Error correcting codes and spatial coupling

These are notes from the lecture of R"udiger Urbanke given at the autumn school “Statistical Physics, Optimization, Inference, and Message-Passing Algorithms”, that took place in Les Houches, France from Monday September 30th, 2013, till Friday October 11th, 2013. The school was organized by Florent Krzakala from UPMC and ENS Paris, Federico Ricci-Tersenghi from La Sapienza Roma, Lenka Zdeborov`a from CEA Saclay and CNRS, and Riccardo Zecchina from Politecnico Torino. The first three sections cover the basics of polar codes and low density parity check codes. In the last three sections, we see how the spatial coupling helps belief propagation decoding.