Reporting uplink channel feedback in wireless communications

Aspects of the present disclosure describe receiving an indication of a covariance matrix from an access point, receiving downlink signaling from the access point, deriving, based at least in part on the covariance matrix or the downlink signaling, one or more precoders for uplink communications over an uplink channel, and indicating, based at least in part on the one or more precoders, uplink channel feedback to the access point.

BACKGROUND

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to wireless communication systems for reporting uplink channel feedback.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. For example, a fifth generation (5G) wireless communications technology (which can be referred to as 5G new radio (5G NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. Some technologies utilize time division duplexing (TDD) for communicating using either downlink or uplink communications in a given period of time. In TDD, channel reciprocity can be used to obtain a channel. In channel reciprocity, for example, an access point can obtain a downlink channel via uplink signaling, such as sounding reference signals (SRS). In another example, using channel reciprocity, a user equipment (UE) can obtain an uplink channel via downlink signaling, such as channel state information reference signal (CSI-RS), etc. Moreover, an access point can derive a precoding matrix indicator (PMI) for downlink transmissions based on the uplink signaling (and/or feedback) from the UE and can provide the PMI or a precoder to the UE for performing uplink precoding.

The access point can provide the precoder to the UE by transmitting a precoded downlink CSI-RS. Due to channel estimation error (e.g., based on channel noise), however, the channel measured by the UE in the downlink may be different than the channel estimated by the access point in the uplink. Thus, the uplink precoder derived from the precoded CSI-RS may suffer from the channel estimation noise seen on the downlink and the uplink, and thus may not be effective for precoding transmissions to the access point. For example, singular value decomposition (SVD)-based precoding, which may be used by UEs in precoding transmissions for an access point, may be sensitive to such noise.

SUMMARY

According to an example, a method for wireless communication is provided. The method includes receiving an indication of a covariance matrix from an access point where the covariance matrix is on the noise and interference experienced on the access point, receiving downlink signaling from the access point, deriving, based at least in part on the covariance matrix or the downlink signaling, one or more precoders for uplink communications over an uplink channel, and indicating, based at least in part on the one or more precoders, uplink channel feedback to the access point.

In another example, a method for wireless communication is provided including receiving an indication of uplink channel feedback from a user equipment (UE), where the uplink channel feedback corresponds to one or more downlink signals transmitted to the UE, determining, based on the uplink channel feedback, whether to specify one or more precoders for the UE or allow the UE to autonomously determine the one or more precoders, and indicating, to the UE, whether to use the one or more precoders or to autonomously determine the one or more precoders.

In yet another example, an apparatus for wireless communication is provided that includes a transceiver for communicating one or more wireless signals via one or more antennas, a memory configured to store instructions, and one or more processors communicatively coupled with the transceiver and the memory. The one or more processors are configured to receive an indication of a covariance matrix from an access point, wherein the covariance matrix is on noise and interference experienced on the access point, receive downlink signaling from the access point, derive, based at least in part on the covariance matrix or the downlink signaling, one or more precoders for uplink communications over an uplink channel, and indicate, based at least in part on the one or more precoders, uplink channel feedback to the access point.

In another example, an apparatus for wireless communication is provided that includes a transceiver for communicating one or more wireless signals via one or more antennas, a memory configured to store instructions, and one or more processors communicatively coupled with the transceiver and the memory. The one or more processors are configured to receive an indication of uplink channel feedback from a UE, wherein the uplink channel feedback corresponds to one or more downlink signals transmitted to the UE, determine, based on the uplink channel feedback, whether to specify one or more precoders for the UE or allow the UE to autonomously determine the one or more precoders, and indicate, to the UE, whether to use the one or more precoders or to autonomously determine the one or more precoders.

DETAILED DESCRIPTION

The described features generally relate to reporting uplink channel feedback in wireless communications, where the uplink feedback may be used to determine a precoder for precoding communications transmitted over an uplink channel. For example, a user equipment (UE) can determine uplink channel feedback based on channel reciprocity with a downlink channel (e.g., in time division duplexing (TDD) communications). In one example, the UE can obtain the uplink channel based on downlink signaling (e.g., downlink channel state information reference signal (CSI-RS). The UE can accordingly transmit uplink channel feedback related to the uplink channel to an access point. For example, the uplink channel feedback may include a modulation and coding scheme (MCS), precoding matrix indicator (PMI), etc. that the UE intends to use in transmitting communications over the uplink channel.

In addition, the access point can determine and indicate, to the UE, whether the UE is to derive a precoder or use a certain precoder. In one example, the indication may be based on the uplink channel feedback received from the UE. In another example, the UE can receive an indication of a covariance matrix from an access point, where the covariance matrix indicates noise and interference experienced at the access point over the downlink channel (or uplink channel in channel reciprocity). In this example, the UE can derive a precoder for precoding uplink communications based on the noise and interference covariance matrix and/or on channel reciprocity from downlink signaling from the access point. In one example, the UE may indicate the channel feedback based on the derived precoder. In another example, based on the uplink channel feedback, the access point can specify, to the UE, whether to derive (or continue to derive for a period of time) the precoder or use a specified precoder in precoding uplink communications (e.g., based on whether the uplink channel feedback indicates an undesirable or unexpected MCS, PMI, etc.).

In an example, the UE can utilize the derived or specified precoder for precoding uplink communications over a data channel, control channel, random access channel (RACH), etc. Moreover, in one example, the UE can determine different precoders for different resource elements, resource blocks, physical resource blocks, etc. based on the noise and interference covariance matrix and channel reciprocity based on corresponding downlink signaling. In any case, the UE can derive the precoder in some instances to conserve signaling used where the access point otherwise indicates the precoder. In other instances, the access point may specify whether to allow the UE to derive the precoder so the access point can retain the ability to specify the precoder (e.g., where the uplink channel feedback is undesirable or unexpected based on the channel estimated by the access point).

The described features will be presented in more detail below with reference toFIGS. 1-7.

Techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms “system” and “network” may often be used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A) are releases of UMTS that use E-UTRA. New Radio (NR) is a new release of UMTS. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., NR or LTE) communications over a shared radio frequency spectrum band. The techniques described herein are applicable to any next generation communications systems including 5th Generation (5G)/NR or LTE/LTE-A applications.

FIG. 1illustrates an example of a wireless communication system100in accordance with various aspects of the present disclosure. The wireless communication system100may include one or more access points, such as base stations105, one or more UEs115, and a core network130. The core network130may provide user authentication, access authorization, tracking, internet protocol (IP) connectivity, and other access, routing, or mobility functions. The base stations105may interface with the core network130through backhaul links132(e.g., S1, etc.). The base stations105may perform radio configuration and scheduling for communication with the UEs115, or may operate under the control of a base station controller (not shown). In various examples, the base stations105may communicate, either directly or indirectly (e.g., through core network130), with one another over backhaul links134(e.g., X1, etc.), which may be wired or wireless communication links.

The base stations105may wirelessly communicate with the UEs115via one or more base station antennas. Each of the base stations105may provide communication coverage for a respective geographic coverage area110. In some examples, base stations105may be referred to as a network entity, a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNodeB (eNB), gNodeB (gNB), Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area110for a base station105may be divided into sectors making up only a portion of the coverage area (not shown). The wireless communication system100may include base stations105of different types (e.g., macro or small cell base stations). Additionally, the plurality of base stations105may operate according to different ones of a plurality of communication technologies (e.g., 5G, fourth generation (4G)/LTE, 3G, Wi-Fi, Bluetooth, etc.), and thus there may be overlapping geographic coverage areas110for different technologies.

In some examples, the wireless communication system100may be or include a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) network. The wireless communication system100may also be a next generation network, such as a 5G wireless communication network. In LTE/LTE-A networks, the term evolved node B (eNB) may be generally used to describe the base stations105, while the term UE may be generally used to describe the UEs115. The wireless communication system100may be a heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB or base station105may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” is a 3GPP term that can be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs115with service subscriptions with the network provider.

A small cell may include a lower-powered base station, as compared with a macro cell, that may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs115with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs115having an association with the femto cell (e.g., UEs115in a closed subscriber group (CSG), UEs115for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers).

The communication networks that may accommodate some of the various disclosed examples may be packet-based networks that operate according to a layered protocol stack and data in the user plane may be based on the IP. A radio link control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A MAC layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat/request (HARD) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE115and the base stations105. The RRC protocol layer may also be used for core network130support of radio bearers for the user plane data. At the physical (PHY) layer, the transport channels may be mapped to physical channels.

The wireless communication links125shown in wireless communication system100may carry uplink (UL) transmissions from a UE115to a base station105, or downlink (DL) transmissions, from a base station105to a UE115. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each wireless communication link125may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies described above. Each modulated signal may be sent on a different sub-carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, etc. The wireless communication links125may transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources). Frame structures may be defined for FDD (e.g., frame structure type 1) and TDD (e.g., frame structure type 2).

In aspects of the wireless communication system100, base stations105or UEs115may include multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stations105and UEs115. Additionally or alternatively, base stations105or UEs115may employ multiple input multiple output (MIMO) techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data.

In aspects of the wireless communication system100, base station105may include a scheduling component240for scheduling one or more UEs115for communicating with the base station105, which can include transmitting downlink communications from the base station105and/or receiving uplink communications from the UE115. For example, scheduling component240may transmit a covariance matrix, where the covariance matrix is on the noise and interference experienced on the access point (e.g., base station105), and/or downlink signaling to the UE115and/or may receive uplink channel feedback that is based on the covariance matrix and/or an uplink channel determined, by the UE115, based on channel reciprocity corresponding to the downlink signaling. The scheduling component240, in an example, can indicate to the UE115whether to derive a precoder or use a specific precoder based at least in part on the uplink channel feedback received from the UE115.

In an example, the UE115may include a communicating component340for communicating with the base station105. For example, communicating component340can receive the covariance matrix, where the covariance matrix is on the noise and interference experienced on the access point (e.g., base station105), and/or downlink signaling from the base station105. In this example, communicating component340can determine one or more precoders based on the covariance matrix and/or downlink signaling. For example, communicating component340can transmit uplink channel feedback to the base station105, such as MCS, PMI, etc., based on the determined precoder. In one example, communicating component340may receive an indication of whether to derive a precoder or use a specific precoder signaled from base station105, and can accordingly use the derived or specific precoder in precoding uplink communications for transmitting to the base station105. Accordingly, the base station105can determine when the uplink channel feedback is in a state such that the UE115can derive the precoder instead of using signaling resources to signal the precoder from the base station105.

Referring toFIG. 2, a block diagram200is shown that includes a portion of a wireless communications system having multiple UEs115in communication with a base station105via wireless communication links125, where the base station105is also connected to a network210. The UEs115may be examples of the UEs described in the present disclosure that are configured to provide uplink channel feedback to one or more base stations105. Moreover the base station105may be an example of the base stations described in the present disclosure that are configured to receive uplink channel feedback from the one or more UEs115.

In an aspect, the base station inFIG. 2may include one or more processors205and/or memory202that may operate in combination with a scheduling component240to perform the functions, methodologies (e.g., method400ofFIG. 4), or other methods presented in the present disclosure. In accordance with the present disclosure, the scheduling component240may include a covariance matrix providing component242for providing a covariance matrix to one or more UEs115, an uplink feedback receiving component244for receiving, from one or more UEs115, feedback corresponding to an uplink channel, and/or an optional precoder configuring component246for configuring the one or more UEs115to derive precoders or utilize one or more specific precoders in precoding uplink communications for transmission to the base station105.

The one or more processors205may include a modem220that uses one or more modem processors. The various functions related to the scheduling component240, and/or its sub-components, may be included in modem220and/or processor205and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors205may include any one or any combination of a modem processor, a baseband processor, a digital signal processor, a transmit processor, a transceiver processor associated with transceiver270, a system-on-chip (SoC), etc. In particular, the one or more processors205may execute functions and components included in the scheduling component240.

In some examples, the scheduling component240and each of the sub-components may comprise hardware, firmware, and/or software and may be configured to execute code or perform instructions stored in a memory (e.g., a computer-readable storage medium, such as memory202discussed below). Moreover, in an aspect, the base station105inFIG. 2may include a radio frequency (RF) front end290and transceiver270for receiving and transmitting radio transmissions to, for example, UEs115. The transceiver270may coordinate with the modem220to transmit messages generated by the scheduling component240to the UEs. RF front end290may be connected to one or more antennas273and can include one or more switches292, one or more amplifiers (e.g., power amplifiers (PAs)294and/or low-noise amplifiers291), one or more filters293, etc. for transmitting and receiving RF signals on uplink channels and downlink channels. In an aspect, the components of the RF front end290can connect with transceiver270. The transceiver270may connect to one or more of modem220and processors205.

The transceiver270may be configured to transmit (e.g., via transmitter (TX) radio275) and receive (e.g., via receiver (RX) radio280) wireless signals through antennas273via the RF front end290. In an aspect, the transceiver270may be tuned to operate at specified frequencies such that the base station105can communicate with, for example, UEs115. In an aspect, for example, the modem220can configure the transceiver270to operate at a specified frequency and power level based on the configuration of the base station105and communication protocol used by the modem220.

The base station105inFIG. 2may further include a memory202, such as for storing data used herein and/or local versions of applications or scheduling component240and/or one or more of its sub-components being executed by processor205. Memory202can include any type of computer-readable medium usable by a computer or processor205, such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory202may be a computer-readable storage medium that stores one or more computer-executable codes defining scheduling component240and/or one or more of its sub-components. Additionally or alternatively, the base station105may include a bus211for coupling one or more of the RF front end290, the transceiver274, the memory202, or the processor205, and to exchange signaling information between each of the components and/or sub-components of the base station105.

In an aspect, the processor(s)205may correspond to one or more of the processors described in connection with the base station inFIG. 7. Similarly, the memory202may correspond to the memory described in connection with the base station inFIG. 7.

Referring toFIG. 3, a block diagram300is shown that includes a portion of a wireless communications system having multiple UEs115in communication with a base station105via wireless communication links125, where the base station105is also connected to a network310. The UEs115may be examples of the UEs described in the present disclosure that are configured to provide uplink channel feedback to one or more base stations105. Moreover the base station105may be an example of the base stations described in the present disclosure that are configured to receive uplink channel feedback from the one or more UEs115.

In an aspect, the UE115inFIG. 3may include one or more processors305and/or memory302that may operate in combination with a communicating component340to perform the functions, methodologies (e.g., method500ofFIG. 5), or other methods presented in the present disclosure. In accordance with the present disclosure, the communicating component340may include a covariance matrix receiving component342for receiving a covariance matrix from the base station105, a precoder deriving component344for determining a precoder for uplink communications based at least in part on the covariance matrix and/or downlink signaling from the base station105, and an uplink feedback providing component346for providing uplink feedback to the base station105, which may be based on the determined precoder and/or the downlink signaling from the base station105(e.g., based on uplink channel reciprocity).

The one or more processors305may include a modem320that uses one or more modem processors. The various functions related to the communicating component340, and/or its sub-components, may be included in modem320and/or processor305and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors305may include any one or any combination of a modem processor, a baseband processor, a digital signal processor, a transmit processor, a transceiver processor associated with transceiver370, a system-on-chip (SoC), etc. In particular, the one or more processors305may execute functions and components included in the communicating component340.

In some examples, the communicating component340and each of the sub-components may comprise hardware, firmware, and/or software and may be configured to execute code or perform instructions stored in a memory (e.g., a computer-readable storage medium, such as memory302discussed below). Moreover, in an aspect, the UE115inFIG. 3may include an RF front end390and transceiver370for receiving and transmitting radio transmissions to, for example, base stations105. The transceiver370may coordinate with the modem320to receive signals to be processed by the communicating component340. RF front end390may be connected to one or more antennas373and can include one or more switches392, one or more amplifiers (e.g., PAs394and/or LNAs391), and one or more filters393for transmitting and receiving RF signals on uplink channels and downlink channels. In an aspect, the components of the RF front end390can connect with transceiver370. The transceiver370may connect to one or more of modem320and processors305.

The transceiver370may be configured to transmit (e.g., via transmitter (TX) radio375) and receive (e.g., via receiver (RX) radio380) wireless signals through antennas373via the RF front end390. In an aspect, the transceiver370may be tuned to operate at specified frequencies such that the UE115can communicate with, for example, base stations105. In an aspect, for example, the modem320can configure the transceiver370to operate at a specified frequency and power level based on the configuration of the UE115and communication protocol used by the modem320.

The UE115inFIG. 3may further include a memory302, such as for storing data used herein and/or local versions of applications or communicating component340and/or one or more of its sub-components being executed by processor305. Memory302can include any type of computer-readable medium usable by a computer or processor305, such as RAM, ROM, tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory302may be a computer-readable storage medium that stores one or more computer-executable codes defining communicating component340and/or one or more of its sub-components. Additionally or alternatively, the UE115may include a bus311for coupling one or more of the RF front end390, the transceiver374, the memory302, or the processor305, and to exchange signaling information between each of the components and/or sub-components of the UE115.

In an aspect, the processor(s)305may correspond to one or more of the processors described in connection with the UE inFIG. 7. Similarly, the memory302may correspond to the memory described in connection with the UE inFIG. 7.

In certain aspects, UEs115can perform channel reciprocity to obtain an uplink channel based on downlink signaling, and/or base stations105can similarly perform channel reciprocity to obtain a downlink channel based on uplink signaling, which can reduce feedback overhead typically associated with obtaining the channels. For example, a base station can derive PMI for precoding downlink transmissions over a channel based on uplink signaling/feedback over the channel, and thus may not need to signal PMI information with demodulation reference signal (DMRS)-based downlink transmission modes to the UE(s). Similarly, the UE may not need to obtain explicit PMI information for demodulating downlink transmissions from the base station over the channel.

In another example, the UE may obtain the PMI information from the base station to accordingly perform uplink precoding. Moreover, for uplink communications, the base station can obtain the uplink channel via uplink signaling (e.g., SRS), and can derive uplink precoding based on the uplink channel, interference, and noise experienced on the base station receiver. The base station can convey the precoder to the UE (e.g., the eNB can explicitly signal the PMI in an uplink grant to the UE, and/or with frequency selective precoding in the uplink, the base station can signal PMI for each of a plurality of sub-bands). In one example, the base station can signal the uplink frequency selected unquantized precoding via a precoded downlink CSI-RS.

In an example, the base station can receive an uplink signal on a k-th subcarrier as:
y[k]=Hu[k]x[k]+n[k]
where x[k] is the signal transmitted from UE, n[k] is the interference seen by base station with covariance matrix Rnn, and Hu[k] is the UL channel on the k-th subcarrier. The base station can obtain whitened channel as:
{tilde over (H)}u[k]=Rnn−1/2Hu[k]=U[k]Λ[k]V[k]*.
Where U[k]Λ[k]V[k]* is the singular value decomposition of matrix {tilde over (H)}u[k] or effectively the singular value decomposition of matrix Rnn−1/2Hu[k].
With channel reciprocity and substantially perfect calibration, HD[k]=(Hu[k])T. The base station can send precoded CSI-RS with (U*[k]Rnn−1/2)T. The downlink channel that the UE measures from precoded CSI-RS can be:
HD[k](U*[k]Rnn−1/2)T=(U*[k]Rnn−1/2HU[k])T=(Λ[k]V[k]*)T=(V[k]*)TΛ[k]
The UE can thus obtain the uplink precoder V[k] from the precoded CSI-RS transmitted by the base station. However, there may be some issues with obtaining the uplink precoder from the precoded CSI-RS in this regard.

For example, with channel estimation error, the channel measured by UE in the downlink is ĤD[k]=HD[k]+N1[k] while the channel estimated by base station in the uplink is ĤU[k]=HU[k]+N2[k], where N1[k] and N2[k] may represent different noise levels. The channel reciprocity can hold for the true channel, but may not be as accurate for the estimated channel. In other words, HD[k]=(Hu[k])T, but ĤD[k]˜=(Ĥu[k])T. The downlink channel the UE measures from precoded CSI-RS can be:
ĤD[k](U*[k]Rnn−1/2)T=(U*[k]Rnn−1/2HU[k]+N1[k])T=(Λ[k]V[k]*)T+(U*Rnn−1/2n[k])T=(V[k]*)TΛ[k]+(U*Rnn−1/2n[k])T
This may imply that the uplink precoder V[k] derived from the precoded CSI-RS may suffer from the channel estimation noise seen on both the downlink and the uplink. In an example, a singular value decomposition (SVD) operation for precoding communications (e.g., by the UE) may be very sensitive to noise, and may thus yield undesirable results when based on the derived precoder V[k]. In addition, if the base station applies some precoding smoothing techniques to allow for continuous precoder, the exact algorithm may need to be specified for the UE to obtain the precoder. Furthermore, the precoded CSI-RS may need to be UE specific, which may imply a nontrivial overhead in the system in the presence of multiple UEs.

Thus, as described further herein for example, the UE115can obtain the UL precoder information based on communications from the base station105(e.g., based on the precoder derived from the precoded CSI-RS and/or based on a covariance matrix indicated by the base station105). In this case, the UL precoder can be implicitly indicated from base station105. Alternatively, the base station105may indicate the UL precoder via explicit signaling (for example, explicit PMI in a physical downlink control channel (PDCCH)). As yet another alternative, the UE may derive the UL precoder based on DL signaling where the DL signaling could be unprecoded CSI-RS as well as noise and interference covariance matrix or the DL signaling could be CSI-RS whitened by noise and interference covariance matrix where the whitening takes the noise and interference covariance matrix experienced by the eNB receiver into account. In addition, for example, the UE115can transmit the uplink channel feedback to the base station105and the base station105can indicate to the UE115whether to use the derived precoder (and/or whether to subsequently derive precoders) or whether to use the precoder indicated by the base station105where the precoder indication from eNB could be either implicit via precoded CSI-RS signaling, explicitly conveyed in the PDCCH, etc.

FIG. 4illustrates a flow chart of an example of a method400for receiving and processing (e.g., by a base station) uplink channel feedback.

At Block402, method400may optionally include indicating a covariance matrix to a UE. In an aspect, covariance matrix providing component242, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can indicate the covariance matrix to the UE115. In an aspect, covariance matrix providing component242can generate the covariance matrix (e.g., Rnn, in the formulas above) based on the noise and interference experienced on the base station receiver (e.g., at transceiver270or a portion thereof). Covariance matrix providing component242can then, for example, transmit the covariance matrix to one or more UEs115over at least one of a dedicated channel (e.g., physical downlink control channel (PDCCH), physical downlink shared channel (PDSCH), etc.), a random access channel, etc. In another example, covariance matrix providing component242can transmit the covariance matrix by precoding a CSI-RS based on the covariance matrix. For example, covariance matrix providing component242can precode the CSI-RS using a whitening matrix from the covariance matrix to account for noise and interference based on the covariance matrix, and can transmit the precoded CSI-RS to the UE115. That is, instead of transmitting unprecoded CSI-RS which allows UE115to measure Hu[k], the covariance matrix providing component242can precode the CSI-RS with Rnn−1/2such that UE115can estimate the whitened UL channel with respect to the covariance matrix experienced at base station (e.g., gNB) receiver, e.g., Rnn−1/2Hu[k]*.

At Block404, method400includes receiving an indication of uplink channel feedback from a UE, where the uplink channel feedback corresponds to one or more downlink signals transmitted to the UE. In an aspect, uplink feedback receiving component244, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can receive an indication of uplink channel feedback from the UE115, where the uplink channel feedback corresponds to one or more downlink signals transmitted to the UE115by the base station105. For example, the one or more downlink signals can correspond to a reference signal, such as a common reference signal (CRS) or CSI-RS, etc., a signal used to transmit a covariance matrix at optional Block402, and/or substantially any downlink signal from the base station105. In an example, the uplink channel feedback can correspond to CSI or other feedback related to an uplink channel based on channel reciprocity with the downlink channel.

For example, channel reciprocity, as used herein, can relate to the concept that links operating on a same or similar frequency band may have similar impulse response regardless of direction. Thus, in channel reciprocity, the impulse response observed in signaling on the downlink can be assumed to be the same for determining an uplink channel (e.g., where the channel is configured in TDD for downlink communications in some time periods and uplink communications in others). Similarly, in an example, in channel reciprocity, the impulse response observed in signaling on the uplink can be assumed to be the same for determining a downlink channel. Accordingly, as described further herein, the UE115can determine CSI feedback for an uplink channel based on impulse response or other properties of the downlink signaling (e.g., the CSI-RS from base station105) that are assumed to be the same or similar for the uplink channel. In addition, the UE115can determine the CSI feedback based on a covariance matrix received from the base station105. The CSI feedback received by uplink feedback receiving component244from the UE115may include a MCS, PMI, etc. determined for a precoder derived from the covariance matrix and/or downlink signaling of the base station105, where the UE115may use (or plan to use) the MCS, PMI, etc. in transmitting uplink communications to the base station105.

In one example, receiving the indication of uplink channel feedback at Block404may optionally include, at Block406, receiving the uplink channel feedback in an uplink control channel with downlink channel feedback. In an aspect, uplink feedback receiving component244, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can receive the uplink channel feedback in the uplink control channel with downlink channel feedback. For example, the UE115can transmit, and the uplink feedback receiving component244can receive, the uplink channel feedback in a physical uplink control channel (PUCCH) or other control channel along with (or without) downlink channel feedback (e.g., CSI or other feedback for one or more downlink channels transmitted by the base station105to the UE115).

In another example, receiving the indication of uplink channel feedback at Block404may optionally include, at Block408, receiving the uplink channel feedback in an uplink data channel. In an aspect, uplink feedback receiving component244, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can receive the uplink channel feedback in the uplink data channel. For example, the uplink data channel may include a physical uplink shared channel (PUSCH) allocated by the base station105to one or more UEs115, and the UE115can transmit the uplink channel feedback (e.g., along with uplink data or otherwise) over the uplink data channel.

At Block410, method400includes determining, based on the uplink channel feedback, whether to specify one or more precoders for the UE or allow the UE to determine the one or more precoders. In an aspect, precoder configuring component246, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can determine, based on the uplink channel feedback, whether to specify one or more precoders for the UE115or allow the UE115to determine the one or more precoders. For example, precoder configuring component246can compare the uplink channel feedback to one or more thresholds or parameters determined for the uplink channel by the base station105, and can determine whether to specify one or more precoders for the UE or allow the UE to autonomously determine the one or more precoders based on the comparison. In a specific example, the uplink channel feedback may include a PMI, MCS, etc. determined based on a derived precoder, as described. Thus, for example, precoder configuring component246can determine whether to specify one or more precoders for the UE or allow the UE to autonomously determine the one or more precoders based on comparing the PMI, MCS, etc. indicated in uplink feedback in uplink control or data channel, to a PMI, MCS, etc. determined by the base station105, and/or the like. For example, precoder configuring component246can determine to specify a precoder for certain PMI and/or MCS values while allowing the UE115to determine the precoder for other PMI and/or MCS values.

At Block412, method400includes indicating, to the UE, whether to use the one or more precoders or to determine the one or more precoders. In an aspect, precoder configuring component246, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can indicate, to the UE115, whether to use the one or more precoders (e.g., as specified by the base station105) or to determine the one or more precoders (e.g., autonomously by the UE115based on covariance matrices, downlink signaling, etc.). For example, precoder configuring component246may indicate, to the UE115, whether to use the one or more precoders or whether to determine the one or more precoders via an indicator transmitted in an uplink grant to the UE115, transmitted in radio resource control (RRC) signaling, and/or the like.

In one example, indicating at Block412may optionally include, at Block414, indicating the one or more precoders to the UE. In an aspect, precoder configuring component246, e.g., in conjunction with processor(s)205, memory202, transceiver270, scheduling component240, etc. can indicate the one or more precoders to the UE115, such that the UE115can obtain the one or more precoders and utilize the one or more precoders in precoding uplink communications for the base station105. In this regard, for example, where the precoder configuring component246indicates one or more precoders, the UE115can determine to utilize the one or more precoders indicated instead of a derived precoder, as described further herein. For example, precoder configuring component246can indicate the one or more precoders as one or more precoding matrices or other corresponding parameters from which the precoder can be determined and/or applied by the UE115.

FIG. 5illustrates a flow chart of an example of a method500for generating and communicating (e.g., by a UE) uplink channel feedback corresponding to an uplink channel.

At Block502, method500includes receiving downlink signaling from the access point. In an aspect, communicating component340, e.g., in conjunction with processor(s)305, memory302, and/or transceiver370, can receive the downlink signaling from the access point (e.g., from base station105). In an example, the downlink signaling may correspond to one or more reference signals (e.g., CSI-RS, CRS, etc.), one or more signals over which a covariance matrix is received by covariance matrix receiving component342, or substantially any downlink signaling that can be used with channel reciprocity to obtain an uplink channel, etc.

In one example, receiving the downlink signaling from the access point may include, at Block504, receiving an indication of a covariance matrix from an access point. In an aspect, covariance matrix receiving component342, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can receive the indication of the covariance matrix from the access point (e.g., base station105), which may include receiving the indication as part of the downlink signaling or separate from the downlink signaling. As described, for example, the base station105may generate the covariance matrix based on the noise and interference experienced at the base station receiver (e.g., transceiver270) over the downlink and/or uplink channel. This example allows multiple UEs to use the CSI-RS, which may be unprecoded, while the covariance matrix can be signaled to each UE. Additionally, covariance matrix receiving component342may receive the covariance matrix from the base station105in an uplink grant, in a RRC message, etc. In another example, covariance matrix receiving component342may receive a CSI-RS from the base station105, where the CSI-RS is precoded based on the covariance matrix (e.g., precoded with a whitening matrix from the covariance matrix), and since the CSI-RS is precoded with respect to the covariance matrix, UE115can measure the whitened channel from the precoded CSI-RS and UE115may not need to determine the covariance matrix (e.g., the covariance matrix becomes identity matrix since base station, e.g., gNB, already whitens the channel).

At Block506, method500includes deriving, based at least in part on the covariance matrix or the downlink signaling, one or more precoders for uplink communications. In an aspect, precoder deriving component344, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can derive, based at least in part on the covariance matrix or the downlink signaling, one or more precoders for uplink communications. For example, precoder deriving component344may measure the downlink channel from the downlink signaling from the base station105as:
HD[k](U*[k]Rnn−1/2)T=(U*[k]Rnn−1/2HU[k])T=(Λ[k]V[k]*)T=(V[k]*)TΛ[k]
In addition, precoder deriving component344may obtain an uplink channel based on channel reciprocity with the downlink signaling. Precoder deriving component344may accordingly obtain the uplink precoder V[k], which can be determined based on using the covariance matrix as Rnnin the above formula, or a similar formula, for determining the downlink signaling/corresponding uplink channel. In another example, precoder deriving component344may apply precoding smoothing techniques, such as incremental SVD, sub-band SVD, etc., to obtain the precoder (e.g., based on the formula above). For example, this can allow for continuous precoding of uplink transmissions where the continuous precoding can be over the entire frequency band for the uplink channel or over a sub-band thereof.

At Block508, method500includes indicating, based at least in part on the one or more precoders, uplink channel feedback to the access point. In an aspect, uplink feedback providing component346, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can indicate, based at least in part on the one or more precoders, uplink channel feedback to the access point (e.g., base station105). In an example, the uplink channel feedback may relate to the uplink channel with the base station105. For example, the uplink channel feedback may include a MCS, PMI, etc., which can be determined for the uplink channel based on the derived precoder. In this case, for example, the UE can derive the precoder based on DL signaling such as CSI-RS and channel reciprocity to obtain uplink channel and/or the noise and interference covariance matrix experienced on the base station receiver (e.g., transceiver270) and can accordingly obtain the corresponding MCS and PMI and feedback to the base station105.

Thus, for example, indicating the uplink channel feedback at Block508may optionally include, at Block510, indicating an MCS or PMI in the uplink channel feedback. In an aspect, uplink feedback providing component346, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can indicate the MCS or PMI in the uplink channel feedback. In an example, the MCS, PMI, etc. may be of a large sub-band granularity (e.g., larger than a granularity for MCS, PMI, etc. determined for the uplink data transmission (e.g., over PUSCH)), as the MCS, PMI, etc. in the uplink channel feedback can be used for confirmation between the UE115and the base station105as to which MCS, PMI, etc. is to be used on the uplink channel. In another example, the UE115may use continuous precoding for actual uplink transmission over the uplink channel (e.g., over PUSCH), as described further herein, where the continuous precoding may be different than the PMI reported to the base station105in the uplink channel feedback. In addition, for example, the base station105may determine the MCS based at least on channel and noise variance detected in the bandwidth assigned for the downlink and uplink channels (e.g., detected based on uplink signals received from the UE115).

In another example, indicating the uplink channel feedback at Block508may optionally include, at Block512, transmitting the uplink channel feedback with downlink channel feedback in an uplink control channel. In an aspect, uplink feedback providing component346, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can transmit the uplink channel feedback along with downlink channel feedback in the uplink control channel (e.g., PUCCH). For example, uplink feedback providing component346can transmit the uplink channel feedback with downlink channel feedback such as CSI feedback for a downlink channel (e.g., PDSCH, etc.) from the base station105. Thus, for example, uplink feedback providing component346can at least one of multiplex the uplink channel feedback and the downlink channel feedback, jointly encode the uplink channel feedback and the downlink channel feedback for transmitting over the uplink feedback channel, etc. In another example, uplink feedback providing component346can transmit the uplink channel feedback separately from the downlink channel feedback over the uplink feedback channel.

In yet another example, indicating the uplink channel feedback at Block508may optionally include, at Block514, transmitting the uplink channel feedback in an uplink data channel. In an aspect, uplink feedback providing component346, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can transmit the uplink channel feedback in the uplink data channel (e.g., PUSCH). For example, uplink feedback providing component346may provide the uplink channel feedback along with (e.g., multiplexed with) uplink data in the uplink data channel.

At Block516, method500optionally includes receiving, in response to indicating the uplink channel feedback, a precoder indication from the access point. In an aspect, precoder deriving component344, e.g., in conjunction with processor(s)305, memory302, communicating component340, and/or transceiver370, can receive, in response to indicating the uplink channel feedback, the precoder indication from the access point (e.g., base station105). As described, the precoder indication may be received from the base station105in an uplink grant (e.g., corresponding to resources for a PUCCH, PUSCH, etc.), in RRC signaling, and/or the like. Moreover, as described, the precoder indication may indicate whether the UE115is to use a precoder specified by the base station105, whether the UE115is to autonomously determine a precoder (e.g., as derived by precoder deriving component344at Block506), an indication of a precoder for the UE115to use in precoding uplink communications as specified by the base station105, etc. In any case, precoder deriving component344can determine which precoder to use based at least in part on the indication, as described.

At Block518, method500optionally includes transmitting uplink communications to the access point over an uplink channel based on at least one precoder of the one or more precoders or one or more other precoders based on a precoder indication. In an aspect, communicating component340, e.g., in conjunction with processor(s)305, memory302, and/or transceiver370, can transmit uplink communications to the access point (e.g., base station105) over an uplink channel based on at least one precoder of the one or more precoders (e.g., as derived by precoder deriving component344) or one or more other precoders based on a precoder indication (e.g., where a precoder indication is received by precoder deriving component344from base station105). In an example, the uplink communications can correspond to uplink data channel (e.g., PUSCH) communications, uplink control channel (e.g., PUCCH) communications, random access channel (e.g., RACH) communications, etc.

In a specific example, in LTE, an explicit transmit diversity scheme may not be applied to physical RACH (PRACH) transmission, and the UE could apply open loop transmit antenna selection transparent to the base station. In LTE, transparent open loop transmit antenna selection or spatial orthogonal resource transmit diversity (SORTD) may be applied to uplink control communications (e.g., PUCCH). In addition, in SORTD, different transmit antennas may use different PUCCH resources. In NR, cyclic delay diversity and precoder cycling may be used for PUCCH and/or PRACH. However, the above transmit diversity schemes are open loop schemes (i.e., the diversity scheme is not a function of uplink channel). With channel reciprocity, as described above, closed-loop transmit diversity scheme can be used for precoding communications over the UL control channel, at least in some cases.

Thus, for example, for PUCCH, the downlink signaling received by the communicating component340(e.g., at Block502) may include CRS, CSI-RS, etc., and the communicating component340can measure the uplink channel based on channel reciprocity with the downlink signaling. In addition, the precoder deriving component344can determine the preferred precoding on the corresponding PUCCH resources based on the measured uplink channel. For example, in deriving the precoder, precoder deriving component344(e.g., at Block506) may take the channel covariance matrix into account if available. In addition, for example, communicating component340can apply precoding smoothing techniques to facilitate continuous precoding to allow the base station105to perform wideband channel estimation. If the PUCCH uses orthogonal frequency division multiplexing (OFDM), communicating component340may apply different precoders on different resource elements, resource blocks, physical resource block groups, etc. in different time periods (e.g., different symbols) based on the measured uplink channel and/or on the covariance matrix. If the PUCCH uses single carrier frequency division multiplexing (SC-FDM), communicating component340may apply a single precoder on the PUCCH over various time periods (e.g., a number of symbols) based on the measured uplink channel and/or on the covariance matrix.

Moreover, for example, communicating component340may determine whether to switch to an open loop diversity scheme if it outperforms the closed loop diversity scheme described in method500and/or vice versa. For example, communicating component340may determine signal-to-noise ratio (SNR) associated with the open loop diversity scheme (e.g., cyclic delay diversity (CDD), PMI cycling, etc.) and a SNR associated with the closed loop described above, and may select the one having the highest SNR, select one or the other based on comparing associated SNR(s) with associated threshold(s), etc.

In addition, for example, for 4-message PRACH between the UE115and base station105, the UE115can send a RACH preamble as message1, and a PUSCH on message3. In this example, precoder deriving component344can determine a precoder (e.g., at Block506) for the preamble transmission on the corresponding PRACH resources based on the measured uplink channel. Precoder deriving component344can determine a precoder (e.g., at Block506) for the resources for message1and message3based on the measured uplink channel as well. With a 2-message PRACH, precoder deriving component344can determine a precoder (e.g., at Block506) for the resources for message1based on the measured uplink channel. Moreover, for example, communicating component340may determine whether to switch to an open loop diversity scheme if it outperforms the closed loop diversity scheme described in method500for PRACH as well. For example, communicating component340may determine signal-to-noise ratio (SNR) associated with the open loop (e.g., cyclic delay diversity (CDD), PMI cycling, etc.) and a SNR associated with the closed loop described above, and may select the one having the highest SNR, select one or the other based on comparing associated SNR(s) with associated threshold(s), etc.

Referring toFIG. 6, a block diagram is shown that includes a portion of a wireless communications system600having a UE115in communication with a base station105. For example, the base station can transmit downlink signaling602, which the UE115can receive. The downlink signaling602may include or otherwise indicate a covariance matrix (e.g., as an explicitly indicated matrix, as a CSI-RS precoded based on the covariance matrix (e.g., and/or an associated whitening matrix), and/or the like). In another example, the downlink signaling602may include a CSI-RS, as described, precoded based on the covariance matrix or otherwise based on a precoder derived from a downlink channel obtained based on channel reciprocity with an uplink channel.

The UE115can determine a precoder at604, where determining the precoder is based at least in part on the downlink signaling602. As described, for example, the UE115can determine the precoder based at least in part on deriving the precoder based on the covariance matrix and/or based on a precoder used in transmitting the CSI-RS. In another example, UE115can determine the precoder based at least in part on obtaining the uplink channel (e.g., based on channel reciprocity with a downlink channel over which downlink signaling602is received), and/or determining conditions of the uplink channel. The UE115can optionally transmit uplink channel feedback606to the base station105, which can include transmitting PMI, MCS, etc. based at least in part on the determined precoder, the covariance matrix, the precoded CSI-RS, etc. In addition, the PMI, MCS, etc. may correspond to parameters the UE115intends to use in transmitting uplink communications to the base station105. In an example, the UE115can transmit the uplink channel feedback606over a control channel (e.g., PUCCH), over a shared data channel (e.g., PUSCH along with data), etc. Moreover, in an example as described, UE115may determine to switch to an open loop precoder in determining the precoder at604, where the UE115determines that the open loop precoder outperforms the closed loop precoder as described (e.g., based on determining a SNR associated with the open loop precoder (e.g., cyclic delay diversity (CDD), PMI cycling, etc.) is higher (e.g., by a threshold) than an a SNR associated with the closed loop precoder.

Base station105can optionally transmit a precoder indication608to the UE115indicating whether the UE115is to use a precoder specified by the base station105or whether the UE115is to autonomously derive a precoder based on other parameters, such as based on the downlink signaling602, as described. In one example, base station105can transmit the precoder indication608to the UE115based on the uplink channel feedback606(e.g., where the channel feedback achieves a threshold, base station105can allow the UE115to determine the precoder). In another example, base station105can transmit the precoder indication608based on the precoder indicated by the UE115(e.g., in the uplink channel feedback606). In one example, the precoder indication608may explicitly indicate the precoder for the UE115to use in transmitting uplink communications to the base station105.

In any case, the UE115can apply the specified or derived precoder at610for transmitting uplink communications. For example, the UE115can apply the precoder using a continuous precoding to allow the base station105to perform wideband channel estimation. In another example, the UE115can apply a different precoder for one or more different REs, RBs, PRBs, etc. over one or more symbols where OFDM is used (e.g., continuously changing the precoder over frequency resources of the REs, RBs, PRBs, etc. for at least a given time period), or may apply a single precoder where SC-FDM is used. In any case, the UE115can accordingly transmit the precoded uplink transmissions612to the base station105. In one example, transmitting the precoded uplink transmission(s)612can include transmitting one or more PRACH messages to perform a PRACH procedure with the base station105.

Additionally, in an example, in determining the precoder at604, the UE115may determine whether to use closed-loop precoder determination, as described above, or an open-loop scheme (e.g., transmit antenna selection, SORTD, cyclic delay diversity, precoder cycling, etc.). For example, UE115can compare SNRs associated with the various schemes, as described above, in determining which precoder determination to use.

FIG. 7is a block diagram of a MIMO communication system700including a base station105and a UE115. The MIMO communication system700may illustrate aspects of the wireless communication system100described with reference toFIG. 1. The base station105may be an example of aspects of the base station105described with reference toFIGS. 1 and 2. The base station105may be equipped with antennas734and735, and the UE115may be equipped with antennas752and753. In the MIMO communication system700, the base station105may be able to send data over multiple communication links at the same time. Each communication link may be called a “layer” and the “rank” of the communication link may indicate the number of layers used for communication. For example, in a 2×2 MIMO communication system where base station105transmits two “layers,” the rank of the communication link between the base station105and the UE115is two.

At the base station105, a transmit (Tx) processor720may receive data from a data source. The transmit processor720may process the data. The transmit processor720may also generate control symbols or reference symbols. A transmit MIMO processor730may perform spatial processing (e.g., precoding) on data symbols, control symbols, or reference symbols, if applicable, and may provide output symbol streams to the transmit modulator/demodulators732and733. Each modulator/demodulator732through733may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator/demodulator732through733may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a DL signal. In one example, DL signals from modulator/demodulators732and733may be transmitted via the antennas734and735, respectively.

The UE115may be an example of aspects of the UEs115described with reference toFIGS. 1 and 3. At the UE115, the UE antennas752and753may receive the DL signals from the base station105and may provide the received signals to the modulator/demodulators754and755, respectively. Each modulator/demodulator754through755may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each modulator/demodulator754through755may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector756may obtain received symbols from the modulator/demodulators754and755, perform MIMO detection on the received symbols, if applicable, and provide detected symbols. A receive (Rx) processor758may process (e.g., demodulate, deinterleave, and decode) the detected symbols, providing decoded data for the UE115to a data output, and provide decoded control information to a processor780, or memory782.

The processor780may in some cases execute stored instructions to instantiate a communicating component340(see e.g.,FIGS. 1 and 3).

On the uplink (UL), at the UE115, a transmit processor764may receive and process data from a data source. The transmit processor764may also generate reference symbols for a reference signal. The symbols from the transmit processor764may be precoded by a transmit MIMO processor766if applicable, further processed by the modulator/demodulators754and755(e.g., for SC-FDMA, etc.), and be transmitted to the base station105in accordance with the communication parameters received from the base station105. At the base station105, the UL signals from the UE115may be received by the antennas734and735, processed by the modulator/demodulators732and733, detected by a MIMO detector736if applicable, and further processed by a receive processor738. The receive processor738may provide decoded data to a data output and to the processor740or memory742.

The processor740may in some cases execute stored instructions to instantiate a communicating component340(see e.g.,FIGS. 1 and 2).

The components of the UE115may, individually or collectively, be implemented with one or more ASICs adapted to perform some or all of the applicable functions in hardware. Each of the noted modules may be a means for performing one or more functions related to operation of the MIMO communication system700. Similarly, the components of the base station105may, individually or collectively, be implemented with one or more ASICs adapted to perform some or all of the applicable functions in hardware. Each of the noted components may be a means for performing one or more functions related to operation of the MIMO communication system700.