Patent Publication Number: US-2020295910-A1

Title: Methods and devices for reference signal configuration

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 16/633,312 filed Jan. 23, 2020, which is a National Stage of International Application No. PCT/CN2017/094022 filed Jul. 24, 20217, the disclosures of which are incorporated herein in their entirety by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present disclosure generally relate to the field of communications, and in particular, to methods and devices for reference signal (RS) configuration. 
     BACKGROUND 
     With the development of communication technologies, multiple types of services 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 beam management, reference signal transmission, and so on, are studied for new radio access. 
     In downlink transmission, a network device (for example, an eNB, a gNB, or a Transmission Reception Point (TRP)) transmits a downlink RS, such as a downlink Demodulation Reference Signal (DMRS), a Channel State Information-Reference Signal (CSI-RS), a downlink Phase Tracking Reference Signal (PTRS), and a fine time/frequency 
     Tracking Reference Signal (TRS), to a terminal device (for example, user equipment (UE)). Upon receipt of the RS, the terminal device may perform quality measurement of the channel between the network device and the terminal device, estimation of the channel, and so on. Generally, the network device transmits a RS configuration to the terminal device prior to the RS transmission, so as to notify the terminal device information of the RS, the allocated resources, and the like. 
     In uplink transmission, a terminal device (for example, UE) transmits an uplink RS, such as an uplink DMRS, an uplink PTRS, and a SRS, to a network device (for example, an eNB, a gNB, or a TRP). Upon receipt of the RS, the network device may perform quality measurement of the channel between the terminal device and the network device, estimation of the channel, and so on. Generally, the network device transmits a RS configuration to the terminal device prior to the RS transmission, so as to notify the terminal device information of the RS, the allocated resources, and the like. 
     Conventionally, a sequence of downlink DMRS (also referred to as a “DMRS sequence”) is fixed and generated with the same initial value for one Physical Downlink Shared Channel (PDSCH). However, such a fixed DMRS sequence cannot support a plurality of RS ports (or layers) for one PDSCH from one or more TRPs. In addition, a sequence of uplink DMRS is fixed and generated with the same initial value for one Physical Uplink Shared Channel (PUSCH). However, such a fixed DMRS sequence cannot support a plurality of RS ports (or layers) for one PUSCH transmitted to one or more TRPs. 
     SUMMARY 
     In general, example embodiments of the present disclosure provide methods and devices for RS configuration. 
     In a first aspect, there is provided a method implemented in a network device. According to the method, one or more RS patterns are determined for a plurality of RS ports. A RS pattern indicates a configuration of a RS to be transmitted between the network device and a terminal device via one or more RS ports. Afterwards, information of the RS patterns is transmitted to the terminal device. 
     In a second aspect, there is provided a method implemented in a terminal device. According to the method, the terminal device receives, from a network device, information of one or more RS patterns for a plurality of RS ports. A RS pattern indicates a configuration of a RS to be transmitted between the network device and the terminal device via one or more RS ports. 
     In a third aspect, there is provided a network device. The network device 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 performs actions. The actions comprise: determining one or more RS patterns for a plurality of RS ports, a RS pattern indicating a configuration of a RS to be transmitted between the network device and a terminal device via one or more RS ports; and transmitting information of the RS patterns to the terminal device. 
     In a fourth aspect, there is provided a terminal device. The terminal device comprises a processor and a memory coupled to the processor. The memory stores instructions that when executed by the processor, cause the terminal device to performs actions. The actions comprise: receiving, from a network device, information of one or more RS patterns for a plurality of RS ports, a RS pattern indicating a configuration of a RS to be transmitted between the network device and the terminal device via one or more RS ports. 
     Other features of the present disclosure will become easily comprehensible through the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIGS. 1A and 1B  are schematic diagrams  100  and  160  of a communication environment in which embodiments of the present disclosure can be implemented, respectively; 
         FIG. 2  shows a flowchart of a method  200  for RS configuration in accordance with some embodiments of the present disclosure; 
         FIGS. 3A-3F  show schematic diagrams of RS patterns according to embodiments of the present disclosure, respectively; 
         FIGS. 4A-4E  show schematic diagrams of indications of RS patterns according to embodiments of the present disclosure, respectively; 
         FIG. 5  shows a flowchart of a method  500  for RS configuration in accordance with some embodiments of the present disclosure; 
         FIG. 6  shows a block diagram of a network device  600  in accordance with some embodiments of the present disclosure; 
         FIG. 7  shows a block diagram of a terminal device  700  in accordance with some embodiments of the present disclosure; and 
         FIG. 8  is a simplified block diagram of a device  800  that is suitable for implementing embodiments of the present disclosure. 
     
    
    
     Throughout the drawings, the same or similar reference numerals represent the same or similar element. 
     DETAILED DESCRIPTION 
     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 described below. 
     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. 
     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 terminal devices can 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 Transmission Reception Point (TRP), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a low power 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 TRP as examples of the network device. 
     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 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 examples of the terminal device. 
     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. The term “includes” and its variants are to be read as open terms that mean “includes, but is not limited to.” 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, may be included below. 
     Communication discussed in the present disclosure may conform to any suitable standards including, but not limited to, New Radio Access (NR), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM) and the like. Furthermore, 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 (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G) communication protocols. 
       FIG. 1A  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 . The network device  110  transmits a reference signal (for example, a downlink DMRS sequence) to the terminal device  120 . For instance, the network device  110  transmits RS(s) via M+N RS ports (referred to as “ports” for short) in one PDSCH. In other words,  FIG. 1A  shows a scenario of totally M+N layers in one PDSCH from one TRP. 
     On the other hand,  FIG. 1A  also shows an uplink transmission in the communication network  100 . In particular, the terminal device  120  transmits a reference signal (for example, an uplink DMRS sequence) to the network device  110 . For instance, the terminal device  120  transmits RS(s) via M+N RS ports (referred to as “ports” for short) in one PUSCH. In other words,  FIG. 1A  also shows a scenario of totally M+N layers in one PUSCH transmitted to one TRP. 
       FIG. 1B  shows another example communication network  160  in which embodiments of the present disclosure can be implemented. The network  160  includes two network devices  110  and  130 , and a terminal device  120 . The network devices  110  and  130  transmit reference signals to the terminal device  120 , respectively. In particular, the network device  110  transmits DMRS sequence(s) via MRS ports to the terminal device  120 , and the network device  110  transmits DMRS sequence(s) via N RS ports to the terminal device  120 . Both of the DMRS transmissions are in one PDSCH. In other words,  FIG. 1B  shows a scenario of totally M+N layers in one PDSCH from 2 TRPs. 
     On the other hand,  FIG. 1B  also shows an uplink transmission in the communication network  100 . In particular, the terminal device  120  transmits reference signals to the network devices  110  and  130 , respectively. In particular, the terminal device  120  transmits DMRS sequence(s) via M RS ports to the network device  110 , and the terminal device  120  transmits DMRS sequence(s) via N RS ports to the network device  130 . Both of the DMRS transmissions are in one PUSCH. In other words,  FIG. 1B  also shows a scenario of totally M+N layers in one PUSCH transmitted to  2  TRPs. 
     It is to be understood that the number of base stations and terminal devices is only for the purpose of illustration without suggesting any limitations. The networks  100  and  160  may include any suitable number of network devices and/or the terminal devices adapted for implementing embodiments of the present disclosure. 
     Conventionally, different RS ports can only transmit the same DMRS sequence in one PDSCH and/or one PUSCH. In other words, the DMRS sequence is fixed and generated with the same initial value for one PDSCH and/or one PUSCH. However, there is no mechanism to support different DMRS sequences to be transmitted via a plurality of RS ports in one PDSCH and/or one PUSCH. 
     In order to solve the problems above and one or more of other potential problems, a solution for RS configuration is provided in accordance with example embodiments of the present disclosure. In one embodiment, flexible RS patterns may be provided to a plurality of RS ports (or layers) from one or more TRPs, for example, the RS ports may be transmitted for one PDSCH. In another embodiment, flexible RS patterns may be provided to a plurality of RS ports (or layers) transmitted to one or more TRPs, for example, the RS ports may be transmitted for one PUSCH. In this way, flexibility of RS configuration can be achieved, while no extra signaling overhead is increased. 
     Principle and implementations of the present disclosure will be described in detail below with reference to  FIGS. 2-8 , in which  FIG. 2  shows a flowchart of a method  200  for RS configuration in accordance with some embodiments of the present disclosure. With the method  200 , the above and other potential deficiencies in the conventional approaches can be overcome. It would be appreciated by those skilled in the art that the method  200  may be implemented by a network device, such as a network device  110  or  130 , or other suitable devices. 
     The method  200  is entered at  210 , where one or more RS patterns are determined for a plurality of RS ports. The RS pattern indicates a configuration of a RS to be transmitted between the network device and a terminal device via one or more RS ports. In some embodiments, a RS pattern may indicate a configuration of a RS to be transmitted to a terminal device via one or more RS ports. Alternatively, or in addition, the RS pattern may also indicate a configuration of a RS to be transmitted from a terminal device via one or more RS ports. 
     According to embodiments of the present disclosure, the RS may include one or more of: a downlink Demodulation Reference Signal (DMRS), an uplink Demodulation 
     Reference Signal (DMRS), a Channel State Information Reference Signal (CSI-RS), a Sounding Reference Signal (SRS), a Phase Tracking Reference Signal (PTRS), Tracking Reference Signal (TRS), and/or the like. For purpose of discussion, some embodiments of the present disclosure are described with reference to DMRS as examples of the RS. 
     In some embodiments, one or more RS sequences may be transmitted via RS ports, and the RS sequences may be generated from one or several initial values. 
     In some embodiments, the RS ports may be divided into a plurality of RS port groups. Then, a RS pattern may be determined for each of the plurality of RS port groups. The RS ports may be divided in several ways, for example, system conditions, standards requirements, time/frequency offset, delay spread, frequency spread, and/or the like. In an embodiment, the RS ports may be divided into a plurality of Quasi-Co-Location (QCL) groups. In this case, a RS port group may be a QCL group. In one embodiment, the RS ports within one group may be QCLed. In another embodiment, the RS ports in different groups may be non-QCLed. 
     In some embodiments, the RS pattern may include factors, such as, an initial value for generating a RS to be transmitted via a RS port or via RS ports in a RS port group, information of the number of symbols used by a RS port or a RS port group, information of resource elements used by a RS port or a RS port group, a multiplexing mode of a RS port or a RS port group, information of RS port group, and so on. Thus, the RS pattern may be determined by determining one or more of the above factors. 
     As an example, the initial value for generating the RS may be determined based on at least one of: a slot index, a symbol index, an identification of a cell (for example cell ID), and identification of the TRP, an identification of the terminal device, a Radio Network Temporary Identity (RNTI), a cyclic prefix (CP) type, a link type (for example downlink or uplink or sidelink), an index of a RS port group, an index of QCL parameter set, a scrambling identity parameter, a higher layer indicated scrambling identity parameter, an identification of DMRS configuration type, an identification of a bandwidth part, an identification of a carrier component, an identification of subcarrier spacing, and so on. 
     According to embodiments of the present disclosure, different RS ports or different RS port groups may have independent initial values for RS sequence generation. The sequence (denoted as R 1 ) may be defined with Pseudo-noise (PN) sequence, and the PN sequence generator may be initialized with an initial value, C init . 
     In some embodiments, different RS ports or RS port groups may have independent RS sequences. In one embodiment, for the DMRS ports corresponding to one PDSCH or PUSCH, different DMRS ports or different DMRS port groups may have independent RS sequences and/or independent initial values for RS sequence generation. In one embodiment, for the DMRS ports corresponding to multiple PDSCHs or multiple PUSCHs or multiple PDCCHs for one UE in the same time and/or frequency resources, different DMRS ports or different DMRS port groups may have independent RS sequences and/or independent initial values for RS sequence generation. 
     In some embodiments, one PTRS port may be associated with one DMRS port in one DMRS ports group. For multiple PTRS ports, the PTRS ports may be associated with different DMRS ports. In one embodiment, the PTRS sequence can be same with that of the associated DMRS port. In another embodiment, for multiple DMRS groups according to one PDSCH or PUSCH, there may be multiple PTRS ports. The PTRS sequence on different PTRS ports may be independent. For example, the PTRS sequence may be generated with independent initial values calculated with at least one of the parameters in 
     QCL parameter set. 
     In some embodiments, the initial value C init  may be calculated with parameter related to at least one of: slots index ns, symbol index  1 , cell_ID N ID , UE_ID U ID , RNTIn RNTI , CP type N CP , link type N link_type , RS port group index G i , QCL parameter set index Q i , scrambling identity parameter-1 S ID , scrambling identity parameter-2 n SCID , bandwidth part ID B ID , carrier component ID C ID , subcarrier spacing ID SC ID , and so on. In an example, the initial value C init  may be obtained by: 
         C   init   =a   0   ·n   s   +a   1   ·l+a   2   ·N   ID   +a   3   ·U   ID   +a   4   ·N   CP   +a   5   ·N   link     type     a   6   ·N   RNTI   +a   7   ·Q   i   +a   8   ·n   SCID   a   9   ·G   i   +a   10   ·S   ID   +a   11   ·B   ID   +a   12   ·C   ID   +a   13   ·SC   ID    +b   j   ·X·y    (1)
 
     where a i  is coefficient, i=0, 1, . . . 13, and any of the coefficient can be zero. If a i =0, it means that the corresponding parameter is not included in the calculation of the initial value. 
     In one embodiment, X is one of the parameters, Y is another one of the parameters, b j  is coefficient for the product of the two or more parameters, j is non-negative integer, and any of the coefficient can be zero. If b j =0, it means that the corresponding product of two or more parameters is not included in the calculation of the initial value. In one embodiment there may be no coefficient of b j , that is there is no product of two or more parameters in the calculation of the initial value. In some embodiments, the initial value may be implemented with one or more bits. 
     In another example, the initial value C init  may be obtained by: 
         C   init   =a   0 ·[ n   s   /K ]+ a   1   ·l+a   2   ·N   ID   +a   3   ·U   ID   +a   4   ·N   CP   +a   5   ·N   link     type     +a   6   ·N   RNTI   +a   7   ·Q   i   +a   8   ·n   SCID   +a   9   ·G   i   +a   10   ·S   ID   +a   11   ·B   ID   +a   12   ·C   ID   +a   13    ·SC   ID   +b   0 ·[ n   s   /K ]· X+b   j   ·Y·Z    (2)
 
     where a i  is coefficient, i=0, 1, . . . 13, and any of the coefficient can be zero. If a i =0, it means that the corresponding parameter is not included in the calculation of the initial value. And K is one of the coefficients for slot index, and K is integer no less than 1. In one embodiment, X is one of the parameters, b 0  is coefficient for the product of [n s /K] and another one or more of the parameters. If b 0 =0, it means that the corresponding product of [n s /K] and another one or more of the parameters is not included in the calculation of the initial value. Y is one of the parameters, Z is another one of the parameters, b j  is coefficient for the product of the two or more parameters, j is positive integer and no less than 1, and any of the coefficient can be zero. If b j =0, it means that the corresponding product of two or more parameters is not included in the calculation of the initial value. In one embodiment there may be no coefficient of b j , that is there is no product of two or more parameters in the calculation of the initial value. In some embodiments, the initial value may be implemented with one or more bits. 
     In some embodiments, UE can obtain at least one of the parameters: slots index ns, symbol index l, cel_ID N ID UE_ID U ID , RNTI n RNTI , CP type N CP , link type N link_type , RS port group index G i , QCL parameter set index Q i , scrambling identity parameter-1 S ID , scrambling identity parameter-2 n SCID , bandwidth part ID BID, carrier component ID C ID , subcarrier spacing ID SC ID , number of symbols in one slot, carrier frequency range, number of RS ports, number of physical resource blocks and so on. For example, for the parameters, UE can be configured with or UE can detect or UE can infer through other information transmitted from the network device. In some embodiments, at least one of the parameters may have one or more values. In some embodiments, for at least one of the different parameters, and/or different values for at least one of the parameters, the initial value for the RS generation may be different. 
     In some embodiments, when at least one of the parameters is configured with different values, the number of bits of the initial value for the RS generation may be different. For example, the parameters include at least one of the value of subcarrier spacing, the number of slots in one subframe or in 1 ms or in 10 ms, the number of symbols in one slot, the value of carrier frequency, and the number of synchronization signal (SS) blocks within an SS burst. In one embodiment, the different values of at least one of the parameters may be divided into R subsets. For each subset, at least one of the values may be included. For different subsets, the number of bits of initial value for RS sequence generation may be different. Specifically, for subset p i  where i=1,2, . . . R, the number of bits of initial value may be d i . For example, the values in different subsets may be non-overlapping or partial overlapping. For another example, the number of values in different subsets may be different or same. For still another example, the number of values in each subset is 1, that is, there may be no grouping for the different values. 
     In some embodiments, when at least one of the parameters is configured with different values, at least one of the coefficients in formula (1) and/or formula (2) may have different values and/or different sets of values and/or different number of values according to the different values for at least one of the configured parameters. 
     In some embodiments, when at least one of the parameters is configured with different values, at least one of the parameters related to the calculation of the initial value may have different values and/or different sets of values and/or different maximum values and/or different number of values. 
     In some embodiments, when at least one of the parameters is configured with different values, the parameters related to calculation of initial value may be different. In other words, for example, when at least one of the parameters is configured with one value, then a set of parameters may be related to the calculation of the initial value. When at least one of the parameters is configured with another value, then another set of parameters may be related to the calculation of the initial value. In some embodiments, when at least one of the parameters is configured with some fixed values, at least one of the parameters may be related to the calculation of the initial value. In other words, when at least one of the parameters is configured with other values, at least one of the parameters may not be related to the calculation of the initial value. 
     In one embodiment, the subcarrier spacing value may be configured with different values, for example the value may be one of {15 kHz, 30 kHz, 60 kHz, 120 kHz, 240 kHz, 480 kHz}. When the subcarrier spacing value is configured with different values, the coefficient(s) for slot index and/or symbol index may have different values. In one example, when the subcarrier spacing value is configured with different values, in formula (1), the coefficient value a 0  and/or a 1  and/or b j  may have different values. In another example, when the subcarrier spacing value is configured with different values, in formula (2), the coefficient(s) a 0  and/or a 1  and/or K and/or b 0  may have different values. In one example, when subcarrier spacing value is configured with 15 kHz, the value K in formula (2) may be 1 and/or 2 and/or 10 and/or 20. In another example, when subcarrier spacing value is configured with 30 kHz, the value K in formula (2) may be 2 and/or 4 and/or 20 and/or 40. In another example, when subcarrier spacing value is configured with 60 kHz, the value K in formula (2) may be 4 and/or 8 and/or 40 and/or 80. In another example, when subcarrier spacing value is configured with 120 kHz, the value K in formula (2) may be 8 and/or 80. In another example, when subcarrier spacing value is configured with 240 kHz, the value K in formula (2) may be 16 and/or 160. In another example, when subcarrier spacing value is configured with 480 kHz, the value K in formula (2) may be 32 and/or 320. 
     In one embodiment, the subcarrier spacing value may be configured with different values, for example the value may be one of {15kHz, 30kHz, 60kHz, 120kHz, 240 kHz, 480 kHz}. When the subcarrier spacing value is configured with different values, the coefficient for CP type may have different values. In one example, when the subcarrier spacing value is configured with different values, in formula (1), the coefficient value a 4  and/or b j  may have different values. In another example, when the subcarrier spacing value is configured with different values, in formula (2), the coefficient(s) a 4  and/or b j (j&gt;=1) may have different values. 
     In another embodiment, the subcarrier spacing value may be configured with a set of values. For example, the set of values may be at least one of {15 kHz, 30 kHz, 60 kHz, 120 kHz, 240 kHz, 480 kHz}. In one embodiment, when the subcarrier spacing value is configured with some of values in the set, the CP type may not be related to the calculation of the initial value. In another embodiment, only when the subcarrier spacing value is configured with some of the values in the set, the CP type may be related to the calculation of the initial value. In one example, when subcarrier spacing value is configured with 60 kHz, the CP type may be related to the calculation of the initial value. In another example, when the subcarrier spacing is configured with other values except 60 kHz, the CP type may not be related to the calculation of the initial value. In another example, when subcarrier spacing value is configured with 60 kHz, the coefficient value of CP type a 4  may be non-zero. In another example, when the subcarrier spacing is configured with other values except 60 kHz, the coefficient value of CP type a 4  may be zero. 
     In one embodiment, the number of symbols in one slot may be configured with different values, for example the value may be 7 and/or 14 when subcarrier spacing value is configured with any of {15 kHz, 30 kHz}. The value may be 7 and/or 14 when subcarrier spacing value is configured with 60 kHz and CP type is configured with normal CP. The value may be 6 and/or 12 when subcarrier spacing value is configured with 60 kHz and CP type is configured with extended CP. The value may be 14 when subcarrier spacing value is configured with any of {120 kHz, 240 kHz, 480 kHz}. When the number of symbols in one slot is configured with different values, the coefficient(s) for slot index and/or symbol index may have different values. In one example, when the number of symbols in one slot is configured with different values, in formula (1), the coefficient value a 0  and/or a 1  and/or b j  may have different values. In another example, when the number of symbols in one slot is configured with different values, in formula (2), the coefficient(s) a 0  and/or a 1  and/or K and/or b 0  may have different values. In one example, when number of symbols in one slot is configured with 7 and subcarrier spacing value is configured with 15 kHz, the value K in formula (2) may be 2 and/or 20. In another example, when number of symbols in one slot is configured with  14  and subcarrier spacing value is configured with 15 kHz, the value K in formula (2) may be 1 and/or 10. In another example, when number of symbols in one slot is configured with 7 and subcarrier spacing value is configured with 30 kHz, the value K in formula (2) may be 4 and/or 40. In another example, when number of symbols in one slot is configured with  14  and subcarrier spacing value is configured with 30 kHz, the value K in formula (2) may be 2 and/or 20. In another example, when number of symbols in one slot is configured with 7 and/or 6 and subcarrier spacing value is configured with 60 kHz, the value K in formula (2) may be 8 and/or 80. In another example, when number of symbols in one slot is configured with 14 and/or 12 and subcarrier spacing value is configured with 60 kHz, the value K in formula (2) may be 4 and/or 40. 
     In some embodiments, the initial value may be changed within a time duration. In some embodiments, the initial value may be repeated after a time duration. For example, the initial value may be calculated at a timing position, and may have same or different values within a time duration from the timing position. And the initial value repeated after a time duration from the timing position. In some embodiments, the time duration may be based on the subcarrier spacing values and/or number of symbols in one slot. For example, the time duration may be one or several slots based on the subcarrier spacing values and/or number of symbols in one slot. In one embodiment, the time duration may be fixed to L ms. In one embodiment, the time duration may be fixed to be lms, that is a time duration of one subframe. 
     In one embodiment, the subcarrier spacing value may be configured with different values, for example the value may be one of {15kHz, 30kHz, 60 kHz, 120 kHz, 240 kHz, 480 kHz}. When the subcarrier spacing value is configured with different values, the values and/or ranges and/or maximum values for slot index and/or symbol index may be different. 
     In one example, when subcarrier spacing value is configured with 15 kHz, the values for slot index may be at least one of {0} or {0, 1} or {0, 1, . . . 9} or {0, 1, 2, . . . 19}. In another example, when subcarrier spacing value is configured with 15 kHz, the maximum value for slot index may be 0 or 1 or 9 or 19. In another example, when subcarrier spacing value is configured with 15 kHz, the number of values for slot index may be 1 or 2 or 10 or 20. In another example, when subcarrier spacing value is configured with 30 kHz, the values for slot index may be at least one of {0,1} or {0, 1, 2, 3} or {0, 1, 2, 3 . . . 19} or {0, 1, 2, . . . 39}. In another example, when subcarrier spacing value is configured with 30 kHz, the maximum value for slot index may be 1 or 3 or 19 or 39. In another example, when subcarrier spacing value is configured with 30 kHz, the number of values for slot index may be 2 or 4 or 20 or 40. In another example, when subcarrier spacing value is configured with 60 kHz, the values for slot index may be at least one of {0, 1, 2, 3} or {0, 1, 2, 3, 4, 5, 6, 7} or {0, 1, 2, 3 . . . 39} or {0, 1, 2, . . . 79}. In another example, when subcarrier spacing value is configured with 60 kHz, the maximum value for slot index may be 4 or 7 or 39 or 79. In another example, when subcarrier spacing value is configured with 60 kHz, the number of values for slot index may be 4 or 8 or 40 or 80. In another example, when subcarrier spacing value is configured with 120 kHz, the values for slot index may be at least one of {0, 1, 2, 3, 4, 5, 6, 7} or {0, 1, 2, . . . 79}. In another example, when subcarrier spacing value is configured with 120 kHz, the maximum value for slot index may be 7 or 79. In another example, when subcarrier spacing value is configured with 120 kHz, the number of values for slot index may be 8 or 80. In another example, when subcarrier spacing value is configured with 240 kHz, the values for slot index may be at least one of {0, 1, 2, 3, , , , 15} or {0, 1, 2, . . . 159}. In another example, when subcarrier spacing value is configured with 240 kHz, the maximum value for slot index may be 15 or 159. In another example, when subcarrier spacing value is configured with 240 kHz, the number of values for slot index may be 16 or 160. In another example, when subcarrier spacing value is configured with 480 kHz, the values for slot index may be at least one of {0, 1, 2, 3, . . . 31} or {0, 1, 2, . . . 319}. In another example, when subcarrier spacing value is configured with 480 kHz, the maximum value for slot index may be 31 or 319. In another example, when subcarrier spacing value is configured with 480 kHz, the number of values for slot index may be 32 or 320. 
     In one example, when subcarrier spacing value is configured with 15 kHz, there may be at least one set of {0, 1, . . . 6} or {0, 1, 2, . . . 13}, and the values for symbol index may be at least one of the values for each set. In another example, when subcarrier spacing value is configured with 30 kHz, there may be at least one set of {0, 1, . . . 6} or {0, 1, 2, . . . 13}, and the values for symbol index may be at least one of the values for each set. In another example, when subcarrier spacing value is configured with 60 kHz, there may be at least one set of {0, 1, . . . 6} or {0, 1, 2, . . . 13} or {0, 1, . . . 5} or {0, 1, . . . 11}, and the values for symbol index may be at least one of the values for each set. In another example, when subcarrier spacing value is configured with 120 kHz or 240 kHz or 480 kHz, the values for symbol index may be at least one of {0, 1, . . . 13}. 
     In one embodiment, the subcarrier spacing value may be configured with different values, for example the value may be one of {15 kHz, 30 kHz, 60 kHz, 120 kHz, 240 kHz, 480 kHz}. When the subcarrier spacing value is configured with different values, the CP type N CP  may have different values and/or different number of values. In one example, when subcarrier spacing value is configured with 15 kHz or 30 kHz or 120 kHz or 240 kHz or 480 kHz, the CP type N CP  may fixed to zero. Or the number of values for CP type is 1. In another example, when subcarrier spacing value is configured with 60 kHz, the CP type N CP  may 0 or 1. Or the number of values for CP type is 2. For example, when the cyclic prefix is configured with normal CP, the CP type parameter N CP  may be 0. For example, when the cyclic prefix is configured with extended CP, the CP type parameter N CP  may be 1. 
     In one embodiment, the number of symbols in one slot may be configured with different values, for example the value may be 7 and/or 14 when subcarrier spacing value is configured with any of {15 kHz, 30 kHz}. The value may be 7 and/or 14 when subcarrier spacing value is configured with 60 kHz and CP type is configured with normal CP. The value may be 6 and/or 12 when subcarrier spacing value is configured with 60 kHz and CP type is configured with extended CP. The value may be 14 when subcarrier spacing value is configured with any of {120 kHz, 240 kHz, 480 kHz}. When the number of symbols in one slot is configured with different values, the symbol index may have different values. 
     In some embodiments, for different DMRS ports or DMRS port groups or QCL parameters set, the DMRS sequence and/or initial value for DMRS sequence generation may be independently configured. Specifically, the DMRS sequence and/or initial value for 
     DMRS sequence generation may be associated to the value of Cell ID of different TRPs/cells. By way of example, for the DMRS ports or DMRS port group QCLed to the RS from TRP 1 , the DMRS sequence and/or initial value for DMRS sequence generation may be associated to the cell ID of TRP 1 . For the DMRS ports or DMRS port group QCLed to the RS from TRP 2 , DMRS sequence and/or initial value for DMRS sequence generation may be associated to the cell ID of TRP 2 . 
     In some embodiments, the scrambling identity parameter S ID  may be one of the parameters related to the calculation of initial value C init . The value of parameter S ID  may be independently configured for different DMRS ports or DMRS port groups or QCL parameters set. For example, if no value if provided by higher layers, then the value may be fixed for one cell or TRP. For example, the value is same with cell ID. For another example, the value of parameter S ID  may be provided in the QCL parameters. For different QCL parameters sets, the value of parameter S ID  may be same or different. In one embodiment, for different DMRS ports or different DMRS port groups or different QCL parameters, the value S ID  is independently configured. Specifically, the value S ID  may be associated to the value of Cell ID of different TRPs/cells. By way of example, for the DMRS ports or DMRS port group QCLed to the RS from TRP 1 , the value S ID  may be the cell ID of TRP 1 . For the DMRS ports or DMRS port group QCLed to the RS from TRP 2 , the value S ID  may be the cell ID of TRP 2 . 
     In one embodiment, the carrier frequency range and/or number of RS ports may be configured with different values. When the carrier frequency range and/or number of RS ports is configured with different values, the coefficient(s) for scrambling ID and/or the values for scrambling ID and/or the number of values for scrambling ID for the initial value of RS sequence generation may have different values. In one example, when the carrier frequency range and/or number of RS ports is configured with different values, in formula (1), the coefficient value a 8  and/or a 10  and/or b j  may have different values. In another example, when the carrier frequency range and/or number of RS ports is configured with different values, in formula (2), the coefficient(s) a 8  and/or a 10  and/or b j  may have different values. In one example, when the carrier frequency range and/or number of RS ports is configured with different values, in formula (1) and/or formula (2), the number of values and/or the values of n SCID  and/or S ID  may be different. 
     In some alternative embodiments, the initial value C init  may be calculated by: 
         C   init =(└ n   s /2┘+1) (2 n   ID   (n     SCID,i     ) +1)2 16   +n   SCID    (3)
 
     where i may be the index of DMRS ports group or QCL parameters set. 
     The quantities n ID   (N     SCID,i     )  may be given by QCL parameters or DMRS port groups. If no value is provided by higher layers n ID   (n     SCID,i     ) =n ID   cell , which is the cell ID of the TRP or cell. Otherwise, n ID   (n,     SCID,i     ) , which is provided in the QCL parameters. 
     For different DMRS groups or different QCL parameters, the value n ID   DMRS,i  is independently configured. Specifically, the value n ID   DMRS,i  may be associated to the value of Cell ID of different TRPs/cells. By way of example, for the DMRS group QCLed to the RS from TRP 1 , the value n ID   DMRS,i  may be the cell ID of TRP 1 . For the DMRS group QCLed to the RS from TRP 2 , the value n ID   DMRS,i  may be the cell ID of TRP 2 . 
     In some embodiments, the DMRS sequence and/or initial value for sequence generation of DMRS for PDCCH may be independently or differently configured for different TRPs and/or different cells and/or different beams and/or different UEs and/or different UE groups. 
     In some embodiments, at least one of symbol index l, RNTI n RNTI , scrambling identity n ID  may be related to the initial value C init  for the generation of DMRS for PDCCH. In one embodiment, for different PDCCHs, for example from different TRPs and/or cells and/or beams and/or different UEs and/or different UE groups, the value of symbol index l and/or the value of RNTI n RNTI  and/or value of scrambling identity n ID  may be different. In another embodiment, for different PDCCHs, for example from different TRPs and/or cells and/or beams and/or different UEs and/or different UE groups, the number of values of symbol index l and/or the number of values of RNTI n RNTI  and/or number of values of scrambling identity n ID  may be different. In another embodiment, for different PDCCHs, for example from different TRPs and/or cells and/or beams and/or different UEs and/or different UE groups, the value of coefficient of symbol index l and/or the value of coefficient of RNTI n RNTI  and/or value of coefficient of scrambling identity n ID  may be different. For example, UE may be configured to decode multiple PDCCHs from multiple TRPs. 
     In some embodiments, when the carrier frequency range and/or bandwidth and/or number of physical resource blocks is configured with different values. At least one of value of symbol index l, value of RNTI n RNTI , value of scrambling identity n ID , number of values of symbol index l, number of values of RNTI n RNTI , number of values of scrambling identity nID, value of coefficient of symbol index  1 , value of coefficient of RNTI n RNTI , value of coefficient of scrambling identity n ID  may be different. In one example, when the number of physical resource blocks is larger than X, the number of symbol index l is 2. In another example, when the number of physical resource blocks is smaller than X, the number of symbol index l is 3. In one example, when the number of physical resource blocks is larger than X, the value of symbol index l is at least one of {0, 1}. In another example, when the number of physical resource blocks is smaller than X, the value of symbol index lis at least one of {0, 1, 2}. In one example, when the carrier frequency range is up to 3 GHz, the number of n ID  is less than 4 or equals to 4. In another example, when the carrier frequency range is from 3 GHz to 6 GHz, the number of n ID  is less than 8 or equals to 8. In another example, when the carrier frequency range is from 6 GHz to 52.6 GHz, the number of n ID  is less than 64 or equals to 64. 
     As a further alternative, in some embodiments, the initial value C init  may be calculated by: 
         c   init =(└ n   s /2┘+1)*(2 N   ID   cell +1*2 16   +n   RNTI *2 i   +n   ID    (4)
 
     For multiple PDCCHs from multiple TRPs, UE may blindly decode PDCCH with different DMRS sequences, where each sequence is generated with initial value according to different TRPs. For example, for different cells, nRNTI is different. 
     For different beams or different multi-users in one TRP, different n ID  may be used. For example, for a broadcast or multi-cast PDCCH, the n ID  may be assumed to be zero. In another example, for one UE, the supported number of different PDCCH DMRS sequence in one TRP equals to or less than 2.{circumflex over ( )}i. 
     According to embodiments of the present disclosure, different sequences may be generated for different RS ports and/or RS ports groups, e.g. for one UE and/or for one PDSCH. For different RS ports, the sequence may be generated with different initial values. For example, for RS port i, the sequence may be generated with an initial value, C init_i . 
     In some embodiments, the RS ports configured for one UE may be divided into groups. For different RS port groups, different sequences may be generated with different initial values. By way of example, for RS ports group j, the sequence is generated with an initial value, C init_j . 
     In some embodiments, the sequence may be generated with the same initial value in one RS port group. For instance, for the RS ports in a RS port group with frequency domain and/or time domain CDM, the sequence should be generated with the same initial value for the RS port group. 
     In some embodiments, the sequence may be generated with same initial value for the adjacent REs in time and/or frequency domain for RS transmission. In some embodiments, the sequence may be generated with same initial value for the adjacent symbols for RS transmission. In some embodiments, the sequence may be generated with same initial value for the REs used for CDM in time and/or frequency domain, in other words, the sequence values may be same on the REs used for CDM in time and/or frequency domain. 
     In some embodiments, in the determination of the RS patterns, if a first RS port and a second port are mapped in the same symbol and multiplexed with Code Division Multiplexing (CDM) in frequency domain, it can be determined that the first and second RS ports use the same RS base sequence. For example, the RS ports multiplexed with CDM in frequency domain may be achieved with that the RS ports are configured with different cyclic shift values based on one same base sequence. For another example, the RS ports multiplexed with CDM in frequency domain may be achieved with that the RS ports are configured with different orthogonal cover code values in the 2 REs in frequency domain, for example {1, 1} and {1, −1}. 
     Alternatively, or in addition, in some embodiments, if a first RS port and a second port are mapped in the same resource elements and multiplexed with the CDM in the frequency domain, it can be determined that the first and second RS ports use the same RS base sequence. 
     Now more examples will be discussed with respect to  FIGS. 3A-3F .  FIGS. 3A-3F  show schematic diagrams of RS patterns according to embodiments of the present disclosure, respectively. As shown in  FIG. 3A , ports A and C are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port A and C are configured with different cyclic shift values). In this example, ports B and D are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port B and D are configured with different cyclic shift values). Port A and/or port C are multiplexed with FDM with port B and/or port D. For example, port A and/or port C are configured with different comb offset values from port B and/or port D (e.g. Interleaved frequency division multiplexing access (IFDMA)). 
     In embodiments described with reference to  FIG. 3B , ports A and C are mapped in the 2 symbols, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port A and C are configured with different cyclic shift values). Ports B and D are mapped in the 2 symbols, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port B and D are configured with different cyclic shift values). Ports E and G are mapped in the 2 symbols, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port E and G are configured with different cyclic shift values). Ports F and H are mapped in the 2 symbols, and multiplexed with CDM in frequency domain, e.g. cyclic shift (port F and H are configured with different cyclic shift values). 
     In the example of  FIG. 3B , port A and/or port C are multiplexed with CDM in time domain (e.g. TD-OCC) with port E and/or port G. For instance, port A and/or port C are configured with different OCC values from port E and/or port G in time domain, e.g. port A and/or port C are configured with OCC {1, 1} in the 2 adjacent resource elements (REs). In the embodiments shown with respect to  FIG. 3B , where the 2 REs are in same frequency location and in 2 different symbols, port E and/or port G are configured with OCC {1, −1} in the 2 adjacent REs. 
     In addition, port B and/or port D may be multiplexed with CDM in time domain (e.g. TD-OCC) with port F and/or port H. Port B and/or port D may be configured with different OCC values from port F and/or port H. For example, port B and/or port D are configured with OCC {1, 1} in the 2 adjacent REs in time domain, and port F and/or port H are configured with OCC {1, −1} in the 2 adjacent REs in time domain. 
     Port A and/or C and/or E and/or G may be multiplexed with port B and/or D and/or F and/or H with FDM manner. By way of example, port A and/or C and/or E and/or G are configured with different resources in frequency domain from those of with port B and/or D and/or F and/or H. For instance, port A and/or C and/or E and/or G are configured with different comb offset values from those of with port B and/or D and/or F and/or H. 
     In embodiments described with reference to  FIG. 3C , ports A and B are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC (e.g. port 
     A is configured with OCC {1, 1} in the 2 adjacent REs in frequency domain, where the 2 REs are in same symbol and 2 different frequency resource elements, and port B may be configured with OCC {1, −1} in 2 adjacent REs in frequency domain. 
     Ports C and D are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC. 
     Ports E and F are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC. 
     Port A and/or port B are multiplexed with FDM with port C and/or port D. For example, port A and/or port B are configured with resources in frequency domain from port C and/or port D. 
     Port A and/or port B are multiplexed with FDM with port E and/or port F. For example, port A and/or port B are configured with resources in frequency domain from port E and/or port F. 
     Port C and/or port D are multiplexed with FDM with port E and/or port F. For example, port C and/or port D are configured with resources in frequency domain from port E and/or port F. 
     It is to be understood that the embodiments show with respect to  FIG. 3C  are for purpose of illustration, rather than limitation. Those skilled in the art would appreciate that the resources for port A and/or B and the resources for port C and/or D and the resources for port E and/or F may be adjacent and/or non-adjacent. Embodiments described with reference to  FIG. 3D  illustrate another example for DMRS configuration with 1 symbol. In the example of  FIG. 3D , the resources for ports A, B, ports C, D and ports E, F are non-adjacent. 
     In embodiments described with reference to  FIG. 3E , ports A, B are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC. By way of example, port A is configured with OCC {1, 1} in the 2 adjacent REs in frequency domain, where the 2 REs are in same symbol and 2 different frequency resource elements, and port B may be configured with OCC {1, −1} in 2 adjacent REs in frequency domain. 
     Ports C and D are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC. 
     Ports E and F are mapped in the same symbol, and multiplexed with CDM in frequency domain, e.g. FD-OCC. 
     Port A and/or port B and port G and/or H are multiplexed with CDM in time domain, e.g. TD-OCC. For example, port A and/or B may be configured with OCC {1, 1} in time domain, port G and/or H may be configured with OCC {1, −1} in time domain. 
     Port C and/or port D and port I and/or J are multiplexed with CDM in time domain, e.g. TD-OCC. For example, port C and/or D may be configured with OCC {1, 1} in time domain, port I and/or J may be configured with OCC {1, −1} in time domain. 
     Port E and/or port F and port K and/or L are multiplexed with CDM in time domain, e.g. TD-OCC. For example, port E and/or F may be configured with OCC {1, 1} in time domain, port K and/or L may be configured with OCC {1, −1} in time domain. 
     Port A and/or port B and/or port G and/or port H are multiplexed with FDM with port C and/or port D and/or port I and/or port J. For example, port A and/or port B and/or port G and/or port H are configured with resources in frequency domain from port C and/or port D and/or port I and/or port J. 
     Port C and/or port D and/or port I and/or port J are multiplexed with FDM with port E and/or port F and/or port K and/or port L. For example, Port C and/or port D and/or port I and/or port J are configured with resources in frequency domain from port E and/or port F and/or port K and/or port L. 
     Port A and/or port B and/or port G and/or port H are multiplexed with FDM with port E and/or port F and/or port K and/or port L. For example, port A and/or port B and/or port G and/or port H are configured with resources in frequency domain from port E and/or port F and/or port K and/or port L. 
     In the example of  FIG. 3F , the resources for ports A, B, G, H, ports C, D, I, J, and ports E, F, K, L are non-adjacent. 
     At  220 , information of the RS patterns is transmitted to the terminal device. In some embodiments, the information of the RS patterns may be transmitted via a high level signaling, for example, a Radio Resource Control (RRC) signaling, a Media Access Control (MAC) layer, and so on. Alternatively or in addition, the information of the RS patterns may be transmitted via a dynamic signaling, such as Downlink Control Information (DCI), or other suitable signaling transmitted on the downlink channel. 
     In some embodiments, the network device may include the information of the RS patterns in a QCL parameter set, and transmit the QCL parameter set to the terminal device. 
     More details of the indication of the RS patterns will be discussed below with reference to  FIGS. 4A- 4E . 
       FIGS. 4A-4E  show schematic diagrams of indications of RS patterns according to embodiments of the present disclosure, respectively, in which a PDSCH with 8 ports is taken for example. In the example of  FIG. 4A , there are 8 ports from one TRP, namely, 
     TRP  1 , these 8 ports may be QCLed with QCL parameter set  1 . The QCL parameter set  1  includes scrambling ID 1  for DMRS, and one sequence may be generated with the initial value. 
     In the example of  FIG. 4B , the first  4  ports (ports A, C, E, G) belong to the TPR  1  and are QCLed with QCL parameter set  2 . Another  4  ports (ports B, D, F, H) belong to another TRP  2  and are QCLed with QCL parameter set  3 . The QCL parameter sets  2  and  3  include scrambling ID 2  and ID 3  for DMRS, respectively, and sequences can be generated with independent initial values. 
       FIG. 4C  shows  8  ports from one TRP, namely, the TRP  1 . Among the  8  ports, the first  4  ports (ports A, C, E, G) belong to one DMRS port group and are QCLed with one RS. The other  4  ports (ports B, D, F, H) belong to another DMRS port group and are QCLed with another RS. The QCL parameter sets  4  and  5  include scrambling ID 4  and ID 5  for DMRS, respectively. 
     In some embodiments, the scrambling ID is same for same TRP. Thus, the scrambling ID 4  equals to the scrambling ID 5  in the example shown with respect to  FIG. 4C . If DMRSs are from the same TRP  1  in embodiments shown with respect to  FIGS. 4A-4C , the scrambling ID 1 =the scrambling ID 2 =the scrambling ID 4 =the scrambling ID 5 . 
     In some embodiments, UE can be configured with a set of RS ports, and the number of RS ports is N, for example the port index is (P 1 , P 2 , P 3 , . . . P N ), where N is integer and 1&lt;−N&lt;−12. For example, N may be at least one of {1, 4, 6, 8, 12}. In some embodiments, subsets of RS ports may be selected from the set of N RS ports, and each subset of RS ports may be one RS group, and the RS ports within the group may be QCLed. 
     In some embodiments, there may be Q groups of RS ports, where is Q integer and Q&gt;=1, and the number of RS ports in each group may be M q , where M q  is integer and 1&lt;=M q &lt;=N, and q is integer and 1&lt;=q&lt;=Q. For each group, the number of RS ports may be independent, that is the number of RS ports in each group may be same or different. For each group, the RS port indices may be independent, that is the RS port indices in each group may be overlapped or non-overlapped or partial overlapped. For example, the number of RS ports and the RS port indices in two groups may be same, and at least one of the QCL parameters corresponding to the two RS port groups may be different. 
     In some embodiments, some RS ports may always be in one QCL group. In some embodiments, the RS ports multiplexed with CDM in frequency domain and/or CDM in time domain should be in one QCL group. In one example, taking  FIG. 3A  for example, the RS ports A and C are multiplexed with CDM in frequency domain, these two ports should be in one QCL group, the RS ports B and D are multiplexed with CDM in frequency domain, these two ports should be in one QCL group. In another example, taking  FIG. 3B  for example, the RS ports A and C are multiplexed with CDM in frequency domain, these two ports should be in one QCL group. The RS ports B and D are multiplexed with CDM in frequency domain, these two ports should be in one QCL group. The RS ports E and G are multiplexed with CDM in frequency domain, these two ports should be in one QCL group. The RS ports F and H are multiplexed with CDM in frequency domain, these two ports should be in one QCL group. In another example, taking  FIG. 3B  for example, the RS ports A and C are multiplexed with CDM in frequency domain, and ports E and G are multiplexed with CDM in frequency domain, and port A and/or C may be multiplexed with port E and/or G with CDM in time domain, these four ports may be in one QCL group. The RS ports B and D are multiplexed with CDM in frequency domain, and the RS ports F and H are multiplexed with CDM in frequency domain, and the port B and/or D may be multiplexed with port F and/or H with CDM in time domain, these four ports may be in one QCL group. In another example, taking  FIG. 3C  for example, the ports A and B may be in one QCL group, the ports C and D may be in one QCL group, the ports E and F may be in one QCL group. In another example, taking  FIG. 3E  for example, the ports A and B may be in one QCL group, the ports C and D may be in one QCL group, the ports E and F may be in one QCL group, the ports G and H may be in one QCL group, the ports I and J may be in one QCL group, the ports K and L may be in one QCL group. In another example, taking 
       FIG. 3E  for example, the ports A, B, G, H may be in one QCL group, the ports C, D, I, J may be in one QCL group, the ports E, F, K, L may be in one QCL group. 
       FIGS. 4D  show schematic diagrams of indications of RS patterns according to embodiments of the present disclosure, respectively, in which a PDSCH with 8 ports is taken for example. In the example of  FIG. 4D , there are 8 ports DMRS, at least one ports from these 8 ports may be grouped in one group, for example Group q, and the RS ports in this group QCLed with one QCL parameter set, for example QCL parameters set q. In one embodiment, the RS sequence for the RS ports in one group may be generated with the initial value related to at least one of the parameters in the QCL parameters set q. 
       FIGS. 4E  shows schematic diagrams of indications of RS patterns according to embodiments of the present disclosure, respectively, in which a PDSCH with 12 ports is taken for example. In the example of  FIG. 4E , there are 12 ports DMRS, at least one ports from these 2 ports may be grouped in one group, for example Group q, and the RS ports in this group QCLed with one QCL parameter set, for example QCL parameters set q. In one embodiment, the RS sequence for the RS ports in one group may be generated with the initial value related to at least one of the parameters in the QCL parameters set q. 
     Now reference is made to  FIG. 5 , which shows a flowchart of a method  500  for RS configuration in accordance with some embodiments of the present disclosure. It would be appreciated that the method  500  may be implemented at a terminal device, for example, the terminal device  120 , or any other suitable device. 
     The method  500  is entered at  510 , where the terminal device  120  receives, from a network device, information of one or more RS patterns for a plurality of RS ports. The RS pattern indicates a configuration of a RS to be transmitted between the network device and the terminal device via one or more RS ports. In some embodiments, a RS pattern may indicate a configuration of a RS to be transmitted to a terminal device via one or more RS ports. Alternatively, or in addition, the RS pattern may also indicate a configuration of a RS to be transmitted from a terminal device via one or more RS ports. The RS patterns may be determined based on the method  200  as discussed above. 
     In some embodiments, the terminal device receives a RS via a RS port. The RS may be for example, a DMRS sequence. Then, the terminal device may demodulate the RS based on the RS patterns. 
     Now reference is made to  FIG. 6 , which shows a block diagram of an apparatus  600  in accordance with an embodiment of the present disclosure. It would be appreciated that the apparatus  600  may be implemented at a network device, for example, the network device  110  or  130 , or any other suitable device. 
     As shown, the apparatus  600  includes a determining unit  610  and a transmitting unit  620 . The determining unit  610  is configured to: determine one or more reference signal (RS) patterns for a plurality of RS ports, a RS pattern indicating a configuration of a 
     RS to be transmitted to a terminal device via one or more RS ports. The second transmitting unit  620  is configured to: transmit information of the RS patterns to the terminal device. 
     In an embodiment, the determining unit  610  may be configured to divide the RS ports into a plurality of RS port groups, and determine a RS pattern for each of the plurality of RS port groups. 
     In an embodiment, a RS port group is a QCL group. 
     In an embodiment, the determining unit  610  may be configured to determine at least one of: an initial value for generating a RS to be transmitted via a RS port or via RS ports in a RS port group; information of a symbol used by a RS port or a RS port group; 
     information of a resource element used by a RS port or a RS port group; a multiplexing mode of a RS port or a RS port group; and information of RS port groups. 
     In an embodiment, the determining unit  610  may be configured to: determine the initial value based on at least one of: a slot index, a symbol index, an identification of a cell, an identification of the network device, an identification of the terminal device, a RNTI, a CP type, a link type, an index of a RS port group, an index of QCL parameter set, a scrambling identity parameter, an identification of DMRS configuration type, an identification of a bandwidth part, an identification of a carrier component, a higher layer indicated scrambling identity parameter and an identification of subcarrier spacing. 
     In an embodiment, the determining unit  610  may be configured to: if a first RS port and a second port are mapped in the same symbol and multiplexed with CDM in frequency domain, determine that the first and second RS ports use the same RS base sequence; and if a first RS port and a second port are mapped in the same resource elements and multiplexed with the CDM in the frequency domain, determine that the first and second RS ports use the same RS base sequence. 
     In an embodiment, the transmitting unit  620  may be configured to: include the information of the RS patterns in a QCL parameter set; and transmit the QCL parameter set to the terminal device. 
     In an embodiment, the RS includes at least one of: a DMRS, a CSI-RS, a SRS, a PTRS, and a TRS. 
     Now reference is made to  FIG. 7 , which shows a block diagram of an apparatus  700  in accordance with an embodiment of the present disclosure. It would be appreciated that the apparatus  700  may be implemented at a terminal device, for example, the terminal device  120 , or any other suitable device. 
     As shown, the apparatus  700  includes a receiving unit  710  configured to: receive, from a network device, information of one or more RS patterns for a plurality of RS ports. A RS pattern indicates a configuration of a RS to be transmitted to the terminal device via one or more RS ports. 
     In an embodiment, the receiving unit  710  may be further configured to receive a RS via a RS port. The apparatus  700  may further include a demodulating unit configured to demodulate the RS based on the RS patterns. 
     In an embodiment, the RS includes at least one of: a DMRS, a CSI-RS, a SRS, a PTRS, and a TRS. 
     It is also to be noted that the apparatus  600  or  700  may be respectively implemented by any suitable technique either known at present or developed in the future. Further, a single device shown in  FIG. 2 or 5  may be alternatively implemented in multiple devices separately, and multiple separated devices may be implemented in a single device. The scope of the present disclosure is not limited in these regards. 
     It is noted that the apparatus  600  or  700  may be configured to implement functionalities as described with reference to  FIG. 2 or 5 . Therefore, the features discussed with respect to the method  200  may apply to the corresponding components of the apparatus  600 , and the features discussed with respect to the method  500  may apply to the corresponding components of the apparatus  600 . It is further noted that the components of the apparatus  600  or  700  may be embodied in hardware, software, firmware, and/or any combination thereof. For example, the components of the apparatus  600  or  700  may be respectively implemented by a circuit, a processor or any other appropriate device. Those skilled in the art will appreciate that the aforesaid examples are only for illustration not limitation. 
     In some embodiment of the present disclosure, the apparatus  600  or  700  may comprise at least one processor. The at least one processor suitable for use with embodiments of the present disclosure may include, by way of example, both general and special purpose processors already known or developed in the future. The apparatus  600  or  700  may further comprise at least one memory. The at least one memory may include, for example, semiconductor memory devices, e.g., RAM, ROM, EPROM, EEPROM, and flash memory devices. The at least one memory may be used to store program of computer executable instructions. The program can be written in any high-level and/or low-level compliable or interpretable programming languages. In accordance with embodiments, the computer executable instructions may be configured, with the at least one processor, to cause the apparatus  600  to at least perform according to the method  200  as discussed above and to cause the apparatus  700  to at least perform according to the method  500  as discussed above. 
     Based on the above description, the skilled in the art would appreciate that the present disclosure may be embodied in an apparatus, a method, or a computer program product. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, 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, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods 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. 
     The various blocks shown in  FIG. 6 or 7  may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). At least some aspects of the exemplary embodiments of the disclosures may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, FPGA or ASIC that is configurable to operate in accordance with the exemplary embodiments of the present disclosure. 
       FIG. 8  is a simplified block diagram of a device  800  that is suitable for implementing embodiments of the present disclosure. As shown, the device  800  includes one or more processors  810 , one or more memories  820  coupled to the processor(s)  810 , one or more transmitters and/or receivers (TX/RX)  840  coupled to the processor  810 . 
     The processor  810  may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device  800  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. 
     The memory  820  may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. 
     The memory  820  stores at least a part of a program  830 . The TX/RX  840  is for bidirectional communications. The TX/RX  840  has at least one antenna to facilitate communication, though in practice a terminal device or a network device mentioned in this disclosure may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements. 
     The program  830  is assumed to include program instructions that, when executed by the associated processor  810 , enable the device  800  to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to  FIGS. 2 and 5 . That is, embodiments of the present disclosure can be implemented by computer software executable by the processor  810  of the device  800 , or by hardware, or by a combination of software and hardware. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination. 
     Similarly, while operations are depicted in the drawings 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. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. 
     Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purpose of limitation.