Methodology and method and apparatus for signaling with capacity optimized constellations

• US 8,842,761 B2
• Filed: 09/14/2012
• Issued: 09/23/2014
• Est. Priority Date: 06/05/2007
• Status: Active Grant

• Current Assignee: Constellation Designs, LLC (SoftBank Group Corp.)
• Original Assignee: Constellations Designs, Inc.
• Inventors: Barsoum, Maged F., Jones, Christopher R.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US13/618,630
• Publication Number:
  US 20130083862A1
• Time in Patent Office: 739 Days
• Field of Search: 375259-262, 375/268, 375/269, 375/295, 375/298, 375/279, 375/280, 375/329, 375/308, 375/316, 375/340, 375/341, 375/332, 332/103, 329/304
• US Class Current: 375/261
• CPC Class Codes: H03M 13/255 with Low Density Parity Check [LDPC] codes
• CPC Class Codes: H03M 13/6325 Error control coding in combination with demodulation
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 27/3405 Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power
• CPC Class Codes: H04L 27/3483 using a modulation of the constellation points
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

Communication systems are described that use geometrically shaped constellations that have increased capacity compared to conventional constellations operating within a similar SNR band. In several embodiments, the geometrically shaped is optimized based upon a capacity measure such as parallel decoding capacity or joint capacity. In many embodiments, a capacity optimized geometrically shaped constellation can be used to replace a conventional constellation as part of a firmware upgrade to transmitters and receivers within a communication system. In a number of embodiments, the geometrically shaped constellation is optimized for an Additive White Gaussian Noise channel or a fading channel. In numerous embodiments, the communication uses adaptive rate encoding and the location of points within the geometrically shaped constellation changes as the code rate changes.

Claims

1. A digital communication system, comprising:

a transmitter configured to transmit signals to a receiver via a communication channel;

wherein the transmitter, comprises;

a coder configured to receive user bits and output encoded bits at an expanded output encoded bit rate using an LDPC code;

a mapper configured to map encoded bits to symbols in a QAM symbol constellation;

a modulator configured to generate a signal for transmission via the communication channel using symbols generated by the mapper; and

wherein the QAM symbol constellation is a geometrically spaced symbol constellation optimized for capacity using parallel decode capacity that provides a given capacity at a reduced signal-to-noise ratio compared to a QAM signal constellation that maximizes d_min.

2. The communication system of claim 1, wherein the geometrically spaced symbol constellation is capacity optimized subject to additional constraints.

3. The communication system of claim 1, wherein the channel is an AWGN channel.

4. The communication system of claim 1, wherein the channel is a fading channel.

5. The communication system of claim 1, wherein the QAM constellation is a QAM-64 constellation.

6. The communication system of claim 5, wherein the LDPC code is a rate 1/2 LDPC code.

7. The communication system of claim 6, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.72, −

0.81, 1.72, −

0.62, 0.62, 0.02, 0.81, −

0.02}.

8. The communication system of claim 5, wherein the LDPC code is a rate 2/3 LDPC code.

9. The communication system of claim 8, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.64, −

0.97, 1.64, −

0.58, 0.58, 0.15, 0.97, −

0.15}.

10. The communication system of claim 5, wherein the LDPC code is a rate 5/6 LDPC code.

11. The communication system of claim 10, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.60, −

1.03, −

0.19, −

0.58, 1.60, 1.03, 0.19, 0.58}.

12. The communication system of claim 1, wherein the QAM constellation is a QAM-256 constellation.

13. The communication system of claim 12, wherein the LDPC code is a rate 1/2 LDPC code.

14. The communication system of claim 13, wherein the symbol constellation is formed using a PAM-16 constellation comprising the set of constellation points {−

1.98, −

1.29, 1.94, −

1.17, −

0.38, −

0.65, −

0.38, −

0.68, 1.09, 0.76, 1.26, 0.76, 0.06, 0.29, 0.06, 0.29}.

15. The communication system of claim 12, wherein the LDPC code is a rate 3/4 LDPC code.

16. The communication system of claim 15, wherein the symbol constellation is formed using a PAM-16 constellation comprising the set of constellation points {−

1.84, −

1.42, 1.84, −

1.11, −

0.40, −

0.65, −

0.29, −

0.83, 1.11, 0.84, 1.42, 0.65, 0.05, 0.29, −

0.05, 0.40}.

17. A digital communication system, comprising:

a receiver configured to receive signals transmitted via a communication channel using a QAM symbol constellation;

wherein the receiver, comprises;

a demodulator configured to demodulate the signal received via the communication channel;

a demapper configured to estimate likelihoods of symbols in a QAM symbol constellation from the demodulated signal;

a decoder that is configured to estimate decoded bits from the likelihoods generated by the demapper using an LDPC code; and

wherein the QAM symbol constellation is a geometrically spaced symbol constellation optimized for capacity using parallel decode capacity that provides a given capacity at a reduced signal-to-noise ratio compared to a QAM signal constellation that maximizes d_min.

18. The communication system of claim 17, wherein the geometrically spaced symbol constellation is capacity optimized subject to additional constraints.

19. The communication system of claim 17, wherein the channel is an AWGN channel.

20. The communication system of claim 17, wherein the channel is a fading channel.

21. The communication system of claim 17, wherein the QAM constellation is a QAM-64 constellation.

22. The communication system of claim 21, wherein the LDPC code is a rate 1/2 LDPC code.

23. The communication system of claim 22, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.72, −

0.81, 1.72, −

0.62, 0.62, 0.02, 0.81, −

0.02}.

24. The communication system of claim 21, wherein the LDPC code is a rate 2/3 LDPC code.

25. The communication system of claim 24, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.64, −

0.97, 1.64, −

0.58, 0.58, 0.15, 0.97, −

0.15}.

26. The communication system of claim 21, wherein the LDPC code is a rate 5/6 LDPC code.

27. The communication system of claim 26, wherein the symbol constellation is formed using a PAM-8 constellation comprising the set of constellation points {−

1.60, −

1.03, −

0.19, −

0.58, 1.60, 1.03, 0.19, 0.58}.

28. The communication system of claim 17, wherein the QAM constellation is a QAM-256 constellation.

29. The communication system of claim 28, wherein the LDPC code is a rate 1/2 LDPC code.

30. The communication system of claim 29, wherein the symbol constellation is formed using a PAM-16 constellation comprising the set of constellation points {−

1.98, −

1.29, 1.94, −

1.17, −

0.38, −

0.65, −

0.38, −

0.68, 1.09, 0.76, 1.26, 0.76, 0.06, 0.29, 0.06, 0.29}.

31. The communication system of claim 28, wherein the LDPC code is a rate 3/4 LDPC code.

32. The communication system of claim 31, wherein the symbol constellation is formed using a PAM-16 constellation comprising the set of constellation points {−

1.84, −

1.42, 1.84, −

1.11, −

0.40, −

0.65, −

0.29, −

0.83, 1.11, 0.84, 1.42, 0.65, 0.05, 0.29, −

0.05, 0.40}.