Improved DMRS-based channel estimation in a communication network

Abstract

Disclosed is a method comprising obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs). The assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station. The method further comprises deriving the filter coefficients based on the obtained assistance information. The method further comprises applying spatial filtering based on the derived filter coefficients. The method further comprises estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration. The method further comprises determining beamforming weights to be used in beamforming at the base station based on the estimated channels.

Description

IMPROVED DMRS-BASED CHANNEL ESTIMATION IN A COMMUNICATION NETWORKFIELD

[0001] The present disclosure relates to improved Demodulation Reference Signal (DMRS)- based channel estimation in a communication network.BACKGROUND

[0002] The information disclosed in this background section is only for enhancement of understanding of the general background of the disclosure and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

[0003] With an increase in wireless communication and requirements of high traffic-streaming bitrates and high Quality of Service (QoS), Open Radio Access Network (O-RAN) was introduced. O-RAN allows operators to manage the network implemented by components from multiple vendors and support the applications of the 5th Generation (5G) and New Radio (NR).

[0004] In O-RAN architecture, multiple User Equipment (UEs) are coupled to base stations. The base stations may be in a disaggregated configuration, comprising Distributed Units (O- DUs) and Radio Units (O-RUs). The base stations deploy high-capacity multiple antennas to facilitate communication with the UEs. Beamforming techniques are used in order to achieve high data rate between the UEs and the base station. For instance, precise alignment of beams at the base station and the UEs are required for beamforming and optimal communication.

[0005] In DMRS based beamforming, channel estimation is performed by the O-RU based on the DMRS. The present disclosure described apparatus, system, and method for improving channel estimation at the O-RU

[0006] Conventionally, multiple UEs can transmit signals and data simultaneously using same Physical Resource Blocks (PRBs). Beamforming at the bases station enables reducing the number of streams from the antennas at the base station so as to correspond to number of UEs simultaneously transmitting the signals. As an example, in a scenario where the base station has 32 antennas and 4 UEs are transmitting simultaneously, then 32 streams from the antennas can be reduced to 4 streams by beamforming. This helps to reduce Fronthaul (FH) bandwidth between the O-DUs and the O-RUs.

[0007] Referring to FIG. 1A, a legacy architecture 100a associated with beamforming at the base station is depicted. In the legacy architecture, beamforming is applied at the O-RU. Further, the O-RU needs to be aware of beamforming weights in order to apply thebeamforming. Further, the beamforming weights are also adapted to channels between the UEs and the base station. The UEs transmit Sounding Reference Signals (SRS) to the base station in advance. The O-DU estimates the channels based on the SRS. Further, the O-DU calculates beamforming weights using the estimated channels and sends the beamforming weights to the O-RU. However, in the legacy architecture, the SRS are sent in advance and then the beamforming weights are calculated and sent to O-RU for beamforming. In between the time when the SRS are transmitted and when the beamforming is applied, the channel conditions may change. In such scenarios, the channel estimation is not accurate due to the changed conditions.

[0008] In order to overcome shortcomings of legacy architecture, Demodulation Reference Signal (DMRS) is considered for channel estimation. In FIG. IB, an Uplink Performance Improvement (ULPI) architecture 100b associated with beamforming at the base station is depicted. FIG. IB depicts ULPI architecture when the O-RU supports DMRS beamforming without equalization. FIG. 1C depicts an ULPI architecture 100c when the O-RU supports DMRS beamforming with equalization. In both the ULPI architectures, the DMRS is used as reference to calculate beamforming weights. In both the ULPI architectures, the O-RU needs to perform extra processing in order to extract the DMRS, DMRS descrambling, perform channel estimation based on the extracted DMRS, and performing beamforming or equalization calculations. This increases the processing required at the O-RU.

[0009] Currently, the existing techniques do not provide an optimal technique for channel estimation at the base station for the UEs. Thus, it is desired to address the above-mentioned disadvantages or other shortcomings or at least provide a useful alternative to overcome the above-mentioned disadvantages.SUMMARY

[0010] This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the disclosure nor is it intended to determine the scope of the disclosure.

[0011] Disclosed herein is a method comprising obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs). The assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O- DU) of the base station. The method further comprises deriving the filter coefficients based on the obtained assistance information. The method further comprises applying spatialfiltering based on the derived filter coefficients. The method further comprises estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration. The method further comprises determining beamforming weights to be used in beamforming at the base station based on the estimated channels.

[0012] Also disclosed here is an apparatus configured to obtain assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs). The assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station. The apparatus is further configured to derive the filter coefficients based on the obtained assistance information. The apparatus is further configured to apply spatial filtering based on the derived filter coefficients. The apparatus is further configured to estimate one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration. The apparatus is further configured to determine beamforming weights to be used in beamforming at the base station based on the estimated channels.

[0013] Also disclosed herein is a non-transitory computer readable medium having recorded thereon instructions executable by a computer. The instructions cause the computer to perform operations comprising obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs). The assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station. The operations further comprise deriving the filter coefficients based on the obtained assistance information. The operations further comprise applying spatial filtering based on the derived filter coefficients. The operations further comprise estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration. The operations further comprise determining beamforming weights to be used in beamforming at the base station based on the estimated channels.

[0014] The disclosed apparatus, method, and non-transitory computer readable medium enable improved channel estimation at the O-RU for the one or more UEs.

[0015] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawing. It is appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be consideredlimiting its scope. The disclosure will be described and explained with additional specificity and detail with the accompanying drawings.BRIEF DESCRIPTION OF FIGURES

[0016] Features, aspects, and advantages of embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and wherein:FIG. 1A illustrates a legacy architecture associated with beamforming at the base station, in accordance with existing arts;FIGS. 1B-1C illustrate ULPI architectures associated with beamforming at the base station, in accordance with existing arts;FIG. 2A illustrates a block diagram of a communication environment depicting a configuration of a User Equipment (UE) and a base station, in accordance with various embodiments of the present disclosure;FIG. 2B illustrates a block diagram depicting the disaggregated architecture of the base station, in accordance with various embodiments of the present disclosure;FIG. 3A illustrates a process for DMRS-based channel estimation, in accordance with a first aspect of the present disclosure;FIG. 3B illustrates a process for DMRS-based channel estimation, in accordance with a second aspect of the present disclosure;FIG. 4 illustrates a flowchart depicting a method for DMRS-based channel estimation, in accordance with various embodiments of the present disclosure; andFIG. 5 illustrates an exemplary use case scenario for improved DMRS-based channel estimation, in accordance with an embodiment of the present disclosure.DETAIEED DESCRIPTION

[0017] The following detailed description of example embodiments refers to the accompanying drawings. The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the implementations. Further, one or more features or components of one embodiment may be incorporated into or combined with another embodiment (or one or more features of another embodiment). Additionally, the flowchart and description of operations provided below relate to one of the various embodiments. It should be noted that it is possible to make other embodiments that do not exactly match the flowchart and its description. It is understood that in other embodiments one or more operations may be omitted, one or moreoperations may be added, one or more operations may be performed simultaneously (at least in part).

[0018] It will be apparent that systems and / or methods, described herein, may be implemented in different forms of hardware, software, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and / or methods is not limiting of the implementations. Thus, the operation and behavior of the systems and / or methods are described herein without reference to specific software code. It is understood that software and hardware may be designed to implement the systems and / or methods based on the description herein.

[0019] Even though particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of implementations comprises each dependent claim in combination with every other claim in the claim set.

[0020] No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to comprise one or more items, and may be used interchangeably with “one or more.” Also, as used herein, the terms “has,” “have,” “having,” “comprise,” “including,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Furthermore, expressions such as “at least one of [A] and [B],” “[A] and / or [B],” or “at least one of [A] or [B]” are to be understood as including only A, only B, or both A and B.

[0021] The foregoing disclosure provides illustration and description but is not intended to be exhaustive or to limit the implementations to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the implementations .

[0022] Unless otherwise defined, all terms, and especially any technical and / or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having ordinary skill in the art.

[0023] Now embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.

[0024] FIG. 2A illustrates an example block diagram of a communication environment 200 depicting a configuration of a User Equipment (UE) 210 and a base station 220, according toone or more embodiments disclosed herein. The base station 220 may be configured to communicate with the one or more UEs 210. The base station 220 may be associated with corresponding multi-antenna arrays to facilitate communication with the one or more UEs 210 by means of beams. The configurations as disclosed in FIG. 2A may include one or more additional elements generally required for the operations of the one or more UEs 210 and the base station 220, and the same have not been depicted for sake of brevity. Hereinafter, it is understood that terms including “unit” or “module” at the end may refer to the unit for processing at least one function or operation and may be implemented in hardware, software, or a combination of hardware and software.

[0025] Referring to FIG. 2A, the one or more UEs 210 may be communicatively coupled to the base station 220 over a communication network. The communication network may be, for instance, Long Term Evolution (LTE), Long Term Evolution-Advanced (LTE-A), and Fifth generation (5G) communication networks. In an embodiment, the communication environment 200 may be a 5thGeneration (5G) New Radio (NR) communication environment. In an embodiment, the communication environment 200 may be an Open Radio Access Network (O-RAN) communication environment. The base station 220 may alternatively be referred to as a gNodeB (gNB).

[0026] It is appreciated that although the details of the present disclosure may be described with reference to the base station 220, the disclosure is not limited thereto and the communication environment 200 may comprise additional base stations (not shown), and details in the present disclosure explained with reference to the base station 220 are equally applicable for the additional base stations as well.

[0027] The base station 220 may comprise an apparatus 221. The apparatus 221 comprises a processor 222, a memory 225, an input component 228, an output component 223, a communication interface 224, a storage component 226, and a bus 227.

[0028] The processor 222, as used herein, means any type of computational circuit that may comprise hardware elements and software elements. The processor 222 may be embodied as a multi-core processor, a single core processor, or a combination of one or more multi-core processors and / or one or more single core processors, a distributed processing system, or the like. The processor 222 may be a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Accelerated Processing Unit (APU), an Application-Specific Integrated Circuit (ASIC), or another type of processing component.

[0029] The processor 222 may be a single processing unit or a number of units, all of which could comprise multiple computing units. The processor 222 may be implemented as one ormore microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and / or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor 222 is configured to fetch and execute computer-readable instructions and data stored in the memory. The processor 222 may comprise one or a plurality of processors. At this time, one or a plurality of processors 222 may be a general-purpose processor, such as a central processing unit (CPU), an application processor (AP), or the like, and an Al-dedicated processor such as a neural processing unit (NPU).

[0030] The memory 225 may comprise a non-transitory computer readable medium. Memory 225 comprises a random-access memory (RAM), a read only memory (ROM), and / or another type of dynamic or static storage device (e.g., a flash memory, a magnetic memory, and / or an optical memory) that stores information and / or instructions for use by processor 222. The memory 225 comprises machine-readable instructions which are executable by the processor 222. These machine-readable instructions when executed by the processor 222 cause the processor 222 to perform one or more method steps of an embodiment described in the present disclosure.

[0031] Storage component 226 stores information and / or software related to the operation and use of the apparatus 221. For example, storage component 226 may comprise a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, and / or a solid-state disk), a compact disc (CD), a digital versatile disc (DVD), a floppy disk, a cartridge, a magnetic tape, and / or another type of non-transitory computer-readable medium, along with a corresponding drive.

[0032] Input component 228 is configured to receive information, such as user input. For example, the input component 228 may comprise, but not be limited to, a touch screen display, a keyboard, a keypad, a mouse, a button, a switch, and / or a microphone. Additionally, or alternatively, the input component 228 may comprise a sensor for sensing information (e.g., a global positioning system (GPS), an accelerometer, a gyroscope, and / or an actuator).

[0033] Output component 223 is configured to provide output information from the apparatus 221. For example, the output component 223 may be, but not limited to, a display, a speaker, instructions to an external device, and / or one or more light-emitting diodes (LEDs).

[0034] Communication interface 224 is an interface that provides a communication connection to other devices, such as external devices and internal devices. The connection by the communication interface 224 can be a wired connection, a wireless connection, or a combination of wired and wireless connections, and can be a direct connection or an indirectconnection via a communication network that exists between the apparatus 221 and other devices. In other words, the standard of the communication interface 224 is not limited.

[0035] The bus 227 acts as an interconnect between the processor 222, the memory 225, the storage component 226, the input component 228, the output component 223, and the communication interface 224 of the apparatus 221. The bus 227 may comprise a wired interconnection or a wireless interconnection.

[0036] The number and arrangement of components shown in FIG. 2 A are provided as an example. In practice, apparatus 221 may comprise additional components, fewer components, different components, or differently arranged components than those shown in FIG. 2A. Additionally, or alternatively, a set of components (e.g., one or more components) of apparatus 221 may perform one or more functions described as being performed by another set of components of apparatus 221. Further, one or more method steps described in any of the embodiments may be performed utilizing a plurality of apparatus 221 in communication with one another.

[0037] In some embodiments, the base station 220 may be implemented as dedicated hardware units. In some embodiments, the base station 220 may be implemented in the form of virtualized software units in hardware or cloud environments. In some embodiments, the base station 220 may be associated with a disaggregated architecture.

[0038] FIG. 2B illustrates a block diagram depicting the disaggregated architecture of the base station 220, in accordance with an embodiment of the present disclosure. The base station 220 may be configured with logical nodes. The base station 220 may comprise a Centralized Unit (O-CU) 231. The O-CU 231 may be logically split into a O-CU Control Plane (O-CU-CP) 232 and one or more CU User Planes (O-CU-UPs) 233. The O-CU 231 may be communicatively coupled to one or more Distributed Units (O-DUs) 234. Further, the one or more O-DUs 234 may be communicatively coupled to one or more Radio Units (O-RUs) 235 via a fronthaul network. The O-CU-CP may be configured for control-plane functionality and one or more O-CU-UPs may be configured for user-plane functionality. The O-DUs 234 may be configured for execution of Radio Link Control (RLC), Medium Access Control (MAC) and upper parts of Physical (PHY) layer protocols of the radio stack. The O-RUs 235 may be configured for execution of lower parts of PHY layer protocols as well as provide antenna capabilities for communication with UE.

[0039] In an embodiment, the base station 220 may form the apparatus 221, in that, the apparatus 221 may refer to the base station 220. In an embodiment, the O-DUs 234 and the O-RUs 235 may form the apparatus 221 of the base station 220, in that, the apparatus 221 ofthe base station 220 may refer to one or more of the O-DUs 234 and the O-RUs 235. In an embodiment, the O-RUs 235 may form the apparatus 221 of the base station 220, in that, the apparatus 221 of the base station 220 may refer to one or more of the O-RUs 235. In an embodiment, the O-DUs 234 may form the apparatus 221 of the base station 220, in that, the apparatus 221 of the base station 220 may refer to one or more of the O-DUs 234.

[0040] It is appreciated that one or more details may be explained with reference to an O-DU 234 and an O-RU 235 among the one or more O-DUs and the one or more O-RUs, however, the details are also applicable for other O-DUs and O-RUs associated with the base station 220.

[0041] Details regarding channel estimation associated with Demodulation Reference Signal (DMRS) based beamforming in the O-RAN communication environment 200 are described. The DMRS based beamforming is used to derive beamformer / equalizer in receiving Physical Uplink Shared Channel (PUSCH) signals. The base station 220 may be configured for improved channel estimation associated with DMRS based beamforming.

[0042] In a first aspect, the apparatus 221 may be configured to obtain assistance information for channel estimation to be performed at the base station 220 for the one or more UEs 210. The assistance information comprises filter coefficients to be used in spatial filtering. The spatial filtering may be used to exploit the correlation between antennas in a receive antenna array and exploit covariance of inter-cell interference causing pilot contamination obtained by an advanced cell coordination scheme, thereby facilitating channel estimation.

[0043] The apparatus 221 may further be configured to derive the filter coefficients based on the obtained assistance information. In the first aspect, as the assistance information comprise the filter coefficients, the apparatus 221 may be configured to derive the filter coefficients by directly using the filter coefficients.

[0044] In an embodiment, the O-DU 234 and the O-RU 235 are operating with DMRF-BF- EQ (when equalisation is performed at the O-RU). In an embodiment, the O-DU 234 and the O-RU 235 are operating with DMRS-BF-NEQ (equalisation is not performed at the O-RU).

[0045] In an embodiment, the filter coefficients received in the assistance information may be calculated at the O-DU 234. That is, the apparatus 221 may be configured to calculate the filter coefficients at the O-DU 234. The filter coefficients may be calculated at the O-DU 234 based on historical data associated with the one or more UEs. The historical data may be stored in a database accessible to the base station 220. In an embodiment, the historical data may be stored in the storage component 226. The historical data may comprise historicalSounding Reference Signals (SRS) transmitted by the one or more UEs over a pre-defined period of time.

[0046] The apparatus 221 may be further configured to transmit the calculated filter coefficients to the O-RU 235. In an embodiment, the O-RU 235 is an Uplink Performance Improvement (ULPI) supported O-RU. The calculated spatial filter coefficients may be transmitted over Fronthaul C-plane to the O-RU 235. The spatial filter coefficients may be transmitted in conjunction with sending scheduling information to the O-RU 235. The spatial filter coefficients may be transmitted in a new Section Extension message following Section Type 5 message.

[0047] Based on the received filter coefficients, the apparatus 221 may be configured to apply spatial filtering. Further, the apparatus 221 may be configured to estimate one or more channels for the one or more UEs based on the applied spatial filtering and the DMRS configuration. The channel estimation may be DMRS -based channel estimation. In an embodiment, the DMRS configuration may be received at the O-RU 235 in Section Extension 24. Further, the apparatus 221 may be configured to determine beamforming weights to be used in beamforming at the base station 220 based on the estimated channels.

[0048] Accordingly, the filter coefficients calculated at the O-DU 234 may be used at the O- RU 235 to improve the performance of DMRS-based channel estimation. In an embodiment, the O-DU 234 provides the spatial filters for the UEs 210 in a Multiple Input Multiple Output (MIMO) user group. In an embodiment, the one or more UEs 210 are scheduled to occupy the same set of radio resources in transmitting PUSCH signals.

[0049] In an embodiment, the apparatus 221 is configured to apply the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs). In a scenario where N filters are provided, each filter is applied for a frequency block of M contiguous PRBs. In some embodiments, M is configured by the O-DU 234 over open M-plane while N is derived from M and a number of allocated PRBs.

[0050] In an embodiment, for each UE among the one or more UEs 210 and a corresponding frequency block, the number of complex filter coefficients may be ( / <A2+ / <’) / 2, where K is the number of antennas in the receive antenna array, to form a conjugate symmetric filtering matrix of size KxK. In an embodiment, to apply the spatial filtering, the UE 210 is configured to apply spatial filtering for each UE with coefficients conveyed in the new section extension in each frequency block, thereby improving the DMRS-based channel estimation.

[0051] In one example of spatial filtering can be performed based on the equation: ht= Tihi, where htis the resultant vector of channel estimate, ftLis of length K the number of antennas in the receiver array, and Ttis filter matrix of size K x K.

[0052] In some embodiments, the O-RU 235 declares support for the new Section Extension message. In an embodiment, the support of the new section extension message is optional. In an embodiment, the support of the new section extension message is per endpoint of the O- RU 235. In an embodiment when the O-RU 235 supports the new section extension message, the O-RU 235 advertises the support. In an embodiment, following the advertisement, the O- RU 235 may advertise the list of values for M (the size of frequency block over which a single filter is applied). Value 0 may be a default value indicating that a single filter is applied for the whole range of allocated PRBs.

[0053] In some embodiments, the O-DU 234 configures the feature of the new Section Extension message. In an embodiment, the support of the new section extension message is optional. In an embodiment, when the O-DU 234 supports the new Section Extension and the O-RU 235 declares the support of the new Section Extension for some of the associated endpoints, the O-DU 234 may configure the O-RU 235 with the feature of the new Section Extension per supported endpoint. In an embodiment, when the O-RU 235 advertises the list of values for M (the size of frequency block over which a single filter is applied) and the number of elements in the list is more than one, in conjunction with configuring the feature of the new Section Extension, the O-RU 235 may select a value from the list and configure the feature with the selected value.

[0054] In a second aspect, the apparatus 221 may be configured to obtain assistance information for channel estimation to be performed at the base station 220 for the one or more UEs 210. The assistance information comprises Sounding Reference Signal (SRS) configurations receiving from the O-DU 234. The apparatus 221 may further be configured to derive the filter coefficients based on the obtained assistance information, i.e., the SRS configurations.

[0055] In the second aspect, as the assistance information comprise the SRS configurations, the apparatus 221 may be configured to derive the filter coefficients by calculating the filter coefficients at the O-RU 235. That is, the apparatus 221 may be configured to receive, at the O-RU 235, the SRS configurations from the O-DU 234, and further, the apparatus 221 may be configured to calculate the filter coefficients for spatial filtering based on the received SRS configurations.

[0056] In an embodiment, the O-RU 235 is an Uplink Performance Improvement (ULPI) supported O-RU. In an embodiment, the O-DU 234 and the O-RU 235 are operating with DMRF-BF-EQ (when equalisation is performed at the O-RU). In an embodiment, the O-DU 234 and the O-RU 235 are operating with DMRS-BF-NEQ (equalisation is not performed at the O-RU).

[0057] In an embodiment, the apparatus 221 may be configured to receive, at the O-RU 235 from the O-DU 234, a mapping between the SRS configurations and corresponding UEs among the one or more UEs 210. The corresponding UEs may comprise, for instance, scheduled UEs. The apparatus 221 may be configured to calculate, at the O-RU 235, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs. Accordingly, the filter coefficients may be derived from the assistance information, i.e., the SRS configurations.

[0058] In an embodiment, the SRS configurations may be sent by the O-DU 234 in a new Section Type message over Open Fronthaul C-plane. In an embodiment, the mapping between scheduled UEs and SRS configurations may be sent by the O-DU 234 in a new Section Extension message following Section Type 5 over the Open Fronthaul C-plane. In some embodiments, the O-RU declares support for the new Section Extension message and new Section Type message. In some embodiments, the O-DU configures the feature of the new Section Extension message and the new Section Type message.

[0059] In some embodiments, the O-RU 235 declares support for the new Section Extension message and the new Section Type message. In an embodiment, the support of the new section extension message and the new Section Type message is optional. In an embodiment, the support of the new section extension message and the new Section Type message is per endpoint of the O-RU 235. In an embodiment when the O-RU 235 supports the new section extension message and the new Section Type message, the O-RU 235 advertises the support.

[0060] In some embodiments, the O-DU 234 configures the feature of the new Section Extension message and the new Section Type message. In an embodiment, the support of the new section extension message and the new Section Type message is optional. In an embodiment, when the O-DU 234 supports the new Section Extension and the new Section Type message, and the O-RU 235 declares the support of the new Section Extension and the new Section Type message for some of the associated endpoints, the O-DU 234 may configure the O-RU 235 with the feature of the new Section Extension and the new Section Type message per supported endpoint.

[0061] Based on the received filter coefficients, the apparatus 221 may be configured to apply spatial filtering. Further, the apparatus 221 may be configured to estimate one or more channels for the one or more UEs based on the applied spatial filtering and the DMRS configuration. The channel estimation may be DMRS -based channel estimation. In an embodiment, the DMRS configuration may be received at the O-RU 235 in Section Extension 24. Further, the apparatus 221 may be configured to determine beamforming weights to be used in beamforming at the base station 220 based on the estimated channels.

[0062] In an embodiment, the O-RU 235 may be configured to calculate statistical correlation of uplink channels over which the UEs transmits SRSs. Based on the SRS configurations, the O-RU 235 may calculate and store the self-correlations of the channels over which the SRSs are transmitted. Further, the O-RU 235 may apply spatial filtering for each UE with the derived spatial filter coefficients to improve the DMRS-based channel estimation.

[0063] Accordingly, the O-DU provides SRS configurations that are used at the O-RU 235 to calculate statistical correlation of uplink channels over which the one or more UEs 210 transmits SRSs. In some cases, each SRS configuration is associated with an SRS identifier while each UE is associated with a UE identifier. In an embodiment, each SRS configuration is linked with an endpoint of the O-RU 235. The filter coefficients calculated at the O-RU 235 may then be used to improve the performance of DMRS-based channel estimation.

[0064] In an embodiment, the one or more UEs 210 are scheduled to occupy the same set of radio resources in transmitting PUSCH signals. In an embodiment, the O-DU 234 provides the mapping between the SRS configurations and corresponding UEs in a MIMO user group. In an embodiment, the mapping between scheduled UEs and SRS configurations may comprise mapping among the SRS identifiers and the UE identifiers. In some embodiments, the mapping may be a one-to-one mapping.

[0065] In a third aspect, the apparatus 221 may be configured to improve channel estimation at the base station 220 for the one or more UEs 210. In the third aspect, the configuration and functionality with respect to the first and second aspects may be provided simultaneously.

[0066] In such an embodiment, the O-DU 234 may provide the O-RU 235 with information to assist in spatial filtering and channel estimation. The information may be sent in a new section extension following Section Type 5 C-plane message. The information may comprise one of:- spatial filter coefficients calculated by the O-DU, or- mapping among the SRS identifiers and the UE identifiers.

[0067] Referring to FIG. 3A, a process 300a for DMRS-based channel estimation is depicted, in accordance with the first aspect of the disclosure. The process 300a depicts communication between the 0-DU 234 and the O-RU 235.

[0068] The O-RU 235 may be associated with a channel estimator unit 235a, a weight calculation unit 235b, and a beamforming unit 235c. The O-DU 234 may be associated with a coefficient calculation unit 234a. At step 302, the O-DU 234 may be configured to calculate the filter coefficients for spatial filtering at the coefficient calculation unit 234a. The filter coefficients may be calculated based on historical data associated with the one or more UEs 210. The historical data may comprise historical SRS transmitted by the one or more UEs 210 over a pre-defined period of time.

[0069] The calculated filter coefficients may then be transmitted to the O-RU 235 as an assistance information, as depicted at step 304. In an embodiment, the calculated filter coefficients may be transmitted over Fronthaul C-plane to the O-RU 235. In an embodiment, the filter coefficients may be transmitted in a new Section Extension message following Section Type 5 message. The filter coefficients may be transmitted in conjunction with sending scheduling information to the O-RU 235.

[0070] At step 306, the DMRS configuration may be received at the O-RU 235 from the O- DU 234 in Section Extension 24. The channel estimator unit 235a at the O-RU 235 may receive the DMRS configuration and the assistance information, i.e., the filter coefficients calculated at the O-DU 234.

[0071] At step 308, the channel estimator unit 235a may be configured to directly use the filter coefficients and apply the filter coefficients in spatial filtering. Further, the channel estimator unit 235a may be configured to estimate one or more channels (H, Q) for the one or more UEs 210 based on the applied spatial filtering and the DMRS configuration.

[0072] At step 310, the weight calculation unit 235b may be configured to determine beamforming weights W to be used in beamforming based on the estimated channels (H, Q). At step 312, the beamforming unit 235c may be configured for beamforming and equalization based on the determined beamforming weights W. . . . Let y be the signal vector that the base station receives over one subcarrier antenna array of K elements. Due to the interference nature of the wireless medium over the subcarrier, the received signal vector can be modelled as y = Hx + v, wherein x is the signal vector transmitted by one or more than one UEs, v is the total sum of interference and background noise and, H is the channel matrix whose elements represent the channels from the UEs to the elements of the receive antenna array.The transmitted signal vector can be reconstructed by applying a set of L beamforming vectors forming matrix W of K rows and L columns to obtain x = Wy (L is the number of UEs transmitting over the subcarrier). W can be calculated based on an estimate of H and a statistical property of v. For example, if H is estimated as H and the covariance of n is estimated as Q, matrix W can be calculated as W = (^HHQ~1H + / ) HHQ~1. The base station can apply the whole W in the beamforming at the O-RU in DMRS-BF-EQ or apply a factor of W in the beamforming at the O-RU in DMRS-BF-NEQ. Choosing to operate with DMRS-BF-EQ or DMRS-BF-NEQ is considered as the trade-off between the reconstructing performance and the complexity at the O-RU.

[0073] Accordingly, the filter coefficients calculated at the O-DU 234 may be used at the O- RU 235 to improve the performance of DMRS-based channel estimation, i.e., better accuracy of H with respect to H. In an embodiment where the O-DU 234 and the O-RU 235 are operating with DMRF-BF-NEQ, equalisation may be performed at the O-DU 234, as depicted at step 314.

[0074] In an embodiment, the filter coefficients may be applied for a corresponding frequency block having a pre-defined number of PRBs. In a scenario where N filters are provided, each filter is applied for a frequency block of M contiguous PRBs. In some embodiments, M is configured by the O-DU 234 over open M-plane while N is derived from M and a number of allocated PRBs.

[0075] Referring to FIG. 3B, a process 300b for DMRS-based channel estimation is depicted, in accordance with the second aspect of the disclosure. The process 300b depicts communication between the O-DU 234 and the O-RU 235.

[0076] The O-RU 235 may be associated with a channel estimator unit 235a, a weight calculation unit 235b, and a beamforming unit 235c, and a coefficient calculation unit 235d. At step 322, the O-DU 234 may be configured to transmit SRS configurations to the O-RU 235. At step 324, the O-DU 234 may be configured to transmit a mapping between the SRS configurations and corresponding UEs among the one or more UEs 210. In an embodiment, the steps 322 and 324 may be performed simultaneously. In an embodiment, the corresponding UEs may comprise scheduled UEs. The SRS configurations and the mapping between the SRS configurations and corresponding UEs may form assistance information for the O-RU 235.

[0077] In an embodiment, the SRS configurations may be sent by the O-DU 234 in a new Section Type message over Open Fronthaul C-plane. In an embodiment, the mapping betweenscheduled UEs and SRS configurations may be sent by the O-DU 234 in a new Section Extension message following Section Type 5 over the Open Fronthaul C-plane.

[0078] At step 326, the coefficient calculation unit 235d at the O-RU 235 may be configured to calculate the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs. That is, the filter coefficients may be derived at the O-RU 235 from the assistance information received from the O-DU 234.

[0079] At step 328, the DMRS configuration may be received at the O-RU 235 from the O- DU 234 in Section Extension 24. The channel estimator unit 235a at the O-RU 235 may receive the DMRS configuration. Further, at step 330, the channel estimator unit 235a at the O-RU 235 may receive the filter coefficients calculated by the coefficient calculation unit 235d.

[0080] At step 332, the channel estimator unit 235a may be configured to use the calculate filter coefficients and apply the filter coefficients in spatial filtering. Further, the channel estimator unit 235a may be configured to estimate one or more channels (H, Q) for the one or more UEs 210 based on the applied spatial filtering and the DMRS configuration. In an embodiment, the O-RU 235 may be configured to calculate statistical correlation of uplink channels over which the UEs transmits SRSs. Based on the SRS configurations, the O-RU 235 may calculate and store the self-correlations of the channels over which the SRSs are transmitted. Further, the O-RU 235 may apply spatial filtering for each UE with the derived spatial filter coefficients to improve the DMRS-based channel estimation.

[0081] At step 334, the weight calculation unit 235b may be configured to determine beamforming weights W to be used in beamforming based on the estimated channels (H, Q). At step 336, the beamforming unit 235c may be configured for beamforming and equalization based on the determined beamforming weights W. . . . Let y be the signal vector that the base station receives over one subcarrier antenna array of K elements. Due to the interference nature of the wireless medium over the subcarrier, the received signal vector can be modelled as y = Hx + v, wherein x is the signal vector transmitted by one or more than one UEs, v is the total sum of interference and background noise and, H is the channel matrix whose elements represent the channels from the UEs to the elements of the receive antenna array. The transmitted signal vector can be reconstructed by applying a set of L beamforming vectors forming matrix W of K rows and L columns to obtain x = Wy (L is the number of UEs transmitting over the subcarrier). W can be calculated based on an estimate of H and astatistical property of v. For example, if H is estimated as H and the covariance of n is estimated as Q, matrix W can be calculated as W = (^HHQ~1H + / ) HhlQ~1. The base station can apply the whole W in the beamforming at the O-RU in DMRS-BF-EQ or apply a factor of W in the beamforming at the O-RU in DMRS-BF-NEQ. Choosing to operate with DMRS-BF-EQ or DMRS-BF-NEQ is considered as the trade-off between the reconstructing performance and the complexity at the O-RU.

[0082] Accordingly, the filter coefficients are calculated at the O-RU 235 and used in spatial filtering to improve the performance of DMRS-based channel estimation, i.e., better accuracy of H with respect to H. In an embodiment where the O-DU 234 and the O-RU 235 are operating with DMRF-BF-NEQ, equalisation may be performed at the O-DU 234, as depicted at step 338.

[0083] FIG. 4 illustrates a flowchart depicting a method 400 for DMRS-based channel estimation, in accordance with an embodiment of the present disclosure. In one embodiment, the steps of the method 400 may be performed at the apparatus 221 of the base station 220, as discussed above with reference to FIGS. 2A-3B.

[0084] At step 402, the method 400 comprises obtaining assistance information for channel estimation to be performed at the base station 220 for one or more UEs 210. The assistance information comprises one of filter coefficients and information associated with SRS configurations received from the O-DU 234 of the base station 220.

[0085] In an embodiment, when the assistance information is the filter coefficients, obtaining the assistance information comprises calculating, at the O-DU 234, the filter coefficients for the one or more UEs 210 based on historical data associated with the one or more UEs. In an embodiment, the historical data comprises historical SRS over a pre-defined period of time. The method further comprises transmitting the calculated filter coefficients to the O-RU 235 associated with the base station 220.

[0086] In an embodiment, when the assistance information is the information associated with the SRS configurations, obtaining the assistance information comprises receiving, at the O- RU 235, the SRS configurations from the O-DU 234 and mapping between the SRS configurations and corresponding UEs among the one or more UEs 210.

[0087] In an embodiment, each of the filter coefficients and the information associated with the SRS configurations is received via one of a new section type message or a new section extension message.

[0088] At step 404, the method 400 comprises deriving the filter coefficients based on the obtained assistance information.

[0089] In an embodiment, when the assistance information is the filter coefficients, deriving the filter coefficients comprises directly using the filter coefficients calculated by the O-DU.

[0090] In an embodiment, when the assistance information is the information associated with the SRS configurations, deriving the filter coefficients comprises calculating, at the O-RU 235, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs 210.

[0091] At step 406, the method 400 comprises applying spatial filtering based on the derived filter coefficients.

[0092] In an embodiment, applying the spatial filtering based on the derived filter coefficients comprises applying the filter coefficients for a corresponding frequency block having a predefined number of PRBs.

[0093] At step 408, the method 400 comprises estimating one or more channels for the one or more UEs based on the applied spatial filtering and DMRS configuration.

[0094] At step 410, the method 400 comprises determining beamforming weights to be used in beamforming at the base station based on the estimated channels.

[0095] While the above-discussed steps in FIG. 4 are shown and described in a particular sequence, the steps may occur in variations to the sequence in accordance with various embodiments. Further, a detailed description related to the various steps of FIG. 4 is already covered in the description related to FIGS. 2A-3B and is omitted herein for the sake of brevity.

[0096] As mentioned previously, it is appreciated that the details of the present disclosure may are equally applicable for multiple O-RUs and O-DUs associated with the base station 220.

[0097] Referring to FIG. 5, an exemplary use case scenario for improved DMRS-based channel estimation is illustrated. As depicted, the O-DU 510 is linked to a first O-RU 512 and a second O-RU 514. The first O-RU 512 is covering cell 522 while the second O-RU 514 is covering cell 524. The first O-RU 512 and the second O-RU 514 are operating at the same carrier frequency.

[0098] Further, a first UE 530 and a second UE 532 may be attached to the cell 522, in that, the first O-RU 512 may be serving the first UE 530 and the second UE 532. A third UE 534 may be attached to the cell 524, in that, the second O-RU 514 may be serving the third UE 534. The first UE 530 and the third UE 534 may have the same DMRS configuration. In sucha scenario, the first UE 530 and the third UE 534 may be assigned with the same DMRS scrambling sequence and same DMRS port.

[0099] In one aspect, in order to mitigate reference signal interference on the first O-RU 512 by the third UE 534, i.e., the UE served by the second O-RU 514, cell coordination may take place at the first O-RU 512. In this regard, channel estimation at the first O-RU 512 needs to be efficient. At the first O-RU 512, the statistical covariances of channels from the first UE 530 and the third UE 534 may be considered for channel estimation. The statistical covariances can be obtained from historical SRS. In such a scenario, the O-DU 510 may assist the first O-RU 512 by considering the statistical covariances of channels from the first UE 530 and the third UE 534. Based on the statistical covariances of channels, spatial filtering may be applied at the first O-RU 512 in order to improve channel estimation for UE 530.

[0100] In another aspect, the channel coefficients of the second UE 532 to the receive antennas are correlated due to a close proximity of antenna elements of receive antenna array. The statistical covariance of the channel from the second UE 532 includes the correlations between channel coefficients. In such a scenario, the O-DU 510 may assist the first O-RU 512 by considering the statistical covariance of signals from the first UE 532. Based on the statistical covariances of channels, spatial filtering may be applied at the first O-RU 512 in order to improve channel estimation for the first UE 532.

[0101] In another aspect, if the covariance of channel of the third UE 534 is not accessible to O-RU 512, the first O-RU 512 still can consider the covariance of channel of the first UE 530 to improve the channel estimation for the first UE 530 with the same principle applied to the second UE 532 without considering the covariance of channel of the third UE 234. In this case, although the lacking knowledge on the interference caused by the UE 534 can make the channel estimation performance for the first UE 530 is not as good as that for the second UE 532, spatial filtering still improves the channel estimation for the first UE 530.

[0102] The present disclosure describes apparatus and methods that enable improved channel estimation at the O-RU for the one or more UEs.[1]. A method comprising: obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; deriving the filter coefficients based on the obtained assistance information; applying spatial filtering based on the derived filter coefficients;estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determining beamforming weights to be used in beamforming at the base station based on the estimated channels.[2]. The method described in [1], wherein when the assistance information is the filter coefficients, obtaining the assistance information comprises: calculating, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmitting the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.[3]. The method described in [2], wherein when the assistance information is the filter coefficients, deriving the filter coefficients comprises directly using the filter coefficients calculated by the O-DU.[4]. The method described in [1], wherein when the assistance information is information associated with the SRS configurations, obtaining the assistance information comprises: receiving, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; and receiving, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.[5]. The method described in [4], wherein when the assistance information is the information associated with the SRS configurations, deriving the filter coefficients comprises: calculating, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.[6]. The method described in [1], wherein applying the spatial filtering based on the derived filter coefficients comprises applying the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs).[7] . The method described in

[0001] , wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.[8]. An apparatus configured to: obtain assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one offilter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; derive the filter coefficients based on the obtained assistance information; apply spatial filtering based on the derived filter coefficients; estimate one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determine beamforming weights to be used in beamforming at the base station based on the estimated channels.[9]. The apparatus described in [8], wherein when the assistance information is the filter coefficients, to obtain the assistance information, the apparatus is configured to: calculate, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmit the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.

[0010] . The apparatus described in [9], wherein when the assistance information is the filter coefficients, the apparatus is configured to derive the filter coefficients by directly using the filter coefficients calculated by the O-DU.

[0011] . The apparatus described in [8], wherein when the assistance information is information associated with the SRS configurations, to obtain the assistance information the apparatus is configured to: receive, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; and receive, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.

[0012] . The apparatus described in

[0011] , wherein when the assistance information is the information associated with the SRS configurations, to derive the filter coefficients the apparatus is configured to: calculate, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.

[0013] . The apparatus described in [8], wherein to apply the spatial filtering based on the derived filter coefficients, the apparatus is configured to apply the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs).

[0014] . The apparatus described in [8], wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.

[0015] . A non-transitory computer readable medium having recorded thereon instructions executable by a computer to cause the computer to perform operations comprising: obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; deriving the filter coefficients based on the obtained assistance information; applying spatial filtering based on the derived filter coefficients; estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determining beamforming weights to be used in beamforming at the base station based on the estimated channels.

[0016] . The non-transitory computer readable medium described in

[0015] , wherein when the assistance information is the filter coefficients, the operation of obtaining the assistance information comprises: calculating, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmitting the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.

[0017] . The non-transitory computer readable medium described in

[0016] , wherein when the assistance information is the filter coefficients, the operation of deriving the filter coefficients comprises directly using the filter coefficients calculated by the O-DU.

[0018] . The non-transitory computer readable medium described in

[0015] , wherein when the assistance information is information associated with the SRS configurations, the operation of obtaining the assistance information comprises: receiving, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; and receiving, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.

[0019] . The non-transitory computer readable medium described in

[0018] , wherein when the assistance information is the information associated with the SRS configurations, the operation of deriving the filter coefficients comprises: calculating, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.

[0020] . The non-transitory computer readable medium described in

[0015] , wherein the operation of applying the spatial filtering based on the derived filter coefficients comprises applying the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs), and wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.

[0103] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the elements. The elements can be at least one of a hardware device or a combination of hardware devices and software modules.

[0104] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

[0105] The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein.

[0106] Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

[0107] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

[0108] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of at least one embodiment, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Claims

1. CLAIMS:

1. A method comprising: obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; deriving the filter coefficients based on the obtained assistance information; applying spatial filtering based on the derived filter coefficients; estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determining beamforming weights to be used for beamforming at the base station based on the estimated channels.

2. The method according to claim 1, wherein when the assistance information is the filter coefficients, obtaining the assistance information comprises: calculating, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmitting the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.

3. The method according to claim 2, wherein when the assistance information is the filter coefficients, deriving the filter coefficients comprises directly using the filter coefficients calculated by the O-DU.

4. The method according to claim 1, wherein when the assistance information is information associated with the SRS configurations, obtaining the assistance information comprises: receiving, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; and receiving, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.

5. The method according to claim 4, wherein when the assistance information is the information associated with the SRS configurations, deriving the filter coefficients comprises:calculating, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.

6. The method according to claim 1, wherein applying the spatial filtering based on the derived filter coefficients comprises applying the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs).

7. The method according to claim 1, wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.

8. An apparatus configured to: obtain assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; derive the filter coefficients based on the obtained assistance information; apply spatial filtering based on the derived filter coefficients; estimate one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determine beamforming weights to be used for beamforming at the base station based on the estimated channels.

9. The apparatus according to claim 8, wherein when the assistance information is the filter coefficients, to obtain the assistance information, the apparatus is configured to: calculate, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmit the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.

10. The apparatus according to claim 9, wherein when the assistance information is the filter coefficients, the apparatus is configured to derive the filter coefficients by directly using the filter coefficients calculated by the O-DU.

11. The apparatus according to claim 8, wherein when the assistance information is information associated with the SRS configurations, to obtain the assistance information the apparatus is configured to: receive, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; andreceive, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.

12. The apparatus according to claim 11, wherein when the assistance information is the information associated with the SRS configurations, to derive the filter coefficients the apparatus is configured to: calculate, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.

13. The apparatus according to claim 8, wherein to apply the spatial filtering based on the derived filter coefficients, the apparatus is configured to apply the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs).

14. The apparatus according to claim 8, wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.

15. A non-transitory computer readable medium having recorded thereon instructions executable by a computer to cause the computer to perform operations comprising: obtaining assistance information for channel estimation to be performed at a base station for one or more User Equipment (UEs), wherein the assistance information comprises one of filter coefficients and information associated with Sounding Reference Signal (SRS) configurations received from an Open Distributed Unit (O-DU) of the base station; deriving the filter coefficients based on the obtained assistance information; applying spatial filtering based on the derived filter coefficients; estimating one or more channels for the one or more UEs based on the applied spatial filtering and Demodulation Reference Signal (DMRS) configuration; and determining beamforming weights to be used for beamforming at the base station based on the estimated channels.

16. The non-transitory computer readable medium according to claim 15, wherein when the assistance information is the filter coefficients, the operation of obtaining the assistance information comprises: calculating, at the O-DU, the filter coefficients for the one or more UEs based on historical data associated with the one or more UEs, wherein the historical data comprises historical SRS over a pre-defined period of time; and transmitting the calculated filter coefficients to an Open Radio Unit (O-RU) associated with the base station.

17. The non-transitory computer readable medium according to claim 16, wherein when the assistance information is the filter coefficients, the operation of deriving the filter coefficients comprises directly using the filter coefficients calculated by the O-DU.

18. The non-transitory computer readable medium according to claim 15, wherein when the assistance information is information associated with the SRS configurations, the operation of obtaining the assistance information comprises: receiving, at an Open Radio Unit (O-RU), the SRS configurations from the O-DU; and receiving, at the O-RU, a mapping between the SRS configurations and corresponding UEs among the one or more UEs.

19. The non-transitory computer readable medium according to claim 18, wherein when the assistance information is the information associated with the SRS configurations, the operation of deriving the filter coefficients comprises: calculating, at the O-RU, the filter coefficients based on the received SRS configurations and the received mapping between the SRS configurations and the corresponding UEs.

20. The non-transitory computer readable medium according to claim 15, wherein the operation of applying the spatial filtering based on the derived filter coefficients comprises applying the filter coefficients for a corresponding frequency block having a pre-defined number of Physical Resource Blocks (PRBs), and wherein each of the filter coefficients and the information associated with the SRS configurations is received via one of a section type message or a section extension message.

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