WO2019173970A1

WO2019173970A1 - Receive filter indication for downlink transmissions

Info

Publication number: WO2019173970A1
Application number: PCT/CN2018/078858
Authority: WO
Inventors: Chenxi HAO; Yu Zhang; Hao Xu; Wanshi Chen; Peter Gaal
Original assignee: Qualcomm Incorporated
Priority date: 2018-03-13
Filing date: 2018-03-13
Publication date: 2019-09-19

Abstract

Certain aspects of the present disclosure provide techniques and apparatus for dynamic switching between non-codebook based and codebook based uplink transmission schemes. An exemplary method generally includes transmitting sounding reference signals (SRSs), to a base station (BS), via one or more SRS resources, wherein each SRS resource comprises one or more SRS ports; receiving, from the BS, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources are used by the BS to derive a downlink (DL) transmit signal; and receiving the DL transmit signal from the BS based on the SRI.

Description

RECEIVE FILTER INDICATION FOR DOWNLINK TRANSMISSIONS

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate generally to wireless communications systems, and more particularly, to techniques for indicating receive filters used by user equipments (UEs) in receiving downlink (DL) transmissions.

Description of Related Art

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power) . Examples of such multiple-access technologies include Long Term Evolution (LTE) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

In some examples, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs) . In LTE or LTE-A network, a set of one or more base stations may define an e NodeB (eNB) . In other examples (e.g., in a next generation or 5G network) , a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs) , edge nodes (ENs) , radio heads (RHs) , smart radio heads (SRHs) , transmission reception points (TRPs) , etc. ) in communication with a number of central units (CUs) (e.g., central nodes (CNs) , access node controllers (ANCs) , etc. ) , where a set of one or more distributed units, in communication with a central unit, may define an access node (e.g., a new radio base station (NR BS) , a new radio node-B (NR NB) , a network node, 5G NB, gNB, etc. ) . A base station or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a base station or to a UE) and uplink channels (e.g., for transmissions from a UE to a base station or distributed unit) .

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. An example of an emerging telecommunication standard is new radio (NR) , for example, 5G radio access. NR is a set of enhancements to the LTE mobile standard promulgated by Third Generation Partnership Project (3GPP) . It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

BRIEF SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how the features of this disclosure provide advantages that include improved communications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide a method for wireless communication that may be performed, for example, by a user equipment (UE) . The method generally includes transmitting sounding reference signals (SRSs) , to a base station (BS) , via one or more SRS resources, wherein each SRS resource comprises one or more SRS ports; receiving, from the BS, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources are used by the BS to derive a downlink (DL) transmit signal; and receiving the DL transmit signal from the BS based on the SRI.

Certain aspects of the present disclosure provide a method for wireless communication that may be performed, for example, by a base station (BS) . The method generally includes receiving, from a user equipment (UE) and via one or more sounding reference signal (SRS) resources, one or more SRSs, wherein each SRS resource comprises one or more SRS ports; estimating a channel to the UE corresponding to the one or more ports of each SRS resource; transmitting, to the UE, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources are used by the BS to derive a downlink (DL) transmit signal; and transmitting the DL transmit signal to the UE based on the SRI.

Aspects generally include methods, apparatus, systems, computer readable mediums, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example telecommunications system, in accordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram illustrating an example logical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example physical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating a design of an example BS and user equipment (UE) , in accordance with certain aspects of the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communication protocol stack, in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates an example of a DL-centric subframe, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example of an UL-centric subframe, in accordance with certain aspects of the present disclosure.

FIG. 8 is a flow diagram illustrating example operations that may be performed by a UE, in accordance with certain aspects of the present disclosure.

FIG. 9 is a flow diagram illustrating example operations that may be performed by a BS, in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates an exemplary transceiver architecture, in accordance with aspects of the present disclosure.

FIG. 11 illustrates an exemplary receiver architecture, in accordance with aspects of the present disclosure.

FIG. 12 illustrates an exemplary set of transmission constellations, in accordance with aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for new radio (NR) (new radio access technology or 5G technology) . NR may support various wireless communication services, such as Enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g. 80 MHz and wider) , millimeter wave (mmW) targeting high carrier frequency (e.g. 27 GHz and higher) , massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low latency communications (URLLC) . These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe.

Aspects of the present disclosure provide techniques and apparatus for dynamic switching between non-codebook and codebook based uplink transmission schemes.

The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

The techniques described herein may be used for various wireless communication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA) , cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA network may implement a radio technology such as NR (e.g. 5G RA) , Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS) . NR is an emerging wireless communications technology under development in conjunction with the 5G Technology Forum (5GTF) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that use E-UTRA. 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 wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later, including NR technologies.

EXAMPLE WIRELESS COMMUNICATIONS SYSTEM

FIG. 1 illustrates an example wireless network 100 in which aspects of the present disclosure may be performed. For example, the wireless network may be a new radio (NR) or 5G network. BS 110 may receive an uplink (UL) signal from UE 120 according to a first UL transmission configuration and determine whether to switch from the first UL transmission configuration to a second UL transmission configuration based on the received UL signal. BS 110 may transmit an indication of whether to switch from the first UL transmission configuration to the second UL transmission configuration to UE 120 to facilitate dynamic switching between non-codebook and codebook based UL transmissions as further described herein with respect to FIGs. 8 and 9.

As illustrated in FIG. 1, the wireless network 100 may include a number of BSs 110 and other network entities. A BS may be a station that communicates with UEs. Each BS 110 may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a Node B and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and gNB, Node B, 5G NB, AP, NR BS, NR BS, or TRP may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in the wireless network 100 through various types of backhaul interfaces such as a direct physical connection, a virtual network, or the like using any suitable transport network.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG) , UEs for users in the home, etc. ) . A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in FIG. 1, the

BSs

110a, 110b and 110c may be macro BSs for the

macro cells

102a, 102b and 102c, respectively. The BS 110x may be a pico BS for a pico cell 102x. The BSs 110y and 110z may be femto BS for the

femto cells

102y and 102z, respectively. A BS may support one or multiple (e.g., three) cells.

The wireless network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., a BS or a UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or a BS) . A relay station may also be a UE that relays transmissions for other UEs. In the example shown in FIG. 1, a relay station 110r may communicate with the BS 110a and a UE 120r in order to facilitate communication between the BS 110a and the UE 120r. A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network 100. For example, a macro BS may have a high transmit power level (e.g., 20 Watts) whereas pico BS, femto BS, and relays may have a lower transmit power level (e.g., 1 Watt) .

The wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, the BSs may have similar frame timing, and transmissions from different BSs may be approximately aligned in time. For asynchronous operation, the BSs may have different frame timing, and transmissions from different BSs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operation.

A network controller 130 may couple to a set of BSs and provide coordination and control for these BSs. The network controller 130 may communicate with the BSs 110 via a backhaul. The BSs 110 may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

The UEs 120 (e.g., 120x, 120y, etc. ) may be dispersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE) , a cellular phone, a smart phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc. ) , an entertainment device (e.g., a music device, a video device, a satellite radio, etc. ) , a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered evolved or machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (e.g., remote device) , or some other entity. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices.

In FIG. 1, a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A finely dashed line with double arrows indicates interfering transmissions between a UE and a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a ‘resource block’ ) may be 12 subcarriers (or 180 kHz) . Consequently, the nominal FFT size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz) , respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (i.e., 6 resource blocks) , and there may be 1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.

While aspects of the examples described herein may be associated with LTE technologies, aspects of the present disclosure may be applicable with other wireless communications systems, such as NR.

NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. A single component carrier bandwidth of 100 MHz may be supported. NR resource blocks may span 12 sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 ms duration. Each radio frame may consist of 2 half frames, each half frame consisting of 5 subframes, with a length of 10 ms. Consequently, each subframe may have a length of 1 ms. Each subframe may indicate a link direction (i.e., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. UL and DL subframes for NR may be as described in more detail below with respect to FIGs. 6 and 7. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. Alternatively, NR may support a different air interface, other than an OFDM-based. NR networks may include entities such CUs and/or DUs.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs) . In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time–frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., a gNB, a 5G NB, a NB, a TRP, or an AP) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells) . For example, the RAN (e.g., a central unit or distributed unit) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals-in some case cases DCells may transmit SS. NR BSs may transmit downlink signals to UEs indicating the cell type. Based on the cell type indication, the UE may communicate with the NR BS. For example, the UE may determine NR BSs to consider for cell selection, access, handover, and/or measurement based on the indicated cell type.

FIG. 2 illustrates an example logical architecture of a distributed radio access network (RAN) 200, which may be implemented in the wireless communication system illustrated in FIG. 1. A 5G access node 206 may include an access node controller (ANC) 202. The ANC may be a central unit (CU) of the distributed RAN 200. The backhaul interface to the next generation core network (NG-CN) 204 may terminate at the ANC. The backhaul interface to neighboring next generation access nodes (NG-ANs) may terminate at the ANC. The ANC may include one or more TRPs 208 (which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, or some other term) . As described above, a TRP may be used interchangeably with “cell. ”

The TRPs 208 may be a DU. The TRPs may be connected to one ANC (ANC 202) or more than one ANC (not illustrated) . For example, for RAN sharing, radio as a service (RaaS) , and service specific AND deployments, the TRP may be connected to more than one ANC. A TRP may include one or more antenna ports. The TRPs may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture 200 may be used to illustrate fronthaul definition. The architecture may be defined that support fronthauling solutions across different deployment types. For example, the architecture may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter) .

The architecture may share features and/or components with LTE. According to aspects, the next generation AN (NG-AN) 210 may support dual connectivity with NR. The NG-AN may share a common fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 208. For example, cooperation may be preset within a TRP and/or across TRPs via the ANC 202. According to aspects, no inter-TRP interface may be present.

According to aspects, a dynamic configuration of split logical functions may be present within the architecture 200. As will be described in more detail with reference to FIG. 5, the Radio Resource Control (RRC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and a Physical (PHY) layers may be adaptably placed at the DU or CU (e.g., TRP or ANC, respectively) . According to certain aspects, a BS may include a central unit (CU) (e.g., ANC 202) and/or one or more distributed units (e.g., one or more TRPs 208) .

FIG. 3 illustrates an example physical architecture of a distributed RAN 300, according to aspects of the present disclosure. A centralized core network unit (C-CU) 302 may host core network functions. The C-CU may be centrally deployed. C-CU functionality may be offloaded (e.g., to advanced wireless services (AWS) ) , in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions. Optionally, the C-RU may host core network functions locally. The C-RU may have distributed deployment. The C-RU may be closer to the network edge.

A DU 306 may host one or more TRPs (edge node (EN) , an edge unit (EU) , a radio head (RH) , a smart radio head (SRH) , or the like) . The DU may be located at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120 illustrated in FIG. 1, which may be used to implement aspects of the present disclosure. One or more components of the BS 110 and UE 120 may be used to practice aspects of the present disclosure. For example, antennas 452, Tx/Rx 222,

processors

466, 458, 464, and/or controller/processor 480 of the UE 120 and/or antennas 434,

processors

460, 420, 438, and/or controller/processor 440 of the BS 110 may be used to perform the operations described herein and illustrated with reference to FIGs. 8 and 9.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, which may be one of the BSs and one of the UEs in FIG. 1. For a restricted association scenario, the base station 110 may be the macro BS 110c in FIG. 1, and the UE 120 may be the UE 120y. The base station 110 may also be a base station of some other type. The base station 110 may be equipped with antennas 434a through 434t, and the UE 120 may be equipped with antennas 452a through 452r.

At the base station 110, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the Physical Broadcast Channel (PBCH) , Physical Control Format Indicator Channel (PCFICH) , Physical Hybrid ARQ Indicator Channel (PHICH) , Physical Downlink Control Channel (PDCCH) , etc. The data may be for the Physical Downlink Shared Channel (PDSCH) , etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal. A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.

At the UE 120, the antennas 452a through 452r may receive the downlink signals from the base station 110 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 454 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive and process data (e.g., for the Physical Uplink Shared Channel (PUSCH) ) from a data source 462 and control information (e.g., for the Physical Uplink Control Channel (PUCCH) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal. The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators 454a through 454r (e.g., for SC-FDM, etc. ) , and transmitted to the base station 110. At the BS 110, the uplink signals from the UE 120 may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120. The receive processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/

processors

440 and 480 may direct the operation at the base station 110 and the UE 120, respectively. The processor 440 and/or other processors and modules at the BS 110 may perform or direct, e.g., the execution of the functional blocks illustrated in FIG. 8 and/or other processes for the techniques described herein. The processor 480 and/or other processors and modules at the UE 120 may also perform or direct, e.g., the execution of the functional blocks illustrated in FIG. 9 and/or other processes for the techniques described herein. The

memories

442 and 482 may store data and program codes for the BS 110 and the UE 120, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing a communications protocol stack, according to aspects of the present disclosure. The illustrated communications protocol stacks may be implemented by devices operating in a in a 5G system (e.g., a system that supports uplink-based mobility) . Diagram 500 illustrates a communications protocol stack including a Radio Resource Control (RRC) layer 510, a Packet Data Convergence Protocol (PDCP) layer 515, a Radio Link Control (RLC) layer 520, a Medium Access Control (MAC) layer 525, and a Physical (PHY) layer 530. In various examples the layers of a protocol stack may be implemented as separate modules of software, portions of a processor or ASIC, portions of non-collocated devices connected by a communications link, or various combinations thereof. Collocated and non-collocated implementations may be used, for example, in a protocol stack for a network access device (e.g., ANs, CUs, and/or DUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack, in which implementation of the protocol stack is split between a centralized network access device (e.g., an ANC 202 in FIG. 2) and distributed network access device (e.g., DU 208 in FIG. 2) . In the first option 505-a, an RRC layer 510 and a PDCP layer 515 may be implemented by the central unit, and an RLC layer 520, a MAC layer 525, and a PHY layer 530 may be implemented by the DU. In various examples the CU and the DU may be collocated or non-collocated. The first option 505-a may be useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-b shows a unified implementation of a protocol stack, in which the protocol stack is implemented in a single network access device (e.g., access node (AN) , new radio base station (NR BS) , a new radio Node-B (NR NB) , a network node (NN) , or the like. ) . In the second option, the RRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525, and the PHY layer 530 may each be implemented by the AN. The second option 505-b may be useful in a femto cell deployment.

Regardless of whether a network access device implements part or all of a protocol stack, a UE may implement an entire protocol stack (e.g., the RRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525, and the PHY layer 530) .

FIG. 6 is a diagram 600 showing an example of a DL-centric subframe. The DL-centric subframe may include a control portion 602. The control portion 602 may exist in the initial or beginning portion of the DL-centric subframe. The control portion 602 may include various scheduling information and/or control information corresponding to various portions of the DL-centric subframe. In some configurations, the control portion 602 may be a physical DL control channel (PDCCH) , as indicated in FIG. 6. The DL-centric subframe may also include a DL data portion 604. The DL data portion 604 may sometimes be referred to as the payload of the DL-centric subframe. The DL data portion 604 may include the communication resources utilized to communicate DL data from the scheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE) . In some configurations, the DL data portion 604 may be a physical DL shared channel (PDSCH) .

The DL-centric subframe may also include a common UL portion 606. The common UL portion 606 may sometimes be referred to as an UL burst, a common UL burst, and/or various other suitable terms. The common UL portion 606 may include feedback information corresponding to various other portions of the DL-centric subframe. For example, the common UL portion 606 may include feedback information corresponding to the control portion 602. Non-limiting examples of feedback information may include an ACK signal, a NACK signal, a HARQ indicator, and/or various other suitable types of information. The common UL portion 606 may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests (SRs) , and various other suitable types of information. As illustrated in FIG. 6, the end of the DL data portion 604 may be separated in time from the beginning of the common UL portion 606. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the subordinate entity (e.g., UE) ) to UL communication (e.g., transmission by the subordinate entity (e.g., UE) ) . One of ordinary skill in the art will understand that the foregoing is merely one example of a DL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

FIG. 7 is a diagram 700 showing an example of an UL-centric subframe. The UL -centric subframe may include a control portion 702. The control portion 702 may exist in the initial or beginning portion of the UL-centric subframe. The control portion 702 in FIG. 7 may be similar to the control portion 602 described above with reference to FIG. 6. The UL-centric subframe may also include an UL data portion 704. The UL data portion 704 may sometimes be referred to as the payload of the UL-centric subframe. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS) . In some configurations, the control portion 702 may be a physical DL control channel (PDCCH) .

As illustrated in FIG. 7, the end of the control portion 702 may be separated in time from the beginning of the UL data portion 704. This time separation may sometimes be referred to as a gap, guard period, guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduling entity) to UL communication (e.g., transmission by the scheduling entity) . The UL-centric subframe may also include a common UL portion 706. The common UL portion 706 in FIG. 7 may be similar to the common UL portion 606 described above with reference to FIG. 6. The common UL portion 706 may additional or alternative include information pertaining to channel quality indicator (CQI) , sounding reference signals (SRSs) , and various other suitable types of information. One of ordinary skill in the art will understand that the foregoing is merely one example of an UL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein. In one example, a frame may include both UL centric subframes and DL centric subframes. In this example, the ratio of UL centric subframes to DL subframes in a frame may be dynamically adjusted based on the amount of UL data and the amount of DL data that are transmitted. For example, if there is more UL data, then the ratio of UL centric subframes to DL subframes may be increased. Conversely, if there is more DL data, then the ratio of UL centric subframes to DL subframes may be decreased.

In some circumstances, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet-of-Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS) , even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum) .

A UE may operate in various radio resource configurations, including a configuration associated with transmitting pilots using a dedicated set of resources (e.g., a radio resource control (RRC) dedicated state, etc. ) or a configuration associated with transmitting pilots using a common set of resources (e.g., an RRC common state, etc. ) . When operating in the RRC dedicated state, the UE may select a dedicated set of resources for transmitting a pilot signal to a network. When operating in the RRC common state, the UE may select a common set of resources for transmitting a pilot signal to the network. In either case, a pilot signal transmitted by the UE may be received by one or more network access devices, such as an AN, or a DU, or portions thereof. Each receiving network access device may be configured to receive and measure pilot signals transmitted on the common set of resources, and also receive and measure pilot signals transmitted on dedicated sets of resources allocated to the UEs for which the network access device is a member of a monitoring set of network access devices for the UE. One or more of the receiving network access devices, or a CU to which receiving network access device (s) transmit the measurements of the pilot signals, may use the measurements to identify serving cells for the UEs, or to initiate a change of serving cell for one or more of the UEs.

In wireless communications, channel state information (CSI) may refers to known channel properties of a communication link. The CSI may represent the combined effects of, for example, scattering, fading, and power decay with distance between a transmitter and receiver. Channel estimation may be performed to determine these effects on the channel. CSI may be used to adapt transmissions based on the current channel conditions, which is useful for achieving reliable communication, in particular, with high data rates in multi-antenna systems. CSI is typically estimated at the receiver, quantized, and fed back to the transmitter.

In certain systems (e.g., LTE) , CSI feedback is based on a pre-defined codebook. This may be referred to as implicit CSI feedback. Precoding may be used for beamforming in multi-antenna systems. Codebook based precoding uses a common codebook at the transmitter and receiver. The codebook includes a set of vectors and matrices. The UE calculates a precoder targeting maximum single-user (SU) multiple input multiple output (MIMO) spectrum efficiency. The implicit CSI feedback may include a rank indicator (RI) , a transmitted precoding matrix indicator (TPMI) , and associated channel quality indicator (CQI) based on the TPMI. The PMI includes a WI precoding matrix and a W2 precoding matrix.

In certain systems (e.g., such as LTE) , UL MIMO is generally achieved with precoder feedback, and thus is based on an uplink (UL) codebook based design. However, compared to LTE, certain systems (e.g., NR-MIMO) may support a non-codebook based UL transmission as one type of UL transmission scheme. Supporting a non-codebook based UL transmission scheme may refer to supporting an uplink transmission (e.g., from the UE) without including precoding information, such as a transmitted precoding matrix indicator (TPMI) , in the UL grant.

In a non-codebook based UL transmission scheme, the UE may be configured with multiple SRS resources (e.g., for sending SRS) , and each SRS resource may include one or more SRS ports. The UE may determine a candidate set of uplink transmit beams (e.g., precoders) based on measurement of downlink reference signals from the BS and channel reciprocity. The UE may use the determined uplink precoder to precode the SRS ports in each SRS resource and transmit the SRS resources to the BS. Upon receiving the SRS resources, the BS can measure the multiple precoded SRS ports, and choose a precoder for the UE to use for PUSCH. The BS can then feedback indicators along with downlink control information (DCI) (e.g., without TPMI) to indicate the rank and selected precoder for PUSCH.

EXAMPLE RECEIVE FILTER INDICATION FOR DOWNLINK TRANSMISSIONS

According to aspects of the present disclosure, a MIMO receiver (e.g., a UE) may use a spatial filter to combine received signals at each receive antenna to recover desired signals. For instance, a UE with 2 receive antennas that needs to recover one layer from received signals may derive a 1x2 vector to use to combine the received signals into the one layer. Typically, the receive filter is derived (e.g., by a receiving device such as a UE) based on the effective channel. As used herein, the effective channel = the product of the channel (including e.g., atmospheric interference effects, fading, shadowing, and other aspects of the wireless channel between a transmitter and a receiver) and the precoder used in transmitting the signal.

In currently known techniques, the effective channel may be obtained by a receiver via channel estimation using demodulation reference signals (DMRS) . That is, the transmitter transmits DMRS using the same precoder as the data, and the received signal is a product of the DMRS, the precoder and the channel plus additive noise. The receiver then compares the received signal to an unaltered DMRS to determine the estimate of the effective channel and uses the estimate of the effective channel to recover the desired signal (s) . In this technique, a receiver (e.g., a UE) does not need to explicitly know the precoder, as the UE determines the effective channel (based on the DMRS) of each received signal and uses the effective channel to derive a receive filter. The receiver is able to determine a receive filter to use without having explicit information regarding the precoder used by the transmitter.

The previously known technique of a receiver deriving a receive filter based on the effective channel (e.g., using DMRS as mentioned above) may be referred to as a linear precoding scheme.

According to aspects of the present disclosure, techniques for use with non-linear precoding schemes (e.g., Tomlinson-Harashima precoding (THP) ) are provided. In a non-linear precoding scheme, a transmitter perturbs a signal as the signal is being transmitted in order to achieve interference pre-cancelation. That is, the transmitter perturbs the signal prior to transmitting the signal such that the perturbed signal plus the interference received by the receiver is very close to the unperturbed signal the transmitter intended the receiver to receive.

In aspects of the present disclosure, a non-linear precoding scheme may include a joint signal-perturbation and receive filter design.

According to aspects of the present disclosure, a transmitter (e.g., a BS) may perturb the data transmitted in a signal without any assumption of a receive filter used by a receiver, e.g., the perturbation is determined based only on the channel. A receiver (e.g., a UE) may derive a receive filter to use in receiving a signal based on a perturbation actually applied to a signal by the transmitter (e.g., a BS) .

According to aspects of the present disclosure, a transmitter (e.g., a BS) may perturbs the data transmitted in a signal based on an assumption of a receive filter used by the receiver (e.g., a UE) in receiving the signal. If a BS perturbs data based on an assumption of a receive filter used by a UE in receiving the signal, then it is desirable for a receiving UE to use the receive filter assumed by the BS to recover the data from the signal.

In aspects of the present disclosure, techniques are provided to enable a receiver (e.g., a UE) to know a receive filter assumed by a transmitter (e.g., a BS) in deriving a perturbation applied to data transmitted in a signal.

In aspects of the present disclosure, techniques are provided to enable a transmitter (e.g., a BS) to transmit an indication of a receive filter assumed by the transmitter in deriving a perturbation applied to data transmitted in a signal.

FIG. 8 is a flow diagram illustrating example operations 800 that may be performed, for example, by a user equipment (e.g., UE 120 of FIG. 1) , for wireless communications, in accordance with certain aspects of the present disclosure. Operations 800 may be implemented as software components that are executed and run on one or more processors (e.g., processor 440 of FIG. 4) . Further, the transmission and reception of signals by the UE in operations 800 may be enabled, for example, by one or more antennas (e.g., antennas 452 of FIG. 4) .

Operations 800 may begin, at block 802, by the UE transmitting sounding reference signals (SRSs) , to a base station (BS) , via one or more SRS resources, wherein each SRS resource comprises one or more SRS ports. For example, UE 120 transmits SRSs to BS 110 (see FIG. 1) via two SRS resources, wherein each SRS resource comprises one SRS port. In the example, the UE may apply a rank-1 precoder to formulate the single SRS port in each resource.

At block 804, operations 800 continue with the UE receiving, from the BS, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources are used by the BS to derive a downlink (DL) transmit signal. Continuing the example from above, the UE 120 receives, from BS 110, an SRI that indicates the first SRS resource of the two SRS resources, wherein the BS uses the port of the first SRS resource to derive a downlink transmit signal.

Operations 800 continue at block 806 with the UE receiving the DL transmit signal from the BS based on the SRI. Continuing the example from above, the UE 120 receives the DL transmit signal based on the SRI received from the BS 110 at block 804. More specifically, the UE may use the precoder used to transmit the single port of the first SRS resource as the receive filter to receive the DL transmit signal.

In another example of operations 800, UE 120 (e.g., at block 802) transmits SRS to BS 110 via two SRS resources, wherein each SRS resource comprises one SRS port. The UE receives (e.g., at block 804) from the BS an SRI indicating both the 1st and 2nd SRS resources are used in deriving the DL transmit signal. Then (e.g., at block 806) , the UE uses the precoder used to transmit the single-port SRS of both the first and second SRS resources as the receive filter to receive the DL transmit signal.

FIG. 9 is a flow diagram illustrating example operations 900 that may be performed, for example, by a base station (e.g., BS 110) , for wireless communications, in accordance with certain aspects of the present disclosure. Operations 900 may be considered complementary to operations 800, described above with reference to FIG. 8. Operations 900 may be implemented as software components that are executed and run on one or more processors (e.g., processor 480 of FIG. 4) . Further, the transmission and reception of signals by the BS in operations 900 may be enabled, for example, by one or more antennas (e.g., antennas 434 of FIG. 4) .

Operations 900 may begin, at block 902, by the BS receiving, from a user equipment (UE) and via one or more sounding reference signal (SRS) resources, one or more SRSs, wherein each SRS resource comprises one or more SRS ports. For example, BS 110 (shown in FIG. 1) receives SRSs from UE 120 (see FIG. 1) via two SRS resources, wherein each SRS resource comprises one SRS port.

At block 904, operations 900 continue with the BS estimating a channel to the UE corresponding to the one or more ports of each SRS resource. Continuing the example from above, BS 110 estimates two channels to the UE corresponding to the two ports of the two SRS resources which the UE used in transmitting the SRSs.

At block 906, operations 900 continue with the BS transmitting, to the UE, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources correspond to the estimated channels that are used by the BS to derive a downlink (DL) transmit signal. Continuing the example from above, BS 110 transmits an SRI that indicates the first SRS resource of the two SRS resources, wherein the BS uses the port of the first SRS resource to derive a downlink transmit signal.

Operations 900 continue at block 908 with the BS transmitting the DL transmit signal to the UE based on the SRI. Still in the example from above, BS 120 transmits the DL transmit signal to UE 110 based on the SRI.

In another example of operations 900, BS 110 (e.g., at block 902) receives, from UE 110 and via four SRS resources, four SRSs, wherein each SRS resource comprises an SRS port. The BS estimates (e.g., at block 904) four channels to the UE, based on the four SRSs received from the UE. The BS transmits (e.g., at block 906) , to the UE, an SRI indicating the second and fourth SRS resources, wherein the second and fourth SRS ports are used by the BS to derive a DL transmit signal. Then (e.g., at block 908) , the BS transmits the DL transmit signal to the UE based on the SRI (e.g., using a precoder derived using the 2 ^nd and 4 ^th SRS resource) .

According to aspects of the present disclosure, a transmitter (e.g., a BS) may use an SRS resource indicator (SRI) to indicate a receive filter to be used by a receiver (e.g., a UE) when receiving a transmission.

In aspects of the present disclosure, a UE may transmit SRS signals (e.g., as in block 802 of FIG. 8) based on an SRS resource set. Each SRS resource set consists of multiple SRS resources (e.g., time and frequency resources, such as a group of resource elements) , each resource with a single port. Each port corresponds to a candidate receive filter to be used, and the precoder used to derive the port is the receive filter to be used by the BS in deriving the perturbation to be applied to the data when deriving the signal to be transmitted.

According to aspects of the present disclosure, a network entity (e.g., a BS) estimates a channel for each single-port SRS resource to obtain the reciprocal channel. The network entity estimates each single-port SRS channel based on the SRS signals transmitted by the UE mentioned above, which the BS receives (e.g., as in block 902 of FIG. 9) . The network (e.g., a BS) derives the perturbation (e.g., a THP perturbation) and precoders using one or multiple single-port SRS resources.

In aspects of the present disclosure, the network (e.g., a BS) may use SRI to indicate which resource (s) and/or port (s) are actually used for the perturbation (e.g., THP) derivation. The BS may convey the SRI to the UE via a transmission, as described above in block 904 in FIG. 9.

According to aspects of the present disclosure, a BS may transmit an SRI as a bitmap with length equal to the number of single-port SRS resources, where each true bit set by the BS in the SRI indicates that a corresponding resource is used by the BS in deriving the signal. A rank of the THP is equal to the number of SRS resources (i.e., the number of true bits) indicated by the SRI. For example, for the case with 2 single-port SRS resources, “10” means that the single-port of the 1 ^st resource is used, while “11” means that the single ports in both resources are used.

In aspects of the present disclosure, a BS may transmit an SRI as a value that indicates one or more SRS resources. The BS and the UE may each obtain a mapping of values to sets of SRS resources. An SRI may comprise a number of bits, wherein the number of bits may be calculated as:

bits, where N is the number of SRS resources, and L is the maximum supported rank. There are a total of

possible selection results, and the first

selection results may be mapped for rank-1 selection, with later selection results mapping to higher rank selections. For example, if there are four single-port SRS resources and the maximum rank is two, then there are ten possible selections. The first to fourth selections are for each of the rank-1 selections (one per each SRS resource) , while the fifth through tenth selections are for the six (combination of four ports taken two at a time) rank-2 selections. In the example, the SRI comprises four bits, as

According to aspects of the present disclosure, an SRI (e.g., a bitmap or value as described above) may be transmitted using a dedicated field in a downlink-transmission-related downlink control information (DCI) or using a specific DCI format.

In aspects of the present disclosure, an SRI may be transmitted associated with a downlink transmission instead of being limited to use with uplink (UL) transmissions, as in previously known techniques.

According to aspects of the present disclosure, the network (e.g., a BS) may use an SRI and a receive filter indicator (RFI) to indicate which resource (s) and/or port (s) are actually used for the perturbation (e.g., THP) derivation.

In aspects of the present disclosure, a UE may transmit SRS signals (e.g., as in block 802 of FIG. 8) based on an SRS resource set. Each SRS resource set consists of multiple SRS resources (e.g., time and frequency resources, such as a resource element) , each resource with multiple ports.

According to aspects of the present disclosure, a network entity (e.g., a BS) estimates a channel for each SRS resource to obtain the reciprocal channel. The network entity estimates each channel based on the SRS signals transmitted by the UE mentioned above, which the BS receives (e.g., as in block 902 of FIG. 9) . The network (e.g., a BS) derives the perturbation (e.g., a THP perturbation) and precoders using one or multiple SRS resources. The network selects the best SRS resource and an associated receive filter to be used by the UE in receiving a DL transmit signal.

In aspects of the present disclosure, the network (e.g., a BS) may use SRI to indicate which resource (s) and/or port (s) are preferred and a receive filter indicator (RFI) to indicate which filter is actually used for the perturbation (e.g., THP) derivation. The BS may convey the SRI to the UE via a transmission, as described above in block 904 in FIG. 9. The BS may convey the RFI to the UE via the same transmission or another transmission.

According to aspects of the present disclosure, the network (e.g., a BS) may transmit one SRI to indicate one selected SRS resource. The receive filter indicated by the RFI (e.g., transmitted by the BS) is associated with the selected SRS resource. More specifically, the UE may apply the selected receive filter to the ports of the selected SRS resource, in order to receive the DL signal.

In aspects of the present disclosure, an RFI refers to a vector and/or matrix selected from a codebook, wherein the codebook is a dedicated codebook or the codebook used for UL precoder selection.

According to aspects of the present disclosure, an SRI may be transmitted using a dedicated field in a downlink-transmission-related downlink control information (DCI) or using a specific DCI format.

In aspects of the present disclosure, an RFI may be transmitted using a dedicated field in a downlink-transmission-related downlink control information (DCI) or using a specific DCI format.

FIG. 10 illustrates an exemplary THP transceiver architecture 1000 that may be used with the disclosed techniques, in accordance with aspects of the present disclosure. The exemplary THP transceiver architecture is described with reference to an exemplary case of a transmission to two users. In the exemplary case, data 1002 to UE1 is transmitted via conventional linear precoding (LP) , as previously described. While a non-linear encoder, i.e., a modulo operation (e.g., Mod Λ ₁) , is illustrated at 1004, no input from signals to other UEs is provided to the non-linear encoder, and so linear precoding is performed (Note that without input from signals to other UEs, the constellation symbols do not change after going through the modulo operation) . In the exemplary case, data 1010 to UE2 is perturbed by an interference caused by UE1 and potentially experienced by UE2 (The interference caused by UE1 is modeled as the product of the signal sent to UE1 and a feedback filter (FB _2, ₁) 1006, which is determined based on the effective channel and the receive filter to be used by UE2) . The perturbation is derived based on an input 1012 from the signal to UE1 to the non-linear encoder 1014. As with the signal to UE1, a modulo operation (e.g., Mod Λ _k) is performed to limit the transmission power used for the transmission. Usage of the modulo operation is described below with reference to FIG. 12. The signals to UE1 and UE2 are transmitted from antennas of the transmitter at 1020. After going through the modulo operation, the signals to UE1 and UE2 are transmitted from antennas of the transmitter at 1020 with a linear precoder, i.e., FeedForward (FF) filter 1 and FF filter 2.

According to aspects of the present disclosure, the exemplary transceiver architecture 1000 provides a perturbation 1030 to a signal K that is derived based on inputs from each of the previous K-1 signals to a set of K-1 previous UEs, where the interference caused to the signal K is modeled as a sum of products of the previous K-1 signals and corresponding feedback filters 1032-1036 (i.e., feedback filters FB _K, ₁ through FB _K, _K-1) .

FIG. 11 illustrates an exemplary THP receiver architecture 1100 that may be used with the disclosed techniques, in accordance with aspects of the present disclosure. The exemplary THP receiver architecture is described with reference to the exemplary case of the transmission to two users described above. In the exemplary case, at UE1, interference from UE2 is rejected via a linear precoder. Also in the exemplary case, at UE2, interference from UE1 is pre-cancelled via a perturbation added by the transceiver, described above with reference to FIG. 10. The perturbation is removed by the NLP decoder 1102. A modulo operation (e.g., Mod Λ _k) is performed at 1104 restore the QAM symbols of the received signal. Usage of the modulo operation is described below with reference to FIG. 12.

FIG. 12 illustrates an exemplary set 1200 of transmission constellations, in accordance with aspects of the present disclosure. An exemplary QAM signal 1202 is to be transmitted to UE2, as described above with reference to FIGs. 10-11. An interference suppression signal 1204 is added to the QAM signal, resulting in an intermediate signal 1206. As the intermediate signal is outside of the QAM signal constellation space, a modulo operation (e.g., [-2τ _th, -2τ _th] ) is applied to the intermediate signal, resulting in a signal after nonlinear operation 1208 that is transmitted by the transmitter. At the receiver, the transmitted signal combines with the interference 1210 to result in a signal 1212 received by the receiver. As the received signal is outside of the QAM signal constellation space, a modulo operation (e.g., [+2τ _th, +2τ _th] ) is applied to the signal 1212, resulting in the receiver recovering the original QAM signal 1202.

According to aspects of the present disclosure, techniques are provided for using THP in some communications situations. In one case, use of THP with UEs each having with one receive antenna and transmitting one layer to each UE is described. In the case of UEs having one receive antenna, a channel triangularization operation may be performed using the below equations:

where the aggregate channel (of two UEs) H is a 2×M _T complex matrix with M _T≥2 representing the number of transmit antennas at the transmitter side. Successive encoding can then be performed with a pre-cancellation:

s ₁=c ₁

In another case, use of THP with UEs each having two receive antennas and transmitting two layers to each UE is described. In the case of UEs each having two receive antennas, a channel block triangularization operation may be performed using the below equations:

Where the aggregate channel (of two UEs) H is a 4×M _T complex matrix with M _T≥4 representing the number of transmit antennas at the transmitter side. Successive encoding can then be performed with a pre-cancellation:

s ₁=c ₁ , and

x=W·s

In another case, use of THP with UEs each having two receive antennas and transmitting one layer to each UE is described. In the case of UEs each having two receive antennas, a channel block triangularization operation may be performed using the below equations:

Where the aggregate channel (of two UEs) H is a 2×M _T complex matrix with M _T≥4 representing the number of transmit antennas at the transmitter side. Successive encoding with a pre-cancellation is not calculable in a same manner as the previous two cases, because d ₂₂ not invertible. In this case, the receiver needs to apply a receive filter, denoted by

to receive the layer-1 signal, so that the equivalent channel, i.e., v×H ₁ and v×H ₂observed by each UE is rank-1. The aggregate channel v×Hbecomes rank-2. By doing channel triangularization to v×H, d ₁₁ is a scalar, thus invertible. The disclosed techniques enable THP to be used in this case, as the disclosed techniques allow the BS to derive the perturbation with an assumption of the receive filter v to be used by each single UE.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure) , ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information) , accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for. ”

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component (s) and/or module (s) , including, but not limited to a circuit, an application specific integrated circuit (ASIC) , or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar numbering.

For example, means for transmitting, means for outputting, means for receiving, means for selecting, means for identifying, means for determining, means for performing, means for obtaining, and/or means for generating may comprise one or more processors or antennas at the BS 110 or UE 120, such as the transmit processor 420, controller/processor 440, receive processor 438, or antennas 434 at the BS 110 and/or the transmit processor 464, controller/processor 480, receive processor 458, or antennas 452 at the UE 120 of FIG. 4.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) or other programmable logic device (PLD) , discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user equipment 120 (see FIG. 1) , a user interface (e.g., keypad, display, mouse, joystick, etc. ) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer-readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor may be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files. Examples of machine-readable storage media may include, by way of example, RAM (Random Access Memory) , flash memory, ROM (Read Only Memory) , PROM (Programmable Read-Only Memory) , EPROM (Erasable Programmable Read-Only Memory) , EEPROM (Electrically Erasable Programmable Read-Only Memory) , registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product.

A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media may comprise a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared (IR) , radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk, and

disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media) . In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal) . Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc. ) , such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

WHAT IS CLAIMED IS:

Claims

A method for wireless communications by a user equipment (UE) , comprising:

transmitting sounding reference signals (SRSs) , to a base station (BS) , via one or more SRS resources, wherein each SRS resource comprises one or more SRS ports;

receiving, from the BS, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources are used by the BS to derive a downlink (DL) transmit signal; and

receiving the DL transmit signal from the BS based on the SRI.
The method of claim 1, wherein receiving the DL transmit signal based on the SRI further comprises:

determining one or more receive filters based at least in part on the one or more ports of each of the one or more SRS resources indicated by the SRI; and

receiving the DL transmit signal using the one or more receive filters.
The method of claim 1, wherein:

the SRI comprises a bitmap with a length equal to a number of the SRS resources.
The method of claim 3, wherein:

each true bit in the bitmap indicates that a corresponding SRS resource is used by the BS for deriving the DL transmit signal.
The method of claim 1, wherein the SRI comprises a value indicating one or more SRS resources are used by the BS for deriving the DL transmit signal.
The method of any of claim 3 and 4, wherein a rank of the DL transmit signal is equal to a number of the indicated SRS resources.
The method of claim 1, wherein receiving the SRI comprises receiving the SRI in a dedicated field in a downlink-transmission-related downlink control information (DCI) or a specific DCI format.
The method of claim 1, further comprising:

receiving one or more receive filter indicators (RFIs) from the BS, wherein each RFI is associated with the one or more ports of a corresponding SRS resource and wherein receiving the DL transmit signal is further based on the RFIs.
The method of claim 8, further comprising:

selecting one or more receive filters, each receive filter indicated by each RFI of the one or more RFIs, from a codebook, wherein receiving the DL transmit signal comprises receiving the DL transmit signal using the receive filters.
The method of claim 9, further comprising:

determining a rank of the DL transmit signal based on a total rank of receive filters indicated by the one or more RFIs.
The method of claim 10, wherein receiving the RFIs comprises receiving the RFIs in a dedicated field in a downlink-transmission-related downlink control information (DCI) or a specific DCI format.
A method for wireless communications by a base station (BS) , comprising:

receiving, from a user equipment (UE) and via one or more sounding reference signal (SRS) resources, one or more SRSs, wherein each SRS resource comprises one or more SRS ports;

estimating a channel to the UE corresponding to the one or more ports of each SRS resource;

transmitting, to the UE, an SRS resource indicator (SRI) that indicates one or more of the SRS resources, wherein the one or more SRS ports of the indicated SRS resources correspond to the estimated channels that are used by the BS to derive a downlink (DL) transmit signal; and

transmitting the DL transmit signal to the UE based on the SRI.
The method of claim 12, wherein deriving the DL transmit signal further comprises:

deriving a precoder for each SRS resource, based on the estimated channels; and

transmitting the DL transmit signal using the derived precoders corresponding to the SRS resources indicated by the SRI.
The method of claim 12, wherein:

the SRI comprises a bitmap with a length equal to a number of the SRS resources.
The method of claim 14, wherein:

each true bit in the bitmap indicates that a corresponding SRS resource is used by the BS for deriving the DL transmit signal.
The method of claim 12, wherein the SRI comprises a value indicating one or more SRS resources are used by the BS for deriving the DL transmit signal.
The method of any of claim 14 and 15, wherein a rank of the DL transmit signal is equal to a number of the indicated SRS resources.
The method of claim 12, wherein transmitting the SRI comprises transmitting the SRI in a dedicated field in a downlink-transmission-related downlink control information (DCI) or a specific DCI format.
The method of claim 12, further comprising:

transmitting one or more receiver filter indicators (RFIs) to the UE, wherein each RFI is associated with the one or more ports of a corresponding SRS resource and wherein transmitting the signal comprises transmitting the signal based on the RFIs.
The method of claim 19, further comprising:

selecting one or more receive filters, each receive filter indicated by an RFI of the one or more RFIs, from a codebook, wherein transmitting the DL transmit signal comprises transmitting the DL transmit signal based on the receive filters.
The method of claim 20, wherein selecting the one or more receive filters comprises selecting the one or more receive filters to have a total rank based on a rank of the DL transmit signal.
The method of claim 21, wherein transmitting the RFIs comprises transmitting the RFIs in a dedicated field in a downlink-transmission-related downlink control information (DCI) or a specific DCI format.