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Constellation Labeling Maps for Low Error Floors

Constellation Labeling Maps for Low Error Floors. Don Torrieri U.S. Army Research Laboratory Matthew C. Valenti West Virginia University. BICM-ID.

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Constellation Labeling Maps for Low Error Floors

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  1. Constellation Labeling Maps for Low Error Floors Don TorrieriU.S. Army Research LaboratoryMatthew C. ValentiWest Virginia University

  2. BICM-ID • In a system with BICM and iterative decoding and demodulation (BICM-ID), soft-decision information is exchanged between the demodulator and the decoder, which itself may be internally iterative.

  3. BICM–ID System

  4. Labeling Maps • Constellation labeling or labeling map is the mapping of a bit pattern to each symbol or point in a signal-set constellation. • Gray labeling map minimizes the number of bit errors that occur if an adjacent symbol of a received symbol is assigned the highest likelihood or largest metric by the decoder.

  5. Labeling Map for 16-QAM

  6. BER Plots vs. SNR • Waterfall region is characterized by a rapid decrease in the BER as the SNR increases • Error-floor region – BER decreases much more slowly • Choice of the labeling map has a major impact on both regions

  7. Applications of Low Error Floor • Radio-relay communications • Space-ground communications • Automatic-repeat request is not feasible because of the variable delays

  8. Demodulator Metric for Bit k • vj is the extrinsic log-likelihood ratio for bit j that is produced by the decoder and fed back to the demodulator

  9. Demodulator Metric for Bit k • Symbols that include the essentially known bits constitute a subset A of the constellation

  10. TV Map • TV labeling map can be constructed by assigning bit patterns to symbols such that the Hamming distance to adjacent symbols always is at least m - 1.

  11. Labeling Map for 64-QAM

  12. BER for 16-QAM

  13. BER for 64-QAM

  14. BER for 256-QAM

  15. CPFSK • Noncoherent q-ary continuous-phase frequency-shift keying (CPFSK) system with modulation index h > 0

  16. BER for 8-CPFSK

  17. BER for 8-CPFSK

  18. Conclusions • TV labeling maps are at least as good as other proposed labeling maps in providing a low error floor or high asymptotic coding gain. • A major advantage of the TV labeling maps is that they are easily generated.

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