1. Constellation Labeling Maps for Low Error Floors Don Torrieri U.S. Army Research Laboratory Matthew C. Valenti West 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

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.