Transmit diversity system, method and computer program product

• US 7,302,238 B2
• Filed: 04/22/2004
• Issued: 11/27/2007
• Est. Priority Date: 04/25/2003
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Fujil, Masaaki
• Primary Examiner(s): Perez-Gutierrez; Rafael
• Assistant Examiner(s): Kirk; Lameka J
• Application Number:
  US10/829,796
• Publication Number:
  US 20040213187A1
• Time in Patent Office: 1,314 Days
• Field of Search: 455/101, 455/500, 455/25, 455/63.4, 455/63.3, 455/509, 455/342, 455/343, 455/272, 370/330, 370/478, 370/315, 370/335, 370/337, 370/342, 370/344, 370/347, 375/299, 375130-153
• US Class Current: 455/101
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 5/026 using code division
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A transmit diversity system, method, and computer program product which can prevent signal power from being wasted and also prevent interference between a plurality of beams. In the transmit diversity system, a transmitter transmits a signal after allocating the signal to a beamspace of multiple beams and a receiver receives the multiple beams and obtains a channel estimate of each of the multiple beams. A beam pair, which has the largest sum of powers of respective channel estimates of two corresponding beams, is selected from a plurality of beam pairs of the multiple beams. One of the two beams of the selected beam pair is selected as a single beam for use if the difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

Claims

1. A transmit diversity system comprising:

a transmitter for allocating a signal to a beamspace of multiple beams, and transmitting the multiple beams;

a receiver for receiving the multiple beams and obtaining a channel estimate of each of the multiple beams;

first selection means for selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair; and

second selection means for selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

2. The system according to claim 1, wherein a power of a channel estimate of said one of the two beams is larger than a power of a channel estimate of the other beam of the two beams.

3. A transmit diversity system comprising:

a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams; and

a code allocation means for allocating spreading codes having a partial correlation of 0 in the time domain spreading, if a single beam used by a user is included in multiple beams used by another user or if one of multiple beams used by the user is used by the another user.

4. The system according to claim 3, wherein the code allocation means additionally allocates spreading codes having a partial correlation of 0 in the time domain spreading to a plurality of users that use a same beam pair.

5. A receiver for receiving a signal allocated to a beamspace of multiple beams and obtaining a channel estimate of each of the multiple beams, said receiver comprising:

first selection means for selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair; and

second selection means for selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

6. A transmitter for receiving a channel estimate from a receiver for receiving a signal allocated to a beamspace of multiple beams and obtaining a channel estimate of each of the multiple beams, said transmitter comprising:

first selection means for selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having largest sum of powers of respective channel estimates of two beams included in said beam pair; and

second selection means for selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

7. A transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said transmitter comprising:

a code allocation means for allocating spreading codes having a partial correlation of 0 in a time domain spreading, if a single beam used by a user is included in multiple beams used by another user or if one of multiple beams used by the user is used by another user.

8. The transmitter according to claim 7, wherein the code allocation means additionally allocates the spreading codes having the partial correlation of 0 in the time domain spreading to a plurality of users that use a same beam pair.

9. A beam selection method in a transmit diversity system including a transmitter for allocating a signal to a beamspace of multiple beams, and transmitting the multiple beams and a receiver for receiving the multiple beams and obtaining a channel estimate of each of the multiple beams, said method comprising the steps of:

a) selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having s largest sum of powers of respective channel estimates of two beams included in said beam pair; and

b) selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

10. The method according to claim 9, wherein a power of a channel estimate of said one of the two beams is larger than a power of a channel estimate of the other beam of the two beams.

11. A spreading code allocation method in a transmit diversity system including a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said method comprising the step of:

allocating spreading codes having a partial correlation of 0 in the time domain spreading, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by the another user.

12. A spreading code allocation method in a transmit diversity system including a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said method comprising the step of:

allocating spreading codes having a partial correlation of 0 in the time domain spreading to a plurality of users that use a same beam pair.

13. A recording medium containing a beam selection program for enabling a receiver to perform a beam selection method in a transmit diversity system, said receiver receiving a signal allocated to a beamspace of multiple beams and obtaining a channel estimate of each of the multiple beams, said method comprising the steps of:

selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair; and

selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

14. A recording medium containing a beam selection program for enabling a transmitter to perform a beam selection method in a transmit diversity system, said transmitter receiving a channel estimate from a receiver for receiving a signal allocated to a beamspace of multiple beams and obtaining a channel estimate of each of the multiple beams, said method comprising the steps of:

selecting a beam pair from a plurality of beam pairs of the multiple beams, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair; and

selecting one of the two beams included in the selected beam pair, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value.

15. A recording medium including a spreading code allocation program for enabling a transmitter to perform a spreading code allocation method in a transmit diversity system, said transmitter space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said method comprising the step of:

allocating spreading codes having a partial correlation of 0 in the time domain spreading, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by another user.

16. The medium according to claim 15, wherein said method further comprises the step of allocating the spreading codes having the partial correlation of 0 in the time domain spreading to a plurality of users that use a same beam pair.

17. A transmit diversity system comprising:

a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams;

a beam allocation means for allocating a space-time coded signal in a spatial domain to a plurality of beams of the multiple beams; and

a spreading code allocation means for allocating a space-time coded signal in a time domain to a plurality of spreading codes in a same spreading area.

18. The system according to claim 17, wherein the beam allocation means selects a beam pair from a plurality of beam pairs of the multiple beams received by a receiver, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair, and, if a difference between the powers of the respective channel estimates of the two beams is larger than a predetermined value, the beam allocation means selects one of the two beams and allocates the space-time coded signal of the spatial domain to said one of the two beams.

19. The system according to claim 18, wherein the spreading code allocation means classifies the beam pair selected by the beam allocation means into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into a same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and the spreading code allocation means allocates spreading codes of a two-dimensional spreading factor to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

20. The system according to claim 18, wherein the spreading code allocation means allocates spreading codes of a two-dimensional spreading factor to said one of the two beams selected by the beam allocation means, said spreading codes being branched from the different branches in the time-domain spreading layer of the spreading code tree.

21. The system according to claim 17, wherein the spreading code allocation means allocates spreading codes having a partial correlation of 0 in a same spreading area, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by another user.

22. A transmit diversity method in a transmit diversity system comprising a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said method comprising the steps of:

a) allocating a space-time coded signal in a spatial domain to a plurality of beams of the multiple beams; and

b) allocating a space-time coded signal in a time domain to a plurality of spreading codes in a same spreading area.

23. The method according to claim 22, wherein, if a difference between powers of respective channel estimates of two beams corresponding to a beam pair selected from a plurality of beam pairs of the multiple beams received by a receiver, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair, is larger than a predetermined value, one of the two beams included in the selected beam pair is selected, and the space-time coded signal of the spatial domain is allocated to said one of the two beams.

24. The method according to claim 23, wherein spreading codes having a partial correlation of 0 in the same spreading area are allocated, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by the another user.

25. The method according to claim 24, wherein said beam pair having the largest sum of powers is classified into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into the same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and spreading codes of a two-dimensional spreading factor are allocated to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

26. The method according to claim 24, wherein spreading codes of a two-dimensional spreading factor are allocated to said one of the two beams selected by the beam allocation means, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

27. The method according to claim 23, wherein said beam pair having the largest sum of powers is classified into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into the same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and spreading codes of a two-dimensional spreading factor are allocated to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

28. The method according to claim 23, wherein spreading codes of a two-dimensional spreading factor are allocated to said one of the two beams selected by the beam allocation means, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

29. The method according to claim 22, wherein spreading codes having a partial correlation of 0 in the same spreading area are allocated, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by the another user.

30. The method according to claim 29, wherein said beam pair having the largest sum of powers is classified into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into the same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and spreading codes of a two-dimensional spreading factor are allocated to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

31. The method according to claim 29, wherein spreading codes of a two-dimensional spreading factor are allocated to said one of the two beams selected by the beam allocation means, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

32. A recording medium including a communication program for enabling a transmit diversity system to perform a transmit diversity method, said transmit diversity system including a transmitter for space-time encoding a signal for transmission into a space-time coded signal, performing time domain spreading and frequency domain spreading of the space-time coded signal to produce a spread signal, and transmitting the spread signal after allocating the spread signal to a beamspace of multiple beams, said method comprising the steps of:

a) allocating a space-time coded signal in a spatial domain to a plurality of beams of the multiple beams; and

b) allocating a space-time coded signal in a time domain to a plurality of spreading codes in a same spreading area.

33. The medium according to claim 32, wherein, in the method, if a difference between powers of respective channel estimates of two beams included in a beam pair selected from a plurality of beam pairs of the multiple beams received by a receiver, said beam pair having a largest sum of powers of respective channel estimates of two beams included in said beam pair, is larger than a predetermined value, one of the two beams included in the selected beam pair is selected, and the space-time coded signal of the spatial domain is allocated to said one of the two beams.

34. The medium according to claim 33, wherein, in the method, spreading codes having a partial correlation of 0 in the same spreading area are allocated, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is by the another user.

35. The medium according to claim 33, wherein, in the method, said beam pair having the largest sum of powers is classified into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into a same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and spreading codes of a two-dimensional spreading factor are allocated to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

36. The medium according to claim 33, wherein, in the method, spreading codes of a two-dimensional spreading factor are allocated to said one of the two beams selected by the beam allocation means, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

37. The medium according to claim 32, wherein, in the method, spreading codes having a partial correlation of 0 in the same spreading area are allocated, if a single beam used by a user is included in multiple beams used by another user, or if one of multiple beams used by the user is used by the another user.

38. The medium according to claim 37, wherein, in the method, said beam pair having the largest sum of powers is classified into beam pair groups in such a manner that beam pairs, which do not interfere with each other, are classified into a same beam pair group and beam pairs, which interfere with each other, are classified into different beam pair groups, and spreading codes of a two-dimensional spreading factor are allocated to the different beam pair groups, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.

39. The medium according to claim 37, wherein, in the method, spreading codes of a two-dimensional spreading factor are allocated to said one of the two beams selected by the beam allocation means, said spreading codes being branched from different branches in a time-domain spreading layer of a spreading code tree.