EP4677754A1

EP4677754A1 - Radio unit and method of operation

Info

Publication number: EP4677754A1
Application number: EP23713449.9A
Authority: EP
Inventors: Nabil LOUADI; Israfil Bahceci
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-03-10
Filing date: 2023-03-10
Publication date: 2026-01-14
Also published as: WO2024191326A1

Abstract

Methods for a radio unit, RU, comprising a plurality of radio frequency, RF, branches coupled to a plurality of antenna branches of an antenna array. During each of plurality of time periods, the RU operates (1110) a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to transmit and/or receive RF signals via a coupled antenna branch. The RU operates (1120) a remainder of the RF branches, other than the subset, in a normal-energy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch. The RU selects (1160) a next subset of the RF branches to be operated in the low-energy state during a next time period. The selection is performed randomly or according to a time-varying pattern that is determined and/or controlled by the RU.

Description

RADIO UNIT AND METHOD OF OPERATION

TECHNICAL FIELD

The present disclosure relates generally to radio units (RUs) comprising a plurality of radio frequency (RF) branches, and more specifically to techniques for selecting subsets of the RF branches to be operated in a low-energy state during respective time periods.

BACKGROUND

Long-Term Evolution (LTE) is an umbrella term for so-called fourth generation (4G) radio access technologies developed within the Third-Generation Partnership Project (3 GPP) and initially standardized in Release 8 (Rel-8) and Release 9 (Rel-9), also known as Evolved UTRAN (E-UTRAN). LTE is targeted at various licensed frequency bands and is accompanied by improvements to non-radio aspects commonly referred to as System Architecture Evolution (SAE), which includes Evolved Packet Core (EPC) network. LTE continues to evolve through subsequent releases.

Currently the fifth generation (“5G”) of cellular systems, also referred to as New Radio (NR), is being standardized within the Third-Generation Partnership Project (3GPP). NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases. NR was initially specified in Rel-15 and continues to evolve through subsequent releases, such as Rel-16 and Rel-17.

In addition to providing coverage via cells as in LTE, NR networks also provide coverage via “beams.” In general, a downlink (DL, i.e., network to UE) “beam” is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE. In NR, for example, RS can include any of the following: synchronization signal/PBCH block (SSB), channel state information RS (CSI-RS), tracking reference signals (or any other sync signal), positioning RS (PRS), demodulation RS (DMRS), phase-tracking reference signals (PTRS), etc. In general, SSB is available to all UEs regardless of the state of their connection with the network, while other RS (e.g., CSI-RS, DM-RS, PTRS) are associated with specific UEs that have a network connection.

5G/NR networks are expected to operate at higher frequencies such as 25-60 GHz, which are typically referred to as “millimeter wave” or “mmW” for short. Such systems are also expected to utilize a variety of multi-antenna technology (e.g., antenna arrays) at the transmitter, the receiver, or both. In general, multi-antenna technology can include a plurality of antennas in combination with advanced signal processing techniques (e.g., beamforming). Multi-antenna technology can be used to improve various aspects of a communication system, including system capacity (e.g., more users per unit bandwidth per unit area), coverage (e.g., larger area for given bandwidth and number of users), and increased per-user data rate (e.g., in a given bandwidth and area).

Availability of multiple antennas at the transmitter and/or the receiver can be utilized in different ways to achieve different goals. For example, multiple antennas at the transmitter and/or the receiver can be used to shape or “form” the overall antenna beam (e.g., transmit and/or receive beam, respectively) in a certain way, with the general goal being to improve the received signal -to-interference-plus-noise ratio (SINR) and, ultimately, system capacity and/or coverage. This can be done, for example, by maximizing the overall antenna gain in the direction of the target receiver or transmitter or by suppressing specific dominant interfering signals. More specifically, the transmitter and/or receiver can determine an appropriate weight for each antenna element in an antenna array so as to produce one or more beams, with each beam covering a particular range of azimuth and elevation relative to the antenna array.

In relatively good channel conditions, the capacity of the channel becomes saturated such that further improving the SINR provides limited capacity improvements. In such cases, using multiple antennas at both the transmitter and the receiver can be used to create multiple parallel communication "channels" over the radio interface. This can facilitate a highly efficient utilization of both the available transmit power and the available bandwidth resulting in, e.g., very high data rates within a limited bandwidth without a disproportionate degradation in coverage. For example, under certain conditions, the channel capacity can increase linearly with the number of antennas and avoid saturation in the data capacity and/or rates. These techniques are commonly referred to as “spatial multiplexing” or multiple-input, multiple-output (MIMO) antenna processing.

Accordingly, spatial multiplexing is a key feature to increase the spectral efficiency and/or capacity of wireless systems, including 5G/NR. Transmitting multiple layers on the same time-frequency resource can increase the data-rate for a single user (referred to as “SU- MIMO”). Alternatively, transmitting multiple layers on the same time-frequency resource to multiple users (referred to as “MU-MIMO”) can increase the system capacity in number of users. In general, the number of antennas required for a MIMO system can be readily determined based on a desired throughput, spectral efficiency, and/or traffic load.

Figure 1 shows an exemplary arrangement used for MIMO transmission and reception in a wireless network, such as a 5G network. In this arrangement, two baseband processing units (BPUs) are coupled to a radio unit (RU). The RU includes a digital front end (DFE) and an analog front end (AFE), which are divided physically and/or virtually into a plurality of radio frequency (RF) branches. For example, the AFE may include transmit power amplifiers (PAs), receive amplifiers, phase shifters, filters, etc. Likewise, the DFE may include digital processing functions, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), etc.

The RU may also include baseband processing circuitry (i.e., in addition to the baseband circuitry in BPUs), which is also divided physically and/or virtually into a plurality of baseband (BB) branches. For example, each BB branch can be coupled to a corresponding RF branch in the RU. As an example, the baseband processing performed by the BB branches in the RU can include layer-1 beamforming (BF).

The RU may include the antenna array, which also may be separate from but coupled to the RU. In either case, the antenna array is divided into a plurality of antenna branches, with each antenna branch being coupled to a corresponding RF branch in the RU. Conversely, each RF branch may be coupled to one or more (e.g., two) antenna branches of the antenna array.

One drawback of MIMO systems using large antenna arrays is that the RU circuitry, including both RF branches and BB branches, consumes a significant amount of energy during normal operation. One analysis of this drawback is by L. Sanguinetti, et al. in “Large System Analysis of the Energy Consumption Distribution in Multi-User MIMO Systems With Mobility," published in IEEE Transactions on Wireless Communications, vol. 14, no. 3, pp. 1730-1745, March 2015. Some MIMO sleep solutions have been developed to reduce the energy consumption. For example, some RU components can be powered down or put into low-power state mode when the RU traffic load decreases. As another example, some antenna selection methods have been used to increase energy efficiency MIMO systems.

SUMMARY

Existing MIMO sleep solutions are driven by the antenna array rather than the RU circuitry that consumes energy. For example, some contiguous portion (e.g., row, column) of a two-dimensional (2D) antenna array is selected for muting during some time period and the RF and/or BB branches coupled to this portion are operated in a low-energy state during that time period. Conventionally, however, the RU circuitry required a significant amount of time to re-enter normal operating state from the low-energy state, making this approach inapplicable to many dynamic traffic scenarios in wireless networks.

Even if the RU circuitry is capable of relatively fast energy state switching, the rigid selection of contiguous portions of the antenna array for muting may result in beamforming capabilities that are sub-optimal or even undesirable. For example, with a row or a column of the antenna branches in the 2D array being muted (due to corresponding RU circuitry being in low-energy state), the RU may be unable to provide beams to support a current spatial arrangement of users and/or to transmit all DL RS ports needed by users.

Furthermore, existing MIMO sleep solutions are further complicated when the RU is connected to multiple BPUs, each of which has different traffic loads, schedules, etc. For example, each BPU may be associated with a different sector of a cell and/or a different radio access technology (RAT), such as LTE and NR.

An object of the invention is to improve energy management in a wireless network (e.g., radio access network, RAN).

Embodiments include methods (e.g., procedures) for an RU comprising a plurality of RF branches coupled to a plurality of antenna branches of an antenna array. The RU can be, or be part of, a radio access network (RAN) node such as a base station, eNB, gNB, ng-eNB, etc.

These exemplary methods can include the following operations during each of a plurality of time periods:

• operating a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to perform at least one of the following via a coupled antenna branch: transmitting RF signals, and receiving RF signals.

• operating a remainder of the RF branches, other than the subset, in a normal-energy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch; and

• selecting a next subset of the RF branches to be operated in the low-energy state during a next time period, which can be performed randomly or according to a time-varying pattern that is determined and/or controlled by the RU.

In some embodiments, the selection of the next subset is performed according to a time-varying pattern controlled by the RU based on information received from one or more BPUs coupled to the RU.

In some embodiments, each selected next subset includes a constant number (X) of RF branches. In some of these embodiments, the antenna array is arranged into a plurality (Y) of slices and each slice includes a plurality of antenna branches at adjacent locations in the antenna array. In such embodiments, selecting the next subset of the RF branches to be operated in the low-energy state during a next time period includes the following operations: selecting a same number (Z) of antenna array branches from each slice of the antenna array; and selecting the RF branches coupled to the Z*Y selected antenna array branches.

In some embodiments, during each of the plurality of time periods, the selection of the next subset of the RF branches is from a set of the RF branches that are eligible to be operated in the low-energy state during the next time period. In such case, these exemplary methods can also include determining the eligible set of RF branches for the next time period based on one or more of the following:

• a maximum number of RF branches to be operated in the low-energy state during the next time period,

• a minimum number of RF branches to be operated in the normal-energy state during the next time period,

• any fault conditions present in the plurality of RF branches,

• one or more slices of the antenna array that should not be muted during the next time period, and

• measurements of RS transmitted or received via the antenna array.

In some of these embodiments, the one or slices of the antenna array that should not be muted during the next time period are used to transmit and/or receive a carrier frequency having a scheduled traffic load that exceeds a threshold during the time period.

In some of these embodiments, the plurality of RF branches are also coupled to a corresponding plurality of BB branches and these exemplary methods can also include receiving an indication of one of the following from one or more BPUs coupled to the RU:

• a first set of BB branches that will carry signals or channels that should not be muted during at least the next time period, or

• a second set of BB branches that can be operated in a low-energy state during at least the next time period.

In some variants, the eligible set of RF branches for the next time period includes RF branches coupled to the second set of BB branches. In other variants, the eligible set of RF branches for the next time period excludes RF branches coupled to the first set of BB branches. In some variants, the signals or channels that should not be muted during at least the next time period include one or more of the following: control channels, common reference signals, userspecific reference signals, and beamformed data channels.

In other of these embodiments, these exemplary methods can also include, during each of the plurality of time periods, measuring uplink RS transmitted by one or more UEs and received via a plurality of the antenna branches and coupled RF branches operating in the normal-energy state and, based on the uplink RS measurements, selecting a set of antenna branches to transmit downlink data to the one or more UEs. In such case, the eligible set of RF branches determined for the next time period excludes the RF branches coupled to the selected set of antenna branches.

In other embodiments, the plurality of RF branches are also coupled to a corresponding plurality of BB branches and during each time period, at least a portion of the BB branches carry user-specific RS to be transmitted via the coupled RF branches. In such embodiments, selecting a next subset of the RF branches to be operated in the low-energy state during a next time period is performed randomly regardless of the user-specific RS to be transmitted during the next time period.

In some of these embodiments, during each time period, one or more RF branches are operated in the low-energy state such that user-specific RS carried by the one or more coupled BB branches are not transmitted during the time period. In some variants of these embodiments, these exemplary methods can also include receiving the following from a UE during each of multiple time periods:

• first measurements of user-specific RS that were transmitted during the time period, and

• second measurements corresponding to user-specific RS that were scheduled for transmission but not transmitted during the time period; and

These exemplary methods can also include estimating a channel matrix for the UE based on the following: the first and second measurements received during the multiple time periods, and a list of the one or more RF branches that were operating in the low-energy state during each of the multiple time periods.

In some variants, estimating the channel matrix for the UE is further based on respective precoders applied by the BB branches to the user-specific RS during the multiple time periods. In such case, these exemplary methods can also include determining one or more revised precoders based on the estimated channel matrix. Each revised precoder corresponds to a different set of RF branches operating in the low-energy state.

In some embodiments, the RU includes the plurality of BB branches that are coupled to the RF branches and these exemplary methods can include one of more of the following operations during each of plurality of time periods:

• operating, in the low-energy state, the BB branches corresponding to the subset of the RF branches being operated in the low-energy state; and

• operating, in the normal-energy state, the BB branches corresponding to the remainder of the RF branches being operated in the normal-energy state.

In some embodiments, the RU can include the antenna array, instead of or in addition to the BB branches.

In some embodiments, these exemplary methods can also include, during each of the plurality of time periods, adjusting respective beamforming gains or weights used by the plurality of RF branches based on the subset of the RF branches being operated in the low- energy state during the time period. In some of these embodiments, adjusting the beamforming gains or weights includes, for a group of antenna branches arranged linearly in the antenna array, increasing the beamforming gains or weights used by RF branches coupled to antenna branches at the edges of the linear arrangement, when one or more other antenna array branches of the group are coupled to RF branches being operated in the low-energy state.

Other embodiments include RUs configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer-readable media storing program instructions that, when executed by processing circuitry, configure such RUs to perform operations corresponding to any of the exemplary methods described herein.

These and other embodiments described herein can provide various benefits and/or advantages. For example, embodiments can achieve significant reduction in RU energy consumption while maintaining performance within bounds deemed acceptable. More specifically, embodiments can facilitate a continuous and predictable reduction in energy consumption by muting at least a minimum number of antenna branches in each time period, with the minimum number selected based on a tradeoff between energy consumption and other performance requirements. Unlike conventional MIMO sleep techniques, embodiments can be used independent of spatial and/or temporal variations in traffic. Embodiments are also robust to faults and over-temperature conditions in the RF branches and can reduce and/or eliminate coordination between BPU(s) and RU required by conventional solutions. In this manner, embodiments can be “baseband agnostic”, such that they can be used in a multi-vendor (e.g., Open RAN) or cloud environment.

These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an exemplary arrangement used for MIMO transmission and reception in a wireless network.

Figure 2 shows an exemplary radio unit (RU) configured for MIMO operation in a wireless network.

Figure 3 shows various examples of how contiguous portions of a 128-branch antenna array can be muted during any given time period.

Figure 4 illustrates limitations on conventional MIMO sleep techniques for an example scenario of two carriers that share an RU.

Figure 5 shows a system in which various embodiments of the present disclosure can be implemented. Figure 6 shows an example of antenna branch muting that varies by time period, according to some embodiments of the present disclosure.

Figure 7 shows an example of how traffic load can influence the selection of antenna branches to be muted or RF branches to be operated in a low-energy (LE) state.

Figure 8 shows an example of how both traffic load and BPU inputs can influence the selection of antenna branches to be muted or RF branches to be operated in the LE state.

Figure 9 shows a mapping of CSLRS ports 0-31 to an antenna array in which various antenna branches are muted.

Figure 10 shows a high-level views of an exemplary 5G/NR network architecture, in which certain embodiments of the present disclosure can be implemented.

Figure 11, which includes Figures 11A-B, shows a flow diagram of an exemplary method (e.g., procedure) for an RU operable in a wireless network (e.g., NG-RAN), according to various embodiments of the present disclosure.

Figure 12 shows a communication system according to some embodiments of the present disclosure.

Figure 13 shows a network node according to some embodiments of the present disclosure.

Figure 14 shows a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods and/or procedures disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein can be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments can apply to any other embodiments, and vice versa. Other objects, features, and advantages of the enclosed embodiments will be apparent from the following description.

Furthermore, the following terms are used throughout the description given below:

• Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., gNB in a 3GPP 5G/NR network or an enhanced or eNB in a 3GPP LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low- power base station (e.g., micro, pico, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

• Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), a PDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.

• Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other wireless devices. Communicating wirelessly can involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

• Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

• Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g., a radio access node or equivalent term) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and/or operable to communicate directly or indirectly with a wireless device and/or with other network nodes or equipment in the cellular communications network, to enable and/or provide wireless access to the wireless device, and/or to perform other functions (e.g, administration) in the cellular communications network.

• Base station: As used herein, a “base station” may comprise a physical or a logical node transmitting or controlling the transmission of radio signals, e.g, eNB, gNB, ng-eNB, en-gNB, centralized unit (CU)/distributed unit (DU), transmitting radio network node, transmission point (TP), transmission reception point (TRP), remote radio head (RRH), remote radio unit (RRU), Distributed Antenna System (DAS), relay, etc.

• Node: As used herein, the term “node” (without prefix) can be any type of node that can in or with a wireless network (including RAN and/or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node) based on its specific characteristics in any given context.

The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and/or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and/or descriptions conflict with the above definitions, the above definitions should control.

Note that the description given herein focuses on a 3 GPP cellular communications system and, as such, 3 GPP terminology or terminology similar to 3 GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system. Furthermore, although the term “cell” is used herein, it should be understood that (particularly with respect to 5G NR) beams may be used instead of cells and, as such, concepts described herein apply equally to both cells and beams.

Figure 2 shows an exemplary radio unit (RU, 200) configured for MIMO operation in a wireless network, such as a 5G network. In this example, the RU includes baseband (BB) processing circuitry (210) that is divided physically and/or virtually into 64 BB branches. The RU also includes digital front end (DFE, 220) and analog front end (AFE, 230) circuitry, which collectively are divided physically and/or virtually into 64 RF branches. Each RF branch is coupled to a corresponding BB branch, such that there is a 1 : 1 relationship (or correspondence) between RF branches and BB branches.

The RU also includes an antenna array (240) that includes 128 antenna branches, which may also be referred to as antenna elements. In the example shown, the antenna array includes 64 pairs of antenna branches, with the two antenna branches in each pair having orthogonal polarizations (e.g., horizontal and vertical). Each RF branch is coupled to two antenna branches, and each antenna branch is coupled to one corresponding RF branch. In other words, there is a 1 :2 relationship (or correspondence) between RF branches and antenna branches.

As briefly mentioned above, one drawback of MIMO systems using large antenna arrays is that the RU circuitry, including RF branches and BB branches, consumes a significant amount of energy during normal operation. Some MIMO sleep solutions have been developed to reduce the energy consumption. For example, some RU components can be powered down or put into low-power state mode when the RU traffic load decreases. As another example, some antenna selection methods have been used to increase energy efficiency MIMO systems, such as described in “Antenna selection in MIMO systems” by S. Sanayei, et al., published in IEEE Communications Magazine, Oct. 2004.

Existing MIMO sleep solutions are driven by the antenna array rather than the RU circuitry that consumes energy. For example, some contiguous portion of a two-dimensional (2D) antenna array is selected for muting during some time period and the RF and/or BB branches coupled to this portion are operated in a low-energy (LE) state during that time period. Figure 3 shows six (6) different examples of how contiguous portions of a 128-branch antenna array can be muted during any given time period. The shaded areas denote antenna branches that are coupled to RF branches that are in the LE state during a given time period. For example, the antenna array may be divided into multiple “slices”, each of which includes multiple contiguous antenna branches. During each time period, one or more slices may be selected for muting, with the corresponding RF branches being placed in the LE state.

Conventionally, however, the RU circuitry required a significant amount of time to reenter normal operating state from the low-energy state, making this approach inapplicable to many dynamic traffic scenarios in wireless networks. More recently, AFEs with very short (e.g., microseconds) recovery time from LE state have been developed. In this manner, whenever an OFDM symbol from a BB branch contains no data to transmit, the associated RF branch (e.g., power amplifier) is placed in the LE state for the duration of that symbol.

Even if the RU circuitry is capable of relatively fast energy state switching, selection of contiguous portions of the antenna array for muting may result in beamforming capabilities that are sub-optimal or even undesirable. In any of the examples shown in Figure 3, the RU may be unable to provide beams to support a current spatial arrangement of users and/or to transmit all DL RS ports needed by users, due to the number and/or physical geometry of antenna branches that are coupled to RF branches that remain in normal operating state.

Furthermore, existing MIMO sleep solutions are further complicated when the RU is connected to multiple BPUs, each of which has different traffic loads, schedules, etc. For example, an RU may be coupled to a first BPU that transmits and receives using the LTE RAT and to a second BPU that transmits and receives using the NR RAT. Each of these BPUs will generally have different traffic loads and traffic schedules. Furthermore, each of the BPUs may serve traffic for multiple sectors and/or carriers used in a cell, which will also have different traffic loads and traffic schedules. Conventionally, an RU can only place one of its RF branches into the LE state when all of the RATs, sectors, and carriers have no traffic to be transmitted on the antenna branch(es) coupled to that RF branch. In practice, this requires significant RU coordination with the BPU to achieve a meaningful reduction in RU energy consumption.

Figure 4 illustrates limitations on conventional MIMO sleep techniques for an example scenario of two carriers that share an RU. The two carriers could use the same or different RATs. The traffic levels (as a percent of maximum) for the two carriers over time are illustrated by the solid and dashed lines. In this example, MIMO sleep is turned on in the RU only when traffic level for both carriers is between X% and Y%, which is the overlap between the shaded and cross-hatched blocks. During these periods, some portion of the RF branches in the RU may be operated in the LE state. During the remainder of the time shown, the RU operates in normal energy state.

Embodiments of the present disclosure address these and other problems, issues, and/or difficulties by techniques that reduce energy consumption by operating a subset of the RF branches of an RU in a LE state during each time period, wherein the subset is selected by the RU randomly or based on a time-varying pattern that is determined and/or controlled by the RU. In the latter case, the time-varying pattern may be controlled by the RU independent of one or more connected BPUs or based on information received from the one or more BPUs.

In some embodiments, the size and composition of the subset can be adapted by the RU over time (e.g., as often as every time period) to meet relevant key performance indicator (KPI) requirements on coverage, capacity, etc. For example, the subset of RF branches can be selected such that corresponding muted antenna branches are dispersed over the antenna array in a pattern that changes randomly or in a time-varying manner for each time period. This type of selection enables a meaningful reduction of energy consumption at virtually all traffic loads while maintaining MIMO performance (e.g., BF gain) with a sufficient number of active (nonmuted) antenna branches.

Conceptually, muting a subset of antenna branches used for BF can be viewed as spatial-temporal beam-weight puncturing, which is analogous to puncturing the redundancy of error-correcting codes by removing bits to reduce overall coded bit rate. In this analogy, physical spatial samples are “punctured” by muting antenna branches to reduce energy consumption while maintaining BF performance within some acceptable bounds.

In some embodiments, a subset of muted antenna branches (or corresponding RF branches in LE state) can be selected based on an underlying BF scheme, e.g., relatively fewer antenna branches are muted when used for BF of signals or channels of greater importance. In some variants, branches that carry signals or channels of highest importance during a time period can be removed from the eligible set from which the subset is selected for muting (antenna branches) or operation in LE state (RF branches). In other embodiments that use random selection without regard to underlying signals or channels, the RU can combine feedback (e.g., CSI feedback) during multiple time periods from UEs that monitor these signals or channels that have been transmitted using some muted antenna branches, which vary during each time period. By combining multiple feedbacks in this manner, the RU can obtain a full picture of the DL channel including the effects of the muted antenna branches.

Embodiments of the present disclosure can provide various benefits, advantages, and/or solutions to problems. At a high level, embodiments can achieve significant reduction in energy consumption while maintaining performance within bounds deemed acceptable. Additionally, some embodiments can be applied independently of spatial and/or temporal variations in traffic, such as varying the subset of antenna branches and corresponding RF branches every time period (e.g., slot, subframe, transmit time interval (TTI), etc.). Additionally, the “punctured” antenna array can be used to create a diverse set of beamforming and common-beam transmission strategies.

In addition, embodiments can facilitate a continuous and predictable reduction in energy consumption. For example, at least a minimum number of antenna branches can be muted in every time period, with that minimum number selected based on a tradeoff between energy consumption and other performance requirements. In contrast, performance gains by conventional MIMO sleep techniques are highly dependent on traffic conditions and require accurate and timely prediction of how many antenna branches can be muted for proper operation. Additionally, embodiments are robust to faults and over-temperature conditions in the RF branches; in fact, embodiments can mitigate such problems by reducing the average duty cycle in normal operating state by occasional placement of each RF branch in the LE state.

Furthermore, embodiments can facilitate user measurement opportunities of DM-RS and CSLRS transmitted from all logical ports mapped to an antenna array, by varying muted antenna branches according to a random or deterministic pattern that changes each time period. These embodiments can significantly improve the performance of codebook based MIMO precoding systems that require user measurement of RS ports and feedback of measurement results. Additionally, embodiments can reduce and/or eliminate the coordination between BPU(s) and RU required by conventional solutions, as discussed above. In some embodiments, the RU can make the selection of antenna branches to mute (or corresponding RF branches to operate in LE state) without any intervention from the BPU(s). Such embodiments are “baseband agnostic”, making them interoperable in a multi-vendor environment (e.g., Open RAN, ORAN) and usable in a cloud RAN arrangement.

In the present disclosure, the term “energy state” is used in relation to circuitry (e.g., RF branch, BB branch, etc.) that consumes energy. More specifically, the term “normalenergy state” refers to a state in which circuitry consumes an amount of energy needed to perform its specified and/or required operations (e.g., transmitting, receiving, processing, etc.). Likewise, the term “low-energy state” refers to a state in which circuitry consumes less energy (e.g., zero) than in the corresponding normal-energy state while performing a subset (or none) of its specified and/or required operations. To give some illustrative examples, circuitry can be placed in a low-energy state by switching off its power source, reducing current and/or voltage level available from the power source, removing a clock or local oscillator (LO) signal that controls operations, reducing the frequency of the clock or LO signal, reducing amplification gain, etc.

In contrast, the term “muted” is used in relation to signals, channels, and antenna branches that transmit and/or receive signals and/or channels. Rather than referring to energy consumption, the term “muted” is used to denote a signal, channel, or antenna branch that is silent or unused. For example, an antenna branch may become muted when an RF branch coupled to it is placed in a low-energy state. Likewise, signals and channels may become muted when one or more RF branches that carry them are placed in a low-energy state.

Figure 5 shows a system in which various embodiments of the present disclosure can be implemented. The system includes an RU (500), a BPU (590), and an antenna array (530) comprising M antenna branches, which can optionally be part of the RU. The RU includes an RF unit (510) that includes N RF branches, of which RF branch N (511) is exemplary. The N RF branches may comprise DFE and AFE circuitry in a similar manner as described above in relation to Figure 2. The N RF branches are coupled to the M antenna branches in a 1 :K relationship, where K is an integer greater than or equal to 1. In an example corresponding to Figure 2 above, K=2 such that each RF branch is coupled to two antenna branches.

Optionally, the RU may include a BB unit (540) with N BB branches, each of which is coupled to a corresponding RF branch in a 1 : 1 relationship. BB branch N (541) is exemplary. When the BB unit is present, it receives BB data for various signals and channels from the BPU. The BB unit may include similar BB processing functionality as described above in relation to Figure 2. It should be understood, however, that a single BPU is exemplary and that multiple BPUs may be connected to RU as described above. In case the BB unit is absent from the RU, the BPU(s) may communicate directly with the RF unit but possibly in a different form than when the BB unit is present.

The RU also includes processing circuitry (520) that controls the RF unit and (when present) the BB unit. The processing circuitry can include various combinations of hardware (e.g., processor(s), controller(s), memory(ies), etc.) and software (e.g., program code, data, etc.) that facilitates and/or enables the operations that it performs. These operations can include selection of RF branches to operate in a LE state during each time period, such as described briefly above and below in more detail. In some embodiments, the processing circuitry can perform and/or determine such selections based on control information received from the BPU. For example, the control information can include one or more of the following:

• mapping between signal s/channels and RF branches;

• requirements for coverage and/or capacity; and

• indication of how many and/or which antenna branches can (or cannot) be muted during one or more subsequent time periods.

The BPU may provide such control information occasionally (e.g., upon change in traffic or other conditions) or periodically. If periodically, the information period may be the same or different than the time period over which the RU maintains its RF branches in normal- or low- energy state. In some cases, the BPU’s control information may be provided as a summary via low-rate connection from BPU to RU. This option may be suitable for RUs that are connected to multiple BPUs that are independent from (e.g., non-cooperative with) each other.

In some embodiments, the RU can select a subset of the antenna branches to be muted during each time period without BPU involvement and then operate the corresponding RF branches in the LE state during the time period. The selection can be performed randomly or based on some time-varying pattern that is not strictly random but is controlled by the RU (e.g., the processing circuitry). When the selection for each time period is random, the array muting pattern is randomized both spatially and temporally, which provides diversity and reduces impact on MIMO performance.

To illustrate this principle, consider a N_row X N_coi 2D antenna array whose BF gains are generated by the set of RF branches in the RU. Let M = 2 ■ N_row ■ N_coi denote the total number of antenna branches, with the factor of two accounting for dual cross-polarized branches at each location in the array. Each RF branch is coupled to a subset of the antenna branches in a 1 :K relationship such as discussed above. Let B_r = {a_{r 0}, a_{r l}, ... , a_{r Kr-1}} denote the antenna branches whose signals are generated by RF branch r. Every T ms (the ’’time period” mentioned above), the RU selects X antennas branches to be muted, suitably distributed over the antenna array. The set of X antenna branches is the same for T ms, and re-evaluted each T ms. The time period T can be predetermined (e.g., by specification), configurable (e.g., by OAM or other network entity), or based on RU implementation. For example, an RU may vary T based on traffic load or other inputs from the connected BPU(s).

For the antenna branches selected to be muted, the RU operates the corresponding RF branches in the LE state during the next T ms. For example, the RU can operate portions of its AFE circuitry and/or its DFE circuitry associated with these RF branches in the LE state. Note that either or both of the transmit and receive circuitry in an RF branch can be operated in the LE state. The choice can be based on factors such as target energy reduction, frequency band, whether RU is arranged for time-division duplexing (TDD) or frequency-division duplexing (FDD), and TDD pattern.

The antenna branches to be muted can be selected randomly or in a time-varying pattern determined by the RU. For example, the antenna array can be divided into Y slices, with each slice containing multiple antenna branches at adjacent locations in the antenna array. A same number, Z, of antenna branches are selected randomly within each slice for muting during each T. An advantage of this approach is that it avoids concentrating the muted antenna branches in one area of the array.

Figure 6 shows an example of these embodiments for a dual-polarized antenna array that includes M = 2-4-8 = 64 branches arranged into Y = 8 slices, with Z = 1 branches being selected from each slice for muting during each time period T (e.g., 100 ms). Thus, a total of Z-Y = 8 antenna branches are selected for muting during each time period, with the corresponding RF branches being operated in the LE during that time period. This is illustrated in Figure 6 for three successive time periods, i.e., TO, TO + T, and TO + 2T. In each time period, the muted branches are identified by dashed lines.

In some embodiments, the RU can select the subset of RF branches to be operated in the LE state (or corresponding antenna branches to be muted) from a set that is eligible for the time period, which may be all or less than all of the RF branches in the RU (or antenna branches in the antenna array). For example, the RU can select the eligible set of branches based on one or more of the following:

• a maximum number of RF branches to be operated in the low-energy state during the next time period (e.g., to maintain desired BF performance and/or current traffic load);

• a minimum number of RF branches to be operated in the normal-energy state during the next time period (e.g., to meet energy consumption requirement); • any fault conditions present in the plurality of RF branches (e.g., overheated and/or faulty RF branches excluded from the eligible set);

• one or more slices of the antenna array that should not be muted during the next time period (e.g., to maintain desired BF patterns);

• a first set of BB branches that will carry signals (e.g., CSI-RS) or channels (e.g., PDCCH) that should not be muted during at least the next time period;

• a second set of BB branches that can be operated in a low-energy state during at least the next time period; and

• measurements of RS transmitted (e.g., CSI-RS measured by UEs) or received (e.g., SRS measured by RU) via the antenna array.

Figure 7 shows an example of how traffic load can influence the selection of antenna branches to be muted or RF branches to be operated in the LE state. In particular, Figure 7 shows a graph of an RU traffic load that is generally decreasing over a relevant duration and how different portions of a 128-branch dual -polarized antenna array are muted according to traffic load. Initially at t = T, for relative high traffic load, a total of 32 antenna branches are muted. At t = 3T, after traffic load has decreased to some degree, a total of 40 antenna branches are muted. At t = 4T, after traffic load has decreased further, a total of 64 antenna branches are muted. The muting is subsequently reduced at t = 6T, where a total of 60 antenna branches are muted. For example, this reduction in muting can be caused to a reduction in the eligible set of antenna or RF branches, e.g., due to fault conditions in RF branches, etc.

Note that the muting shown in Figure 7 can be generally performed by the RU without interaction with a BPU, using random and/or time-varying patterns determined by the RU. Figure 8 shows an example of how both traffic load and BPU inputs can influence the selection of antenna branches to be muted or RF branches to be operated in the LE state. This example involves the same time-varying traffic load as shown in Figure 7. From t = T to t = 3T, the RU selects a total of 32 antenna branches to be muted according to a regular, time-varying pattern. For example, this pattern can be based on information from the BPU that indicates which antenna, BB, and/or RF branches will carry non-mutable signals or channels during these respective time periods. In other words, the RU excludes the BPU-indicated branches from the eligible set for each time period. For example, the non-mutable signals or channels can include control channels (e.g., PDCCH), common reference signals (e.g., SSB), user-specific reference signals (e.g., DM-RS, PT-RS), and beamformed data channels (e.g., PDSCH).

At t = 4T and t = 5T, the RU selects the same antenna branches for muting as selected for the same time periods with the same traffic load in Figure 7. For example, this can be due to the BPU not indicating any non-mutable signals or channels during 4T and 5T, such that the RU selects the eligible set based on only on traffic load conditions as in Figure 7. At t = 6T and t = 7T, however, the RU selects spatially contiguous blocks of 64 antenna elements to be muted. These patterns can be based on information from the BPU that indicates one or more slices of the antenna array that should not be muted during the next time period, e.g., to maintain desired BF patterns.

In embodiments exemplified by Figure 8, the RU (e.g., processing circuitry) can use an algorithm to optimize energy consumption by continuously searching for the maximum number of antenna branches that can be muted (or corresponding RF branches that can be operated in LE state) and their optimal positions in the antenna array, while maintaining compliance with a preconfigured set of KPIs for throughput, latency, BF gains/pattems, etc. Such an algorithm can utilize control information from the BPU(s), such as discussed above in relation to Figures 5 and 8. In some variants, the algorithm can utilize and/or be based on artificial intelligence and/or machine learning (collectively “AI/ML”).

3 GPP specifications for MIMO precoding generally do not refer to physical antenna branches (or elements). Instead, these specifications refer to logical abstractions of antenna elements called “antenna ports”, which are defined with respect to the RS of a corresponding transmission. For example, an antenna port is defined such that the channel over which a symbol on the antenna port is conveyed can be inferred from the channel over which another symbol (e.g., RS) on the same antenna port is conveyed. These RS include demodulation reference signal (DM-RS), phase tracking reference signal (PT-RS), and channel state information reference signal (CSI-RS), among others.

In general, DM-RS is used by the UE to estimate the channels of data resource elements (Res, corresponding to the DM-RS antenna ports) for coherent demodulation of downlink data. According to 3GPP specifications, DM-RS are linearly precoded by a matrix IF in the same way as physical DL shared channel (PDSCH). A UE observes a noisy version of a DM-RS at the channel output. The UE’s channel estimation algorithm tries to estimate the corresponding channel seen by DM-RS, which includes propagation channel H, multi-antenna precoding IF, and the reference signal port to physical antenna mapping F. In other words:

H_DMRS := HFW.

The UE’s estimate of H_DMRS , i.e., H_DMRS, can be used to coherently demodulate data because DM-RS and PDSCH are associated by transmission over the same antenna ports and, therefore, include the linear precoding, same antenna mapping, and same propagation channel.

CSI-RS mapping is slightly different than DM-RS in terms of precoders that it goes through before reception. Since a primary purpose of CSI-RS is to obtain the channel state information and noise/interference estimates for link adaptation and precoder suggestions to the base station (e.g., gNB), a baseline for CSI-RS mapping is that it at least goes through the physical antenna mapping F before experiencing the channel H. In other word, the multiantenna precoding matrix V for CSI-RS can be different from the multi-antenna precoding matrix W used for DM-RS.

In codebook-based MIMO precoding based on UE measurements of DL CSI-RS that are fed back to the gNB, the multi-antenna precoding matrix V can be set to be the identity matrix. In reciprocity-based MIMO precoding, the multi-antenna precoding matrix V can be calculated based on gNB measurement of UL SRS transmitted by the UE, which effectively reduces the number of DL CSI-RS ports required.

Embodiments of the present disclosure are applicable to MIMO precoding based on either UL SRS (non-codebook-based) or CSI-RS (codebook-based) measurements. In the former case, the RU can perform a convex optimization that determines the best set of antenna (or RF) branches to facilitate a desired MIMO precoding matrix based on UL SRS measured by the RU (or by a coupled BPU). For codebook-based solutions using DL CSI-RS, muting antenna branches and placing corresponding RF branches in LE state may cause muting of certain CSI- RS logical ports needing to be measured by UEs. This is illustrated in Figure 9, which shows a mapping of CSI-RS ports 0-31 to an antenna array. In particular, ports 0-15 are mapped to the antenna array in a first transmission and ports 16-31 are mapped to the antenna array in a second transmission. The shaded boxes illustrate antenna branches that are muted in each transmission, due to being coupled to RF branches being operated in the LE state.

In this example, CSI-RS ports 3 and 5 are fully muted during the first transmission and CSI-RS ports 19 and 21 are fully muted during the second transmission. Other ports are partially muted during each transmission. When UEs measured these fully- or partially-muted CSI-RS ports, their resulting CSI feedback is unreliable for use in determining MIMO precoding matrices. Three options for addressing this problem are described below.

As a first option, the RU can refrain from muting antenna branches that carry CSI-RS ports, i.e., during OFDM symbols in which CSI-RS are transmitted. For example, CSI-RS may be transmitted once every 20ms by default, but this frequency can be increased or decreased according to need. Put differently, the RU excludes RF branches carrying CSI-RS during each time period from the eligible set from which the subset is selected for operation in the LE state. In these embodiments, the UE only measures and sends feedback for non-muted CSI-RS ports, which enables the RU (or BPU) to determine MIMO precoding matrices in a conventional way.

As a second option, the RU can select antenna branches for muting (or RF branches for operating in LE state) regardless of whether they carry CSI-RS during the relevant time period. In these embodiments, the RU (or BPU) can combine or fuse UE CSI feedback from multiple symbols carrying CSI-RS, some of which may not have been actually received by the UE due to muting of antenna branches (e.g., randomly) without regard to CSI-RS traffic. Removing the CSI-RS dependence from the selection of the eligible set for muting (or operating in LE state) simplifies this operation and allows the RU to operate without BPU coordination, which is advantageous as discussed above. Moreover, randomizing the selection of muted antenna branches over two dimensions (spatial and time) enables UEs to perform valid measurements for all needed CSI over some extended time period during which all CSI- RS ports are non-muted intermittently.

In other words, even though a UE measures partial CSI information due to antenna branch muting during each time period, the RU knows the mapping between CSI-RS ports and muted/non-muted antenna branches for each time period. As such, the RU (or BPU) can combine the UE’s CSI feedback that may be incomplete in each individual instance to form a complete channel estimate over an extended time period during which the muted antenna branches have been varied (e.g., randomly) by the RU.

In mathematical notation, the CSI feedback for a transmission instance with muting pattern z = 1...N can be denoted by port-to-antenna mapping matrix VP; with entries corresponding to muted antenna branch(es) set to 0. The channel matrix for muting pattern z can be denoted H_t. The RU knows the precoder P_t associated with the transmission instance HiWi and thus it can estimate the N_rowN_coi X N_u channel matrix H_u for all entries from each antenna for UE-it based on the following maximization of conditional density: from which the precoder for any desired muting branch can be determined using any channel aware precoder design method. Note that Hf_ua is an estimate of the unknown channel matrix H_u .

As a third option, the RU can select antenna branches for muting (or RF branches for operating in LE state) regardless of whether they carry CSI-RS during the relevant time period, similar to the second option. In addition, the RU (or BPU) can instruct UEs (e.g., via RRC, MAC, or LI signaling) to reset their channel estimation filters according to the time period for which the RU selects the antenna branches to be muted (or RF branches to be operated in LE state).

In some embodiments, the RU is configured to use one of the above three options exclusively. In other embodiments, the RU can choose which of the above options to use in any given scenario. This choice may be made independent from the BPU or based on information provided by the BPU. For example, the BPU’s control information can indicate which BB and/or RF branches will carry CSI-RS (or other DL RS), and the RU can decide whether to select antenna branches for muting (or RF branches for operating in LE state) regardless of or based on the branches indicated by the BPU.

In typical 5G network operation, a codebook (B) of N BF vectors (bl ... bN) corresponding to respective spatial orientations (1 ... N) can be used for coverage of a cell. Such a codebook can also be referred to as “grid of beams” (GoB). Choice of BF vectors (bl ... bN) dictates beam parameters such as peak power and width of beam main lobe as well as level of beam sidelobes. Conventional choices for BF vectors (bl ... bN) produce beam parameters that are unsuitable in some manner, such as too low peak power or too high sidelobes.

The maximum gain for BF can be achieved with a codebook of N Discrete Fourier Transform (DFT) vectors. In other words, the vectors (bl ... bN) correspond to N different DFT orthogonal basis functions. The DFT vectors provide a set of beams equally spaced in orientation over a range of interest. This arrangement provides the narrowest beam and also full utilization of PA operating range, but at the expense of high sidelobes (i.e., in directions other than the desired orientation of the main lobe). These high sidelobes produce interference to other beams, which can be problematic when transmitting multiple layers and/or beams.

One way to reduce sidelobes and improve layer isolation is amplitude “tapering”, i.e., by reducing amplitude of certain elements of each BF vector (bl ... bN) in a systematic way. This is also referred to as “windowing” the beamforming vectors. For example, a Bartlett window reduces the maximum sidelobe to ~19dB below the peak beam power, but at the expense of a peak power loss of 3-4 dB relative to the non-windowed beams. As another example, a Hamming window reduces the maximum sidelobe to ~26dB below the respective peaks for the beams, but again at the expense of a peak power loss of 3-4 dB relative to the non-windowed beams. Both windows produce beams with wider main lobes (or apertures) than the non-windowed case, with Hamming windowed beams having wider main lobes than Bartlett windowed beams.

In some embodiments, the selection of antenna branches to be muted can be performed to minimize tapering needed to cover the same cell area with a larger aperture size. For example, the muting pattern can be selected such that less tapering is required to obtain the same BF gain in a larger area (or more BF in the same area). In practical terms for a ID or 2D antenna array where linear arrangements of branches are used for BF, using less tapering means increasing the BF gains of antenna branches at the edges (or ends) of the linear arrangements, when certain other antenna branches in the linear arrangements are being muted.

In other words, by muting certain antenna branches that correspond to particular elements of each BF vector (bl ... bN), the resulting shape of the beams can be adapted to have desirable properties and require less tapering to avoid undesirable sidelobes. Additionally, reducing the tapering results in an improved trade-off between coverage vs. PA energy consumption during common beam weight based transmissions. In addition, embodiments can benefit from pattern diversity that can mimic the gains from beam-formed control channel transmissions schemes.

Figure 10 illustrates an exemplary high-level view of the 5G network architecture, consisting of a Next Generation RAN (NG-RAN) 1099 and a 5G Core (5GC) 1098. NG-RAN 1099 can include a set of gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs 1000, 1050 connected via interfaces 1002, 1052, respectively. In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface 1040 between gNBs 1000 and 1050. With respect the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof.

NG-RAN 199 is layered into a Radio Network Layer (RNL) and a Transport Network Layer (TNL). The NG-RAN architecture, /.< ., the NG-RAN logical nodes and interfaces between them, is defined as part of the RNL. For each NG-RAN interface (NG, Xn, Fl) the related TNL protocol and the functionality are specified. The TNL provides services for user plane transport and signaling transport.

The NG-RAN nodes shown in Figure 10 include a central (or centralized) unit (CU or gNB-CU) and one or more distributed (or decentralized) units (DU or gNB-DU). For example, gNB 1000 includes gNB-CU 1010 and gNB-DUs 1020 and 1030. CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are logical nodes that host lower-layer protocols and can include, depending on the functional split, various subsets of the gNB functions. As such, each of the CUs and DUs can include various circuitry needed to perform their respective functions, including processing circuitry, transceiver and/or communication interface circuitry, power supply circuitry, etc.

A gNB-CU connects to gNB-DUs over respective Fl logical interfaces, such as interfaces 1022 and 1032 shown in Figure 10. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB. In other words, the Fl interface is not visible beyond gNB-CU.

In the context of the exemplary 5G network architecture shown in Figure 10, various embodiments of the RU discussed above or below can be part of, or coupled to, any of the DUs shown. For example, each DU can include one or more BPUs that are coupled to the RUs (e.g., as shown in Figures 1 and 5) as well as the RU itself.

Various features of the embodiments described above correspond to various operations illustrated in Figure 11, which includes Figures 11A-B that show an exemplary method e.g., procedure) for an RU comprising a plurality of radio frequency (RF) branches coupled to a plurality of antenna branches of an antenna array (e.g., in a 1:K relationship such as discussed above). The method can be performed by an RU configured for operation in a wireless network (e.g., NG-RAN), such as described elsewhere herein. Although Figure 11 shows specific blocks in a particular order, the operations of the exemplary method can be performed in different orders than shown and can be combined and/or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

The exemplary method can include the operations of blocks 1110, 1120, and 1160, which are performed during each of a plurality of time periods. In block 1110, the RU can operate a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to perform at least one of the following via a coupled antenna branch: transmitting RF signals, and receiving RF signals. In block 1120, the RU can operate a remainder of the RF branches, other than the subset, in a normal-energy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch. In block 1160, the RU can select a next subset of the RF branches to be operated in the low-energy state during a next time period. The selection is performed according to one of the following: randomly, or a time-varying pattern that is determined and/or controlled by the RU.

In some embodiments, the selection of the next subset is performed according to a timevarying pattern controlled by the RU based on information received from one or more BPUs coupled to the RU.

In some embodiments, each selected next subset includes a constant number (X) of RF branches. In some of these embodiments, the antenna array is arranged into a plurality (Y) of slices and each slice includes a plurality of antenna branches at adjacent locations in the antenna array. In such embodiments, selecting the next subset of the RF branches to be operated in the low-energy state during a next time period in block 1160 includes the following operations, labelled with corresponding sub-block numbers:

• (1161) selecting a same number (Z) of antenna array branches from each slice of the antenna array; and

• (1162) selecting the RF branches coupled to the Z*Y selected antenna array branches.

In some embodiments, during each of the plurality of time periods, the selection of the next subset of the RF branches in block 1160 is from a set of the RF branches that are eligible to be operated in the low-energy state during the next time period. In such case, the exemplary method can also include the operations of block 1150, where the RU can determine the eligible set of RF branches for the next time period based on one or more of the following: • a maximum number of RF branches to be operated in the low-energy state during the next time period,

• any fault conditions present in the plurality of RF branches,

• measurements of RS transmitted or received via the antenna array.

In some of these embodiments, the plurality of RF branches are also coupled to a corresponding plurality of BB branches and the exemplary method also includes the operations of block 1140, where the RU can receive an indication of one of the following from one or more BPUs coupled to the RU:

In some variants of these embodiments, the eligible set of RF branches for the next time period includes RF branches coupled to the second set of BB branches. In other variants of these embodiments, the eligible set of RF branches for the next time period excludes RF branches coupled to the first set of BB branches. In some variants of these embodiments, the signals or channels that should not be muted during at least the next time period include one or more of the following: control channels, common reference signals, user-specific reference signals, and beamformed data channels.

In other of these embodiments, the exemplary method can also include operations of blocks 1130-1135 during each of the plurality of time periods. In block 1130, the RU can measure uplink RS transmitted by one or more UEs and received via a plurality of the antenna branches and coupled RF branches operating in the normal-energy state. In block 1135, based on the uplink RS measurements, the RU can select a set of antenna branches to transmit downlink data to the one or more UEs. In such case, the eligible set of RF branches determined for the next time period (e.g., in block 1150) excludes the RF branches coupled to the selected set of antenna branches. In other embodiments, the plurality of RF branches are also coupled to a corresponding plurality of BB branches and during each time period, at least a portion of the BB branches carry user-specific RS to be transmitted via the coupled RF branches. In such embodiments, selecting a next subset of the RF branches to be operated in the low-energy state during a next time period in block 1160 is performed randomly regardless of the user-specific RS to be transmitted during the next time period.

In some of these embodiments, during each time period, one or more RF branches are operated in the low-energy state such that user-specific RS carried by the one or more coupled BB branches are not transmitted during the time period. In some variants of these embodiments, the exemplary method can also include the operations of blocks 1170-1175. In block 1170, the RU can receive the following from a UE during each of multiple time periods:

In block 1175, the RU can estimate a channel matrix for the UE based on the following: the first and second measurements received during the multiple time periods, and a list of the one or more RF branches that were operating in the low-energy state during each of the multiple time periods.

In some further variants of these embodiments, estimating the channel matrix for the UE in block 1175 is further based on respective precoders applied by the BB branches to the userspecific RS during the multiple time periods. In such case, the exemplary method also includes the operations of block 1180, where the RU can determine one or more revised precoders based on the estimated channel matrix. Each revised precoder corresponds to a different set of RF branches operating in the low-energy state.

In some embodiments, the RU includes the plurality of BB branches that are coupled to the RF branches and the exemplary method can include one of more of the following operations during each of plurality of time periods, labelled with corresponding block numbers:

• (1115) operating, in the low-energy state, the BB branches corresponding to the subset of the RF branches being operated in the low-energy state; and

• (1125) operating, in the normal-energy state, the BB branches corresponding to the remainder of the RF branches being operated in the normal-energy state.

Put more simply, the RU may apply corresponding energy-reduction mechanisms towards BB branches as it applies towards RF branches. In some embodiments, the RU can include the antenna array, instead of or in addition to the BB branches. In some embodiments, the exemplary method can also include the operations of block 1190, where during each of the plurality of time periods, the RU can adjust respective beamforming gains or weights used by the plurality of RF branches based on the subset of the RF branches being operated in the low-energy state during the time period. In some of these embodiments, adjusting the beamforming gains or weights in block 1190 includes the operations of sub-block 1191, where for a group of antenna branches arranged linearly in the antenna array, the RU can increase the beamforming gains or weights used by RF branches coupled to antenna branches at the edges of the linear arrangement, when one or more other antenna array branches of the group are coupled to RF branches being operated in the low-energy state. These embodiments are an example of the tapering reduction discussed in more detail above.

As mentioned above, the exemplary method shown in Figure 11 can be implemented by a RU comprising a plurality of RF branches coupled to a plurality of antenna branches of an antenna array (e.g., in a 1:K relationship such as discussed above). For example, the RU can also comprise processing circuitry that is operably coupled to the RF circuit branches and arranged to execute computer program code. Specifically, execution of the computer program code configures the RU to perform operations corresponding to any of the embodiments of the exemplary method shown in Figure 11. In different variants, the RU may also comprise the antenna array and/or a plurality of BB branches coupled to the plurality of RF branches (e.g., in a 1 : 1 relationship such as discussed above).

Additionally, the exemplary method shown in Figure 11 can be realized as a non- transitory, computer-readable medium storing computer-executable instructions. When executed by processing circuitry of an RU comprising a plurality of RF branches coupled to a plurality of antenna branches of an antenna array, the instructions configure the node to perform operations corresponding to any of those described above with reference to Figure 11.

Additionally, the exemplary method shown in Figure 11 can be realized as a computer program comprising computer-executable instructions. When executed by processing circuitry of an RU comprising a plurality of RF branches coupled to a plurality of antenna branches of an antenna array, the instructions configure the node to perform operations corresponding to any of those described above with reference to Figure 11.

Figure 12 shows an example of a communication system 1200 in accordance with some embodiments. In this example, communication system 1200 includes a telecommunication network 1202 that includes an access network 1204 (e.g., RAN) and a core network 1206, which includes one or more core network nodes 1208. Access network 1204 includes one or more access network nodes, such as network nodes 1210a-b (one or more of which may be generally referred to as network nodes 1210), or any other similar 3 GPP access node or non-3GPP access point. Network nodes 1210 facilitate direct or indirect connection of UEs, such as by connecting UEs 1212a-d (one or more of which may be generally referred to as UEs 1212) to core network 1206 over one or more wireless connections.

Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 1200 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. Communication system 1200 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

In the context of communication system 1200 shown in Figure 10, various embodiments of the RU discussed above or below can be part of, or coupled to, any of network nodes 1210. For example, each network node 1210 can include one or more BPUs that are coupled to the RUs (e.g., as shown in Figures 1 and 5) as well as the RU itself.

UEs 1212 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with network nodes 1210 and other communication devices. Similarly, network nodes 1210 are arranged, capable, configured, and/or operable to communicate directly or indirectly with UEs 1212 and/or with other network nodes or equipment in telecommunication network 1202 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in telecommunication network 1202.

In the depicted example, core network 1206 connects network nodes 1210 to one or more hosts, such as host 1216. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 1206 includes one more core network nodes (e.g., core network node 1208) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 1208. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

Host 1216 may be under the ownership or control of a service provider other than an operator or provider of access network 1204 and/or telecommunication network 1202, and may be operated by the service provider or on behalf of the service provider. Host 1216 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

As a whole, communication system 1200 of Figure 12 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: GSM, UMTS, LTE, NR, other suitable 2G-5G standards, and any applicable future generation 3 GPP standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as WiMax, Bluetooth, Z- Wave, Near Field Communication (NFC), ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

In some examples, telecommunication network 1202 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 1202 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 1202. For example, telecommunication network 1202 may provide URLLC services to some UEs, while providing eMBB services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive loT services to other UEs.

In some examples, UEs 1212 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1204 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1204. Additionally, a UE may be configured for operating in single- or multi -RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR, and LTE, such as being configured for multi-radio dual connectivity (MR-DC).

In the example, hub 1214 communicates with access network 1204 to facilitate indirect communication between one or more UEs (e.g., UE 1212c and/or 1212d) and network nodes (e.g., network node 1210b). In some examples, hub 1214 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1214 may be a broadband router enabling access to core network 1206 for the UEs. As another example, hub 1214 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1210, or by executable code, script, process, or other instructions in hub 1214. As another example, hub 1214 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 1214 may be a content source. For example, hub 1214 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1214 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In another example, hub 1214 acts as a proxy server or orchestrator for UEs 1212, in particular in if one or more of the UEs are low energy loT devices.

Figure 13 shows a network node 1300 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (e.g., radio access points) and base stations (e.g., radio base stations, Node Bs, eNBs, and gNBs).

Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

Network node 1300 includes a processing circuitry 1302, a memory 1304, a communication interface 1306, and a power source 1308. Network node 1300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 1300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 1300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1304 for different RATs) and some components may be reused (e.g., a same antenna 1310 may be shared by different RATs).

Processing circuitry 1302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 1300 components, such as memory 1304, to provide network node 1300 functionality.

In some embodiments, processing circuitry 1302 includes a system on a chip (SOC). In some embodiments, processing circuitry 1302 includes one or more of radio frequency (RF) transceiver circuitry 1312 and baseband processing circuitry 1314. In some embodiments, the radio frequency (RF) transceiver circuitry 1312 and the baseband processing circuitry 1314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1312 and baseband processing circuitry 1314 may be on the same chip or set of chips, boards, or units.

Memory 1304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions (collectively denoted computer program 1304a) that may be used by processing circuitry 1302. Memory 1304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by processing circuitry 1302 and utilized by network node 1300. Memory 1304 may be used to store any calculations made by processing circuitry 1302 and/or any data received via communication interface 1306. In some embodiments, processing circuitry 1302 and memory 1304 is integrated.

Communication interface 1306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, communication interface 1306 comprises port(s)/terminal(s) 1316 to send and receive data, for example to and from a network over a wired connection. Communication interface 1306 also includes radio front-end circuitry 1318 that may be coupled to, or in certain embodiments a part of, antenna 1310. Radio front-end circuitry 1318 comprises filters 1320 and amplifiers 1322. Radio frontend circuitry 1318 may be connected to an antenna 1310 and processing circuitry 1302. The radio front-end circuitry may be configured to condition signals communicated between antenna 1310 and processing circuitry 1302.

Radio front-end circuitry 1318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1320 and/or amplifiers 1322. The radio signal may then be transmitted via antenna 1310. Similarly, when receiving data, antenna 1310 may collect radio signals which are then converted into digital data by radio front-end circuitry 1318. The digital data may be passed to processing circuitry 1302. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

In certain alternative embodiments, network node 1300 does not include separate radio front-end circuitry 1318, instead, processing circuitry 1302 includes radio front-end circuitry and is connected to antenna 1310. Similarly, in some embodiments, all or some of RF transceiver circuitry 1312 is part of communication interface 1306. In still other embodiments, communication interface 1306 includes one or more ports or terminals 1316, radio front-end circuitry 1318, and RF transceiver circuitry 1312, as part of a radio unit (not shown), and communication interface 1306 communicates with the baseband processing circuitry 1314, which is part of a digital unit (not shown).

Antenna 1310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. Antenna 1310 may be coupled to radio front-end circuitry 1318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, antenna 1310 is separate from network node 1300 and connectable to network node 1300 through an interface or port.

Antenna 1310, communication interface 1306, and/or processing circuitry 1302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, antenna 1310, communication interface 1306, and/or processing circuitry 1302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

Power source 1308 provides power to the various components of network node 1300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1308 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1300 with power for performing the functionality described herein. For example, network node 1300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 1308. As a further example, power source 1308 may comprise a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

Embodiments of network node 1300 may include additional components beyond those shown in Figure 13 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, network node 1300 may include user interface equipment to allow input of information into network node 1300 and to allow output of information from network node 1300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1300.

Figure 14 is a block diagram illustrating a virtualization environment 1400 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1400 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. Applications 1402 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

Hardware 1404 includes processing circuitry, memory that stores software and/or instructions (collectively denoted computer program product 1404a) executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1406 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1408a and 1408b (one or more of which may be generally referred to as VMs 1408), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer 1406 may present a virtual operating platform that appears like networking hardware to the VMs 1408.

VMs 1408 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1406. Different embodiments of the instance of a virtual appliance 1402 may be implemented on one or more of VMs 1408, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, each VM 1408 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1408, and that part of hardware 1404 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1408 on top of the hardware 1404 and corresponds to the application 1402.

Hardware 1404 may be implemented in a standalone network node with generic or specific components. Hardware 1404 may implement some functions via virtualization. Alternatively, hardware 1404 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1410, which, among others, oversees lifecycle management of applications 1402. In some embodiments, hardware 1404 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1412 which may alternatively be used for communication between hardware nodes and radio units.

The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various exemplary embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and/or electronic devices and can include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure. As described herein, device and/or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and/or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and/or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

Claims

1. A method for a radio unit, RU, comprising a plurality of radio frequency, RF, branches coupled to a plurality of antenna branches of an antenna array, the method comprising the following operations during each of plurality of time periods: operating (1110) a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to perform at least one of the following via a coupled antenna branch: transmitting RF signals, and receiving RF signals; operating (1120) a remainder of the RF branches, other than the subset, in a normalenergy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch; and selecting (1160) a next subset of the RF branches to be operated in the low-energy state during a next time period, wherein the selection is performed according to one of the following: randomly, or a time-varying pattern that is determined and/or controlled by the RU.

2. The method of claim 1, wherein the selection of the next subset is performed according to a time-varying pattern controlled by the RU based on information received from one or more baseband processing unit, BPUs, coupled to the RU.

3. The method of any one of claims 1-2, wherein each selected next subset includes a constant number, X, of RF branches.

4. The method of claim 3, wherein: the antenna array is arranged into a plurality, Y, of slices; each slice includes a plurality of antenna branches at adjacent locations in the antenna array.

5. The method of claim 4, wherein selecting (160) the next subset of the RF branches to be operated in the low-energy state during a next time period comprises: selecting (1161) a same number, Z, of antenna array branches from each slice of the antenna array; and selecting (1162) the RF branches coupled to the Z*Y selected antenna array branches.

6. The method of any one of claims 1-5, wherein during each of the plurality of time periods: the selection of the next subset of the RF branches is from a set of the RF branches that are eligible to be operated in the low-energy state during the next time period; and the method comprises determining (1150) the eligible set of RF branches for the next time period based on one or more of the following: a maximum number of RF branches to be operated in the low-energy state during the next time period, a minimum number of RF branches to be operated in the normal-energy state during the next time period, any fault conditions present in the plurality of RF branches, one or more slices of the antenna array that should not be muted during the next time period, and measurements of reference signals, RS, transmitted or received via the antenna array.

7. The method of claim 6, wherein the one or slices of the antenna array that should not be muted during the next time period are used to transmit and/or receive a carrier frequency having a scheduled traffic load that exceeds a threshold during the time period.

8. The method of any one of claims 6-7, wherein: the plurality of RF branches are also coupled to a corresponding plurality of baseband, BB, branches; and the method comprises receiving (1140) an indication of one of the following from one or more baseband processing unit, BPUs, coupled to the RU: a first set of BB branches that will carry signals or channels that should not be muted during at least the next time period, or a second set of BB branches that can be operated in a low-energy state during at least the next time period.

9. The method of claim 8, wherein one of the following applies: the eligible set of RF branches for the next time period includes RF branches coupled to the second set of BB branches; or the eligible set of RF branches determined for the next time period excludes RF branches coupled to the first set of BB branches.

10. The method of any one of claims 8-9, wherein the signals or channels that should not be muted during at least the next time period include one or more of the following: control channels, common reference signals, user-specific reference signals, and beamformed data channels.

11. The method of claim 6, comprising, during each of the plurality of time periods: measuring (1130) uplink RS transmitted by one or more user equipment, UEs, and received via a plurality of the antenna branches and coupled RF branches operating in the normal-energy state; and based on the uplink RS measurements, selecting (1135) a set of antenna branches to transmit downlink data to the one or more UEs, wherein the eligible set of RF branches determined for the next time period excludes the RF branches coupled to the selected set of antenna branches.

12. The method of any one of claims 1-4, wherein: the plurality of RF branches are also coupled to a corresponding plurality of baseband, BB, branches; and during each time period, at least a portion of the BB branches carry user-specific RS to be transmitted via the coupled RF branches; and selecting (1160) a next subset of the RF branches to be operated in the low-energy state during a next time period is performed randomly regardless of the user-specific RS to be transmitted during the next time period.

13. The method of claim 12, wherein during each time period, one or more RF branches are operated in the low-energy state such that user-specific RS carried by the one or more coupled BB branches are not transmitted during the time period.

14. The method of claim 13, comprising: receiving (1170) the following from a user equipment, UE, during each of multiple time periods: first measurements of user-specific RS that were transmitted during the time period, and second measurements corresponding to user-specific RS that were scheduled for transmission but not transmitted during the time period; and estimating (1175) a channel matrix for the UE based on the following: the first and second measurements received during the multiple time periods, and a list of the one or more RF branches that were operating in the low-energy state during each of the multiple time periods.

15. The method of claim 14, wherein: estimating (1175) the channel matrix for the UE is based on respective precoders applied by the BB branches to the user-specific RS during the multiple time periods; and the method comprises determining (1180) one or more revised precoders based on the estimated channel matrix, wherein each revised precoder corresponds to a different set of RF branches operating in the low-energy state.

16. The method of any one of claims 8-15, wherein the RU includes the plurality of BB branches and the method comprises one or more of the following, during each of plurality of time periods: operating (1115), in the low-energy state, the BB branches corresponding to the subset of the RF branches being operated in the low-energy state; and operating (1125), in the normal-energy state, the BB branches corresponding to the remainder of the RF branches being operated in the normal-energy state.

17. The method of any one of claims 1-16, wherein the RU includes the antenna array.

18. The method of any one of claims 1-17, comprising, during each of the plurality of time periods, adjusting (1190) respective beamforming gains or weights used by the plurality of RF branches based on the subset of the RF branches being operated in the low-energy state during the time period.

19. The method of claim 18, wherein adjusting (1190) the respective beamforming gains or weights comprises, for a group of antenna branches arranged linearly in the antenna array, increasing (1191) the beamforming gains used by RF branches coupled to antenna branches at the edges of the linear arrangement, when one or more other antenna array branches of the group are coupled to RF branches being operated in the low-energy state.

20. A radio unit, RU (1020, 1030) comprising: a plurality of radio frequency, RF, branches (220, 230, 511, 1318) configured to be coupled to a plurality of antenna branches (531) of an antenna array (240, 530); and processing circuitry (520, 1302) operably coupled to the RF circuit branches and arranged to execute computer program code that configures the RU to perform the following operations during each of plurality of time periods: operate a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to perform at least one of the following via a coupled antenna branch: transmitting RF signals, and receiving RF signals; operate a remainder of the RF branches, other than the subset, in a normal-energy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch; and select a next subset of the RF branches to be operated in the low-energy state during a next time period, wherein the selection is performed according to one of the following: randomly, or a time-varying pattern that is determined and/or controlled by the RU.

21. The RU of claim 20, wherein the processing circuity is arranged to execute computer program code that configures the RU to perform operations corresponding to any of the methods of claims 2-19.

22. A radio unit, RU (1020, 1030) comprising a plurality of radio frequency, RF, branches (220, 230, 511, 1318) configured to be coupled to a plurality of antenna branches (531) of an antenna array (240, 530), the RU being configured to perform the following operations during each of plurality of time periods: operate a subset of the RF branches in a low-energy state in which each RF branch of the subset is unable to perform at least one of the following via a coupled antenna branch: transmitting RF signals, and receiving RF signals; operate a remainder of the RF branches, other than the subset, in a normal-energy state in which each RF branch of the remainder transmits and receives RF signals via a coupled antenna branch; and select a next subset of the RF branches to be operated in the low-energy state during a next time period, wherein the selection is performed according to one of the following: randomly, or a time-varying pattern that is determined and/or controlled by the RU.

23. The RU of claim 22, being configured to perform operations corresponding to any of the methods of claims 2-19.

24. The RU of any one of claims 20-23, comprising the antenna array.

25. A non-transitory, computer-readable medium (1304) storing computer-executable instructions that, when executed by processing circuitry (520, 1302) of a radio unit, RU (1020, 1030) comprising a plurality of radio frequency, RF, branches (220, 230, 511, 1318) coupled to a plurality of antenna branches (531) of an antenna array (240, 530), configure the RU to perform operations corresponding to any of the methods of claims 1-19.

26. A computer program (1304a) comprising computer-executable instructions that, when executed by processing circuitry (520, 1302) of a radio unit, RU (1020, 1030) comprising a plurality of radio frequency, RF, branches (220, 230, 511, 1318) coupled to a plurality of antenna branches (531) of an antenna array (240, 530), configure the RU to perform operations corresponding to any of the methods of claims 1-19.