Multi-user multiple-input and multiple output using master unit

Abstract

A master unit is configured to: receive resource blocks from distributed unit; receive channel estimates or suggested beamforming weights from distributed unit; examine: (1) channel estimates to associate coefficients with corresponding antenna elements of radio units or (2) suggested beamforming weights to associate coefficients with corresponding antenna elements of radio units; select subset of antenna elements corresponding to: (1) subset of coefficients of channel estimates having highest magnitudes or (2) subset of coefficients of suggested beamforming weights having highest magnitudes; determine derived beamforming weights based on: (1) subset of coefficients of channel estimates having highest magnitudes or (2) subset of coefficients of suggested beamforming weights having highest magnitudes; apply derived beamforming weights to resource blocks; and transport resource blocks to remote units having antenna elements corresponding to: (1) subset of coefficients of channel estimates having highest magnitudes or (2) subset of coefficients of suggested beamforming weights having highest magnitudes.

Description

MULTI-USER MULTIPLE-INPUT ANDMULTIPLE OUTPUT USING MASTER UNITCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Indian Provisional Patent Application Serial No. 202441002806, filed on January 15, 2024 and entitled “SMART REUSE USING MASTER UNIT”, which is hereby incorporated herein by reference in its entirety.BACKGROUND

[0002] The O-RAN Alliance promulgates a group of specifications for implementing radio access networks in an open manner. (“O-RAN” is acronym for “Open RAN ”) In O-RAN, each base station is typically implemented in a disaggregated manner in which each base station is partitioned into at least one central unit (CU), at least one distributed unit (DU), and one or more radio units (RUs). Each CU typically implements Layer 3 and non-time critical Layer 2 functions for the associated base station. Each DU is typically configured to implement the time critical Layer 2 functions and at least some of the Layer 1 (also referred to as the Physical Layer) functions for the associated base station. Each RU is typically configured to implement the radio frequency (RF) interface and the physical layer functions for the associated base station that are not implemented in the DU.SUMMARY

[0003] A master unit for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO) comprises circuitry configured to: receive resource blocks from a distributed unit of the open radio access network implementing multiuser multiple-input and multiple-output (MU-MIMO); receive channel estimates or suggested beamforming weights from the distributed unit; examine one of (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates havingthe highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0004] A method for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO) comprises: receiving, at a master unit of the open radio access network, resource blocks from a distributed unit; receiving, at the master unit, channel estimates or suggested beamforming weights from the distributed unit; examining, at the master unit, one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determining, at the master unit, derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; applying the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0005] An open radio access network implementing multi-user multiple-input and multipleoutput (MU-MIMO), the open radio access network comprising: a plurality of radio units, wherein each of the plurality of radio units includes first circuitry for exchanging radio frequency signals with at least one user equipment; and a master unit communicatively coupled to the plurality of radio units, the master unit including second circuitry configured to: receive resource blocks from a distributed unit; receive channel estimates or suggested beamforming weights from the distributed unit; examine one of: (1) the channel estimates toassociate first coefficients of the channel estimates with corresponding respective antenna elements of the plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units of the plurality of radio units, the subset of radio units having the subset of antenna elements corresponding to:(1) the first subset of coefficients of the channel estimates having the highest magnitudes or(2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.BRIEF DESCRIPTION OF DRAWINGS

[0006] Understanding that the drawings depict only exemplary configurations and are not therefore to be considered limiting in scope, the exemplary configurations will be described with additional specificity and detail through the use of the accompanying drawings, in which:

[0007] Figures 1A-1B are block diagrams illustrating an exemplary embodiment of a communication system in which the techniques described below can be used.

[0008] Figure 2 is a block diagram illustrating an example communication system that includes a portion of the broader communication system shown in Figures 1 A-1B.

[0009] Figures 3-3B are flow diagram illustrating exemplary methods for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU- MIMO).

[0010] In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the exemplary configurations.DETAILED DESCRIPTION

[0011] In 0-RAN, each base station is typically implemented in a disaggregated manner in which each base station is partitioned into at least one central unit (CU), at least onedistributed unit (DU), and one or more radio units (RUs). Used herein, the term “north” or “northbound” means “upstream” or toward a core network, while the term and the term “south” or “southbound” means “downstream” or toward the one or more RUs.

[0012] The O-RAN specifications define a “shared cell” configuration or implementation in which a single cell is served using multiple RUs. The O-RAN shared cell implementation attempts to make more efficient use of bandwidth to and from DUs (compared to O-RAN 1.0) in order to support communicating front-haul data with the multiple RUs. The O-RAN shared cell implementation is described in detail at Section 13 “Support of Shared Cell” in the O-RAN Working Group 4 (Open Fronthaul Interfaces WG) Control, User and Synchronization Plane Specification version 10.0 from October 2022 (O-RAN.WG4.CUS.0- vlO.OO, hereinafter “Support of Shared Cell O-RAN Specification”, available at pages 252- 270 of PDF at https: / / orandownloadsweb. azurewebsites. net / download?id=364).

[0013] In the O-RAN shared cell implementation, there are generally two modes of operation in the fronthaul: Fronthaul Multiplexer (FHM) mode and Cascade mode. Examples implementing a shared cell include a FHM in order to more efficiently support one-DU-to- many-RU mapping. In examples, the FHM: (1) replicates the downlink packet stream (from the DU) for each RU; and (2) uses combining / digital summation on the uplink packet stream from the RUs (before sending to the DU). The combining / digital summation includes: (1) adding the corresponding in-phase (I) samples in corresponding physical resource blocks (PRBs) (from all the RUs); (2) adding the corresponding quadrature-phase (Q) samples in corresponding PRBs (from all the RUs); and (3) sending a combined stream of I / Q data from the FHM to the DU. The combining / digital summation may optionally include some overflow management. Using the shared cell implementation, the DU can send and receive a single packet stream (with a bandwidth of approximately N PRBs) instead of M packet streams (one for each RU with a total bandwidth of approximately N PRBs x M RUs).

[0014] A FHM may be limited in how many RUs can connect to it (such as no more than 8 RUs in examples). In examples, multiple FHM are cascaded and / or branched from one another to support larger quantities of RUs. In examples, each FHM only implements fronthaul transport functionality and does not include radio functionality for transmitting and receiving RF signals with UEs. In examples, multicast is used in the downlink to reduce fronthaul bandwidth and unicast is used in the uplink.

[0015] O-RAN does not currently consider reuse scenarios and its DU-RU interface is not defined for efficient implementation of reuse. As used herein, reuse refers to the same frequency resource(s) being used for multiple sets of UEs, each set of UEs being under adifferent, geographically diverse set of RUs. In examples, single physical cell identity (PCI) and reuse can be performed using the existing O-RAN defined interface to maintain O-RAN compliance. In examples, intelligence is added to a virtual Master Unit (vMU) or other Master Unit (MU) to interoperate with a multi-user multiple-input and multiple-output (MU- MIMO) capable DU while keeping the MU-MIMO capable DU agnostic to the distributed nature of RUs. In examples, the MU-MIMO capable DU is a Sounding Reference Signal (SRS) based MU-MIMO DU. In examples, the MU-MIMO capable DU is a Channel Start Information Reference Signal (CSI-RS) based MU-MIMO DU. In examples, an O-RAN interface is used between the DU and the vMU. In examples, the DU and the vMU support beamforming approaches defined by O-RAN.

[0016] In conventional MU-MIMO, the MU-MIMO DU has a co-located array of antennas at an O-RU. In conventional MU-MIMO, the MU-MIMO DU assumes that at the O-RU there is a co-located antenna array that is calibrated to support coherent beamforming for MU-MIMO. In conventional MU-MIMO, the base station (BS) decides on resources to be allocated to the UEs in the MU-MIMO and the number of layers for each UE. In conventional MU-MIMO, the base station defines the precoder matrix (or beam weight sets) for the antenna array. In conventional MU-MIMO, the base station does channel estimation and precoder determination based on: (1) periodic SRS from UEs; and / or (2) UE CSI reports. In conventional MU-MIMO, the base station may utilize various beamforming algorithms, such as maximum ratio transmission (MRT), zero-forcing (ZF), regularized zero-forcing (RZF), etc.

[0017] In conventional MU-MIMO, a grouping selection is performed by a DU to select UEs. In examples, the grouping selection performed by a DU for selecting the UEs is complex and is based on stacked channel estimates Ge and the cross correlation of a matrix where Ge is a stacked set of channel matrices. In examples, each UE has a channel matrix between its antennas and the antennas of the base station which in the case of distributed RUs there would be at least one set of rows or columns of antennas (such as two antennas, four antennas, or greater quantities of antennas) for each RU. So, each UE has such a channel matrix and the DU operations are based on stacking a set of channel matrices. In examples, when the DU is going to determine a subset of a group of UEs to put in reuse, it stacks the channel matrices for the entire group into one composite matrix Ge and selects the subset for reuse based on cross-correlation R = GeGe’, which gives the cross correlation between the channel matrices for each pair of individual UEs in the group. The DU selects for reuse a subset of the group of UEs for which each pair- wise cross-correlation is low, for each pair ofUEs in the subset. RZF beamforming weights are calculated based on a stacked BF = Ge’(R+o-2 i)-i.

[0018] In examples, O-RAN defines four beamforming methods for beam management, including: (1) predefined beamforming; (2) channel information based beamforming; (3) weight based beamforming; and (4) attribute based beamforming. In examples, any of predefined beamforming, channel information based beamforming, and weight based beamforming can be used with distributed RUs. In examples, different Synchronization Signal Blocks (SSBs) or Channel Start Information Reference Signal (CSI-RS) is associated or transmitted with different beams.

[0019] In examples using predefined beamforming, the beams are pre-defined in the O-RU and can be applied in either the frequency domain (applicable to MU-MIMO) or time domain (analog beam steering) and the DU associates different Synchronization Signal Blocks (SSBs) or Channel Start Information Reference Signal (CSI-RS) to each beam. In examples using predefined beamforming, the beam management system is not aware of the specifics of the beams and the beam system is just able to determine which beams it wants to use for specific RU by way of using different beams for different Channel Start Information Reference Signal (CSI-RS) and then from the feedback from the UE knows which beams are preferred.

[0020] In examples using channel information based beamforming, the channel information is passed to the RU via O-RAN Section Type 6. In examples using channel information based beamforming, the master unit forwards from the RU PRB particular for SRS to the DU and the DU estimates the channels from the SRS and uses this as a basis for selecting UEs to be put in reuse with multi user MIMO and for calculating the appropriate beams to use which are dependent on the specific UEs that are put in reuse. In examples using channel information based beamforming, the DU assumes the MU or RU calculate the beamforming. In examples using channel information based beamforming, the DU expects coherent phase information in these channels and specific phase information incorporated into the beamforming weights in order to cancel interference that would otherwise be there with this reuse. In examples using channel information based beamforming, the DU periodically sends the channel per UE (identified by Ueld) over the C-plane to the O-RU which stores it and keeps it updated. In examples using channel information based beamforming, the DU also indicates the Ueld(s) corresponding to the data (C-plane). In examples using channel information based beamforming, the O-RU determines the appropriate precoder / beamforming weights based on the channel(s) of the UE(s).

[0021] In examples using weight-based beamforming, the O-DU configures the beamforming weights per beam-id. In examples using attribute based dynamic beamforming, it is necessary to specify azimuth, zenith, etc. for each beam.

[0022] In conventional approaches for MU-MIMO based on uplink (UL) channel estimates / reciprocity, the base station (BS) estimates the uplink (UL) channel matrix (He) for each base station (BS) antenna element for each UE based on reception of its assigned SRS at a specific periodicity (Tsrs) of the sounding reference signal (SRS). In conventional approaches, the base station (BS) selects a group of UEs for reuse by selecting low crosscorrelations among their uplink (UL) channel matrix (He). In examples, low cross correlation is indicative of a good candidates UEs to put in reuse. In examples, the base station (BS) computes the beamforming weights based on the uplink (UL) channel matrix (He) using a beamforming algorithm (such as maximum ratio transmission (MRT), zeroforcing (ZF), regularized zero-forcing (RZF), etc.) to eliminate or reduce reuse interference associated with the correlation. In examples, this methodology can be used for base stations with either distributed RUs or a collocated array.

[0023] Conventional coherent selection of beamforming is complex and it’s interference rejection performance is sensitive to uplink (UL) / downlink (DL) channel mismatch due to either: (1) clock error that varies over the base station (BS) antenna elements which leads to mismatch between the uplink and downlink channels (which is particularly challenging for distributed RUs); or (2) channel aging due during Tsrs due to mobility of the UE such that the SRS is aged out by the time you use it to construct beams. In examples, when the DU calculates a set of beams based on the uplink channel matrices estimates it has, these are not particularly well matched to the actual channel in the downlink in the presence of these errors. This is particularly challenging for distributed RUs.

[0024] In noncoherent examples, once a master unit (MU) receives either the channel estimates or the actual beamforming weights from the DU, the MU can identify the UE’s primary radio point(s) (RP(s)). In examples, beamforming weight is 1 in primary RPs and 0 in other RPs. In examples, given beamforming weights, a group of UEs for MU-MIMO is selected for low signal to interference (SIR) ratio based on |He|2. In examples, there is less capacity density potential for noncoherent systems than coherent systems, but the noncoherent systems exhibit much less sensitivity to clock errors and UE mobility.

[0025] Figures 1A-1B are block diagrams illustrating an example of a communication system 100. Figure 1 A shows a general example using a master unit (MU) 106, while Figure IB shows a specific example using a virtual master unit (vMU) 106. In the example shownin Figures 1A-1B, the communication system 100 is implemented using an O-RAN or other point-to-multipoint distributed base station architecture. The communication system 100 may also be referred to here as a “O-RAN” or a “O-RAN system.” In examples, communication system 100 includes at least one central unit (CU or O-CU) 102, at least one distributed unit (DU or O-DU) 104, at least one master unit (MU or vMU) 106, and at least one radio unit (RU or O-RU) 108 (such as radio unit (RU or O-RU) 108-1 and any quantity of optional radio unit (RU or O-RU) 108-2 through optional radio unit (RU or O-RU) 108- A) configured to serve at least one user equipment (UE) 112 within the site at which wireless services is being provided.

[0026] In examples, the at least one CU 102, at least one DU 104, and at least one RU 108 implement a “base station”, “base station entity”, or “base station system” (which in the context of a fourth generation (4G) Long Term Evolution (LTE) system, may also be referred to as an “evolved NodeB”, “eNodeB”, or “eNB”; in the context of a fifth generation (5G) New Radio (NR) system, may also be referred to as a “gNodeB” or “gNB”; and may take different names in other current or future generations of radio access networks (RAN) and communication networks). In examples, the at least one CU 102 and / or at least one DU 104 are located remotely from the site at which wireless service is being provided, e.g., in centralized banks of nodes. Additionally, the RUs 108 may be physically separated from each other at the site at which wireless service is being provided, although they are each communicatively coupled to at least one DU 104 via at least one fronthaul network 120. A base station may be used to provide UEs 112 with mobile access to the wireless network operator's core network 114 to enable UEs 112 to wirelessly communicate data and voice (using, for example, Voice over LTE (VoLTE) technology or a 3GPP 5G RAN providing wireless service using a 5G air interface, Internet of Things (loT), Ultra Reliable Low Latency Communications (URLLC), etc.).

[0027] In examples, the communication system 100 implements a base station as a respective 5G NR gNB (only one of which is shown in Figures 1 A-1B for ease of illustration). In such a configuration, each CU 102 implements Layer 3 and non-time critical Layer 2 functions for the 5G NR gNB. In examples, each CU 102 may be further partitioned into at least one control-plane entity (“CU-CP”) and at least one user-plane entity (“CU-UP”) that handle the control-plane and user-plane processing of the CU 102, respectively. In examples, each DU 104 is configured to implement the time critical Layer 2 functions and, except as described below, at least some of the Layer 1 functions for the gNB. In this example, the master unit (MU) 106 in Figure 1 A and more specifically the virtual master unit(vMU) 106 in Figure IB is connected between the DU 104 and each RU 108. In examples, the MU / vMU 106 manipulates uplink signals transmitted to the DU 104 and transforms signals from the DU 104 to support reuse with the distributed RUs 108 even though the DU 104 is not aware of the distributed RUs 108 and remains configured as if there is an antenna array at an 0-RU (rather than distributed RUs 108). In this example, each RU 108 is configured to implement the physical layer functions for the gNB that are not implemented in the DU 104 or MU / vMU 106 as well as the RF interface. Also, each RU 108 includes or is coupled to a respective set of one or more antennas 110 (such as any of antenna(s) 110-1, antennas(s) 110-2, antennas(s) 110-3, and any quantity of antennas 110-4 through 110- A) used to radiate downlink RF signals to UEs 112 and receive uplink RF signals transmitted by UEs 112. In examples, precoding is performed on each antenna 110 within a respective set of one or more antennas 110 for each RU 108. In examples, the precoder weights (derived beamforming weights) used for a given UE and a respective RU 108 is either derived from the channel estimates or suggested beamforming weights provided by the distributed unit (DU) 104 or selected arbitrarily.

[0028] In general, the communication system 100 is configured to provide wireless service to various items of user equipment (UEs) 112 (such as user equipment (UE) 112-1 and any quantity of optional user equipment (UE) 112-2 through optional user equipment (UE) 112- B). Unless explicitly stated to the contrary, references to Layer 1, Layer 2, Layer 3, and other or equivalent layers (such as the Physical Layer or the Media Access Control (MAC) Layer) refer to layers of the particular wireless interface (for example, Fourth Generation (4G) Long Term Evolution (LTE) or Fifth Generation (5G) New Radio (NR)) used for wirelessly communicating with UEs 112. Furthermore, it is also to be understood that 5G NR embodiments can be used in both standalone and non- standalone modes (or other modes developed in the future) and the following description is not intended to be limited to any particular mode. Moreover, although some embodiments are described here as being implemented for use with 5GNR, other embodiments can be implemented for use with other wireless interfaces and the following description is not intended to be limited to any particular wireless interface.

[0029] In examples, the at least one CU 102 is communicatively coupled to at least one corresponding core network 114 of the associated wireless operator via at least one backhaul network 116. The at least one backhaul network 116 is typically a public wide area network such as the Internet, though it is understood that the at least one backhaul network 116 can be implemented in other ways. In examples, at least one DU 104 is communicatively coupled toat least one CU 102 via at least one midhaul network 118. In examples, the midhaul interface promulgated by the O-RAN Alliance is used for the at least one midhaul network 118 between the DU 104 and the at least one CU 102. In examples, at least one RU 108 is communicatively coupled to at least one DU 104 via at least one fronthaul network 120. In examples, the fronthaul interface promulgated by the O-RAN Alliance is used for the at least one fronthaul network 120 between each RU 108 and a respective DU 104. In examples, each of the at least one backhaul network 116, the at least one midhaul network 118, and / or the at least one fronthaul network 120 may be implemented with one or more switches, routers, and / or other networking devices. In some examples, the at least one backhaul network 116, the at least one midhaul network 118, and / or the at least one fronthaul network 120 may be implemented with switched Ethernet using a switched Ethernet network and an Ethernet switch.

[0030] Although Figures 1 A-1B (and the description set forth herein more generally) are described in the context of 5G embodiments where each logical base station entity is partitioned into a CU 102, DUs 104, and RUs 108 and, for at least some of the physical channels, some physical-layer processing is performed in the DUs 104 with the remaining physical-layer processing being performed in the RUs 108, it is to be understood that the techniques described here can be used with other wireless interfaces (for example, 4G LTE) and with other ways of implementing a base station entity (for example, using a conventional baseband band unit (BBU) / remote radio head (RRH) architecture). Accordingly, references to a CU, DU, MU, or RU in this description and associated figures can also be considered to refer more generally to any entity (including, for example, any “base station” or “RAN” entity) implementing any of the functions or features described here as being implemented by a CU, DU, MU, or RU.

[0031] Each CU 102, DU 104, MU 106, and RU 108, and any of the specific features described here as being implemented thereby, can be implemented in hardware, software, or combinations of hardware and software, and the various implementations (whether hardware, software, or combinations of hardware and software) can also be referred to generally as “circuitry,” a “circuit,” or “circuits” that is or are configured to implement at least some of the associated functionality. When implemented in software, such software can be implemented in software or firmware executing on one or more suitable programmable processors (or other programmable device) or configuring a programmable device (for example, processors or devices included in or used to implement special-purpose hardware, general-purpose hardware, and / or a virtual platform). In such a software example, thesoftware can comprise program instructions that are stored (or otherwise embodied) on or in an appropriate non-transitory storage medium or media (such as flash or other non-volatile memory, magnetic disc drives, and / or optical disc drives) from which at least a portion of the program instructions are read by the programmable processor or device for execution thereby (and / or for otherwise configuring such processor or device) in order for the processor or device to perform one or more functions described here as being implemented by the software. Such hardware or software (or portions thereof) can be implemented in other ways (for example, in a field programmable gate array (FPGA), application specific integrated circuit (ASIC), etc.).

[0032] Moreover, each CU 102, DU 104, MU 106, and RU 108, can be implemented as a physical network function (PNF) (for example, using dedicated physical programmable devices and other circuitry) and / or a virtual network function (VNF) (for example, using one or more general purpose servers (possibly with hardware acceleration) in a scalable cloud environment and in different locations within an operator’s network (for example, in the operator’s “edge cloud” or “central cloud”). Each VNF can be implemented using hardware virtualization, operating system virtualization (also referred to as containerization), and application virtualization as well as various combinations of two or more the preceding. Where containerization is used to implement a VNF, it may also be referred to as a “containerized network function” (CNF). For example, in the exemplary embodiment shown in Figures 1 A-1B, each RU 108 is implemented as a PNF and is deployed in or near a physical location where radio coverage is to be provided and each CU 102, DU 104, and MU 106 are implemented using a respective set of one or more VNFs deployed in a distributed manner within one or more clouds (for example, within an “edge” cloud or “central” cloud). Each CU 102, DU 104, MU 106, and RU 108, and any of the specific features described here as being implemented thereby, can be implemented in other ways.

[0033] The links shown in the communication system 100 could be implemented with one or more switches, routers, and / or other networking devices. The physical links between devices in the at least one backhaul network 116, the at least one midhaul network 118, and / or the at least one fronthaul network 120 may be implemented using different media, such as conductive media (copper, multi-rate, multi-mode cables, etc.) and optical media (fiber optic cables). In examples, each RU 108 and each physical node on which each DU 104 is implemented includes one or more Ethernet network interfaces to couple each RU 108 and each physical node implementing the DU 104 and / or the MU 106 to the at least onefronthaul network 120 in order to facilitate communications between the DU 104 and / or MU 106 and the RUs 108.

[0034] The RUs 108 may be deployed at a site to provide wireless coverage and capacity for one or more wireless network operators. The site at which wireless service is being provided may cover, for example, a building or campus or other grouping of buildings (used, for example, by one or more businesses, governments, other enterprise entities) or some other public venue (such as a hotel, resort, amusement park, hospital, shopping center, university campus, arena, or an outdoor area such as a ski area, stadium or a densely populated downtown area). In some configurations, the site at which wireless service is being provided is at least partially (and optionally entirely) indoors, but other alternatives are possible.

[0035] Each UE 112 may be a computing device with at least one processor that executes instructions stored in memory, e.g., a mobile phone, tablet computer, mobile media device, mobile gaming device, laptop computer, vehicle-based computer, a desktop computer, etc.

[0036] Each CU 102, DU 104, MU 106, and RU 108 can be implemented so as to use an air interface that supports one or more of frequency-division duplexing (FDD) and / or timedivision duplexing (TDD). Also, the CU 102, DU(s) 104, MU(s) 106, and RUs 108 can be implemented to use an air interface that supports one or more of the multiple-input-multiple- output (MIMO), single-input-single-output (SISO), single-input-multiple-output (SIMO), and / or beamforming schemes. For example, the CU 102, DU(s) 104, MU(s) 106, and RUs 108 can implement one or more of the 5G NR transmission modes. Moreover, the communication system 100 can be configured to support multiple air interfaces and / or to support multiple wireless operators.

[0037] In examples in the downlink, the DU 104 communicates downlink control-plane messages, downlink user-plane messages, and uplink control-plane messages to the MU 106, which copies and forwards the downlink control-plane messages, downlink user-plane messages, and uplink control-plane messages toward the RUs 108. RUs 108 use the downlink control-plane messages and downlink user-plane messages to wirelessly transmit / receive / exchange radio frequency signals using a respective set of antennas 110 for reception by UEs 112.

[0038] In examples in the uplink, the MU 106 combines user data received from the RUs 108. RUs 108 wirelessly receive data on air media using an antenna. In examples, the combining is an uplink summation. In examples, the combining is uplink coherent combining that requires phase information for the data.

[0039] In examples in the uplink, for each uplink slot, the serving DU schedules one or more UEs to transmit during that slot. In examples, the DU sends uplink control-plane messages to each RU identifying the resource blocks (RBs) for which the RU should provide baseband IQ data. The RBs for which the RU should provide baseband IQ data are also referred to here as “front-hauled RBs.”

[0040] In embodiments where the baseband IQ data communicated over the fronthaul comprises frequency-domain baseband IQ data, the front-hauled RBs comprise only those RBs that have been assigned to the scheduled UEs 112 for uplink transmissions during that slot. In embodiments where the baseband IQ data communicated over the fronthaul comprises time-domain baseband IQ data, the front-hauled RBs comprise all of the RBs for the slot (due to the time-domain nature of the baseband IQ data). During each uplink slot, for each antenna port, each RU 108 generates respective baseband IQ data for each front-hauled RB from a uplink RF analog signal received via a respective one of the antennas associated with that RU 108. For each RU 108, for each uplink slot, the RU 108 generates uplink userplane message that include the baseband IQ data generated at that RU 108 for the various front-hauled RBs and antenna ports and communicates the uplink user-plane messages northbound.

[0041] Each CU 102, DU 104, MU 106, and RU 108, and any of the specific features described here as being implemented thereby, can be implemented in other ways. Additionally, it should be noted that the systems and methods described herein may also be used in other distributed RANs, e.g., a distributed antenna system (DAS).

[0042] Figure 2 is a block diagram illustrating an example of a communication system 200. In the example shown in Figure 2, the communication system 200 is implemented using an 0-RAN or other point-to-multipoint distributed base station architecture. In examples, communication system 200 includes a distributed unit (DU or 0-DU) 202 (which can be an implementation of DU 104 in Figure 1 A or Figure IB as described herein), at least one master unit (MU) 204 (which can be an implementation of an MU 106 in Figure 1 A or a virtual MU (vMU) 106 in Figure IB as described herein), and a plurality of radio units (RUs or O-RUs) 206 (such as radio unit (RU or 0-RU) 206-1, radio unit (RU or 0-RU) 206-2, and any quantity of optional radio unit (RU or 0-RU) 206-3 through optional radio unit (RU or 0-RU) 206-C which can be implementations of RU 108 in Figure 1 A or Figure IB as described herein) configured to serve at least one user equipment (UE) 208 (such as user equipment (UE) 208-1 through user equipment (UE) 208-D which can be implementations ofUE 112 in Figure 1 A or Figure IB as described herein). In examples, the at least one master unit (MU) 204 is communicatively coupled to the DU 202 through a fronthaul network 210.

[0043] In examples, a RU 206-1 is communicatively coupled to the master unit (MU) 204 via a communication link 212-1 such that the RU 206-1 is communicatively coupled to the DU 202 via the master unit (MU) 204. In examples, a RU 206-2 is communicatively coupled to the master unit (MU) 204 via a communication link 212-2 such that the RU 206-2 is communicatively coupled to the DU 202 via the master unit (MU) 204. In examples, any additional RU 206 are communicatively coupled to the master unit (MU) 204 via communication link 212 such that the RU 206 is communicatively coupled to the DU 202 via the master unit (MU) 204.

[0044] In examples, the DU 202 is performing Sounding Reference Signal (SRS) based MU-MIMO. In examples, the DU 202 is performing Channel Start Information Reference Signal (CSI-RS) based MU-MIMO. In examples, the DU 202 determines multi-user UEs 208 to put into reuse and the number of layers for each UE 208. In examples, the DU 202 selects the UEs 208 to put in reuse based on channel estimates derived by the SRS and then provides the UE 208 selections to the MU 204. In examples, the number of layers is capped by the maximum layers for the particular RU 206. In examples, the DU 202 conveys channel information to the MU 204 using O-RAN functional split Option 2. In other examples, the DU 202 conveys channel information to the MU 204 using other functional split options (such as Option 1, Option 3, Option 4, Option 5, Option 6, Option 7, Option 8, or any other functional split option number) or in other ways. In examples, the MU 204 defines noncoherent simulcast RUs 206 from the channel information received from the DU 202. In examples, the non-coherent simulcast RUs 206 are defined using Quantized Signature Vectors (QSVs). In examples, the MU 204 is aware of the decisions for the UE 208 selections that have been scheduled in reuse and their resource blocks and the MU 204 provides the channel estimates. In examples, the MU 204 keeps the DU 202 updated with channel estimates for the UEs 208 or it passes along the suggested beamforming weights. In examples, the DU 202 remains agnostic to non-coherent transmissions from the RUs 206 and is expecting it is interfacing with a single O-RU with an antenna array. In examples, no changes need to be made to the O-RAN standards compliant RUs 206. In examples, the RUs 206 operate in O-RAN 7.2-A mode. In examples, communication between the DU 202 and the MU 204 is compliant with O-RAN 7.2-B mode. In examples, communication between the MU 204 and the RUs 206 is compliant with O-RAN 7.2-A mode. In examples, theinterface between DU 202 and the MU 204 is compliant with O-RAN option 7.3 or O-RAN Uplink Performance Improvement (ULPI).

[0045] In examples, the RUs 206 are updated with either channel estimates. In examples, dynamic suggested beamforming weights are sent to the master unit. In examples, the combination of the MU 204 and RUs 206 appears as a category B RU to the DU 202 (where category B RUs are RUs that determine the precoder matrix (or beam weight set) for the antenna array). This results in the DU 202 being configured as if it is communicating with an O-RU that has an antenna array, when in fact the DU 202 is transporting data with the MU 204 as part of a distributed antenna system with the RUs 206 where the MU 204 transports data between itself and the RUs 206 over fronthaul. In examples, the RUs 206 are category A RUs (where Category A RUs are RUs that do not determine the precoder matrix (or beam weight set) for the antenna array).

[0046] In examples, the MU 204 receives either the transport blocks or resource blocks and either channel estimates or suggested beamforming weights from the DU 202. In examples, the DU 202 calculates the suggested beamforming weights from the channel estimates and then passes the suggested beamforming weights to the MU 204. In examples, the DU passes the calculated channel estimates to the MU 204 and the MU derives the coefficients for the suggested beamforming weights. In examples, the MU 204 generates resource blocks and communicates the resource blocks to the RU(s) 206 (which are O-RAN 7.2 compliant RUs). In examples, the MU 204 examines either (1) the channel estimates for the UEs 208 that are put in reuse for a given transmission time interval (TTI); or (2) the beamforming weight. In examples, the DU 202 sends beam IDs to the MU 204. In examples, the MU 204 then identifies each coefficient (of the channel estimates or the beamforming weight) that corresponds to an antenna element that the MU 204 knows this mapping and selects all the number of antenna elements used which have the highest coefficients in either the channel estimates or suggested beamforming weights and the corresponding RU(s) 206 are the RU(s) 206 to which the resource blocks are transported to for each specific EU 208. In examples, each specific UE 208 has a respective set of RU(s) 206 and within the channel estimates for the respective set of RU(s) 206 is a channel estimate that the MU 204 ascertains is closest to the UE 208. In examples, those RU(s) with the channel estimate that is MU 204 ascertains is closest to the UE 208 are the RU(s) which receive the transport blocks. In examples, reuse can be applied to the uplink (UL) traffic of multiple UEs 208 using a similar approach.

[0047] In examples, the DU 202 is still configured to exchange data with an RU with an antenna array and DU 202 expects either (1) that the antenna array of the RU is applying thecoherent weights to the data; or (2) that the RU computes the suggested beamforming weights based on the channel estimates. In examples, either the DU 202 passes along the channel matrixes (Ge) or passes along the suggested beamforming weights such that the MU 204 has access to the channel matrix or the beamforming weight for the UE(s) 208. In examples, the MU 204 simply picks out the highest magnitude terms in the channel matrix or the beamforming weight matrix and those terms correspond to a known RU 206 for that UE 208. In examples, a high magnitude means that the UE 208 is close to the particular RU 206 and the transport box for that UE 208 is set only to that RU 206 for transmission and no other RUs 206 receive or transmit for that UE 208. In examples, a set of highest magnitude coefficients are selected and applied to the resources blocks. In examples, the resources blocks are transported to a set of radio units having the set of antenna elements corresponding to the set of highest magnitude coefficients.

[0048] In examples, a first UE 208 is selected by the MU 204 (such as by using a roundrobin approach, Proportional Fair (PF) scheduling, or Quality of Service (QoS) scheduling) to ensure that each UE 208 gets a fair scheduling rate that is at least the same scheduling rate as with SU-MIMO. In examples, subsequent UE(s) 208 are selected based on the uplink (UL) channel matrices to get low coherent cross-correlation or high noncoherent signal to interference (SIR) ratio. In examples where the DU 202 receives information about the UE 208 selection, the DU 202 can select UE(s) 208 for a high noncoherent SIR and the UE 208 gets extra scheduling opportunities in the schedule according to its separation from the other UEs 208. In examples, if a particular UE 208 is highly separated from the other UEs 208, then the particular UE 208 will get additional scheduling opportunities, though every UE 208 gets a fair number of scheduling opportunities.

[0049] In examples, each RUs 206 are not aware of what the other RUs 206 are doing. In examples, multicast is used from the MU 204 to the RU 206 so that a given set of data is received only by the RU 206 that will use it and does not go to other RUs 206 that the data is not intended for. In examples, the selection occurs in a near-real time RAN Intelligent Controller (RIC) that is performing some MU-MIMO optimizations. In examples, the computations for the selection may occur every TTI because there could be a new set of UEs 208 ever TTI and there could potentially be a new set of suggested beamforming weights. In examples, the suggested beamforming weights need to be examined to quickly determine which RUs 206 are to receive which transport blocks and PRBs so that transport can be executed and then they can start again the next TTI (which may a short time thereafter, such as only 500 microseconds later).

[0050] In examples, the simulcast groups can change every TTI and may even potentially change within a TTI. In examples, precoder resource block groups include some number of resource blocks which support the same UEs 208 for reuse and use the same beamforming weights or simulcast group over the PRBs in that group. In examples, it changes in the next group such you can have a different set of UEs 208 in reuse for the next group and potentially even have the same UEs 208 put in reuse in the two different groups. In examples, a different RU 206 is simulcast in that next group than in the first group. In examples, changes to the simulcast zone for a UE 208 occur even across the PRB groups’ TTIs. In examples, different UEs are put into reuse from one TTI to the next and a different set of simulcast groups is used from one TTI to the next.

[0051] In examples, when a UE 208 connects to a 5G or LTE cell, the UE 208 is provided resources (including Sounding Reference Signal (SRS) resources). In examples, the assigned resource (such as a time domain or frequency domain resource) for a UE 208 has the opportunity to transmit uplink an SRS signal wideband, from which the base station is able to derive a channel estimate. In examples, the SRS provides information in the uplink to the DU 202 by way of the RU 206 and the MU 204. In examples, the resource blocks in which UEs 208 you have receptions of UEs 208 SRS transmissions and that is the basis in the DU 202 when it received these resource block groups, it processes them in order to determine channel estimates for the UEs 208. In examples, resource block groups for a particular TTI and channel estimates are used as the basis for selecting the UEs 208 to put in reuse. In examples, suggested beamforming weights are used as basis for selecting the UEs to put in reuse.

[0052] In examples, the process of selecting UEs 208 is based on the correlation. In examples, the mutual cross correlations of each of the UEs 208 is analyzed. In examples, where the cross correlation is low between UEs, those are good candidate UEs 208 for being put in reuse together. In examples, the DU 202 searches for UEs 208 that have low correlation in order to put them in reuse. In examples where two UEs 208 are under different RUs 206, the power and the channel matrices are in two different RUs 206. In examples, when you cross corelate those, you get low correlation there as well even with the noncoherent beamforming approach.

[0053] In examples, the DU 202 communicates with the MU 204 as if it were a single RU and then the MU 204 performs the mapping to get it to the right RUs 206. In examples, the DU 202 is not aware that there is further splitting apart and transmission to the separate RUs 206. In examples, the system 200 has a higher SIR than conventional approach usingcoherent beamforming, except for very small differential RU 206 clock errors and small channel age. In examples, the distributed RUs 206 are less sensitive to clock errors than the conventional coherent selection and beamforming that is highly sensitive to clock errors. In examples, the distributed RUs 206 are also less sensitive to doppler effects. In examples, when a UE 208 transmits an SRS and then moves away from the position in which it originally transmitted the SRS, the channel has changed and so the coherent computation of the suggested beamforming weights is no longer well matched to the downlink channel that exists at the later time following the SRS. In examples, UE selection based on the channel matrix correlation has a lower SIR than UE selection based on the conventional coherent selection, but still performs well.

[0054] In examples, the system 200 can support a conventional DU 202 that selects UEs 208 for MU-MIMO and shares channel information with the RU 206, expecting the RU 206 to apply the beamforming. In examples, the system 200 applies unicast / simulcast transmission for the UEs 208 to their respective primary RUs 206 as determined from the channel estimates. In examples, any transmission initiated to any given UE 208 from its associated RUs 206 results in low interference for any other UE 208 scheduled on the same time or frequency resources. In examples, the system 200 is less complex and has more robust performance compared to conventional coherent selection and beamforming. In examples, much of the SIR benefit and robustness is lost if the DU 202 performs UE selection based on coherent channel cross-correlation without limiting the selections.

[0055] Figures 3-3B are flow diagram illustrating exemplary methods 300-300B for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO). Figure 3 shows example method 300 that broadly covers examples using channel estimates or suggested beamforming weights. Figure 3 A shows example method 300A that more narrowly covers examples using channel estimates. Figure 3B shows example method 300B that more narrowly covers examples using suggested beamforming weights. Example methods (such as example method 300, example method 300A, or example method 300B) can be implemented using any of master unit (MU) 106 or virtual master unit (MU) 106 and any other components of example communication system 100 shown in Figures 1 A-1B and described above or master unit (MU) 204 and any other components of example communication system 200 shown in Figure 2 and described above.

[0056] Example method 300 begins at step 302 with receiving, at a master unit of the open radio access network, resource blocks from a distributed unit. In examples, the method 300 includes receiving, at the master unit, resource block groups and selecting, at the master unit,which user equipment to put in reuse based on the resource block groups. Example method 300 proceeds to step 304 with receiving, at the master unit, channel estimates or suggested beamforming weights from the distributed unit. In examples using channel estimates according to method 300 A of Figure 3 A, step 304 A comprises receiving, at the master unit, the channel estimates from the distributed unit. In examples using channel estimates according to example method 300A of Figure 3A, the example method 300A further comprises receiving the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units. In examples using suggested beamforming weights according to example method 300B of Figure 3B, step 304B comprises receiving, at the master unit, the suggested beamforming weights from the distributed unit.

[0057] Example method 300 proceeds to step 306 with examining, at the master unit, one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units. In examples using channel estimates according to example method 300A of Figure 3 A, step 306A comprises examining, at the master unit, the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units. In examples using suggested beamforming weights according to example method 300B of Figure 3B, step 306B comprises examining, at the master unit, the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights the corresponding respective antenna elements of the plurality of radio units.

[0058] Example method 300 proceeds to step 308 with selecting, at the master unit, a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes. In examples using channel estimates according to example method 300A of Figure 3A, step 308A comprises selecting, at the master unit, the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes. In examples using suggested beamforming weights according to example method 300B of Figure 3B, step 308 includes selecting, at the master unit, the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0059] Example method 300 proceeds to step 310 with determining, at the master unit, derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes. In examples using channel estimates according to example method 300A of Figure 3 A, step 310A includes determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes. In examples using suggested beamforming weights according to example method 300B of Figure 3B, step 310B includes determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0060] Example method 300 proceeds to step 312 with applying the derived beamforming weights to the resource blocks. Example method 300 proceeds to step 314 with transporting, from the master unit, the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes. In examples using channel estimates according to method 300 A of Figure 3 A, step 314A includes transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes. In examples using suggested beamforming weights according to example method 300B of Figure 3B, step 314B includes transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes. In examples using either resource blocks or suggested beamforming weights (including any of method 300 of Figure 3, method 300A of Figure 3A, or method 300 of Figure 3B), transporting the resource blocks to the subset of radio units using multicast is only to the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes. In examples using either resource blocks or suggested beamforming weights (including any of method 300 of Figure 3, method 300A of Figure 3A, or method 300 of Figure 3B), the method further comprises deriving precoderweights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

[0061] In examples, any transmission initiated to any given UE from its associated RUs results in low interference for any other UE scheduled on the same time or frequency resources. In examples, transporting, from the master unit, the resource blocks to the set of radio units having the set of antenna elements corresponding to the set of highest magnitude coefficients of the at least one of the channel estimates or the beamforming weight sets results in low coherent cross-correlation. In examples, transporting, from the master unit, the resource blocks to the set of radio units occurs using multicast to only the set of radio units having the set of antenna elements corresponding to the set of highest magnitude coefficients of the at least one of the channel estimates or the beamforming weight sets. In examples, method 300 further includes receiving, at the distributed unit, resource block groups; and selecting, at the distributed unit, which user equipment to put in reuse base on the resource block groups.

[0062] Terminology

[0063] Brief definitions of terms, abbreviations, and phrases used throughout this application are given below.

[0064] The term “determining” and its variants may include calculating, extracting, generating, computing, processing, deriving, modeling, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may also include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

[0065] The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on”. Additionally, the term “and / or” means “and” or “or”. For example, “A and / or B” can mean “A”, “B”, or “A and B”. Additionally, “A, B, and / or C” can mean “A alone,” “B alone,” “C alone,” “A and B,” “A and C,” “B and C” or “A, B, and C.”

[0066] The terms “connected”, “coupled”, and “communicatively coupled” and related terms may refer to direct or indirect connections. If the specification states a component or feature “may,” “can,” “could,” or “might” be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0067] The terms “responsive” or “in response to” may indicate that an action is performedcompletely or partially in response to another action. The term “module” refers to a functional component implemented in software, hardware, or firmware (or any combination thereof) component.

[0068] The methods disclosed herein comprise one or more steps or actions for achieving the described method. Unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

[0069] While detailed descriptions of one or more configurations of the disclosure have been given above, various alternatives, modifications, and equivalents will be apparent to those skilled in the art without varying from the spirit of the disclosure. For example, while the configurations described above refer to particular features, functions, procedures, components, elements, and / or structures, the scope of this disclosure also includes configurations having different combinations of features, functions, procedures, components, elements, and / or structures, and configurations that do not include all of the described features, functions, procedures, components, elements, and / or structures. Accordingly, the scope of the present disclosure is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof. Therefore, the above description should not be taken as limiting.EXAMPLES

[0070] Example 1 includes a master unit for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO), the master unit comprising: circuitry configured to: receive resource blocks from a distributed unit of the open radio access network implementing multi-user multiple-input and multiple-output (MU- MIMO); receive channel estimates or suggested beamforming weights from the distributed unit; examine one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the firstsubset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0071] Example 2 includes the master unit of Example 1, further comprising wherein the circuitry is configured to: receive the channel estimates from the distributed unit; examine the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units; select the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

[0072] Example 3 includes the master unit of Example 2, wherein the circuitry is configured to: receive the channel estimates as a channel matrix; and examine the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

[0073] Example 4 includes the master unit of any of Examples 1-3, further comprising wherein the circuitry is configured to: receive the suggested beamforming weights from the distributed unit; examine the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0074] Example 5 includes the master unit of any of Examples 1-4, wherein the circuitry is configured to transport the resource blocks to the subset of radio units using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0075] Example 6 includes the master unit of any of Examples 1-5, wherein the circuitry is configured to: derive precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

[0076] Example 7 includes a method for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO), the method comprising: receiving, at a master unit of the open radio access network, resource blocks from a distributed unit; receiving, at the master unit, channel estimates or suggested beamforming weights from the distributed unit; examining, at the master unit, one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determining, at the master unit, derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; applying the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0077] Example 8 includes the method of Example 7, further comprising: receiving, at the master unit, the channel estimates from the distributed unit; examining, at the master unit, the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units; selecting, at themaster unit, the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes; applying, at the master unit, the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

[0078] Example 9 includes the method of Example 8, further comprising: receiving, at the master unit, the channel estimates as a channel matrix; and examining, at the master unit, the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

[0079] Example 10 includes the method of any of Examples 8-9, further comprising: receiving, at the distributed unit, resource block groups; and selecting, at the distributed unit, which user equipment to put in reuse based on the resource block groups.

[0080] Example 11 includes the method of any of Examples 7-10, further comprising: receiving, at the master unit, the suggested beamforming weights from the distributed unit; examining, at the master unit, the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; applying, at the master unit, the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0081] Example 12 includes the method of any of Examples 7-11, wherein transporting, from the master unit, the resource blocks to the subset of radio units occurs using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) thesecond subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0082] Example 13 includes the method of any of Examples 7-12, further comprising: deriving precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

[0083] Example 14 includes an open radio access network implementing multi-user multipleinput and multiple-output (MU-MIMO), the open radio access network comprising: a plurality of radio units, wherein each of the plurality of radio units includes first circuitry for exchanging radio frequency signals with at least one user equipment; and a master unit communicatively coupled to the plurality of radio units, the master unit including second circuitry configured to: receive resource blocks from a distributed unit; receive channel estimates or suggested beamforming weights from the distributed unit; examine one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of the plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units of the plurality of radio units, the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0084] Example 15 includes the open radio access network of Example 14, further comprising wherein the second circuitry of the master unit is configured to: receive the channel estimates from the distributed unit; examine the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units; select the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the first subset ofcoefficients of the channel estimates having the highest magnitudes; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

[0085] Example 16 includes the open radio access network of Example 15, wherein the second circuitry of the master unit is configured to: receive the channel estimates as a channel matrix; and examine the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

[0086] Example 17 includes the open radio access network of any of Examples 14-16, further comprising wherein the second circuitry of the master unit is configured to: receive the suggested beamforming weights from the distributed unit; examine the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; determine the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0087] Example 18 includes the open radio access network of any of Examples 14-17, wherein the second circuitry of the master unit is configured to transport the resource blocks to the subset of radio units using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

[0088] Example 19 includes the open radio access network of any of Examples 14-18, wherein the second circuitry of the master unit being configured to derive precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

[0089] Example 20 includes the open radio access network of any of Examples 14-19, further comprising: the distributed unit including third circuitry configured to: receive resource block groups; and select which user equipment to put in reuse based on the resource block groups.

Claims

CLAIMSWhat is claimed is:

1. A master unit for use in an open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO), the master unit comprising: circuitry configured to: receive resource blocks from a distributed unit of the open radio access network implementing multi-user multiple-input and multiple-output (MU-MIMO); receive channel estimates or suggested beamforming weights from the distributed unit; examine one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

2. The master unit of claim 1, further comprising wherein the circuitry is configured to: receive the channel estimates from the distributed unit; examine the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units;select the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

3. The master unit of claim 2, wherein the circuitry is configured to: receive the channel estimates as a channel matrix; and examine the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

4. The master unit of claim 1, further comprising wherein the circuitry is configured to: receive the suggested beamforming weights from the distributed unit; examine the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; select the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

5. The master unit of claim 1, wherein the circuitry is configured to transport the resource blocks to the subset of radio units using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients ofthe channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

6. The master unit of claim 1, wherein the circuitry is configured to: derive precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

7. A method for use in an open radio access network implementing multi-user multipleinput and multiple-output (MU-MIMO), the method comprising: receiving, at a master unit of the open radio access network, resource blocks from a distributed unit; receiving, at the master unit, channel estimates or suggested beamforming weights from the distributed unit; examining, at the master unit, one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of a plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determining, at the master unit, derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; applying the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to a subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

8. The method of claim 7, further comprising: receiving, at the master unit, the channel estimates from the distributed unit;examining, at the master unit, the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes; applying, at the master unit, the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

9. The method of claim 8, further comprising: receiving, at the master unit, the channel estimates as a channel matrix; and examining, at the master unit, the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

10. The method of claim 8, further comprising: receiving, at the distributed unit, resource block groups; and selecting, at the distributed unit, which user equipment to put in reuse based on the resource block groups.

11. The method of claim 7, further comprising: receiving, at the master unit, the suggested beamforming weights from the distributed unit; examining, at the master unit, the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights the corresponding respective antenna elements of the plurality of radio units; selecting, at the master unit, the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes;determining, at the master unit, the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; applying, at the master unit, the derived beamforming weights to the resource blocks; and transporting, from the master unit, the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

12. The method of claim 7, wherein transporting, from the master unit, the resource blocks to the subset of radio units occurs using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

13. The method of claim 7, further comprising: deriving precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

14. An open radio access network implementing multi-user multiple-input and multipleoutput (MU-MIMO), the open radio access network comprising: a plurality of radio units, wherein each of the plurality of radio units includes first circuitry for exchanging radio frequency signals with at least one user equipment; and a master unit communicatively coupled to the plurality of radio units, the master unit including second circuitry configured to: receive resource blocks from a distributed unit; receive channel estimates or suggested beamforming weights from the distributed unit; examine one of: (1) the channel estimates to associate first coefficients of the channel estimates with corresponding respective antenna elements of the plurality of radio units or (2) the suggested beamforming weights to associate second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units;select a subset of antenna elements corresponding to: (1) a first subset of coefficients of the channel estimates having highest magnitudes or (2) a second subset of coefficients of the suggested beamforming weights having the highest magnitudes; determine derived beamforming weights for application to the resource blocks based on: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to a subset of radio units of the plurality of radio units, the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

15. The open radio access network of claim 14, further comprising wherein the second circuitry of the master unit is configured to: receive the channel estimates from the distributed unit; examine the channel estimates to associate the first coefficients of the channel estimates with the corresponding respective antenna elements of the plurality of radio units; select the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes; determine the derived beamforming weights to apply to the resource blocks based on the first subset of coefficients of the channel estimates having the highest magnitudes; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the first subset of coefficients of the channel estimates having the highest magnitudes.

16. The open radio access network of claim 15, wherein the second circuitry of the master unit is configured to: receive the channel estimates as a channel matrix; and examine the channel estimates by examining coefficients of the channel matrix to associate each coefficient of the channel matrix with the corresponding respective antenna elements of the plurality of radio units.

17. The open radio access network of claim 14, further comprising wherein the second circuitry of the master unit is configured to: receive the suggested beamforming weights from the distributed unit; examine the suggested beamforming weights to associate the second coefficients of the suggested beamforming weights with the corresponding respective antenna elements of the plurality of radio units; determine the derived beamforming weights to apply to the resource blocks based on the second subset of coefficients of the suggested beamforming weights having the highest magnitudes; apply the derived beamforming weights to the resource blocks; and transport the resource blocks to the subset of radio units having the subset of antenna elements corresponding to the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

18. The open radio access network of claim 14, wherein the second circuitry of the master unit is configured to transport the resource blocks to the subset of radio units using multicast to only the subset of radio units having the subset of antenna elements corresponding to: (1) the first subset of coefficients of the channel estimates having the highest magnitudes or (2) the second subset of coefficients of the suggested beamforming weights having the highest magnitudes.

19. The open radio access network of claim 14, wherein the second circuitry of the master unit being configured to derive precoder weights for user equipment of the open radio access network based on the channel estimates or the suggested beamforming weights received from the distributed unit.

20. The open radio access network of claim 14, further comprising: the distributed unit including third circuitry configured to: receive resource block groups; and select which user equipment to put in reuse based on the resource block groups.

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