METHOD FOR DETERMINING BEAMFORMING PARAMETERS IN A WIRELESS COMMUNICATION SYSTEM AND TO A WIRELESS COMMUNICATION SYSTEM

• US 20120230380A1
• Filed: 03/11/2011
• Published: 09/13/2012
• Est. Priority Date: 03/11/2011
• Status: Abandoned Application

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: KEUSGEN, Wilhelm, PETER, Michael, KORTKE, Andreas
• Application Number:
  US13/045,944
• Publication Number:
  US 20120230380A1
• Time in Patent Office: Days
• US Class Current: 375/227
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0465 taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
• CPC Class Codes: H04B 7/0482 Adaptive codebooks
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas
• CPC Class Codes: H04B 7/0695 using beam selection
• CPC Class Codes: H04B 7/0874 using subgroups of receive antennas
• CPC Class Codes: H04B 7/088 using beam selection

Abstract

A method for determining a beamforming vector or a beamforming channel matrix in a communication system including a transmitting station and a receiving station, and a communication system are described. The transmitting and receiving stations include respective antenna groups and respective codebooks include a plurality of predefined beamforming vectors for the antenna group.

Claims

1. A method for determining a beamforming vector of an antenna group of a transmitting station in a wireless communication system and a beamforming vector of an antenna group of a receiving station in the wireless communication system, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, the method comprising:

performing a test transmission from the transmitting station to the receiving station using a test signal and a beamforming vector pair, the beamforming vector pair including a beamforming vector selected from the codebook of the transmitting station and a beamforming vector selected from the codebook of the receiving station,

determining a transmission characteristic of the test transmission at the receiving station,

repeating the test transmission and the determination of the transmission characteristic using different beamforming vector pairs, wherein the beamforming vectors in the beamforming vector pair are selected such that each beamforming vector from the codebook of the transmitting station encounters all beamforming vectors from the codebook of the receiving station, and

determining the beamforming vectors of the transmitting and receiving stations from the beamforming vector pair for which the transmission characteristic has a predefined value.

2. The method of claim 1, wherein determining the transmission characteristic is done at the receiving station, and wherein the transmitting station is informed about the beamforming vector determined from the beamforming vector pair.

3. The method of claim 2, wherein informing the transmitting station comprises sending the determined beamforming vector or an information identifying the determined beamforming vector to the transmitting station.

4. The method of claim 1, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein the method is performed for both directions for obtaining for the station a transmit beamforming vector when the station operates as a transmitting station, and for obtaining a receive beamforming vector when the station operates as a receiving station.

5. The method of claim 1, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein a station uses the same antennas for transmitting and receiving, and wherein a beamforming vector determined for the station is used both for transmitting and receiving.

6. The method of claim 1, wherein the beamforming vectors of the transmitting and receiving stations are provided in respective codebook matrices of the transmitting and receiving stations, and wherein training matrices for the transmitting and receiving stations are provided,

wherein the training matrix for the transmitting station comprises K_R-times the beamforming vectors of the transmitting station, K_R being the number of beamforming vectors in the codebook of the receiving station,

wherein the training matrix for the receiving station comprises K_T-times the beamforming vectors of the receiving station, K_T being the number of beamforming vectors in the codebook of the transmitting station, and

wherein the order of the beamforming vectors in the transmitting matrices is selected such that each beamforming vector from the codebook of a transmitting station encounters all beamforming vectors from the codebook of the receiving station.

7. The method of claim 6, wherein the training matrices are determined as follows:

T_T=1_1,KRC_T,

or

T_R=C_R1_1,KT,

wherein;

T_T=training matrix for beamforming at the transmitting station,

T_R=training matrix for beamforming at the receiving station,

C_T=codebook matrix of the transmitting station,

C_R=codebook matrix of the receiving station,

1_1,KT=a row vector having K_T elements that are each 1,

1_1,KR=a row vector having K_R elements that are each 1.

8. The method of claim 1, wherein the transmission characteristic comprises a receive power, a signal-to-noise ratio (SNR), a signal-to-interference ratio (SIR), and a signal to interference-plus-noise ratio (SINR), and wherein the predefined value comprises a maximum of the receive power, of the signal-to-noise ratio (SNR), of the signal-to-interference ratio (SIR), and of the signal to interference-plus-noise ratio (SINR).

9. A wireless communication system comprising:

a transmitting station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the transmitting station, and

a receiving station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the receiving station,

wherein, for determining a beamforming vector of the antenna groups of the transmitting and receiving stations, the wireless communication system is configured to;

perform a test transmission from the transmitting station to the receiving station using a test signal and a beamforming vector pair, the beamforming vector pair including a beamforming vector selected from the codebook of the transmitting station and a beamforming vector selected from the codebook of the receiving station,

determine a transmission characteristic of the test transmission at the receiving station,

repeat the test transmission and the determination of the transmission characteristic using different beamforming vector pairs, wherein the beamforming vectors in the beamforming vector pair are selected such that each beamforming vector from the codebook of the transmitting station encounters all beamforming vectors from the codebook of the receiving station, and

determine the beamforming vectors of the transmitting and receiving stations from the beamforming vector pair for which the transmission characteristic has a predefined value.

10. A method for determining a beamforming channel matrix describing a radio channel between a transmitting station and a receiving station of a wireless communication system, the transmitting and receiving stations comprising respective antenna groups and respective codebooks comprising a plurality of predefined beamforming vectors for the antenna group, the method comprising:

performing a plurality of test transmissions from the transmitting station to the receiving station using a test signal, wherein for each of the plurality of test transmissions the beamforming vectors at the transmitting station and at the receiving station are varied on the basis of a transmit estimate matrix and a receive estimate matrix, wherein each element of an estimate matrix defines the beamforming weight for a specific antenna from the antenna group used during a specific test transmission, and

determining from all test transmissions the beamforming channel matrix.

11. The method of claim 10, wherein an estimate matrix comprises the beamforming vectors for the transmitting station or the receiving station in chronological order starting with column 1, and wherein the estimate matrix for the transmitting and receiving stations is determined on the basis of a base estimate matrix for the transmitting station and the receiving station, respectively.

12. The method of claim 11, wherein the base estimate matrix comprises the beamforming weights and is a square matrix.

13. The method of claim 12, wherein the wireless communication system uses equal-gain beamforming, and wherein the base estimate matrix is a unitary matrix.

14. The method of claim 13, wherein the unitary base estimate matrix comprises a Hadamard matrix, a matrix having four equidistant phase states, a matrix having √

{square root over (N)} equidistant phase states, or a matrix having N equidistant phase states.

15. The method of claim 10, wherein the transmit and receive estimate matrices are defined as follows:

E_T=1_1,NB_T,

and

E_R=B_R1_1,M,

wherein;

E_T=transmit estimate matrix,

B_T=base transmit estimate matrix having the dimension M×

M for a transmitting station having M transmit antennas,

E_R=receive estimate matrix,

B_R=base receive estimate matrix having the dimension N×

N for a receiving station having N receive antennas,

1_1,N=a row vector having N elements that are equal 1, and

1_1,M=a row vector having M elements that are equal 1,

wherein [E_T]_m,k describes a beamforming weight for the m-th transmit antenna during the k-th test transmission of N·

M test transmissions, and

wherein [E_R]_n,k describes a beamforming weight for the n-th receive antenna during the k-th transmission of the N·

M test transmissions.

16. The method of claim 10, wherein the beamforming channel matrix is estimated as follows:

h=S<sup>−

1</sup>d,

wherein;

h=vec(H)=vectorized beamforming channel matrix,

S=S=(B_RB_T)^T

B_R=base receive estimate matrix,

B_T=base transmit estimate matrix, and

d=transfer coefficient vector for each test signal.

17. The method of claim 16, wherein the base estimate matrices are unitary matrices, and wherein the beamforming channel matrix is estimated as follows:

h=S^Hd.

18. The method of claim 10, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein the method is performed for both directions for obtaining for the station a transmit beamforming channel matrix when the station operates as a transmitting station, and for obtaining a receive beamforming channel matrix when the station operates as the receiving station.

19. The method of claim 10, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein a station uses the same antennas for transmitting and receiving, and wherein the beamforming channel matrix determined for the station is used both for transmitting and receiving.

20. A wireless communication network comprising:

a transmitting station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the transmitting station, and

a receiving station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the receiving station,

wherein, for determining a beamforming channel matrix describing a radio channel between a transmitting station and a receiving station of the wireless communication system, the wireless communication system is configured to;

perform a plurality of test transmissions from the transmitting station to the receiving station using a test signal, wherein for each of the plurality of test transmissions the beamforming vectors at the transmitting station and at the receiving station are varied on the basis of a transmit estimate matrix and a receive estimate matrix, wherein each element of an estimate matrix defines the beamforming weight for a specific antenna from the antenna group used during a specific test transmission, and

determine from all test transmissions the beamforming channel matrix.

21. A method for determining a beamforming vector of an antenna group of a transmitting station in a wireless communication system and a beamforming vector of an antenna group of a receiving station in the wireless communication system, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, the method comprising:

determining from the codebook of the transmitting or receiving station the beamforming vector yielding a first predefined result when applying the beamforming weights defined in the beamforming vector to a known beamforming channel matrix describing the radio channel between the transmitting station and the receiving station, and

determining from the codebook of the receiving or transmitting station the beamforming vector yielding a second predefined result when applying the beamforming weights defined in the beamforming vector to a combination of the known beamforming channel matrix and the determined transmit or receive beamforming vector.

22. The method of claim 21, wherein for determining the beamforming vectors an optimization method or a search across all beamforming vectors of the respective codebook is made.

23. The method of claim 21, wherein determining the beamforming vector for the transmitting station comprises selecting the beamforming vector w_CH from the codebook C_T of the transmitting station in accordance with the following equation:

24. The method of claim 23, wherein determining the beamforming vector for the receiving station comprises selecting the beamforming vector z_CH from the codebook C_R of the receiving station in accordance with the following equation:

25. The method of claim 23, wherein determining the beamforming vector for the receiving station comprises determining z_H as follows and selecting from the codebook the beamforming vector z_CH having the maximum correlation with z_H:

26. The method of claim 21, wherein determining the beamforming vector for the receiving station comprises selecting the beamforming vector z_CH from the codebook C_R of the receiving station in accordance with the following equation:

27. The method of claim 26, wherein determining the beamforming vector for the transmitting station comprises selecting the beamforming vector w_CH from the codebook C_T of the transmitting station in accordance with the following equation:

28. The method of claim 26, wherein determining the beamforming vector for the transmitting station comprises determining W_H as follows and selecting from the codebook the beamforming vector w_CH having the maximum correlation with w_H:

29. The method of claim 21, wherein the wireless communication system comprises a multicarrier system having K subcarriers, and wherein from the plurality of beamforming matrices H^(k) for the respective subcarriers the beamforming channel matrix H⁽¹⁾ which has the largest sum of the absolute values of the matrix values is selected for determining the beamforming vectors.

30. The method of claim 21, wherein the beamforming channel matrix H^(l) is determined from a subset of the plurality of beamforming matrices H^(k) for the respective subcarriers, and wherein l is determined as follows:

31. The method of claim 21, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein the method is performed for both directions for obtaining for the station a transmit beamforming vector when the station operates as a transmitting station, and for obtaining a receive beamforming vector when the station operates as a receiving station.

32. The method of claim 21, wherein the wireless communication system comprises a plurality of stations allowing for a bidirectional transmission there between, wherein a station uses the same antennas for transmitting and receiving, and wherein a beamforming vector determined for the station is used both for transmitting and receiving.

33. A wireless communication system comprising:

a transmitting station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the transmitting station, and

a receiving station comprising an antenna group and a codebook comprising a plurality of predefined beamforming vectors for the antenna group of the receiving station,

wherein, for determining a beamforming vector of the antenna groups of the transmitting and receiving stations, the wireless communication system is configured to;

determine from the codebook of the transmitting or receiving station the beamforming vector yielding a first predefined result when applying the beamforming weights defined in the beamforming vector to a known beamforming channel matrix describing the radio channel between the transmitting station and the receiving station, and

determine from the codebook of the receiving or transmitting station the beamforming vector yielding a second predefined result when applying the beamforming weights defined in the beamforming vector to a combination of the known beamforming channel matrix and the determined transmit or receive beamforming vector.

34. A method for determining a beamforming vector for a transmitting station in a wireless communication system and a beamforming vector for a receiving station in the wireless communication system, wherein at least one of the transmitting station and the receiving station comprises a hybrid MIMO beamforming configuration including a plurality of MIMO branches, each MIMO branch comprising a plurality of antennas, the method comprising:

splitting the hybrid MIMO beamforming system into a plurality of subsystems, and

determining the beamforming parameters for each subsystem separately.

35. The method of claim 34, wherein both the transmitting station and the receiving station comprise a hybrid MIMO beamforming configuration.

36. The method of claim 35, wherein splitting the hybrid MIMO beamforming system comprises assigning each MIMO transmit branch to a MIMO receive branch and each MIMO receive branch to a MIMO transmit branch.

37. The method of claim 36, wherein the branches are assigned such that the number of MIMO receive branches assigned to the same MIMO transmit branch or the number of MIMO transmit branches assigned to the same MIMO receive branch is minimized.

38. The method of claim 36, wherein assigning comprises:

assigning the branches such that, in case a plurality of MIMO receive branches is allocated to the same MIMO transmit branch, the MIMO receive branches whose MIMO antennas are spatially as far as possible apart from one another are assigned to the same MIMO transmit branch, or

assigning the branches such that, in case a plurality of MIMO transmit branches is allocated to the same MIMO receive branch, the MIMO transmit branches whose MIMO antennas are spatially as far as possible apart from one another are assigned to the same MIMO receive branch.

39. The method of claim 38, wherein dependent on the MIMO signal processing not the MIMO branches having the most distant antennas but those MIMO branches having their antennas as close as possible are used.

40. The method of claim 36, wherein the hybrid MIMO beamforming system is split into asymmetric subsystems comprising only one MIMO branch on the transmitting side or on the receiving side.

41. The method of claim 40, wherein splitting the hybrid MIMO beamforming system comprises:

dividing the hybrid MIMO beamforming system into

42. The method of claim 41, wherein the hybrid MIMO beamforming system is a hybrid SIMO beamforming system with P=1 and Q>

1, or wherein the hybrid MIMO beamforming system is a hybrid MISO beamforming system with P>

1 and Q=1.

43. The method of claim 42, comprising the following steps for the SIMO beamforming system:

determining for the

44. The method of claim 42, comprising the following steps for the MISO beamforming system:

determining for the

45. The method of claim 35, wherein determining the beamforming parameters for each subsystem comprises one or more of the following:

(1) determining the beamforming vector of the transmitting station and of the receiving station in the wireless communication system, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, by

performing a test transmission from the transmitting station to the receiving station using a test signal and a beamforming vector pair, the beamforming vector pair including a beamforming vector selected from the codebook of the transmitting station and a beamforming vector selected from the codebook of the receiving station,

determining a transmission characteristic of the test transmission at the receiving station,

repeating the test transmission and the determination of the transmission characteristic using different beamforming vector pairs, wherein the beamforming vectors in the beamforming vector pair are selected such that each beamforming vector from the codebook of the transmitting station encounters all beamforming vectors from the codebook of the receiving station, and

determining the beamforming vectors of the transmitting and receiving stations from the beamforming vector pair for which the transmission characteristic has a predefined value, or

(2) determining the beamforming channel matrix describing a radio channel between the transmitting station and the receiving station, the transmitting and receiving stations comprising respective antenna groups and respective codebooks comprising a plurality of predefined beamforming vectors for the antenna group, by

performing a plurality of test transmissions from the transmitting station to the receiving station using a test signal, wherein for each of the plurality of test transmissions the beamforming vectors at the transmitting station and at the receiving station are varied on the basis of a transmit estimate matrix and a receive estimate matrix, wherein each element of an estimate matrix defines the beamforming weight for a specific antenna from the antenna group used during a specific test transmission, and

determining from all test transmissions the beamforming channel matrix, or

(3) determining a beamforming vector the transmitting station and the receiving station, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, by

determining from the codebook of the transmitting or receiving station the beamforming vector yielding a first predefined result when applying the beamforming weights defined in the beamforming vector to a known beamforming channel matrix describing the radio channel between the transmitting station and the receiving station, and

determining from the codebook of the receiving or transmitting station the beamforming vector yielding a second predefined result when applying the beamforming weights defined in the beamforming vector to a combination of the known beamforming channel matrix and the determined transmit or receive beamforming vector.

46. A wireless communication system comprising:

a transmitting station, and

a receiving station,

wherein at least one of the transmitting station and the receiving station comprises a hybrid MIMO beamforming configuration including a plurality of MIMO branches, each MIMO branch comprising a plurality of antennas, and

wherein the system is configured to

split the hybrid MIMO beamforming system into a plurality of subsystems, and

determine the beamforming vectors for each subsystem separately.

47. A non-transitory computer readable medium including a computer program including instructions for performing a method for determining a beamforming vector of an antenna group of a transmitting station in a wireless communication system and a beamforming vector of an antenna group of a receiving station in the wireless communication system, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, when executing the instructions by a computer, the method comprising:

performing a test transmission from the transmitting station to the receiving station using a test signal and a beamforming vector pair, the beamforming vector pair including a beamforming vector selected from the codebook of the transmitting station and a beamforming vector selected from the codebook of the receiving station,

determining a transmission characteristic of the test transmission at the receiving station,

repeating the test transmission and the determination of the transmission characteristic using different beamforming vector pairs, wherein the beamforming vectors in the beamforming vector pair are selected such that each beamforming vector from the codebook of the transmitting station encounters all beamforming vectors from the codebook of the receiving station, and

determining the beamforming vectors of the transmitting and receiving stations from the beamforming vector pair for which the transmission characteristic has a predefined value.

48. A non-transitory computer readable medium including a computer program including instructions for performing a method for determining a beamforming channel matrix describing a radio channel between a transmitting station and a receiving station of a wireless communication system, the transmitting and receiving stations comprising respective antenna groups and respective codebooks comprising a plurality of predefined beamforming vectors for the antenna group, when executing the instructions by a computer, the method comprising:

performing a plurality of test transmissions from the transmitting station to the receiving station using a test signal, wherein for each of the plurality of test transmissions the beamforming vectors at the transmitting station and at the receiving station are varied on the basis of a transmit estimate matrix and a receive estimate matrix, wherein each element of an estimate matrix defines the beamforming weight for a specific antenna from the antenna group used during a specific test transmission, and

determining from all test transmissions the beamforming channel matrix.

49. A non-transitory computer readable medium including a computer program including instructions for performing a method for determining a beamforming vector of an antenna group of a transmitting station in a wireless communication system and a beamforming vector of an antenna group of a receiving station in the wireless communication system, wherein each of the transmitting station and the receiving station comprises a codebook including a plurality of predefined beamforming vectors, when executing the instructions by a computer, the method comprising:

determining from the codebook of the transmitting or receiving station the beamforming vector yielding a first predefined result when applying the beamforming weights defined in the beamforming vector to a known beamforming channel matrix describing the radio channel between the transmitting station and the receiving station, and

determining from the codebook of the receiving or transmitting station the beamforming vector yielding a second predefined result when applying the beamforming weights defined in the beamforming vector to a combination of the known beamforming channel matrix and the determined transmit or receive beamforming vector.

50. A non-transitory computer readable medium including a computer program including instructions for performing a method for determining a beamforming vector for a transmitting station in a wireless communication system and a beamforming vector for a receiving station in the wireless communication system, wherein at least one of the transmitting station and the receiving station comprises a hybrid MIMO beamforming configuration including a plurality of MIMO branches, each MIMO branch comprising a plurality of antennas, when executing the instructions by a computer, the method comprising:

splitting the hybrid MIMO beamforming system into a plurality of subsystems, and

determining the beamforming parameters for each subsystem separately.