Open-loop diversity technique for systems employing multi-transmitter antennas

1. A method for use in a system adapted to transmit at least four series of transmit sequences over at least four transmit antennas, the method comprising the step of:

space-time coding at least two pairs of symbol sub-streams, each of the pairs of symbol sub-streams being space-time coded to form a respective pair of the transmit-sequence chains, the space-time coding being such that at least one of the formed pairs of the transmit-sequence chains is a function of symbols of the respective pair of symbol sub-streams and not a function of the symbols of the other pair of symbol sub-streams;

wherein each transmit sequence of a particular transmit-sequence chain is a function of 1) a symbol of one of the symbol sub-streams of the respective symbol sub-stream pair and 2) a complex conjugate of a symbol of the other symbol sub-stream of the respective symbol sub-stream pair.

2. The invention of claim 1 , wherein:

each transmit sequence has a duration of four symbol periods; and

portions of the at least four transmit-sequence chains are representable by a matrix where:

each row of the matrix represents one transmit sequence of a respective different one of the transmit-sequence chains; and

each column of the matrix represents one symbol period.

3. The invention of claim 2 , wherein the matrix is orthogonal.

4. The invention of claim 1 , wherein portions of the at least four transmit-sequence chains are representable by a matrix where:

each row of the matrix represents one transmit sequence of a respective different one of the transmit-sequence chains;

each column of the matrix represents one symbol period and the matrix is

[

b

1

b

1

-

b

2

*

-

b

2

*

b

2

b

2

b

1

*

b

1

*

b

3

-

b

3

-

b

4

*

b

4

*

b

4

-

b

4

b

3

*

-

b

3

*

]

,

where:

b 1 and b 2 are symbols of first and second symbol sub-streams, respectively, of one of the symbol-sub-stream pairs,

b 3 and b 4 are symbols of first and second symbol sub-streams. respectively, of another of the symbol-sub-steam pairs, and

b* 1 , b* 2 , b* 3 , and b* 4 are complex conjugates of b 1 , b 2 , b 3 , and b 4 , respectively.

5. The invention of claim 1 , wherein portions of the at least four transmit-sequence chains are representable by a matrix where:

each row of the matrix represents one transmit sequence of a respective different one of the transmit-sequence chains;

each column of the matrix represents one symbol period; and

the matrix is

[

b

1

-

b

2

*

0

0

b

2

b

1

*

0

0

0

0

b

3

-

b

4

*

0

0

b

4

b

3

*

]

,

where:

b 1 and b 2 are symbols of first and second symbol sub-streams, respectively, of one of the symbol-sub-stream pairs,

b 3 and b 4 are symbols of first and second symbol sub-streams, respectively, of another of the symbol-sub-stream pairs, and

b* 1 , b* 2 , b* 3 , and b* 4 are complex conjugates of b 1 , b 2 , b 3 , and b 4 , respectively.

6. The invention of claim 1 , wherein the space-time coding step comprises the steps of:

space-time coding a first pair of symbol sub-streams to form a first pair of transmit-sequence chains, the first pair of transmit-sequence chains being a function of the symbols of the first symbol-sub-stream pair and not a function of the symbols of a second symbol-sub-stream pair; and

space-time coding the second pair of symbol sub-streams to form a second of transmit-sequence chains, the second pair of transmit-sequence chains being a function of the symbols of the second symbol-sub-stream pair and not a function of the symbols of the first symbol-sub-stream pair.

7. The invention of claim 1 , further comprising the step of:

transmitting the at least four transmit-sequence chains on a respective one of the transmit antennas.

8. The invention of claim 1 , further comprising the step of:

spreading at least a plurality of symbols of the transmit-sequence chains using a spreading code.

9. The invention of claim 1 , further comprising the steps of:

channel coding each of at least four data sub-streams using a channel code; and

mapping each of the channel-coded primitive data stream into symbol-space to produce a respective one of the symbol sub-streams.

10. A transmitter adapted to transmit at least four symbol sub-streams, the transmitter comprising:

a space-time encoder adapted to space-time code at least two pairs of symbol sub-streams, each of the pairs of symbol sub-streams being space-time coded to form a respective pair of the transmit-sequence chains, the space-time coding being such that at least one of the formed pairs of the transmit-sequence chains is a function of symbols of the respective pair of symbol sub-streams and not a function of the symbols of the other pair of symbol sub-streams;

wherein each transmit sequence of a particular transmit-sequence chain is a function of 1) a symbol of one of the symbol sub-streams of the respective symbol-sub-stream pair and 2) a complex conjugate of a symbol of the other symbol sub-stream of the respective symbol sub-stream pair; and

at least four transmit antennas, each having an input for receiving at least one of the at least four transmit-sequence chains, the input coupled to an output of the space-time encoder.

11. The invention of claim 10 , wherein:

each transmit sequence has a duration of four symbol periods; and

portions of the at least four transmit-sequence chains are representable by a matrix where:

each row of the matrix represents one transmit sequence of a respective different one of the transmit-sequence chains, and

each column of the matrix represents one symbol period.

12. The invention of claim 11 , wherein the matrix is orthogonal.

13. The invention of claim 10 , wherein portions of the at least four transmit-sequence chains are representable by a matrix where:

each row of the matrix represents one transmit sequence of a respective different one of the transmit-sequence chains;

each column of the matrix represents one symbol period; and

the matrix is one of the matrices of the set of matrices consisting of:

[

b

1

b

1

-

b

2

*

-

b

2

*

b

2

b

2

b

1

*

b

1

*

b

3

-

b

3

-

b

4

*

b

4

*

b

4

-

b

4

b

3

*

-

b

3

*

]

⁢

⁢

and

⁢

[

b

1

-

b

2

*

0

0

b

2

b

1

*

0

0

0

0

b

3

-

b

4

*

0

0

b

4

b

3

*

]

,

where;

b 1 and b 2 are symbols of first and second symbol sub-streams, respectively, of one of the symbol-sub-stream pairs,

b 3 and b 4 are symbols of first and second symbol sub-streams, respectively, of another of the symbol-sub-stream pairs, and

b* 1 , b* 2 , b* 3 , and b* 4 are complex conjugates of b 1 , b 2 , b 3 , and b 4 , respectively.

14. The invention of claim 10 , wherein the space-time encoder is adapted to spread at least a plurality of symbols of the transmit-sequence chains using a spreading code.

15. The invention of claim 10 , wherein the transmitter further comprises:

an input; and

at least one channel encoder being interposed between the input and the space-time encoder, the channel encoder being adapted to channel code a data sub-stream using a channel code.

16. The invention of claim 15 , wherein the transmitter further comprises at least one mapper, the mapper being interposed between the channel encoder and the space-time encoder, the mapper being adapted to map the channel coded data sub-stream into symbol-space to produce a respective one of the symbol sub-streams.

17. A base station of a wireless communication system, the base station comprising the transmitter of claim 10 .

18. A mobile terminal comprising the transmitter of claim 10 .

19. The invention of claim 10 , further comprising a plurality of radio frequency units, each having an input coupled to a respective output of the space-time encoder, each radio frequency unit adapted to convert a respective transmit sequence series from baseband to a radio frequency modulated signal.