CN112119617A

CN112119617A - Eigenvalue based channel hardening and explicit feedback

Info

Publication number: CN112119617A
Application number: CN201880093411.6A
Authority: CN
Inventors: 毛小矛; F·沃克; R·阿梅德; W·J·希勒里; E·维索特斯基
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Oyj
Priority date: 2018-05-17
Filing date: 2018-05-17
Publication date: 2020-12-22
Anticipated expiration: 2038-05-17
Also published as: CN112119617B; EP3794785A4; EP3794785A1; WO2019218317A1

Abstract

An apparatus includes at least one processor and at least one memory including computer program code. The at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: one or more eigenvectors associated with one or more uplink reference signals are calculated. The at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to: one or more channel hardening matrices based on the one or more eigenvectors are applied to one or more downlink channel state information reference signals. The at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to: explicit channel state information is received from the user equipment.

Description

Eigenvalue based channel hardening and explicit feedback

Technical Field

Certain embodiments may relate to a communication system. For example, some embodiments may relate to channel state information feedback.

Background

The Channel State Information (CSI) may include implicit feedback, explicit feedback, and/or a linear combination codebook, which is a mixture of implicit and explicit feedback. Explicit feedback directly returns channel information. A Discrete Fourier Transform (DFT) vector may be selected and applied to the hardened channel, which may reduce the dimension of the channel from M · N to B · N, where M is the number of transmit antennas, N is the number of receive antennas, and B is the number of precoders employed. Since the DFT precoder is considered to be a narrow beam applied to the channel, the resulting aggregated channel matrix becomes sparse due to the channel hardening effect. However, providing explicit feedback typically requires a large amount of network resources for the reporting function to maintain the accuracy of the CSI reports.

Disclosure of Invention

According to one embodiment, a method may comprise: one or more eigenvectors associated with the one or more uplink reference signals are calculated by the network entity. The method may further comprise: applying, by the network entity, one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The method may further comprise: explicit channel state information is received by a network entity from a user equipment.

According to one embodiment, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: one or more eigenvectors associated with one or more uplink reference signals are calculated. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: applying one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to: explicit channel state information is received from the user equipment.

According to one embodiment, an apparatus may comprise: means for calculating one or more eigenvectors associated with one or more uplink reference signals. The apparatus may further include: means for applying one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The apparatus may further include: means for receiving explicit channel state information from a user equipment.

According to one embodiment, in certain embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, perform a process. The process can include a method that can calculate one or more eigenvectors associated with one or more uplink reference signals. The process may include a method that may apply one or more channel hardening matrices based on one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The process can include a method that can receive explicit channel state information from a user equipment.

According to one embodiment, a computer program product may have instructions encoded for performing a process according to some embodiments. The process can include a method that can calculate one or more eigenvectors associated with one or more uplink reference signals. The process may include a method that may also apply one or more channel hardening matrices based on one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The process may include a method that may also receive explicit channel state information from the user equipment.

According to one embodiment, an apparatus may include circuitry configured to calculate one or more eigenvectors associated with one or more uplink reference signals. The apparatus may also include circuitry configured to apply one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals. The apparatus may also include circuitry configured to receive explicit channel state information from the user equipment.

According to one embodiment, a method may comprise: aggregating, by a user equipment, one or more downlink channels by collecting one or more channel impulse responses. The method may further comprise: estimating, by the user equipment, one or more channel state information reference signals (CSI-RSs) based on the aggregated one or more downlink channels. The method may further comprise: sending, by the user equipment, explicit channel state information feedback to the network entity based on the estimated one or more CSI-RSs.

According to one embodiment, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: one or more downlink channels are aggregated by collecting one or more channel impulse responses. The at least one memory and the computer program code may be configured, with the at least one processor, to further cause the apparatus at least to: estimating one or more channel state information reference signals (CSI-RSs) based on the aggregated one or more downlink channels. The at least one memory and the computer program code may be configured, with the at least one processor, to further cause the apparatus at least to: sending explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

According to one embodiment, an apparatus may comprise means for aggregating one or more downlink channels by collecting one or more channel impulse responses. The apparatus may also include means for estimating one or more channel state information reference signals (CSI-RS) based on the aggregated one or more downlink channels. The apparatus may also include means for sending explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

According to one embodiment, in certain embodiments, a non-transitory computer-readable medium may be encoded with instructions that, when executed in hardware, may perform a process. The process may include a method that may aggregate one or more downlink channels by collecting one or more channel impulse responses. The process may include a method that may also estimate one or more channel state information reference signals (CSI-RS) based on the aggregated one or more downlink channels. The process may include a method that may also send explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

According to one embodiment, an apparatus may include circuitry configured to aggregate one or more downlink channels by collecting one or more channel impulse responses. The apparatus may include circuitry further configured to estimate one or more channel state information reference signals (CSI-RS) based on the aggregated one or more downlink channels. The apparatus may include circuitry further configured to transmit explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

According to one embodiment, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: one or more downlink channels are aggregated by collecting one or more channel impulse responses. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: estimating one or more channel state information reference signals (CSI-RSs) based on the aggregated one or more downlink channels. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: sending the one or more CSI-RSs based on the estimation to a network entity, and sending explicit channel state information feedback to the network entity.

Drawings

For a proper understanding of the present disclosure, reference should be made to the accompanying drawings, in which:

fig. 1 illustrates an example of a signaling diagram in accordance with some embodiments.

Fig. 2 illustrates an example of a method performed by a network entity, in accordance with certain embodiments.

Fig. 3 illustrates an example of a method performed by a user equipment, according to some embodiments.

FIG. 4 illustrates an example of a system according to some embodiments.

Detailed Description

The features, structures, or characteristics of some embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, use of the phrases "some embodiments," "other embodiments," or other similar language throughout this specification refers to the fact that: the particular features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of the invention. Thus, appearances of the phrases "in certain embodiments," "in some embodiments," "in other embodiments," or other similar language throughout this specification do not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Some embodiments may help improve explicit feedback for user equipment. Example embodiments described herein may have various benefits and/or advantages. For example, some embodiments may reduce the amount of network resources required for explicit reporting by a user equipment while maintaining CSI reporting accuracy. The eigenvectors may be used to harden the channel, resulting in a sparse channel with less network resource overhead. Furthermore, Uplink (UL) and/or Downlink (DL) channel reciprocity and channel hardening at a network entity, such as the gNB, may make channel hardening transparent to a User Equipment (UE), thereby freeing the UE from having to report eigenvectors or DFT precoder indices. A further reduction in network resource usage can be achieved while maintaining high accuracy of explicit feedback using eigen decomposition techniques. Accordingly, certain embodiments are directed to improvements in computer-related techniques, particularly by conserving network resources and reducing power consumption of UEs and/or network entities located within the network.

Fig. 1 shows an example of a signaling diagram illustrating the communication between a user equipment 130 and a network entity 140. User device 130 may be similar to user device 410 and network entity 140 may be similar to network entity 420, both shown in fig. 4. In step 101, the UE 130 may transmit one or more UE reference signals to the network entity 140. In step 103, the network entity 140 may estimate one or more uplink reference signals based on the UE reference signals received from the UE 130.

In step 105, the network entity 140 may calculate one or more UE channel feature vectors based on the estimated one or more uplink reference signals. In some embodiments, one or more downlink channel matrices at physical resource block/subband i estimated from uplink sounding reference signal may be represented by h_iAnd (4) showing. R may then be used_i(n)＝h_i ^H·h_iTo determine a spatial channel covariance matrix with the current subframe n, where H is the conjugate transpose of the matrix (such as the spatial channel covariance matrix). In addition, R may be used_i(n)＝U_i·Λ_i·U_i ^HTo determine R_i(n) a characteristic decomposition in which U_iIs a square matrix, U_iJ (th) column q_i，jIs R_iA feature vector of (n), and Λ_iIs a diagonal matrix, Λ_iIs a corresponding eigenvalue, in particular λ_i，jWhere i denotes a PRB index or a subband index, and j denotes an element index of the jth row and jth column in the diagonal matrix. In some embodiments, one or more taps of the channel impulse response may be retained after each selected eigenvector is applied by channel hardening. By applying one or more channel hardening matrices to one or more CSI-RS ports, one or more aggregated channels at the UE may be sparse, resulting in a reduced number of CIR taps observed in the time domain. In some embodiments, the number of taps may be limited to one, causing the UE to report explicit feedback with reduced overhead.

In step 107, the network entity 140 may select one or more of the one or more UE channel feature vectors. For example, the number of selected feature vectors may be represented as B_i. In some embodiments, one or more eigenvectors may be selected to harden one or more channels by setting a threshold t for the eigenvalues. The characteristic values may be in random order, increasing order or decreasing order, such as λ_i，1≥λ_i，2≥λ_i，3≥λ_i，…. When the eigenvalues are sorted in descending order, if the jth eigenvalue is greater than the threshold t, then the jth eigenvector may be used to form a channel hardening matrix. In one embodiment, feature vectors 1, 2, may be used_maxTo form a channel hardening matrix, where j_max＝max{j：λ_i，jT }. In some embodiments, the threshold t may depend on the network entity, the UE channel, and/or the network entity scheduling capability.

One or more values (such as B) when the eigenvectors in the hardening matrix are considered as beam basis_i) It may be necessary to have more than the total number of transmission layers, such as r, in order to create orthogonality between the layers, e.g., B_i＝max(j_maxR). For an explicit polarized (X-pol) antenna array, where B can be determined by providing orthogonality between layers using cross-polarization isolation_iIn which B is_i＝max(j_maxR/2). In embodiments using an X-pol antenna array, the transmitted polarization layer may experience reduced polarization interference. In addition, at a plurality of bitsIn the case where co-located x-pol antenna arrays experience channel variations, one or more channel hardening matrices may be applied in half the dimension associated with each polarization.

In some embodiments, the UE may be equipped with more Receive (RX) antennas than Transmit (TX) antennas. In this example, UE TX antenna switching may be provided to enhance UL/DL reciprocity and/or to obtain full DL channel functionality by estimating one or more UL Sounding Reference Signals (SRS).

In various embodiments, the UL/DL reciprocity may preferably be adjusted. For example, in Frequency Division Duplex (FDD) systems for paired spectrum, only long-term spatial information may be extracted from the UL, and/or may be mapped to DL transmissions. Estimating a UE downlink channel matrix h for a Physical Resource Block (PRB)/subband i from one or more UL SRSs_iIn an embodiment, the spatial channel covariance matrix at the current subframe n may be determined by averaging all PRBs/subbands, e.g., r (n) - Σ_ih_i ^H·h_iWhere H is the conjugate transpose. Therefore, r (n) ═ U · Λ · U may be used^HTo determine an eigen decomposition of a spatial channel covariance matrix, such as R (n), where U is a square matrix and the jth column of U is the eigenvector q of R (n)_jAnd Λ is a diagonal matrix, the diagonal elements of Λ being the corresponding eigenvalues.

In step 109, the network entity 140 may form one or more channel hardening matrices based on the one or more selected eigenvectors. For example, one or more channel hardening matrices may be formed from Q_iAnd may be a subband short-term channel hardening matrix and/or a wideband long-term channel hardening matrix. In such an embodiment, may pass through Φ_i＝h_i·Q_iThe resulting channel is determined. In one embodiment, Q_i＝[q_i，l，q_i，2，…，q_i，Bi]。

In addition, channel state information reporting in the time and/or frequency domain may be applied to Φ_iTo provide explicit CSI feedback. For example, after eigen decomposition of the spatial channel covariance matrix, multiple may be selectedA feature vector (such as B)_i) And used to form a matrix (such as Q) such that Q_iQ, thereby hardening the channel for all PRBs/subbands. A similar procedure may be performed in a Time Division Duplex (TDD) system.

In various embodiments, the formation of one or more channel hardening matrices may be based in part on one or more of: antenna array type, duplex mode (TDD or FDD), one or more thresholds, or other factors.

In step 111, the network entity 140 may apply one or more channel hardening matrices to one or more user equipment downlink channel state information reference signals. The one or more channel hardening matrices may be applied as precoders to one or more user equipment downlink channel state information reference signals in several ways. For example, network entity 140 may apply each precoder in one or more channel hardening matrices to one or more antenna ports in a channel state information reference signal (CSI-RS) resource. In another example, the network entity may apply each precoder in the one or more channel hardening matrices to a single CSI-RS resource in the set of CSI-RS resources. In this example, each CSI-RS resource in the set of CSI-RS resources may have multiple antenna ports, allowing the UE to perform further channel hardening. In addition, the configuration of precoders in one or more channel hardening matrices may be periodically updated, e.g., by transmitting semi-permanent and/or aperiodic CSI-RSs to the UE. In step 113, the network entity 140 may transmit one or more CSI-RS signals to the user equipment 130 over a downlink channel.

In step 115, the user equipment 130 may estimate one or more CSI-RSs. In addition, the user equipment may aggregate the one or more downlink channels by collecting one or more channel impulse responses before estimating the one or more CSI-RSs. In some embodiments, the user equipment may aggregate the one or more CSI-RSs in several ways. For example, the user equipment may aggregate one or more CSI-RSs by collecting one or more channel impulse responses from each CSI-RS port in the CSI-RS resources associated with each user equipment RX antenna. In another example, the user equipment may aggregate the one or more CSI-RSs by collecting channel impulse responses from each CSI-RS port associated with each CSI-RS in the set of CSI-RS resources associated with each user equipment RX antenna. In some embodiments, the user equipment may support reporting one or more channel impulse responses for the aggregated channel in the time/frequency domain without having to send the DFT beam index.

In step 117, the user equipment 130 may send explicit channel state information feedback to the network entity. In some embodiments, the user equipment 130 may report one or more channel-hardened precoder indexes to the network entity 140 with the channel impulse response of the aggregated channel in the time/frequency domain, without the DFT beam index. In addition, the user equipment 130 may report reciprocity-based explicit feedback in PUCCH-based periodic CSI reports.

Fig. 2 illustrates an example method performed by a network entity. The network entity may be similar to network entity 420 shown in fig. 4. In step 201, a network entity may receive one or more reference signals from a user equipment. As an example, the user device may be similar to user device 410 shown in fig. 4. In step 203, the network entity may estimate one or more uplink reference signals. In step 205, the network entity may obtain user equipment downlink channel information associated with a downlink channel of the user equipment.

In step 207, the network entity may calculate one or more eigenvectors associated with the one or more uplink reference signals. In some embodiments, one or more downlink channel matrices at physical resource block/subband i estimated from uplink sounding reference signal may be represented by h_iAnd (4) showing. R may then be used_i(n)＝h_i ^H·h_iTo determine the spatial channel covariance matrix for the current subframe n, where H is the conjugate transpose. In addition, R may be used_i(n)＝U_i·Λ_i·U_i ^HTo determine R_i(n) a characteristic decomposition in which U_iIs a square matrix, U_iJ (th) column q_i，jIs R_iA feature vector of (n), and Λ_iIs a diagonal matrix, Λ_iIs a corresponding eigenvalue, in particular λ_i，jWhere i denotes a PRB index or a subband index, and j denotes an element index of the jth row and jth column in the diagonal matrix. In some embodiments, one or more taps of the channel impulse response may be retained after each selected eigenvector is applied by channel hardening. By applying one or more channel hardening matrices to one or more CSI-RS ports, one or more aggregated channels at the UE may be sparse, resulting in a reduced number of CIR taps observed in the time domain. In some embodiments, the number of taps may be limited to one, where the UE may report explicit feedback with reduced overhead.

In step 209, the network entity may select one or more feature vectors. For example, the number of selected feature vectors may be represented as B_i. In some embodiments, one or more eigenvectors may be selected to harden one or more channels by setting a threshold t for the eigenvalues. The characteristic values may be in random order, increasing order or decreasing order, such as λ_i，j≥λ_i，2≥λ_i，3≥λ_i，…. When the eigenvalues are sorted in descending order, if the jth eigenvalue is greater than the threshold t, then the jth eigenvalue may be used to form a channel hardening matrix. In one embodiment, feature vectors 1, 2, may be used_maxTo form a channel hardening matrix, where j_max＝max{j：λ_i，jT }. In some embodiments, the threshold t may depend on the network entity, the UE channel, and/or the network entity scheduling capability.

Although the eigenvectors in the hardening matrix may be considered as beam basis, one or more values (such as B)_i) It may be necessary to have more than the total number of transmission layers, such as r, in order to create orthogonality between the layers, e.g., B_i＝max(j_maxR). For an explicit polarized (X-pol) antenna array, where B can be determined by providing orthogonality between layers using cross-polarization isolation_iIn which B is_i＝max(j_maxR/2). In embodiments using an X-pol antenna array, layers transmitted in one or more polarizations may experience reduced polarization interference. In addition, where multiple co-located x-pol antenna arrays experience channel variations, one or more channel hardening matrices may be applied in half the dimension associated with each polarization.

In various embodiments, the UL/DL reciprocity may preferably be adjusted. For example, in Frequency Division Duplex (FDD) systems for paired spectrum, long-term spatial information may be extracted from the UL and/or may be mapped to the DL transmission. Estimating the UE downlink channel matrix h for PRB/subband i from UL SRS_iIn an embodiment, the spatial channel covariance matrix at the current subframe n may be determined by averaging all PRBs/subbands, e.g., r (n) - Σ_ih_i ^H·h_iWhere H is the conjugate transpose. Therefore, r (n) ═ U · Λ · U may be used^HTo determine an eigen decomposition of a spatial channel covariance matrix, where U is a square matrix whose j-th column is the eigenvector q of R (n)_jAnd Λ is a diagonal matrix, the diagonal elements of Λ being the corresponding eigenvalues.

In step 211, the network entity may form one or more channel hardening matrices based on the one or more selected eigenvectors. For example, one or more channel hardening matrices may be formed from Q_iAnd may be a subband short-term channel hardening matrix and/or a wideband long-term channel hardening matrix. In such an embodiment, may pass through Φ_i＝h_i·Q_iTo determine the resulting channel phi_i. In one embodiment, Q_i＝[q_i，l，q_i，2，...，q_i，Bi]。

In response, channel state information reporting in the time and/or frequency domain may be appliedAt phi_iTo provide explicit CSI feedback. For example, after eigen decomposition of the spatial channel covariance matrix, a plurality of eigenvectors (such as B) may be selected_i) And used to form a matrix (such as Q). In an example embodiment, wherein Q_iEqual to Q, which may harden the channel for all PRBs/subbands. A similar procedure may be performed in a TDD system.

The formation of the one or more channel hardening matrices may be based on one or more of: antenna array type, duplex method (TDD or FDD), one or more thresholds, or other factors.

In step 213, the network entity may apply one or more channel hardening matrices to one or more user equipment downlink channel state information reference signals. The one or more channel hardening matrices may be applied as precoders to one or more user equipment downlink channel state information reference signals in several ways. For example, the network entity may apply each precoder in the one or more channel hardening matrices to one or more antenna ports in the CSI-RS resource. In another example, the network entity may apply each precoder in the one or more channel hardening matrices to a single CSI-RS resource in the set of CSI-RS resources. In this example, each CSI-RS resource in the set of CSI-RS resources may have multiple antenna ports, allowing the UE to perform further channel hardening. In addition, the configuration of precoders in one or more channel hardening matrices may be periodically updated, e.g., by transmitting semi-permanent and/or aperiodic CSI-RSs to the UE.

In step 215, the network entity may transmit one or more downlink channel state information reference signals to the user equipment. In step 217, the network entity may receive explicit channel state information feedback from the user equipment.

Fig. 3 illustrates an example method performed by a user device similar to user device 410 shown in fig. 4. In step 301, the user equipment may transmit one or more UE reference signals to a network entity similar to network entity 420 in fig. 4. In step 303, the user equipment may aggregate one or more downlink channels by collecting one or more channel impulse responses from the network entity.

In step 305, the user equipment may estimate one or more channel state information reference signals (CSI-RS) based on the aggregated one or more downlink channels. In some embodiments, the user equipment may aggregate the one or more CSI-RSs in several ways. For example, the user equipment may aggregate one or more CSI-RSs by collecting one or more channel impulse responses from each CSI-RS port in the CSI-RS resources associated with each user equipment RX antenna. In another example, the user equipment may aggregate one or more CSI-RSs by collecting channel impulse responses from each CSI-RS port associated with each CSI-RS in the set of CSI-RS resources associated with each user equipment RX antenna. In some embodiments, the user equipment may support reporting one or more channel impulse responses for the aggregated channel in the time/frequency domain without having to send the DFT beam index.

In step 307, the user equipment may send explicit channel state information feedback to the network entity based on the estimated one or more CSI-RSs. In some embodiments, the user equipment may report the channel-hardening precoder index to the channel impulse response of the aggregated channel in the time/frequency domain without the DFT beam index. In some embodiments, the UE may send explicit feedback based on reciprocity in PUCCH-based periodic CSI reports.

FIG. 4 illustrates an example of a system according to some embodiments. In one embodiment, a system may include a plurality of devices, such as, for example, a user device 410 and a network entity 420.

The UE 410 may include one or more of the following: a mobile device, such as a mobile phone, a smart phone, a Personal Digital Assistant (PDA), a tablet computer, or a portable media player; a digital camera; a portable camera; a video game machine; a navigation unit, such as a Global Positioning System (GPS) device; a desktop or portable computer; single-location devices, such as sensors or smart meters; or any combination thereof. Network entity 420 may be one or more of the following: a base station, such as an evolved node b (enb) or 5G or a new radio node b (gnb); a service gateway; a server; and/or any other access node; or a combination thereof. Further, the user equipment 410 and/or the network entity 420 may be one or more of a citizen broadband radio service device (CBSD).

One or more of these devices may include at least one processor, indicated 411 and 421, respectively. At least one memory may be provided in one or more of the devices indicated at 412 and 422. The memory may be fixed or removable. The memory may include computer program instructions or computer code embodied therein. The

processors

411 and 421 and

memories

412 and 422, or a subset thereof, may be configured to provide the means corresponding to the various blocks of fig. 1-3. Although not shown, the device may also include positioning hardware, such as GPS or micro-electro-mechanical systems (MEMS) hardware, which may be used to determine the location of the device. Other sensors are also permissible and may be included to determine position, altitude, orientation, and the like, such as a barometer, compass, and the like.

As shown in fig. 4,

transceivers

413 and 423 may be provided, and one or more devices may also include at least one antenna, shown as 414 and 424, respectively. The device may have many antennas, such as an antenna array configured for multiple-input multiple-output (MIMO) communication, or multiple antennas for multiple radio access technologies. For example, other configurations of these devices may be provided.

Transceivers

413 and 423 may be transmitters, receivers, or both transmitters and receivers, or units or devices that may be configured for both transmission and reception.

Processors

411 and 421 may be embodied by any computing or data processing device, such as a Central Processing Unit (CPU), Application Specific Integrated Circuit (ASIC), or similar device. The processor may be implemented as a single controller, or as multiple controllers or processors.

Memories

412 and 422 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A Hard Disk Drive (HDD), Random Access Memory (RAM), flash memory, or other suitable memory may be used. The memory may be combined as the processor on a single integrated circuit, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and processable by the processor may be computer program code in any suitable form, such as a compiled or interpreted computer program written in any suitable programming language. The memory may or may not be removable.

The memory and computer program instructions may be configured with the processor for a particular device to cause a hardware apparatus, such as a user equipment, to perform any of the processes described below (e.g., see fig. 1-3). Thus, in certain embodiments, a non-transitory computer readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, some embodiments may be performed entirely in hardware.

In some embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in fig. 1-3. For example, the circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry. In another example, the circuitry may be a combination of hardware circuitry and software, such as a combination of analog and/or digital hardware circuit(s) and software or firmware, and/or a combination of any portion of hardware processor(s) and software (including digital signal processor (s)), software, and at least one memory that work together to cause the apparatus to perform various processes or functions. In yet another example, the circuitry may be hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), including software, such as firmware for operation. Software in the circuitry may not be present when the hardware operation does not require software.

One of ordinary skill in the art will readily appreciate that certain embodiments discussed above may be practiced with steps in a different order and/or with hardware elements in configurations other than those disclosed. Accordingly, it will be apparent to those skilled in the art that certain modifications, variations, and alternative constructions will be apparent, while remaining within the spirit and scope of the invention. Therefore, to ascertain the metes and bounds of the invention, the appended claims should be referenced.

Part of the vocabulary

3GPP third generation partnership project

5G fifth generation wireless system

ASIC specific integrated circuit

CBRS citizen broadband radio service

CIR channel impulse response

CPU central processing unit

CSI channel state information

CSI-RS channel state information reference signal

DFT discrete Fourier transform

DL downlink

eNB evolved node B

FDD frequency division duplex

FTT fast Fourier transform

gNB next generation node B

GPS global positioning system

HDD hard disk drive

Inverse Fast Fourier Transform (IFFT)

LTE Long term evolution

MEMS micro-electro-mechanical system

MIMO multiple input multiple output

MU multiuser

NR RAN next generation radio access network

NR new radio

PDA personal digital assistant

PRB physical resource block

PUCCH physical uplink control channel

QCL quasi co-location

RAM random access memory

RX-reception

SRS sounding reference signal

TDD time division duplex

TX transmission

UE user equipment

UL uplink

Claims

1. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to:

calculating one or more eigenvectors associated with one or more uplink reference signals;

applying one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals; and

explicit channel state information is received from the user equipment.

2. The apparatus of claim 1, wherein the one or more channel hardening matrices are at least one of subband short-term channel hardening matrices and/or wideband long-term channel hardening matrices.

3. The apparatus of claim 1 or 2, wherein the formation of the one or more channel hardening matrices is based on one or more of a system configuration and a scheduling decision.

4. The apparatus of any of claims 1-3, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

a spatial channel covariance matrix is determined with a current subframe based on one or more channel vectors at physical resource blocks/subbands estimated from one or more uplink sounding reference signals.

5. The apparatus of any of claims 1-4, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

forming the one or more channel hardening matrices based on the one or more selected eigenvectors.

6. The apparatus of any of claims 1-5, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

transmitting one or more downlink reference signals to the user equipment.

7. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

aggregating one or more downlink channels by collecting one or more channel impulse responses;

estimating one or more channel state information reference signals (CSI-RSs) based on the aggregated one or more downlink channels; and

sending explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

8. The apparatus of claim 7, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to:

receiving one or more downlink reference signals from the network entity.

9. The apparatus of claim 7 or 8, wherein the one or more channel impulse responses are collected from each CSI-RS port in CSI-RS resources associated with each receive antenna.

10. The apparatus of any of claims 7-9, wherein the one or more channel impulse responses are collected from each CSI-RS port associated with one or more CSI-RSs in a set of CSI-RS resources associated with each receive antenna.

11. A method, comprising:

calculating, by a network entity, one or more eigenvectors associated with one or more uplink reference signals;

applying, by the network entity, one or more channel hardening matrices based on the one or more eigenvectors to one or more user equipment downlink channel state information reference signals; and

receiving, by the network entity, explicit channel state information from a user equipment.

12. The method of claim 11, wherein the one or more channel hardening matrices are at least one of sub-band short-term channel hardening matrices and/or wideband long-term channel hardening matrices.

13. The method of any of claims 11 or 12, wherein the formation of the one or more channel hardening matrices is based on one or more of a system configuration and a scheduling decision.

14. The method of any of claims 11 to 13, further comprising:

determining, by the network entity, a spatial channel covariance matrix with a current subframe based on one or more channel vectors at physical resource blocks/subbands estimated from an uplink sounding reference signal.

15. The method of any of claims 11 to 14, further comprising:

forming, by the network entity, the one or more channel hardening matrices based on the one or more selected eigenvectors.

16. The method of any of claims 11 to 15, further comprising:

transmitting, by the network entity, one or more downlink reference signals to the user equipment.

17. A method, comprising:

aggregating, by a user equipment, one or more downlink channels by collecting one or more channel impulse responses;

estimating, by the user equipment, one or more channel state information reference signals (CSI-RSs) based on the aggregated one or more downlink channels; and

sending, by the user equipment, explicit channel state information feedback to a network entity based on the estimated one or more CSI-RSs.

18. The method of claim 17, further comprising:

receiving, by the user equipment, one or more downlink reference signals from the network entity.

19. The method of claim 17 or 18, wherein the one or more channel impulse responses are collected from each CSI-RS port in CSI-RS resources associated with each receive antenna.

20. The method of any of claims 17-19, wherein the one or more channel impulse responses are collected from each CSI-RS port associated with one or more CSI-RSs in a set of CSI-RS resources associated with each receive antenna.

21. A non-transitory computer-readable medium encoding instructions that, when executed in hardware, perform the processes of any of claims 1-20.

22. An apparatus comprising means for performing a process according to any one of claims 1 to 20.

23. An apparatus comprising circuitry configured to cause the apparatus to perform the process of any of claims 1-20.

24. A computer program product encoded with instructions for performing a process according to any of claims 1-20.