(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(l9) Worl~~;:::~~:! Property ~ 1111111111111111 IIIIII IIIII IIIII IIIII IIII I II Ill lllll lllll lllll lllll lllll 11111111111111111111111
`~ (tow)
`lntoern2atoio2naol /Plu blh8" ca6ti8on6NAumlber
`;;;;;..,,-""
`WI PO I PCT
`
`International Bureau
`(43) International Publication Date
`18 June 2020 (18.06.2020)
`
`(51) International Patent Classification:
`H04L 1/00 (2006.01)
`
`(21) International Application Number:
`PCT/CN2018/l2ll72
`
`(22) International Filing Date:
`14 December 2018 (14.12.2018)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(71) Applicant: NEC CORPORATION [JP/JP]; 7-l, Shiba 5-
`Chome, Minato-ku, Tokyo 108-8001 (JP).
`
`(72) Inventor; and
`(71) Applicant (for SC only): GAO, Yukai [CN/CN]; 6F, Build(cid:173)
`ing D2, Liangmaqiao Diplomatic Office Building, No. 19
`Dongfangdonglu, Chaoyang District, Beijing 100600 (CN).
`
`(72) Inventor: WANG, Gang; 6F, Building D2, Liangmaqiao
`Diplomatic Office Building, No. 19 Dongfangdonglu,
`Chaoyang District, Beijing 100600 (CN).
`
`(74) Agent: KING & WOOD MALLESONS; 20th Floor,
`East Tower, World Financial Centre, No. I Dongsanhuan
`Zhonglu, Chaoyang District, Beijing 100020 (CN).
`
`(81) Designated States (unless otherwise indicated, for every
`kind of national protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, EH, EN, BR, BW, BY, BZ,
`CA, CH, CL, CN, CO, CR, CU, CZ, DE, DJ, DK, DM, DO,
`DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN,
`HR, HU, ID, IL, IN, IR, IS, JO, JP, KE, KG, KH, KN, KP,
`KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, ME,
`MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI, NO, NZ,
`OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA,
`SC, SD, SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN,
`TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW.
`
`(84) Designated States (unless otherwise indicated, for every
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ,
`UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ,
`TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK,
`EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV,
`MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM,
`TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ, GW,
`KM, ML, MR, NE, SN, TD, TG).
`
`Declarations under Rule 4.17:
`ofinventorship (Rule 4.17(iv))
`
`(54) Title: DMRS CONFIGURATION
`
`,.- 810
`
`RECEIVE DCI FROM AT LEAST ONE OF A PLURALITY OF TRPS
`
`!
`
`,.-820
`
`DETERMINE, FROM THE DCI,
`A CONFIGURATION FOR DMRS TRANSMISSION BETWEEN THE
`PLURALITY OF TRPS AND THE TERMINAL DEVICE
`
`FIG.8
`
`(57) Abstract: Embodiments of the present disclosure provide methods, devices and computer readable media for Demodulation Ref(cid:173)
`erence Signal (DMRS) configuration. In example embodiments, a method implemented at a terminal device is provided. The method
`comprises receiving downlink control information (DCI) from at least one of a plurality of Transmission and Reception Points (TRPs)
`in communication with the terminal device, the plurality ofTRPs being associated with different reference signal (RS) sets. The method
`further comprises determining, from the DCI, a configuration for Demodulation Reference Signal (DMRS) transmission between the
`plurality of TRPs and the terminal device. The configuration at least indicates one or more DMRS ports from a first number of DMRS
`CDM groups to be used for the DMRS transmission and respective numbers of DMRS CDM groups associated with the different RS
`sets. In this way, multi-user scheduling is enabled for multi-TRP transmission. Moreover, interference cancellation can be achieved
`more accurately.
`
`[Continued on next page]
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`iiiiiiiiiiii
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`iiiiiiiiiiii
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`-iiiiiiiiiiii
`!!!!!!!! -iiiiiiiiiiii
`!!!!!!!! ----
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`- !
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`!!!!!!! -
`
`!!!!!!!!
`iiiiiiiiiiii
`iiiiiiiiiiii
`
`iiiiiiiiiiii
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`iiiiiiiiiiii -iiiiiiiiiiii
`
`!!!!!!!!
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`WO 2020/118686 Al 111111 IIIIIIII II IIIIII IIIII 11111 IIIII IIII I II Ill lllll lllll lllll lllll lllll llll lllllll llll 11111111
`
`Published:
`-
`with international search report (Art. 21 (3))
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`

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`WO 2020/118686
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`PCT/CN2018/121172
`
`DMRS CONFIGURATION
`
`TECHNICAL FIELD
`
`[0001] Embodiments of the present disclosure generally relate to wireless communication,
`
`5
`
`and in particular, to methods, devices and computer readable media for Demodulation
`
`Reference Signal (DMRS) configuration.
`
`BACKGROUND
`
`[0002] With the development of communication technologies, multiple types of services
`
`10
`
`or traffic have been proposed, for example, enhanced mobile broadband (eMBB) generally
`
`requiring high data rate, massive machine type communication (mMTC) typically requiring
`
`long battery lifetime, and ultra-reliable and low latency communication (URLLC).
`
`Meanwhile, multi-antenna schemes, such as multi-Transmission and Reception Point
`
`(multi-TRP) transmission and/or multi-panel transmission, are studied for new radio access
`
`15
`
`(NR).
`
`[0003] Conventionally, a network device (for example, an eNB or a gNB) transmits a
`
`downlink DMRS to a terminal device (for example, a user equipment) in the system for
`
`channel demodulation. The terminal device may receive the downlink DMRS on
`
`allocated resources. The terminal device may also transmit an uplink DMRS to the
`
`20
`
`network device on corresponding allocated resources.
`
`For indicating the allocated
`
`resources and other necessary information for the DMRS transmission, the network device
`
`may transmit DMRS configurations to the terminal device prior to the transmissions of the
`
`DMRSs. One or more DMRS tables used for indication of different DMRS configurations
`
`have been specified in current 3GPP specifications. However, there tables are typically
`
`25
`
`designed for single TRP transmission, in which the support for multi-user scheduling or
`
`interference cancelling is insufficient.
`
`SUMMARY
`
`[0004]
`
`In general, example embodiments of the present disclosure provide methods,
`
`30
`
`devices and computer readable media for DMRS configuration.
`
`[0005]
`
`In a first aspect, there is provided a method implemented at a terminal device.
`
`The method comprises: receiving downlink control infonnation (DCI) from at least one of a
`
`1
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`plurality of Transmission and Reception Points (TRPs) in communication with the tenninal
`
`device, the plurality of TRPs being associated with different reference signal (RS) sets; and
`
`determining, from the DCI, a configuration for Demodulation Reference Signal (DMRS)
`
`transmission between the plurality of TRPs and the terminal device, wherein the
`
`5
`
`configuration at least indicates one or more DMRS ports from a first number of DMRS
`
`CDM groups to be used for the DMRS transmission and respective numbers of DMRS
`
`CDM groups associated with the different RS sets.
`
`[0006]
`
`In a second aspect, there is provided a method implemented at a network device.
`
`The method comprises: determining a configuration for Demodulation Reference Signal
`
`10
`
`(DMRS) transmission between a terminal device served by the network device and a
`
`plurality of Transmission and Reception Points (TRPs) in communication with the terminal
`
`device, wherein the plurality of TRPs are associated with different reference signal (RS)
`
`sets, and the configuration at least indicates one or more DMRS ports from a first number
`
`of DMRS CDM groups to be used for the DMRS transmission and respective numbers of
`
`15 DMRS CDM groups associated with the different RS sets; generating downlink control
`
`information (DCI) indicating the configuration; and transmitting the DCI to the terminal
`
`device via at least one of the plurality of TRPs.
`
`[0007]
`
`In a third aspect, there is provided a terminal device. The terminal device
`
`comprises a processor and a memory coupled to the processor. The memory stores
`
`20
`
`instructions that when executed by the processor, cause the terminal device to perform
`
`actions. The actions comprise: receiving downlink control information (DCI) from at
`
`least one of a plurality of Transmission and Reception Points (TRPs) in communication
`
`with the terminal device, the plurality of TRPs being associated with different reference
`
`signal (RS) sets; and detennining, from the DCI, a configuration for Demodulation
`
`25
`
`Reference Signal (DMRS) transmission between the plurality of TRPs and the terminal
`
`device, wherein the configuration at least indicates one or more DMRS ports from a first
`
`number of DMRS CDM groups to be used for the DMRS transmission and respective
`
`numbers ofDMRS CDM groups associated with the different RS sets.
`
`[0008]
`
`In a fourth aspect, there is provided a network device. The network device
`
`30
`
`comprises a processor and a memory coupled to the processor. The memory stores
`
`instructions that when executed by the processor, cause the network device to perform
`
`actions. The actions comprise: determining a configuration for Demodulation Reference
`
`Signal (DMRS) transmission between a tenninal device served by the network device and a
`
`2
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`plurality of Transmission and Reception Points (TRPs) in communication with the terminal
`
`device, wherein the plurality of TRPs are associated with different reference signal (RS)
`
`sets, and the configuration at least indicates one or more OMRS ports from a first number
`
`of OMRS COM groups to be used for the OMRS transmission and respective numbers of
`
`5 OMRS COM groups associated with the different RS sets; generating downlink control
`
`information (OCI) indicating the configuration; and transmitting the OCI to the tenninal
`
`device via at least one of the plurality of TRPs.
`
`[0009]
`
`In a fifth aspect, there is provided a computer readable medium having instructions
`
`stored thereon. The instructions, when executed on at least one processor, cause the at
`
`10
`
`least one processor to carry out the method according to the first aspect of the present
`
`disclosure.
`
`[0010]
`
`In a sixth aspect, there is provided a computer readable medium having
`
`instructions stored thereon. The instructions, when executed on at least one processor,
`
`cause the at least one processor to carry out the method according to the second aspect of
`
`15
`
`the present disclosure.
`
`[0011]
`
`In a seventh aspect, there is provided a computer program product that is tangibly
`
`stored on a computer readable storage medium. The computer program product includes
`
`instructions which, when executed on at least one processor, cause the at least one
`
`processor to carry out the method according to the first aspect or the second aspect of the
`
`20
`
`present disclosure.
`
`[0012] Other features of the present disclosure will become easily comprehensible
`
`through the following description.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`25
`
`[0013] Through the more detailed description of some embodiments of the present
`
`disclosure in the accompanying drawings, the above and other objects, features and
`
`advantages of the present disclosure will become more apparent, wherein:
`
`[0014] FIGs. lA-1B show an example communication network in which embodiments of
`
`the present disclosure can be implemented;
`
`30
`
`[0015] FIGs. 2A-20 shows diagrams of configuration patterns for different OMRS types
`
`according to some embodiments of the present disclosure;
`
`3
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`[0016] FIG. 3 shows a diagram of an example scenario ofmulti-TRP transmission;
`
`[0017] FIG. 4 shows a signaling interaction diagram of a process for DMRS configuration
`
`according to some implementations of the present disclosure;
`
`[0018] FIGs. 5A-5B show an example of DMRS configuration for DMRS type 1
`
`5
`
`according to some implementations of the present disclosure;
`
`[0019] FIGs. 6A-6C show an example of DMRS configuration for DMRS type 2
`
`according to some implementations of the present disclosure;
`
`[0020] FI Gs. 7 A-7B show an example of DMRS configuration for DMRS type 2
`
`according to some implementations of the present disclosure;
`
`10
`
`[0021] FIG. 8 shows a flowchart of an example method for DMRS configuration
`
`according to some embodiments of the present disclosure;
`
`[0022] FIG. 9 shows a flowchart of an example method for DMRS configuration
`
`according to some embodiments of the present disclosure; and
`
`[0023] FIG. 10 is a simplified block diagram of a device that is suitable for implementing
`
`15
`
`embodiments of the present disclosure.
`
`[0024] Throughout the drawings, the same or similar reference numerals represent the
`
`same or similar element.
`
`DETAILED DESCRIPTION
`
`20
`
`[0025] Principle of the present disclosure will now be described with reference to some
`
`example embodiments.
`
`It is to be understood that these embodiments are described only
`
`for the purpose of illustration and help those skilled in the art to understand and implement
`
`the present disclosure, without suggesting any limitations as to the scope of the disclosure.
`
`The disclosure described herein can be implemented in various manners other than the ones
`
`25
`
`described below.
`
`[0026]
`
`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.
`
`[0027] As used herein, the singular forms 'a', 'an' and 'the' are intended to include the
`
`30
`
`plural forms as well, unless the context clearly indicates otherwise. The tenn 'includes'
`
`and its variants are to be read as open terms that mean 'includes, but is not limited to.'
`
`4
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`
`The term 'based on' is to be read as 'at least in part based on.' The term 'one embodiment'
`
`and 'an embodiment' are to be read as 'at least one embodiment.' The term 'another
`
`embodiment' is to be read as 'at least one other embodiment.' The terms 'first,' 'second,'
`
`and the like may refer to different or same objects. Other definitions, explicit and implicit,
`
`5 may be included below.
`
`[0028)
`
`In some examples, values, procedures, or apparatus are referred to as 'best,'
`
`'lowest,' 'highest,' 'minimum,' 'maximum,' or the like.
`
`It will be appreciated that such
`
`descriptions are intended to indicate that a selection among many used functional
`
`alternatives can be made, and such selections need not be better, smaller, higher, or
`
`10
`
`otherwise preferable to other selections.
`
`[0029] FIG. IA shows an example communication network 100 in which embodiments of
`
`the present disclosure can be implemented. The network 100 includes a network device
`
`110 and a terminal device 120 served by the network device 110. The network 100 may
`
`provide one or more serving cells 102 to serve the terminal device 120.
`
`It is to be
`
`15
`
`understood that the number of network devices, terminal devices and/or serving cells is
`
`only for the purpose of illustration without suggesting any limitations to the present
`
`disclosure. The network 100 may include any suitable number of network devices,
`
`terminal devices and/or serving cells adapted for implementing implementations of the
`
`present disclosure.
`
`20
`
`[0030] As used herein, the term 'terminal device' refers to any device having wireless or
`
`wired communication capabilities. Examples of the terminal device include, but not
`
`limited to, user equipment (UE), personal computers, desktops, mobile phones, cellular
`
`phones, smart phones, personal digital assistants (PDAs), portable computers, image
`
`capture devices such as digital cameras, gaming devices, music storage and playback
`
`25
`
`appliances, or Internet appliances enabling wireless or wired Internet access and browsing
`
`and the like. For the purpose of discussion, in the following, some embodiments will be
`
`described with reference to UE as an example of the terminal device 220.
`
`[0031) As used herein, the term 'network device' or 'base station' (BS) refers to a device
`
`which is capable of providing or hosting a cell or coverage where tenninal devices can
`
`30
`
`communicate. Examples of a network device include, but not limited to, a Node B
`
`(NodeB or NB), an Evolved NodeB (eNodeB or eNB), a next generation NodeB (gNB), a
`
`Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a low power
`
`5
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`node such as a femto node, a pico node, and the like. For the purpose of discussion, in the
`
`following, some embodiments will be described with reference to gNB as examples of the
`
`network device 110.
`
`[0032)
`
`In the communication network 100 as shown in FIG. IA, the network device 110
`
`5
`
`can communicate data and control information to the tenninal device 120 and the terminal
`
`device 120 can also communication data and control information to the network device 110.
`
`A link from the network device 110 to the terminal device 120 is referred to as a downlink
`
`(DL), while a link from the terminal device 120 to the network device 110 is referred to as
`
`an uplink (UL).
`
`10
`
`[0033) The communications in the network 100 may conform to any suitable standards
`
`including, but not limited to, Global System for Mobile Communications (GSM), Long
`
`Term Evolution (LTE), LIE-Evolution, LIE-Advanced (LTE-A), Wideband Code Division
`
`Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio
`
`Access Network (GERAN), Machine Type Communication (MTC) and
`
`the like.
`
`15
`
`Furthennore, the communications may be performed according to any generation
`
`communication protocols either currently known or to be developed in the future.
`
`Examples of the communication protocols include, but not limited to, the first generation
`
`(lG), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth
`
`generation (4G), 4.5G, the fifth generation (5G) communication protocols.
`
`20
`
`[0034) The network device 110 ( such as, a gNB) may be equipped with one or more TRPs
`
`or antenna panels. As used herein, the term 'TRP' refers to an antenna array (with one or
`
`more antenna elements) available to the network device located at a specific geographical
`
`location. For example, a network device may be coupled with multiple TRPs in different
`
`geographical locations to achieve better coverage. The one or more TRPs may be
`
`25
`
`included in a same serving cell or different serving cells.
`
`[0035)
`
`It is to be understood that the TRP can also be a panel, and the panel can also refer
`
`to an antenna array (with one or more antenna elements) or a group of antennas. Although
`
`some embodiments of the present disclosure are described with reference to multiple TRPs
`
`for example, these embodiments are only for the purpose of illustration and help those
`
`30
`
`skilled in the art to understand and implement the present disclosure, without suggesting
`
`any limitations as to the scope of the present disclosure.
`
`It is to be understood that the
`
`present disclosure described herein can be implemented in various manners other than the
`
`6
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`WO 2020/118686
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`ones described below.
`
`PCT/CN2018/121172
`
`[0036) FIG. 1B shows an example scenario of the network 100 as shown in FIG. IA. As
`
`shown in FIG. 1B, for example, the network device 110 may communicate with the
`
`terminal device 120 via the TRPs 130-1 and 130-2 (collectively referred to as "TRPs 130"
`
`5
`
`or individually referred to as "TRP 130"). The first and second TRPs 130-1 and 130-2
`
`may be included in a same serving cell (such as, the cell 102 as shown in FIG. lA) or
`
`different serving cells provided by the network device 110.
`
`[0037)
`
`In the network 100 as shown in FIGs IA and 1B, a demodulation reference signal
`
`(DMRS) may be a type of reference signal that provides modulation/demodulation
`
`10
`
`information related to a communication channel for accurate or coherent decoding of
`
`information transmitted via the communication channel.
`
`[0038) Prior to the UL or DL DMRS transmission, the network device 110 may allocate
`
`corresponding resources (also referred to as "DMRS resources") for DMRS transmission
`
`and/or specify which DMRS sequence is to be transmitted.
`
`In some scenarios, both the
`
`15
`
`network device 110 and the terminal device 120 are equipped with multiple antenna ports
`
`and can transmit specified RS sequences with the antenna ports. A set of DMRS resources
`
`associated with a number of DMRS ports are also specified. A DMRS port may be
`
`referred to as a specific mapping of part or all of a DMRS sequence to one or more resource
`
`elements (REs) of a resource region allocated for RS transmission in time, frequency,
`
`20
`
`and/or code domains.
`
`In NR, different DMRS ports may be multiplexed based on Code
`
`Division Multiplexing (CDM) technology in time and/or frequency domain, and/or based
`
`on Frequency Division Multiplexing (FDM) technology. For example, a group of DMRS
`
`ports may also referred to as a "DMRS port group" or "DMRS group". A group of DMRS
`
`ports multiplexed based on CDM technology can also be referred as a "CDM group".
`
`25
`
`[0039)
`
`In some embodiments, such resource allocation information as well as other
`
`necessary information may be indicated to the terminal device 120 prior to the transmission
`
`of the DMRSs. For example, the DMRS configurations can be transmitted via higher
`
`layer signaling (such as Radio Resource Control (RRC) and/or Medium Access Control
`
`(MAC) Control Element (CE)) and/or dynamic signaling (such as downlink control
`
`30
`
`information (DCI)) to the terminal device.
`
`[0040)
`
`In some embodiments, a number of codewords may be configured for the tenninal
`
`device 120. For example, the number may be 1 or 2. For example, the number of
`
`7
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`codewords may be configured by signaling in Radio Resource Control (RRC) and/or
`
`Medium Access Control (MAC) and/or Physical Layer (PHY).
`
`[0041]
`
`In some embodiments, a set of parameters for DMRS configuration may be
`
`configured for the tenninal device 120. The set of parameters may include at least one of
`
`5
`
`the maximum number/length of the symbols for DMRS, a type of DMRS, and etc. For
`
`example, the set of parameters may be configured by signaling in Radio Resource Control
`
`(RRC) and/or Medium Access Control (MAC) and/or Physical Layer (PHY).
`
`[0042]
`
`In some embodiments, the maximum number/length (for example, the maximum
`
`number/length is M) of symbols for DMRS may be the maximum number of symbols for
`
`10
`
`each DMRS transmission occasion in one PDSCH transmission duration, and one DMRS
`
`transmission occasion may be the DMRS transmission in K consecutive symbols. For
`example, M may be 1, 2, 3 or 4. For example, K may be 1, 2, 3 or 4, and K is no greater
`
`than M.
`
`In some embodiments, the maximum number/length (for example, the maximum
`
`number/length is M) of symbols for DMRS may be the maximum number of symbols for
`
`15
`
`the front-loaded DMRS, where the front-loaded DMRS is the first DMRS transmission
`
`occasion in K consecutive symbols in one PDSCH transmission duration. For example, M
`
`may be 1, 2, 3 or 4. For example, K may be 1, 2, 3 or 4, and K is no greater than M.
`
`[0043]
`
`In some embodiments, the type of DMRS may refer to the DMRS configuration
`
`pattern in time and/or frequency domain. There are up to two types of DMRS can be
`
`20
`
`configured for a tenninal device (for example, DMRS type 1 and/or DMRS type 2). FIGs.
`
`2A-2D shows configuration patterns of the two different DMRS types. For DMRS type 1,
`
`one or two symbols can be supported. As shown in Fig. 2A, for DMRS type 1 associated
`
`with one symbol, up to 4 DMRS ports (represented as DMRS ports {0, 1, 2, 3}) can be
`
`supported. As shown in Fig. 2B, for DMRS type 1 associated with two symbols, up to 8
`
`25 DMRS ports (represented as DMRS ports {0, 1, 2, 3, 4, 5, 6, 7}) can be supported. For
`
`example, for DMRS type 1, there may be up to two CDM groups. One CDM group may
`
`occupy REs with even indices within one RB including 12 REs, for example, REs 0, 2, 4, 6,
`
`8 and 10, where the RE index starts from 0. The other CDM group may occupy REs with
`
`odd indices within one RB, for example, REs 1, 3, 5, 7, 9 and 11, where the RE index starts
`
`30
`
`from 0. For DMRS type 2, one or two symbols can be supported. As shown in Fig. 2C,
`
`for DMRS type 2 associated with one symbol, up to 6 DMRS ports (represented as DMRS
`
`ports {0, 1, 2, 3, 4, 5}) can be supported. As shown in Fig. 2D, for DMRS type 2
`
`associated with two symbols, up to 12 DMRS ports (represented as DMRS ports {0, 1, 2, 3,
`
`8
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`4, 5, 6, 7, 8, 9, 10, 11}) can be supported. For example, for DMRS type 2, there may be
`
`up to three CDM groups. One CDM group may occupy REs 0, 1, 6 and 7; one CDM
`
`group may occupy REs 2, 3, 8 and 9; and one CDM group may occupy REs 4, 5, 10 and 11,
`
`where the RE index starts from 0.
`
`In FIGs 2A-2D, different fill patterns may represent
`
`5
`
`different CDM groups.
`
`[0044)
`
`In some embodiments, as an example of grouping of the DMRS ports, for DMRS
`
`type 1 as defined in 3GPP specifications, up to 2 DMRS groups (DMRS group GI and/or
`
`DMRS group G2) may be configured. For example, if two DMRS groups are configured,
`
`DMRS group GI may include at least one DMRS port from {0,1,4,5}, and DMRS group
`
`10 G2 may include at least one DMRS port from {2,3,6,7}. As another example, if only one
`
`DMRS group is configured, there is only one DMRS group G 1 or DMRS group G2, and
`
`DMRS group G 1 or DMRS group G2 may include at least one DMRS port from
`
`{O, 1,2,3,4,5,6, 7}.
`
`[0045)
`
`In some embodiments, as an example of grouping of the DMRS ports, for DMRS
`
`15
`
`type 2 as defined in 3GPP specifications, up to 2 DMRS groups (DMRS group Gl and/or
`
`DMRS group G2) may be configured. For example, if two DMRS groups are configured,
`
`DMRS group GI may include at least one DMRS port from {0,1,6,7, 4,5,10,11}, and
`
`DMRS group G2 may include at least one DMRS port from {2,3,8,9}. As another
`
`example, if two DMRS groups are configured, DMRS group G 1 may include at least one
`
`20 DMRS port from {0,1,6,7}, and DMRS group G2 may include at least one DMRS port
`
`from {2,3,8,9, 4,5,10,11}. As another example, if two DMRS groups are configured,
`
`DMRS group Gl may include at least one DMRS port from {0,1,6,7,2,3,8,9}, and DMRS
`
`group G2 may include at least one DMRS port from {4,5,10,11 }. As another example, if
`
`only one DMRS group is configured, there is only one DMRS group GI or DMRS group
`
`25 G2, and DMRS group G 1 or DMRS group G2 may include at least one DMRS port from
`
`{0,1,2,3,4,5,6,7,8,9,10,11 }.
`
`[0046)
`
`In some embodiments, as an example of grouping of the DMRS ports, for DMRS
`
`type 2 as defined in 3GPP specifications, three DMRS groups (DMRS group GI, DMRS
`
`group G2, and DMRS group G3) maybe configured. For example, if three DMRS groups
`
`30
`
`are configured, DMRS group GI may include at least one DMRS port from {0,1,6,7},
`
`DMRS group G2 may include at least one DMRS port from {2,3,8,9}, and DMRS group
`
`G3 may include at least one DMRS port from {4,5,10,11 }.
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`[0047]
`
`In some embodiments, the tenninal device 120 may be configured with a DMRS
`
`type and/or a maximum number/length of DMRS and/or the number of codewords.
`
`If the
`
`terminal device 120 is configured with a given DMRS type, a given value of the maximum
`
`number/length of DMRS, and a given value of the number of codewords, there is one
`
`s
`
`corresponding table for indication of at least one of antenna ports, the number of DMRS
`
`CDM group(s) without data, the number of front-loaded DMRS symbols, the number of
`
`DMRS port(s), and respective indices for the DMRS port(s).
`
`[0048] As described above, prior to transmission of DMRSs, the network device may
`
`transmit DMRS configurations to a terminal device for indicating the allocated resources
`
`10
`
`and other necessary infonnation for the DMRS transmission. One or more DMRS tables
`
`used for indication of different DMRS configurations have been specified in current 3GPP
`
`specifications. However, there tables are typically designed for single TRP transmission,
`
`in which the support for multi-user scheduling or interference cancelling is insufficient.
`
`[0049] For example, in current specifications, it has been specified that, for DMRS type 1,
`
`15
`
`if a terminal device is scheduled with one codeword and assigned with the antenna port
`
`mapping with indices of {2, 9, 10, 11 or 30} in Table 1 as below, or if the terminal device is
`
`scheduled with two codewords, the terminal device may assume that all of the remaining
`
`orthogonal antenna ports are not associated with transmission of Physical Downlink Shared
`
`Channel (PDSCH) to another terminal device.
`
`20
`
`2
`9
`10
`11
`30
`
`0,1
`0-2
`0-3
`0,2
`0,2,4,6
`
`1
`
`2
`
`2
`2
`2
`2
`
`0
`1
`2
`
`3
`
`2
`2
`
`2
`
`2
`
`0-4
`0, 1,2,3,4,6
`0, 1,2,3,4,5,6
`0,1,2,3,4,5,6,7
`
`2
`
`2
`
`2
`
`2
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`For DMRS type 2, if a terminal device is scheduled with one codeword and assigned with
`
`the antenna port mapping with indices of {2, 10 or 23} in Table 2 as below, or if the
`
`terminal device is scheduled with two codewords, the terminal device may assume that all
`
`of the remaining orthogonal antenna ports are not associated with transmission of POSCH
`
`5
`
`to another terminal device.
`
`2
`10
`23
`
`1
`2
`2
`
`0,1
`0-3
`0,2
`
`1
`1
`1
`
`0
`1
`2
`
`3
`4
`5
`
`3
`3
`2
`
`2
`2
`2
`
`0-4
`0-5
`0,1,2,3,6
`0, 1,2,3,6,8
`0, 1,2,3,6, 7,8
`0,1,2,3,6,7,8,9
`
`1
`
`2
`2
`2
`
`2
`
`[0050] However, for multi-TRP transmission, the above assumptions may be not sufficient.
`
`For example, FIG. 3 shows an example scenario of multi-TRP transmission.
`
`In the
`
`example as shown in FIG. 3, it is assumed that DMRS type 1 and one codeword are
`
`10
`
`configured. As shown in FIG. 3, two TRPs 310-1 and 310-2 communicate with a terminal
`
`device 320. The tenninal device 320 is configured with DMRS ports O and 2 for OL
`
`DMRS transmission. For example, DMRS port O coming from CDM group O 1s
`
`associated with the TRP 310-1, which DMRS port 2 coming from CDM group 1 1s
`
`associated with the TRP 310-2.
`
`In this event, the index of the antenna port mapping is 11
`
`15
`
`as shown above in Table 1. That is, the terminal device 320 may assume that all of other
`
`orthogonal antenna ports than OMRS ports O and 2 are not associated with transmission of
`
`POSCH to another terminal device.
`
`[0051] However, in the scenario as shown in FIG.3, DMRS port 2 may or may not be used
`
`for DMRS transmission from the TRP 310-1 to another tenninal device.
`
`If DMRS port 2
`
`20
`
`is used for DMRS transmission from the TRP 310-1 to another terminal device, the
`
`terminal device 320 may suffer from interference from the other terminal device.
`
`In
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`addition, DMRS port 1 may or may not be used for DMRS transmission from the TRP
`
`310-2 to another terminal device.
`
`If DMRS port 1 is used for DMRS transmission from
`
`the TRP 310-2 to another tenninal device, the terminal device 320 may also suffer from
`
`interference from the other terminal device. As can be seen that, in current DMRS tables,
`
`5
`
`such information has not been indicated.
`
`In this event, the terminal device 320 cannot
`
`perform interference cancellation accurately.
`
`[0052] Embodiments of the present disclosure provide a solution for DMRS configuration.
`
`This solution enables multi-user scheduling for multi-TRP transmission.
`
`In addition,
`
`according to this solution, interference from other terminal devices can be indicated, and
`
`10
`
`thus interference cancellation can be achieved more accurately.
`
`[0053] Principles and implementations of the present disclosure will be described in detail
`
`below with reference to FIG. 4, which shows a process 400 for DMRS configuration
`
`according to some implementations of the present disclosure.
`
`For the purpose of
`
`discussion, the process 400 will be described with reference to FIG. 1B. The process 400
`
`15 may involve the network device 110, the terminal device 120 and the TRPs 130 in FIG. 1B.
`
`[0054] As