Multi-dimensional fractional number of bits modulation scheme

• US 20030215023A1
• Filed: 05/10/2002
• Published: 11/20/2003
• Est. Priority Date: 05/10/2002
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Chang, Anchung, Patel, Samir B., Long, Chu-Sieng
• Granted Patent: US 7,161,991 B2
• Time in Patent Office: Days
• US Class Current: 375/265
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/006 Trellis-coded modulation

Abstract

A method of encoding information bits of a communication signal for a communication system (10) is provided. The method includes decomposing the communication signal having a corresponding M₁-ary modulation constellation into a M₂-ary constellation, and a M₃-ary constellation to generate one or more symbols S_i. The one or more symbols S_i are mapped using a bit-to-symbol table to generate an encoded communication signal. Decoding methods are also provided for uncoded modulation and trellis coded modulation (TCM). A transmitter (20) comprising an encoder (12) for performing TCM that is capable of transmitting a fractional number of information bits per transmitted symbol is also provided.

Claims

1. A trellis coded modulation transmitter encoder for a communication system comprising:

a first serial-to-parallel converter converting an input signal into a first parallel signal;

a swap controller electrically coupled to said first serial-to-parallel converter and swapping order of information bits in said first parallel signal to generate a parallel interchange signal;

a parallel-to-serial converter electrically coupled to said swap controller and converting said interchange signal into a serial interchange signal;

a padder electrically coupled to said parallel-to-serial converter and padding said serial interchange signal with redundant bits to generate a padded interchange signal;

a second serial-to-parallel converter electrically coupled to said padder and converting said padded interchange signal into a convolutional encoder input signal;

a convolutional encoder electrically coupled to said second serial-to-parallel converter and coding said convolutional encoder input signal to generate a convolutional encoder output signal; and

a signal set mapper electrically coupled to said convolutional encoder and mapping said convolutional encoder output signal to generate a modulated signal.

2. A system as in claim 1 wherein said convolutional encoder is guiding said redundant bits via a first channel into said signal set mapper.

3. A system as in claim 2 wherein said first channel is a redundant channel.

4. A system as in claim 2 wherein said swap controller maps said encoder output signal to generate said modulated signal in response to bits received from said first channel.

5. A system as in claim 1 wherein said convolutional encoder comprises a plurality of convolutional encoder channels and at least one convolutional encoder channel of said plurality of convolutional encoder channels comprises a redundant circuit.

6. A system as in claim 5 wherein said redundant circuit comprises:

at least one redundant channel comprising;

at least one delay component electrically coupled to at least one convolutional encoder channel of said plurality of convolutional encoder channels; and

a feedback loop electrically coupling a redundant channel output to a delay component of said at least one delay component.

7. A system as in claim 1 wherein said redundant bits are indicative of when to transmit an outer symbol.

8. A system as in claim 1 wherein said swap controller generates a position signal and said padder pads said serial interchange signal in response to said position signal.

9. A system as in claim 1 wherein said second serial-to-parallel converter comprises a plurality of second serial-to-parallel converter output channels and each of said output channels in said plurality of second serial-to-parallel converter output channels are electrically coupled to at least one convolutional encoder input channel.

10. A method of encoding information bits of a communication signal for a communication system comprising:

decomposing the communication signal having a corresponding M₁-ary constellation into a M₂-ary constellation, and a M₃-ary constellation to generate a symbol series comprising one or more symbols S_i; and

mapping said one or more symbols S_i using a bit-to-symbol table to generate an encoded communication signal.

11. A method as in claim 10 wherein said M₂-ary constellation and said M₃-ary constellation are quadrature amplitude modulation (QAM) constellations or a phase shift keying (PSK) constellations.

12. A method as in claim 10 further comprising:

assigning at least one symbol in said one or more symbols S_i to have one or more constellation bits and one or more position bits.

13. A method as in claim 10 wherein M₂ is 2^m inner points and M₃ is 2^x outer points.

14. A method as in claim 13 wherein decomposing the communication signal further comprises adjusting the communication signal to have at least one constellation bit that is indicative of said M₂-ary constellation or said M₃-ary constellation.

15. A method as in claim 14 wherein decomposing the communication signal further comprises assigning (m−

1)•

(2<sup>m−

x</sup>)+1 information bits to 2<sup>m−

x</sup> inner symbols in response to said constellation bit.

16. A method as in claim 15 wherein decomposing the communication signal further comprises assigning (m−

1)•

(2<sup>m−

x</sup>)+1 information bits to 2<sup>m−

x</sup>−

1 inner symbols and one outer symbol in response to said constellation bit.

17. A method as in claim 16 wherein assigning (m−

1)•

(2<sup>m−

x</sup>)+1 information bits comprises;

determining an outer symbol position in response to m−

x position bits; and

swapping said S_i symbols in response to said m−

x position bits.

18. A method as in claim 17 wherein assigning (m−

1)•

(2<sup>m−

x</sup>)+1 information bits comprises selecting said outer symbol from 2^x QAM to maximize a minimum distance d_free.

19. A method of decoding information bits for a communication system that uses uncoded modulation comprising:

receiving modified I-Q signals;

denoting said modified I-Q signals into one or more symbols S_i;

determining one or more distances dⁱ_M2-ary and one or more distances dⁱ_M3-ary for each of said one or more symbols S_i and calculating a distance total D_I-Q;

determining one or more possible distance totals D_h for said modified I-Q signals;

comparing said distance total D_I-Q for said modified I-Q signals with said one or more possible distances totals D_h; and

outputting a decoded communication signal.

20. A method of decoding information bits for a communication system that uses trellis-coded modulation comprising:

receiving a modified I-Q signals;

denoting said modified I-Q signals into a plurality of symbols S_i; and

decoding said plurality of symbols S_i simultaneously.