HK1157090A - Spatial interference mitigation schemes for wireless communication - Google Patents

Description

Spatial interference suppression scheme for wireless communications

This application claims priority to U.S. provisional application No.61/053,564, entitled "SPATIALINTERFERENCE AVOIDANCE TECHNIQUES," filed on 15.5.2008 and U.S. provisional application No.61/117,852, entitled "SPATIALINTERFERENCE AVOIDANCE TIMELINE," filed on 25.11.2008, both of which are assigned to the assignee of the present application and are hereby incorporated by reference.

Technical Field

The present disclosure relates generally to communication, and more specifically to techniques for sending and receiving data in a wireless communication network.

Background

Wireless communication networks are widely deployed today to provide various communication content such as voice, video, packet data, messaging, broadcast, and so on. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple access networks include: code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and single carrier FDMA (SC-FDMA) networks.

A wireless communication network may include multiple base stations that may support communication for multiple User Equipments (UEs). A UE may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base stations to the UEs, and the uplink (or reverse link) refers to the communication link from the UEs to the base stations.

One UE may be within the coverage of multiple base stations. One base station may be selected to serve the UE, with the remaining base stations being non-serving base stations. The UE may be subject to strong interference on the downlink with the non-serving base station and/or cause strong interference on the uplink with the non-serving base station. It is desirable to be able to transmit data in some way to achieve good performance even in the presence of strong non-serving base stations.

Disclosure of Invention

Techniques for transmitting and receiving data using spatial interference suppression (interference) in a wireless communication network are described. Spatial interference suppression refers to interference reduction by the interfered station based on spatial nulling (spatial nulling) and/or receiver spatial processing. Spatial nulling refers to steering transmissions in a direction away from the interfered station to reduce interference to the interfered station. Receiver spatial processing refers to detecting multiple receive antennas to recover the desired signal components and suppress interference. Spatial interference suppression is also known as cooperative beamforming (CEB).

In one design of data transmission on the downlink using spatial interference mitigation, a cell may receive precoding information from a first UE and Spatial Feedback Information (SFI) from a second UE that is not in communication with the cell. The SFI includes various types of information for spatial nulling, as described below. The cell may select a precoding matrix based on the precoding information from the first UE and the SFI from the second UE. The precoding matrix may control transmission toward the first UE and away from the second UE. The cell may transmit a reference signal according to the precoding matrix. The cell may also send a Resource Quality Information (RQI) request to the first UE, receiving an RQI determined by the first UE based on the reference signal. The cell may determine a Modulation and Coding Scheme (MCS) based on the RQI. The cell may then send a data transmission to the first UE using the precoding matrix and in accordance with the MCS.

In one design of data transmission on the uplink using spatial interference mitigation, a UE may send a resource request to a serving cell in communication with the UE. The UE may receive the SFI from a second cell that is not in communication with the UE. The UE may transmit reference signals, e.g., according to the SFI. The UE may receive grant information (grant) including an MCS determined by the serving cell based on the reference signal. The UE may then send a data transmission to the serving cell in accordance with the MCS and the SFI to reduce interference to a second cell.

Various aspects and features of the disclosure are described in further detail below.

Drawings

Fig. 1 illustrates a wireless communication network.

Fig. 2 illustrates downlink data transmission using spatial interference suppression.

Fig. 3A to 3D depict downlink data transmission in fig. 2.

Fig. 4 illustrates uplink data transmission using spatial interference mitigation.

Fig. 5 and 6 illustrate a process and apparatus, respectively, for transmitting data on a downlink using spatial interference mitigation.

Fig. 7 and 8 illustrate a process and apparatus, respectively, for receiving data on a downlink using spatial interference mitigation.

Fig. 9 and 10 illustrate a process and apparatus, respectively, for transmitting data on the uplink using spatial interference suppression.

Fig. 11 and 12 illustrate a process and apparatus, respectively, for receiving data on the uplink using spatial interference suppression.

Fig. 13 shows a block diagram of a base station and a UE.

Detailed Description

The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms "network" and "system" may be used interchangeably from time to time. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA 2000, and so on. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. CDMA 2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks may implement wireless technologies such as global system for mobile communications (GSM). OFDMA networks may implement methods such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, flashAnd so on. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, and GSM are described in documents from an organization entitled "3 rd Generation partnership project" (3 GPP). CDMA 2000 and UMB are described in documents from an organization named "3 rd generation partnership project 2" (3GPP 2). The techniques described herein may be used for these and other wireless networks and wireless technologies mentioned above. For clarity, certain aspects of these techniques are described below for LTE, and LTE terminology is used in much of the description below.

Fig. 1 shows a wireless communication network 100, which network 100 may be an LTE network or some other network. Wireless network 100 may include a plurality of evolved node bs (enbs) and other network entities. For simplicity, only two enbs 110a and 110b are shown in fig. 1. An eNB may be a station in communication with a UE and may also be referred to as a base station, a node B, an access point, and so on. Each eNB 110 may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to a coverage area of an eNB and/or an eNB subsystem serving this coverage area, depending on the context in which the term is used.

An eNB may provide communication coverage for a macro cell, pico cell, femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., within a few kilometers) that may allow unrestricted access by UEs with service subscriptions. A pico cell covers a relatively small geographic area that may allow unrestricted access by UEs with service subscriptions. A femto cell covers a relatively small geographic area (e.g., in a house) that may allow restricted access by UEs associated with the femto cell (e.g., UEs of users in the house). The eNB for the macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. An eNB for a femto cell may be referred to as a femto eNB or a home eNB. In the example shown in fig. 1, eNB 110a may be a macro eNB for macro cell X. eNB 110b may be a pico eNB for pico cell Y or a femto eNB for femto cell Y. An eNB may support one or more (e.g., three) cells.

Wireless network 100 may also include relay stations. A relay station is a station that receives data transmissions and/or other information from an upstream station (e.g., an eNB or UE) and sends these data transmissions and/or other information to a downstream station (e.g., a UE or eNB). A relay station may also be a UE that relays transmissions for other UEs.

Wireless network 100 may be a homogeneous network including only one type of eNB (e.g., macro eNB only or femto eNB only). Wireless network 100 may also be a heterogeneous network including different types of enbs (e.g., macro enbs, pico enbs, femto enbs, relays, etc.). These different types of enbs may have different transmit power levels, different coverage areas, and different effects on interference in wireless network 100. For example, macro enbs may have a high transmit power level (e.g., 20 watts), while pico enbs, femto enbs, and relays may have a lower transmit power level (e.g., 1 watt). The techniques described herein may be used for homogeneous and heterogeneous networks.

Network controller 130 may couple to a set of enbs and provide coordination and control for these enbs. Network controller 130 may communicate with enbs 110 via a backhaul. enbs 110 may also communicate with each other (e.g., directly or indirectly via a wireless or wired backhaul).

The UEs may be dispersed throughout the wireless network 100, and each UE may be stationary or mobile. For simplicity, only four UEs 120a, 120b, 120c, and 120d, also referred to as UEs 1, 2, 3, and 4, respectively, are shown in fig. 1. A UE may also be referred to as a terminal, mobile station, subscriber unit, station, etc. A UE may be a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless telephone, a Wireless Local Loop (WLL) station, and so forth. In fig. 1, a solid line with a single arrow indicates desired data transmission from a serving cell to a UE, and a dotted line with a single arrow indicates interference transmission from an interfering cell to the UE. A serving cell is a cell designated to serve a UE on the downlink and/or uplink. The non-serving cell may be an interfering cell that causes interference to the UE on the downlink and/or an interfered cell that is interfered by the UE on the uplink. For simplicity, uplink transmissions are not shown in fig. 1.

LTE uses 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, and so on. Each subcarrier may be modulated with data. Generally, modulation symbols are transmitted in the frequency domain with OFDM and in the time domain with SC-FDM. The total number of subcarriers (K) depends on the system bandwidth. For example, K may be equal to 128, 256, 512, 1024 or 2048 for a system bandwidth of 1.25, 2.5, 5, 10 or 20MHz, respectively. The system bandwidth may also be divided into sub-bands, each covering 1.08MHz in LTE.

In LTE, the transmission timeline of each link may be divided into units of subframes. Each subframe has a predetermined duration (e.g., 1 millisecond (ms)), and each subframe may include two slots. Each slot may include 6 symbol periods for an extended cyclic prefix and 7 symbol periods for a normal cyclic prefix. The available time-frequency resources for each link may be divided into resource blocks. Each resource block may cover a particular time and frequency size, e.g., 12 subcarriers in one slot in LTE.

The UE may communicate with a serving cell in a dominant interference scenario, where: (i) a UE is strongly interfered by one or more interfering cells on the downlink, and/or (ii) a serving cell is strongly interfered by one or more interfering UEs on the uplink. The dominant interference scenario may be due to range extension, in which the UE is connected to a cell with lower path loss and lower geometry detected by the UE among all cells. For example, in fig. 1, UE 2 may detect macro cell X and pico cell Y for which UE 2 has lower received power than macro cell X. However, if the path loss of cell Y is lower than that of macro cell X, it is desirable that UE 2 be able to connect to pico cell Y. This may result in less interference to the wireless network for a given data rate for UE 2. The dominant interference scenario may also be due to restricted association. For example, in fig. 1, UE1 is in the vicinity of femto cell Y, for which it may have a high received power. However, UE1 cannot access femto cell Y due to restricted association, and then UE1 connects to unrestricted macro cell X with lower received power. UE1 then experiences strong interference from femto cell Y on the downlink, and UE1 also causes strong interference to cell Y on the uplink.

In an aspect, spatial interference suppression may be performed for data transmission on the downlink to reduce interference to the UE. In one design, the UE may determine and provide Spatial Feedback Information (SFI) for the interfering cell. The interfering cell may send its transmissions according to the SFI to reduce interference to the UE.

The following types of information are available:

spatial feedback information-information used to reduce interference to interfered stations;

spatial nulling information-information used to steer transmissions in a direction away from the interfered station;

precoding information-information used to control the transmission in the direction towards the target station;

null gain information-information representing interference reduction due to spatial interference suppression.

For spatial interference suppression on the downlink, the SFI may include: (i) spatial nulling information for an interfering cell, which uses this information to control its transmissions away from the UE; (ii) precoding information for a serving cell of a UE, which the interfering cell uses to control its transmission in a direction away from the serving cell to the UE; (iii) (iii) null gain information and/or (iv) other information. Different types of information for the SFI may be determined as described below.

In one design, the UE may estimate the downlink channel response of the interfering cell based on, for example, a reference signal or pilot transmitted on the downlink by the cell. The downlink channel estimate may be given by an R × T channel matrix, which is represented by:

formula (1)

Wherein: h_iuIs downlink from interfering cell i to UE uThe channel matrix of the link channel is,

h_rtis the complex gain between the transmit antenna T of the interfering cell and the receive antenna R of the UE, where R1.

T is the number of transmit antennas of the interfering cell,

r is the number of receive antennas of the UE.

Channel matrix H_iuR rows including R receive antennas for the UE. H_iuWith one channel vector h for one receive antenna of the UE_iuAnd correspondingly. If the UE is equipped with a single antenna, then H_iuComprising a single row of single-channel vectors. Thus, when there is only one row or column, the matrix is degraded into a vector. The downlink channel estimate may be obtained for all or a portion of the system bandwidth (e.g., for one subband over which the UE may be scheduled).

In a first SFI design, the SFI may include a Channel Direction Indicator (CDI) for the interfering cell. The CDI for the interfering cell may be determined in various ways. In one design, the UE may quantize H based on a codebook of quantized channel matrices_iu. The UE may evaluate each quantized channel matrix in the codebook as follows:

formula (2)

Wherein: h_lIs the ith quantized channel matrix in the codebook,

Q_H，lis represented by H_lAnd H_iuA measure of the orthogonality between the two signals,

"H" means Hermite conjugate or complex conjugate.

The metric Q may be calculated for each quantized channel matrix in the codebook_H，l. Having a maximum Q_H，lAnd with H_iuQuantized channel matrix H that matches as closely as possible_lIs selected and provided as the CDI of the interfering cell. Thus, the channel matrix H can be represented_iuQuantified as AND H_iuMaximum correlation (rather than maximum orthogonality to H)_iu) H of (A) to (B)_l. In another design, the UE may quantize H according to a codebook of quantized channel vectors_iuAnd obtain H_iuThe quantized channel vector of each row of (a). The UE may also quantize H in other manners_iu. The size of the codebook of quantized channel matrices or vectors may be selected to obtain good null performance with reduced signaling overhead. The CDI of the interfering cell may include an index of the quantized channel matrix, an index of each quantized channel vector, and/or other information. The UE may send the CDI as an SFI to the interfering cell. Due to reported H_lIndicating the direction from the interfering cell to the UE, the interfering cell may select the precoding matrix to be as orthogonal as possible to H_lIn order to reduce interference to the UE.

In a second SFI design, the SFI may include a Precoding Matrix Indicator (PMI) for the interfering cell. The PMI for the interfering cell may be determined in various ways. In one design, the UE may select from a codebook of precoding matrices as orthogonal as possible to H_iuThe precoding matrix of (2). The UE may evaluate each precoding matrix in the codebook as follows:

Q_P，l＝||H_iu P_l| |, formula (3)

Wherein: p_lIs the l-th precoding matrix in the codebook,

Q_P，lis represented by P_lAnd H_iuA measure of orthogonality therebetween.

The UE may select the UE with the smallest Q_P，lThe precoding matrix of (1), the matrix and H_iuMost orthogonal. The UE may transmit the index of the precoding matrix as an SFI of the interfering cell. The selected precoding matrix may comprise the "best" set of linear combinations of active antennas that result in the greatest amount of interference reduction at the UE.

In another design, the UE may calculate to be as orthogonal to H as possible_iuIs precoding matrix P_iu. The UE may perform eigenvalue decomposition as follows:

formula (4)

Wherein: e is H_iuIs used to generate a unitary matrix of T x T of the eigenvectors of (a),

Λ is H_iuT x T diagonal matrix of eigenvalues of.

The unitary matrix E is characterized by E^HE ═ I, where I is the identity matrix. E are orthogonal to each other, each column having a unit power. The downlink channel from the interfering cell to the UE has S eigenmodes, where S ≦ min { R, T }. The T columns of E are also called T eigenvectors, which can send information about H_iuData of the eigenmodes of (a). The diagonal element of Λ is denoted H_iuCharacteristic value of the power gain of the eigenmode of (a). The T diagonal elements of Λ are correlated with the T eigenvectors of E. If R < T, then Λ may include up to R non-zero diagonal elements, with the remaining diagonal elements being zero. Eigenvectors in E corresponding to zero diagonal elements in Λ and H_iuAre orthogonal and are included in a precoding matrix P_iuIn (1). The UE may quantize P_iu(e.g., as above for H)_iuSaid) to obtain the SFI for the interfering cell. The UE may send the SFI to the interfering cell, which may then select a precoding momentArray to match quantized P as closely as possible_iuTo reduce interference to the UE.

In another design, the UE may be equipped with multiple receive antennas and may determine the precoding matrix for the interfering cell by considering its receive nulling capability. The UE may derive the spatial filter matrix from the channel matrix of the serving cell. The UE may then perform receiver spatial processing on the transmission from the serving cell using the spatial filter matrix. The UE may assume that each precoding matrix in the codebook is evaluated with the UE using the spatial filter matrix. The UE may select a precoding matrix that provides the best receiver performance using the spatial filter matrix. The UE may provide the selected precoding matrix as an SFI of the interfering cell.

In a third SFI design, the SFI for the interfering cell may include a CDI or PMI of the serving cell. The UE may estimate the downlink channel of the serving cell and may determine the downlink channel matrix H from the serving cell_suTo determine the CDI or PMI. The CDI may include an index of the quantized channel matrix, an index of each quantized channel vector, and so on. The PMI may include an index of a precoding matrix or vector used by a serving cell of the UE, and so on. The UE may send the CDI or PMI of the serving cell as the SFI of the interfering cell. Since the CDI/PMI of the serving cell indicates the direction from the serving cell to the UE, the interfering cell may select the precoding matrix to be as orthogonal as possible to the CDI/PMI of the serving cell to reduce interference to the UE. For example, the interfering cell may schedule the UE that is least affected by the beam selected by the serving cell.

In another design, the SFI of the interfering cell may include a set of orthogonal vectors that assume the UE performs some receiver spatial processing. For example, the SFI may include a channel matrix H_iuOf one or more principal eigenvectors orthogonal to each other, wherein the channel matrix H_iuThe one or more principal eigenvectors of (a) may be obtained as shown in equation (4). As another example, it may be assumed thatThe UE performs some receiver spatial processing for data transmission from the serving cell. The SFI may then include one or more vectors that are orthogonal to the effective channel between the transmit antennas of the interfering cell and the output of the receiver spatial processing of the UE.

In general, the spatial nulling information for the interfering cell may include the CDI or PMI of the interfering cell, the CDI or PMI of the serving cell, and/or some other information. The interfering cell may use the spatial nulling information to determine a precoding matrix to steer transmissions of the interfering cell in a direction away from the UE.

In one design, the SFI may include a Transmit Null Gain (TNG) that results from an interfering cell using spatial null information provided by the UE. The UE may estimate the following values: (i) interference power I from interfering cell_SFIWherein the interfering cell uses spatial nulling information; (ii) interference power I from interfering cell_OLWherein the interfering cell does not use spatial nulling information (or operates open loop). The UE may determine the transmit null gain as I_SFIAnd I_OLThe ratio of. Thus, if the interfering cell uses spatial nulling information instead of open loop transmission, the transmit nulling gain may indicate a reduction in interference power from the interfering cell. The interfering cell may determine a transmit power level to use to obtain a target interference level for the UE. When the interfering cell uses the spatial nulling information, the interfering cell can increase the transmit power level by a transmit nulling gain.

In another design, the SFI may include a Receive Null Gain (RNG) of the interfering cell due to the UE performing receiver spatial processing on the serving cell. This design is particularly applicable when the interfering cell is equipped with a single transmit antenna and is not able to control the spatial nulling. The receive nulling gain, which may indicate an amount of interference power reduction due to the UE performing receiver spatial processing, may be determined as described below. The interfering cell may then determine its transmit power level based on the receive nulling gain, e.g., to achieve a target interference level for the UE. The receive null gain may also be a factor in the target interference level for the UE. The interfering cell may not need to know the value of the receive null gain, but the resulting target interference level of the UE.

The UE may transmit an SFI for the interfering cell to support spatial interference mitigation. The SFI may include CDI or PMI of the interferer cell, CDI or PMI of the serving cell, transmit null gain, receive null gain, and/or other information. In one design, the UE may send the SFI directly to the interfering cell. In another design, the UE may send the SFI to the serving cell, where the serving cell forwards the SFI to the interfering cell via layer 3(L3) signaling exchange, e.g., over a backhaul. The UE may send the SFI at a very fast rate, where the rate depends on the mobility of the UE and possibly other factors. For example, the UE may send the SFI to the interfering macro cell at a faster rate to enable the cell to transmit nulls under low mobility conditions of the UE. In UE static or semi-static conditions, the UE may transmit SFI to the interfering pico cell or femto cell at a slower rate. The UE may also send the SFI when requested, as described below. Generally, the SFI should correspond to a relatively recent channel estimate in order to obtain good transmit nulling.

In another aspect, spatial interference suppression may be performed for data transmission on the uplink to reduce interference to the cell. Spatial interference suppression may be performed on the uplink in different ways depending on whether the UEs are equipped with one or more transmit antennas.

In one design, an interfering UE equipped with multiple transmit antennas may spatially control its transmissions to reduce interference to one cell. The cell may estimate an uplink channel from the interfering UE to the cell and determine spatial nulling information based on the estimated uplink channel (e.g., using any of the designs described above for the downlink). The cell also determines transmit null gains, e.g., as described above for the downlink. The SFI of the interfering UE may include spatial nulling information, transmit nulling gain, and so on. The cell may transmit the SFI to the interfering UE. The interfering UE may use the SFI to spatially control its transmission in a direction away from the cell and/or reduce its transmit power.

In another design, a cell may perform receive interference nulling for an interfering UE equipped with a single transmit antenna. The cell may select one UE to serve by considering the interfering UE.

The cell may obtain received symbols, which may be expressed as:

r_s＝h_us s_u+h_js s_j+n_s＝h_us s_u+n_tsequation (5)

Wherein: s_uIs a data symbol transmitted by the served UE u,

s_jis the data symbol transmitted by the interfering UE j,

h_usis the channel vector of the uplink channel from the served UE u to the cell s,

h_jsis the channel vector of the uplink channel from the interfering UE j to cell s,

r_sis a vector of symbols received by cell s,

n_tsis a vector of the total noise and interference of cell s,

n_sis a vector of the total noise and interference in cell s except from UE j.

The cell may perform receiver spatial processing to recover data symbols from served UEs and suppress/null data symbols from interfering UEs. The cell may select the spatial filter vector m such that: (i)) The vector m matches as much as possible the h of the served UE_us(ii) a (ii) Vector m is as close as possible to h of interfering UE_jsAre orthogonal. In one design, spatial filter vector m may be determined based on a Minimum Mean Square Error (MMSE) receive filter and may be calculated asWhere a is a scaling factor, R_nnIs the covariance matrix of the total noise and interference. In another design, the cell may evaluate each entry in the codebook of spatial filter vectors, selecting the spatial filter vector with the best signal-to-noise-plus-interference ratio (SINR). The cell may also determine the spatial filter vector in other ways.

The cell may perform receiver spatial processing as follows:

formula (6)

Wherein:is the detected symbol of the served UE u,

n_sis the noise and interference after receiver spatial processing in cell s.

The process shown in equation (6) may be performed for each subcarrier in each symbol period.

The cell may determine a receive nulling gain for the interfering UE that results from the cell performing receiver spatial processing on the served UE. The cell can estimate: (i) interference power I from interfering UE in case of cell performing receiver spatial processing_RXP(ii) a (ii) Interference power I from interfering UE without receiver spatial processing in the cell_{no_RXP}. The cell may determine the receive null gain as I_RXPAnd I_{no_RXP}The ratio of. Thus, the receive null gain may indicate a reduction in interference power due to the cell performing receiver spatial processing. The cell may provide a receive nulling gain to the interfering UE. A cell or interfering UE may calculate a target transmit power level for the UE by considering the receive nulling gain in order to obtain a target interference level for the cell. The interfering UE can increase its transmit power by the receive nulling gain.

The cell may determine a receive null gain for a particular pair of served and interfering UEs. If the pair of UEs is not desired, the cell may calculate an expected (e.g., average) receive nulling gain or a worst-case receive nulling gain based on the number of UEs that may be served and their channel conditions. It is particularly suitable to use receive nulling gain in a femto configuration, where each femto cell may serve only one or a few UEs, each femto cell having only one or a few interfering UEs. Thus, in a femto configuration, there are a limited number of served UE and interfering UE pairs.

The cell may transmit an SFI for the interfering UE. The SFI may be: (i) when the UE is equipped with multiple antennas, including spatial nulling information and/or transmit nulling gain; (ii) when the UE is equipped with a single antenna, including receive null gain; and/or (iii) other information. In one design, a cell may send an SFI directly to an interfering UE. In another design, the cell may send the SFI to a serving cell of the interfering UE via L3 signaling exchange, e.g., over a backhaul. The serving cell then transmits the SFI to the interfering UE. The cell may transmit the SFI at the appropriate rate. The quantization of the SFI may be chosen to obtain good spatial nulling. The same or different levels of quantization may be used for SFI sent over the air and SFI forwarded via the backhaul.

Spatial interference suppression may be performed on the downlink and uplink in various ways. In one design, spatial interference mitigation for a given link is triggered when granted (rather than being performed at all times). For example, spatial interference mitigation may be triggered when a dominant interferer is detected. In one design, the SFI may be sent at an appropriate rate to support spatial interference suppression. In another design, the SFI may be sent by triggering some event, which may reduce signaling overhead. For example, if there is a significant change in the spatial nulling information, transmit nulling gain, and/or receive nulling gain (e.g., when the change in the spatial nulling information or nulling gain exceeds a certain threshold), then the SFI is sent.

The spatial interference suppression techniques described herein may be used for Frequency Division Duplex (FDD) networks as well as Time Division Duplex (TDD) networks. For FDD, different frequency channels may be allocated to the downlink and uplink, and the channel response of the downlink may not be very correlated with the channel response of the uplink. As described above, for an FDD network, the UE may estimate the downlink channel response of the interfering cell, determine the SFI from the downlink channel response, and transmit the SFI to the interfering cell. As also described above, the cell may also estimate an uplink channel response of the interfering UE, determine an SFI from the uplink channel response, and transmit the SFI to the interfering UE. For TDD, the downlink and uplink may share the same frequency channel, and the channel response for the downlink may be correlated with the channel response for the uplink. For a TDD network, an interfering cell may estimate an uplink channel response for a UE from a reference signal from the UE, estimate a downlink channel response from the uplink channel response, and use the downlink channel response to control its transmissions in a direction away from the UE. An interfering UE may also estimate a downlink channel response for a cell based on a reference signal from the cell, estimate an uplink channel response based on the downlink channel response, and use the uplink channel response to control its transmissions in a direction away from the cell. Thus, an interfering station can obtain the SFI from its channel estimate without having to receive the SFI from the interfered station.

Spatial interference suppression may be supported for a given link using various signaling messages and a time axis. Some exemplary timelines and messages for spatial interference mitigation on the downlink and uplink are described below.

Fig. 2 shows a design of a downlink data transmission scheme 200 using spatial interference suppression. For simplicity, fig. 2 shows only two cells X and Y and two UEs 1 and 2 in fig. 1. Cell X is the serving cell for UE1, which is the interfering cell for UE 2. Cell Y is the serving cell for UE 2, which for UE1 is the interfering cell.

Cell X has data to send to UE1, which knows that UE1 is strongly interfered on the downlink. For example, cell X may receive pilot measurement reports from UE1 that indicate and/or identify strong interferer cell Y. Cell X may send an SFI request to UE1 to ask UE1 to: (i) determine an SFI and send the SFI to the interfering cell Y, and/or (ii) determine feedback and send the feedback to the serving cell X. The SFI request may include various types of information, as shown below. Likewise, cell Y has data to send to UE 2, and cell Y knows that UE 2 is strongly interfered on the downlink. Cell Y then sends an SFI request to UE 2 to ask UE 2 to determine and send the SFI to interfering cell X.

UE1 may receive an SFI request from its serving cell X. For example, as described above, in response to the SFI request, UE1 may estimate the downlink channel response of interfering cell Y, determining the SFI of cell Y from the downlink channel response. UE1 then transmits the SFI to interfering cell Y. UE1 may also estimate the downlink channel response of its serving cell X, determine precoding information (e.g., CDI or PMI) for cell X, and send the precoding information to cell X. Likewise, UE 2 may receive an SFI request from its serving cell Y, estimate a downlink channel response of interfering cell X, determine an SFI for cell X from the downlink channel response, and transmit the SFI to cell X. UE 2 may also estimate the downlink channel response of its serving cell Y, determine the precoding information for cell Y, and send this precoding information to cell Y.

Cell X may receive precoding information from UE1 and SFI from interfered UE 2. Cell X may determine precoding matrix P for data transmission based on precoding information from UE1 and SFI from UE 2_X. Cell X may also determine a transmit power level P for data transmission based on the transmit nulling gain from UE 2, the target interference level for UE 2, and/or other information_data，X. Cell X may then use the precoding matrix P_XAnd according to the transmission power level P_RQI-RS，XTo transmit a Resource Quality Indicator (RQI) reference signal, wherein a power level P is transmitted_RQI-RS，XMay be equal to P_data，XOr P_data，XA scaled version of (a). The reference signal or pilot is a transmission that is previously known to both the transmitter and the receiver. The RQI reference signal may also be referred to as a power decision pilot. The RQI reference signal may be a controlled reference signal transmitted using a precoding matrix and/or the RQI reference signal may have a variable transmit power level. Cell X may also send an RQI request to UE1 and/or other UEs served by cell X. The RQI request may require UE1 to estimate the channel quality of cell X from the RQI reference signal and send the RQI to cell X. Likewise, cell Y may determine precoding matrix P for data transmission based on precoding information from UE 2 and SFI from UE1_Y. Cell Y may also determine a transmit power level P for data transmission based on the transmit null gain from UE1, the target interference level for UE1, and/or other information_data，Y. Cell Y may then use the precoding matrix P_YAnd according to the transmission power level P_RQI-RS，YTransmitting RQI reference signal, wherein the power level P is transmitted_RQI-RS，YIs equal to P_data，YOr P_data，YA scaled version of (a). Cell Y may also send RQI requests to UE 2 and/or other UEs served by cell Y.

UE1 may receive RQI reference signals from cells X and Y and RQI requests from its serving cell X. In response to the RQI request, UE1 may estimate the channel quality of serving cell X from the RQI reference signals from all cells. The RQI reference signal may enable UE1 to more accurately estimate the channel quality that UE1 would expect for data transmission from serving cell X by considering the precoding matrix and the transmit power levels these cells are expected to use. UE1 may determine an RQI that includes an SINR estimate for the channel quality, a Modulation and Coding Scheme (MCS) determined based on the SINR estimate, and so on. UE1 may send an RQI to its serving cell X. Likewise, UE 2 may receive RQI reference signals from cells X and Y, as well as RQI requests from its serving cell Y. UE 2 may estimate the channel quality of serving cell Y, determine an RQI, and send this RQI to cell Y.

Cell X may receive the RQI from UE1, schedule UE1 for data transmission, select an MCS based on the RQI, and process the data for UE1 based on the selected MCS. Cell X may generate a Downlink (DL) grant (grant), also referred to as a resource allocation, scheduling grant, and so on. The downlink grant may indicate the allocated resources, the selected MCS, and the like. Cell X may send a downlink grant and data transmission to UE 1. UE1 may receive the downlink grant and the data transmission and decode the received transmission according to the selected MCS. UE1 may generate Acknowledgement (ACK) information indicating whether the data was decoded correctly or in error. UE1 may send ACK information to its serving cell X. Cell Y may likewise send data transmissions to UE 2.

Fig. 3A to 3D illustrate message transmission for the downlink data transmission scheme in fig. 2. Each cell first selects one or more UEs that may perform data transmission on a set of time-frequency resources (e.g., one or more resource blocks). The initial UE selection may be based on various factors such as the priorities of the UEs in the different cells, channel information for the UEs, downlink buffer status of the cells, quality of service (QoS) requirements, network optimization criteria (e.g., throughput, fairness), and so forth. The channel information for these UEs may be long-term, and they may be exchanged between these cells via the backhaul (e.g., the X2 interface in LTE). The selected UE may be considered a temporarily scheduled UE. Each cell may send an SFI request to each selected UE, as shown in fig. 3A. Each selected UE may determine precoding information (e.g., CDI) and transmit this precoding information to its serving cell and may also determine SFI and transmit SFI to each interfering cell indicated in the SFI request for that UE, as shown in fig. 3B.

Each cell may receive precoding information from each selected UE and an SFI from each interfered UE. Each cell may save (honor) or discard (dismiss) these SFIs from the interfered UE based on, for example, utility level, priority, etc. Each cell may schedule one or more UEs for data transmission on a set of time-frequency resources based on various factors, such as those described above for initial UE selection. The scheduled UE may be the same as or different from the originally selected UE for each cell. A given cell may not be able to apply the appropriate precoding matrix to the selected UE, e.g., the given cell may then schedule another UE due to a scheduling conflict between the cell and another cell. For example, cell Y may select UE 2 first, cell Y may not be able to use the appropriate precoding matrix for UE 2 due to scheduling conflicts with cell X, and then cell Y schedules UE 4, where UE 4 is less affected by the interference of cell X. This flexibility allows the cell to schedule some UEs that may benefit from the spatial beams available to these cells.

Each cell may determine a precoding matrix for the scheduled UE and may also determine a transmit power level for data transmission. Each cell may then send an RQI reference signal along with an RQI request to each scheduled UE, as shown in fig. 3C. A given cell may send RQI requests and SFI requests to different UEs. For example, cell Y may send an SFI request to UE 2 and a RQI request to UE 4 at a later time. A cell may also send RQI requests to multiple UEs using the same set of time-frequency resources in order for the cell to make opportunistic scheduling decisions based on RQIs from these UEs. Each scheduled UE may determine an RQI and transmit the RQI to its serving cell, as shown in fig. 3D.

In the designs shown in fig. 2 through 3D, the serving cell may send an SFI request to the UE to ask the UE to send an SFI to the interfering cell. In another design, the interfering cell may send an SFI request to the UE to request the UE to send an SFI to the cell. The SFI request may also be sent by other entities. For example, the UE may autonomously decide to transmit the SFI to the strong interferer cell.

Fig. 4 shows a design of an uplink data transmission scheme 400 that uses spatial interference mitigation. For simplicity, fig. 4 shows only two cells X and Y and two UEs 1 and 2 in fig. 1. Cell X is the serving cell for UE1, which is interfered by UE 2 on the uplink. Cell Y is the serving cell for UE 2, which is interfered by UE1 on the uplink.

UE1 has data to send to its serving cell X and may send a resource request. The resource request indicates the priority of the request, the amount of data to be transmitted by the UE1, etc. In one design not shown in fig. 4, UE1 does not send an SFI request to interfered cell Y. For this design, if cell Y determines that UE1 is expected to perform spatial interference mitigation, then the interfered cell Y may send an SFI to the UE. In another design shown in fig. 4, UE1 may send an SFI request to interfered cell Y to ask cell Y to determine and send an SFI to UE 1. UE1 may also send a reference signal with the resource request in order for each cell to determine spatial nulling information or precoding information for UE 1.

Serving cell X receives a resource request from UE1 and possibly also an SFI request from UE 2. Cell X may send a reference signal request to UE1 to request UE1 to send an RQI reference signal. Cell X may also determine precoding information (e.g., CDI or PMI) for UE1 and send this precoding information to UE1 (not shown in fig. 4). Cell Y may receive the SFI request from UE1, determine the SFI from the uplink transmission from UE1, and send the SFI to UE 1. If UE1 is equipped with a single transmit antenna, the SFI may include receive nulling gain and/or other information for UE 1. If UE1 is equipped with multiple transmit antennas, the SFI may include spatial nulling information (e.g., CDI or PMI for cell Y) to cause UE1 to steer its transmissions in a direction away from cell Y.

UE1 may receive a reference signal request from its serving cell X, an SFI from the interfered cell Y, and possibly precoding information from serving cell X. If UE1 is equipped with a single transmit antenna, then UE1 may determine a transmit power level P for data transmission based on the receive null gain from cell Y, the target interference level for cell Y, and/or other information_data，1. If UE1 is equipped with multiple transmit antennas, then UE1 may determine a precoding matrix P for data transmission based on precoding information from cell X and spatial nulling information from cell Y₁. UE1 then transmits at power level P_RQI-RS，1And possibly using a precoding matrix P₁To transmit the RQI reference signal. P_RQI-RS，1May be equal to P_data，1Or P_data，1A scaled version of (a).

Serving cell X may receive RQI reference signals from UE1 and UE 2. Cell X may determine the channel quality of UE1 from the RQI reference signal and select the MCS for UE1 based on the channel quality. Cell X may generate an uplink grant that includes the selected MCS, the allocated resources, the transmit power level for the allocated resources, and/or other information. Cell X may send an uplink grant to UE 1. UE1 may receive the uplink grant, process the data according to the selected MCS, and send a data transmission on the allocated resources. Cell X may receive data transmissions from UE1, decode the received transmissions, determine ACK information based on the decoding results, and send the ACK information to UE 1.

In the design shown in fig. 2, the SFI request may be in downlink subframe t₁SFI may be sent in uplink subframe t₂The RQI request and RQI reference signals may be sent in downlink subframe t₃RQI may be sent in uplink subframe t₄Where the downlink grant and data may be in a downlink subframe t₅Sending, ACK information may be in uplink subframe t₆And (5) sending. Sub-frame t₁、t₂、t₃、t₄、t₅And t₆May be separated by the same or a different number of subframes (e.g., by two to four subframes between consecutive subframes used for transmission). In one design, downlink subframe t₁、t₃And t₅Belonging to a downlink interlace, which may include downlink subframes separated by L subframes, where L may be any suitable value. Uplink subframe t₂、t₄And t₆Belonging to one uplink interlace, which may include uplink subframes separated by L subframes.

In the design shown in fig. 4, the resource request and the SFI request may be in an uplink subframe t₁The SFI and reference signal request can be sent in a downlink subframe t₂Where RQI reference signals may be transmitted in uplink subframe t₃Where the uplink grant may be in the downlink subframe t₄Where data may be sent in uplink subframe t₅The ACK information may be sent in a downlink subframe t₆Is sent. Sub-frame t₁、t₂、t₃、t₄、t₅And t₆May be spaced apart by the same or different number of subframes. In one design, uplink subframe t₁、t₃And t₅Belonging to an uplink interlace, downlink subframe t₂、t₄And t₆Belonging to a downlink interlace.

In one design, resources for message and data transmission may be explicitly communicated. For example, in fig. 2, an SFI request may request an SFI for a particular data resource, an RQI request may request an RQI for a particular data resource, and so on. In another design, resources used to send messages, resources used to send reference signals, and resources used to send data transmissions may be implicitly communicated. For example, in fig. 2, the SFI request may be at a downlink resource R_SFI-REQUp sending, which may request to link to R_SFI-REQOf downlink data resources R_DATAThe SFI of (1). With the same data resource R_DATAThe RQI reference signals of all corresponding cells may overlap such that the UEs may measure the total amount of interference experienced by the UEs by all cells. SFI may be on uplink resource R_SFIUp transmission, wherein the uplink resource R_SFICan be linked to a downlink resource R for sending SFI requests_SFI-REQOr uplink resource R_SFIMay be explicitly indicated in the SFI request. The RQI request may be at downlink resource R_RQI-REQUp sending of request for linking to R_RQI-REQOf downlink resources R_RQI-RSRQI of (a). May be based on the downlink resource R_RQI-RSAn RQI reference signal transmitted on to determine RQI, which may be on an uplink resource R_RQIUp transmission, wherein the uplink resource R_RQICan be linked to a downlink resource R_RQI-REQOr explicitly indicated in the RQI request. RQI reference signals may be in downlink resources R_RQI-RSUplink RQI reference signal can be transmitted on downlink data resource R_DATAThe precoding matrix used above and the transmit power level.

The messages and transmissions used for spatial interference mitigation may include various types of information. For example, messages and transmissions on the downlink for spatial interference mitigation may include the information described below.

In one design, the SFI request to the UE may include one or more of the following:

each interfering cell to which the UE should send an SFI;

the time-frequency resources on which the SFI is determined;

uplink resources for transmitting the SFI;

the priority of the SFI request;

a target interference level;

and/or other information.

The interfering cell may be identified from a pilot measurement report sent by the UE to the serving cell. In one design, each interfering cell may be identified by a brief cell Identifier (ID) (e.g., using 2-3 bits per interfering cell) to reduce signaling overhead. In another design, a bitmap may be used for a set of interfering cells reported by the UE, and each interfering cell may be associated with one bit in the bitmap. The number of interfering cells may be limited (e.g., to six cells) in order to reduce signaling overhead. The interfering cell may also be limited to a cell whose received power is within a predetermined range of values (e.g., within 10 dB) of the received power of the serving cell. The UE may transmit the SFI to each of the interfering cells indicated in the SFI request.

The time-frequency resources on which the SFI is determined may be the entire system bandwidth or a portion of the system bandwidth, e.g., one sub-band, one or more resource blocks, etc. These resources may be explicitly indicated by the SFI request (e.g., by a resource index) or implicitly conveyed (e.g., linked to the resource on which the SFI request was sent).

The priority of the SFI request may be determined based on various factors. In one design, the priority may be determined based on the medium-and long-term utility function. The priority may also include a short-term priority different from a long-term priority. The priority may be quantized to several values (e.g., 1 to 2 bits) to reduce signaling overhead. In one design, the priority may BE determined by a type of data to BE transmitted (e.g., Best Effort (BE), Assured Forwarding (AF), Expedited Forwarding (EF), etc.).

In one design, the SFI of the interfering cell may include one or more of the following:

spatial nulling information, e.g., CDI or PMI of the interferer cell, CDI or PMI of the serving cell, etc.;

transmit null gain and/or receive null gain;

time-frequency resources on which interference of the interfering cell is reduced;

a target interference level for the UE;

priority of requests to reduce interference of an interfering cell;

the type of feedback information;

and/or other information.

The CDI or PMI of the interfering cell and the CDI or PMI of the serving cell may be determined as described above. Sufficient resolution (e.g., 8 to 10 bits) may be provided for the CDI/PMI of each cell to achieve the desired transmit null performance. The serving cell may request the UE to simultaneously transmit the CDI/PMI of the aggressor cell and the CDI/PMI of the serving cell, so as to enable accurate scheduling coordination between different cells. As described above, transmit null gains and/or receive null gains may also be determined and reported.

The time-frequency resources over which interference is reduced may be explicitly indicated by the SFI (e.g., with a resource index) or implicitly communicated (e.g., linked to the resources over which the SFI is sent). The time-frequency resources may cover one subband in one subframe, multiple subbands in one subframe, one subband over multiple subframes, or some other time-frequency dimension. The priority in the SFI may be equal to the priority in the SFI request. In a wideband configuration (e.g., over a 5MHz bandwidth), a different SFI may be transmitted for each bandwidth portion (e.g., 5MHz) to reduce feedback payload. The type of feedback information may indicate whether the SFI includes: (i) a CDI corresponding to a channel between an interfering cell and a UE; (ii) PMI used by the serving cell of the UE. Either or both types of information may be useful for scheduling decisions for the interfering cell.

In one design, the RQI request to the UE may include one or more of the following:

the time-frequency resources on which the RQI is determined;

uplink resources for transmitting RQI;

the priority of the RQI request;

and/or other information.

In one design, the RQI reference signal may be for one cell in a designated resource at subframe t₃RQI reference signals may convey precoding matrices and transmit power levels that are likely to be used in subframe t₅＝t₃On the corresponding resource in + Δ, where Δ may be a fixed offset. For example, the transmit power level in the respective resource may be the same as or different from the transmit power level transmitted in the RQI reference signal, depending on QoS, channel quality conditions, and so on. In one design, all cells may transmit their RQI reference signals on the same resources and use different cell-specific scrambling. This allows the UE to measure the desired signal component from the serving cell and the interference from the interfering cell based on the different scrambling codes for the serving cell and the interfering cell. The RQI reference signal may use a relatively small amount of overhead to make accurate measurements of resource-specific channel conditions. The amount of overhead depends on the desired granularity of the resource.

In one design, an RQI from the UE to the serving cell may convey the channel quality of the time-frequency resources explicitly or implicitly indicated in the RQI request. The RQI may include quantized channel qualities (e.g., having four or more bits) for each of at least one layer of the at least one layer for data transmission to the UE. Each layer corresponds to a spatial channel in a MIMO channel from the serving cell to the UE. The RQI may also include the quantized channel quality of the base layer and the differential value of each of the other layers. The RQI may also include a Rank Indicator (RI) (e.g., having one or two bits) to convey the number of layers for data transmission.

Messages and transmissions for spatial interference mitigation on the uplink may include: (i) information similar to that described above for spatial interference suppression on the downlink; and/or (ii) other information.

In one design, the UE may send the SFI and/or the RQI on a control segment for no other transmissions. For example, cell X may reserve a control segment for UEs in cell Y and possibly other cells to send an SFI and/or an RQI to cell X. The UE may transmit an SFI or an RQI to a cell using OFDMA or NxSC-FDMA.

In one design, messages and transmissions for spatial interference suppression may be sub-sampled (sub-sample) to reduce signaling overhead. For example, the messages and transmission sequences shown in fig. 2 may be transmitted once per scheduling time interval, and scheduling decisions (e.g., selected precoding matrix and transmit power level) may be valid for the entire scheduling time interval. The scheduling interval may cover M subframes in one interlace or some other suitable duration. Each interlace may include a plurality of subframes spaced apart by L subframes. The scheduling intervals of different interlaces may be staggered in time to avoid long initial delays caused by subsampling. In another design, for persistent scheduling, the message may include a persistence bit to indicate that it has validity for the extended time period.

The messages and transmissions in fig. 2 and 4 may be sent in different channels. For example, in LTE, a cell may send SFI and RQI requests to a UE on a Physical Downlink Control Channel (PDCCH). In one design, a cell may send an SFI request or an RQI request using an existing Downlink Control Information (DCI) format, e.g., by differently scrambling a Cyclic Redundancy Check (CRC) to distinguish the SFI or RQI request from other types of messages. In another design, the cell may send the SFI request or the RQI request using a new DCI format. A cell may commonly transmit a plurality of SFIs or RQIs in an interval corresponding to one PDCCH using different CRCs. The cell may also send a downlink grant on the PDCCH to the scheduled UE. The cell may also send data on a Physical Downlink Shared Channel (PDSCH) in one or several HARQ transmissions. The cell may also transmit a dedicated reference signal on the PDSCH to the scheduled UE.

The UE may send the SFI, RQI, and/or ACK information on: (i) transmitting on a Physical Uplink Control Channel (PUCCH) if only the control information is transmitted; or (ii) on a Physical Uplink Shared Channel (PUSCH) if both data and control information are transmitted. Thus, if data is also being transmitted, the SFI and RQI may be transmitted in-band. The PUCCH may carry up to 12 information bits on two Resource Blocks (RBs) of one subframe. The 12 information bits may be encoded using a (20, 12) block code (block code) to obtain 20 code bits, and the 20 code bits may be further processed and transmitted over the two RBs. In one design, a larger payload of Q bits (e.g., 13 to 16 bits) for the SFI may be transmitted on the PUCCH using a higher coding rate (e.g., a (20, Q) coding rate), where Q is greater than 12. In another design, a larger payload may be transmitted using a new PUCCH format. The payload may be encoded using a convolutional code or a Reed-Muller code and transmitted over two "half RBs". Each "half RB" may cover six subcarriers in one slot of six or seven symbol periods, and each "half RB" includes a reference signal in the middle two symbol periods of the slot. In another design, the larger payload may be divided into multiple portions, and each portion may be transmitted using an existing PUCCH format. The multiple portions may be sent on different sets of subcarriers of the same subframe or different sets of subcarriers of different subframes with NxSC-FDMA such that higher transmit power can be used for each portion. The various messages and transmissions in fig. 2 and 4 may also be sent on other data and/or control channels.

The spatial interference mitigation techniques described herein may increase the dimensionality on the downlink as well as the uplink. These techniques may provide substantial gains in unplanned configurations (e.g., for coverage extension), restricted association scenarios, and other scenarios. These techniques are particularly advantageous in scenarios where several served UEs are subject to strong interference from some neighboring cells (e.g., femto deployment) and bursty traffic scenarios.

The techniques described herein may also be used for inter-site packet sharing (ISPS) and cooperative noise suppression (CS). For ISPS, multiple cells (of the same or different enbs) may transmit packets to a single UE. Each cell may send data transmissions for the cell to the UE based on the precoding information determined by the UE for the cell. For ISPS, each cell other than the serving cell may steer its transmission in a direction toward the UE (rather than away from the UE) based on precoding information from the UE. For CS, the interfering cell may reduce its transmit power (possibly to zero) to reduce interference to UEs in neighboring cells. The interfering cell may decide whether to control away from the UE or just reduce its transmit power.

Fig. 5 shows a design of a process 500 for transmitting data on the downlink using spatial interference mitigation in a wireless communication network. Process 500 may be performed by a cell (as described below) or some other entity. The cell may receive precoding information from the first UE (block 512). The cell may also receive an SFI from a second UE, where the second UE is not in communication with the cell (block 514). The second UE may transmit the SFI to the cell in response to: (i) an SFI request sent by a serving cell of a second UE; or (ii) an SFI request sent by the cell to the second UE. The cell may also send an SFI request to the first UE to request the first UE to send an SFI to the at least one interfering cell. The SFI request and the SFI may include any of the information described above. The cell may send the data transmission using the precoding information from the first UE and/or the SFI from the second UE.

In one design, the cell may determine whether to schedule the first UE based on precoding information from the first UE, SFI from the second UE, and/or other information. If the decision is to schedule the first UE, the cell may select a precoding matrix based on the precoding information from the first UE and the SFI from the second UE (block 516). The cell may also determine a transmit power level from the SFI from the second UE. The cell may transmit a reference signal based on the precoding matrix and at the determined transmit power level (block 518). The cell may send an RQI request to the first UE (block 520), receive an RQI determined by the first UE based on the reference signal (block 522). The RQI request and RQI may include any of the information described above. The cell may determine an MCS based on the RQI from the first UE (block 524), send a data transmission to the first UE using the precoding matrix and based on the MCS (block 526).

The cell may decide to schedule a third UE that was not requested to transmit precoding information to the cell in block 512. The cell may transmit the reference signal based on the SFI from the second UE and precoding information that may have been previously received from a third UE. The cell may also transmit an RQI request to the third UE, receiving an RQI determined by the third UE based on the reference signal. The cell may determine an MCS based on the RQI from the third UE and send a data transmission to the third UE based on the MCS. The cell may also transmit RQI requests to a plurality of UEs, receive RQIs from each UE, and schedule at least one UE of the plurality of UEs for data transmission.

The cell may also receive an SFI from a fourth UE. The second UE and the fourth UE communicate with different neighboring cells. The cell sends a data transmission to the first UE using the precoding information from the first UE, the SFI from the second UE, the SFI from the fourth UE, and so on.

Fig. 6 shows a design of an apparatus 600 for transmitting data on a downlink using spatial interference mitigation. The apparatus 600 comprises: a module 612 for receiving precoding information sent by a first UE to a cell; a module 614 for receiving an SFI from a second UE, the second UE not in communication with the cell; a module 616 for selecting a precoding matrix based on the precoding information from the first UE and the SFI from the second UE; a module 618 for transmitting a reference signal according to the precoding matrix; means 620 for sending an RQI request to the first UE; a module 622 for receiving an RQI determined by the first UE based on the reference signal; a module 624 for determining the MCS based on the RQI from the first UE; a module 626 for sending a data transmission to the first UE using the precoding information from the first UE and/or the SFI (e.g., precoding matrix) from the second UE and according to the MCS.

Fig. 7 shows a design of a process 700 for receiving data on a downlink using spatial interference mitigation in a wireless communication network. Process 700 may be performed by a UE (described below) or some other entity. The UE may communicate with a first cell (block 712), receive an SFI request from the first cell (block 714). In response to the SFI request, the UE may transmit an SFI for a second cell, where the second UE is not in communication with the UE (block 716). The UE may send the SFI directly to the second cell or to the first cell, which then forwards this SFI to the second cell via the backhaul. The SFI request and the SFI may include any of the information described above. The UE may also send precoding information to the first cell (block 718). The UE may receive a data transmission sent by the first cell to the UE based on the precoding information.

In one design, the UE may receive a first reference signal transmitted by a first cell, e.g., using a first precoding matrix determined based on precoding information from the UE (block 720). The UE may also receive a second reference signal, which may be transmitted by the second cell, e.g., using a second precoding matrix determined based on the SFI from the UE (block 722). The UE may determine an RQI based on the first reference signal and the second reference signal (block 724). The UE may receive an RQI request from the first cell (block 726), in response to which the UE transmits an RQI to the first cell (block 728). Thereafter, the UE may receive a data transmission sent by the first cell based on the precoding information (e.g., the first precoding matrix) and according to the determined MCS based on the RQI (block 730). The UE may also receive a transmission sent by the second cell based on the SFI (e.g., the second precoding matrix) to reduce interference to the UE (block 732).

Fig. 8 shows a design of an apparatus 800 for receiving data on a downlink using spatial interference mitigation. The apparatus 800 comprises: a module 812 for communicating with a first cell via a UE; a module 814 for receiving an SFI request sent by a first cell to a UE; a module 816 for transmitting an SFI for a second cell, wherein the second cell is not in communication with the UE; module 818 for sending precoding information to the first cell; a module 820 for receiving a first reference signal transmitted by a first cell based on precoding information from a UE; a module 822 for receiving a second reference signal transmitted by a second cell based on the SFI from the UE; a module 824 for determining an RQI from the first reference signal and the second reference signal; a module 826 for receiving an RQI request from a first cell; a module 828 for transmitting RQI to a first cell; means 830 for receiving a data transmission sent by a first cell based on the precoding information and in accordance with an MCS determined based on the RQI; a module 832 for receiving a transmission sent by a second cell based on the SFI to reduce interference to the UE.

Fig. 9 shows a design of a process 900 for transmitting data on the uplink using spatial interference mitigation in a wireless communication network. Process 900 may be performed by a UE (described below) or some other entity. The UE may send a resource request to a first cell in communication with the UE (block 912). The UE may send an SFI request to a second cell that is not in communication with the UE (block 914). Alternatively, the first cell may send an SFI request to the second cell. In either case, the UE may receive an SFI sent by the second cell to the UE in response to the SFI request (block 916). For example, the UE may transmit a reference signal in response to a reference signal request received from the first cell (block 918). The UE may receive grant information including an MCS determined by the first cell based on the reference signal (block 920). The UE may then send a data transmission to the first cell in accordance with the MCS and the SFI to reduce interference to the second cell (block 922).

In one design, the UE may be equipped with multiple transmit antennas. The UE may receive precoding information from the first cell. The UE may select the precoding matrix based on the precoding information from the first cell and the spatial nulling information from the second cell. The UE may then send a data transmission using the precoding matrix. In another design, the UE may be equipped with a single antenna. The UE may obtain a receive null gain from the SFI from the second cell. The UE may determine a transmit power level based on the receive null gain and send a data transmission to the first cell at the transmit power level.

Fig. 10 shows a design of an apparatus 1000 for transmitting data on the uplink using spatial interference mitigation. The apparatus 1000 comprises: a module 1012 for transmitting a resource request from a UE to a first cell in communication with the UE; a module 1014 for sending an SFI request to a second cell not in communication with the UE; means 1016 for receiving an SFI from a second cell; a module 1018 for transmitting a reference signal; a module 1020 configured to receive grant information, the grant information including an MCS determined by the first cell based on the reference signal; a module 1022 for sending a data transmission to the first cell according to the MCS and the SFI to reduce interference to the second cell.

Fig. 11 shows a design of a process 1100 for receiving data on the uplink using spatial interference mitigation in a wireless communication network. Process 1100 may be performed by a cell (as described below) or some other entity. A cell may receive a resource request from a first UE in communication with the cell (block 1112). The cell may receive an SFI request (block 1114), e.g., from a second UE not in communication with the cell or from a serving cell of the second UE, in response to which the cell may transmit an SFI to the second UE (block 1116). The cell may receive a first reference signal from a first UE, where the first UE transmits the reference signal in response to a reference signal request from the cell (block 1118). The cell may also receive a second reference signal transmitted by a second UE based on the SFI (block 1120). The cell may determine an RQI for the first UE based on the first reference signal and the second reference signal (block 1122). The cell may determine an MCS based on the RQI (block 1124), and the cell may send grant information including the MCS to the first UE (block 1126). The cell may receive a data transmission sent by the first UE based on the MCS (block 1128). The data transmission is less interfered with by transmissions sent by a second UE based on the SFI.

Fig. 12 shows a design of an apparatus 1200 for receiving data on an uplink using spatial interference mitigation. The apparatus 1200 includes: a module 1212 for receiving a resource request sent by a first UE to a cell in communication with the first UE; a module 1214 for receiving an SFI request from, e.g., a second UE not in communication with the cell; a module 1216 for transmitting the SFI to the second UE; a module 1218 for receiving a first reference signal from a first UE; a module 1220 for receiving a second reference signal transmitted by a second UE based on the SFI; a module 1222 to determine an RQI for the first UE from the first reference signal and the second reference signal; a module 1224 for determining an MCS based on the RQI; a module 1226 for sending grant information including the MCS to the first UE; a module 1228 for receiving a data transmission sent by the first UE based on the MCS.

The modules in fig. 6, 8, 10, and 12 may comprise processors, electronics devices, hardware devices, electronics components, logic circuits, memories, software codes, firmware codes, etc., or any combination thereof.

Fig. 13 shows a block diagram of a design of base station/eNB 110 and UE 120, where base station/eNB 110 and UE 120 may be one base station/eNB and one UE in fig. 1. Base station 110 is equipped with T antennas 1334a through 1334T and UE 120 is equipped with R antennas 1352a through 1352R, where generally T ≧ 1 and R ≧ 1.

At base station 110, a transmit processor 1320 receives data from a data source 1312 and messages from a controller/processor 1340. For example, controller/processor 1340 may provide messages for spatial interference mitigation shown in fig. 2 and 4. Transmit processor 1320 may process (e.g., encode, interleave, and symbol map) the data and messages, respectively, to provide data symbols and control symbols. The transmit processor 1320 may also generate reference symbols for the RQI reference signal and/or other reference signals or pilots. A Transmit (TX) multiple-input multiple-output (MIMO) processor 1330 may spatially process (e.g., precode) the data symbols, the control symbols, and/or the reference symbols, if any, and may provide T output symbol streams to T Modulators (MODs) 1332a through 1332T. Each modulator 1332 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 1332 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample streams to obtain a downlink signal. T downlink signals from modulators 1332a through 1332T may be transmitted via T antennas 1334a through 1334T, respectively.

At UE 120, antennas 1352a through 1352r may receive the downlink signals from base station 110 and may provide received signals to demodulators (DEMODs) 1354a through 1354r, respectively. Each demodulator 1354 conditions (e.g., filters, amplifies, downconverts, and digitizes) a respective received signal to obtain input samples. Each demodulator 1354 may further process the input samples (e.g., for OFDM) to obtain received symbols. A MIMO detector 1356 may obtain received symbols from all R demodulators 1354a through 1354R, perform MIMO detection on the received symbols, if any, and provide detected symbols. A receive processor 1358 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE 120 to a data sink 1360, and provide decoded messages to a controller/processor 1380.

On the uplink, at UE 120, a transmit processor 1364 may receive and process data from a data source 1362 and receive and process messages (e.g., for spatial interference suppression) from a controller/processor 1380. The transmit processor 1364 may also generate reference symbols for the RQI reference signal and/or other reference signals or pilots. These symbols from transmit processor 1364 may be precoded by a TX MIMO processor 1366 if applicable, further processed by modulators 1354a through 1354r, and transmitted to base station 110. At base station 110, the uplink signals from UE 120 are received by antennas 1334, processed by demodulators 1332, detected by a MIMO detector 1336 (if any), and further processed by a receive processor 1338 to obtain the decoded data and messages transmitted by UE 120.

Controllers/processors 1340 and 1380 may direct the operation at base station 110 and UE 120, respectively. Processor 1340 and/or other processors and modules of base station 110 may perform or direct process 500 in fig. 5, process 1100 in fig. 11, and/or other processes for the techniques described herein. Processor 1380 and/or other processors and modules of UE 120 may perform or direct process 700 in fig. 7, process 900 in fig. 9, and/or other processes for the techniques described herein. Memories 1342 and 1382 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 1344 may schedule UEs for data transmission on the downlink and/or uplink and provide resource grant information for the scheduled UEs.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein 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, 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 conventional 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.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor such 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. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. Of course, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary designs, the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. 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, 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 (disc), as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to these disclosures will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (61)

1. A method for transmitting data in a wireless communication network, comprising:

receiving precoding information transmitted by a first User Equipment (UE) to a cell;

receiving Spatial Feedback Information (SFI) sent by a second UE to the cell, the second UE not in communication with the cell; and

the cell sends a data transmission using at least one of precoding information from the first UE and an SFI from the second UE.

2. The method of claim 1, wherein the second UE transmits the SFI to the cell in response to an SFI request sent by a second cell to the second UE.

3. The method of claim 1, further comprising:

sending an SFI request to the first UE to request the first UE to send an SFI to a second cell.

4. The method of claim 1, wherein the SFI from the second UE comprises at least one of: spatial nulling information for the cell, precoding information for a serving cell of the second UE, nulling gain information, resources for reducing interference of the cell, a target interference level of the second UE, and a priority of interference reduction for the cell.

5. The method of claim 1, further comprising:

receiving an SFI directed to the cell by a third UE, wherein the second UE and the third UE communicate with other cells different from the cell, an

Wherein the cell transmits the data transmission using at least one of precoding information from the first UE, an SFI from the second UE, and an SFI from the third UE.

6. The method of claim 1, further comprising:

and judging whether to schedule the first UE according to the precoding information from the first UE and the SFI from the second UE.

7. The method of claim 1, further comprising:

selecting a precoding matrix according to precoding information from the first UE and an SFI from the second UE; and

transmitting a reference signal according to the precoding matrix.

8. The method of claim 7, further comprising:

determining a transmit power level of the reference signal according to the SFI from the second UE, wherein the reference signal is transmitted at the determined transmit power level.

9. The method of claim 7, further comprising:

transmitting a Resource Quality Information (RQI) request to the first UE; and

receiving a RQI determined by the first UE based on the reference signal.

10. The method of claim 9, wherein the RQI request comprises at least one of: resources for determining the RQI, resources for sending the RQI, and a priority of the RQI request.

11. The method of claim 9, wherein sending the data transmission comprises:

determining a Modulation and Coding Scheme (MCS) according to a RQI from the first UE; and

sending the data transmission to the first UE according to the MCS.

12. The method of claim 1, further comprising:

transmitting a reference signal according to an SFI from the second UE;

transmitting a Resource Quality Information (RQI) request to a third UE; and

receiving a RQI determined by the third UE based on the reference signal.

13. The method of claim 12, wherein transmitting the reference signal comprises:

transmitting the reference signal further according to precoding information from the third UE.

14. The method of claim 12, wherein sending the data transmission comprises:

determining a Modulation and Coding Scheme (MCS) according to a RQI from the third UE; and

sending the data transmission to the third UE according to the MCS.

15. The method of claim 1, further comprising:

transmitting Resource Quality Information (RQI) requests to a plurality of UEs;

receiving an RQI from each UE of the plurality of UEs; and

scheduling at least one of the plurality of UEs for data transmission.

16. An apparatus for wireless communication, comprising:

means for receiving precoding information transmitted by a first User Equipment (UE) to a cell;

means for receiving Spatial Feedback Information (SFI) transmitted by a second UE to the cell, the second UE not in communication with the cell; and

means for transmitting, by the cell, a data transmission using at least one of precoding information from the first UE and an SFI from the second UE.

17. The apparatus of claim 16, further comprising:

means for transmitting an SFI request to the first UE to request the first UE to transmit an SFI to a second cell.

18. The apparatus of claim 16, further comprising:

means for selecting a precoding matrix based on precoding information from the first UE and an SFI from the second UE; and

means for transmitting a reference signal according to the precoding matrix.

19. The apparatus of claim 18, further comprising:

means for sending a Resource Quality Information (RQI) request to the first UE; and

means for receiving an RQI determined by the first UE based on the reference signal.

20. The apparatus of claim 16, further comprising:

means for transmitting a reference signal according to an SFI from the second UE;

means for sending a Resource Quality Information (RQI) request to a third UE; and

means for receiving an RQI determined by the third UE based on the reference signal.

21. An apparatus for wireless communication, comprising:

at least one processor configured to:

receiving precoding information transmitted by a first User Equipment (UE) to a cell;

receiving Spatial Feedback Information (SFI) sent by a second UE to the cell, wherein the second UE is not in communication with the cell; and

cause the cell to send a data transmission using at least one of precoding information from the first UE and an SFI from the second UE.

22. The apparatus of claim 21, wherein the at least one processor is configured to:

sending an SFI request to the first UE to request the first UE to send an SFI to a second cell.

23. The apparatus of claim 21, wherein the at least one processor is configured to:

selecting a precoding matrix according to precoding information from the first UE and an SFI from the second UE; and

transmitting a reference signal according to the precoding matrix.

24. The apparatus of claim 23, wherein the at least one processor is configured to:

transmitting a Resource Quality Information (RQI) request to the first UE; and

receiving a RQI determined by the first UE based on the reference signal.

25. The apparatus of claim 21, wherein the at least one processor is configured to:

transmitting a reference signal according to an SFI from the second UE;

transmitting a Resource Quality Information (RQI) request to a third UE; and

receiving a RQI determined by the third UE based on the reference signal.

26. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to receive precoding information transmitted by a first User Equipment (UE) to a cell;

code for causing the at least one computer to receive Spatial Feedback Information (SFI) sent by a second UE to the cell, wherein the second UE is not in communication with the cell; and

code for causing the at least one computer to cause the cell to send a data transmission using at least one of precoding information from the first UE and an SFI from the second UE.

27. A method for receiving data in a wireless communication network, comprising:

user Equipment (UE) communicating with a first cell; and

the UE transmits Spatial Feedback Information (SFI) for a second cell with which the UE is not in communication.

28. The method of claim 27, wherein the communication by the UE comprises:

transmitting, by the UE, precoding information to the first cell; and

receiving a data transmission by the first cell to the UE based on the precoding information.

29. The method of claim 27, wherein transmitting the SFI for the second cell comprises:

transmitting, by the UE, an SFI for the second cell to the second cell.

30. The method of claim 27, wherein transmitting the SFI for the second cell comprises:

sending, by the UE, an SFI for the second cell to the first cell, the SFI being forwarded by the first cell to the second cell via a backhaul.

31. The method of claim 27, further comprising:

receiving an SFI request sent by the first cell to the UE, wherein the SFI is sent by the UE to the second cell in response to the SFI request.

32. The method of claim 31, wherein the SFI request comprises at least one of: a list of at least one cell for transmitting an SFI, resources for determining the SFI, resources for transmitting the SFI, a priority of the SFI request, and a target interference level of the UE.

33. The method of claim 27, wherein the SFI comprises a Channel Direction Indicator (CDI) or a Precoding Matrix Indicator (PMI) for the second cell.

34. The method of claim 28, further comprising:

receiving a first reference signal transmitted by the first cell using a first precoding matrix determined based on precoding information from the UE; and

determining Resource Quality Information (RQI) from the first reference signal.

35. The method of claim 34, further comprising:

receiving a second reference signal transmitted by the second cell using a second precoding matrix determined based on an SFI from the UE, wherein the RQI is further determined from the second reference signal.

36. The method of claim 34, further comprising:

receiving an RQI request from the first cell; and

transmitting the RQI to the first cell in response to the RQI request.

37. The method of claim 34, wherein receiving the data transmission comprises:

receiving a data transmission sent by the first cell using the first precoding matrix and also according to a modulation and coding scheme determined based on the RQI.

38. The method of claim 27, further comprising:

receiving a transmission sent by the second cell based on the SFI to reduce interference to the UE.

39. An apparatus for wireless communication, comprising:

means for communicating with a first cell by a User Equipment (UE); and

means for transmitting, by the UE, Spatial Feedback Information (SFI) for a second cell, wherein the UE is not in communication with the second cell.

40. The apparatus of claim 39, wherein the means for communicating by the UE comprises:

means for transmitting precoding information to the first cell by the UE; and

means for receiving a data transmission by the first cell to the UE based on the precoding information.

41. The apparatus of claim 39, further comprising:

means for receiving an SFI request sent by the first cell to the UE, wherein the SFI is sent by the UE to the second cell in response to the SFI request.

42. The apparatus of claim 40, further comprising:

means for receiving a first reference signal transmitted by the first cell using a first precoding matrix determined based on precoding information from the UE;

means for receiving a second reference signal transmitted by the second cell using a second precoding matrix determined based on a SFI from the UE; and

means for determining Resource Quality Information (RQI) from the first reference signal and the second reference signal.

43. The apparatus of claim 42, further comprising:

means for receiving an RQI request from the first cell; and

means for sending the RQI to the first cell in response to the RQI request.

44. A method for transmitting data in a wireless communication network, comprising:

transmitting a resource request from a User Equipment (UE) to a first cell;

receiving Spatial Feedback Information (SFI) transmitted by a second cell to the UE, wherein the UE is not in communication with the second cell; and

sending a data transmission from the UE to the first cell in accordance with the SFI to reduce interference to the second cell.

45. The method of claim 44, further comprising:

transmitting, from the UE, an SFI request to the second cell, wherein the SFI is transmitted to the UE by the second cell in response to the SFI request.

46. The method of claim 44, further comprising:

transmitting, by the UE, a reference signal; and

receiving grant information, wherein the grant information includes a Modulation and Coding Scheme (MCS) determined by the first cell based on the reference signal, wherein the data transmission is transmitted by the UE based on the MCS.

47. The method of claim 46, further comprising:

receiving a reference signal request from the first cell, wherein the reference signal is transmitted by the UE in response to the request.

48. The method of claim 44, further comprising:

receiving precoding information from the first cell; and

selecting a precoding matrix based on precoding information from the first cell and an SFI from the second cell, wherein the UE utilizes the precoding matrix to transmit the data transmission.

49. The method of claim 44, wherein sending the data transmission comprises:

determining a transmit power level as a function of a receive null gain of the SFI from the second cell; and

sending the data transmission at the determined transmit power level.

50. An apparatus for wireless communication, comprising:

means for transmitting a resource request from a User Equipment (UE) to a first cell;

means for receiving Spatial Feedback Information (SFI) transmitted by a second cell to the UE, wherein the UE is not in communication with the second cell; and

means for transmitting a data transmission from the UE to the first cell in accordance with the SFI to reduce interference to the second cell.

51. The apparatus of claim 50, further comprising:

means for transmitting, by the UE, a reference signal; and

means for receiving grant information, wherein the grant information includes a Modulation and Coding Scheme (MCS) determined by the first cell based on the reference signal;

wherein the UE sends the data transmission based on the MCS.

52. The apparatus of claim 50, further comprising:

means for receiving precoding information from the first cell;

means for selecting a precoding matrix based on precoding information from the first cell and an SFI from the second cell; and

wherein the UE transmits the data transmission using the precoding matrix.

53. The apparatus of claim 50, wherein the means for sending a data transmission comprises:

means for determining a transmit power level as a function of a receive nulling gain of an SFI from the second cell; and

means for transmitting the data transmission at the determined transmit power level.

54. A method for receiving data in a wireless communication network, comprising:

receiving a resource request sent by a first User Equipment (UE) to a cell;

transmitting Spatial Feedback Information (SFI) from the cell to a second UE, wherein the second UE is not in communication with the cell; and

receiving a data transmission sent by the first UE to the cell, the data transmission being less interfered by transmissions sent by the second UE based on the SFI.

55. The method of claim 54, further comprising:

receiving an SFI request sent by the second UE or a serving cell of the second UE to the cell, wherein the cell sends the SFI to the second UE in response to the SFI request.

56. The method of claim 54, further comprising:

receiving a first reference signal transmitted by the first UE;

receiving a second reference signal transmitted by the second UE based on the SFI; and

determining Resource Quality Information (RQI) for the first UE from the first reference signal and the second reference signal.

57. The method of claim 56, further comprising:

transmitting a reference signal request to the first UE, wherein the first UE transmits the first reference signal in response to the request.

58. The method of claim 56, further comprising:

determining a Modulation and Coding Scheme (MCS) from the RQI; and

transmitting, to the first UE, grant information including the MCS, wherein the first UE transmits the data transmission based on the MCS.

59. An apparatus for wireless communication, comprising:

means for receiving a resource request sent by a first User Equipment (UE) to a cell;

means for transmitting Spatial Feedback Information (SFI) from the cell to a second UE, wherein the second UE is not in communication with the cell; and

means for receiving a data transmission sent by the first UE to the cell, the data transmission being less interfered by transmissions sent by the second UE based on the SFI.

60. The apparatus of claim 59, further comprising:

means for receiving a first reference signal transmitted by the first UE;

means for receiving a second reference signal transmitted by the second UE based on the SFI; and

means for determining Resource Quality Information (RQI) for the first UE from the first reference signal and the second reference signal.

61. The apparatus of claim 60, further comprising:

means for determining a Modulation and Coding Scheme (MCS) based on the RQI;

means for transmitting grant information including the MCS to the first UE, wherein the first UE transmits the data transmission based on the MCS.