Turbo Decoding, Detection and its Wireless Applications

Abstract

In 1948 Shannon quantified the performance limits of communications systems transmitting over Gaussian channels and the ensuing era witnessed the creation of diverse solutions approaching these limits within an infinitesimally low margin. Many of these near-capacity solutions have also found their way into standardized systems. At the time of writing the challenge is to approach the capacity of wireless multiple-antenna-aided systems at a low complexity, high effective throughput and low delay, regardless of the prevalent channel characteristics. A historical perspective of turbo coding and turbo transceivers inspired by the generic turbo principles is provided, as it evolved from Shannon's visionary predictions. More specifically, we commence by discussing the turbo principles, which have been shown to be capable of performing close to Shannon capacity limit. We continue by reviewing the classic Maximum A posteriori Probability (MAP) decoder. These discussions are followed by studying the effect of a range of system parameters in a systematic fashion, in order to gauge their performance ramifications. In the second part of this treatise we focus our attention on the family of iterative receivers designed for wireless communication systems, which were partly inspired by the invention of turbo codes. More specifically, the family of iteratively detected joint coding and modulation schemes, turbo equalization, concatenated space-time and channel coding arrangements, as well as multi-user detection and three-stage multimedia systems are highlighted.