Patent Description:
Demodulation Reference Signals (DMRS) are used for coherent demodulation of physical layer downlink (DL) data channels, i.e., Physical Downlink Shared Channel (PDSCH), and physical layer uplink (UL) data channels, i.e., Physical Uplink Shared Channel (PUSCH), as well as Physical Layer Downlink Control Channel (PDCCH). The DMRS is confined to Resource Blocks (RBs) carrying the associated physical layer data channel and is mapped on allocated Resource Elements (REs) of the Orthogonal Frequency Division Multiplexing (OFDM) time-frequency grid in New Radio (NR) such that the receiver can efficiently handle time/frequency-selective fading radio channels.

The mapping of DMRS to REs is configurable in both frequency domain and time domain, with two mapping types in the frequency domain (configuration type <NUM> and type <NUM>) and two mapping types in the time domain (mapping type A and type B) defining the symbol position of the first DMRS within a transmission interval. The DMRS mapping in time domain can further be single-symbol based or double-symbol based where the latter means that DMRS is mapped in pairs of two adjacent OFDM symbols.

<FIG> shows the mapping of front-loaded DMRS for configuration type <NUM> and type <NUM> with single-symbol and double-symbol DMRS with the first DMRS in the third OFDM symbol (OFDM symbol #<NUM>) of a transmission interval of fourteen (<NUM>) OFDM symbols. The vertical axis represents frequency in subcarriers starting from subcarrier #<NUM>, and the horizontal axis represents time in OFDM symbols starting from OFDM symbol #<NUM> in a single RB. From <FIG>, it can be observed that type <NUM> and type <NUM> differ with respect to the number of supported DMRS Code Division Multiplexing (CDM) groups where type <NUM> supports two CDM groups and Type <NUM> supports three CDM groups.

The mapping structure of type <NUM> is sometimes referred to as a <NUM>-comb structure with two CDM groups defined in the frequency domain by the set of subcarriers {<NUM>,<NUM>,<NUM>,. } and {<NUM>,<NUM>,<NUM>,. The comb mapping structure is a prerequisite for transmissions requiring low Peak-to-Average Power Reduction (PAPR) / Cubic Metric (CM) and is thus used in conjunction with Discrete Fourier Transformation-Spread-OFDM (DFT-S-OFDM), also referred to as transform precoding. In contrast, in Cyclic Prefix OFDM (CP-OFDM) in which transform precoding is disabled, both type <NUM> and type <NUM> mapping are supported.

A DMRS antenna port is mapped to the REs within one CDM group only. For a single front-loaded DMRS symbol, two antenna ports can be mapped to each CDM group whereas, for two front-loaded DMRS symbols, four antenna ports can be mapped to each CDM group. Hence, the maximum number of DMRS ports for type <NUM> is either four (with a single front-loaded symbol) or eight (with two front-loaded symbols) and for type <NUM> it is either six or twelve. An Orthogonal Cover Code (OCC) of length <NUM> ([+<NUM>,+<NUM>],[+<NUM>,-<NUM>]) is used to separate antenna ports mapped on the same REs within a CDM group. The OCC is applied in the frequency domain as well as in the time domain when two front-loaded DMRS symbols are configured.

Table <NUM> and Table <NUM> below show the PDSCH DMRS port to CDM group mapping for configuration type <NUM> and type <NUM>, respectively. For PDSCH DMRS Type <NUM>, ports <NUM>, <NUM>, <NUM>, and <NUM> are in CDM group λ=<NUM> and ports <NUM>, <NUM>, <NUM>, and <NUM> are in CDM group λ=<NUM>. For PDSCH DMRS Type <NUM>, ports <NUM>, <NUM>, <NUM>, and <NUM> are in CDM group λ=<NUM>, ports <NUM>, <NUM>, <NUM>, and <NUM> are in CDM group λ=<NUM>, and ports <NUM>, <NUM>, <NUM>, and <NUM> are in CDM group λ=<NUM>.

The Downlink Control Information (DCI) carried by PDCCH contains a bit field that indicates the antenna port(s) (i.e., DMRS port(s)) and the number of antenna ports (i.e. the number of data layers) scheduled. For example, if port <NUM> is indicated, then the PDSCH is a single layer transmission and the UE will use the DMRS defined by port <NUM> to demodulate the PDSCH.

An example is shown in Table <NUM> below for DMRS Type <NUM> and with a single front loaded DMRS symbol (maxLength=<NUM>). The DCI indicates a "Value", and the corresponding DMRS port(s) can be found from the corresponding row in the table. The "Value" also indicates the number of CDM groups without data. This means that, if <NUM> is indicated, one CDM group contains the DMRS port(s), and the other CDM group in the same DMRS symbol can be used for data transmission to the UE (PDSCH case) in case the PDSCH time allocation includes the DMRS symbol(s). If the "Value" is <NUM>, neither of the CDM groups can be used for data transmission even when the DMRS port(s) indicated for the UE is only in one CDM group. This configuration can be used to support Multi-User Multiple Input Multiple Output (MIMO) (MU-MIMO) by scheduling multiple User Equipments (UEs) in the same resource with each UE configured with different DMRS port(s). It can also be used to boost DMRS transmit power by <NUM> decibels (dB) if only a single UE is scheduled and the DMRS port(s) is in one CDM group, also referred to as Single User MIMO (SU-MIMO).

Table <NUM> shows the corresponding table for DMRS Type <NUM> with a single front loaded DMRS symbol (maxLength=<NUM>). In this case, two codewords can be supported with more than four DMRS ports. Indication of up to six DMRS ports (up to six layers) is possible with this configuration.

Table <NUM> and Table <NUM> are the antenna port mapping tables for DMRS with two front loaded symbols. In these tables, additional entries are added to support different combinations of DMRS ports and CDM groups.

Thus, in NR Release <NUM>, the antenna port table size varies with different DMRS configurations, i.e., type <NUM> or type <NUM> and the number of front loaded DMRS symbols. In NR Release <NUM>, a UE determines the size of the antenna port bit field in DCI format 1_1 based on the DMRS configuration. Similarly, various antenna port tables are defined for DMRS port indication for UL PUSCH transmission. The table size also varies depending on DMRS configuration and whether transform precoding is enabled.

DCI format 1_1 is used in NR for the scheduling of PDSCH. It contains an "antenna port(s)" bit field for indication of DMRS port(s) used in a scheduled PDSCH by the DCI. The size of the bit field can be <NUM>, <NUM>, or <NUM> bits, depending on the DMRS configuration as defined by Tables <NUM>. <NUM>-<NUM>/<NUM>/<NUM>/<NUM> in 3GPP TS <NUM> as described above, where the number of CDM groups without data with values of <NUM>, <NUM>, and <NUM> refers to CDM groups {<NUM>}, {<NUM>,<NUM>}, and {<NUM>, <NUM>, <NUM>}, respectively. The antenna ports {p<NUM>,. , pv-<NUM>} are determined according to the ordering of DMRS port(s) given by Tables <NUM>. <NUM>-<NUM>/<NUM>/<NUM>/<NUM> in 3GPP TS <NUM>.

For single Transmission/Reception Point (TRP) transmission, two DMRS ports of a PDSCH can be in either a same CDM group or two different CDM groups. For multi-TRP transmission, DMRS transmitted from different TRPs must be allocated in different CDM groups.

DCI format 0_1 is used for the scheduling of PUSCH in one cell. It also contains an "antenna ports" bit field for indication of DMRS port(s) used in a scheduled PUSCH by the DCI. The size of the bit field can be <NUM>, <NUM>, <NUM>, or <NUM> bits, depending on the DMRS configuration and on whether transform precoding is enabled or disabled.

To support Ultra-Reliable Low-Latency Communication (URLLC) services and to provide more reliable PDCCH detection, in NR Release <NUM>, it was agreed that a new compact DCI will be introduced. The new DCI is intended to have a configurable size for the "antenna ports" field, where the configurable size can have a smaller range of values than what is supported in NR Release <NUM>.

There currently exist certain challenge(s). One challenge is how to determine and indicate antenna ports for the new compact DCI format that has configurable antenna ports field size. Design of a new set of antenna tables with smaller sizes than the existing tables for the same DMRS configuration for the new compact DCI format is a related challenge.

Document Document "<NPL>, discloses an evaluation of remaining issues on DMRS location and DMRS table configuration. The following proposals were made. Proposal #<NUM>: If the scheduled duration of PDSCH/PUSCH is less than the minimum supported value defined for semi-statically configured DL-DMRS-add-pos, the maximum number of DMRS that can be supported for the scheduled duration of PDSCH/PUSCH is transmitted on the specified location. Proposal #<NUM>: To reduce DCI payload for Type II DMRS port indication, DMRS port table for DL-DMRS-config-type=<NUM>, DL-DMRS-max-len=<NUM> is additionally used for DL-DMRS-config-type=<NUM>, DL-DMRS-max-len=<NUM>. Proposal #<NUM>: To reduce DCI payload for Type II DMRS port indication, DMRS port table for DL-DMRS-config-type=<NUM>, DL-DMRS-max-len=<NUM> is additionally used for DL-DMRS-config-type=<NUM>, DL-DMRS-max-len=<NUM> with some modification.

Document "<NPL>, discloses an evaluation of the design of the new DCI format. The following proposals were made. Proposal <NUM>: Downlink DCI format for NR URLLC should at least contain the fields Header/Identifier for DCI format, Carrier indicator, Frequency-domain PDSCH resources, Time-domain PDSCH resources, VRB-to-PRB mapping, MCS, New data indicator, Redundancy version, HARQ process number, Downlink Assignment Index, TPC command for PUCCH, Antenna port indicator, ARI (A/N resource index), HARQ timing indicator, Rate-matching indicator, and SRS-request. Proposal <NUM>: Uplink DCI format for NR URLLC should at least contain the fields Header/Identifier for DCI format, Carrier indicator, Waveform indicator, Frequency-domain PUSCH resources, Time-domain PUSCH resources, Frequency hopping indicator, MCS, New data indicator, Redundancy version, HARQ process number, TPC command for PUSCH, SRI and TPMI. Proposal <NUM>: DCI formats <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> can be used to schedule URLLC transmissions.

Systems and methods are disclosed herein for determining and indicating antenna ports with a configurable antenna port field in Downlink Control Information (DCI).

According to the present disclosure, methods, a wireless communication device, a network node and computer-readable media according to the independent claims are provided.

Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a radio access network of a cellular communications network that operates to wirelessly transmit and/or receive signals.

Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Function (AMF), a UPF, a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

As discussed above, there currently exist certain challenge(s) in relation to the new compact Downlink Control Information (DCI) agreed to in NR Release <NUM>. One challenge is how to determine and indicate antenna ports for the new compact DCI format that has configurable antenna ports field size. Design of a new set of antenna tables with smaller sizes than the existing tables for the same DMRS configuration for the new compact DCI format is a related challenge.

Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. For Ultra-Reliable Low-Latency Communication (URLLC) services, a different set of antenna tables with smaller sizes can be configured to a UE. The size of the "antenna ports" field in DCI can be configurable, with the size of this field potentially being smaller than that of the existing non-fallback DCI (i.e., DCI format <NUM>-<NUM> or <NUM>-<NUM>). For example, the size of the antenna ports field can be from <NUM> to (N<NUM>-<NUM>) bits for the new DCI scheduling downlink (DL) transmission and the new DCI scheduling UL transmission. Here, N<NUM> is the number of bits for the antenna port field in the existing DCI format 1_1 and 0_1. In one solution, the tables associated with different sizes of the antenna ports field are nested such that the first <NUM>^(N-<NUM>) entries of a table associated with a N bits antenna port field forms the table associated with a (N-<NUM>) bits antenna port field. In a second solution, a bitmap is used together with a DMRS configuration and either the new or existing antenna tables to construct an antenna port table for DCI with N bits configured antenna port field. The same methodology can be applied to the new DCI scheduling DL data transmission, as well as UL data transmission.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. In one embodiment, a method performed by a wireless device for determining an antenna port includes receiving a configuration and control information from a network node. The control information includes an antenna port field. A format of the control information is determined, and the format of the control information is associated with an antenna port field size. A table to be used for determining the antenna port is identified based on the configuration and the antenna port field size. The antenna port is determined based on the table and the value of the antenna port field. In one embodiment, the configuration is a demodulation reference signal (DMRS) configuration, the control information is DCI, and the table is a DMRS antenna port table. In one embodiment, identifying the table to be used for determining the antenna port comprises identifying a subset of a master table to be used for determining the antenna port.

In some cases, the wireless device may receive a table indicator from the network node, which is used to identify the table or the subset of the table. The table indicator may be a bitmap such that set bits in the bitmap indicate that a corresponding row in the master table is included in the subset of the table.

Certain embodiments may provide one or more of the following technical advantage(s). With nested antenna tables, UE and gNB memory and table management can be saved, e.g., a single pointer can be used for different sizes of the tables for a given DMRS configuration. With the bitmap-based solution, the existing antenna tables can be used without defining a new set of tables.

<FIG> illustrates one example of a cellular communications system <NUM> in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system <NUM> is a <NUM> system (5GS) including a NR RAN or LTE RAN (i.e., E-UTRA RAN). In this example, the RAN includes base stations <NUM>-<NUM> and <NUM>-<NUM>, which in <NUM> NR are referred to as gNBs or ng-eNBs (i.e., LTE RAN nodes connected to 5GC), controlling corresponding (macro) cells <NUM>-<NUM> and <NUM>-<NUM>. The base stations <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as base stations <NUM> and individually as base station <NUM>. Likewise, the (macro) cells <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as (macro) cells <NUM> and individually as (macro) cell <NUM>. The RAN may also include a number of low power nodes <NUM>-<NUM> through <NUM>-<NUM> controlling corresponding small cells <NUM>-<NUM> through <NUM>-<NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells <NUM>-<NUM> through <NUM>-<NUM> may alternatively be provided by the base stations <NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as low power nodes <NUM> and individually as low power node <NUM>. Likewise, the small cells <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as small cells <NUM> and individually as small cell <NUM>. The cellular communications system <NUM> also includes a core network <NUM>, which in the 5GS is referred to as the <NUM> core (5GC). The base stations <NUM> (and optionally the low power nodes <NUM>) are connected to the core network <NUM>.

Thus, the wireless communication devices <NUM> are sometimes referred to herein as "UEs <NUM>".

The Release <NUM> antenna table design was mainly for enhanced Mobile Broadband (eMBB) in which a UE may support up to eight Multiple-Input Multiple-Output (MIMO) layers for high peak data rate or up to twelve UEs may be scheduled in the same resource by using orthogonal DMRS to maximize system throughput. Even larger number of UEs can be co-scheduled with non-orthogonal DMRS ports, i.e. where different scrambling sequences are used for the DMRS ports to different users.

For high reliability services, such as URLLC, the main design goal is to deliver data reliably. Therefore, for URLLC, neither Multi-User MIMO (MU-MIMO) nor Single-User MIMO (SU-MIMO) with more than two layers may be supported in the DL. Similarly, up to two layers per UE may be supported in the UL.

Related to the anticipated reduction of MIMO layers for data transmission, it has been agreed that the new DCI format for PDSCH scheduling supports a single transport block (TB) only. Hence, it does not include information specific for transport block <NUM> (i.e., Modulation and Coding Scheme (MCS), New Data Indicator (NDI), Redundancy Version (RV)). Additionally, Code Block Group (CBG) transmission is not supported for both PDSCH and PUSCH. For PDSCH scheduling, the DCI fields excluded are: "CBG transmission information" and "CBG flushing information". For PUSCH scheduling, the DCI field excluded is "CBG transmission information".

In the following discussion, a new proposed DCI format for scheduling downlink data transmission is called DCI format 1_X, and a new proposed DCI format for scheduling uplink data transmission is called DCI format 0_X. Here "1_X" and "0_X" are temporary labels and stand in for the DCI formats that may be adopted by NR specification, which use higher-layer configurable antenna port field size. DCI format 1_X and 0_X can be used to serve any type of traffic including eMBB and URLLC (i.e., not limited to URLLC traffic only).

Also, DCI format 1_X and 0_X may be used to activate and/or release semi-persistently scheduled transmissions. That is, DCI format 0_X may be used to activate and/or release one or more configurations of uplink configured grant (UL CG), and DCI format 1_X can be used to activate and/or release one or more configurations of downlink semi-persistent scheduled (DL SPS) transmission. When used for activation of UL CG or DL SPS, the antenna port information carried by DCI format 0_1 and 1_1, respectively, is used by the associated PUSCH and PDSCH transmissions, respectively.

Additionally, while DCI format 1_X and 0_X are used to discuss downlink and uplink data transmission, respectively, the same methodology can be applied to sidelink. For example, another DCI format (for example, DCI format 3_X) can be constructed for sidelink, where the antenna port field of DCI format 3_X is configurable.

A flowchart of a general embodiment is depicted in <FIG>. In step <NUM>, a UE <NUM> may receive higher-layer configuration (e.g., Radio Resource Control (RRC) configuration) from the network (e.g., from a base station <NUM>) regarding one or more of the following:.

In step <NUM>, the UE <NUM>, while receiving a DCI via a PDCCH, detects the DCI format. The detected DCI format can be DCI format 0_1/1_1 which is supported from NR Release <NUM> or the new compact DCI format 0_X/1_X for UL/DL introduced in NR Release <NUM>.

Depending on whether the detected DCI belongs to one of DCI formats 0_1/1_1 or the detected DCI belongs to one of DCI format 0_X/1_X (i.e., the UL/DL new compact DCI formats introduced in NR Release <NUM>), the UE <NUM> follows different procedures for determining and indicating the DMRS antenna ports. If the UE <NUM> detected DCI format 1_1 or DCI format 0_1, the process moves to step <NUM>. In step <NUM>, if the UE <NUM> detected DCI format 1_1, the DMRS table to be used is identified purely based on DMRS configuration. If the UE <NUM> detected DCI format 0_1, the DMRS table to be used is identified using both the DMRS configuration and the enabling/disabling of transform precoding. In step <NUM>, the DMRS antenna port is then determined based on the "Value" of the antenna port field that corresponds to an entry in the identified DMRS table.

If the UE <NUM> detected DCI format 1_X or 0_X, the process moves to step <NUM>. In step <NUM>, if the UE <NUM> detected DCI format 1_X, the DMRS table to be used is identified among one or more tables by jointly using the following:.

Consider an example where the UE <NUM> is configured with a particular DMRS configuration (type <NUM> DMRS with maximum number of front loaded DMRS symbols is maxLength=<NUM>). In this case, there may be different DMRS tables predefined in specifications for this DMRS configuration corresponding to different number of bits in the antenna ports field. A first DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, and antenna port field size of <NUM> bit. A second DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, and antenna port field size of <NUM> bits. A third DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, and antenna port field size of <NUM> bits. Hence, using this embodiment, the UE <NUM> can identify which DMRS table to use among the three tables by jointly using the DMRS configuration and the antenna port field size configured for DCI format 1_X. For example, if DCI format 1_X contains an antenna port field of size <NUM>, then the third predefined DMRS table is determined by the UE <NUM>. Note that this embodiment is different from what is known in NR Release <NUM> where the DMRS table to be used in the case of DCI format 1_1 is only based on DMRS configuration.

In an alternative embodiment, the DMRS configuration defines a single, "master" antenna port table in the same fashion as in NR Release <NUM>, but the antenna port field size configured for DCI format 1_X defines an antenna port table subset, where the antenna port subset corresponds to a subset of rows of the master antenna port table. For instance, an antenna port field size of <NUM> bits may corresponds to the entire master antenna port table while an antenna port field size of <NUM> bits may corresponds to a subset of rows form the master antenna port table, where the size of the subset is equal to half the number of rows of the table.

In a further variant of this embodiment, the different DMRS tables corresponding different antenna port field sizes may have different properties with respect to support of the number of front loaded DMRS symbols, the number of CDM groups without data, and the number of supported ranks. Details of these embodiments are described further below. Note that even though the above embodiments are written in terms of different DMRS tables corresponding to different antenna port field sizes, these embodiments can be easily extended for the case where different subsets of a larger DMRS table corresponding to different antenna port field sizes.

If the UE <NUM> detected DCI format 0_X, then in step <NUM> the DMRS table to be used is identified among one or more tables by jointly using the following:.

Consider an example where the UE <NUM> is configured with a particular DMRS configuration (type <NUM> DMRS with maximum number of front loaded DMRS symbols is maxLength=<NUM>) with transform precoder disabled. In this case, there may be different DMRS tables predefined in specifications for this DMRS configuration and transform precoder disabled corresponding to different number of bits in the antenna ports field. A first DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, transform precoder disabled, rank =<NUM> and antenna port field size of <NUM> bit. A second DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, transform precoder disabled, rank = <NUM> and antenna port field size of <NUM> bits. A third DMRS table may correspond to DMRS type <NUM>, maxLength=<NUM>, transform precoder disabled, rank =<NUM>, and antenna port field size of <NUM> bits. Hence, using this embodiment, the UE <NUM> can identify which DMRS table to use among the three tables by jointly using the DMRS configuration and the antenna port field size configured for DCI format 0_X. For example, if DCI format 0_X is configured with an antenna port field of size <NUM>, then the third predefined DMRS table is determined by the UE. Note that this embodiment is different from what is known in NR Release <NUM> where the DMRS table to be used in the case of DCI format 0_1 is only based on DMRS configuration and enabling/disabling of transform precoder.

From step <NUM>, the DMRS antenna port is determined based on the "Value" of the antenna port field that corresponds to the entry in the identified DMRS table (step <NUM>). As will be appreciated by one of skill in the art, once the UE <NUM> has determined the DMRS antenna port, the UE <NUM> uses the determined DMRS antenna port for demodulation.

In some embodiments, the new set of antenna port indication tables may be designed to accommodate both one and two front-loaded DMRS configurations. For example, two front-loaded DMRS symbol may be configured to improve channel estimation performance. In some embodiments, whether both single front-loaded DMRS symbols and two front-loaded DMRS symbols are supported in a DMRS table or whether only single front-loaded DMRS symbol is supported in a DMRS table depends on the antenna port field size associated with the DMRS table. For example, if the antenna port field size is <NUM>, then only two entries are possible in the DMRS table. In this case, the DMRS table may only support single front-loaded DMRS symbol. However, if antenna port field size is <NUM>, then up to eight entries are possible in the DMRS table. Hence, a combination of both single front-loaded DMRS symbols and two front-loaded DMRS symbols are supported in different entries of a DMRS table. The benefit of including different entries (some entries with single front-loaded DMRS symbols and some other entries with two front-loaded DMRS symbols) is as follows. A UE that may have good coverage may require only a single front-loaded DMRS symbol as the channel estimation accuracy should already be good enough for this UE. However, a UE that may not have good coverage may require additional two front-loaded DMRS symbol entries to improve channel estimation performance.

In some embodiments, the new tables may include one or more than one CDM group without data for DMRS for power boosting purpose. For example, 3dB power boosting if two CDM groups without data is configured. In some embodiments, whether one CDM groups without data for DMRS and more than one CDM group without data is supported in a DMRS table depends on the antenna port field size associated with the DMRS table. For example, if the antenna port field size is <NUM>, then only two entries are possible in the DMRS table. In this case, the DMRS table may only support entries with one CDM groups without data for DMRS. However, if antenna port field size is <NUM>, then up to eight entries are possible in the DMRS table. Hence, in this case, a combination of entries with some entries supporting only one CDM groups without data for DMRS and some entries supporting more than one CDM groups without data for DMRS are supported of a DMRS table with eight entries. The benefit of including different entries (some entries with one CDM groups without data for DMRS and some other entries with more than one CDM groups without data for DMRS) is as follows. A UE that may have good coverage may require one CDM groups without data for DMRS as this UE likely does not need DMRS power boosting. For this UE, the data can be transmitted in the other CDM groups. However, a UE that may not have good coverage may benefit from DMRS power boosting. Hence, for this UE it is beneficial to indicate more than one CDM groups without data for DMRS.

In some embodiments, the new tables support both type <NUM> and type <NUM> DMRS configurations. For example, using type <NUM> configuration for better channel estimation and type <NUM> for more DMRS power boosting as three CDM groups without data can be configured.

The new tables may also support PDSCH transmission over more than one TRP for increased reliability through TRP diversity. The new tables may also support PUSCH transmission towards more than one TRP for increased reliability through TRP diversity.

With the above consideration in mind, some examples of antenna tables for different DMRS configurations are shown in Table <NUM> to Table <NUM>, which may be used for DCI format 1_X. In allocating the table entries, the more reliable schemes such as, a single layer MIMO transmission and DMRS with power boosting, can be allocated first so that they can be selected by a DCI with smaller antenna port field size. Small DCI size also means more reliable PDCCH transmission and better coverage. This would help to ensure similar reliability and coverage for PDSCH (or PUSCH) and PDCCH.

For a given DMRS type configured by higher layer parameter dmrs-Type, a maximum front-loaded symbol length given by higher layer parameter maxLength, a corresponding antenna port table from Table <NUM> to Table <NUM> can be determined. The table can be considered as some sort of a "master" table.

For the examples in Table <NUM> to Table <NUM>, the size of the "antenna ports" field of DCI Format 1_X can be configured with N=<NUM>, <NUM>, <NUM>, <NUM>, or <NUM> bits. Note that <NUM><=N<= N<NUM>, where <NUM>^N<NUM> is the size of the "master" tables.

In one embodiment, the first <NUM>^N entries of the master antenna port table would be used when the number of configured bits for the "antenna ports" field is N><NUM>, i.e., the tables with different sizes are nested.

For example, for type <NUM> DMRS with a maximum of one front-loaded symbol, if N=<NUM> is configured, the <NUM>st two entries in Table <NUM> would be used and only a single layer transmission is supported, either with or without 3dB power boosting. If up-to-<NUM> layers are to be supported, N=<NUM> may be configured. If multi-TRP is also to be supported, N=<NUM> may be configured so that Value=<NUM> can be signaled.

For type <NUM> DMRS with maximum two front-loaded symbols, if N=<NUM> is configured, the <NUM>st two entries (or rows) in Table <NUM> would be used and only a single layer transmission with 3dB power boosting is supported, either with one or two front-loaded symbols. If N=<NUM> is configured, the <NUM>st <NUM> entries (or <NUM> rows) would be used to also support a single layer without power boosting. If N=<NUM> is configured, the <NUM>st <NUM> entries (or <NUM> rows) would be used to support up-to-<NUM> layers. If multi-TRP is also to be supported, N=<NUM> may be configured so that Value=<NUM>,<NUM> can be signaled.

Alternatively, for type <NUM> DMRS with maximum two front-loaded symbols, only two front-loaded symbols are considered for more reliability on DMRS based channel estimation. The corresponding example is shown in Table <NUM>, where up to 3bits may be configured.

Similarly, for type <NUM> DMRS with maximum one front-loaded symbol, if N=<NUM> is configured, the 1st two entries in Table <NUM> would be used and only a single layer transmission with power boosting is supported, either with 3dB or <NUM>. 77dB power boosting. If up-to-<NUM> layers are to be supported, N=<NUM> may be configured. If multi-TRP or more than 3dB power boosting is also to be supported, N=<NUM> may be configured.

For type <NUM> DMRS with maximum two front-loaded symbols, if N=<NUM> is configured, the <NUM>st two entries in Table <NUM> would be used and only a single layer transmission with <NUM>. 77dB power boosting is supported, either with one or two front-loaded symbols. If N=<NUM> is configured, the 1st <NUM> entries would be used to also support 3dB power boosting. If N=<NUM> is configured, the 1st <NUM> entries would be used to support up-to-<NUM> layers. If multi-TRP or more than 3dB power boosting is to be supported, N=<NUM> may be configured.

Again, for type <NUM> DMRS with maximum two front-loaded symbols, an alternative option is to consider only two front-loaded symbols for more reliability on DMRS based channel estimation. The corresponding example is shown in Table <NUM>, where up to <NUM> bits may be configured.

In another embodiment, the subset of entries of the antenna port table which are to be used for a configured N may be flexibly configured by the gNB to the UE as part of the DMRS configuration based on either the examples shown in Table <NUM> to Table <NUM> or based on the existing antenna port tables specified in Tables <NUM>. <NUM>-<NUM>/<NUM>/<NUM>/<NUM> of 3GPP TS38. For instance, a bitmap of size <NUM>^N<NUM> may be used, wherein the bitmap has <NUM>^N bits set to one and where a bit set to one indicates that the corresponding row of the master antenna port table is included in the antenna port subset. The least significant bit (LSB) of the bitmap can be associated with the first row and the most significant bit (MSB) with the last row of the master antenna port table. Alternatively, the LSB may be associated with the last row and the MSB with the first row. The subset of entries forms a new table of size <NUM>^N in increasing order of "Value" in the master antenna port table.

In a variant of this embodiment, the number of bits of the antenna port field is not explicitly indicated to the UE but is implicitly indicated via the configuration bitmap. For instance, if the bitmap contains M ones, the UE determines that the antenna port field size is N = [log<NUM> M]. In case Tables <NUM>. <NUM>-<NUM>/<NUM>/<NUM>/<NUM> of 3GPP TS38. <NUM> is used for the purpose, N<NUM> is the number of bits for "antenna port" field in the existing DCI format 1_1.

For UL transmission associated with DCI format 0_X, it is assumed that only up to rank <NUM> transmission is supported. Some limited MU-MIMO use cases may be supported. While not described in the example tables below, it is also possible that the tables are constructed to include uplink multi-TRP support, similar to those for DL transmission.

Examples of the antenna tables for DCI format 0_X are shown in Table <NUM> to Table <NUM>, where N=<NUM>, <NUM>, <NUM>, or <NUM> may be configured for the antenna port field size in the DCI. For a given DMRS type, dmrs-Type, a maximum front-loaded symbol length, maxLength, a rank, and whether transform precoder is disabled, a corresponding antenna port table is determined. The table can be considered as a "master" table. When N=<NUM> is configured, the first entry of the table is used. When N=<NUM> is configured, the two code points (<NUM>,<NUM>) of the antenna port field are mapped to the first two entries of the master table, i.e., mapped to Value=<NUM> and <NUM>, respectively. When N=<NUM> is configured, the four code points (<NUM>,<NUM>,<NUM>,<NUM>) are mapped to the first four entries of the master table. Similarly, when N=<NUM>, the eight code points are mapped to the eight entries of the master table. In the sense that the tables for N=<NUM>, <NUM>, <NUM>, and <NUM> are nested. Although maximum N<NUM>=<NUM> (i.e., <NUM> entries in the master tables) is illustrated in the examples, a smaller or larger value can be used.

In an alternative embodiment, the subset of entries of the master antenna port table corresponding to N may be flexibly configured by the gNB to the UE as part of the DMRS configuration. For instance, a bitmap of size-<NUM>^ N0 may be used, wherein the bitmap has <NUM>^N bits set to one and where a bit set to one indicates that the corresponding row of the master antenna port table is included in the antenna port subset. The master antenna port table can be either one of Table <NUM> to Table <NUM>, in which case N<NUM>=<NUM>, or one of tables <NUM>. <NUM>-<NUM> to <NUM>. <NUM>-<NUM> of 3GPP TS38. <NUM> and in which case N<NUM>=<NUM> is the size of the "antenna ports" field in DCI Format <NUM>-<NUM> for a given DMRS type, dmrs-Type, a maximum front-loaded symbol length, maxLength, a rank, and whether transform precoder is disabled. In a variant of this embodiment, the number of bits of the antenna port field, N, is not explicitly indicated to the UE but is implicitly indicated via the configuration bitmap. For instance, if the bitmap contains M ones, the UE determines that the antenna port field size is N = [log<NUM> M].

<FIG> is a schematic block diagram of a radio access node <NUM> according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node <NUM> may be, for example, a base station <NUM> or <NUM> or a network node that implements all or part of the functionality of the base station <NUM> or gNB described herein. As illustrated, the radio access node <NUM> includes a control system <NUM> that includes one or more processors <NUM> (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory <NUM>, and a network interface <NUM>. The one or more processors <NUM> are also referred to herein as processing circuitry. In addition, the radio access node <NUM> may include one or more radio units <NUM> that each includes one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The radio units <NUM> may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) <NUM> is external to the control system <NUM> and connected to the control system <NUM> via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) <NUM> and potentially the antenna(s) <NUM> are integrated together with the control system <NUM>. The one or more processors <NUM> operate to provide one or more functions of a radio access node <NUM> as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory <NUM> and executed by the one or more processors <NUM>.

As used herein, a "virtualized" radio access node is an implementation of the radio access node <NUM> in which at least a portion of the functionality of the radio access node <NUM> is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the radio access node <NUM> may include the control system <NUM> and/or the one or more radio units <NUM>, as described above. The control system <NUM> may be connected to the radio unit(s) <NUM> via, for example, an optical cable or the like. The radio access node <NUM> includes one or more processing nodes <NUM> coupled to or included as part of a network(s) <NUM>. If present, the control system <NUM> or the radio unit(s) are connected to the processing node(s) <NUM> via the network <NUM>. Each processing node <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and a network interface <NUM>.

In this example, functions <NUM> of the radio access node <NUM> described herein are implemented at the one or more processing nodes <NUM> or distributed across the one or more processing nodes <NUM> and the control system <NUM> and/or the radio unit(s) <NUM> in any desired manner. In some particular embodiments, some or all of the functions <NUM> of the radio access node <NUM> described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) <NUM>. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) <NUM> and the control system <NUM> is used in order to carry out at least some of the desired functions <NUM>. Notably, in some embodiments, the control system <NUM> may not be included, in which case the radio unit(s) <NUM> communicate directly with the processing node(s) <NUM> via an appropriate network interface(s).

<FIG> is a schematic block diagram of a wireless communication device <NUM> according to some embodiments of the present disclosure. As illustrated, the wireless communication device <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and one or more transceivers <NUM> each including one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The transceiver(s) <NUM> includes radio-front end circuitry connected to the antenna(s) <NUM> that is configured to condition signals communicated between the antenna(s) <NUM> and the processor(s) <NUM>, as will be appreciated by on of ordinary skill in the art. The processors <NUM> are also referred to herein as processing circuitry. The transceivers <NUM> are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device <NUM> described above may be fully or partially implemented in software that is, e.g., stored in the memory <NUM> and executed by the processor(s) <NUM>. Note that the wireless communication device <NUM> may include additional components not illustrated in <FIG> such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the wireless communication device <NUM> and/or allowing output of information from the wireless communication device <NUM>), a power supply (e.g., a battery and associated power circuitry), etc..

With reference to <FIG>, in accordance with an embodiment, a communication system includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a RAN, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 906A, 906B, 906C, such as Node Bs, eNBs, gNBs, or other types of wireless Access Points (APs), each defining a corresponding coverage area 908A, 908B, 908C. Each base station 906A, 906B, 906C is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first UE <NUM> located in coverage area 908C is configured to wirelessly connect to, or be paged by, the corresponding base station 906C. A second UE <NUM> in coverage area 908A is wirelessly connectable to the corresponding base station 906A.

The client application <NUM> may be operable to provide a service to a human or nonhuman user via the UE <NUM>, with the support of the host computer <NUM>.

It is noted that the host computer <NUM>, the base station <NUM>, and the UE <NUM> illustrated in <FIG> may be similar or identical to the host computer <NUM>, one of the base stations 906A, 906B, 906C, and one of the UEs <NUM>, <NUM> of <FIG>, respectively.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms the last segment. More precisely, the teachings of these embodiments may improve memory consumption and processing resources and thereby provide benefits such as improved performance, decreased power consumption, and the like.

<FIG> is a flow chart that illustrates the operation of a network node (e.g., base station <NUM>) in accordance with at least some aspects of the embodiments described above. As illustrated, in step <NUM>, the network node sends a configuration to a UE <NUM>. As discussed above, the configuration may be regarding one or more of the following:.

In step <NUM>, the network node sends DCI to the UE <NUM> via PDCCH. The DCI is in a particular DCI format (e.g., DCI format 0_1/0_1 or DCI format 0_X/1_X). The DMRS table to be used to interpret the value in the antenna ports field of the DCI is determined as described above. Note that the relationship between the DMRS table used to interpret the value in the antenna ports field and the size, or bit-width, of the antenna ports field may be any of those described above.

Claim 1:
A method performed by a wireless communication device (<NUM>, <NUM>) for a cellular communications system (<NUM>), the method comprising:
• receiving (<NUM>), from a network node, a demodulation reference signal, DMRS, configuration that comprises an indication of a type of DMRS used and a maximum number of front-loaded DMRS symbols, and an antenna port field configuration for indicating a size of an antenna port field having a configurable size in a downlink control information, DCI, format;
• receiving (<NUM>) a DCI of the DCI format from the network node for a corresponding physical channel, the received DCI comprising an antenna port field;
• determining (<NUM>) the size of the antenna port field of the received DCI and a DMRS port table for interpreting a value comprised in the antenna port field of the received DCI based on at least the DMRS configuration and the antenna port field configuration; and
• determining (<NUM>) one or more DMRS ports in the DMRS table used for the corresponding physical channel based on one or more of the determined size of the antenna port field, the DMRS port table, and the value of the antenna port field comprised in the DCI,
wherein the size of the antenna port field is <NUM> and the one or more DMRS ports are determined by the first entry of the determined DMRS table.