WO2017219268A1

WO2017219268A1 - Snr cqi feedback mechanism for mu-mimo and/or must

Info

Publication number: WO2017219268A1
Application number: PCT/CN2016/086689
Authority: WO
Inventors: Jing Sun; Chao Wei; Wanshi Chen; Aleksandar Damnjanovic; Peter Gaal; Juan Montojo
Original assignee: Qualcomm Incorporated
Priority date: 2016-06-22
Filing date: 2016-06-22
Publication date: 2017-12-28

Abstract

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may transmit, to a base station, CSI associated with a single-user transmission. The apparatus may also receive, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a MCS. For example, the MCS may be based on the first CSI. The apparatus may also determine CQI associated with a multi-user transmission. In addition, the apparatus may transmit, to the base station, the CQI associated with the multi-user transmission.

Description

SNR CQI FEEDBACK MECHANISM FOR MU-MIMO AND/OR MUST

BACKGROUND

Field

The present disclosure relates generally to communication systems, and more particularly, to signal-to-noise ratio (SNR) channel quality information (CQI) feedback mechanism for multi-user multiple-input multiple-output (MU-MIMO) and/or multi-user superposition transmissions (MUST) .

Background

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. Examples of such multiple-access technologies include 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.

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 telecommunication standard is Long Term Evolution (LTE) . LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP) . LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

In some wireless communication systems, CSI feedback may not be available for a MU-MIMO and/or a MUST. Instead, a UE may report CSI based on a single-user transmission. The CSI based on a single-user transmission may assume that there no intra-eNB interference and that full power is allocated to the UE. For example, the UE may report a CSI based on a single-user transmission even when the UE is served in multi-user transmission (e.g., MU-MIMO and MUST) .

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

In some wireless communication systems, CSI feedback may not be available for a MU-MIMO and/or a MUST. Instead, a UE may report CSI based on a single-user transmission. The CSI based on a single-user transmission may assume there is no intra-eNB interference and that full power is allocated to the UE. For example, the UE may report a CSI based on a single-user transmission even when the UE is served in multi-user transmission (e.g., MU-MIMO and MUST) .

When the UE is served in a multi-user fashion, power loss may occur due to a power split between the UE and the other UEs being served in the multi-user transmission. In addition, interference may be caused by the transmission to the other UEs. The power loss and/or the interference caused by the multi-user transmission may not be captured in the CSI feedback from the UE. Therefore, the base station may need perform a conversion of the CSI feedback that is based on the single-user transmission to estimate the multi-user signal-to-noise ratio (SNR) to determine a modulation and coding scheme for the multi-user transmission. The base station may rely on an outer loop (e.g., closed loop) mechanism that may take a certain period of time to converge in adjusting for a potential SNR conversion error. In addition, the pairing (e.g., of UEs in the multi-user transmission) may need to be relatively static for the outer loop mechanism to converge.

The present disclosure provides a solution by enabling a decoding SNR CQI feedback mechanism for MU-MIMO and MUST.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may receive, from a UE, first CSI associated with a single-user transmission. The apparatus may also transmit, to the UE, a downlink scheduling grant associated with a first multi-user configuration having an MCS, the MCS being based on the first CSI. In addition, the apparatus may receive, from the UE, CQI associated with a first multi-user transmission.

In another aspect, the apparatus may transmit, to a base station, CSI associated with a single-user transmission. The apparatus may also receive, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a MCS. For example, the MCS may be based on the first CSI and a multi-user transmission. The apparatus may also determine CQI associated with the multi-user transmission. In addition, the apparatus may transmit, to the base station, the CQI associated with the multi-user transmission.

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

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network.

FIGs. 2A, 2B, 2C, and 2D are diagrams illustrating LTE examples of a DL frame structure, DL channels within the DL frame structure, an UL frame structure, and UL channels within the UL frame structure, respectively.

FIG. 3 is a diagram illustrating an example of an evolved Node B (eNB) and UE in an access network.

FIG. 4 is a diagram illustrating an exemplary wireless communications system in accordance with one aspect of the present disclosure.

FIG. 5 is a diagram illustrating on aspect of the present disclosure.

FIGs. 6A and 6B are a flowchart of a method of wireless communication.

FIG. 7 is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus.

FIG. 8 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

FIG. 9 is a flowchart of a method of wireless communication.

FIG. 10 is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus.

FIG. 11 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs) , central processing units (CPUs) , application processors, digital signal processors (DSPs) , reduced instruction set computing (RISC) processors, systems on a chip (SoC) , baseband processors, field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more example embodiments, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM) , a read-only memory (ROM) , an electrically erasable programmable ROM (EEPROM) , optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

FIG. 1 is a diagram illustrating an example of a wireless communications system and an access network 100. The wireless communications system (also referred to as a wireless wide area network (WWAN) ) includes base stations 102, UEs 104, and an Evolved Packet Core (EPC) 160. The base stations 102 may include macro cells (high power cellular base station) and/or small cells (low power cellular base station) . The macro cells include eNBs. The small cells include femtocells, picocells, and microcells.

The base stations 102 (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) ) interface with the EPC 160 through backhaul links 132 (e.g., S1 interface) . In addition to other functions, the base stations 102 may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity) , inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS) , subscriber and equipment trace, RAN information management (RIM) , paging, positioning, and delivery of warning messages. The base stations 102 may communicate directly or indirectly (e.g., through the EPC 160) with each other over backhaul links 134 (e.g., X2 interface) . The backhaul links 134 may be wired or wireless.

The base stations 102 may wirelessly communicate with the UEs 104. Each of the base stations 102 may provide communication coverage for a respective geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, the small cell 102'may have a coverage area 110'that overlaps the coverage area 110 of one or more macro base stations 102. A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs) , which may provide service to a restricted group known as a closed subscriber group (CSG) . The communication links 120 between the base stations 102 and the UEs 104 may include uplink (UL) (also referred to as reverse link) transmissions from a UE 104 to a base station 102 and/or downlink (DL) (also referred to as forward link) transmissions from a base station 102 to a UE 104. The communication links 120 may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations 102 /UEs 104 may use spectrum up to Y MHz (e.g., 5, 10, 15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL) . The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell) .

The wireless communications system may further include a Wi-Fi access point (AP) 150 in communication with Wi-Fi stations (STAs) 152 via communication links 154 in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs 152 /AP 150 may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available. The small cell 102' may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102'may employ LTE and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP 150. The small cell 102', employing LTE in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. LTE in an unlicensed spectrum may be referred to as LTE-unlicensed (LTE-U) , licensed assisted access (LAA) , or MuLTEfire.

The EPC 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a Serving Gateway 166, a Multimedia Broadcast Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172. The MME 162 may be in communication with a Home Subscriber Server (HSS) 174. The MME 162 is the control node that processes the signaling between the UEs 104 and the EPC 160. Generally, the MME 162 provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway 166, which itself is connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as other functions. The PDN Gateway 172 and the BM-SC 170 are connected to the IP Services 176. The IP Services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS) , a PS Streaming Service (PSS) , and/or other IP services. The BM-SC 170 may provide functions for MBMS user service provisioning and delivery. The BM-SC 170 may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN) , and may be used to schedule MBMS transmissions. The MBMS Gateway 168 may be used to distribute MBMS traffic to the base stations 102 belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information.

The base station may also be referred to as a Node B, evolved Node B (eNB) , an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS) , an extended service set (ESS) , or some other suitable terminology. The base station 102 provides an access point to the EPC 160 for a UE 104. Examples of UEs 104 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA) , a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player) , a camera, a game console, a tablet, a smart device, a wearable device, or any other similar functioning device. The UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

Referring again to FIG. 1, in certain aspects, the UE 104 may be configured to perform an SNR CQI feedback mechanism for MU-MIMO and/or MUST (198) .

FIG. 2A is a diagram 200 illustrating an example of a DL frame structure in LTE. FIG. 2B is a diagram 230 illustrating an example of channels within the DL frame structure in LTE. FIG. 2C is a diagram 250 illustrating an example of an UL frame structure in LTE. FIG. 2D is a diagram 280 illustrating an example of channels within the UL frame structure in LTE. Other wireless communication technologies may have a different frame structure and/or different channels. In LTE, a frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent the two time slots, each time slot including one or more time concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs) ) . The resource grid is divided into multiple resource elements (REs) . In LTE, for a normal cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols (for DL, OFDM symbols； for UL, SC-FDMA symbols) in the time domain, for a total of 84 REs. For an extended cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme.

As illustrated in FIG. 2A, some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRS) (also sometimes called common RS) , UE-specific reference signals (UE-RS) , and channel state information reference signals (CSI-RS) . FIG. 2A illustrates CRS for

antenna ports

0, 1, 2, and 3 (indicated as R₀, R₁, R₂, and R₃, respectively) , UE-RS for antenna port 5 (indicated as R₅) , and CSI-RS for antenna port 15 (indicated as R) . FIG. 2B illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol 0 of slot 0, and carries a control format indicator (CFI) that indicates whether the physical downlink control channel (PDCCH) occupies 1, 2, or 3 symbols (FIG. 2B illustrates a PDCCH that occupies 3 symbols) . The PDCCH carries downlink control information (DCI) within one or more control channel elements (CCEs) , each CCE including nine RE groups (REGs) , each REG including four consecutive REs in an OFDM symbol. A UE may be configured with a UE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs (FIG. 2B shows two RB pairs, each subset including one RB pair) . The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK) /negative ACK (NACK) feedback based on the physical uplink shared channel (PUSCH) . The primary synchronization channel (PSCH) is within symbol 6 of slot 0 within

subframes

0 and 5 of a frame, and carries a primary synchronization signal (PSS) that is used by a UE to determine subframe timing and a physical layer identity. The secondary synchronization channel (SSCH) is within symbol 5 of slot 0 within

subframes

0 and 5 of a frame, and carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI) . Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) is within

symbols

0, 1, 2, 3 of slot 1 of subframe 0 of a frame, and carries a master information block (MIB) . The MIB provides a number of RBs in the DL system bandwidth, a PHICH configuration, and a system frame number (SFN) . The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs) , and paging messages.

As illustrated in FIG. 2C, some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the eNB. The UE may additionally transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by an eNB for channel quality estimation to enable frequency-dependent scheduling on the UL. FIG. 2D illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth. The PUCCH carries uplink control information (UCI) , such as scheduling requests, a channel quality indicator (CQI) , a precoding matrix indicator (PMI) , a rank indicator (RI) , and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR) , a power headroom report (PHR) , and/or UCI.

FIG. 3 is a block diagram of an eNB 310 in communication with a UE 350 in an access network. In the DL, IP packets from the EPC 160 may be provided to a controller/processor 375. The controller/processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor 375 provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs) , RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release) , inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting； PDCP layer functionality associated with header compression /decompression, security (ciphering, deciphering, integrity protection, integrity verification) , and handover support functions； RLC layer functionality associated with the transfer of upper layer packet data units (PDUs) , error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs) , re-segmentation of RLC data PDUs, and reordering of RLC data PDUs； and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs) , demuliplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

The transmit (TX) processor 316 and the receive (RX) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor 356. The TX processor 368 and the RX processor 356 implement layer 1 functionality associated with various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they may be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 310. These soft decisions may be based on channel estimates computed by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 310 on the physical channel. The data and control signals are then provided to the controller/processor 359, which implements layer 3 and layer 2 functionality.

The controller/processor 359 can be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller/processor 359 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

Similar to the functionality described in connection with the DL transmission by the eNB 310, the controller/processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting； PDCP layer functionality associated with header compression /decompression, and security (ciphering, deciphering, integrity protection, integrity verification) ； RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs； and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demuliplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator 358 from a reference signal or feedback transmitted by the eNB 310 may be used by the TX processor 368 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 368 may be provided to different antenna 352 via separate transmitters 354TX. Each transmitter 354TX may modulate an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 310 in a manner similar to that described in connection with the receiver function at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers information modulated onto an RF carrier and provides the information to a RX processor 370.

The controller/processor 375 can be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE 350. IP packets from the controller/processor 375 may be provided to the EPC 160. The controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

When the UE is served in a multi-user fashion, power loss may occur due to a power split between the UE other UEs being served in the multi-user transmission. In addition, interference may be caused by the transmission to the other UEs. The power loss and/or the interference caused by the multi-user transmission may not be captured in the CSI feedback from the UE, which is based on a single-user transmission. Therefore, the base station may need perform a conversion of the CSI feedback that is based on the single-user transmission to estimate the multi-user signal-to-noise ratio (SNR) to determine a modulation and coding scheme for the multi-user transmission. The base station may rely on an outer loop (e.g., closed loop) mechanism that may take a certain period of time to converge in adjusting for a potential SNR conversion error. In addition, the pairing (e.g., of UEs in the multi-user transmission) may need to be relatively static for the outer loop mechanism to converge.

FIG. 4 is a diagram illustrating an exemplary communications system 400 that enables SNR channel quality information feedback for an MU-MIMO and an MUST. The communications system 400 may include a base station 404 located in serving cell 402. In addition, a UE 406 located in serving cell 402 may be in communication with the base station 404.

In an aspect, the base station 404 may receive first CSI 410 (e.g., RI/PMI/CQI) associated with a single-user transmission from the UE 406. In addition, the base station 404 may receive a different CSI 420 associated with a different single-user transmission from UE 416. The base station 404 may schedule 414 the

UEs

404, 416 using a first multi-user configuration. For example, the first multi-user configuration may be related to a MU-MIMO or a MUST.

The base station 404 may transmit a downlink scheduling grant 412 (e.g., a PDSCH grant) associated with the first multi-user configuration to each of the

UEs

404, 416. In an aspect, the first multi-user configuration may have a modulation and coding scheme (MCS) that is based on the first CSI 410 received from the UE 406 and/or the different CSI 420 received from the UE 416. In addition, the downlink scheduling grant 412 may be for a demodulation reference signal (DMRS) -based PDSCH. Additionally and/or alternatively, the downlink scheduling grant 412 may be for a CRS-based PDSCH. When the downlink scheduling grant 412 is for a CRS-based PDSCH, the base station 404 may transmit and/or signal information 424 indicating the first multi-user configuration to the

UEs

406, 416. For example, the information 424 may include information about the other UE paired in the multi-user transmission. When each of the

UEs

406, 416 receives the PDSCH, the

UEs

406, 416 may each decode the PDSCH and determine a rank indicator (RI) and/or precoding matrix indicator (PMI) associated with the PDSCH. In addition, the

UEs

406, 416 may each determine 408 a CQI associated with the multi-user transmission 412 received from the base station 404. For example, the CQI determined 408 by each of the

UEs

406, 416 may indicate an SNR (e.g., a decoding SNR CQI) or SNR range associated with the first multi-user transmission. The decoding SNR CQI may be conditioned on the RI and PMI associated with the PDSCH. The decoding SNR CQI may have the same length as the CSI associated with the single-user transmission such that same PUCCH format may be used for both the CSI and the decoding SNR CQI. The same PUCCH format may be used for both periodic and aperiodic reporting.

In an aspect, the

UEs

406, 416 may determine an SNR when demodulating the PDSCH. Furthermore, when the SNR (s) is/are determined at each of the

UEs

406, 416, the actual power and interference information of the multi-user transmission is used. Therefore, the decoding SNR CQI may no longer be based a single-user transmission. When a minimum mean square error (MMSE) receiver is used by the

UEs

406, 416 to demodulate the PDSCH, the SNR may be a side product of the demodulation. Additionally and/or alternatively, when a maximum likelihood (ML) receiver is used by the

UEs

406, 416 to demodulate the PDSCH, the SNR may be determined (e.g., by the UEs) using QR decomposition (e.g., decomposition of a matrix A into a product A ＝ QR of an orthogonal matrix Q and an upper triangular matrix R) .

In another aspect, if the

UEs

406, 416 receive the information 424 indicating the first multi-user configuration (e.g., when the downlink scheduling grant is for a CRS-based PDSCH) , the

UEs

406, 416 may each determine 408 a decoding SNR CQI based on the information 424 indicating the first multi-user configuration and the first multi-user transmission 412. In a further aspect, the

UEs

406, 416 may each determine 408 the decoding SNR CQI associated with the first multi-user transmission by determining, from the downlink scheduling grant 412, at least one DMRS port associated with the other UE included in the first multi-user transmission. In addition, the

UEs

406, 416 may each determine 408 the decoding SNR CQI associated with the multi-user transmission by further determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the pairing of the second UE and the first UE in the multi-user transmission. In one aspect, the

UEs

406, 416 may each transmit a decoding

SNR CQI

410, 420 to the base station 404 in a PUCCH or in UCI on a PUSCH. In another aspect, the

UEs

406, 416 may each transmit the decoding

SNR CQI

410, 420 to the base station 404 with an ACK/NACK transmission. In addition, the decoding

SNR CQI

410, 420 and the CSI associated with the single-user transmission may be transmitted by each of the

UEs

406, 416 as independent feedback to the base station 404.

In another aspect, the decoding

SNR CQI

410, 420 and the CSI associated with the single-user transmission may be transmitted by each

UE

406, 416 on the PUCCH or the PUSCH alternatively (e.g., not in the same subframe) . For example, the decoding

SNR CQI

UE

406, 416 using time division multiplexing (TDM) .

In a further aspect, the CSI associated with the single-user transmission may be given priority over the decoding SNR CQI in a TDM scenario, as discussed infra with respect to FIG. 5. For example, if one or both of the

UEs

406, 416 is able to transmit either the CSI associated with the single-user transmission or the decoding SNR CQI in a single subframe, the UE may transmit the CSI associated with the single-user transmission in an earlier subframe and the decoding SNR CQI will be transmitted in a later subframe. Additionally, if a decoding SNR CQI is not transmitted by one or more of the

UEs

406, 416, the base station 404 may send a trigger to the UE (s) that did not transmit the decoding

SNR CQI

410, 420 in a later subframe, to cause the UE (s) that did not transmit the decoding

SNR CQI

410, 420 to transmit the decoding

SNR CQI

410, 420 at a later time.

When the decoding

SNR CQI

410, 420 is received at the base station, the base station may decode the decoding

SNR CQI

410, 420 and may schedule 414 the

UEs

406, 416 using a second multi-user configuration based on a second CSI. For example, the second multi-user configuration may be different than the first multi-user configuration. For example, the base station 404 may use the updated RI/PMI/CQI from single-user transmission to form the second multi-user configuration. Additionally and/or alternatively, the base station 404 may update 414 the MCS of the first multi-user configuration based on a pairing of the

first CSI

410, 420 with the decoding

SNR CQI

410, 420. For example, the base station 404 may use the decoding

SNR CQI

410, 420 from one of the

UEs

406, 416 paired with the RI/PMI/CQI from the single-user transmission to update the MCS for the first multi-user configuration. In an aspect, base station 404 may determine RI/PMI the decoding SNR CQI 410 is based on using the report timing information. For example, The base station 404 may compare 414 the decoding

SNR CQI

410, 420 with an estimated SNR based on the up-to-date RI/PMI/CQI report and pick the better one.

The base station 404 may include multiple outer loop offsets. For example, the outer loop offsets may include 1) a single user mode offset, 2) a multi-user mode offset that uses the decoding SNR, and 3) a multi-user mode offset that uses an estimated SNR determined by the base station 404 based on the CSI associated with the single-user transmission. The outer loop offsets 1) and 2) may be the same outer loop offset because both of outer loop offsets 1) and 2) use an SNR that is based on an accurate interference/transmission power assumption. The outer loop offset 3) may need a separate outer loop offset because the base station 404 may have to estimate/predict/guess the SNR. Therefore, the outer loop offset 3) may need a larger backoff to capture a wider distribution of SNR prediction error.

In addition, a scheduler of the base station 404 may select between using normal CSI (e.g., associated with a single-user transmission) or the decoding SNR CQI (e.g., associated with a multi-user transmission) for each scheduling of a UE using a multi-user configuration. In other words, the decoding SNR CQI may add another choice for the scheduler. After backoff, this provides another SNR that translates to a rate and can be compared with the other two rates directly in the proportional fair scheduling (PFS) metric domain, and may allow the scheduler to determine when to switch out of the mode using decoding SNR CQI.

FIG. 5 illustrates an exemplary CSI triggering mechanism 500 used for transmission of a CSI 506 and a decoding SNR CQI 508 associated with the single-user in a TDM scenario. In the example illustrated in FIG. 5, the UE 406 is unable to transmit the CSI 506 and the decoding SNR CQI 508 in the same subframe. Therefore, the CSI 506 is transmitted in an earlier subframe (e.g., subframe 4) than the decoding SNR CQI 508 (e.g.,

subframes

5, 6, and/or 7) .

Referring to FIG. 5, the UE 406 receives a CSI request 502 for aperiodic CSI (A-CSI) reporting and a PDSCH grant 502 in subframe 0. The CSI reference resource (e.g., a group of downlink physical resource blocks in a DL subframe used for deriving CQI) contains the CSI-RS (e.g., whether or not PDSCH is scheduled) and the UE 406 may report the CSI 506 associated with the single-user transmission that includes RI/PMI/CQI in UL subframe 4. The subframe in which the CSI reference resource is transmitted may be the first valid DL subframe occurring on or prior to a CSI triggering subframe 506. Whether the CSI reference resource is transmitted on a CSI trigger subframe 506 or prior to the CSI trigger subframe 506 depends on whether the UE is configured with single or multiple CSI processes. In the example illustrated in FIG. 5, the CSI reference resource is in the same subframe as the CSI request 502. With respect to

subframes

1, 2, and 3, the CSI reference resource 504 does not contain CSI-RS and the PDSCH is scheduled in the same subframe as the CSI trigger DCI. Because the CSI reference resource 504 does not contain CSI-RS and the PDSCH is scheduled in the same subframe as the CSI trigger DCI, the UE 406 may be triggered to report the decoding SNR CQI 508. For example, the decoding SNR CQI 508 may be transmitted by the UE in

UL subframes

5, 6, and/or 7.

FIGs. 6A and 6B are a flowchart 600 of a method of wireless communication. The method may be performed by an eNB (e.g., the base station 404) . Operations indicated with dashed lines represent optional operations for various aspects of the disclosure. As seen in FIG. 6A, at 602, the base station may receive, from a UE, first CSI associated with a single-user transmission. For example, referring to FIG. 4, the base station 404 may receive first CSI 410 associated with a single-user transmission from the UE 406.

At 604, the base station may schedule the UE using a first multi-user transmission. For example, referring to FIG. 4, the base station 404 may schedule 414 the UE using a first multi-user configuration. For example, the first multi-user configuration may be related to a MU-MIMO or a MUST.

At 606, the base station may transmit, to the UE, a downlink scheduling grant associated with the first multi-user configuration having an MCS based on the first CSI. For example, referring to FIG. 4, the base station 404 may transmit a downlink scheduling grant 412 associated with the first multi-user configuration. In an aspect, the first multi-user configuration may have an MCS that is based on the

first CSI

410, 420. In addition, the downlink scheduling grant 412 may be for a DMRS-based PDSCH. Additionally and/or alternatively, the downlink scheduling grant may be for a CRS-based PDSCH. When the downlink scheduling grant 412 is for a CRS-based PDSCH, the base station 404 may transmit and/or signal information 424 indicating the first multi-user configuration to the UE 406.

At 608, the base station may receive, from the UE, CQI associated with a first multi-user transmission. For example, referring to FIG. 4, the UE 406 may receive a first multi-user transmission 412 from the base station 404. In response to the first multi-user transmission 412, the UE 406 may transmit the decoding SNR CQI 410 associated with the first multi-user transmission to the base station 404 in a PUCCH or in UCI on a PUSCH. In another aspect, the UE 406 may transmit the decoding SNR CQI 410 to the base station 404 with an ACK/NACK transmission. In other words, the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted as independent feedback to the base station 404. In another aspect, the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted on the PUCCH or PUSCH at the same time. For example, the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted using TDM. In a further aspect, the CSI associated with the single-user transmission may be given priority over the decoding SNR CQI, as discussed infra with respect to FIG. 5. If the UE 406 is able to transmit either the CSI associated with the single-user transmission or the decoding SNR CQI, the UE may transmit the CSI associated with the single-user transmission in an earlier subframe and the decoding SNR CQI may be transmitted in a later subframe. Additionally, if a decoding SNR CQI is not transmitted by the UE 406, the base station 404 may send a trigger to the UE in a later subframe, to cause the UE 406 to transmit the decoding SNR CQI at a later time.

At 610, the base station may signal, to the UE, information indicating the first multi-user transmission. For example, referring to FIG. 4, when the downlink scheduling grant 412 is for a CRS-based PDSCH, the base station 404 may transmit and/or signal additional information 412 that indicates the scheduling grant 412 is for a CRS-based PDSCH.

At 612, the base station may decode the CQI. For example, referring to FIG. 4, when the decoding SNR CQI 410 is received at the base station, the base station may decode the decoding SNR CQI 410.

At 614, the base station may perform multi-user transmission procedure A or multi-user transmission procedure B. For example, referring to FIG. 4, the base station 404 may compare 414 the decoding SNR CQI 410 with an estimated SNR based on the up-to-date RI/PMI report and pick the better one.

Multi-User Transmission Procedure A

As seen in FIG. 6B, at 616, the base station may schedule the UE using a second multi-user configuration based on a second CSI. In an aspect, the second multi-user configuration may be different than the first multi-user configuration. For example, referring to FIG. 4, when the decoding SNR CQI 410 is received at the base station, the base station may decode the decoding SNR CQI 410 and may schedule 414 the UE 406 using a second multi-user configuration based on a second CSI. For example, the second multi-user configuration may be different than the first multi-user configuration. For example, the base station may use the updated RI/PMI/CQI from single-user transmission to form the second multi-user configuration.

Multi-User Transmission Procedure B

Alternatively, as also seen in FIG. 6B, at 618, the base station may update and/or modify the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI. For example, referring to FIG. 4, the base station 404 may update 414 the MCS of the first multi-user configuration based on a pairing of the first CSI 410 with the decoding SNR CQI 410. For example, the base station 404 may use the decoding SNR CQI 410 paired with the RI/PMI from the single-user transmission to update the MCS for the first multi-user configuration. In an aspect, base station 404 may determine RI/PMI the decoding SNR CQI 410 is based on using the report timing information.

FIG. 7 is a conceptual data flow diagram 700 illustrating the data flow between different means/components in an exemplary apparatus 702. The apparatus may be a base station. The apparatus includes a transmission component 712 that may transmit a single-user transmission 775 to a UE 755. The apparatus includes a reception component 704 that receives, from a UE, first CSI 705 associated with a single-user transmission. The apparatus also includes a scheduling component 706 that may schedule the UE using a first multi-user configuration. The scheduling component 706 may also schedule a downlink scheduling grant for the UE. The scheduling component 706 may send a signal 765 associated with the downlink scheduling grant to the transmission component 712. The transmission component 712 may transmit, to the UE 755, a downlink scheduling grant 775 associated with a first multi-user configuration having a MCS based on the first CSI and the first multi-user transmission. The scheduling component 706 may send a signal 765 associated with the first multi-user transmission to the transmission component 712. The transmission component 712 may transmit the first multi-user transmission 775 to the UE. The reception component 704 may also receive, from the UE 755, CQI 705 associated with the first multi-user transmission. The transmission component 712 may signal, to the UE 755, information 775 indicating the first multi-user configuration. The reception component 704 may receive, from the UE 755, CQI 705 (e.g., decoding SNR CQI) associated with the first multi-user transmission. The reception component may send a signal 725 associated with the CQI to the decoding component 708. The decoding component 708 may decode the CQI. The decoding component 708 may send a signal 735 associated with the decoded CQI to the updating component 710. The updating component 710 may update the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI. The updating component may send a signal 745 associated with the MCS to the scheduling component 706. The scheduling component 706 may use the MCS when scheduling another multi-user transmission. The scheduling component 706 may schedule the UE using a second multi-user configuration based on a second CSI (e.g., a CSI estimated by the scheduling component 706) . The second multi-user configuration may be different than the first multi-user configuration. The scheduling component 706 may send a signal 765 associated with the second multi-user transmission to the transmission component 712. The transmission component 712 may transmit multi-user transmission 775 based on the second multi-user configuration to the UE 755.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of FIGs. 6A and 6B. As such, each block in the aforementioned flowcharts of FIGs. 6A and 6B may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

FIG. 8 is a diagram 800 illustrating an example of a hardware implementation for an apparatus 702'employing a processing system 814. The processing system 814 may be implemented with a bus architecture, represented generally by the bus 824. The bus 824 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 814 and the overall design constraints. The bus 824 links together various circuits including one or more processors and/or hardware components, represented by the processor 804, the

components

704, 706, 708, 710, 712, and the computer-readable medium /memory 806. The bus 824 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system 814 may be coupled to a transceiver 810. The transceiver 810 is coupled to one or more antennas 820. The transceiver 810 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 810 receives a signal from the one or more antennas 820, extracts information from the received signal, and provides the extracted information to the processing system 814, specifically the reception component 704. In addition, the transceiver 810 receives information from the processing system 814, specifically the transmission component 712, and based on the received information, generates a signal to be applied to the one or more antennas 820. The processing system 814 includes a processor 804 coupled to a computer-readable medium /memory 806. The processor 804 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 806. The software, when executed by the processor 804, causes the processing system 814 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 806 may also be used for storing data that is manipulated by the processor 804 when executing software. The processing system 814 further includes at least one of the

components

704, 706, 708, 710, 712. The components may be software components running in the processor 804, resident/stored in the computer readable medium /memory 806, one or more hardware components coupled to the processor 804, or some combination thereof. The processing system 814 may be a component of the eNB 310 and may include the memory 376 and/or at least one of the TX processor 316, the RX processor 370, and the controller/processor 375.

In one configuration, the apparatus 702/702'for wireless communication includes means for means for receiving, from a UE, first CSI associated with a single-user transmission. In another configuration, the apparatus 702/702'for wireless communication includes means for transmitting, to the UE, a downlink scheduling grant associated with a first multi-user configuration having a MCS, the MCS being based on the first CSI. In a further configuration, the apparatus 702/702'for wireless communication includes means for receiving, from the UE, CQI associated with the first multi-user transmission. In another configuration, the apparatus 702/702'for wireless communication includes means for scheduling the UE using the first multi-user configuration. In an aspect, the CQI includes an SNR associated with the first multi-user transmission. In another aspect, the downlink scheduling grant is for a DMRS-based PDSCH. In a further aspect, the downlink scheduling grant is for a CRS-based PDSCH. In another configuration, the apparatus 702/702'for wireless communication includes means for signaling, to the UE, information indicating the first multi-user configuration. In an aspect, the CQI received from the UE may be based on the signaled information associated with the first multi-user transmission. In another configuration, the apparatus 702/702'for wireless communication includes means for decoding the CQI. In a further configuration, the apparatus 702/702'for wireless communication includes means for performing a multi-user transmission procedure by scheduling the UE using a second multi-user configuration based on a second CSI, the second multi-user configuration being different than the first multi-user configuration, or by updating the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI. In an aspect, the CQI is received in an uplink control channel or in UCI on an uplink data channel. In another aspect, the CQI is received with an ACK/NACK transmission. The aforementioned means may be one or more of the aforementioned components of the apparatus 702 and/or the processing system 814 of the apparatus 702'configured to perform the functions recited by the aforementioned means. As described supra, the processing system 814 may include the TX Processor 316, the RX Processor 370, and the controller/processor 375. As such, in one configuration, the aforementioned means may be the TX Processor 316, the RX Processor 370, and the controller/processor 375 configured to perform the functions recited by the aforementioned means.

FIG. 9 is a flowchart 900 of a method of wireless communication. The method may be performed by a UE (e.g., the UE 406) . Operations indicated with dashed lines represent optional operations for various aspects of the disclosure.

At 902, the UE may transmit, to a base station, CSI associated with a single-user transmission. For example, referring to FIG. 4, the base station 404 may receive first CSI 410 associated with a single-user transmission from the UE 406.

At 904, the UE may receive, from the base station, a first downlink scheduling grant associated with a multi-user configuration having an MCS based on the first CSI. For example, referring to FIG. 4, the base station 404 may transmit a downlink scheduling grant 412 associated with the first multi-user configuration. In an aspect, the first multi-user configuration may have a MCS that is based on the first CSI 410. In addition, the downlink scheduling grant 412 may be for a DMRS-based PDSCH. Additionally and/or alternatively, the downlink scheduling grant may be for a CRS-based PDSCH.

At 906, the UE may receive, from the base station, information indicating the multi-user transmission. For example, referring to FIG. 4, when the downlink scheduling grant 412 is for a CRS-based PDSCH, the base station 404 may transmit and/or signal additional information 424 that indicates the first multi-user configuration.

At 908, the UE may determine CQI associated with the multi-user transmission. For example, referring to FIG. 4, if the UE 406 receives the information 412 associated with the first multi-user transmission (e.g., when the downlink scheduling grant is for a CRS-based PDSCH) , the UE 406 may determine 408 the decoding SNR CQI based on the information 424 indicating the multi-user configuration. In a further aspect, the UE 406 may determine 408 the decoding SNR CQI associated with the multi-user transmission by determining, from the downlink scheduling grant 412, at least one DMRS port associated with a second UE. For example, the second UE may be paired with the first UE in the multi-user transmission. In addition, the UE 406 may determine 408 the decoding SNR CQI associated with the multi-user transmission by further determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.

For example, at 910, the UE may determine CQI associated with the multi-user transmission by determining, from the downlink scheduling grant, at least one DMRS port associated with a second UE, the second UE being paired with the first UE in the multi-user transmission. For example, referring to FIG. 4, the UE 406 may determine 408 the decoding SNR CQI associated with the multi-user transmission by determining, from the downlink scheduling grant 412, at least one DMRS port associated with a second UE. For example, the second UE may be paired with the first UE in the multi-user transmission.

In addition, at 912, the UE may determine CQI associated with the multi-user transmission by determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission. For example, referring to FIG. 4, the UE 406 may determine 408 the decoding SNR CQI associated with the multi-user transmission by further determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.

At 914, the UE may transmit, to the base station, the CQI associated with the multi-user transmission. For example, referring to FIG. 4, the UE 406 may transmit the decoding SNR CQI 410 to the base station 404 in a PUCCH or in UCI on a PUSCH. In another aspect, the UE 406 may transmit the decoding SNR CQI 410 to the base station 404 with an ACK/NACK transmission. In other words, the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted as independent feedback to the base station 404. the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted on the PUCCH or PUSCH at the same time. For example, the decoding SNR CQI 410 and the CSI associated with the single-user transmission may be transmitted using TDM. In a further aspect, the CSI associated with the single-user transmission may be given priority over the decoding SNR CQI. If the UE 406 is able to transmit either the CSI associated with the single-user transmission or the decoding SNR CQI, the UE may transmit the CSI associated with the single-user transmission in an earlier subframe and the decoding SNR CQI may be transmitted in a later subframe. Additionally, if a decoding SNR CQI is not transmitted by the UE 406, the base station 404 may send a trigger to the UE in a later subframe, to cause the UE 406 to transmit the decoding SNR CQI at a later time.

FIG. 10 is a conceptual data flow diagram 1000 illustrating the data flow between different means/components in an exemplary apparatus 1002. The apparatus may be a UE. The apparatus includes a reception component 1004 that receives a single-user transmission 1005 from a base station 1055. The reception component 1004 may transmit a signal 1015 associated with the single-user transmission to the determination component 1006. The determination component 1006 may determine CSI associated with the single-user transmission. The determination component may send a signal 1025 associated with the CSI to the transmission component 1008. The transmission component 1008 may transmit, to the base station 1055, CSI associated with the single-user transmission. The reception component 1004 may also receive, from the base station, a first downlink scheduling grant 1004 associated with a multi-user configuration having an MCS based on the first CSI. In addition, the reception component 1004 may receive, from the base station 1055, information 1005 indicating the multi-user configuration. The reception component 1004 may also receive a multi-user transmission from the base station 1055. The reception component 1004 may send a signal 1015 associated with the downlink scheduling grant, the multi-user transmission, and/or the information indicating the multi-user configuration to the determination component 1006. The determination component 1006 may determine CQI associated with the multi-user transmission. For example, the determination component 1006 may determine, from the downlink scheduling grant, at least one DMRS port associated with a second UE. In an aspect, the second UE may be paired with the first UE in the multi-user transmission. In addition, the determination component 1006 may determine an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission. Further, the determination component 1006 may send a signal 1025 associated with the CQI (e.g., decoding SNR CQI) to the transmission component 1008. The transmission component 1008 may transmit the CQI 1035 to the base station 1055.

The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of FIG. 9. As such, each block in the aforementioned flowchart of FIG. 9 may be performed by a component and the apparatus may include one or more of those components. The components may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof.

FIG. 11 is a diagram 1100 illustrating an example of a hardware implementation for an apparatus 1002'employing a processing system 1114. The processing system 1114 may be implemented with a bus architecture, represented generally by the bus 1124. The bus 1124 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1114 and the overall design constraints. The bus 1124 links together various circuits including one or more processors and/or hardware components, represented by the processor 1104, the

components

1004, 1006, 1008, and the computer-readable medium /memory 1106. The bus 1124 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system 1114 may be coupled to a transceiver 1110. The transceiver 1110 is coupled to one or more antennas 1120. The transceiver 1110 provides a means for communicating with various other apparatus over a transmission medium. The transceiver 1110 receives a signal from the one or more antennas 1120, extracts information from the received signal, and provides the extracted information to the processing system 1114, specifically the reception component 1004. In addition, the transceiver 1110 receives information from the processing system 1114, specifically the transmission component 1008, and based on the received information, generates a signal to be applied to the one or more antennas 1120. The processing system 1114 includes a processor 1104 coupled to a computer-readable medium /memory 1106. The processor 1104 is responsible for general processing, including the execution of software stored on the computer-readable medium /memory 1106. The software, when executed by the processor 1104, causes the processing system 1114 to perform the various functions described supra for any particular apparatus. The computer-readable medium /memory 1106 may also be used for storing data that is manipulated by the processor 1104 when executing software. The processing system 1114 further includes at least one of the

components

1004, 1006, 1008. The components may be software components running in the processor 1104, resident/stored in the computer readable medium /memory 1106, one or more hardware components coupled to the processor 1104, or some combination thereof. The processing system 1114 may be a component of the UE 350 and may include the memory 360 and/or at least one of the TX processor 368, the RX processor 356, and the controller/processor 359.

In one configuration, the apparatus 1002/1002'for wireless communication includes means for transmitting, to a base station, CSI associated with a single-user transmission. In another configuration, the apparatus 1002/1002'for wireless communication includes means for receiving, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a MCS. In an aspect, the MCS may be based on the first CSI. In a further configuration, the apparatus 1002/1002'for wireless communication includes means for determining CQI associated with the multi-user transmission. In yet another configuration, the apparatus 1002/1002'for wireless communication includes means for transmitting, to the base station, the CQI associated with the multi-user transmission. In an aspect, the CQI includes an SNR associated with the multi-user transmission. In another aspect, the downlink scheduling grant is for a DMRS-based PDSCH. In still another aspect, the means for determining the CQI associated with the multi-user transmission is configured to determine, from the downlink scheduling grant, at least one DMRS port associated with a second UE, the second UE being paired with the first UE in the multi-user transmission, and to determine an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission. In a further aspect, the downlink scheduling grant is for a CRS-based PDSCH. In another configuration, the apparatus 1002/1002'for wireless communication includes means for receiving, from the base station, information associated with the multi-user transmission. In an aspect, the CQI is determined based on the received information associated with the multi-user transmission. In another aspect, the CQI may be transmitted in an uplink control channel or in UCI on an uplink data channel. In yet another aspect, the CQI is included with an ACK/NACK transmission. The aforementioned means may be one or more of the aforementioned components of the apparatus 1002 and/or the processing system 1014 of the apparatus 1002'configured to perform the functions recited by the aforementioned means. As described supra, the processing system 1014 may include the TX Processor 368, the RX Processor 356, and the controller/processor 359. As such, in one configuration, the aforementioned means may be the TX Processor 368, the RX Processor 356, and the controller/processor 359 configured to perform the functions recited by the aforementioned means.

It is understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

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. ” 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. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. 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. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

Claims

A method of wireless communication, comprising:

receiving, from a user equipment (UE) , first channel state information (CSI) associated with a single-user transmission；

transmitting, to the UE, a downlink scheduling grant associated with a first multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI； and

receiving, from the UE, channel quality information (CQI) associated with a first multi-user transmission.
The method of claim 1, further comprising:

scheduling the UE using the first multi-user configuration.
The method of claim 1, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the first multi-user transmission.
The method of claim 1, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The method of claim 1, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared data channel (PDSCH) .
The method of claim 5, further comprising:

signaling, to the UE, information indicating the first multi-user configuration.

.
The method of claim 1, further comprising:

decoding the CQI； and

performing a multi-user transmission procedure by

scheduling the UE using a second multi-user configuration based on a second CSI, the second multi-user configuration being different than the first multi-user configuration； or

updating the MCS in the first multi-user configuration based on a pairing of the first CSI with the decoded CQI.
The method of claim 1, wherein the CQI is received in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The method of claim 1, wherein the CQI is received with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
A method of wireless communication of a first user equipment (UE) , comprising:

transmitting, to a base station, channel state information (CSI) associated with a single-user transmission；

receiving, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI；

determining channel quality information (CQI) associated with a multi-user transmission； and

transmitting, to the base station, the CQI associated with the multi-user transmission.
The method of claim 10, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the multi-user transmission.
The method of claim 10, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The method of claim 12, wherein the determining the CQI associated with the multi-user transmission comprises:

determining, from the downlink scheduling grant, at least one DMRS port associated with a second UE, the second UE being paired with the first UE in the multi-user transmission； and

determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.
The method of claim 10, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared channel (PDSCH) .
The method of claim 14, further comprising:

receiving, from the base station, information indicating the multi-user configuration.

.
The method of claim 10, wherein the CQI is transmitted in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The method of claim 10, wherein the CQI is included with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
An apparatus for wireless communication, comprising:

means for receiving, from a user equipment (UE) , first channel state information (CSI) associated with a single-user transmission；

means for transmitting, to the UE, a downlink scheduling grant associated with a first multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI； and

means for receiving, from the UE, channel quality information (CQI) associated with a first multi-user transmission.
The apparatus of claim 18, further comprising:

means for scheduling the UE using the first multi-user configuration.
The apparatus of claim 18, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the first multi-user transmission.
The apparatus of claim 18, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 18, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 22, further comprising:

means for signaling, to the UE, information indicating the first multi-user configuration.
The apparatus of claim 18, further comprising:

means for decoding the CQI； and

means for performing a multi-user transmission procedure, the means for performing being configured to

schedule the UE in a second multi-user configuration based on a second CSI, the second multi-user configuration being different than the first multi-user configuration； or

update the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI.
The apparatus of claim 18, wherein the CQI is received in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The apparatus of claim 18, wherein the CQI is received with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
An apparatus for wireless communication, comprising:

means for transmitting, to a base station, channel state information (CSI) associated with a single-user transmission；

means for receiving, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI；

means for determining channel quality information (CQI) associated with a multi-user transmission； and

means for transmitting, to the base station, the CQI associated with the multi-user transmission.
The apparatus of claim 27, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the multi-user transmission.
The apparatus of claim 27, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 29, wherein the means for determining the CQI associated with the multi-user transmission is configured to:

determine, from the downlink scheduling grant, at least one DMRS port associated with a second user equipment (UE) , the second UE being paired with a first UE in the multi-user transmission； and

determine an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.
The apparatus of claim 27, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared channel (PDSCH) .
The apparatus of claim 31, further comprising:

means for receiving, from the base station, information indicating the multi-user configuration.
The apparatus of claim 27, wherein the CQI is transmitted in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The apparatus of claim 27, wherein the CQI is included with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
An apparatus for wireless communication, comprising:

a memory； and

at least one processor coupled to the memory and configured to:

receive, from a user equipment (UE) , first channel state information (CSI) associated with a single-user transmission；

transmit, to the UE, a downlink scheduling grant associated with a first multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI； and

receive, from the UE, channel quality information (CQI) associated with a first multi-user transmission.
The apparatus of claim 35, wherein the at least one processor is further configured to:

schedule the UE using the first multi-user configuration.
The apparatus of claim 35, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the first multi-user transmission.
The apparatus of claim 35, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 35, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 39, wherein the at least one processor is further configured to:

signal, to the UE, information indicating the first multi-user configuration.
The apparatus of claim 35, wherein the at least one processor is further configured to:

decode the CQI； and

perform a multi-user transmission procedure by

scheduling the UE using a second multi-user configuration based on a second CSI, the second multi-user configuration being different than the first multi-user configuration； or

updating the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI.
The apparatus of claim 35, wherein the CQI is received in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The apparatus of claim 35, wherein the CQI is received with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
An apparatus for wireless communication, comprising:

a memory； and

at least one processor coupled to the memory and configured to:

transmit, to a base station, channel state information (CSI) associated with a single-user transmission；

receive, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI；

determine channel quality information (CQI) associated with a multi-user transmission； and

transmit, to the base station, the CQI associated with the multi-user transmission.
The apparatus of claim 44, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the multi-user transmission.
The apparatus of claim 44, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The apparatus of claim 46, wherein the at least one processor is configured to determine the CQI associated with the multi-user transmission by:

determining, from the downlink scheduling grant, at least one DMRS port associated with a second UE, the second UE being paired with the first UE in the multi-user transmission； and

determining an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.
The apparatus of claim 44, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared channel (PDSCH) .
The apparatus of claim 48, wherein the at least one processor is further configured to:

receive, from the base station, information indicating the multi-user configuration.
The apparatus of claim 44, wherein the CQI is transmitted in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The apparatus of claim 44, wherein the CQI is included with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
A computer-readable medium storing computer executable code, comprising code to:

receive, from a user equipment (UE) , first channel state information (CSI) associated with a single-user transmission；

transmit, to the UE, a downlink scheduling grant associated with a first multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI； and

receive, from the UE, channel quality information (CQI) associated with a first multi-user transmission.
The computer-readable medium of claim 52, wherein the code is further configured to:

schedule the UE using the first multi-user configuration.
The computer-readable medium of claim 52, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the first multi-user transmission.
The computer-readable medium of claim 52, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The computer-readable medium of claim 52, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared data channel (PDSCH) .
The computer-readable medium of claim 56, wherein the code is further configured to:

signal, to the UE, information indicating the multi-user configuration.
The computer-readable medium of claim 52, wherein the code is further configured to:

decode the CQI； and

perform a multi-user transmission procedure by

scheduling the UE in a second multi-user configuration based on a second CSI, the second multi-user configuration being different than the first multi-user configuration； or

updating the MCS of the first multi-user configuration based on a pairing of the first CSI with the decoded CQI.
The computer-readable medium of claim 52, wherein the CQI is received in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The computer-readable medium of claim 52, wherein the CQI is received with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.
A computer-readable medium storing computer executable code, comprising code to:

transmit, to a base station, channel state information (CSI) associated with a single-user transmission；

receive, from the base station, a first downlink scheduling grant associated with a multi-user configuration having a modulation and coding scheme (MCS) , the MCS being based on the first CSI；

determine channel quality information (CQI) associated with a multi-user transmission； and

transmit, to the base station, the CQI associated with the multi-user transmission.
The computer-readable medium of claim 61, wherein the CQI includes a signal-to-noise ratio (SNR) associated with the multi-user transmission.
The computer-readable medium of claim 61, wherein the downlink scheduling grant is for a demodulation reference signals (DMRS) -based physical downlink shared data channel (PDSCH) .
The computer-readable medium of claim 63, wherein the code to determine the CQI associated with the multi-user transmission is configured to:

determine, from the downlink scheduling grant, at least one DMRS port associated with a second UE, the second UE being paired with the first UE in the multi-user transmission； and

determine an SNR based on at least one of an estimated interference or an estimated transmission power associated with the second UE being paired with the first UE in the multi-user transmission.
The computer-readable medium of claim 61, wherein the downlink scheduling grant is for a cell-specific reference signals (CRS) -based physical downlink shared channel (PDSCH) .
The computer-readable medium of claim 65, wherein the code is further configured to:

receive, from the base station, information indicating the multi-user configuration.
The computer-readable medium of claim 61, wherein the CQI is transmitted in an uplink control channel or in uplink control information (UCI) on an uplink data channel.
The computer-readable medium of claim 61, wherein the CQI is included with an acknowledgement (ACK) /negative acknowledgement (NACK) transmission.