# Introduction to coding theory (CMU, Spr 2010)

## March 20, 2010

### Lecture 15 summary

Filed under: Lecture summary — Venkat Guruswami @ 6:04 pm

We finished the analysis of GMD decoding for concatenated codes. We saw how to use concatenation with outer code that can correct a small fraction of worst-case errors to construct codes that achieve the Shannon capacity of the BEC and BSC, together with polynomial time encoding/decoding. We began the discussion of low-density parity-check codes, and saw why unbalanced bipartite expanders with expansion more than $D/2$ give rise to asymptotically good binary linear codes.