Guest editorial - the turbo principle: from theory to practice II

I N 1997, Hagenauer coined the phrase “the turbo principle” to describe the fundamental strategy underlying the success of turbo decoding, namely the iterated exchange of soft information between different blocks in a communications receiver in order to improve overall system performance. This principle, embodied in the iterative decoding of parallel concatenated “turbo codes” (Berrou, Glavieux, and Thitimajshima, 1993), as well as in the message-passing decoding of low-density parity-check codes (Gallager, 1963), is now widely recognized as a very general and powerful concept in communication theory, with applications that go beyond the practical decoding of these near capacity achieving codes. 1