Nova Patents
EP2437451B1

Method, user equipment and system for implementing coordinated multi-point transmission

Abstract

This record has no abstract on file.

EP2437451B1, drawing sheet 1
Sheet 1 of 43

Term

4.1 yearsleft in the term

Expires 15 November 2030.

  1. Priority
  2. Filed
  3. Granted
  4. Today
  5. Expires

7 claims: 3 independent, 4 dependent

  1. 1
    A method for implementing coordinated multi-point transmission, comprising:obtaining (101), at a user equipment, UE, phase differences between other coordinated cells and a current service cell by calculating channel cross-covariance matrixes over time between the current service cell and the other coordinated cells;feeding back (102) the phase differences, which are arguments of elements on the main diagonal of the cross-covariance matrixes, to corresponding base stations of the other coordinated cells, respectively, to implement phase compensation;receiving (103), by the UE, signals transmitted by the base stations of the coordinated cells after the phase compensation;wherein the other coordinated cells are cells among all coordinated cells other than the current service cell, and the channel cross-covariance matrixes between the current service cell and the other coordinated cells are calculated based on channel coefficients of the current service cell and channel coefficients of the other coordinated cells, such that each channel cross-covariance matrix R xy (f) between the current service cell and a cell among the other coordinated cells is : R xy f = H x f H H y f = R 11 R 12 R 13 R 14 R 21 R 22 R 23 R 24 R 31 R 32 R 33 R 34 R 41 R 42 R 43 R 44 wherein H x ( f ) is the frequency-domain channel coefficient vector of the current service cell, H x ( f ) H is the transposition of H x ( f ), H y ( f ) is the frequency-domain channel coefficient vector of the cell among the other coordinated cells, which includes calculating an argument of each element on the main diagonal of R xy ( f ), wherein values of the arguments R 11 , R 22 , R 33 , R 44 are the phase differences of the signals transmitted by four antennae of the cell among the other coordinated cells with respect to the current service cell;determining, by the UE, the start point of the window of a Fast Fourier Transform, FFT, according to a principle of maximum combination energy;and combining the signals received at the UE after the phase compensation by using the Fast Fourier Transform algorithm according to the determined start point of the window of the FFT;wherein said determining the start point of the window of a Fast Fourier Transform according to a principle of maximum combination energy comprises: after the UE receives the signals transmitted by the base stations of the coordinated cells after the phase compensation, the UE selects, in turn, one of coordinated cells as a reference cell, and for each reference cell, the UE takes the k-th path from the reference cell to the UE as a reference path, takes the time delay of the reference cell with respect to the current service cell as a reference time delay, and calculates the time delay differences of the time delay of paths to the UE of the other coordinated cells with respect to the reference time delay and calculates a weighting value for the signals transmitted by each of said coordinated cells when performing a diversity combination at the UE using the FFT, according to the time delay difference of each coordinated cell with respect to the reference time delay, and obtains a reference energy value corresponding to the reference cell by calculating the reference energy value after combining the received signals according to the weighting value corresponding to each coordinated cell;determining, as a first cell, a reference cell corresponding to the maximum value of multiple reference energy values, each corresponding to a respective reference cell, wherein the time start point after removing a Cyclic Preamble of the signals of said first cell is the start point of the window of the Fast Fourier Transform;wherein if the time delay difference of a coordinated cell with respect to the reference time delay is τ, then the weighting value of the signals transmitted by said coordinated cell when combining is c τ = { 0 τ < − T u T u + τ T u − T u < τ < 0 1 0 < τ < T CP τ − T CP T u T CP < τ < T CP + T u 0 T CP + T u < τ wherein T u is the width of an orthogonal frequency division multiplexing symbol, and T CP is the length of a Cyclic Preamble.
  2. 4
    A user equipment, UE, (61), comprising:a phase calculating unit (21), for obtaining phase differences between other coordinated cells and a current service cell by calculating channel cross-covariance matrixes over time between the current service cell and the other coordinated cells;a feedback unit (22) for feeding back the phase differences which are arguments of elements on the main diagonal of the cross-covariance matrixes, to corresponding base stations of the other coordinated cells, respectively, to implement phase compensation;a receiving unit (23) for receiving signals transmitted by the base stations of the coordinated cells after the phase compensation, wherein the other coordinated cells are cells among all the coordinated cells other than the current service cell, and the channel cross-covariance matrixes between the current service cell and the other coordinated cells are calculated based on channel coefficients of the current service cell and channel coefficients of the other coordinated cells, such that each channel cross-covariance matrix R xy (f) between the current service cell and a cell among the other coordinated cells is: R xy f = H x f H H y f = R 11 R 12 R 13 R 14 R 21 R 22 R 23 R 24 R 31 R 32 R 33 R 34 R 41 R 42 R 43 R 44 wherein H x ( f ) is the frequency-domain channel coefficient vector of the current service cell, H x ( f ) H is the transposition of H x ( f ), and H y ( f ) is the frequency-domain channel coefficient vector of the cell among the other coordinated cells, which includes calculating an argument of each element on the main diagonal of R xy ( f ), wherein values of the arguments R 11 , R 22 , R 33 , R 44 are the phase differences of the signals transmitted by four antennae of the cell among the other coordinated cells with respect to the current service cell;further comprising: a determining unit (51), for determining the start point of the window of a Fast Fourier Transform, FFT, according to a principle of maximum combination energy;a combining unit (52) for combining the signals received after the phase compensation by using the Fast Fourier Transform algorithm according to the determined start point of the window of the FFT;wherein said determining unit (51) comprises: after the receiving unit (23) receives the signals transmitted by the base stations of the coordinated cells after phase compensation, the UE selects, in turn, one of the coordinated cells as a reference cell, and for each reference cell, the UE takes the k-th path from the reference cell to the UE as a reference path, takes the time delay of the reference cell with respect to the current service cell as a reference time delay, and calculates using a time delay calculating module (511) the time delay differences of the time delay of paths to the UE of the other coordinated cells with respect to the reference time delay and calculates using a weighting value calculating module (512) a weighting value for the signals transmitted by each of said coordinated cells when performing a diversity combination using the FFT, according to the time delay difference of each coordinated cell with respect to the reference time delay and obtains by using a determining module (513), a reference energy value corresponding to the reference cell by calculating the reference energy value after combining the received signals according to the weighting value corresponding to each coordinated cell;determining, as a first cell, a reference cell corresponding to the maximum value of multiple reference energy values, each corresponding to a respective reference cell, wherein the time start point after removing a Cyclic Preamble of the signals of said first cell is the start point of the window of the Fast Fourier Transform;and wherein if the time delay difference of a coordinated cell with respect to the reference time delay is τ, then the weighting value of the signals transmitted by said coordinated cell when combining is c τ = { 0 τ < − T u T u + τ T u − T u < τ < 0 1 0 < τ < T CP τ − T CP T u T CP < τ < T CP + T u 0 T CP + T u < τ wherein T u is the width of an orthogonal frequency division multiplexing symbol, and T CP is the length of a Cyclic Preamble.
  3. 7
    A system for implementing coordinated multi-point transmission, comprising a user equipment, UE, (61) and at least two base stations (62, 63), wherein the at least two base stations belong to at least two coordinated cells in a mode of multi-point transmission, respectively, wherein the at least two base stations are configured to transmit pilot signals outwards and the UE is a user equipment according to one or more of claims 4-6;the user equipment is configured to detect the pilot signals corresponding to the at least two base stations, respectively.
Independent claims3