Interleaver for IEEE 802.11n standard
A MIMO wireless system includes a transmitter having a parser that parses a bit stream into multiple spatial data streams and multiple interleavers corresponding to the multiple spatial data streams, where each interleaver interleaves the bits in the corresponding spatial data stream by performing frequency rotation after an interleaving operation, to increase diversity of the wireless system. The MIMO wireless system also includes a receiver that has deinterleavers that deinterleaves spatial bit streams transmitted by the transmitter.
1. A method of data communication in a wireless system, comprising the steps of:
parsing a bit stream into multiple spatial data streams;
interleaving the bits in each of one or more spatial data streams by performing frequency rotation after an interleaving operation, to increase diversity of the wireless system, wherein frequency rotation is performed according to relation:
r =( j −((2× i ss )mod 3+3×floor( i ss /3))× N rot ×N BPSC )mod N CBPS , j= 0, 1, . . . , N CBPS −1,
wherein
N BPSC is the number of coded bits per subcarrier,
N CBPS is a block size corresponding to a number of coded bits in a single Orthogonal Frequency Division Multiplexing (OFDM) symbol,
j is an index after a second permutation and before a third permutation,
r is an index after the third permutation,
i SS =0, 1, . . . , N SS −1 is the index of the spatial stream on which interleaving is operating, N ss is the number of spatial streams, and
N rot is a base rotation number in use and
transmitting the bits of each spatial data stream.
2. The method of claim 1 wherein the number of frequency rotations for a spatial data stream is a function of the number of the total spatial data streams.
3. The method of claim 1 wherein the steps of interleaving the bits in a spatial data stream includes the steps of performing a first interleaving permutation to ensure that adjacent coded bits are mapped onto nonadjacent subcarriers in one data stream for transmission, and a second permutation to ensure that coded bits are mapped alternately onto less and more significant bits of the constellation, and a third interleaving permutation providing the frequency rotation, varying on different spatial data streams to increase diversity of the wireless system.
4. The method of claim 1 , wherein the steps of interleaving the bits in a spatial data stream includes the steps of: (a) ensuring that adjacent coded bits are mapped onto nonadjacent sub-carriers, and (b) ensuring that coded bits are mapped alternately onto less and more significant bits of the constellation whereby long runs of low reliability (LSB) bits are avoided.
5. The method of claim 4 wherein each spatial data stream interleaver array includes N row rows and N column columns of bits, wherein:
the steps (a) of ensuring that adjacent coded bits are mapped onto nonadjacent sub-carriers is according to relation:
i=N row ×( k mod N column )+floor( k/N column ), k= 0, 1, . . . , N CBPS −1,
the steps (b) of ensuring that coded bits are mapped alternately onto less and more significant bits of the constellation whereby long runs of low reliability (LSB) bits are avoided is according to relation:
j=s ×floor( i/s )+( i+N CBPS −floor( N column ×i/N CBPS ))mod s, i= 0, 1, . . . , N CBPS −1,
where s is determined according to s=max(N BPSC /2,1), and
k denotes the index of the coded bit before a first permutation.
6. The method of claim 4 further including the steps of receiving the transmitted bits of each spatial bit stream, and deinterleaving the received bits according to relations:
x d =( x dd +((2× i ss )mod 3+3×floor( i ss /3))× N rot ×N BPSC )mod N CBPS , x dd =0, 1 , . . . , N CBPS −1
j d =s ×floor( j dd /s )+( j +floor( N column ×j dd /N CBPS ))mod s j dd =0, 1, . . . , N CBPS −1,
i d =N column ×i dd −( N CBPS −1)×floor( N column ×i dd /N CBPS ), i dd =0, 1 , . . . , N CBPS −1,
wherein the index of the coded bit before the first permutation is denoted by x dd , and x d is the index after the first and before the second permutation, and j d is the index after the second permutation and before the third permutation, i d is the index after the third permutation, and N CBPS denotes a block size corresponding to the number of coded bits in a single OFDM symbol, i SS =0, 1, . . . , N SS −1 is the index of the spatial stream on which this interleaving is operating, and N rot is a base rotation number in use.
7. The method of claim 1 wherein the wireless system comprises a multiple-input multiple-output (MIMO) system.
8. The method of claim 7 wherein the wireless system comprises an OFDM MIMO system.
9. The method of claim 1 wherein the steps of parsing the bit stream further includes the steps of bitwise or group-wise round robin parsing to increase spatial diversity.
10. The method of claim 9 wherein the steps of parsing the bit stream further includes the steps of bitwise round robin parsing such that one bit of the bit stream is parsed to one data stream each time.
11. The method of claim 1 further including the steps of puncturing each spatial data stream after the step of parsing.
12. The method of claim 11 wherein the step of puncturing for each spatial data stream is based on the channel condition.
13. A wireless communication system, comprising:
a transmitter including:
a parser that parses a bit stream into multiple spatial data streams;
multiple interleavers corresponding to the multiple spatial data streams, wherein each of one or more interleavers interleaves the bits in the corresponding spatial data stream by performing frequency rotation after an interleaving operation, to increase diversity of the wireless system, wherein frequency rotation is performed according to relation:
r =( j −((2× i ss )mod 3+3×floor( i ss /3))× N rot ×N BPSC )mod N CBPS , j= 0, 1 , . . . , N CBPS −1,
wherein
N BPSC is the number of coded bits per subcarrier,
N CBPS is a block size corresponding to a number of coded bits in a single Orthogonal Frequency Division Multiplexing (OFDM) symbol,
j is an index after a second permutation and before a third permutation,
r is an index after the third permutation,
i SS =0, 1, . . . , N SS −1 is the index of the spatial stream on which interleaving is operating, N ss is the number of spatial streams, and
N rot is a base rotation number in use; and
a modulator that transmits the bits of each spatial data stream; and
a receiver that receives and deinterleaves the transmitted bits.
14. The system claim 13 wherein an interleaver performs a first interleaving permutation to ensure that adjacent coded bits are mapped onto nonadjacent subcarriers in one data stream for transmission, and a second permutation to ensure that coded bits are mapped alternately onto less and more significant bits of the constellation, and a third interleaving permutation varying on different spatial data streams by performing different frequency rotation to increase diversity of the wireless system.
15. The system of claim 14 , wherein the interleaver performs interleaving the bits in each spatial data stream by: (a) ensuring that adjacent coded bits are mapped onto nonadjacent sub-carriers, and (b) ensuring that coded bits are mapped alternately onto less and more significant bits of the constellation whereby long runs of low reliability (LSB) bits are avoided.
16. The system of claim 15 wherein each spatial data stream interleaver array includes N row rows and N column columns of bits, wherein:
ensuring that adjacent coded bits are mapped onto nonadjacent sub-carriers is according to relation:
i=N row ×( k mod N column )+floor( k/N column ), k= 0, 1 , . . . , N CBPS −1,
ensuring that coded bits are mapped alternately onto less and more significant bits of the constellation whereby long runs of low reliability (LSB) bits are avoided is according to relation:
j=s ×floor( i/s )+( i+N CBPS −floor( N column ×i/N CBPS ))mod s, i= 0, 1 , . . . , N CBPS −1,
where s is determined according to s=max(N BPSC /2,1), and
k denotes the index of the coded bit before a first permutation.
17. The system of claim 16 wherein the receiver includes a plurality of deinterleavers such that each deinterleaver deinterleaves the bits in a received spatial data stream.
18. The system of claim 17 wherein each deinterleaver deinterleaves the received bits according to relations:
x d =( x dd +((2× i ss )mod 3+3×floor( i ss /3))× N rot ×N BPSC )mod N CBPS , x dd =0, 1 , . . . , N CBPS −1
j d =s ×floor( j dd /s )+( j +floor( N column ×j dd /N CBPS ))mod s j dd =0, 1 , . . . , N CBPS −1,
i d =N column ×i dd −( N CBPS −1)×floor( N column ×i dd /N CBPS ), i dd =0, 1, . . . , N CBPS −1,
wherein the index of the coded bit before the first permutation is denoted by x dd , and x d is the index after the first and before the second permutation, j d is the index after the second permutation and before the third permutation, i d is the index after the third permutation, N CBPS denotes a block size corresponding to the number of coded bits in a single OFDM symbol, i SS =0, 1, . . . , N SS −1 is the index of the spatial stream on which this interleaver is operating, and N rot is a base rotation number in use.
19. The system of claim 13 wherein the wireless system comprises a MIMO system.
20. The system of claim 19 wherein the wireless system comprises an OFDM MIMO system.
21. The system of claim 13 wherein the parser parses the bit stream by bitwise round robin parsing, to increase spatial diversity.
22. The system of claim 21 wherein the parser parses the bit stream by bitwise round robin parsing such that one bit of the bit stream is parsed to one data stream each time.
23. A wireless apparatus, comprising:
a transmitter including:
a parser that parses a bit stream into multiple spatial data streams;
multiple interleavers corresponding to the multiple spatial data streams, wherein each of one or more interleavers interleaves the bits in the corresponding spatial data stream by performing frequency rotation after an interleaving operation, to increase diversity of the wireless system, wherein frequency rotation is performed according to relation:
r =( j −((2× i ss )mod 3+3×floor( i ss /3))× N rot ×N BPSC )mod N CBPS , j= 0, 1 , . . . , N CBPS −1,
wherein
N BPSC is the number of coded bits per subcarrier,
N CBPS is a block size corresponding to a number of coded bits in a single Orthogonal Frequency Division Multiplexing (OFDM) symbol,
j is an index after a second permutation and before a third permutation,
r is an index after the third permutation,
i SS =0, 1, . . . , N SS −1 is the index of the spatial stream on which interleaving is operating, N ss is the number of spatial streams, and
N rot is a base rotation number in use; and
a modulator that transmits the bits of each spatial data stream.