This is a short review of the concept of channel coding with some perspective on the history of this field.<p>No real technical information there... The title is a bit misleading. If you want to understand Gallager codes (LDPC codes) better look elsewhere (Gallager's paper or thesis might be a better starting point: <a href="http://www.rle.mit.edu/rgallager/documents/ldpc.pdf" rel="nofollow">http://www.rle.mit.edu/rgallager/documents/ldpc.pdf</a>)