Space-time bit-interleaved coded modulation for wideband transmission

• US 20030235149A1
• Filed: 06/24/2002
• Published: 12/25/2003
• Est. Priority Date: 06/24/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Chan, Albert, Lee, Inkyu, Sundberg, Carl-Erik Wilhelm
• Granted Patent: US 7,359,313 B2
• Time in Patent Office: Days
• US Class Current: 370/206
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0055 MAP-decoding
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/03171 Arrangements involving maximum a posteriori probability [MAP] detection
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 27/22 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits

Abstract

A system employs space-time coding characterized at the transmitter by bit-interleaved coded modulation (BICM) combined with multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) modulation. Space-Time coding techniques improve transmission efficiency in radio channels by using multiple transmit and/or receive antennas and coordination of the signaling over these antennas. Bit-interleaved coded modulation provides good diversity gain with higher-order modulation schemes that employ binary convolutional codes. OFDM modulation allows for wideband transmission over frequency selective radio channels. A receiver demodulates the OFDM signal and applies multi-input, multi-output (MIMO) demapping to estimate the BICM encoded bitstream. After deinterleaving of the BICM encoded bitstream, maximum a posteriori (MAP) decoding is applied to the resulting bit stream to generate soft output values. The MIMO demapping and MAP decoding processes exchange likelihood information to improve the bit error rate performance over several iterations of demapping/decoding. By applying well-known turbo-decoding principles to iteratively demap and decode, the overall receiver performance is significantly improved.

Claims

1. A method of processing data for transmission through a channel, the method comprising the steps of:

(a) applying coded modulation to the data to generate an encoded bitstream;

(b) forming at least two parallel streams from the encoded bitstream;

(c) modulating each parallel stream to form a corresponding sequence of frequency domain symbols; and

(d) transforming, for each parallel steam, F frequency domain symbols into F subchannels, wherein F is an integer greater than 1.

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

(e) transferring, for each parallel steam, the F subchannels to the channel.

3. The invention of claim 1, wherein step (a) comprises the steps of:

(a1) applying a convolutional code to the data; and

(a2) interleaving the data to form the encoded bitstream.

4. The invention of claim 1, wherein step (b) forms the at least two parallel streams via a serial-to-parallel conversion.

5. The invention of claim 1, wherein step (c) modulates each parallel stream to form frequency domain symbols of a multi-level, m-ary signal-point constellation, wherein m is an integer greater than 1.

6. The invention of claim 1, wherein step (d) transforms F frequency domain symbols into F subchannels by the step of applying a Fourier transform to the F frequency domain symbols.

7. The invention of claim 1, wherein steps (c) and (d) apply orthogonal frequency domain multiplexing (OFDM) to the parallel streams.

8. The invention of claim 1, wherein the method is embodied in a processor of a wideband wireless communication transmitter.

9. A method of generating data from two or more groups of F subchannels, the method comprising the steps of:

(a) applying a subchannel of each group to a corresponding multi-input, multi-output (MIMO) demapper;

(b) generating, by each MIMO demapper,

     1) a corresponding estimate of two or more parallel streams and

     2) likelihood information based on extrinsic information;

(c) combining the estimates of the two or more parallel streams into an estimate of an encoded bitstream; and

(d) decoding the estimate of the encoded bitstream based on the likelihood information, wherein the decoding generates the extrinsic information.

10. The invention of claim 9, further comprising the step of repeating steps (b) through (d) to iteratively decode the estimate of the encoded bitstream into the data.

11. The invention of claim 9, wherein step (d) decodes user data encoded by the steps of applying a convolutional code to the data and interleaving the data to form the encoded bitstream.

12. The invention of claim 9, wherein, for step (b) the likelihood information is generated by the step of evaluating the expression:

13. The invention of claim 9, wherein step (d) comprises the steps of:

(d1) deinterleaving the encoded bit stream;

(d2) applying maximum a posteriori (MAP) decoding to the deinterleaved encoded bitstream;

(d3) generating reliability information for the encoded bitstream;

(d4) interleaving the reliability information; and

(d5) forming the extrinsic information from interleaved reliability information.

14. The invention of claim 9, wherein the F subchannels for the encoded bitstream are formed by the steps of:

(e) applying coded modulation to the data to generate the encoded bitstream;

(f) forming at least two parallel streams from the encoded bitstream;

(g) modulating each parallel stream to form a corresponding sequence of frequency domain symbols; and

(h) transforming, for each parallel steam, F frequency domain symbols into F subchannels, wherein F is an integer greater than 1.

15. The invention of claim 9, wherein the method is embodied in a processor of a wideband wireless communication receiver.

16. Apparatus for processing data for transmission through a channel, the apparatus comprising:

an encoder configured to apply coded modulation to the data to generate an encoded bitstream;

a serial-to-parallel converter configured to form at least two parallel streams from the encoded bitstream;

a modulator configured to modulate each parallel stream into a corresponding sequence of frequency domain symbols; and

a transform module configured to transform, for each parallel steam, F frequency domain symbols into F subchannels, wherein F is an integer greater than 1.

17. The invention of claim 16, further comprising at least two antennas configured to transfer, for each parallel steam, the F subchannels to the channel.

18. The invention of claim 16, wherein the encoder comprises:

a convolutional encoder that applies a convolutional code to the data; and

an interleaver configured to interleave the data to form the encoded bitstream.

19. The invention of claim 16, wherein the modulator modulates each parallel stream to form frequency domain symbols of a multi-level, m-ary signal-point constellation, wherein m is an integer greater than 1.

20. The invention of claim 16, wherein the transform module is subband coding module.

21. The invention of claim 16, wherein the transform module is configured to transform F frequency domain symbols into F subchannels by applying a Fourier transform to the F frequency domain symbols.

22. The invention of claim 16, wherein the modulator and transform module apply orthogonal frequency domain multiplexing (OFDM) to the parallel streams.

23. The invention of claim 16, wherein the apparatus is embodied in a wideband wireless communication transmitter.

24. The invention of claim 16, wherein the apparatus is embodied in an integrated circuit.

25. Apparatus for generating data from two or more groups of F subchannels, the apparatus comprising:

a multi-input, multi-output (MIMO) demapper configured to generate, based on the two or more groups of F subchannels, a corresponding estimate of two or more parallel streams and

     2) likelihood information based on extrinsic information;

a parallel-to-serial converter configured to combine the estimates of the two or more parallel streams into an estimate of an encoded bitstream; and

a decoder configured to decode the estimate of the encoded bitstream based on the likelihood information, wherein the decoder generates the extrinsic information.

26. The invention of claim 25, wherein the MIMO demapper and the decoder are configured to iteratively decode the estimate of the encoded bitstream into the data.

27. The invention of claim 25, wherein step (d) decodes user data encoded by the steps of applying a convolutional code to the data and interleaving the data to form the encoded bitstream.

28. The invention of claim 25, wherein, for the MIMO demapper, the likelihood information is generated by the step of evaluating the expression:

29. The invention of claim 25, wherein the decoder comprises:

a deinterleaver configured to deinterleaving the encoded bit stream;

a maximum a posteriori (MAP) decoder configured to apply MAP decoding to the deinterleaved encoded bitstream and configures to generate reliability information for the encoded bitstream;

an interleaver configured to interleave the reliability information; and

means for forming the extrinsic information from interleaved reliability information.

30. The invention of claim 25, wherein the F subchannels for the encoded bitstream are formed by:

(A) applying coded modulation to the data to generate the encoded bitstream;

(B) forming at least two parallel streams from the encoded bitstream;

(C) modulating each parallel stream to form a corresponding sequence of frequency domain symbols; and

(D) transforming, for each parallel steam, F frequency domain symbols into F subchannels, wherein F is an integer greater than 1.

31. The invention of claim 25, wherein the apparatus is embodied in a processor of a wideband wireless communication receiver.

32. The invention of claim 25, wherein the apparatus is embodied in an integrated circuit.

33. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for processing data for transmission through a channel, the method comprising the steps of:

(a) applying coded modulation to the data to generate an encoded bitstream;

(b) forming at least two parallel streams from the encoded bitstream;

(c) modulating each parallel stream to form a corresponding sequence of frequency domain symbols; and

(d) transforming, for each parallel steam, F frequency domain symbols into F subchannels, wherein F is an integer greater than 1.

34. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method for generating data from two or more groups of F subchannels, the method comprising the steps of:

(a) applying a subchannel of each group to a corresponding multi-input, multi-output (MIMO) demapper;

(b) generating, by each MIMO demapper,

     1) a corresponding estimate of two or more parallel streams and

     2) likelihood information based on extrinsic information;

(c) combining the estimates of the two or more parallel streams into an estimate of an encoded bitstream; and

(d) decoding the estimate of the encoded bitstream based on the likelihood information, wherein the decoding generates the extrinsic information.