SYSTEMS AND METHODS FOR UNEQUAL ERROR PROTECTION AND SOFT DECISION CALCULATIONS

• US 20100091909A1
• Filed: 10/07/2009
• Published: 04/15/2010
• Est. Priority Date: 10/10/2008
• Status: Abandoned Application

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Ericson, Daniel Wayne, Ni, Jun, Ban, Liang
• Application Number:
  US12/574,987
• Publication Number:
  US 20100091909A1
• Time in Patent Office: Days
• US Class Current: 375/329
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 1/0078 Avoidance of errors by organising the transmitted data in a format specifically designed to deal with errors, e.g. location forward error control, e.g. FEC, CRC H04L1/004; adaptive formatting H04L1/0006; mappings H04L27/00
• CPC Class Codes: H04L 1/0086 Unequal error protection H04L27/00 and H04L1/004 take precedence for layer 1/2 aspects, e.g. bit loading
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• 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 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/18 Phase-modulated carrier systems, i.e. using phase-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2003 for continuous phase modulation frequency shift keying H04L27/10

Abstract

A wireless communications device (200) is provided. The device includes a demodulator (210) configured for computing estimated bits for a modulated input signal 220 representing a the symbols associated with a frame, the estimated bits including estimated values for a frame of bits and at least one forward error correction (FEC) error bit encoded into the symbols. The device further includes an FEC decision decoder (212) configured for receiving at least a first portion of the estimated bits and calculating values for a first portion of the frame bits associated with the first portion of said the estimated bits, where the estimated bits are computed based on a condition of a communication channel associated with the modulated input signal and a frequency deviation associated with said demodulator.

Claims

1. A wireless communications device, comprising:

a demodulator configured for computing a plurality of estimated bits for a modulated input signal representing a plurality of symbols associated with a frame, said plurality of estimated bits comprising estimated values for a plurality of frame bits and at least one forward error correction (FEC) error bit encoded into said plurality of symbols; and

at least one FEC decision decoder configured for receiving at least a first portion of said plurality of estimated bits and calculating values for a first portion of said plurality of frame bits associated with said first portion of said plurality of estimated bits,

wherein said plurality of estimated bits are computed based on a condition of a communication channel associated with said modulated input signal and a frequency deviation (L) associated with said demodulator.

2. The wireless communications device of claim 1, wherein said condition of said communications channel is signal to noise ratio (SNR).

3. The wireless communications device of claim 2, wherein said demodulator is further configured to compute said plurality of estimated bits based on a log-likelihood ratio (LLR) value for each of said plurality of symbols, and wherein said LLR value is given by:

LLR=SNR×

L^α

where α

is a weighting factor.

4. The wireless communications device of claim 3, wherein said weighting factor is pre-defined.

5. The wireless communications device of claim 3, wherein said weighting factor is adjusted dynamically.

6. The wireless communications device of claim 1, wherein said FEC decision decoder is further configured to operate using a Turbo code algorithm.

7. The wireless communications device of claim 1, wherein said FEC error bit is associated with a portion of said plurality of frame bits, and further comprising a bit prioritization element configured for directing said FEC error bit and said portion of said frame bits into said FEC decision decoder.

8. The wireless communications device of claim 7, where said bit prioritization element is further configured for directing a second portion of said plurality of frame bits to bypass said FEC decision decoder.

9. The wireless communications device of claim 1, wherein said modulated input signal comprises a continuous phase modulated signal.

10. A method for operating a wireless communications device in a wireless communications network, comprising:

demodulating a modulated input signal received over a communication channel, said modulated input signal comprising a plurality of symbols associated with a frame;

computing a plurality of estimated bits from said modulated input signal, said plurality of estimated bits comprising estimated values for a plurality of frame bits and at least one forward error correction (FEC) error bit encoded into said plurality of symbols; and

calculating values for at least a first portion of said plurality of frame bits associated with said first portion of said plurality of estimated bits,

wherein said plurality of estimated bits are computed based on a condition of said communication channel and a frequency deviation (L) associated with said demodulating.

11. The method of claim 10, wherein said condition of said communications channel is selected to be signal to noise ratio (SNR).

12. The method of claim 11, wherein said computing comprises determining said plurality of estimated bits based on a log-likelihood ratio (LLR) value for each of said plurality of symbols, and wherein said LLR value is given by:

LLR=SNR×

L^α

where α

is a weighting factor.

13. The method of claim 12, wherein said weighting factor is pre-defined.

14. The method of claim 12, wherein said weighting factor is adjusted dynamically.

15. The method of claim 10, wherein calculating is performed using a Turbo code algorithm.

16. The method of claim 10, wherein said FEC error bit is associated with a portion of said plurality of frame bits, and wherein said calculating further comprises directing said FEC error bit and said portion of said frame bits into said FEC decision decoder.

17. The method of claim 16, further comprising directing a second portion of said plurality of frame bits to bypass said FEC decision decoder.

18. A method of performing soft decision calculations in a multi-level continuous phase modulation (CPM) system, the method comprising:

determining phase and amplitude information for an input modulated signal; and

performing said soft decision calculations using the determined phase and amplitude information.

19. The method of claim 18, wherein said performing comprises computing a log-likelihood ratio (LLR) value, and wherein said LLR value is given by:

LLR=SNR×

L^α

where SNR is said amplitude information, L is said phase information, and α

is a weighting factor.

20. The method of claim 19, wherein said soft decisions calculations are performed using a block Turbo code algorithm.