, rank, UL MU-MIMO indication, and scramble the DCI grant by an RNTI.

[0181] At 560, the BS transmits to the UE uplink scheduling grant indicating at least one parameter impacting DMRS configuration type selection at least when a second DMRS configuration type is initially configured.

[0182] At 562, the UE determines DMRS configuration type, and DMRS configuration type 1 is determined when it is initially configured. Additionally, or alternatively, DMRS configuration type 2 or type 3 is dynamically determined according to some pre-defined rules based on at least one of the received indication in L1 and / or higher layer configuration and / or RNTI used for DCI scrambling when the initial DMRS configuration type is not indicating configuration type 1.

[0183] At 564, the UE determines DMRS sequence based on the received indication and determined DMRS configuration type. The determination of DMRS sequence at 564 may be similar to the determination of DMRS sequence at 414 of Fig. 4A, and thus the description thereof will be omitted. At 566, the UE determines UL power level or EPRE of DMRS REs and data REs based on the determined DMRS configuration set. The determination of power level at 566 may be similar to the determination of power level at 416 of Fig. 4A, and thus the description thereof will be omitted. At 568, the UE transmits UL transmission using the determined DMRS configuration type, and associated power level (DMRS and data EPRE).

[0184] Hereinafter, an example signaling process 600A according to the embodiment of Fig. 6A will be described with reference to Fig. 6A. For the purpose of discussion, the communication process 600A will be described with reference to Fig. 1. However, this communication process 600A may be likewise applied to other similar communication scenarios.

[0185] As shown in Fig. 6A, the network device 102 transmits (605) to the terminal device 101 (the terminal device 101 may also be a first terminal device of at least two co-scheduled terminal devices) configuration information about a set of DMRS configuration types and an indication of UL MU-MIMO scheduling. The (first) terminal device 101 receives (610) the configuration information. The network device 102 then transmits (615) indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types. Then, the (first) terminal device 101 obtains (620) this information via this indicating information. In other example, theffirst) terminal device 101 may obtain this information based on predefined rule in the specs. The terminal device may assume different DMRS configuration type among coscheduled UEs if UE doesn’t receive an indication from NW and UE receives at least indication of UL MU-MIMO is configured, or vice versa (i.e., assume same DMRS type unless different DMRS type is indicated, that is to say, no indication may mean same DMRS configuration type among co-scheduled UEs). Then, the (first) terminal device 101 may determine (625) based on the configuration information and the obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device (i.e. the terminal device 101). Then, the (first) terminal device 101 transmits (630) the uplink transmission to the network device 102, and the network device 102 receives (635) the uplink transmission.

[0186] In some embodiments, the (first) terminal device may receive, from the network device, an indication indicating that which fallback DMRS configuration subset type is to be used for the uplink transmission, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; and then, the (first) terminal device may determine to use the fallback DMRS configuration subset type as the target DMRS configuration subset type for the uplink transmission. For example, UE may receive explicit indication from NW of fallback DMRS configuration subset type, and / or may receive an indication of DMRS configuration (not DMRS config type, such as, DMRS CDM group, etc.) and determine fallback DMRS configuration subset type based on pre-defined rule in the spec and the received indication (e.g., CDM group). In this way, the at least one terminal device or even all terminal devices of the at least two co-scheduled terminal devices fallback to the fallback DMRS configuration subset type, and the fallback DMRS configuration subset type is pre-configured or pre-defined configuration subset type in a specification which is the same among the co-scheduled terminal devices having a same CDM group.

[0187] For example, at least one UE or all UEs having different DMRS configuration type may fallback to a pre-configured by or pre-defined in specs configuration type subset which is the same among those coscheduled UEs having same CDM group. UE may further receiver indication which fallback DMRS configuration subset type to be used based on the obtained information indicating whether the at least two co-scheduled terminal devices comprising the first terminal device do not have same DMRS configuration type.

[0188] In some embodiments, the (first)terminal device may receive, from the network device, an indication indicating to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information regardless of the obtained information indicating whether the at least two coscheduled terminal devices do have same DMRS configuration type or do not have same DMRS configuration type, and then the(first) terminal device may determine to use the configured DMRS configuration type for the uplink transmission. For example, if the UE receives a configured DMRS configuration type for the uplink transmission thereof in the configuration information transmitted at 605, the UE may do not fallback to any other DMRS config subset type regardless of obtained information. In other words, the initial configured DMRS config type will be maintained regardless of the obtained informationindicating whether the at least two co-scheduled terminal devices do or do not have same DMRS configuration type.

[0189] For example, one UE may receive instruction to use the initially configured DMRS configuration type in all cases e.g., UE have low coverage or high path loss and NW avoids compromising its performance with lower DMRS Res. UE may further receiver indication to use the received configured DMRS configuration type regardless of the obtained information indicating whether the at least two co-scheduled terminal devices comprising the UE do have or not have same DMRS configuration type.

[0190] In some embodiments, the (first) terminal device may determine to use the received and configured target DMRS configuration type for uplink transmission, based on the obtained information indicating the at least two co-scheduled terminal devices do have same DMRS configuration type. For example, the UE determines to use the received and configured DMRS configuration type based on the obtained information indicating that the at least two co-scheduled terminal devices comprising the UE have same DMRS configuration type.

[0191] In some embodiments, the first terminal device may determine to use a certain DMRS configuration subset type as the target DMRS configuration subset type, based on obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type, and the determined certain DMRS configuration subset type is selected from a plurality of DMRS configuration subset types of a certain DMRS configuration type, the first DMRS configuration subset type has a first number of DMRS resource elements, and the certain DMRS configuration type has a second number of DMRS resource elements, and the second number is larger than the first number.

[0192] For example, UE determines to use (for example, pre-configured or pre-defined) DMRS configuration type subset based on the obtained information indicating that the at least two co-scheduled terminal devices comprising the UE do not have same DMRS configuration type, and the determined DMRS configuration subset type is selected from a plurality of DMRS configuration subsets of a certain DMRS configuration type.

[0193] In some embodiments, the first terminal device may receive, a further DMRS configuration information about (i) orthogonal cover code (OCC) configuration in time domain (TD) and / or frequency domain (FD); (ii) CDM group; or combination thereof. The CDM group is used by the first terminal device to determine the target configuration subset type for uplink transmission, and the target configuration subset type is a subset type of a certain DMRS configuration type with the configured CDM group.

[0194] For example, the DMRS configuration information may comprises OCC configuration in frequency domain and potentially in time domain, CDM group, etc. As example CDM group is also used to determine the configuration type subset since the subset configuration type should a subset from the DMRS configuration type with the configured CDM group. OCC configuration is used later to apply it on DMRS REs for configuration subset type (e.g., 2 DMRS REs) and / or configured DMRS configuration type (type 1, 2or 3). For example, FD OCC is applied by the UE based on the OCC configuration among non-consecutive DMRS REs that are overlapping with the predefined [fallback] configuration subset type.

[0195] Therefore, in some embodiments, the terminal device may determine to use a certain DMRS configuration type as the target DRMS configuration type, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type, then determine DMRS REs of the target DRMS configuration type overlapping with DMRS REs of a fallback DMRS configuration subset type, and then apply FD OCC on two or more non-consecutive DMRS REs overlapping with the fallback DMRS configuration subset type. The fallback DMRS configuration subset type may be used for other terminal device of the co-scheduled terminal devices.

[0196] Therefore, the process 600A proposes a subset of DMRS configuration type for efficient coexistence between UL MU-MIMO UEs using potentially different waveforms (DFT-s-OFDM and CP-OFDM) or different DMRS configuration types. For example, it may maintain DMRS orthogonality across layers & UEs (e.g., configuration type3 cannot be used with co-scheduled UE in UL MU-MIMO using DMRS configuration type 2 to avoid pilot contamination among those UEs).

[0197] In one example, all UEs should be using the same DMRS configuration type (e.g., either type 1 or type 2 or type 3 etc.). In another example, UE can use different DMRS configuration types and any DMRS configuration type with smaller number of DMRS REs / RB is a subset from the other DMRS configuration type with same or larger number of DMRS REs / RB in the same CDM group (UE or layers are separated via OCC).

[0198] As example, at least one UE is using configuration type X and other UE(s) may use configuration type Y where all DMRS REs in configuration type Y are also used in DMRS configuration type X but the opposite is not necessary, e.g. where every other DMRS RE in configuration type X (e.g., type 1 or type 2) is still carrying DMRS with configuration type Y i.e., number of DMRS REs in type Y= (number of DMRS REs in configuration type X) / 2).

[0199] More examples for derivatives configuration type Y from configuration type X will be shown in Fig.6C. As shown in Fig. 6C, the left column(s) is the derivatives configuration type(s) Y, and the right most column is the configuration type X. For example, Y=Y2 may be one pre-defined fallback DMRS configuration subset type possible with all DMRS configuration types.

[0200] It needs to note that the derivatives / subset configuration type Y from configuration type X (1st column Y1 and 2nd column Y2 derivatives from configuration type X=1) are not necessarily suitable between each other (e.g., Y1 and Y2), but they are suitable to be used with the original configuration type X and one of these possible derivatives (Y1 or Y2) can be selected / configured to be used.

[0201] For example, in MU-MIMO UE can be configured with different DMRS configuration types and any DMRS configuration type with smaller number of DMRS REs / RB is a subset from the other DMRS configuration type with same or larger number of DMRS REs / RB in the same CDM group (UE or layers may be separated via OCC but not necessarily). Actually, transmitted layers / DMRS may be signaled with DCI,e.g. using antenna ports signaling. Further, when at least one derivative configuration type is used, FD-OCC for UEs using the main configuration type X is applied on subset of non-consecutive REs overlapping with derivative configuration type Y. NW may indicate modified FD_OCC application for UEs when at least one co-scheduled UL MU-MIMO is using a derivative configuration type.

[0202] Hereinafter, the exemplary signaling process 600B according to the embodiment of Fig. 6A will be described with reference to Fig. 6B. It should be appreciated that the UE is an example of the terminal device 101, and the BS is an example of the network device 102.

[0203] As shown in Fig. 6B, the UE, at 652, transmits capability indication for [DFT-s-OFDM] multi-layer support implicitly indicating subset of DMRS configuration type support, and / or a separate dedicated capability for subset of DMRS Configuration type support. Therefore, in some embodiments, the first terminal device may transmit to the network device capability indication for the set of DMRS configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types. The capability indication comprises: support of waveforms for multi-layer uplink transmission; support of waveforms for multi-layer uplink transmission along with implicitly indicating of support of the least one subset type of a DMRS configuration type; support of the least one subset type of the DMRS configuration type; or combination thereof.

[0204] The BS at 654 configures DMRS configuration types and / or configuration type subsets for at least two UE. Then, the BS, at 656, indicates the configured DMRS configuration types and / or configuration type subsets to the UE. Thus, in some embodiments, the network device 102 may transmit, to a first terminal device 101, configuration information about a set of DMRS configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling, and the terminal device may receive the configuration information.

[0205] Then, the BS, at 658, determines scheduling parameters for at least two UEs in UL MU-MIMO, and indicates whether / which DMRS configuration type subset of the configured type to select or indication of different DMRS configuration type is being configured among co-scheduled UEs. Thus, in some embodiments, the network device may determine scheduling parameters comprising the indicating information, and the indicating information is about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types for the at least two co-scheduled terminal devices.

[0206] Then, the BS, at 660, transmits an uplink scheduling grant(s) for at least two UEs in UL MU-MIMO indicating whether / which DMRS configuration subset to select and / or UEs have same / different DMRS configuration type. Thus, in some embodiments, the network device 102 may transmit, to the first terminal device 101 , indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types. In one example, the terminal device may obtain, via an indication from the network device, theinformation about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types. In another example, the UE may obtain it by itself based on pre-defined rule in the specification, and if there is no indication from the network device, it may mean same DMRS configuration type among co-scheduled UEs or vice versa.

[0207] Then, the UE, at 662, may determine which DMRS configuration type or subset to use based on at the configured DMRS configuration types and the received indicating information. As mentioned above, in some examples, the UE may determine to maintain using of the initially configured DMRS configuration type regardless of the indicating information indicating whether the co-scheduled UEs do or do not have the same DMRS configuration type, and in some other examples, the UE may determine to use a fallback configuration subset type based on the indicating information indicating that the co-scheduled UEs do not have the same DMRS configuration type.

[0208] Then, the UE, at 664, may determine the group of DMRS REs in each RB where FD OCC is applied and determine the non-DMRS REs. For example, the UE (which uses a certain DMRS config type) determines DMRS REs of DMRS configuration type overlapping with DMRS REs of [pre-defined] fallback DMRS configuration subset type (for example, the fallback DMRS configuration subset type for other UEs of the co-scheduled UEs), and the UE may apply FD OCC on the two or more non-consecutive DMRS REs overlapping with the fallback DMRS config subset type.

[0209] Fig. 6D illustrates application of FD OCC on the DMRS REs in accordance with the conventional method, and Fig. 6E illustrates application of FD OCC on the DMRS REs in accordance with some embodiments of the present disclosure.

[0210] For example, as shown in Fig. 6D, in the conventional method, FD OCC is applied on two or more consecutive DMRS REs (as 5G NR) when obtained information indicates the same DMRS configuration type among co-scheduled UE (one of the above). Example of Fig. 6D is of FD OCC of length 2 where each pair of consecutive DMRS REs apply an OCC.

[0211] As shown in Fig. 6E, in some embodiments, OCC configuration is used to apply it on DMRS REs for configuration subset type (e.g., 2 DMRS REs) and / or configured DMRS configuration type (type 1, 2 or 3). For example, FD OCC is applied by the UE based on the OCC configuration among non-consecutive DMRS REs that are overlapping with the predefined [fallback] configuration subset type. For UE using certain DMRS config type, FD OCC is applied on two or more non-consecutive DMRS REs overlapping with DMRS REs of the fallback DMRS config subset type when obtained information indicates different DMRS configuration type among co-scheduled UE. Example of FIG. 6E is of with FD OCC of length 2 where OCC is applied on non-consecutive DMRS REs in the config type according to the overlapping with fallback config subset type.

[0212] Then, the UE, at 666, may determine UL power level or EPRE of DMRS at least based on thedetermined DMRS configuration type and / or its subset. Thus, the terminal device may determine, based on the determined DMRS configuration type or the determined DMRS configuration subset type, a DMRS power level for the uplink transmission. Then, the UE, at 668, may transmit UL transmission using the determined DMRS configuration type or its subset and associated power level.

[0213] Fig. 7A illustrates another flowchart of an example method 700A implemented at a terminal device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 700A will be described from the perspective of the terminal device 101 with reference to Fig. 1.

[0214] At block 701, the terminal device receives, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission. At block 703, the terminal device determines, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types. The at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0215] In some embodiments, the first parameter set is further indicative of a rank for the uplink transmission, the first DMRS configuration type is further supporting a first rank below a rank threshold, and the second DMRS configuration type and the third DMRS configuration type are further supporting a second rank above a rank threshold.

[0216] In some embodiments, the terminal device receives from the network device, configuration information on the at least two DMRS configuration types. The terminal device obtains, configuration information on a plurality of waveforms and modulation order with or without shaping or indication comprising: (i) a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) supporting any modulation order or shaping, (ii) a discrete fourier transform-spread OFDM (DFT-s-OFDM) supporting a modulation order with or without a shaping above a modulation order threshold, or (iii) a DFT-s-OFDM supporting a modulation order with or without shaping below the modulation order threshold, or combination thereof.

[0217] In some embodiments, the terminal device transmits, to the network device, the uplink transmission, by using the first DMRS configuration type together with at least one of the CP-OFDM and the DFT-s-OFDM; transmits, to the network device, the uplink transmission, by using the third configuration type together with the DFT-s-OFDM; transmits, to the network device, the uplink transmission, by using the third configuration type together with the CP-OFDM, when at least one layer for other co-scheduled terminal device in uplink multi-user multiple input multiple output (MU-MIMO) scenario is using the DFT-s-OFDM supporting the modulation order with or without shaping below the modulation order threshold; or transmits, to the network device, the uplink transmission, by using the second configuration type together with the CP-OFDM, or byusing the second configuration type together with the DFT-s-OFDM supporting the modulation order with or without shaping above the modulation order threshold.

[0218] In some embodiments, the terminal device determines a waveform from the CP-OFDM and the DFT-s-OFDM; and transmits the uplink transmission by using the determined DMRS configuration type for the uplink transmission regardless of the selected waveform.

[0219] In some embodiments, the terminal device receives, from the network device, a second parameter set comprising an indication indicative of a DMRS sequence; and determines, based on the second parameter set, a DMRS sequence on the total number of orthogonal ports or layers for the uplink transmission.

[0220] In some embodiments, the indication indicative of the DMRS sequence comprises: an indication of transform precoding; an indication of a DMRS configuration; an indication of a modulation order; an indication of a modulation and coding scheme (MCS); an indication of a configured DMRS Configuration type; an indication of cyclic shift for the DMRS sequence; or an indication of time domain (TD) and / or FD (frequency domain) orthogonal cover code (OCC) for the DMRS sequence; or combination thereof.

[0221] In some embodiments, the terminal device may apply the cyclic shift to the DMRS sequence; or apply the TD and / or FD OCC to the DMRS sequence, and in a same code division multiplexing (CDM) group, a first DMRS sequence which has been shifted by the cyclic shift is different from a second DMRS sequence which has been applied with the TD OCC and / or FD OCC.

[0222] In some embodiments, in the same code division multiplexing (CDM) group, a first subset of terminal devices or a first subset of layers per terminal device use a first cyclic shift, a second subset of terminal devices or a second subset of layers per terminal device use a second cyclic shift; or in the same CDM group, the first subset of terminal devices or the first subset of layers per terminal device use a first TD OCC and / or FD OCC, the second subset of terminal devices or the second subset of layers per terminal device use a second TD OCC and / or FD OCC.

[0223] In some embodiments, the terminal device may determine, based on the determined DMRS configuration type for the uplink transmission, a DMRS power level for the uplink transmission. In some embodiments, the DMRS power level comprises: an energy per resource element (EPRE) for the DMRS; a power boost factor for the DMRS; or an amplitude scaling factor for the DMRS, or combination thereof.

[0224] In some embodiments, the terminal device may transmit, to the network device, capability indication for the at least two DMRS configuration types or at least for the third DMRS configuration type. In some embodiments, the capability indication comprises: support of waveforms for multi-layer uplink transmission; support of at least DFT-s-OFDM waveform for multi-layer uplink transmission along with implicitly indicating of support of the third DMRS configuration type; support of the third DMRS configuration type; or combination thereof.

[0225] In some embodiments, the terminal device may receive an indication indicative of a DMRS configuration type for the uplink transmission of the terminal device, and the DMRS configuration for theterminal device is determined by the network device based on comparison between the number threshold and the total number of orthogonal ports or layers to be used, and the terminal device is caused to determine the DMRS configuration type to be used in the uplink transmission further based on the indication indicative of the DMRS configuration type for the terminal device.

[0226] In some embodiments, the terminal device may transmit, to the network device, the uplink transmission, based on the determined DMRS configuration type for the uplink transmission and a determined DMRS power level.

[0227] Fig. 7B illustrates another flowchart of an example method 700B implemented at a first network device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 700B will be described from the perspective of the network device 102 with reference to Fig. 1.

[0228] As shown in Fig. 7B, at block 702, the network device transmits, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission. At 704, the network device receives, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS) configuration type among at least two DMRS configuration types. The at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0229] In some embodiments, the network device may determine configuration information on the at least two DMRS configuration types for at least two co-scheduled terminal devices comprising the terminal device; and may transmit, to the terminal device, the configuration information and an indication of the number threshold.

[0230] In some embodiments, the network device may receive, from a terminal device, capability indication of the terminal device for the at least two DMRS configuration types.

[0231] In some embodiments, the network device may determine, based on comparison between the number threshold and the total number of orthogonal ports or layers to be used in uplink transmission, a DMRS configuration type for uplink transmission of the terminal device; and transmit, to the terminal device, an uplink scheduling grant comprising an indication of the determined DMRS configuration type to be used for the uplink transmission of the terminal device.

[0232] In some embodiments, the first parameter set is further indicative of a rank for the uplink transmission, the first DMRS configuration type is further supporting a first rank below a rank threshold, and the second DMRS configuration type and the third DMRS configuration type are further supporting a second rank above a rank threshold.

[0233] In some embodiments, the network device may receive, from the terminal device, the uplink transmission, via: the first DMRS configuration type together with at least one of a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) and a discrete fourier transform-spread OFDM (DFT-s-OFDM) regardless of a modulation order; the third configuration type together with the DFT-s-OFDM; the third configuration type together with the CP-OFDM, when at least one layer for other co-scheduled terminal device in uplink multi-user multi input multi out (MU-MIMO) scenario is using the DFT-s-OFDM supporting a modulation order with or without shaping below a modulation order threshold; or the second configuration type together with the CP-OFDM or with the DFT-s-OFDM supporting the modulation order with or without shaping above the modulation order threshold; or combination thereof.

[0234] In some embodiments, the network device may transmit, to the terminal device, an uplink scheduling grant comprising a second parameter set comprising an indication indicative of a DMRS sequence.

[0235] In some embodiments, the indication indicative of the DMRS sequence comprises: an indication of transform precoding; an indication of a DMRS configuration; an indication of a modulation order; an indication of a modulation and coding scheme (MCS); an indication of a configured DMRS Configuration type; an indication of cyclic shift for the DMRS sequence; an indication of time domain (TD) and / or FD (frequency domain) orthogonal cover code (OCC) for the DMRS sequence; or combination thereof.

[0236] Fig. 8A illustrates another flowchart of an example method 800A implemented at a terminal device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 800A will be described from the perspective of the terminal device 101 with reference to Fig. 1.

[0237] At block 801 , the terminal device receives, from a network device, at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission. At block 803, the terminal device determines, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0238] In some embodiments, the terminal device may determine the DMRS configuration type for the uplink transmission to be one of a second DMRS configuration type and a third DMRS configuration type, and the second or third DMRS configuration type supports a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are noncontiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0239] In some embodiments, the terminal device may determine the DMRS configuration type for the uplink transmission to be one of the second DMRS configuration type and the third DMRS configuration type based on the at least one predefined rule and at least one of the following at least one parameter: a transform precoding indication; a modulation order or modulation and coding scheme (MCS) indication; a MCS tableindication; a resource allocation type indication; a shaping or power boost feature indication; a configured grant indication; a radio network temporary identifier (RNTI) used for cyclic redundancy check (CRC) scrambling of a downlink control information (DCI); a codebook subset indication; a transmit precoding matrix indicator (TPMI) transmitted precoding matrix indicator; a rank indication; a maximum MIMO layer indication; an uplink multi-user multi-input-multi-output (MU-MIMO) configuration indication; a frequency division resource allocation (FDRA) allocation indication; a DMRS sequence type indication; or a number of DMRS symbol.

[0240] In some embodiments, the terminal device may determine to use a first DMRS configuration type for the uplink transmission, based on determining that a radio resource control (RRC) DMRS type parameter is absent or the initially indicated DMRS configuration type is indicating the first DMRS configuration type, and the first DMRS configuration type supports a number of orthogonal ports or layers below a number threshold; or determine, based on the at least one parameter and the at least one predefined rule, to use a second or third DMRS configuration type for the uplink transmission, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type, and the second or third DMRS configuration type supports a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0241] In some embodiments, the at least one parameter is the transform precoding indication, an enabling of which indicates a waveform of a discrete fourier transform-spread OFDM (DFT-s-OFDM), and a disabling of which indicates a waveform of a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM); and the terminal device may determine to use the third DMRS configuration type for the waveform of DFT-s-OFDM; or determine to use the second DMRS configuration type for the waveform of CP-OFDM.

[0242] In some embodiments, the at least one parameter is the UL MU-MIMO configuration indication, and the UL MU-MIMO configuration indication is part of scheduling DCI; or the UL MU-MIMO configuration indication comprises at least one of the MU-MIMO indication or waveform indication.

[0243] In some embodiments, the terminal device may upon reception of the UL MU-MIMO configuration indication, determine to use the second DMRS configuration type with a waveform of CP-OFDM and / or DFT-s-OFDM, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type, or the second DMRS configuration type or the third DMRS configuration type is the initially indicated DMRS configuration type; or upon reception of the UL MU-MIMO configuration indication, determine to use the third DMRS configuration type, based on determining that at least one co-scheduled terminal device of the terminal device uses the waveform of DFT-s-OFDM.

[0244] In some embodiments, the at least one parameter is the modulation order or MCS indication that is more or less than a pre-defined or configured threshold. In some embodiments, the terminal device may determine to use the third DMRS configuration type for the uplink transmission, based on determining thatthe modulation order or the MCS is below the pre-defined threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type with the waveform of the DFT-s-OFDM supporting a modulation order with or without shaping above a modulation order threshold, based on determining that the modulation order or the MCS is more than the threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0245] In some embodiments, the at least one parameter is the TPMI transmit precoding matrix indicator; and the terminal device may determine to use the third DMRS configuration type with the waveform of DFT-s-OFDM for the TPMI comprised in a non-coherent codebook subset, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the third DMRS configuration type with the waveform of the DFT-s-OFDM, based on determining that a determined precoding metric comprises at most one layer per antenna port and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0246] In some embodiments, the at least one parameter is the resource allocation type indication, and the terminal device may determine to use the third DMRS configuration type, based on determining that contiguous RB allocation is configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type, based on determining that contiguous RB allocation is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0247] In some embodiments, the at least one parameter is the DMRS sequence type indication, and the terminal device may determine to use the second DMRS configuration type, based on determining that a DMRS sequence type with peak to average power ratio (PAPR) below a PAPR threshold is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the third DMRS configuration type, based on determining that a DMRS sequence type with PAPR below the PAPR threshold is configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0248] In some embodiments, the at least one parameter is the shaping or power boost feature indication, and the terminal device may determine to use the third DMRS configuration type for the shaping or power boost feature indication indicating a power boost above a threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type without the shaping or power boost feature indication indicating the power boost above the threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0249] In some embodiments, the at least one parameter is the configured grant configuration indication comprising configured grant (CG) type 1 , or configured grant type 2, or dynamic grant (DG) PUSCH, and theterminal device may determine to use the initially indicated DMRS configuration type for the CG type 1 or CG type 2; or determine to use the determined DMRS configuration type for the DG PUSCH or CG type 2.

[0250] In some embodiments, the number of DMRS symbol comprises a number of allocated DMRS symbols per uplink transmission and / or PUSCH time domain allocation length.

[0251] In some embodiments, the terminal device may determine, based on the at least one parameter and the determined DMRS configuration type, a DMRS sequence for the uplink transmission. In some embodiments, the terminal device may determine, based on the determined DMRS configuration type, a DMRS power level for the uplink transmission. In some embodiments, DMRS power level comprises: an energy per resource element (EPRE) for the DMRS; a power boost factor for the DMRS; an amplitude scaling factor for the DMRS; or combination thereof.

[0252] In some embodiments, the terminal device may transmit, to the network device, capability indication for DMRS configuration types for the uplink transmission. In some embodiments, the capability indication comprises at least one of the following: support of waveforms for multi-layer uplink transmission; support of at least DFT-s-OFDM waveforms for multi-layer uplink transmission along with implicitly indicating of support of the third DMRS configuration type; or support of the third DMRS configuration type; or combination thereof.

[0253] In some embodiments, the terminal device may transmit, to the network device, the uplink transmission, based on the determined DMRS configuration type and the determined DMRS power level.

[0254] Fig. 8B illustrates another flowchart of an example method 800B implemented at a network device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 800B will be described from the perspective of the network device 102 with reference to Fig. 1.

[0255] As block 802, the network device transmits, to a terminal device, an indication indicative of an initially indicated DMRS configuration type. At block 804, the network device transmits, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device. At block 806, the network device receives, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0256] In some embodiments, the network device may determine the initially indicated DMRS configuration type for the terminal device; and transmit, the indication of the initially indicated DMRS configuration type via a radio resource control (RRC) message, and the initially indicated DMRS configuration type is selected from a first configuration type supporting a number of orthogonal ports or layers below a number threshold, a second configuration type and a third configuration type supporting a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRSREs in a same symbol.

[0257] In some embodiments, the network device may determine an uplink scheduling grant comprising the at least one parameter; and transmit the at least one parameter by transmitting the uplink scheduling grant. In some embodiments, the network device may receive, from a terminal device, capability indication of the terminal device for the initially indicated DMRS configuration types and the DMRS configuration type for the uplink transmission.

[0258] In some embodiments, at least one parameter comprises: a transform precoding indication; a modulation order or modulation and coding scheme (MCS) indication; a MCS table indication; a resource allocation type indication; a shaping or power boost feature indication; a configured grant indication; a radio network temporary identifier (RNTI) used for cyclic redundancy check (CRC) scrambling of a downlink control information (DCI); a codebook subset indication; a transmit precoding matrix indicator (TPMI) transmitted precoding matrix indicator; a rank indication; a maximum MIMO layer indication; an uplink multi-user multi-input-multi-output (MU-MIMO) configuration indication; a frequency division resource allocation (FDRA) allocation indication; a DMRS sequence type indication; a number of DMRS symbol; or combination thereof.

[0259] Fig. 9A illustrates another flowchart of an example method 900A implemented at a terminal device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 900A will be described from the perspective of the first terminal device 101 with reference to Fig. 1.

[0260] At block 901 , the first terminal device 101 receives, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multiuser multi-input-multi-output (UL MU-MIMO) scheduling. At block 903, the first terminal device 101 obtains obtain information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types. At block 905, the first terminal device 101 determines, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0261] In some embodiments, the first terminal device may receive, from the network device, an indication indicating that which fallback DMRS configuration subset type is to be used for the uplink transmission, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; and determine to use the fallback DMRS configuration subset type as the target DMRS configuration subset type for the uplink transmission, and at least one terminal device of the at least two co-scheduled terminal devices fallback to the fallback DMRS configuration subset type, and the fallback DMRS configuration subset type is pre-configured or pre-defined configuration subset type.

[0262] In some embodiments, the first terminal device may receive, from the network device, an indication indicating to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information, regardless of the obtained information indicating whether the at least two co-scheduled terminal devices do have same DMRS configuration type or do not have same DMRS configuration type; and determine to use the configured DMRS configuration type for the uplink transmission.

[0263] In some embodiments, the first terminal device may determine to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information for uplink transmission, based on the obtained information indicating the at least two co-scheduled terminal devices do have same DMRS configuration type.

[0264] In some embodiments, the first terminal device may determine to use a certain DMRS configuration subset type as the target DMRS configuration subset type, based on obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type, and the determined certain DMRS configuration subset type is selected from a plurality of DMRS configuration subset types of a certain DMRS configuration type, the first DMRS configuration subset type has a first number of DMRS resource elements, and the certain DMRS configuration type has a second number of DMRS resource elements, and the second number is larger than the first number.

[0265] In some embodiments, the first terminal device may receive, a further DMRS configuration information about (i) orthogonal cover code (OCC) configuration in time domain (TD) and / or frequency domain (FD); (ii) CDM group; or combination thereof.

[0266] In some embodiments, the CDM group is used by the first terminal device to determine the target configuration subset type for uplink transmission, and the target configuration subset type is a subset type of a certain DMRS configuration type with the configured CDM group.

[0267] In some embodiments, the target DMRS configuration type is selected from a first DMRS configuration type, a second DMRS configuration type, a third DMRS configuration type.

[0268] In some embodiments, the at least two co-scheduled terminal devices are separated via an orthogonal cover code (OCC); or different layers per terminal device are separated via the OCC.

[0269] In some embodiments, the first terminal device may determine a group of DMRS resource elements (Res) in at least one resource block where frequency domain OCC (FD OCC) is applied; and determine a group of non DMRS REs in the at least one resource block.

[0270] In some embodiments, the first term device may determine to use a certain DMRS configuration type as the target DRMS configuration type, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; determine DMRS REs of the target DRMS configuration type overlapping with DMRS REs of a fallback DMRS configuration subset type; and apply FD OCC on two or more non-consecutive DMRS REs overlapping with the fallback DMRS configuration subset type.

[0271] In some embodiments, the first terminal device may determine, based on the determined DMRS configuration type or the determined DMRS configuration subset type, a DMRS power level for the uplink transmission.

[0272] In some embodiments, the DMRS power level comprises an energy per resource element (EPRE) for the DMRS; a power boost factor for the DMRS; an amplitude scaling factor for the DMRS; or a combination thereof.

[0273] In some embodiments, the first terminal device may transmit, to the network device, capability indication for the set of demodulation reference signal (DMRS) configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types. The capability indication comprises support of waveforms for multi-layer uplink transmission; support of waveforms for multi-layer uplink transmission along with implicitly indicating of support of the least one subset type of a DMRS configuration type; or support of the least one subset type of the DMRS configuration type.

[0274] In some embodiments, the first terminal device may transmit, to the network device, the uplink transmission, based on the determined DMRS configuration type or the determined DMRS configuration subset type, and the determined DMRS power level.

[0275] Fig. 9B illustrates another flowchart of an example method 900B implemented at a network device in accordance with some other embodiments of the present disclosure. For the purpose of discussion, the method 900B will be described from the perspective of the network device 102 with reference to Fig. 1.

[0276] At block 902, the network device 102 transmits, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multiuser multi-input-multi-output (UL MU-MIMO) scheduling. At block 904, the network device 102 transmits, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types. At block 906, the network device 102 receives, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0277] In some embodiments, the network device may determine the configuration information for the at least two co-scheduled terminal devices.

[0278] In some embodiments, the network device may determine scheduling parameters comprising the indicating information for the at least two co-scheduled terminal devices; and transmit, to the first terminal device, a scheduling grant for the least two co-scheduled terminal devices.

[0279] In some embodiments, the network device may receive, from the first terminal device, capability indication for the set of DMRS configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types.

[0280] In some embodiments, an apparatus (for example, the (first) terminal device 101) capable of performing the method 700A may comprise means for performing the respective steps of the method 700A. The means may be implemented in any suitable form. For example, the means may be implemented in acircuitry or software module.

[0281] In some embodiments, the apparatus comprises means for receiving, from a network device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; and means for determining, based on the first parameter set, a demodulation reference signal (DMRS) configuration type to be used for the uplink transmission among at least two DMRS configuration types. The at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0282] In some embodiments, the apparatus may further comprise means for receiving from the network device, configuration information on the at least two DMRS configuration types. The apparatus may further comprise means obtaining, configuration information on a plurality of waveforms and modulation order with or without shaping or indication comprising: (i) a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) supporting any modulation order or shaping, (ii) a discrete fourier transform-spread OFDM (DFT-s-OFDM) supporting a modulation order with or without a shaping above a modulation order threshold, or (iii) a DFT-s-OFDM supporting a modulation order with or without shaping below the modulation order threshold, or combination thereof.

[0283] In some embodiments, the apparatus may further comprise means for transmitting, to the network device, the uplink transmission, by using the first DMRS configuration type together with at least one of the CP-OFDM and the DFT-s-OFDM; means for transmitting, to the network device, the uplink transmission, by using the third configuration type together with the DFT-s-OFDM; means for transmitting, to the network device, the uplink transmission, by using the third configuration type together with the CP-OFDM, when at least one layer for other co-scheduled terminal device in uplink multi-user multiple input multiple output (MU-MIMO) scenario is using the DFT-s-OFDM supporting the modulation order with or without shaping below the modulation order threshold; or means for transmitting, to the network device, the uplink transmission, by using the second configuration type together with the CP-OFDM, or by using the second configuration type together with the DFT-s-OFDM supporting the modulation order with or without shaping above the modulation order threshold.

[0284] In some embodiments, the apparatus may further comprise means for determining a waveform from the CP-OFDM and the DFT-s-OFDM; and means for transmitting the uplink transmission by using the determined DMRS configuration type for the uplink transmission regardless of the selected waveform.

[0285] In some embodiments, the apparatus may further comprise means for receiving, from the network device, a second parameter set comprising an indication indicative of a DMRS sequence; and means for determining, based on the second parameter set, a DMRS sequence on the total number of orthogonal portsor layers for the uplink transmission.

[0286] In some embodiments, the apparatus may further comprise means for applying the cyclic shift to the DMRS sequence; or the TD and / or FD OCC to the DMRS sequence, and in a same code division multiplexing (CDM) group, a first DMRS sequence which has been shifted by the cyclic shift is different from a second DMRS sequence which has been applied with the TD OCC and / or FD OCC.

[0287] In some embodiments, the apparatus may further comprise means for determining, based on the determined DMRS configuration type for the uplink transmission, a DMRS power level for the uplink transmission.

[0288] In some embodiments, the apparatus may further comprise means for transmitting, to the network device, capability indication for the at least two DMRS configuration types or at least for the third DMRS configuration type.

[0289] In some embodiments, the apparatus may further comprise means for receiving an indication indicative of a DMRS configuration type for the uplink transmission of the terminal device, and the DMRS configuration for the terminal device is determined by the network device based on comparison between the number threshold and the total number of orthogonal ports or layers to be used, and the apparatus may the DMRS configuration type to be used in the uplink transmission further based on the indication indicative of the DMRS configuration type for the terminal device. In some embodiments, the apparatus may further comprise means for transmitting, to the network device, the uplink transmission, based on the determined DMRS configuration type for the uplink transmission and a determined DMRS power level.

[0290] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 700A. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.,

[0291] In some embodiments, an apparatus (for example, the network device 102) capable of performing the method 700B may comprise means for performing the respective steps of the method 700B. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0292] In some embodiments, the apparatus comprises means for transmitting, to a terminal device, a first parameter set indicative of at least a total number of orthogonal ports or layers to be used in uplink transmission; means for receiving, from the terminal device, the uplink transmission that is based on a demodulation reference signal (DMRS) configuration type among at least two DMRS configuration types. The at least two DMRS configuration types comprises a first DMRS configuration type supporting a first number of orthogonal ports or layers below a number threshold, and a second configuration type and a third configuration type supporting a second number of orthogonal ports or layers above the number threshold, and in the third configuration type, DMRS resource elements (REs) are non-contiguous in frequency domainand at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0293] In some embodiments, the apparatus may further comprise means for determining configuration information on the at least two DMRS configuration types for at least two co-scheduled terminal devices comprising the terminal device; and means for transmitting, to the terminal device, the configuration information and an indication of the number threshold.

[0294] In some embodiments, the apparatus may further comprise means for receiving, from a terminal device, capability indication of the terminal device for the at least two DMRS configuration types. In some embodiments, the apparatus may further comprise means for determining, based on comparison between the number threshold and the total number of orthogonal ports or layers to be used in uplink transmission, a DMRS configuration type for uplink transmission of the terminal device; and means for transmitting, to the terminal device, an uplink scheduling grant comprising an indication of the determined DMRS configuration type to be used for the uplink transmission of the terminal device.

[0295] In some embodiments, the apparatus may further comprise means for receiving, from the terminal device, the uplink transmission, via: the first DMRS configuration type together with at least one of a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) and a discrete fourier transform-spread OFDM (DFT-s-OFDM) regardless of a modulation order; the third configuration type together with the DFT-s-OFDM; the third configuration type together with the CP-OFDM, when at least one layer for other co-scheduled terminal device in uplink multi-user multi input multi out (MU-MIMO) scenario is using the DFT-s-OFDM supporting a modulation order with or without shaping below a modulation order threshold; or the second configuration type together with the CP-OFDM or with the DFT-s-OFDM supporting the modulation order with or without shaping above the modulation order threshold; or combination thereof.

[0296] In some embodiments, the apparatus may further comprise means for transmitting, to the terminal device, an uplink scheduling grant comprising a second parameter set comprising an indication indicative of a DMRS sequence.

[0297] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 700B. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.,

[0298] ,

[0299] In some embodiments, an apparatus (for example, the terminal device 101) capable of performing the method 800A may comprise means for performing the respective steps of the method 800A. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0300] In some embodiments, the apparatus comprises means for receiving, from a network device, at least one parameter that is to be used to determine a DMRS configuration type for uplink transmission; meansfor determining, based on the at least one scheduling parameter and at least one predefined rule for determining the DMRS configuration type for the uplink transmission, the DMRS configuration type for the uplink transmission that is same as or different from an initially indicated DMRS configuration type that is indicated by the network device.

[0301] In some embodiments, means for determining may determine the DMRS configuration type for the uplink transmission to be one of a second DMRS configuration type and a third DMRS configuration type, and the second or third DMRS configuration type supports a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are noncontiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0302] In some embodiments, means for determining may determine the DMRS configuration type for the uplink transmission to be one of the second DMRS configuration type and the third DMRS configuration type based on the at least one predefined rule and at least one of the following at least one parameter: a transform precoding indication; a modulation order or modulation and coding scheme (MCS) indication; a MCS table indication; a resource allocation type indication; a shaping or power boost feature indication; a configured grant indication; a radio network temporary identifier (RNTI) used for cyclic redundancy check (CRC) scrambling of a downlink control information (DCI); a codebook subset indication; a transmit precoding matrix indicator (TPMI) transmitted precoding matrix indicator; a rank indication; a maximum MIMO layer indication; an uplink multi-user multi-input-multi-output (MU-MIMO) configuration indication; a frequency division resource allocation (FDRA) allocation indication; a DMRS sequence type indication; or a number of DMRS symbol.

[0303] In some embodiments, means for determining may determine to use a first DMRS configuration type for the uplink transmission, based on determining that a radio resource control (RRC) DMRS type parameter is absent or the initially indicated DMRS configuration type is indicating the first DMRS configuration type, and the first DMRS configuration type supports a number of orthogonal ports or layers below a number threshold; or determine, based on the at least one parameter and the at least one predefined rule, to use a second or third DMRS configuration type for the uplink transmission, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type, and the second or third DMRS configuration type supports a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0304] In some embodiments, the at least one parameter is the transform precoding indication, an enabling of which indicates a waveform of a discrete fourier transform-spread OFDM (DFT-s-OFDM), and a disabling of which indicates a waveform of a cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM); and means for determining may determine may determine to use the third DMRS configuration type for thewaveform of DFT-s-OFDM; or determine to use the second DMRS configuration type for the waveform of CP-OFDM.

[0305] In some embodiments, the at least one parameter is the UL MU-MIMO configuration indication, and the UL MU-MIMO configuration indication is part of scheduling DCI; or the UL MU-MIMO configuration indication comprises at least one of the MU-MIMO indication or waveform indication.

[0306] In some embodiments, means for determining may upon reception of the UL MU-MIMO configuration indication, determine to use the second DMRS configuration type with a waveform of CP-OFDM and / or DFT-s-OFDM, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type, or the second DMRS configuration type or the third DMRS configuration type is the initially indicated DMRS configuration type; or upon reception of the UL MU-MIMO configuration indication, determine to use the third DMRS configuration type, based on determining that at least one co-scheduled terminal device of the terminal device uses the waveform of DFT-s-OFDM.

[0307] In some embodiments, the at least one parameter is the modulation order or MOS indication that is more or less than a pre-defined or configured threshold. In some embodiments, means for determining may determine to use the third DMRS configuration type for the uplink transmission, based on determining that the modulation order or the MCS is below the pre-defined threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type with the waveform of the DFT-s-OFDM supporting a modulation order with or without shaping above a modulation order threshold, based on determining that the modulation order or the MCS is more than the threshold and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0308] In some embodiments, the at least one parameter is the TPMI transmit precoding matrix indicator; and means for determining may determine to use the third DMRS configuration type with the waveform of DFT-s-OFDM for the TPMI comprised in a non-coherent codebook subset, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the third DMRS configuration type with the waveform of the DFT-s-OFDM, based on determining that a determined precoding metric comprises at most one layer per antenna port and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0309] In some embodiments, the at least one parameter is the resource allocation type indication, and means for determining may determine to use the third DMRS configuration type, based on determining that contiguous RB allocation is configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type, based on determining that contiguous RB allocation is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0310] In some embodiments, the at least one parameter is the DMRS sequence type indication, andmeans for determining may determine to use the second DMRS configuration type, based on determining that a DMRS sequence type with peak to average power ratio (PAPR) below a PAPR threshold is not configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the third DMRS configuration type, based on determining that a DMRS sequence type with PAPR below the PAPR threshold is configured and the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0311] In some embodiments, the at least one parameter is the shaping or power boost feature indication, and means for determining may determine to use the third DMRS configuration type for the shaping or power boost feature indication indicating a power boost above a threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type; or determine to use the second DMRS configuration type without the shaping or power boost feature indication indicating the power boost above the threshold, based on determining that the initially indicated DMRS configuration type is not indicating the first DMRS configuration type.

[0312] In some embodiments, the at least one parameter is the configured grant configuration indication comprising configured grant (CG) type 1, or configured grant type 2, or dynamic grant (DG) PUSCH, and means for determining may determine to use the initially indicated DMRS configuration type for the CG type 1 or CG type 2; or determine to use the determined DMRS configuration type for the DG PUSCH or CG type 2.

[0313] In some embodiments, the number of DMRS symbol comprises a number of allocated DMRS symbols per uplink transmission and / or PUSCH time domain allocation length. In some embodiments, the apparatus may further comprise means for determining, based on the at least one parameter and the determined DMRS configuration type, a DMRS sequence for the uplink transmission.

[0314] In some embodiments, the apparatus may further comprise means for determining, based on the determined DMRS configuration type, a DMRS power level for the uplink transmission.

[0315] In some embodiments, the apparatus may further comprise means for transmitting, to the network device, capability indication for DMRS configuration types for the uplink transmission. In some embodiments, the apparatus may further comprise means for transmitting, to the network device, the uplink transmission, based on the determined DMRS configuration type and the determined DMRS power level.

[0316] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 800A. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0317] In some embodiments, an apparatus (for example, the network device 102) capable of performing the method 800B may comprise means for performing the respective steps of the method 800B. The means may be implemented in any suitable form. For example, the means may be implemented in acircuitry or software module.

[0318] In some embodiments, the apparatus comprises means for transmitting, to a terminal device, an indication indicative of an initially indicated DMRS configuration type; means for transmitting, to the terminal device, at least one parameter that is to be used by the terminal device to determine a DMRS configuration type for uplink transmission of the terminal device; and means for receiving, from the terminal device, the uplink transmission that is based on the DMRS configuration type for uplink transmission, and the DMRS configuration type is determined by the terminal device, based on the at least one parameter and at least one predefined rule, to be same as or different from the initially indicated DMRS configuration type.

[0319] In some embodiments, the apparatus may further comprise means for determining the initially indicated DMRS configuration type for the terminal device; and means for transmitting, the indication of the initially indicated DMRS configuration type via a radio resource control (RRC) message, and the initially indicated DMRS configuration type is selected from a first configuration type supporting a number of orthogonal ports or layers below a number threshold, a second configuration type and a third configuration type supporting a number of orthogonal ports or layers above the number threshold, and in the third DMRS configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

[0320] In some embodiments, the apparatus may further comprise means for determining an uplink scheduling grant comprising the at least one parameter; and transmit the at least one parameter by transmitting the uplink scheduling grant. In some embodiments, the apparatus may further comprise means for receiving, from a terminal device, capability indication of the terminal device for the initially indicated DMRS configuration types and the DMRS configuration type for the uplink transmission.

[0321] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 800B. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0322] In some embodiments, an apparatus (for example, the first terminal device 101) capable of performing the method 900A may comprise means for performing the respective steps of the method 900A. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0323] In some embodiments, the apparatus comprises means for receiving, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; means for obtaining obtain information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and means for determining, based on the configuration information and obtained information, a target DMRS configurationtype or a target DMRS configuration subset type for uplink transmission of the first terminal device.

[0324] In some embodiments, the apparatus may further comprise means for receiving, from the network device, an indication indicating that which fallback DMRS configuration subset type is to be used for the uplink transmission, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; and means for determining may determine to use the fallback DMRS configuration subset type as the target DMRS configuration subset type for the uplink transmission, and at least one terminal device of the at least two co-scheduled terminal devices fallback to the fallback DMRS configuration subset type, and the fallback DMRS configuration subset type is preconfigured or pre-defined configuration subset type.

[0325] In some embodiments, the apparatus may further comprise means for receiving, from the network device, an indication indicating to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information, regardless of the obtained information indicating whether the at least two co-scheduled terminal devices do have same DMRS configuration type or do not have same DMRS configuration type; and means for determining may determine to use the configured DMRS configuration type for the uplink transmission.

[0326] In some embodiments, means for determining may determine to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information for uplink transmission, based on the obtained information indicating the at least two co-scheduled terminal devices do have same DMRS configuration type.

[0327] In some embodiments, means for determining may determine to use a certain DMRS configuration subset type as the target DMRS configuration subset type, based on obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type, and the determined certain DMRS configuration subset type is selected from a plurality of DMRS configuration subset types of a certain DMRS configuration type, the first DMRS configuration subset type has a first number of DMRS resource elements, and the certain DMRS configuration type has a second number of DMRS resource elements, and the second number is larger than the first number.

[0328] In some embodiments, the apparatus may further comprise means for receiving, a further DMRS configuration information about (i) orthogonal cover code (OCC) configuration in time domain (TD) and / or frequency domain (FD); (ii) CDM group; or combination thereof.

[0329] In some embodiments, the CDM group is used by the first terminal device to determine the target configuration subset type for uplink transmission, and the target configuration subset type is a subset type of a certain DMRS configuration type with the configured CDM group. In some embodiments, the target DMRS configuration type is selected from a first DMRS configuration type, a second DMRS configuration type, a third DMRS configuration type.

[0330] In some embodiments, the apparatus may further comprise means for determining a group ofDMRS resource elements (Res) in at least one resource block where frequency domain OCC (FD OCC) is applied; and means for determining a group of non DMRS REs in the at least one resource block.

[0331] In some embodiments, means for determining may determine to use a certain DMRS configuration type as the target DRMS configuration type, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; the apparatus may further comprise means for determining DMRS REs of the target DRMS configuration type overlapping with DMRS REs of a fallback DMRS configuration subset type; and means for applying FD OCC on two or more non-consecutive DMRS REs overlapping with the fallback DMRS configuration subset type.

[0332] In some embodiments, the apparatus may further comprise means for determining, based on the determined DMRS configuration type or the determined DMRS configuration subset type, a DMRS power level for the uplink transmission.

[0333] In some embodiments, the apparatus may further comprise means for transmitting, to the network device, capability indication for the set of demodulation reference signal (DMRS) configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types.

[0334] In some embodiments, the apparatus may further comprise means for transmitting, to the network device, the uplink transmission, based on the determined DMRS configuration type or the determined DMRS configuration subset type, and the determined DMRS power level.

[0335] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 900A. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0336] In some embodiments, an apparatus (for example, the network device 102) capable of performing the method 900B may comprise means for performing the respective steps of the method 900B. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0337] In some embodiments, the apparatus may comprise means for transmitting, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling; means for transmitting, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; and means for receiving, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

[0338] I n some embodiments, the apparatus may further comprise means for determining the configurationinformation for the at least two co-scheduled terminal devices. In some embodiments, the apparatus may further comprise means for determining scheduling parameters comprising the indicating information for the at least two co-scheduled terminal devices; and means for transmitting, to the first terminal device, a scheduling grant for the least two co-scheduled terminal devices.

[0339] In some embodiments, the apparatus may further comprise means for receiving, from the first terminal device, capability indication for the set of DMRS configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types.

[0340] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of the method 900B. In some embodiments, the means comprises at least one processor and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

[0341] Fig. 10 illustrates a simplified block diagram of a device 1000 that is suitable for implementing some exemplary embodiments of the present disclosure. The device 1000 may be provided to implement a communication device, for example, the network device 102, or the terminal device 101 or 103 as shown in Fig. 1. As shown, the device 1000 includes one or more processors 1010, one or more memories 1020 coupled to the processor 1010, and one or more communication modules 1040 coupled to the processor 1010.

[0342] The communication module 1040 is for bidirectional communications. The communication module 1040 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

[0343] The processor 1010 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0344] The memory 1020 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1024, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 1022 and other volatile memories that will not last in the power-down duration.

[0345] A computer program 1030 includes computer executable instructions that are executed by the associated processor 1010. The program 1030 may be stored in the ROM 1024. The processor 1010 may perform any suitable actions and processing by loading the program 1030 into the RAM 1022.

[0346] The embodiments of the present disclosure may be implemented by means of the program 1030so that the device 1000 may perform any process of the disclosure as discussed above. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0347] In some exemplary embodiments, the program 1030 may be tangibly contained in a computer-readable medium which may be included in the device 1000 (such as in the memory 1020) or other storage devices that are accessible by the device 1000. The device 1000 may load the program 1030 from the computer-readable medium to the RAM 1022 for execution. The computer-readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like.

[0348] Fig. 11 illustrates a block diagram of an example of a computer-readable medium 1100 in accordance with some exemplary embodiments of the present disclosure. The computer-readable medium 1100 has the program 1030 stored thereon. It is noted that although the computer-readable medium 1100 is depicted in form of CD or DVD, the computer-readable medium 1100 may be in any other form suitable for carry or hold the program 1030.

[0349] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0350] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0351] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processingapparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0352] In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer-readable medium, and the like.

[0353] The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer-readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0354] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0355] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A first terminal device, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the first terminal device at least to:receive, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;obtain information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; anddetermine, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

2. The first terminal device of claim 1 , wherein the first terminal device is further caused to: receive, from the network device, an indication indicating that which fallback DMRS configuration subset type is to be used for the uplink transmission, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type; and determine to use the fallback DMRS configuration subset type as the target DMRS configuration subset type for the uplink transmission;wherein at least one terminal device of the at least two co-scheduled terminal devices fallback to the fallback DMRS configuration subset type, andwherein the fallback DMRS configuration subset type is pre-configured or pre-defined configuration subset type.

3. The first terminal of claim 1 , wherein the first terminal device is further caused to:receive, from the network device, an indication indicating to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information, regardless of the obtained information indicating whether the at least two co-scheduled terminal devices do have same DMRS configuration type or do not have same DMRS configuration type; anddetermine to use the configured DMRS configuration type for the uplink transmission.

4. The first terminal device of claim 1 , wherein the first terminal device is further caused to:determine to use a configured DMRS configuration type of the set of DMRS configuration types in the configuration information for uplink transmission, based on the obtained information indicating the at least two co-scheduled terminal devices do have same DMRS configuration type.

5. The first terminal device of claim 1 , wherein the first terminal device is further caused to: determine to use a certain DMRS configuration subset type as the target DMRS configuration subset type, based on obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type,wherein the determined certain DMRS configuration subset type is selected from a plurality of DMRS configuration subset types of a certain DMRS configuration type, the first DMRS configuration subset type has a first number of DMRS resource elements, and the certain DMRS configuration type has a second number of DMRS resource elements, and the second number is larger than the first number.

6. The first terminal device of any of claims 1 to 5, wherein the first terminal device is further caused to:receive, a further DMRS configuration information about at least one of the following:(i) orthogonal cover code (OCC) configuration in time domain (TD) and / or frequency domain (FD); or(ii) code division multiplexing (CDM) group.

7. The first terminal device of 6, wherein the CDM group is used by the first terminal device to determine the target configuration subset type for uplink transmission,wherein the target configuration subset type is a subset type of a certain DMRS configuration type with the configured CDM group.

8. The first terminal device of any of claims 1 to 7, wherein the target DMRS configuration type is selected from a first DMRS configuration type, a second DMRS configuration type, a third DMRS configuration type, wherein the first DMRS configuration type supports a first number of orthogonal ports or layers below a number threshold, and the second configuration type and the third configuration type support a second number of orthogonal ports or layers above the number threshold, wherein the second number is larger than the first number; andin the third DMRS configuration type, DMRS resource elements (REs) are non-contiguous in frequency domain and at least two non-DMRS REs are separating consecutive DMRS REs in a same symbol.

9. The first terminal device of any of claims 1 to 8, wherein:the at least two co-scheduled terminal devices are separated via an orthogonal cover code (OCC); ordifferent layers per terminal device are separated via the OCC.

10. The first terminal device of any of claims 1 to 9, wherein the first terminal device is further caused to:determine a group of DMRS resource elements (Res) in at least one resource block where frequency domain OCC (FD OCC) is applied; anddetermine a group of non DMRS REs in the at least one resource block.

11. The first terminal device of claim 10, wherein the first term device is further caused to: determine to use a certain DMRS configuration type as the target DRMS configuration type, based on the obtaining information indicating that the at least two co-scheduled terminal devices do not have same DMRS configuration type;determine DMRS REs of the target DRMS configuration type overlapping with DMRS REs of a fallback DMRS configuration subset type; andapply FD OCC on two or more non-consecutive DMRS REs overlapping with the fallback DMRS configuration subset type.

12. The first terminal device of any of claims 1 to 11 , wherein the first terminal device is further caused to:determine, based on the determined DMRS configuration type or the determined DMRS configuration subset type, a DMRS power level for the uplink transmission.

13. The first terminal device of claim 12, wherein the DMRS power level comprises at least one of the following:an energy per resource element (EPRE) for the DMRS;a power boost factor for the DMRS; oran amplitude scaling factor for the DMRS.

14. The first terminal device of any of claims 1 to 13, wherein the first terminal device is further caused to:transmit, to the network device, capability indication for the set of demodulation reference signal (DMRS) configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types.

15. The first terminal device of claim 14, wherein the capability indication comprises at least one of the following:support of waveforms for multi-layer uplink transmission;support of waveforms for multi-layer uplink transmission along with implicitly indicating of support of the least one subset type of a DMRS configuration type; orsupport of the least one subset type of the DMRS configuration type.

16. The first terminal device of any of claims 1 to 15, wherein the first terminal device is further caused to:transmit, to the network device, the uplink transmission, based on the determined DMRS configuration type or the determined DMRS configuration subset type, and the determined DMRS power level.

17. A network device, comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the network device at least to:transmit, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;transmit, to the first terminal device, indicating information about whether at least two coscheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types;receive, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

18. The network device of claim 17, wherein the network device is further caused to: determine the configuration information for the at least two co-scheduled terminal devices.

19. The network device of claim 17 or 18, wherein the network device is further caused to:determine scheduling parameters comprising the indicating information for the at least two coscheduled terminal devices; andtransmit, to the first terminal device, a scheduling grant for the least two co-scheduled terminal devices.

20. The network device of any of clams 17 to 19, wherein the network device is further caused to: receive, from the first terminal device, capability indication for the set of DMRS configuration types and / or the at least one subset type of at least one of the set of the DMRS configuration types.

21. A method at a terminal device comprising:receiving, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;obtaining information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; anddetermining, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

22. A method at a network device comprising:transmitting, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;transmitting, to the first terminal device, indicating information about whether at least two coscheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types;receiving, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

23. An apparatus comprising:means for receiving, from a network device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;means for obtaining information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types; andmeans for determining, based on the configuration information and obtained information, a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission of the first terminal device.

24. An apparatus comprising:means for means for transmitting, to a first terminal device, configuration information about a set of demodulation reference signal (DMRS) configuration types and an indication of uplink multi-user multi-input-multi-output (UL MU-MIMO) scheduling;means for transmitting, to the first terminal device, indicating information about whether at least two co-scheduled terminal devices comprising the first terminal device in MU-MIMO have same DMRS configuration type or have different DMRS configuration types;means for receiving, from the first terminal device, an uplink transmission that is based a target DMRS configuration type or a target DMRS configuration subset type for uplink transmission determined by the first terminal device based on the configuration information and the indicating information.

25. A computer readable medium comprising program instructions for causing an apparatus to perform at least the method of claim 21 or 22.

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