Technical Field

The invention relates to a network access node and a client device for antenna port indication for multi TRP/panel transmissions. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

In 3GPP new radio (NR) Rel. 15, two configuration types of demodulation reference signal (DMRS) pattern have been specified for both downlink (DL) and uplink (UL) DMRS, i.e. DMRS configuration type 1 and DMRS configuration type 2, respectively. DMRS configuration type 1 uses an interleaved frequency division multiple access (IFDMA) based approach with an aim to be used for scenarios of up to 8 orthogonal antenna ports, while DMRS configuration type 2 uses 2-FD-OCC (frequency-domain orthogonal cover code) with an aim for scenarios of up to 12 orthogonal antenna ports. Detailed description of DMRS pattern for physical downlink shared channel (PDSCH) can be found in section 7.4.1.1 .2 in TS 38.211 f40. For DMRS configuration type 1 , DMRS port indexing for two-symbol DMRS with cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM), DMRS port indexing in code division multiplexing/multiplex (CDM) group is {0,1 , 4, 5}, {2, 3, 6, 7}. For DMRS configuration type 2, DMRS port indexing for two-symbol DMRS with CP-OFDM, DMRS port indexing in CDM group is {0,1 , 6, 7}, {2, 3, 8, 9}, {4,5,10,11 }.

Further, for downlink control information (DCI) Format 1 _ 1 , advanced multiple input multiple output (MIMO) schemes are supported by antenna port indication for both single user MIMO (SU-MIMO) and multi user MIMO (MU-MIMO). The antenna port indicator occupies 4, 5, or 6 bits as defined by Tables 7.3.1 .2.2-1 /2/3/4, where the number of CDM groups without data of values 1 , 2, and 3 refers to CDM groups {0}, {0,1 }, and {0, 1 ,2}, respectively.

In NR Rel. 15, the following MIMO features are included: limited support for multi transmission and reception (TRP) or multi panel operation, flexible channel state indication (CSI) acquisition and beam management, Type I (low-resolution) and II (high-resolution) codebooks supporting up to 32 ports, and flexible reference signal (RS) for MIMO transmission, especially CSI-RS, DMRS, and sounding reference signal (SRS). One aspect that can be enhanced is to support multi-TRP/panel transmission including improved reliability and robustness with both ideal and non-ideal backhaul. A design target is to specify in the downlink for an efficient support of a non-coherent joint transmission in multi TRP/panel/beam scenario. A typical multi TRP scenario with ideal backhaul is with a single physical downlink control channel (PDCCH) from one TRP and two physical downlink shared channels (PDSCHs) (or two layers of a codeword) from two TRPs with ideal backhaul.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a wireless communication system, the network access node being configured to

determine a set of antenna ports for downlink reference signals in disjoint ordered subsets of antenna ports, wherein

a first subset of antenna ports are associated to a first transmission configuration indicator, TCI, state and belong to at least one code division multiplexing, CDM, group, and a second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group; and

transmit a downlink control information to a client device, wherein the downlink control information comprises an indicator indicating the set of antenna ports for downlink reference signals in the ordered subsets of antenna ports.

The invention hence discloses an antenna port indication method where the first and second TCI states can be easily mapped to the antenna ports with the use of ordered first and second subsets of antenna ports.

Antenna ports herein can be understood as DMRS ports in 3GPP NR systems. Hence, the invention can be applicable for both DMRS configuration type 1 and type 2.

The indicator of the DCI can be represented as an indicator value, e.g. as a bitstream. Based on such a bitstream the first and second subsets can be derived, e.g. from an antenna port indictor table for reference signals. Such a table can be given by a standard.

An advantage of the network access node according to the first aspect is that it provides more scheduling flexibility of antenna port scheduling associated with multiple TCI states compared to conventional solutions. Thereby, e.g. better robustness and higher data rate transmissions can be achieved in the wireless communication system.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports and the second subset of antenna ports are disjoint.

That the first and second subsets of antenna ports are disjoint can mean that they don’t comprise any common antenna ports, hence comprises different antenna ports. This means that the antenna ports of the first subset are exclusive to the first subset and the antenna ports of the second subset are exclusive to the second subset.

An advantage with this implementation form is that simplified signaling can be archived with this implementation form. This is due to the fact that each antenna port is clearly mapped to a single TCI state.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports and the second subset of antenna ports are indicated in an ordered sequence.

Order sequence can mean that the antenna ports in each subset are arranged in a specific order according to the antenna port indexing. For example, the antenna ports may be arranged in descending or ascending indexing order.

An advantage with this implementation form is that the antenna ports can easily be associated to the different TCI states and thereby signaling overhead can be reduced.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports and the second subset of antenna ports are indicated in an ascending order.

An advantage with this implementation form is that the antenna ports can easily be associated to the different TCI states and thereby signaling overhead can be reduced.

In an implementation form of a network access node according to the first aspect, the indication of the first subset of antenna ports and the second subset of antenna ports are distinguished from each other with a punctuation mark. The punctuation mark is in more general terms a distinguishing mark, i.e. a mark that distinguishes and separates the first and second subsets. Examples of punctuation marks are comma, semicolon, apostrophe, bracket, dash, hyphen, colon, etc.

An advantage with this implementation form is that a simple way of distinguishing the different subsets is provided.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports belong to a first CDM group and the second subset of antenna ports belong to a second CDM group.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 1 is supported.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports belong to one CDM group and the second subset of antenna ports belong to two other CDM groups.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 2 is supported.

In an implementation form of a network access node according to the first aspect, the first subset of antenna ports belong to two CDM groups, and the second subset of antenna ports belong to one other CDM group.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 2 is supported.

In an implementation form of a network access node according to the first aspect, the downlink control information is associated with multi transmission and reception point transmissions.

An advantage with this implementation form is that this implementation form can support multi transmission and reception point transmissions. According to a second aspect of the invention, the above mentioned and other objectives are achieved with a client device for a wireless communication system, the client device being configured to

receive downlink control information from a network access node, wherein the downlink control information comprises an indicator indicating a set of antenna ports for downlink reference signals in ordered disjoint subsets of antenna ports, wherein

a first subset of antenna ports are associated to a first TCI state and belong to at least one CDM group, and

a second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group; and

determine the set of antenna ports for the downlink reference signals based on the indicator in the downlink control information.

An advantage of the client device according to the second aspect is that it provides more scheduling flexibility of antenna port scheduling associated with multiple TCI states compared to conventional solutions. Thereby, e.g. higher data rate transmissions can be achieved in the wireless communication system.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports and the second subset of antenna ports are disjoint.

An advantage with this implementation form is that simplified signaling can be archived with this implementation form.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports and the second subset of antenna ports are indicated in an ordered sequence.

An advantage with this implementation form is that the antenna ports can easily be associated to the different TCI states and thereby signaling overhead can be reduced.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports and the second subset of antenna ports are indicated in an ascending order.

An advantage with this implementation form is that the antenna ports can easily be associated to the different TCI states and thereby signaling overhead can be reduced. In an implementation form of a client device according to the second aspect, the first subset of antenna ports and the second subset of antenna ports are distinguished from each other with a punctuation mark.

An advantage with this implementation form is that a simple way of distinguishing the different subsets is provided.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports belong to a first CDM group and the second subset of antenna ports belong to a second CDM group.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 1 is supported.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports belong to one CDM group and the second subset of antenna ports belong to two other CDM groups.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 2 is supported.

In an implementation form of a client device according to the second aspect, the first subset of antenna ports belong to two CDM groups, and the second subset of antenna ports belong to one other CDM group.

An advantage with this implementation form is that a flexible antenna port indication solution is provided meaning higher data rates in the wireless communication system. Further, DMRS configuration type 2 is supported.

In an implementation form of a client device according to the second aspect, the client device is configured to

receive the downlink control information in a physical downlink control channel; and wherein the determined set of antenna ports are associated with a downlink data transmission in a physical downlink shared channel. An advantage with this implementation form is that it is compatible with current downlink control and data channel design.

In an implementation form of a client device according to the second aspect, the client device is configured to

receive the downlink data transmission in the physical downlink shared channel;

decode the downlink data transmission according to the determined set of antenna ports.

An advantage with this implementation form is that it is compatible with current downlink control and data channel design.

In an implementation form of a client device according to the second aspect, decode the downlink data transmission comprises

estimate a first set of channels associated with the first TCI state based on downlink reference signals from the first subset of antenna ports;

estimate a second set of channels associated with the second TCI state based on downlink reference signals from the second subset of antenna ports;

decode the downlink data transmission based on the first set of estimated channels and the second set of estimated channels.

An advantage with this implementation form is that it is compatible with current downlink control and data channel design. Further, due to the flexible antenna port indication solution higher data rates in the wireless communication system is possible.

In an implementation form of a client device according to the second aspect, the downlink control information is associated with multi transmission and reception point transmissions.

An advantage with this implementation form is that this implementation form can support multi transmission and reception point transmissions.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node, the method comprises

determining a set of antenna ports for downlink reference signals in disjoint ordered subsets of antenna ports, wherein

a first subset of antenna ports are associated to a first transmission configuration indicator, TCI, state and belong to at least one CDM group, and a second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group; and

transmitting a downlink control information to a client device, wherein the downlink control information comprises an indicator indicating the set of antenna ports for downlink reference signals in the ordered subsets of antenna ports.

The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.

The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the network access node according to the first aspect.

According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device, the method comprises

receiving downlink control information from a network access node (100), wherein the downlink control information comprises an indicator indicating a set of antenna ports for downlink reference signals in ordered disjoint subsets of antenna ports, wherein

a first subset of antenna ports are associated to a first TCI state and belong to at least one CDM group, and

a second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group; and

determining the set of antenna ports for the downlink reference signals based on the indicator in the downlink control information.

The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the client device according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.

The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the client device according to the second aspect.

The invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to embodiments of the invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

- Fig. 1 shows a network access node according to an example of the invention;

- Fig. 2 shows a method for a network access node according to an example of the invention;

- Fig. 3 shows a client device according to an example of the invention;

- Fig. 4 shows a method for a client device according to an example of the invention;

- Fig. 5 shows a wireless communication system according to an example of the invention; and

- Fig. 6 shows a method for a client device according to an example of the invention.

Detailed Description

The issue of antenna port indication in 3GPP NR has previously been discussed. For NR Rel. 16, it has been agreed that each transmission configuration indicator (TCI) code point in a DCI can correspond to 1 or 2 TCI states. When 2 TCI states are indicated, there should be a mapping between the TCI states and the DMRS CDM groups given that DMRS ports in one CDM group are quasi-collocation (QCL), especially for the DMRS type 2 case which has up to 3 CDM groups. A user equipment (UE) is radio resource configuration (RRC) configured with a list of up to M candidate TCI states at least for the purposes of QCL indication.

• For QCL indication for PDSCH:

o When TCI states are used for QCL indication, the UE receives an N-bit TCI field in DCI

^■ The UE assumes that the PDSCH DMRS is QCLed with the DL RS(s) in the RS Set corresponding to the signaled TCI state In NR Rel. 15, one TCI code point corresponds to only one TCI state. When a TCI state is enabled, the network indicates the TCI state to UE, and the UE may assume that the DM-RS ports of PDSCH of a serving cell are quasi co-located with the RS(s) in the TCI state with respect to the QCL type parameter(s) given by the indicated TCI state. In NR there are four QCL types defined, and qcl-Type1 is for the first DL RS, and qcl-Type2 is for the second DL RS if qcl-Type2 is configured.

The inventors have therefore concluded that there is a need for a method and an apparatus for efficient and effective antenna port indication method when two TCI states are indicated for a single PDCCH based multi TRP transmission. Therefore, embodiments of the invention relate to methods and devices for antenna port indication in wireless communication systems.

Fig. 1 shows a network access node 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the network access node 100 comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The network access node 100 may be configured for both wireless and wired communications in wireless and wired communication systems, respectively. The wireless communication capability is provided with an antenna or antenna array 1 10 coupled to the transceiver 104, while the wired communication capability is provided with a wired communication interface 1 12 coupled to the transceiver 104. That the network access node 100 is configured to perform certain actions can in this disclosure be understood to mean that the network access node 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.

According to embodiments of the invention the network access node 100 is configured to determine a set of antenna ports for downlink reference signals in disjoint ordered subsets of antenna ports. A first subset of antenna ports are associated to a TCI state and belong to at least one CDM group. A second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group. The network access node 100 is further configured to transmit a DCI to a client device 300. The DCI comprises an indicator indicating the set of antenna ports for downlink reference signals in the ordered subsets of antenna ports.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a network access node 100, such as the one shown in Fig. 1 . The method 200 comprises determining 202 a set of antenna ports for downlink reference signals in disjoint ordered subsets of antenna ports. A first subset of antenna ports are associated to a first TCI state and belong to at least one CDM group. A second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group. The method 200 further comprises transmitting 204 a DCI to a client device 300. The DCI comprises an indicator indicating the set of antenna ports for downlink reference signals in the ordered subsets of antenna ports.

Fig. 3 shows a client device 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, the client device 300 comprises a processor 302, a transceiver 304 and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The client device 300 further comprises an antenna or antenna array 310 coupled to the transceiver 304, which means that the client device 300 is configured for wireless communications in a wireless communication system. That the client device 300 is configured to perform certain actions can in this disclosure be understood to mean that the client device 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.

According to embodiments of the invention the client device 300 is configured to receive a DCI from a network access node 100. The DCI comprises an indicator indicating a set of antenna ports for downlink reference signals in ordered disjoint subsets of antenna ports. A first subset of antenna ports are associated to a first TCI state and belong to at least one CDM group. A second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group. The client device 300 is further configured to determine the set of antenna ports for the downlink reference signals based on the indicator in the DCI.

Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a client device 300, such as the one shown in Fig. 3. The method 400 comprises receiving 402 a DCI from a network access node 100. The DCI comprises an indicator indicating a set of antenna ports for downlink reference signals in ordered disjoint subsets of antenna ports. A first subset of antenna ports are associated to a first TCI state and belong to at least one CDM group. A second subset of antenna ports are associated to a second TCI state and belong to at least one other CDM group. The method 400 further comprises determining 404 the set of antenna ports for the downlink reference signals based on the indicator in the DCI.

In embodiments of the invention, the first subset of antenna ports and the second subset of antenna ports are disjoint. That the first and second subsets of antenna ports are disjoint can mean that the first and second subsets don’t have any common antenna ports, hence comprises different antenna ports. This is e.g. the case when wherein the first subset of antenna ports belong to a first CDM group and the second subset of antenna ports belong to a second CDM group where the first and second CDM groups are different CDM groups. In this embodiment the first subset of antenna ports can comprise antenna ports from any of CDM group 0, 1 , and 2 and the second subset of antenna ports can comprise antenna ports from any of CDM group 0, 1 , and 2 for the DMRS configuration type 2 where there are 3 CDM groups but the first subset of antenna ports and the second subset of antenna ports does not comprise antenna ports from the same CDM group since they are disjoint. In DMRS configuration type 1 , CDM group 2 does not exist.

In embodiments of the invention, the first subset of antenna ports and the second subset of antenna ports are indicated in an ordered sequence. Herein order sequence can mean that the antenna ports in each subset are arranged in a specific order according to the antenna port indexing. For example, the antenna ports may be arranged in descending or ascending indexing order. In an embodiment of the invention, the first subset of antenna ports and the second subset of antenna ports are indicated in an ascending order.

Fig. 5 shows a wireless communication system 500 according to an embodiment of the invention. The wireless communication system 500 comprises a network access node 100 and a client device 300 configured to operate in the wireless communication system 500. For simplicity, the wireless communication system 500 shown in Fig. 5 only comprises one network access node 100 and one client device 300. However, the wireless communication system 500 may comprise any number of network access nodes 100 and any number of client devices 300 without deviating from the scope of the invention.

In the wireless communication system 500, the network access node transmits a DCI to the client device 300 in a PDCCH 510. The DCI comprises an indicator indicating the set of antenna ports for downlink reference signals in the ordered subsets of antenna ports. The client device 300 receives the DCI from the network access node 100, and thereafter determines the set of antenna ports for the downlink reference signals based on the indicator in the DCI. After having determined the set of antenna ports for the downlink reference signals the client device 300 receives downlink data transmission in a PDSCH 520 from the network access node 100 using the determined set of antenna ports. In embodiments of the invention, the downlink data transmission is multi TRP transmissions and hence the DCI is therefore in this case associated with the multi TRP transmissions.

A general procedure of utilizing TCI information and DMRS ports information in the DCI for a PDSCH reception according to embodiments of the invention is illustrated in the flow chart 600 of Fig. 6. The embodiment illustrated in Fig. 6 is set in a 3GPP NR context and hence the expressions, terminology and system design herein used. Embodiments of the invention are however not limited thereto.

At step 602 in Fig. 6: a client device 300 receives a DCI in a PDCCH and determines a set of antenna ports associated with a downlink data transmission in a corresponding PDSCH. In other words, the client device 300 upon detection of the PDCCH with a configured DCI format 1_0 or 1_1 decodes the corresponding PDSCH as indicated by the DCI. Further, in the DCI scheduling information of the PDSCH is indicated, which may include TCI information and DMRS port information for the PDSCH. The TCI information indicates the QCL relationship between the DMRS and DL RS(s), such as SSB or CSI-RS, and thereby for example which beam the respective DMRS and DL RS belong to. Hence, the DCI information gives information about which DMRS ports that are allocated to a first TCI state or a corresponding first beam and which DMRS ports that are allocated to a second TCI state or a corresponding second beam.

At step 604 in Fig. 6: the client device 300 performs channel estimation on respective antenna ports for the PDSCH according to the indicated QCL information and the DMRS port(s), and hence estimate the channel for respective beam from different TRPs. In other words, the client device 300 estimates a first set of channels associated with the first TCI state based on downlink reference signals from the first subset of antenna ports; and estimates a second set of channels associated with the second TCI state based on downlink reference signals from the second subset of antenna ports. The first and second set of channels are in embodiments set of radio channels.

At step 606 in Fig. 6: the client device 300 performs demodulation and decoding of the PDSCH channel transmitted in respective beam using the estimated channels in step 604. The client device 300 finally decodes the downlink data transmission based on the first set of estimated channels and the second set of estimated channels obtained in step 604.

Table 1 below illustrates an embodiment of the invention designed for DMRS configuration type 1 with max length of DMRS symbol that equals to 1 and two TCI states, i.e. a first TCI state and a second TCI state, are indicated. According to this embodiment, the first subset of antenna ports belong to a first CDM group and the second subset of antenna ports belong to a second CDM group. For example, if there are three CDM groups, i.e. CDM group 0, CDM group 1 and CDM group 2, the following non-limiting cases can be supported: [CDM group 0; CDM group 1 ], [CDM group 1 ; CDM group 0], [CDM group 0; CDM group 2], and [CDM group 2; CDM group 0]. The punctuation mark is in this case semicolon and differentiates the antenna ports allocated for TCI state 1 and TCI state 2, respectively.

In Table 1 there are 6 example entries (rows) for DMRS ports shown and one reserved entry (the last row). A reserved entry is an entry that is not currently allocated. For each entry, the DMRS ports are ordered in two different subsets, separated by a punctuation mark, in this case a semicolon. Take the first entry as an example, the first subset is composed of DMRS ports 0 and 1 which belong to CDM group 0, while the second subset is composed of DMRS port 2 which belongs to CDM group 1. The other entries in Table 1 follow similar structure.

It is further noted that the first entry and the second entry in Table 1 are different from each other in the sense that the order of the subsets are different which means their mapping to the TCI states are different. For example, in the first entry, antenna port 0 and 1 are associated with the first TCI state of the two TCI states indicated by the TCI code point in a DCI, while antenna port 2 is associated with the second TCI state of the two TCI states indicated by the TCI code point in the DCI, and vice versa. This implies that the first and second subsets of antenna ports are permuted in different entries which means that there is a one-to-one mapping to the first and second TCI states, respectively. The indicator in the DCI can be given as an indicator value. In Table 1 the indicator value is given in an integer representation. However, the indicator value can also be given in any other suitable format such as in hexadecimal representation of positive integers 1 , 2, 3,... or letters A, B, C,.., or bit streams, etc.

Table 1 Table 2 illustrates another embodiment of the invention designed for DMRS configuration type 1 with max length of DMRS symbol that equals to 1 and for one or two TCI states. In Table 2 the indicator value is also given in positive integer numbers. It is also noted that some of the entries only relate to the case of one CDM group (e.g. entry 0 and 1 ) whilst other entries relate to the case of two CDM groups and they are permuted in ordered subsets marked by a semicolon, e.g. entry 12, 13 and 14.

Table 2

Table 3 illustrates yet another embodiment of the invention which in this case is designed for DMRS configuration type 2 with max length of DMRS symbol that equals to 1 and the two TCI states are indicated. According to this embodiment, for some entries, the first subset of antenna ports belong to one CDM group and the second subset of antenna ports belong to one other CDM groups; while for some other entries, the first subset of antenna ports belong to one CDM group and the second subset of antenna ports belong to two other CDM groups; or the first subset of antenna ports belong to two CDM groups, and the second subset of antenna ports belong to one other CDM group.

Example entries for DMRS port indication are presented for both single code word enabled cases and dual code word enabled cases in Table 3. A codeword in this context refers a stream of cyclic redundancy check (CRC) coded bits from one transport block (TB). For each entry, the DMRS ports are ordered in first and second subsets, separated by a punctuation mark, in this case a semicolon. Take the first entry (row) for single code word enabled cases (left part) as an example, the first segment is composed of DMRS ports 0 and 1 which belong to CDM group 0, while the second segment is composed of DMRS port 2 which belongs to CDM group 1 . The other entries follow similar structure.

It is noted that the first entry and the second entry, in the left part of Table 3, are different from each other in the sense that the order of the subsets are different. For example, in the first entry, antenna port O and 1 are associated with the first TCI state of the two TCI states indicated by the TCI code point in a DCI, while antenna port 2 is associated with the second TCI state of the two TCI states indicated by the TCI code point in the DCI, and vice versa. Hence, also in this case the first and second subsets of antenna ports are permuted.

Furthermore, consider the first entry for dual code word enabled cases, in the right part in Table 3. The first subset is composed of DMRS ports 0 and 1 which belong to CDM group 0, while the second subset is composed of DMRS port 2, 3 and 4, which belong to CDM group 1 and CDM group 2. The other entries follow similar structure. It is also herein noted that the first entry and the second entry, in the right part of Table 3, are different from each other in the sense that division of the DMRS ports are different. For example, in the first entry, subset port 0 and 1 are associated with the first TCI state of the two TCI states indicated by the TCI code point in a DCI, while subset port 2, 3 and 4 belonging to CDM group 1 and group 2 are associated with the second TCI state of the two TCI states indicated by the TCI code point in the DCI, and vice versa.

Table 3

It should furthermore be noted that embodiments of the invention can advantageously be applied and incorporated in 3GPP NR specifications. Therefore, in the following disclosure non-limiting examples of such applications are described.

Considering the existing DMRS port indication table in NR Rel. 15, to enhance the DMRS port indication for Rel. 16, a new form of DMRS antenna port indication table can be introduced, where each entry is arranged according to the disjoint ordering of antenna ports according to embodiments of the invention. Each subset of DMRS ports of two first and second subsets corresponds to mapping to the corresponding TCI state of two TCI states indicated by the TCI code point in a DCI. When there are three CDM groups for DMRS ports, the first TCI state can be mapped to one or two CDM groups. A DMRS port indication table according to embodiments of the invention could be introduced in section 7.3.1.2.2 in standard TS 38.212. The new DMRS port indication tables can be applied by an indicator or an implicit derivation method which indicates that two TCI states are enabled for single PDCCH based multi TRP transmission. Or in another words, the following example entries can be added to existing antenna port indication tables in section 7.3.1.2.2 in TS 38.212. It is noted that the DMRS ports in each entry are ordered into first and second subsets by a semicolon. The first subset is associated to the first indicated TCI state, while the second subset is associated to the second indicated TCI state. Table 4 is used for DMRS configuration type 1 and Table 5 is used for DMRS configuration type 2.

Table 4: 7.3.1.2.2-x: Antenna port(s) (1000 + DMRS port), dmrs-Type= 1 , maxLength^, two TCI states

Table 5: Antenna port(s) (1000 + DMRS port), dmrs-Type= 2, maxLength^, two TCI states

The client device 300 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer- comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as New Radio.

The network access node 100 herein may also be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter,“gNB”,“gNodeB”,“eNB”, “eNodeB”,“NodeB” or“B node”, depending on the technology and terminology used. The radio network access node may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio network access node may also be a base station corresponding to the fifth generation (5G) wireless systems.

Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that embodiments of the network access node 100 and the client device 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged togetherfor performing the solution.

Especially, the processor(s) of the network access node 100 and the client device 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression“processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.