RU2810537C1 - Device and methods for indicating dmrs ports for user devices - Google Patents

Abstract

FIELD: wireless communications.

SUBSTANCE: method for specifying DMRS ports for at least one UE in a wireless communication system is carried out at a base station (TRP) supporting the simultaneous transmission of multiple spatial MIMO data streams, each of which is associated with a different DMRS port. The method comprises the steps of selecting a DMRS port group containing serial DMRS port indexes to be used on the UE from a total number of serial DMRS port indexes available for use on the UE, and obtaining a code parameter representing the selected DMRS port group, and signal the UE with service information including the received code parameter.

EFFECT: providing the ability to support a larger number of demodulation reference signal (DMRS) ports, ensuring adaptability of the DMRS structure depending on bandwidth requirements, with the ability to vary its frequency and time density without modifying the DMRS structure itself.

22 cl, 44 dwg, 4 tbl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates generally to wireless communications using advanced demodulation reference signals (DMRS), and more particularly to devices and methods for indicating DMRS ports to user devices.

BACKGROUND ART

At the present stage, there is an increasingly active deployment of ^5th generation (5G) wireless communication networks of the New Radio (NR) standard, the advantages and capabilities of which are widely known.

Base stations (Transmission-Reception Point, TRP) in the 5G NR system use complex antenna arrays containing multiple transceiver antenna elements, which allow efficient implementation of MIMO (multiple-input-multi-channel-output) technology when transmitting data (for example, physical Downlink shared data channel (PDSCH)) a number of parallelly transmitted spatial MIMO streams or layers (MIMO-layers) are formed.

The digital signal is transmitted or received using one or more digital ports connected to the antenna elements of the base station, using a radio frequency unit that performs the function of converting the digital signal to analog and vice versa. Thus, for the 3.5 GHz frequency range, up to 64 digital antenna ports can be used, allowing base stations to use various spatial digital signal processing schemes. For example, using spatial multiplexing (SM) technology, it is possible to reuse the same time-frequency resources to transmit multiple signals (MIMO streams) to one or more user equipment (UE), and using adaptive beamforming technology ( beamforming) provides dynamic focusing of the energy of the transmitted signal in one or more specified directions. By using advanced modulation techniques such as Orthogonal Frequency Division Modulation (OFDM), efficient wideband signal transmission is achieved. OFDM ensures orthogonality of signals simultaneously transmitted on different subcarriers (i.e., orthogonality in the frequency domain). Spatial MIMO streams are generally not orthogonal, and signals transmitted in different MIMO streams interfere with each other at the receiver end. To reduce mutual interference, as a rule, various adaptive beamforming techniques are used at the transmitter and receiver.

Accordingly, transmitted MIMO streams are properly received by user devices that also support these technologies.

Multiple MIMO streams transmitted from a base station may all be destined for one UE, in which case single-user MIMO (SU-MIMO), or may be destined for different UEs, in which case multi-user MIMO (MU) -MIMO).

Dedicated reference signals (RS) are used to enable communication between various devices in a 5G NR system, including base stations and user devices. One such reference signal is the demodulation reference signal (DMRS). DMRS signals are transmitted only as part of the corresponding physical channel (specifically the following physical data channels: PDSCH and physical uplink shared data channel (PUSCH)). Thus, they are not continuously or periodically transmitted reference signals, which impose additional bandwidth overhead. More specifically, a different DMRS signal is transmitted along with each of the PDSCH/PUSCH spatial MIMO streams simultaneously transmitted by the corresponding transmitting side; In addition, the same adaptive spatial signal processing (precoding) is used for the DMRS signal. Each DMRS signal in a 5G NR communication system is associated with a unique index (number) called a DMRS port. Thus, for example, each PDSCH spatial MIMO stream transmitted from a TRP in a 5G NR communication system has a unique DMRS port assigned to it; therefore, the number of MIMO layers is equal to the number of DMRS ports.

The transmission sequence of multiple spatial MIMO streams together with DMRS signals is illustrated in FIG. 1.

In FIG. Figure 1 shows a simplified diagram of spatial processing at the transmitter, where at the first stage adaptive digital spatial signal processing is carried out, converting the input signal of MIMO streams into a signal from digital antenna ports. At the same time, the corresponding spatial processing in OFDM systems can be carried out in the frequency domain, which allows for flexible formation of different radiation patterns on different subcarriers. Following the digital spatial processing procedure, an analog beamforming procedure is applied to convert the digital port input signal into signals from the physical subarray antennas. This spatial signal processing is carried out in the time domain for the entire OFDM signal, which imposes restrictions on the number of simultaneously formed beams.

The main purpose of DMRS signals is to ensure coherent reception of physical data channels (PDSCH and PUSCH). More specifically, during passage through the communication channel, each of the transmitted MIMO streams is subject to various types of distortions, and in order to correctly receive this MIMO stream, a channel estimation procedure is carried out on the receiver side, the algorithms of which use the DMRS corresponding to this MIMO stream. signal. Channel estimation is a critical procedure in 5G NR communication system, and its reliability is of utmost importance. In this regard, high-quality reception of DMRS signals on the receiving side is of great importance.

To simultaneously transmit multiple DMRS signals of the corresponding MIMO layers in the 5G NR communication system, they are properly multiplexed by resource elements (RE). In the context of multiplexing DMRS signals, two types of DMRS structures are supported in the 5G NR communication system: a Type 1 DMRS structure (Tue 1) and a Type 2 DMRS structure (Tue 2), which are illustrated in the resource element grid in FIG. 2a and 2b, where each RE is defined by a subcarrier in the frequency domain and an OFDM symbol in the time domain.

First of all, subcarriers in the frequency domain are divided into CDM groups. For a Type 1 structure, two CDM groups are defined, in which case the distribution of subcarriers in the frequency domain is uniform, i.e. the distance between the subcarriers of different CDM groups is always the same (see Fig. 2a). CDM groups are indexed by the index Δ. Further, in each of the two CDM groups, the DMRS signals are multiplexed by applying frequency domain (FD) orthogonal codes (OCC) of length 2 and time domain (TD) OCC of length 2. Each of the FD-OCC and each of the TD -OCC also has its own index. Thus, in the Type 1 structure, 8 DMRS signals are multiplexed: 2 CDM groups × 2 FD-OCC of length 2 × 2 TD-OCC of length 2, i.e. 8 DMRS ports are defined for the corresponding 8 parallel spatial MIMO streams.

For the Type 2 structure, three CDM groups are defined with a non-uniform distribution in the frequency domain (see Fig. 2b). Next, in each of the three CDM groups, the DMRS signals are multiplexed again by using FD-OCC of length 2 and TD-OCC of length 2. Thus, in the Type 2 structure, 12 DMRS signals are multiplexed: 3 CDM groups × 2 FD- OCC of length 2×2 TD-OCC of length 2, i.e. 12 DMRS ports are defined for the corresponding 12 spatial MIMO streams.

Therefore, the 5G NR communication system supports a maximum of 12 spatial MIMO streams on the TRP side.

It must be emphasized that the multiplexed DMRS signals in each CDM group of both Type 1 and Type 2 structures are orthogonal, i.e. do not create mutual interference. Orthogonality in this case is of utmost importance for the correct reception of DMRS signals and, therefore, reliable channel estimation.

It should be noted here that although, as follows from the above, up to 12 MIMO streams are generally supported on the base station side, in SU-MIMO mode a maximum of 8 MIMO streams are supported, i.e. No more than 8 MIMO streams can be transmitted to one UE at a time. In addition, the 5G NR communication system provides semi-static switching between Type 1 and Type 2 DMRS structures through Radio Resource Control (RRC) signaling when the maximum number of transmitted MIMO streams needs to be increased or decreased accordingly; in other words, their number before transmission is not known a priori. Thus, the UE must know in advance which DMRS ports to use for receiving the downlink (DL) data channel as well as transmitting the uplink (UL) data channel.

The general scheme of informing the user equipment (UE) about the used DMRS ports in the 5G NR system is shown in Fig. 3.

According to Fig. 3, initially a physical downlink control channel (PDCCH) carrying an overhead message in the form of downlink control information (DCI) is transmitted from the TRP to the UE. In DCI, the user equipment is informed of the PDSCH/PUSCH transmission parameters selected by the scheduler on the TRP side, primarily that a PDSCH transmission is scheduled to be transmitted to the user equipment. The DCI also communicates to the UE the DMRS port numbers to be used for demodulating the scheduled number of MIMO PDSCH streams as well as for scheduling PUSCH transmissions. In addition, the DCI may include other service information, such as information about the modulation and coding scheme (MCS), frequency domain resource allocation (FDRA), adaptive spatial signal processing, etc.

The above information is relatively fast (in terms of low latency) because it is carried out at the physical layer in a compact DCI message. At the same time, this compactness implies a strict limitation on the total number of bits in a DCI message (no more than 50-70 bits in a 5G NR system), and, therefore, information about the DMRS ports used must be encoded in DCI while minimizing bit consumption.

In FIG. 4a, 4b illustrate the data organization approach used in the 5G NR system to implement informing the UE about the DMRS ports to be used. In accordance with the above multiplexing, each DMRS port can be associated with a unique set of CDM group index, FD-OCC and TD-OCC. It should be noted that the concept of 'DMRS port' is often directly related to the unique combination of CDM group, FD-OCC and TD-OCC. In FIG. 4a, the correspondence of the DMRS port number to the combination of the above parameters is shown in table form for DMRS Type 1. For this type of DMRS, where no more than four DMRS ports can be used on the UE side (i.e., the UE can simultaneously receive or transmit no more than 4 spatial MIMO streams of the physical data channel), FIG. 4b illustrates in tabular form the encoding of a combination of DMRS ports for use (right column) using a uniquely assigned code parameter (left column). It is the value of such a code parameter that is transmitted from the TRP as part of the DCI to the UE to inform the UE about the specific combination of DMRS ports that should be used for PDSCH or for PUSCH. It should be noted here that the '0', '1', '2', '3' DMRS port index notation used in the right column of the table in FIG. 4b is correspondingly equivalent to the '1000', '1001', '1002', '1003' DMRS port index notation used in the left column of the table in FIG. 4a; These notations may be used interchangeably throughout this application in a manner understandable to one skilled in the art.

With respect to the middle column in the table in FIG. 4b, it should be noted that the OFDM symbols allocated for the transmission of DMRS signals may be partially used for the transmission of a physical data channel (PDSCH or PUSCH). Specifically, the code parameter for informing the UE of the DMRS port combination according to FIG. 4b corresponds to the number of CDM groups not used for data transmission. For example, for a code parameter equal to '0', the first CDM group of the DMRS OFDM symbol shall be used for DMRS transmission, while the second CDM group shall be used for physical data channel (PDSCH) transmission. For a code parameter equal to '3', the physical data channel on the OFDM symbol allocated for DMRS is not transmitted. In this case, the first and second CDM groups are used to transmit DMRS for two or more users. Multiplexing the DMRS with the data channel in a single OFDM symbol reduces the overhead associated with DMRS transmission.

Fig. 5a-5c illustrate methods for allocating time resources in a 5G NR wireless communication system at a physical layer.

The 5G NR system supports two types of timing resource allocation schemes for transmitting a physical data channel: Type A and Type B. In FIG. 5a shows the first approach (Type A), in which the minimum unit of time resource allocation for PDSCH transmission is one downlink slot (DL slot) consisting of 14 OFDM symbols. Illustration in Fig. Figure 5a is shown for the frequency range used in 5G NR with a carrier frequency of about 3.5 GHz. Similarly, the minimum unit of time resource allocation for PUSCH transmission is one slot (UL slot). Type A is characterized by a limited ability to vary the starting OFDM symbol (from 0 to 3) of the data channel within the slot.

In FIG. Figure 5b illustrates an example of the distribution of time resources according to the Type A scheme over a larger time interval. Each 10 ms frame in the system is divided into a number of downlink-uplink (DL/UL) periods, each of which includes an appropriate number of DL slots and UL slots, separated by a guard interval to allow switching between DL and UL. As can be seen from the illustrations in Fig. 5a, 5b, OFDM symbols are allocated in each DL/UL slot for transmitting the physical control channel and DMRS signals. It should be noted that the ratio between the number of DL slots and UL slots in the DL/UL period is flexible.

Type A is typically used for enhanced mobile broadband (eMBB) traffic, which corresponds to, for example, regular Internet traffic in smartphones.

In FIG. 5c illustrates another of the time resource allocation types used in 5G NR, namely Type B, whose minimum time resource allocation unit is a minislot. Here, within a slot, a user may be allocated one or more PDSCH transmissions, each with a duration of one mini-slot of 2 (as shown in FIG. 5c), 4 or 7 OFDM symbols. Typically associated with each of these PDSCH transmissions is a downlink physical control channel (DL-ctrl), each minislot also containing DMRS signals (not shown in FIG. 5c). The same is true for PUSCH broadcasts. This type, in particular, is characterized by greater flexibility in varying the starting symbol of the data channel (from 0 to 12) within a slot. Information about the starting symbols of the PDSCH minislots is reported to the UE in DL-ctrl.

Type B is typically used for ultra-reliable low-latency communications (URLLC) traffic, which is mostly used for communications in industrial applications (eg between robots, etc.) where reliability/reliability and latency requirements are high.

It should be noted again that the frame, slot, mini-slot configurations shown are quite flexible in 5G NR, and FIG. 5a-5c are provided by way of illustration only to provide a comprehensive understanding of the present application.

Finally, although, in accordance with the above discussion, the DMRS signals transmitted from one base station are orthogonal, i.e. they do not interfere with each other within the cell served by the base station, however, there is no inherent orthogonality between the DMRS signals of neighboring cells, which can lead to mutual interference at cell boundaries. To randomize interference, with respect to DMRS signals transmitted from base station, quadrature phase modulation (QPSK modulation) is also performed. In a 5G NR system, QPSK modulation is carried out using a Gold sequence of length 31 with initialization common across CDM groups or individual for each CDM group. In the latter case, two initial seeds are configured for each base station via RRC signaling and dynamically communicated to the UE via DCI for subsequent demodulation. Thus, the sets of initialization values are different for different TRPs, which ensures that the DMRS signals transmitted by different TRPs are different. It should be noted that a similar procedure is used in UL to randomize the interference between DMRS signals from users served by neighboring TRPs.

Aspects of the functioning of 5G NR wireless communication systems, briefly described above, are disclosed in detail in the specifications TS 38.211, 38.212 "NR; Physical channels and modulation", v17.3.0, 2022-09-21, 3gpp.org, which are included in their entirety in this description is by reference.

Although the deployment of 5G NR systems in the world is just beginning to gain momentum, active research is already underway in various directions to standardize next-generation wireless communication systems, the so-called. 6G, which will have characteristics superior to 5G NR.

In particular, for the 6G operating range 10-12 GHz (UPPER MID BAND), base stations (TRPs) are planned to support ultra-large antenna arrays, with at least 1024 antenna elements, hybrid analog and digital beamforming with a large number of antenna ports (≥ 128 ). Thus, with support, in particular, up to 64 simultaneously transmitted spatial MIMO streams in UPPER MID BAND communication systems, the concept of a radio interface with an ultra-large antenna array (Massive MIMO) will be taken to a fundamentally new level.

6G plans to support a set of reference signals similar to those used in 5G NR, such as DM-RS, CSI-RS, SRS, PT-RS, PSS/SSS. Details regarding the said RS are given in the above specifications. At the same time, approaches to working with reference signals used in 5G NR cannot always be extrapolated to next-generation wireless communication systems.

In particular, the above-described DMRS structures used in 5G NR systems can multiplex a maximum of 12 DMRS signals, while in a 6G system, the parallel transmission of at least 64 spatial MIMO channels and, accordingly, 64 DMRS signals must be ensured. In other words, existing DMRS structures cannot provide multiplexing of the number of DMRS signals required for 6G.

Then, as previously stated with reference to FIG. 2a, 2b, the Type 2 DMRS structure is characterized by a non-uniform distribution of subcarriers in the frequency domain, in contrast to the uniform nature of the Type 1 structure. These two types of DMRS structure use significantly different channel estimation algorithms, while the Type 2 non-uniform structure algorithm is characterized by higher complexity. This is not a serious problem for the relatively small number of DMRS ports in 5G NR, but may be unacceptable for a significantly larger number in 6G, since the complexity of the channel estimation algorithm in the case of the above-mentioned unevenness increases significantly.

Further, if there is a need to regulate the density of the DMRS structure in the frequency domain (in connection with regulating the number of available DMRS ports), the 5G NR communication system carries out a corresponding switch between Type 1 and Type 2 structures, with which various channel estimation algorithms are associated, differing in that number according to complexity. Despite the fact that this switching, as mentioned earlier, is semi-static in nature, i.e. Dynamic switching between Type 1 and Type 2 fabrics is not supported in 5G NR. In other words, there is very limited flexibility in adapting the DMRS structure, with switching between virtually inconsistent types of structures. In 6G, implementing such an approach would lead to an unacceptable increase in complexity on the receiver side.

Thus, there is an urgent need to develop a new DMRS structure for next generation wireless communication systems (including 6G), which would satisfy the following design requirements:

support for more DMRS ports (up to 64);

adaptability of the DMRS structure depending on throughput requirements, with the ability to vary its density in frequency and time without modifying the DMRS structure itself;

maintaining low complexity of the channel estimation algorithm.

At the same time, in the context of designing next-generation wireless communication systems (including 6G), the following problem also arises, in view of the above-described need to support a larger number of DMRS ports due to a significant increase in the supported number of spatial MIMO streams (up to 64). The current 5G NR DMRS port designation scheme (see, for example, Fig. 4a, 4b) supports a maximum of 12 DMRS ports on the TRP side and a maximum of 8 DMRS ports per UE, while there is currently no systematic approach, which would allow this existing scheme to be extended to the larger number of DMRS ports required - specifically 64 on the TRP side and 16 on the UE side.

As noted earlier, information about DMRS, incl. DMRS ports to be used must be communicated to user devices with low latency, typically using DCI signaling on the PDCCH; at the same time, a fairly strict limitation is imposed on the total number of bits in the DCI. As a consequence, attempting to directly extrapolate existing approaches (e.g., described with reference to FIGS. 4a, 4b) in next-generation wireless communication systems to communicate DMRS port information to the UE on the PDCCH will result in an unacceptably large number of bits in the DCI where it must be transmitted. a lot of service data in addition to the information related to DMRS, as discussed above.

In the prior art, technical solutions are known related to specifying DMRS ports for advanced communication systems. Such technical solutions are proposed, in particular, in US 10419180, US 10715300, US 2021/0167914.

US 10419180 proposes a DMRS port indication method, whereby a DMRS port indication table is provided covering all transmission cases, maximally supporting 8 layers, and 4 bits specified by the DMRS port indication information can indicate all cases in the DMRS port indication table. , in combination with the cases of single codeword transmission and double codeword transmission according to the corresponding standard, so that the bit load associated with specifying DMRS ports can be reduced. The main disadvantages of the proposed solution in US 10419180 in this context are the use of a table-based approach for specifying DMRS ports, and the fact that it supports a maximum of 8 MIMO layers per UE.

US 10715300 proposes a method for specifying DMRS, targeting NR standard scenarios. According to this method, the transmitting end determines, from a plurality of DMRS configuration information groups, DMRS configuration information corresponding to the current DMRS transmission scheme. At the transmitting end, DMRS indication information is obtained based on this DMRS configuration information. DMRS indication information is sent from the transmitting end. As a result, more layers are supported and the overhead associated with the indication is reduced. The main disadvantage of the solution proposed in US 10715300 is the difficulty of supporting a flexible DMRS configuration with a different number of antenna ports.

In accordance with the solution proposed in US 2021/0167914, a wireless communication device receives configuration parameters indicating a cell bandwidth portion (BWP) associated with a maximum number of transmission layers and a corresponding plurality of DMRS ports. The wireless communication device receives a DCI containing an antenna ports indication value. A subset of DMRS ports from a plurality of DMRS ports is determined based on the maximum number of transmission layers associated with the BWP. A transport block is received through a given BWP with one or more DMRS ports selected based on the antenna ports indication value from a subset of DMRS ports. The main disadvantage of the approach proposed in US 2021/0167914 is the relatively small reduction in overhead associated with specifying DMRS ports in the DCI, due to the maximum number of MIMO layers configured per BWP.

SUMMARY OF THE INVENTION

The objective of the present invention is to create techniques for encoding information transmitted from TRP about a subset of DMRS ports to be used on the UE, which would avoid these negative effects, primarily a significant increase in the bit load on service information.

In the context of solving this problem, according to a first aspect of the present invention, a method for specifying demodulation reference signal ports (DMRS ports) for at least one user equipment (UE) in a wireless communication system is provided at a base station (TRP). The TRP is configured to support the simultaneous transmission of multiple spatial MIMO streams for data transmission, with each of the multiple MIMO streams associated with a different DMRS port.

The proposed method contains a step at which a hierarchy of groups of DMRS ports is formed, with each node of the hierarchy corresponding to a group of one or more DMRS ports, with each node at the lowest level of the hierarchy corresponding to one of a given number N' of DMRS ports, where N '>0. At each subsequent hierarchy level, each node corresponds to a DMRS port group obtained by combining the same number of different DMRS port groups from the previous hierarchy level, with the highest level of the DMRS port group hierarchy being the hierarchy level at which the number of DMRS ports in each DMRS port group is equal to M, where M≤N' represents the total number of DMRS ports available for use on the UE.

Further, the method includes a step in which each node of the generated hierarchy of DMRS port groups is represented by a code set. Each code set consists of a first subset of bits and a second subset of bits, the number of bits in the first subset and the number of bits in the second subset being variable. For each node of the DMRS port group hierarchy at a specific hierarchy level, the bits of the first subset encode the number of DMRS ports in each DMRS port group at that specific hierarchy level, and the bits of the second subset encode the group of DMRS ports corresponding to this hierarchy node.

Next, the method comprises the steps of: selecting, in a hierarchy of DMRS port groups, a group containing C DMRS ports to be used on the UE, where C≤M; determining a code set corresponding to the selected group of DMRS ports; and signaling the overhead information to the UE, wherein the overhead information includes said specific code set.

According to an embodiment of the present invention, a DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams, corresponding N DMRS signals are multiplexed, where N≥N', N>M. Each of the DMRS signals is uniquely identified by a DMRS port such that each DMRS port is associated with a unique combination of a code division multiplexing (CDM) group index, a frequency domain orthogonal code (OCC) index, and a time domain OCC index used for said multiplexing the corresponding DMRS signal.

According to an embodiment of the present invention, N' and M are integers of power 2, for example, N'=64, M=16, or N'=M=16 when N=64. The sequential nodes at the lowest level of the DMRS port group hierarchy correspond to the sequential DMRS port indexes, respectively. In the above-mentioned formation of a hierarchy of DMRS port groups, each DMRS port group of the next hierarchy level is obtained by combining two adjacent DMRS port groups from the previous hierarchy level so that each DMRS port group of the previous hierarchy level is part of only one DMRS port group subsequent level of hierarchy. In each code subset, the second subset of bits is the postfix subset, and the first subset of bits is the prefix subset.

According to an embodiment of the present invention, said signaling is carried out by transmitting a physical downlink control channel (PDCCH) with downlink control information (DCI) including said overhead information.

According to an embodiment of the present invention, said DMRS ports C should be used at the UE to receive Physical Downlink Shared Data Channel (PDSCH) MIMO streams. Alternatively, the C DMRS ports may be used at the UE to transmit Physical Uplink Shared Channel (PUSCH) MIMO streams.

According to a second aspect of the present invention, a method for specifying DMRS ports for at least one UE in a wireless communication system is provided on a TRP. The TRP is configured to support the simultaneous transmission of multiple spatial MIMO streams for data transmission, with each of the multiple MIMO streams associated with a different DMRS port.

The proposed method comprises the steps of: selecting a group of DMRS ports containing C serial DMRS port indexes to be used on the UE from a total number of M serial DMRS port indexes available for use on the UE, where C≤M; and obtaining a code parameter P representing the selected group of DMRS ports, wherein the code parameter is determined as follows:

if (C-1)≤M/2

Р=М⋅(С-1)+s,

otherwise

P=M⋅(M - C+1)+(N - 1 - s),

where s is the starting index of the DMRS port in the selected group of DMRS ports, s=0,1,…,C-1.

Further, the method comprises signaling the UE with overhead information including the received code parameter P.

According to an embodiment of the present invention, in the case where a limitation is imposed on the bit size of the code parameter, at least one C value is excluded from use in said acquisition.

According to an embodiment of the present invention, a DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams, corresponding N DMRS signals are multiplexed, where M<N. Each of the DMRS signals is uniquely identified by a DMRS port such that associated with each DMRS port is a unique combination of a CDM group index, a frequency domain OSS index, and a time domain OSS index used for said multiplexing of the corresponding DMRS signal. Preferably N=64, M=16.

According to an embodiment of the present invention, said signaling is performed by transmitting a PDCCH with a DCI including said overhead information.

According to an embodiment of the present invention, said DMRS ports C must be used at the UE to receive MIMO PDSCH streams C. Alternatively, the C DMRS ports may be used by the UE to transmit C MIMO PUSCH streams.

According to a third aspect of the present invention, a method for specifying DMRS ports for at least one UE in a wireless communication system is provided on a TRP. The TRP is configured to support the simultaneous transmission of multiple spatial MIMO streams for data transmission, with each of the multiple MIMO streams associated with a different DMRS port.

The proposed method comprises the steps of: selecting a group of DMRS ports containing C DMRS port indices to be used on the UE from a total number M of consecutive DMRS port indices available for use on the UE, where C≤M; and obtaining a code parameter P representing the selected group of DMRS ports, wherein the code parameter is determined by combinatorial coding as follows:

, Where

{p _i } - ordered set of indices p _i of the selected group of DMRS ports, i=0,…,C-1, p _i =1,2,…,M,

Further, the method comprises signaling the UE with overhead information including the received code parameter P and C.

According to an embodiment of the present invention, a DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams, corresponding N DMRS signals are multiplexed, where M<N. Each of the DMRS signals is uniquely identified by a DMRS port such that associated with each DMRS port is a unique combination of a CDM group index, a frequency domain OSS index, and a time domain OSS index used for said multiplexing of the corresponding DMRS signal. Preferably N=64, M=16.

According to an embodiment of the present invention, said signaling is performed by transmitting a PDCCH with a DCI including said overhead information.

According to an embodiment of the present invention, said DMRS ports C must be used at the UE to receive MIMO PDSCH streams C. Alternatively, the C DMRS ports may be used by the UE to transmit C MIMO PUSCH streams.

According to a fourth aspect of the present invention, there is provided a base station (TRP) in a wireless communication system, comprising at least: transceiver devices; data processing devices; and data storage devices storing computer-executable codes that, when executed by data processing devices, cause a base station to perform a method according to any embodiment of the first to third aspects of the present invention. Also provided is a computer-readable storage medium on which computer-executable codes are stored which, when executed by at least one TRP processing device in a wireless communication system, cause the TRP to perform a method according to any embodiment of the first to third aspects of the present invention.

The technical result provided by the present invention is to create techniques that provide efficient encoding of overhead information transmitted from TRP about a subset of DMRS ports to be used by the UE, with a relatively small bit load on overhead information.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an illustrative diagram of spatial signal processing at the transmitter side;

Fig. 2a, 2b show a Type 1 5G NR DMRS structure and a 5G NR Type 2 DMRS structure, respectively;

Fig. 3 - general scheme for informing the UE about the used DMRS ports in 5G NR;

Fig. 4a, 4b illustrate an approach according to 5G NR for informing the UE of DMRS ports to be used;

Fig. 5a-5c - illustrations of time resource allocation in 5G NR;

Fig. 6 is an illustrative diagram of a wireless communication system in which embodiments of the present invention may be implemented;

Fig. 7 is a schematic diagram of a DMRS structure according to a preferred embodiment of the present application;

Fig. 8 is a schematic diagram of a DMRS structure according to another embodiment of the present application;

Fig. 9 is a block diagram of an embodiment of a method for multiplexing DMRS signals according to the present application;

Fig. 10 is a schematic diagram of an adapted DMRS structure according to an embodiment of the present application;

Fig. 11 is a block diagram of an embodiment of a wireless communication method according to the present application;

Fig. 12a-12d are illustrative embodiments of adaptation according to the present application;

Fig. 13a, 13b illustrate the selection of a reduced OSS DFT configuration according to an embodiment of the present application;

Fig. 14 is a block diagram of another embodiment of a wireless communication method according to the present application;

Fig. 15 is a flowchart of a method for specifying DMRS ports for a UE according to one embodiment of the present invention;

Fig. 16a, 16b, 17 - illustrations of the tree hierarchy of groups of DMRS ports and their coding;

Fig. 18 is a flowchart of a method for specifying DMRS ports for a UE according to another embodiment of the present invention;

Fig. 19a-19c are illustrations of a tabular representation of the formation of groups of adjacent DMRS ports;

Fig. 20 is a flowchart of a method for specifying DMRS ports for a UE according to another embodiment of the present invention;

Fig. 21 is an example of encoding a combination of DMRS ports according to an embodiment of the method of FIG. 20;

Fig. 22a is an illustration of a general DMRS port table pre-processing approach for the case of eliminating a portion of DMRS ports according to an embodiment of the present invention;

Fig. 22b is an example implementation of the general approach of FIG. 22a;

Fig. 23 is an illustration of an attempt to use a 5G NR approach to time resource allocation in a next generation wireless communication system;

Fig. 24a, 24b illustrate exemplary embodiments of time domain resource aggregation for the DL portion of a DL/UL frame period according to the present application;

FIGS. 25a, 25b are high-level views of resource aggregation according to the present application; FIGS.

Fig. 26a, 26b are illustrations of periodic allocation of DMRS subblocks when allocating time domain resources according to an embodiment of the present application;

Fig. 27 is an illustration of time domain resource aggregation to enable pipelining of code block processing at the receiver side according to an embodiment of the present application;

Fig. 28a, 28b is a flowchart of a time domain resource allocation method according to an embodiment of the present application.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings, wherein like reference numerals denote like elements. It should be understood that embodiments of the invention may take various forms and should not be construed as limited to the descriptions given here. Accordingly, illustrative embodiments are described below with reference to the drawings to explain aspects of the present invention.

In FIG. 6 generally illustrates a wireless communication system in which various aspects of the present invention may be implemented. As shown in FIG. 6, user equipments (UEs) 601 communicate with base stations (TRPs) 602 on a radio access network (RAN) 600. UEs 601 (eg, UEs 601-1, 601-2, 601-3, ...) are distributed across the RAN 600. and each of the UEs 601 may be fixed or mobile. Well-known examples of UEs are smartphones, tablets, modems, etc.

Base stations 602 (eg, TRP 602-A, 602-B, 602-C) may provide radio coverage for a specific geographic area, often referred to as a "cell." Base stations 602 are generally of a stationary design, but may also be of a mobile design. In general, base stations may be macro-TRP (as illustrated by TRPs 602-A, 602-B, 602-C in FIG. 6), as well as pico-TRP for pico cells or femto-TRP for femto cells. Cells, in turn, can be divided into sectors.

The operation of base stations 602 may be coordinated and controlled by a network controller in communication with them (eg, via a backhaul). The RAN 600 may be in communication with a core network (CN) (eg, through a network controller) that provides various network functions, such as, for example, access and mobility control, session management, authentication server function, application function, and the like. . However, base stations 602 in RAN 600 may also be connected to each other (eg, through a direct physical connection).

When a user device moves within the RAN 600, it may be handed over from one TRP to another TRP. For example, service to UE 601-3 may be transferred from TRP 602-B to TRP 602-A. This reconfigures the relevant UE operational parameters to operate with the new TRP. UE service switching can also occur between sectors of the same TRP.

The 5G NR wireless communication system implements the concept of cloud RAN (Cloud RAN, C-RAN), which consists of dividing the base station into three parts and using a special interface defined for exchanging information between these functional parts. Thus, the TRP can be divided into a radio unit (RU), which performs the functions of a radio transceiver, a distributed unit (DU) for L1 (physical layer) calculations and L2 (MAC layer) calculations, and a centralized unit (CU) for L2 and L3 (layer RRC). This separation allows the CUs to be centralized at the appropriate central network node, while the DUs can be more distributed at the cell sites. In this case, switching connections between cell sites can be carried out at the L1 level, that is, with relatively low delays. Support for this concept is expected in next-generation wireless networks.

It should be noted that the description in FIG. 6 and the figure itself are for illustrative, non-limiting purposes only, for the purpose of outlining the general operating environment of the present invention. Although in Fig. 6 illustrates only the known basic components of a communication system, it should be understood that the communication system may further include many other elements.

Each of the TRPs 602 shown in FIG. 6 includes hardware and logic to implement the corresponding functions in the TRP. The hardware includes, in particular, an antenna array consisting of the transmit-receive antenna elements discussed above, various specially configured processors, controllers, data storage devices, other circuit elements, as well as the buses connecting them. Logic means includes software stored in the corresponding storage devices and configuring the corresponding circuit elements. Software also includes firmware directly embedded in processors and controllers. Said hardware is configured to, inter alia, perform various processing on the transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplification, filtering, digitization, (de)interleaving, resource allocation, reception/transmission planning.

Likewise, each of the UEs 601 shown in FIG. 6 includes hardware and logic for implementing corresponding functions in the UE. The hardware includes, in particular, transceiver devices with associated antenna elements, various specially configured processor(s), controllers, data storage devices, other circuit elements, as well as the buses connecting them. Logic means includes software stored in the corresponding storage devices and configuring the corresponding circuit elements. Software also includes firmware directly embedded in the controllers. Said hardware is configured to, inter alia, perform various processing on the transmitted and received signals, including (de)modulation, (de)multiplexing, (de)coding, amplification, filtering, digitization, (de)interleaving. In addition, the UE contains user interaction facilities, including a touch screen, speakers/microphone, buttons, as well as user applications stored in the UE memory and executed by the UE processor in the associated operating system.

Examples of the above-mentioned processors/controllers include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), discrete hardware chips, and the like.

(Micro)software executed by processors/controllers should be interpreted broadly to mean machine-executable instructions, instruction sets, program code, code segments, subroutines, program modules, objects, procedures, and the like. The software is stored on suitable computer-readable media, which may be embodied, for example, in the form of RAM, ROM, EEPROM, solid-state memory, magnetic memory, optical memory, and the like. , on which corresponding program codes and data structures can be written or stored and accessed by the corresponding processors/controllers.

The above TRP and UE hardware and software elements are configured to enable the TRP and UE to perform the methods of this application that are described below. The actual implementation of TRP and UE component hardware and their specialized configuration, incl. by appropriate logical means is known in the art to which this application relates. In this case, various functions according to the methods corresponding to this application can be performed in a plurality of individual elements or one or more integral elements, which is determined by the design structural characteristics.

I. Multiplexing of DMRS signals

Next, with reference to Fig. 7-9 describe a method for multiplexing DMRS signals for broadband transmission according to the present application.

The proposed method is implemented on a communication device of the transmitting side in a wireless communication system, preferably a next generation communication system. The transmitting side communication device supports simultaneous transmission of multiple spatial MIMO streams to transmit one physical data channel. As stated earlier, each of the multiple MIMO streams has a different DMRS signal associated with the others. The transmitting side communication device may be a TRP (eg, TRP 602 of FIG. 6), in which case the physical data channel is PDSCH. Alternatively, the transmitting side communication device may be a UE (eg, UE 601 of FIG. 6), in which case the physical data channel is PUSCH.

Below, without loss of generality, description will be made for the case where the communication device of the transmitting side is the TRP.

As noted above, the 6G wireless system for the 10-12 GHz range implies support for a significantly larger number of spatial MIMO streams than 5G NR. The case of 64 simultaneously transmitted spatial MIMO streams will now be considered as a preferred exemplary embodiment of the present invention. As will be shown below, the proposed technical solution covers cases of both larger and smaller numbers of MIMO flows.

In FIG. 7, the DMRS structure of this application is illustrated on a time-frequency grid of resource elements (RE). This DMRS structure provides multiplexing of 64 DMRS signals for, respectively, 64 spatial MIMO PDSCH streams. That is, DMRS signals are multiplexed across resource elements of the DMRS structure.

As noted earlier, on a time-frequency grid, each RE in the frequency domain is defined by an OFDM subcarrier, and in the time domain by an OFDM symbol. According to OFDM, the frequency range of the system is divided into a set of subcarriers, and each of the OFDM subcarriers can be modulated with data. The total number of OFDM subcarriers depends on the frequency range of the system, and the spacing between adjacent subcarriers can be fixed or variable. Thus, 5G NR supports a basic subcarrier spacing (SCS) of 15 kHz, and also supports other SCS relative to the basic SCS, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.

As shown in FIG. 7, each of the OFDM subcarriers in the proposed DMRS structure is assigned to one of four CDM groups. Each of the CDM groups depicted in FIG. 7 has its own index Δ, from 0 to 3, and is shown in a different way. In each of the CDM groups, the modulation of the DMRS signals is carried out using a discrete Fourier transform (DFT)-based FD-OCC (DFT FD-OCC) of length 4 and a DFT-based TD-OCC (DFT TD-OCC) of length 4.

In general, DFT FD-OCC are given by the following equation

where k _ƒ is the index of the frequency domain orthogonal code, K _ƒ is the code length, j is the imaginary unit. In the considered case, K _ƒ =A _r and possible FD-OCC DFTs are illustrated in Table 1.

Similarly, in general, DFT TD-OCC are given by the following equation

where k _t is the index of the time domain orthogonal code, K _t is the code length. In the case under consideration, K _t =4, and the possible DFTs of TD-OCC are illustrated in Table 2.

As a result, the DMRS signals in each CDM group are mutually orthogonal.

So, the proposed DMRS structure provides orthogonal multiplexing of 64 DMRS signals: 4 CDM groups × 4 DFT FD-OCC of length 4 × 4 DFT TD-OCC of length 4.

From Fig. 7 it can be seen that the DMRS structure is continuously repeated over a set of OFDM subcarriers, while this structure is uniform in the frequency domain - the distance between the subcarriers of any one CDM group in the DMRS structure is the same, due to which, in turn, the complexity of the channel estimation algorithm on the receiving side is maintained at a relatively low level.

As noted earlier, the DMRS structure described above is preferred, but not the only one possible. Below in Fig. 8 shows a uniform DMRS structure according to the present application, providing orthogonal multiplexing of 128 DMRS signals for, respectively, 128 simultaneously transmitted spatial MIMO PDSCH streams through the use of DFT TD-OCC of length 8, i.e. in Equation (2) K _t =8.

In modern communication systems, resource planning in the frequency domain is carried out not at the level of individual subcarriers, but with some granularity. Say, in a 5G NR wireless communication system, the minimum resource allocation unit in the frequency domain is 1 resource block (RB) consisting of 12 consecutive OFDM subcarriers.

As can be seen from FIG. 7, 8, the boundary of the present application DMRS structure containing 16 consecutive OFDM subcarriers in the frequency domain will not coincide with the boundary of one RB. Therefore, the present application proposes to schedule transmission resources at a granularity such that, in the frequency domain, an integer boundary of 5 consecutive DMRS structures is aligned with an integer boundary of P _PRBs of consecutive PRBs. In the case illustrated in FIG. 7, 8, resource planning in the frequency domain should be carried out with a granularity of 4 PRB (P _PRB = 4), which will accommodate 3 consecutive DMRS structures (S = 3). More examples of resource scheduling granularity will be shown below.

Next, with reference to Fig. 9 describes an embodiment of a method 900 for multiplexing DMRS signals according to the present application. By way of illustration, and not limitation, method 900 is implemented at a base station (eg, TRP 602 in FIG. 6) that supports the simultaneous transmission of multiple spatial MIMO PDSCH streams.

At step 910, for N MIMO streams (N is a positive integer), a DMRS structure is determined consisting of RE resource elements over which the corresponding N DMRS signals are multiplexed. In this case, each of the OFDM subcarriers in the DMRS structure is assigned to one of the L CDM groups so that the distance between the OFDM subcarriers of any one CDM group in the DMRS structure is the same. Each CDM group provides multiplexing of DMRS signals by using DFT FD-OCC of length K _f and DFT TD-OCC of length K _t . As stated earlier, the DMRS structure is continuously repeated over a set of OFDM subcarriers in the frequency domain.

For the case considered in FIG. 7, L=A, K _f =A, K _t =A and, accordingly, N=64; for the case considered in Fig. 8, L=A, K _f =A, K _t =8 and, accordingly, N=128. Below are examples with other values of the specified integer parameters. It should be noted here that _Kf according to the present disclosure may also take a value of 8.

As previously stated, step 910 of method 900 may also be performed on a UE supporting wideband transmission, given that the UE supports a lower maximum number of simultaneous MIMO streams than TRP. Let's say, for the above case of planned support for 64 DMRS ports per TRP for 10-12 GHz 6G, a maximum of 16 DMRS ports will be supported per UE.

The method 900 may include subsequent steps performed on the TRP associated with using the DMRS structure determined at step 910 to perform communication.

Thus, at step 920, the TRP scheduler schedules PDSCH transmission to one or more UEs (eg, UE 601 of FIG. 6) using N MIMO streams. Also at this stage, the TRP scheduler can also schedule PUSCH transmission from the UE.

At step 940, the TRP sends overhead information to the UE. The overhead information contains information about the DMRS structure determined at step 910, including at least the parameters L, K _f and K _t . More detailed signaling aspects for UE information regarding DMRS are described below.

According to a preferred embodiment, overhead information is transmitted to the UE in the DCI carried by the PDCCH. The DCI also contains other information, as discussed above with reference to FIG. 3. In particular, the UE is also informed by the DCI that a transmission is scheduled for it.

According to other embodiments, overhead information may be transmitted to the UE at the RRC layer (i.e. L3) or at the MAC layer (i.e. L2), which are higher layers than the physical layer (i.e. L1), on which DCI is transmitted.

At step 950, the TRP performs a scheduled wideband PDSCH transmission.

Below with reference to Fig. 10-14 will describe options for adapting the proposed DMRS structure according to this application.

The need for such adaptation may arise in cases where the transmission of a large number (for example, 64) spatial MIMO streams is no longer required, for example, in view of reducing the user load on the data channel, in which case they are reduced at the base station. Naturally, the DMRS structure must be adapted to such a reduction by a corresponding reduction in the number of DMRS signals orthogonally multiplexed in it, or, in other words, by a corresponding reduction in the DMRS capacity.

One adaptation embodiment is based on the fact that DFT OSSs are highly parameterizable. So, in Fig. 10 shows the adaptation of the DMRS structure by setting the length K _f ′ DFT FD-OCC and the length K _t ′ DFT TD-OCC to 2 (see Equations (1), (2)), with the same four CDM groups.

This DMRS structure, which is continuously repeated over a set of OFDM subcarriers, provides orthogonal multiplexing of 16 DMRS ports for, respectively, 16 MIMO streams. This adapted structure has lower DMRS capacity, but also lower overhead and higher quality channel estimation due to the higher DMRS density in the frequency domain.

As shown in FIG. 10, resource scheduling in the frequency domain in the case of this adaptation will be carried out with a granularity of 2 PRBs, which will accommodate 3 consecutive DMRS structures.

An additional possible implementation of the considered one embodiment is to adapt the DMRS structure by using two CDM groups and again setting the FD-OCC DFT length and the TD-OCC DFT length to 2. The resulting adapted DMRS structure provides orthogonal multiplexing of 8 DMRS ports for, respectively, 8 MIMO streams. It should be emphasized that this adapted DMRS structure exactly corresponds to the 5G NR Type 1 DMRS structure discussed above with reference to FIG. 2a. Thus, the DMRS structure proposed here is backward compatible and can be used in legacy wireless communication systems.

It should also be noted in light of the above that the DMRS structure shown in FIG. 7 can be obtained by adapting the DMRS structure shown in FIG. 8 by setting the TD-OCC DFT length to 4 while keeping the FD-OCC DFT length constant and four CDM groups.

Next, with reference to Fig. 11 describes an embodiment of a wireless communication method 1100 according to the present application. Method 1100 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports simultaneous transmission of N spatial MIMO PDSCH streams (eg, 64), each of which is associated with a different DMRS signal.

At step 1110, a PDSCH is scheduled to be transmitted to at least one UE (eg, UE 601 of FIG. 6) using a desired number of M MIMO streams out of N MIMO streams, where M is a positive integer less than N (eg, M=16 or 8).

At step 1120, a corresponding adaptation of the DMRS structure initially defined for the N MIMO streams is performed (see step 910 with reference to FIG. 9). As noted above, this initial DMRS structure is characterized by the use of L CDM groups (_L=4), DFT FD-OCC of length K _f and DFT TD-OCC of length K _t . For the exemplary case T=64 considered, this initial DMRS structure is illustrated in FIG. 7, where K _f =4 and K _t =4.

The DMRS structure is adapted at step 1120 by reducing the length K _f DFT FD-OCC to and/or length K _t DFT TD-OCC up to . Where - a positive integer less than K _f and - positive integer less than K _t ; wherein L can be set to 2 or 4. The adapted DMRS structure provides multiplexing of M DMRS signals for M MIMO streams.

For the case illustrated in FIG. 10 (M=16), L remains equal to 4, And For the case illustrated in FIG. 2a (M=8), L is set equal to 2, And

At step 1140, similar to step 940, the TRP sends overhead information to the UE. The overhead information contains information about the DMRS structure adapted at step 1120, including at least parameters L, And .

At step 1150, similar to step 950, a scheduled PDSCH transmission is performed.

Another option for adapting the DMRS structure proposed here is based on excluding specific FD-OCC DFTs and/or specific TD-OCC DFTs from the corresponding available OSS DFTs, in the required number and without changing their length.

Another adaptation option under consideration, like the one discussed earlier, is aimed at changing the corresponding density of DMRS signals in order to improve the quality of channel estimation at the receiving side.

Generally speaking, there is a DMRS structure of the present application with a set of K _f DFT FD-OCC and a set of K _t DFT TD-OCC available. For the DMRS structure illustrated in FIG. 7, the available DFT OSS sets are shown in Tables 1 and 2, respectively (K _f =4, K _t =4). The approach under consideration, in general, is based on the exclusion of orthogonal codes from the available DFT FD-OCC set and/or from the available DFT TD-OCC set, i.e. creating a corresponding reduced subset of them such that the reduced subset includes DFT OSSs for which the distance between code indices modulo code length is maximum. This maximization, in turn, ensures an increase in the efficiency of channel estimation at the receiving side, which will be discussed in more detail below.

The approach to the adaptation option under consideration in accordance with this application is generally illustrated in Fig. 12a-12d: Fig. 12a, 12c - for DFT TD-OCC and Fig. 12b, 12d - for DFT FD-OCC.

In each of Fig. 12a, 12b, the available DFT OSS sets are shown on a circle for clarity, with the orthogonal codes indexed in the set counterclockwise. Although 8 OSS DFTs are shown, it should be understood that the available set may contain a different number of OSS DFTs, as implied by the ellipses in these figures.

The reduced DFT FD-OCC subset is defined according to the following expression:

Where

K _{t_reduced} - the required number of orthogonal codes in the subset, i.e. after reduction; K _t - length of DFT TD-OCC;

- DFT TD-OCC subset index;

- DFT TD-OCC index in a reduced subset;

- the operation of rounding to the nearest smaller integer; mod{a, b} (or b⋅mod(a)) - the operation of taking the remainder of dividing b by a;

k _t is the index of the DFT TD-OCC code sequence (code vector) in the initially available DFT TD-OCC set (see, for example, Table 2).

Black circles in Fig. 12a illustrates the TD-OCC DFTs constituting the reduced subset.

At the same time, in Fig. 12 c specifically illustrates possible options for reducing the initially available set of 8 TD-OCC DFTs, which corresponds to the exemplary DMRS structure in FIG. 8, to a subset of 4 DFT TD-OCC according to this application. As can be seen from this figure, subset 0 of 4 DFT TD-OCC with indices k _t {0,2,4,6} and subset 1 of 4 DFT TD-OCC with indices k _t {1,3,5, 7} according to Equation (3).

Next, the reduced DFT FD-OCC subset is similarly defined according to the following expression:

Where

- the required number of orthogonal codes in the reduced subset;

K _f - length of DFT FD-OCC;

- DFT FD-OCC subset index;

- DFT FD-OCC index in the reduced subset;

k _ƒ is the index of the DFT FD-OCC code sequence in the initially available DFT FD-OCC set (see, for example, Table 1).

Black circles in Fig. 12b also illustratively denotes the FD-OCC DFTs constituting the reduced subset. At the same time, in Fig. 12d shows, by way of illustration only, possible options for reducing the available set of 2 DFT FD-OCCs to 1 DFT FD-OCC according to this application.

On the circles in Fig. 12a-12c shows the maximum 'distance' between the DFT OSSs remaining in the reduced subset. It should also be understood that the three DFT TD-OCC reduced subset configuration shown illustratively in FIG. 12a is not the only possible implementation, and subsets of the same size can be obtained from other code sequences k _t with the same 'distance' characteristic. Likewise, the four DFT FD-OCC reduced subset configuration shown as an illustration in FIG. 12b is not the only possible implementation, and subset(s) of the same size can be obtained from other code sequences k _ƒ with the same 'distance' characteristic. Such possible implementations of one configuration are illustrated in FIG. 12s.

Table 3 below shows various configurations of reduced orthogonal code subsets for the DMRS structure proposed here, illustrated in FIG. 7 and in Tables 1, 2.

According to the above, DMRS capacity in Table 3 refers to the required number of DMRS ports used.

The selection of a reduced DFT OSS configuration from a corresponding initially available set of orthogonal codes is illustrated in FIG. 13a, 13b.

In FIG. 13a shows the formation of a reduced subset 0 consisting of a DFT FD-OCC with index 0 and a DFT FD-OCC with index 2, according to the approach of the subject embodiment of the present application, which corresponds to configuration 1 or 3 of Table 3. Similarly, in FIG. 13b shows the formation of reduced subset 1 consisting of DFT TD-OCC with index 1 and DFT TD-OCC with index 3, corresponding to configuration 2 or 3 of Table 3.

It must be emphasized here that the required orthogonality is maintained in each of the considered possible options for reduced DFT OSS subsets.

The above-described other embodiment of the adaptation of the DMRS structure provides additional gain on the receiving side, since the approach proposed in this application to the generation of reduced code sets in order to reduce the capacity of the DMRS provides a more reliable elimination of mutual interference between DMRS signals, especially in view of various types of distortions to which the transmitted MIMO streams may be subject to propagation; this, in turn, leads to better performance of channel estimation at the receiving end.

It should be clarified here that when using orthogonal codes (OCC) in the DMRS structure, in order to eliminate mutual interference between orthogonal codes on the receiver side, it is necessary to de-spread the received DMRS sequence over the entire length of the corresponding orthogonal code (for example, at a length of 4 , which corresponds to a number of embodiments of the present application). The procedure for generating a reduced set of SSNs with inter-code distance maximization, as discussed above with reference to FIG. 12-13 provides complete interference suppression by compressing the received DMRS sequence to a shorter length (eg, length 2). This minimizes the impact of possible loss of orthogonality between codes in scenarios with significant frequency-selective or time-sensitive channel fading.

Next, with reference to Fig. 14 describes another embodiment of a wireless communication method 1400 according to the present application. Method 14 00 is performed at a base station (eg, TRP 602 of FIG. 6) that supports simultaneous transmission of N spatial MIMO PDSCH streams (eg, 64), each of which is associated with a different DMRS signal.

At step 1410, a PDSCH is scheduled to be transmitted to at least one UE (eg, UE 601 in FIG. 6) using a desired number of M MIMO streams out of N MIMO streams, where M is a positive integer less than N (eg, M=32, 16 or 8).

At step 1420, a corresponding adaptation of the DMRS structure initially defined for the N MIMO streams is performed (see step 910 with reference to FIG. 9). As noted above, this initial DMRS structure is characterized by the use of L CDM groups (L=4), DFT FD-OCC of length K _f and DFT TD-OCC of length K _t . For the exemplary case of N=64 considered, this initial DMRS structure is illustrated in FIG. 7, where K _f =4 and K _t =4.

The DMRS structure is adapted at step 1420 by reducing the K _{f of} the initially available FD-OCC DFTs to a reduced subset of DFT FD-OCC and/or K _t initially available DFT TD-OCC to a reduced subset of DFT TD-OCC, - a positive integer less than K _f and - positive integer less than K _t ; wherein L can be set to 2 or 4. The adapted DMRS structure provides multiplexing of M DMRS signals for M MIMO streams. Said reduction is carried out in such a way that the corresponding reduced subset includes DFT-based OSSs for which the distance between code indices modulo code length is maximum, as disclosed above with reference to FIG. 12, 13 and Table 3.

At step 1440, similar to step 940, the TRP sends overhead information to the UE. The service information, in addition to the parameters L, K _f and K _t , also contains an indication of the reduced DFT FD-OCC subset and/or the reduced DFT TD-OCC subset. Aspects of overhead signaling, including the indication of orthogonal code set(s), will be disclosed below.

At step 1450, similar to step 950, a scheduled PDSCH transmission is performed.

It should be noted that with any of the above adaptation options, the DMRS structure corresponding to this application remains constant and maintains uniformity in the frequency domain. That is, the technical solution proposed here avoids the transition to, in fact, a fundamentally different DMRS structure when it is necessary to change the DMRS capacity, as, for example, in the case of switching between Type 1 and Type 2 in 5G NR, and the associated increase in the complexity of the channel estimation algorithm on the receiving side.

According to this application, the combined use of both disclosed options for adapting the DMRS structure is not excluded. For example, the DMRS structure shown in FIG. 8 can be adapted to the DMRS structure shown in FIG. 7 by correspondingly reducing the length of the TD-OCC DFT as discussed previously, and subsequently further adaptation can be performed on this adapted DMRS structure by eliminating orthogonal codes in accordance with the disclosure in FIG. 12, 13 with reference to Table 3.

Although the above-described adaptation methods of the present application have been described for the case of decreasing DMRS capacity, it should be understood that they are also applicable for the case of increasing capacity, where it may again be necessary to transmit a larger number of MIMO streams.

Thus, with reference to FIG. 11 illustrates an embodiment of a wireless communication method 1100 corresponding to at least a partial inversion of the first embodiment of DMRS structure adaptation. Method 1100 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports simultaneous transmission of N spatial MIMO PDSCH streams (eg, 64), each of which is associated with a different DMRS signal. The embodiment discussed here assumes that the TRP currently uses a previously adapted DMRS structure in which M (M<N) DMRS signals are multiplexed (eg, the adapted DMRS structure illustrated in FIG. 10, where M=16).

At step 1110, another PDSCH transmission is scheduled to at least one UE (eg, UE 601 of FIG. 6) using M' MIMO streams, where M<M'≤N.

At step 1120, the DMRS structure is adapted by increasing the length accordingly DFT FD-OCC to Where and/or increase in length DFT TD-OCC to Where (see Equations (1), (2)).

The adapted DMRS structure provides multiplexing of M' DMRS signals for M' MIMO streams. For the example case M'=N=64 discussed herein, the resulting DMRS structure at step 1120 is illustrated in FIG. 7, where And at L=4.

At step 1140, the TRP sends overhead information to the UE. The overhead information contains information about the DMRS structure obtained at step 1120, including at least parameters L, And .

At step 1150, another PDSCH transmission is scheduled.

For the case of inversion of the mentioned other implementation of DMRS structure adaptation, the base station uses a new, increased value of the number of SSNs, for example, (see Equation (3)) and/or (see Equation (4)) and signals this new value(s) to the UE.

In summary, the DMRS structure of this application, on the one hand, provides multiplexing of a larger number of DMRS signals to meet the requirements of next generation wireless communication systems (specifically 64 in the case of the 10-12 GHz 6G frequency range), and, on the other hand, has flexible, dynamic (as opposed to semi-static in 5G NR) adaptability, without significantly changing the DMRS structure itself (i.e. the proposed DMRS structure is unified) and maintaining proper quality and low complexity of channel estimation on the receiving side, as well as support for reverse compatibility.

Further, as stated several times before, DMRS signals transmitted from one base station are orthogonal, i.e. they do not interfere with each other within the cell served by that base station. For example, referring to the diagram in FIG. 6, the DMRS signals transmitted from the TRP 602-B do not interfere with each other in each of the UEs 601-1, UE 601-2, UE 601-3 located in the cell served by the TRP 602-B; The DMRS signals transmitted from the TRP 602-C do not cause mutual interference on each of the UEs 601-4, UE 601-5, UE 601-6, UE 601-7 located in the cell served by the TRP 602-C. At the same time, the orthogonality between the DMRS signals of neighboring cells is not initially guaranteed, which can lead to mutual interference at cell boundaries. As can be seen from Fig. 6, the UE 601-3 is simultaneously within the radio coverage areas of the TRP 602-A and TRP 602-B and in close proximity to the edge of the cell served by the TRP 602-C base station. Therefore, at the UE 601-3, interference may occur between DMRS signals received simultaneously from TRP 602-A, TRP 602-B, TRP 602-C. This possible non-orthogonality may result in a highly undesirable reduction in the quality of the channel estimate in the UE 601-3.

As with prior art wireless communication systems discussed above, the present application, in order to overcome this problem, performs QPSK modulation on the DMRS signals transmitted from each TRP to provide inter-TRP randomization of the DMRS signals and , thereby avoiding mutual interference between them. As in the case of the mentioned known systems (in particular 5G NR), according to the present application the sequence of QPSK symbols for modulating the DMRS structure is obtained from pseudo noise (PN) sequences. More specifically, the PN sequences are Gold sequences of length 31. The initialization of the PN sequences is individually configurable for each base station. The initialization parameter (seed) of the PN sequence is referred to herein as N _ID .

The initialization of PN sequences in accordance with the present application is illustrated below in Table 4 for the case of using the unified DMRS structure proposed here (see, for example, FIG. 7).

According to this application, a set of sets of initialization parameters is proposed . For Table 4, such sets correspond to its columns. Each initialization parameter in each of the sets is set independently for each of the L CDM groups, i.e. in general i=0,…,L - 1; specifically for the case of Fig. 7 and Table 4 i=0, 1, 2, 3. Next, a unique parameter is associated with each of the sets of initialization parameters - scrambling parameter n _SCID - which, in fact, uniquely identifies the corresponding set of initialization parameters. The initialization parameter sets identified by any different n _SCIDs are element-wise distinct. Order of initialization parameters i=0, 1, 2, 3 in the initialization parameter sets, respectively identified by the four scrambling parameters n _SCID , are specifically illustrated in Table 4. However, the cells highlighted in Table 4 with a thicker line refer to the case of a structure with two CDMs. groups (ie L=2, Δ=0, 1, i=0, 1), which corresponds to the above-described 5G NR DMRS structures, as well as the above-mentioned adapted DMRS structure according to the present application. Each of the neighboring base stations is assigned its own different n _SCID , i.e. its own different set of initialization parameters.

In order to clarify the above, from Table 4, for a set of initialization parameters identified by n _SCID equal to O, the CDM group signals with index Δ=0 are modulated by the PN sequence initialized CDM group signals with index Δ=1 are modulated by a PN sequence initialized CDM group signals with index Δ=2 are modulated by a PN sequence initialized and CDM group signals with index Δ=3 are modulated by a PN sequence initialized A similar picture will occur in cases of n _SCID equal to 1, 2 or 3.

The use of scrambling parameters that uniquely identify the corresponding different sets of initialization parameters of PN sequences makes it possible to quickly, dynamically notify user devices about which initialization parameters need to be used for QPSK demodulation of received signals. This notification is preferably carried out by the DCI transmitted on the PDCCH. For example, including an n _SCID of 1 in the DCI carried by a TRP (eg, TRP 602-B of FIG. 6) causes all UEs currently served by that TRP to use the initialization parameter set for CDM groups Δ=0, 1, 2, 3, respectively. It should be noted that using a single n _SCID parameter avoids unnecessary bit load on the DCI. This also ensures fast (i.e., with low delays) switching of the set of initialization parameters on the UE side. Following the above example, if subsequently the UE (for example, UE 601-3 of FIG. 6) receives from a TRP (for example, TRP 602-A of FIG. 6), a DCI with a different scrambling parameter, for example, n _SCID equal to 3, then the UE 601-3 provides prompt switching to the corresponding set of initialization parameters It should be noted that the example given here of switching PN sequence initialization parameters is for illustrative purposes only.

It must be emphasized here that thanks to the use of C-RAN technology, which was discussed above, in current and future wireless communication systems, in particular, fast switching of UEs between base stations is ensured. Consequently, there is a need for corresponding operational switching between sets of initialization parameters. The technical solution described here allows us to provide the required efficiency.

Thus, each of the methods 900, 1100, 1400 described above with reference to FIGS. 9, 11, 14, is supplemented, preferably before stages 940, 1140, 1440 of sending service information, by stage 930, 1130, 1430, at which DMRS is modulated with a sequence of QPSK symbols, which is obtained from PN sequences, each of which is initialized with a different parameter N An initialization _ID from a set containing L initialization parameters, wherein each of the L sets of initialization parameters is associated with a different scrambling parameter n _SCID , and in each of the L sets of initialization parameters, each of the L initialization parameters is set differently for each of the L CDM groups, so that for each of the L CDM groups the initialization parameters are different for different scrambling parameters (see Table 4 for an illustration). Here, the PDSCH or PUSCH transmission scheduling overhead information, respectively transmitted at steps 940, 1140, 1440 preferably via DCI to each of the UEs served by the base station, further comprises the current value of the scrambling parameter n _SCID used for said modulation to instruct the UE to use the set of initialization parameters it identifies.

As noted earlier, a similar procedure is applied in the uplink to randomize the interference between DMRS signals from UEs served by neighboring TRPs.

The present DMRS signal multiplexing approaches disclosed above with reference to FIGS. 7-14 are summarized by the following mathematical expression describing the value a of the DMRS signal for DMRS port p on subcarrier k and OFDM symbol 1:

Where

- power offset for DMRS;

- DFT FD-OCC (see Equation (1) and explanations thereto), where k _ƒ is the index of the DFT FD-OCC code vector, K _ƒ is the length of the DFT FD-OCC, k' is the index of the DMRS subcarrier in the CDM group ( for the DMRS structure according to this application shown in Fig. 7, see Table 1: K _ƒ =4, k'=0, 1, 2, 3, k _f =0 _f 1, 2, 3);

- DFT TD-OCC (see Equation (2) and explanations thereto),

where k _t is the index of the DFT TD-OCC code vector, K _t is the length of the DFT TD-OCC, - index of the DMRS OFDM symbol in the CDM group (for the DMRS structure according to this application, shown in Fig. 7, see Table 2: K _t =4, k _t =0, 1, 2, 3);

k is the subcarrier index, where Δ is the CDM group index, L is the number of CDM groups (for the DMRS structure according to this application, shown in Fig. 7, L=4, ).;

l is the index of the OFDM symbol, where - index of the starting OFDM symbol of the block of time slots PDSCH in the DL/UL period, - DMRS transmission event index in the DL/UL period, 1, 2, T _DMRS - DMRS period. We are talking about DL/UL periods, as well as parameters T _DMRS will be discussed in more detail in the following sections of the description of the present invention;

r(n) is a QPSK sequence, where c(…) is a Gold sequence of length 31, which is unique for each CDM group and, accordingly, is initialized for each CDM group with its own c _init . For the embodiment discussed above with reference to Table 4,

Where

n _SCID - scrambling parameter (as stated above with reference to Table 4, can be dynamically specified in the DCI among the values {00, 01, 10, 11}),

N _ID - initialization parameter (see Table 4, while

)

- number of OFDM symbols in the DL/UL period,

- DL/UL period index.

II. Specifying DMRS ports for UE

In view of what was said above when describing the prior art, in the context of designing next generation wireless communication systems (including 6G), the following problem arises.

On the one hand, it is necessary to increase the capacity of the DMRS structure due to a significant increase in the supported number of spatial MIMO streams for broadband data transmission. At the same time, the existing scheme for specifying DMRS ports in 5G NR, briefly described above with reference to Fig. 4a, 4b, supports a maximum of 12 DMRS ports on the TRP side and a maximum of 8 DMRS ports per UE (SU-MIMO), with no systematic approach currently available to extend this existing scheme to the larger number of DMRS ports required - specifically, 64 on the TRP side and 16 on the UE side.

On the other hand, information about DMRS, incl. DMRS ports to be used must be communicated to user devices with low latency, typically using DCI transmission on the PDCCH; however, there is a hard limit on the total number of DCI bits, as noted above. As a consequence, attempting to directly extrapolate the existing design or similar approaches in next generation wireless communication systems to communicate to the UE the DMRS ports to be used over the physical control channel will result in an unacceptably large number of bits in the DCI.

In this context, the present invention provides techniques for efficiently encoding TRP overhead information about a subset of DMRS ports to be used by the UE with a relatively low bit overhead.

Embodiment 1: Tree-based indication of DMRS ports with prefix encoding

Next, with reference to Fig. 15-17 describe a tree-based implementation of specifying prefix-encoded DMRS ports according to the present invention. First of all, with reference to FIG. 15 describes an embodiment of a method 1500 for specifying DMRS ports for at least one UE in a wireless communication system according to a general approach consistent with this embodiment. Method 1500 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports simultaneous transmission of N spatial MIMO PDSCH streams (eg, 64), each of which is associated with a different DMRS signal.

At step 1510, a tree hierarchy of DMRS port groups is formed, where each node in the hierarchy corresponds to a group of one or more DMRS ports. Thus, each node at the lowest (leaf) level of the hierarchy corresponds to one of a given number N' of DMRS ports. Preferably, N'=N, i.e. the total number of DMRS ports available for use on the TRP. At each subsequent level of the tree hierarchy, counting from its leaf level, each node corresponds to a group of DMRS ports obtained by combining the same number of different groups of DMRS ports from the previous hierarchy level. The topmost (root) level of the DMRS port group tree is the level at which the number of DMRS ports in each DMRS port group is equal to the total number M of DMRS ports available for use on the UE (for example, 16), where M≤N' .

At step 1520, each node of the generated DMRS port group tree is represented by a code set. Each code set consists of a first subset of bits and a second subset of bits, the number of bits in the first subset and the number of bits in the second subset being variable. For each node of the DMRS port group hierarchy at a specific hierarchy level, the bits of the first subset encode the number of DMRS ports in each DMRS port group at that specific hierarchy level, and the bits of the second subset encode the group of DMRS ports corresponding to this hierarchy node.

At step 1530, a group containing C DMRS ports to be used on the UE, where C≤M, is selected from the tree hierarchy of DMRS port groups.

At step 1540, a code set corresponding to the selected group of DMRS ports is determined from the code sets obtained at step 1520.

At step 1550, overhead information is signaled to the UE, which includes the code set determined at step 1540. This signaling is preferably accomplished by the DCI transmitted on the PDCCH. The code set message at step 1550 may direct the UE to use C's selected DMRS ports to receive C MIMO PDSCH streams. Alternatively, the message may direct the UE to use selected C DMRS ports to transmit C MIMO PUSCH streams.

The general approach outlined above with reference to FIG. 15 is illustrated in FIG. 16a, 16b by a specific embodiment of a pairwise hierarchical association of groups of DMRS ports, in which case N and M are integers of degree 2.

In FIG. 16a, 16b show a single tree of DMRS port groups obtained according to the particular embodiment under consideration for the case of N'=N=64 and M=16 (upper part of the figures), as well as their corresponding code sets (lower part of the figures).

The indices used in the presented tree hierarchy of DMRS port groups correspond to sequential DMRS port indices. Each node at the lowest level of the hierarchy (leaf) corresponds to one of the 64 DMRS ports available for use on the TRP. Starting from the leaf level, each DMRS port group of the subsequent tree level is obtained by combining two adjacent DMRS port groups from the previous hierarchy level so that each DMRS port group of the previous hierarchy level is part of only one DMRS port group of the subsequent hierarchy level. At the topmost level of the tree under consideration, the nodes correspond to four combinations of 16 consecutive DMRS ports that may be available for use on the UE.

Next, in each code subset, which are illustrated in the lower portion of FIG. 16a, 16b, the second subset of bits is a postfix subset, and the first subset of bits is a prefix subset. For each node of the tree hierarchy of DMRS port groups at a specific level, the prefix subset bits encode the number of DMRS ports in each DMRS port group at that specific hierarchy level, and the postfix subset bits encode the specific DMRS port group corresponding to this node. Thus, according to the illustration in FIG. 16a, the group of DMRS ports {12,13,14,15} is represented by the code set {0,0,1,0,0,1,1}, in which the prefix (0,0,1) essentially encodes the level tree, on which the nodes represent groups of 4 DMRS ports each, and the postfix (0,0,1,1) encodes a specific group {12,13,14,15} at this level. Accordingly, at step 1550, the code set {0,0,1,0,0,1,1} will be signaled to the DCI. Likewise, in FIG. 16a, a tree leaf corresponding to DMRS port 8 is represented by the code set {1,0,0,1,0,0,0}, in which the lowest level of the tree is encoded with the prefix (1), and the postfix (0,0,1, 0,0,0) codes a particular single port. In this case, at step 1550, the code set {1,0,0,1,0,0,0} will be signaled to the DCI. In both illustrative cases considered, the code set size is only 7 bits, i.e. the bit load on the DCI to indicate the required combination of DMRS ports is low.

In FIG. 17 similarly illustrates an adaptation of the approach under consideration, when groups of DMRS ports are formed from a total of 16 DMRS ports, i.e. N'=M=16 (upper part of the figure), and are accordingly represented by code sets (lower part of the figure). Each leaf at the lowest level of the tree hierarchy corresponds to a specific one of the 16 DMRS ports, and the highest level corresponds to a combination of all 16 consecutive DMRS ports. Each code set similarly encodes the tree level with its prefix part, and a specific group of DMRS ports with its postfix part. In the illustrative case discussed here, the code set size is 5 bits, i.e. the bit load on the DCI to indicate the required combination of DMRS ports is again quite low.

It should be understood that shown in FIG. 16, 17 and the corresponding disclosure, the bit representation of the code sets is illustrative, but not the only possible one. Thus, without loss of generality, in each code set its postfix subset can encode the level of the DMRS group tree, and the prefix subset can encode a specific DMRS group from this level; in addition or in addition, in one or both of the postfix subset and the prefix subset, other combinations of bits for encoding may be used - in particular, the values of the bits in one or both of the postfix subset and the prefix subset may be respectively inverted: 0→1 , 1→0.

The advantages of the discussed embodiment 1 of the present invention are very low bit load on the DCI and good scalability. Its main disadvantage is low flexibility, since only a relatively small number of strictly defined combinations of adjacent DMRS ports can be specified for use.

Implementation option 2: specifying adjacent DMRS ports

Next, with reference to Fig. 18, 19 describe a mapping-based implementation of indicating adjacent DMRS ports according to the present invention. First of all, with reference to FIG. 18 describes an embodiment of a method 1800 for specifying DMRS ports for at least one UE in a wireless communication system according to a general approach consistent with this embodiment. Method 1800 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports the simultaneous transmission of multiple spatial MIMO PDSCH streams, each of which is associated with a different DMRS signal.

At step 1810, a group of DMRS ports containing C serial DMRS port indexes to be used on the UE is selected from the total number M of serial DMRS port indexes available for use on the UE, where C≤M.

At step 1820, a code parameter P representing the group of DMRS ports selected at step 1810 is obtained. The code parameter is calculated as follows: if

otherwise

where s is the starting index of the DMRS port in the selected group of DMRS ports, s=0,1,…,C - 1.

At step 1830, overhead information is signaled to the UE, which includes a binary representation of the code parameter P obtained at step 1820. This signaling is preferably accomplished by the DCI transmitted on the PDCCH. At the UE, the corresponding group of DMRS ports to be used can be obviously reconstructed from the received code parameter P. Here, similar to Embodiment 1, the code parameter message at step 1830 can direct the UE to use the selected C DMRS ports for C MIMO reception. - PDSCH streams, or instruct the UE to use selected C DMRS ports to transmit C MIMO PUSCH streams.

If a requirement is imposed to limit the bit size of the code parameter P, then the possible values of C can be further limited at step 1810 as 2 ^γ 3 ^ς , where γ and ς are non-negative integers, for example, C = 2, 3, 4, 6, 8 , 9, 12, 16.

The general approach outlined above with reference to FIG. 18 is illustrated in FIG. 19a-19 with a tabular representation of specific embodiments of the formation of possible groups of adjacent DMRS ports from a total number of M=16 consecutive DMRS port indexes.

For example, by signaling the code parameter P=72 at step 1830, the UE is instructed to use the DMRS port combination {8,9,10,11,13} (see FIG. 19b).

Crossing out the table in Fig. 19c illustrates the above-mentioned limitation of C values at step 1810 of method 1800; those. C=9 is excluded from use.

In the illustrative case considered here, the size of the code parameter does not exceed 8 bits, i.e. The bit load on the DCI to indicate the required combination of DMRS ports is again low, although generally higher than that of Embodiment 1 of the present invention.

The advantages of the discussed embodiment 2 of the present invention are low bit load on the DCI, good scalability for different numbers of supported DMRS ports, and greater flexibility compared to embodiment 1 in terms of greater flexibility in selecting combinations of DMRS ports. It should also be noted that the coding considered here is highly efficient in terms of compact representation of all possible groups of adjacent DMRS ports from the total available number using the code parameter defined by Equation (6), without scatters or omissions.

Embodiment 3: Designating DMRS ports based on combinatorial coding

Next, with reference to Fig. 20, 21 describe a combinatorial coding-based implementation of indicating generally non-contiguous DMRS ports according to the present invention. First of all, with reference to FIG. 20 describes an embodiment of a method 2000 for specifying DMRS ports for at least one UE in a wireless communication system according to a general approach consistent with this embodiment. Method 2000 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports simultaneous transmission of multiple spatial MIMO PDSCH streams, each of which is associated with a different DMRS signal.

At step 2010, a DMRS port group containing C DMRS port indices to be used on the UE is selected from a total number of M consecutive DMRS port indices available for use on the UE, where C≤M.

At step 2020, a code parameter P representing the group of DMRS ports selected at step 2010 is obtained. The code parameter is calculated by combinatorial coding as follows:

Where

(p _i ) - an ordered set of indices p _i of the selected group of DMRS ports, i=0,…,C-1, p _i =1,2,…,M.

At step 2030, overhead information is signaled to the UE, which includes a binary representation of the code parameter P obtained at step 2020, as well as the value C. This signaling is preferably accomplished by the DCI transmitted on the PDCCH. Here, similar to embodiments 1 and 2 described above, the code parameter message at step 2030 may direct the UE to use selected C DMRS ports to receive C MIMO PDSCH streams, or direct the UE to use selected C DMRS ports to transmit C MIMO streams. PUSCH streams.

Let us assume, for illustration of the general approach disclosed above with reference to FIG. 20 that at step 2010, the following combination of C=4 DMRS ports - {9,10,13,14} - is selected for use on the UE, where, in total, M=16 DMRS ports are available for use. Then, using Equation (7) for the 2020 stage, we obtain the code parameter:

This example is illustrated in Fig. 21.

Accordingly, by signaling the code parameter P=60 and C=4 at step 2030, the UE is instructed to use a non-sequential combination of DMRS ports {9,10,13,14} (see FIG. 21). In the illustrative example discussed here, the bit load on the DCI is 14 bits.

There are a number of known approaches that can be implemented at the UE to recover the DMRS port combination to be used based on the received overhead information transmitted from the TRP at step 2030, most notably the code parameter obtained through combinatorial coding according to Equation (7).

The main advantage of the discussed embodiment 3 of the present invention is significantly higher flexibility even compared to embodiment 2, since embodiment 3 allows you to specify a virtually arbitrary combination of DMRS ports. The disadvantage of this embodiment is the noticeably higher bit load on the DCI.

Below will be described the possible application of the above-described embodiments 1-3 of the present invention for the case where the reduction of the number of MIMO flows and the corresponding adaptation of the DMRS structure are carried out at the TRP, embodiments of which were described in detail above in subsection I of the description of the invention with reference to FIG. 10-14.

It should be noted here that in Embodiments 1 to 3 of the present invention, where appropriate encoding of DMRS port indices for their signaling in DCI is performed, it is assumed that there is a table characterizing DMRS ports like the one illustrated in FIG. 4a. For example, when using the DMRS structure of the present application on the TRP, illustrated in FIG. 7, 64 DMRS ports will be indexed in such a common table, each of which will have its own unique set of CDM group, DFT FD-OCC of length 4 and DFT TD-OCC of length 4.

In the present context of adapting the DMRS structure, before the method according to any of the embodiments 1-3 of the present invention disclosed above in this subsection of the invention is implemented, an appropriate 'decimation' of said common table must be performed so that the encoding according to these embodiments was performed for current DMRS ports.

In FIG. 22a shows a general approach for preprocessing the DMRS port table in the case of excluding some DMRS ports from use due to the above-mentioned adaptation of the DMRS structure.

First, _a bit flipping permutation ( _bit reversal permutation). Let's say for the one illustrated in FIG. 7 of the DMRS structure according to this application, Δ={ 0, 1, 2, 3 }, k _ƒ ={0,1,2,3}, k _t ={0,1,2,3} (respectively, N=64 in Fig. 22a). Briefly speaking, in a bit-flip permutation, each index in each of these sets is represented in binary, then the bit order is inverted on that binary representation (i.e., the first bit becomes last, and the last bit first; the second bit becomes penultimate, and the penultimate one is second; etc.), after which the inverted bit representation is converted back to a numeric representation. The result is the corresponding transformed index constellations, which are indicated in FIG. 22a as {Δ'}, respectively.

The corresponding exclusion is performed on one or more of these converted index collections.

Exception for each of {Δ'}, indicated in Fig. 21a as optional, which means that it is not necessary that all of these sets be reduced - as follows from the corresponding disclosure according to subsection I of the description of the invention, the reduction can be performed only in relation to a specific one of these sets, or in relation to two of them, or regarding them all. As a result of this reduction, corresponding thinned sets of indices are obtained, which are indicated in Fig. 22a as {Δ'}, respectively. Ultimately, based on the general table of DMRS ports, an adapted, reduced table is built, which lists the indices of DMRS ports according to thinned sets of indexes {Δ'}, .

The general approach described above with reference to FIG. 22a is illustrated with the specific example of FIG. 22b. This example essentially corresponds to the adaptation of the DMRS structure illustrated in FIG. 8, according to the approach disclosed with reference to FIG. 12 s in subsection I of the description of the invention.

As can be seen from FIG. 22b, decimation is performed on the TD-OCC DFT only by discarding the last four indices in their transformed population, which corresponds to the left branch in FIG. 12s. The result is a reduced DMRS port table with no entries for DMRS port indexes with TD-OCC DFTs excluded.

It should be noted here that, from a mathematical point of view, the bit-flip permutation-based decimation described with reference to FIG. 22a, 22b are equivalent to the adaptation embodiment of the present application disclosed in subsection I of the specification with reference to FIG. 12-14.

As discussed above, the methods according to embodiments 1-3 of the present invention in the present case will be carried out based on the abbreviated tables obtained according to the approach disclosed above with reference to FIGS. 22a, 22b. This can be illustrated by the DMRS port group tree shown in FIG. 17 as corresponding to the exclusion of 48 DMRS ports from the total available number of 64, which case corresponds to the tree hierarchy of DMRS port groups in FIG. 16a, 16b. From these figures it can be seen that for the code representation of a tree node in FIG. 16a, 16b require 7 bits, whereas the tree node encoding of FIG. 17 requires 5 bits. That is, by applying the approach according to FIG. 22a, 22b, further reduction of the bit load on the DCI can be provided.

It should be emphasized that although the embodiments of the present invention discussed in this subsection of the specification used the DMRS structures disclosed with reference to FIGS. 7, 8, it should be understood that the approach proposed here for specifying DMRS ports for UEs may be equally applicable to other promising DMRS structures planned for use in next generation wireless communication systems.

III. Time Domain Resource Allocation

In view of the above discussion of the prior art, increasing the capacity of the new DMRS structure for next generation wireless communication systems (including 6G) results in such a structure occupying a larger number of OFDM symbols in the time domain. If one uses 5G NR time resource allocation, for example, according to Type A described with reference to FIG. 5a, 5b, then having a larger DMRS structure along with a control channel in each slot will lead to an undesirable increase in overhead. This aspect is clearly illustrated in FIG. 23, where by way of example, the new DMRS structure referred to is the DMRS structure proposed herein described with reference to FIG. 7, and from the right side of FIG. 23 shows that for 6G PDSCH transmission, only 4 OFDM symbols will remain in the slot.

It should be recalled here that in Type A 5G NR, it is typically necessary to allocate at least one OFDM symbol for the DMRS signal(s) in each slot. Thus, the DMRS signal will be transmitted to the UE with every slot even if there is no change in the DMRS port allocation; also in each slot at least one symbol is occupied by the control channel.

Therefore, in this context, improved techniques for allocating time domain resources for broadband data transmission are required to avoid these negative effects.

The present application proposes an aggregated approach to resource allocation in the time domain, both at the slot and mini-slot levels, which is discussed in detail below with reference to FIG. 24-28.

As with 5G NR, from a macro-level perspective, a 10 ms frame is divided into a number of equal DL/UL periods, with the duration of the DL/UL period being configurable at the base station. A base station may communicate a predetermined DL/UL period length to the UEs it serves using the aforementioned DCI (L1) signaling, MAC (L2) signaling, RRC (L3) signaling, or even some combination thereof. Each DL/UL period is divided into slots, and each slot can consist of 14 or 12 (if the slot uses an extended cyclic prefix) OFDM symbols. In total, each DL/UL period contains OFDM symbols.

Typically, a portion of the DL/UL period slots is allocated to downstream (DL) transmission (DL portion), and another portion of the DL/UL period slots may be allocated to uplink (UL) transmission (UL portion). The DL portion and the UL portion are separated from each other by a guard interval (GI) to provide time for switching between DL and UL transmission to occur. A portion of a slot in the DL part or UL part is usually allocated for the guard interval. It should be noted that the allocation of slots between the DL and UL parts is configurable at the base station - say, all OFDM symbols of the DL/UL period can be allocated only for the DL part.

The present application proposes flexible aggregation of slots or minislots such that a larger unit of resource allocation/scheduling is introduced in the time domain than a single slot (Type A in 5G NG) or a single minislot (Type B in 5G NG). That is, it is assumed that the allocation of time domain resources for data transmission can be carried out in such aggregate units.

Below with reference to Fig. 24a, 24b, exemplary aggregation embodiments for the DL portion of a DL/UL frame period will first be described.

In FIG. 24a shows the OFDM symbols constituting three slots of the DL portion of the DL/UL period along the time axis. These slots are aggregated into a single bundle of slots, which constitutes a new time domain scheduling/allocation unit.

Unlike the corresponding Type A 5G NR (see Fig. 5a), contiguous OFDM symbols allocated for transmission of the downlink control channel (DL-ctrl) are allocated per block of slots, and not per slot, as is the case Type A 5G NR.

Contiguous OFDM symbols are also allocated to convey the DMRS structure; such adjacent symbols may be referred to as a DMRS subblock in the following text. The DMRS structure multiplexes DMRS signals for the required number of MIMO streams of the transmitted PDSCH. Here, by way of example, the DMRS structure of the present application described with reference to FIG. 1 is assumed to be the DMRS structure. 7. Each DMRS subblock transmission event in the DL/UL period is indexed by an index

It should be emphasized that the distribution of DMRS subblocks shown in FIG. 24a is illustrative and other distributions thereof may be used. Further discussed above are lower and higher capacity DMRS structures having, respectively, higher and lower density in the time domain and/or frequency domain than the illustrated structure of FIG. 7; that is, shown in FIG. 24a, the size of a DMRS subblock of 4 OFDM symbols also does not impose a limitation. Aspects of DMRS subblock allocation will be discussed in more detail below.

The remaining OFDM symbols in the block of slots may be allocated for PDSCH transmission. Although in Fig. 24a shows the allocation of all other symbols, it should be understood that a smaller number may be allocated for PDSCH transmission. Further, each slot in FIG. 24a is shown containing 14 OFDM symbols; at the same time, as mentioned earlier, a slot can contain 12 OFDM symbols. These points do not impose any restrictions on the technical solution under consideration.

In FIG. 24b along the same time axis shows the OFDM symbols constituting four minislots of the DL portion of the DL/UL period, each of which contains 4 OFDM symbols. These minislots are aggregated into a single block of minislots, which also constitutes a new time domain resource scheduling/allocation unit. Unlike the corresponding 5G NR Type B (see FIG. 5c), adjacent OFDM downlink control channel symbols (DL-ctrl), as in the case of FIG. 24a, are allocated based on the entire block of minislots, and not for each minislot, as in the case of Type B 5G NR. It should be noted that in the example under consideration, adjacent OFDM symbols allocated for DL-ctrl transmission precede the block of minislots and are not part of it. This does not impose a limitation, and a block of minislots can be organized to include OFDM DL-ctrl symbols.

Similar to the consideration in FIG. 24a, a DMRS subblock may also be allocated in the minislot block for transmitting the DMRS structure. Here, for illustration purposes only, the DMRS subblock is shown occupying an entire minislot in the block of minislots following the DL-ctrl symbols.

The remaining OFDM symbols in the block of minislots may be allocated for PDSCH transmission. Although in Fig. 24b shows the allocation of all remaining symbols, it should be understood that fewer may be allocated for PDSCH transmission.

Next, each minislot in FIG. 24b is shown containing 4 OFDM symbols; at the same time, as previously stated, a minislot may also consist of 1 or 2 or 7 OFDM symbols, and the DMRS subblock itself may have a different size, as noted with respect to FIG. 24a, and not be aligned to the boundaries of the minislot. These points do not impose any restrictions on the technical solution under consideration.

The minislot duration is generally set on the TRP and signaled from the TRP to the UE using an overhead message. For example, an RRC message or a DCI message can be used to indicate the duration of a minislot. A combination of RRC and DCI messages may also be used, where the RRC message specifies a subset of minislot duration values: for example, a subset of {2, 7} is specified from the aggregate set of {2, 4, 7, 14}, and the DCI message specifies one specific value from this subset (eg, 1 bit in DCI selects either 2 or 7) that is relevant to the current PDSCH transmission.

In FIG. 25a, 25b the aggregation proposed in this application is shown from a macro-level perspective.

In FIG. 25a shows the case where a block of slots or minislots occupies the entire DL portion, and FIG. 25b illustrates the case where a block of slots or minislots is preceded by a slot. For the embodiment of FIG. 25b, it should be emphasized that the above-mentioned OFDM symbols for DL-ctrl are included in the previous slot, while this DL-ctrl contains overhead information for scheduling a block of slots/minislots. In other words, the presence of OFDM symbols DL-ctrl in a block of slots, as shown in FIG. 24a is not mandatory according to this application. The embodiment of FIG. 25b can be considered as corresponding to a combination of the known approach (Type A 5G NR) and the approach proposed in this application. It should also be understood that a block of slots/minislots may be preceded by more than one slot; In addition, it is possible for a block of slots/minislots to precede one or more slots.

It should be explained that according to the approach proposed herein, the DL-ctrl may generally be located at any location in the DL/UL period according to the control channel decoding configuration. The main requirement is that for a particular UE, the DL-ctrl transmission takes place before the start of a block of slots/minislots so that the UE can receive the control channel and decode the DCI, which will contain PDSCH scheduling information (including information about the start of transmission of a block of slots/ minislots and its duration).

From the illustrations of Fig. 25a, 25b clearly shows the reduction in overhead - thus, reserving OFDM symbol(s) for DL-ctrl for each slot/minislot is avoided; It also makes it possible to use less frequent DMRS transmissions in the DL/UL period without reducing the quality of the channel estimate.

According to a preferred embodiment, DMRS subblocks are allocated to the DL portion with a given period T _DMRS . In FIG. 26a shows a periodic sequence of DMRS subblocks allocated to transmit a DMRS structure with a constant density in a block of slots/minislots. This case corresponds to the illustration in FIG. 24a.

It must be emphasized that the periodic configuration of DMRS sub-blocks does not necessarily have to take place exactly within the boundaries of a block of slots/minislots, as shown in FIG. 24a, 26a - say, in the embodiment of FIG. 25b, a given DMRS periodicity may not be tied to slot/minislot block boundaries. In other words, this does not impose a limitation on the technical solution discussed here.

In FIG. 26b shows another preferred embodiment, where DMRS sub-blocks are allocated to the DL part also with a given period T _DMRS , but the number of resources allocated for transmission of the DMRS structure in the first DMRS sub-block is greater than the number of resources allocated for transmission of the DMRS structure in each of the subsequent DMRS subblocks. In particular, as can be seen from FIG. 26b, the number of OFDM symbols of the subsequent DMRS sub-block is less than the number of OFDM symbols of the first DMRS sub-block, in contrast to FIG. 26a, and in the case of FIG. 26b, the first DMRS sub-block may be referred to as a high-density (HD) DMRS sub-block, and each subsequent sub-block as a low-density (LD) DMRS sub-block. In this case, obviously, there is an additional reduction in the overhead.

For example, a DMRS structure corresponding to that illustrated in FIG. 10 or 2a, can be transmitted with duplication in the HD DMRS subblock, thus occupying 4 OFDM symbols in the time domain, and without duplication in each subsequent LD DMRS subblock, occupying 2 OFDM symbols. This example can be considered conditionally corresponding to the illustration in FIG. 26b.

The situation illustrated in FIG. 26b may occur in the following case. When establishing a connection between the TRP and the UE, the UE side may require more reliable channel estimation, and this may require greater DMRS density in the time and frequency domain, and therefore an HD DMRS subblock will be allocated. Subsequently, after the connection is established, the channel estimation at the UE will be carried out, essentially, at the adjustment level, based on the existing relevant information/measurements obtained previously. In this case, LD DMRS subblocks will be used for DMRS transmission.

It should be emphasized that the considered periodic approach to DMRS allocation is preferred, but not restrictive, and DMRS subblocks can be allocated in a non-periodic manner, which, in particular, follows from the illustration in FIG. 25a, 25b.

As noted above, scheduling of time domain resources for data transmission is carried out by the scheduler within the base station (TRP), and UEs are informed of the resources reserved by the scheduler via the downlink control channel transmitted from the TRP. According to the present application, a block of slots or mini-slots can be used as a unit of scheduling/allocating time domain resources for transmission, as opposed to a single slot or mini-slot according to 5G NR. The aggregation configuration of the present application is specified by the base station (TRP) and its information is signaled to the UE on the downlink control channel (DL-ctrl). According to a preferred embodiment, this information is at least partially conveyed in a DCI message carried on the PDCCH. In DCI, in particular, an indication of the beginning of a block of slots/minislots in the DL/UL period, the duration of a block of slots/minislots, an indication of the number of slots/minislots allocated in a block of slots/minislots for PDSCH, a DMRS period, which, in general, may be signaled. be different for DL part and UL part. It should be noted that the DCI may also signal other service information discussed in this and previous subsections of the description of the invention.

As the beginning of a block of slots/minislots, its initial OFDM symbol can be indicated in the DCI within the DL/UL period; For a block of slots, the start slot can be specified as its starting slot.

The duration of a block of slots/minislots is set on TRP depending on the decision of the scheduler, which may depend on the size of the data transmitted to the user, the need to transmit data to another user, the type of traffic transmitted, the state of the channel (modulation, coding rate, number of MIMO channels), transmission of other scheduled signals, etc.

The slot/minislot block _DMRS period T may be set to TRP depending on the rate of change of the transmission channel over time. Thus, there may be a rapid change in the channel due, in particular, to the movement of the UE, and due to this change, the TRP may decide to adjust the _DMRS T downwards so that DMRS signals are sent more frequently to adjust accordingly.

Next, channel coding is typically performed on the data to be transmitted on the PDSCH. Channel coding is block-based, and as a result, the encoded data is represented as code blocks of a certain length. A possible channel coding option is LDPC coding. The code blocks are then appropriately mapped to time-frequency resources for transmission on the PDSCH. Each code block is mapped onto the entire time-frequency resource.

Moreover, if, when mapping code blocks to time-frequency resources, the existing procedure for determining the number of code blocks for data transmission, which is described in the TS 38.212 5G NR specification, is directly applied, then this procedure will have to be applied to the entire block of slots/minislots according to this application ( for example, the entire DL portion of a DL/UL period), and as a consequence, the timing of an integer number of code blocks will only be guaranteed towards the end of such a block of slots/minislots. That is, by directly using the existing approach, the timing of an integer number of code blocks will generally not be guaranteed to match the slot or minislot boundary. As a consequence, processing of received data cannot begin at the receiver side until the entire aggregated block of slots/minislots has been received. In other words, on the receiver side there is downtime associated with the need to buffer received code blocks while waiting for the end of receiving the aggregated block in order to begin processing them.

The flexible time domain resource aggregation approach proposed herein eliminates this problem and improves the pipelining efficiency of code block processing at the receiver side, as illustrated in FIG. 27.

According to a preferred embodiment, the number and length of code blocks are selected according to the duration of the minislot so that, when allocating time-frequency resources for each set of code blocks in the said number, the boundaries of this set in the time domain are aligned precisely with the boundaries of the minislot in the block of minislots. More specifically, the number and length of code blocks are selected according to the number of available REs in a minislot, the modulation used, and the channel coding rate. Moreover, in the embodiment under consideration, the use of the aforementioned existing procedure for determining the number of code blocks described in the TS 38.212 5G NR specification is, in fact, carried out specifically in relation to each group of OFDM symbols constituting a minislot separately.

In FIG. 27 shows the alignment of sets of three code blocks along minislot boundaries in a block of minislots. As a consequence, data processing at the receiver can begin virtually immediately after receiving the first minislot containing three (ie, an integer) code blocks; then, upon receipt of the second minislot, the next three code blocks will be processed; etc. It is obvious that in the embodiment under consideration, downtime associated with processing of received data is reduced to a significant extent. It should also be noted that the considered embodiment is highly flexible, since, in addition to the length and number of code blocks, the duration of the minislot itself is flexibly configurable.

It should be emphasized that although the above embodiment is preferred for aggregation at the minislot level, it is equally applicable to aggregation at the slot level. Because of the above, if implemented at the slot level, there will obviously be greater latency than in the illustrated minislot case.

The time domain resource aggregation techniques of the present application described above with reference to FIG. 24-27 regarding the DL part of the DL/UL period of a frame are also applicable to its UL part. The specific thing in this case is that the TRP scheduler decision is the same for the DL part and the UL part, and the time domain resource allocation information for the UL part is also signaled in the downlink control channel (DL-ctrl), as discussed higher. Thus, the start and duration of UL transmission of a block of slots/minislots is selected at the TRP and signaled to the UE via overhead information in the downlink control channel; more specifically, this selection is carried out by the TRP scheduler and signaling is carried out by the DCI on the PDCCH.

Accordingly, the uplink control channel, which in this case is PUCCH, will have generally different functionality in relation to the downlink control channel. In particular, there is no mandatory requirement in the UL part that the control channel precedes the DMRS and PUSCH; Moreover, in the UL part there may be no uplink control channel at all.

So, in Fig. 25a, 25b, for illustrative purposes only, the control channel is shown at the tail of a block of slots/minislots and containing acknowledgment information (ACK/NACK). However, in the UL portion, the OFDM symbols allocated for the uplink control channel may precede the OFDM symbols allocated for DMRS and PUSCH. It should be emphasized that, in general, a block of slots/minislots according to the present application can be essentially anywhere in the UL part.

Since the PUCCH is not directly related to resource scheduling, it is possible that the PUCCH transmission will not be related to the block(s) of slots/minislots (or slots or minislots in general), for example, used to transmit a Scheduling Reguest or information channel state information (CSI), or when the PUCCH transmission will relate to previous slots, minislots or block(s) of slots/minislots.

Next, with reference to Fig. 28a, 28b describe an embodiment of a time domain resource allocation method 2800 according to the present application. By way of illustration, method 2800 is implemented at a base station (eg, TRP 602 of FIG. 6) that supports the simultaneous transmission of multiple spatial MIMO PDSCH streams.

Below with reference to Fig. 28a discusses steps 2810-2860 of method 2800 performed on the DL portion of a DL/UL frame period.

At step 2810, a predetermined number of contiguous OFDM symbols are allocated for transmission of a downlink control channel, which is preferably a PDCCH.

At step 2820, a DL block of time slots is generated containing an integer number of contiguous time slots, each time slot including a predetermined number of OFDM symbols. In this case, the PDCCH, which must be carried in the OFDM symbols of the DL part allocated to it, refers to the entire block of time slots. According to the above disclosure, a time slot may be a slot that may contain 12 or 14 OFDM symbols, or a mini-slot that may contain 1, 2, 4 or 7 OFDM symbols.

At step 2830, at least one DL DMRS subblock is allocated to transmit DMRS signals for the required number of MIMO PDSCH streams.

At step 2840, OFDM symbols are allocated in the DL block of time slots for PDSCH transmission.

Possible options for the relative arrangement of OFDM symbols for the PDCCH, DL DMRS subblock(s) and block(s) of slots/minislots in the DL part are described above, including with reference to FIG. 24-26.

At step 2850, a DL block of time slots is allocated for the scheduled DL transmission.

As has been repeatedly stated previously, the PDCCH, more specifically the DCI message, must carry overhead information. In addition to the service information discussed above, in the case under consideration, the service information will include an indication of the start of the DL block of time slots and the duration of the DL block of time slots. If, according to a preferred embodiment (see FIG. 26), DMRS subblocks are organized with a period T _DMRS , then T _DMRS is also included in the overhead information.

At step 2860, for the data to be transmitted in the OFDM symbols allocated to the PDSCH in the DL block of time slots, the size and number of code blocks to perform channel coding (preferably LDPC) are determined, and code blocks representing the encoded data are obtained. The number and length of code blocks are selected so that, when allocating time-frequency resources for each set of code blocks in the said number, the boundaries of this set in the time domain are aligned with the boundaries of the time interval in the block of time intervals (see Fig. 27).

Below with reference to Fig. 28b discusses steps 2870-2875 of method 2800 performed on the UL portion of the DL/UL period.

At step 2870, a UL block of time slots is generated containing an integer number of contiguous time slots.

At step 2871, at least one UL DMRS subblock is allocated to transmit a DMRS structure in which DMRS signals are multiplexed for the desired number of MIMO PUSCH streams.

At step 2872, OFDM symbols are allocated in the UL block of time slots for PUSCH transmission.

At step 2873, a predetermined number of contiguous OFDM symbols are allocated for PUCCH transmission.

Possible options for the relative arrangement of OFDM symbols for PUCCH, UL DMRS subblock(s) and block(s) of slots/minislots in the UL part are described above.

At step 2874, a UL block of slots is allocated for UL transmission.

At step 2875, similar to step 2860, channel coding is performed on the data to be transmitted in the OFDM symbols allocated to the PUSCH in the UL block of time slots, selecting the number and length of code blocks accordingly.

It should be emphasized that although the embodiments discussed in this subsection of the specification used the DMRS structure disclosed with reference to FIG. 7, and other DMRS structures proposed in this application, it should be understood that the approach to time domain resource allocation proposed herein may be equally applicable to other promising DMRS structures planned for use in next generation wireless communication systems.

It should also be understood that the illustrated exemplary embodiments are merely preferred and not the only possible embodiments of the present invention. More precisely, the scope of the present invention is defined by the following claims and their equivalents.

Claims (47)

1. A method of specifying demodulation reference signal ports (DMRS ports) for at least one user equipment (UE) in a wireless communication system, carried out at a base station (TRP), wherein the TRP is configured to support simultaneous transmission of multiple spatial MIMO streams for transmitting data, wherein a different DMRS port is associated with each of the plurality of MIMO streams, wherein the method comprises the steps of: form a hierarchy of groups of DMRS ports, with each node of the hierarchy corresponding to a group of one or more DMRS ports, with each node at the lowest level of the hierarchy corresponding to one of a given number N' of DMRS ports, where N' is a positive integer, and , at each subsequent hierarchy level, each node corresponds to a DMRS port group obtained by combining the same number of different DMRS port groups from the previous hierarchy level, with the highest level of the DMRS port group hierarchy being the hierarchy level at which the number of DMRS ports in each DMRS port group is equal to M, where M is a positive integer less than or equal to N' representing the total number of DMRS ports available for use on the UE; represent each node of the generated hierarchy of DMRS port groups with a code set, wherein each code set consists of a first subset of bits and a second subset of bits, wherein the number of bits in the first subset and the number of bits in the second subset are variables, and for each node of the DMRS group hierarchy -ports at a specific hierarchy level, the bits of the first subset encode the number of DMRS ports in each group of DMRS ports at this specific hierarchy level, and the bits of the second subset encode the group of DMRS ports corresponding to this hierarchy node; selecting, in the hierarchy of DMRS port groups, a group containing C DMRS ports to be used on the UE, where C is a positive integer less than or equal to M; determining a code set corresponding to the selected group of DMRS ports; And signaling the service information to the UE, the service information including said specific code set. 2. The method according to claim 1, in which the DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams the corresponding N DMRS signals are multiplexed, where N is a positive integer, N ≤ N', N > M, and Each of the DMRS signals is uniquely identified by a DMRS port such that each DMRS port is associated with a unique combination of a code division multiplexing (CDM) group index, a frequency domain orthogonal code (OCC) index, and a time domain OCC index used for said multiplexing the corresponding DMRS signal. 3. The method of claim 2, wherein N' and M are integers of degree 2, wherein successive nodes at the lowest level of the DMRS port group hierarchy correspond to successive DMRS port indices, respectively; wherein, in the said formation of a hierarchy of DMRS port groups, each group of DMRS ports of a subsequent hierarchy level is obtained by combining two adjacent groups of DMRS ports from the previous hierarchy level so that each group of DMRS ports of the previous hierarchy level is part of only one DMRS group -ports of the next hierarchy level; wherein in each code subset, the second subset of bits is the postfix subset, and the first subset of bits is the prefix subset. 4. The method according to claim 3, in which N=64, while N'=64, M=16, or N'=M=16. 5. The method of claim 1 or 2, wherein said signaling is carried out by transmitting a physical downlink control channel (PDCCH) with downlink control information (DCI) including said overhead information. 6. Method according to any one of paragraphs. 1-5, wherein said DMRS ports C are to be used by the UE to receive Physical Downlink Shared Data Channel (PDSCH) MIMO streams. 7. Method according to any one of paragraphs. 1-5, wherein said DMRS ports C may be used by the UE to transmit Physical Uplink Shared Channel (PUSCH) MIMO streams. 8. A method for specifying demodulation reference signal ports (DMRS ports) for at least one user equipment (UE) in a wireless communication system, carried out at a base station (TRP), wherein the TRP is configured to support simultaneous transmission of multiple spatial MIMO streams for transmitting data, wherein a different DMRS port is associated with each of the plurality of MIMO streams, wherein the method comprises the steps of: selecting a DMRS port group containing C serial DMRS port indexes to be used on the UE from a total number of M serial DMRS port indexes available for use on the UE, where C, M are positive integers, C ≤ M; a code parameter P representing the selected group of DMRS ports is obtained, wherein the code parameter is determined as follows: if (C - 1) ≤ M/2, P = M⋅(C - 1) + s, otherwise P = M⋅(M - C + 1) + (N - 1 - s), where s is the starting index of the DMRS port in the selected group of DMRS ports, s = 0, 1, ..., C - 1; And signaling the overhead information to the UE, wherein the overhead information includes the received code parameter. 9. The method of claim 8, wherein, in the case of a limitation on the bit size of the code parameter, at least one C value is excluded from use in said acquisition. 10. The method according to claim 8 or 9, in which a DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams the corresponding N DMRS signals are multiplexed, where N is a positive integer, M < N, and each of the DMRS signals is uniquely identified by a DMRS port such that each DMRS port is associated with a unique combination of a CDM group index, a frequency domain OSS index, and a time domain OSS index used for said multiplexing of the corresponding DMRS signal. 11. The method according to claim 10, in which N=64, M=16. 12. Method according to any one of paragraphs. 8-10, wherein said signaling is carried out by transmitting a PDCCH with a DCI including said overhead information. 13. Method according to any one of paragraphs. 8-12, in which said DMRS ports C are to be used by the UE to receive MIMO PDSCH streams C. 14. Method according to any one of paragraphs. 8-12, in which said DMRS ports C may be used by the UE to transmit MIMO PUSCH streams C. 15. A method for specifying demodulation reference signal ports (DMRS ports) for at least one user equipment (UE) in a wireless communication system, carried out at a base station (TRP), wherein the TRP is configured to support simultaneous transmission of multiple spatial MIMO streams for transmitting data, wherein a different DMRS port is associated with each of the plurality of MIMO streams, wherein the method comprises the steps of: selecting a DMRS port group containing C DMRS port indices to be used on the UE from a total number of M consecutive DMRS port indices available for use on the UE, where C, M are positive integers, C ≤ M; a code parameter P representing the selected group of DMRS ports is obtained, wherein the code parameter is determined by combinatorial coding as follows: Where - ordered set of indexes selected group of DMRS ports, And signaling the overhead information to the UE, wherein the overhead information includes a received code parameter and C. 16. The method according to claim 15, in which a DMRS time-frequency structure is defined on the TRP, in which for N MIMO streams the corresponding N DMRS signals are multiplexed, where N is a positive integer, M < N, and each of the DMRS signals is unique is identified by a DMRS port such that each DMRS port is associated with a unique combination of a CDM group index, a frequency domain OSS index, and a time domain OSS index used for said multiplexing of the corresponding DMRS signal. 17. The method according to claim 16, in which N=64, M=16. 18. The method of claim 15 or 16, wherein said signaling is carried out by transmitting a PDCCH with a DCI including said overhead information. 19. Method according to any one of paragraphs. 15-18, in which said DMRS ports C are to be used by the UE to receive MIMO PDSCH streams C. 20. Method according to any one of paragraphs. 15-18, in which said DMRS ports C may be used by the UE to transmit PUSCH MIMO streams C. 21. A base station (TRP) in a wireless communication system, comprising at least: transceiver devices; data processing devices; And data storage devices in which computer-executable codes are stored, which, when executed by data processing devices, ensure that the base station carries out the method according to any one of the preceding paragraphs. 22. A computer-readable storage medium on which computer-executable codes are stored which, when executed by at least one base station processing device (TRP) in a wireless communication system, cause the TRP to perform the method of any one of claims. 1-20.