Multiple transmit antenna interleaver design

1. A wireless device comprising:

a case; and

a wireless transmitter comprising:

an interleaver circuit operable to process bits of an input symbol to form N orthogonal frequency division multiplex (OFDM) transmit streams comprising K subcarriers, wherein each input symbol comprises KN subsymbols, wherein each subsymbol comprises B bits of the input symbol, and wherein each subsymbol is communicated via an associated subcarrier of the N transmit streams, the circuit comprising:

one or more interleavers operable to perform at least one permutation upon bits of the input symbol,

a block mapper operable to group the bits into subsymbols, group the subsymbols into blocks of subsymbols, and spread the bits across the N transmit streams before the bits are spread across the K subcarriers, and

the one or more interleavers operable to rotate the subsymbol blocks between the N transmit streams, wherein N is greater than 1.

2. The wireless device according to claim 1 , the wireless transmitter further comprising a bit to stream allocator operable in a mode selected from a plurality of modes based on a state of a control signal.

3. The wireless device according to claim 1 , wherein bit k of the input symbol is mapped to bit i of a first bit sequence according to the formula:

i

=

BKN

r

⁢

(

k

⁢

⁢

mod

⁢

⁢

r

)

+

⌊

k

r

⌋

k

=

0

,

1

,

…

⁢

,

BKN

-

1

wherein r denotes interleaving depth; and

wherein

⌊

k

r

⌋

denotes the largest integer not exceeding the value

k

r

.

4. The wireless device according to claim 3 , wherein bit i of the first bit sequence is mapped to bit j of a second bit sequence according to the formula:

j

=

s

⁢

⌊

i

s

⌋

+

mod

⁡

(

i

+

BKN

-

⌊

r

⁢

⁢

i

BKN

⌋

,

s

)

i

=

0

,

1

,

…

⁢

,

BKN

-

1

wherein s=max(B/2,1); and

wherein r denotes interleaving depth.

5. The wireless device according to claim 4 , wherein the

block mapper groups B bits of the second bit sequence to form subsymbols and groups subsymbols into blocks comprising

K

rot

subsymbols; and

wherein rot is the number of blocks transmitted via each of the N transmit streams and is any integer divisor of K.

6. The wireless device according to claim 1 , wherein the blocks of subsymbols are distributed across the transmit streams according to an index, m, defined by the formula:

m =(rot* q *( N− 1)+ p )mod( N* rot);

wherein

p=N *(0:rot−1)+ q ; and

wherein rot denotes any integer divisor of K, q denotes integer values such that 0≦q≦N−1, N denotes the number of transmit streams having indexes 0 through N−1; and (0:rot−1) denotes the sequence 0, 1, 2, . . . , (rot−1).

7. The wireless device according to claim 1 wherein the interleaver circuit is operable in a mode compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11a standard (1999) and/or successor standards.

8. The wireless device according to claim 1 wherein the interleaver circuit is operable in a mode compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11g standard (2003) and/or successor standards.

9. A wireless device comprising:

a case; and

a wireless transmitter comprising an interleaver circuit operable to process bits of an input symbol for transmission via a plurality of orthogonal frequency division multiplex (OFDM) transmit signals, the interleaver circuit comprising:

a plurality of interleavers operable to interchange bits of the input symbol, each interleaver operable according to an associated permutation;

wherein the plurality of interleavers are operable to allocate bits of the input symbol to form subsymbols, each subsymbol associated with a subcarrier of one of the plurality of OFDM transmit signals;

wherein the plurality of interleavers comprises a block mapper operable to group subsymbols into blocks of subsymbols; and

the plurality of interleavers operable to rotate blocks of subsymbols between the plurality of OFDM transmit signals.

10. The wireless device according to claim 9 wherein the interleaver circuit is operable in a mode compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11a standard (1999) and/or successor standards.

11. The wireless device according to claim 9 wherein the interleaver circuit is operable in a mode compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11g standard (2003) and/or successor standards.

12. A method of operating a wireless device to interleave bits of an input symbol for transmission over a plurality of transmit antennas, each of the transmit antennas radiating a corresponding one of a plurality of orthogonal frequency division multiplex streams, each comprising a plurality of subcarriers, the method comprising:

interleaving bits of the input symbol according to at least one permutation;

allocating interleaved bits to sub-symbols;

mapping sub-symbols to blocks; and

rotating the blocks between the plurality of transmit antennas using the plurality of orthogonal frequency division multiplex streams, thereby gaining tone separation between adjacent bits of the input symbol.

13. The method according to claim 12 , wherein the at least one permutation is compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11a standard (1999) and/or successor standards.

14. The method according to claim 13 , wherein the at least one permutation is compliant with the Institute of Electrical and Electronics Engineers (IEEE) 802.11g standard (2003) and/or successor standards.

15. The method according to claim 13 , further comprising allocating the interleaved bits to subsymbols of all subcarriers of one of the plurality of orthogonal frequency division multiplex streams before allocating the interleaved bits to subsymbols of all subcarriers of another of the plurality of orthogonal frequency division multiplex streams.

16. The method according to claim 13 , wherein an order of allocation of interleaved bits to bits of subsymbols alternates for successive subsymbols.

17. The method according to claim 13 , wherein the bits of an input symbol are allocated to all subsymbols for one subcarrier of all of the plurality of orthogonal frequency division multiplex streams, before bits of the input symbol are allocated to all subsymbols of another subcarrier of all of the plurality of orthogonal frequency division multiplex streams.

18. The method according to claim 17 , wherein an order of allocation of interleaved bits to bits of subsymbols alternates as subsymbols are allocated to each of the plurality of orthogonal frequency division multiplex streams.

19. A method of operating a wireless device to process bits of an input symbol for transmission via a plurality of orthogonal frequency division multiplex (OFDM) transmit signals, the method comprising:

interchanging bits of the input symbol by a plurality of interleavers, each interleaver interchanging bits according to an associated permutation;

allocating bits of the input symbol to form subsymbols, each subsymbol associated with a subcarrier of one of the plurality of OFDM transmit signals;

block mapping to group subsymbols into blocks of subsymbols; and

rotating blocks of subsymbols between the plurality of OFDM transmit signals.

20. The method according to claim 19 , wherein the at least one permutation is compliant with:

the Institute of Electrical and Electronics Engineers (IEEE) 802.11a standard (1999) and/or successor standards; or

the Institute of Electrical and Electronics Engineers (IEEE) 802.11g standard (2003) and/or successor standards.