RU2839976C1 - Method for limiting channel estimation in time domain for downlink transmission (versions) and devices implementing said method - Google Patents

Abstract

FIELD: communication technique.

SUBSTANCE: invention relates to methods, devices and systems for communication between a base station (BS) and user equipment (UE), which enable time-domain channel estimation limiting for downlink transmission. Method for communication with user equipment implemented by a base station comprises: setting possible values of time interval parameter of channel estimation performed by UE using a demodulation reference signal (DMRS) for receiving a physical downlink shared channel (PDSCH), within which absence of change of precoder applied to PDSCH transmission is expected, and, using the downlink control information (DCI) signalling, transmitting to the UE an indication of the scheduled PDSCH transmission and an indication of the parameter to be applied of the possible parameter values; and performing scheduled PDSCH transmission to UE.

EFFECT: enabling a base station to allocate time domain resources more flexibly without adversely affecting the demodulation procedure at the user side.

35 cl, 12 dwg, 3 tbl

Description

Field of technology

[0001] The present invention relates to methods, devices and communication systems between a base station (BS) and user equipments (UE) that provide the ability to constrain channel estimation in the time domain for downlink transmission.

State of the art

[0002] The 6G system, operating in the high and mid-band (7-13 GHz) range, will support large MIMO (Multiple Integer Mode) antenna arrays with ≥ 1024 antenna elements, with hybrid analog and digital beamforming at BSs with a large number of antenna ports ≥ 128. Like 5G NR, the 6G system is expected to support a similar set of reference signals such as DMRS (Demodulation Reference Signal), CSI-RS (Channel State Information Reference Signal), SRS (Sounding Reference Signal), PT-RS (Phase Tracking Reference Signal), PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal). DMRS is used to ensure correct demodulation of the physical shared channels of the downlink and uplink (PDSCH and PUSCH). DMRS are transmitted together with PDSCH and PUSCH, i.e. they are transmitted on demand, which avoids "always on" signals. DMRS are pre-coded in the same way as PDSCH and PUSCH, i.e. DMRS have the same performance advantages as the mentioned physical data channels.

[0003] In order to provide more flexible scheduling and precoding of the downlink (DL) in the frequency domain, 5G NR supports a Precoding Resource Group (PRG), which is a set of adjacent Physical Resource Blocks (PRBs) in the frequency domain on which the BS applies the same precoding matrix (hereinafter referred to as “precoder” for short). Thus, the UE can typically perform channel estimation for downlink demodulation within said PRG. In other words, if the PRG value is set to, for example, 2 adjacent PRBs, then the UE can perform channel estimation for each such PRB or for both at once, and applying the channel estimate obtained in this PRG to demodulate the channel in the next PRG may result in demodulation errors due to the channel “discontinuity” caused by applying different precoders in these PRGs, i.e. in the next PRG the BS could for various reasons change the precoder used for DL transmission. Thus, the use of PRG allows minimizing errors generated by the “break” of the channel in the frequency domain.

[0004] The 6G communication technology is expected to support PDSCH transmission with different transmission time intervals (TTI) or with different time domain resource allocations (TDRA), including with a duration longer than one slot. However, in the 5G NR communication technology, the channel estimation constraints and precoding assumptions for DMRS are supported only in the frequency domain. Therefore, the existing capabilities of the channel estimation constraints and precoding assumptions for DMRS in the prior art are not flexible enough. This results in a number of problems that need to be addressed. Problem 1: The UE always assumes unconstrained channel estimates (which may also be referred to as channel measurements) for DMRS in the time domain. Problem 2: The time domain resource allocation of paired users, i.e., those users that are paired in a multi-user multiple-input multiple-output (MU-MIMO) mode, must be aligned to ensure correct DL precoding/decoding. Issue 3: The current BS (i.e. BS in 5G NR) will not be able to update the DL precoding within the PDSCH transmission in the transmission timeslot even if its duration is more than 1 slot.

[0005] For the above reasons, the capabilities of channel estimation and precoding constraints for DMRS should be improved. In particular, the maximum time domain resource allocation (TDRA) for 6G XMIMO (extreme massive MIMO) is likely to be extended beyond one slot (or 14 symbols). For such a long TDRA, more flexible MU-MIMO scheduling in the time domain should be supported. A possible change in DL precoding should be signaled within the TDRA for PDSCH.

The essence of the invention

[0006] The present invention completely solves or at least alleviates the problems of the prior art. It should be understood that some embodiments of the present invention may solve all of the above-mentioned problems, while another one or more embodiments may not solve all of the above-mentioned problems at once, but instead solve one or more (but not all) of the above-mentioned problems. In addition, one skilled in the art will understand that the disclosed invention may solve other, related problems of the prior art that are not explicitly mentioned herein. The main technical advantage of the present invention is to enable a base station to more flexibly allocate time domain resources without negatively affecting the demodulation procedure at the user side.

[0007] In a first aspect of the present invention, there is provided a method implemented by a BS for communicating with one or more UEs, comprising: defining possible values of a channel estimation time interval parameter performed by the one or more UEs using one or more DMRSs for receiving a PDSCH; using downlink control information (DCI) signaling, transmitting to the one or more UEs an indication of a scheduled PDSCH transmission and an indication of a value of said parameter to be applied from among the possible values of the parameter; and performing the scheduled PDSCH transmission to the one or more UEs.

[0008] According to a development of the first aspect, the value of the channel estimation time interval parameter indicates a group of orthogonal frequency division multiplexing (OFDM) symbols within which the UE will expect that the base station will not change the precoder used for transmitting the PDSCH.

[0009] According to a development of the first aspect, the value of the channel estimation time interval parameter is defined by the total number of OFDM symbols contained in the channel estimation time interval, or by the number of OFDM symbols in which DMRS appears, within a TTI or TDRA, where the UE will expect no change by the base station of the precoder applied to the PDSCH transmission.

[0010] According to the development of the first aspect, the setting of possible values of the channel estimation time interval parameter is the configuration of these values using radio resource control (RRC) signaling or medium access control (MAC) signaling.

[0011] According to the development of the first aspect, the assignment of possible values of the channel estimation time interval parameter is a predetermination of these values in the specification of the communication standard.

[0012] According to the development of the first aspect, the indication of the value of said parameter to be applied from among the possible values of the parameter is an explicit indication or an implicit indication of the value of said parameter.

[0013] According to the development of the first aspect, a certain implicitly indicated value of said parameter is inferred from the absence in the DCI of an explicit indication of any value of said parameter.

[0014] According to the development of the first aspect, a certain implicitly indicated value of the mentioned parameter is the default value of this parameter or another predetermined value.

[0015] According to a development of the first aspect, the default value of the mentioned parameter indicates to the UE that no change in the precoder used by the base station is expected during the entire PDSCH transmission time interval.

[0016] According to the development of the first aspect, a certain implicitly indicated value of said parameter is derived from the absence in the DCI of an explicit indication of any value of said parameter and/or depending on the format of the signaled DCI.

[0017] According to a development of the first aspect, a certain implicitly indicated value of said parameter is derived based on the absence of an explicit indication of any value of said parameter in the DCI and on the basis of whether the time domain resources allocated for the PDSCH transmission exceed a threshold value predefined in the specification of the communication standard or configured by means of higher layer signaling, wherein the time domain resources are the number of OFDM symbols or the number of slots in the PDSCH transmission.

[0018] According to the development of the first aspect, a certain implicitly indicated value of said parameter is derived based on the absence of an explicit indication of any value of said parameter in the DCI and on the basis of whether the number of occurrences of DMRS symbols exceeds a threshold value predefined in the specification of the communication standard or configured using higher-layer signaling.

[0019] According to the development of the first aspect, one or more bits are allocated in DCI to explicitly indicate the value of the mentioned parameter.

[0020] According to a development of the first aspect, the method further comprises transmitting an explicit indication for the scheduled PDSCH transmission using DCI signaling, such as a precoder change with power reallocation or a precoder change with full precoder recalculation.

[0021] In a second aspect of the present invention, there is provided a base station comprising a operatively connected transmitting and receiving unit, an antenna, a processor, and a readable medium storing instructions executable by the processor which, when executed by the processor, cause the base station to perform the communication method of the first aspect of the present invention or any development of the first aspect of the present invention.

[0022] In a third aspect of the present invention, there is provided a computer-readable medium storing executable instructions which, when executed by a device, cause the device to perform the communication method of the first aspect of the present invention or any development of the first aspect of the present invention.

[0023] In a fourth aspect of the present invention, there is provided a method implemented by a UE for communicating with a BS, comprising: receiving, using DCI signaling, an indication of a scheduled PDSCH transmission and an indication of a channel estimation time interval parameter value to be applied from possible values of said parameter; performing channel estimation using one or more DMRS occurrences within the PDSCH transmission channel estimation time interval indicated by the received value of said parameter; and demodulating the PDSCH transmission based on the received channel estimate.

[0024] According to a development of the fourth aspect, the value of the channel estimation time interval parameter indicates a group of symbols within which the UE will expect that the base station will not change the precoder applied to the PDSCH transmission, wherein the symbols are OFDM symbols.

[0025] According to the development of the fourth aspect, the value of the channel estimation time interval parameter is specified by the total number of OFDM symbols contained in the channel estimation time interval, or the number of OFDM symbols in which DMRS appears, within a TTI or TDRA, where the UE will expect no change by the base station of the precoder applied to the PDSCH transmission.

[0026] According to the development of the fourth aspect, the possible values of said parameter are configured using radio resource control (RRC) signaling or medium access control (MAC) signaling.

[0027] According to the development of the fourth aspect, the possible values of the mentioned parameter are predetermined in the specification of the communication standard.

[0028] According to the development of the fourth aspect, the indication of the value of said parameter to be applied from among the possible values of the parameter is an explicit indication or an implicit indication of the value of said parameter.

[0029] According to the development of the fourth aspect, a certain implicitly indicated value of said parameter is derived by the UE based on the absence of an explicit indication of any value of said parameter in the DCI.

[0030] According to the development of the fourth aspect, the certain implicitly indicated value of the mentioned parameter is the default value of this parameter or another predetermined value.

[0031] According to the development of the fourth aspect, the default value of the mentioned parameter indicates to the UE that no change in the precoder used by the base station is expected during the entire PDSCH transmission time interval.

[0032] According to the development of the fourth aspect, a certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI and/or depending on the format of the signaled DCI.

[0033] According to the development of the fourth aspect, a certain implicitly indicated value of said parameter is derived by the UE based on the absence of an explicit indication of any value of said parameter in the DCI and on the basis of whether the time domain resources allocated for the PDSCH transmission exceed a threshold value predefined in the specification of the communication standard or configured by means of higher layer signaling, wherein the time domain resources are the number of OFDM symbols or the number of slots in the PDSCH transmission.

[0034] According to the development of the fourth aspect, a certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI and on the basis of whether the number of occurrences of DMRS symbols exceeds a threshold value predefined in the specification of the communication standard or configured by higher layer signaling.

[0035] According to the development of the fourth aspect, one or more bits are allocated in the DCI to explicitly indicate the value of the mentioned parameter.

[0036] According to a development of the fourth aspect, the method further comprises receiving an explicit indication for the scheduled PDSCH transmission using the DCI signaling of a precoder change type with power reallocation or a precoder change type with full precoder recalculation.

[0037] In a fifth aspect of the present invention, there is provided a user equipment comprising a operatively connected transmitting and receiving unit, an antenna, a processor, and a readable medium storing instructions executable by the processor which, when executed by the processor, cause the user equipment to perform the communication method according to the fourth aspect of the present invention or according to any development of the fourth aspect of the present invention.

[0038] In a sixth aspect of the present invention, there is provided a computer-readable medium storing executable instructions that, when executed by a device, cause the device to perform the communication method of the fourth aspect of the present invention or any development of the fourth aspect of the present invention.

[0039] In a seventh aspect of the present invention, there is provided a communication system comprising at least one base station according to the second aspect of the present invention or according to any development of the second aspect of the present invention and at least one user equipment according to the fifth aspect of the present invention or according to any development of the fifth aspect of the present invention, wherein said at least one base station and said at least one user equipment communicate with each other in a communication network served by said at least one base station.

Brief description of the drawings

[0040] These and other aspects, features and advantages of the present invention will be described in detail below with reference to the following accompanying figures. Where reference signs are used, the same reference signs in different figures denote the same objects. In the accompanying figures:

[FIG. 1] Fig. 1 illustrates a simplified diagram of a transmitting/receiving unit 200.1 and antennas 200.2 included in the BS 200 and used to transmit PDSCH together with DMRS to the UE 400 and receive PUSCH together with DMRS from the UE 400.

[FIG. 2] Fig. 2 illustrates the structure of DMRS type 1 in 5G NR.

[FIG. 3] Fig. 3 illustrates the structure of DMRS type 2 in 5G NR.

[FIG. 4] Fig. 4 is a block diagram of PRG selection for PDSCH in 5G NR.

[FIG. 5] Fig. 5 is a block diagram of selecting a channel estimation time interval for PDSCH according to the present invention.

[FIG. 6] Fig. 6 is a non-limiting example of a PDSCH transmission structure according to the present invention.

[FIG. 7] Fig. 7 is a diagram of interaction between BS 200 and UE 400 according to the present invention.

[FIG. 8] Fig. 8 illustrates three non-limiting examples of PDSCH transmissions, each of which has its own PDSCH channel estimation time interval set over DMRS according to the present invention.

[FIG. 9] Fig. 9 illustrates two non-limiting embodiments of setting the PDSCH channel estimation time interval over DMRS according to the present invention.

[FIG. 10] Fig. 10 illustrates a schematic representation of a BS 200 according to the present invention.

[FIG. 11] Fig. 11 illustrates a schematic diagram of a UE 400 according to the present invention.

[FIG. 12] Fig. 12 illustrates a schematic representation of a communication system 500 according to the present invention.

Detailed description of the invention

[0041] DMRS for 5G NR are generated using pseudo-random sequences and are defined in the 3GPP TS 38.211 specification for PDSCH and PUSCH. In Rel-18 5G NR, four types of DMRS are supported: DMRS Type 1, the structure of which is schematically illustrated in Fig. 2 , DMRS Type 2, the structure of which is schematically illustrated in Fig. 3 , as well as DMRS extended Type 1 (eType 1) and DMRS extended Type 2 (eType 2).

[0042] DMRS type 1 has two code division multiplexing (CDM) groups, two frequency domain orthogonal code sequences (FD-OCC), two time domain orthogonal code sequences (TD-OCC) for a two-symbol DMRS configuration. In other words, DMRS type 1 supports a total of 2×2×2=8 orthogonal sequences/8 orthogonal DMRS ports that can be used for data transmission. Thus, DMRS type 1 supports a maximum of eight ports for a two-symbol DMRS configuration. As shown in FIG. 2 , for DMRS type 1, a uniform CDM group is used, i.e., within a CDM group, the used subcarriers are distributed uniformly.

[0043] DMRS type 2 has three code division multiplexing (CDM) groups, two orthogonal code sequences in the frequency domain (FD-OCC), two orthogonal code sequences in the time domain (TD-OCC) for a two-symbol DMRS configuration. In other words, DMRS type 2 supports a total of 3×2×2=12 orthogonal sequences/12 orthogonal DMRS ports that can be used for data transmission. Thus, DMRS type 12 supports a maximum of twelve ports for a two-symbol DMRS configuration. As shown in Fig. 3 , for DMRS type 2, a more localized CDM group is used, i.e., within a CDM group, the used subcarriers are distributed more locally.

[0044] DMRS extended type 1 (DMRS eType 1) and DMRS extended type 2 (DMRS eType 2) are respectively versions of DMRS type 1 and DMRS type 2 that are extended by using four FD-OCCs. Thus, DMRS extended type 1 and DMRS extended type 2 respectively double the number of DMRS type 1 ports and the number of DMRS type 2 ports.

[0045] The downlink precoding for the PDSCH follows a frequency domain granularity determined by the PRG size. In other words, it is assumed that the precoder applied to the corresponding transmission (DL or UL) will remain the same within a PRG in the frequency domain. The PRG may take values of 2 PRB, 4 PRB, or be wideband, i.e., cover the entire frequency domain resource allocation (FDRA). Possible PRG sizes may be specified in advance, and then the specific PRG size values to be used in a particular case may be signaled using RRC signaling and/or DCI signaling.

[0046] There are several reasons why the BS may decide to change the precoder. First, the transmission channel is frequency-selective and, accordingly, the optimal precoder may change in a given situation. Second, the frequency domain resource scheduler available in the communication network (e.g. as part of the BS or in interaction with the BS) is made more flexible; there may be multiple users in the system and for the MU-MIMO mode, when several users are served on the same frequency-time resources, the scheduler may change the previously made decision: for example, all frequency-time resources were assigned for transmission from UE1 (with a large transmission packet, see packet 'B' in Fig. 6 ), and a smaller part of the frequency-time resources (relative to the resources allocated to UE1) was assigned to another user UE2 (with a smaller transmission packet, see packet 'A' in Fig. 6 ). That is, in some resources, MU-MIMO is used, and in another part of the resources, in which only UE1 transmits, the single-user spatial signal coding mode (SU-MIMO) is used. In this non-limiting example, the BS may change the precoder when switching from MU-MIMO operation to SU-MIMO operation.

[0047] In general, it is usually impossible or difficult for the BS to communicate to the UE detailed information about how the BS allocates resources or what precoder change scheme is used in a given case, since the BS must be flexible in these matters, or the precoder may change according to some complex algorithm. This is why the above-mentioned PRG is used for the frequency domain in 5G NR, within which the UE assumes that the precoder will remain unchanged. Thus, a PRG is understood here, and this understanding is consistent with 5G NR, as a resource block group consisting of a set of frequency-domain contiguous resource blocks, which are contiguous resource blocks with the same precoding. However, the use of a PRG per se is not an obligation for the BS not to change the precoder, but rather a strong recommendation. In other words, the BS has the right not to change the precoder even if a PRG is used, i.e. the frequency granularity of the precoder change is always no higher than the granularity of the PRG.

[0048] The PRG size selection procedure for PDSCH in 5G NR is schematically illustratedFig. 4And is described in detail in the specification Ref: TS 38.214 “NR; Physical layer procedures for data”, v18.2.0, 2024-03-29, 3gpp.org. The PRG size depends on the DCI format, i.e. the format of the downlink control information that is transmitted from the BS to the UE. As a non-limiting example, in 5G NR, the following logic for determining the PRG size is often used. If a PDSCH transmission is scheduled with DCI format 1_0 signaling, then the PRG size value to be applied in this scheduled PDSCH transmission will be inferred to be ‘n2’=2 PRBs. Other possible values include, but are not limited to, ‘n4’=4 PRBs, ‘wideband’=all PRBs in the FDRA for PDSCH. If the PDSCH transmission is scheduled using DCI format 1_1 signaling, then a semi-statically defined PRG size value will be derived according to the RRC signaling or a dynamically defined PRG size value will be derived according to the RRC signaling and the DCI signaling.

[0049] There are two DCI formats: DCI format 1_0 and DCI format 1_1. DCI format 1_0 is used for communication with the UE by default. This DCI format 1_0 is compact and immutable (i.e., its structure does not change). This DCI format 1_0 is used in cases where, for example, the UE is reconfigured in order to provide initial communication with the UE. For this DCI format 1_0, a specific PRG size value may be predefined. In 5G NR, for DCI format 1_0, the PRG size value is predefined to be 2. Thus, if, for example, a PDSCH is scheduled by DCI signaling having format 1_0, then the UE may output a PRG size value equal to, but not limited to, the predefined value ‘n2’ (i.e., two adjacent PRBs).

[0050] DCI format 1_1 is a more advanced format, the structure and size of which may vary depending on the configuration of the UE. The signaling of DCI having DCI format 1_1 assumes in 5G NR, as shown in Fig. 4 , (1) a semi-static setting of the PRG size value via RRC signaling and (2) a dynamic setting of the PRG size value via RRC signaling and DCI. In the case of a semi-static setting, the PRG size value is determined according to a configured value that the UE receives from the RRC layer. In the case of a dynamic setting, the PRG size value is determined based on pre-configured values (of which there may be several) received from the RRC layer and additionally based on information contained in the DCI, namely depending on the number of PRBs that are allocated to the UE according to the DCI and a bit in the DCI.

[0051] The logic for semi-static assignment/derivation of the PRG size value via RRC signaling is now described in more detail. In this embodiment, the derivation of the PRG size to the UE may be performed according to the following pseudocode:

Pseudocode 1 :

If bundleSize =n4 then PRG size=n4
If bundleSize =wideband, then PRG size=wideband
Otherwise (default option), PRG size=n2

[0052] The 'PRG size' parameter is the size of the PRG whose value is output, and the 'bundleSize' parameter is a configuration parameter that is communicated to the user via RRC signaling.

[0053] The logic for dynamically setting the PRG size value via RRC and DCI signaling is now described in more detail. In this embodiment, the PRG size can be derived according to the following pseudocode:

Pseudocode 2 :

RRC signaling - bundleSizeSet1 = {n4, wideband, n2-wideband, n4-wideband}
RRC signaling - bundleSizeSet2 ={n4, wideband}
DCI alarm
If the DCI field specifies bundleSizeSet1, then
If bundleSizeSet1=n4 then PRG size=n4
If bundleSizeSet1=wideband then PRG size=wideband
If bundleSizeSet1=n2-wideband then
If the number of N_PRBs > (BWP size)/2, then
PRG size=wideband ;
otherwise,
PRG size=n2 .
If bundleSizeSet1=n4-wideband then
If the number of N_PRBs > (BWP size)/2, then
PRG size=wideband ;
otherwise,
PRG size=n4 .
If the DCI field specifies bundleSizeSet2
If bundleSizeSet2=n4 then
PRG size=n4
If bundleSizeSet2=wideband then
PRG size=wideband

[0054] The 'bundleSizeSet1' and 'bundleSizeSet2' parameters are signalled to the user via RRC and may take one of the values specified in Pseudo-code 2 above in curly brackets {}. The value of the 'N_PRBs' parameter in the DCI specifies the number of PRBs allocated for data transmission. The value of the 'BWP size' parameter in the DCI specifies the size of the portion of the channel bandwidth configured for the user. In this variant, 1 bit in the DCI is used for dynamic switching between the 'bundleSizeSet1' and 'bundleSizeSet2' parameters, and the PRG size depends on the value of the 'N_PRBs' parameter, i.e. the number of PRBs allocated for the PDSCH. Given the derived PRG value, the UE will perform channel estimation per PRG or per frequency domain unit that is smaller than one PRG (e.g. per PRB). This will allow the UE to avoid erroneous channel estimates in most cases due to a possible change of the precoder used by the base station. The value 'n4' corresponds to 4 PRBs, the value 'wideband' corresponds to all PRBs (i.e. the entire FDRA for PDSCH), the value 'n2-wideband' corresponds to 2 PRBs or all PRBs, and the value 'n4-wideband' corresponds to 4 PRBs or all PRBs. However, these values can be reassigned in other ways. Further details on deriving the PRG size value are described in TS 38.214 “NR; Physical layer procedures for data”, v18.2.0, 2024-03-29, 3gpp.org.

[0055] Now, with reference to Fig. 1, we consider a schematic representation of a transmitting/receiving unit 200.1 and antennas 200.2 included in the BS 200 and used for transmitting PDSCH together with DMRS to UE 400 and receiving PUSCH together with DMRS from UE 400. On the left in the figure, PDSCH/PUSCH transmissions for different MIMO layers and the corresponding DMRS antenna ports 'A', 'B', ..., 'ZZ' are shown. The number of MIMO layers usually corresponds to the number of DMRS ports and can be equal to, but not limited to, 64. Each transmission (e.g., PDSCH transmission for MIMO layer 'A') is transmitted with a corresponding DMRS signal transmitted from the corresponding DMRS antenna port (i.e., in this example, from the DMRS antenna port 'A'). On the receiving side of this transmission and the corresponding DMRS signal (for example the DMRS signal transmitted from the antenna DMRS port 'A'), the channel estimation is performed on the DMRS signal and the results of this estimation are used to demodulate the corresponding transmission (in this example the PDSCH transmission for the MIMO layer 'A'). Each transmission, as shown in Fig. 1 , is subjected to digital and analog pre-coding in the transmitting and receiving unit 200.1 and is emitted by the corresponding subset of physical antennas. In the present application, the digital and analog pre-coding can be performed by any methods known from the prior art.

[0056] The present invention will now be described in the context of a 6G communication system, bearing in mind the possibility of using in such a system data transmissions whose duration, namely TDRA, exceeds 1 slot or 14 OFDM symbols, since for xMIMO, from the point of view of implementation and overhead, it is highly desirable that the TDRA in MU-MIMO be sufficiently large.

[0057] There may be several OFDM symbols in the time domain in which DMRS (DMRS occasions) occur. Currently, the UE always assumes that the precoder will remain constant throughout the TDRA. That is, the UE may actually jointly process several DMRS symbols if they were transmitted from the BS within the TDRA several times, since there are configurations when DMRS are transmitted several times in the time domain. At this point, the UE assumes that the precoder will not change in any way in the time domain within a slot, which leads to the problem that if the BS transmits data in a certain transmission mode (e.g. in MU-MIMO), then it must maintain this mode throughout the TDRA, even if there is no longer a reason to use this mode in a part of the TDRA (e.g., in this part of the TDRA it would be better to use SU-MIMO, since in this part of the interval the transmission is carried out for one user). This degrades the performance of the communication for at least some users (in the above non-limiting example: for the user to which it would be possible to transmit in SU-MIMO, but which is forced to transmit in MU-MIMO mode when there are no transmissions to other users in this TDRA). In other words, if the BS has the opportunity or need to change the precoder, or this BS has otherwise calculated a new optimal precoder value given the problem identified above, the BS cannot change the precoder, since the UE assumes, or the BS knows that the UE assumes, that the precoder will not change during the entire TDRA.

[0058] In the present invention, as indicated above, the possibility of transmitting a signal over a TDRA longer than one slot (equal to 14 OFDM symbols) (e.g. over several adjacent slots or over a duration of more than 14 OFDM symbols) is considered. In such cases, the BS needs to have some flexibility for the scheduler so that during transmission in MU-MIMO it would be possible to change the transmission of data to several users. For example, on some part of the TDRA longer than 1 slot, the base station applies one MU-MIMO scheme, and on another arbitrary part of the TDRA (e.g. in the remaining part of the TDRA) - another MU-MIMO scheme or even another mode, i.e. SU-MIMO. Such a change in the MU-MIMO transmission scheme or the spatial coding mode of the signal itself entails a change in the precoder applied by the base station to the transmission.

[0059] In another non-limiting example, if there are UEs with different sizes of transmitted packets, a UE with a long packet will use more time resources than another UE with a shorter packet. And the transmission to these two UEs, performed in MU-MIMO mode, will entail a change in the scheduler decision in the time domain. In addition, for various reasons related to the computational delay at the BS, calculating the precoder at the BS based on the channel estimate reported by the user takes some time and the BS, for various reasons, may not have time to calculate the most recent precoder of this transmission based on the most recent data at the beginning of the transmission. Therefore, it would be useful to give the BS the opportunity to change the precoder in the downlink channel due to the new received channel estimates.

[0060] To solve the above problems, the present invention proposes to use a “channel estimation time interval”, which is a group of (the same) precoding symbols (Precoding Symbol Group, PSG), on which the UE can assume the persistence of the precoder. Further, with reference toFig. 5-9a detailed description will be given logics selecting a channel estimation time interval for PDSCH and a communication method in which this logic is used, according to the present invention.

[0061] The method for communicating with one or more UEs implemented by the BS begins with specifying possible values of a channel estimation time interval parameter in step S100. Channel estimation will be performed by one or more UEs using one or more DMRSs for receiving the PDSCH. The value of the channel estimation time interval parameter indicates a group of OFDM symbols (i.e., a PSG) within which the UE will expect that the base station will not change the precoder used for transmitting the PDSCH. Furthermore, it is noted that the value of the channel estimation time interval parameter determines the regularity of the occurrence of the channel estimation time interval within the transmission. As a non-limiting example, if the value of the channel estimation time interval is set to two occurrences of the DMRS in a TDRA (i.e., Y=2, as illustrated in Fig. 9 below), this means that in this TDRA (if its duration allows, i.e., for its duration more than two occurrences of the DMRS) the next channel estimation time interval occurs every two occurrences of the DMRS. The definition of S100 of possible values of the channel estimation time interval parameter is the configuration of these values using RRC signaling or MAC signaling, or the predefinition of these values in the specification of the communication standard and the storage of the corresponding values in the devices (e.g. in the memory of the BS and/or UE) for reference during operation.

[0062] The value of the channel estimation time interval parameter in one embodiment is defined by the total number of OFDM symbols included in the channel estimation time interval. In a non-limiting example, the value of the channel estimation time interval parameter may be set to 14 OFDM symbols, which would mean to the UE that the channel estimation time interval in the TDRA in this case will be a time period of 14 OFDM symbols from the beginning of this TDRA. In another non-limiting example, the value of the channel estimation time interval parameter may be set to 7 OFDM symbols, which would mean to the UE that the channel estimation time interval in the TDRA in this case will be a time period of 7 OFDM symbols from the beginning of this TDRA. The values of 7 and 14 OFDM symbols indicated in the examples above should not be interpreted as limiting the present invention, since the channel estimation time interval may be set to OFDM symbol values that are less than or greater than 7, as well as OFDM symbol values that are less than or greater than 14.

[0063] In an alternative embodiment, the value of the channel estimation time interval parameter is defined by the number of OFDM symbols in the TDRA in which the DMRS appears, i.e. the number of occurrences of the DMRS in the TDRA. In a non-limiting example, the value of the channel estimation time interval parameter may be defined to be 2 occurrences of the DMRS in the TTDRA, which would mean for the UE that the channel estimation time interval in the TDRA in this case will be the time period starting with the occurrence of the first DMRS of the two DMRSs and ending with the occurrence of the third DMRS in the TDRA. The occurrence of the third DMRS in the TDRA would mean the end of the current PSG and the beginning of the next PSG. The number of OFDM symbols in the TDRA in which the DMRS appears equal to 2, as indicated in the example above, should not be interpreted as limiting the present invention, since the channel estimation time interval may be set equal to the number of OFDM symbols in the TDRA in which the DMRS appears, which is greater than or less than 2.

[0064] After step S100 is performed, the method proceeds to step S105, wherein using DCI signaling, one or more indications of a scheduled PDSCH transmission and a corresponding one or more indications of a value of said parameter to be applied from among previously defined possible values of this parameter are transmitted to one or more UEs. The indication of a value of said parameter to be applied from among possible values of the parameter may be an explicit indication or an implicit indication of a value of said parameter.

[0065] A certain implicitly indicated value of said parameter is derived from the absence of an explicit indication of any value of said parameter in the DCI. In other words, if an explicit indication of any value of said parameter is absent in the signaled DCI, the UE may derive a default value of said parameter or any other predefined value. A non-limiting example of a default value of said parameter in this case may be the value ‘allSymbols’, i.e. a value that indicates to the UE that no change in the precoder used by the base station is expected over the entire TDRA of the received PDSCH. The specific value ‘allSymbols’ is not a limitation, since the default value of said parameter may be any other predefined value of said parameter (e.g. a value of the channel estimation time interval set to 14 OFDM symbols or two occurrences of DMRS in a TTI or TDRA, etc.).

[0066] In another embodiment, a certain implicitly indicated value of said parameter is derived from the absence of an explicit indication of any value of said parameter in the DCI and/or depending on the format of the signaled DCI. As shown in FIG. 5, scheduling a PDSCH transmission using a DCI having a DCI format of 1_0 may implicitly indicate to the UE, but not limited to this particular value, a value of 'wideband'. Scheduling a PDSCH transmission using a DCI having a DCI format of 1_1 may result in (1) a semi-static setting/derivation of a channel estimation time interval value via RRC signaling or (2) a dynamic setting/derivation of a channel estimation time interval value via RRC signaling and DCI. The derivation of the channel estimation time interval value is performed at the UE side.

[0067] The logic of semi-static assignment/derivation of the channel estimation time interval value (i.e., PSG size) via RRC signaling will now be described in more detail using a non-limiting example of implementing the present invention in this part. In this embodiment, the derivation of the PSG size to the UE may be performed according to the following pseudo-code:

Pseudocode 3 :

If timeBundleSize =n2, then PSG size= t2
If timeBundleSize =allSymbols then PSG size= all
Otherwise (default option), PSG size= t1

[0068] Parameter'PSG size'is the sizeP.S.G., measured in the number of DMRS symbols with the same precoder, the value of which is output, and the parameter'timeBundleSize’ is a configuration parameter that is communicated to the user via RRC signalling. The value ‘t2’ may correspond to two occurrences of DMRS (see item 1 onFig. 8), the value ‘all’ may correspond to the total number of DMRS occurrences over the entire TDRA of the PDSCH transmission (i.e., over the entire TDRA), the value ‘t1’ may correspond to one DMRS occurrence. If the time slot value is specified by the total number of OFDM symbols in the TDRA, rather than the number of DMRS occurrences in the TDRA, then the value ‘t2’ may correspond to the OFDM symbols in the TDRA corresponding to two DMRS signals (see the topFig. 9), the value 'all' may correspond to the total number of OFDM symbols in the TDRA, the value 't1' may correspond to OFDM symbols corresponding to one occurrence of the DMRS. However, neither the designations of the specific values (i.e. 't2', 'all', 't1') nor the specific values themselves should be interpreted as any limitations of the present invention, since both the designations of the specific values and the specific values themselves may be reassigned otherwise.

[0069] The logic for dynamically setting/deriving the channel estimation time interval value (i.e., the PSG size) via RRC and DCI signaling will now be described in more detail using a non-limiting example of implementing the present invention in this part. In this embodiment, the derivation of the PSG size may be performed according to the following pseudo-code:

Pseudocode 4 :

RRC signaling - timeBundleSizeSet1 ={n2, n2-all}
RRC signaling - timeBundleSizeSet2 = {n1, all}
DCI alarm
If the DCI field specifies bundleSizeSet1, then
If bundleSizeSet1=n2 then PSG size= t2
If bundleSizeSet1=n2-all then
If the number N_symbols > X=14, then
PSG size=t2 ;
otherwise,
PSG size=all .
If the DCI field specifies timeBundleSizeSet2
If timeBundleSizeSet2=n1, then
PSG size=t2
If bundleSizeSet2=all then
PSG size=all

[0070] The parameters 'timeBundleSizeSet1' and 'timeBundleSizeSet2' are signaled to the user by RRC and may take one of the values specified above in Pseudo-Code 4 in curly brackets {}. The value of the parameter 'N_symbols' in DCI specifies the number of OFDM symbols allocated for data transmission, i.e. the number of OFDM symbols in the TDRA. In an alternative implementation of the mentioned logic, the parameter 'N_symbols' may be replaced by the parameter 'N_DMRS_occasions' representing the number of DMRS occurrences in time resources allocated for data transmission (e.g. in the TDRA), and the parameter 'X' representing the threshold value of the number of OFDM symbols for PDSCH transmission may be correspondingly replaced by the parameter 'Y' representing the threshold number of DMRS occurrences. In this variant, 1 bit in DCI is used to dynamically switch between the parameters 'timeBundleSizeSet1' and 'timeBundleSizeSet2' , and the PSG size depends on the value of the parameter 'N_symbols' or 'N_DMRS_occasions'. Given the derived PSG value, the UE will perform channel estimation per PSG or per time domain unit that is smaller than one PSG (e.g. per part of OFDM symbols where DMRS appear in TDRA). Due to this, the UE will perform channel estimation in most cases according to changes in the time domain precoder used by the base station.

[0071] The value 't2' may correspond to two occurrences of DMRS, the value 'all' may correspond to the total number of occurrences of DMRS throughout the TDRA of the received PDSCH (i.e., throughout the entire TDRA), and the value 't1' may correspond to one occurrence of DMRS. If the value of the time interval is specified by the total number of OFDM symbols in the TDRA, rather than by the number of occurrences of DMRS in the TDRA, then the value 't2' may correspond to the OFDM symbols in the TDRA PDSCH corresponding to two occurrences of DMRS, the value 'all' may correspond to all OFDM symbols in the TDRA, and the value 't1' may correspond to the OFDM symbols in the TDRA PDSCH corresponding to one occurrence of DMRS. However, neither the designations of the specific values (i.e., 't2', 'all', 't1') and parameters ('N_symbols', 'N_DMRS_occasions', 'X', 'Y'), nor the specific values themselves, including the specific values of the mentioned parameters, should be interpreted as any limitations of the present invention, since both the designations of the specific values and the specific values themselves can be reassigned differently. In one embodiment, the base station scheduler can simultaneously perform both the configuration and indication to the UE: PRG (according to pseudo-code 1 or 2), and the configuration of the PSG (according to pseudo-code 3 or 4).

[0072] Thus, in one embodiment of the present invention, a certain implicitly indicated value of said parameter is derived based on the absence of an explicit indication of any value of said parameter in the DCI and on whether the time domain resources ‘N_symbols’ allocated for PDSCH transmission exceed a corresponding threshold value X, where the value of X is predefined in the specification of the communication standard (for example, but not limited to said value, X=14) or configured using higher layer signaling, wherein the time domain resources in this embodiment are the number of OFDM symbols.

[0073] In another embodiment of the present invention, a certain implicitly indicated value of said parameter is derived based on the absence of an explicit indication of any value of said parameter in the DCI and on the basis of whether the time domain resources ‘N_slots’ (this parameter is used in this embodiment instead of ‘N_symbols’) allocated for the PDSCH transmission exceed a corresponding threshold value X, where the value of X is predefined in the specification of the communication standard (for example, but not limited to said value, X=1) or configured by higher layer signaling, wherein the time domain resources in this embodiment are the number of slots allocated in the time domain for the PDSCH transmission.

[0074] In yet another embodiment of the present invention, a certain implicitly indicated value of said parameter is derived based on the absence of an explicit indication of any value of said parameter in the DCI and based on whether the number of occurrences of DMRS symbols ‘N_DMRS_occasions’ exceeds a threshold value Y, where the value Y is predefined in a communication standard specification or configured using higher layer signaling.

[0075] In an alternative embodiment, the value of the channel estimation time interval parameter is explicitly indicated by one or more bits in the signaled DCI. Tables 1 and 2 below provide examples of explicit signaling of a time domain configuration for channel estimation.

[0076] Table 1 : Non-limiting example of single-bit signaling in DCI time domain configurations for channel estimation.

Field in DCI Meaning 0 Unconstrained time domain channel estimation, i.e. the signaled value of the channel estimation time interval parameter in this case is the value ‘all’ (i.e. over the entire TTI or all TDRAs) 1 Time domain channel estimation with constraint. For example, the signaled value of the channel estimation time interval parameter in this case is the value 't2' (i.e. two occurrences of DMRS or 14 OFDM symbols in the above non-limiting example, as illustrated in Fig. 9 )

[0077] Table 2 : Non-limiting example of two-bit signaling in DCI time domain configurations for channel estimation.

Field in DCI Meaning 00 Unconstrained time domain channel estimation, i.e. the signaled value of the channel estimation time interval parameter in this case is the value ‘all’ (i.e. over the entire TTI or all TDRAs) 01 Time domain channel estimation with constraint. For example, the signaled value of the channel estimation time interval parameter in this case is the value 't2' (i.e. two occurrences of DMRS or 14 OFDM symbols in the above non-limiting example, as illustrated in Fig. 9 ) 10 Time domain channel estimation with constraint. For example, the signaled value of the channel estimation time interval parameter in this case is the value ‘t1’ (i.e. one occurrence of DMRS or 7 OFDM symbols in the non-constrained example above) 11 Time domain channel estimation with constraint. For example, the signaled value of the channel estimation time interval parameter in this case is a different value (for example, but not limited to, three occurrences of DMRS or 21 OFDM symbols)

[0078] The mappings between a specific bit value and a time domain configuration for channel estimation may be predefined in the communication standard specification and stored, for example, in the form of a look-up table, in the memory of the BS and/or UE. Bit values from a number of bits greater than 2 may be used to support a larger number of code points. In addition, the DCI may further explicitly indicate for the scheduled PDSCH transmission a type of precoder change with power reallocation (e.g., with a step of -3 dB, 0 dB, +3 dB) or a type of precoder change with full precoder recalculation. The type of precoder change may be indicated by the same bit value (examples of which are given in Tables 1 and 2 above, i.e., in the same DCI field) that specifies a specific value of the channel estimation time interval parameter and will further, in this case, determine a specific type of precoder change. Alternatively, the precoder change type may be indicated by a bit value in another DCI field (examples of which are given in Table 3 below), which will contain a bit value explicitly indicating only the precoder change type.

[0079] Table 3 : Non-limiting example of two-bit signaling in DCI of the precoder change type.

Field in DCI Meaning 00 type of precoder change with full recalculation of the precoder (recalculation of the precoder in this case can be carried out by any method known from the prior art, i.e. this should not be interpreted as a limitation of the present invention) 01 type of precoder change with power redistribution in +3dB steps 10 precoder change type with power redistribution in -3dB increments 11 type of precoder change with power redistribution in steps of +6 dB

[0080] The precoder change type with power reallocation may be signaled if during the length of the PDSCH transmission the number of active users changes; for example, UE#1 and UE#2 were transmitting, and from a certain OFDM symbol the signal transmission of UE#2 is not carried out. In this case, the precoder change occurs, but it is only due to the fact that the amount of power that is allocated for the MIMO layer transmission to the user UE#1 may be increased, in which case the base station 200 may signal via the DCI to UE#1 the precoder change type bit value '01' (according to Table 3 above) to dynamically reconfigure UE#1 to receive the PDSCH transmission with a higher power. In this case, UE#1 understands that a simple power reallocation occurs, and UE#1 in this case may not perform a full channel re-estimation, but perform an appropriate scaling of the channel estimate obtained in the previous channel estimation time interval.

[0081] The precoder change type with full precoder recalculation, signaled by the precoder change type bit value '00' (according to Table 3 above), causes the UE to perform a full channel re-estimation. In this case, the UE understands that a full channel re-estimation is necessary, and the UE in this case does not use the channel estimates that it obtained from the DMRS symbols of the previous channel estimation time interval, but performs a full update of the channel estimate on the corresponding DMRS symbols of the next arrived (i.e. current) channel estimation time interval.

[0082] After performing step S105, the method proceeds to performing step S110, in which the BS performs the scheduled PDSCH transmission(s) respectively to said one or more UEs. A non-limiting example of the structure of such a PDSCH transmission according to the present invention is illustrated inFig. 6. In the one shown onFig. 6In this situation, the BS first transmits a PDSCH transmission-related packet ‘A’ to UE#2 and simultaneously transmits a PDSCH transmission-related packet ‘B’ to UE#1. Packet ‘A’ is smaller in size than packet ‘B’, so it occupies less time domain resources than packet ‘B’, i.e. TDRA of packet ‘A’ < TDRA of packet ‘B’. Both transmissions shown were scheduled using DCI signaling with an explicit or implicit PSG size of two DMRS occurrences. This provides configurable constraints on the time domain channel estimation performed by DMRS users, allowing the BS to schedule the downlink in the time domain more flexibly for different users. In the case illustrated inFig. 6situations the BS has the opportunity to change (if the BS deems such a change necessary, for any reasons known to it) the precoder applied to the ‘B’ packet related to the PDSCH transmission on UE#1, and, optionally, to signal to the UE a specific type of precoder change (as described above in relation toTables 3), starting from the third occurrence of DMRS in the TDRA, while UE#1 will still be able to successfully demodulate the second half of packet ‘B’, since it will have recalculated the channel estimate on the third and, if necessary, fourth occurrence of DMRS, which was signalled to it earlier by an explicit or implicit indication of a PSG size equal to two occurrences of DMRS (as in the lower partFig. 9), and, optionally, the type of precoder change.

[0083] Fig. 8, 9 show non-limiting examples of different configurations of time domain channel estimation constraints signaled by base station 200 and taken into account by user equipment 400 when estimating a channel for demodulating a PDSCH transmission.

[0084] OnFig. 8above shows a PDSCH transmission in which there are four OFDM symbols in which DMRS occurs (i.e., four occurrences of DMRS) over which the UE 400 will perform channel estimation. The channel estimation is limited in the time domain in this case to two occurrences of DMRS, i.e., the UE will perform another channel estimation every two occurrences of DMRS in the time domain of the PDSCH transmission. A similar limitation in the channel estimation time interval is illustrated inFig. 9below.

[0085] OnFig. 8in the middle shows a PDSCH transmission which also has four DMRS occurrences. The channel estimation is limited in the time domain in this case to one DMRS occurrence, i.e. the UE will perform another channel estimation for each new DMRS occurrence in the time domain of the PDSCH transmission.

[0086] OnFig. 8down shows a PDSCH transmission that also has four DMRS occurrences. In this case, the time domain channel estimate is not limited (i.e., the value 'all' is signaled). In this case, the UE could theoretically use the channel estimate obtained from the FL DMRS to demodulate the PDSCH transmission over its entire time slot, since in this case the base station is not expected to change the precoder over the entire time slot of the PDSCH transmission.

[0087] OnFig. 9above shows a PDSCH transmission, which also has four occurrences of DMRS. The channel estimation is limited in the time domain in this case to 14 OFDM symbols, i.e. the UE will perform the next channel estimation on one or each new occurrence of DMRS in the next 14 OFDM symbols of the PDSCH transmission. In other words, the channel estimation time interval limitation can be specified not only by the number of DMRS occurrences, but also by the number of OFDM symbols. In yet another alternative, the channel estimation time interval limitation can be specified by the number of slots.

[0088] In a second aspect of the present invention, there is provided a base station 200, schematically shown in Fig. 10 , comprising a operatively connected transmitting and receiving unit 200.1, an antenna 200.2, a processor 200.3, and a readable medium 200.4 storing instructions executable by the processor, which, when executed by the processor, cause the base station to perform the communication method according to the first aspect of the present invention or according to any development of the first aspect of the present invention. The base station 200 can be implemented as, but not limited to, Node B, eNodeB, gNodeB.

[0089] The transmitting and receiving unit 200.1 and the antenna 200.2 may generally correspond to what is illustrated in Fig. 1 . The transmitting and receiving unit 200.1 and the antenna 200.2 may be adapted for operation in the upper part of the mid-frequency range (7-13 GHz). The transmitting and receiving unit 200.1 is designed to transmit and receive radio signals. It includes amplifiers, modulators, demodulators and other components necessary for converting signals into the radio frequency range and back. The transmitting and receiving unit 200.1 may support multi-channel data transmission using xMIMO technology, which allows for an increase in throughput. The transmitting and receiving unit 200.1 and the antenna 200.2 are responsible for digital and analog pre-coding/decoding of the signal. The transceiver unit 200.1 and the antenna 200.2 support operation in time division duplex mode and frequency division duplex mode, and comply with 3GPP specifications.

[0090] The antenna 200.2 provides for the emission and reception of radio signals transmitted and received by the transceiver unit 200.1. The antenna can be implemented as an adaptive antenna array, which allows the signal to be directed in the desired direction and minimizes interference. As an example, and not by way of limitation, the antenna 200.2 can have 1024 antenna elements and 128 digital ports. In another example, the antenna 200.2 can have 3072 antenna elements and 256 digital ports. In another non-limiting example, illustrated in Fig. 1 , the antenna 200.2 can have 4096 antenna elements and 256 digital ports.

[0091] The processor 200.3 is responsible for processing all signals from all components of the base station 200 and for performing any steps of the above-described communication method according to the first aspect of the present invention or according to any development of the first aspect of the present invention. In other words, the processor 200.3 is designed to perform operations necessary for controlling the operation of the base station 200 and executing executable instructions stored on the readable medium 200.4. The processor 200.3 in the BS 200 may be one or more of the following processors, but is not limited to the following types of processors: central processing units (CPUs), which are general-purpose processors that perform basic computing tasks in computers, servers and mobile devices; graphic processing units (GPUs), which are specialized processors for processing graphics and performing parallel computing; Coprocessors, which are auxiliary processors that work in tandem with the CPU to perform specific tasks such as, but not limited to, mathematical calculations or encryption; Digital Signal Processors (DSPs), which are processors optimized for real-time digital signal processing used in telecommunications and multimedia; Systems on a Chip (SoCs), which are integrated chips that include, but are not limited to, a CPU, GPU, DSP, and other components intended for mobile devices and embedded systems; Microcontrollers (MCUs), which are compact processors with integrated memory and peripherals used in embedded systems and the IoT; Field Programmable Gate Arrays (FPGAs), which are programmable processors that allow the user to configure their architecture to perform specialized tasks; Neural Network Processors (NPUs), which are specialized processors optimized for machine learning and artificial intelligence tasks; Machine vision processors (VPUs), which are specialized microprocessors that are a type of AI accelerator designed to hardware accelerate the operation of machine vision algorithms.

[0092] The processor 200.3 may be manufactured using any technology known in the art, such as, but not limited to, CMOS technology, silicon-on-insulator (SOI) technology, silicon-germanium (SiGe) technology, gallium nitride (GaN) technology, graphene transistor technology, FinFET technology, GAAFET technology, etc. The processor 200.3 may be multi-core and support parallel data processing, which increases the operating efficiency of the BS 200.

[0093] Readable medium 200.4 is a memory device that stores executable instructions for processor 200.3. These instructions include instructions for executing the communication method according to the first aspect of the present invention or any development of the first aspect of the present invention, as well as any other instructions for controlling data transmission, signal processing, network resource management and other functions. Readable medium 200.4 in BS 200 may be one or more of the following media, but is not limited to the following types of media: read-only memory (ROM), including, but not limited to, Mask ROM, PROM, EPROM, EEPROM; random access memory (RAM), including, but not limited to, DRAM, SDRAM, DDR SDRAM, MRAM, SRAM, PRAM, RRAM, FRAM, Nano-RAM, CBRAM nvSRAM; Flash memory, including but not limited to NAND flash memory, NOR flash memory, USB flash memory; Solid State Drives, including but not limited to SSD, including but not limited to SATA SSD, NVMe SSD; Optical Discs, including but not limited to CD-ROM, DVD, Blu-ray; Magnetic Storage, including but not limited to HDD, Magnetic Tape; Memory Cards, including but not limited to SD Cards, MicroSD.

[0094] The readable medium 200.4 may be manufactured using any technology known in the art, such as, but not limited to, CMOS technology, silicon-on-insulator (SOI) technology, FinFET technology, 3D NAND technology, etc.

[0095] It should be understood that not all components of the base station 200 are shown in Fig. 10. In particular, in addition to the components shown, the base station 200 may include other software and/or hardware components, such as, but not limited to, a power supply; a frequency-time resource scheduler, implemented in software, hardware, or software and hardware and included in the base station 200 or located outside the base station 200, but in communication with it; a cooling system; input-output interfaces; switches and interconnections; a modulator/demodulator; a multiplexer/demultiplexer; filters; power control circuits; an operating system (OS) and other software. The base station 200 may be referred to differently, such as a transmit-receive point (TRP).

[0096] In a third aspect of the present invention, there is provided a computer-readable medium storing executable instructions which, when executed by a device, cause the device to perform the communication method according to the first aspect of the present invention or any development of the first aspect of the present invention. The readable medium may correspond to the readable medium 200.4 described above, so its repeated description is omitted here. The instructions may be in any language and be presented in any form, provided that such language and form of instructions can be understood by the processor 200.3 and other equipment of the base station 200 and the instructions can be executed to perform the communication method according to the first aspect of the present invention or any development of the first aspect of the present invention, or to implement any other necessary functionality.

[0097] Further with links toFig. 5 And 7a description is given of a method for communication with a BS implemented by the user equipment. The communication method starts with step S300, in which an indication of a scheduled PDSCH transmission and an indication of a channel estimation time interval parameter value to be applied from possible (pre-configured) values of said parameter are received using DCI signaling. Technically, the reception of the transmission by the user equipment 400 can be carried out according to any method known from the prior art, at least with the help of the components illustrated inFig. 1 And Fig. 11. The DCI signaling and the output of the explicit and implicit channel estimation time interval parameter value can be performed in a similar manner to that described above with reference toTables 1-3 And Pseudocodes 3-4, therefore, a detailed description of these features of the present invention is not given here again.

[0098] After performing step S300, the UE 400 performs step S305, in which a channel estimate is calculated based on one or more occurrences of the DMRS within a time interval of the PDSCH transmission channel estimation indicated by the received value of said parameter, and then step S310, in which the UE 400 demodulates the PDSCH transmission based on the obtained channel estimate. The channel estimation by the DMRS and the transmission demodulation themselves may be performed by any methods known in the art, for example, but not limited to, any methods used in 5G NR for estimating the channel between the BS and the UE by the DMRS and demodulating the transmission.

[0099] Similar to the communication method implemented by the base station 200 described above with reference to Figs. 5 and 7 , Tables 1-3 and Pseudocodes 1-4 , the value of the channel estimation time interval parameter indicates a group of symbols within which the UE 400 will expect that the base station 200 will not change the precoder applied to the PDSCH transmission, where the symbols are OFDM symbols. The value of the channel estimation time interval parameter is specified by the total number of OFDM symbols contained in the channel estimation time interval or the number of OFDM symbols in which DMRS appears within the transmission time interval (TTI/TDRA) where the UE 400 will expect that the base station 200 will not change the precoder applied to the PDSCH transmission.

[00100] The possible values of said parameter are configured and output to the UE 400 via RRC signaling or MAC signaling. The possible values of said parameter are predefined in the specification of a communication standard and output to the UE 400 according to such predefinition. An indication to the UE 400 of the value of said parameter to be used by the BS 200 from among the possible values of the parameter may be received at the UE 400 as an explicit indication of a specific value of this parameter (e.g. a bit value in a specific DCI field) or represent an implicit logical deduction of this value based on indirect parameters (e.g. depending on the format of the DCI received at the UE 400, or depending on the above-described parameters ‘N_symbols’, ‘N_DMRS_occasions’, ‘X, ‘Y’, etc.).

[00101] Thus, in an embodiment of the method implemented by the UE 400, a certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI. In this case, the certain implicitly indicated value of said parameter may be a default value of this parameter or another predetermined value. The default value of said parameter may indicate to the UE that no change in the precoder used by the base station is expected during the entire PDSCH transmission time interval. In another embodiment, the certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI and/or depending on the format of the signaled DCI.

[00102] In another embodiment of the method, a certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI and/or based on whether the time domain resources allocated for the PDSCH transmission exceed a threshold value predefined in the specification of the communication standard or configurable by higher layer signaling, wherein the time domain resources are a number of OFDM symbols or a number of slots in the PDSCH transmission. In another embodiment, a certain implicitly indicated value of said parameter is output to the UE based on the absence of an explicit indication of any value of said parameter in the DCI and/or based on whether the number of occurrences of DMRS symbols exceeds a threshold value predefined in the specification of the communication standard or configurable by higher layer signaling. One or more bits are allocated in the DCI for explicitly indicating the value of said parameter (see Tables 1-2 above). In another embodiment, the method further comprises receiving an explicit indication for the scheduled PDSCH transmission using DCI signaling (see Table 3 above) of a precoder change type with power reallocation or a precoder change type with full precoder recalculation.

[00103] In a fifth aspect of the present invention, there is provided a user equipment 400, schematically shown in Fig. 11 , comprising a operatively connected transmitting and receiving unit 400.1, an antenna 400.2, a processor 400.3, and a readable medium 400.4 storing instructions executable by the processor, which, when executed by the processor, cause the user equipment to perform the communication method according to the fourth aspect of the present invention or according to any development of the fourth aspect of the present invention.

[00104] The user equipment 400 includes various electronic devices of the user, which are connected to telecommunication networks to provide access to various services and functions. Thus, the user equipment 400 may be, but is not limited to, a smartphone, a tablet, a smart watch, smart glasses, a fitness tracker, an augmented reality (AR) and/or virtual reality (VR) headset, a laptop, a desktop computer, a mini PC, a smart TV, a streaming media device, a medical device, a payment processing device, equipment installed on a vehicle, including an entertainment system, an Internet of Things (IoT) device, a smart sensor, a monitoring device, etc. The user equipment 400 may be referred to differently, such as a user terminal, a terminator, a user device, a mobile device, etc.

[00105] The description of possible implementations of the transmitting and receiving unit 200.1, the antenna 200.2, the processor 200.3, and the readable medium 200.4 contained in the BS 200 are essentially applicable, with obvious changes, respectively, as descriptions of possible implementations of the transmitting and receiving unit 400.1, the antenna 400.2, the processor 400.3, and the readable medium 400.4 contained in the UE 400. Therefore, such descriptions are not repeated here.

[00106] In a sixth aspect of the present invention, there is provided a computer-readable medium storing executable instructions which, when executed by a device, cause the device to perform the communication method according to the fourth aspect of the present invention or any development of the fourth aspect of the present invention. The description of possible implementations of the readable medium 200.4 is essentially applicable with obvious changes as a description of the readable medium according to the sixth aspect of the present invention. Therefore, its repeated description is not given here. The instructions can be composed in any language and be presented in any form, provided that such language and form of instructions can be understood by the processor 400.3 and other components of the user equipment 400 and the instructions can be executed to perform the communication method according to the fourth aspect of the present invention or any development of the fourth aspect of the present invention, or to implement any other necessary functionality.

[00107] Fig. 12 illustrates a schematic diagram of a communication system 500 according to a seventh aspect of the present invention. The communication system 500 comprises one BS 200, which is configured to serve user equipments 400 in three deployed cells 1, 2, 3. The BS may correspond to the BS 200 described in detail above with reference to Fig. 10 , and each user equipment 400 may correspond to a UE 400 described in detail above with reference to Fig. 11 , so a detailed description of the BS 200 and the UE 400 is not given here again. The communication system 500 may simultaneously support several active radio access technologies (RATs) from, for example, 4G LTE, 5G NR, 6G.

[00108] The specific details shown in Fig. 11 should not be considered as limitations of the present technology, since the system 500 may have a different architecture and be characterized/illustrated differently, for example, each cell of cell 1, cell 2, cell 3 may have its own BS 200, the number of UEs 400 in the cells may differ from that shown, cells 1, 2, 3 may represent one larger cell, the shape and space covered by the cells may differ from that shown, etc. The number of cells may be greater or less than 3.

[00109] Industrial applicability

[00110] The present invention can be applied in 3GPP compliant communication networks with BS and UE supporting xMIMO up to 256 digital ports/4096 antenna elements. The proposed frequency range for using the disclosed invention is the upper part of the mid-frequency band (7-13 GHz). The technical solutions according to the present disclosure can be implemented with analog/digital single-beam/multi-beam beamforming and TDD and/or FDD duplex modes. Other applications of the technology disclosed herein will be clear to those of ordinary skill in the art after reading this detailed description of the present application.

[00111] At least one aspect of the disclosed technical solution can be implemented by means of an AI model. The AI-related function can be performed by means of a permanent memory, random access memory, and processor(s) (CPU, GPU, NPU). The processor(s) controls the processing of input data in accordance with a predetermined operating rule or an artificial intelligence (AI) model stored in the permanent memory and random access memory. The predetermined operating rule or an artificial intelligence model is provided by means of training. Here, “providing by means of training” means that by applying a learning algorithm to a set of training data, a predetermined operating rule or an AI model with a desired characteristic is created. As a non-limiting example, an AI model may be created that predicts, in real time for subsequent explicit signaling and dynamic handover to the UE, time domain channel estimation constraints (i.e., channel estimation time interval parameter values) and/or precoder change type based on parameters associated with the current state of the base station 200 and/or user equipment 400 and/or communication system 500. Such parameters may be, but are not limited to, the current number of transmitting/receiving users in the communication system, channel state information (CSI) transmitted from users, etc. In this case, a set of optimal time domain channel estimation constraints and/or precoder change types in pair with parameters associated with different states of the base station 200 and/or user equipment 400 and/or communication system 500 may be used as training data for training such an AI model. The training may be performed within the device itself that uses the AI model according to the embodiment (i.e., online), and/or may be implemented via a separate server/system (i.e., offline).

[00112] The AI model may be a decision tree-based algorithm or may consist of a plurality of neural network layers. Each layer has a plurality of weight values and performs the layer operation by calculating based on the result of the calculation in the previous layer and applying a plurality of weight coefficients and other parameter values. Examples of decision tree-based algorithms include random forest, tree ensembles, etc., and examples of neural networks include, but are not limited to, a convolutional neural network (CNN), a deep neural network (DNN), a recurrent neural network (RNN), a restricted Boltzmann machine (RBM), a deep belief network (DBN), a bidirectional network, a recurrent deep neural network (BRDNN), a generative adversarial network (GAN), networks based on a transformer architecture, a deep Q-network, large language models, and so on.

[00113] A learning algorithm is a method for learning a predetermined target device or target function based on a corresponding set of training data, which causes, enables, controls, or provides output data of the target device or target function. Examples of learning algorithms include, but are not limited to, supervised learning, unsupervised learning, semi-supervised learning, or reinforcement learning, and so on.

[00114] It may be understood by one skilled in the art that the various illustrative logical blocks (functional blocks or modules) and steps (operations) used in embodiments of the disclosed technical solution may be implemented by electronic hardware, computer software, or a combination of both. Whether the functions are implemented by hardware or software depends on the specific applications and design requirements of the overall system. One skilled in the art may use various methods for implementing the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments disclosed in this application.

[00115] It should also be noted that the order of the steps of any disclosed method is not strict, since some one or more steps may be rearranged in the actual order of execution and/or combined with another one or more steps, and/or broken down into a larger number of sub-steps.

[00116] Throughout this application, reference to an element in the singular does not exclude the presence of a plurality of such elements in the actual practice of the invention, and conversely, reference to an element in the plural does not exclude the presence of only one such element in the actual practice of the invention. Any specific value or range of values recited above should not be interpreted in a limiting sense, but instead such specific value or range of values should be considered to represent the midpoint of a specified larger range, up to about 50% or more% on either side of the specifically recited value or the boundaries of a specifically recited smaller range.

[00117] Although this disclosure has been shown and described with reference to specific embodiments and examples thereof, those skilled in the art will understand that various changes in form and content may be made without departing from the spirit and scope of this disclosure as defined by the appended claims and their equivalents. In other words, the above detailed description is based on specific examples and possible implementations of the present invention, but should not be interpreted to mean that only the expressly disclosed implementations are feasible. It is intended that any change or replacement that can be made in this disclosure by an ordinary person without creative and/or technical input should fall within the scope of protection (including equivalents) provided by the following claims.

Claims (45)

1. A method implemented by a base station (BS) for communicating with one or more user equipment (UE), comprising: setting (S100) possible values of a channel estimation time interval parameter within which no change of a precoder applied to the transmission of a physical downlink shared channel (PDSCH) is expected, wherein said channel estimation is performed by one or more UEs using one or more demodulation reference signals (DMRS) for receiving the PDSCH; using downlink control information (DCI) signaling, transmitting (S105) to one or more UEs an indication of a scheduled PDSCH transmission and an indication of a value of said parameter to be applied from among the possible values of the parameter; and performing (S110) a scheduled PDSCH transmission to one or more UEs. 2. The method of claim 1, wherein the value of the channel estimation time interval parameter indicates a group of orthogonal frequency division multiplexing (OFDM) symbols within which the UE will expect that the base station will not change the precoder used to transmit the PDSCH. 3. The method of claim 1, wherein the value of the channel estimation time interval parameter is defined by the total number of OFDM symbols contained in the channel estimation time interval, or by the number of OFDM symbols in which DMRS occurs, within a transmission time interval (TTI) or time domain resource allocation (TDRA) where the UE will expect no change by the base station of the precoder applied to the PDSCH transmission. 4. The method according to claim 1, wherein the setting (S100) of possible values of the channel estimation time interval parameter is configuring these values using radio resource control (RRC) signaling or medium access control (MAC) signaling. 5. The method according to claim 1, wherein the assignment (S100) of possible values of the channel estimation time interval parameter is a predetermination of these values in the specification of the communication standard. 6. The method according to claim 1, wherein the indication of the value of said parameter to be applied from among the possible values of the parameter is an explicit indication or an implicit indication of the value of said parameter. 7. The method according to claim 6, wherein a certain implicitly indicated value of said parameter is derived from the absence in the DCI of an explicit indication of any value of said parameter. 8. The method according to claim 7, wherein the defined implicitly indicated value of said parameter is the default value of this parameter or another predetermined value. 9. The method according to claim 8, wherein the value of said default parameter indicates to the UE that no change in the precoder used by the base station is expected over the entire PDSCH transmission time interval. 10. The method according to claim 6, wherein the determined implicitly indicated value of said parameter is derived based on the absence in the DCI of an explicit indication of any value of said parameter and/or depending on the format of the signaled DCI. 11. The method according to claim 6, wherein the determined implicitly indicated value of said parameter is derived based on the absence in the DCI of an explicit indication of any value of said parameter and based on whether the time domain resources allocated for PDSCH transmission exceed a threshold value predefined in the specification of the communication standard or configurable using higher layer signaling, where the time domain resources are the number of OFDM symbols or the number of slots in the PDSCH transmission. 12. The method according to claim 6, wherein the determined implicitly indicated value of said parameter is derived based on the absence in the DCI of an explicit indication of any value of said parameter and based on whether the number of occurrences of DMRS symbols exceeds a threshold value predefined in a communication standard specification or configurable using higher layer signaling. 13. The method according to claim 6, wherein one or more bits are allocated in the DCI to explicitly indicate the value of said parameter. 14. The method of claim 1, further comprising transmitting an explicit indication for the scheduled PDSCH transmission using DCI signaling of a precoder change type with power reallocation or a precoder change type with full precoder recalculation. 15. The method according to claim 1, further comprising changing the precoder of the PDSCH transmission when performing this PDSCH transmission to one or more UEs in the next upcoming channel estimation time interval within this PDSCH transmission, indicated by the value of the channel estimation time interval parameter, where the value of the channel estimation time interval parameter specifies the regularity of the occurrence of the channel estimation time interval within the PDSCH transmission. 16. A base station (200) comprising a functionally connected transmitting and receiving unit (200.1), an antenna (200.2), a processor (200.3) and a readable medium (200.4) storing instructions executable by the processor which, when executed by the processor, cause the base station to perform the communication method according to any one of paragraphs 1-15. 17. A computer-readable medium storing executable instructions that, when executed by a device, cause the device to perform the communication method of any one of paragraphs 1-15. 18. A method implemented by user equipment (UE) for communicating with a base station (BS), comprising: receiving (S300), using downlink control information (DCI) signaling, an indication of a scheduled transmission of a physical downlink shared channel (PDSCH) and an indication of a value of a channel estimation time interval parameter to be applied, within which no change of a precoder applied to the PDSCH transmission is expected, from among possible values of said parameter; performing (S305) channel estimation using one or more occurrences of a demodulation reference signal (DMRS) within a PDSCH transmission channel estimation time interval indicated by a received value of said parameter; and demodulation (S310) of the PDSCH transmission based on the obtained channel estimate. 19. The method of claim 18, wherein the value of the channel estimation time interval parameter indicates a group of symbols within which the UE will expect no change by the base station of the precoder applied to the PDSCH transmission, wherein the symbols are orthogonal frequency division multiplexing (OFDM) symbols. 20. The method of claim 18, wherein the value of the channel estimation time interval parameter is defined by the total number of OFDM symbols contained in the channel estimation time interval, or the number of OFDM symbols in which DMRS occurs, within a transmission time interval (TTI) or time domain resource allocation (TDRA) where the UE will expect no change by the base station of the precoder applied to the PDSCH transmission. 21. The method according to claim 18, wherein the possible values of said parameter are configured using radio resource control (RRC) signaling or medium access control (MAC) signaling. 22. The method according to claim 18, wherein the possible values of said parameter are predetermined in the specification of the communication standard. 23. The method according to claim 18, wherein the indication of the value of said parameter to be applied from among the possible values of the parameter is an explicit indication or an implicit indication of the value of said parameter. 24. The method according to claim 23, wherein a certain implicitly indicated value of said parameter is output to the UE based on the absence in the DCI of an explicit indication of any value of said parameter. 25. The method according to claim 24, wherein the defined implicitly indicated value of said parameter is the default value of this parameter or another predetermined value. 26. The method according to claim 25, wherein the value of said default parameter indicates to the UE that no change in the precoder used by the base station is expected over the entire PDSCH transmission time interval. 27. The method according to claim 23, wherein a certain implicitly indicated value of said parameter is output to the UE based on the absence in the DCI of an explicit indication of any value of said parameter and/or depending on the format of the signaled DCI. 28. The method according to claim 23, wherein the determined implicitly indicated value of said parameter is derived by the UE based on the absence in the DCI of an explicit indication of any value of said parameter and based on whether the time domain resources allocated for PDSCH transmission exceed a threshold value predefined in the specification of the communication standard or configurable using higher layer signaling, where the time domain resources are the number of OFDM symbols or the number of slots in the PDSCH transmission. 29. The method according to claim 23, wherein the determined implicitly indicated value of said parameter is derived by the UE based on the absence in the DCI of an explicit indication of any value of said parameter and based on whether the number of occurrences of DMRS symbols exceeds a threshold value predefined in the specification of the communication standard or configurable using higher layer signaling. 30. The method according to claim 23, wherein one or more bits are allocated in the DCI to explicitly indicate the value of said parameter. 31. The method of claim 18, further comprising receiving an explicit indication for the scheduled PDSCH transmission using DCI signaling of a precoder change type with power reallocation or a precoder change type with full precoder recalculation. 32. The method of claim 18, further comprising, when the received PDSCH transmission extends beyond the channel estimation time interval specified by the base station, recalculating the channel estimate by the user equipment based on one or more DMRSs occurring in the subsequent channel estimation time interval, and applying the recalculated channel estimate to demodulate the PDSCH transmission received in the subsequent channel estimation time interval, where the value of the channel estimation time interval parameter specifies the regularity of the occurrence of the channel estimation time interval within the PDSCH transmission. 33. User equipment (400) comprising a functionally connected transmitting and receiving unit (400.1), an antenna (400.2), a processor (400.3) and a readable medium (400.4) storing instructions executable by the processor which, when executed by the processor, cause the user equipment to perform the communication method according to any of paragraphs 18-32. 34. A computer-readable medium storing executable instructions that, when executed by a device, cause the device to perform the communication method of any one of paragraphs 18-32. 35. A communication system (500) comprising at least one base station (200) according to claim 16 and at least one user equipment (400) according to claim 33, wherein said at least one base station and said at least one user equipment communicate with each other.