Systems and methods for transmit diversity for DFT precoded channels

1. In a mobile terminal having a first antenna and a second antenna, a transmit diversity method for discrete Fourier transform (DFT) precoded channels, the method comprising:

producing a block of data symbols;

transforming said block of data symbols to produce a first block of transformed symbols and a second block of transformed symbols;

using the first antenna, transmitting the first block of transformed symbols and a first reference sequence, wherein the transmitting step occurs during a slot of a subframe of a radio frame; and

using the second antenna, transmitting, during said slot, the second block of transformed symbols and a second reference sequence, wherein

the first block of transformed symbols is transmitted using only a first set of subcarriers,

the second block of transformed symbols is transmitted using only a second set of subcarriers that is orthogonal to the first set of subcarriers, and

the first reference sequence and the second reference sequence are transmitted using a third set of subcarriers that comprises that first set of subcarriers and the second set of subcarriers.

2. The method of claim 1 , wherein the first reference sequence is orthogonal to the second reference sequence.

3. The method of claim 2 , wherein the first reference sequence is a cyclic shift of the second reference sequence.

4. The method of claim 1 , wherein the step of transforming said block of data symbols comprises:

dividing the block of data symbols into at least a first sub-block and a second sub-block;

applying a discrete Fourier transform (DFT) to the first sub-block to produce the first block of transformed symbols; and

applying a discrete Fourier transform (DFT) to the second sub-block to produce the second block of transformed symbols.

5. The method of claim 4 , wherein the block of data symbols consists of twelve data symbols, and the step of transforming said block of twelve data symbols comprises:

dividing the block of twelve symbols into a first sub-block of six symbols and a second sub-block of six symbols;

applying a DFT of size six to the first sub-block of six symbols to produce the first block of transformed symbols; and

applying a DFT of size six to the second sub-block of six symbols to produce the second block, of transformed symbols.

6. The method of claim 1 , wherein

the step of transmitting the first block of transformed symbols comprises mapping each symbol within the first block of transformed symbols to a particular subcarrier within the first set of subcarriers and applying an inverse fast Fourier transform (IFFT) to the first block of transformed symbols; and

the step of transmitting the second block of transformed symbols comprises mapping each symbol within the second block of transformed symbols to a particular subcarrier within the second set of subcarriers and applying the IFFT to the second block of transformed symbols.

7. The method of claim 1 , further comprising

producing a second block of data symbols;

transforming said second block of data symbols to produce a third block of transformed symbols and a fourth block of transformed symbols;

using the first antenna, transmitting the third block of transformed symbols and the first reference sequence, wherein the transmitting step occurs during a second slot of the subframe; and

using the second antenna, transmitting, during the second slot, the fourth block of transformed symbols and the second reference sequence, wherein

the third block of transformed symbols is transmitted using a fourth set of subcarriers, and

the fourth block of transformed symbols is transmitted using a fifth set of subcarriers that is orthogonal with the fourth set of subcarriers.

8. The method of claim 7 , wherein

the first and fifth sets of subcarriers consist only of even indexed subcarriers and the second and fourth sets of subcarriers consist only of odd indexed subcarriers, or

the first and fifth sets of subcarriers consist only of odd indexed subcarriers and the second and fourth sets of subcarriers consist only of even indexed subcarriers.

9. The method of claim 1 , further comprising obtaining a block, of message bits, wherein the step of producing the block of data symbols comprising generating the block of data symbols from the block of message bits.

10. The method of claim 9 , wherein the step of obtaining the block of message bits comprises:

obtaining a sequence of message bits;

encoding the sequence of message bits to produce an encoded sequence of message bits; and

scrambling the encoded sequence of message bits to produce the block of message bits.

11. The method of claim 1 , wherein

the first set of subcarriers comprises a set of two or more orthogonal subcarriers,

the second set of subcarriers comprises a set of two or more orthogonal subcarriers, and

no subcarrier included in the first set of subcarriers is included in the second set of subcarriers.

12. The method of claim 11 , wherein

the first set of subcarriers comprises a first subcarrier (f 0 ) and a second subcarrier (f 2 ), wherein f 0 and f 2 are orthogonal,

the second set of subcarriers comprises a third subcarrier (f 1 ) and a fourth subcarrier (f 3 ), wherein f 1 and f 3 are orthogonal,

the first set of subcarriers does not include f 1 or f 3 ,

the second set of subcarriers does not include f 0 or f 2 ,

subcarrier f 1 is positioned between subcarriers f 0 and f 2 , and

subcarrier f 2 is positioned between subcarriers f 1 and f 3 .

13. The method of claim 11 , wherein

the first set of subcarriers consists of six different subcarriers f i , where i=0, 2, 4, 6, 8, 10,

the second set of subcarriers consists of six different subcarriers f j , where j=1, 3, 5, 7, 9, 11, and

f x , is directly between f x−1 and f x+1 , for x=1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

14. A transmit diversity apparatus for discrete Fourier transform (DFT) precoded channels, the apparatus comprising:

a first antenna;

a second antenna; and

a data processor coupled to the first antenna and the second antenna, the data processor being configured to: (a) produce a block of data symbols from a set of message bits; (b) transform said block of data symbols to produce a first block of transformed symbols and a second block of transformed symbols; (c) use the first antenna to transmit, during a slot of a subframe of a radio frame, the first block of transformed symbols and a first reference sequence; and (d) use the second antenna to transmit, during said slot, the second block of transformed symbols and a second reference sequence, wherein

the data processor is further configured such that (a) the first block of transformed symbols is transmitted using only a first set of subcarriers, (b) the second block of transformed symbols is transmitted using only a second set of subcarriers that is orthogonal to the first set of subcarriers, and (c) the first reference sequence and the second reference sequence are transmitted using a third set of subcarriers that comprises that first set of subcarriers and the second set of subcarriers.

15. The apparatus of claim 14 , wherein the first reference sequence is orthogonal to the second reference sequence.

16. The apparatus of claim 15 , wherein the first reference sequence is a cyclic shift of the second reference sequence.

17. The apparatus of claim 14 , wherein the data processor is further configured such that the data processor transforms said block of data symbols by:

dividing the block of data symbols into at least a first sub-block and a second sub-block;

applying a discrete Fourier transform (DFT) to the first sub-block to produce the first block of transformed symbols; and

applying a discrete Fourier transform (DFT) to the second sub-block to produce the second block of transformed symbols.

18. The apparatus of claim 17 , wherein the block of data symbols consists of twelve data symbols, and the data processor is further configured such that the data processor transforms said block of data symbols by:

dividing the block of twelve symbols into a first sub-block of six symbols and a second sub-block of six symbols;

applying a DFT of size six to the first sub-block of six symbols to produce the first block of transformed symbols; and

applying a DFT of size six to the second sub-block of six symbols to produce the second block of transformed symbols.

19. The apparatus of claim 14 , wherein the data processor is further configured such that the data processor:

maps each symbol within the first block of transformed symbols to a particular subcarrier within the first set of subcarriers and applies an inverse fast Fourier transform (IFFT) to the first block of transformed symbols; and

maps each symbol within the second block of transformed symbols to a particular subcarrier within the second set of subcarriers and applies the IFFT to the second block of transformed symbols.

20. The apparatus of claim 14 , wherein the data processor is further configured to:

produce a second block of data symbols;

transform said second block of data symbols to produce a third block of transformed symbols and a fourth block of transformed symbols;

use the first antenna to transmit, during a second slot of the subframe, the third block of transformed symbols and the first reference sequence; and

use the second antenna to transmit, during the second slot, the fourth block of transformed symbols and the second reference sequence, wherein

the data processor is further configured such that (a) the third block of transformed symbols is transmitted using a fourth set of subcarriers, (b) the fourth block of transformed symbols is transmitted using a fifth set of subcarriers, and (c) the fourth set of subcarriers is orthogonal with the fifth set of subcarriers.

21. The apparatus of claim 20 , wherein

the first and fifth sets of subcarriers consist only of even indexed subcarriers and the second and fourth sets of subcarriers consist only of odd indexed subcarriers, or

the first and fifth sets of subcarriers consist only of odd indexed subcarriers and the second and fourth sets of subcarriers consist only of even indexed subcarriers.

22. The apparatus of claim 14 , wherein the set of message bits comprises one or more HARQ feedback bits.

23. The apparatus of claim 22 , wherein the set of message bits further comprises a scheduling request bit.

24. The apparatus of claim 22 , wherein the HARQ feedback bits comprises bits obtained by a logical AND operation of several individual HARQ feedback bits.

25. A mobile terminal comprising a transmit diversity apparatus for discrete Fourier transform (DFT) precoded channels, the apparatus comprising:

a first antenna;

a second antenna; and

a data processor coupled to the first antenna and the second antenna, the data processor being configured to: (a) produce a block of data symbols from a bit sequence; (c) transform said block of data symbols to produce a first block of transformed symbols and a second block of transformed symbols; (d) use the first antenna to transmit, during a slot of a subframe of a radio frame, the first block of transformed symbols and a first reference sequence; and (e) use the second antenna to transmit, during said slot, the second block of transformed symbols and a second reference sequence, wherein

the data processor is further configured such that (a) the first block of transformed symbols is transmitted using only a first set of subcarriers, (b) the second block of transformed symbols is transmitted using only a second set of subcarriers that is orthogonal to the first set of subcarriers, and (c) the first reference sequence and the second reference sequence are transmitted using a third set of subcarriers that comprises that first set of subcarriers and the second set of subcarriers.