Nova Patents
EP1471663A2

Transmit diversity system, method and computer program product

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.

EP1471663A2, drawing sheet 1
Sheet 1 of 48

Term

Term ended

Projected expiry passed 26 April 2024, 2.4 years ago.

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36 claims: 13 independent, 23 dependent

  1. 1
    A transmit diversity system comprising:a base station (2) and a mobile station (1) each station comprising a receiver and a transmitter whereby the mobile station (1) is configured to generate and transmit a selected beam index based on power estimates of received signals (S 1 , S 2 , S 1 *, S 2 *), and the base station (2) is configured to perform spreading code allocation control based on the selected beam index.
  2. 2
    A transmit diversity system comprising:a base station (2) and a mobile station (1) each station comprising a receiver and a transmitter whereby the mobile station (1) is configured to calculate and transmit power estimates of received signals (S 1 , S 2 , S 1 *, S 2 *) to the base station (2), and the base station (2) is configured to generate a selected beam index based on the power estimates and performs spreading code allocation control based on the selected beam index.
  3. 7
    The system of any one of the claims 1 to 6 further comprising a beam allocation means for allocating a space-time coded signal in a spatial domain to a plurality of beams of the multiple beams.
  4. 11
    The system of any one of the claims 6 to 10, wherein the transmitter of the base station (2) is further configured to receive the selected beam index, whereby the code allocation means (26) is configured 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.
  5. 13
    The system according to any one of the claims 6 to 12, 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.
  6. 14
    The system according to any one of the claims 6 to 13, 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.
  7. 15
    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.
  8. 20
    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.
  9. 25
    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. 27
    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.
  11. 29
    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.
  12. 30
    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.
  13. 31
    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.
  14. 33
    A mobile station (1) comprising a receiver and a transmitter, whereby the mobile station (1) is configured to generate and transmit a selected beam index based on power estimates of received signals (S 1 , S 2 , S 1 *, S 2 *).
  15. 34
    A mobile station (1) comprising a receiver and a transmitter, whereby the mobile station (1) is configured to calculate and transmit power estimates of received signals (S 1 , S 2 , S 1 *, S 2 *).
  16. 35
    A base station (2) comprising a receiver and a transmitter, whereby the base station (2) is configured to receive a selected beam index transmitted by a mobile station (1) and to perform spreading code allocation control based on the selected beam index.
  17. 36
    A base station (2) comprising a receiver and a transmitter, whereby the base station (2) is configured to receive power estimates of signals (S 1 , S 2 , S 1 *, S 2 *) transmitted by a mobile station (1), and the base station (2) is further configured to generate a selected beam index based on the power estimates and performs spreading code allocation control based on the selected beam index.
Independent claims17