Method and adaptive bit interleaver for wideband systems using adaptive bit loading

• US 20050135493A1
• Filed: 12/18/2003
• Published: 06/23/2005
• Est. Priority Date: 12/18/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Maltsev, Alexander A., Davydov, Alexei V., Sadri, Ali S.
• Granted Patent: US 7,570,695 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 1/0042 Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 27/2628 Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators H04L27/2634 takes precedence
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

An adaptive interleaver for wideband orthogonal frequency division multiplexed (OFDM) communications permutes a variable number of coded bits per OFDM symbol (Ncbps). The variable number of coded bits is calculated based on individual subcarrier modulation assignments for orthogonal subcarriers of a wideband channel. The interleaver matrix size may be based on the variable number of coded bits per OFDM symbol and the number of subchannels that comprise the wideband channel. The interleaver may add padding bits to the interleaver matrix to fill any remaining positions, and after performing an interleaving operation, the interleaver may prune the padding bits to provide a sequence of interleaved bits for subsequent modulation on the orthogonal subcarriers. A receiver may include an adaptive deinterleaver to reverse the process.

Claims

1. A method comprising:

inputting a variable number of coded bits to an interleaver matrix, wherein the variable number of coded bits is based on individual subcarrier modulation assignments for orthogonal frequency division multiplexed subcarriers;

adding padding bits to the interleaver matrix to fill any remaining positions; and

after performing an interleaving operation, pruning the padding bits to provide a sequence of interleaved bits for subsequent modulation on the plurality of orthogonal subcarriers.

2. The method of claim 1 further comprising modulating the sequence of interleaved bits on the plurality of orthogonal subcarriers in accordance with the individual subcarrier modulation assignments,

wherein the variable number of coded bits represents an orthogonal frequency division multiplexed symbol and is determined based on a number of the orthogonal subcarriers and a number of bits associated with the individual subcarrier modulation assignments, the individual subcarrier modulation assignments comprising between zero and ten bits per symbol.

3. The method of claim 2 wherein the number of orthogonal subcarriers comprises a wideband channel,

wherein the wideband channel has several frequency-separated subchannels having a portion of the orthogonal subcarriers that comprises the wideband channel,

wherein each orthogonal subcarrier of an associated subchannel has a null at substantially a center frequency of other subcarriers of the associated subchannel.

4. The method of claim 3 comprising performing separate interleaving operations for the subchannels, wherein an approximately equal portion of the variable number of encoded bits is interleaved for each of the subchannels.

5. The method of claim 2 wherein the method is performed by a transmitting station and further comprises:

receiving the individual subcarrier modulation assignments from a receiving station, the subcarrier modulation assignments based on channel conditions associated with the individual subcarriers, the channel conditions including a signal to interference and noise ratio (SINR); and

transmitting a plurality of symbols modulated on the orthogonal subcarriers, the plurality of symbols comprising the orthogonal frequency division multiplexed symbol.

6. The method of claim 2 further comprising:

calculating the variable number of coded bits based on the number of the orthogonal subcarriers in a wideband channel and a number of coded bits to be modulated on the subcarriers; and

determining a size of the interleaver matrix based on the variable number of coded bits and a number of subchannels that comprise the wideband channel, wherein the interleaver matrix comprises a predetermined number of columns for each subchannel of the wideband channel.

7. The method of claim 1 wherein inputting comprises inputting the variable number of coded bits into the interleaver matrix in a row-by-row fashion, and

wherein interleaving comprises reading bits from the interleaver matrix in a column-by-column fashion.

8. The method of claim 7 wherein the pruning comprising removing the padding bits during the reading to provide the sequence of interleaved bits for subsequent subcarrier modulation.

9. The method of claim 7 wherein interleaving comprises reading bits including the padding bits from the interleaver matrix, and

wherein the pruning comprising removing the padding bits after the reading to provide the sequence of interleaved bits for subsequent subcarrier modulation.

10. The method of claim 1 wherein each of the individual subcarrier modulation assignments comprises one of no modulation, BPSK modulation, QPSK modulation, 8-PSK modulation, 16-QAM, 32-QAM, 64-QAM, 128-QAM and 256-QAM for each of the orthogonal subcarriers.

11. The method of claim 3 wherein the wideband channel comprises up to four subchannels having bandwidths of approximately 20 MHz,

wherein each of the subchannels has up to 48 orthogonal data subcarriers, and

wherein each orthogonal data subcarrier is assigned one of the individual subcarrier modulation assignments comprising between zero and ten bits per symbol, and

wherein each subcarrier is modulated in accordance with the assigned subcarrier modulation assignment.

12. A method comprising:

generating a variable number of coded bits representing an orthogonal frequency division multiplexed symbol received over a wideband channel, the wideband channel comprising one or more subchannels having a plurality of orthogonal subcarriers, the orthogonal frequency division multiplexed subcarriers having been modulated in accordance with individual subcarrier modulation assignments;

inserting padding bits to locations within the variable number of coded bits to generate a block of bits, the locations being calculated based on the number of coded bits per the orthogonal frequency division multiplexed symbol and a number of columns of a deinterleaver matrix;

inputting the block of bits to the deinterleaver matrix to fill the matrix; and

after performing a deinterleaving operation, pruning the padding bits to provide a sequence of deinterleaved bits.

13. The method of claim 12 further comprising:

demodulating each of the subcarriers to generate a number of bits from each subcarrier, the number being based on one of the individual subcarrier modulation assignments associated with each subcarrier.

14. The method of claim 13 wherein the individual subcarrier modulation assignments comprise between zero and ten bits per subcarrier,

wherein the subcarriers associated with a subchannel have a null at substantially a center frequency of other subcarriers of the associated subchannel,

wherein the deinterleaver matrix comprises a predetermined number of columns for each of the subchannels comprising the wideband channel, and

the method further comprises providing the sequence of deinterleaved bits for subsequent forward error correction.

15. A transmitter comprising:

an interleaver to input a variable number of coded bits to an interleaver matrix, to add padding bits to the interleaver matrix to fill any remaining positions of the matrix, and to prune the padding bits after interleaving to provide a sequence of interleaved bits for subsequent modulation on a plurality of orthogonal frequency division multiplexed subcarriers; and

a processor to calculate the variable number of coded bits based on individual subcarrier modulation assignments for the subcarriers.

16. The transmitter of claim 15 further comprising a subcarrier modulator to modulate the sequence of interleaved bits on the plurality of subcarriers in accordance with the individual subcarrier modulation assignments,

wherein the variable number of coded bits is determined based on a number of the subcarriers and a number of bits associated with each of the individual subcarrier modulation assignments, the individual subcarrier modulation assignments comprising between zero and ten bits per symbol.

17. The transmitter of claim 16 wherein the processor is to calculate the variable number of coded bits based on the number of the orthogonal subcarriers in a wideband channel and a number of coded bits to be individually modulated on the subcarriers, and

wherein the processor is to determine a size of the interleaver matrix based on the variable number of coded bits and a number of subchannels that comprise the wideband channel, wherein the interleaver matrix comprises a predetermined number of columns for each subchannel of the wideband channel.

18. The transmitter of claim 17 wherein the individual subcarrier modulation assignments are received from a receiving station, the subcarrier modulation assignments calculated by the receiver station based on channel conditions associated with the individual subcarriers, the channel conditions including a signal to interference and noise ratio (SINR).

19. The transmitter of claim 18 wherein the transmitter further comprises radio frequency circuitry to transmit a plurality of symbols modulated on the subcarriers that comprise the orthogonal frequency division multiplexed symbol.

20. A receiver comprising:

a subcarrier demodulator to generate a variable number of coded bits comprising an orthogonal frequency division multiplexed symbol received over a wideband channel; and

an adaptive deinterleaver to insert padding bits to locations within the variable number of coded bits to generate a block of bits, the locations being calculated based on the variable number of coded bits and a number of columns of a deinterleaver matrix, the deinterleaver is to input the block of bits to the deinterleaver matrix, and is to prune the padding bits after performing a deinterleaving operation to provide a sequence of deinterleaved bits.

21. The receiver of claim 20 wherein the wideband channel comprises one or more subchannels having a plurality of orthogonal subcarriers, the orthogonal subcarriers having been modulated in accordance with individual subcarrier modulation assignments, and

wherein each orthogonal subcarrier is associated with a subchannel and has a null at substantially a center frequency of other subcarriers of the associated subchannel.

22. The receiver of claim 21 wherein the subcarrier demodulator is to demodulate each of the subcarriers and is to generate a number of bits from each subcarrier, the number being based on the individual subcarrier modulation assignment associated with each of the subcarriers.

23. A wireless communication device comprising:

a substantially omnidirectional antenna; and

a transmitter comprising an adaptive interleaver to input a variable number of coded bits comprising an orthogonal division frequency multiplexed symbol to an interleaver matrix, to add padding bits to the interleaver matrix to fill any remaining positions of the matrix, and to prune the padding bits after interleaving to provide a sequence of interleaved bits for subsequent modulation on a plurality of orthogonal frequency division multiplexed subcarriers.

24. The device of claim 23 wherein the transmitter further comprises:

a processor to calculate the variable number of coded bits based on individual subcarrier modulation assignments for the subcarriers; and

a subcarrier modulator to modulate the sequence of interleaved bits on the plurality of subcarriers in accordance with the individual subcarrier modulation assignments,

wherein the variable number of coded bits is determined based on a number of the subcarriers and a number of bits associated with each of the individual subcarrier modulation assignments, the individual subcarrier modulation assignments comprising between zero and ten bits per symbol.

25. The device of claim 24 wherein the processor is to calculate the variable number of coded bits based on the number of the orthogonal subcarriers of the wideband channel and a number of coded bits to be individually modulated on the subcarriers, and

wherein the processor is to determine a size of the interleaver matrix based on the variable number of coded bits and a number of subchannels that comprise a wideband channel, wherein the interleaver matrix comprises a predetermined number of columns for each subchannel of the wideband channel, and

wherein the individual subcarrier modulation assignments are received from a receiving station, the subcarrier modulation assignments calculated by the receiver station based on channel conditions associated with the individual subcarriers, the channel conditions including a signal to interference and noise ratio (SINR).

26. The device of claim 23 further comprising a receiver having a subcarrier demodulator to generate a variable number of coded receive bits comprising a orthogonal frequency division multiplexed symbol received over a wideband channel,

wherein the receiver further includes an adaptive deinterleaver to insert padding bits to locations within the variable number of coded receive bits to generate a block of receive bits, the locations being calculated based on the variable number of coded receive bits and a number of columns of a deinterleaver matrix, and

wherein the deinterleaver is to input the block of receive bits to the deinterleaver matrix and to prune the padding bits after performing a deinterleaving operation to provide a sequence of deinterleaved bits.

27. The device of claim 25 wherein the wideband channel comprises one or more subchannels having a plurality of orthogonal subcarriers, the orthogonal subcarriers having been modulated in accordance with individual subcarrier modulation assignments, and

wherein each orthogonal subcarrier is associated with a subchannel and has a null at substantially a center frequency of other subcarriers of the associated subchannel.

28. A machine-readable medium that provides instructions, which when executed by one or more processors, cause said processors to perform operations comprising:

inputting a variable number of coded bits to an interleaver matrix, wherein the variable number of coded bits is based on individual subcarrier modulation assignments for orthogonal frequency division multiplexed subcarriers;

adding padding bits to the interleaver matrix to fill any remaining positions; and

after performing an interleaving operation, pruning the padding bits to provide a sequence of interleaved bits for subsequent modulation on the plurality of orthogonal subcarriers.

29. The machine-readable medium of claim 28 wherein the instructions, when further executed by one or more of said processors cause said processors to perform operations further comprising modulating the sequence of interleaved bits on the plurality of orthogonal subcarriers in accordance with the individual subcarrier modulation assignments,

wherein the variable number of coded bits represents an orthogonal frequency division multiplexed symbol, and is determined based on a number of the orthogonal subcarriers and a number of bits associated with each of the individual subcarrier modulation assignments, the individual subcarrier modulation assignments comprising between zero and ten bits per symbol.

30. The machine-readable medium of claim 28 wherein the instructions, when further executed by one or more of said processors cause said processors to perform operations wherein the number of orthogonal subcarriers comprises a wideband channel,

wherein the wideband channel has several frequency-separated subchannels having a portion of the orthogonal subcarriers that comprises the wideband channel,

wherein each orthogonal subcarrier of a subchannel has a null at substantially a center frequency of other subcarriers of the subchannel.