USOO9083411 B2
`
`(12) United States Patent
`Li et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9,083,411 B2
`Jul. 14, 2015
`
`(54) DEVICE AND METHOD OF CHANNEL
`INFORMATION FEEDBACK FOR
`MULT-CELL MIMO
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`(75) Inventors: Dong Li, Shanghai (CN); Hao Liu,
`Shanghai (CN); Hongwei Yang,
`Shanghai (CN); Yang Song, Shanghai
`(CN)
`(73) Assignee: Alcatel Lucent, Boulogne-Billancourt
`(FR)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 301 days.
`
`(*) Notice:
`
`(21) Appl. No.:
`
`13/521,901
`
`(22) PCT Filed:
`
`Jan. 13, 2010
`
`(86). PCT No.:
`S371 (c)(1)
`(2), (4) Date:
`
`PCT/CN2010/000057
`
`Jul. 12, 2012
`
`(87) PCT Pub. No.: WO2011/085516
`PCT Pub. Date: Jul. 21, 2011
`
`(65)
`
`Prior Publication Data
`US 2012/O289275A1
`Nov. 15, 2012
`(51) Int. Cl.
`H04B I7/00
`H04B 7/06
`H04B 7/02
`(52) U.S. Cl.
`CPC .............. H04B 7/0632 (2013.01); H04B 7/024
`(2013.01); H04B 70626 (2013.01)
`(58) Field of Classification Search
`O
`See application file for complete search history.
`
`(2006.01)
`(2006.01)
`(200 6. 01)
`
`2007/0174038 A1* 7/2007 Wang et al. ....................... TO4f1
`2009/0010215 A1
`1/2009 Kim et al.
`2010.0002607 A1
`1/2010 Kim et al.
`2010.003414.6 A1
`2/2010 Hou et al. ..................... 370,328
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`CN
`CN
`
`6, 2008
`101.207896. A
`2, 2009
`101373998 A
`(Continued)
`OTHER PUBLICATIONS
`
`International Search Report for PCT/CN2010/000057 dated Oct. 21,
`2010.
`
`(Continued)
`
`Primary Examiner — Nay A Maung
`Assistant Examiner — Alejandro Rivero
`(74) Attorney, Agent, or Firm — Fay Sharpe LLP
`
`ABSTRACT
`(57)
`A mobile terminal is provided in the present invention, com
`prising: a channel state information feedback calculating unit
`configured to calculate a channel state information feedback
`between the mobile terminal and a serving cell of the mobile
`terminal and those between the mobile terminal and all coop
`erating cells; a channel quality information feedback calcu
`lating unit configured to calculate a channel quality informa
`tion feedback for the serving cell of the mobile terminal; and
`a transmission unit configured to transmit the channel state
`information feedbacks and the channel quality information
`feedback to the serving cell. The present invention greatl
`9.
`p
`greauly
`improves the performance of a LTE-A System and greatly
`reduces feedback overhead. The present invention is a scal
`able feedback solution and may be flexibly applied to various
`coordinated multipoint transmission scenarios.
`9 Claims, 4 Drawing Sheets
`
`S3)
`
`S32
`
`S34
`
`KA sun Y
`Y-- /
`
`.
`. . . .
`Calculating per-cell CDF feedback
`—
`
`Calculating inter-cell relative
`amplitude feedbacks and relative
`phase feedbacks
`
`w
`
`-----
`
`S38
`
`Calculating Colfeedback
`corresponding to a serving cel
`
`S38
`
`S43
`
`Feeding back the calculated channel
`information to the serving cell
`
`C Ed
`
`LG Elecs. Ex. 1023
`LG Elecs. v. Pantech Corp.
`IPR2023-01273 Page 1
`
`

`

`US 9,083,411 B2
`Page 2
`
`(56)
`
`References Cited
`
`OTHER PUBLICATIONS
`
`U.S. PATENT DOCUMENTS
`
`2010/0220601 A1* 9, 2010 Vermani et al. ...........
`2011/0206106 A1* 8, 2011 Mallik et al. ..............
`
`3793.
`
`FOREIGN PATENT DOCUMENTS
`
`101453.259 A
`CN
`2182663 A1
`EP
`WO WO 2010/017482 A1
`
`6, 2009
`5, 2010
`2, 2010
`
`“Investigation on Quantization Scheme of Explicit Spatial Channel
`Feedback for CoMP Joint Transmission in LTE-Advanced iGPP
`TSG RAN WG1 Meeting #58bis, R1-094244, Miyazaki, Japan, Oct.
`12-16, 2009, pp. 1-8.
`Song Yang, et al., “ . . . MIMO. . . .” Modern Science & Technology
`of Telecommunications, Dec. 12, 2005, pp. 31-35.
`Chang Yongyu, et al., “ .
`. . MIMO . .
`. .” Modern Science &
`Technology of Telecommunications, Jul. 2006, pp. 50-53.
`* cited by examiner
`
`IPR2023-01273 Page 2
`
`

`

`U.S. Patent
`
`Jul. 14, 2015
`
`Sheet 1 of 4
`
`US 9,083,411 B2
`
`ro
`
`?,Ž
`
`
`
`?uuntuneinaleoxocopao, iso |
`
`
`
`
`
`
`
`
`
`IPR2023-01273 Page 3
`
`

`

`U.S. Patent
`
`Jul. 14, 2015
`
`Sheet 2 of 4
`
`US 9,083,411 B2
`
`-----
`
`-----
`
`24
`
`Coordinated
`multipoint
`pre-coding and
`transmitting unit
`
`23
`
`Coordinated
`multipoint pre-coder
`calculating unit
`
`User scheduling
`I and transmission
`format determining
`unit
`
`21
`
`--------.
`
`SINR calculating
`unit
`
`Transmission unit
`-
`
`Fig. 2
`
`IPR2023-01273 Page 4
`
`

`

`U.S. Patent
`
`Jul. 14, 2015
`
`Sheet 3 of 4
`
`US 9,083,411 B2
`
`S30
`
`/ XX-SW
`
`S.
`
`Start /
`Y- --------------X /
`T
`
`S32
`
`Calculating per-cell CDI feedback
`
`S34
`
`Calculating inter-cell relative
`amplitude feedbacks and relative
`
`S36
`
`Calculating CQI feedback
`Corresponding to a serving cell
`
`S38
`
`Feeding back the calculated channel
`information to the serving cell
`
`S40
`
`( End )
`
`Fig. 3
`
`IPR2023-01273 Page 5
`
`

`

`U.S. Patent
`
`Jul. 14, 2015
`
`Sheet 4 of 4
`
`US 9,083,411 B2
`
`Base station 1
`
`
`
`Base station 2
`
`IPR2023-01273 Page 6
`
`

`

`US 9,083,411 B2
`
`1.
`DEVICE AND METHOD OF CHANNEL
`INFORMATION FEEDBACK FOR
`MULTI-CELL MIMO
`
`10
`
`15
`
`FIELD OF THE INVENTION
`
`The present invention relates to the wireless communica
`tion field, and more particularly to a device and method of
`channel information feedback for multi-cell MIMO.
`
`BACKGROUND OF THE INVENTION
`
`Up to now, for 3GPP LTE-A systems, channel feedback
`mechanisms for support of Downlink Coordinated Multi
`Point (DL CoMP) are still under discussion and formulation.
`The existing solutions for channel feedback to enable the
`Downlink Coordinated Multi-Point transmission include: 1)
`Precoding Matrix Index (PMI) feedback; 2) Uplink (UL)
`Sounding feedback; and 3) physical channel matrix feedback.
`The above feedback methods, however, have the following
`defects:
`1) PMI feedback is more efficient in single Base Station
`(BS) transmission modes. However, in multi-cell transmis
`sion, the PMI feedback may largely limit the freedom of
`precoding operation of involved multiple cells.
`2) UL sounding feedback is more efficient in Time Divi
`sion Duplex (TDD) mode, but it is difficult to be applied in
`Frequency Division Duplex (FDD) mode. Additionally,
`asymmetric interference distribution among Downlink (DL)
`and Uplink (UL) will damage the accuracy of channel infor
`mation estimation;
`3) Physical channel matrix feedback will lead to too large
`feedback overhead. For example, the feedback solutions as
`described by NTT DoCoMo in Proposal R1-094244 in 3GPP
`RAN WG1 #58 bits meeting, no matter the channel vector
`quantization based method (case 1) or the channel element
`quantization based method (case 2), will lead to a large feed
`back overhead (e.g., up to 26.6 bits/subband/cell in case 1 and
`up to 53.3 bits/subband/cell in case 2), which may be unac
`ceptable in practical systems.
`
`25
`
`30
`
`35
`
`40
`
`SUMMARY OF THE INVENTION
`
`In order to solve the above problems, a solution of Channel
`State Information (CSI) Channel Quality Information (CQI)
`feedback for support of Downlink Coordinated Multi-Point
`(DL CoMP) is proposed in the present invention. Specifically,
`the present invention provides a CSI feedback solution for
`support of DL CoMP and an associated CQI feedback solu
`tion, and the two solutions together form a whole channel
`information feedback solution for support of CoMP.
`The main ideas of the present invention are as follows:
`1) The CSI feedback consists of Channel Vector Quantiza
`tion (CVO) based per-cell Channel Directional Information
`(CDI) feedback and scalar quantization based inter-cell rela
`tive phase and/or amplitude feedbacks. The accuracy for the
`CDI feedback can be enhanced by transforming by a channel
`covariance matrix the codebook based on which the CVO is
`performed.
`2) The CQI feedback only corresponds to a serving cell and
`denotes the ratio of the signal power received from the serving
`cell and the noise plus interference power from cells out of the
`cooperating cell set. Here, the CQI feedback indicates a spe
`cific value of power ratio, and the final expected value of
`post-detection Signal to Interference plus Noise Ratio (SINR)
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`may be derived by the base station from the COI feedback and
`inter-cell relative amplitude feedbacks depending on the
`transmission mode applied.
`According to one aspect of the present invention, a mobile
`terminal is provided, including: a channel State information
`feedback calculating unit configured to calculate a channel
`state information feedback between the mobile terminal and
`a serving cell of the mobile terminal and those between the
`mobile terminal and all cooperating cells; a channel quality
`information feedback calculating unit configured to calculate
`a channel quality information feedback for the serving cell of
`the mobile terminal; and a transmission unit configured to
`transmit the channel state information feedbacks and the
`channel quality information feedback to the serving cell.
`Preferably, the channel state information feedback
`includes a channel vector quantization based per-cell channel
`directional information feedback and Scalar quantization
`based inter-cell relative phase and/or amplitude feedbacks,
`and the channel State information feedback calculating unit
`includes: a channel directional information feedback calcu
`lating unit configured to calculate the channel vector quanti
`zation based per-cell channel directional information feed
`back; and a relative amplitude and/or phase feedback
`calculating unit configured to calculate the scalar quantiza
`tion based inter-cell relative phase and/or amplitude feed
`backs.
`Preferably, the relative amplitude and/or phase feedback
`calculating unit includes at least one of a relative amplitude
`feedback calculating Subunit configured to calculate scalar
`quantization based inter-cell relative amplitude feedbacks;
`and a relative phase feedback calculating subunit configured
`to calculate Scalar quantization based inter-cell relative phase
`feedbacks.
`Preferably, the channel directional information feedback
`calculating unit transforms, by a channel covariance matrix, a
`codebook based on which the channel vector quantization is
`performed.
`According to another aspect of the present invention, a base
`station is provided, including: a transmission unit configured
`to receive from a mobile terminal a channel state information
`feedback between the mobile terminal and a serving cell of
`the mobile terminal and those between the mobile terminal
`and all cooperating cells, as well as a channel quality infor
`mation feedback for the serving cell of the mobile terminal; a
`Signal to Interference plus Noise Ratio calculating unit con
`figured to calculate an expected post-detection Signal to
`Interference plus Noise Ratio based on the channel state
`information feedbacks and the channel quality information
`feedback received by the transmission unit, depending on a
`transmission mode applied; a user scheduling and transmis
`sion format determining unit configured to perform user
`scheduling and transmission format determination based on
`the post-detection Signal to Interference plus Noise Ratio; a
`coordinated multipoint pre-coder calculating unit configured
`to calculate a coordinated multipoint pre-coding matrix based
`on a channel state information feedback between a scheduled
`mobile terminal and a serving cell of the scheduled mobile
`terminal and those between the scheduled mobile terminal
`and all cooperating cells; and a coordinated multipoint pre
`coding and transmitting unit configured to perform a corre
`sponding pre-coding processing on user data and transmit the
`user data based on the coordinated multipoint pre-coding
`matrix calculated by the coordinated multipoint pre-coder
`calculating unit.
`Preferably, the transmission format determination includes
`modulation and coding scheme determination.
`
`IPR2023-01273 Page 7
`
`

`

`US 9,083,411 B2
`
`3
`Preferably, a Zero-Forcing algorithm or a Block-Diagonal
`ization algorithm is used to implement the calculation of the
`coordinated multipoint pre-coder calculating unit.
`According to a further aspect of the present invention, a
`channel information feedback method is provided, including:
`calculating a channel State information feedback between a
`mobile terminal and a serving cell of the mobile terminal and
`those between the mobile terminal and all cooperating cells;
`calculating a channel quality information feedback for the
`serving cell of the mobile terminal; and transmitting the chan
`nel state information feedbacks and the channel quality infor
`mation feedback to the serving cell.
`Preferably, the channel state information feedback
`includes a channel vector quantization based per-cell channel
`directional information feedback and scalar quantization
`based inter-cell relative phase and/or amplitude feedbacks.
`Preferably, a codebook based on which the channel vector
`quantization is performed is transformed by a channel cova
`riance matrix when calculating a channel directional infor
`mation feedback, so as to improve the accuracy of the code
`book based vector quantization.
`According to still a further aspect of the present invention,
`a communication system is provided, including the mobile
`terminal and the base station described above.
`The present invention may greatly improve the perfor
`mance of the LTE-A System, and has the following advan
`tages:
`1) The vector quantization based per-cell CDI feedback
`and the scalar quantization based inter-cell relative phase and
`amplitude feedbacks may greatly reduce the feedback over
`head.
`2) A user only needs to feedback the CQI related to the
`serving cell and the base station can derive the CQIs of other
`cooperating cells according to the inter-cell CSI feedbacks,
`thereby further reducing the feedback overhead.
`3) The present invention is a scalable feedback solution and
`may be flexibly applied to various CoMP transmission sce
`narios.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and other features of the present invention will
`become more apparent from the following detailed descrip
`tion in connection with the accompanying drawings, in which
`FIG. 1 is a block diagram illustrating a mobile terminal
`according to an embodiment of the present invention;
`FIG. 2 is a block diagram illustrating a base station accord
`ing to an embodiment of the present invention;
`FIG. 3 is a flowchart illustrating a channel information
`feedback method performed by a mobile terminal according
`to an embodiment of the present invention; and
`FIG. 4 is an illustrative communication system including
`the mobile terminal and the base station according to the
`present invention.
`
`DETAILED DESCRIPTION OF EMBODIMENTS
`
`The principle and implementation of the present invention
`become more apparent by making references to the following
`description of specific embodiments of the present invention
`in conjunction with the accompanying drawings. It should be
`noted that the present invention shall not be restricted to the
`specific embodiments described below. In addition, for sake
`of conciseness, well known components directly related to
`the present invention are not shown in the accompanying
`drawings.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`4
`FIG. 1 is a block diagram illustrating a mobile terminal
`according to an embodiment of the present invention. In FIG.
`1, the mobile terminal 1 includes a CSI feedback calculating
`unit 10, a COI feedback calculating unit 11 and a transmission
`unit 12. The CSI feedback calculating unit 10 includes a CDI
`feedback calculating unit 110 and a relative amplitude/phase
`feedback calculating unit 120, and the relative amplitude/
`phase feedback calculating unit 120 further includes a relative
`amplitude feedback calculating subunit 120-1 and a relative
`phase feedback calculating subunit 120-2. In operation, the
`CSI feedback calculating unit 10 and the CQI feedback cal
`culating unit 11 respectively calculate the CSI feedback and
`the CQI feedback, and transmit the calculated CSI feedback
`and CQI feedback to the transmission unit 12, which in turn
`transmit them to the serving cell. In the following, respective
`components of the mobile terminal 1 will be described in
`detail.
`The CSI feedback calculating unit 10 includes a CDI feed
`back calculating unit 110 and a relative amplitude/phase feed
`back calculating unit 120 respectively configured to calculate
`a vector quantization based per-cell CDI feedback and scalar
`quantization based inter-cell relative phase and/or amplitude
`feedbacks. In the following, the channel between cellieS and
`the user is denoted as HeC''', where S denotes the cooper
`ating cell index set with size of ISI (i.e., the number of cells in
`the cooperating cell set), and CY' denotes NxM complex
`signal space, while M and N respectively indicate the number
`of antennas at the base station and the user terminal. Without
`loss of generality, it is assumed that the serving cell for the
`user has an index of kandall cooperating cells have the same
`number of transmit antennas.
`The specific operation on how the CDT feedback calculat
`ing unit 110 calculates the per-cell CDI feedbacks for all
`channels from all cooperating cells to the user is described as
`below. In this example, the per-cell CDI feedback is based on
`the vector quantization depending on a codebook. The code
`book is denoted as V-V, V,..., V}, where VeC'''
`represents the codewords with unit norm. Thus the number of
`bits required to index the codewords within the codebook
`may be expressed as log.", where L is the number of the
`codewords within the codebook. C''' denotes Mx1 complex
`signal space.
`Firstly, the CDI feedback calculating unit 110 calculates a
`receiving vector W. An example of the receiving vector is the
`left dominant singular vector of the channel associated with
`the serving cell as follows:
`
`SD
`
`Hi Fit ... unX V1 ...
`
`where u, for i=1,..., N and v, for i=1,..., M. denote left
`singular vectors and right singular vectors, respectively. The
`matrix X is a diagonal matrix with singular values in descend
`ing order. Generally, it is assumed that the number of data
`streams for peruser is one. In this case, the receiving combing
`vector may be
`
`60
`
`65
`
`Then, the CDI feedback calculating unit 110 calculates the
`equivalent channels hieS. Considering the receiving com
`bining operation by the vector W, the equivalent channels
`between the cooperating cells ieS and the user can be
`expressed as h, WHeC''.
`Thereafter, the CDI feedback calculating unit 110 per
`forms vector quantization for all the equivalent channels
`based on the codebook. Specifically speaking, the CDI feed
`
`IPR2023-01273 Page 8
`
`

`

`5
`back calculating unit 110 searches the codebook for a code
`word that is closest to the normalized equivalent channel to be
`quantized:
`
`fi, = argmindh, V.), ie S
`Vigev;
`
`(1)
`
`where and h,'h'/h,II and d(h,', V.) denotes a distortion
`measure between the normalized equivalent channel (to be
`quantized) and the codeword V. For example, a most popu
`lar distortion measure is Euclidean distance metric, defined as
`follows:
`
`10
`
`15
`
`Under the Euclidean distance metric, it can be derived that
`Equation (1) is equivalent to
`
`US 9,083,411 B2
`
`6
`Secondly, phases of all non-serving cells against the serv
`ing cell are calculated as
`6-0-0, mod 21, ieSk,
`where the set S \ k represents a set of indexes of the
`cooperating cells other than the index k of the serving cell. It
`is to be noted that the mode 2 L operation is performed to
`assure that the angle falls within the range of I-7C, JL).
`Thirdly, Scalar quantization is performed on the obtained
`relative phases to obtain the indexes to be fed back:
`
`0; = argmin:10 - 0}, i e S \k
`epeG
`
`where 0–0, 0, ... 0-denotes the codebook for scalar
`quantization of relative phases. Assuming the relative phases
`are distributed evenly within the range of I-71, t), the code
`book for the scalar quantization may be designed as:
`
`Vigev;
`
`Al, where A =
`, 7t-A, where - p.
`
`Peienents
`
`Finally, the CDI feedback calculating unit 110 provides the
`calculated CDI feedback to the transmission unit 12 so as to
`feed the index of the equivalent channel quantization back to
`its serving cell (i.e., cell k in the assumptions) via the trans
`mission unit 12.
`Optionally, accuracy of the codebook based vector quan
`tization may be improved by transformation of the codebook
`using a cell-specific covariance matrix, as follows:
`
`25
`
`30
`
`The relative phase feedback calculating subunit 120-2 cal
`culates relative amplitude information of the equivalent chan
`nel h, the serving-cell channel h.
`In particular, firstly, magnitudes of the equivalent channels
`after being projected onto its vector quantization ion version
`are calculated as
`
`, l = 1, ...
`
`35
`
`Secondly, relative amplitudes of all non-serving cells
`against the serving cell are calculated as
`
`In this case, the equation (2) may be replaced with the
`following:
`
`40
`
`W
`A
`
`Alif Ak.
`Ak f Ai,
`
`f Ai < Ak
`f Aks Ai
`
`i e SVk.
`
`i-aging (vii)
`
`45
`
`However, the per-cell CDI feedback only involves direc
`tional information of the equivalent channels but lacks of
`amplitude and/or phase information, which, however, is nec
`essary for multi-cell coordinated precoding operations. Thus,
`the specific operation that the relative amplitude/phase feed
`back calculating unit 120 calculates the fed back amplitude/
`phase information is described as below. In the present inven
`tion, in order to save feedback overhead, only the relative
`values of the phase and amplitude of the equivalent channels
`of the non-serving cooperating cells relative to that of the
`serving cell are calculated.
`The relative amplitude feedback calculating subunit 120-1
`calculates relative phase information of the equivalent chan
`nel h, against the serving-cell channel h.
`In particular, firstly, missed phases in the quantization of
`the equivalent channels are calculated as
`0-angle(h,h).ieS
`where function angle( ) returns the phase of the input
`complex value in the range of I-71, t).
`
`50
`
`55
`
`60
`
`65
`
`It is to be noted that the relative amplitudes are constrained
`to (0, 1 depending on the relationship between A, and A.
`which will facilitate Subsequent Scalar quantization.
`Thirdly, Scalar quantization is performed on the obtained
`relative amplitudes to obtain the indexes to be fed back:
`
`A, argminA, A}
`Age A
`
`where A-A A2 ... A denotes the codebook for scalar
`quantization of relative amplitudes. It is to be noted that one
`bit indicating the relationship between A, and A (e.g. 0 for
`A.<A and 1 otherwise) shall be fed back together with the
`index of A, such that the base station can clearly reconstruct
`the relationship between different amplitudes of the equiva
`lent channels. Assuming that the relative amplitudes are dis
`tributed evenly within the range of (0, 1, the codebook for the
`Scalar quantization may be designed as:
`
`O elements
`
`IPR2023-01273 Page 9
`
`

`

`US 9,083,411 B2
`
`5
`
`10
`
`15
`
`7
`Finally, the relative amplitude/phase feedback calculating
`unit 120 provides the calculated relative amplitude feedbacks
`and relative phase feedbacks to the transmission unit 12 so as
`to feed them back to the serving cell (i.e., cell kin the assump
`tions) via the transmission unit 12.
`In practical systems, COI feedback is required to imple
`ment the channel-dependent user scheduling and transmis
`sion format determination (e.g., the modulation and coding
`scheme). Thus, an efficient COI feedback solution is very
`important for system operations. In the traditional systems, a
`CQI feedback is nothing but a direct indicator for the recom
`mended modulation and coding scheme. This COI feedback
`is called as implicit CQI feedback in this application docu
`ment. Implicit CQI feedback is an efficient scheme for single
`cell operations, especially for Single User MIMO (SU
`MIMO). However, for multi-cell transmissions, it is difficult
`or even impossible for the implicit CQI feedback to feedback
`the recommended modulation and coding scheme itself.
`Instead, in Such a case, it is more convenient to feedback a
`specific value, based on which the base station can calculate
`the final channel quality for each involved user. This method
`is called as explicit CQI feedback in this application docu
`ment.
`The CQI feedback calculating unit 11 is an explicit CQI
`feedback calculating unit for multi-cell MIMO transmis
`sions. The COI feedback calculating unit 11 operates in con
`junction with the CSI feedback calculating unit 10 described
`above such that the inter-cell relative amplitude feedbacks
`may be shared between CSI feedback and CQI feedback.
`Thus, the mobile terminal only needs to feedback the CQI
`related to the serving cell as follows:
`
`W
`y; =
`
`for Ai < Ak
`
`2
`5 Ai,
`M2
`5 f A, for Ai as Ak
`
`i e SVk.
`
`Then, based on the obtained CQI values of the user asso
`ciated with all the cooperating cells, the SINR calculating unit
`20 may calculate the expected post-detection Signal to Inter
`ference plus Noise Ratio (SINR) depending on the transmis
`sion mode applied. Based on the calculated post-detection
`SINR, the userscheduling and transmission format determin
`ing unit 21 performs the user scheduling and transmission
`format determination (e.g., modulation and coding scheme
`determination).
`The coordinated multipoint pre-coder calculating unit 23
`calculates a coordinated multipoint pre-coding matrix based
`on a channel state information feedback between a scheduled
`user and a serving cell of the scheduled user and those
`between the scheduled user and all cooperating cells. In the
`calculation of the coordinated multipoint pre-coder, different
`downlink coordinated multipoint transmission modes need
`different channel state information feedbacks. Specifically,
`the coordinated multipoint Scheduling/beam forming trans
`mission mode only needs the codebook based per-cell chan
`nel directional feedback; the coordinated multipoint joint
`transmission mode based on per-cell local pre-coding needs
`inter-cell relative phase information in addition to the code
`book based per-cell channel directional feedback information
`to enhance the transmission performance; for the coordinated
`multipoint joint transmission mode based on multi-cell global
`pre-coding, both the codebook based per-cell channel direc
`tional feedback information and the inter-cell relative phase
`and amplitude information are needed. The calculation of the
`coordinated multipoint pre-coder may beachieved based on a
`Zero-Forcing algorithm or a Block-Diagonalization algo
`rithm.
`Thereafter, the coordinated multipoint pre-coding and
`transmitting unit 24 performs a corresponding pre-coding
`processing on user databased on the coordinated multipoint
`pre-coding matrix calculated by the coordinated multipoint
`pre-coder calculating unit 23, and then transmits the pre
`coded user data.
`FIG. 3 is a flowchart illustrating a channel information
`feedback method performed by a mobile terminal according
`to an embodiment of the present invention. The method starts
`at Step S30. At Step S32, the Channel Vector Quantization
`(CVO) based per-cell Channel Directional Information (CDI)
`feedback is calculated. At Step S34, the scalar quantization
`based inter-cell relative amplitude and/or phase feedbacks are
`calculated. At Step S36, the CQI feedback corresponding to a
`serving cell is calculated. At Step S38, the calculated channel
`information is fed back to the serving cell. Finally, the method
`ends at Step S40.
`FIG. 4 is an illustrative communication system including
`the mobile terminal and the base station according to the
`present invention. The communication system includes
`Mobile Terminals MS1 and MS2 and Base Station 1 and Base
`Station 2. For example, Mobile Terminals MS1 and MS2 may
`be the mobile terminal of the present invention as shown in
`FIG. 1, and Base Station 1 and Base Station 2 may be the base
`station of the present invention as shown in FIG. 2. In FIG.4,
`Mobile Terminals MS1 and MS2 respectively transmit
`respective downlink coordinated multipoint CSI and CQI
`feedbacks to respective serving cell, and Base Station 1 and
`Base Station 2 calculate the post-detection SINR based on the
`
`25
`
`30
`
`HT
`
`A ||h ||
`* - P - P.
`
`ise
`
`F.
`
`It is to be noted that the CQI feedback can be based on
`Scalar quantization, as follows:
`
`3 = argmind (5, y)}
`yge T
`
`35
`
`40
`
`45
`
`50
`
`where T-Y y . . . Y. denotes the codebook for the CQI
`scalar quantization, and d(e. Y) denotes the distortion mea
`sure. Finally, the CQI feedback calculating unit 11 provides
`the calculated CQI feedback to the transmission unit 12 so as
`to feed it back to the serving cell (i.e., cell k in the assump
`tions) via the transmission unit 12.
`FIG. 2 is a block diagram illustrating a base station accord
`ing to an embodiment of the present invention. In FIG. 2, the
`base station 2 includes a transmission unit 22, a SINR calcu
`lating unit 20, a user Scheduling and transmission format
`determining unit 21, a coordinated multipoint pre-coder cal
`culating unit 23 and a coordinated multipoint pre-coding and
`transmitting unit 24. In a case that the COIs for non-serving
`cells are not fed back, the SINR calculating unit 20 in the base
`station firstly derives the CQI values corresponding to the
`non-serving cooperating cells based on the COI feedback of 65
`the serving cell and the inter-cell relative amplitude feed
`backs as follows:
`
`55
`
`60
`
`IPR2023-01273 Page 10
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`5
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`10
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`15
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`25
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`35
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`feedback information, and perform user scheduling and
`transmission format determination based on the SINR.
`Although the present invention has been illustrated above
`by making references to the preferred embodiments of the
`present invention, those skilled in the art will understand that
`various modifications, replacements and changes may be
`made on the present invention without departure from the
`spirit and scope of the present invention. Thus, the present
`invention shall be defined by the appended claims and their
`equivalents, rather than the embodiments described above.
`What is claimed is:
`1. A mobile terminal, comprising:
`a channel state information feedback calculating unit con
`figured to calculate channel state information feedback
`between the mobile terminal and a serving cell of the
`mobile terminal and between the mobile terminal and all
`cooperating cells;
`a channel quality information feedback calculating unit
`configured to calculate channel quality information
`feedback for the serving cell of the mobile terminal; and
`a transmission unit configured to transmit the channel state
`information feedback and the channel quality informa
`tion feedback to the serving cell,
`wherein the channel state information feedback includes
`a channel vector quantization-based per-cell channel
`directional information feedback and scalar quantiza
`tion-based inter-cell relative phase and amplitude
`feedback, and the channel state information feedback
`calculating unit comprises:
`a channel directional information feedback calculat
`ing unit configured to calculate the channel vector
`quantization-based per-cell channel directional
`information feedback; and
`a relative phase and amplitude feedback calculating
`unit configured to calculate the scalar quantization
`based inter-cell relative phase and amplitude feed
`back.
`2. The mobile terminal according to claim 1, wherein the
`relative phase and amplitude feedback calculating unit com
`prises at least one of
`40
`a relative amplitude feedback calculating subunit config
`ured to calculate Scalar quantization based inter-cell
`relative amplitude feedback; and
`a relative phase feedback calculating Subunit configured to
`calculate Scalar quantization based inter-cell relative
`phase feedback.
`3. The mobile terminal according to claim 1, wherein the
`channel directional information feedback calculating unit
`transforms, by a channel covariance matrix, a codebook
`based on which the channel vector quantization is performed.
`4. A base station, comprising:
`a transmission unit configured to receive from a mobile
`terminal channel state information feedback between
`the mobile terminal and a serving cell of the mobile
`terminal and between the mobile terminal and all coop
`erating cells, as well as a channel quality information
`feedback for the serving cell of the mobile terminal;
`a Signal to Interference plus Noise Ratio calculating unit
`configured to calculate an expected post-detection Sig
`nal to Interference plus Noise Ratio based on the channel
`st