Multi-channel parallel/serial concatenated convolutional codes and trellis coded modulation encoder/decoder

• US 6,088,387 A
• Filed: 12/31/1997
• Issued: 07/11/2000
• Est. Priority Date: 12/31/1997
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Sadjadpour, Hamid R., Gelblum, Ehud Alexander
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GHAYOUR, MOHAMMAD H
• Application Number:
  US09/001,342
• Time in Patent Office: 923 Days
• Field of Search: 375/222, 375/260, 375/295, 375/265, 714/755, 714/756, 714/801, 714/792
• US Class Current: 375/222
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0013 Rate matching, e.g. puncturing or repetition of code symbols
• CPC Class Codes: H04L 1/005 Iterative decoding, including iteration between signal detection and decoding operation
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes
• CPC Class Codes: H04L 27/2602 Signal structure

Abstract

A method and apparatus to transmit turbo-encoded data in a multitone channel assigns the original data and selected parity bits across multitone subchannels allowing transmission of an entire turbo-encoded block withing one or few symbol time frame. Parity bits are selected by a procedure using data derived by optimization using simulation of a single-channel system. The optimization determines, for a specified bit error rate, for each possible number of information bits per symbol, the code rate corresponding to the lowest signal-to-noise ratio. Alternatively, in the simulation non-identical integer values may be applied to the channels to approximate non-integer values of code rate and information bits-per-channel in the aggregate. The optimized data are used to determine an optimal code rate and SNR for each channel. In assigning the respective bits to the channels, the number of parity bits in each channel are shared.

Claims

1. A modem for communicating over a network having channels, comprising:

a multichannel modulator connected to generate respective symbols representing bits applied to said multichannel modulator on each of said channels;

a controller;

a turbo-encoder having first and second Recursive Systematic Convolutional encoders (RSC encoders) receiving data from an input data source and connected to apply to said multichannel modulator first parity bits from said first RSC encoder and second parity bits from said second RSC encoder under control of said controller;

said controller being programmed to measure respective transmission characteristics of said channels;

said controller being programmed to apply information bits and only a portion of said first and second parity bits to said multichannel modulator responsive to a result of a measuring of said respective transmission characteristics of said channels.

2. A modem as in claim 1, wherein said controller is programmed to apply, to said multichannel modulator, a first number of said first parity bits in a given time period and a second number, substantially equal to said first number, of said second parity bits in said given time period.

3. A modem as in claim 1, wherein:

each respective symbol is such that at least one the bits applied to said multichannel modulator, for each of the symbols, is a most protected bit; and

said controller is programmed to apply said first and second parity bits to said multichannel modulator such that said at least one most protected bit is at least one of said first and second parity bits.

4. A modem as in claim 1, wherein:

at least one of the symbols is a QAM tone having an I-channel-most-protected-bit and a Q-channel most protected bit; and

said controller is programmed to apply said first and second parity bits to said multichannel modulator such that, when two of said first and second parity bits are applied to said multichannel modulator for transmission through a single channel, said I-channel-most-protected-bit is said first parity bit and Q-channel-most-protected-bit is said second parity bit.

5. A modem as in claim 1, wherein said controller is programmed to control a respective signal power level applied in each of said channels responsively to the result of said measuring of said respective transmission characteristics of said channels.

6. A method for encoding data for transmission in a multichannel network, comprising the steps of:

a. measuring a transmission characteristic of a first channel of said multichannel network;

b. measuring a transmission characteristic of a second channel of said multichannel network;

c. encoding an information data stream, wherein said encoding step includes encoding said information data stream to produce a first parity bit stream and interleaving said information data stream and encoding the result of said interleaving to produce a second parity bit stream, said total parity bit stream includes said first and second parity bit streams to generate a total parity bit stream;

d. selecting a portion of said total parity bit stream for transmission in said first channel responsive to a result of said steps a and b.

7. A method as in claim 6, wherein:

said step d includes selecting, for application to said first channel, a first portion of said first parity bit stream responsive to a result of said step a;

said step d further includes selecting, for application to said second channel, a second portion of said second parity bit stream responsive to a result of said step a;

said first and second portions each containing a substantially equal number of said first and second parity bits.

10. A method as in claim 7, further comprising the steps of:

interleaving said information data stream to produce an interleaved information data stream;

applying said total parity bit stream and said interleaved information data stream to said channel.

11. A method as in claim 10, further comprising the steps of:

calculating soft predictions of said total parity bit stream and said interleaved information data stream from said total parity bit stream and said interleaved information data stream applied to said channel;

deinterleaving said soft predictions of said information data stream; and

applying results of said steps calculating and deinterleaving to a decoder.

8. A modem for communicating over a network having channels, comprising:

a multichannel modulator connected to generate a respective symbol representing bits applied to said multichannel modulator on each of said channels;

a controller;

a turbo-encoder having first and second Recursive Systematic Convolutional encoders (RSC encoders) receiving data from an input data source and connected to apply to said multichannel modulator first parity bits from said first RSC encoder and second parity bits from said second RSC encoder under control of said controller;

said controller having a memory for storing measured respective transmission characteristics of said channels;

said controller being programmed to apply said information bits and only a portion of said first and second parity bits to said multichannel modulator responsively to said measured said respective transmission characteristics of said channels.

9. A modem for communicating over a network having channels, comprising:

a uniform interleaver;

a multichannel modulator connected to generate a respective symbol representing bits applied to said multichannel modulator on each of said channels;

a controller;

a turbo-encoder having first and second Recursive Systematic Convolutional encoders (RSC encoders) receiving data from an input data source and connected to apply to said multichannel modulator first parity bits from said first RSC encoder and second parity bits from said second RSC encoder under control of said controller;

said controller being programmed to measure respective transmission characteristics of said channels;

said controller being programmed to apply information bits to said uniform interleaver and selected ones of said first and second parity bits to said multichannel modulator, said selected ones being selected by said controller responsively to a result of a measuring of said respective transmission characteristics of said channels;

said uniform interleaver being connected to apply information bits also being to said multichannel modulator after being interleaved by said uniform interleaver.