Implement position-aware density evolution for SC-LDPC codes:
- sc_density_evolution(): flooding-schedule DE tracking per-position
error rates, demonstrating the wave decoding effect
- compute_sc_threshold(): binary search for SC-LDPC threshold
Uses flooding schedule (not layered) to avoid belief divergence
from cross-position message interference in the coupled chain.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Implement windowed_decode() for SC-LDPC codes using flooding
min-sum with sliding window of W positions. Supports both
normalized and offset min-sum modes.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Implement spatially-coupled LDPC code construction with:
- split_protograph(): split base matrix edges into w components
- build_sc_chain(): build full SC-LDPC H matrix with L positions
- sc_encode(): GF(2) Gaussian elimination encoder for SC chain
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
