WO2012024837A1

WO2012024837A1 - Method and system for precoding

Info

Publication number: WO2012024837A1
Application number: PCT/CN2010/076383
Authority: WO
Inventors: David Mazzarese; Yongxing Zhou
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2010-08-26
Filing date: 2010-08-26
Publication date: 2012-03-01
Also published as: US20140133595A1; BR112013004549B1; BR112013004549A2; US9270352B2; ES2555534T3; EP2594030A1; US20120328039A1; US20150078474A1; EP2594030B1; KR101517456B1; EP2945308A1; HUE027153T2; EP2945308B1; US20150311966A1; EP2594030A4; KR20130036072A; US8908791B2; CN102835054B; US8665984B2; CN102835054A

Abstract

The present invention relates to a method for channel state feedback in a communication system. The method comprises obtaining a reference signal from an access point; deriving a rank indication, a codebook subset selection indication and a precoding matrix index based on the obtained reference signal;sending a first feedback message conveying the rank indication and the codebook subset selection indication, and sending a second feedback message conveying the precoding matrix index, to the access point; and receiving, from the access point, data precoded by a matrix derived based on the rank indication, the codebook subset selection indication and the precoding matrix index.

Description

Method and System for Prccoding

Field of the Invention

The present invention relates to communication technology, and in particular to a method and system for precoding.

Background of the Invention

In MIMO OFDMA cellular systems, closed-loop MIMO precoding is defined to enable high throughput downlink transmission to fixed and nomadic users. Feedback information is obtained by the transmitter via the report of a precoding matrix index (PMI) from a receiver to a transmitter. This PMI is used to represent a matrix in a codebook (a set of matrices), and the PMI is used by the transmitter to derive a downlink precoder.

Simple codebook structures are used in the first generation of MIMO OFDMA systems, such that the PMI can be represented with a few bits. Small codebooks can be used to achieve a coarse quantization of the spatial channel. For example, a 4-bit codebook is defined and the 4-bit PMI can be reported via a capacity-limited feedback channel called PUCCH [1,2]. Precoding matrices are defined for each possible transmission rank, which determines the size of the precoding matrix. The overall codebook is a set of matrices for each rank. The feedback report thus consists of a rank indication (RI) and a PMI in the codebook subset of the given rank RI. Since the rank of the propagation channel varies slowly in comparison with fast fading over which the PMI is adapted, the rank indication is reported with a longer period than the PMI.

Since the rank indication remains valid during several reports of the PMI, it can be encoded with a better error protection code in order to ensure that consecutive PMI reports are not invalidated by one erroneous RI report. In general, this is naturally ensured by the fact that the rank can take values in a limited range, such as {1, 2, 3, 4} in LTE (Long Term Evolution) system Rel-8, due to the limitation to a maximum of 4 antennas at the transmitter and 4 antennas at the receiver. Thus the RI can be represented by 2 bits. Since the PMI is in general reported along with a channel quality indication (CQI) ,which is short for CQI that represents the channel quality assuming that the transmitter precodes with the reported PMI, the total size of the feedback message that contains the PMI+CQI is larger than the 4 bits used to represent just the PMI. For example, in LTE Rel-8, the message size will be 8 to 1 1 bits with one to two CQIs, respectively. The PUCCH is transmitted in a fixed-size time-frequency resource with a fixed modulation. The 2 bits of RI that are reported individually are better protected than the 8 or 1 1 bits of PMI and CQI that are jointly reported, since the 2 bits of RI enjoy a lower error-correction encoding rate.

Summary of the Invention

According to one aspect of the present invention, a method for precoding in a wireless communication system is provided, which comprises: obtaining, by a receiver, a reference signal from a transmitter;

deriving, by the receiver, a rank indication, a codebook index ni in a first codebook Cj ,codebook indices kj and in a second codebook C_2,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the obtained reference signal;

sending, by the receiver, the rank indication, the codebook index ni in the first codebook Ci, the codebook indices kj and &₂ in the second codebook C₂,, the wideband CQIi and the subband CQI₂, to the transmitter; and

receiving, by the receiver, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices ni, kj and &₂·

A user equipment is provided , which comprises: a obtaining unit, configured to obtain a reference signal from a transmitter; a deriving unit, configured to derive a rank indication, a codebook index n ₁ in a first codebook Cj and codebook indices kj and ¾ in a second codebook C2,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the reference signal obtained by the obtaining unit;

a sending unit, configured to send the rank indication, the codebook index ni in the first codebook Ci, the codebook indices kj and &₂ in the second codebook C_2,, the wideband CQIi and the subband CQI₂ derived by the deriving unit, to the transmitter; and

a receiving unit, configured to receive, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices ni, ki and &2 ·

A transmitter is provided ,which comprises: a receiving unit, configured to receive a rank indication, a codebook index ni in a first codebook Ci, codebook indices ki and & in a second codebook C_2,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

a deriving unit, configured to derive a first precoder determined based on the rank indication and the indices nj, ki and ^received by the receiving unit; and

a precoding unit, configured to precode the data to be sent to the user equipment by the first precoder derived by the deriving unit; and

a sending unit , configured to send the data precoded by the precoding unit to the user equipment.

Another method for precoding in a wireless communication system is provided, which comprises: receiving , by a transmitter ,a rank indication, a codebook index ni in a first codebook Cj, codebook indices ki and &2 in a second codebook C_2,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

deriving, by the transmitter ,a first precoder determined based on the rank indication and the indices nj, kj and received by the transmitter;

precoding , the transmitter, the data to be sent to the user equipment by the first precoder derived by the transmitter; and

sending, the transmitter, the data precoded by the precoding unit to the user equipment.

A system for precoding is provided, which comprises: a transmitter detailed above and the user equipment detailed above. Brief Description of the Drawings

Fig. 1 shows a flowchart of a method for precoding in an embodiment of the present invention;

Fig. 2 shows a flowchart of a method for precoding in another embodiment of the invention;

Fig. 3 shows a flowchart of a method for precoding in another embodiment of the invention;

Fig. 4 shows a user equipment in an embodiment of the invention;

Fig. 5 shows a transmitter in an embodiment of the invention;

Fig. 6 shows a flowchart of a method for precoding in an embodiment of the present invention; and

Fig. 7 shows a system in an embodiment of the invention.

Detailed Description of the Embodiments

Emobiments of the present invention relates to a method for reporting multiple quantized representation of the channel state information of the propagation channel in a capacity-limited feedback channel using a double codebook structure. The wireless communication system comprises at least one transmitter and at least one receiver. The transmittermay be configured in an network entity, such as a base station, an eNodeB or an access point. The receiver may be configured in a user euipment (UE), such as a mobile device, a cellular telephone, a wireless enabled personal digital assitant (PDA) a wireless enaled laptop computer, or other such devices. At least one reference signal to the receiver and a feedback channel from the rccicvcr allow the transmission from the transmitter using codebook-based precoding when the transmitter is equipped with multiple transmit antennas.

For high-throughput operation in MIMO OFDMA systems, such as LTE system, IEEE 802.16e/m system or other such systems, a receiver may be asked to feedback one PMI for each subband of the bandwidth of the system, since it offers a better granularity than a wideband precoder and allows the transmitter to adapt its precoder to the frequency-selectivity of the wireless propagation channel, as well as providing information for multiuser diversity scheduling. In order to take advantage of these properties while limiting the rate of feedback in the channel to acceptable level, a receiver may be asked to report the PMIs for a set of selected subbands that do not span the entire bandwidth of operation. Additionally, in order to ensure a smooth operation of the scheduler at the transmitter, it is often also required that the receiver reports a wideband PMI along with the subband PMIs of selected subbands, so that the transmitter has channel state information for scheduling that receiver in any of the subbands for which a subband PMI is not reported. As pointed out above, a CQI is reported in association with a PMI, so a wideband CQI is reported along the wideband PMI, while a subband CQI is reported for each of the subband PMIs.

Enhancements of the feedback for closed-loop precoding beyond the simple 4-bit codebook or antenna array sizes for larger transmission would require more complex codebook structures, as well as a larger codebook size. A first type of enhanced codebook contains matrices that provide a quantization of the MIMO propagation channel between an array of transmitting antennas and an array of receiving antennas as presented in [3], where the matrices take the form: w ^{T T}M⁽¹I⁾1 W ^{T T}M⁽²I⁾2

The inner precoder has a block diagonal structure

_W ⁽D Mil

_W ⁽D

For rank 1, the precoder could be formed as

The rank 2 case would follow similarly as

The second matrix represents a co-phasing factor that reflects short-term channel variations and can be made to adjust the structure of the overall precoder W to match either a single-polarized linear uniform array (ULA) or a cross-polarized array at the transmitter.

The embodiments of the invention described herein may be used for various broadband wireless communication systems where a double codebook of precoding matrices is known by a transmitter and a receiver and the transmitter is equipped with multiple antennas, some of which may have the same or different polarizations. And the codebook is used for sending feedback information from the receiver to the transmitter via a capacity-limited feedback channel.A double codebook is composed of two codebooks, which are sets of matrices, and the combination of one matrix from a first codebook C\ and one matrix from a second codebook C₂ forms a precoder that can be used by the transmitter to send data to a receiver via multiple transmit antennas.

In an embodiment, a receiver, which can be UE, is connected to a transmitter ,which can be an access point for a duration much longer than the transmission time interval. During this duration, the receiver would send several feedback reports containing indices in a double codebook to recommend one or several precoders to the transmitter.

In one embodiment, at least one message including a rank indication, a first codebook index nj in a first codebook Cj, and two codebook indices kj and & in a second codebook C2_, which is contained in at least one report, is fed back from the receiver to the transmitter. The indices (nj, kj) represent a wideband precoder Wi in the double codebook, while the indices (nj, k ) represent a subband precoder W₂ in the double codebook, based on the same matrix with index nj in the codebook Cj. A wideband channel quality indicator , that is CQI, is also reported in reference to the wideband precoder represented by (nj, kj), while a subband channel quality indicator (CQI) is also reported in reference to the subband precoder represented by (n 1, ki).

In some embodiments where the index kj is not reported, it is assumed to be predefined with a common assumption known by both the receiver and the transmiter.

In an embodiment, a method for precoding feedback in a wireless communication system is disclosed. Referring to Figure 1, including:

S201 Obtaining, by a user equipment, a reference signal from a transmitter; S202 Deriving , by the user equipment , a rank indication, a first codebook index nj in a first codebook Cj, two codebook indices kj and k2 in a second codebook C2, a wideband CQIi associated with a wideband precoding matrix represented by indices (nj, kj), and a subband CQI₂ associated with a wideband precoding matrix represented by indices («/, ki), based on the obtained reference signal;

S203» sending, by the user equipment, a feedback report conveying the rank indication, the first codebook index ni, the two codebook indices ki and &₂, the wideband CQIi , and the subband CQI₂, to the transmitter ; and

S204_^ receiving, by the user equipment from the transmitter, data precoded by a a first precoder determined by the transmitter based on the rank indication and the indices nj, kj and fe.

In one enbodiment the first precoder determined by the transmitter based on the rank indication and the indices ni, kj and comprises: the first precoder is determined by the transmitter based on the rank indication ,a second precoder and a third precoder, wherein the second precoder is determined by the indices ni and kj at the transmitter, which represents a wideband precoder,and the third precoder is determined by the indices ni and ^¾ at the transmitter ,which represents a subband precoder.

wherein the second precoder is determined by the indices ni and kj at the transmitter comprises: the second precoder is determined as W = W^W^ ,and the represents the matrix determined by the index nj in the codebook Cj ,and the W^²⁾ represents the matrix determined by the index kj in the codebook C _,

the third precoder is determined by the indices n 1 and at the transmitter comprises: the third precoder is determined as W = W^W^ , and the represents the matrix determined by the index nj in the codebook Ci _, ,and the represents the matrix determined by the index Λ¾ in the codebook C2.

In one embodiment the second precoder is determined by the indices nj and ki at the transmitter comprises: the second precoder is determined as W = 'W„ ,and the ⁾ represents the matrix determined by the index kj in the codebook C2 ,and the represents the matrix determined by the index ni in the codebook _/

the third precoder is determined by the indices ni and 2 at the transmitter comprises: the third precoder is determined as W = W^W^ ,and the W^²⁾ represents the matrix determined by the index &2 in the codebook C2 ,and the represents the matrix determined by the index ni in the codebook Ci .

The method above allows to reduce the number of reported indices for representing two precoders in a double codebook, and there is no performance impact.

In one embodiment, the transmitter may ask the receiver to feed back in a series of messages as exemplified in figure 2. A first message contains the rank indication. A second message contains the indices nj and kj and the wideband channel quality indicator CQIi. A third message contains the index &2 and the subband channel quality indicator CQI2.And the receiver receives, from the transmitter, data precoded by a matrix derived based on the rank indication and the indices nl , kl and k2.

In one embodiment, the transmitter may ask the receiver to feed back in a series of compact messages that can contain one matrix index, as exemplified in figure 3. A first message contains the rank indication. A second message contains the index ni and the wideband CQIi. A third message contains the index Λ¾ and the subband CQI₂. And the index ki may be implicitly known by both the transmitter and the receiver as a fixed matrix in the codebook C₂. And the receiver receives, from the transmitter, data precoded by a matrix derived based on the rank indication and the indices nl, kl and k2. In one embodiment, a precoding matrix in the double codebook is derived as W = W⁽²⁾W⁽¹⁾ , where W⁽¹⁾ is a matrix from the codebook Ci, while W⁽²⁾ is a matrix from the codebook C₂. The wideband precoder W_j is derived at the receiver as W, = W ²⁾ , while the subband precoder W₂ is derived as W₂ = WfWj' . A wideband CQI, denoted as CQIi, represents the channel quality assuming the wideband precoding matrix is used at the transmitter. A subband CQI, denoted as CQI₂, represents the channel quality assuming the subband precoding matrix is used at the transmitter. In one embodiment, the index kj is pre-defined at both the transmitter and receiver based on a fixed assumption, and the matrix which the index kj represents may be the identity matrix, in which case the wideband precoder is simply represented as .

In one embodiment, a precoding matrix in the double codebook is derived as W = W⁽¹⁾W⁽²⁾ , where W⁽¹⁾ is a matrix from the codebook Ci, while W⁽²⁾ is a matrix from the codebook C₂. The wideband precoder W_j is derived at the receiver as W_t = W^W^ , while the subband precoder W₂ is derived as W₂ = W^W_A ⁽²⁾ . A wideband CQI, denoted as CQIi, represents the channel quality assuming the wideband precoding matrix is used at the transmitter. A subband CQI, denoted as CQI₂, represents the channel quality assuming the subband precoding matrix is used at the transmitter. In one embodiment the index kj is pre-defined at both the transmitter and receiver based on a fixed assumption, and the matrix which the index kj represents may be the identity matrix or a block matrix composed of identity matrices of smaller dimension. In one embodiment, a precoding matrix in the double codebook is derived as W = W⁽¹⁾W⁽²⁾ , where W⁽¹⁾ is a matrix from the codebook Ci, while W⁽²⁾ is a matrix from the codebook C₂. The wideband precoder W_j is derived at the receiver as W_t = W<^1} W<²⁾ , while the subband precoder is W₂ derived as W₂ = W<^1} W£° . A wideband CQI, denoted as CQIi, represents the channel quality assuming the wideband precoding matrix is used at the transmitter. A subband CQI, denoted as CQI₂, represents the channel quality assuming the subband precoding matrix is used at the transmitter. In one embodiment the index kj is reported based on a subset of the codebook C₂, and kj may be reported with fewer bits than the index fe- For example, &2 is the index in the subset of the codebook C₂.

In one embodiment, a precoding matrix in the double codebook is derived as W = W⁽¹⁾W⁽²⁾ , where R = W⁽¹⁾ is a normalized covariance matrix from the codebook Ci, while W⁽²⁾ is a matrix from the codebook C₂. The wideband precoder W_j is derived at the receiver as W, = W^W^ , while the subband precoder W₂ is derived as

W₂ = W_J1 ⁽ _| ¹⁾w ²⁾ . A wideband CQI, denoted as CQIi, represents the channel quality assuming the wideband precoding matrix is used at the transmitter. A subband CQI, denoted as CQI₂, represents the channel quality assuming the subband precoding matrix is used at the transmitter. In one embodiment the index ki is not reported but it is predefined at both the transmitter and receiver based on a common assumption, this matrix which the index kj represents may be the principal eigenvector of the matrix R, or the best approximation of the principal eigenvector of the matrix R by a vector in the codebook C₂. Note that for skilled person in the art, the embodiment above may be used for at least one subband.

The method above allows to reduce the number of reported indices and save the system resources , without performance reducing. It is understandable to those skilled in the art that all or part of the steps of the foregoing embodiments may be implemented by hardware instructed by a computer program. The program may be stored in a computer-readable storage medium. When being executed, the program performs all or part of the steps in foregoing method embodiments.

In another embodiment of the present invention, a user equipment that can realize all the above method is also disclosed. Referring to Figure 4 , the user equipment 1900 includes:

a obtaining unit 1901, configured to obtain a reference signal from a transmitter; a deriving unit 1902, configured to derive a rank indication, a codebook index ni in a first codebook Ci and codebook indices kj and &2 in a second codebook C2_,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the reference signal obtained by the obtaining unit;,

a sending unit 1903, configured to send the rank indication, the codebook index ni in the first codebook Cj, the codebook indices kj and &2 in the second codebook C2_,, the wideband CQIi and the subband CQI₂ derived by the deriving unit, to the transmitter;and

a receiving unit 1904, configured to receive, from the transmittter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices m, ki and &2 ·

Note that for skilled person in the art, the embodiment above may be used for at least one subband.

The embodiment above allows to reduce the number of reported indices and save the system resources , without performance reducing.In another embodiment of the present inventions transmitter is described as figure 5. In this embodiment ,the transmitter may be a base station.

The transmitter, comprising: a receiving unit 2001, configured to receive a rank indication, a codebook index ni in a first codebook Cy, codebook indices ki and &2 in a second codebook C2_,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

a deriving unit 2002, configured to derive a first precoder determined based on the rank indication and the indices ni, ki and ^ received by the receiving unit 2001 ; and a precoding unit 2003, configured to precode the data to be sent to the user equipment by the first precoder derived by the deriving unit 2002;and

a sending unit 2004, configured to send the data precoded by the precoding unit 2003 to the user equipment. the deriving unit comprising:

a first deriving module, configured to derive a second precoder representing a wideband precoder determined by the indices ni and ki ;and

a second deriving module, configured to a third precoder representing a subband precoder determined by the indices nj and fe- the deriving unit comprising:

a first deriving module, configured to derive a second precoder representing a wideband precoder determined by the indices ni and kj ;and

a second deriving module, configured to a third precoder representing a subband precoder determined by the indices nj and fe. the first deriving module comprising:

a first determining submodule, configured to determine the matrix by the index ni in the codebook Ci_:

a second determining submodule, configured to determine the matrix W_A ⁽²⁾ by the index kj in the codebook _2, and

a third determining submodule, configured to determine the second precoder W_i as W, = W^W^ ; the second deriving module comprising:

a fourth determining submodule, configured to determine the matrix by the index ni in the codebook C_/;

a fifth determining submodule, configured to determine the matrix W^²⁾ by the index ₂ in the codebook _2;and a sixth determining submodule, configured to determine the third precoder W₂ as W₂ = W<ⁿw£²⁾ ; or,

the first deriving module comprising:

the first determining submodule, configured to determine the matrix W^²⁾ by the index kj in the codebook C_2,

the second determining submodule, configured to determine the matrix by the index nj in the codebook Cj_; the third determining submodule, configured to determine the second precoder W_t as W, = W<²⁾ ; the second deriving module comprising:

the fourth determining submodule, configured to determine the matrix w ²⁾ by the index in the codebook C_2,

the fifth determining submodule, configured to determine the matrix W_n ⁽¹ by the index ni in the codebook C?_;

sixth determining submodule, configured to determine the third precoder W₂ as

The embodiment above allows to reduce the number of reported indices and save the system resources , without performance reducing.

In one embodiment^ method for precoding in a wireless communication system is detailed in figure 6. The method comprise:

52101, a transmitter receives a rank indication, a codebook index «_/ in a first codebook Ci, codebook indices kj and &₂ in a second codebook C2_,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

52102, the transmitter derives a first precoder determined based on the rank indication and the indices ni, kj and ^received by the transmitter; S2103, the transmitter precodes the data to be sent to the user equipment by the first precoder derived by the transmitter; and

S2104, the transmitter sends the data precoded by the precoding unit to the user equipment. wherein the transmitter deriving a first precoder determined based on the rank indication and the indices nj, kj and ^received by the transmitter, comprising: the transmitter deriving the first precoder determined based on the rank indication ,a second precoder and a third precoder, in which the second precoder is determined by the indices ni and ki at the transmitter, which represents a wideband precoder,and the third precoder is determined by the indices ni and &2 at the transmitter ,which represents a subband precoder.

wherein the second precoder is determined by the indices ni and ki at the transmitter comprises: the second precoder W_j is determined as W_j = W^W^ ,in which the represents the matrix determined by the index nj in the codebook Cj ,and the W ²⁾ represents the matrix determined by the index kj in the codebook C2,

the third precoder is determined by the indices n 1 and &2 at the transmitter comprises: the third precoder W₂ is determined as W₂ = W^W^ , in which the W_n ⁽¹⁾ represents the matrix determined by the index ni in the codebook Cj , ,and the W ²⁾ represents the matrix determined by the index &2 in the codebook C2.

wherein the second precoder is determined by the indices ni and ki at the transmitter comprises: the second precoder W₁ is determined as W₁ = W^W^ ,in which the W^²⁾ represents the matrix determined by the index kj in the codebook C2 ,and the W_n ⁽¹⁾ represents the matrix determined by the index ni in the codebook C_/

the third precoder is determined by the indices n 1 and &2 at the transmitter comprises: the third precoder W₂ is determined as W₂ = 'W^ ' ,in which the ⁾ represents the matrix determined by the index &2 in the codebook C2 ,and the represents the matrix determined by the index ni in the codebook C_/.

In one embodiment, a system for precoding is detailed in figure 7. The system comprises a transmitter 1701 and a user equipmentl702. The transmitter may be a base station.

The user equipment may comprise a receiving unit, configured to receive a reference signal from a transmitter;

a deriving unit, configured to derive a rank indication, a codebook index ni in a first codebook Ci and codebook indices ki and k2 in a second codebook C2_,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the reference signal obtained by the receiving unit;,

a sending unit, configured to send the rank indication, the codebook index ni in the first codebook Cj, the codebook indices kj and 2 in the second codebook C2_,, the wideband CQIi and the subband CQI₂ derived by the deriving unit, to the transmitter; and

a receiving unit, configured to receive, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices nj, kj and k2

The transmitter may comprise a receiving unit 2001, configured to receive a rank indication, a codebook index ni in a first codebook Ci, codebook indices ki and ^¾ in a second codebook C2_,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

a deriving unit, configured to derive a first precoder determined based on the rank indication and the indices nj, kj and ^received by the receiving unit; and

a precoding unit, configured to precode the data to be sent to the user equipment by the first precoder derived by the deriving unit;and a sending unit, configured to send the data precoded by the precoding unit 2003 to the user equipment. the deriving unit comprising:

a first deriving module, configured to derive a second precoder representing a wideband precoder determined by the indices nj and kj ;and

a second deriving module, configured to a third precoder representing a subband precoder determined by the indices m and fo. the first deriving module comprising:

a first determining submodule, configured to determine the matrix by the index n i in the codebook _/

a second determining submodule, configured to determine the matrix W^²⁾ by the index kj in the codebook _2, and

a fourth determining submodule, configured to determine the matrix by the index in the codebook C_/;

a fifth determining submodule, configured to determine the matrix W^²⁾ by the index in the codebook C_2;and

a sixth determining submodule, configured to determine the third precoder

or,

the first deriving module comprising:

the first determining submodule, configured to determine the matrix W ²⁾ by the index kj in the codebook C_2, the second determining submodule, configured to determine the matrix by the index ni in the codebook _/ the third determining submodule, configured to determine the second precoder W_t as W, = W<²⁾ Wj ; the second deriving module comprising:

the fourth determining submodule, configured to determine the matrix W^²⁾ by the index in the codebook _2,

the fifth determining submodule, configured to determine the matrix by the index ni in the codebook Ci_:

sixth determining submodule, configured to determine the third precoder W₂ as w, = w,⁽²⁾w ^} .

All functional units in the embodiments of the present invention may be integrated into a processing module, or exist independently, or two or more of such units are integrated into a module. The integrated module may be hardware or a software module. When being implemented as a software module and sold or applied as an independent product, the integrated module may also be stored in a computer-readable storage medium.

The storage medium may be a Read-Only Memory (ROM), magnetic disk or Compact Disk (CD).

Elaborated above are a media content transmission method and a network-side equipment under the present invention. Although the invention is described through some exemplary embodiments, the invention is not limited to such embodiments. It is apparent that those skilled in the art can make modifications and variations to the invention without departing from the scope of the invention. The invention is intended to cover the modifications and variations provided that they fall in the scope of protection defined by the following claims or their equivalents.

Claims

Claims What is claimed is:

1.A method for cprecoding in a wireless communication system, comprising: obtaining, by a receiver, a reference signal from a transmitter; deriving, by the receiver, a rank indication, a codebook index nj in a first codebook Cj ,codebook indices kj and in a second codebook C _,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the obtained reference signal;

sending, by the receiver, the rank indication, the codebook index ni in the first codebook Ci, the codebook indices kj and &2 in the second codebook C2_,, the wideband CQTi and the subband CQT₂, to the transmitter; and

receiving, by the receiver, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices nj, &/ and &2.

2. The method according to claim 1, wherein the first precoder determined by the transmitter based on the rank indication and the indices nj, ki and comprises:

the first precoder determined by the transmitter based on the rank indication, a second precoder and a third precoder, in which the second precoder is determined by the indices ni and kj at the transmitter, which represents a wideband precoder,and the third precoder is determined by the indices nj and &2 at the transmitter ,which represents a subband precoder.

3. The method according to claim 2, wherein the second precoder is determined by the indices nj and kj at the transmitter comprises: the second precoder W_j is determined as W_x = W^W^ ,in which the represents the matrix determined by the index ni in the codebook Cj ,and the W^²⁾ represents the matrix determined by the index kj in the codebook C2_,

the third precoder is determined by the indices n 1 and &2 at the transmitter comprises: the third precoder W₂ is determined as W₂ = W„ ⁾ , in which the represents the matrix determined by the index ni in the codebook Ci _, ,and the W ²⁾ represents the matrix determined by the index k2 in the codebook C2.

4.The method according to claim 3, wherein the W ²⁾ is the identity matrix or a block matrix composed of identity matrices of smaller dimension.

5. The method according to claim 2, wherein the second precoder is determined by the indices nj and kj at the transmitter comprises: the second precoder W_j is determined as W_j = W^²⁾ ,in which the W ²⁾ represents the matrix determined by the index kj in the codebook C2 ,and the W„⁽¹⁾ represents the matrix determined by the index ni in the codebook Ci_:

the third precoder is determined by the indices n1 and £₂ at the transmitter comprises: the third precoder W₂ is determined as W₂ = W^W^ ,in which the W^²⁾ represents the matrix determined by the index &₂ in the codebook C2 ,and the W_n ⁽¹⁾ represents the matrix determined by the index ni in the codebook Cj .

6. The method according to claim 2, wherein the receiver deriving a wideband channel quality indication CQIi comprises:

the receiver calculating the wideband channel quality indication CQIi based on that the second precoder is to be determined by the indices ni and ki at the transmitter;and

the receiver deriving a subband channel quality indication CQI₂ comprises: the receiver calculating the subband channel quality indication CQI₂ based on that the third precoder is to be determined by the indices n1 and &₂ at the transmitter.

7. The method according to claim 1, wherein:

the codebook C₂ and codebook Ci are derived by both the transmitter and by the receiver.

8. The method according to claim 1, wherein the receiver sending the codebook index ni in a first codebook Ci, the codebook indices kj and &₂ in a second codebook C2 to the ransmitter comprises:

the receiver sends the indices ni and kj in a first report, and the index &₂ in a second report, to the transmitter.

9. A user equipment, comprising:

a obtaining unit, configured to obtain a reference signal from a transmitter; a deriving unit, configured to derive a rank indication, a codebook index « _/ in a first codebook C; and codebook indices kj and ¾ in a second codebook C2_,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the reference signal obtained by the obtaining unit;

a sending unit, configured to send the rank indication, the codebook index ni in the first codebook Ci, the codebook indices kj and ^¾ in the second codebook C2_,, the wideband CQIi and the subband CQI₂ derived by the deriving unit, to the transmitter; and

a receiving unit, configured to receive, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices nj, kj and &₂ ·

10. A transmitter, comprising:

a receiving unit, configured to receive a rank indication, a codebook index ni in a first codebook Cj, codebook indices kj and k2 in a second codebook C2_,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

11. The transmitter according to claim 10, wherein the deriving unit comprising: a first deriving module, configured to derive a second precoder representing a wideband precoder determined by the indices nj and kj ;and

a second deriving module, configured to a third precoder representing a subband precoder determined by the indices ni and fe.

12. The transmitter according to claim 11, wherein the first deriving module comprising:

a second determining submodule, configured to determine the matrix W^²⁾ by the index kj in the codebook C₂ and

a third determining submodule, configured to determine the second precoder

the second deriving module comprising:

a fourth determining submodule, configured to determine the matrix by the index n 1 in the codebook Ci_:

a fifth determining submodule, configured to determine the matrix w ²⁾ by the index &₂ in the codebook C2 and

a sixth determining submodule, configured to determine the third precoder

13. The transmitter according to claim 11 , wherein

the first deriving module comprising:

the first determining submodule, configured to determine the matrix W ² by the index kj in the codebook C_2,

the second determining submodule, configured to determine the matrix by the index n 1 in the codebook Cj_; the third determining submodule, configured to determine the second precoder W_t as W_t = W^W^ ; the second deriving module comprising:

the fourth determining submodule, configured to determine the matrix W^²⁾ by the index Λ¾ in the codebook C_2, the fifth determining submodule, configured to determine the matrix

⁾ by the index n j in the codebook C sixth determining submodule, configured to determine the third precoder

14. The transmitter according to any one of claims 10 to 13,whcrcin the transmitter is a base station.

15. A method for precoding in a wireless communication system, comprising:

receiving , by a transmitter ,a rank indication, a codebook index ni in a first codebook Ci, codebook indices kj and &₂ in a second codebook C₂,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

16. The method according to claim 15, wherein the transmitter deriving a first precoder determined based on the rank indication and the indices nj, kj and received by the transmitter, comprising:

deriving, the transmitter, the first precoder determined based on the rank indication ,a second precoder and a third precoder, in which the second precoder is determined by the indices ni and k/ at the transmitter, which represents a wideband precoder,and the third precoder is determined by the indices nj and at the transmitter ,which represents a subband precoder.

17. The method according to claim 16,wherein the second precoder is determined by the indices nj and kj at the transmitter comprises: the second precoder W_j is determined as W, = W^W^ ,in which the represents the matrix determined by the index ni in the codebook Cj ,and the W ²⁾ represents the matrix determined by the index kj in the codebook C_2, the third precoder is determined by the indices nj and &2 at the transmitter comprises: the third precoder W₂ is determined as W₂ = W^W^ , in which the represents the matrix determined by the index nj in the codebook Cj , ,and the W ²⁾ represents the matrix determined by the index &2 in the codebook C2.

18. The method according to claim 16, wherein the second precoder is determined by the indices ni and kj at the transmitter comprises: the second precoder W_l is determined as W_l = W^W^ ,in which the W ²⁾ represents the matrix determined by the index kj in the codebook C2 ,and the W_n ⁽¹⁾ represents the matrix determined by the index n 1 in the codebook Ci_:

the third precoder is determined by the indices n 1 and &2 at the transmitter comprises: the third precoder W₂ is determined as W₂ = W^²⁾W_n ⁽¹⁾ ,in which the W^²⁾ represents the matrix determined by the index &2 in the codebook C2 ,and the

represents the matrix determined by the index n 1 in the codebook Cy.

19. A system for precoding , comprising:

a transmitter according to any one of claims 10 to 13 and a user equipment according to claim 9.

20. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to obtain a reference signal from a transmitter;

code for causing at least one computer to derive a rank indication, a codebook index nj in a first codebook Cj and codebook indices kj and Λ¾ in a second codebook C2_,, a wideband channel quality indicator CQIi and a subband channel quality indicator CQI₂, based on the reference signal;

code for causing at least one computer to send the rank indication, the codebook index ni in the first codebook Ci, the codebook indices kj and &2 in the second codebook C2_,, the wideband CQIi and the subband CQ1₂ to the transmitter; and code for causing at least one computer to receive, from the transmitter, the data precoded by a first precoder determined by the transmitter based on the rank indication and the indices nj, kj and k2_.21. A computer program product, comprising:

a computer-readable medium comprising:

code for causing at least one computer to receive a rank indication, a codebook index ni in a first codebook Ci, codebook indices kj and &2 in a second codebook C2_,, the wideband channel quality indicator CQIi and the subband channel quality indicator CQI₂ from a user equipment;

code for causing at least one computer to derive a first precoder determined based on the rank indication and the indices nj, kj and received;

code for causing at least one computer to precode the data to be sent to the user equipment by the first precoder derived; and

code for causing at least one computer to send the data precoded to the user equipment.