Guest editorial capacity approaching codes

Since the introduction of Turbo Codes in 1993, it has become possible to design practical channel coding systems that operate close to capacity at moderate bit error rates (BERs) over the additive white Gaussian noise (AWGN) channel. There are two key ingredients in the design of such systems: (1) the use of simple component codes concatenated in such a way as to produce a random-like codeword weight distribution; and (2) the use of suboptimal iterative decoding algorithms that repeatedly exchange soft information and whose complexity grows only linearly with block length.