Configuration of downlink multi-user multiple-input multiple-output reception for co-scheduled user equipments

Abstract

The present disclosure relates to a technique for enhancing Downlink (DL) Multi-User Multiple-Input Multiple-Output (MU-MIMO) reception for co-scheduled UEs by performing inter-user inference cancellation based on properly generated Downlink Control Information (DCI) More specifically, the DCI is generated and transmitted by a network node to a target UE in response to UE-related information that indicates that the target UE is configured for the DL MU-MIMO reception together with other co-scheduled UEs. The DCI indicates at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception, and further indicates a modulation scheme and / or a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs. By using the DCI, the target UE may efficiently implement the DL MU-MIMO reception together with the co- scheduled UEs.

Description

[0001] CONFIGURATION OF DOWNLINK MULTI-USER MULTIPLE-INPUT MULTIPLE-OUTPUT RECEPTION FOR CO-SCHEDULED USER EQUIPMENTS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to the field of wireless communications. In particular, the present disclosure relates to techniques for configuring Downlink (DL) Multiuser Multiple-Input Multiple-Output (MU-MIMO) reception for co-scheduled User Equipments (UEs) in a wireless communication network.

[0004] BACKGROUND

[0005] MIMO has been widely studied over the past two decades because it can provide spatial multiplexing gains, diversity gains, and interference reduction capabilities. Initially, Single- User MIMO (SU-MIMO) was mainly studied to improve system performance. In recent years, for further improvement, the focus has shifted to more practical Multi-User MIMO (MU- MIMO) systems, where typically a base station (BS) or gNB simultaneously serves multiple UEs.

[0006] Compared to the SU-MIMO scenario, the MU-MIMO scenario involves serving more than one UE by using the same Resource Blocks (RBs). However, this does not mean that the more UEs on the same RBs, the better. Due to spatial correlation and power limitation, if all UEs are scheduled in the same group, they may have a low Signal-to-lnterference-plus-Noise Ratio (SINR). To solve the scheduling problem and reduce computational complexity, UE grouping can be used, according to which all UEs are divided (e.g., based on their spatial correlation) into different groups to improve overall performance. After grouping, the groups of UEs are served by using different RBs. In this way, the number of UEs served by the same RBs can be reduced and UE performance can be improved.

[0007] In the MU-MIMO scenario, since a single BS or gNB communicates with many UEs simultaneously using the same RBs, the signal received by each UE suffers from interference caused by the signals intended for other UEs served by the same BS or gNB. This interference is known as inter-user interference. To cancel or mitigate the inter-user interference, different interference cancellation schemes are applied at a receiver included in each UE. For proper inter-user interference cancellation, it is required for the receiver to know essential information about the interfering MIMO layers associated with all co-scheduled UEs (i.e., UEs from one or more groups). It has been proposed to provide such information via assistant Downlink Control Information (DCI)-based network signaling. However, in this case, one other problem arises, which is related to an agreed signaling scheme in terms of network scheduling flexibility. More specifically, such a signaling scheme will impose a constraint for co-scheduled UEs to use a certain modulation order, such as Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (16-QAM), etc. Moreover, there is currently no signaling which would let a target UE know about the number of co-scheduled UEs (i.e., groups of UEs). All of this leads to reduced network scheduling flexibility.

[0008] SUMMARY

[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure.

[0010] It is an objective of the present disclosure to provide a technical solution that enhances Downlink (DL) MU-MIMO reception for co-scheduled UEs by performing the inter-user inference cancellation based on properly generated DCL

[0011] The objective above is achieved by the features of the independent claims in the appended claims. Further embodiments and examples are apparent from the dependent claims, the detailed description, and the accompanying drawings.

[0012] According to a first aspect, a UE in a wireless communication network is provided. The UE comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least as follows. At first, the UE transmits UE-related information to a network node in the wireless communication network. The UE-related information indicates that the UE is able to support DL MU-MIMO reception. Next, the UE receives DCI from the network node, which indicates at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs. After that, the UE configures the DL MU -Ml MO reception based on the received DCI. By using the DCI, the UE may efficiently (in terms of inter-user inference cancellation) implement the DL MU-MIMO reception together with other co-scheduled UEs.

[0013] In one example embodiment of the first aspect, the UE-related information further indicates at least one of: a maximum number of groups of co-scheduled UEs at which the UE is able to support the DL MU-MIMO reception; a total number of MIMO layers supported by the UE for the DL MU-MIMO reception; and a maximum modulation index supported by the UE. By using this additional information from the UE, the network node may generate more suitable DCI for the UE.

[0014] In one example embodiment of the first aspect, the DCI further indicates a DMRS initialization value for the UE that is the same as or different from the DMRS initialization value for each of the at least one group of co-scheduled UEs. By doing so, the network node may configure the UE to use the same or different DMRS initialization value compared to the rest co-scheduled UEs, which may result in better network scheduling flexibility.

[0015] In one example embodiment of the first aspect, the UE-related information further indicates an ability of the UE to support more than one DMRS sequence, and the DCI further indicates a DMRS sequence for each of the UE and the at least one group of co-scheduled UEs. This additional information may also allow the network node to generate more suitable DCI for the UE.

[0016] In one example embodiment of the first aspect, the DMRS sequence is the same or different for each of the UE and the at least one group of co-scheduled UEs. This may again result in better network scheduling flexibility.

[0017] In one example embodiment of the first aspect, the DCI further indicates a modulation scheme for the UE that is the same as or different from the modulation scheme for each of the at least one group of co-scheduled UEs. This may additionally improve network scheduling flexibility. According to a second aspect, a network node in a wireless communication network is provided. The network node comprises at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the network node to perform at least as follows. At first, the network node receives UE-related information from a UE in the wireless communication network. The UE-related information indicates that the UE is able to support DL MU -Ml MO reception. Next, the network node uses the UE-related information to generate DCI for the UE. More specifically, the DCI indicates at least one group of co-scheduled UEs served by the network node for the DL MU- MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a DMRS initialization value for each of the at least one group of co-scheduled UEs. After that, the network node transmits the DCI to the UE. By using the DCI, the network node may configure the UE to implement the efficient (in terms of inter-user inference cancellation) DL MU-MIMO reception together with other co-scheduled UEs.

[0018] In one example embodiment of the second aspect, the UE-related information further indicates at least one of: a maximum number of groups of co-scheduled UEs at which the UE is able to support the DL MU-MIMO reception; a total number of MIMO layers supported by the UE for the DL MU-MIMO reception; and a maximum modulation index supported by the UE. By using this additional information from the UE, the network node may generate more suitable DCI for the UE.

[0019] In one example embodiment of the second aspect, the DCI further indicates a DMRS initialization value for the UE that is the same as or different from the DMRS initialization value for each of the at least one group of co-scheduled UEs. By doing so, the network node may configure the UE to use the same or different DMRS initialization value compared to the rest co-scheduled UEs, which may result in better network scheduling flexibility.

[0020] In one example embodiment of the second aspect, the UE-related information further indicates an ability of the UE to support more than one DMRS sequence, and the DCI further indicates a DMRS sequence for each of the UE and the at least one group of co-scheduled UEs. This additional information may also allow the network node to generate more suitable DCI for the UE. In one example embodiment of the second aspect, the DMRS sequence is the same or different for each of the UE and the at least one group of co-scheduled UEs. This may again result in better network scheduling flexibility.

[0021] In one example embodiment of the second aspect, the DCI further indicates a modulation scheme for the UE that is the same as or different from the modulation scheme for each of the at least one group of co-scheduled UEs. This may additionally improve network scheduling flexibility.

[0022] According to a third aspect, a method for operating a UE in a wireless communication network is provided. The method starts with the step of transmitting UE-related information to a network node in the wireless communication network. The UE-related information indicates that the UE is able to support DL MU -Ml MO reception. Next, the method proceeds to the step of receiving DCI from the network node, which indicates at least one group of coscheduled UEs served by the network node for the DL MU-MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a DMRS initialization value for each of the at least one group of coscheduled UEs. After that, the method goes on to the step of configuring the DL MU-MIMO reception based on the DCI. By using the DCI, the UE may efficiently (in terms of inter-user inference cancellation) implement the DL MU-MIMO reception together with other coscheduled UEs.

[0023] According to a fourth aspect, a method for operating a network node in a wireless communication network is provided. The method starts with the step of receiving UE-related information from a UE in the wireless communication network. The UE-related information indicates that the UE supports DL MU-MIMO reception. Then, the method proceeds to the step of using the UE-related information to generates DCI for the UE. The DCI indicates at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a DMRS initialization value for each of the at least one group of co-scheduled UEs. After that, the method goes on to the step of transmitting the DCI to the UE. By using the DCI, the network node may configure the UE to implement the efficient (in terms of inter-user inference cancellation) DL MU-MIMO reception together with other co-scheduled UEs. According to a fifth aspect, a computer program product is provided. The computer program product comprises a computer-readable storage medium that stores a computer code. Being executed by at least one processor, the computer code causes the at least one processor to perform the method according to the third aspect. By using such a computer program product, it is possible to simplify the implementation of the method according to the third aspect in any UE, like the UE according to the first aspect.

[0024] According to a sixth aspect, a computer program product is provided. The computer program product comprises a computer-readable storage medium that stores a computer code. Being executed by at least one processor, the computer code causes the at least one processor to perform the method according to the fourth aspect. By using such a computer program product, it is possible to simplify the implementation of the method according to the fourth aspect in any network node, like the network node according to the second aspect.

[0025] According to a seventh aspect, a UE in a wireless communication network is provided. The UE comprises a means for transmitting UE-related information to a network node in the wireless communication network. The UE-related information indicates that the UE is able to support DL MU -Ml MO reception. The UE further comprises a means for receiving DCI from the network node, which indicates at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a DMRS initialization value for each of the at least one group of co-scheduled UEs. The UE further comprises a means for configuring the DL MU-MIMO reception based on the received DCI. By using the DCI, the UE may efficiently (in terms of inter-user inference cancellation) implement the DL MU-MIMO reception together with other co-scheduled UEs.

[0026] According to an eighth aspect, a network node in a wireless communication network is provided. The network node comprises a means for receiving UE-related information from a UE in the wireless communication network. The UE-related information indicates that the UE is able to support DL MU-MIMO reception. The network node further comprises a means forgenerating DCI for the UE based on the UE-related information. More specifically, the DCI indicates at least one group of co-scheduled UEs served by the network node for the DL MU- MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a DMRS initialization value for each of the at least one group of co-scheduled UEs. The network node further comprises a means for transmitting the DCI to the UE. By using the DCI, the network node may configure the UE to implement the efficient (in terms of inter-user inference cancellation) DL MU -Ml MO reception together with other co-scheduled UEs.

[0027] Other features and advantages of the present disclosure will be apparent upon reading the following detailed description and reviewing the accompanying drawings.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present disclosure is explained below with reference to the accompanying drawings in which:

[0030] FIG. 1 shows a block diagram of a UE in accordance with one example embodiment;

[0031] FIG. 2 shows a flowchart of a method for operating the UE of FIG. 1 in accordance with one example embodiment;

[0032] FIG. 3 shows a block diagram of a network node in accordance with one example embodiment;

[0033] FIG. 4 shows a flowchart of a method for operating the network node of FIG. 3 in accordance with one example embodiment;

[0034] FIG. 5 shows a block diagram of a wireless communication system in accordance with one example embodiment, in which DCI signaling is used to implement DL MU-MIMO reception in case of two groups of co-scheduled UEs; and

[0035] FIG. 6 shows a block diagram of a wireless communication system in accordance with another example embodiment, in which DCI signaling is used to implement DL MU-MIMO reception in case of three groups of co-scheduled UEs.

[0036] DETAILED DESCRIPTION

[0037] Various embodiments of the present disclosure are further described in more detail with reference to the accompanying drawings. However, the present disclosure can be embodied in many other forms and should not be construed as limited to any certain structure or function discussed in the following description. In contrast, these embodiments are provided to make the description of the present disclosure detailed and complete.

[0038] According to the detailed description, it will be apparent to the ones skilled in the art that the scope of the present disclosure encompasses any embodiment thereof, which is disclosed herein, irrespective of whether this embodiment is implemented independently or in concert with any other embodiment of the present disclosure. For example, the apparatuses and methods disclosed herein can be implemented in practice by using any numbers of the embodiments provided herein. Furthermore, it should be understood that any embodiment of the present disclosure can be implemented using one or more of the elements presented in the appended claims.

[0039] Unless otherwise stated, any embodiment recited herein as "example embodiment" should not be construed as preferable or having an advantage over other embodiments.

[0040] According to the example embodiments disclosed herein, a User Equipment (UE) may refer to an electronic computing device that is configured to perform wireless communications. The UE may be implemented as a mobile station, a mobile terminal, a mobile subscriber unit, a mobile phone, a cellular phone, a smart phone, a cordless phone, a personal digital assistant (PDA), a wireless communication device, a desktop computer, a laptop computer, a tablet computer, a gaming device, a netbook, a smartbook, an ultrabook, a medical mobile device or equipment, a biometric sensor, a wearable device (e.g., a smart watch, smart glasses, a smart wrist band, etc.), an entertainment device (e.g., an audio player, a video player, etc.), a vehicular component or sensor (e.g., a driver-assistance system), a smart meter / sensor, an unmanned vehicle (e.g., an industrial robot, a quadcopter, etc.) and its component (e.g., a self-driving car computer), industrial manufacturing equipment, a global positioning system (GPS) device, an Internet-of-Things (loT) device, an Industrial loT (I loT) device, a machine-type communication (MTC) device, a group of Massive loT (MIoT) or Massive MTC (mMTC) devices / sensors, or any other suitable mobile device configured to support wireless communications. In some embodiments, the UE may refer to at least two collocated and inter-connected UEs thus defined. As used in the example embodiments disclosed herein, a network node may refer to a fixed point of communication or communication node for a UE in a particular wireless communication network. More specifically, the network node may be used to connect the UE to a Data Network (DN) through a Core Network (CN) and may be referred to as a base transceiver station (BTS) in terms of the 2G communication technology, a NodeB in terms of the 3G communication technology, an evolved NodeB (eNodeB or eNB) in terms of the 4G communication technology, and a gNB in terms of the 5G New Radio (NR) communication technology. The network node may serve different cells, such as a macrocell, a microcell, a picocell, a femtocell, and / or other types of cells. The macrocell may cover a relatively large geographic area (e.g., at least several kilometers in radius). The microcell may cover a geographic area less than two kilometers in radius, for example. The picocell may cover a relatively small geographic area, such, for example, as offices, shopping malls, train stations, stock exchanges, etc. The femtocell may cover an even smaller geographic area (e.g., a home). Correspondingly, the network node serving the macrocell may be referred to as a macro node, the network node serving the microcell may be referred to as a micro node, and so on.

[0041] According to the example embodiments disclosed herein, a wireless communication network, in which a UE and a network node communicate with each other, may refer to a cellular or mobile network, a Wireless Local Area Network (WLAN), a Wireless Personal Area Networks (WPAN), a Wireless Wide Area Network (WWAN), a satellite communication (SATCOM) system, or any other type of wireless communication networks. Each of these types of wireless communication networks supports wireless communications according to one or more communication protocol standards. For example, the cellular network may operate according to the Global System for Mobile Communications (GSM) standard, the Code-Division Multiple Access (CDMA) standard, the Wide-Band Code-Division Multiple Access (WCDM) standard, the Time-Division Multiple Access (TDMA) standard, or any other communication protocol standard, the WLAN may operate according to one or more versions of the IEEE 802.11 standards, the WPAN may operate according to the Infrared Data Association (IrDA), Wireless USB, Bluetooth, or ZigBee standard, and the WWAN may operate according to the Worldwide Interoperability for Microwave Access (WiMAX) standard. Data transmission between UEs, between network nodes, or between UEs and network nodes may be performed using a MIMO technology. The MIMO technology involves employing multiple transmit antennas at a transmitting entity (e.g., a UE or network node) and multiple receive antennas at a receiving entity (e.g., another UE or network node) for data transmission. A MIMO channel formed by the transmit antennas and receive antennas may be decomposed into spatial layers (also known as MIMO layers). The MIMO layers may be used to transmit data in parallel to achieve higher throughput and / or redundantly to achieve greater reliability. The MIMO layers may experience various deleterious channel conditions (e.g., fading, multipath, interference effects, etc.), for which reason they may achieve different Signal-to-Noise Ratios (SNRs) or Signal-to-lnterference-and-Noise Ratios (SINRs). The SNR or SINR of each MIMO layer determines its transmission capacity, which is typically quantified by a particular data rate that may be reliably transmitted on the MIMO layer. For a time-varying wireless channel, the channel conditions change over time and the SNR or SINR of each MIMO layer also changes over time. The different SNRs or SINRs of the MIMO layers plus the time-varying nature of the SNR or SINR for each MIMO layer make it challenging to efficiently transmit data in a MIMO system.

[0042] A Single-User MIMO (SU-MIMO) technology focuses all the streams of antenna arrays on a single UE. The SU-MIMO technology allows data to be transferred simultaneously through more than one data streams to one UE. The advantage of the SU-MIMO technology is that there are no interferences and radio channel estimation is easier to achieve. However, its downside is that it can only serve one UE at a time and if a transmission matrix is uncorrelated, MIMO cannot be used.

[0043] A Multi-User MIMO (MU-MIMO) utilizes more than one antenna to create several connections simultaneously to different UEs to improve network capacity. The MU-MIMO technology, in other words, is used for the environments where many users are trying to connect to a wireless communication network at the same time. It allows multiple users to have access to a network node at the same time. Thus, the MU-MIMO technology involves using multiple data streams to different co-scheduled UEs simultaneously. The advantage of the MU-MIMO technology is that the number of antennas in the co-scheduled UEs does not have to be increased, but the co-scheduled UEs should be able to send channel estimation to the serving network node and the serving network node needs to find optimal UEs for such MU -Ml MO communications, which can turn out to be challenging. Moreover, the problem of the so-called inter-user interference should be resolved to provide efficient DL MU-MIMO reception at the co-scheduled UEs.

[0044] The example embodiments disclosed herein provide a technical solution that enhances Downlink (DL) MU-MIMO reception for co-scheduled UEs by performing the inter-user inference cancellation based on properly generated Downlink Control Information (DCI). More specifically, the DCI is generated and transmitted by a network node to a target UE in response to UE-related information that indicates that the target UE is configured for the DL MU-MIMO reception together with other co-scheduled UEs. The DCI, in turn, indicates at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception and further indicates at least one of a modulation scheme applied for each of the at least one group of co-scheduled UEs and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs. By using the DCI, the target UE may efficiently (in terms of inter-user inference cancellation) implement the DL MU-MIMO reception together with the co-scheduled UEs.

[0045] FIG. 1 shows a block diagram of a UE 100 in accordance with one example embodiment. The UE 100 is intended to communicate with a network node and / or one or more other UEs in any of the above-described communication networks. As shown in FIG. 1, the UE 100 comprises a processor 102 and a memory 104. The memory 104 stores processor-executable instructions 206 which, when executed by the processor 102, cause the processor 102 to perform the aspects of the present disclosure, as will be described below in more detail. It should be noted that the number, arrangement, and interconnection of the constructive elements constituting the UE 100, which are shown in FIG. 1, are not intended to be any limitation of the present disclosure, but merely used to provide a general idea of how the constructive elements may be implemented within the UE 100. For example, the processor 102 may be replaced with several processors, as well as the memory 104 may be replaced with several removable and / or fixed storage devices, depending on particular applications. Furthermore, it is assumed that the processor 102 is capable of performing different operations required to perform data reception and transmission, such, for example, as signal modulation / demodulation, encoding / decoding, etc. In another embodiment, the UE 100 may further comprise an individual transceiving unit comprising an antenna array and controlled by the processor 102.

[0046] The processor 102 may be implemented as a CPU, general-purpose processor, singlepurpose processor, microcontroller, microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), digital signal processor (DSP), complex programmable logic device, etc. It should be also noted that the processor 102 may be implemented as any combination of one or more of the aforesaid. As an example, the processor 102 may be a combination of two or more microprocessors.

[0047] The memory 104 may be implemented as a classical nonvolatile or volatile memory used in the modern electronic computing machines. As an example, the nonvolatile memory may include Read-Only Memory (ROM), ferroelectric Random-Access Memory (RAM), Programmable ROM (PROM), Electrically Erasable PROM (EEPROM), solid state drive (SSD), flash memory, magnetic disk storage (such as hard drives and magnetic tapes), optical disc storage (such as CD, DVD and Blu-ray discs), etc. As for the volatile memory, examples thereof include Dynamic RAM, Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDR SDRAM), Static RAM, etc.

[0048] The processor-executable instructions 106 stored in the memory 104 may be configured as a computer-executable program code which causes the processor 102 to perform the aspects of the present disclosure. The computer-executable program code for carrying out operations or steps for the aspects of the present disclosure may be written in any combination of one or more programming languages, such as Java, C++, or the like. In some examples, the computer-executable program code may be in the form of a high-level language or in a pre-compiled form and be generated by an interpreter (also pre-stored in the memory 104) on the fly.

[0049] FIG. 2 shows a flowchart of a method 200 for operating the UE 100 in accordance with one example embodiment. The method 200 starts with a step S202, in which the processor 102 transmits (e.g., by using the antenna array of the transceiving unit) UE-related information to a network node (e.g., BTS or gNB) in the wireless communication network. The UE-related information indicates that the UE is configured to support DL MU-MIMO reception. For example, such an indication may be in the form of a certain bit value or flag set transmitted via dedicated signaling (e.g., Radio Resource Control (RRC) signaling) to the network node. Moreover, the step S202 may be initiated either by the UE 100 itself (e.g., when it enters a new cell) or in response to a corresponding request from the network node. Next, the method 200 goes on to a step S204, in which the processor 102 receives (e.g., by using the antenna array of the transceiving unit) DCI from the network node. The DCI indicates one or more groups of co-scheduled UEs served by the network node for the DL MU-MIMO reception, as well as further indicates one or more of the following: a modulation scheme (e.g., Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM) with different Modulation Orders (MOs) or indices, etc.) applied for each group of co-scheduled UEs; and a DMRS initialization value for each group of co-scheduled UEs. The DMRS initialization value is well-known in this technical field (e.g., see "cjnit" value in 3GPP TS 38.211 7.4. 1.1.1), and it may be made up of various components, such as a Physical Cell ID, a Synchronization Signal Block (SSB) Index and a Half Frame Number. That is, by decoding a certain DMRS, the UE 100 may derive the SSB Index and the Half Frame number. It should be noted that the step S204 may also be performed by using any suitable dedicated signaling, such as RRC signaling. Next, the method 200 proceeds to a step S206, in which the processor 102 configures the DL MU-MIMO reception based on the received DCI. More specifically, the processor 102 uses the DCI to properly determine demodulation / processing parameters for a DL signal or a DL channel (e.g., Physical Data Shared Channel (PDSCH)). In other words, the DCI thus configured will improve the overall channel estimation performance, for which reason the UE 100 may determine its advanced receiver processing and related parameters such that the cancellation / suppression of the inter-user interference caused by multiple groups of co-scheduled UE is possible.

[0050] As for the DCI itself, it may be configured as a tabular data structure comprising a set of indexed bit fields each associated with a certain MU-MIMO setup (e.g., a certain combination of a DMRS initialization value or sequence and the modulation scheme). The DCI may additionally indicate the index of that bit field which the processor 102 should consider when configuring the DL MU-MIMO reception in the step S206 of the method 200. One non- restrictive example of the tabular DCI is given below as Table 1. Table 1. DCI fields for DL MU-MIMO reception, in case of two groups of co-scheduled UEs

[0051] It should be noted that the bit fields having indices 0-6 in Table 1 referto use scenarios when there is only a single group of co-scheduled UEs. These bit fields may be not indicated in Table 1 at all, provided that the network node may form more than one UE group; in this case, the rest bit fields may be properly re-indexed or, in other words, renumbered. As also follows from Table 1, each of the two groups of co-scheduled UEs may be configured with the same or different modulation scheme. The same is true for the DMRS initialization value or sequence - i.e., each of the two groups of co-scheduled UEs may be provided with the same or different DMRS initialization value or sequence. For those UEs whose DMRS initialization value is given, channel estimation may be performed. Based on this, an interference covariance matrix may be calculated, and the UEs may use it, e.g., defining a noise whitening filter and using that in receiver processing. This way, the interference between the co-scheduled UEs in one group or the groups of co-scheduled UEs may be removed more precisely in the UE 100.

[0052] In general, it is up to a serving network node to decide whether a DMRS sequence is initialized with the same initialization value for all UEs in a serving cell. If the same DMRS initialization value is applied within the cell, the UE 100 may reduce its advanced receiver processing complexity (no need and no possibility for extra effective channel (including precoding and radio channel) estimation associated with interfering co-scheduled UEs). If different DMRS initialization values are applied for the group(s) of co-scheduled UEs within the serving cell, or if the group(s) of co-scheduled UEs with different DMRS initialization values are associated with a neighboring cell, the corresponding DMRS initialization values are indicated for the UE 100. By doing so, it is possible to allow the UE 100 to estimate effective channels associated with the interference from the co-scheduled UEs / PDSCH transmission to the UE 100. Of course, this effective channel estimation gives a kind of approximation of the exact co-scheduled UE / PDSCH interference (even though a modulation order is indicated), because the UE 100 would need to know also a DMRS type (e.g., e- typel / 2 or type-l / type2) and the number of MIMO layers of the co-scheduled UEs to estimate more precisely the actual effective channels associated with the co-scheduled UEs. An alternative scenario could be also that a first group of co-scheduled UEs uses the same DMRS initialization value as the UE 100 and a second group of co-scheduled UEs uses a different DMRS initialization value compared to the UE 100, where the first group of coscheduled UEs are within the same cell as the UE 100 and the second group of co-scheduled UEs are in a neighboring cell. This would give additional flexibility for a network scheduler to pair said different groups either in the serving and / or neighboring cells, given that the network implementation itself allows this pairing. As for the possibility of using the same or different modulation schemes for the UE 100 and co-scheduled UEs in one or more groups, it should be noted that, from the standpoint of the UE 100, the same modulation scheme may potentially result in complexity reduction in its receiver processing, e.g., in the reduced Maximum Likelihood (ML) type of receiver processing. If the UE 100 is co-scheduled with different groups of co-scheduled UEs with a different modulation order and the UE 100 does not know the modulation order, the interference-related information is not as accurate as knowing the modulation order. From the standpoint of the network node, it is always the best if the network scheduler is allowed to determine the paired co-scheduled UEs / PDSCH transmissions with the UE 100 (with advanced receiver processing capability) and also indicate the modulation order associated with the group(s) of co-scheduled UEs. As a result of this, the network node may exploit maximally the UE processing capabilities for the DL MU-MIMO reception, resulting in an enhanced spectral efficiency and higher data rates in the serving cell.

[0053] It is worth noting that the present disclosure is not limited to the two groups of co-scheduled UEs which are indicated in Table 1. In other embodiments, the number of the groups of coscheduled UEs indicated in the DCI may depend on the capabilities of the UE 100 itself. More specifically, the processor 102 of the UE 100 may additionally indicate, in the UE-related information, the maximum number of groups of co-scheduled UEs together with which the UE 100 is configured to support the efficient (in terms of the inter-user inference cancellation) DL MU-MIMO reception. Additionally, the processor 102 of the UE 100 may indicate, in the UE-related information, a total number of MIMO layers supported by the UE 100 for the DL MU-MIMO reception, a maximum modulation index or order supported by the UE 100, as well as an ability of the UE 100 to support more than one RS sequence. By using all this additional information from the UE 100, the network node may generate the most suitable DCI for the UE 100.

[0054] One other embodiment is possible, in which the DCI further indicates a modulation scheme for the UE 100 itself. In this embodiment, the modulation scheme to be used by the UE 100 may be the same as or different from the modulation scheme assigned to each group of coscheduled UEs. At the same time, the UE 100 may derive information about its own modulation scheme associated with MIMO layers based on a DL grant provided by the network node. FIG. 3 shows a block diagram of a network node 300 in accordance with one example embodiment. The network node 300 is intended to communicate with the UE 100 in any of the above-described communication networks. As shown in FIG. 3, the network node 300 comprises a processor 302 and a memory 304. The memory 304 stores processor-executable instructions 306 which, when executed by the processor 302, cause the processor 302 to implement the aspects of the present disclosure, as will be described below in more detail. It should be again noted that the number, arrangement, and interconnection of the constructive elements constituting the network node 300, which are shown in FIG. 3, are not intended to be any limitation of the present disclosure, but merely used to provide a general idea of how the constructive elements may be implemented within the network node 300. In general, the processor 302, the memory 304, and the processor-executable instructions 306 may be implemented in the same or similar manner as the processor 102, the memory 104, and the processor-executable instructions 106, respectively.

[0055] FIG. 4 shows a flowchart of a method 400 for operating the network node 300 in accordance with one example embodiment. The method 400 starts with a step S402, in which the processor 302 receives the UE-related information from the processor 102 of the UE 100 in the wireless communication network. As noted earlier, the UE-related information indicates that the UE 100 supports the DL MU -Ml MO reception. Additionally, the UE-related information may indicate the maximum number of groups of co-scheduled UEs at which the UE 100 can efficiently support the DL MU-MIMO reception, the total number of the MIMO layers supported by the UE 100, the maximum modulation index or order supported by the UE 100, and / or and the ability of the UE 100 to support more than one RS sequence. Next, the method 400 goes on to a step S404, in which the processor 302 uses the received UE- related information to properly generate the DCI for the UE 100. For example, the DCI may be generated as Table 1 discussed above. After that, the method 400 proceeds to a step S406, in which the processor 302 transmits the DCI to the processor 102 of the UE 100.

[0056] FIG. 5 shows a block diagram of a wireless communication system 500 in accordance with one example embodiment. As shown in FIG. 5, DCI signaling is used in the system 500 to implement the DL MU-MIMO reception in case of two groups 502, 504 of co-scheduled UEs (e.g., mobile phones). It is assumed that a target UE (i.e., the one which would like to initiate the DL MU-MIMO reception) is included in the first group 502 of co-scheduled UEs, and a network node 506 (e.g., gNB) generates and transmits the DCI to the target UE in accordance with the method 400. The DCI may be implemented, for example, as Table 1 or it may simply indicate the two groups 502, 504 of co-scheduled UEs and group-specific information in the form of the following messages: "Group#l=MO#x" and "Group#2=MO#y" (where each of "x" and "y" refers to a certain MO or index of the same modulation scheme, such as QAM, for example). By using the DCI, the target UE may properly configure the DL MU-MIMO reception (i.e., properly perform the DL channel estimation and the inter-user inference cancellation).

[0057] FIG. 6 shows a block diagram of a wireless communication system 600 in accordance with another example embodiment. As shown in FIG. 6, DCI signaling is used in the system 600 to implement the DL MU-MIMO reception in case of three groups 602, 604, 606 of co-scheduled UEs (e.g., mobile phones). It is assumed that a target UE (i.e., the one which would like to initiate the DL MU-MIMO reception) is included in the first group 602 of co-scheduled UEs, and a network node 608 (e.g., gNB) generates and transmits the DCI to the target UE in accordance with the method 400. The DCI may be implemented, for example, as Table 1 or it may simply indicate the three groups 602, 604, 606 of co-scheduled UEs and group-specific information in the form of the following messages: "Group#l=MO#x", "Group#2=MO#z", and "Group#3=MO#y" (where each of "x", "y" and "z" refers to a certain MO or index of the same modulation scheme, such as QAM, for example). By using the DCI, the target UE may properly configure the DL MU-MIMO reception (i.e., properly perform the DL channel estimation and the inter-user inference cancellation).

[0058] It should be noted that each step or operation of the methods 200 and 400, or any combinations of the steps or operations, can be implemented by various means, such as hardware, firmware, and / or software. As an example, one or more of the steps or operations described above can be embodied by processor executable instructions, data structures, program modules, and other suitable data representations. Furthermore, the processorexecutable instructions which embody the steps or operations described above can be stored on a corresponding data carrier and executed by the processors 102 and 302, respectively. This data carrier can be implemented as any computer-readable storage medium configured to be readable by said at least one processor to execute the processor executable instructions. Such computer-readable storage media can include both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, the computer-readable media comprise media implemented in any method or technology suitable for storing information. In more detail, the practical examples of the computer-readable media include, but are not limited to information-delivery media, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD), holographic media or other optical disc storage, magnetic tape, magnetic cassettes, magnetic disk storage, and other magnetic storage devices.

[0059] Although the example embodiments of the present disclosure are described herein, it should be noted that any various changes and modifications could be made in the embodiments of the present disclosure, without departing from the scope of legal protection which is defined by the appended claims. In the appended claims, the word "comprising" does not exclude other elements or operations, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS1. A User Equipment (UE) in a wireless communication network, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: transmit, to a network node in the wireless communication network, UE- related information indicating that the UE is able to support Downlink (DL) Multi-User Multiple-Input Multiple-Output (MU-MIMO) reception; receive, from the network node, Downlink Control Information (DCI) indicating at least one group of co-scheduled UEs served by the network node for the DL MU- MIMO reception, the DCI further indicating at least one of: a modulation scheme applied for each of the at least one group of co-scheduled UEs; and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs; and configure the DL MU-MIMO reception based on the DCI.

2. The UE of claim 1, wherein the UE-related information further indicates at least one of: a maximum number of groups of co-scheduled UEs at which the UE is able to support the DL MU-MIMO reception; a total number of MIMO layers supported by the UE for the DL MU-MIMO reception; and a maximum modulation index supported by the UE.

3. The UE of claim 1 or 2, wherein the DCI further indicates a DMRS initialization value for the UE that is the same as or different from the DMRS initialization value for each of the at least one group of co-scheduled UEs.

4. The UE of any one of claims 1 to 3, wherein the UE-related information further indicates an ability of the UE to support more than one DMRS sequence, and whereinthe DCI further indicates a DMRS sequence for each of the UE and the at least one group of co-scheduled UEs.

5. The UE of claim 4, wherein the DMRS sequence is the same or different for each of the UE and the at least one group of co-scheduled UEs.

6. The UE of any one of claims 1 to 5, wherein the DCI further indicates a modulation scheme for the UE that is the same as or different from the modulation scheme for each of the at least one group of co-scheduled UEs.

7. A network node in a wireless communication network, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network node at least to: receive, from a User Equipment (UE) in the wireless communication network, UE-related information indicating that the UE is able to support Downlink (DL) Multiuser Multiple-Input Multiple-Output (MU-MIMO) reception; based on the UE-related information, generate Downlink Control Information (DCI) indicating at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception, the DCI further indicating at least one of: a modulation scheme applied for each of the at least one group of co-scheduled UEs; and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs; and transmit the DCI to the UE.

8. The network node of claim 7, wherein the UE-related information further indicates at least one of: a maximum number of groups of co-scheduled UEs at which the UE is able to support the DL MU-MIMO reception; a total number of MIMO layers supported by the UE for the DL MU-MIMO reception; and a maximum modulation index supported by the UE.

9. The network node of claim 7 or 8, wherein the DCI further indicates a DMRS initialization value for the UE that is the same as or different from the DMRS initialization value for each of the at least one group of co-scheduled UEs.

10. The network node of any one of claims 7 to 9, wherein the UE-related information further indicates an ability of the UE to support more than one DMRS sequence, and wherein the DCI further indicates a DMRS sequence for each of the UE and the at least one group of co-scheduled UEs.

11. The network node of claim 10, wherein the DMRS sequence is the same or different for each of the UE and the at least one group of co-scheduled UEs.

12. The network node of any one of claims 6 to 9, wherein the DCI further indicates a modulation scheme for the UE that is the same as or different from the modulation scheme for each of the at least one group of co-scheduled UEs.

13. A method for operating a User Equipment (UE) in a wireless communication network, comprising: transmitting, to a network node in the wireless communication network, UE- related information indicating that the UE is able to support Downlink (DL) Multi-User Multiple-Input Multiple-Output (MU-MIMO) reception; receiving, from the network node, Downlink Control Information (DCI) indicating at least one group of co-scheduled UEs served by the network node forthe DL MU-MIMO reception, the DCI further indicating at least one of: a modulation scheme applied for each of the at least one group of co-scheduled UEs; and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs; and configuring the DL MU-MIMO reception based on the DCI.

14. A method for operating a network node in a wireless communication network, comprising:receiving, from a User Equipment (UE) in the wireless communication network, UE-related information indicating that the UE is able to support Downlink (DL) Multiuser Multiple-Input Multiple-Output (MU-MIMO) reception; based on the UE-related information, generating Downlink Control Information (DCI) indicating at least one group of co-scheduled UEs served by the network node for the DL MU-MIMO reception, the DCI further indicating at least one of: a modulation scheme applied for each of the at least one group of co-scheduled UEs; and a Demodulation Reference Signal (DMRS) initialization value for each of the at least one group of co-scheduled UEs; and transmitting the DCI to the UE.

15. A computer program product comprising a computer-readable storage medium, wherein the computer-readable storage medium stores a computer code which, when executed by at least one processor, causes the at least one processor to perform the method according to claim 13.

16. A computer program product comprising a computer-readable storage medium, wherein the computer-readable storage medium stores a computer code which, when executed by at least one processor, causes the at least one processor to perform the method according to claim 14.

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